ORCID Profile
0000-0002-7040-5498
Current Organisation
Swinburne University of Technology
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Astronomical and Space Sciences | Cosmology and Extragalactic Astronomy | Stellar Astronomy and Planetary Systems | Astronomical and Space Instrumentation | Atomic and Molecular Physics | Atomic molecular and optical physics | Engineering/Technology Instrumentation | Astrobiology | Astronomy And Astrophysics | Nanofabrication growth and self assembly | Astronomical instrumentation | Particle Physics | Photonics optoelectronics and optical communications | Nonlinear optics and spectroscopy | Quantum Optics And Lasers
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Physical Sciences | Measurement standards and calibration services not elsewhere classified | Physical sciences | Scientific instrumentation |
Related Links
Publications
Relativistic effects in Ni II and the search for variation of the fine-structure constant
Publisher: American Physical Society (APS)
Date: 19-03-2001
The clustering of luminous red galaxies around Mg ii absorbers
Publisher: Oxford University Press (OUP)
Date: 10-2004
Markov Chain Monte Carlo methods applied to measuring the fine structure constant from quasar spectroscopy
Publisher: Cambridge University Press (CUP)
Date: 11-2009
DOI: 10.1017/S1743921310009555
Abstract: Recent attempts to constrain cosmological variation in the fine structure constant, α, using quasar absorption lines have yielded two statistical s les which initially appear to be inconsistent. One of these s les was subsequently demonstrated to not pass consistency tests it appears that the optimisation algorithm used to fit the model to the spectra failed. Nevertheless, the results of the other hinge on the robustness of the spectral fitting program VPFIT, which has been tested through simulation but not through direct exploration of the likelihood function. We present the application of Markov Chain Monte Carlo (MCMC) methods to this problem, and demonstrate that VPFIT produces similar values and uncertainties for Δα/α, the fractional change in the fine structure constant, as our MCMC algorithm, and thus that VPFIT is reliable.
Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra
Publisher: Oxford University Press (OUP)
Date: 10-2003
The Magellan uniform survey of damped Lyman α systems – II. Paucity of strong molecular hydrogen absorption★
Publisher: Oxford University Press (OUP)
Date: 05-08-2014
Discovery of a Perseus-like cloud in the early Universe
Publisher: EDP Sciences
Date: 2017
DOI: 10.1051/0004-6361/201629173
Abstract: We present the discovery of a molecular cloud at z abs ≈ 2.5255 along the line of sight to the quasar SDSS J 000015.17+004833.3. We use a high-resolution spectrum obtained with the Ultraviolet and Visual Echelle Spectrograph together with a deep multi-wavelength medium-resolution spectrum obtained with X-shooter (both on the Very Large Telescope) to perform a detailed analysis of the absorption lines from ionic, neutral atomic and molecular species in different excitation levels, as well as the broad-band dust extinction. We find that the absorber classifies as a D ed Lyman- α system (DLA) with log N (H i ) (cm -2 ) = 20.8 ± 0.1. The DLA has super-solar metallicity ( Z ~ 2.5 Z ⊙ , albeit to within a factor of two to three) with a depletion pattern typical of cold gas and an overall molecular fraction f = 2 N (H 2 )/(2 N (H 2 ) + N (H i )) ~ 50%. This is the highest f -value observed to date in a high- z intervening system. Most of the molecular hydrogen arises from a clearly identified narrow ( b ~ 0.7km s -1 ), cold component in which carbon monoxide molecules are also found, with log N (CO)≈ 15. With the help of the spectral synthesis code Cloudy, we study the chemical and physical conditions in the cold gas. We find that the line of sight probes the gas deep after the H i -to-H 2 transition in a ~4−5 pc-size cloud with volumic density n H ~ 80 cm -3 and temperature of only 50 K. Our model suggests that the presence of small dust grains (down to about 0.001 μ m) and high cosmic ray ionisation rate ( ζ H ~ a few times 10 -15 s -1 ) are needed to explain the observed atomic and molecular abundances. The presence of small grains is also in agreement with the observed steep extinction curve that also features a 2175 Å bump. Interestingly, the chemical and physical properties of this cloud are very similar to what is seen in diffuse molecular regions of the nearby Perseus complex, despite the former being observed when the Universe was only 2.5 Gyr old. The high excitation temperature of CO rotational levels towards J0000+0048 betrays however the higher temperature of the cosmic microwave background. Using the derived physical conditions, we correct for a small contribution (0.3 K) of collisional excitation and obtain T CMB ( z = 2.53) ≈ 9.6 K, in perfect agreement with the predicted adiabatic cooling of the Universe.
Laser frequency comb techniques for precise astronomical spectroscopy
Publisher: Oxford University Press (OUP)
Date: 12-03-2012
Probing Galactic variations in the fine-structure constant using solar twin stars: Systematic errors
Publisher: Oxford University Press (OUP)
Date: 16-12-2022
Abstract: Sun-like stars are a new probe of variations in the fine-structure constant, α, via the solar twins approach: velocity separations of close pairs of absorption lines are compared between stars with very similar stellar parameters, i.e. effective temperature, metallicity, and surface gravity within 100 K, 0.1 dex, and 0.2 dex of the Sun’s values. Here, we assess possible systematic errors in this approach by analysing ≳10 000 archival exposures from the High-Accuracy Radial Velocity Planetary Searcher (HARPS) of 130 stars covering a much broader range of stellar parameters. We find that each transition pair’s separation shows broad, low-order variations with stellar parameters that can be accurately modelled, leaving only a small residual, intrinsic star-to-star scatter of 0–33 m s−1 (average ≈7 m s−1, ≈1 × 10−4 Å at 5000 Å). This limits the precision available from a single pair in a single star. We consider potential systematic errors from a range of instrumental and astrophysical sources (e.g. wavelength calibration, charge transfer inefficiency, stellar magnetic activity, line blending) and conclude that variations in elemental abundances, isotope ratios, and stellar rotational velocities may explain this star-to-star scatter. Finally, we find that the solar twins approach can be extended to solar analogues – within 300 K, 0.3 dex, and 0.4 dex of the Sun’s parameters – without significant additional systematic errors, allowing a much larger number of stars to be used as probes of variation in α, including at much larger distances.
MUSE Analysis of Gas around Galaxies (MAGG) – V. Linking ionized gas traced by C iv and Si iv absorbers to Ly α emitting galaxies at z ≈ 3.0–4.5
Publisher: Oxford University Press (OUP)
Date: 13-07-2023
Abstract: We study the connection between Ly α emitters (LAEs) and metal-enriched ionized gas traced by C iv absorption at redshift z ≈ 3–4 in 28 quasar fields with high-resolution spectroscopy from the MUSE Analysis of Gas Around Galaxies survey. In a s le of 220 C iv absorbers, we identify 143 LAEs connected to C iv gas within a line-of-sight separation $\\pm 500\\rm \\, km\\, s^{-1}$, equal to a detection rate of 36 ± 5 per cent once we account for multiple LAEs connected to the same absorber. The luminosity function of LAEs associated with absorbers has an ≈2.4 higher normalization than the field. The analysis of the LAE–C iv correlation function suggests that metal-enriched gas arises both in the haloes of the LAEs and from locations not connected to galaxies. C iv absorbers with higher equivalent width are more often associated with LAEs and C iv systems are twice less likely, especially at low equivalent width, to be found near LAEs than strong H i absorbers. The covering fraction in groups is up to ≈3 times larger than for isolated galaxies. Similar results are found using Si iv as tracer of ionized gas. We propose three components to model the gas environment of LAEs: (i) the circumgalactic medium of galaxies, accounting for the strongest correlations between absorption and emission (ii) overdense gas filaments connecting galaxies, driving the excess of LAEs at a few times the virial radius and the modulation of the luminosity and cross-correlation functions for strong absorbers (iii) an enriched and more diffuse medium, accounting for weaker C iv absorbers farther from galaxies.
New constraint on cosmological variation of the proton-to-electron mass ratio from Q0528−250
Publisher: Oxford University Press (OUP)
Date: 06-10-2011
A cold component and the complex velocity structure of DLA1331 + 170
Publisher: Oxford University Press (OUP)
Date: 30-12-2010
Measuring the halo mass of Mg II absorbers from their cross-correlation with Luminous Red Galaxies
Publisher: Cambridge University Press (CUP)
Date: 03-2005
H2/HD molecular data for analysis of quasar spectra in search of varying constants
Publisher: EDP Sciences
Date: 02-2019
DOI: 10.1051/0004-6361/201834782
Abstract: Context. Absorption lines of H 2 and HD molecules observed at high redshift in the line of sight towards quasars are a test ground to search for variation of the proton-to-electron mass ratio μ . For this purpose, results from astronomical observations are compared with a compilation of molecular data of the highest accuracy, obtained in laboratory studies as well as in first-principles calculations. Aims. A comprehensive line list is compiled for H 2 and HD absorption lines in the Lyman ( B 1 Σ u + − X 1 Σ g + ) and Werner ( C 1 Π u − X 1 Σ g + ) band systems up to the Lyman cutoff at 912 Å. Molecular parameters listed for each line i are the transition wavelength λ i , the line oscillator strength f i , the radiative d ing parameter of the excited state Γ i , and the sensitivity coefficient K i for a variation of the proton-to-electron mass ratio. Methods. The transition wavelengths λ i for the H 2 and HD molecules are determined by a variety of advanced high-precision spectroscopic experiments involving narrowband vacuum ultraviolet lasers, Fourier-transform spectrometers, and synchrotron radiation sources. Results for the line oscillator strengths f i , d ing parameters Γ i , and sensitivity coefficients K i are obtained in theoretical quantum chemical calculations. Results. A new list of molecular data is compiled for future analyses of cold clouds of hydrogen absorbers, specifically for studies of μ -variation from quasar data. The list is applied in a refit of quasar absorption spectra of B0642–5038 and J1237+0647 yielding constraints on a variation of the proton-to-electron mass ratio Δ μ / μ consistent with previous analyses.
Signatures of Cool Gas Fueling a Star-Forming Galaxy at Redshift 2.3
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-07-2013
Abstract: Numerical models predict that in order to keep forming stars, galaxies should be continuously replenished with gas from the intergalactic medium. Using data from the Very Large Telescope in Chile, Bouché et al. (p. 50 ) report observations that are consistent with accretion of cold, chemically pristine gas onto a star-forming galaxy at a time when the cosmic star-formation activity was at its peak.
Initial Development of a Patient Reported Experience Measure for Older Adults Attending the Emergency Department: Part I—Interviews with Service Users
Publisher: MDPI AG
Date: 28-02-2023
DOI: 10.3390/HEALTHCARE11050717
Abstract: Older adults are a major Emergency Department (ED) user group who may be especially vulnerable to the consequences of crowding and sub-optimal care. Patient experience is a critical component of high-quality ED care and has previously been conceptualised using a framework focusing on patients’ needs. This study aimed to explore the experiences of older adults attending the ED in relation to the existing needs-based framework. Semi-structured interviews were conducted during an emergency care episode with 24 participants aged over 65 years in a United Kingdom ED with an annual census ~100,000. Questions exploring patient experiences of care confirmed that meeting the communication, care, waiting, physical, and environmental needs were prominent determinants of experience for older adults. A further analytical theme emerged which did not align to the existing framework, focused on ‘team attitudes and values’. This study builds on existing knowledge relating to the experience of older adults in the ED. In addition, data will also contribute to the generation of candidate items for the development of a patient reported experience measure for older adults attending the ED.
Detailed elemental abundances of binary stars: searching for signatures of planet formation and atomic diffusion
Publisher: Oxford University Press (OUP)
Date: 02-09-2021
Abstract: Binary star systems are assumed to be co-natal and coeval, and thus to have identical chemical composition. In this work, we aim to test the hypothesis that there is a connection between observed element abundance patterns and the formation of planets using binary stars. Moreover, we also want to test how atomic diffusion might influence the observed abundance patterns. We conduct a strictly line-by-line differential chemical abundance analysis of seven binary systems. Stellar atmospheric parameters and elemental abundances are obtained with extremely high precision (& .5 per cent) using the high-quality spectra from Very Large Telescope/ultraviolet–visual Echelle spectrograph and Keck/high-resolution Echelle spectrometer. We find that four of seven binary systems show subtle abundance differences (0.01–0.03 dex) without clear correlations with the condensation temperature, including two planet-hosting pairs. The other three binary systems exhibit similar degree of abundance differences correlating with the condensation temperature. We do not find any clear relation between the abundance differences and the occurrence of known planets in our systems. Instead, the overall abundance offsets observed in the binary systems (four of seven) could be due to the effects of atomic diffusion. Although giant planet formation does not necessarily imprint chemical signatures on to the host star, the differences in the observed abundance trends with condensation temperature, on the other hand, are likely associated with erse histories of planet formation (e.g. formation location). Furthermore, we find a weak correlation between abundance differences and binary separation, which may provide a new constraint on the formation of binary systems.
On the absence of molecular absorption in high-redshift millimetre-band searches
Publisher: Oxford University Press (OUP)
Date: 08-2011
Revision of VLT/UVES constraints on a varying fine-structure constant
Publisher: Oxford University Press (OUP)
Date: 03-2008
Relationship between the Metallicity of the Circumgalactic Medium and Galaxy Orientation
Publisher: American Astronomical Society
Date: 23-09-2019
CONSTRAINT ON A COSMOLOGICAL VARIATION IN THE PROTON-TO-ELECTRON MASS RATIO FROM ELECTRONIC CO ABSORPTION
Publisher: American Astronomical Society
Date: 29-07-2016
Fundamental physics with ESPRESSO: Constraining a simple parametrisation for varying α
Publisher: EDP Sciences
Date: 10-2022
DOI: 10.1051/0004-6361/202243795
Abstract: Context. The spectrograph ESPRESSO recently obtained a limit on the variation of the fine-structure constant, α , through measurements along the line of sight of a bright quasar with a precision of 1.36 ppm at 1 σ level. This imposes new constraints on cosmological models with a varying α . We assume such a model where the electromagnetic sector is coupled to a scalar field dark energy responsible for the current acceleration of the Universe. We parametrise the variation of α with two extra parameters, one defining the cosmological evolution of the quintessence component and the other fixing the coupling with the electromagnetic field. Aims. The objective of this work is to constrain these parameters with both astrophysical and local probes. We also carried out a comparative analysis of how each data probe may constrain our parametrisation. Methods. We performed a Bayesian analysis by comparing the predictions of the model with observations. The astrophysical datasets are composed of quasar spectra measurements, including the latest ESPRESSO data point, as well as Planck observations of the cosmic microwave background. We combined these with local results from atomic clocks and the MICROSCOPE experiment. Results. The constraints placed on the quintessence parameter are consistent with a null variation of the field, and are therefore compatible with a ΛCDM cosmology. The constraints on the coupling to the electromagnetic sector are dominated by the Eötvös parameter local bound. Conclusions. More precise measurements with ESPRESSO will be extremely important to study the cosmological evolution of α as it probes an interval of redshift not accessible to other types of observations. However, for this particular model, current available data favour a null variation of α resulting mostly from the strong MICROSCOPE limits.
A NEW METHOD FOR DETECTING VELOCITY SHIFTS AND DISTORTIONS BETWEEN OPTICAL SPECTRA
Publisher: American Astronomical Society
Date: 13-11-2013
Spatial variation in the fine-structure constant - new results from VLT/UVES
Publisher: Oxford University Press (OUP)
Date: 25-04-2012
Codex
Publisher: Springer Berlin Heidelberg
Date: 2008
A new measurement of the intergalactic temperature at z ∼ 2.55–2.95
Publisher: Oxford University Press (OUP)
Date: 07-11-2017
New Results on Quasar Outflows
Publisher: Cambridge University Press (CUP)
Date: 08-2009
DOI: 10.1017/S1743921310006836
Abstract: Accretion disk outflows are an important part of the quasar phenomenon. They might play a major role in distributing metals to the galactic surroundings, halting growth of the central black hole and providing kinetic energy “feedback” to regulate star formation in the host galaxies. Some models of galaxy evolution indicate that feedback requires kinetic energy luminosities, L K , that are ~5% of the quasar bolometric L K / L = Ṁ w ν 2 /2η:Ṁ acc c 2 ~ 5% is possible if Ṁ w ~ Ṁ acc (with ν~ 0.1 c , and η ~ 0.1). Here we describe results from two studies designed to test the theoretical energetics of radiatively driven outflows and derive observational constraints on the outflow geometry and physical properties emphasizing weaker outflow features like NALs and mini-BALs.
A high-velocity narrow absorption line outflow in the quasar J212329.46 − 005052.9
Publisher: Oxford University Press (OUP)
Date: 10-2010
DISCOVERY OF THE TRANSITION OF A MINI-BROAD ABSORPTION LINE INTO A BROAD ABSORPTION LINE IN THE SDSS QUASAR J115122.14+020426.3
Publisher: American Astronomical Society
Date: 29-08-2013
Dust-reddening and gravitational lensing of SDSS QSOs due to foreground damped Lymanαsystems
Publisher: Oxford University Press (OUP)
Date: 10-2004
HALO GAS AND GALAXY DISK KINEMATICS DERIVED FROM OBSERVATIONS AND ΛCDM SIMULATIONS OF Mg II ABSORPTION-SELECTED GALAXIES AT INTERMEDIATE REDSHIFT
Publisher: American Astronomical Society
Date: 16-02-2010
HIGH-RESOLUTION MOLECULAR SPECTROSCOPY OF H2 AT 10% THE AGE OF THE UNIVERSE; TESTING THE CONSTANCY OF PHYSICAL LAW
Publisher: University of Illinois at Urbana-Champaign
Date: 19-06-2014
Possible evidence for a variable fine-structure constant from QSO absorption lines: motivations, analysis and results
Publisher: Oxford University Press (OUP)
Date: 11-11-2001
Limits on a Gravitational Field Dependence of the Proton-Electron Mass Ratio from
Publisher:
American Physical Society (APS)
Date:
18-09-2014
Publisher: American Physical Society (APS)
Date: 18-09-2014
Metal-enriched, subkiloparsec gas clumps in the circumgalactic medium of a faint z = 2.5 galaxy★
Publisher: Oxford University Press (OUP)
Date: 07-11-2014
The kinematic signature of damped Lyman alpha systems: using theD-index to screen for high column density H i absorbers★
Publisher: Oxford University Press (OUP)
Date: 21-01-2009
ANDES, the high resolution spectrograph for the ELT: science case, baseline design and path to construction
Publisher: SPIE
Date: 29-08-2022
DOI: 10.1117/12.2628689
Temperature controlled c axis elongated low symmetry phase BiFeO3 thin film on STO substrate
Publisher: AIP Publishing
Date: 2013
DOI: 10.1063/1.4789399
Abstract: BiFeO3 thin films with a mixture of tunable R-like and c axis elongated low symmetry phase (T-like phase) are fabricated on STO (001) substrate through controlling of the substrate temperature. Almost pure T-like phase can be grown on STO substrate at 600°C. Comparing with the situations on LAO (001), it is found that, strains from the LAO substrate may be the only reason that induces the T-like phase at higher temperatures. At lower temperatures, the island growth induced strains alone can also generate T-like phase on STO substrate.
On variations in the fine-structure constant and stellar pollution of quasar absorption systems
Publisher: Oxford University Press (OUP)
Date: 04-2005
Spin temperatures and covering factors for H i 21-cm absorption in damped Lymanαsystems
Publisher: Oxford University Press (OUP)
Date: 02-2005
Impact of instrumental systematic errors on fine-structure constant measurements with quasar spectra
Publisher: Oxford University Press (OUP)
Date: 18-12-2014
A survey for redshifted molecular and atomic absorption lines - I. The Parkes half-Jansky flat-spectrum red quasar sample
Publisher: Oxford University Press (OUP)
Date: 08-2006
The probabilistic random forest applied to the QUBRICS survey: improving the selection of high-redshift quasars with synthetic data
Publisher: Oxford University Press (OUP)
Date: 03-10-2022
Abstract: Several recent works have focused on the search for bright, high-z quasars (QSOs) in the South. Among them, the QUasars as BRIght beacons for Cosmology in the Southern hemisphere (QUBRICS) survey has now delivered hundreds of new spectroscopically confirmed QSOs selected by means of machine learning algorithms. Building upon the results obtained by introducing the probabilistic random forest (PRF) for the QUBRICS selection, we explore in this work the feasibility of training the algorithm on synthetic data to improve the completeness in the higher redshift bins. We also compare the performances of the algorithm if colours are used as primary features instead of magnitudes. We generate synthetic data based on a composite QSO spectral energy distribution. We first train the PRF to identify QSOs among stars and galaxies, then separate high-z quasar from low-z contaminants. We apply the algorithm on an updated data set, based on SkyMapper DR3, combined with Gaia eDR3, 2MASS, and WISE magnitudes. We find that employing colours as features slightly improves the results with respect to the algorithm trained on magnitude data. Adding synthetic data to the training set provides significantly better results with respect to the PRF trained only on spectroscopically confirmed QSOs. We estimate, on a testing data set, a completeness of $\\sim 86{{\\ \\rm per\\ cent}}$ and a contamination of $\\sim 36{{\\ \\rm per\\ cent}}$. Finally, 206 PRF-selected candidates were observed: 149/206 turned out to be genuine QSOs with z & 2.5, 41 with z & 2.5, 3 galaxies and 13 stars. The result confirms the ability of the PRF to select high-z quasars in large data sets.
The connection between metallicity and metal-line kinematics in (sub-)damped Lyα systems
Publisher: Oxford University Press (OUP)
Date: 04-2007
Ca ii and Na i Absorption Signatures from the Circumgalactic Gas of the Milky Way
Publisher: Springer Netherlands
Date: 2008
A second-order ferromagnetic transition in the martensitic state of Ni49.5Mn32.5Cu4Sn14: A critical behavior study
Publisher: AIP Publishing
Date: 15-01-2009
DOI: 10.1063/1.3068180
Abstract: A second-order ferromagnetic transition is observed in the martensitic state of Ni49.5Mn32.5Cu4Sn14 alloy and the critical behavior around the transition is investigated by dc magnetization measurements. With the help of modified Arrott plots, Kouvel–Fisher method, and Widom scaling relation, the values of TcM (ferromagnetic transition temperature in the martensite), and critical exponents: β (associated with the spontaneous magnetization), γ (relevant to the initial susceptibility), and δ (associated with the critical magnetization isotherm) are obtained. The scaling plots show that the obtained values of the critical exponents are reliable. The values of the critical exponents of Ni49.5Mn32.5Cu4Sn14 are different from those predicted by several theoretical models, i.e., mean-field theory, three-dimensional Heisenberg model, and three-dimensional Ising model. The magnetic interactions exhibit two different behaviors: long-range magnetic interaction below TcM and local magnetic interaction above TcM. The change in Mn moments may be responsible for the change in magnetic interactions around TcM.
Cosmic dynamics in the era of Extremely Large Telescopes
Publisher: Oxford University Press (OUP)
Date: 05-2008
Keck telescope constraint on cosmological variation of the proton-to-electron mass ratio
Publisher: Oxford University Press (OUP)
Date: 11-04-2010
Exploring the origins of a new, apparently metal-free gas cloud atz = 4.4
Publisher: Oxford University Press (OUP)
Date: 06-12-2020
The host galaxies of strong Ca II quasar absorption systems at z < 0.5
Publisher: Oxford University Press (OUP)
Date: 21-08-2007
The outer halo globular clusters of M31
Publisher: Oxford University Press (OUP)
Date: 05-2009
ON A VARIATION OF THE PROTON-ELECTRON MASS RATIO
Publisher: WORLD SCIENTIFIC
Date: 04-2008
Analytical model for the expansion of tubes under tension
Publisher: Elsevier BV
Date: 2010
Searching for space-time variation of the fine structure constant using QSO spectra: overview and future prospects
Publisher: Cambridge University Press (CUP)
Date: 11-2009
DOI: 10.1017/S1743921310009440
Abstract: Current theories that seek to unify gravity with the other fundamental interactions suggest that spatial and temporal variation of fundamental constants is a possibility, or even a necessity, in an expanding Universe. Several studies have tried to probe the values of constants at earlier stages in the evolution of the Universe, using tools such as big-bang nucleosynthesis, the Oklo natural nuclear reactor, quasar absorption spectra, and atomic clocks (see, e.g. Flambaum & Berengut (2009)).
Revisiting the origin of the high metallicities of sub-damped Lyman-alpha systems
Publisher: Oxford University Press (OUP)
Date: 11-06-2009
Imprints of the first billion years: Lyman limit systems atz∼ 5
Publisher: Oxford University Press (OUP)
Date: 13-10-2018
Deuterium abundance in the most metal-poor damped Lyman alpha system: converging on Ωb,0h2
Publisher: Oxford University Press (OUP)
Date: 21-12-2008
First Constraint on Cosmological Variation of the Proton-to-Electron Mass Ratio from Two Independent Telescopes
Publisher: American Physical Society (APS)
Date: 06-05-2011
Precise limits on cosmological variability of the fine-structure constant with zinc and chromium quasar absorption lines
Publisher: Oxford University Press (OUP)
Date: 20-06-2016
The UVES Large Program for testing fundamental physics – III. Constraints on the fine-structure constant from three telescopes
Publisher: Oxford University Press (OUP)
Date: 23-09-2014
The UVES Large Program for testing fundamental physics I. Bounds on a change inαtowards quasar HE 2217−2818
Publisher: EDP Sciences
Date: 07-2013
Use of the 82Sr/82Rb Generator in Clinical PET Studies
Publisher: Elsevier BV
Date: 1990
DOI: 10.1016/0883-2897(90)90023-T
Abstract: The use of the 82Sr/82Rb generator in clinical positron emission tomography (PET) studies of myocardial perfusion has been described. An infusion pump is used to deliver the short-lived 82Rb from the generator to the patient. Various characteristics of the generator and the infusion system are described. The 82Rb yield was 69.8 +/- 13.3% and the 82Sr breakthrough was always less than the limit of 0.02 microCi/mCi 82Rb. The yield of 82Rb increased with the flow rate and the potency of the generator. Patients with coronary artery disease were studied for myocardial perfusion abnormalities by the 82Rb PET technique and images of excellent diagnostic quality were obtained.
MAGiiCAT IV. KINEMATICS OF THE CIRCUMGALACTIC MEDIUM AND EVIDENCE FOR QUIESCENT EVOLUTION AROUND RED GALAXIES
Publisher: American Astronomical Society
Date: 18-02-2016
Survey for Distant Solar Twins (SDST) – I. epic method for stellar parameter measurement
Publisher: Oxford University Press (OUP)
Date: 18-02-2022
Abstract: Solar twins are stars of key importance to the field of astronomy and offer a multitude of science applications. Only a small number (≲200) of solar twins are known today, all of which are relatively close to our Sun (${\\lesssim}{800}\\, {\\rm pc}$). The goal of our Survey for Distant Solar Twins (SDST) is to identify many more solar twin and solar analogue stars out to much larger distances (${\\sim}{4}\\, {\\rm kpc}$). In this paper, we present a new method to identify solar twins using relatively low S/N, medium resolving power ($R\\sim 28\\, 000$) spectra that will be typical of such distant targets observed with HERMES on the ${3.9}\\, {\\rm m}$ Anglo-Australian Telescope (AAT). We developed a novel approach, namely epic, to measure stellar parameters (SPs) which we use to identify stars similar to our Sun. epic determines the stellar atmospheric parameters (effective temperature Teff, surface gravity log g, and metallicity [Fe/H]) using differential equivalent width (EW) measurements of selected spectroscopic absorption features and a simple model, trained on previously analysed spectra, that connects these EWs to the SPs. The reference for the EW measurements is a high S/N solar spectrum which is used to minimize several systematic effects. epic is fast, optimized for Sun-like stars and yields SP measurements with small enough uncertainties to enable spectroscopic identification of solar twin and analogue stars up to ${\\sim}{4}\\, {\\rm kpc}$ away using AAT/HERMES, i.e. $\\sigma \\left(T_{\\mathrm{eff}}, \\log g, \\textrm {[Fe/H]}\\right) = \\left({50}\\, {\\rm K}, {0.08}\\, {\\rm dex}, {0.03}\\, {\\rm dex}\\right)$ on average at S/N = 25.
One- and two-dimensional spin systems in the regime close to deconfinement of spinons
Publisher: American Physical Society (APS)
Date: 08-1999
THE REDSHIFT DISTRIBUTION OF INTERVENING WEAK Mg II QUASAR ABSORBERS AND A CURIOUS DEPENDENCE ON QUASAR LUMINOSITY
Publisher: American Astronomical Society
Date: 08-04-2013
The thermal history of the intergalactic medium down to redshift z = 1.5: a new curvature measurement
Publisher: Oxford University Press (OUP)
Date: 15-05-2014
DOI: 10.1093/MNRAS/STU660
MUSE Analysis of Gas around Galaxies (MAGG) – I: Survey design and the environment of a near pristine gas cloud at z ≈ 3.5
Publisher: Oxford University Press (OUP)
Date: 04-11-2019
Abstract: We present the design, methods, and first results of the MUSE Analysis of Gas around Galaxies (MAGG) survey, a large programme on the Multi-Unit Spectroscopic Explorer (MUSE) instrument at the Very Large Telescope (VLT), which targets 28 z & 3.2 quasars to investigate the connection between optically thick gas and galaxies at z ∼ 3–4. MAGG maps the environment of 52 strong absorption line systems at z ≳ 3, providing the first statistical s le of galaxies associated with gas-rich structures in the early Universe. In this paper, we study the galaxy population around a very metal poor gas cloud at z ≈ 3.53 towards the quasar J124957.23−015928.8. We detect three Lyα emitters within $\\lesssim 200~\\rm km~s^{-1}$ of the cloud redshift, at projected separations $\\lesssim 185~\\rm ~kpc$ (physical). The presence of star-forming galaxies near a very metal-poor cloud indicates that metal enrichment is still spatially inhomogeneous at this redshift. Based on its very low metallicity and the presence of nearby galaxies, we propose that the most likely scenario for this Lyman Limit System (LLS) is that it lies within a filament which may be accreting on to a nearby galaxy. Taken together with the small number of other LLSs studied with MUSE, the observations to date show a range of different environments near strong absorption systems. The full MAGG survey will significantly expand this s le and enable a statistical analysis of the link between gas and galaxies to pin down the origin of these erse environments at z ≈ 3–4.
An ALMA Early Science survey of molecular absorption lines toward PKS 1830−211
Publisher: EDP Sciences
Date: 06-2014
MAGIICAT I. THE Mg II ABSORBER-GALAXY CATALOG
Publisher: American Astronomical Society
Date: 07-10-2013
A limit on variations in the fine-structure constant from spectra of nearby Sun-like stars
Publisher: American Association for the Advancement of Science (AAAS)
Date: 11-11-2022
Abstract: The fine structure constant α sets the strength of the electromagnetic force. The Standard Model of particle physics provides no explanation for its value, which could potentially vary. The wavelengths of stellar absorption lines depend on α but are subject to systematic effects owing to astrophysical processes in stellar atmospheres. We measured precise line wavelengths from observations of 17 stars, selected to have almost identical atmospheric properties to those of the Sun (solar twins), which reduces those systematic effects. We found that α varies by ≲ 50 parts per billion within 50 parsecs from Earth. Combining the results from all 17 stars provides an empirical local reference for stellar measurements of α, with an ensemble precision of 12 parts per billion.
New searches for H i 21 cm in damped Lyman α absorption systems
Publisher: Oxford University Press (OUP)
Date: 27-11-2009
Selection of ThAr lines for wavelength calibration of echelle spectra and implications for variations in the fine-structure constant
Publisher: Oxford University Press (OUP)
Date: 10-05-2007
DOI: 10.1111/J.1365-2966.2007.11768.X
Abstract: Echelle spectrographs currently provide some of the most precise and detailed spectra in astronomy, the interpretation of which sometimes depends on the wavelength calibration accuracy. In some applications, such as constraining cosmological variations in the fundamental constants from quasar absorption lines, the wavelength calibration is crucial. Here we detail an algorithm for selecting thorium–argon (ThAr) emission lines for wavelength calibration which incorporates the properties of both a new laboratory wavelength list and the spectrograph of interest. We apply the algorithm to the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph (UVES) and demonstrate a factor of ≳3 improvement in the wavelength calibration residuals (i.e. random errors) alone. It is also found that UVES spectra calibrated using a previous, widely distributed line-list contain systematic ±30 –75 m s−1 distortions of the wavelength scale over both short and long wavelength ranges. These distortions have important implications for current UVES constraints on cosmological variations in the fine-structure constant. The induced systematic errors are most severe for Mg/Feii quasar absorbers in the redshift range 1.2 ≲zabs≲ 2.3, with in idual absorbers studied by recent authors containing systematic errors up to four times larger than quoted statistical errors.
Further constraints on variation of the fine-structure constant from alkali-doublet QSO absorption lines
Publisher: Oxford University Press (OUP)
Date: 11-11-2001
New limit on a varying proton-to-electron mass ratio from high-resolution optical quasar spectra
Publisher: Cambridge University Press (CUP)
Date: 11-2009
DOI: 10.1017/S1743921310009580
Abstract: Molecular transitions recently discovered at redshift z abs =2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-electron mass ratio, μ ≡ m p / m e . Observed with the Keck telescope, the optical spectrum has the highest resolving power and largest number (86) of H 2 transitions in such analyses so far. Also, (7) HD transitions are used for the first time to constrain μ-variation. These factors, and an analysis employing the fewest possible free parameters, strongly constrain μ's relative deviation from the current laboratory value: Δμ/μ =(+5.6±5.5 stat ±2.7 sys )×10 −6 . This is the first Keck result to complement recent constraints from three systems at z abs .5 observed with the Very Large Telescope.
Oxygen-driven anisotropic transport in ultra-thin manganite films
Publisher: Springer Science and Business Media LLC
Date: 13-11-2013
DOI: 10.1038/NCOMMS3778
MgII absorbers in high-resolution quasar spectra. I. voigt profile models
Publisher: American Astronomical Society
Date: 11-2020
Abstract: We present the Voigt profile (VP) models, column densities, Doppler b parameters, kinematics, and distribution of components for 422 Mg ii absorbers found in a survey of 249 HIRES and UVES quasar spectra. The equivalent width range of the s le is 0.006 ≤ W r (2796) ≤ 6.23 Å and the redshift range is 0.19 ≤ z ≤ 2.55, with a mean of . Based on historical precedent, we classified 180 absorbers as weak systems ( W r (2796) 0.3 Å) and 242 as strong systems ( W r (2796) ≥ 0.3 Å). Assuming a minimum number of significant components per system, the VP fitting, yielded a total of 2989 components, with an average of 2.7 and 10.3 components found for the weak and strong Mg ii subs les, respectively. The VP component line density for the full s le is 8.62 ± 0.23 clouds Å −1 . The distribution of VP component column density over the range 12.4 ≤ log N (Mg ii ) ≤ 17.0 cm −2 is well modeled with a power-law slope of −1.45 ± 0.01. The median Doppler b parameters are 4.5 ± 3.5 km s −1 , 6.0 ± 4.5 km s −1 , and 5.7 ± 4.4 km s −1 for the weak, strong, and full s les. We modeled the probability of component velocity splitting (the two-point velocity correlation function) of our full s le using a three-component composite Gaussian function. Our resulting velocity dispersions are σ 1 = 25.4 km s −1 , σ 2 = 68.7 km s −1 , and σ 3 = 207.1 km s −1 . These data provide an excellent database for studying the cosmic evolution of Mg ii absorber kinematic evolution.
Search for Cosmological μ-Variation from High-Redshift H2 Absorption; A Status Report
Publisher: Springer Berlin Heidelberg
Date: 2011
A Correlation between Galaxy Morphology and Mgii Halo Absorption Strength
Publisher: American Astronomical Society
Date: 20-06-2007
DOI: 10.1086/517990
The dust content of damped Lyman α systems in the Sloan Digital Sky Survey
Publisher: Oxford University Press (OUP)
Date: 07-11-2015
The UVES Spectral Quasar Absorption Database (SQUAD) data release 1: the first 10 million seconds
Publisher: Oxford University Press (OUP)
Date: 22-10-2018
The density, the cosmic microwave background, and the proton-to-electron mass ratio in a cloud at redshift 0.9
Publisher: EDP Sciences
Date: 29-04-2009
MAGiiCAT V. ORIENTATION OF OUTFLOWS AND ACCRETION DETERMINE THE KINEMATICS AND COLUMN DENSITIES OF THE CIRCUMGALACTIC MEDIUM
Publisher: American Astronomical Society
Date: 09-10-2015
Enhanced magnetoresistance through magnetic-field-induced phase transition in Ni2MnGa co-doped with Co and Mn
Publisher: Elsevier BV
Date: 03-2010
An absorption-selected survey of neutral gas in the Milky Way halo
Publisher: EDP Sciences
Date: 06-2012
Atomic Transition Frequencies, Isotope Shifts, and Sensitivity to Variation of the Fine Structure Constant for Studies of Quasar Absorption Spectra
Publisher: Springer Berlin Heidelberg
Date: 2011
Subaru Telescope limits on cosmological variations in the fine-structure constant
Publisher: Oxford University Press (OUP)
Date: 29-07-2017
A Unique View of AGN-driven Molecular Outflows: The Discovery of a Massive Galaxy Counterpart to aZ= 2.4 High-metallicity Damped LyαAbsorber
Publisher: American Astronomical Society
Date: 10-07-2017
Diffuse interstellar bands in z < 0.6 Ca II absorbers
Publisher: Oxford University Press (OUP)
Date: 2008
THE HIGHLY IONIZED CIRCUMGALACTIC MEDIUM IS KINEMATICALLY UNIFORM AROUND GALAXIES
Publisher: American Astronomical Society
Date: 10-01-2017
Low-mass Group Environments Have No Substantial Impact on the Circumgalactic Medium Metallicity
Publisher: American Astronomical Society
Date: 16-04-2020
Primordial Helium-3 Redux: The Helium Isotope Ratio of the Orion Nebula*
Publisher: American Astronomical Society
Date: 06-2022
Abstract: We report the first direct measurement of the helium isotope ratio, 3 He/ 4 He, outside of the Local Interstellar Cloud, as part of science-verification observations with the upgraded CRyogenic InfraRed Echelle Spectrograph. Our determination of 3 He/ 4 He is based on metastable He i * absorption along the line of sight toward Θ 2 A Ori in the Orion Nebula. We measure a value 3 He/ 4 He = (1.77 ± 0.13) × 10 −4 , which is just ∼40% above the primordial relative abundance of these isotopes, assuming the Standard Model of particle physics and cosmology, ( 3 He/ 4 He) p = (1.257 ± 0.017) × 10 −4 . We calculate a suite of galactic chemical evolution simulations to study the Galactic build up of these isotopes, using the yields from Limongi & Chieffi for stars in the mass range M = 8–100 M ⊙ and Lagarde et al. for M = 0.8–8 M ⊙ . We find that these simulations simultaneously reproduce the Orion and protosolar 3 He/ 4 He values if the calculations are initialized with a primordial ratio 3 He / 4 He p = ( 1.043 ± 0.089 ) × 10 − 4 . Even though the quoted error does not include the model uncertainty, this determination agrees with the Standard Model value to within ∼2 σ . We also use the present-day Galactic abundance of deuterium (D/H), helium (He/H), and 3 He/ 4 He to infer an empirical limit on the primordial 3 He abundance, 3 He / H p ≤ ( 1.09 ± 0.18 ) × 10 − 5 , which also agrees with the Standard Model value. We point out that it is becoming increasingly difficult to explain the discrepant primordial 7 Li/H abundance with nonstandard physics, without breaking the remarkable simultaneous agreement of three primordial element ratios (D/H, 4 He/H, and 3 He/ 4 He) with the Standard Model values.
Relativistic frequency shifts in Cr, Ti, Fe, Ni, Ca, Na, and V to search for variations in the fine-structure constant
Publisher: American Physical Society (APS)
Date: 10-06-2022
The CGM at Cosmic Noon with KCWI: Outflows from a Star-forming Galaxy at z = 2.071
Publisher: American Astronomical Society
Date: 12-2020
Constraint on a Varying Proton-Electron Mass Ratio 1.5 Billion Years after the Big Bang
Publisher: American Physical Society (APS)
Date: 19-02-2015
Redshifted H i and OH absorption in radio galaxies and quasars
Publisher: Oxford University Press (OUP)
Date: 21-02-2011
Possible evidence for a variable fine-structure constant from QSO absorption lines: systematic errors
Publisher: Oxford University Press (OUP)
Date: 11-11-2001
Stringent Null Constraint on Cosmological Evolution of the Proton-to-Electron Mass Ratio
Publisher: American Physical Society (APS)
Date: 19-12-2008
Probing variations in fundamental constants with radio and optical quasar absorption-line observations
Publisher: Oxford University Press (OUP)
Date: 2007
Gas Kinematics in the Multiphase Circumgalactic Medium
Publisher: Cambridge University Press (CUP)
Date: 03-2016
DOI: 10.1017/S1743921316011042
Abstract: We use high-resolution Keck, VLT, or Hubble Space Telescope spectra of background quasars to examine the kinematic properties of the multiphase, metal-enriched circumgalactic medium in the outskirts of galaxies at 0.08 z gal 1.0, focusing on the low-ionization Mg ii and high-ionization O vi doublets. The absorption kinematics of low-ionization gas in the circumgalactic medium depend strongly on the star formation activity and the location about the host galaxy, where the largest velocity dispersions are associated with blue, face-on galaxies probed along the minor axis. Conversely, high-ionization gas kinematics are independent of galaxy star formation activity and orientation.
Laser Comb: A Novel Calibration System for High Resolution Spectrographs
Publisher: Springer Berlin Heidelberg
Date: 2008
MUSE Analysis of Gas around Galaxies (MAGG) – IV. The gaseous environment of z ∼ 3–4 Ly α emitting galaxies
Publisher: Oxford University Press (OUP)
Date: 28-10-2022
Abstract: We study the link between galaxies and H i-selected absorption systems at z ∼ 3–4 in the MUSE Analysis of Gas around Galaxies (MAGG) survey, an ESO large programme consisting of integral field spectroscopic observations of 28 quasar fields hosting 61 strong absorbers with $\\rm N_{\\rm H\\,{\\small I}}\\gtrsim 10^{16.5}~\\rm cm^{-2}$. We identify 127 Ly α emitting galaxies (LAEs) around the absorbers, corresponding to a detection rate of 82 ± 16 per cent. The luminosity function of these LAEs is ≈5 times higher in normalization than the field population and we detect a significant clustering of galaxies with respect to the gas, confirming that high column density absorbers and LAEs trace each other. Between 30 and 40 per cent of the absorbers are associated with multiple LAEs, which lie preferentially along filaments. Galaxies in groups also exhibit a three times higher covering factor of optically thick gas compared to isolated systems. No significant correlations are identified between the emission properties of LAEs and the absorption properties of optically thick gas clouds, except for a weak preference of brighter and multiple galaxies to reside near broad absorbers. Based on the measured impact parameters and the covering factor, we conclude that the near totality of optically thick gas in the Universe can be found in the outer circumgalactic medium (CGM) of LAEs or in the intergalactic medium (IGM) in proximity to these galaxies. Thus, LAEs act as tracers of larger scale structures within which both galaxies and optically thick clouds are embedded. The patchy and inhomogeneous nature of the CGM and IGM explains the lack of correlations between absorption and emission properties. This implies that very large s les are needed to unveil the trends that encode the properties of the baryon cycle.
A precise deuterium abundance: remeasurement of the z = 3.572 absorption system towards the quasar PKS1937–101
Publisher: Oxford University Press (OUP)
Date: 22-03-2017
DOI: 10.1093/MNRAS/STX681
Erratum: Precise limits on cosmological variability of the fine-structure constant with zinc and chromium quasar absorption lines
Publisher: Oxford University Press (OUP)
Date: 04-10-2016
The kinetic temperature in a damped Lyman α absorption system in Q2206−199 - an example of the warm neutral medium
Publisher: Oxford University Press (OUP)
Date: 21-03-2012
Origin of Metals around Galaxies. I. Catalogs of Metal-line Absorption Doublets from High-resolution Quasar Spectra
Publisher: American Astronomical Society
Date: 20-07-2018
The imperative to reduce carbon emissions in astronomy
Publisher: Springer Science and Business Media LLC
Date: 10-09-2020
The Neutral Hydrogen Cosmological Mass Density at z = 5
Publisher: Cambridge University Press (CUP)
Date: 03-2016
DOI: 10.1017/S1743921316011595
Abstract: We present the largest homogeneous survey of redshift 4.4 d ed Lyα systems (DLAs) using the spectra of 163 quasars that comprise the Giant Gemini GMOS (GGG) survey. With this survey we make the most precise high-redshift measurement of the cosmological mass density of neutral hydrogen, Ω HI . After correcting for systematic effects using a combination of mock and higher-resolution spectra, we find Ω HI = 0.98 +0.20 -0.18 × 10 −3 at 〈 z 〉 = 4.9, assuming a 20% contribution from lower column density systems below the DLA threshold. By comparing to literature measurements at lower redshifts, we show that Ω HI can be described by the functional form Ω HI ( z ) ∝ (1 + z ) 0.4 . This gradual decrease from z = 5 to 0 suggests that in the galaxies which dominate the cosmic star formation rate, H i is a transitory gas phase fuelling star formation which must be continually replenished by more highly-ionized gas from the intergalactic medium, and from recycled galactic winds.
WAVELENGTH CALIBRATION OF THE VLT-UVES SPECTROGRAPH
Publisher: American Astronomical Society
Date: 07-10-2010
A Catalogue of Damped Lyman Alpha Absorption Systems and Radio Flux Densities of the Background Quasars
Publisher: Cambridge University Press (CUP)
Date: 2002
DOI: 10.1071/AS01077
Abstract: We present a catalogue of the 322 d ed Lyman alpha absorbers taken from the literature. All d ed Lyman alpha absorbers are included, with no selection on redshift or quasar magnitude. Of these, 123 are candidates and await confirmation using high resolution spectroscopy. For all 322 objects we catalogue the radio properties of the background quasars, where known. Around 60 quasars have radio flux densities above 0.1 Jy and approximately half of these have optical magnitudes brighter than V = 18. This compilation should prove useful in several areas of extragalactic/cosmological research.
Constraint on a varying proton-to-electron mass ratio from molecular hydrogen absorption towards quasar SDSS J123714.60+064759.5
Publisher: Oxford University Press (OUP)
Date: 22-09-2015
High-resolution absorption spectroscopy of the circumgalactic medium of the Milky Way
Publisher: Wiley
Date: 2014
Are strong Mg II absorbers the signature of outflows?
Publisher: Elsevier BV
Date: 02-2007
Metal-enriched halo gas across galaxy overdensities over the last 10 billion years
Publisher: Oxford University Press (OUP)
Date: 25-09-2021
Abstract: We present a study of metal-enriched halo gas traced by Mg ii and C iv absorption at z & 2 in the MUSE Analysis of Gas around Galaxies survey and the Quasar Sightline and Galaxy Evolution survey. Using these large and complete galaxy surveys in quasar fields, we study the dependence of the metal distribution on galaxy properties and overdensities, out to physical projected separations of 750 kpc. We find that the cool, low-ionization gas is significantly affected by the environment across the full redshift range probed, with ≈2–3 times more prevalent and stronger Mg ii absorption in higher overdensity group environments and in regions with greater overall stellar mass and star formation rates. Complementary to these results, we have further investigated the more highly ionized gas as traced by C iv absorption, and found that it is likely to be more extended than the Mg ii gas, with ≈2 times higher covering fraction at a given distance. We find that the strength and covering fraction of C iv absorption show less significant dependence on galaxy properties and environment than the Mg ii absorption, but more massive and star-forming galaxies nevertheless also show ≈2 times higher incidence of C iv absorption. The incidence of Mg ii and C iv absorption within the virial radius shows a tentative increase with redshift, being higher by a factor of ≈1.5 and ≈4, respectively, at z & 1. It is clear from our results that environmental processes have a significant impact on the distribution of metals around galaxies and need to be fully accounted for when analysing correlations between gaseous haloes and galaxy properties.
A robust deuterium abundance; re-measurement of the z = 3.256 absorption system towards the quasar PKS 1937−101
Publisher: Oxford University Press (OUP)
Date: 14-01-2015
Collaborative Workspaces to Accelerate Discovery
Publisher: Cambridge University Press (CUP)
Date: 2017
DOI: 10.1017/PASA.2017.15
Abstract: By applying a display ecology to the Deeper, Wider, Faster proactive, simultaneous telescope observing c aign, we have shown a dramatic reduction in the time taken to inspect DECam CCD images for potential transient candidates and to produce time-critical triggers to standby telescopes. We also show how facilitating rapid corroboration of potential candidates and the exclusion of non-candidates improves the accuracy of detection and establish that a practical and enjoyable workspace can improve the experience of an otherwise taxing task for astronomers. We provide a critical road test of two advanced displays in a research context—a rare opportunity to demonstrate how they can be used rather than simply discuss how they might be used to accelerate discovery.
Analysis of carbon monoxide absorption at zabs ≃ 2.5 to constrain variation of the proton-to-electron mass ratio
Publisher: Oxford University Press (OUP)
Date: 07-02-2017
DOI: 10.1093/MNRAS/STX331
A search for high-redshift molecular absorption lines towards millimetre-loud, optically faint quasars
Publisher: Oxford University Press (OUP)
Date: 07-2003
High-precision limit on variation in the fine-structure constant from a single quasar absorption system
Publisher: Oxford University Press (OUP)
Date: 08-10-2016
The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time
Publisher: Oxford University Press (OUP)
Date: 14-10-2014
MUSE analysis of gas around galaxies (MAGG) – III. The gas and galaxy environment of z = 3–4.5 quasars
Publisher: Oxford University Press (OUP)
Date: 08-03-2021
Abstract: We present a study of the environment of 27 z = 3–4.5 bright quasars from the MUSE Analysis of Gas around Galaxies (MAGG) survey. With medium-depth Multi Unit Spectroscopic Explorer (MUSE) observations (4 h on target per field), we characterize the effects of quasars on their surroundings by studying simultaneously the properties of extended gas nebulae and Ly α emitters (LAEs) in the quasar host haloes. We detect extended (up to ≈100 kpc) Ly α emission around all MAGG quasars, finding a very weak redshift evolution between z = 3 and z = 6. By stacking the MUSE datacubes, we confidently detect extended emission of C iv and only marginally detect extended He ii up to ≈40 kpc, implying that the gas is metal enriched. Moreover, our observations show a significant overdensity of LAEs within 300 $\\rm km~s^{-1}$ from the quasar systemic redshifts estimated from the nebular emission. The luminosity functions and equivalent width distributions of these LAEs show similar shapes with respect to LAEs away from quasars suggesting that the Ly α emission of the majority of these sources is not significantly boosted by the quasar radiation or other processes related to the quasar environment. Within this framework, the observed LAE overdensities and our kinematic measurements imply that bright quasars at z = 3–4.5 are hosted by haloes in the mass range $\\approx 10^{12.0}\\small{--}10^{12.5}~\\rm M_\\odot$.
Constraining the temperature–density relation of the intergalactic medium with the Lyman α and β forests
Publisher: Oxford University Press (OUP)
Date: 10-12-2015
Does the fine structure constant vary? A third quasar absorption sample consistent with varying α
Publisher: Springer Science and Business Media LLC
Date: 2003
Laboratory atomic transition data for precise optical quasar absorption spectroscopy
Publisher: Oxford University Press (OUP)
Date: 12-2013
The UVES large program for testing fundamental physics – II. Constraints on a change in μ towards quasar HE 0027−1836★
Publisher: Oxford University Press (OUP)
Date: 22-08-2013
The SINFONI Mg
ii
Program for Line Emitters (SIMPLE): Discovering Starbursts near QSO Sight Lines
Publisher: American Astronomical Society
Date: 11-10-2007
DOI: 10.1086/523594
PRECISION MEASURES OF THE PRIMORDIAL ABUNDANCE OF DEUTERIUM
Publisher: American Astronomical Society
Date: 03-01-2014
Colloquium: Search for a drifting proton-electron mass ratio from
Publisher:
American Physical Society (APS)
Date:
04-05-2016
Publisher: American Physical Society (APS)
Date: 04-05-2016
Probing Galactic variations in the fine-structure constant using solar twin stars: methodology and results
Publisher: Oxford University Press (OUP)
Date: 16-12-2022
Abstract: The rich absorption spectra of Sun-like stars are enticing probes for variations in the fine-structure constant, α, which gauges the strength of electromagnetism. While in idual line wavelengths are sensitive to α, they are also sensitive to physical processes in the stellar atmospheres, which has precluded their use so far. Here we demonstrate a new differential approach using solar twins: velocity separations between close pairs of transitions are compared across stars with very similar physical properties, strongly suppressing astrophysical and instrumental systematic errors. We utilize 423 archival exposures of 18 solar twins from the High-Accuracy Radial velocity Planetary Searcher (HARPS), in which calibration errors can be reduced to ≲3 m s−1. For stars with ≈10 high-signal-to-noise ratio spectra (≥200 per pixel), velocity separations between pairs are measured with ≈10 m s−1 statistical precision. A companion paper assesses a range of systematic error sources using 130 stars, with a greater range of stellar parameters, providing accurate corrections for astrophysical effects and a residual, intrinsic star-to-star scatter of 0–13 m s−1. Within these uncertainties, we find no evidence for velocity separation differences in 17 transition pairs between solar twins. In a second companion paper, this is found to limit local (≲50 pc) variations in α to ≈50 parts per billion, ∼2 orders of magnitude less than other Galactic constraints.
Laser Frequency Combs for Astronomical Observations
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-09-2008
Abstract: A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of ∼1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrated the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of ∼9 meters per second at ∼1.5 micrometers—beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceleration.
A Catalog of High-velocity C iv Mini-broad Absorption Lines in the VLT-UVES and Keck-HIRES Archives
Publisher: American Astronomical Society
Date: 02-2021
Detection of broad 21-cm absorption at zabs = 0.656 in the complex sight-line towards 3C 336
Publisher: Oxford University Press (OUP)
Date: 10-2007
A 22-GHz search for molecular absorption at z 3 with the upgraded ATCA
Publisher: Oxford University Press (OUP)
Date: 21-03-2003
Catalogue of candidate emission-line objects in the Small Magellanic Cloud
Publisher: Oxford University Press (OUP)
Date: 02-2000
Strong Limit on a Variable Proton-to-Electron Mass Ratio from Molecules in the Distant Universe
Publisher: American Association for the Advancement of Science (AAAS)
Date: 20-06-2008
Abstract: The Standard Model of particle physics assumes that the so-called fundamental constants are universal and unchanging. Absorption lines arising in molecular clouds along quasar sightlines offer a precise test for variations in the proton-to-electron mass ratio, μ, over cosmological time and distance scales. The inversion transitions of ammonia are particularly sensitive to μ as compared to molecular rotational transitions. Comparing the available ammonia spectra observed toward the quasar B0218+357 with new, high-quality rotational spectra, we present the first detailed measurement of μ with this technique, limiting relative deviations from the laboratory value to |Δμ/μ| 1.8 × 10 –6 (95% confidence level) at approximately half the universe's current age—the strongest astrophysical constraint to date. Higher-quality ammonia observations will reduce both the statistical and systematic uncertainties in these observations.
MASE: A New Data-Reduction Pipeline for the Magellan Echellette Spectrograph
Publisher: IOP Publishing
Date: 12-2009
DOI: 10.1086/648597
Possible Population III remnants at redshift 3.5
Publisher: Oxford University Press (OUP)
Date: 12-01-2016
Morphological properties of z∼ 0.5 absorption-selected galaxies: the role of galaxy inclination
Publisher: Oxford University Press (OUP)
Date: 11-08-2011
Low-column density HVC and IVC gas in the halo of the Milky Way
Publisher: EDP Sciences
Date: 2012
DOI: 10.1051/EAS/1256051
Are strong MgII Absorbers Signatures of Outflows?
Publisher: EDP Sciences
Date: 2012
DOI: 10.1051/EAS/1256050
New perspectives on strong z≃ 0.5 Mg ii absorbers: are halo mass and equivalent width anticorrelated?
Publisher: Oxford University Press (OUP)
Date: 08-2006
MUSE Analysis of Gas around Galaxies (MAGG) – II: metal-enriched halo gas around z ∼ 1 galaxies
Publisher: Oxford University Press (OUP)
Date: 12-10-2020
Abstract: We present a study of the metal-enriched cool halo gas traced by Mg ii absorption around 228 galaxies at z ∼ 0.8–1.5 within 28 quasar fields from the MUSE Analysis of Gas around Galaxies survey. We observe no significant evolution in the Mg ii equivalent width versus impact parameter relation and in the Mg ii covering fraction compared to surveys at z ≲ 0.5. The stellar mass, along with distance from galaxy centre, appears to be the dominant factor influencing the Mg ii absorption around galaxies. With a s le that is 90 per cent complete down to a star formation rate of ≈0.1 $\\rm M_\\odot yr^{-1}$ and up to impact parameters ≈250–350 kpc from quasars, we find that the majority ($67^{+12}_{-15}$ per cent or 14/21) of the Mg ii absorption systems are associated with more than one galaxy. The complex distribution of metals in these richer environments adds substantial scatter to previously reported correlations. Multiple galaxy associations show on average five times stronger absorption and three times higher covering fraction within twice the virial radius than isolated galaxies. The dependence of Mg ii absorption on galaxy properties disfavours the scenario in which a widespread intragroup medium dominates the observed absorption. This leaves instead gravitational interactions among group members or hydrodynamic interactions of the galaxy haloes with the intragroup medium as favoured mechanisms to explain the observed enhancement in the Mg ii absorption strength and cross-section in rich environments.
Fundamental physics with ESPRESSO: Constraints on Bekenstein and dark energy models from astrophysical and local probes
Publisher: American Physical Society (APS)
Date: 10-06-2022
Fundamental physics with ESPRESSO: Towards an accurate wavelength calibration for a precision test of the fine-structure constant
Publisher: EDP Sciences
Date: 02-2021
DOI: 10.1051/0004-6361/202039345
Abstract: Observations of metal absorption systems in the spectra of distant quasars allow one to constrain a possible variation of the fine-structure constant throughout the history of the Universe. Such a test poses utmost demands on the wavelength accuracy and previous studies were limited by systematics in the spectrograph wavelength calibration. A substantial advance in the field is therefore expected from the new ultra-stable high-resolution spectrograph E SPRESSO , which was recently installed at the VLT. In preparation of the fundamental physics related part of the E SPRESSO GTO program, we present a thorough assessment of the E SPRESSO wavelength accuracy and identify possible systematics at each of the different steps involved in the wavelength calibration process. Most importantly, we compare the default wavelength solution, which is based on the combination of Thorium-Argon arc l spectra and a Fabry-Pérot interferometer, to the fully independent calibration obtained from a laser frequency comb. We find wavelength-dependent discrepancies of up to 24 m s −1 . This substantially exceeds the photon noise and highlights the presence of different sources of systematics, which we characterize in detail as part of this study. Nevertheless, our study demonstrates the outstanding accuracy of E SPRESSO with respect to previously used spectrographs and we show that constraints of a relative change of the fine-structure constant at the 10 −6 level can be obtained with E SPRESSO without being limited by wavelength calibration systematics.
A survey for redshifted molecular and atomic absorption lines - II. Associated H i, OH and millimetre lines in thez≳ 3 Parkes quarter-Jansky flat-spectrum sample
Publisher: Oxford University Press (OUP)
Date: 12-2008
Improved constraints on possible variation of physical constants from H I 21-cm and molecular QSO absorption lines
Publisher: Oxford University Press (OUP)
Date: 11-11-2001
HALO GAS CROSS SECTIONS AND COVERING FRACTIONS OF Mg II ABSORPTION SELECTED GALAXIES
Publisher: American Astronomical Society
Date: 05-02-2008
Constraint on a variation of the proton-to-electron mass ratio from H2 absorption towards quasar Q2348−011
Publisher: Oxford University Press (OUP)
Date: 2012
Probing the circumgalactic medium of active galactic nuclei with background quasars
Publisher: Oxford University Press (OUP)
Date: 28-11-2014
Low-column density gas in the halo of the Milky Way
Publisher: Sissa Medialab
Date: 27-01-2010
DOI: 10.22323/1.089.0019
Modifier effect of the Toll-like receptor 4 D299G polymorphism in children with cystic fibrosis
Publisher: Springer Science and Business Media LLC
Date: 10-07-2006
DOI: 10.1007/S00005-006-0029-8
Abstract: Clinical phenotype varies amongst cystic fibrosis (CF) patients with identical CF transmembrane regulator (CFTR) genotype, suggesting genetic modifiers exist. One potential modifier is the Toll-like receptor 4 (TLR4) gene. TLR4 binds lipopolysaccharide (LPS), a constituent of Pseudomonas aeruginosa (PA), activating innate immunity and promoting inflammation. TLR4 polymorphisms are associated with LPS-hyporesponsiveness and may be protective in CF due to decreased inflammation. DNA was extracted from blood of recruited CF subjects, and PCR performed to establish TLR4 D299G genotype. Case-notes were reviewed to obtain clinical data. Subjects possessing the TLR4 299G allele were compared with age, sex, and CFTR genotype-matched wild-type (299DD) subjects and also with all controls. 100 subjects (mean age 8.9 years) were studied, with 11 299DG heterozygotes identified. On case-matched analyses, no statistically significant differences between groups were found for mean +/- SEM rates of change of %predicted FEV(1)/year (0.9 +/- 2.3 (DD) vs. - 3.9 +/- 2.8 (DG), p = 0.22), %predicted FEV(1) (76 +/- 8 vs. 74 +/- 11), p = 0.91), or z scores for height ( - 0.47 +/- 0.26 vs. - 0.24 +/- 0.19, p = 0.48) and weight ( - 0.01 +/- 0.22 vs. - 0.29 +/- 0.27, p = 0.44). Median +/- SE survival age at first PA isolation was also not significantly different (3.5 +/- 2.1 vs. 6.5 +/- 2.4 years, p = 0.29). No statistically significant differences were noted when 299DG heterozygotes were compared with all controls. Potential reasons for absence of modifier effect include the basolateral location of TLR4 receptors on respiratory epithelium, or because inflammatory response to PA in the CF airway is so overwhelming that even a blunted response (as suggested for the 299G allele) results in increased inflammation and lung damage.
The explosion energy of early stellar populations: the Fe-peak element ratios in low-metallicity damped Lyα systems★
Publisher: Oxford University Press (OUP)
Date: 19-03-2013
DOI: 10.1093/MNRAS/STT282
A precise architecture characterization of theπMensae planetary system
Publisher: EDP Sciences
Date: 10-2020
DOI: 10.1051/0004-6361/202038416
Abstract: Context. The bright star π Men was chosen as the first target for a radial velocity follow-up to test the performance of ESPRESSO, the new high-resolution spectrograph at the European Southern Observatory’s Very Large Telescope. The star hosts a multi-planet system (a transiting 4 M ⊕ planet at ~0.07 au and a sub-stellar companion on a ~2100-day eccentric orbit), which is particularly suitable for a precise multi-technique characterization. Aims. With the new ESPRESSO observations, which cover a time span of 200 days, we aim to improve the precision and accuracy of the planet parameters and search for additional low-mass companions. We also take advantage of the new photometric transits of π Men c observed by TESS over a time span that overlaps with that of the ESPRESSO follow-up c aign. Methods. We analysed the enlarged spectroscopic and photometric datasets and compared the results to those in the literature. We further characterized the system by means of absolute astrometry with H IPPARCOS and Gaia . We used the high-resolution spectra of ESPRESSO for an independent determination of the stellar fundamental parameters. Results. We present a precise characterization of the planetary system around π Men. The ESPRESSO radial velocities alone (37 nightly binned data with typical uncertainty of 10 cm s −1 ) allow for a precise retrieval of the Doppler signal induced by π Men c. The residuals show a root mean square of 1.2 m s −1 , which is half that of the HARPS data based on the residuals, we put limits on the presence of additional low-mass planets (e.g. we can exclude companions with a minimum mass less than ~2 M ⊕ within the orbit of π Men c). We improve the ephemeris of π Men c using 18 additional TESS transits, and, in combination with the astrometric measurements, we determine the inclination of the orbital plane of π Men b with high precision ( i b =45.8 −1.1 +1.4 deg). This leads to the precise measurement of its absolute mass m b =14.1 −0.4 +0.5 M Jup , indicating that π Men b can be classified as a brown dwarf. Conclusions. The π Men system represents a nice ex le of the extreme precision radial velocities that can be obtained with ESPRESSO for bright targets. Our determination of the 3D architecture of the π Men planetary system and the high relative misalignment of the planetary orbital planes put constraints on and challenge the theories of the formation and dynamical evolution of planetary systems. The accurate measurement of the mass of π Men b contributes to make the brown dwarf desert a bit greener.
The neutral gas extent of galaxies as derived from weak intervening Ca ii absorbers
Publisher: EDP Sciences
Date: 17-02-2011
Large Exchange Bias after Zero-Field Cooling from an Unmagnetized State
Publisher: American Physical Society (APS)
Date: 17-02-2011
Exploring variations in the fundamental constants with ELTs: the CODEX spectrograph on OWL
Publisher: Cambridge University Press (CUP)
Date: 11-2005
Accurate laboratory ultraviolet wavelengths for quasar absorption-line constraints on varying fundamental constants
Publisher: Oxford University Press (OUP)
Date: 21-07-2006
ANALYSIS OF MOLECULAR HYDROGEN ABSORPTION TOWARD QSO B0642–5038 FOR A VARYING PROTON-TO-ELECTRON MASS RATIO
Publisher: American Astronomical Society
Date: 21-01-2014
Ca II and Na I absorption signatures from extraplanar gas in the halo of the Milky Way
Publisher: EDP Sciences
Date: 24-06-2008
Molecular fraction limits in damped Lyman α absorption systems
Publisher: Oxford University Press (OUP)
Date: 08-2004
New H i 21-cm absorbers at low and intermediate redshifts
Publisher: Oxford University Press (OUP)
Date: 24-08-2015
The Magellan uniform survey of damped Lyman α systems – I. Cosmic metallicity evolution★
Publisher: Oxford University Press (OUP)
Date: 22-08-2013
Survey for distant solar twins (SDST) – II. Design, observations, and data
Publisher: Oxford University Press (OUP)
Date: 21-10-2022
Abstract: Studies of solar twins have key impacts on the astronomical community, but only ∼100–200 nearby solar twins (& kpc) have been reliably identified over the last few decades. The aim of our survey (SDST) is to identify ∼150–200 distant solar twins and analogues (up to ≲4 kpc) closer to the Galactic Centre. We took advantage of the precise Gaia and Skymapper surveys to select Sun-like candidates in a 2-deg field, which were observed with the HERMES spectrograph on the Anglo-Australian Telescope. We successfully built up the required signal-to-noise ratio (25-per-pixel in the HERMES red band) for most targets as faint as Gaia G of 17.4 mag. The stellar photometric/astrometric parameters (e.g. Teff, log g, mass) of our candidates are derived in this paper, while the spectroscopic parameters will be presented in the third paper in this SDST series. The selection success rate – the fraction of targets which belong to solar twins or analogues – was estimated from simulated survey data and the Besançon stellar population model, and compared with the actual success rate of the survey. We find that expected and actual success rates agree well, indicating that the numbers of solar twins and analogues we discover in SDST are consistent with expectations, affirming the survey approach. These distant solar analogues are prime targets for testing for any variation in the strength of electromagnetism in regions of higher dark matter density, and can make additional contributions to our understanding of, e.g. Galactic chemical evolution in the inner Milky Way.
ESPRESSO at VLT
Publisher: EDP Sciences
Date: 2021
DOI: 10.1051/0004-6361/202038306
Abstract: Context. ESPRESSO is the new high-resolution spectrograph of ESO’s Very Large Telescope (VLT). It was designed for ultra-high radial-velocity (RV) precision and extreme spectral fidelity with the aim of performing exoplanet research and fundamental astrophysical experiments with unprecedented precision and accuracy. It is able to observe with any of the four Unit Telescopes (UTs) of the VLT at a spectral resolving power of 140 000 or 190 000 over the 378.2 to 788.7 nm wavelength range it can also observe with all four UTs together, turning the VLT into a 16 m diameter equivalent telescope in terms of collecting area while still providing a resolving power of 70 000. Aims. We provide a general description of the ESPRESSO instrument, report on its on-sky performance, and present our Guaranteed Time Observation (GTO) program along with its first results. Methods. ESPRESSO was installed on the Paranal Observatory in fall 2017. Commissioning (on-sky testing) was conducted between December 2017 and September 2018. The instrument saw its official start of operations on October 1, 2018, but improvements to the instrument and recommissioning runs were conducted until July 2019. Results. The measured overall optical throughput of ESPRESSO at 550 nm and a seeing of 0.65″ exceeds the 10% mark under nominal astroclimatic conditions. We demonstrate an RV precision of better than 25 cm s −1 during a single night and 50 cm s −1 over several months. These values being limited by photon noise and stellar jitter shows that the performance is compatible with an instrumental precision of 10 cm s −1 . No difference has been measured across the UTs, neither in throughput nor RV precision. Conclusions. The combination of the large collecting telescope area with the efficiency and the exquisite spectral fidelity of ESPRESSO opens a new parameter space in RV measurements, the study of planetary atmospheres, fundamental constants, stellar characterization, and many other fields.
CODEX: measuring the acceleration of the universe and beyond
Publisher: Cambridge University Press (CUP)
Date: 11-2005
Fundamental physics with ESPRESSO: Precise limit on variations in the fine-structure constant towards the bright quasar HE 0515−4414
Publisher: EDP Sciences
Date: 02-2022
DOI: 10.1051/0004-6361/202142257
Abstract: The strong intervening absorption system at redshift 1.15 towards the very bright quasar HE 0515−4414 is the most studied absorber for measuring possible cosmological variations in the fine-structure constant, α . We observed HE 0515−4414 for 16.1 h with the Very Large Telescope and present here the first constraint on relative variations in α with parts-per-million (ppm) precision from the new ESPRESSO spectrograph: Δ α / α = 1.3 ± 1.3 stat ± 0.4 sys ppm. The statistical uncertainty (1 σ ) is similar to the ensemble precision of previous large s les of absorbers and derives from the high signal-to-noise ratio achieved (≈105 per 0.4 km s −1 pixel). ESPRESSO’s design, and the calibration of our observations with its laser frequency comb, effectively removed wavelength calibration errors from our measurement. The high resolving power of our ESPRESSO spectrum ( R = 145 000) enabled the identification of very narrow components within the absorption profile, allowing a more robust analysis of Δ α / α . The evidence for the narrow components is corroborated by their correspondence with previously detected molecular hydrogen and neutral carbon. The main remaining systematic errors arise from ambiguities in the absorption profile modelling, effects from redispersing the in idual quasar exposures, and convergence of the parameter estimation algorithm. All analyses of the spectrum, including systematic error estimates, were initially blinded to avoid human biases. We make our reduced ESPRESSO spectrum of HE 0515−4414 publicly available for further analysis. Combining our ESPRESSO result with 28 measurements, from other spectrographs, in which wavelength calibration errors have been mitigated yields a weighted mean Δ α / α = −0.5 ± 0.5 stat ± 0.4 sys ppm at redshifts 0.6−2.4.
Low Serum Mannose‐Binding Lectin Level Increases the Risk of Death due to Pneumococcal Infection
Publisher: Oxford University Press (OUP)
Date: 15-08-2008
DOI: 10.1086/590006
High-precision wavelength calibration of astronomical spectrographs with laser frequency combs
Publisher: Oxford University Press (OUP)
Date: 15-08-2007
Enriched haloes at redshift z = 2 with no star formation: implications for accretion and wind scenarios★
Publisher: Oxford University Press (OUP)
Date: 26-09-2011
THE TRANSITIONAL STRIPPED-ENVELOPE SN 2008ax: SPECTRAL EVOLUTION AND EVIDENCE FOR LARGE ASPHERICITY
Publisher: American Astronomical Society
Date: 06-09-2011
Galaxy group at z=0.3 associated with the damped Lyman α system towards quasar Q1127-145
Publisher: Oxford University Press (OUP)
Date: 20-05-2010
Constraint on a varying proton-to-electron mass ratio from H2and HD absorption atzabs≃ 2.34
Publisher: Oxford University Press (OUP)
Date: 22-11-2016
Evolution of C iv Absorbers. II. Where Does C iv Live?
Publisher: American Astronomical Society
Date: 2022
Abstract: We use the observed cumulative statistics of C iv absorbers and dark matter halos to infer the distribution of C iv -absorbing gas relative to galaxies at redshifts 0 ≤ z ≤ 5. We compare the cosmic incidence dN/dX of C iv absorber populations and galaxy halos, finding that massive L ≥ L ⋆ halos alone cannot account for all the observed W r ≥ 0.05 Å absorbers. However, the dN/dX of lower-mass halos exceeds that of W r ≥ 0.05 Å absorbers. We also estimate the characteristic gas radius of absorbing structures required for the observed C iv dN/dX , assuming each absorber is associated with a single galaxy halo. The W r ≥ 0.3 Å and W r ≥ 0.6 Å C iv gas radii are ∼30%–70% (∼20%–40%) of the virial radius of L ⋆ (0.1 L ⋆ ) galaxies, and the W r ≥ 0.05 Å gas radius is ∼100%–150% (∼60%–100%) of the virial radius of L ⋆ (0.1 L ⋆ ) galaxies. For stronger absorbers, the gas radius relative to the virial radius rises across Cosmic Noon and falls afterwards, while for weaker absorbers, the relative gas radius declines across Cosmic Noon and then dramatically rises at z 1. A strong luminosity-dependence of the gas radius implies highly extended C iv envelopes around massive galaxies before Cosmic Noon, while a luminosity-independent gas radius implies highly extended envelopes around dwarf galaxies after Cosmic Noon. From available absorber-galaxy and C iv evolution data, we favor a scenario in which low-mass galaxies enrich the volume around massive galaxies at early epochs and propose that the outer halo gas ( .5 R v ) was produced primarily in ancient satellite dwarf galaxy outflows, while the inner halo gas ( .5 R v ) originated from the central galaxy and persists as recycled accreting gas.
Are strong z ≃ 0.5 MgII absorbers the signature of super-winds?
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S174392130601026X
Abstract: BACKGROUND: In the process of galaxy formation, super-nova driven feedback from low-mass galaxies is the process that most readily account for the galaxy mass-metallicity relation and for the shallower galaxy luminosity function (LF) compared to the halo mass function. Absorption-selected galaxies are prime candidates for the sites of starburst activity as (1) they probe the gaseous halos of galaxies up to ~50 kpc (Steidel 1995), and (2) galaxies on the faint end of the LF are likely dominating the statistics. Galaxies selected via their MgII λ2796/2803 doublet absorption against background QSOs are especially well suited as Mg is produced by type II supernova. GOAL: Our project was to constrain the physical models of the gaseous halos by measuring the dark matter halo-mass ( M h ) of the MgII host-galaxies statistically , i.e. without identifying spectroscopically the host-galaxy. METHOD: We have used the cross-correlation w ( r θ ) (over co-moving scales r θ :0.05–13 h −1 Mpc) between our s le of 1800 z ≃ 0.5 MgII absorbers with equivalent w width W 2796 r −0.3 Å, and 250,000 Luminous Red Galaxies (LRGs), both selected from SDSS/DR3. The cross-correlation relies on the LRG photometric redshifts, but is not affected from contaminants such as stars or foreground and background galaxies as shown theoretically in Bouché et al. 2005 and empirically in Bouché et al . 2006. RESULTS: From the cross-correlation analysis, we found (Bouché et al . 2006) (i) that the absorber host-halo mean mass is 〈 log M h ( M ⊙ )〉 = 11.94 ±0.31(stat) +0.24 −0.25 (sys), i.e. about 1/2 L *, and (ii) an anti-correlation between halo mass M h and equivalent width W 2796 r . INTERPRETATION: One SDSS MgII absorber (system) is made of several sub-components or clouds and the stronger the equivalent with of the absorber, the more clouds per system spread over a larger velocity range (Δ v ). This follows since each sub-component has a velocity width of ~ 5 kms s −1 (Churchill 1997). As result, the equivalent width W 2796 r is a measure of velocity width (Δ v ) as demonstrated by Ellison 2006. Together with our SDSS results, these relations imply a mass–velocity M h –Δ v anti-correlation. If the clouds in the host-halos were virialized, velocity and mass would have been correlated. CONCLUSION: Therefore, our M h –Δ v anti-correlation shows that the clouds are not virialized in the gaseous halos of the hosts. This conclusion is best understood in the context of starburst driven outflows where the velocity Δ v is related to bulk motion. This opens the possibility to study M82-analogs up to z ~ 2.0 using the MgII selection.
Revisiting VLT/UVES Constraints on a Varying Fine-structure Constant
Publisher: Springer Berlin Heidelberg
Date: 2008
Further Evidence for Cosmological Evolution of the Fine Structure Constant
Publisher: American Physical Society (APS)
Date: 09-08-2001
The neutral hydrogen cosmological mass density atz= 5
Publisher: Oxford University Press (OUP)
Date: 02-07-2015
Keck constraints on a varying fine-structure constant: wavelength calibration errors
Publisher: Cambridge University Press (CUP)
Date: 11-2009
DOI: 10.1017/S174392131000952X
Abstract: The Keck telescope's High Resolution Spectrograph (HIRES) has previously provided evidence for a smaller fine-structure constant, α, compared to the current laboratory value, in a s le of 143 quasar absorption systems: Δα/α=(-0.57±0.11)×10 −5 . The analysis was based on a variety of metal-ion transitions which, if α varies, experience different relative velocity shifts. This result is yet to be robustly contradicted, or confirmed, by measurements on other telescopes and spectrographs it remains crucial to do so. It is also important to consider new possible instrumental systematic effects which may explain the Keck/HIRES results. Griest et al. (2009) recently identified distortions in the echelle order wavelength scales of HIRES with typical litudes ±250 m s −1 . Here we investigate the effect such distortions may have had on the Keck/HIRES varying α results. Using a simple model of these intra-order distortions, we demonstrate that they cause a random effect on Δα/α from absorber to absorber because the systems are at different redshifts, placing the relevant absorption lines at different positions in different echelle orders. The typical magnitude of the effect on Δα/α is ~0.4×10 −5 for in idual absorbers which, compared to the median error on Δα/α in the s le, ~1.9×10 −5 , is relatively small. Consequently, the weighted mean value changes by less than 0.05×10 −5 if the corrections we calculate are applied. Unsurprisingly, with corrections this small, we do not find direct evidence that applying them is actually warranted. Nevertheless, we urge caution, particularly for analyses aiming to achieve high precision Δα/α measurements on in idual systems or small s les, that a much more detailed understanding of such intra-order distortions and their dependence on observational parameters is important if they are to be avoided or modelled reliably.
Limits on Variations in Fundamental Constants from 21-cm and Ultraviolet Quasar Absorption Lines
Publisher: American Physical Society (APS)
Date: 22-07-2005
A new analysis of fine-structure constant measurements and modelling errors from quasar absorption lines
Publisher: Oxford University Press (OUP)
Date: 17-10-2015
A new candidate for probing Population III nucleosynthesis with carbon-enhanced damped Lyα systems
Publisher: Oxford University Press (OUP)
Date: 27-07-2012
COSMOLOGICAL CONCORDANCE OR CHEMICAL COINCIDENCE? DEUTERATED MOLECULAR HYDROGEN ABUNDANCES AT HIGH REDSHIFT
Publisher: American Astronomical Society
Date: 13-07-2010
Dust depletion, chemical uniformity and environment of CaII H&K quasar absorbers
Publisher: Oxford University Press (OUP)
Date: 02-2009
Discovery of three new near-pristine absorption clouds at z = 2.6–4.4
Publisher: Oxford University Press (OUP)
Date: 10-06-2022
Abstract: We report the discovery of three new ‘near-pristine’ Lyman limit systems (LLSs), with metallicities ≈1/1000 solar, at redshifts 2.6, 3.8, and 4.0, with a targeted survey at the Keck Observatory. High-resolution echelle spectra of eight candidates yielded precise column densities of hydrogen and weak, but clearly detected, metal lines in seven LLSs we previously reported the one remaining, apparently metal-free LLS, to have metallicity & /10 000 solar. Robust photoionization modelling provides metallicities [Si/H] = −3.05 to −2.94, with 0.26 dex uncertainties (95 per cent confidence) for three LLSs, and $\\textrm {[Si/H]} \\gtrsim -2.5$ for the remaining four. Previous simulations suggest that near-pristine LLSs could be the remnants of PopIII supernovae, so comparing their detailed metal abundances with nucleosynthetic yields from supernovae models is an important goal. Unfortunately, at most two different metals were detected in each new system, despite their neutral hydrogen column densities ($10^{19.2}\\textrm {--}10^{19.4}\\, \\textrm {cm}^{-2}$) being two orders of magnitude larger than the two previous, serendipitously discovered near-pristine LLSs. Nevertheless, the success of this first targeted survey for near-pristine systems demonstrates the prospect that a much larger, future survey could identify clear observational signatures of PopIII stars. With a well-understood selection function, such a survey would also yield the number density of near-pristine absorbers that, via comparison to future simulations, could reveal the origin(s) of these rare systems.
Indications of a Spatial Variation of the Fine Structure Constant
Publisher: American Physical Society (APS)
Date: 31-10-2011
Survey for Distant Solar Twins (SDST) – III. Identification of new solar twin and solar analogue stars
Publisher: Oxford University Press (OUP)
Date: 06-02-2023
Abstract: The Survey for Distant Solar Twins aims to find stars very similar to the Sun at distances of 1–$4\\, {\\rm kpc}$, several times more distant than any currently known solar twins and analogues. The goal is to identify the best stars with which to test whether the fine-structure constant, α, varies with dark matter density in our Galaxy. Here, we use epic, our line-by-line differential technique, to measure the stellar parameters – effective temperature Teff, surface gravity log g, and metallicity [Fe/H] – from moderate-resolution (R ≲ 32 000) spectra of 877 solar twin and analogue candidates (547 at 1–$4\\, {\\rm kpc}$) observed with the High Efficiency and Resolution Multi-Element Spectrograph (HERMES) on the Anglo-Australian Telescope. These are consistent with expectations for Teff and log g from photometry, and for [Fe/H] from the Besançon stellar population model. epic provides small enough uncertainties ($\\sim 90\\, {\\rm K}$, $0.08\\, {\\rm dex}$, and $0.05\\, {\\rm dex}$, respectively), even at the low signal-to-noise ratios available (${\\rm S/N}\\gtrsim$ 25 per pixel), to identify 299 new solar analogues ($\\ge 90~{{\\ \\rm per\\ cent}}$ confidence) and 20 solar twins (≥50 per cent confidence), 206 and 12 of which are at 1–$4\\, {\\rm kpc}$. By extending epic to measure line broadening and lithium abundance from HERMES spectra, and with ages derived from isochrone fitting with our stellar parameters, we identify 174 solar analogues at 1–$4\\, {\\rm kpc}$ that are relatively inactive, slowly rotating, and with no evidence of spectroscopic binarity. These are the preferred targets for follow-up spectroscopy to measure α.
ESPRESSO observations of HE 0107−5240 and other CEMP-no stars with [Fe/H] ≤ –4.5
Publisher: EDP Sciences
Date: 12-2022
DOI: 10.1051/0004-6361/202244627
Abstract: Context. HE 0107−5240 is a hyper metal-poor star with [Fe/H] = −5.39, one of the lowest-metallicity stars known. Its stellar atmosphere is enhanced in carbon, with [C/Fe] = +4.0, without a detectable presence of neutron-capture elements. Therefore, it belongs to the carbon-enhanced metal-poor (CEMP−no) group, along with the majority of the most metal-poor stars known to date. Recent studies have revealed variations in the line-of-sight velocity of HE 0107−5240, suggesting it belongs to a binary system. CEMP-no stars are the closest descendants of the very first Pop III stars, and binarity holds important clues for the poorly known mechanism that leads to their formation. Aims. We performed high-resolution observations with the E SPRESSO spectrograph at the VLT to constrain the kinematical properties of the binary system HE 0107−5240 and to probe the binarity of the s le of the eight most metal-poor stars with [Fe/H] ≤ −4.5. Methods. Radial velocities are obtained by using a cross-correlation function in the interval 4200−4315 Å , which contains the relatively strong CH band, against a template that could be either a synthetic spectrum or a combined observed spectrum in an iterative process. A Bayesian method is applied to calculate the orbit using the E SPRESSO measurements and others from the literature. Chemical analysis has also been performed for HE 0107−5240, employing spectral synthesis with the SYNTHE and ATLAS codes. Results. Observations of HE 0107−5240 spanning more than 3 years show a monotonic decreasing trend in radial velocity at a rate of approximately 0.5 m s −1 d −1 . A maximum v rad was reached between March 13, 2012, and December 8, 2014. The period is constrained at P orb = 13009 −1370 +1496 d. New, more stringent upper limits have been found for several elements: (a) [Sr/Fe] and [Ba/Fe] are lower than −0.76 and +0.2, respectively, confirming the star is a CEMP-no (b) A(Li) 0.5 is well below the plateau at A(Li) = 1.1 found in the lower red giant branch stars, suggesting Li was originally depleted and (c) the isotopic ratio 12 C/ 13 C is 87 ± 6, showing very low 13 C in contrast to what is expected from a ‘spinstar’ progenitor. Conclusions. We confirm that HE 0107−5240 is a binary star with a long period of about 13 000 d (∼36 yr). The carbon isotopic ratio excludes the possibility that the companion has gone through the asymptotic giant branch phase and transferred mass to the currently observed star. The binarity of HE 0107−5240 implies that some of the first generations of low-mass stars formed in multiple systems and indicates that the low metallicity does not preclude the formation of binaries. Finally, a solid indication of v rad variation has also been found in SMSS 1605−1443.
Fundamental constants and high-resolution spectroscopy
Publisher: Wiley
Date: 2014
A method for detecting gravitational waves coincident with gamma-ray bursts
Publisher: Oxford University Press (OUP)
Date: 08-2000
Comment on “Limits on the Time Variation of the Electromagnetic Fine-Structure Constant in the Low Energy Limit from Absorption Lines in the Spectra of Distant Quasars”
Publisher: American Physical Society (APS)
Date: 06-12-2007
MAGiiCAT VI. The Mg ii Intragroup Medium Is Kinematically Complex
Publisher: American Astronomical Society
Date: 20-12-2018
Does the fine structure constant vary? A detailed investigation into systematic effects
Publisher: Springer Science and Business Media LLC
Date: 2003
Evolution of C iv Absorbers. I. The Cosmic Incidence
Publisher: American Astronomical Society
Date: 11-2020
Abstract: We present a large high-resolution study of the distribution and evolution of C iv absorbers, including the weakest population with equivalent widths . By searching 369 high-resolution, high signal-to-noise ratio spectra of quasars at from Keck/HIRES and VLT/UVES, we find 1268 C iv absorbers with Å (our ∼50% completeness limit) at redshifts . A Schechter function describes the observed equivalent width distribution with a transition from power-law to exponential decline at . The power-law slope α rises by ∼7%, and the transition equivalent width W ⋆ falls by ∼20% from to 3.6. We find that the comoving redshift path density, , of Å absorbers rises by ∼1.8 times from z ≃ 4.0 to 1.3, while the Å rises by a factor of ∼8.5. We quantify the observed evolution by a model in which decreases linearly with increasing redshift. The model suggests that populations with larger thresholds evolve faster with redshift and appear later in the universe. The cosmological Technicolor Dawn simulations at z = 3–5 overproduce the observed abundance of absorbers with while yielding better agreement at higher . Our empirical linear model successfully describes C iv evolution in the simulations and the observed evolution of Å C iv for the past . Combining our measurements with the literature gives us a picture of C iv absorbing structures becoming more numerous and/or larger in physical size over the last of cosmic time ( z ∼ 6–0).
C3PO: towards a complete census of co-moving pairs of stars - I. High precision stellar parameters for 250 stars
Publisher: Oxford University Press (OUP)
Date: 29-09-2023
Cosmological evolution of heavy-element andH2abundances
Publisher: Oxford University Press (OUP)
Date: 06-2004
A search for molecules in damped Lyman-alpha absorbers occulting millimetre-loud quasars
Publisher: EDP Sciences
Date: 21-10-2002
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