Search

We test cosmological hydrodynamical simulations of galaxy formation regarding the properties of the blue cloud (BC), green valley (GV), and red sequence (RS), as measured on the 4000Å break strength versus stellar mass plane at z  = 0.1. We analyse the RefL0100N1504 run of EAGLE and the TNG100 run of IllustrisTNG project, by comparing them with the Sloan Digital Sky Survey (SDSS), while taking into account selection bias. Our analysis focuses on the GV, within stellar mass |$\log \, \mathrm{{\it M}_\star /M_{\odot }} \simeq 10\!-\!11$|⁠ , selected from the bimodal distribution of galaxies on the D n (4000) versus stellar mass plane, following Angthopo et al. methodology. Both simulations match the fraction of AGN in the GV. However, they overproduce quiescent GV galaxies with respect to observations, with IllustrisTNG yielding a higher fraction of quiescent GV galaxies than EAGLE. In both, GV galaxies have older luminosity-weighted ages with respect to the SDSS, while a better match is found for mass-weighted ages. We find EAGLE GV galaxies quench their star formation early, but undergo later episodes of star formation, matching observations. In contrast, IllustrisTNG GV galaxies have a more extended star formation history, and quench more effectively at later cosmic times, producing the excess of quenched galaxies in GV compared with SDSS, based on the 4000Å break strength. These results suggest the AGN feedback subgrid physics, more specifically, the threshold halo mass for black hole input and the black hole seed mass, could be the primary cause of the overproduction of quiescent galaxies found with respect to the observational constraints. [ABSTRACT FROM AUTHOR]

We report the discovery of BOSS-EUVLG1 at z  = 2.469, by far the most luminous, almost un-obscured star-forming galaxy known at any redshift. First classified as a QSO within the Baryon Oscillation Spectroscopic Survey, follow-up observations with the Gran Telescopio Canarias reveal that its large luminosity, M UV ≃ −24.40 and log(L Lyα/erg s–1) ≃ 44.0, is due to an intense burst of star formation, and not to an active galactic nucleus or gravitational lensing. BOSS-EUVLG1 is a compact (r eff ≃ 1.2 kpc), young (4–5 Myr) starburst with a stellar mass log(M */M⊙) = 10.0 ± 0.1 and a prodigious star formation rate of ≃1000 M⊙ yr−1. However, it is metal- and dust-poor [12 + log(O/H) = 8.13 ± 0.19, E (B – V) ≃ 0.07, log(L IR/ L UV) < −1.2], indicating that we are witnessing the very early phase of an intense starburst that has had no time to enrich the ISM. BOSS-EUVLG1 might represent a short-lived (<100 Myr), yet important phase of star-forming galaxies at high redshift that has been missed in previous surveys. Within a galaxy evolutionary scheme, BOSS-EUVLG1 could likely represent the very initial phases in the evolution of massive quiescent galaxies, even before the dusty star-forming phase. [ABSTRACT FROM AUTHOR]

We have developed a new tool to analyse galaxies in the eagle simulations as close as possible to observations. We investigated the evolution of their kinematic properties by means of the angular momentum proxy parameter, λRe, for galaxies with M ⋆ ≥ 5 × 109 M⊙ in the RefL0100N1504 simulation up to redshift two (z  = 2). Galaxies in the simulation show a wide variety of kinematic features, similiar to those found in integral-field spectroscopic studies. At z  = 0 the distribution of galaxies in the λRe–ε plane is also in good agreement with results from observations. Scaling relations at z  = 0 indicate that there is a critical mass, M crit /M⊙ = 1010.3, that divides two different regimes when we include the λRe parameter. The simulation shows that the distribution of galaxies in the λRe–ε plane evolves with time until z  = 2 when galaxies are equally distributed in both λRe and ε. We studied the evolution of λRe with time and found that there is no connection between the angular momentum at z  = 2 and z  = 0. All systems reach their maximum λRe at z  = 1 and then steadily lose angular momentum regardless of their merger history, except for the high star-forming systems that sustain that maximum value over time. The evolution of λRe in galaxies that have not experienced any merger in the last 10 Gyr can be explained by their level of gas accretion. [ABSTRACT FROM AUTHOR]

We present the public data release of halo and galaxy catalogues extracted from the eagle suite of cosmological hydrodynamical simulations of galaxy formation. These simulations were performed with an enhanced version of the gadget code that includes a modified hydrodynamics solver, time-step limiter and subgrid treatments of baryonic physics, such as stellar mass loss, element-by-element radiative cooling, star formation and feedback from star formation and black hole accretion. The simulation suite includes runs performed in volumes ranging from 25 to 100 comoving megaparsecs per side, with numerical resolution chosen to marginally resolve the Jeans mass of the gas at the star formation threshold. The free parameters of the subgrid models for feedback are calibrated to the redshift z = 0 galaxy stellar mass function, galaxy sizes and black hole mass–stellar mass relation. The simulations have been shown to match a wide range of observations for present-day and higher-redshift galaxies. The raw particle data have been used to link galaxies across redshifts by creating merger trees. The indexing of the tree produces a simple way to connect a galaxy at one redshift to its progenitors at higher redshift and to identify its descendants at lower redshift. In this paper we present a relational database which we are making available for general use. A large number of properties of haloes and galaxies and their merger trees are stored in the database, including stellar masses, star formation rates, metallicities, photometric measurements and mock g r i images. Complex queries can be created to explore the evolution of more than 10 5 galaxies, examples of which are provided in the Appendix. The relatively good and broad agreement of the simulations with a wide range of observational datasets makes the database an ideal resource for the analysis of model galaxies through time, and for connecting and interpreting observational datasets. [ABSTRACT FROM AUTHOR]

ABSTRACT We examine the rotation rates, sizes and star formation (SF) efficiencies of a representative population of simulated disc galaxies extracted from the Galaxies-Intergalactic Medium Interaction Calculation (GIMIC) suite of cosmological hydrodynamic simulations. These simulations include efficient, but energetically feasible supernova feedback, but have not been tuned in any way to produce 'realistic' disc galaxies. Yet, they generate a large number of discs, without requiring extremely high resolution. Over the wide galaxy stellar mass range, 9.0 ≲ log 10 [ M*(M⊙)] < 10.5, the simulations reproduce the observed Tully-Fisher relation, the rotation curves of disc galaxies in bins of stellar mass, the mass-size relation of disc galaxies, the optical rotation to virial circular velocity ratio (' Vopt/ Vvir') and the SF efficiencies of disc galaxies as inferred from stacked weak lensing and stacked satellite kinematics observations. They also reproduce the specific star formation rates of ∼ L* galaxies but predict too low levels of SF for low-mass galaxies, which is plausibly due to the finite resolution of the simulations. At higher stellar masses, log10[ M*(M⊙)] > 10.6, the simulated galaxies are too concentrated and have too high SF efficiencies. We conjecture that this shortcoming reflects the neglect of feedback from accreting supermassive black holes in these simulations. We conclude that it is possible to generate a representative population of disc galaxies that reproduces many of the observed trends of local disc galaxies using standard numerical hydrodynamic techniques and a plausible implementation of the 'subgrid' astrophysical processes thought to be relevant to galaxy formation. [ABSTRACT FROM AUTHOR]