ORCID Profile
0000-0002-8175-7229
Current Organisations
Vrije Universiteit Amsterdam
,
Macquarie University
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Astronomical and Space Sciences | Cosmology and Extragalactic Astronomy | Astronomical and Space Instrumentation | Photonics, Optoelectronics and Optical Communications | Galactic Astronomy |
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Publisher: American Astronomical Society
Date: 20-01-2017
Publisher: Oxford University Press (OUP)
Date: 22-03-2014
DOI: 10.1093/MNRAS/STU330
Publisher: SPIE
Date: 16-07-2010
DOI: 10.1117/12.856776
Publisher: Elsevier BV
Date: 02-2007
Publisher: Sissa Medialab
Date: 27-01-2010
DOI: 10.22323/1.089.0056
Publisher: Oxford University Press (OUP)
Date: 09-2000
Publisher: Elsevier BV
Date: 03-2023
Publisher: SPIE
Date: 29-08-2022
DOI: 10.1117/12.2630348
Publisher: Elsevier BV
Date: 2006
Publisher: EDP Sciences
Date: 05-2019
DOI: 10.1051/0004-6361/201834941
Abstract: Context . Photometric surveys of galaxy clusters have revealed a large number of ultra compact dwarfs (UCDs) around predominantly massive elliptical galaxies. Their origin is still debated as some UCDs are considered to be the remnant nuclei of stripped dwarf galaxies while others seem to mark the high-mass end of the star cluster population. Aims . We aim to characterize the properties of a UCD found at very close projected distance ( r wproj = 1.1 kpc) from the centre of the low-mass ( M ∼ 10 10 M ⊙ ) early-type galaxy FCC 47. This is a serendipitous discovery from MUSE adaptive optics science verification data. We explore the potential origin of this UCD as either a massive cluster or the remnant nucleus of a dissolved galaxy. Methods . We used archival Hubble Space Telescope data to study the photometric and structural properties of FCC 47-UCD1. In the MUSE data, the UCD is unresolved, but we used its spectrum to determine the radial velocity and metallicity. Results . The surface brightness of FCC 47-UCD1 is best described by a single King profile with low concentration C = R t / R c ∼ 10 and large effective radius ( r eff = 24 pc). Its integrated magnitude and blue colour ( M g = −10.55 mag, ( g − z ) = 1.46 mag) combined with a metallicity of [M/H] = −1.12 ± 0.10 dex and an age 8 Gyr obtained from the full fitting of the MUSE spectrum suggests a stellar population mass of M * = 4.87 × 10 6 M ⊙ . The low S/N of the MUSE spectrum prevents detailed stellar population analysis. Due to the limited spectral resolution of MUSE, we can only give an upper limit on the velocity dispersion ( σ 17 km s −1 ), and consequently on its dynamical mass ( M dyn 1.3 × 10 7 M ⊙ ). Conclusions . The origin of the UCD cannot be constrained with certainty. The low metallicity, old age, and magnitude are consistent with a star cluster origin, whereas the extended size is consistent with an origin as the stripped nucleus of a dwarf galaxy with a initial stellar mass of a few 10 8 M ⊙ .
Publisher: EDP Sciences
Date: 06-2019
DOI: 10.1051/0004-6361/201935360
Abstract: The stellar initial mass function (IMF) regulates the baryonic cycle within galaxies, and is a key ingredient for translating observations into physical quantities. Although it was assumed to be universal for decades, there is now growing observational evidence showing that the center of massive early-type galaxies hosts a larger population of low-mass stars than is expected based on observations from the Milky Way. Moreover, these variations in the IMF have been found to be related to radial metallicity variations in massive galaxies. We present here a two-dimensional stellar population analysis of the massive lenticular galaxy FCC 167 (NGC 1380) as part of the Fornax3D project. Using a newly developed stellar population fitting scheme, we derive a full two-dimensional IMF map of an early-type galaxy. This two-dimensional analysis allows us go further than a radial analysis, showing how the metallicity changes along a disk-like structure while the IMF follows a distinct, less disky distribution. Thus, our findings indicate that metallicity cannot be the sole driver of the observed radial IMF variations. In addition, a comparison with the orbital decomposition shows suggestive evidence of a coupling between stellar population properties and the internal dynamical structure of FCC 167, where metallicity and IMF maps seem to track the distribution of cold and warm orbits, respectively.
Publisher: American Astronomical Society
Date: 25-06-2020
Abstract: This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library “MaStar”). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).
Publisher: Oxford University Press (OUP)
Date: 22-03-2021
Abstract: We present spatially resolved two-dimensional maps and radial trends of the stellar populations and kinematics for a s le of six compact elliptical galaxies (cE) using spectroscopy from the Keck Cosmic Web Imager (KCWI). We recover their star formation histories, finding that all except one of our cEs are old and metal rich, with both age and metallicity decreasing toward their outer radii. We also use the integrated values within one effective radius to study different scaling relations. Comparing our cEs with others from the literature and from simulations we reveal the formation channel that these galaxies might have followed. All our cEs are fast rotators, with relatively high rotation values given their low ellipticites. In general, the properties of our cEs are very similar to those seen in the cores of more massive galaxies, and in particular, to massive compact galaxies. Five out of our six cEs are the result of stripping a more massive (compact or extended) galaxy, and only one cE is compatible with having been formed intrinsically as the low-mass compact object that we see today. These results further confirm that cEs are a mixed-bag of galaxies that can be formed following different formation channels, reporting for the first time an evolutionary link within the realm of compact galaxies (at all stellar masses).
Publisher: Macquarie University
Date: 2020
DOI: 10.25949/ZDAW-RX65
Publisher: Oxford University Press (OUP)
Date: 31-07-2021
Abstract: Accurate astrometry is a key deliverable for the next generation of multiconjugate adaptive optics (MCAO) systems. The MCAO-Assisted Visible Imager and Spectrograph (MAVIS) is being designed for the Very Large Telescope Adaptive Optics Facility and must achieve 150 $\\mu$as astrometric precision (50 $\\mu$as goal). To test this before going on-sky, we have created MAVIS Image Simulator (mavisim), a tool to simulate MAVIS images. mavisim accounts for three major sources of astrometric error: high- and low-order point spread function (PSF) spatial variability, tip–tilt residual error, and static field distortion. When exploring the impact of these three error terms alone, we recover an astrometric accuracy of 50 $\\mu$as for all stars brighter than m = 19 in a 30 s integration using PSF-fitting photometry. We also assess the feasibility of MAVIS detecting an intermediate-mass black hole (IMBH) in a Milky Way globular cluster. We use an N-body simulation of an NGC 3201-like cluster with a central 1500 M⊙ IMBH as input to mavisim and recover the velocity dispersion profile from proper motion measurements. Under favourable astrometric conditions, the dynamical signature of the IMBH is detected with a precision of ∼0.20 km s−1 in the inner ∼4 arcsec of the cluster where Hubble Space Telescope (HST) is confusion limited. This precision is comparable to measurements made by Gaia, HST, and Multi Unit Spectroscopic Explorer (MUSE) in the outer ∼60 arcsec of the cluster. This study is the first step towards building a science-driven astrometric error budget for an MCAO system and a prediction of what MAVIS could do once on sky.
Publisher: Oxford University Press (OUP)
Date: 23-03-2018
DOI: 10.1093/MNRAS/STY778
Publisher: American Astronomical Society
Date: 05-2021
Abstract: The Milky Way disk consists of two prominent components—a thick, alpha-rich, low-metallicity component and a thin, metal-rich, low-alpha component. External galaxies have been shown to contain thin- and thick-disk components, but whether distinct components in the [ α /Fe]–[Z/H] plane exist in other Milky Way-like galaxies is not yet known. We present Very Large Telescope (VLT)—Multi Unit Spectroscopic Explorer (MUSE) observations of UGC 10738, a nearby, edge-on Milky Way-like galaxy. We demonstrate through stellar population synthesis model fitting that UGC 10738 contains alpha-rich and alpha-poor stellar populations with similar spatial distributions to the same components in the Milky Way. We discuss how the finding that external galaxies also contain chemically distinct disk components may act as a significant constraint on the formation of the Milky Way’s own thin and thick disk.
Publisher: American Astronomical Society
Date: 21-06-2019
Publisher: SPIE
Date: 13-12-2020
DOI: 10.1117/12.2561930
Publisher: EDP Sciences
Date: 26-02-2013
Publisher: Oxford University Press (OUP)
Date: 22-09-2016
Publisher: EDP Sciences
Date: 03-2022
DOI: 10.1051/0004-6361/202142614
Abstract: We present the blind Westerbork Coma Survey probing the H I content of the Coma galaxy cluster with the Westerbork Synthesis Radio Telescope. The survey covers the inner ∼1 Mpc around the cluster centre, extending out to 1.5 Mpc towards the south-western NGC 4839 group. The survey probes the atomic gas in the entire Coma volume down to a sensitivity of ∼10 19 cm −2 and 10 8 M ⊙ . Combining automated source finding with source extraction at optical redshifts and visual verification, we obtained 40 H I detections of which 24 are new. Over half of the s le displays perturbed H I morphologies indicative of an ongoing interaction with the cluster environment. With the use of ancillary UV and mid-IR, data we measured their stellar masses and star formation rates and compared the H I properties to a set of field galaxies spanning a similar stellar mass and star formation rate range. We find that ∼75% of H I -selected Coma galaxies have simultaneously enhanced star formation rates (by ∼0.2 dex) and are H I deficient (by ∼0.5 dex) compared to field galaxies of the same stellar mass. According to our toy model, the simultaneous H I deficiency and enhanced star formation activity can be attributed to either H I stripping of already highly star forming galaxies on a very short timescale, while their H 2 content remains largely unaffected, or to H I stripping coupled to a temporary boost of the H I -to-H 2 conversion, causing a brief starburst phase triggered by ram pressure before eventually quenching the galaxy.
Publisher: American Astronomical Society
Date: 24-03-2015
Publisher: Oxford University Press (OUP)
Date: 28-09-2017
Publisher: Springer Science and Business Media LLC
Date: 12-12-2022
Publisher: American Astronomical Society
Date: 30-07-2010
Publisher: Oxford University Press (OUP)
Date: 06-06-2020
Abstract: We present population-orbit superposition models for external galaxies based on Schwarzschild’s orbit-superposition method, by tagging the orbits with age and metallicity. The models fit the density distributions, kinematic, and age and metallicity maps from integral field unit (IFU) spectroscopy observations. We validate the method and demonstrate its power by applying it to mock data, similar to those obtained by the Multi-Unit Spectroscopic Explorer (MUSE) IFU on the Very Large Telescope (VLT). These mock data are created from Auriga galaxy simulations, viewed at three different inclination angles (ϑ = 40°, 60°, 80°). Constrained by MUSE-like mock data, our model can recover the galaxy’s stellar orbit distribution projected in orbital circularity λz versus radius r, the intrinsic stellar population distribution in age t versus metallicity Z, and the correlation between orbits’ circularity λz and stellar age t. A physically motivated age–metallicity relation improves the recovering of intrinsic stellar population distributions. We decompose galaxies into cold, warm, and hot+counter-rotating components based on their orbit circularity distribution, and find that the surface density, velocity, velocity dispersion, and age and metallicity maps of each component from our models well reproduce those from simulation, especially for projections close to edge-on. These galaxies exhibit strong global age versus σz relation, which is well recovered by our model. The method has the power to reveal the detailed build-up of stellar structures in galaxies, and offers a complement to local resolved, and high-redshift studies of galaxy evolution.
Publisher: Oxford University Press (OUP)
Date: 22-08-2022
Abstract: In this work, we investigate how the central stellar metallicity ([Z/H]) of 1363 galaxies from the SAMI galaxy survey is related to their stellar mass and a proxy for the gravitational potential, $\\Phi = \\log _{10}\\left(\\frac{M_*}{M_{\\odot }} \\right) - \\log _{10}\\left(\\frac{r_e}{\\mathrm{kpc}} \\right)$. In agreement with previous studies, we find that passive and star-forming galaxies occupy different areas of the [Z/H]–M* plane, with passive galaxies having higher [Z/H] than star-forming galaxies at fixed mass (a difference of 0.23 dex at log10(M*/M⊙) = 10.3). We show for the first time that all galaxies lie on the same relation between [Z/H] and Φ, and show that the offset in [Z/H] between passive and star-forming galaxies at fixed Φ is smaller than or equal to the offset in [Z/H] at fixed mass (an average Δ[Z/H] of 0.11 dex at fixed Φ compared to 0.21 dex at fixed mass). We then build a simple model of galaxy evolution to explain and understand our results. By assuming that [Z/H] traces Φ over cosmic time and that the probability that a galaxy quenches depends on both its mass and size, we are able to reproduce these offsets in stellar metallicity with a model containing instantaneous quenching. We therefore conclude that an offset in metallicity at fixed mass cannot by itself be used as evidence of slow quenching processes, in contrast to previous studies. Instead, our model implies that metal-rich galaxies have always been the smallest objects for their mass in a population. Our findings reiterate the need to consider galaxy size when studying stellar populations.
Publisher: Oxford University Press (OUP)
Date: 27-09-2017
Publisher: Research Square Platform LLC
Date: 19-03-2021
DOI: 10.21203/RS.3.RS-333773/V1
Abstract: Driven by gravity, galaxies are expected to continuously grow through the merging of smaller systems. To derive their past merger history is challenging, as the accreted stars disperse quickly yet, it is a needed step to test the theory of hierarchical evolution. The merger histories of the most massive Local Group spirals, the Milky Way and M31, have been re- cently uncovered by using the motion and chemistry of their in idual stars. On the other hand, the details of the merger history of galaxies at larger distance have so far remained hidden. Here we report the discovery of an ancient, massive merger event in the lenticu- lar galaxy NGC 1380 in the Fornax cluster. By applying a recently developed population-orbital superposition model (Zhu at al 2020) to NGC 1380’s surface brightness as well as stellar kinematic, age, and metallicity maps from VLT/MUSE IFU data (Sarzi et al 2018), we obtain the stellar orbits, age and metallicity distributions of this galaxy. The highly radial orbits which make up an inner stellar halo are ∼ 13 Gyr old with metallicity Z/Z⊙ ∼ 1.2 and comprise a stellar mass of M∗,halo(r Re)∼3.4×10^10 M⊙. By comparing to analogues from the cosmological galaxy simulation TNG50 (Pillepich 2019), we find that the formation of the inner stellar halo of NGC 1380 requires a merger with a massive satellite galaxy with stellar mass of ∼ 3 × 10^10 M⊙ that occurred roughly ∼ 10 Gyr ago. Moreover, we infer the total accreted stellar mass of NGC 1380 to be ∼ 6 × 10^10 M⊙. The massive merger in NGC 1380 is the first major merger event found in a normal phase-mixed galaxy beyond the Local Volume, and it is the oldest and most massive one identified in nearby galaxies so far. Our chemo-dynamical method, when applied to extended deep IFU data and in combination with cosmological galaxy simulations, can quantitatively unravel the merger history of a large number of nearby galaxies.
Publisher: Oxford University Press (OUP)
Date: 10-03-2023
Abstract: Most dynamical models of galaxies to date assume axisymmetry, which is not representative of a significant fraction of massive galaxies. We have built triaxial orbit-superposition Schwarzschild models of galaxies observed by the SAMI Galaxy Survey, in order to reconstruct their inner orbital structure and mass distribution. The s le consists of 153 passive galaxies with total stellar masses in the range 109.5 to $10^{12} \\, {\\rm M}_{\\odot }$. We present an analysis of the internal structures and intrinsic properties of these galaxies as a function of their environment. We measure their environment using three proxies: central or satellite designation, halo mass and local 5th nearest neighbour galaxy density. We find that although these intrinsic properties correlate most strongly with stellar mass, environment does play a secondary role: at fixed stellar mass, galaxies in the densest regions are more radially anisotropic. In addition, central galaxies, and galaxies in high local densities show lower values of edge-on spin parameter proxy λRe, EO. We also find suggestions of a possible trend of the fractions of orbits with environment for lower mass galaxies (between 109.5 and $10^{11} \\, {\\rm M}_{\\odot }$) such that, at fixed stellar mass, galaxies in higher local densities and halo mass have higher fractions of hot orbits and lower fractions of warm orbits. Our results demonstrate that after stellar mass, environment does play a role in shaping present-day passive galaxies.
Publisher: SPIE
Date: 14-06-2006
DOI: 10.1117/12.672289
Publisher: Oxford University Press (OUP)
Date: 11-03-2005
Publisher: EDP Sciences
Date: 07-2020
DOI: 10.1051/0004-6361/202038076
Abstract: Fast radio bursts (FRBs) are millisecond-scale radio pulses, which originate in distant galaxies and are produced by unknown sources. The mystery remains partially because of the typical difficulty in localising FRBs to host galaxies. Accurate localisations delivered by the Commensal Real-time ASKAP Fast Transients (CRAFT) survey now provide an opportunity to study the host galaxies and potential transient counterparts of FRBs at a large range of wavelengths. In this work, we investigate whether the first three FRBs accurately localised by CRAFT have supernova-like transient counterparts. We obtained two sets of imaging epochs with the Very Large Telescope for three host galaxies, one soon after the burst detection and one several months later. After subtracting these images no optical counterparts were identified in the associated FRB host galaxies, so we instead place limits on the brightness of any potential optical transients. A Monte Carlo approach, in which supernova light curves were modelled and their base properties randomised, was used to estimate the probability of a supernova associated with each FRB going undetected. We conclude that Type Ia and IIn supernovae are unlikely to accompany every apparently non-repeating FRB.
Publisher: EDP Sciences
Date: 05-2020
DOI: 10.1051/0004-6361/201936862
Abstract: Extragalactic planetary nebulae (PNe) are detectable through relatively strong nebulous [O III ] emission and act as direct probes into the local stellar population. Because they have an apparently universal invariant magnitude cut-off, PNe are also considered to be a remarkable standard candle for distance estimation. Through detecting PNe within the galaxies, we aim to connect the relative abundances of PNe to the properties of their host galaxy stellar population. By removing the stellar background components from FCC 167 and FCC 219, we aim to produce PN luminosity functions (PNLF) of these galaxies, and thereby also estimate the distance modulus to these two systems. Finally, we test the reliability and robustness of our novel detection and analysis method. It detects unresolved point sources by their [O III ] 5007 Å emission within regions that have previously been unexplored. We model the [O III ] emissions in the spatial and spectral dimensions together, as afforded to us by the Multi Unit Spectroscopic Explorer, and we draw on data gathered as part of the Fornax3D survey. For each source, we inspect the properties of the nebular emission lines to remove other sources that might hinder the safe construction of the PNLF, such as supernova remnants and H II regions. As a further step, we characterise any potential limitations and draw conclusions about the reliability of our modelling approach through a set of simulations. By applying this novel detection and modelling approach to integral field unit observations, we report for the distance estimates and luminosity-specific PNe frequency values for the two galaxies. Furthermore, we include an overview of source contamination, galaxy differences, and possible effects on the PNe populations in the dense stellar environments.
Publisher: American Astronomical Society
Date: 04-05-2015
Publisher: Cambridge University Press (CUP)
Date: 12-2006
Publisher: Oxford University Press (OUP)
Date: 08-09-2017
Publisher: EDP Sciences
Date: 09-2015
Publisher: EDP Sciences
Date: 06-2021
DOI: 10.1051/0004-6361/202140644
Abstract: Nuclear star clusters (NSCs) are the densest stellar systems in the Universe and are found in the centres of all types of galaxies. They are thought to form via mergers of star clusters such as ancient globular clusters (GCs) that spiral to the centre as a result of dynamical friction or through in situ star formation directly at the galaxy centre. There is evidence that both paths occur, but the relative contribution of either channel and their correlation with galaxy properties are not yet constrained observationally. Our aim was to derive the dominant NSC formation channel for a s le of 25 nucleated galaxies, mostly in the Fornax galaxy cluster, with stellar masses between M gal ∼ 10 8 and 10 10.5 M ⊙ and NSC masses between M NSC ∼ 10 5 and 10 8.5 M ⊙ . Using Multi-Unit Spectroscopic Explorer data from the Fornax 3D survey and the ESO archive, we derived star formation histories, mean ages, and metallicities of NSCs, and compared them to the host galaxies. In many low-mass galaxies, the NSCs are significantly more metal poor than their hosts, with properties similar to GCs. In contrast, in the massive galaxies we find erse star formation histories and cases of ongoing or recent in situ star formation. Massive NSCs ( 10 7 M ⊙ ) occupy a different region in the mass–metallicity diagram than lower-mass NSCs and GCs, indicating a different enrichment history. We find a clear transition of the dominant NSC formation channel with both galaxy and NSC mass. We hypothesise that while GC accretion forms the NSCs of the dwarf galaxies, central star formation is responsible for the efficient mass build up in the most massive NSCs in our s le. At intermediate masses both channels can contribute. The transition between these formation channels seems to occur at galaxy masses M gal ∼ 10 9 M ⊙ and NSC masses M NSC ∼ 10 7 M ⊙ .
Publisher: American Astronomical Society
Date: 12-2021
Publisher: Cambridge University Press (CUP)
Date: 07-2014
DOI: 10.1017/S1743921315003373
Abstract: In this contributed talk I present recent results on the connection between stellar population properties and the normalisation of the stellar initial mass function (IMF) measured using stellar dynamics, based on a large s le of 260 early-type galaxies observed as part of the ATLAS 3D project. This measure of the IMF normalisation is found to vary non-uniformly with age- and metallicity-sensitive absorption line strengths. Applying single stellar population models, there are weak but measurable trends of the IMF with age and abundance ratio. Accounting for the dependence of stellar population parameters on velocity dispersion effectively removes these trends, but subsequently introduces a trend with metallicity, such that ‘heavy’ IMFs favour lower metallicities. The correlations are weaker than those found from previous studies directly detecting low-mass stars, suggesting some degree of tension between the different approaches of measuring the IMF. Resolving these discrepancies will be the focus of future work.
Publisher: EDP Sciences
Date: 07-2016
Publisher: EDP Sciences
Date: 03-2020
DOI: 10.1051/0004-6361/201937040
Abstract: We study the evidence for a ersity of formation processes in early-type galaxies by presenting the first complete volume-limited s le of slow rotators with both integral-field kinematics from the ATLAS 3D Project and high spatial resolution photometry from the Hubble Space Telescope. Analysing the nuclear surface brightness profiles of 12 newly imaged slow rotators, we classify their light profiles as core-less, and place an upper limit to the core size of about 10 pc. Considering the full magnitude and volume-limited ATLAS 3D s le, we correlate the presence or lack of cores with stellar kinematics, including the proxy for the stellar angular momentum ( λ Re ) and the velocity dispersion within one half-light radius ( σ e ), stellar mass, stellar age, α -element abundance, and age and metallicity gradients. More than half of the slow rotators have core-less light profiles, and they are all less massive than 10 11 M ⊙ . Core-less slow rotators show evidence for counter-rotating flattened structures, have steeper metallicity gradients, and a larger dispersion of gradient values (Δ[Z/H]¯ = −0.42 ± 0.18) than core slow rotators (Δ[Z/H]¯ = −0.23 ± 0.07). Our results suggest that core and core-less slow rotators have different assembly processes, where the former, as previously discussed, are the relics of massive dissipation-less merging in the presence of central supermassive black holes. Formation processes of core-less slow rotators are consistent with accretion of counter-rotating gas or gas-rich mergers of special orbital configurations, which lower the final net angular momentum of stars, but support star formation. We also highlight core fast rotators as galaxies that share properties of core slow rotators (i.e. cores, ages, σ e , and population gradients) and core-less slow rotators (i.e. kinematics, λ Re , mass, and larger spread in population gradients). Formation processes similar to those for core-less slow rotators can be invoked to explain the assembly of core fast rotators, with the distinction that these processes form or preserve cores.
Publisher: Oxford University Press (OUP)
Date: 08-2006
Publisher: American Astronomical Society
Date: 13-11-2017
Publisher: Cambridge University Press (CUP)
Date: 11-2017
DOI: 10.1017/S1743921318002880
Abstract: Measurements of current rates of core-collapse supernovæ (CCSNe) suffer from significant uncertainties, probably due to the large fraction of CCSNe that explode in crowded regions which have bright background emission and significant dust extinction. Conventional optical (seeing-limited) SN surveys generally fail to detect them, but including them is crucial to the accurate determination of CCSN rates. Project SUNBIRD aims to tighten the present constraints on the fraction of CCSNe that are missed by conventional SN surveys. We are monitoring more than 25 dusty luminous infrared galaxies that are actively star-forming, for evidence of dust-obscured CCSNe, in an effort to characterise the population of CCSNes exploding in those nuclear regions of dusty LIRGs. We observe in the near-infrared, which is less affected by dust extinction compared to the optical we are using Gemini South and Keck, and we make use of state-of-the-art laser guide-star adaptive optics instruments to achieve a spatial resolution ’.1, which is sufficient to resolve close to the galactic nucleus. During the project’s first year we discovered three CCSNe and one candidate one, with nuclear offsets as small as 200 pc, as cited in the poster. Aggregating the new discoveries with the CCSNe found in previous programmes employing AO, we compared the distribution of nuclear offsets of AO CCSN discoveries with all other documented CCSNe discovered in LIRGs. The poster showed that our method is singularly effective at uncovering CCSNe in the nuclear regions of LIRGs, and that while optical surveys dominate SNe discoveries far from a galaxy’s centre, near infra-red AO observations are needed to probe the regions within 1 kpc of the nucleus.
Publisher: American Astronomical Society
Date: 10-12-2014
Publisher: EDP Sciences
Date: 07-2022
DOI: 10.1051/0004-6361/202243290
Abstract: This work is based on high-quality integral-field spectroscopic data obtained with the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT). The 21 brightest ( m B ≤ 15 mag) early-type galaxies (ETGs) inside the virial radius of the Fornax cluster are observed out to distances of ∼2−3 R e . Deep imaging from the VLT Survey Telescope (VST) is also available for the s le ETGs. We investigated the variation of the galaxy structural properties as a function of the total stellar mass and cluster environment. Moreover, we correlated the size scales of the luminous components derived from a multi-component decomposition of the VST surface-brightness radial profiles of the s le ETGs with the MUSE radial profiles of stellar kinematic and population properties. The results are compared with both theoretical predictions and previous observational studies and used to address the assembly history of the massive ETGs of the Fornax cluster. We find that galaxies in the core and north-south clump of the cluster, which have the highest accreted mass fraction, show milder metallicity gradients in their outskirts than the galaxies infalling into the cluster. We also find a segregation in both age and metallicity between the galaxies belonging to the core and north-south clump and the infalling galaxies. The new findings fit well within the general framework for the assembly history of the Fornax cluster.
Publisher: Oxford University Press (OUP)
Date: 14-04-2018
DOI: 10.1093/MNRAS/STY913
Publisher: American Astronomical Society
Date: 09-2023
Publisher: Oxford University Press (OUP)
Date: 16-09-2016
Publisher: Oxford University Press (OUP)
Date: 14-10-2016
Publisher: SPIE
Date: 13-12-2020
DOI: 10.1117/12.2561433
Publisher: Oxford University Press (OUP)
Date: 28-11-2014
Publisher: EDP Sciences
Date: 10-2021
DOI: 10.1051/0004-6361/202141348
Abstract: The stellar initial mass function (IMF) is central to our interpretation of astronomical observables and to our understanding of most baryonic processes within galaxies. The universality of the IMF, suggested by observations in our own Milky Way, has been thoroughly revisited due to the apparent excess of low-mass stars in the central regions of massive quiescent galaxies. As part of the efforts within the Fornax 3D project, we aim to characterize the two-dimensional IMF variations in a s le of 23 quiescent galaxies within the Fornax cluster. For each galaxy in the s le, we measured the mean age, metallicity, [Mg/Fe], and IMF slope maps from spatially resolved integrated spectra. The IMF maps show a variety of behaviors and internal substructures, roughly following metallicity variations. However, metallicity alone is not able to fully explain the complexity exhibited by the IMF maps. In particular, for relatively metal-poor stellar populations ([M/H] ≲ −0.1), the slope of the IMF seems to depend on the (specific) star formation rate at which stars were formed. Moreover, metallicity maps have systematically higher ellipticities than IMF slope ones. At the same time, both metallicity and IMF slope maps have at the same time higher ellipticities than the stellar light distribution in our s le of galaxies. In addition we find that, regardless of the stellar mass, every galaxy in our s le shows a positive radial [Mg/Fe] gradient. This results in a strong [Fe/H]–[Mg/Fe] relation, similar to what is observed in nearby, resolved galaxies. Since the formation history and chemical enrichment of galaxies are causally driven by changes in the IMF, our findings call for a physically motivated interpretation of stellar population measurements based on integrated spectra that take into account any possible time evolution of the stellar populations.
Publisher: Oxford University Press (OUP)
Date: 07-06-2022
Abstract: Variations of the stellar initial mass function (IMF) in external galaxies have been inferred from a variety of independent probes. Yet the physical conditions causing these variations remain largely unknown. In this work, we explore new spatially resolved measurements of the IMF for three edge-on lenticular galaxies in the Fornax cluster. We utilize existing orbit-based dynamical models in order to fit the new IMF maps within an orbital framework. We find that, within each galaxy, the high-angular momentum disc-like stars exhibit an IMF which is rich in dwarf stars. The centrally concentrated pressure-supported orbits exhibit similarly dwarf-rich IMF. Conversely, orbits at large radius which have intermediate angular momentum exhibit IMF which are markedly less dwarf-rich relative to the other regions of the same galaxy. Assuming that the stars which reside, in the present-day, on dynamically hot orbits at large radii are dominated by accreted populations, we interpret these findings as a correlation between the dwarf-richness of a population of stars, and the mass of the host in which it formed. Specifically, deeper gravitational potentials would produce more dwarf-rich populations, resulting in the relative deficiency of dwarf stars which originated in the lower mass accreted satellites. The central and high-angular momentum populations are likely dominated by in situ stars, which were formed in the more massive host itself. There are also global differences between the three galaxies studied here, of up to ∼0.3 dex in the IMF parameter ξ. We find no local dynamical or chemical property which alone can fully account for the IMF variations.
Publisher: Oxford University Press (OUP)
Date: 11-12-2017
Publisher: EDP Sciences
Date: 05-2019
DOI: 10.1051/0004-6361/201834808
Abstract: Different massive black hole mass – host galaxy scaling relations suggest that the growth of massive black holes is entangled with the evolution of their host galaxies. The number of measured black hole masses is still limited and additional measurements are necessary to understand the underlying physics of this apparent coevolution. We add six new black hole mass ( M BH ) measurements of nearby fast rotating early-type galaxies to the known black hole mass s le, namely NGC 584, NGC 2784, NGC 3640, NGC 4570, NGC 4281, and NGC 7049. Our target galaxies have effective velocity dispersions ( σ e ) between 170 and 245 km s −1 , and thus this work provides additional insight into the black hole properties of intermediate-mass early-type galaxies. We combined high-resolution adaptive-optics SINFONI data with large-scale MUSE, VIMOS and SAURON data from ATLAS 3D to derive two-dimensional stellar kinematics maps. We then built both Jeans Anisotropic Models and axisymmetric Schwarzschild models to measure the central black hole masses. Our Schwarzschild models provide black hole masses of (1.3 ± 0.5) × 10 8 M ⊙ for NGC 584, (1.0 ± 0.6) × 10 8 M ⊙ for NGC 2784, (7.7 ± 5) × 10 7 M ⊙ for NGC 3640, (5.4 ± 0.8) × 10 8 M ⊙ for NGC 4281, (6.8 ± 2.0) × 10 7 M ⊙ for NGC 4570, and (3.2 ± 0.8) × 10 8 M ⊙ for NGC 7049 at 3 σ confidence level, which are consistent with recent M BH − σ e scaling relations. NGC 3640 has a velocity dispersion dip and NGC 7049 a constant velocity dispersion in the center, but we can clearly constrain their lower black hole mass limit. We conclude our analysis with a test on NGC 4570 taking into account a variable mass-to-light ratio ( M / L ) when constructing dynamical models. When considering M / L variations linked mostly to radial changes in the stellar metallicity, we find that the dynamically determined black hole mass from NGC 4570 decreases by 30%. Further investigations are needed in the future to account for the impact of radial M / L gradients on dynamical modeling.
Publisher: EDP Sciences
Date: 04-2022
DOI: 10.1051/0004-6361/202142790
Abstract: The role played by environment in galaxy evolution is a topic of ongoing debate among astronomers. There has been little success in elucidating the degree to which environment can alter, re-shape, or drive galaxy evolution, that is, using either observations or simulations. However, our knowledge of the effect of environment on gas metallicity gradients remains limited. Here we present our analysis of the gas metallicity gradients for a s le of ten Fornax cluster galaxies observed with MUSE as part of the Fornax3D project. We used detailed maps of emission lines to determine precise values of gas metallicity and metallicity gradients. The integrated gas metallicity of our Fornax cluster galaxies shows slightly higher metallicities (∼0.045 dex) in comparison to a control s le. In addition, we find signs of a mass and metallicity segregation from the center to the outskirts of the cluster. By comparing our Fornax cluster metallicity gradients with a control s le we find a general median offset of ∼0.04 dex/ R e , with eight of our galaxies showing flatter or more positive gradients. The intermediate infallers in our Fornax s le show more positive gradients with respect to the control s le. We find no systematic difference between the gradients of recent and intermediate infallers when considering the projected distance of each galaxy to the cluster center. To identify the origin of the observed offset in the metallicity gradients, we performed a similar analysis with data from the TNG50 simulation. We identify 12 subhalos in Fornax-like clusters and compared their metallicity gradients with a control s le of field subhalos. This exercise also shows a flattening in the metallicity gradients for galaxies in Fornax-like halos, with a median offset of ∼0.05 dex/ R e . We also analyzed the merger history, Mach numbers (ℳ), and ram pressure stripping of our TNG50 s le. We conclude that the observed flattening in metallicity gradients is likely due to a combination of galaxies traveling at supersonic velocities (ℳ 1), which are experiencing high ram pressure stripping and flybys.
Publisher: Oxford University Press (OUP)
Date: 08-2006
Publisher: Oxford University Press (OUP)
Date: 04-08-2023
Abstract: FRB 20210912A is a fast radio burst (FRB), detected and localized to subarcsecond precision by the Australian Square Kilometre Array Pathfinder. No host galaxy has been identified for this burst despite the high precision of its localization and deep optical and infrared follow-up, to 5σ limits of R = 26.7 mag and Ks = 24.9 mag with the Very Large Telescope. The combination of precise radio localization and deep optical imaging has almost always resulted in the secure identification of a host galaxy, and this is the first case in which the line of sight is not obscured by the Galactic disc. The dispersion measure of this burst, DMFRB = 1233.696 ± 0.006 pc cm−3, allows for a large source redshift of z & 1 according to the Macquart relation. It could thus be that the host galaxy is consistent with the known population of FRB hosts, but is too distant to detect in our observations (z & 0.7 for a host like that of the first repeating FRB source, FRB 20121102A) that it is more nearby with a significant excess in DMhost, and thus dimmer than any known FRB host or, least likely, that the FRB is truly hostless. We consider each possibility, making use of the population of known FRB hosts to frame each scenario. The fact of the missing host has ramifications for the FRB field: even with high-precision localization and deep follow-up, some FRB hosts may be difficult to detect, with more distant hosts being the less likely to be found. This has implications for FRB cosmology, in which high-redshift detections are valuable.
Publisher: EDP Sciences
Date: 05-2019
DOI: 10.1051/0004-6361/201935154
Abstract: We have used deep MUSE observations to perform a stellar-kinematic and population analysis of FCC 153 and FCC 177, two edge-on S0 galaxies in the Fornax cluster. The geometrical definition of the different structural components of these two galaxies allows us to describe the nature of their thick disks. These are both old, relatively metal poor and [Mg/Fe]-enhanced, and their star formation history (SFH) reveals a minor younger component whose chemical properties suggest its later accretion. Moreover, the outer regions of these geometrically defined thick disks show higher values of metallicity and lower values of [Mg/Fe]. These stars probably formed in the thin-disk region and they were dynamically heated to form the flares present in these two galaxies. We propose different formation scenarios for the three populations of these thick disks: in-situ formation, accretion and disk heating. A clear distinction in age is found between the metal poor and [Mg/Fe]-enhanced thick disks (old, ∼12 − 13 Gyr), and the metal rich and less [Mg/Fe]-enhanced thin disks (young, ∼4 − 5 Gyr). These two galaxies show signs of relatively recent star formation in their thin disks and nuclear regions. While the thin disks show more continuous SFHs, the nuclei display a rather bursty SFH. These two galaxies are located outside of the densest region of the Fornax cluster where FCC 170 resides. This other edge-on S0 galaxy has recently been studied, and we have compared and discussed our results with this previous study. The differences between these three galaxies, at different distances from the cluster center, suggest that the environment can have a strong effect on the galaxy evolutionary path.
Publisher: American Astronomical Society
Date: 11-05-2018
Publisher: Springer Science and Business Media LLC
Date: 09-2014
DOI: 10.1038/NATURE13762
Abstract: Ultra-compact dwarf galaxies are among the densest stellar systems in the Universe. These systems have masses of up to 2 × 10(8) solar masses, but half-light radii of just 3-50 parsecs. Dynamical mass estimates show that many such dwarfs are more massive than expected from their luminosity. It remains unclear whether these high dynamical mass estimates arise because of the presence of supermassive black holes or result from a non-standard stellar initial mass function that causes the average stellar mass to be higher than expected. Here we report adaptive optics kinematic data of the ultra-compact dwarf galaxy M60-UCD1 that show a central velocity dispersion peak exceeding 100 kilometres per second and modest rotation. Dynamical modelling of these data reveals the presence of a supermassive black hole with a mass of 2.1 × 10(7) solar masses. This is 15 per cent of the object's total mass. The high black hole mass and mass fraction suggest that M60-UCD1 is the stripped nucleus of a galaxy. Our analysis also shows that M60-UCD1's stellar mass is consistent with its luminosity, implying a large population of previously unrecognized supermassive black holes in other ultra-compact dwarf galaxies.
Publisher: Oxford University Press (OUP)
Date: 23-03-2017
DOI: 10.1093/MNRAS/STX713
Publisher: American Astronomical Society
Date: 13-08-2015
Publisher: Oxford University Press (OUP)
Date: 16-01-2018
DOI: 10.1093/MNRAS/STY127
Publisher: EDP Sciences
Date: 08-2019
DOI: 10.1051/0004-6361/201935832
Abstract: Context . Nuclear star clusters (NSCs) are found in at least 70% of all galaxies, but their formation path is still unclear. In the most common scenarios, NSCs form in-situ from the galaxy’s central gas reservoir, through the merging of globular clusters (GCs), or through a combination of both. Aims . As the scenarios pose different expectations for angular momentum and stellar population properties of the NSC in comparison to the host galaxy and the GC system, it is necessary to characterise the stellar light, NSC, and GCs simultaneously. The large NSC ( r eff = 66 pc) and rich GC system of the early-type Fornax cluster galaxy FCC 47 (NGC 1336) render this galaxy an ideal laboratory to constrain NSC formation. Methods . Using Multi Unit Spectroscopic Explorer science verification data assisted by adaptive optics, we obtained maps for the stellar kinematics and stellar-population properties of FCC 47. We extracted the spectra of the central NSC and determined line-of-sight velocities of 24 GCs and metallicities of five. Results . The galaxy shows the following kinematically decoupled components (KDCs): a disk and a NSC. Our orbit-based dynamical Schwarzschild model revealed that the NSC is a distinct kinematic feature and it constitutes the peak of metallicity and old ages in FCC 47. The main body consists of two counter-rotating populations and is dominated by a more metal-poor population. The GC system is bimodal with a dominant metal-poor population and the total GC system mass is ∼17% of the NSC mass (∼7 × 10 8 M ⊙ ). Conclusions . The rotation, high metallicity, and high mass of the NSC cannot be explained by GC-inspiral alone. It most likely requires additional, quickly quenched, in-situ formation. The presence of two KDCs likely are evidence of a major merger that has significantly altered the structure of FCC 47, indicating the important role of galaxy mergers in forming the complex kinematics in the galaxy-NSC system.
Publisher: EDP Sciences
Date: 31-03-2023
DOI: 10.1051/0004-6361/202244558
Abstract: We apply a population-orbit superposition metho1d to 16 galaxies in the Fornax cluster observed with MUSE/VLT in the context of the Fornax3D project. By fitting the luminosity distribution, stellar kinematics, and age and metallicity maps simultaneously, we obtained the internal stellar orbit distribution, as well as the age and metallicity distribution of stars on different orbits for each galaxy. Based on the model, we decompose each galaxy into a dynamically cold disk (orbital circularity λ z ≥ 0.8) and a dynamically hot non-disk component (orbital circularity λ z 0.8), and obtain the surface-brightness, age, and metallicity radial profiles of each component. The galaxy infall time into the cluster is strongly correlated with galaxy cold-disk age with older cold disks in ancient infallers. We quantify the infall time t infall of each galaxy with its cold-disk age using a correlation calibrated with TNG50 cosmological simulations. For galaxies in the Fornax cluster, we found that the luminosity fraction of cold disk in galaxies with t infall 8 Gyr are a factor of ∼4 lower than in more recent infallers while controlling for total stellar mass. Nine of the 16 galaxies have spatially extended cold disks, and most of them show positive or zero age gradients stars in the inner disk are ∼2 − 5 Gyr younger than that in the outer disk, in contrast to the expectation of inside-out growth. Our results indicate that the assembly of cold disks in galaxies is strongly affected by their infall into clusters, by either removal of gas in outer regions or even tidally stripping or heating part of the pre-existing disks. Star formation in outer disks can stop quickly after the galaxy falls into the cluster, while star formation in the inner disks can last for a few Gyrs more, building the positive age gradient measured in cold disks.
Publisher: Springer Science and Business Media LLC
Date: 23-04-2018
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.25
Abstract: We present an overview of the M iddle A ges G alaxy P roperties with I ntegral Field Spectroscopy (MAGPI) survey, a Large Program on the European Southern Observatory Very Large Telescope. MAGPI is designed to study the physical drivers of galaxy transformation at a lookback time of 3–4 Gyr, during which the dynamical, morphological, and chemical properties of galaxies are predicted to evolve significantly. The survey uses new medium-deep adaptive optics aided Multi-Unit Spectroscopic Explorer (MUSE) observations of fields selected from the Galaxy and Mass Assembly (GAMA) survey, providing a wealth of publicly available ancillary multi-wavelength data. With these data, MAGPI will map the kinematic and chemical properties of stars and ionised gas for a s le of 60 massive ( ${ }7 \\times 10^{10} {\\mathrm{M}}_\\odot$ ) central galaxies at $0.25 z .35$ in a representative range of environments (isolated, groups and clusters). The spatial resolution delivered by MUSE with Ground Layer Adaptive Optics ( $0.6-0.8$ arcsec FWHM) will facilitate a direct comparison with Integral Field Spectroscopy surveys of the nearby Universe, such as SAMI and MaNGA, and at higher redshifts using adaptive optics, for ex le, SINS. In addition to the primary (central) galaxy s le, MAGPI will deliver resolved and unresolved spectra for as many as 150 satellite galaxies at $0.25 z .35$ , as well as hundreds of emission-line sources at $z 6$ . This paper outlines the science goals, survey design, and observing strategy of MAGPI. We also present a first look at the MAGPI data, and the theoretical framework to which MAGPI data will be compared using the current generation of cosmological hydrodynamical simulations including EAGLE , Magneticum , HORIZON-AGN , and Illustris-TNG . Our results show that cosmological hydrodynamical simulations make discrepant predictions in the spatially resolved properties of galaxies at $z\\approx 0.3$ . MAGPI observations will place new constraints and allow for tangible improvements in galaxy formation theory.
Publisher: EDP Sciences
Date: 08-2022
DOI: 10.1051/0004-6361/202243109
Abstract: We report the discovery of ancient massive merger events in the early-type galaxies NGC 1380 and NGC 1427, members of the Fornax galaxy cluster. Both galaxies have been observed by the MUSE integral-field-unit instrument on the VLT as part of the Fornax3D project. By fitting recently developed population-orbital superposition models to the observed surface brightness, stellar kinematic, age, and metallicity maps, we obtain the stellar orbits, age, and metallicity distributions of each galaxy. We then decompose each galaxy into multiple orbital-based components, including a dynamically hot inner stellar halo component that is identified as the relic of past massive mergers. By comparing to analogs from cosmological galaxy simulations, chiefly TNG50, we find that the formation of such a hot inner stellar halo requires the merger with a now-destroyed massive satellite galaxy of $ 3.7_{-1.5}^{+2.7} \\times 10^{10} $ M ⊙ (about one-fifth of its current stellar mass) in the case of NGC 1380 and of $ 1.5_{-0.7}^{+1.6} \\times10^{10} $ M ⊙ (about one-fourth of its current stellar mass) in the case of NGC 1427. Moreover, we infer that the last massive merger in NGC 1380 happened ∼10 Gyr ago based on the stellar age distribution of the regrown dynamically cold disk, whereas the merger in NGC 1427 ended t ≲ 8 Gyr ago based on the stellar populations in its hot inner stellar halo. The major merger event in NGC 1380 is the first one with both merger mass and merger time quantitatively inferred in a galaxy beyond the local volume. Moreover, it is the oldest and most massive merger uncovered in nearby galaxies so far.
Publisher: American Astronomical Society
Date: 05-2022
Abstract: Dynamical models are crucial for uncovering the internal dynamics of galaxies however, most of the results to date assume axisymmetry, which is not representative of a significant fraction of massive galaxies. Here, we build triaxial Schwarzschild orbit-superposition models of galaxies taken from the SAMI Galaxy Survey, in order to reconstruct their inner orbital structure and mass distribution. The s le consists of 161 passive galaxies with total stellar masses in the range 10 9.5 –10 12 M ⊙ . We find that the changes in internal structures within 1 R e are correlated with the total stellar mass of the in idual galaxies. The majority of the galaxies in the s le (73% ± 3%) are oblate, while 19% ± 3% are mildly triaxial and 8% ± 2% have triaxial rolate shape. Galaxies with log M ⋆ / M ⊙ 10.50 are more likely to be non-oblate. We find a mean dark matter fraction of f DM = 0.28 ± 0.20, within 1 R e . Galaxies with higher intrinsic ellipticity (flatter) are found to have more negative velocity anisotropy β r (tangential anisotropy). β r also shows an anticorrelation with the edge-on spin parameter λ Re , EO , so that β r decreases with increasing λ Re , EO , reflecting the contribution from disk-like orbits in flat, fast-rotating galaxies. We see evidence of an increasing fraction of hot orbits with increasing stellar mass, while warm and cold orbits show a decreasing trend. We also find that galaxies with different ( V / σ – h 3 ) kinematic signatures have distinct combinations of orbits. These results are in agreement with a formation scenario in which slow- and fast-rotating galaxies form through two main channels.
Publisher: EDP Sciences
Date: 05-2020
DOI: 10.1051/0004-6361/202037686
Abstract: Globular cluster (GC) systems of massive galaxies often show a bimodal colour distribution. This has been interpreted as a metallicity bimodality, created by a two-stage galaxy formation where the red, metal-rich GCs were formed in the parent halo and the blue metal-poor GCs were accreted. This interpretation, however, crucially depends on the assumption that GCs are exclusively old stellar systems with a linear colour–metallicity relation (CZR). The shape of the CZR and range of GC ages are currently under debate because their study requires high quality spectra to derive reliable stellar population properties. We determined metallicities with full spectral fitting from a s le of 187 GCs with a high spectral signal-to-noise ratio in 23 galaxies of the Fornax cluster that were observed as part of the Fornax 3D project. The derived CZR from this s le is non-linear and can be described by a piecewise linear function with a break point at ( g − z ) ∼ 1.1 mag. The less massive galaxies in our s le ( M * 10 10 M ⊙ ) appear to have slightly younger GCs, but the shape of the CZR is insensitive to the GC ages. Although the least massive galaxies lack red, metal-rich GCs, a non-linear CZR is found irrespective of the galaxy mass, even in the most massive galaxies ( M * ≥ 10 11 M ⊙ ). Our CZR predicts narrow unimodal GC metallicity distributions for low mass and broad unimodal distributions for very massive galaxies, dominated by a metal-poor and metal-rich peak, respectively, and bimodal distributions for galaxies with intermediate masses (10 10 ≤ M * 10 11 M ⊙ ) as a consequence of the relative fraction of red and blue GCs. The erse metallicity distributions challenge the simple differentiation of GC populations solely based on their colour.
Publisher: SPIE
Date: 30-09-2004
DOI: 10.1117/12.552912
Publisher: EDP Sciences
Date: 05-2020
DOI: 10.1051/0004-6361/202037685
Abstract: Globular clusters (GCs) are found ubiquitously in massive galaxies and due to their old ages, they are regarded as fossil records of galaxy evolution. Spectroscopic studies of GC systems are often limited to the outskirts of galaxies, where GCs stand out against the galaxy background and serve as bright tracers of galaxy assembly. In this work, we use the capabilities of the Multi Unit Explorer Spectrograph (MUSE) to extract a spectroscopic s le of 722 GCs in the inner regions (≲3 R eff ) of 32 galaxies in the Fornax cluster. These galaxies were observed as part of the Fornax 3D project, a MUSE survey that targets early and late-type galaxies within the virial radius of Fornax. After accounting for the galaxy background in the GC spectra, we extracted line-of-sight velocities and determined metallicities of a sub-s le of 238 GCs. We found signatures of rotation within GC systems, and comparing the GC kinematics and that of the stellar body shows that the GCs trace the spheroid of the galaxies. While the red GCs prove to closely follow the metallicity profile of the host galaxy, the blue GCs show a large spread of metallicities but they are generally more metal-poor than the host.
Publisher: AIP
Date: 2008
DOI: 10.1063/1.2973563
Publisher: Oxford University Press (OUP)
Date: 12-06-2018
Publisher: Oxford University Press (OUP)
Date: 26-09-2019
Publisher: EDP Sciences
Date: 08-2018
DOI: 10.1051/0004-6361/201833137
Abstract: The Fornax cluster provides a uniquely compact laboratory in which to study the detailed history of early-type galaxies and the role played by the environment in driving their evolution and their transformation from late-type galaxies. Using the superb capabilities of the Multi Unit Spectroscopic Explorer on the Very Large Telescope, high-quality integral-field spectroscopic data were obtained for the inner regions of all the bright ( m B ≤ 15) galaxies within the virial radius of Fornax. The stellar haloes of early-type galaxies are also covered out to about four effective radii. State-of-the-art stellar dynamical and population modelling allows characterising the disc components of fast-rotating early-type galaxies, constraining radial variations in the stellar initial-mass functions and measuring the stellar age, metallicity, and α -element abundance of stellar haloes in cluster galaxies. This paper describes the s le selection, observations, and overall goals of the survey, and provides initial results based on the spectroscopic data, including the detailed characterisation of stellar kinematics and populations to large radii decomposition of galaxy components directly via their orbital structure the ability to identify globular clusters and planetary nebulae, and derivation of high-quality emission-line diagnostics in the presence of complex ionised gas.
Publisher: EDP Sciences
Date: 02-2019
DOI: 10.1051/0004-6361/201834465
Abstract: Galaxies continuously reprocess their interstellar material. We can therefore expect changing dust grain properties in galaxies that have followed different evolutionary pathways. Determining the intrinsic dust grain mix of a galaxy helps in reconstructing its evolutionary history. Early-type galaxies occasionally display regular dust lanes in their central regions. Owing to the relatively simple geometry and composition of their stellar bodies, these galaxies are ideal to disentangle dust mix variations from geometric effects. We therefore modelled the various components of such a galaxy (FCC 167). We reconstructed its recent history and investigated the possible fate of the dust lane. Observations from MUSE and the Atacama Large Millimeter/submillimeter Array (ALMA) reveal a nested interstellar medium structure. An ionised-gas disc pervades the central regions of FCC 167, including those occupied by the main dust lane. Inward of the dust lane, we also find a disc/ring of cold molecular gas where stars are forming and HII regions contribute to the ionised-gas emission. Further in, the gas ionisation points towards an active galactic nucleus and the fuelling of a central supermassive black hole from its surrounding ionised and molecular reservoir. Observational constraints and radiative transfer models suggest the dust and gas are distributed in a ring-like geometry and the dust mix lacks small grains. The derived dust destruction timescales from sputtering in hot gas are short, and we conclude that the dust must be strongly self-shielding and clumpy or will quickly be eroded and disappear. Our findings show how detailed analyses of in idual systems can complement statistical studies of dust-lane ETGs.
Publisher: American Astronomical Society
Date: 15-05-2018
Publisher: American Astronomical Society
Date: 29-06-2017
Publisher: Oxford University Press (OUP)
Date: 09-05-2015
DOI: 10.1093/MNRAS/STV866
Publisher: EDP Sciences
Date: 07-2019
DOI: 10.1051/0004-6361/201935721
Abstract: The 31 brightest galaxies ( m B ≤ 15 mag) inside the virial radius of the Fornax cluster were observed from the centres to the outskirts with the Multi Unit Spectroscopic Explorer on the Very Large Telescope. These observations provide detailed high-resolution maps of the line-of-sight kinematics, line strengths of the stars, ionised gas reaching 2–3 R e for 21 early-type galaxies, and 1–2 R e for 10 late-type galaxies. The majority of the galaxies are regular rotators, with eight hosting a kinematically distinct core. Only two galaxies are slow rotators. The mean age, total metallicity, and [Mg/Fe] abundance ratio in the bright central region inside 0.5 R e and in the galaxy outskirts are presented. Extended emission-line gas is detected in 13 galaxies, most of them are late-type objects with wide-spread star formation. The measured structural properties are analysed in relation to the galaxies’ position in the projected phase space of the cluster. This shows that the Fornax cluster appears to consist of three main groups of galaxies inside the virial radius: the old core a clump of galaxies, which is aligned with the local large-scale structure and was accreted soon after the formation of the core and a group of galaxies that fell in more recently.
Publisher: Oxford University Press (OUP)
Date: 02-05-2023
Abstract: We investigate the impact of environment on the internal mass distribution of galaxies using the Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey. We use 2D resolved stellar kinematics to construct Jeans dynamical models for galaxies at mean redshift z ∼ 0.3, corresponding to a lookback time of 3–4 Gyr. The internal mass distribution for each galaxy is parametrized by the combined mass density slope γ (baryons + dark matter), which is the logarithmic change of density with radius. We use a MAGPI s le of 28 galaxies from low-to-mid density environments and compare to density slopes derived from galaxies in the high density Frontier Fields clusters in the redshift range 0.29 & z & 0.55, corresponding to a lookback time of ∼5 Gyr. We find a median density slope of γ = −2.22 ± 0.05 for the MAGPI s le, which is significantly steeper than the Frontier Fields median slope (γ = −2.00 ± 0.04), implying the cluster galaxies are less centrally concentrated in their mass distribution than MAGPI galaxies. We also compare to the distribution of density slopes from galaxies in ATLAS3D at z ∼ 0, because the s le probes a similar environmental range as MAGPI. The ATLAS3D median total slope is γ = −2.25 ± 0.02, consistent with the MAGPI median. Our results indicate environment plays a role in the internal mass distribution of galaxies, with no evolution of the slope in the last 3–4 Gyr. These results are in agreement with the predictions of cosmological simulations.
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S174392130700258X
Abstract: The Virgo Cluster spiral NGC 4569 is known for its compact starburst in the core and unusual outflow of Hα emitting gas perpendicular to the galaxy disk. Recent radio polarimetric observations with the Effelsberg telescope reveal huge magnetized outflows. Preliminary results of our XMM-Newton observations uncover not only hot gas in the disk but also an extensive X-ray envelope around it. We investigate the possibility of starburst-induced galactic outflows in various gas phases and cluster influence on the galaxy evolution.
Publisher: SPIE
Date: 16-07-2010
DOI: 10.1117/12.856572
Publisher: Oxford University Press (OUP)
Date: 21-02-2018
DOI: 10.1093/MNRAS/STY456
Publisher: SPIE
Date: 06-07-2018
DOI: 10.1117/12.2309893
Publisher: Oxford University Press (OUP)
Date: 23-10-2017
Publisher: Cambridge University Press (CUP)
Date: 04-2006
Publisher: Oxford University Press (OUP)
Date: 11-11-2009
Publisher: SPIE
Date: 13-12-2020
DOI: 10.1117/12.2563235
Publisher: Cambridge University Press (CUP)
Date: 07-2007
DOI: 10.1017/S1743921308017961
Abstract: We present results on the stellar populations of a s le of 18 late-type spirals, based on data acquired with the integral-field spectrograph SAURON at the WHT. We present the two-dimensional line-strength maps, the central line indices, and estimate the star formation time-scale. In an exponentially declining SFR scenario, we find a trend between the time-scale τ and the central velocity dispersion: more massive galaxies show shorter burst durations. A detailed study on these data is published by Ganda et al . (2007).
Publisher: Oxford University Press (OUP)
Date: 19-08-2020
Abstract: We present the discovery with Keck of the extremely infrared (IR) luminous transient AT 2017gbl, coincident with the Northern nucleus of the luminous infrared galaxy (LIRG) IRAS 23436+5257. Our extensive multiwavelength follow-up spans ∼900 d, including photometry and spectroscopy in the optical and IR, and (very long baseline interferometry) radio and X-ray observations. Radiative transfer modelling of the host galaxy spectral energy distribution and long-term pre-outburst variability in the mid-IR indicate the presence of a hitherto undetected dust obscured active galactic nucleus (AGN). The optical and near-IR spectra show broad ∼2000 km s−1 hydrogen, He i, and O i emission features that decrease in flux over time. Radio imaging shows a fast evolving compact source of synchrotron emission spatially coincident with AT 2017gbl. We infer a lower limit for the radiated energy of 7.3 × 1050 erg from the IR photometry. An extremely energetic supernova would satisfy this budget, but is ruled out by the radio counterpart evolution. Instead, we propose AT 2017gbl is related to an accretion event by the central supermassive black hole, where the spectral signatures originate in the AGN broad line region and the IR photometry is consistent with re-radiation by polar dust. Given the fast evolution of AT 2017gbl, we deem a tidal disruption event (TDE) of a star a more plausible scenario than a dramatic change in the AGN accretion rate. This makes AT 2017gbl the third TDE candidate to be hosted by a LIRG, in contrast to the so far considered TDE population discovered at optical wavelengths and hosted preferably by post-starburst galaxies.
Publisher: European Southern Observatory (ESO)
Date: 2019
Publisher: American Astronomical Society
Date: 17-04-2017
Publisher: SPIE
Date: 04-08-2016
DOI: 10.1117/12.2230740
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.47
Publisher: Springer Science and Business Media LLC
Date: 11-11-2010
Publisher: Oxford University Press (OUP)
Date: 03-2010
Publisher: Oxford University Press (OUP)
Date: 19-01-2017
DOI: 10.1093/MNRAS/STX101
Publisher: AIP
Date: 2010
DOI: 10.1063/1.3458490
Publisher: American Astronomical Society
Date: 07-2022
Abstract: We analyze spatially resolved and co-added SDSS-IV MaNGA spectra with signal-to-noise ratio ∼100 from 2200 passive central galaxies ( z ∼ 0.05) to understand how central galaxy assembly depends on stellar mass ( M * ) and halo mass ( M h ). We control for systematic errors in M h by employing a new group catalog from Tinker and the widely used Yang et al. catalog. At fixed M * , the strengths of several stellar absorption features vary systematically with M h . Completely model-free, this is one of the first indications that the stellar populations of centrals with identical M * are affected by the properties of their host halos. To interpret these variations, we applied full spectral fitting with the code alf . At fixed M * , centrals in more massive halos are older, show lower [Fe/H], and have higher [Mg/Fe] with 3.5 σ confidence. We conclude that halos not only dictate how much M * galaxies assemble but also modulate their chemical enrichment histories. Turning to our analysis at fixed M h , high- M * centrals are older, show lower [Fe/H], and have higher [Mg/Fe] for M h 10 12 h −1 M ⊙ with confidence σ . While massive passive galaxies are thought to form early and rapidly, our results are among the first to distinguish these trends at fixed M h . They suggest that high- M * centrals experienced unique early formation histories, either through enhanced collapse and gas fueling or because their halos were early forming and highly concentrated, a possible signal of galaxy assembly bias.
Publisher: Springer Science and Business Media LLC
Date: 27-05-2010
Publisher: SPIE
Date: 06-07-2018
DOI: 10.1117/12.2313059
Publisher: Oxford University Press (OUP)
Date: 27-04-2019
Abstract: We present a combination of the Schwarzschild orbit-superposition dynamical modelling technique with the spatially resolved mean stellar age and metallicity maps to uncover the formation history of galaxies. We apply this new approach to a remarkable five-pointing mosaic of VLT/MUSE observations obtained by Guérou et al. (2016) extending to a maximum galactocentric distance of ${\\sim } {120}{\\, {\\rm arcsec}}\\ \\left({5.6}\\, {\\rm kpc}\\right)$ along the major axis, corresponding to ∼2.5Re. Our method first identifies ‘families’ of orbits from the dynamical model that represent dynamically distinct structures of the galaxy. In idual ages and metallicities of these components are then fit for using the stellar-population information. Our results highlight components of the galaxy that are distinct in the combined stellar dynamics opulations space, which implies distinct formation paths. We find evidence for a dynamically cold, metal-rich disc, consistent with a gradual in situ formation. This disc is embedded in a generally old population of stars, with kinematics ranging from dispersion dominated in the centre to an old, diffuse, metal-poor stellar halo at the extremities. We find also a direct correlation between the dominant dynamical support of these components, and their associated age, akin to the relation observed in the Milky Way. This approach not only provides a powerful model for inferring the formation history of external galaxies but also paves the way to a complete population-dynamical model.
Publisher: EDP Sciences
Date: 03-2021
DOI: 10.1051/0004-6361/202039644
Abstract: In order to assess the impact of the environment on the formation and evolution of galaxies, accurate assembly histories of such galaxies are needed. However, these measurements are observationally difficult owing to the ersity of formation paths that lead to the same present-day state of a galaxy. In this work, we apply a powerful new technique in order to observationally derive accurate assembly histories through a self-consistent combined stellar dynamical and population galaxy model. We present this approach for three edge-on lenticular galaxies from the Fornax3D project – FCC 153, FCC 170, and FCC 177 – in order to infer their mass assembly histories in idually and in the context of the Fornax cluster. The method was tested on mock data from simulations to quantify its reliability. We find that the galaxies studied here have all been able to form dynamically-cold (intrinsic vertical velocity dispersion σ z ≲ 50 km s −1 ) stellar disks after cluster infall. Moreover, the pre-existing (old) high angular momentum components have retained their angular momentum (orbital circularity λ z 0.8) through to the present day. Comparing the derived assembly histories with a comparable galaxy in a low-density environment – NGC 3115 – we find evidence for cluster-driven suppression of stellar accretion and merging. We measured the intrinsic stellar age–velocity-dispersion relation and find that the shape of the relation is consistent with galaxies in the literature across redshift. There is tentative evidence for enhancement in the luminosity-weighted intrinsic vertical velocity dispersion due to the cluster environment. But importantly, there is an indication that metallicity may be a key driver of this relation. We finally speculate that the cluster environment is responsible for the S0 morphology of these galaxies via the gradual external perturbations, or ‘harassment’, generated within the cluster.
Publisher: SPIE
Date: 14-06-2006
DOI: 10.1117/12.669772
Publisher: American Astronomical Society
Date: 26-10-2021
Publisher: SPIE
Date: 13-09-2012
DOI: 10.1117/12.925507
Publisher: EDP Sciences
Date: 06-2018
DOI: 10.1051/0004-6361/201732448
Abstract: Context. The merging of galaxies is one key aspect in our favourite hierarchical ΛCDM Universe and is an important channel leading to massive quiescent elliptical galaxies. Understanding this complex transformational process is ongoing. Aims. We aim to study NGC 7252, which is one of the nearest major-merger galaxy remnants, observed ~1 Gyr after the collision of presumably two gas-rich disc galaxies. It is therefore an ideal laboratory to study the processes inherent to the transformation of disc galaxies to ellipticals. Methods. We obtained wide-field IFU spectroscopy with the VLT-VIMOS integral-field spectrograph covering the central 50′′ × 50′′ of NGC 7252 to map the stellar and ionised gas kinematics, and the distribution and conditions of the ionised gas, revealing the extent of ongoing star formation and recent star formation history. Results. Contrary to previous studies, we find the inner gas disc not to be counter-rotating with respect to the stars. In addition, the stellar kinematics appear complex with a clear indication of a prolate-like rotation component which suggests a polar merger configuration. The ongoing star formation rate is 2.2 ± 0.6 M ⊙ yr −1 and implies a typical depletion time of ~2 Gyr given the molecular gas content. Furthermore, the spatially resolved star formation history suggests a slight radial dependence, moving outwards at later times. We confirm a large AGN-ionised gas cloud previously discovered ~5 kpc south of the nucleus, and find a higher ionisation state of the ionised gas at the galaxy centre relative to the surrounding gas disc. Although the higher ionisation towards the centre is potentially degenerate within the central star forming ring, it may be associated with a low-luminosity AGN. Conclusions. Although NGC 7252 has been classified as post-starburst galaxy at the centre, the elliptical-like major-merger remnant still appears very active. A central kpc-scale gas disc has presumably re-formed quickly within the last 100 Myr after final coalescence. The disc features ongoing star formation, implying Gyr long timescale to reach the red sequence through gas consumption alone. While NGC 7252 is useful to probe the transformation from discs to ellipticals, it is not well-suited to study the transformation from blue to red at this point.
Publisher: Oxford University Press (OUP)
Date: 24-07-2018
Publisher: Oxford University Press (OUP)
Date: 21-03-2006
Publisher: SPIE
Date: 09-08-2016
DOI: 10.1117/12.2233927
Publisher: Oxford University Press (OUP)
Date: 11-11-2022
Abstract: We study the evolution of kinematically defined stellar discs in 10 Fornax-like clusters identified in the TNG50 run from the IllustrisTNG suite of cosmological simulations. We considered disc galaxies with present-day stellar mass M⋆ ≥ 3 × 108 M⊙ and follow their evolution since first entering their host cluster. Very few stellar discs survive since falling in such dense environments, ranging from 40 per cent surviving to all being disrupted. Such survival rates are consistent with what reported earlier for the two more massive, Virgo-like clusters in TNG50. In absolute terms, however, the low number of present-day disc galaxies in Fornax-like clusters could be at odds with the presence of three edge-on disc galaxies in the central regions of the actual Fornax cluster, as delineated by the Fornax3D survey. When looking at the Fornax analogues from random directions and with the same selection function of Fornax3D, the probability of finding three edge-on disc galaxies in any one Fornax-like cluster in TNG50 is rather low, albeit not impossible. We also compared the stellar-population properties near the equatorial plane derived from integral-field spectroscopy for the three edge-ons in Fornax to similar line-of-sight integrated values for present-day disc galaxies in TNG50. For one of these, the very old and metal-rich stellar population of its disc cannot be matched by any the disc galaxies in TNG50, including objects in the field. We discuss possible interpretations of these findings, while pointing to future studies on passive cluster spirals as a way to further test state-of-the-art cosmological simulations.
Publisher: American Astronomical Society
Date: 14-04-2010
Publisher: EDP Sciences
Date: 26-02-2019
DOI: 10.1051/0004-6361/201833193
Abstract: We present and discuss the stellar kinematics and populations of the S0 galaxy FCC 170 (NGC 1381) in the Fornax cluster, using deep MUSE data from the Fornax 3D survey. We show the maps of the first four moments of the stellar line-of-sight velocity distribution and of the mass-weighted mean stellar age, metallicity, and [Mg/Fe] abundance ratio. The high-quality MUSE stellar kinematic measurements unveil the structure of this massive galaxy: a nuclear disk, a bar seen as a boxy bulge with a clear higher-velocity-dispersion X shape, a fast-rotating and flaring thin disk and a slower rotating thick disk. Whereas their overall old age makes it difficult to discuss differences in the formation epoch between these components, we find a clear-cut distinction between metal-rich and less [Mg/Fe]-enhanced populations in the thin-disk, boxy-bulge and nuclear disk, and more metal-poor and [Mg/Fe]-enhanced stars in the thick disk. Located in the densest region of the Fornax cluster, where signs of tidal stripping have been recently found, the evolution of FCC 170 might have been seriously affected by its environment. We discuss the possibility of its “preprocessing” in a subgroup before falling into the present-day cluster, which would have shaped this galaxy a long time ago. The thick disk displays a composite star formation history, as a significant fraction of younger stars co-exist with the main older thick-disk population. The former subpopulation is characterized by even lower-metallicity and higher-[Mg/Fe] values, suggesting that these stars formed later and faster in a less chemically evolved satellite, which was subsequently accreted. Finally, we discuss evidence that metal-rich and less [Mg/Fe]-enhanced stars were brought in the outer parts of the thick disk by the flaring of the thin disk.
Publisher: IOP Publishing
Date: 26-04-2005
Publisher: American Astronomical Society
Date: 04-03-2019
Publisher: Elsevier BV
Date: 2019
Publisher: Springer Berlin Heidelberg
Date: 2008
Publisher: Cambridge University Press (CUP)
Date: 2016
DOI: 10.1017/PASA.2016.29
Abstract: Integral field unit spectrographs allow the 2D exploration of the kinematics and stellar populations of galaxies, although they are generally restricted to small fields-of-view. Using the large field-of-view of the DEIMOS multislit spectrograph on Keck and our Stellar Kinematics using Multiple Slits technique, we are able to extract sky-subtracted stellar light spectra to large galactocentric radii. Here, we present a new DEIMOS mask design named SuperSKiMS that explores large spatial scales without sacrificing high spatial s ling. We simulate a set of observations with such a mask design on the nearby galaxy NGC 1023, measuring stellar kinematics and metallicities out to where the galaxy surface brightness is orders of magnitude fainter than the sky. With this technique we also reproduce the results from literature integral field spectroscopy in the innermost galaxy regions. In particular, we use the simulated NGC 1023 kinematics to model its total mass distribution to large radii, obtaining comparable results with those from published integral field unit observation. Finally, from new spectra of NGC 1023, we obtain stellar 2D kinematics and metallicity distributions that show good agreement with integral field spectroscopy results in the overlapping regions. In particular, we do not find a significant offset between our Stellar Kinematics using Multiple Slits and the ATLAS 3D stellar velocity dispersion at the same spatial locations.
Publisher: Oxford University Press (OUP)
Date: 26-04-2020
Abstract: We study a s le of 148 early-type galaxies in the Coma cluster using SDSS photometry and spectra, and calibrate our results using detailed dynamical models for a subset of these galaxies, to create a precise benchmark for dynamical scaling relations in high-density environments. For these galaxies, we successfully measured global galaxy properties, modelled stellar populations, and created dynamical models, and support the results using detailed dynamical models of 16 galaxies, including the two most massive cluster galaxies, using data taken with the SAURON IFU. By design, the study provides minimal scatter in derived scaling relations due to the small uncertainty in the relative distances of galaxies compared to the cluster distance. Our results demonstrate low (≤55 per cent for 90th percentile) dark matter fractions in the inner 1Re of galaxies. Owing to the study design, we produce the tightest, to our knowledge, IMF–σe relation of galaxies, with a slope consistent with that seen in local galaxies. Leveraging our dynamical models, we transform the classical Fundamental Plane of the galaxies to the Mass Plane. We find that the coefficients of the Mass Plane are close to predictions from the virial theorem, and have significantly lower scatter compared to the Fundamental Plane. We show that Coma galaxies occupy similar locations in the (M*–Re) and (M*−σe) relations as local field galaxies but are older. This, and the fact we find only three slow rotators in the cluster, is consistent with the scenario of hierarchical galaxy formation and expectations of the kinematic morphology–density relation.
Publisher: SPIE
Date: 14-06-2006
DOI: 10.1117/12.669942
Publisher: OSA
Date: 2011
Publisher: Oxford University Press (OUP)
Date: 08-01-2020
Abstract: Ground-based near-infrared (NIR) astronomy is severely h ered by the forest of atmospheric emission lines resulting from the rovibrational decay of OH molecules in the upper atmosphere. The extreme brightness of these lines, as well as their spatial and temporal variability, makes accurate sky subtraction difficult. Selectively filtering these lines with OH suppression instruments has been a long standing goal for NIR spectroscopy. We have shown previously the efficacy of fibre Bragg gratings (FBGs) combined with photonic lanterns for achieving OH suppression. Here we report on PRAXIS, a unique NIR spectrograph that is optimized for OH suppression with FBGs. We show for the first time that OH suppression (of any kind) is possible with high overall throughput (18 per cent end-to-end), and provide ex les of the relative benefits of OH suppression.
Publisher: Zenodo
Date: 2019
Publisher: Cambridge University Press (CUP)
Date: 08-2012
DOI: 10.1017/S1743921313005085
Abstract: I present a brief review of the stellar population properties of massive galaxies, focusing on early-type galaxies in particular, with emphasis on recent results from the ATLAS 3D Survey. I discuss the occurence of young stellar ages, cold gas, and ongoing star formation in early-type galaxies, the presence of which gives important clues to the evolutionary path of these galaxies. Consideration of empirical star formation histories gives a meaningful picture of galaxy stellar population properties, and allows accurate comparison of mass estimates from populations and dynamics. This has recently provided strong evidence of a non-universal IMF, as supported by other recent evidences. Spatially-resolved studies of stellar populations are also crucial to connect distinct components within galaxies to spatial structures seen in other wavelengths or parameters. Stellar populations in the faint outer envelopes of early-type galaxies are a formidable frontier for observers, but promise to put constraints on the ratio of accreted stellar mass versus that formed ‘in situ’ - a key feature of recent galaxy formation models. Galaxy environment appears to play a key role in controlling the stellar population properties of low mass galaxies. Simulations remind us, however, that current day galaxies are the product of a complex assembly and environment history, which gives rise to the trends we see. This has strong implications for our interpretation of environmental trends.
Publisher: EDP Sciences
Date: 19-12-2016
Publisher: Oxford University Press (OUP)
Date: 15-07-2021
Abstract: The change of the total mass density slope, γ, of early-type galaxies through cosmic time is a probe of evolutionary pathways. Hydrodynamical cosmological simulations show that at high redshifts density profiles of early-type galaxies were on average steep (γ ∼ −3). As redshift approaches zero, gas-poor mergers progressively cause the total mass density slope to approach the ‘isothermal’ slope of γ ∼ −2. Simulations therefore predict steep density slopes at high redshifts, with little to no evolution in density slopes below z ∼ 1. Gravitational lensing results in the same redshift range find the opposite, namely a significant trend of shallow density slopes at high redshifts, becoming steeper as redshift approaches zero. Gravitational lensing results indicate a different evolutionary mechanism for early-type galaxies than dry merging, such as continued gas accretion or off-axis mergers. At redshift zero, isothermal solutions are obtained by both simulations and dynamical modelling. This work applies the Jeans dynamical modelling technique to observations of galaxies at intermediate redshifts (0.29 & z & 0.55) in order to derive density slopes to address the tension between observations and simulations. We combine two-dimensional kinematic fields from Multi Unit Spectroscopic Explorer data with Hubble Space Telescope photometry. The density slopes of 90 early-type galaxies from the Frontier Fields project are presented. The total s le has a median of γ = −2.11 ± 0.03 (standard error), in agreement with dynamical modelling studies at redshift zero. The lack of evolution in total density slopes in the past 4–6 Gyr supports a dry merging model for early-type galaxy evolution.
Location: Netherlands
Start Date: 06-2016
End Date: 12-2022
Amount: $665,352.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2016
End Date: 08-2022
Amount: $312,485.00
Funder: Australian Research Council
View Funded ActivityStart Date: 11-2022
End Date: 12-2023
Amount: $1,749,940.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2019
End Date: 12-2021
Amount: $656,639.00
Funder: Australian Research Council
View Funded ActivityStart Date: 05-2016
End Date: 12-2017
Amount: $175,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 04-2015
End Date: 12-2016
Amount: $560,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2017
End Date: 12-2018
Amount: $400,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2015
End Date: 12-2015
Amount: $430,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 07-2017
End Date: 12-2024
Amount: $30,300,000.00
Funder: Australian Research Council
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