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The formation and evolution of galaxies with low neutral atomic hydrogen (HI) masses, M$_{rm HI}$$<$10$^{8}h^{-2}$M$_{odot}$, are affected by host dark matter halo mass and photoionisation feedback from the UV background after the end of reionization. We study how the physical processes governing the formation of galaxies with low HI mass are imprinted on the distribution of neutral hydrogen in the Universe using the hierarchical galaxy formation model, GALFORM. We calculate the effect on the correlation function of changing the HI mass detection threshold at redshifts $0 le z le 0.5$. We parameterize the clustering as $xi(r)=(r/r_{0})^{-gamma}$ and we find that including galaxies with M$_{rm HI}$$<$10$^{8}h^{-2}$M$_{odot}$ increases the clustering amplitude $r_{0}$ and slope $gamma$ compared to samples of higher HI masses. This is due to these galaxies with low HI masses typically being hosted by haloes with masses greater than 10$^{12}{h}^{-1}$M$_{odot}$, and is in contrast to optically selected surveys for which the inclusion of faint, blue galaxies lowers the clustering amplitude. We show the HI mass function for different host dark matter halo masses and galaxy types (central or satellite) to interpret the values of $r_{0}$ and $gamma$ of the clustering of HI-selected galaxies. We also predict the contribution of low HI mass galaxies to the 21cm intensity mapping signal. We calculate that a dark matter halo mass resolution better than $sim$10$^{10}{h}^{-1}$M$_{odot}$ at redshifts higher than 0.5 is required in order to predict converged 21cm brightness temperature fluctuations.
We present initial results from the textit{COS and Gemini Mapping the Circumgalactic Medium} (mbox{CGMCGM} $equiv$ CGM$^{2}$) survey. The CGM$^{2}$ survey consists of 1689 galaxies, all with high-quality Gemini GMOS spectra, within 1 Mpc of twenty-tw
We report ALMA observations of the neutral atomic carbon transitions [CI] and multiple CO lines in a sample of $sim30$ main sequence galaxies at $zsim1$, including novel information on [CI](2-1) and CO(7-6) for 7 of such normal objects. We complement
We use observations made with the Giant Metrewave Radio Telescope (GMRT) to probe the neutral hydrogen (HI) gas content of field galaxies in the VIMOS VLT Deep Survey (VVDS) 14h field at $z approx 0.32$. Because the HI emission from individual galaxi
The spatial distribution of neutral hydrogen (HI) in the Universe contains a wealth of cosmological information. The 21 cm emission line can be used to map the HI up to very high redshift and therefore reveal us something about the evolution of the l
We have studied the small scale distribution of atomic hydrogen (HI) using 21-cm absorption spectra against multiple-component background radio continuum sources from the 21-SPONGE survey and the Millennium Arecibo Absorption Line Survey. We have fou