1. |
- de Jong, R. S., et al.
(author)
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4MOST : Project overview and information for the First Call for Proposals
- 2019
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In: The Messenger. - : European Southern Observatory. - 0722-6691. ; 175, s. 3-11
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Journal article (other academic/artistic)abstract
- We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (R = λ/Δλ ~ 6500), and 812 fibres transferring light to the high-resolution spectrograph (R ~ 20 000). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations.
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2. |
- Bacon, David J., et al.
(author)
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Cosmology with Phase 1 of the Square Kilometre Array Red Book 2018 : Technical specifications and performance forecasts
- 2020
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In: Publications Astronomical Society of Australia. - : Cambridge University Press (CUP). - 1323-3580 .- 1448-6083. ; 37
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Journal article (peer-reviewed)abstract
- We present a detailed overview of the cosmological surveys that we aim to carry out with Phase 1 of the Square Kilometre Array (SKA1) and the science that they will enable. We highlight three main surveys: a medium-deep continuum weak lensing and low-redshift spectroscopic HI galaxy survey over 5 000 deg2; a wide and deep continuum galaxy and HI intensity mapping (IM) survey over 20 000 deg2 from z = 0.35 to 3; and a deep, high-redshift HI IM survey over 100 deg2 from z = 3 to 6. Taken together, these surveys will achieve an array of important scientific goals: measuring the equation of state of dark energy out to z = 3 with percent-level precision measurements of the cosmic expansion rate; constraining possible deviations from General Relativity on cosmological scales by measuring the growth rate of structure through multiple independent methods; mapping the structure of the Universe on the largest accessible scales, thus constraining fundamental properties such as isotropy, homogeneity, and non-Gaussianity; and measuring the HI density and bias out to z = 6. These surveys will also provide highly complementary clustering and weak lensing measurements that have independent systematic uncertainties to those of optical and near-infrared (NIR) surveys like Euclid, LSST, and WFIRST leading to a multitude of synergies that can improve constraints significantly beyond what optical or radio surveys can achieve on their own. This document, the 2018 Red Book, provides reference technical specifications, cosmological parameter forecasts, and an overview of relevant systematic effects for the three key surveys and will be regularly updated by the Cosmology Science Working Group in the run up to start of operations and the Key Science Programme of SKA1.
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3. |
- Binggeli, Christian, 1989-
(author)
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Galaxies in the epoch of reionization : Investigating the high-redshift galaxy population through simulations and observations
- 2021
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Doctoral thesis (other academic/artistic)abstract
- The cosmic reionization is the last major gas phase transition in cosmic history, yet it remains poorly understood. Current constraints indicate that early star-forming galaxies drove the reionization process through producing and releasing large numbers of ionizing photons into the intergalactic medium. However, our understanding of the ionizing escape fraction (fesc) and the general properties of high-redshift galaxies is still limited.In this thesis, simulated galaxies and observations are used to investigate epoch-of-reionization galaxies and to explore methods that can aid future investigations of such objects. Using simulations, we have shown that it may be possible to constrain fesc in epoch-of-reionization galaxies using quite simple diagnostics that should be observable with the upcoming James Webb Space Telescope (JWST). We also show that variations in star formation activity larger than those predicted in our simulations may lead to a possible degeneracy with high fesc. However, auxiliary information obtained with the JWST may allow us to disentangle variations in the star formation activity from high fesc.We compare galaxies from several simulations to the recently spectroscopically confirmed z=9.1096 galaxy MACS1149-JD1. We find that none of the simulations are able to reproduce the large Balmer break observed in MACS1149-JD1, and argue that unless it represents an outlier in the high-redshift galaxy population, this may indicate that the simulations fail to capture some key physics. Finally, we present ALMA observations of the z=7.6637 galaxy z7_GSD_3811. This object remains undetected in several commonly detected FIR emission lines and FIR dust emission. Using SED-fitting and by comparing our observations to models and low-redshift observations, we show that our non-detections could indicate that the object is poor in metals and dust.Our findings could help future observers to further constrain the nature of high-redshift galaxies and their role in reionization.
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4. |
- Contarini, S., et al.
(author)
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Euclid : cosmological forecasts from the void size function
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 667
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Journal article (peer-reviewed)abstract
- The Euclid mission - with its spectroscopic galaxy survey covering a sky area over 15 000 deg(2) in the redshift range 0.9 < z < 1.8 - will provide a sample of tens of thousands of cosmic voids. This paper thoroughly explores for the first time the constraining power of the void size function on the properties of dark energy (DE) from a survey mock catalogue, the official Euclid Flagship simulation. We identified voids in the Flagship light-cone, which closely matches the features of the upcoming Euclid spectroscopic data set. We modelled the void size function considering a state-of-the art methodology: we relied on the volume-conserving (Vdn) model, a modification of the popular Sheth & van de Weygaert model for void number counts, extended by means of a linear function of the large-scale galaxy bias. We found an excellent agreement between model predictions and measured mock void number counts. We computed updated forecasts for the Euclid mission on DE from the void size function and provided reliable void number estimates to serve as a basis for further forecasts of cosmological applications using voids. We analysed two different cosmological models for DE: the first described by a constant DE equation of state parameter, w, and the second by a dynamic equation of state with coefficients w(0) and w(a). We forecast 1 sigma errors on w lower than 10% and we estimated an expected figure of merit (FoM) for the dynamical DE scenario FoM(w0,wa) = 17 when considering only the neutrino mass as additional free parameter of the model. The analysis is based on conservative assumptions to ensure full robustness, and is a pathfinder for future enhancements of the technique. Our results showcase the impressive constraining power of the void size function from the Euclid spectroscopic sample, both as a stand-alone probe, and to be combined with other Euclid cosmological probes.
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5. |
- Farahi, A., et al.
(author)
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Mass variance from archival X-ray properties of Dark Energy Survey Year-1 galaxy clusters
- 2019
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In: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 490:3, s. 3341-3354
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Journal article (peer-reviewed)abstract
- Using archival X-ray observations and a lognormal population model, we estimate constraints on the intrinsic scatter in halo mass at fixed optical richness for a galaxy cluster sample identified in Dark Energy Survey Year-One (DES-Y1) data with the redMaPPer algorithm. We examine the scaling behaviour of X-ray temperatures, T-X, with optical richness, lambda(RM), for clusters in the redshift range 0.2 < z < 0.7. X-ray temperatures are obtained from Chandra and XMM observations for 58 and 110 redMaPPer systems, respectively. Despite non-uniform sky coverage, the T-X measurements are > 50 per cent complete for clusters with lambda(RM) > 130. Regression analysis on the two samples produces consistent posterior scaling parameters, from which we derive a combined constraint on the residual scatter, sigma(ln) (T) (vertical bar) (lambda) = 0.275 +/- 0.019. Joined with constraints for T-X scaling with halo mass from the Weighing the Giants program and richness-temperature covariance estimates from the LoCuSS sample, we derive the richness-conditioned scatter in mass, sigma(ln) (M) (vertical bar) (lambda) = 0.30 +/- 0.04((stat)) +/- 0.09((sys)), at an optical richness of approximately 100. Uncertainties in external parameters, particularly the slope and variance of the T-X-mass relation and the covariance of T-X and lambda(RM) at fixed mass, dominate the systematic error. The 95 per cent confidence region from joint sample analysis is relatively broad, sigma(ln) (M) (vertical bar) (lambda) is an element of [0.14, 0.55], or a factor 10 in variance.
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6. |
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7. |
- Hamaus, N., et al.
(author)
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Euclid : Forecasts from redshift-space distortions and the Alcock-Paczynski test with cosmic voids
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658
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Journal article (peer-reviewed)abstract
- Euclid is poised to survey galaxies across a cosmological volume of unprecedented size, providing observations of more than a billion objects distributed over a third of the full sky. Approximately 20 million of these galaxies will have their spectroscopy available, allowing us to map the three-dimensional large-scale structure of the Universe in great detail. This paper investigates prospects for the detection of cosmic voids therein and the unique benefit they provide for cosmological studies. In particular, we study the imprints of dynamic (redshift-space) and geometric (Alcock-Paczynski) distortions of average void shapes and their constraining power on the growth of structure and cosmological distance ratios. To this end, we made use of the Flagship mock catalog, a state-of-the-art simulation of the data expected to be observed with Euclid. We arranged the data into four adjacent redshift bins, each of which contains about 11000 voids and we estimated the stacked void-galaxy cross-correlation function in every bin. Fitting a linear-theory model to the data, we obtained constraints on f/b and DMH, where f is the linear growth rate of density fluctuations, b the galaxy bias, D-M the comoving angular diameter distance, and H the Hubble rate. In addition, we marginalized over two nuisance parameters included in our model to account for unknown systematic effects in the analysis. With this approach, Euclid will be able to reach a relative precision of about 4% on measurements of f/b and 0.5% on DMH in each redshift bin. Better modeling or calibration of the nuisance parameters may further increase this precision to 1% and 0.4%, respectively. Our results show that the exploitation of cosmic voids in Euclid will provide competitive constraints on cosmology even as a stand-alone probe. For example, the equation-of-state parameter, w, for dark energy will be measured with a precision of about 10%, consistent with previous more approximate forecasts.
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8. |
- Manolopoulou, M., et al.
(author)
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Environmental dependence of X-ray and optical properties of galaxy clusters
- 2021
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 500:2, s. 1953-1963
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Journal article (peer-reviewed)abstract
- Galaxy clusters are widely used to constrain cosmological parameters through their properties, such as masses, luminosity, and temperature distributions. One should take into account all kind of biases that could affect these analyses in order to obtain reliable constraints. In this work, we study the difference in the properties of clusters residing in different large-scale environments, defined by their position within or outside of voids, and the density of their surrounding space. We use both observational and simulation cluster and void catalogues, i.e. XMM Cluster Survey (XCS) and redMaPPer clusters, Baryon Oscillation Spectroscopic Survey (BOSS) voids, and Magneticum simulations. We devise two different environmental proxies for the clusters and study their redshift, richness, mass, X-ray luminosity, and temperature distributions, as well as some properties of their galaxy populations. We use the Kolmogorov-Smirnov two-sample test to discover that richer and more massive clusters are more prevalent in overdense regions and outside of voids. We also find that clusters of matched richness and mass in overdense regions and outside voids tend to have higher X-ray luminosities and temperatures. These differences could have important implications for precision cosmology with clusters of galaxies, since cluster mass calibrations can vary with environment.
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9. |
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10. |
- Palmese, A., et al.
(author)
-
Stellar mass as a galaxy cluster mass proxy : application to the Dark Energy Survey redMaPPer clusters
- 2020
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In: \mnras. - : Oxford University Press (OUP). ; 493:4, s. 4591-4606
-
Journal article (peer-reviewed)abstract
- We introduce a galaxy cluster mass observable, μ⋆, based on the stellar masses of cluster members, and we present results for the Dark Energy Survey (DES) Year 1 (Y1) observations. Stellar masses are computed using a Bayesian model averaging method, and are validated for DES data using simulations and COSMOS data. We show that μ⋆ works as a promising mass proxy by comparing our predictions to X-ray measurements. We measure the X-ray temperature–μ⋆ relation for a total of 129 clusters matched between the wide-field DES Y1 redMaPPer catalogue and Chandra and XMM archival observations, spanning the redshift range 0.1 < z < 0.7. For a scaling relation that is linear in logarithmic space, we find a slope of α = 0.488 ± 0.043 and a scatter in the X-ray temperature at fixed μ⋆ of σlnTX|μ⋆=0.266+0.019−0.020 for the joint sample. By using the halo mass scaling relations of the X-ray temperature from the Weighing the Giants program, we further derive the μ⋆-conditioned scatter in mass, finding σlnM|μ⋆=0.26+0.15−0.10. These results are competitive with well-established cluster mass proxies used for cosmological analyses, showing that μ⋆ can be used as a reliable and physically motivated mass proxy to derive cosmological constraints.
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11. |
- Pezzotta, A., et al.
(author)
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Euclid preparation XLI. Galaxy power spectrum modelling in real space
- 2024
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 687
-
Journal article (peer-reviewed)abstract
- We investigate the accuracy of the perturbative galaxy bias expansion in view of the forthcoming analysis of the Euclid spectroscopic galaxy samples. We compare the performance of a Eulerian galaxy bias expansion using state-of-the-art prescriptions from the effective field theory of large-scale structure (EFTofLSS) with a hybrid approach based on Lagrangian perturbation theory and high-resolution simulations. These models are benchmarked against comoving snapshots of the flagship I N-body simulation at z = (0.9, 1.2, 1.5, 1.8), which have been populated with H alpha galaxies leading to catalogues of millions of objects within a volume of about 58 h(-3) Gpc(3). Our analysis suggests that both models can be used to provide a robust inference of the parameters (h, omega c) in the redshift range under consideration, with comparable constraining power. We additionally determine the range of validity of the EFTofLSS model in terms of scale cuts and model degrees of freedom. From these tests, it emerges that the standard third-order Eulerian bias expansion - which includes local and non-local bias parameters, a matter counter term, and a correction to the shot-noise contribution - can accurately describe the full shape of the real-space galaxy power spectrum up to the maximum wavenumber of k(max) = 0.45 h Mpc(-1), and with a measurement precision of well below the percentage level. Fixing either of the tidal bias parameters to physically motivated relations still leads to unbiased cosmological constraints, and helps in reducing the severity of projection effects due to the large dimensionality of the model. We finally show how we repeated our analysis assuming a volume that matches the expected footprint of Euclid, but without considering observational effects, such as purity and completeness, showing that we can get constraints on the combination (h, omega c) that are consistent with the fiducial values to better than the 68% confidence interval over this range of scales and redshifts.
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12. |
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13. |
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14. |
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15. |
- Sahlén, Martin, Associate Professor (docent), 1979-, et al.
(author)
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Galaxy population constraints on cosmology and star formation in the early Universe
- 2021
-
In: The Astrophysical Journal.
-
Journal article (peer-reviewed)abstract
- We present the first post-cosmic-microwave-background early-Universe observational constraints on $\textbackslashsigma_8$, $\textbackslashOmega_\textbackslashrm m$, mean galaxy star-forming efficiency and galaxy UV magnitude scatter at redshifts $z = 4-10$. We perform a simultaneous 11-parameter cosmology and star-formation physics fit using the new code GalaxyMC, with redshift $z\textgreater4$ galaxy UV luminosity and correlation function data. Consistent with previous studies, we find evidence for redshift-independent star formation physics, regulated by halo assembly. For a flat $\textbackslashLambda$CDM universe with a low-redshift Hubble constant and a Type Ia supernovae $\textbackslashOmega_\textbackslashrm m$ prior, we constrain $\textbackslashsigma_8 = 0.81 \textbackslashpm 0.03$, and a mean star-forming efficiency peaking at $\textbackslashlog_10 \textbackslashrm SFE = -[(0.09 \textbackslashpm 0.20) + (0.58 \textbackslashpm 0.29) \textbackslashtimes \textbackslashlog_10 (1+z)]$ for halo mass $\textbackslashlog_10 M_\textbackslashrm p / h⌃-1 M_\textbackslashodot = 11.48 \textbackslashpm 0.09$. The suppression of star formation due to feedback is given by a double power law in halo mass with indices $\textbackslashalpha = 0.56 \textbackslashpm 0.08, \textbackslashbeta = -1.03 \textbackslashpm 0.07$. The scatter in galaxy UV magnitude for fixed halo mass is $\textbackslashsigma_M = 0.56 \textbackslashpm 0.08$. Without a prior on $\textbackslashOmega_\textbackslashrm m$ we obtain $\textbackslashsigma_8 = 0.78 \textbackslashpm 0.06$, $\textbackslashOmega_\textbackslashrm m = 0.33 \textbackslashpm 0.07$ and at most $1\textbackslashsigma$ differences in all other parameter values. Our best-fit galaxy luminosity functions yield a reionization optical depth $\textbackslashtau \textbackslashapprox 0.048$, consistent with the Planck 2018 value.
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16. |
- Turner, D. J., et al.
(author)
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The XMM Cluster Survey : an independent demonstration of the fidelity of the eFEDS galaxy cluster data products and implications for future studies
- 2022
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 517:1, s. 657-674
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Journal article (peer-reviewed)abstract
- We present the first comparison between properties of clusters of galaxies detected by the eROSITA Final Equatorial-Depth Survey (eFEDS) and the XMM Cluster Survey (XCS). We have compared, in an ensemble fashion, properties from the eFEDS X-ray cluster catalogue with those from the Ultimate XMM eXtragaLactic (XXL) survey project (XXL-100-GC). We find the redshift and temperature (T-X) distributions to be similar, with a larger proportion of clusters above 4 keV in the XXL-100-GC sample; fractional temperature uncertainties are significantly larger in eFEDS compared to XXL. We find 62 eFEDS cluster candidates with XMM data (eFEDS-XMM sample); 10 do not have good enough XMM data to confirm or deny, 11 are classed as sample contaminants, and 4 have their X-ray flux contaminated by another source. The majority of eFEDS-XMM sources have longer XMM exposures than eFEDS, and most eFEDS positions are within 100 kpc of XCS positions. Our eFEDS-XCS sample of 37 clusters is used to calculate minimum sample contamination fractions of similar to 18 and similar to 9 per cent in the eFEDS X-ray and optically confirmed samples, respectively, in general agreement with eFEDS findings. We directly compare 29 X-ray luminosities (L-X) measured by eFEDS and XCS, finding excellent agreement. Eight clusters have a T-X measured by XCS and eFEDS, and we find that XMM temperatures are 25 +/- 9 per cent larger than their eROSITA counterparts. Finally, we construct L-X-T-X scaling relations based on eFEDS and XCS measurements, which are in tension; the tension is decreased when we measure a third scaling relation with calibrated XCS temperatures.
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17. |
- Upsdell, E. W., et al.
(author)
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The XMM cluster survey : exploring scaling relations and completeness of the dark energy survey year 3 redMaPPer cluster catalogue
- 2023
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 522:4, s. 5267-5290
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Journal article (peer-reviewed)abstract
- We cross-match and compare characteristics of galaxy clusters identified in observations from two sky surveys using two completely different techniques. One sample is optically selected from the analysis of 3 years of Dark Energy Survey observations using the redMaPPer cluster detection algorithm. The second is X-ray selected from XMM observations analysed by the XMM Cluster Survey. The samples comprise a total area of 57.4 deg(2), bounded by the area of four contiguous XMM survey regions that overlap the DES footprint. We find that the X-ray-selected sample is fully matched with entries in the redMaPPer catalogue, above lambda > 20 and within 0.1 < z < 0.9. Conversely, only 38 per cent of the redMaPPer catalogue is matched to an X-ray extended source. Next, using 120 optically clusters and 184 X-ray-selected clusters, we investigate the form of the X-ray luminosity-temperature (L-X -T-X ), luminosity-richness (L-X - lambda), and temperature-richness (T-X - lambda) scaling relations. We find that the fitted forms of the L-X -T-X relations are consistent between the two selection methods and also with other studies in the literature. However, we find tentative evidence for a steepening of the slope of the relation for low richness systems in the X-ray-selected sample. When considering the scaling of richness with X-ray properties, we again find consistency in the relations (i.e. L-X - lambda and T-X - lambda) between the optical and X-ray-selected samples. This is contrary to previous similar works that find a significant increase in the scatter of the luminosity scaling relation for X-ray-selected samples compared to optically selected samples.
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18. |
- Vikaeus, Anton, et al.
(author)
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Conditions for detecting lensed Population III galaxies in blind surveys with the James Webb Space Telescope, the Roman Space Telescope, and Euclid
- 2022
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 512:2, s. 3030-3044
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Journal article (peer-reviewed)abstract
- Dark matter haloes that reach the H i-cooling mass without prior star formation or external metal pollution represent potential sites for the formation of small - extremely faint - Population III galaxies at high redshifts. Gravitational lensing may in rare cases boost their fluxes to detectable levels, but to find even a small number of such objects in randomly selected regions of the sky requires very large areas to be surveyed. Because of this, a small, wide-field telescope can in principle offer better detection prospects than a large telescope with a smaller field of view. Here, we derive the minimum comoving number density required to allow gravitational lensing to lift such objects at redshift z = 5-16 above the detection thresholds of blind surveys carried out with the James Webb space telescope (JWST), the Roman space telescope (RST) and Euclid. We find that the prospects for photometric detections of Pop III galaxies are promising, and that they are better for RST than for JWST and Euclid. However, the Pop III galaxies favoured by current simulations have number densities too low to allow spectroscopic detections based on the strength of the He ii1640 emission line in any of the considered surveys unless very high star formation efficiencies (epsilon greater than or similar to 0.1) are evoked. We argue that targeting individual cluster lenses instead of the wide-field surveys considered in this paper results in better spectroscopic detection prospects, while for photometric detection, the wide-field surveys perform considerably better.
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19. |
- Weltman, A., et al.
(author)
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Fundamental physics with the Square Kilometre Array
- 2020
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In: Publications Astronomical Society of Australia. - : CAMBRIDGE UNIV PRESS. - 1323-3580 .- 1448-6083. ; 37
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Research review (peer-reviewed)abstract
- The Square Kilometre Array (SKA) is a planned large radio interferometer designed to operate over a wide range of frequencies, and with an order of magnitude greater sensitivity and survey speed than any current radio telescope. The SKA will address many important topics in astronomy, ranging from planet formation to distant galaxies. However, in this work, we consider the perspective of the SKA as a facility for studying physics. We review four areas in which the SKA is expected to make major contributions to our understanding of fundamental physics: cosmic dawn and reionisation; gravity and gravitational radiation; cosmology and dark energy; and dark matter and astroparticle physics. These discussions demonstrate that the SKA will be a spectacular physics machine, which will provide many new breakthroughs and novel insights on matter, energy, and spacetime.
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20. |
- Wetzell, V, et al.
(author)
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Velocity dispersions of clusters in the Dark Energy Survey Y3 redMaPPer catalogue
- 2022
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In: Monthly notices of the Royal Astronomical Society. - : Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 514:4, s. 4696-4717
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Journal article (peer-reviewed)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 sample consists of 126 clusters with sufficient spectroscopy for individual 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 samples; 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 sample, 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.
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21. |
- Wilson, Susan, et al.
(author)
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The XMM Cluster Survey : evolution of the velocity dispersion-temperature relation over half a Hubble time
- 2016
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In: Montly notices of the royal astronomical society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 463:1, s. 413-428
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Journal article (peer-reviewed)abstract
- We measure the evolution of the velocity dispersion–temperature (σv–TX) relation up to z = 1 using a sample of 38 galaxy clusters drawn from the XMM Cluster Survey. This work improves upon previous studies by the use of a homogeneous cluster sample and in terms of the number of high-redshift clusters included. We present here new redshift and velocity dispersion measurements for 12 z > 0.5 clusters observed with the Gemini Multi Object Spectographs instruments on the Gemini telescopes. Using an orthogonal regression method, we find that the slope of the relation is steeper than that expected if clusters were self-similar, and that the evolution of the normalization is slightly negative, but not significantly different from zero (σv ∝ T0.86±0.14E(z)−0.37±0.33). We verify our results by applying our methods to cosmological hydrodynamical simulations. The lack of evolution seen in our data is consistent with simulations that include both feedback and radiative cooling.
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22. |
- Zackrisson, Erik, et al.
(author)
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Bubble mapping with the Square Kilometre Array - I. Detecting galaxies with Euclid, JWST, WFIRST, and ELT within ionized bubbles in the intergalactic medium at z > 6
- 2020
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 493:1, s. 855-870
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Journal article (peer-reviewed)abstract
- The Square Kilometre Array (SKA) is expected to provide the first tomographic observations of the neutral intergalactic medium at redshifts z > 6 and pinpoint the locations of individual ionized bubbles during early stages of cosmic reionization. In scenarios where star-forming galaxies provide most of the ionizing photons required for cosmic reionization, one expects the first ionized bubbles to be centred on overdensities of such galaxies. Here, we model the properties of galaxy populations within isolated, ionized bubbles that SKA-1 should be able to resolve at z approximate to 7-10, and explore the prospects for galaxy counts within such structures with various upcoming near-infrared telescopes. We find that, for the bubbles that are within reach of SKA-1 tomography, the bubble volume is closely tied to the number of ionizing photons that have escaped from the galaxies within. In the case of galaxy-dominated reionization, galaxies are expected to turn up above the spectroscopic detection threshold of JWST and ELT in even the smallest resolvable bubbles at z <= 10. The prospects of detecting galaxies within these structures in purely photometric surveys with Euclid, WFIRST, JWST, or ELT are also discussed. While spectroscopy is preferable towards the end of reionization to provide a robust sample of bubble members, multiband imaging may be a competitive option for bubbles at z approximate to 10, due to the very small number of line-of-sight interlopers expected at these redshifts.
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23. |
- Zhang, Y., et al.
(author)
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Galaxies in X-ray selected clusters and groups in Dark Energy Survey data - II. Hierarchical Bayesian modelling of the red-sequence galaxy luminosity function
- 2019
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In: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 488:1, s. 1-17
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Journal article (peer-reviewed)abstract
- Using similar to 100 X-ray selected clusters in the Dark Energy Survey Science Verification data, we constrain the luminosity function ( LF) of cluster red-sequence galaxies as a function of redshift. This is the first homogeneous optical/X-ray sample large enough to constrain the evolution of the LF simultaneously in redshift ( 0.1 < z < 1.05) and cluster mass ( 13.5 <= log(10)( M-200crit) similar to< 15.0). We pay particular attention to completeness issues and the detection limit of the galaxy sample. We then apply a hierarchical Bayesian model to fit the cluster galaxy LFs via a Schechter function, including its characteristic break ( m*) to a faint end power-law slope ( alpha). Our method enables us to avoid known issues in similar analyses based on stacking or binning the clusters. We find weak and statistically insignificant (similar to 1.9 sigma) evolution in the faint end slope alpha versus redshift. We also find no dependence in alpha or m* with the X-ray inferred cluster masses. However, the amplitude of the LF as a function of cluster mass is constrained to similar to 20 per cent precision. As a by-product of our algorithm, we utilize the correlation between the LF and cluster mass to provide an improved estimate of the individual cluster masses as well as the scatter in true mass given the X-ray inferred masses. This technique can be applied to a larger sample of X-ray or optically selected clusters from the Dark Energy Survey, significantly improving the sensitivity of the analysis.
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