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Dive into the research topics where Vicente Rodriguez-Gomez is active.

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Featured researches published by Vicente Rodriguez-Gomez.


Monthly Notices of the Royal Astronomical Society | 2014

Introducing the Illustris project: the evolution of galaxy populations across cosmic time

Shy Genel; Mark Vogelsberger; Volker Springel; Debora Sijacki; Dylan Nelson; Greg Snyder; Vicente Rodriguez-Gomez; Paul Torrey; Lars Hernquist

We present an overview of galaxy evolution across cosmic time in the Illustris Simulation. Illustris is an N-body/hydrodynamical simulation that evolves 2*1820^3 resolution elements in a (106.5Mpc)^3 box from cosmological initial conditions down to z=0 using the AREPO moving-mesh code. The simulation uses a state-of-the-art set of physical models for galaxy formation that was tuned to reproduce the z=0 stellar mass function and the history of the cosmic star-formation rate density. We find that Illustris successfully reproduces a plethora of observations of galaxy populations at various redshifts, for which no tuning was performed, and provide predictions for future observations. In particular, we discuss (a) the buildup of galactic mass, showing stellar mass functions and the relations between stellar mass and halo mass from z=7 to z=0, (b) galaxy number density profiles around massive central galaxies out to z=4, (c) the gas and total baryon content of both galaxies and their halos for different redshifts, and as a function of mass and radius, and (d) the evolution of galaxy specific star-formation rates up to z=8. In addition, we (i) present a qualitative analysis of galaxy morphologies from z=5 to z=0, for the stellar as well as the gaseous components, and their appearance in HST mock observations, (ii) follow galaxies selected at z=2 to their z=0 descendants, and quantify their growth and merger histories, and (iii) track massive z=0 galaxies to high redshift and study their joint evolution in star-formation activity and compactness. We conclude with a discussion of several disagreements with observations, and lay out possible directions for future research.


Monthly Notices of the Royal Astronomical Society | 2015

The merger rate of galaxies in the Illustris Simulation: a comparison with observations and semi-empirical models

Vicente Rodriguez-Gomez; Shy Genel; Mark Vogelsberger; Debora Sijacki; Annalisa Pillepich; Laura V. Sales; Paul Torrey; Greg Snyder; Dylan Nelson; Volker Springel; Chung-Pei Ma; Lars Hernquist

We have constructed merger trees for galaxies in the Illustris simulation by directly tracking the baryonic content of subhaloes. These merger trees are used to calculate the galaxy–galaxy merger rate as a function of descendant stellar mass, progenitor stellar mass ratio, and redshift. We demonstrate that the most appropriate definition for the mass ratio of a galaxy–galaxy merger consists in taking both progenitor masses at the time when the secondary progenitor reaches its maximum stellar mass. Additionally, we avoid effects from ‘orphaned’ galaxies by allowing some objects to ‘skip’ a snapshot when finding a descendant, and by only considering mergers which show a well-defined ‘infall’ moment. Adopting these definitions, we obtain well-converged predictions for the galaxy–galaxy merger rate with the following main features, which are qualitatively similar to the halo–halo merger rate except for the last one: a strong correlation with redshift that evolves as ∼(1 + z)^(2.4–2.8), a power law with respect to mass ratio, and an increasing dependence on descendant stellar mass, which steepens significantly for descendant stellar masses greater than ∼2 × 10^(11)M_⊙. These trends are consistent with observational constraints for medium-sized galaxies (M* ≳ 10^(10) M_⊙), but in tension with some recent observations of the close pair fraction for massive galaxies (M* ≳ 10^(11) M_⊙), which report a nearly constant or decreasing evolution with redshift. Finally, we provide a fitting function for the galaxy–galaxy merger rate which is accurate over a wide range of stellar masses, progenitor mass ratios, and redshifts.


Monthly Notices of the Royal Astronomical Society | 2016

The stellar mass assembly of galaxies in the Illustris simulation: growth by mergers and the spatial distribution of accreted stars

Vicente Rodriguez-Gomez; Annalisa Pillepich; Laura V. Sales; Shy Genel; Mark Vogelsberger; Qirong Zhu; Sarah Wellons; Dylan Nelson; Paul Torrey; Volker Springel; Chung-Pei Ma; Lars Hernquist

We use the Illustris simulation to study the relative contributions of in situ star formation and stellar accretion to the build-up of galaxies over an unprecedentedly wide range of masses (M_* = 10^9-10^(12) M_⊙), galaxy types, environments, and assembly histories. We find that the ‘two-phase’ picture of galaxy formation predicted by some models is a good approximation only for the most massive galaxies in our simulation – namely, the stellar mass growth of galaxies below a few times 10^(11) M_⊙ is dominated by in situ star formation at all redshifts. The fraction of the total stellar mass of galaxies at z = 0 contributed by accreted stars shows a strong dependence on galaxy stellar mass, ranging from about 10 per cent for Milky Way-sized galaxies to over 80 per cent for M_* ≈ 10^(12) M_⊙ objects, yet with a large galaxy-to-galaxy variation. At a fixed stellar mass, elliptical galaxies and those formed at the centres of younger haloes exhibit larger fractions of ex situ stars than disc-like galaxies and those formed in older haloes. On average, ∼50 per cent of the ex situ stellar mass comes from major mergers (stellar mass ratio μ > 1/4), ∼20 per cent from minor mergers (1/10 < μ < 1/4), ∼20 per cent from very minor mergers (μ < 1/10), and ∼10 per cent from stars that were stripped from surviving galaxies (e.g. flybys or ongoing mergers). These components are spatially segregated, with in situ stars dominating the innermost regions of galaxies, and ex situ stars being deposited at larger galactocentric distances in order of decreasing merger mass ratio.


Monthly Notices of the Royal Astronomical Society | 2015

The Formation of Massive, Compact Galaxies at z = 2 in the Illustris Simulation

Sarah Wellons; Paul Torrey; Chung-Pei Ma; Vicente Rodriguez-Gomez; Mark Vogelsberger; Mariska Kriek; Pieter G. van Dokkum; Erica J. Nelson; Shy Genel; Annalisa Pillepich; Volker Springel; Debora Sijacki; Gregory F. Snyder; Dylan Nelson; Laura V. Sales; Lars Hernquist

Massive, quiescent galaxies at high redshift have been found to be considerably more compact than galaxies of similar mass in the local universe. How these compact galaxies formed has yet to be determined, though several progenitor populations have been proposed. Here we investigate the formation processes and quantify the assembly histories of such galaxies in Illustris, a suite of hydrodynamical cosmological simulations encompassing a sufficiently large volume to include rare objects, while simultaneously resolving the internal structure of galaxies. We select massive ( 10 11 M ) and compact (stellar half-mass radius < 2 kpc) galaxies from the simulation at z = 2. Within the Illustris suite, we find that these quantities are not perfectly converged, but are reasonably reliable for our purposes. The resulting population is composed primarily of quiescent galaxies, but we also find several star-forming compact galaxies. The simulated compact galaxies are similar to observed galaxies in star formation activity and appearance. We follow their evolution at high redshift in the simulation and find that there are multiple pathways to form these compact galaxies, dominated by two mechanisms: (i) intense, centrally concentrated starbursts generally triggered by gas-rich major mergers between z 2 4, reducing the galaxies’ half-mass radii by a factor of a few to below 2 kpc, and (ii) assembly at very early times when the universe was much denser; the galaxies formed compact and remained so until z 2.


Monthly Notices of the Royal Astronomical Society | 2014

Halo mass and assembly history exposed in the faint outskirts: the stellar and dark matter haloes of Illustris galaxies

Annalisa Pillepich; Mark Vogelsberger; Alis J. Deason; Vicente Rodriguez-Gomez; Shy Genel; Dylan Nelson; Paul Torrey; Laura V. Sales; Federico Marinacci; Volker Springel; Debora Sijacki; Lars Hernquist

We use the Illustris Simulations to gain insight into the build-up of the outer, low-surface brightness regions which surround galaxies. We characterize the stellar haloes by means of the logarithmic slope of the spherically-averaged stellar density profiles, alphaSTARS at z=0, and we relate these slopes to the properties of the underlying Dark-Matter (DM) haloes, their central galaxies, and their assembly histories. We analyze a sample of ~5,000 galaxies resolved with more than 5x10^4 particles each, and spanning a variety of morphologies and halo masses (3x10^11 < Mvir < 10^14 Msun). We find a strong trend between stellar halo slope and total halo mass, where more massive objects have shallower stellar haloes than the less massive ones (-5.5 \pm 0.5 < alphaSTARS <-3.5 \pm 0.2 in the studied mass range). At fixed halo mass, we show that disk-like, blue, young, and more massive galaxies are surrounded by significantly steeper stellar haloes than elliptical, red, older, and less massive galaxies. Overall, the stellar density profiles fall off much more steeply than the underlying DM, and no clear trend holds between stellar slope and DM halo concentration. However, DM haloes which formed more recently, or which accreted larger fractions of stellar mass from infalling satellites, exhibit shallower stellar haloes than their older analogs with similar masses, by up to Delta(alphaSTARS) ~ 0.5-0.7. Our findings, combined with the most recent measurements of the strikingly different stellar power-law indexes for M31 and the Milky Way, appear to favour a massive M31, and a Milky Way characterized by a much quieter accretion history over the past 10 Gyrs than its companion.


The Astrophysical Journal | 2015

GALACTIC ANGULAR MOMENTUM IN THE ILLUSTRIS SIMULATION: FEEDBACK AND THE HUBBLE SEQUENCE

Shy Genel; S. Michael Fall; Lars Hernquist; Mark Vogelsberger; Gregory F. Snyder; Vicente Rodriguez-Gomez; Debora Sijacki; Volker Springel

We study the stellar angular momentum of thousands of galaxies in the Illustris cosmological simulation, which captures gravitational and gas dynamics within galaxies, as well as feedback from stars and black holes. We find that the angular momentum of the simulated galaxies matches observations well, and in particular two distinct relations are found for late-type versus early-type galaxies. The relation for late-type galaxies corresponds to the value expected from full conservation of the specific angular momentum generated by cosmological tidal torques. The relation for early-type galaxies corresponds to retention of only ~30% of that, but we find that those early-type galaxies with low angular momentum at z=0 nevertheless reside at high redshift on the late-type relation. Some of them abruptly lose angular momentum during major mergers. To gain further insight, we explore the scaling relations in simulations where the galaxy formation physics is modified with respect to the fiducial model. We find that galactic winds with high mass-loading factors are essential for obtaining the high angular momentum relation typical for late-type galaxies, while AGN feedback largely operates in the opposite direction. Hence, feedback controls the stellar angular momentum of galaxies, and appears to be instrumental for establishing the Hubble sequence.


Monthly Notices of the Royal Astronomical Society | 2016

The diverse evolutionary paths of simulated high-z massive, compact galaxies to z = 0

Sarah Wellons; Paul Torrey; Chung-Pei Ma; Vicente Rodriguez-Gomez; Annalisa Pillepich; Dylan Nelson; Shy Genel; Mark Vogelsberger; Lars Hernquist

Massive quiescent galaxies have much smaller physical sizes at high redshift than today. The strong evolution of galaxy size may be caused by progenitor bias, major and minor mergers, adiabatic expansion, and/or renewed star formation, but it is difficult to test these theories observationally. Herein, we select a sample of 35 massive, compact galaxies (M_* = 1–3 × 10^(11) M_⊙, M_*/R^(1.5) > 10^(10.5) M_⊙/kpc^(1.5)) at z = 2 in the cosmological hydrodynamical simulation Illustris and trace them forwards to z = 0 to uncover their evolution and identify their descendants. By z = 0, the original factor of 3 difference in stellar mass spreads to a factor of 20. The dark matter halo masses similarly spread from a factor of 5 to 40. The galaxies’ evolutionary paths are diverse: about half acquire an ex situ envelope and are the core of a more massive descendant, a third survive undisturbed and gain very little mass, 15 per cent are consumed in a merger with a more massive galaxy, and a small remainder are thoroughly mixed by major mergers. The galaxies grow in size as well as mass, and only ∼10 per cent remain compact by z = 0. The majority of the size growth is driven by the acquisition of ex situ mass. The most massive galaxies at z = 0 are the most likely to have compact progenitors, but this trend possesses significant dispersion which precludes a direct linkage to compact galaxies at z = 2. The compact galaxies’ merger rates are influenced by their z = 2 environments, so that isolated or satellite compact galaxies (which are protected from mergers) are the most likely to survive to the present day.


Monthly Notices of the Royal Astronomical Society | 2013

Sussing merger trees: the Merger Trees Comparison Project

Chaichalit Srisawat; Alexander Knebe; Frazer R. Pearce; Aurel Schneider; Peter A. Thomas; Peter Behroozi; K. Dolag; Pascal J. Elahi; Jiaxin Han; John C. Helly; Yipeng Jing; Intae Jung; Jaehyun Lee; Yao Yuan Mao; Julian Onions; Vicente Rodriguez-Gomez; Dylan Tweed; Sukyoung K. Yi

Merger trees follow the growth and merger of dark-matter haloes over cosmic history. As well as giving important insights into the growth of cosmic structure in their own right, they provide an essential backbone to semi-analytic models of galaxy formation. This paper is the first in a series to arise from the Sussing Merger Trees Workshop in which 10 different tree-building algorithms were applied to the same set of halo catalogues and their results compared. Although many of these codes were similar in nature, all algorithms produced distinct results. Our main conclusions are that a useful merger-tree code should possess the following features: (i) the use of particle IDs to match haloes between snapshots; (ii) the ability to skip at least one, and preferably more, snapshots in order to recover subhaloes that are temporarily lost during merging; (iii) the ability to cope with (and ideally smooth out) large, temporary fluctuations in halo mass. Finally, to enable different groups to communicate effectively, we defined a common terminology that we used when discussing merger trees and we encourage others to adopt the same language. We also specified a minimal output format to record the results.


Monthly Notices of the Royal Astronomical Society | 2015

An analysis of the evolving comoving number density of galaxies in hydrodynamical simulations

Paul Torrey; Sarah Wellons; Francisco Machado; Brendan F. Griffen; Dylan Nelson; Vicente Rodriguez-Gomez; R. McKinnon; Annalisa Pillepich; Chung-Pei Ma; Mark Vogelsberger; Volker Springel; Lars Hernquist

We present an analysis of the evolving comoving cumulative number density of galaxy populations found in the Illustris simulation. Cumulative number density is commonly used to link galaxy populations across different epochs by assuming that galaxies preserve their number density in time. Our analysis allows us to examine the extent to which this assumption holds in the presence of galaxy mergers or when rank ordering is broken owing to variable stellar growth rates. Our primary results are as follows: (1) the inferred average stellar mass evolution obtained via a constant comoving number density assumption is systematically biased compared to the merger tree results at the factor of ∼2(4) level when tracking galaxies from redshift z = 0 to 2(3); (2) the median number density evolution for galaxy populations tracked forward in time is shallower than for galaxy populations tracked backward; (3) a similar evolution in the median number density of tracked galaxy populations is found regardless of whether number density is assigned via stellar mass, stellar velocity dispersion, or halo mass; (4) explicit tracking reveals a large diversity in the stellar and dark matter assembly histories that cannot be captured by constant number density analyses; (5) the significant scatter in galaxy linking methods is only marginally reduced (∼20 per cent) by considering additional physical galaxy properties. We provide fits for the median evolution in number density for use with observational data and discuss the implications of our analysis for interpreting multi-epoch galaxy property observations.


Monthly Notices of the Royal Astronomical Society | 2017

The role of mergers and halo spin in shaping galaxy morphology

Vicente Rodriguez-Gomez; Laura V. Sales; Shy Genel; Annalisa Pillepich; Jolanta Zjupa; Dylan Nelson; Brendan F. Griffen; Paul Torrey; Gregory F. Snyder; Mark Vogelsberger; Volker Springel; Chung-Pei Ma; Lars Hernquist

Mergers and the spin of the dark matter halo are factors traditionally believed to determine the morphology of galaxies within a

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Lars Hernquist

University of California

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Mark Vogelsberger

Massachusetts Institute of Technology

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Paul Torrey

Massachusetts Institute of Technology

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Laura V. Sales

University of California

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Chung-Pei Ma

University of California

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