Kavli Affiliate: Robert A. Simcoe
| First 5 Authors: , , , ,
| Summary:
We report statistically significant detection of H I 21-cm emission from
intermediate-redshift ($zapprox0.2$-0.6) galaxies. By leveraging
multi-sightline galaxy survey data from the Cosmic Ultraviolet Baryon Survey
(CUBS) and deep radio observations from the MeerKAT Absorption Line Survey
(MALS), we have established a sample of $approx6000$ spectroscopically
identified galaxies in 11 distinct fields to constrain the neutral gas content
at intermediate redshifts. The galaxies sample a broad range in stellar mass —
$8lesssimlogM_rmstar/rmM_odotlesssim11$ with a median of
$langlelogM_rmstar/rmM_odotrangle_rmmedapprox10$ — and a wide
range in redshift — $0.24lesssim zlesssim0.63$ with a median of $langle
zrangle_rmmed=0.44$. Our detected emission-line signal exceeds $4,sigma$
significance in the stacked spectra of all subsamples, and the observed total H
I 21-cm line flux translates to a H I mass
$M_rmH;Iapprox10^10rmM_odot$. We find a high H I-to-stellar mass
ratio of $M_mathrmH;I/M_rmstarapprox6$ for low-mass galaxies with
$langlelogM_rmstar/rmM_odotrangle approx9.3$ ($>3.7,sigma$). For
galaxies with $langlelogM_rmstar/rmM_odotrangleapprox10.6$, we
find $M_mathrmH;I/M_rmstarapprox0.3$ ($>4.7,sigma$). Additionally,
the redshift evolution of H I mass in both low- and high-mass field galaxies,
inferred from the stacked emission-line signal, aligns well with the
expectation from the cosmic star formation history. This suggests that the
overall decline in the cosmic star formation activity across the general galaxy
population may be connected to a decreasing supply of neutral hydrogen.
Finally, our analysis has revealed significant 21-cm signals at distances
greater than 75 kpc from these intermediate-redshift galaxies, indicating a
substantial reservoir of H I gas in their extended surroundings.
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