32 research outputs found
A case study of early galaxy cluster with the Athena X-IFU
Context: Observations of the hot gas in distant clusters of galaxies, though
challenging, are key to understand the role of intense galaxy activity,
super-massive black hole feedback and chemical enrichment in the process of
massive halos assembly. Aims: We assess the feasibility to retrieve, using
X-ray hyperspectral data only, the thermodymamical hot gas properties and
chemical abundances of a galaxy cluster of mass M500=7 x , extracted from the Hydrangea hydrodynamical simulation. Methods: We
create mock X-ray observations of the future X-ray Integral Field Unit (X-IFU)
onboard the Athena mission. By forward-modeling the measured 0.4-1 keV surface
brightness, the projected gas temperature and abundance profiles, we
reconstruct the three-dimensional distribution for the gas density, pressure,
temperature and entropy. Results: Thanks to its large field-of-view, high
throughput and exquisite spectral resolution, one X-IFU exposure lasting 100ks
enables reconstructing density and pressure profiles with 20% precision out to
a characteristic radius of R500, accounting for each quantity's intrinsic
dispersion in the Hydrangea simulations. Reconstruction of abundance profiles
requires both higher signal-to-noise ratios and specific binning schemes. We
assess the enhancement brought by longer exposures and by observing the same
object at later evolutionary stages (). Conclusions: Our analysis
highlights the importance of scatter in the radially binned gas properties,
which induces significant effects on the observed projected quantities. The
fidelity of the reconstruction of gas profiles is sensitive to the degree of
gas components mixing along the line-of-sight. Future analyses should aim at
involving dedicated hyper-spectral models and fitting methods that are able to
grasp the complexity of such three-dimensional, multi-phase, diffuse gas
structures.Comment: 15 pages, 11 figures, 3 tables. Accepted for publication in A&
The stellar mass function and evolution of the density profile of galaxy clusters from the Hydrangea simulations at
Galaxy clusters are excellent probes to study the effect of environment on
galaxy formation and evolution. Along with high-quality observational data,
accurate cosmological simulations are required to improve our understanding of
galaxy evolution in these systems. In this work, we compare state-of-the-art
observational data of massive galaxy clusters ()
at different redshifts () with predictions from the Hydrangea suite of
cosmological hydrodynamic simulations of 24 massive galaxy clusters ( at ). We compare three fundamental observables of
galaxy clusters: the total stellar mass to halo mass ratio, the stellar mass
function (SMF), and the radial mass density profile of the cluster galaxies. In
the first two of these, the simulations agree well with the observations,
albeit with a slightly too high abundance of galaxies at . The NFW concentrations of
cluster galaxies increase with redshift, in contrast to the decreasing dark
matter halo concentrations. This previously observed behaviour is therefore due
to a qualitatively different assembly of the smooth DM halo compared to the
satellite population. Quantitatively, we however find a discrepancy in that the
simulations predict higher stellar concentrations than observed at lower
redshifts (), by a factor of 2. This may be due to selection
bias in the simulations, or stem from shortcomings in the build-up and
stripping of their inner satellite halo.Comment: 14 pages, 9 figures (excluding appendices), Accepted for publication
in MNRA
The XXL Survey IV. Mass-temperature relation of the bright cluster sample
The XXL survey is the largest survey carried out by XMM-Newton. Covering an area of 50deg, the survey contains galaxy clusters out to a redshift 2 and to an X-ray flux limit of . This paper is part of the first release of XXL results focussed on the bright cluster sample. We investigate the scaling relation between weak-lensing mass and X-ray temperature for the brightest clusters in XXL. The scaling relation is used to estimate the mass of all 100 clusters in XXL-100-GC. Based on a subsample of 38 objects that lie within the intersection of the northern XXL field and the publicly available CFHTLenS catalog, we derive the of each system with careful considerations of the systematics. The clusters lie at and span a range of . We combine our sample with 58 clusters from the literature, increasing the range out to 10keV. To date, this is the largest sample of clusters with measurements that has been used to study the mass-temperature relation. The fit () to the XXL clusters returns a slope and intrinsic scatter ; the scatter is dominated by disturbed clusters. The fit to the combined sample of 96 clusters is in tension with self-similarity, and . Overall our results demonstrate the feasibility of ground-based weak-lensing scaling relation studies down to cool systems of temperature and highlight that the current data and samples are a limit to our statistical precision. As such we are unable to determine whether the validity of hydrostatic equilibrium is a function of halo mass. An enlarged sample of cool systems, deeper weak-lensing data, and robust modelling of the selection function will help to explore these issues further
LoCuSS: Testing hydrostatic equilibrium in galaxy clusters
We test the assumption of hydrostatic equilibrium in an X-ray luminosity selected sample of 50 galaxy clusters at from the Local Cluster Substructure Survey (LoCuSS). Our weak-lensing measurements of control systematic biases to sub-4 per cent, and our hydrostatic measurements of the same achieve excellent agreement between XMM-Newton and Chandra. The mean ratio of X-ray to lensing mass for these 50 clusters is , and for the 44 clusters also detected by Planck, the mean ratio of Planck mass estimate to LoCuSS lensing mass is . Based on a careful like-for-like analysis, we find that LoCuSS, the Canadian Cluster Comparison Project (CCCP), and Weighing the Giants (WtG) agree on at . This small level of hydrostatic bias disagrees at with the level required to reconcile Planck cosmology results from the cosmic microwave background and galaxy cluster counts
Planck intermediate results. III. The relation between galaxy cluster mass and Sunyaev-Zeldovich signal
We examine the relation between the galaxy cluster mass M and
Sunyaev-Zeldovich (SZ) effect signal D_A^2 Y for a sample of 19 objects for
which weak lensing (WL) mass measurements obtained from Subaru Telescope data
are available in the literature. Hydrostatic X-ray masses are derived from
XMM-Newton archive data and the SZ effect signal is measured from Planck
all-sky survey data. We find an M_WL-D_A^2 Y relation that is consistent in
slope and normalisation with previous determinations using weak lensing masses;
however, there is a normalisation offset with respect to previous measures
based on hydrostatic X-ray mass-proxy relations. We verify that our SZ effect
measurements are in excellent agreement with previous determinations from
Planck data. For the present sample, the hydrostatic X-ray masses at R_500 are
on average ~ 20 per cent larger than the corresponding weak lensing masses, at
odds with expectations. We show that the mass discrepancy is driven by a
difference in mass concentration as measured by the two methods, and, for the
present sample, the mass discrepancy and difference in mass concentration is
especially large for disturbed systems. The mass discrepancy is also linked to
the offset in centres used by the X-ray and weak lensing analyses, which again
is most important in disturbed systems. We outline several approaches that are
needed to help achieve convergence in cluster mass measurement with X-ray and
weak lensing observations.Comment: 19 pages, 9 figures, matches accepted versio
The XXL Survey IV. Mass-temperature relation of the bright cluster sample
The XXL survey is the largest survey carried out by XMM-Newton. Covering an area of 50deg, the survey contains galaxy clusters out to a redshift 2 and to an X-ray flux limit of . This paper is part of the first release of XXL results focussed on the bright cluster sample. We investigate the scaling relation between weak-lensing mass and X-ray temperature for the brightest clusters in XXL. The scaling relation is used to estimate the mass of all 100 clusters in XXL-100-GC. Based on a subsample of 38 objects that lie within the intersection of the northern XXL field and the publicly available CFHTLenS catalog, we derive the of each system with careful considerations of the systematics. The clusters lie at and span a range of . We combine our sample with 58 clusters from the literature, increasing the range out to 10keV. To date, this is the largest sample of clusters with measurements that has been used to study the mass-temperature relation. The fit () to the XXL clusters returns a slope and intrinsic scatter ; the scatter is dominated by disturbed clusters. The fit to the combined sample of 96 clusters is in tension with self-similarity, and . Overall our results demonstrate the feasibility of ground-based weak-lensing scaling relation studies down to cool systems of temperature and highlight that the current data and samples are a limit to our statistical precision. As such we are unable to determine whether the validity of hydrostatic equilibrium is a function of halo mass. An enlarged sample of cool systems, deeper weak-lensing data, and robust modelling of the selection function will help to explore these issues further
FLAMINGO: calibrating large cosmological hydrodynamical simulations with machine learning
To fully take advantage of the data provided by large-scale structure surveys, we need to quantify the potential impact of baryonic effects, such as feedback from active galactic nuclei (AGN) and star formation, on cosmological observables. In simulations, feedback processes originate on scales that remain unresolved. Therefore, they need to be sourced via subgrid models that contain free parameters. We use machine learning to calibrate the AGN and stellar feedback models for the FLAMINGO (Fullhydro Large-scale structure simulations with All-sky Mapping for the Interpretation of Next Generation Observations) cosmological hydrodynamical simulations. Using Gaussian process emulators trained on Latin hypercubes of 32 smaller volume simulations, we model how the galaxy stellar mass function (SMF) and cluster gas fractions change as a function of the subgrid parameters. The emulators are then fit to observational data, allowing for the inclusion of potential observational biases. We apply our method to the three different FLAMINGO resolutions, spanning a factor of 64 in particle mass, recovering the observed relations within the respective resolved mass ranges. We also use the emulators, which link changes in subgrid parameters to changes in observables, to find models that skirt or exceed the observationally allowed range for cluster gas fractions and the SMF. Our method enables us to define model variations in terms of the data that they are calibrated to rather than the values of specific subgrid parameters. This approach is useful, because subgrid parameters are typically not directly linked to particular observables, and predictions for a specific observable are influenced by multiple subgrid parameters
X-IFU/Athena view of the most distant galaxy clusters in the Universe
International audienceThe X-ray Integral Field Unit (X-IFU) on-board the second large ESA mission "Athena" will be a high spatial (5") and spectral (2.5eV) resolution X-ray imaging spectrometer, operating in the 0.2-12 keV energy band. It will address the science question of the assembly and evolution through cosmic time of the largest halos of matter in the Universe, groups and clusters of galaxies. To this end, we present an on-going feasibility study to demonstrate the X-IFU capabilities to unveil the physics of massive halos at their epoch of formation. Starting from a distant (z=2) group of galaxies (M500 = 7 10^13 Mâ/h) extracted from the HYDRANGEA cosmological and hydrodynamical numerical simulations, we perform an end-to-end simulation of X-IFU observations. From the reconstruction of the global, 1D and 2D quantities, we plan to investigate the various X-IFU science cases for clusters of galaxies, such as the chemical enrichment of the intra-cluster medium (ICM), the dynamical assembly of groups and clusters and the impact of feedback from galaxy and super-massive black hole evolution
A case study of an early galaxy cluster with the Athena X-IFU
Observations of the hot gas in distant clusters of galaxies, though challenging, are key to understanding the role of intense galaxy activity, supermassive black hole feedback, and chemical enrichment in the process of massive halo assembly. Using X-ray hyperspectral data
alone, we assess the feasibility of retrieving the thermodynamical hot gas properties and chemical abundances of a galaxy cluster of mass , extracted from the Hydrangea hydrodynamical simulations. We created mock X-ray observations of the future X-ray Integral Field Unit (X-IFU) on board the Athena mission. By forward-modelling the measured \,keV surface brightness, the projected gas temperature and abundance profiles, we reconstructed the three-dimensional distribution for the gas density, pressure, temperature, and entropy. Thanks to its large field of view, high throughput, and exquisite spectral resolution, one X-IFU exposure lasting 100\,ks enabled the reconstruction of density and pressure profiles with precision out to a characteristic radius of z=11.5$). Our analysis highlights the importance of scatter in the radially binned gas properties, which induces significant effects on the observed projected quantities. The fidelity of the reconstruction of gas profiles is sensitive to the degree of mixing of the gas components along the line of sight. Future analyses should aim to involve dedicated hyper-spectral models and fitting methods that are able to grasp the complexity of such three-dimensional, multi-phase, diffuse gas structures
X-IFU/Athena view of the most distant galaxy clusters in the Universe
International audienceThe X-ray Integral Field Unit (X-IFU) on-board the second large ESA mission "Athena" will be a high spatial (5") and spectral (2.5eV) resolution X-ray imaging spectrometer, operating in the 0.2-12 keV energy band. It will address the science question of the assembly and evolution through cosmic time of the largest halos of matter in the Universe, groups and clusters of galaxies. To this end, we present an on-going feasibility study to demonstrate the X-IFU capabilities to unveil the physics of massive halos at their epoch of formation. Starting from a distant (z=2) group of galaxies (M500 = 7 10^13 Mâ/h) extracted from the HYDRANGEA cosmological and hydrodynamical numerical simulations, we perform an end-to-end simulation of X-IFU observations. From the reconstruction of the global, 1D and 2D quantities, we plan to investigate the various X-IFU science cases for clusters of galaxies, such as the chemical enrichment of the intra-cluster medium (ICM), the dynamical assembly of groups and clusters and the impact of feedback from galaxy and super-massive black hole evolution