A Pilot Survey of HI in Field Galaxies at Redshift z~0.2

TL;DR

This pilot survey using Arecibo successfully detected HI emission from massive, isolated disk galaxies at redshift around 0.2, demonstrating the telescope's capability to study galaxy gas content at significant look-back times.

Contribution

First successful detection of HI in field galaxies at z~0.2 using Arecibo, extending the observational reach of HI studies to higher redshifts.

Findings

Detected HI in 10 galaxies at z=0.17-0.25

Galaxies have high HI mass fractions (~10-30%)

Demonstrated Arecibo's effectiveness for high-redshift HI observations

Abstract

We present the first results of a targeted survey carried out with the 305 m Arecibo telescope to detect HI-line emission from galaxies at redshift z>0.16. The targets, selected from the Sloan Digital Sky Survey database, are non-interacting disk galaxies in relatively isolated fields. We present here the HI spectra and derived HI parameters for ten objects detected in this pilot program. All are massive disk galaxies in the redshift interval 0.17-0.25 (i.e. 2-3 Gyr look-back time), with HI masses M_HI=3-8 x 10^10 Msun and high gas mass fractions (HI - to - stellar mass ratios ~10-30%). Our results demonstrate the efficacy of exploiting Arecibo's large collecting area to measure the HI mass and rotational velocity of galaxies above redshift z=0.2. In particular, this sample includes the highest redshift detections of HI emission from individual galaxies made to date. Extension of this pilot program will allow us to study the HI properties of field galaxies at cosmological distances, thus complementing ongoing radio synthesis observations of cluster samples at z~0.2.