The HI Mass Function of Star-forming Galaxies at $zapprox1$
Aditya Chowdhury, Nissim Kanekar, Jayaram N. Chengalur
arXiv:2404.06546v1 Announce Type: new
Abstract: We present the first estimate of the HI mass function (HIMF) of star-forming galaxies at $zapprox1$, obtained by combining our measurement of the scaling relation between HI mass ($M_{HI}$) and B-band luminosity ($M_B$) of star-forming galaxies with literature estimates of the B-band luminosity function at $zapprox1$. We determined the $M_{HI}-M_B$ relation by using the GMRT-CATz1 survey of the DEEP2 fields to measure the average HI mass of blue galaxies at $z=0.74-1.45$ in three separate $M_B$ subsamples. This was done by separately stacking the HI 21 cm emission signals of the galaxies in each subsample to detect, at (3.5-4.4)$sigma$ significance, the average HI 21 cm emission of each subsample. We find that the $M_{HI}-M_B$ relation at $zapprox1$ is consistent with that at $zapprox0$. We combine our estimate of the $M_{HI}-M_B$ relation at $zapprox1$ with the B-band luminosity function at $zapprox1$ to determine the HIMF at $zapprox1$. We find that the number density of galaxies with $M_{HI}>10^{10} M_odot$ (higher than the knee of the local HIMF) at $zapprox1$ is a factor of $approx4-5$ higher than that at $zapprox0$, for a wide range of assumed scatters in the $M_{HI}-M_B$ relation. We rule out the hypothesis that the number density of galaxies with $M_{HI}>10^{10} M_odot$ remains unchanged between $z approx 1$ and $zapprox0$ at $gtrsim99.7$% confidence. This is the first statistically significant evidence for evolution in the HIMF of galaxies from the epoch of cosmic noon.arXiv:2404.06546v1 Announce Type: new
Abstract: We present the first estimate of the HI mass function (HIMF) of star-forming galaxies at $zapprox1$, obtained by combining our measurement of the scaling relation between HI mass ($M_{HI}$) and B-band luminosity ($M_B$) of star-forming galaxies with literature estimates of the B-band luminosity function at $zapprox1$. We determined the $M_{HI}-M_B$ relation by using the GMRT-CATz1 survey of the DEEP2 fields to measure the average HI mass of blue galaxies at $z=0.74-1.45$ in three separate $M_B$ subsamples. This was done by separately stacking the HI 21 cm emission signals of the galaxies in each subsample to detect, at (3.5-4.4)$sigma$ significance, the average HI 21 cm emission of each subsample. We find that the $M_{HI}-M_B$ relation at $zapprox1$ is consistent with that at $zapprox0$. We combine our estimate of the $M_{HI}-M_B$ relation at $zapprox1$ with the B-band luminosity function at $zapprox1$ to determine the HIMF at $zapprox1$. We find that the number density of galaxies with $M_{HI}>10^{10} M_odot$ (higher than the knee of the local HIMF) at $zapprox1$ is a factor of $approx4-5$ higher than that at $zapprox0$, for a wide range of assumed scatters in the $M_{HI}-M_B$ relation. We rule out the hypothesis that the number density of galaxies with $M_{HI}>10^{10} M_odot$ remains unchanged between $z approx 1$ and $zapprox0$ at $gtrsim99.7$% confidence. This is the first statistically significant evidence for evolution in the HIMF of galaxies from the epoch of cosmic noon.