Under pressure: quenching star formation in low-mass satellite galaxies via stripping

Abstract

Recent studies of galaxies in the local Universe, including those in the Local Group, find that the efficiency of environmental (or satellite) quenching increases dramatically at satellite stellar masses below ∼ 10 8 M . This suggest a physical scale where quenching transitions from a slow "starvation" mode to a rapid "stripping" mode at low masses. We investigate the plausibility of this scenario using observed HI surface density profiles for a sample of 66 nearby galaxies as inputs to analytic calculations of ram-pressure and turbulent viscous stripping. Across a broad range of host properties, we find that stripping becomes increasingly effective at M * 10 8−9 M , reproducing the critical mass scale observed. However, for canonical values of the circumgalactic medium density (n halo < 10 −3.5 cm −3 ), we find that stripping is not fully effective; infalling satellites are, on average, stripped of only 40 − 60% of their cold gas reservoir, which is insufficient to match observations. By including a host halo gas distribution that is clumpy and therefore contains regions of higher density, we are able to reproduce the observed HI gas fractions (and thus the high quenched fraction and short quenching timescale) of Local Group satellites, suggesting that a host halo with clumpy gas may be crucial for quenching low-mass systems in Local Group-like (and more massive) host halos.

Galaxy Zoo: the interplay of quenching mechanisms in the group environment★

“…However we find that this is not the case (see Figure 11b). This therefore rules out RPS as the dominant environmental quenching mechanism, in support of the simulations of Emerick et al (2016) and Fillingham et al (2016) which showed that RPS could only remove 40 − 60% of a satellite's gas. However, this conclusion may be due to the stellar mass range spanned by the gz2-group-q satellite galaxies which all have M * 10 9 M , as simulations by Fillingham et al (2016) suggest that RPS only becomes effective in lower mass satellites with M * 10 8−9 M , in agreement with Hester (2006).…”

“…In order to compare groups of different sizes, the virial radius is used as a normalisation factor to this projected group-centric radius. Here we use a proxy to the virial radius, R200 (see Navarro et al 1995), the radius within which the group mass overdensity is 200 times the critical density, ρcrit(z), as defined by Finn et al 2005:…”

“…Above this mass threshold in the simulations of Fillingham et al (2016), a 'starvation' (or strangulation) mode (Larson et al 1980;Balogh et al 2000) dominates, where a galaxy's extended gaseous halo is removed causing a quench, as cold gas for use in star formation can no longer be fed from the extended halo. This idea is supported by observations by Peng et al (2015) which show that strangulation is a dominant mechanism for galaxies with M * < 10 11 M with a quenching timescale of 4 Gyr.…”

Farthest Neighbor: The Distant Milky Way Satellite Eridanus II*

“…As a quiescent dwarf galaxy located close to, but beyond, the virial radius of Milky Way, EriII is a key object for studying environmental influences on low-mass galaxies and the quenching of star formation in such systems (Weisz et al 2014;Wetzel et al 2015;Wheeler et al 2015;Fillingham et al 2016).…”

A deep Parkes H i survey of the Sculptor group and filament: H i mass function and environment

“…Environmental effects such as ram-pressure stripping or tidal interaction provide another potential mechanism for the removal of gas from galaxies (Gavazzi et al 2005;Hester 2006;Fillingham et al 2016). However, environmentally induced gas removal processes are expected to be more efficient in dense environments and should therefore lead to a flattening of the slope of the HIMF in dense clusters rather than loose groups, e.g.…”