Minor versus major mergers: the stellar mass growth of massive galaxies from z = 3 using number density selection techniques

Context. Despite the insights gained in the last few years, our knowledge about the formation and evolution scenario for the spheroid-dominated galaxies is still incomplete. New and more powerful cosmological simulations have been developed that together with more precise observations open the possibility of more detailed study of the formation of early-type galaxies (ETGs). Aims. The aim of this work is to analyse the assembly histories of ETGs in a Λ cold dark matter cosmology, focussing on the archeological approach given by the mass-growth histories. Methods. We inspected a sample of dispersion-dominated galaxies selected from the largest volume simulation of the EAGLE project. This simulation includes a variety of physical processes such as radiative cooling, star formation (SF), metal enrichment, and stellar and active galactic nucleus (AGN) feedback. The selected sample comprised 508 spheroid-dominated galaxies classified according to their dynamical properties. Their surface brightness profile, the fundamental relations, kinematic properties, and stellar-mass growth histories are estimated and analysed. The findings are confronted with recent observations. Results. The simulated ETGs are found to globally reproduce the fundamental relations of ellipticals. All of them have an inner disc component where residual younger stellar populations (SPs) are detected. A correlation between the inner-disc fraction and the bulge-to-total ratio is reported. We find a relation between kinematics and shape that implies that dispersion-dominated galaxies with low V/σL (where V is the average rotational velocity and σL the one dimensional velocity dispersion) tend to have ellipticity smaller than ∼0.5 and are dominated by old stars. On average, less massive galaxies host slightly younger stars. More massive spheroids show coeval SPs while for less massive galaxies (stellar masses lower than ∼1010 M⊙), there is a clear trend to have rejuvenated inner regions, showing an age gap between the inner and the outer regions up to ∼2 Gyr, in apparent contradiction with observational findings. We find evidences suggesting that both the existence of the disc components with SF activity in the inner region and the accretion of satellite galaxies in outer regions could contribute to the outside-in formation history in galaxies with low stellar mass. On the other hand, there are non-negligible uncertainties in the determination of the ages of old stars in observed galaxies. Stronger supernova (SN) feedback and/or the action of AGN feedback for galaxies with stellar masses lower than 1010 M⊙ could contribute to prevent the SF in the inner regions.

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MERGERS AND STAR FORMATION: THE ENVIRONMENT AND STELLAR MASS GROWTH OF THE PROGENITORS OF ULTRA-MASSIVE GALAXIES SINCEZ= 2

The Astrophysical Journal ◽

10.3847/0004-637x/816/2/86 ◽

2016 ◽

Vol 816 (2) ◽

pp. 86 ◽

Cited By ~ 22

Author(s):

Benedetta Vulcani ◽

Danilo Marchesini ◽

Gabriella De Lucia ◽

Adam Muzzin ◽

Mauro Stefanon ◽

...

Keyword(s):

Star Formation ◽

Stellar Mass ◽

Mass Growth ◽

Massive Galaxies

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A study of stellar orbit fractions: simulated IllustrisTNG galaxies compared to CALIFA observations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2164 ◽

2019 ◽

Vol 489 (1) ◽

pp. 842-854 ◽

Cited By ~ 3

Author(s):

Dandan Xu ◽

Ling Zhu ◽

Robert Grand ◽

Volker Springel ◽

Shude Mao ◽

...

Keyword(s):

Observational Data ◽

Mass Range ◽

Stellar Mass ◽

Model Uncertainties ◽

Massive Galaxies ◽

Hubble Sequence ◽

Galaxy Sample ◽

The Mean ◽

Stellar Orbit

ABSTRACT Motivated by the recently discovered kinematic ‘Hubble sequence’ shown by the stellar orbit-circularity distribution of 260 CALIFA galaxies, we make use of a comparable galaxy sample at z = 0 with a stellar mass range of $M_{*}/\mathrm{M}_{\odot }\in [10^{9.7},\, 10^{11.4}]$ selected from the IllustrisTNG simulation and study their stellar orbit compositions in relation to a number of other fundamental galaxy properties. We find that the TNG100 simulation broadly reproduces the observed fractions of different orbital components and their stellar mass dependences. In particular, the mean mass dependences of the luminosity fractions for the kinematically warm and hot orbits are well reproduced within model uncertainties of the observed galaxies. The simulation also largely reproduces the observed peak and trough features at $M_{*}\approx 1\rm {-}2\times 10^{10}\, \mathrm{M}_{\odot }$ in the mean distributions of the cold- and hot-orbit fractions, respectively, indicating fewer cooler orbits and more hotter orbits in both more- and less-massive galaxies beyond such a mass range. Several marginal disagreements are seen between the simulation and observations: the average cold-orbit (counter-rotating) fractions of the simulated galaxies below (above) $M_{*}\approx 6\times 10^{10}\, \mathrm{M}_{\odot }$ are systematically higher than the observational data by $\lesssim 10{{\ \rm per\ cent}}$ (absolute orbital fraction); the simulation also seems to produce more scatter for the cold-orbit fraction and less so for the non-cold orbits at any given galaxy mass. Possible causes that stem from the adopted heating mechanisms are discussed.

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Emerge: Empirical predictions of galaxy merger rates since z ∼ 6

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3746 ◽

2020 ◽

Author(s):

Joseph A O’Leary ◽

Benjamin P Moster ◽

Thorsten Naab ◽

Rachel S Somerville

Keyword(s):

Galaxy Formation ◽

Power Law ◽

Stellar Mass ◽

Direct Result ◽

Mass Relation ◽

Massive Galaxies ◽

The Galaxy ◽

Major Merger ◽

Low Mass ◽

Merger Rate

Abstract We explore the galaxy-galaxy merger rate with the empirical model for galaxy formation, emerge. On average, we find that between 2 per cent and 20 per cent of massive galaxies (log10(m*/M⊙) ≥ 10.3) will experience a major merger per Gyr. Our model predicts galaxy merger rates that do not scale as a power-law with redshift when selected by descendant stellar mass, and exhibit a clear stellar mass and mass-ratio dependence. Specifically, major mergers are more frequent at high masses and at low redshift. We show mergers are significant for the stellar mass growth of galaxies log10(m*/M⊙) ≳ 11.0. For the most massive galaxies major mergers dominate the accreted mass fraction, contributing as much as 90 per cent of the total accreted stellar mass. We reinforce that these phenomena are a direct result of the stellar-to-halo mass relation, which results in massive galaxies having a higher likelihood of experiencing major mergers than low mass galaxies. Our model produces a galaxy pair fraction consistent with recent observations, exhibiting a form best described by a power-law exponential function. Translating these pair fractions into merger rates results in an inaccurate prediction compared to the model intrinsic values when using published observation timescales. We find the pair fraction can be well mapped to the intrinsic merger rate by adopting an observation timescale that decreases linearly with redshift as Tobs = −0.36(1 + z) + 2.39 [Gyr], assuming all observed pairs merge by z = 0.

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Realistic mock observations of the sizes and stellar mass surface densities of massive galaxies in FIRE-2 zoom-in simulations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3765 ◽

2020 ◽

Vol 501 (2) ◽

pp. 1591-1602

Author(s):

T Parsotan ◽

R K Cochrane ◽

C C Hayward ◽

D Anglés-Alcázar ◽

R Feldmann ◽

...

Keyword(s):

Galaxy Formation ◽

Surface Density ◽

Stellar Mass ◽

Massive Galaxies ◽

Star Forming ◽

Stellar Feedback ◽

Central Surface ◽

Stellar Ages ◽

The Galaxy ◽

Zoom In

ABSTRACT The galaxy size–stellar mass and central surface density–stellar mass relationships are fundamental observational constraints on galaxy formation models. However, inferring the physical size of a galaxy from observed stellar emission is non-trivial due to various observational effects, such as the mass-to-light ratio variations that can be caused by non-uniform stellar ages, metallicities, and dust attenuation. Consequently, forward-modelling light-based sizes from simulations is desirable. In this work, we use the skirt dust radiative transfer code to generate synthetic observations of massive galaxies ($M_{*}\sim 10^{11}\, \rm {M_{\odot }}$ at z = 2, hosted by haloes of mass $M_{\rm {halo}}\sim 10^{12.5}\, \rm {M_{\odot }}$) from high-resolution cosmological zoom-in simulations that form part of the Feedback In Realistic Environments project. The simulations used in this paper include explicit stellar feedback but no active galactic nucleus (AGN) feedback. From each mock observation, we infer the effective radius (Re), as well as the stellar mass surface density within this radius and within $1\, \rm {kpc}$ (Σe and Σ1, respectively). We first investigate how well the intrinsic half-mass radius and stellar mass surface density can be inferred from observables. The majority of predicted sizes and surface densities are within a factor of 2 of the intrinsic values. We then compare our predictions to the observed size–mass relationship and the Σ1−M⋆ and Σe−M⋆ relationships. At z ≳ 2, the simulated massive galaxies are in general agreement with observational scaling relations. At z ≲ 2, they evolve to become too compact but still star forming, in the stellar mass and redshift regime where many of them should be quenched. Our results suggest that some additional source of feedback, such as AGN-driven outflows, is necessary in order to decrease the central densities of the simulated massive galaxies to bring them into agreement with observations at z ≲ 2.

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On the formation of massive galaxies: a simultaneous study of number density, size and intrinsic colour evolution in GOODS

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2009.14828.x ◽

2009 ◽

Vol 396 (3) ◽

pp. 1573-1578 ◽

Cited By ~ 35

Author(s):

Ignacio Ferreras ◽

Thorsten Lisker ◽

Anna Pasquali ◽

Sadegh Khochfar ◽

Sugata Kaviraj

Keyword(s):

Number Density ◽

Massive Galaxies ◽

Simultaneous Study ◽

Intrinsic Colour

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THE STELLAR MASS STRUCTURE OF MASSIVE GALAXIES FROMz= 0 TOz= 2.5: SURFACE DENSITY PROFILES AND HALF-MASS RADII

The Astrophysical Journal ◽

10.1088/0004-637x/763/2/73 ◽

2013 ◽

Vol 763 (2) ◽

pp. 73 ◽

Cited By ~ 71

Author(s):

Daniel Szomoru ◽

Marijn Franx ◽

Pieter G. van Dokkum ◽

Michele Trenti ◽

Garth D. Illingworth ◽

...

Keyword(s):

Surface Density ◽

Stellar Mass ◽

Density Profiles ◽

Massive Galaxies

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Constraining the stellar mass function from the deficiency of tidal disruption flares in the nuclei of massive galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz652 ◽

2019 ◽

Vol 485 (3) ◽

pp. 4413-4422 ◽

Cited By ~ 1

Author(s):

Daniel J D’Orazio ◽

Abraham Loeb ◽

James Guillochon

Keyword(s):

Black Hole ◽

Mass Function ◽

Stellar Mass ◽

High Mass ◽

Black Hole Mass ◽

Tidal Disruption ◽

Massive Black Hole ◽

Massive Black Holes ◽

Massive Galaxies ◽

O 10

ABSTRACT The rate of tidal disruption flares (TDFs) per mass of the disrupting black hole encodes information on the present-day mass function (PDMF) of stars in the clusters surrounding super massive black holes. We explore how the shape of the TDF rate with black hole mass can constrain the PDMF, with only weak dependence on black hole spin. We show that existing data can marginally constrain the minimum and maximum masses of stars in the cluster, and the high-mass end of the PDMF slope, as well as the overall TDF rate. With $\mathcal {O}(100)$ TDFs expected to be identified with the Zwicky Transient Facility, the overall rate can be highly constrained, but still with only marginal constraints on the PDMF. However, if ${\lesssim } 10 {{\ \rm per\ cent}}$ of the TDFs expected to be found by LSST over a decade ($\mathcal {O}(10^3)$ TDFs) are identified, then precise and accurate estimates can be made for the minimum stellar mass (within a factor of 2) and the average slope of the high-mass PDMF (to within $\mathcal {O}(10{{\ \rm per\ cent}})$) in nuclear star clusters. This technique could be adapted in the future to probe, in addition to the PDMF, the local black hole mass function and possibly the massive black hole binary population.

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