First results from the IllustrisTNG simulations: the stellar mass content of groups and clusters of galaxies

Abstract

The IllustrisTNG project is a new suite of cosmological magneto-hydrodynamical simulations of galaxy formation performed with the AREPO code and updated models for feedback physics. Here we introduce the first two simulations of the series, TNG100 and TNG300, and quantify the stellar mass content of about 4000 massive galaxy groups and clusters (10 13 M 200c /M 10 15 ) at recent times (z 1). The richest clusters have half of their total stellar mass bound to satellite galaxies, with the other half being associated with the central galaxy and the diffuse intra-cluster light. Haloes more massive than about 5 × 10 14 M have more diffuse stellar mass outside 100 kpc than within 100 kpc, with power-law slopes of the radial mass density distribution as shallow as the dark matter's ( −3.5 α 3D−3). Total halo mass is a very good predictor of stellar mass, and vice versa: at z = 0, the 3D stellar mass measured within 30 kpc scales as ∝ (M 500c ) 0.49 with a ∼ 0.12 dex scatter. This is possibly too steep in comparison to the available observational constraints, even though the abundance of TNG less massive galaxies ( 10 11 M in stars) is in good agreement with the measured galaxy stellar mass functions at recent epochs. The 3D sizes of massive galaxies fall too on a tight (∼0.16 dex scatter) power-law relation with halo mass, with r stars 0.5 ∝ (M 200c ) 0.53 . Even more fundamentally, halo mass alone is a good predictor for the whole stellar mass profiles beyond the inner few kpc, and we show how on average these can be precisely recovered given a single mass measurement of the galaxy or its halo.

Interacting galaxies in the IllustrisTNG simulations - I: Triggered star formation in a cosmological context

“…Illus-trisTNG is the successor to the Illustris simulations (see below), with numerous updates that are described in the public data release (Nelson et al 2019). Weinberger et al (2018) and Pillepich et al (2018a) provide a complete description of the physical models. Additional details about these simulations are given by Pillepich et al (2018b), Springel et al (2018), Nelson et al (2018), Naiman et al (2018), and Marinacci et al (2018).…”

“…The baryonic simulations follow the evolution of dark matter, stars, gas and supermassive black holes from a redshift of 127 to the present epoch using the AREPO moving-mesh code (Springel 2010). Star formation occurs above a threshold density criterion, and is regulated by a subgrid model for the interstellar medium (Springel & Hernquist 2003;Nelson et al 2015;Pillepich et al 2018a). Where needed for stellar evolution and mass return calculations, a Chabrier (2003) initial mass function is used.…”

Aging haloes: implications of the magnitude gap on conditional statistics of stellar and gas properties of massive haloes

“…But this simple model ignores non-spherical and non-gravitational effects such as hierarchical mergers driven by large-scale filaments and feedback by star formation, supernovae, and active galactic nuclei (AGN). A central focus of recent observations and modern simulations has been on understanding these non-gravitational effects and feedback processes, which leads to a comprehensive understanding of the ways in which the galaxies are forming and evolving as a function of their host halo mass and redshift (McCarthy et al 2017;Pillepich et al 2018b;Mulroy et al 2019). While the first principle approaches have been made progress in making more realistic galaxy population, empirical approaches are complementary in gaining insight into the physics of these systems.…”

On the (Lack of) Evolution of the Stellar Mass Function of Massive Galaxies from z = 1.5 to 0.4

“…Numerical simulations (e.g., Oser et al 2010;Wellons et al 2015), semi-analytic models (SAM; e.g., Lee & Yi 2013, 2017, and stellar-mass-halo-mass (SHAM) analyses (e.g., Moster et al 2013Moster et al , 2018Behroozi et al 2013b;Rodríguez-Puebla et al 2017) generally show that the fraction of accreted stars through mergers increase with total galaxy stellar mass or halo mass (e.g., Lackner et al 2012;Cooper et al 2013;Rodriguez-Gomez et al 2016;Qu et al 2017;Pillepich et al 2018). For example, Qu et al (2017) analyzed the mass assembly of central galaxies in the EA-GLE cosmological simulation and found that ∼ 20% of the stellar mass of present day massive galaxies (> 10 11 M ) is built up through mergers, and more massive galaxies have experienced more stellar-mass growth by mergers.…”