arXiv subjects

A. Finoguenov

Publications and source records attributed to A. Finoguenov.

At least 55 records · Page 3Linked to original sources

arXiv2021

Three Lyman-alpha emitting filaments converging to a massive galaxy group at z=2.91: discussing the case for cold gas infall

We have discovered a 300kpc-wide giant Lya nebula centered on the massive galaxy group RO-1001 at z=2.91 in the COSMOS field. Keck Cosmic Web Imager observations reveal three cold gas filaments converging into the center of the potential well of its ~4x10^13Msun dark matter halo, hosting 1200Msun/yr of star formation as probed by ALMA and NOEMA observations. The nebula morphological and kinematics properties and the prevalence of blueshifted components in the Lya spectra are consistent with a scenario of gas accretion. The upper limits on AGN activity and overall energetics favor gravity as the primary Lya powering source and infall as the main source of gas flows to the system. Although interpretational difficulties remain, with outflows and likely also photoionization with ensuing recombination still playing a role, this finding provides arguably an ideal environment to quantitatively test models of cold gas accretion and galaxy feeding inside an actively star-forming massive halo at high redshift.

astro-ph.GA↗

arXiv2021

SPIDERS: An Overview of The Largest Catalogue of Spectroscopically Confirmed X-ray Galaxy Clusters

SPIDERS is the spectroscopic follow-up effort of the Sloan Digital Sky Survey IV (SDSS-IV) project for the identification of X-ray selected galaxy clusters. We present our catalogue of 2740 visually inspected galaxy clusters as a part of the SDSS Data Release 16 (DR16). Here we detail the target selection, our methods for validation of the candidate clusters, performance of the survey, the construction of the final sample, and a full description of what is found in the catalogue. Of the sample, the median number of members per cluster is approximately 10, with 818 having 15 or greater. We find that we are capable of validating over 99% of clusters when 5 redshifts are obtained below $z<0.3$ and when 9 redshifts are obtained above $z>0.3$. We discuss the improvements of this catalogue's identification of cluster using 33,340 redshifts, with $Δz_{\rm{phot}} / Δz_{\rm{spec}} \sim 100$, over other photometric and spectroscopic surveys, as well as present an update to previous ($σ- L_{X}$) and ($σ- λ$) relations. Finally, we present our cosmological constraints derived using the velocity dispersion function.

astro-ph.CO↗

arXiv2021

Environments of a sample of AzTEC submillimetre galaxies in the COSMOS field

Submillimetre galaxies (SMGs) are bright sources at submillimetre wavelengths. Made up of mostly of high-z galaxies, SMGs are amongst the most luminous dusty galaxies in the Universe. Studying their environments and clustering strength is thus important to put these galaxies in a cosmological context. We present an environmental study of a sample of 116 SMGs in 96 ALMA observation fields, which were initially discovered with the AzTEC camera on ASTE and identified with high-resolution ALMA imaging within the COSMOS survey field, having either spectroscopic or unambiguous photometric redshift. We analysed their environments making use of the latest release of the COSMOS photometric catalogue, COSMOS2015, a catalogue that contains precise photometric redshifts for more than half a million objects over the 2deg2 COSMOS field. We searched for dense galaxy environments computing the so-called overdensity parameter as a function of distance within a radius of 5 arcmin from the SMG. We validated this approach spectroscopically for those SMGs for which spectroscopic redshift is available. As an additional test, we searched for extended X-ray emission as a proxy for the hot intracluster medium, performing an X-ray stacking analysis in the 0.5-2 keV band with a 32 arcsec aperture and our SMG position using all available XMM-Newton and Chandra X-ray observations of the COSMOS field. We find that 27% (31 out of 116) of the SMGs in our sample are located in a galactic dense environment; a fraction that is similar to previous studies. The spectroscopic redshift is known for 15 of these 31 sources, thus this photometric approach is tested using spectroscopy. We are able to confirm that 7 out of 15 SMGs lie in high-density peaks. However, the search for associated extended X-ray emission via an X-ray stacking analysis leads to a detection that is not statistically significant.

astro-ph.GA↗

arXiv2021

CODEX Weak Lensing Mass Catalogue and implications on the mass-richness relation

The COnstrain Dark Energy with X-ray clusters (CODEX) sample contains the largest flux limited sample of X-ray clusters at $0.35 < z < 0.65$. It was selected from ROSAT data in the 10,000 square degrees of overlap with BOSS, mapping a total number of 2770 high-z galaxy clusters. We present here the full results of the CFHT CODEX program on cluster mass measurement, including a reanalysis of CFHTLS Wide data, with 25 individual lensing-constrained cluster masses. We employ $lensfit$ shape measurement and perform a conservative colour-space selection and weighting of background galaxies. Using the combination of shape noise and an analytic covariance for intrinsic variations of cluster profiles at fixed mass due to large scale structure, miscentring, and variations in concentration and ellipticity, we determine the likelihood of the observed shear signal as a function of true mass for each cluster. We combine 25 individual cluster mass likelihoods in a Bayesian hierarchical scheme with the inclusion of optical and X-ray selection functions to derive constraints on the slope $α$, normalization $β$, and scatter $σ_{\ln λ| μ}$ of our richness-mass scaling relation model in log-space: $\left<\ln λ| μ\right> = αμ+ β$, with $μ= \ln (M_{200c}/M_{\mathrm{piv}})$, and $M_{\mathrm{piv}} = 10^{14.81} M_{\odot}$. We find a slope $α= 0.49^{+0.20}_{-0.15}$, normalization $ \exp(β) = 84.0^{+9.2}_{-14.8}$ and $σ_{\ln λ| μ} = 0.17^{+0.13}_{-0.09}$ using CFHT richness estimates. In comparison to other weak lensing richness-mass relations, we find the normalization of the richness statistically agreeing with the normalization of other scaling relations from a broad redshift range ($0.0<z<0.65$) and with different cluster selection (X-ray, Sunyaev-Zeldovich, and optical).

astro-ph.CO↗

arXiv2020

The eROSITA X-ray telescope on SRG

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. By the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. At the end of this program, the eROSITA all-sky survey in the soft X-ray band (0.2--2.3\,keV) will be about 25 times more sensitive than the ROSAT All-Sky Survey, while in the hard band (2.3--8\,keV) it will provide the first ever true imaging survey of the sky. The eROSITA design driving science is the detection of large samples of galaxy clusters up to redshifts $z>1$ in order to study the large-scale structure of the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGNs, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astrophysical phenomena, including X-ray binaries, active stars, and diffuse emission within the Galaxy. Results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. With this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements.

astro-ph.HE↗

arXiv2020

SPIDERS: overview of the X-ray galaxy cluster follow-up and the final spectroscopic data release

SPIDERS (The SPectroscopic IDentification of eROSITA Sources) is a large spectroscopic programme for X-ray selected galaxy clusters as part of the Sloan Digital Sky Survey-IV (SDSS-IV). We describe the final dataset in the context of SDSS Data Release 16 (DR16): the survey overall characteristics, final targeting strategies, achieved completeness and spectral quality, with special emphasis on its use as a galaxy cluster sample for cosmology applications. SPIDERS now consists of about 27,000 new optical spectra of galaxies selected within 4,000 photometric red sequences, each associated with an X-ray source. The excellent spectrograph efficiency and a robust analysis pipeline yield a spectroscopic redshift measurement success rate exceeding 98%, with a median velocity accuracy of 20 km s$^{-1}$ (at $z=0.2$). Using the catalogue of 2,740 X-ray galaxy clusters confirmed with DR16 spectroscopy, we reveal the three-dimensional map of the galaxy cluster distribution in the observable Universe up to $z\sim0.6$. We highlight the homogeneity of the member galaxy spectra among distinct regions of the galaxy cluster phase space. Aided by accurate spectroscopic redshifts and by a model of the sample selection effects, we compute the galaxy cluster X-ray luminosity function and we present its lack of evolution up to $z=0.6$. Finally we discuss the prospects of forthcoming large multiplexed spectroscopic programmes dedicated to follow up the next generation of all-sky X-ray source catalogues.

astro-ph.GA↗

arXiv2020

The miniJPAS survey: a preview of the Universe in 56 colours

The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will soon start to scan thousands of square degrees of the northern extragalactic sky with a unique set of $56$ optical filters from a dedicated $2.55$m telescope, JST, at the Javalambre Astrophysical Observatory. Before the arrival of the final instrument (a 1.2 Gpixels, 4.2deg$^2$ field-of-view camera), the JST was equipped with an interim camera (JPAS-Pathfinder), composed of one CCD with a 0.3deg$^2$ field-of-view and resolution of 0.23 arcsec pixel$^{-1}$. To demonstrate the scientific potential of J-PAS, with the JPAS-Pathfinder camera we carried out a survey on the AEGIS field (along the Extended Groth Strip), dubbed miniJPAS. We observed a total of $\sim 1$ deg$^2$, with the $56$ J-PAS filters, which include $54$ narrow band (NB, $\rm{FWHM} \sim 145$Angstrom) and two broader filters extending to the UV and the near-infrared, complemented by the $u,g,r,i$ SDSS broad band (BB) filters. In this paper we present the miniJPAS data set, the details of the catalogues and data access, and illustrate the scientific potential of our multi-band data. The data surpass the target depths originally planned for J-PAS, reaching $\rm{mag}_{\rm {AB}}$ between $\sim 22$ and $23.5$ for the NB filters and up to $24$ for the BB filters ($5σ$ in a $3$~arcsec aperture). The miniJPAS primary catalogue contains more than $64,000$ sources extracted in the $r$ detection band with forced photometry in all other bands. We estimate the catalogue to be complete up to $r=23.6$ for point-like sources and up to $r=22.7$ for extended sources. Photometric redshifts reach subpercent precision for all sources up to $r=22.5$, and a precision of $\sim 0.3$% for about half of the sample. (Abridged)

astro-ph.CO↗

arXiv2020

The relation between the diffuse X-ray luminosity and the radio power of the central AGN in galaxy groups

Our understanding of how AGN feedback operates in galaxy clusters has improved in recent years owing to large efforts in multi-wavelength observations and hydrodynamical simulations. However, it is much less clear how feedback operates in galaxy groups, which have shallower gravitational potentials. In this work, using very deep VLA and new MeerKAT observations from the MIGHTEE survey, we compiled a sample of 247 X-ray selected galaxy groups detected in the COSMOS field. We have studied the relation between the X-ray emission of the intra-group medium and the 1.4 GHz radio emission of the central radio galaxy. For comparison, we have also built a control sample of 142 galaxy clusters using ROSAT and NVSS data. We find that clusters and groups follow the same correlation between X-ray and radio emission. Large radio galaxies hosted in the centres of groups and merging clusters increase the scatter of the distribution. Using statistical tests and Monte-Carlo simulations, we show that the correlation is not dominated by biases or selection effects. We also find that galaxy groups are more likely than clusters to host large radio galaxies, perhaps owing to the lower ambient gas density or a more efficient accretion mode. In these groups, radiative cooling of the ICM could be less suppressed by AGN heating. We conclude that the feedback processes that operate in galaxy clusters are also effective in groups.

astro-ph.GA↗

arXiv2020

CODEX clusters. The Survey, the Catalog, and Cosmology of the X-ray Luminosity Function

Large area catalogs of galaxy clusters constructed from ROSAT All Sky Survey provide the base for our knowledge on the population of clusters thanks to the long-term multiwavelength efforts on their follow-up. Advent of large area photometric surveys superseding in depth previous all-sky data allows us to revisit the construction of X-ray cluster catalogs, extending the study to lower cluster masses and to higher redshifts and to provide the modelling of the selection function. We perform a wavelet detection of X-ray sources and make extensive simulations of the detection of clusters in the RASS data. We assign an optical richness to each of the 24,788 detected X-ray sources in the 10,382 square degrees of SDSS BOSS area, using redMaPPer version 5.2. We name this survey COnstrain Dark Energy with X-ray (CODEX) clusters. We show that there is no obvious separation of sources on galaxy clusters and AGN, based on distribution of systems on their richness. This is a combination of increasing number of galaxy groups and their selection as identification of an X-ray sources either by chance or due to groups hosting an AGN. To clean the sample, we use a cut on the optical richness at the level corresponding to the 10\% completeness of the survey and include it into the modelling of cluster selection function. We present the X-ray catalog extending to a redshift of 0.6 down to X-ray fluxes of $10^{-13}$ ergs s$^{-1}$ cm$^{-2}$. We provide the modelling of the sample selection and discuss the redshift evolution of the high end of the X-ray luminosity function (XLF). Our results on $z<0.3$ XLF are in agreement with previous studies, while we provide new constraints on the $0.3<z<0.6$ XLF. We find a lack of strong redshift evolution of the XLF, provide exact modeling of the effect of low number statistics and AGN contamination and present the resulting constraints on the flat $Λ$CDM.

astro-ph.CO↗

arXiv2020

Mass Calibration of the CODEX Cluster Sample using SPIDERS Spectroscopy -- II. The X-ray Luminosity-Mass Relation

We perform the calibration of the X-ray luminosity--mass scaling relation on a sample of 344 CODEX clusters with $z<0.66$ using the dynamics of their member galaxies. Spectroscopic follow-up measurements have been obtained from the SPIDERS survey, leading to a sample of 6,658 red member galaxies. We use the Jeans equation to calculate halo masses, assuming an NFW mass profile and analyzing a broad range of anisotropy profiles. With a scaling relation of the form $L_{\rm{X}} \propto \text{A}_{\rm{X}}M_{\text{200c}}^{\text{B}_{\rm{X}}} E(z)^2 (1+z)^{γ_{\rm{X}}}$, we find best fit parameters $ \text{A}_{\rm{X}}=5.7^{+0.4}_{-0.5} (\pm0.6)\times10^{43}\,\mathrm{erg\,s^{-1}}$, $\text{B}_{\rm{X}}=2.5\pm0.2(\pm0.07)$, $γ_{\rm{X}}=-2.6^{+1.1}_{-1.2}(\pm0.74)$, where we include systematic uncertainties in parentheses and for a pivot mass and redshift of $3\times10^{14}M_\odot$ and 0.16, respectively. We compare our constraints with previous results, and we combine our sample with the SPT SZE--selected cluster subsample observed with \XMM\, extending the validity of our results to a wider range of redshifts and cluster masses.

astro-ph.CO↗

arXiv2020

Kinematic unrest of low mass galaxy groups

In an effort to better understand the formation of galaxy groups, we examine the kinematics of a large sample of spectroscopically confirmed X-ray galaxy groups in the Cosmic Evolution Survey (COSMOS) with a high sampling of galaxy group members up to $z=1$. We compare our results with predictions from the cosmological hydrodynamical simulation of {\sc Horizon-AGN}. Using a phase-space analysis of dynamics of groups with halo masses of $M_{\mathrm{200c}}\sim 10^{12.6}-10^{14.50}M_\odot$, we show that the brightest group galaxies (BGG) in low mass galaxy groups ($M_{\mathrm{200c}}<2 \times 10^{13} M_\odot$) have larger proper motions relative to the group velocity dispersion than high mass groups. The dispersion in the ratio of the BGG proper velocity to the velocity dispersion of the group, $σ_{\mathrm{BGG}}/σ_{group}$, is on average $1.48 \pm 0.13$ for low mass groups and $1.01 \pm 0.09$ for high mass groups. A comparative analysis of the {\sc Horizon-AGN} simulation reveals a similar increase in the spread of peculiar velocities of BGGs with decreasing group mass, though consistency in the amplitude, shape, and mode of the BGG peculiar velocity distribution is only achieved for high mass groups. The groups hosting a BGG with a large peculiar velocity are more likely to be offset from the $L_x-σ_{v}$ relation; this is probably because the peculiar motion of the BGG is influenced by the accretion of new members.

astro-ph.GA↗

arXiv2019

The Chandra COSMOS Legacy Survey: clustering dependence of Type 2 AGN on host galaxy properties

Aims. We perform clustering measurements of 800 X-ray selected Chandra COSMOS Legacy (CCL) Type 2 AGN with known spectroscopic redshift to probe the halo mass dependence on AGN host galaxy properties, such as galaxy stellar mass Mstar, star formation rate (SFR) and specific black hole accretion rate (BHAR), in the redshift range z = [0 - 3]. Methods. We split the sample of AGN with known spectroscopic redshits according to Mstar, SFR and specific BHAR, while matching the distributions in terms of the other parameters, including redshift. We measure the projected two-point correlation function wp(rp) and model it with the 2-halo term to derive the large-scale bias b and the corresponding typical mass of the hosting halo, for the different subsamples. Results. We found no significant dependence of the large-scale bias and typical halo mass on galaxy stellar mass and specific BHAR for CCL Type 2 AGN at mean z~1, while a negative dependence on SFR is observed, with lower SFR AGN residing in richer environment. Mock catalogs of AGN matched to have the same X-ray luminosity, stellar mass, specific BHAR and SFR of CCL Type 2 AGN, almost reproduce the observed Mstar, specific BHAR and SFR-Mh relations, when assuming a fraction of satellite AGN of 15%, which corresponds to a ratio between the probabilities of satellite and central AGN of being active Q = 2. Mock matched normal galaxies follow a slightly steeper Mstar -Mh relation with low mass mock galaxies residing in less massive halos than mock AGN of similar mass, and are less biased than mock AGN with similar specific BHAR and SFR, at least for Q > 1.

astro-ph.GA↗

arXiv2019

Stellar mass -- halo mass relation for the brightest central galaxies of X-ray clusters since z~0.65

We present the brightest cluster galaxies (BCGs) catalog for SPectroscoic IDentification of eROSITA Sources (SPIDERS) DR14 cluster program value-added catalog. We list the 416 BCGs identified as part of this process, along with their stellar mass, star formation rates, and morphological properties. We identified the BCGs based on the available spectroscopic data from SPIDERS and photometric data from SDSS. We computed stellar masses and SFRs of the BCGs on the basis of SDSS, WISE, and GALEX photometry using spectral energy distribution fitting. Morphological properties for all BCGs were derived by Sersic profile fitting using the software package SIGMA in different optical bands (g,r,i). We combined this catalog with the BCGs of galaxy groups and clusters extracted from the deeper AEGIS, CDFS, COSMOS, XMM-CFHTLS, and XMM-XXL surveys to study the stellar mass - halo mass relation using the largest sample of X-ray groups and clusters known to date. This result suggests that the mass growth of the central galaxy is controlled by the hierarchical mass growth of the host halo. We find a strong correlation between the stellar mass of BCGs and the mass of their host halos. This relation shows no evolution since z $\sim$ 0.65. We measure a mean scatter of 0.21 and 0.25 for the stellar mass of BCGs in a given halo mass at low ( $0.1<z < 0.3$ ) and high ( $0.3<z<0.65$ ) redshifts, respectively. We further demonstrate that the BCG mass is covariant with the richness of the host halos in the very X-ray luminous systems. We also find evidence that part of the scatter between X-ray luminosity and richness can be reduced by considering stellar mass as an additional variable.

astro-ph.GA↗

arXiv2019

Sunyaev-Zel'dovich detection of the galaxy cluster Cl J1449+0856 at z = 1.99: the pressure profile in uv space

We present Atacama Large Millimetre Array and Atacama Compact Array observations of the Sunyaev-Zel'dovich effect in the z = 2 galaxy cluster Cl J1449+0856, an X-ray-detected progenitor of typical massive clusters in the present day Universe. While in a cleaned but otherwise untouched 92 GHz map of this cluster, little to no negative signal is visible, careful subtraction of known sub-millimetre emitters in the uv plane reveals a decrement at 5$σ$ significance. The total signal is -190$\pm$36 $μ$Jy, with a peak offset by 5"-9" ($\sim$50 kpc) from both the X-ray centroid and the still-forming brightest cluster galaxy. A comparison of the recovered uv-amplitude profile of the decrement with different pressure models allows us to derive total mass constraints consistent with the $\sim$6$\times$10$^{13}$ M$_{\odot}$ estimated from X-ray data. Moreover, we find no strong evidence for a deviation of the pressure profile with respect to local galaxy clusters, although a slight tension at small-to-intermediate spatial scales suggests a flattened central profile, opposite to what seen in a cool core and possibly an AGN-related effect. This analysis of the lowest mass single SZ detection so far illustrates the importance of interferometers when observing the SZ effect in high-redshift clusters, the cores of which cannot be considered quiescent, such that careful subtraction of galaxy emission is necessary.

astro-ph.CO↗

arXiv2019

The XMM-Newton Wide Field Survey in the COSMOS Field: Clustering Dependence of X-ray Selected AGN on Host Galaxy Properties

We study the spatial clustering through the projected two-point correlation function of $632$ $(1130)$ XMM-COSMOS Active Galactic Nuclei (AGNs) with known spectroscopic (spectroscopic or photometric) redshifts in the range $z = [0.1 - 2.5]$ in order to measure the AGN bias and estimate the typical mass of the hosting dark matter (DM) halo as a function of AGN host galaxy properties. We create AGN subsamples in terms of stellar mass $M_*$ and specific black hole accretion rate $L_X/M_*$, to probe how AGN environment depends on these quantities. For the full spectroscopic AGN sample, we measure a typical DM halo mass of $\log (M_\mathrm{halo} / h^{-1}\mathrm{M}_\odot)= 12.79_{-0.43}^{+0.26}$, similar to galaxy group environments and in line with previous studies for moderate-luminosity X-ray selected AGN. We find no significant dependence on $L_X/M_*$, with $\log (M_\mathrm{halo} / h^{-1}\mathrm{M}_\odot) = 13.06_{-0.38}^{+0.23}$ ($12.97_{-1.26}^{+0.39}$) for the low (high) $L_X/M_*$ subsample. We also find no difference in the hosting halos in terms of $M_*$ with $\log (M_\mathrm{halo} / h^{-1}\mathrm{M}_\odot) = 12.93_{-0.62}^{+0.31}$ ($12.90_{-0.62}^{+0.30}$) for the low (high) $M_*$ subsample. By comparing the $M_*-M_\mathrm{halo}$ relation derived for XMM-COSMOS AGN subsamples with what is expected for normal non-active galaxies by abundance matching and clustering results, we find that the typical DM halo mass of our high $M_*$ AGN subsample is similar to that of non-active galaxies. However, AGNs in our low $M_*$ subsample are found in more massive halos than non-active galaxies. By excluding AGNs in galaxy groups from the clustering analysis, we find evidence that the result for low $M_*$ may be due a larger fraction of AGNs as satellites in massive halos.

astro-ph.GA↗

arXiv2019

Mass Calibration of the CODEX Cluster Sample using SPIDERS Spectroscopy -- I. The Richness-Mass Relation

We use galaxy dynamical information to calibrate the richness-mass scaling relation of a sample of 428 galaxy clusters that are members of the CODEX sample with redshifts up to z~0.7. These clusters were X-ray selected using the ROSAT All-Sky Survey (RASS), cross-matched to associated systems in the redMaPPer catalog from the Sloan Digital Sky Survey. The spectroscopic sample we analyze was obtained in the SPIDERS program and contains ~7800 red member galaxies. Adopting NFW mass and galaxy density profiles and a broad range of orbital anisotropy profiles, we use the Jeans equation to calculate halo masses. Modeling the scaling relation as $λ\propto \text{A}_λ {M_{\text{200c}}}^{\text{B}_λ} ({1+z})^{γ_λ}$, we find the parameter constraints $\text{A}_λ=38.6^{+3.1}_{-4.1}\pm3.9$, $\text{B}_λ=0.99^{+0.06}_{-0.07}\pm0.04$, and $γ_λ=-1.13^{+0.32}_{-0.34}\pm0.49$. We find good agreement with previously published mass trends with the exception of those from stacked weak lensing analyses. We note that although the lensing analyses failed to account for the Eddington bias, this is not enough to explain the differences. We suggest that differences in the levels of contamination between pure redMaPPer and RASS+redMaPPer samples could well contribute to these differences. The redshift trend we measure is more negative than but statistically consistent with previous results. We suggest that our measured redshift trend reflects a change in the cluster galaxy red sequence fraction with redshift, noting that the trend we measure is consistent with but somewhat stronger than an independently measured redshift trend in the red sequence fraction. We also examine the impact of a plausible model of correlated scatter in X-ray luminosity and optical richness, showing it has negligible impact on our results.

astro-ph.CO↗

arXiv2019

Active Galactic Nuclei and their Large-scale Structure: an eROSITA mock catalogue

In the context of the upcoming SRG/eROSITA survey, we present an N-body simulation-based mock catalogue for X-ray selected AGN samples. The model reproduces the observed hard X-ray AGN luminosity function (XLF) and the soft X-ray logN-logS from redshift 0 to 6. The XLF is reproduced to within $\pm5\%$ and the logN-logS to within $\pm20\%$. We develop a joint X-ray -- optical extinction and classification model. We adopt a set of empirical spectral energy distributions to predict observed magnitudes in the UV, optical and NIR. With the latest eROSITA all sky survey sensitivity model, we create a high-fidelity full-sky mock catalogue of X-ray AGN. It predicts their distributions in right ascension, declination, redshift and fluxes. Using empirical medium resolution optical spectral templates and an exposure time calculator, we find that $1.1\times10^6$ ($4\times10^5$) fiber-hours are needed to follow-up spectroscopically from the ground the detected X-ray AGN with an optical magnitude $21<r<22.8$ ($22.8<r<25$) with a 4-m (8-m) class multi-object spectroscopic facility. We find that future clustering studies will measure the AGN bias to the percent level at redshift $z<1.2$ and should discriminate possible scenarios of galaxy-AGN co-evolution. We predict the accuracy to which the baryon acoustic oscillation standard ruler will be measured using X-ray AGN: better than 3\% for AGN between redshift 0.5 to 3 and better than 1\% using the Ly$α$ forest of X-ray QSOs discovered between redshift 2 and 3. eROSITA will provide an outstanding set of targets for future galaxy evolution and cosmological studies.

astro-ph.GA↗

arXiv2019

Group connectivity in COSMOS: a tracer of mass assembly history

Cosmic filaments are the channel through which galaxy groups assemble their mass. Cosmic connectivity, namely the number of filaments connected to a given group, is therefore expected to be an important ingredient in shaping group properties. The local connectivity is measured in COSMOS around X-Ray detected groups between redshift 0.5 and 1.2. To this end, large-scale filaments are extracted using the accurate photometric redshifts of the COSMOS2015 catalogue in two-dimensional slices of thickness 120 comoving Mpc centred on the group's redshift. The link between connectivity, group mass and the properties of the brightest group galaxy (BGG) is investigated. The same measurement is carried out on mocks extracted from the lightcone of the hydrodynamical simulation Horizon-AGN in order to control systematics. More massive groups are on average more connected. At fixed group mass in low-mass groups, BGG mass is slightly enhanced at high connectivity, while in high mass groups BGG mass is lower at higher connectivity. Groups with a star-forming BGG have on average a lower connectivity at given mass. From the analysis of the Horizon-AGN simulation, we postulate that different connectivities trace different paths of group mass assembly: at high group mass, groups with higher connectivity are more likely to have grown through a recent major merger, which might be in turn the reason for the quenching of the BGG. Future large-field photometric surveys, such as Euclid and LSST, will be able to confirm and extend these results by probing a wider mass range and a larger variety of environment.

astro-ph.GA↗