The Population of Galaxies that Contribute to The HI Mass Function. (arXiv:1909.03077v1 [astro-ph.GA])

The Population of Galaxies that Contribute to The HI Mass Function. (arXiv:1909.03077v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Dutta_S/0/1/0/all/0/1">Saili Dutta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Khandai_N/0/1/0/all/0/1">Nishikanta Khandai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dey_B/0/1/0/all/0/1">Biprateep Dey</a>

We look at the contribution of different galaxy populations to the atomic
hydrogen (HI) mass function (HIMF) and the HI density parameter,
$Omega_{text{HI}}$, in the local Universe. Our analysis is based on a sample
of 7857 HI-selected galaxies selected from a volume common to the SDSS and
ALFALFA surveys (40$%$ catalog — $alpha.40$). We define different
populations of galaxies in the color(u-r)-magnitude($M_{text{r}}$) plane and
compute the HIMF for each of them. Additionally we compute the HIMF for dark
galaxies; these are undetected in SDSS and represent $sim 2%$ of the total
sample. We find that the bright red population dominates the total HIMF for
$log_{10}(M_{text{HI}}h^2_{70}/M_{odot}) geq 10.4$. The full red population
— bright and faint — represents about $sim 17%$ of the $Omega_{text{HI}}$
budget, while that of the dark population is $sim 3%$. The HIMF about the
knee, $log_{10}(M_{text{HI}}h^2_{70}/M_{odot}) in [8,10.4]$, is dominated
by the faint and bright blue populations, the latter dominating at larger
masses in this interval. Their total contribution to $Omega_{text{HI}}$ is
$sim 55-70%$, the variation depending on the definition of population. The
dominant populations at the low mass end,
$log_{10}(M_{text{HI}}h^2_{70}/M_{odot}) leq 8.0$ are the faint blue and
faint bluer populations, the latter’s dominance being sensitive to its
definition. The full blue (blue–bluer bright and faint) population represents
$sim 80%$ of $Omega_{text{HI}}$. A bimodal HIMF suggested by our results is
however not seen since the amplitude of the HIMF of the bright red population
is small compared to that of the bright blue population.

We look at the contribution of different galaxy populations to the atomic
hydrogen (HI) mass function (HIMF) and the HI density parameter,
$Omega_{text{HI}}$, in the local Universe. Our analysis is based on a sample
of 7857 HI-selected galaxies selected from a volume common to the SDSS and
ALFALFA surveys (40$%$ catalog — $alpha.40$). We define different
populations of galaxies in the color(u-r)-magnitude($M_{text{r}}$) plane and
compute the HIMF for each of them. Additionally we compute the HIMF for dark
galaxies; these are undetected in SDSS and represent $sim 2%$ of the total
sample. We find that the bright red population dominates the total HIMF for
$log_{10}(M_{text{HI}}h^2_{70}/M_{odot}) geq 10.4$. The full red population
— bright and faint — represents about $sim 17%$ of the $Omega_{text{HI}}$
budget, while that of the dark population is $sim 3%$. The HIMF about the
knee, $log_{10}(M_{text{HI}}h^2_{70}/M_{odot}) in [8,10.4]$, is dominated
by the faint and bright blue populations, the latter dominating at larger
masses in this interval. Their total contribution to $Omega_{text{HI}}$ is
$sim 55-70%$, the variation depending on the definition of population. The
dominant populations at the low mass end,
$log_{10}(M_{text{HI}}h^2_{70}/M_{odot}) leq 8.0$ are the faint blue and
faint bluer populations, the latter’s dominance being sensitive to its
definition. The full blue (blue–bluer bright and faint) population represents
$sim 80%$ of $Omega_{text{HI}}$. A bimodal HIMF suggested by our results is
however not seen since the amplitude of the HIMF of the bright red population
is small compared to that of the bright blue population.

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