The galaxy H i–(sub)halo connection and the H i spatial clustering of local galaxies

Abstract

We extend the local stellar galaxy-(sub)halo connection to the atomic hydrogen (H i) component by seeding semi-empirically galaxies into a large N-body dark matter (DM) simulation. The main input to construct the mock galaxy catalog are: our constrained stellar mass-to-(sub)halo circular velocity (M*–VDM) relation, assuming a scatter independent of any galaxy property, and the empirical $M_{\rm H\, \small {I}}$ conditional probability distributions given M* for central and satellite galaxies. We find that the $\langle \log {M_{\rm H\, \small {I}}}\rangle -\log {M_{\rm DM}}$ relation is not a monotonic increasing function. It increases with mass up to ${M_{\rm DM}}\sim 10^{12}$ M⊙, attaining a maximum of $\langle \log ({M_{\rm H\, \small {I}}}/{M_{\odot }})\rangle \sim 9.2$, and at higher (sub)halo masses, $\langle \log ({M_{\rm H\, \small {I}}})\rangle$ decreases slightly with MDM. The scatter around it is also large and mass dependent. The bivariate $M_{\rm H\, \small {I}}$ and MDM distribution is broad and bimodal, specially at ${M_{\rm DM}}\gtrsim 10^{12}$ M⊙, which is inherited from the input $M_{\rm H\, \small {I}}$ conditional distributions. We also report the total (central+satellites) H i gas mass within haloes, $M^{\rm tot}_{\rm H\, \small {I}}$, as a function of MDM. The mean ${M^{\rm tot}_{\rm H\, \small {I}}}$-${M_{\rm DM}}$ relation is an increasing monotonic function. The galaxy spatial clustering increases weakly as the $M_{\rm H\, \small {I}}$ threshold increases. Our H i mock galaxies cluster more in comparison to the blind H i ALFALFA survey but we show that it is mainly due to the selection effects. We discuss the implications of our results in the light of predictions from semi-analytical models and hydrodynamics simulations of galaxy evolution.

What determines the HI gas content in galaxies?: morphological dependence of the HI gas fraction across M*-SFR plane

“…A simple approach to remove the stellar mass dependence is to check the H I scaling relations of each subsample. Calette et al (2018) compared the H I scaling relation of late-type galaxies and early-type galaxies and concluded that late-type galaxies have higher H I gas fraction than early-type galaxies at all stellar mass range. However, the stellar mass is not the only parameter that determines the H I gas mass of the host galaxies, and other parameters can also affect the scaling relation (Cortese et al 2011;Brown et al 2015;Cook et al 2019).…”

“…With the recent large, H I 21 cm line survey in the local universe, such as the GALEX Arecibo SDSS Survey (GASS; Catinella et al 2013) and the Arecibo Legacy Fast ALFA (ALFALFA) survey (Haynes et al 2018), it has become possible to investigate the morphological dependence of the H I gas fraction of local galaxies in a more statistical way. By using the data from the GASS survey and various morphological classifications from the visual classification to the automated methods, Calette et al (2018) reported that late-type galaxies tend to have higher H I gas fraction than earlytype galaxies at a given stellar mass. While Calette et al (2018) divided their sample into stellar mass bins, they did not split the sample by star formation rates (SFR).…”

“…By using the data from the GASS survey and various morphological classifications from the visual classification to the automated methods, Calette et al (2018) reported that late-type galaxies tend to have higher H I gas fraction than earlytype galaxies at a given stellar mass. While Calette et al (2018) divided their sample into stellar mass bins, they did not split the sample by star formation rates (SFR). Because late-type galaxies tend to have higher SFRs than early-type galaxies in general and are expected to have a large gas reservoir, the morphological dependence reported in Calette et al (2018) might be produced by the different SFR between the early-and late-type galaxy samples.…”

“…While Calette et al (2018) divided their sample into stellar mass bins, they did not split the sample by star formation rates (SFR). Because late-type galaxies tend to have higher SFRs than early-type galaxies in general and are expected to have a large gas reservoir, the morphological dependence reported in Calette et al (2018) might be produced by the different SFR between the early-and late-type galaxy samples. Moreover, some outliers do not follow the general trend between the average star formation activity and gas content or galaxy morphology, such as the H I-excess systems (early-type galaxies with large H I reservoirs and negligible star-formation; Geréb et al 2016Geréb et al , 2018 or passive spirals (e.g., George 2017; Guo et al 2020 but see also Cortese 2012).…”

“…However, we should note that Cook et al (2019) selected star-forming galaxies by simply excluding the quiescent galaxy population based on the distance from the star formation main sequence (Catinella et al 2018;Janowiecki et al 2019). Also, their morphological classification is different from that of Calette et al (2018). In these ways, the sample definition and/or the morphological classifications vary from study to study, making it difficult to interpret the impact of galaxy morphologies on their H I gas content.…”