The neutral hydrogen properties of galaxies in gas-rich groups

Abstract

We present an analysis of the integrated neutral hydrogen (H i) properties for 27 galaxies within nine low mass, gas-rich, late-type dominated groups which we denote "Choirs". We find that majority of the central Choir galaxies have average H i content: they have a normal gas-mass fraction with respect to isolated galaxies of the same stellar mass. In contrast, we find more satellite galaxies with a lower gas-mass fraction than isolated galaxies of the same stellar mass. A likely reason for the lower gas content in these galaxies is tidal stripping. Both the specific star formation rate and the star formation efficiency of the central group galaxies are similar to galaxies in isolation. The Choir satellite galaxies have similar specific star formation rate as galaxies in isolation, therefore satellites that exhibit a higher star formation efficiency simply owe it to their lower gas-mass fractions. We find that the most H i massive galaxies have the largest H i discs and fall neatly onto the H i size-mass relation, while outliers are galaxies that are experiencing interactions. We find that high specific angular momentum could be a reason for galaxies to retain the large fraction of H i gas in their discs. This shows that for the Choir groups with no evidence of interactions, as well as those with traces of minor mergers, the internal galaxy properties dominate over the effects of residing in a group. The probed galaxy properties strengthen evidence that the Choir groups represent the early stages of group assembly.

Environmental processing of galaxies in H i-rich groups

“…In Džudžar et al (2019a) we analysed the integrated H i properties of 27 galaxies within nine Choir groups and compared them to a sample of isolated galaxies. We explored the H i mass fraction, specific star formation rate, star formation efficiency, H i deficiency, H i mass-size relation and stability parameter of the group galaxies with respect to the isolated galaxies.…”

“…Presented H i maps and spectra use velocities in the optical convention. The group distances are based on the multipole attractor model (Mould et al 2000), as in (Meurer et al 2006;Sweet et al 2013 andDžudžar et al 2019a).…”

From massive spirals to dwarf irregulars: a new set of tight scaling relations for cold gas and stars driven by disc gravitational instability

“…Obreschkow et al (2016) proposed a hybrid stability model that predicts the mass fraction of atomic (hydrogen+helium) gas as a function of mass and specific angular momentum of the whole (gas+stars) disc, assuming a constant H i velocity dispersion: fHI = min{1, 2.5 q 1.12 }, where q = j disc σHI/GM disc and σHI = 10 km s −1 . Such a ⋆ E-mail: romeo@chalmers.se stability model has been tested in a variety of applications (e.g., Lagos et al 2017;Lutz et al 2017Lutz et al , 2018Stevens et al 2018;Wang et al 2018;Džudžar et al 2019;Murugeshan et al 2019;Stevens et al 2019). Another important contribution is the one by Zasov & Zaitseva (2017), who showed that the relation between atomic gas mass and disc specific angular momentum is equally well described by a simpler stability model controlled by Qgas, the gas Toomre parameter, assuming that Qgas is approximately constant within a galaxy (like σgas).…”

Group pre-processing versus cluster ram-pressure stripping: the case of ESO156−G029

“…Using data from the H i modeling and the Ks-band (background subtracted) galaxy image, we derive the total baryonic specific angular momentum (j) and stability parameter (q) of the galaxy utilizing the robust method described in Murugeshan et al (2019). We determine that the global stability parameter (q) is in overall agreement with the one determined analytically by Džudžar et al (2019). Obreschkow et al (2016) observe a tight positive correlation between the atomic gas-mass fraction and the global stability parameter q (with its ability to regulate star formation efficiency) which consequently determines the atomic gas fraction.…”

“…The integrated properties of ESO156-G029 were shown in Džudžar et al (2019) -galaxy with ID: HIPASSJ0400-52:S1. We found that ESO156-G029 is an H i-rich galaxy with a large gas-mass fraction and a low specific star formation efficiency.…”