arXiv subjects

Sofía A. Cora

Publications and source records attributed to Sofía A. Cora.

At least 37 records · Page 2Linked to original sources

arXiv2021

The Three Hundred Project: The gas disruption of infalling objects in cluster environments

We analyse the gas content evolution of infalling haloes in cluster environments from THE THREE HUNDRED project, a collection of 324 numerically modelled galaxy clusters. The haloes in our sample were selected within $5R_{200}$ of the main cluster halo at $z=0$ and have total halo mass $M_{200}\geq10^{11} h^{-1} M_{\odot}$. We track their main progenitors and study their gas evolution since their crossing into the infall region, which we define as $1-4R_{200}$. Studying the radial trends of our populations using both the full phase space information and a line-of-sight projection, we confirm the Arthur et al. (2019) result and identify a characteristic radius around $1.7R_{200}$ in 3D and at $R_{200}$ in projection at which infalling haloes lose nearly all of the gas prior their infall. Splitting the trends by subhalo status we show that subhaloes residing in group-mass and low-mass host haloes in the infall region follow similar radial gas-loss trends as their hosts, whereas subhaloes of cluster-mass host haloes are stripped of their gas much further out. Our results show that infalling objects suffer significant gaseous disruption that correlates with time-since-infall, cluster-centric distance and host mass, and that the gaseous disruption they experience is a combination of subhalo pre-processing and object gas depletion at a radius which behaves like an accretion shock.

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arXiv2020

Investigating The Growing Population of Massive Quiescent Galaxies at Cosmic Noon

We explore the buildup of quiescent galaxies using a sample of 28,469 massive ($M_\star \ge 10^{11}$M$_\odot$) galaxies at redshifts $1.5<z<3.0$, drawn from a 17.5 deg$^2$ area (0.33 Gpc$^3$ comoving volume at these redshifts). This allows for a robust study of the quiescent fraction as a function of mass at $1.5<z<3.0$ with a sample $\sim$40 times larger at log($M_{\star}$/$\rm M_{\odot}$)$\ge11.5$ than previous studies. We derive the quiescent fraction using three methods: specific star-formation rate, distance from the main sequence, and UVJ color-color selection. All three methods give similar values at $1.5<z<2.0$, however the results differ by up to a factor of two at $2.0<z<3.0$. At redshifts $1.5 < z < 3.0$ the quiescent fraction increases as a function of stellar mass. By $z=2$, only 3.3 Gyr after the Big Bang, the universe has quenched $\sim$25% of $M_\star = 10^{11}$M$_\odot$ galaxies and $\sim$45% of $M_\star = 10^{12}$M$_\odot$ galaxies. We discuss physical mechanisms across a range of epochs and environments that could explain our results. We compare our results with predictions from hydrodynamical simulations SIMBA and IllustrisTNG and semi-analytic models (SAMs) SAG, SAGE, and Galacticus. The quiescent fraction from IllustrisTNG is higher than our empirical result by a factor of $2-5$, while those from SIMBA and the three SAMs are lower by a factor of $1.5-10$ at $1.5<z<3.0$.

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arXiv2020

The effect of gas accretion on the radial gas metallicity profile of simulated galaxies

We study the effect of the gas accretion rate ($\dot M_{\rm accr}$) on the radial gas metallicity profile (RMP) of galaxies using the EAGLE cosmological hydrodynamic simulations, focusing on central galaxies of stellar mass $M_\star \gtrsim 10^9 \, {\rm M_\odot}$ at $z \le 1$. We find clear relations between $\dot M_{\rm accr}$ and the slope of the RMP (measured within an effective radius), where higher $\dot M_{\rm accr}$ are associated with more negative slopes. The slope of the RMPs depends more strongly on $\dot M_{\rm accr}$ than on stellar mass, star formation rate or gas fraction, suggesting $\dot M_{\rm accr}$ to be a more fundamental driver of the RMP slope of galaxies. We find that eliminating the dependence on stellar mass is essential for pinning down the properties that shape the slope of the RMP. Although $\dot M_{\rm accr}$ is the main property modulating the slope of the RMP, we find that it causes other correlations that are more easily testable observationally: at fixed stellar mass, galaxies with more negative RMP slopes tend to have higher gas fractions and SFRs, while galaxies with lower gas fractions and SFRs tend to have flatter metallicity profiles within an effective radius.

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arXiv2019

Properties of subhalos in the interacting dark matter scenario

One possible and natural derivation from the collisionless cold dark matter (CDM) standard cosmological framework is the assumption of the existence of interactions between dark matter (DM) and photons or neutrinos. Such possible interacting dark matter (IDM) model would imply a suppression of small-scale structures due to a large collisional damping effect, even though the weakly interacting massive particle (WIMP) can still be the DM candidate. Because of this, IDM models can help alleviate alleged tensions between standard CDM predictions and observations at small mass scales. In this work, we investigate the properties of DM halo substructure or subhalos formed in a high-resolution cosmological N-body simulation specifically run within these alternative models. We also run its CDM counterpart, which allowed us to compare subhalo properties in both cosmologies. We show that, in the lower mass range covered by our simulation runs, both subhalo concentrations and abundances are systematically lower in IDM compared to the CDM scenario. Yet, as in CDM, we find that median IDM subhalo concentration values increase towards the innermost regions of their hosts for same mass subhalos. Also similarly to CDM, we find IDM subhalos to be more concentrated than field halos of the same mass. Our work has a direct application on studies aimed at the indirect detection of DM where subhalos are expected to boost the DM signal of their host halos significantly. From our results, we conclude that the role of halo substructure in DM searches will be less important in interacting scenarios than in CDM, but is nevertheless far from being negligible.

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arXiv2018

Semi-Analytic Galaxies - I. Synthesis of environmental and star-forming regulation mechanisms

We present results from the semi-analytic model of galaxy formation SAG applied on the MultiDark simulation MDPL2. SAG features an updated supernova (SN) feedback scheme and a robust modelling of the environmental effects on satellite galaxies. This incorporates a gradual starvation of the hot gas halo driven by the action of ram pressure stripping (RPS), that can affect the cold gas disc, and tidal stripping (TS), which can act on all baryonic components. Galaxy orbits of orphan satellites are integrated providing adequate positions and velocities for the estimation of RPS and TS. The star formation history and stellar mass assembly of galaxies are sensitive to the redshift dependence implemented in the SN feedback model. We discuss a variant of our model that allows to reconcile the predicted star formation rate density at $z \gtrsim 3$ with the observed one, at the expense of an excess in the faint end of the stellar mass function at $z=2$. The fractions of passive galaxies as a function of stellar mass, halo mass and the halo-centric distances are consistent with observational measurements. The model also reproduces the evolution of the main sequence of star forming central and satellite galaxies. The similarity between them is a result of the gradual starvation of the hot gas halo suffered by satellites, in which RPS plays a dominant role. RPS of the cold gas does not affect the fraction of quenched satellites but it contributes to reach the right atomic hydrogen gas content for more massive satellites ($M_{\star}\gtrsim 10^{10}\,{\rm M}_{\odot}$).

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arXiv2018

Semi-Analytic Galaxies - II. Revealing the role of environmental and mass quenching in galaxy formation

We use the semi-analytic model of galaxy formation SAG to study the relevance of mass and environmental quenching on satellite galaxies. We find that environmental processes dominate the star formation (SF) quenching of low-mass satellites ($M_{\star} \lesssim 10^{10.5}\, {\rm M}_{\odot}$), whereas high-mass galaxies typically quench as centrals. High-mass galaxies that remain actively forming stars while being accreted are found to be mainly affected by mass quenching after their first infall. For a given stellar mass, our model predicts SF quenching to be less efficient in low-mass haloes both before and after infall, in contradiction with common interpretations of observational data. Our model supports a two-stage scenario to explain the SF quenching. Initially, the SF of satellites resembles that of centrals until the gas cooling rate is reduced to approximately half its value at infall. Then, the SF fades through secular processes that exhaust the cold gas reservoir. This reservoir is not replenished efficiently due to the action of either ram-pressure stripping (RPS) of the hot gas in low-mass satellites, or feedback from the active galactic nucleus (AGN) in high-mass satellites. The delay times for the onset of SF quenching are found to range from $\approx 3\,{\rm Gyr}$ to $\approx 1\,{\rm Gyr}$ for low-mass ($M_{\star} \approx 10^{10}\, {\rm M}_{\odot}$) and high-mass ($M_{\star} \approx 10^{11}\, {\rm M}_{\odot}$) satellites, respectively. SF fades in $\approx 1.5\,{\rm Gyr}$, largely independent of stellar mass. We find that the SF quenching of low-mass satellites supports the so-called delay-then-rapid quenching scenario. However, the SF history of $z=0$ passive satellites of any stellar mass is better described by a delay-then-fade quenching scenario.

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arXiv2018

The Three Hundred project: a large catalogue of theoretically modelled galaxy clusters for cosmological and astrophysical applications

We introduce the THE THREE HUNDRED project, an endeavour to model 324 large galaxy clusters with full-physics hydrodynamical re-simulations. Here we present the data set and study the differences to observations for fundamental galaxy cluster properties and scaling relations. We find that the modelled galaxy clusters are generally in reasonable agreement with observations with respect to baryonic fractions and gas scaling relations at redshift z = 0. However, there are still some (model-dependent) differences, such as central galaxies being too massive, and galaxy colours (g - r) being bluer (about 0.2 dex lower at the peak position) than in observations. The agreement in gas scaling relations down to 10^{13} h^{-1} M_{\odot} between the simulations indicates that particulars of the sub-grid modelling of the baryonic physics only has a weak influence on these relations. We also include - where appropriate - a comparison to three semi-analytical galaxy formation models as applied to the same underlying dark-matter-only simulation. All simulations and derived data products are publicly available.

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arXiv2018

Semi-analytic galaxies -- III. The impact of supernova feedback on the mass-metallicity relation

We use the semi-analytic model (SAM) of galaxy formation and evolution SAG coupled with the MULTIDARK simulation MDPL2 to study the evolution of the stellar mass-gas metallicity relation of galaxies (MZR). We test several implementations of the dependence of the mass loading due to supernovae (SNe). We find that no evolution in the normalization of the MZR is obtained unless we introduce an explicit scaling of the reheated and ejected mass with redshift as $(1+z)^β$. The latter is in agreement with results from the FIRE simulations, and it should encompass small scale properties of the interstellar medium varying over time, which are not captured in SAMs, as well as other energy sources in addition to SNe. Increasing $β$ leads to stronger evolution of the MZR normalization; $β= 1.9$ reproduces the observed MZR in the range $0 < z < 3.5$. A stronger redshift dependence of outflows reduces the levels of star formation at earlier epochs with the consequent decrease of metal production. This leads to a slower increase of the gas metallicity compared to the stellar mass build-up. The cold gas can be contaminated either by receiving a direct injection of the material recycled by stellar winds and SNe or by gas cooling. The relative role of each process for a given stellar mass depends on the criterion adopted to regulate the fate of the recycled material. However, modifying the metal loading of the outflows has mild impact on the zero-point evolution and does not affect our conclusions.

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arXiv2018

Cosmic CARNage II: the evolution of the galaxy stellar mass function in observations and galaxy formation models

We present a comparison of the observed evolving galaxy stellar mass functions with the predictions of eight semi-analytic models and one halo occupation distribution model. While most models are able to fit the data at low redshift, some of them struggle to simultaneously fit observations at high redshift. We separate the galaxies into 'passive' and 'star-forming' classes and find that several of the models produce too many low-mass star-forming galaxies at high redshift compared to observations, in some cases by nearly a factor of 10 in the redshift range $2.5 < z < 3.0$. We also find important differences in the implied mass of the dark matter haloes the galaxies inhabit, by comparing with halo masses inferred from observations. Galaxies at high redshift in the models are in lower mass haloes than suggested by observations, and the star formation efficiency in low-mass haloes is higher than observed. We conclude that many of the models require a physical prescription that acts to dissociate the growth of low-mass galaxies from the growth of their dark matter haloes at high redshift.

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arXiv2018

DESCQA: An Automated Validation Framework for Synthetic Sky Catalogs

The use of high-quality simulated sky catalogs is essential for the success of cosmological surveys. The catalogs have diverse applications, such as investigating signatures of fundamental physics in cosmological observables, understanding the effect of systematic uncertainties on measured signals and testing mitigation strategies for reducing these uncertainties, aiding analysis pipeline development and testing, and survey strategy optimization. The list of applications is growing with improvements in the quality of the catalogs and the details that they can provide. Given the importance of simulated catalogs, it is critical to provide rigorous validation protocols that enable both catalog providers and users to assess the quality of the catalogs in a straightforward and comprehensive way. For this purpose, we have developed the DESCQA framework for the Large Synoptic Survey Telescope Dark Energy Science Collaboration as well as for the broader community. The goal of DESCQA is to enable the inspection, validation, and comparison of an inhomogeneous set of synthetic catalogs via the provision of a common interface within an automated framework. In this paper, we present the design concept and first implementation of DESCQA. In order to establish and demonstrate its full functionality we use a set of interim catalogs and validation tests. We highlight several important aspects, both technical and scientific, that require thoughtful consideration when designing a validation framework, including validation metrics and how these metrics impose requirements on the synthetic sky catalogs.

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arXiv2016

Testing LSST Dither Strategies for Survey Uniformity and Large-Scale Structure Systematics

The Large Synoptic Survey Telescope (LSST) will survey the southern sky from 2022--2032 with unprecedented detail. Since the observing strategy can lead to artifacts in the data, we investigate the effects of telescope-pointing offsets (called dithers) on the $r$-band coadded 5$σ$ depth yielded after the 10-year survey. We analyze this survey depth for several geometric patterns of dithers (e.g., random, hexagonal lattice, spiral) with amplitude as large as the radius of the LSST field-of-view, implemented on different timescales (per season, per night, per visit). Our results illustrate that per night and per visit dither assignments are more effective than per season. Also, we find that some dither geometries (e.g., hexagonal lattice) are particularly sensitive to the timescale on which the dithers are implemented, while others like random dithers perform well on all timescales. We then model the propagation of depth variations to artificial fluctuations in galaxy counts, which are a systematic for large-scale structure studies. We calculate the bias in galaxy counts caused by the observing strategy, accounting for photometric calibration uncertainties, dust extinction, and magnitude cuts; uncertainties in this bias limit our ability to account for structure induced by the observing strategy. We find that after 10 years of the LSST survey, the best dither strategies lead to uncertainties in this bias smaller than the minimum statistical floor for a galaxy catalog as deep as $r$$<$27.5. A few of these strategies bring the uncertainties close to the statistical floor for $r$$<$25.7 after only one year of survey.

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arXiv2015

Calibration of semi-analytic models of galaxy formation using Particle Swarm Optimization

We present a fast and accurate method to select an optimal set of parameters in semi-analytic models of galaxy formation and evolution (SAMs). Our approach compares the results of a model against a set of observables applying a stochastic technique called Particle Swarm Optimization (PSO), a self-learning algorithm for localizing regions of maximum likelihood in multidimensional spaces that outperforms traditional sampling methods in terms of computational cost. We apply the PSO technique to the SAG semi-analytic model combined with merger trees extracted from a standard $Λ$CDM N-body simulation. The calibration is performed using a combination of observed galaxy properties as constraints, including the local stellar mass function and the black hole to bulge mass relation. We test the ability of the PSO algorithm to find the best set of free parameters of the model by comparing the results with those obtained using a MCMC exploration. Both methods find the same maximum likelihood region, however the PSO method requires one order of magnitude less evaluations. This new approach allows a fast estimation of the best-fitting parameter set in multidimensional spaces, providing a practical tool to test the consequences of including other astrophysical processes in SAMs.

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arXiv2014

Properties of Submillimeter Galaxies in a Semi-analytic Model using the "Count Matching" Approach: Application to the ECDF-S

We present a new technique for modeling submillimeter galaxies (SMGs): the "Count Matching" approach. Using lightcones drawn from a semi-analytic model of galaxy formation, we choose physical galaxy properties given by the model as proxies for their submillimeter luminosities, assuming a monotonic relationship. As recent interferometric observations of the Extended Chandra Deep Field South show that the brightest sources detected by single-dish telescopes are comprised by emission from multiple fainter sources, we assign the submillimeter fluxes so that the combined LABOCA plus bright-end ALMA observed number counts for this field are reproduced. After turning the model catalogs given by the proxies into submillimeter maps, we perform a source extraction to include the effects of the observational process on the recovered counts and galaxy properties. We find that for all proxies, there are lines of sight giving counts consistent with those derived from LABOCA observations, even for input sources with randomized positions in the simulated map. Comparing the recovered redshift, stellar mass and host halo mass distributions for model SMGs with observational data, we find that the best among the proposed proxies is that in which the submillimeter luminosity increases monotonically with the product between dust mass and SFR. This proxy naturally reproduces a positive trend between SFR and bolometric IR luminosity. The majority of components of blended sources are spatially unassociated.

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arXiv2011

How accurate is it to update the cosmology of your halo catalogues?

We test and present the application of the full rescaling method by Angulo & White (2010) to change the cosmology of halo catalogues in numerical simulations for cosmological parameter search using semi-analytic galaxy properties. We show that a reduced form of the method can be applied in small simulations with box side of ~50/h Mpc. We perform statistical tests on the accuracy of the properties of rescaled individual haloes, and also on the rescaled population as a whole. We find that individual positions and velocities are recovered with almost no detectable biases. The dispersion in the recovered halo mass does not seem to depend on the resolution of the simulation. Regardless of the halo mass, the individual accretion histories, spin parameter evolution and fraction of mass in substructures are well recovered. The mass of rescaled haloes can be underestimated (overestimated) for negative (positive) variations of either sigma_8 or Omega_m, in a way that does not depend on the halo mass. Statistics of abundances and correlation functions of haloes show also small biases of <10 percent when moving away from the base simulation by up to 2 times the uncertainty in the WMAP7 cosmological parameters. The merger tree properties related to the final galaxy population in haloes also show small biases; the time since the last major merger, the assembly time-scale, and a time-scale related to the stellar ages show correlated biases which indicate that the spectral shapes of galaxies would only be affected by global age changes of ~150 Myr. We show some of these biases for different separations in the cosmological parameters with respect to the desired cosmology so that these can be used to estimate the expected accuracy of the resulting halo population. We also present a way to construct grids of simulations to provide stable accuracy across the Omega_m vs sigma_8 parameter space.

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arXiv2011

Development of the Red Sequence in Galaxy Clusters

We investigate the origin of the color-magnitude relation (CMR) observed in cluster galaxies by using a combination of a cosmological N-body simulation of a cluster of galaxies and a semi-analytic model of galaxy formation. The departure of galaxies in the bright end of the CMR with respect to the trend defined by less luminous galaxies could be explained by the influence of minor mergers.

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arXiv2011

The bright end of the colour-magnitude relation of cluster galaxies

We investigate the development of the red sequence (RS) of cluster galaxies by using a semi-analytic model of galaxy formation. Results show good agreement between the general trend of the simulated RS and the observed relation in early-type galaxies. However, the most luminous galaxies ($M_V \lesssim -20$) depart from the linear fit to observed data, displaying almost constant colours. We analyze the dependence with redshift of the fraction of stellar mass contributed to each galaxy by different processes (i.e., quiescent star formation, disc instability and mergers), finding that the evolution of the bright end, since $z\approx 2$, is mainly driven by minor and major dry mergers. Since the most luminous galaxies have a narrow spread in ages ($1.0\times 10^{10}$ yr $<t<1.2\times 10^{10}$ yr), their metallicities are the main factor that affects their colours. Galaxies in the bright end reach an upper limit in metallicity as a result of the competition of the mass of stars and metals provided by the star formation within the galaxies and by the accretion of merging satellites. Star formation activity in massive galaxies (M_\star \gtrsim 10^{10} M_{\odot}$) contribute with stellar components of high metallicity, but this fraction of stellar mass is negligible. Mergers contribute with a larger fraction of stellar mass ($\approx 10-20$ per cent), but the metallicity of the accreted satellites is lower by $\approx 0.2$ dex than the mean metallicity of galaxies they merge with. The effect of dry mergers is to increase the mass of galaxies in the bright end, without significantly altering their metallicities, and hence,their colours, giving rise to the break in the RS. These results are found for clusters with different virial masses, supporting the idea of the universality of the CMR in agreement with observational results.

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arXiv2011

Chemical effects on the development of the colour-magnitude relation of cluster galaxies

We investigate the development of the colour-magnitude re- lation (CMR) of cluster galaxies. This study is carried out using a semi- analytic model of galaxy formation and evolution coupled to a sample of simulated galaxy clusters of different masses, reinforcing the conclusions reached by Jiménez et al. (2009). We compare both simulated and obeserved CMRs in different colour-magnitude planes, finding a very good agreement in all cases. This indicates that model parameters are correctly tuned, giving accurate values of the main properties of galaxies for further use in our study. In the present work, we perform a statistical analysis of the relative contribution to the stellar mass and metallicity of galaxies along the CMR by the different processes involved in their formation and evolution (i.e. quiescent star formation, disc instability events and galaxy mergers). Our results show that a mix of minor and major dry mergers at low redshifts is relevant in the evolution of the most luminous galaxies in the CMR. These processes contribute with low metallicity stars to the remnant galaxies, thus increasing the galaxy masses without significantly altering their colours. These results are found for all simulated clusters, supporting the idea of the universality of the CMR in agreement with observational results.

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arXiv2011

Ram pressure profiles in galaxy groups and clusters

Using a hybrid method which combines non-radiative hydrodynamical simulations with a semi-analytic model of galaxy formation, we determine the ram pressure as a function of halocentric distance experienced by galaxies in haloes with virial masses 12.5 <= log (M_200 h/M_Sun) < 15.35, for redshifts 0 <= z <= 3. The ram pressure is calculated with a self-consistent method which uses the simulation gas particles to obtain the properties of the intergalactic medium. The ram pressure profiles obtained can be well described by beta profile models, with parameters that depend on redshift and halo virial mass in a simple fashion. The fitting formulae provided here will prove useful to include ram pressure effects into semi-analytic models based on methods which lack gas physics, such as dark matter-only simulations or the Press-Schechter formalism.

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