The morphology–density relation: impact on the satellite fraction

Abstract

In the past years several authors studied the abundance of satellites around galaxies in order to better estimate, for example, the halo masses of the host galaxies. To investigate this connection, we analyze a sample of galaxies with stellar masses M star ≥ 10 10 M ⊙ , taken from the hydrodynamical cosmological simulation suit Magneticum. We find that the satellite fraction of centrals is independent of their morphology. With the exception of very massive galaxies at low redshift, our results do not support the assumption that the dark matter haloes of spheroidal galaxies are significantly more massive than those of disc galaxies at fixed stellar mass. We show that the density-morphology-relation, i.e. the correlation between the quiescent fraction of satellites and the environmental density, starts to build up at z ∼ 2 and is independent of the star formation properties of the central galaxies. We conclude that environmental quenching is more important for satellite galaxies than for centrals. Our simulations also indicate that conformity is already in place at z = 2, where formation redshift and current star formation rate (SFR) of central and satellite galaxies already clearly correlate. Centrals with low SFRs tend to have formed earlier (at fixed stellar mass) while centrals with high SFR formed later, with a typical formation redshift well in agreement with current observations. However, we confirm the recent observations that the apparent number of satellites of spheroidal galaxies is significantly larger than for disc galaxies. This difference completely originates from the inclusion of companion galaxies, i.e. galaxies that do not sit in the potential minimum of a massive dark matter halo. Thus, due to the density-morphological-relation the number of satellites is not a good tracer for the halo mass, unless samples are restricted to the central galaxies of dark matter haloes only.

Gone after one orbit: How cluster environments quench galaxies

“…environment, is the determining factor in galaxy quenching. Findings based on a smaller Magneticum box with higher resolution further support this notion, stating that environmental quenching is more important for satellite galaxies than for centrals (Teklu et al 2017).…”

Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity?

“…The simulations are described in detail in Paper I (Hirschmann et al 2014), which demonstrated that AGN luminosities together with their anti-hierarchical trend are consistent with observations over cosmic time. In addition, our simulations can successfully reproduce various other observed galaxy and BH properties (e.g., Teklu et al 2015;Steinborn et al 2015;Teklu et al 2017;Teklu et al 2018;Schulze et al 2018) providing an ideal testbed for our study. We emphasize that thanks to the uniquely large simulated volume of (500 Mpc) 3 , we are able to study the AGN-merger connection for the rarest very luminous quasars, which are not accessible in most other state-of-art simulations (like EAGLE, Illustris).…”

“…• 68Mpc/uhr: This simulation has a volume of (68Mpc) 3 combined with a comparably high resolution, with dark matter and gas particles masses of M dm = 3.7 · 10 7 M /h and Mgas = 7.3 · 10 6 M /h, respectively. This resolution is high enough to largely capture the internal structure and morphology of galaxies (Teklu et al 2015(Teklu et al , 2017. Note that BH accretion rates in the intrinsic, code-based time resolution are stored only at z ≥ 1.5, allowing us to study detailed BH light curves down to that redshift (Fig.…”

SDSS-IV MaNGA: Uncovering the Angular Momentum Content of Central and Satellite Early-type Galaxies

“…They report that the overall scatter is dominated by intrinsic scatter between halo mass and M L , while the details of the group finder (interlopers, incompleteness effects) are a relatively small component. Campbell et al (2015) demonstrate that in general it is possible to extract meaningful physical correlations from Y07 as a function of color, stellar mass, and halo mass despite misidentifications and errors in halo mass (although see also Teklu et al 2017).…”