The Population of Galaxies that Contribute to The HI Mass Function. (arXiv:1909.03077v2 [astro-ph.GA] UPDATED)

The Population of Galaxies that Contribute to The HI Mass Function. (arXiv:1909.03077v2 [astro-ph.GA] UPDATED)
<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 luminous red population dominates the total HIMF for
$log_{10}(M_{text{HI}}h^2_{70}/M_{odot}) geq 10.4$. The full red population
— luminous 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 luminous 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 luminous 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 luminous red
population is small compared to that of the luminous 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 luminous red population dominates the total HIMF for
$log_{10}(M_{text{HI}}h^2_{70}/M_{odot}) geq 10.4$. The full red population
— luminous 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 luminous 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 luminous 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 luminous red
population is small compared to that of the luminous blue population.

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