BUDHIES I: characterizing the environments in and around two clusters at z~0.2

TL;DR

This study combines optical spectroscopy and HI detection to analyze the environments of galaxies in and around two clusters at z~0.2, revealing their velocity dispersions and substructures.

Contribution

It provides the first detailed environmental characterization of HI-rich galaxies in these clusters using combined radio and optical data.

Findings

Detected HI in over 150 galaxies in and around two clusters.

Measured redshifts and EW[OII] for approximately 600 galaxies.

Analyzed cluster velocity dispersions and substructures.

Abstract

We present the optical spectroscopy for the Blind Ultra Deep HI Environmental Survey (BUDHIES). With the Westerbork Synthesis Radio Telescope, BUDHIES has detected HI in over 150 galaxies in and around two Abell clusters at z~0.2. With the aim of characterizing the environments of the HI-detected galaxies, we obtained multi-fiber spectroscopy with the William Herschel Telescope. In this paper, we describe the spectroscopic observations, report redshifts and EW[OII] measurements for ~600 galaxies, and perform an environmental analysis. In particular, we present cluster velocity dispersion measurements for 5 clusters and groups in the BUDHIES volume, as well as a detailed substructure analysis.