arXiv subjects

Hernan Muriel

Publications and source records attributed to Hernan Muriel.

At least 19 recordsLinked to original sources

arXiv2022

Reconstructing Orbits of Galaxies in Extreme Regions (ROGER) III: galaxy evolution patterns in projected phase space around massive X-ray clusters

We use the ROGER code by de los Rios et al. to classify galaxies around a sample of X-ray clusters into five classes according to their positions in the projected phase space diagram: cluster galaxies, backsplash galaxies, recent infallers, infalling galaxies, and interlopers. To understand the effects of the cluster environment to the evolution of galaxies, we compare across the five classes: stellar mass, specific star formation rate, size, and morphology. Following the guidelines of Coenda et al., a separate analysis is carried out for red and blue galaxies. For red galaxies, cluster galaxies differ from the other classes, having a suppressed specific star formation rate, smaller sizes, and are more likely to be classified as ellipticals. Differences are smaller between the other classes, however backsplash galaxies have significantly lower specific star formation rates than early or recent infalling galaxies. For blue galaxies, we find evidence that recent infallers are smaller than infalling galaxies and interlopers, while the latter two are comparable in size. Our results provide evidence that, after a single passage, the cluster environment can diminish a galaxy's star formation, modify its morphology, and can also reduce in size blue galaxies. We find evidence that quenching occurs faster than morphological transformation from spirals to ellipticals for all classes. While quenching is evidently enhanced as soon as galaxies get into clusters, significant morphological transformations require galaxies to experience the action of the physical mechanisms of the cluster for longer timescales.

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arXiv2020

The GOGREEN and GCLASS Surveys: First Data Release

We present the first public data release of the GOGREEN and GCLASS surveys of galaxies in dense environments, spanning a redshift range $0.8<z<1.5$. The surveys consist of deep, multiwavelength photometry and extensive Gemini GMOS spectroscopy of galaxies in 26 overdense systems ranging in halo mass from small groups to the most massive clusters. The objective of both projects was primarily to understand how the evolution of galaxies is affected by their environment, and to determine the physical processes that lead to the quenching of star formation. There was an emphasis on obtaining unbiased spectroscopy over a wide stellar mass range ($M\gtrsim 2\times 10^{10}~\mathrm{M}_\odot$), throughout and beyond the cluster virialized regions. The final spectroscopic sample includes 2771 unique objects, of which 2257 have reliable spectroscopic redshifts. Of these, 1704 have redshifts in the range $0.8<z<1.5$, and nearly 800 are confirmed cluster members. Imaging spans the full optical and near-infrared wavelength range, at depths comparable to the UltraVISTA survey, and includes \textit{HST}/WFC3 F160W (GOGREEN) and F140W (GCLASS). This data release includes fully reduced images and spectra, with catalogues of advanced data products including redshifts, line strengths, star formation rates, stellar masses and rest-frame colours. Here we present an overview of the data, including an analysis of the spectroscopic completeness and redshift quality.

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arXiv2020

Simulating the Spatial Distribution and Kinematics of Globular Clusters within Galaxy Clusters in Illustris

We study the assembly of globular clusters (GCs) in 9 galaxy clusters using the cosmological simulation Illustris. GCs are tagged to individual galaxies at their infall time. The tidal removal of GCs from their galaxies and the distribution of the GCs within the cluster is later followed self-consistently by the simulation. The method relies on the simple assumption of a single power-law relation between halo mass (M_vir) and mass in GCs (M_GC) as found in observations. We find that the GCs specific frequency $S_N$ as a function of V-band magnitude naturally reproduces the observed "U"-shape, due to the combination of a power law M_GC-M_vir relation and the non-linear M_*-M_vir relation from the simulation. Additional scatter in the $S_N$ values are traced back to galaxies with early infall times due to the evolution in the M_*-M_vir relation with redshift. GCs that have been tidally removed from their galaxies form today the intra-cluster component from which about ~60% were brought in by galaxies that orbit today within the cluster potential. The remaining "orphan" GCs are contributed by satellite galaxies with a wide range of stellar masses that are fully tidally disrupted at z=0. This intra-cluster component is a good dynamical tracer of the dark matter potential. As a consequence of the accreted nature of most intra-cluster GCs, their orbits are fairly radial with a predicted orbital anisotropy β>= 0.5. However, local tangential motions may appear as a consequence of localized substructure, providing a possible interpretation to the β<0 values suggested in observations of M87.

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arXiv2017

Gemini Observations of Galaxies in Rich Early Environments (GOGREEN) I: Survey Description

We describe a new Large Program in progress on the Gemini North and South telescopes: Gemini Observations of Galaxies in Rich Early Environments (GOGREEN). This is an imaging and deep spectroscopic survey of 21 galaxy systems at $1 10$ in halo mass. The scientific objectives include measuring the role of environment in the evolution of low-mass galaxies, and measuring the dynamics and stellar contents of their host haloes. The targets are selected from the SpARCS, SPT, COSMOS and SXDS surveys, to be the evolutionary counterparts of today's clusters and groups. The new red-sensitive Hamamatsu detectors on GMOS, coupled with the nod-and-shuffle sky subtraction, allow simultaneous wavelength coverage over $λ\sim 0.6$--$1.05μ$m, and this enables a homogeneous and statistically complete redshift survey of galaxies of all types. The spectroscopic sample targets galaxies with AB magnitudes $z^{\prime}<24.25$ and [3.6]$μ$m$<22.5$, and is therefore statistically complete for stellar masses $M_\ast\gtrsim10^{10.3}M_\odot$, for all galaxy types and over the entire redshift range. Deep, multiwavelength imaging has been acquired over larger fields for most systems, spanning $u$ through $K$, in addition to deep IRAC imaging at 3.6$μ$m. The spectroscopy is $\sim 50$ per cent complete as of semester 17A, and we anticipate a final sample of $\sim 500$ new cluster members. Combined with existing spectroscopy on the brighter galaxies from GCLASS, SPT and other sources, GOGREEN will be a large legacy cluster and field galaxy sample at this redshift that spectroscopically covers a wide range in stellar mass, halo mass, and clustercentric radius.

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arXiv2015

Galaxies infalling into groups: filaments vs. isotropic infall

We perform a comparative analysis of the properties of galaxies infalling into groups classifying them accordingly to whether they are: falling along filamentary structures; or they are falling isotropically. For this purpose, we identify filamentary structures connecting massive groups of galaxies in the SDSS. We perform a comparative analysis of some properties of galaxies in filaments, in the isotropic infall region, in the field, and in groups. We study the luminosity functions (LF) and the dependence of the specific star formation rate (SSFR) on stellar mass, galaxy type, and projected distance to the groups that define the filaments. We find that the LF of galaxies in filaments and in the isotropic infalling region are basically indistinguishable between them, with the possible exception of late-type galaxies. On the other hard, regardless of galaxy type, their LFs are clearly different from that of field or group galaxies. Both of them have characteristic absolute magnitudes and faint end slopes in between the field and group values. More significant differences between galaxies in filaments and in the isotropic infall region are observed when we analyse the SSFR. We find that galaxies in filaments have a systematically higher fraction of galaxies with low SSFR as a function of both, stellar mass and distance to the groups, indicating a stronger quenching of the star formation in the filaments compared to both, the isotropic infalling region, and the field. Our results suggest that some physical mechanisms that determine the differences observed between field galaxies and galaxies in systems, affect galaxies even when they are not yet within the systems.

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arXiv2012

Comparing galaxy populations in compact and loose groups of galaxies

We perform a comparison of the properties of galaxies in compact groups, loose groups and in the field to deepen our understanding of the physical mechanisms acting upon galaxy evolution in different environments. We select samples of galaxies in compact groups identified by McConnachie et al., loose groups identified by Zandivarez and Martinez, and field galaxies from the Sloan Digital Sky Survey. We compare properties of the galaxy populations in these different environments: absolute magnitude, colour, size, surface brightness, stellar mass and concentration. We also study the fraction of red and early type galaxies, the luminosity function, the colour-luminosity and luminosity-size relations. The population of galaxies in compact groups differ from that of loose groups and the field. The fraction of read and early type galaxies is higher in compact groups. On average, galaxies in compact groups are systematically smaller, more concentrated and have higher surface brightness than galaxies in the field and in loose groups. For fixed absolute magnitude, or fixed surface brightness, galaxies in compact groups are smaller. The physical mechanisms that transform galaxies into earlier types could be more effective within compact groups given the high densities and low velocity dispersion that characterise that particular environment, this could explain the large fraction of red and early type galaxies we found in compact groups. Galaxies inhabiting compact groups have undergone a major transformation compared to galaxies that inhabit loose groups.

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arXiv2011

Relating bars with the environment in the nearby Universe

We study the correlation between the fraction of barred spiral galaxies and environmental parameters of galaxies to understand in which environments the bars are more commonly found. For this purpose we apply the Blanton et al. technique to a sample of spiral galaxies drawn from the Nair & Abraham catalogue. Our results agree with previous findings in which the fraction of barred galaxies is almost insensitive to environment.

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arXiv2011

The Luminosity Profiles of Brightest Cluster Galaxies

(Abridged) We have derived detailed R band luminosity profiles and structural parameters for a total of 430 brightest cluster galaxies (BCGs), down to a limiting surface brightness of 24.5 mag/arcsec^2. Light profiles were initially fitted with a Sersic's R^(1/n) model, but we found that 205 (~48) BCGs require a double component model to accurately match their light profiles. The best fit for these 205 galaxies is an inner Sersic model, with indices n~1-7, plus an outer exponential component. Thus, we establish the existence of two categories of the BCGs luminosity profiles: single and double component profiles. We found that double profile BCGs are brighter ~0.2 mag than single profile BCG. In fact, the Kolmogorov-Smirnov test applied to these subsamples indicates that they have different total magnitude distributions, with mean values M_R=-23.8 +/- 0.6 mag for single profile BCGs and M_R=-24.0 +/- 0.5 mag for double profile BCGs. We find that partial luminosities for both subsamples are indistinguishable up to r = 15 kpc, while for r > 20 kpc the luminosities we obtain are on average 0.2 mag brighter for double profile BCGs. This result indicates that extra-light for double profile BCGs does not come from the inner region but from the outer regions of these galaxies. The best fit slope of the Kormendy relation for the whole sample is a = 3.13 +/- 0.04$. However, when fitted separately, single and double profile BCGs show different slopes: a_(single) = 3.29 +/- 0.06 and a_(double)= 2.79 +/- 0.08. On the other hand, we did not find differences between these two BCGs categories when we compared global cluster properties such as the BCG-projected position relative to the cluster X-ray center emission, X-ray luminosity, or BCG orientation with respect to the cluster position angle.

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arXiv2009

The environmental dependence of the red galaxy sequence

The dependence of the sequence of red galaxies (RS) with the environment is investigated using field, group, and cluster galaxies drawn from the SDSS. Our work focuses in studying the mean colour ($μ_R$) and the scatter ($σ_R$) of the RS as a function absolute magnitude in different environments characterised either by the mass of the system in which the galaxies are located or by the distance to the system's centre. The same analysis is carried out using red early type galaxies. For a given luminosity, $μ_R$ of field galaxies is bluer and $σ_R$ is larger than their group and cluster counterparts irrespective of mass and position within the systems. Among systems of galaxies, high mass groups and clusters have the reddest $μ_R$ and the smallest $σ_R$. These differences almost disappear when red early type galaxies alone are considered. Galaxies in the core and in the outskirts of groups have similar $μ_R$, whereas galaxies in clusters show a strong dependence on cluster centric distance. Red early type galaxies in the outskirts of clusters have $σ_R$ values as large as field galaxies', while galaxies in the inner regions of clusters have lower values. We find that bright red early type galaxies have reached nearly the same evolutionary stage in all environments. Our results suggest that the cluster environment is not necessary to populate the RS. We propose a scenario in which the RS in massive systems is populated by two different star formation history galaxies: red early type galaxies that formed the bulk of their stars during the early stages of massive halo assembly, and red galaxies that passed most of their lives inhabiting poor groups or the field and fell into massive systems at lower redshifts.

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arXiv2009

Tidal Stripping of Globular Clusters in the Virgo Cluster

With the aim of finding evidence of tidal stripping of globular clusters (GCs) we analysed a sample of 13 elliptical galaxies taken from the ACS Virgo Cluster Survey (VCS). These galaxies belong to the main concentration of the Virgo cluster (VC) and present absolute magnitudes $-18.5<M_z<-22.5$. We used the public GC catalog of Jordán et al. (2008) and separated the GC population into metal poor (blue) and metal rich (red) according to their integrated colors. The galaxy properties were taken from \citet{Peng:2008}. We found that: 1) The specific frequencies ($S_N$) of total and blue GC populations increase as a function of the projected galaxy distances $r_p$ to M87. A similar result is observed when 3-dimensional distances $r_{3D}$ are used. The same behaviours are found if the analysis are made using the number of GCs per $10^9\Msun$ ($T$). The correlations with the clustocentric distance of the host galaxy are interpreted as evidence of GCs stripping due to tidal forces. 2) No correlation is found between the slope of GC density profiles of host galaxies and the galaxy distance to M87 (Virgo central galaxy). 3) We also computed the local density of GCs ($ρ_{out}$) located further than $6.2 \kpc$ from the galaxy center for nine galaxies of our sample. We find that the GC population around most of these galaxies is mainly composed of blue GCs. Our results suggest that the number and the fraction of blue and red GCs observed in elliptical galaxies located near the centers of massive clusters, could be significantly different from the underlying GC population. These differences could be explained by tidal stripping effects that occur as galaxies approach the centers of clusters.

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arXiv2008

Fossil Groups in the Millennium Simulation. Evolution of the Brightest Galaxies

We create a catalogue of simulated fossil groups and study their properties, in particular the merging histories of their first-ranked galaxies. We compare the simulated fossil group properties with those of both simulated non-fossil and observed fossil groups. Using simulations and a mock galaxy catalogue, we searched for massive ($>$ 5 $\times$ 10$^{13} h^{-1} {\cal M}_\odot$) fossil groups in the Millennium Simulation Galaxy Catalogue. In addition, attempted to identify observed fossil groups in the Sloan Digital Sky Survey Data Release 6 using identical selection criteria. Our predictions on the basis of the simulation data are:(a) fossil groups comprise about 5.5% of the total population of groups/clusters with masses larger than 5 x 10$^{13} h^{-1} {\cal M}_\odot$. This fraction is consistent with the fraction of fossil groups identified in the SDSS, after all observational biases have been taken into account; (b) about 88% of the dominant central objects in fossil groups are elliptical galaxies that have a median R-band absolute magnitude of $\sim -23.5-5 log h$, which is typical of the observed fossil groups known in the literature; (c)first-ranked galaxies of systems with $ {\cal M} >$ 5 x 10$^{13} h^{-1} {\cal M}_\odot$, regardless of whether they are either fossil or non-fossil, are mainly formed by gas-poor mergers; (d) although fossil groups, in general, assembled most of their virial masses at higher redshifts in comparison with non-fossil groups, first-ranked galaxies in fossil groups merged later, i.e. at lower redshifts, compared with their non-fossil-group counterparts. We therefore expect to observe a number of luminous galaxies in the centres of fossil groups that show signs of a recent major merger.

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arXiv2008

On the relationship between environment and galaxy properties in clusters of galaxies

We study the correlation between different properties of bright (L>L*) galaxies in clusters and the environment in the Sloan Digital Sky Survey (SDSS). Samples of clusters of galaxies used in this paper are those selected by Coenda & Muriel that are drawn from the Popesso et al. and Koester et al. samples. Galaxies in these clusters have been identified in the Main Galaxy Sample of the Fifth Data Release (DR5) of SDSS. We analyse which galaxy properties correlate best with either, cluster mass or cluster-centric distance using the technique by Blanton et al. We find that galaxy properties do not clearly depend on cluster mass for clusters more massive than M~10^{14}M_sun. On the other hand, galaxy properties correlate with cluster-centric distance. The property most affected by the cluster-centric distance is g-r colour, closely followed by the u-r colour. These results are irrespective of the cluster selection criteria. The two samples of clusters were identified based on the X-ray emission and the galaxy colours, respectively. Moreover, the parameter that best predicts environment (i.e. cluster-centric distance) is the same found by Martinez & Muriel for groups of galaxies and Blanton at al. for the local density of field galaxies.

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arXiv2006

Groups of galaxies: relationship between environment and galaxy properties

We analyse how the properties of galaxies in groups identified in the Sloan Digital Sky Survey depend on the environment. In particular, we study the relationship between galaxy properties and group mass and group-centric distance. Among the galaxy properties we have considered here, we find that the $g-r$ colour is the most predictive parameter for group mass, while the most predictive pair of properties are $g-r$ colour and $r-$band absolute magnitude. Regarding the position inside the systems, the $g-r$ colour is the best tracer of group-centric distance and the most predictive pair of properties are $g-r$ colour and spectral type taken together. These results remain unchanged when a subsample of high mass groups is analysed. The same happens if the brightest group galaxies are excluded.

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arXiv2005

Structure and dynamics of the Shapley Supercluster

We present results of our wide-field redshift survey of galaxies in a 285 square degree region of the Shapley Supercluster (SSC), based on a set of 10529 velocity measurements (including 1201 new ones) on 8632 galaxies obtained from various telescopes and from the literature. Our data reveal that the main plane of the SSC (v~ 14500 km/s) extends further than previous estimates, filling the whole extent of our survey region of 12~degrees by 30~degrees on the sky (30 x 75~h-1 Mpc). There is also a connecting structure associated with the slightly nearer Abell~3571 cluster complex (v~ 12000km/s. These galaxies seem to link two previously identified sheets of galaxies and establish a connection with a third one at V= 15000 km/s near R.A.= 13h. They also tend to fill the gap of galaxies between the foreground Hydra-Centaurus region and the more distant SSC. In the velocity range of the Shapley Supercluster (9000 km/s < cz < 18000 km/s), we found redshift-space overdensities with b\_j < 17.5 of ~5.4 over the 225 square degree central region and ~3.8 in a 192 square degree region excluding rich clusters. Over the large region of our survey, we find that the intercluster galaxies make up 48 per cent of the observed galaxies in the SSC region and, accounting for the different completeness, may contribute nearly twice as much mass as the cluster galaxies. In this paper, we discuss the completeness of the velocity catalogue, the morphology of the supercluster, the global overdensity, and some properties of the individual galaxy clusters in the Supercluster.

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arXiv2005

Systems of Galaxies in the SDSS: the fundamental plane

We analyse a subsample of the galaxy groups obtained by Merchán & Zandivarez (2005) from the SDSS DR3 to study the fundamental plane and the mass to light ratio of galaxy groups. We find a fundamental plane given by $L_R \propto R^{1.3} σ^{0.7}$. We do not find differences when different dynamical sates or redshift ranges are analysed. We find that the mass to light ratio increases with group mass as $M/L_R \propto M^{0.36}$.

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arXiv2005

2dFGRS and SDSS Galaxy Group Density Profiles

We have analysed the distribution of galaxies in groups identified in the largest redshift surveys at the present: the final release of the 2dF Galaxy Redshift Survey and the first release of the Sloan Digital Sky Survey. Our work comprises the study of the galaxy density profiles and the fraction of galaxies per spectral type as a function of the group-centric distance. We have calculated the projected galaxy density profiles of galaxy groups using composite samples in order to increase the statistical significance of the results. Special cares have been taken in order to avoid possible biases in the group identification and the construction of the projected galaxy density profile estimator. The results show that the projected galaxy density profiles obtained for both redshift surveys are in agreement with a projected Navarro, Frenk & White predictions in the range $0.15< r/r_{200} < 1$, whereas a good fit for the measured profiles in the whole range of $r/r_{200}$ is given by a projected King profile. We have adopted a generalized King profile to fit the measured projected density profiles per spectral type. In order to infer the 3-D galaxy density profiles, we deproject the 2-D density profiles using a deprojection method similar to the developed by Allen & Fabian. From 2-D and 3-D galaxy density profiles we have estimated the corresponding galaxy fractions per spectral type. The 2-D fraction of galaxies computed using the projected profiles show a similar segregation of galaxy spectral types as the obtained by Dom\'ınguez et al. for groups in the early data release of the 2dF Galaxy Redshift Survey. As expected, the trends obtained for the 3-D galaxy fractions show steeper slopes than the observed in the 2-D fractions.

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arXiv2003

Faint galaxy population in clusters: X-ray emission, cD halos and projection effects

We analyze samples of nearby clusters taken from the Abell catalog and the X-ray Sample of Bright Clusters(De Grandi et al 1999) including a wide range of X-ray luminosities.Using the usually adopted background subtraction procedures, we find that galaxies in clusters selected by means of their X-ray emission show a flat luminosity function (faint end slope $α\simeq -1.1$) consistent with that derived for galaxies in the field and groups. By contrast, the sample of Abell clusters that do not have an X-ray counterpart shows a galaxy luminosity function with a steep faint end ($α\simeq -1.6$). We investigate the possibility that cD halos could be formed by the disruption of galaxies in rich relaxed clusters that show an apparently flat faint end galaxy luminosity function (Lopez-Cruz et al 1997). We find that clusters dominated by a central cD galaxy (Bautz-Morgan classes I and II) show the same systematic trend: X-ray selected clusters have flatter faint end slopes than those clusters with no detected X-ray emission. Thus, it is likely the X-ray selection and not the cluster domination by central galaxies what correlates with background decontamination estimates of the galaxy luminosity function. Moreover, no significant correlation between X-ray luminosity and the galaxy LF faint end slope is found. These results do not support a scenario where flat faint end slopes are a consequence of cD formation via the disruption of faint galaxies. We argue that the clusters without X-ray emission are strongly affected by projection effects which give rise to spurious faint end slopes estimated using background subtraction procedures (Valotto et al 2001).

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arXiv2002

Velocity dispersions and cluster properties in the SARS (Southern Abell Redshift Survey) clusters. Paper II

We report an analysis of the dynamical structure of clusters of galaxies from a survey of photometric and spectroscopic observations in the fields of southern Abell Clusters. We analyze the galaxy velocity field in extended regions up to 7 h^-1 Mpc from cluster centers and we estimate mean velocity dispersions and their radial dependence. Only one from a total number of 41 Abell clusters does not correspond to a dynamically bound system. However, four of these bound objects are double clusters. We estimate that 20 % (7 clusters) of the 35 remaining are subject to serious projection effects. Normalizing the clustercentric distances by means of the overdensity radius r_200, and the velocity dispersion profiles (VDPs) by the corresponding mean cluster velocity dispersion, we computed the average VDP. Our results indicate a flat behavior of the mean VDP at large distances from the cluster center. Nevertheless, we found that for the inner part of the clusters (r/r_200 leq 1) the VDP is up to a 10% smaller than at larger radii.

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