arXiv subjects

Facundo Rodriguez

Publications and source records attributed to Facundo Rodriguez.

35 records · Page 2Linked to original sources

arXiv2023

Anisotropic correlation functions as tracers of central galaxy alignments in simulations

Motivated by observational results, we use IllustrisTNG hydrodynamical numerical simulations to study the alignment of the central galaxies in groups with the surrounding structures. This approach allows us to analyse galaxy and group properties not available in observations. To perform this analysis, we use a modified version of the two-point cross-correlation function and a measure of the angle between the semi-major axes of the central galaxies and the larger structures. Overall, our results reproduce observational ones, as we find large-scale anisotropy, which is dominated by the red central galaxies. In addition, the latter is noticeably more aligned with their group than the blue ones. In contrast to the observations, we find a strong dependence of the anisotropy on the central galaxy with mass, probably associated with the inability of observational methods to determine them. This result allows us to link the alignment to the process of halo assembly and the well-known dependence of halo anisotropy on mass. When we include the dark matter distribution in our analysis, we conclude that the galaxy alignment found in simulations (and observations) can be explained by a combination of physical processes at different scales: the central galaxy aligns with the dark matter halo it inhabits, and this, in turn, aligns with the surrounding structures at large scales.

astro-ph.CO↗

arXiv2022

Tracking the evolution of satellite galaxies: mass stripping and dark-matter deficient galaxies

Satellite galaxies undergo a variety of physical processes when they are accreted by groups and clusters, often resulting in the loss of baryonic and dark matter (DM) mass. In this work, we evaluate the predictions from the IllustrisTNG hydrodynamical simulation regarding the evolution of the matter content of satellites, focusing on a population that are accreted at $z>1$ and retain their identity as satellites down to $z=0$. At fixed host halo mass, the amount of DM and stellar mass stripped depends mostly on the pericentric distance, $d_{\rm peri}$, here normalised by host halo virial radius. The closest encounters result in significant loss of DM, with subhaloes retaining between 20 and a few per cent of their $z=1$ mass. At fixed $d_{\rm peri}$, DM mass stripping seems more severe in lower mass haloes. Conversely, the average satellite in higher mass haloes has its stellar mass growth halted earlier, having lost a higher fraction of stellar mass by $z=0$. We also show that mass stripping has a strong impact on the quenched fractions. The IllustrisTNG boxes are qualitatively consistent in these predictions, with quantitative differences mostly originating from the distinct subhalo mass ranges covered by the boxes. Finally, we have identified DM-deficient systems in all TNG boxes. These objects are preferentially found in massive clusters ($M_{\rm host } \gtrsim 10^{13}$ M$_\odot$), had very close encounters with their central galaxies ($d_{\rm peri}\simeq0.05\, R_{\rm vir}$), and were accreted at high redshift ($z_{\rm infall} \gtrsim 1.4$), reinforcing the notion that tidal stripping is responsible for their remarkable lack of DM.

astro-ph.GA↗

arXiv2022

Alignment of the central galaxies with the environment

In this work, we combine ellipticity and major axis position angle measurements from the Sloan Digital Sky Server Data Release 16 (SDSS DR16) with the group finder algorithm of Rodriguez \& Merchán to determine the alignment of the central galaxies with the surrounding structures and satellite galaxies lying in their group. We use two independent methods: A modified version of the two-point cross-correlation function and the angle between the central galaxy orientation and the satellite galaxies relative position. The first method allows us to study the inner and outer regions of the cluster, while the second method provides information within the halos. Our results show that central galaxies present anysotropy in the correlation function up to $\sim 10 h^{-1}Mpc$, which becomes $\sim$10\% stronger for the brightest ones ($^{0.1}M_{r}<-21.5$). When we split the galaxy sample by colour, we find that red central galaxies are the main contributors to this anisotropy. We also show that this behaviour does not depend on the group mass or central galaxy ellipticity. Finally, our results are in agreement with previous findings, showing that the two-point cross-correlation function is a good tracer of the galaxy alignments using all galaxies and not only those of the group to which it belongs. In addition, this feature allows us to explore the behaviour of the alignment on larger scales.

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arXiv2022

New catalogue of dark-matter halo properties identified in MICE-GC -- I. Analysis of density profile distributions

Constraints on dark matter halo masses from weak gravitational lensing can be improved significantly by using additional information about the morphology of their density distribution, leading to tighter cosmological constraints derived from the halo mass function. This work is the first of two in which we investigate the accuracy of halo morphology and mass measurements in 2D and 3D. To this end, we determine several halo physical properties in the MICE-Grand Challenge dark matter only simulation. We present a public catalogue of these properties that includes density profiles and shape parameters measured in 2D and 3D, the halo centre at the peak of the 3D density distribution as well as the gravitational and kinetic energies and angular momentum vectors. The density profiles are computed using spherical and ellipsoidal radial bins, taking into account the halo shapes. We also provide halo concentrations and masses derived from fits to 2D and 3D density profiles using NFW and Einasto models for halos with more than $1000$ particles ($\gtrsim 3 \times 10^{13} h^{-1} M_{\odot}$). We find that the Einasto model provides better fits compared to NFW, regardless of the halo relaxation state and shape. The mass and concentration parameters of the 3D density profiles derived from fits to the 2D profiles are in general biased. Similar biases are obtained when constraining mass and concentrations using a weak-lensing stacking analysis. We show that these biases depend on the radial range and density profile model adopted in the fitting procedure, but not on the halo shape.

astro-ph.CO↗

arXiv2022

On the environmental influence of groups and clusters of galaxies beyond the virial radius: Galactic conformity at few Mpc scales

The environment within dark matter haloes can quench the star formation of galaxies. However, environmental effects beyond the virial radius of haloes ($\gtrsim$ 1 Mpc) are less evident. An example is the debated correlation between colour or star formation in central galaxies and neighbour galaxies in adjacent haloes at large separations of several Mpc, referred to as two-halo galactic conformity. We use two galaxy catalogues generated from different versions of the semi-analytic model SAG applied to the MDPL2 cosmological simulation and the IllustrisTNG300 cosmological hydrodynamical simulation to study the two-halo conformity by measuring the quenched fraction of neighbouring galaxies as a function of the real-space distance from central galaxies. We find that low-mass central galaxies in the vicinity of massive systems ($M_{\rm 200c}$ $\geq$ 10$^{13}$ $h^{-1}~\rm M_{\odot}$) out to 5 $h^{-1}$ Mpc are preferentially quenched compared to other central galaxies at fixed stellar mass $M_{\star}$ or fixed host halo mass $M_{\rm 200c}$ at $z$ ~ 0. In all the galaxies catalogues is consistent that the low-mass ($M_{\star} < 10^{10}$ $h^{-1}~\rm M_{\odot}$ or $M_{\rm 200c} < 10^{11.8}$ $h^{-1}~\rm M_{\odot}$) central galaxies in the vicinity of clusters and, especially, groups of galaxies mostly produce the two-halo galactic conformity. On average, the quenched low-mass central galaxies are much closer to massive haloes than star-forming central galaxies of the same mass (by a factor of ~5). Our results agree with other works regarding the environmental influence of massive haloes that can extend beyond the virial radius and affect nearby low-mass central galaxies.

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arXiv2022

Galaxy populations in haloes in high-density environments

There are hints suggesting that properties of galaxy populations in dark matter haloes may depend on their large-scale environment. Recent works point out that very low-density environments influence halo occupation distribution (HOD), however there is not a similar analysis focused on high-density environments. Here we use a simulated set of future virialized superstructures (FVS) to analyse the occupation of galaxies in haloes within these high globally dense regions. We use a publicly available simulated galaxy set constructed with a semi-analytical model to identify FVS in the simulation. Then, we computed the HOD within these superstructures for different absolute magnitude thresholds and make several analysis including the comparison to the global HOD results. We study the dependence on the results on properties of the FVS such as density and volume as well as consider the morphology of galaxies. We also analysed the properties of the stellar content of galaxies and the formation time of the haloes inside FVS. We find a significant increase in the HOD inside FVS. This result is present for all absolute magnitude thresholds explored. The effect is larger in the densest regions of FVS, but does not depend on the volume of the superstructure. We also find that the stellar-mass content of galaxies considerably differs inside the superstructures. Low mass haloes have their central and satellite galaxies with a higher stellar mass content (50%), and exhibit mean star ages (20%) older than average. For massive haloes in FVS we find that only the stellar mass of satellite galaxies varies considerably corresponding to a decrease of 50%. We find a significant statistical difference between the formation times of haloes in FVS and the average population. Haloes residing in superstructures formed earlier, a fact that leads to several changes in the HOD and their member galaxy properties.

astro-ph.CO↗

arXiv2022

How do galaxies populate halos in extreme density environments? An analysis of the Halo Occupation Distribution in SDSS

Recent works have shown that the properties of galaxy populations in dark matter halos vary with large-scale environments. These results suggest a variation in the halo occupation distribution (HOD) in extreme density environments. To analyse these effects, we identify cosmic voids and future virialised structures (FVS) in the SDSS-DR12 and estimate the HOD within these superstructures using group catalogues as dark matter halo proxies. Our goal is to use observational galaxy data to characterise the HOD within voids and FVS, explore the different properties of these galaxies populations and compare them with the general results outside these superstructures. Using a galaxy group catalogue we compute the HOD within both types of superstructures. We also study the dependence on the results on the main void and FVS properties. We also analysed the mean stellar age of the galaxies inside these regions. In all cases, we compare the results with those derived from the Field sample. Inside voids, we find a strong decrease in HOD concerning the Field results. The mean number of satellites fall to 50%. Inside FVS, the HOD shows a significant increase to the Field, with a 40% excess in the mean number of satellites. In both regions, the differences with respect to the Field increases for the extreme values of the density environments. We obtain no signs of variations related to intrinsic characteristics of voids and FVS. We find that the cumulative distribution of the mean age of stars of the central galaxy also varies in these regions. Finally, we explore the HOD for the 25% youngest (oldest) galaxies. We find that for the low-mass groups the youngest galaxies are only present inside voids. On the other hand, for the high-mass groups the FVS environments show the same increase in the HOD concerning the Field. We find that cosmic voids lack of oldest galaxies.

astro-ph.CO↗

arXiv2021

The galaxy size - halo mass scaling relations and clustering properties of central and satellite galaxies

In this work, we combine size and stellar mass measurements from the Sloan Digital Sky Server (SDSS) with the group finder algorithm of Rodriguez \& Merchán in order to determine the stellar and halo mass -- size relations of central and satellite galaxies separately. We show that, while central and satellite galaxies display similar stellar mass -- size relations, their halo mass -- size relations differ significantly. As expected, more massive haloes tend to host larger central galaxies. However, the size of satellite galaxies depends only slightly on halo virial mass. We show that these results are compatible with a remarkably simple model in which the size of central and satellite galaxies scales as the cubic root of their host halo mass, with the normalization for satellites being $\sim$ 30 \% smaller than that for central galaxies, which can be attributed to tidal stripping. We further check that our measurements are in excellent agreement with predictions from the IllustrisTNG hydrodynamical simulation. In the second part of this paper, we analyse how the clustering properties of central and satellite galaxies depend on their size. We demonstrate that, independently of the stellar mass threshold adopted, smaller galaxies are more tightly clustered than larger galaxies when either the entire sample or only satellites are considered. The opposite trend is observed on large scales when the size split is performed for the central galaxies alone. Our results place significant constraints for halo-galaxy connection models that link galaxy size with the properties of their hosting haloes.

astro-ph.GA↗

arXiv2021

Dark matter in Actor-Network Theory context (La materia oscura en el contexto de la teoría del actor-red)

The aim of this work is to use some categories of Actor-Network Theory (ANT) developed by Bruno Latour in the book Reassembling the Social -- An Introduction to Actor-Network Theory to analyze a current controversy that occurs in the area of cosmology: the dark matter existence and its characteristics. The central idea of this article is to try to decipher which type of agent is the dark matter and open the discussion about this topic from a sociological perspective.

physics.hist-ph↗

arXiv2021

On the weak lensing masses of a new sample of galaxy groups

Galaxy group masses are important to relate these systems with the dark matter halo hosts. However, deriving accurate mass estimates is particularly challenging for low-mass galaxy groups. Moreover, calibration of bservational mass-proxies using weak-lensing estimates have been mainly focused on massive clusters. We present here a study of halo masses for a sample of galaxy groups identified according to a spectroscopic catalogue, spanning a wide mass range. The main motivation of our analysis is to assess mass estimates provided by the galaxy group catalogue derived through an abundance matching luminosity technique. We derive total halo mass estimates according to a stacking weak-lensing analysis. Our study allows to test the accuracy of mass estimates based on this technique as a proxy for the halo masses of large group samples. Lensing profiles are computed combining the groups in different bins of abundance matching mass, richness and redshift. Fitted lensing masses correlate with the masses obtained from abundance matching. However, when considering groups in the low- and intermediate-mass ranges, masses computed according to the characteristic group luminosity tend to predict higher values than the determined by the weak-lensing analysis. The agreement improves for the low-mass range if the groups selected have a central early-type galaxy. Presented results validate the use of mass estimates based on abundance matching techniques which provide good proxies to the halo host mass in a wide mass range.

astro-ph.CO↗

arXiv2020

Combining FOF and halo-based algorithms for the identification of galaxy groups

Galaxy groups provide the means for a great diversity of studies that contribute to a better understanding of the structure of the universe on a large scale and allow the properties of galaxies to be linked to those of the host halos. However, the identification of galaxy systems is a challenging task and therefore it is necessary to improve the techniques involved as much as possible. In view of the large present and forthcoming galaxy catalogues, we propose, implement, and evaluate an algorithm that combines the two most popular techniques used to identify galaxy systems. The algorithm can be easily applied to any spectroscopic galaxy catalogue, but here we demonstrate its use on the Sloan Digital Sky Survey. Assuming that a galaxy group is a gravitationally bounded system that has at least one bright galaxy, we begin by identifying groups with a Friends-Of-Friends algorithm adapted to fit this definition. In view of the shortcomings of this method, particularly the lack of ability to identify low-number groups, and consequently the inability to study the occupation of halos throughout the mass range, we improve it by adding a halo-based procedure. To assess the performance, we construct a mock catalogue from a semi-analytical model to compare the groups identified using our method with those obtained from the simulation. The comparison of groups extracted using our method with those of a mock catalogue shows that the proposed algorithm provides excellent results. The modifications introduced to the Friends-Of-Friends algorithm in the first part of the procedure to fit the adopted group definition gave reliable groups. Furthermore, the incorporation of the halo-based method reduces the interlopers while more accurately reproducing the number of galaxies per group. As a specific application, we use the algorithm to extract groups from the Sloan Digital Sky Survey.

astro-ph.CO↗

arXiv2020

How galaxies populate haloes in very low-density environments? An analysis of the Halo Occupation Distribution in cosmic voids

Evidence shows properties of dark matter haloes may vary with large-scale environment. By studying the halo occupation distribution in cosmic voids it is possible to obtain useful information that can shed light on the subject. The history of the formation of the haloes and galaxies residing in these regions is likely to differ from the global behaviour given their extreme environment. We use two public access simulated galaxy catalogues constructed with different methods: a semi-analytical model and a hydrodynamic simulation. In both, we identify cosmic voids and we measure the halo occupation distribution inside these regions for different absolute magnitude thresholds. We compare these determinations with the overall results and we study the dependence of different characteristics of the voids. Also, we analyze the stellar content and the formation time of the haloes inside voids and confront the general halo population results. Inside the voids, we find a significantly different halo occupation distribution with respect to the general results. This is present in all absolute magnitude ranges explored. We obtain no signs of variation related to void characteristics indicating that the effects depend only on the density of the large-scale environment. Additionally, we find that the stellar mass content also differs within voids, which host haloes with less massive central galaxies (10%) as well as satellites with significantly lower stellar mass content (30%). Finally, we find a slight difference between the formation times of the haloes which are younger in voids than the average population. These characteristics indicate that haloes populating voids have had a different formation history, inducing significant changes on the halo occupation distribution.

astro-ph.CO↗

arXiv2020

Close galaxy pairs with accurate photometric redshifts

Context. Studies of galaxy pairs can provide valuable information to jointly understand the formation and evolution of galaxies and galaxy groups. Consequently, taking into account the new high precision photo-z surveys, it is important to have reliable and tested methods that allow us to properly identify these systems and estimate their total masses and other properties. Aims. In view of the forthcoming Physics of the Accelerating Universe Survey (PAUS) we propose and evaluate the performance of an identification algorithm of projected close isolated galaxy pairs. We expect that the photometric selected systems can adequately reproduce the observational properties and the inferred lensing mass - luminosity relation of a pair of truly bound galaxies that are hosted by the same dark matter halo. Methods. We develop an identification algorithm that considers the projected distance between the galaxies, the projected velocity difference and an isolation criteria in order to restrict the sample to isolated systems. We apply our identification algorithm using a mock galaxy catalog that mimics the features of PAUS. To evaluate the feasibility of our pair finder, we compare the identified photometric samples with a test sample that considers that both members are included in the same halo. Also, taking advantage of the lensing properties provided by the mock catalog, we apply a weak lensing analysis to determine the mass of the selected systems. Results. Photometric selected samples tend to show high purity values, but tend to misidentify truly bounded pairs as the photometric redshift errors increase. Nevertheless, overall properties such as the luminosity and mass distributions are successfully reproduced. We also accurately reproduce the lensing mass - luminosity relation as expected for galaxy pairs located in the same halo.

astro-ph.GA↗

arXiv2020

The manifestation of secondary halo bias on the galaxy population from IllustrisTNG300

We use the improved IllustrisTNG300 magneto-hydrodynamical cosmological simulation to revisit the effect that secondary halo bias has on the clustering of the central galaxy population. With a side length of 205 $h^{-1}$Mpc and significant improvements on the sub-grid model with respect to the previous Illustris boxes, IllustrisTNG300 allows us to explore the dependencies of galaxy clustering over a large cosmological volume and wide halo-mass range. We show, at high statistical significance, that the halo assembly bias signal (i.e., the secondary dependence of halo bias on halo formation redshift) manifests itself on the clustering of the central galaxy population when this is split by stellar mass, colour, specific star formation rate, and surface density. A significant detection is also obtained for galaxy size: at fixed halo mass, larger central galaxies are more tightly clustered than smaller central galaxies in haloes of mass M$_{\rm vir} \lesssim 10^{12.5}$ $h^{-1}$M$_{\odot}$. This effect, however, seems to be uncorrelated with halo formation time, unlike the rest of the secondary dependencies analysed. We also explore the transmission of the halo spin bias signal, i.e., the secondary dependence of halo bias on halo spin. Although galaxy spin retains little information about the total spin of the halo, the correlation is enough to produce a significant galaxy spin bias signal. We discuss possible ways to probe the spin bias effects with observations.

astro-ph.GA↗

arXiv2018

Weak lensing analysis of galaxy pairs using CS82 data

In this work we analyze a sample of close galaxy pairs (relative projected separation $<25 h^{-1}$kpc and relative radial velocities $< 350$ km s$^{-1}$) using a weak lensing analysis based on the CFHT Stripe 82 Survey. We determine halo masses for the Total sample of pairs as well as for Interacting, Red and Higher luminosity pair subsamples with $\sim 3σ$ confidence. The derived lensing signal for the total sample can be fitted either by a singular isothermal sphere with $σ_V = 223 \pm 24$ km s$^{-1}$ or a NFW profile with $R_{200} = 0.30 \pm 0.03\,h^{-1}$ Mpc. The pair total masses and total $r$ band luminosities imply an average mass-to-light ratio of $\sim 200\,h\,M_\odot/L_\odot$. On the other hand, Red pairs which include a larger fraction of elliptical galaxies, show a larger mass-to-light ratio of $\sim 345\,h\,M_\odot/L_\odot$. Derived lensing masses were compared to a proxy of the dynamical mass, obtaining a good correlation. However, there is a large discrepancy between lensing masses and the dynamical mass estimates, which could be accounted by astrophysical processes such as dynamical friction, by the inclusion of unbound pairs, and by significant deviations of the density distribution from a SIS and NFW profiles in the inner regions. We also compared lensing masses with group mass estimates obtained from the Yang et al. galaxy group catalog, finding a very good agreement with the sample of groups with 2 members. Red and Blue pairs show large differences between group and lensing masses, which is likely due to the single mass-to-light ratio adopted to compute the group masses.

astro-ph.GA↗

arXiv2017

Weak lensing measurement of the mass-richness relation using the SDSS database

We study the mass-richness relation using galaxy catalogues and images from the Sloan Digital Sky Survey. We use two independent methods, in the first one, we calibrate the scaling relation with weak-lensing mass estimates. In the second procedure we apply a background subtraction technique to derive the probability distribution, $P(M \mid N)$, that groups with $N$-members have a virialized halo mass $M$. Lensing masses are derived in different richness bins for two galaxy systems sets: the maxBCG catalogue and a catalogue based on a group finder algorithm developed by Yang et al. MaxBCG results are used to test the lensing methodology. The lensing mass-richness relation for the Yang et al. group sample shows a good agreement with $P(M \mid N)$ obtained independently with a straightforward procedure.

astro-ph.CO↗

arXiv2015

Taking advantage of photometric galaxy catalogues to determine the halo occupation distribution

Context. Halo occupation distribution (HOD) is a powerful statistic that allows the study of several aspects of the matter distribution in the Universe, such as evaluating semi-analytic models of galaxy formation or imposing constraints on cosmological models. Consequently, it is important to have a reliable method for estimating this statistic, taking full advantage of the available information on current and future galaxy surveys. Aims. The main goal of this project is to combine photometric and spectroscopic information using a discount method of background galaxies in order to extend the range of absolute magnitudes and to increase the upper limit of masses in which the HOD is estimated. We also evaluate the proposed method and apply it to estimating the HOD on the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) galaxy survey. Methods. We propose the background subtraction technique to mel information provided by spectroscopic galaxy groups and photometric survey of galaxies. To evaluate the feasibility of the method, we implement the proposed technique on a mock catalogue built from a semi-analytic model of galaxy formation. Furthermore, we apply the method to the SDSS DR7 using a galaxy group catalogue taken from spectroscopic version and the corresponding photometric galaxy survey. Results. We demonstrated the validity of the method using the mock catalogue.We applied this technique to obtain the SDSS DR7 HOD in absolute magnitudes ranging from $M=-21.5$ to $M=-16.0$ and masses up to $\simeq 10^{15} M_{\odot}$ throughout this range. On the brighter extreme, we found that our results are in excellent agreement with those obtained in previous works.

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