ORCID Profile
0000-0002-6211-499X
Current Organisation
Universidad Complutense de Madrid
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Astronomical Society
Date: 02-04-2019
Publisher: American Astronomical Society
Date: 21-02-2019
Publisher: Oxford University Press (OUP)
Date: 27-06-2020
Abstract: Obtaining accurate distributions of galaxy redshifts is a critical aspect of weak lensing cosmology experiments. One of the methods used to estimate and validate redshift distributions is to apply weights to a spectroscopic s le, so that their weighted photometry distribution matches the target s le. In this work, we estimate the selection bias in redshift that is introduced in this procedure. We do so by simulating the process of assembling a spectroscopic s le (including observer-assigned confidence flags) and highlight the impacts of spectroscopic target selection and redshift failures. We use the first year (Y1) weak lensing analysis in Dark Energy Survey (DES) as an ex le data set but the implications generalize to all similar weak lensing surveys. We find that using colour cuts that are not available to the weak lensing galaxies can introduce biases of up to Δz ∼ 0.04 in the weighted mean redshift of different redshift intervals (Δz ∼ 0.015 in the case most relevant to DES). To assess the impact of incompleteness in spectroscopic s les, we select only objects with high observer-defined confidence flags and compare the weighted mean redshift with the true mean. We find that the mean redshift of the DES Y1 weak lensing s le is typically biased at the Δz = 0.005−0.05 level after the weighting is applied. The bias we uncover can have either sign, depending on the s les and redshift interval considered. For the highest redshift bin, the bias is larger than the uncertainties in the other DES Y1 redshift calibration methods, justifying the decision of not using this method for the redshift estimations. We discuss several methods to mitigate this bias.
Publisher: Oxford University Press (OUP)
Date: 19-02-2019
DOI: 10.1093/MNRAS/STZ463
Publisher: Oxford University Press (OUP)
Date: 03-06-2022
Abstract: Cosmological analyses of s les of photometrically identified type Ia supernovae (SNe Ia) depend on understanding the effects of ‘contamination’ from core-collapse and peculiar SN Ia events. We employ a rigorous analysis using the photometric classifier SuperNNova on state-of-the-art simulations of SN s les to determine cosmological biases due to such ‘non-Ia’ contamination in the Dark Energy Survey (DES) 5-yr SN s le. Depending on the non-Ia SN models used in the SuperNNova training and testing s les, contamination ranges from 0.8 to 3.5 per cent, with a classification efficiency of 97.7–99.5 per cent. Using the Bayesian Estimation Applied to Multiple Species (BEAMS) framework and its extension BBC (‘BEAMS with Bias Correction’), we produce a redshift-binned Hubble diagram marginalized over contamination and corrected for selection effects, and use it to constrain the dark energy equation-of-state, w. Assuming a flat universe with Gaussian ΩM prior of 0.311 ± 0.010, we show that biases on w are & .008 when using SuperNNova, with systematic uncertainties associated with contamination around 10 per cent of the statistical uncertainty on w for the DES-SN s le. An alternative approach of discarding contaminants using outlier rejection techniques (e.g. Chauvenet’s criterion) in place of SuperNNova leads to biases on w that are larger but still modest (0.015–0.03). Finally, we measure biases due to contamination on w0 and wa (assuming a flat universe), and find these to be & .009 in w0 and & .108 in wa, 5 to 10 times smaller than the statistical uncertainties for the DES-SN s le.
Publisher: Oxford University Press (OUP)
Date: 11-01-2023
Abstract: We present the luminosity functions and host galaxy properties of the Dark Energy Survey (DES) core-collapse supernova (CCSN) s le, consisting of 69 Type II and 50 Type Ibc spectroscopically and photometrically confirmed supernovae over a redshift range 0.045 & z & 0.25. We fit the observed DES griz CCSN light curves and K-correct to produce rest-frame R-band light curves. We compare the s le with lower redshift CCSN s les from Zwicky Transient Facility (ZTF) and Lick Observatory Supernova Search (LOSS). Comparing luminosity functions, the DES and ZTF s les of SNe II are brighter than that of LOSS with significances of 3.0σ and 2.5σ, respectively. While this difference could be caused by redshift evolution in the luminosity function, simpler explanations such as differing levels of host extinction remain a possibility. We find that the host galaxies of SNe II in DES are on average bluer than in ZTF, despite having consistent stellar mass distributions. We consider a number of possibilities to explain this – including galaxy evolution with redshift, selection biases in either the DES or ZTF s les, and systematic differences due to the different photometric bands available – but find that none can easily reconcile the differences in host colour between the two s les and thus its cause remains uncertain.
Publisher: Oxford University Press (OUP)
Date: 23-06-2022
Abstract: We measure the velocity dispersions of clusters of galaxies selected by the red-sequence Matched-filter Probabilistic Percolation (redMaPPer) algorithm in the first three years of data from the Dark Energy Survey (DES), allowing us to probe cluster selection and richness estimation, λ, in light of cluster dynamics. Our s le consists of 126 clusters with sufficient spectroscopy for in idual velocity dispersion estimates. We examine the correlations between cluster velocity dispersion, richness, X-ray temperature, and luminosity, as well as central galaxy velocity offsets. The velocity dispersion–richness relation exhibits a bimodal distribution. The majority of clusters follow scaling relations between velocity dispersion, richness, and X-ray properties similar to those found for previous s les however, there is a significant population of clusters with velocity dispersions that are high for their richness. These clusters account for roughly 22 per cent of the λ & 70 systems in our s le, but more than half (55 per cent) of λ & 70 clusters at z & 0.5. A couple of these systems are hot and X-ray bright as expected for massive clusters with richnesses that appear to have been underestimated, but most appear to have high velocity dispersions for their X-ray properties likely due to line-of-sight structure. These results suggest that projection effects contribute significantly to redMaPPer selection, particularly at higher redshifts and lower richnesses. The redMaPPer determined richnesses for the velocity dispersion outliers are consistent with their X-ray properties, but several are X-ray undetected and deeper data are needed to understand their nature.
Publisher: American Astronomical Society
Date: 30-07-2018
Publisher: Elsevier BV
Date: 10-2018
Publisher: American Astronomical Society
Date: 20-10-2022
Abstract: The Dark Energy Spectroscopic Instrument (DESI) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3.°2 diameter prime-focus corrector a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0.″1 and a median signal-to-noise ratio of 7 of the [O ii ] doublet at 8 × 10 −17 erg s −1 cm −2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned.
Publisher: Oxford University Press (OUP)
Date: 20-10-2014
Publisher: Oxford University Press (OUP)
Date: 20-10-2022
Abstract: We use stacked spectra of the host galaxies of photometrically identified Type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) to search for correlations between Hubble diagram residuals and the spectral properties of the host galaxies. Utilizing full spectrum fitting techniques on stacked spectra binned by Hubble residual, we find no evidence for trends between Hubble residuals and properties of the host galaxies that rely on spectral absorption features (& .3σ), such as stellar population age, metallicity, and mass-to-light ratio. However, we find significant trends between the Hubble residuals and the strengths of [O ii] (4.4σ) and the Balmer emission lines (3σ). These trends are weaker than the well-known trend between Hubble residuals and host galaxy stellar mass (7.2σ) that is derived from broad-band photometry. After light-curve corrections, we see fainter SNe Ia residing in galaxies with larger line strengths. We also find a trend (3σ) between Hubble residual and the Balmer decrement (a measure of reddening by dust) using H β and H γ. The trend, quantified by correlation coefficients, is slightly more significant in the redder SNe Ia, suggesting that the bluer SNe Ia are relatively unaffected by dust in the interstellar medium of the host and that dust contributes to current Hubble diagram scatter impacting the measurement of cosmological parameters.
Publisher: Oxford University Press (OUP)
Date: 27-10-2021
Abstract: In this paper, we present and validate the galaxy s le used for the analysis of the baryon acoustic oscillation (BAO) signal in the Dark Energy Survey (DES) Y3 data. The definition is based on a colour and redshift-dependent magnitude cut optimized to select galaxies at redshifts higher than 0.5, while ensuring a high-quality determination. The s le covers ${\\sim }\\, 4100$ deg2to a depth of i = 22.3 (AB) at 10σ. It contains 7031 993 galaxies in the redshift range from $z$ = 0.6 to 1.1, with a mean effective redshift of 0.835. Redshifts are estimated with the machine learning algorithm dnf, and are validated using the VIPERS PDR2 s le. We find a mean redshift bias of $z_{\\mathrm{bias}} {\\sim }\\, 0.01$ and a mean uncertainty, in units of 1 + $z$, of $\\sigma _{68} {\\sim }\\, 0.03$. We evaluate the galaxy population of the s le, showing it is mostly built upon Elliptical to Sbc types. Furthermore, we find a low level of stellar contamination of $\\lesssim 4{{\\ \\rm per\\ cent}}$. We present the method used to mitigate the effect of spurious clustering coming from observing conditions and other large-scale systematics. We apply it to the BAO s le and calculate weights that are used to get a robust estimate of the galaxy clustering signal. This paper is one of a series dedicated to the analysis of the BAO signal in DES Y3. In the companion papers, we present the galaxy mock catalogues used to calibrate the analysis and the angular diameter distance constraints obtained through the fitting to the BAO scale.
Publisher: American Astronomical Society
Date: 26-11-2018
Publisher: Oxford University Press (OUP)
Date: 05-05-2020
Abstract: The distribution of cosmological neutral hydrogen will provide a new window into the large-scale structure of the Universe with the next generation of radio telescopes and surveys. The observation of this material, through 21 cm line emission, will be confused by foreground emission in the same frequencies. Even after these foregrounds are removed, the reconstructed map may not exactly match the original cosmological signal, which will introduce systematic errors and offset into the measured correlations. In this paper, we simulate future surveys of neutral hydrogen using the Horizon Run 4 (HR4) cosmological N-body simulation. We generate H i intensity maps from the HR4 halo catalogue, and combine with foreground radio emission maps from the Global Sky Model, to create accurate simulations over the entire sky. We simulate the H i sky for the frequency range 700–800 MHz, matching the sensitivity of the Tianlai pathfinder. We test the accuracy of the fastICA, PCA, and log-polynomial fitting foreground removal methods to recover the input cosmological angular power spectrum and measure the parameters. We show the effect of survey noise levels and beam sizes on the recovered the cosmological constraints. We find that while the reconstruction removes power from the cosmological 21 cm distribution on large scales, we can correct for this and recover the input parameters in the noise-free case. However, the effect of noise and beam size of the Tianlai pathfinder prevents accurate recovery of the cosmological parameters when using only intensity mapping information.
Publisher: Royal Society of Chemistry (RSC)
Date: 17-09-2014
DOI: 10.1039/C4CP03298E
Abstract: An experimental study of Xe and Kr adsorption in metal-organic frameworks CPO-27-Ni, CPO-27-Mg, and ZIF-8 was carried out. In situ synchrotron X-ray powder diffraction experiments allowed precise determination of the adsorption sites and sequence of their filling with increasing of gas pressure at different temperatures. Structural investigations were used for interpretation of gas adsorption measurements.
Publisher: Oxford University Press (OUP)
Date: 20-11-2012
Publisher: American Astronomical Society
Date: 18-11-2020
Publisher: Wiley
Date: 22-01-2020
DOI: 10.1002/BSE.2468
Publisher: Oxford University Press (OUP)
Date: 18-04-2018
DOI: 10.1093/MNRAS/STY957
Publisher: Oxford University Press (OUP)
Date: 08-07-2021
Abstract: The use of continuum emission radio galaxies as cosmological tracers of the large-scale structure will soon move into a new phase. Upcoming surveys from the Australian Square Kilometre Array Pathfinder (ASKAP), MeerKAT, and the Square Kilometre Array project (SKA) will survey the entire available sky down to an $\\sim 100\\, \\mu$Jy flux limit, increasing the number of detected extra-galactic radio sources by several orders of magnitude. External data and machine learning algorithms will also enable some low-resolution radial selection (photometric redshift binning) of the s le, increasing the cosmological utility of the s le observed. In this paper, we discuss the flux limit required to detect enough galaxies to decrease the shot-noise term in the error to be 10 per cent of the total. We show how future surveys of this type will be limited by available technology. The confusion generated by the intrinsic sizes of galaxies may have the consequence that surveys of this type eventually reach a hard flux limit of ∼100 nJy, as is predicted by the current modelling of AGN sizes by simulations such as the Tiered Radio Extragalactic Continuum Simulation (T-RECS). Finally, when considering the multitracer approach, where galaxies are split by type to measure some bias ratio, we find that there are not enough AGN present to achieve a reasonable level of shot noise for this kind of measurement.
Publisher: National Library of Serbia
Date: 2021
Abstract: Introduction/Objective. Essential Science Indicators (ESI) Highly Cited Papers (HCPs) refer to the most influential scientific articles and breakthrough research within a research field in the past decade. This study aimed to identify the characteristics of ESI HCPs in the subject category Dentistry, Oral Surgery and Medicine, to recognize authors, institutions and countries of origin, and determine research trends that attracted the most scientific interest in dentistry. Methods. A descriptive analysis of bibliographic data, network extraction and visualization were completed. Furthermore, analyzed ESI HCPs were classified according to a field of interest, main research domain, type of study, and level of evidence. Results. The set of 185 dental HCPs was published in 42 journals from 2010 to 2020, with an average number of 211.7 citations per paper. Nearly half of HCPs were issued by the Journal of Dental Research, Dental Materials, and Journal of Clinical Periodontology. There were 765 authors affiliated with 351 institutions from 42 countries. The most productive institutions were the University of Hong Kong, the University of Michigan, and the University of Bern. The United States of America contributed with the highest number of publications, followed by China, and the United Kingdom. Dental materials, dental implantology, periodontology, and oral and maxillofacial surgery represented areas of significant interest within this subject category. The highest proportion of HCPs were narrative and systematic reviews, expert opinions, consensus reports, and in vitro ?r lab studies. Conclusion. Results obtained from this study can provide valuable information for researchers to better identify present and future hotspots in dental research.
Publisher: Oxford University Press (OUP)
Date: 23-10-2021
Abstract: We present the statistical methods that have been developed to analyse the OzDES reverberation mapping s le. To perform this statistical analysis we have created a suite of customizable simulations that mimic the characteristics of each source in the OzDES s le. These characteristics include: the variability in the photometric and spectroscopic light curves, the measurement uncertainties, and the observational cadence. By simulating the sources in the OzDES s le that contain the C iv emission line, we developed a set of criteria that rank the reliability of a recovered time-lag depending on the agreement between different recovery methods, the magnitude of the uncertainties, and the rate at which false positives were found in the simulations. These criteria were applied to simulated light curves and these results used to estimate the quality of the resulting Radius–Luminosity relation. We grade the results using three quality levels (gold, silver, and bronze). The input slope of the R–L relation was recovered within 1σ for each of the three quality s les, with the gold standard having the lowest dispersion with a recovered a R–L relation slope of 0.454 ± 0.016 with an input slope of 0.47. Future work will apply these methods to the entire OzDES s le of 771 AGN.
Publisher: Oxford University Press (OUP)
Date: 22-02-2018
DOI: 10.1093/MNRAS/STY466
Publisher: Oxford University Press (OUP)
Date: 26-10-2022
Abstract: Cosmological analyses with type Ia supernovae (SNe Ia) often assume a single empirical relation between colour and luminosity (β) and do not account for varying host-galaxy dust properties. However, from studies of dust in large s les of galaxies, it is known that dust attenuation can vary significantly. Here, we take advantage of state-of-the-art modelling of galaxy properties to characterize dust parameters (dust attenuation AV, and a parameter describing the dust law slope RV) for 1100 Dark Energy Survey (DES) SN host galaxies. Utilizing optical and infrared data of the hosts alone, we find three key aspects of host dust that impact SN cosmology: (1) there exists a large range (∼1–6) of host RV (2) high-stellar mass hosts have RV on average ∼0.7 lower than that of low-mass hosts (3) for a subs le of 81 spectroscopically classified SNe there is a significant (& σ) correlation between the Hubble diagram residuals of red SNe Ia and the host RV that when corrected for reduces scatter by $\\sim 13{{\\ \\rm per\\ cent}}$ and the significance of the ‘mass step’ to ∼1σ. These represent independent confirmations of recent predictions based on dust that attempted to explain the puzzling ‘mass step’ and intrinsic scatter (σint) in SN Ia analyses.
Publisher: American Astronomical Society
Date: 10-2022
Abstract: Current and future cosmological analyses with Type Ia supernovae (SNe Ia) face three critical challenges: (i) measuring the redshifts from the SNe or their host galaxies (ii) classifying the SNe without spectra and (iii) accounting for correlations between the properties of SNe Ia and their host galaxies. We present here a novel approach that addresses each of these challenges. In the context of the Dark Energy Survey (DES), we analyze an SN Ia s le with host galaxies in the redMaGiC galaxy catalog, a selection of luminous red galaxies. redMaGiC photo- z estimates are expected to be accurate to σ Δ z /(1+ z ) ∼ 0.02. The DES-5YR photometrically classified SN Ia s le contains approximately 1600 SNe, and 125 of these SNe are in redMaGiC galaxies. We demonstrate that redMaGiC galaxies almost exclusively host SNe Ia, reducing concerns relating to classification uncertainties. With this subs le, we find similar Hubble scatter (to within ∼0.01 mag) using photometric redshifts in place of spectroscopic redshifts. With detailed simulations, we show that the bias due to using redMaGiC photo- z s on the measurement of the dark energy equation of state w is up to Δ w ∼ 0.01–0.02. With real data, we measure a difference in w when using the redMaGiC photo- z s versus the spec- z s of Δ w = 0.005. Finally, we discuss how SNe in redMaGiC galaxies appear to comprise a more standardizable population, due to a weaker relation between color and luminosity ( β ) compared to the DES-3YR population by ∼5 σ . These results establish the feasibility of performing redMaGiC SN cosmology with photometric survey data in the absence of spectroscopic data.
Publisher: Oxford University Press (OUP)
Date: 04-11-2020
Abstract: We explore the cosmological multitracer synergies between an emission-line galaxy distribution from the Dark Energy Spectroscopic Instrument and a Tianlai Project 21-cm intensity map. We use simulated maps generated from a particle simulation in the light-cone volume (Horizon Run 4), sky-trimmed and including the effects of foreground contamination, its removal and instrument noise. We first validate how the foreground residual affects the recovered 21-cm signal by putting different levels of foreground contamination into the 21-cm maps. We find that the contamination cannot be ignored in the angular autocorrelation power spectra of H i even when it is small, but it has no influence on the accuracy of the angular cross-correlation power spectra between H i and galaxies. In the foreground-cleaned map case, as information is lost in the cleaning procedure, there is also a bias in the cross-correlation power spectrum. However, we found that the bias from the cross-correlation power spectrum is scale-independent, which is easily parametrized as part of the model, while the offset in the H i autocorrelation power spectrum is non-linear. In particular, we tested that the cross-correlation power also benefits from the cancellation of the bias in the power spectrum measurement that is induced by the instrument noise, which changes the shape of the autocorrelation power spectra but leaves the cross-correlation power spectra unaffected. We then modelled the angular cross-correlation power spectra to fit the baryon acoustic oscillation feature in the broad-band shape of the angular cross-correlation power spectrum, including contamination from the residual foreground and the effect of instrument noise. We forecast a constraint on the angular diameter distance DA for the Tianlai Pathfinder redshift 0.775 & z & 1.03, giving a distance measurement with a precision of 2.7 per cent at that redshift.
Publisher: American Physical Society (APS)
Date: 23-11-2015
Publisher: Oxford University Press (OUP)
Date: 29-07-2022
Abstract: The evolution of the gravitational potentials on large scales due to the accelerated expansion of the Universe is an important and independent probe of dark energy, known as the integrated Sachs–Wolfe (ISW) effect. We measure this ISW effect through cross-correlating the cosmic microwave background maps from the Planck satellite with a radio continuum galaxy distribution map from the recent Rapid ASKAP Continuum Survey (RACS). We detect a positive cross-correlation at $\\sim 2.8\\, \\sigma$ relative to the null hypothesis of no correlation. We parametrize the strength of the ISW effect through an litude parameter and find the constraints to be $A_{\\mathrm{ISW}} = 0.94^{+0.42}_{-0.41}$, which is consistent with the prediction of an accelerating universe within the current concordance cosmological model, ΛCDM. The credible interval on this parameter is independent of the different bias models and redshift distributions that were considered when marginalizing over the nuisance parameters. We also detect a power excess in the galaxy autocorrelation angular power spectrum on large scales (ℓ ≤ 40), and investigate possible systematic causes.
Publisher: Oxford University Press (OUP)
Date: 20-06-2022
Abstract: As part of the cosmology analysis using Type Ia Supernovae (SN Ia) in the Dark Energy Survey (DES), we present photometrically identified SN Ia s les using multiband light curves and host galaxy redshifts. For this analysis, we use the photometric classification framework SuperNNovatrained on realistic DES-like simulations. For reliable classification, we process the DES SN programme (DES-SN) data and introduce improvements to the classifier architecture, obtaining classification accuracies of more than 98 per cent on simulations. This is the first SN classification to make use of ensemble methods, resulting in more robust s les. Using photometry, host galaxy redshifts, and a classification probability requirement, we identify 1863 SNe Ia from which we select 1484 cosmology-grade SNe Ia spanning the redshift range of 0.07 & z & 1.14. We find good agreement between the light-curve properties of the photometrically selected s le and simulations. Additionally, we create similar SN Ia s les using two types of Bayesian Neural Network classifiers that provide uncertainties on the classification probabilities. We test the feasibility of using these uncertainties as indicators for out-of-distribution candidates and model confidence. Finally, we discuss the implications of photometric s les and classification methods for future surveys such as Vera C. Rubin Observatory Legacy Survey of Space and Time.
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2022.48
Publisher: Oxford University Press (OUP)
Date: 26-07-2017
Publisher: Oxford University Press (OUP)
Date: 16-01-2023
Abstract: Reverberation mapping measurements have been used to constrain the relationship between the size of the broad-line region and luminosity of active galactic nuclei (AGN). This R–L relation is used to estimate single-epoch virial black hole masses, and has been proposed to use to standardize AGN to determine cosmological distances. We present reverberation measurements made with Hβ from the 6-yr Australian Dark Energy Survey (OzDES) Reverberation Mapping Program. We successfully recover reverberation lags for eight AGN at 0.12 & z & 0.71, probing higher redshifts than the bulk of Hβ measurements made to date. Our fit to the R–L relation has a slope of α = 0.41 ± 0.03 and an intrinsic scatter of σ = 0.23 ± 0.02 dex. The results from our multi-object spectroscopic survey are consistent with previous measurements made by dedicated source-by-source c aigns, and with the observed dependence on accretion rate. Future surveys, including LSST, TiDES, and SDSS-V, which will be revisiting some of our observed fields, will be able to build on the results of our first-generation multi-object reverberation mapping survey.
Publisher: American Physical Society (APS)
Date: 08-02-2022
Publisher: Oxford University Press (OUP)
Date: 30-05-3202
Abstract: We present a description of the Australian Dark Energy Survey (OzDES) and summarize the results from its 6 years of operations. Using the 2dF fibre positioner and AAOmega spectrograph on the 3.9-m Anglo-Australian Telescope, OzDES has monitored 771 active galactic nuclei, classified hundreds of supernovae, and obtained redshifts for thousands of galaxies that hosted a transient within the 10 deep fields of the Dark Energy Survey. We also present the second OzDES data release, containing the redshifts of almost 30 000 sources, some as faint as rAB = 24 mag, and 375 000 in idual spectra. These data, in combination with the time-series photometry from the Dark Energy Survey, will be used to measure the expansion history of the Universe out to z ∼ 1.2 and the masses of hundreds of black holes out to z ∼ 4. OzDES is a template for future surveys that combine simultaneous monitoring of targets with wide-field imaging cameras and wide-field multi-object spectrographs.
Publisher: IOP Publishing
Date: 2022
DOI: 10.1088/1475-7516/2022/01/020
Abstract: We present forecasts on the detectability of Ultra-light axion-like particles (ULAP) from future 21 cm radio observations around the epoch of reionization (EoR). We show that the axion as the dominant dark matter component has a significant impact on the reionization history due to the suppression of small scale density perturbations in the early universe. This behavior depends strongly on the mass of the axion particle. Using numerical simulations of the brightness temperature field of neutral hydrogen over a large redshift range, we construct a suite of training data. This data is used to train a convolutional neural network that can build a connection between the spatial structures of the brightness temperature field and the input axion mass directly. We construct mock observations of the future Square Kilometer Array survey, SKA1-Low, and find that even in the presence of realistic noise and resolution constraints, the network is still able to predict the input axion mass. We find that the axion mass can be recovered over a wide mass range with a precision of approximately 20%, and as the whole DM contribution, the axion can be detected using SKA1-Low at 68% if the axion mass is M X 1.86 × 10 -20 eV although this can decrease to M X 5.25 × 10 -21 eV if we relax our assumptions on the astrophysical modeling by treating those astrophysical parameters as nuisance parameters.
Publisher: Oxford University Press (OUP)
Date: 21-05-2019
Abstract: We present a s le of 21 hydrogen-free superluminous supernovae (SLSNe-I) and one hydrogen-rich SLSN (SLSN-II) detected during the five-year Dark Energy Survey (DES). These SNe, located in the redshift range 0.220 & z & 1.998, represent the largest homogeneously selected s le of SLSN events at high redshift. We present the observed g, r, i, z light curves for these SNe, which we interpolate using Gaussian processes. The resulting light curves are analysed to determine the luminosity function of SLSNe-I, and their evolutionary time-scales. The DES SLSN-I s le significantly broadens the distribution of SLSN-I light-curve properties when combined with existing s les from the literature. We fit a magnetar model to our SLSNe, and find that this model alone is unable to replicate the behaviour of many of the bolometric light curves. We search the DES SLSN-I light curves for the presence of initial peaks prior to the main light-curve peak. Using a shock breakout model, our Monte Carlo search finds that 3 of our 14 events with pre-max data display such initial peaks. However, 10 events show no evidence for such peaks, in some cases down to an absolute magnitude of & −16, suggesting that such features are not ubiquitous to all SLSN-I events. We also identify a red pre-peak feature within the light curve of one SLSN, which is comparable to that observed within SN2018bsz.
Publisher: Oxford University Press (OUP)
Date: 12-2021
Abstract: We present multiwavelength spectral and temporal variability analysis of PKS 0027-426 using optical griz observations from Dark Energy Survey between 2013 and 2018 and VEILS Optical Light curves of Extragalactic TransienT Events (VOILETTE) between 2018 and 2019 and near-infrared (NIR) JKs observations from Visible and Infrared Survey Telescope for Astronomy Extragalactic Infrared Legacy Survey (VEILS) between 2017 and 2019. Multiple methods of cross-correlation of each combination of light curve provides measurements of possible lags between optical–optical, optical–NIR, and NIR–NIR emission, for each observation season and for the entire observational period. Inter-band time lag measurements consistently suggest either simultaneous emission or delays between emission regions on time-scales smaller than the cadences of observations. The colour–magnitude relation between each combination of filters was also studied to determine the spectral behaviour of PKS 0027-426. Our results demonstrate complex colour behaviour that changes between bluer when brighter, stable when brighter, and redder when brighter trends over different time-scales and using different combinations of optical filters. Additional analysis of the optical spectra is performed to provide further understanding of this complex spectral behaviour.
Publisher: Oxford University Press (OUP)
Date: 29-08-2018
Publisher: arXiv
Date: 2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3DT52579A
Abstract: A single-crystal to single-crystal transformable coordination polymer compound was hydrothermally synthesized. The structural rearrangement is induced by selecting a ligand that contains both strong and weaker coordinating groups. Both hydrated and dehydrated structures were determined by single crystal X-ray analysis.
Publisher: EDP Sciences
Date: 02-2021
DOI: 10.1051/0004-6361/202039682
Abstract: We present the first measurements of the projected clustering and intrinsic alignments (IA) of galaxies observed by the Physics of the Accelerating Universe Survey (PAUS). With photometry in 40 narrow optical passbands (4500 Å–8500 Å), the quality of photometric redshift estimation is σ z ∼ 0.01(1 + z ) for galaxies in the 19 deg 2 Canada-France-Hawaii Telescope Legacy Survey W3 field, allowing us to measure the projected 3D clustering and IA for flux-limited, faint galaxies ( i 22.5) out to z ∼ 0.8. To measure two-point statistics, we developed, and tested with mock photometric redshift s les, ‘cloned’ random galaxy catalogues which can reproduce data selection functions in 3D and account for photometric redshift errors. In our fiducial colour-split analysis, we made robust null detections of IA for blue galaxies and tentative detections of radial alignments for red galaxies (∼1 − 3 σ ), over scales of 0.1 − 18 h −1 Mpc. The galaxy clustering correlation functions in the PAUS s les are comparable to their counterparts in a spectroscopic population from the Galaxy and Mass Assembly survey, modulo the impact of photometric redshift uncertainty which tends to flatten the blue galaxy correlation function, whilst steepening that of red galaxies. We investigate the sensitivity of our correlation function measurements to choices in the random catalogue creation and the galaxy pair-binning along the line of sight, in preparation for an optimised analysis over the full PAUS area.
Publisher: Oxford University Press (OUP)
Date: 09-04-2019
DOI: 10.1093/MNRAS/STZ978
Abstract: We present an improved measurement of the Hubble constant (H0) using the ‘inverse distance ladder’ method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) at redshift 0.018 & z & 0.85 to existing distance measurements of 122 low-redshift (z & 0.07) SNe Ia (Low-z) and measurements of Baryon Acoustic Oscillations (BAOs). Whereas traditional measurements of H0 with SNe Ia use a distance ladder of parallax and Cepheid variable stars, the inverse distance ladder relies on absolute distance measurements from the BAOs to calibrate the intrinsic magnitude of the SNe Ia. We find H0 = 67.8 ± 1.3 km s−1 Mpc−1 (statistical and systematic uncertainties, 68 per cent confidence). Our measurement makes minimal assumptions about the underlying cosmological model, and our analysis was blinded to reduce confirmation bias. We examine possible systematic uncertainties and all are below the statistical uncertainties. Our H0 value is consistent with estimates derived from the Cosmic Microwave Background assuming a ΛCDM universe.
Publisher: Oxford University Press (OUP)
Date: 05-08-2021
Abstract: Reverberation mapping is a robust method to measure the masses of supermassive black holes outside of the local Universe. Measurements of the radius–luminosity (R−L) relation using the Mg ii emission line are critical for determining these masses near the peak of quasar activity at z ≈ 1−2, and for calibrating secondary mass estimators based on Mg ii that can be applied to large s les with only single-epoch spectroscopy. We present the first nine Mg ii lags from our 5-yr Australian Dark Energy Survey reverberation mapping programme, which substantially improves the number and quality of Mg ii lag measurements. As the Mg ii feature is somewhat blended with iron emission, we model and subtract both the continuum and iron contamination from the multiepoch spectra before analysing the Mg ii line. We also develop a new method of quantifying correlated spectroscopic calibration errors based on our numerous, contemporaneous observations of F-stars. The lag measurements for seven of our nine sources are consistent with both the H β and Mg ii R−L relations reported by previous studies. Our simulations verify the lag reliability of our nine measurements, and we estimate that the median false positive rate of the lag measurements is $4{{\\ \\rm per\\ cent}}$.
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.42
Abstract: We present the data and initial results from the first pilot survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The survey covers $270 \\,\\mathrm{deg}^2$ of an area covered by the Dark Energy Survey, reaching a depth of 25–30 $\\mu\\mathrm{Jy\\ beam}^{-1}$ rms at a spatial resolution of $\\sim$ 11–18 arcsec, resulting in a catalogue of $\\sim$ 220 000 sources, of which $\\sim$ 180 000 are single-component sources. Here we present the catalogue of single-component sources, together with (where available) optical and infrared cross-identifications, classifications, and redshifts. This survey explores a new region of parameter space compared to previous surveys. Specifically, the EMU Pilot Survey has a high density of sources, and also a high sensitivity to low surface brightness emission. These properties result in the detection of types of sources that were rarely seen in or absent from previous surveys. We present some of these new results here.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3DT52385C
Abstract: There are only limited reports on vanadium(iv) oxyfluorides (VOFs) with extended crystal structures. Here we expand and enrich the list of existing VOFs with a series of 14 new materials "VOF-n (n = 1-14)" prepared using ionothermal and solvothermal synthesis methods. All of these materials arise from the condensation of a dimeric structural motif. These VOFs can be classified into three groups depending on their key structural features layer structures: VOF-1"[HN2C7H6][V2O2F5]", VOF-2"[HN2C4H4][V2O2F5]", VOF-3"[HN2C3H4][V2O2F5]" and VOF-4"V2(N2C4H4)O2F4", ladder like structures: VOF-5"[NH4(HN2C3H4)][V2O2F6]", VOF-6"[K(HN2C3H4)][V2O2F6]", VOF-7"[HNH2CH2CH3][VOF3]", VOF-8"[HN2C7H6][VOF3]", VOF-9"[H2N2C4H6][V2O2F6]", VOF-10"β-RbVOF3", VOF-11"α-KVOF3", VOF-12"β-KVOF3", VOF-13"[H2(NH2)2(CH2)2][V2O2F6]", and a chain structure: VOF-14"[H2N2C6H12][V2O2F7]". The crystal structures of VOF-n are presented, and their synthetic and structural relationships are discussed.
Publisher: Oxford University Press (OUP)
Date: 28-03-2016
DOI: 10.1093/MNRAS/STW721
Location: Spain
Location: Korea, Republic of
Location: United States of America
Start Date: 2009
End Date: 2013
Funder: Consejo Superior de Investigaciones Científicas
View Funded ActivityStart Date: 2013
End Date: 2016
Funder: U.S. Department of Energy
View Funded ActivityStart Date: 2016
End Date: 2018
Funder: Australian Research Council
View Funded Activity