scholarly journals An EAGLE’s view of ex situ galaxy growth

2020 ◽  
Vol 497 (1) ◽  
pp. 81-93 ◽  
Author(s):  
Thomas A Davison ◽  
Mark A Norris ◽  
Joel L Pfeffer ◽  
Jonathan J Davies ◽  
Robert A Crain
Keyword(s):  
Analytical Techniques ◽  
Mass Range ◽  
Morphological Type ◽  
Stellar Mass ◽  
Ex Situ ◽  
Large Field ◽  
Mass Fractions ◽  
Satellite Galaxies ◽  
Galaxy Assembly ◽  
Field Unit

ABSTRACT Modern observational and analytical techniques now enable the direct measurement of star formation histories and the inference of galaxy assembly histories. However, current theoretical predictions of assembly are not ideally suited for direct comparison with such observational data. We therefore extend the work of prior examinations of the contribution of ex situ stars to the stellar mass budget of simulated galaxies. Our predictions are specifically tailored for direct testing with a new generation of observational techniques by calculating ex situ fractions as functions of galaxy mass and morphological type, for a range of surface brightnesses. These enable comparison with results from large field of view (FoV) Integral Field Unit (IFU) spectrographs, and increasingly accurate spectral fitting, providing a look-up method for the estimated accreted fraction. We furthermore provide predictions of ex situ mass fractions as functions of galaxy mass, galactocentric radius, and environment. Using z = 0 snapshots from the 100 and 25 cMpc3 EAGLE (Evolution and Assembly of GaLaxies and their Environments) simulations, we corroborate the findings of prior studies, finding that ex situ fraction increases with stellar mass for central and satellite galaxies in a stellar mass range of 2 × 107 to 1.9 × 1012 M⊙. For those galaxies of mass M* > 5 × 108 M⊙, we find that the total ex situ mass fraction is greater for more extended galaxies at fixed mass. When categorizing satellite galaxies by their parent group/cluster halo mass, we find that the ex situ fraction decreases with increasing parent halo mass at fixed galaxy mass. This apparently counterintuitive result may be due to high passing velocities within large cluster haloes inhibiting efficient accretion on to individual galaxies.

scholarly journals The distinct stellar-to-halo mass relations of satellite and central galaxies: insights from the IllustrisTNG simulations

2020 ◽  
Vol 500 (3) ◽  
pp. 3957-3975
Author(s):  
Christoph Engler ◽  
Annalisa Pillepich ◽  
Gandhali D Joshi ◽  
Dylan Nelson ◽  
Anna Pasquali ◽  
...  
Keyword(s):  
Dark Matter ◽  
Environmental Effects ◽  
Total Mass ◽  
Local Density ◽  
Stellar Mass ◽  
Mass Relation ◽  
Systematic Deviation ◽  
Dynamical Mass ◽  
Mass Fractions ◽  
Satellite Galaxies

ABSTRACT We study the stellar-to-halo mass relation (SHMR) for central and satellite galaxies with total dynamical masses above $10^{10.5}\, \rm {M}_\odot$ using the suite of cosmological magnetohydrodynamical simulations IllustrisTNG. In particular, we quantify environmental effects on satellite populations from TNG50, TNG100, and TNG300 located within the virial radius of group- and cluster-like hosts with total masses of $10^{12\!-\!15.2}\, \rm {M}_\odot$. At fixed stellar mass, the satellite SHMR exhibits a distinct shift towards lower dynamical mass compared to the SHMR of centrals. Conversely, at fixed dynamical mass, satellite galaxies appear to have larger stellar-to-total mass fractions than centrals by up to a factor of a few. The systematic deviation from the central SHMR is larger for satellites in more massive hosts, at smaller cluster-centric distances, with earlier infall times, and that inhabits higher local density environments; moreover, it is in place already at early times (z ≲ 2). Systematic environmental effects might contribute to the perceived galaxy-to-galaxy variation in the measured SHMR when galaxies cannot be separated into satellites and centrals. The SHMR of satellites exhibits a larger scatter than centrals (by up to ∼0.8 dex), over the whole range of dynamical mass. The shift of the satellite SHMR results mostly from tidal stripping of their dark matter, which affects satellites in an outside-in fashion: The departure of the satellite SHMR from the centrals’ relation diminishes for measurements of dynamical mass in progressively smaller apertures. Finally, we provide a family of fitting functions for the SHMR predicted by IllustrisTNG.

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

2019 ◽  
Vol 489 (1) ◽  
pp. 842-854 ◽  
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.

scholarly journals The weak imprint of environment on the stellar populations of galaxies

2020 ◽  
Vol 500 (4) ◽  
pp. 4469-4490 ◽  
Author(s):  
James Trussler ◽  
Roberto Maiolino ◽  
Claudia Maraston ◽  
Yingjie Peng ◽  
Daniel Thomas ◽  
...  
Keyword(s):  
Environmental Effects ◽  
Unique Feature ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Star Forming ◽  
Sky Survey ◽  
Satellite Galaxies ◽  
Projected Distance ◽  
Environmental Dependence

ABSTRACT We investigate the environmental dependence of the stellar populations of galaxies in Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Echoing earlier works, we find that satellites are both more metal-rich (<0.1 dex) and older (<2 Gyr) than centrals of the same stellar mass. However, after separating star-forming, green valley, and passive galaxies, we find that the true environmental dependence of both stellar metallicity (<0.03 dex) and age (<0.5 Gyr) is in fact much weaker. We show that the strong environmental effects found when galaxies are not differentiated result from a combination of selection effects brought about by the environmental dependence of the quenched fraction of galaxies, and thus we strongly advocate for the separation of star-forming, green valley, and passive galaxies when the environmental dependence of galaxy properties are investigated. We also study further environmental trends separately for both central and satellite galaxies. We find that star-forming galaxies show no environmental effects, neither for centrals nor for satellites. In contrast, the stellar metallicities of passive and green valley satellites increase weakly (<0.05 and <0.08 dex, respectively) with increasing halo mass, increasing local overdensity and decreasing projected distance from their central; this effect is interpreted in terms of moderate environmental starvation (‘strangulation’) contributing to the quenching of satellite galaxies. Finally, we find a unique feature in the stellar mass–stellar metallicity relation for passive centrals, where galaxies in more massive haloes have larger stellar mass (∼0.1 dex) at constant stellar metallicity; this effect is interpreted in terms of dry merging of passive central galaxies and/or progenitor bias.

scholarly journals The stellar mass assembly of low-redshift, massive, central galaxies in SDSS and the TNG300 simulation

2020 ◽  
Vol 497 (4) ◽  
pp. 4262-4275
Author(s):  
Thomas M Jackson ◽  
A Pasquali ◽  
C Pacifici ◽  
C Engler ◽  
A Pillepich ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Stellar Mass ◽  
Spectral Energy ◽  
Distribution Fitting ◽  
Stellar Ages ◽  
Mass Assembly ◽  
Galaxy Assembly ◽  
The Times ◽  
Stellar Masses ◽  
Kinetic Mode

ABSTRACT The stellar mass assembly of galaxies can be affected by both secular and environmental processes. In this study, for the first time, we investigate the stellar mass assembly of $\sim 90\, 000$ low-redshift, central galaxies selected from SDSS group catalogues ($M_{\rm Stellar}\gtrsim 10^{9.5}\, \mathrm{M}_{\odot }$, $M_{\rm Halo}\gtrsim 10^{12}\, \mathrm{M}_{\odot }$) as a function of both stellar mass and halo mass. We use estimates of the times at which 10, 50, and 90 per cent of the stellar mass were assembled from photometric spectral energy distribution fitting, allowing a more complete investigation than single stellar ages alone. We consider trends in both stellar mass and halo mass simultaneously, finding dependences of all assembly times on both. We find that galaxies with higher stellar masses (at constant halo mass) have on average older lookback times, similar to previous studies of galaxy assembly. We also find that galaxies at higher halo mass (at constant stellar mass) have younger lookback times, possibly due to a larger reservoir of gas for star formation. An exception to this is a subsample with high stellar-to-halo mass ratios, which are likely massive, field spirals. We compare these observed trends to those predicted by the TNG300 simulation, finding good agreement overall as a function of either stellar mass or halo mass. However, some differences in the assembly times (of up to ∼3 Gyr) appear when considering both stellar mass and halo mass simultaneously, noticeably at intermediate stellar masses (MStellar ∼ 1011 M⊙). These discrepancies are possibly linked to the quenched fraction of galaxies and the kinetic mode active galactic nucleus feedback implemented in TNG300.

scholarly journals The emergence of the galactic stellar mass function from a non-universal IMF in clusters

2018 ◽  
Vol 614 ◽  
pp. A43 ◽  
Author(s):  
Sami Dib ◽  
Shantanu Basu
Keyword(s):  
Mass Range ◽  
Mass Function ◽  
Stellar Mass ◽  
Stellar Clusters ◽  
Galactic Clusters ◽  
Power Law Function ◽  
Low Mass ◽  
Mass Functions ◽  
Characteristic Mass ◽  
The Imf

We investigate the dependence of a single-generation galactic mass function (SGMF) on variations in the initial stellar mass functions (IMF) of stellar clusters. We show that cluster-to-cluster variations of the IMF lead to a multi-component SGMF where each component in a given mass range can be described by a distinct power-law function. We also show that a dispersion of ≈0.3 M⊙ in the characteristic mass of the IMF, as observed for young Galactic clusters, leads to a low-mass slope of the SGMF that matches the observed Galactic stellar mass function even when the IMFs in the low-mass end of individual clusters are much steeper.

scholarly journals Investigating the Stellar Mass Growth Histories of Satellite Galaxies as a Function of Infall Time Using Phase-space

2019 ◽  
Vol 876 (2) ◽  
pp. 145 ◽  
Author(s):  
Rory Smith ◽  
Camilla Pacifici ◽  
Anna Pasquali ◽  
Paula Calderón-Castillo
Keyword(s):  
Phase Space ◽  
Stellar Mass ◽  
Mass Growth ◽  
Satellite Galaxies

scholarly journals A galaxy’s accretion history unveiled from its integrated spectrum

2019 ◽  
Author(s):  
Alina Boecker ◽  
Ryan Leaman ◽  
Glenn van de Ven ◽  
Mark A Norris ◽  
J Ted Mackereth ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Mass Function ◽  
Stellar Mass ◽  
Ex Situ ◽  
Future Application ◽  
Chemical Enrichment ◽  
Spectral Fitting ◽  
Regularization Techniques ◽  
Galaxy Masses

Abstract We present a new method of quantifying a galaxy’s accretion history from its integrated spectrum alone. Using full spectral fitting and calibrated regularization techniques we show how we can accurately derive a galaxy’s mass distribution in age-metallicity space and further separate this into stellar populations from different chemical enrichment histories. By exploiting the fact that accreted lower mass galaxies will exhibit an offset to lower metallicities at fixed age compared to the in-situ stellar population, we quantify the fraction of light that comes from past merger events, that are long since mixed in phase-space and otherwise indistinguishable. Empirical age-metallicity relations (AMRs) parameterized for different galaxy masses are used to identify the accreted stellar populations and link them back to the progenitor galaxy’s stellar mass. This allows us to not only measure the host galaxy’s total ex-situ mass fraction (facc), but also quantify the relative amount of accreted material deposited by satellite galaxies of different masses, i.e. the accreted satellite mass function in analogy to the subhalo mass function. Using mock spectra of present-day, early-type galaxies with total stellar mass ∼109 − 1012 M⊙ from the EAGLE simulation suite we demonstrate that our method can recover the total accreted fraction to within $\approx 38 \%$, the stellar mass of the most massive accreted subhalo to within $\approx 56 \%$ and the slope of the accreted satellite mass function to within $\approx 17 \%$ of the true values from the EAGLE merger trees. Future application of this method to observations could potentially provide us accretion histories of hundreds of individual galaxies, for which deep integrated light spectroscopy is available.

scholarly journals Satellite galaxies in the Illustris-1 simulation: anisotropic locations around relatively isolated hosts

2019 ◽  
Vol 489 (1) ◽  
pp. 459-469 ◽  
Author(s):  
Tereasa G Brainerd ◽  
Masaya Yamamoto
Keyword(s):  
Dark Matter ◽  
Mass Density ◽  
Stellar Mass ◽  
Stellar Surface ◽  
Surface Mass ◽  
Degree Of Anisotropy ◽  
Surface Mass Density ◽  
The Mean ◽  
Satellite Galaxies ◽  
Stellar Masses

ABSTRACT We investigate the locations of satellite galaxies in the z = 0 redshift slice of the hydrodynamical Illustris-1 simulation. As expected from previous work, the satellites are distributed anisotropically in the plane of the sky, with a preference for being located near the major axes of their hosts. Due to misalignment of mass and light within the hosts, the degree of anisotropy is considerably less when satellite locations are measured with respect to the hosts’ stellar surface mass density than when they are measured with respect to the hosts’ dark matter surface mass density. When measured with respect to the hosts’ dark matter surface mass density, the mean satellite location depends strongly on host stellar mass and luminosity, with the satellites of the faintest, least massive hosts showing the greatest anisotropy. When measured with respect to the hosts’ stellar surface mass density, the mean satellite location is essentially independent of host stellar mass and luminosity. In addition, the satellite locations are largely insensitive to the amount of stellar mass used to define the hosts’ stellar surface mass density, as long as at least 50–70 per cent of the hosts’ total stellar mass is used. The satellite locations are dependent upon the stellar masses of the satellites, with the most massive satellites having the most anisotropic distributions.

scholarly journals Properties of satellite galaxies in nearby groups

2014 ◽  
Vol 11 (S308) ◽  
pp. 475-476
Author(s):  
Jaan Vennik
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
Stellar Mass ◽  
Line Of Sight ◽  
Limited Sample ◽  
Velocity Modulation ◽  
Star Forming ◽  
Relative Line ◽  
Satellite Galaxies ◽  
Kinematical Data

AbstractWe studied the variation of stellar mass and various star-formation characteristics of satellite galaxies in a volume limited sample of nearby groups as a function of their group-centric distance and of their relative line-of-sight velocity in the group rest frame. We found clear radial dependencies, e.g. massive, red and passive satellites being distributed predominantly near the center of composite group. We also found some evidence of velocity modulation of star-forming properties of satellite galaxies near the group virial radius. We conclude that using kinematical data, it should be feasible to separate dynamical classes of bound, in-falling and 'backsplash' satellite galaxies.

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