Probable detection of HI at $z\simeq 1.3$ from DEEP2 galaxies using the GMRT

TL;DR

This study reports a tentative detection of HI 21 cm emission from galaxies at redshift around 1.3 using GMRT data stacking, aligning with simulations and addressing systematics.

Contribution

First attempt to detect HI emission at z~1.3 through stacking of DEEP2 galaxy data with GMRT, demonstrating feasibility and consistency with models.

Findings

Detected HI signal at 2.5-4.7 sigma significance

Signal strength consistent with N-body simulations

Addressed impact of residual systematics

Abstract

We have observed the DEEP2 galaxies using the Giant Meterwave Radio Telescope in the frequency band of 610 MHz. There are $\simeq 400$ galaxies in the redshift range $1.24 < z < 1.36$ and within the field of view $\simeq 44'$, of the GMRT dishes. We have coadded the HI 21 cm-line emissions at the locations of these DEEP2 galaxies. We apply stacking on three different data cubes: primary beam uncorrected, primary beam corrected (uniform weighing ) and primary beam corrected (optimal weighing). We obtain a peak signal strength in the range $8\hbox{--}25 \, \rm \mu$Jy/beam for a velocity width in the range $270\hbox{--} 810 \, \rm km \, sec^{-1}$. The error on the signal, computed by bootstrapping, lies in the range $2.5\hbox{--}6 \, \rm \mu$Jy/beam, implying a 2.5--4.7-$\sigma$ detection of the signal at $z \simeq 1.3$. We compare our results with N-body simulations of the signal at $z\simeq 1$ and find reasonable agreement. We also discuss the impact of residual continuum and systematics.