The IMACS Cluster Building Survey. I. Description of the Survey and Analysis Methods

TL;DR

This paper details the IMACS Cluster Building Survey's methodology, including data collection, calibration of star formation rates, and criteria for identifying starburst activity in galaxies at intermediate redshifts.

Contribution

It introduces new calibration techniques for star formation rates and criteria for detecting starbursts, enhancing understanding of galaxy transformation in cluster environments.

Findings

Tight relation between star formation rate per B luminosity and extinction ratio.

New calibration methods for optical and infrared star formation indicators.

Criteria established for identifying ongoing and recent starbursts.

Abstract

The IMACS Cluster Building Survey uses the wide field spectroscopic capabilities of the IMACS spectrograph on the 6.5m Baade Telescope to survey the large-scale environment surrounding rich intermediate-redshift clusters of galaxies. The goal is to understand the processes which may be transforming star-forming field galaxies into quiescent cluster members as groups and individual galaxies fall into the cluster from the surrounding supercluster. This first paper describes the survey: the data taking and reduction methods. We provide new calibrations of star formation rates derived from optical and infrared spectroscopy and photometry. We demonstrate that there is a tight relation between the observed star formation rate per unit B luminosity, and the ratio of the extinctions of the stellar continuum and the optical emission lines. With this, we can obtain accurate extinction-corrected colors of galaxies. Using these colors as well as other spectral measures, we determine new criteria for the existence of ongoing and recent starbursts in galaxies.