SHELS: Complete Redshift Surveys of Two Widely Separated Fields

TL;DR

The SHELS survey provides comprehensive redshift data for two fields, enabling detailed studies of galaxy properties, large-scale structure, and cosmic variance, with new measurements of nearly 10,000 galaxy redshifts per field.

Contribution

This work presents the first complete redshift survey of two widely separated fields, including 16,055 galaxy redshifts, and compares galaxy properties across fields to assess cosmic variance.

Findings

Mass-metallicity relation is consistent between fields.

Star-forming galaxy fraction increases with redshift similarly in both fields.

Cosmic variance accounts for differences in galaxy counts.

Abstract

The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey. Both fields are more than 94% complete to a Galactic extinction corrected R0 = 20.2. Here we describe the redshift survey of the F1 field centered at R.A. = 00h53m25.3s and Decl = 12d33m55s; like F2, the F1 field covers 4 sq deg. The redshift survey of the F1 field includes 9426 new galaxy redshifts measured with Hectospec on the MMT (published here). As a guide to future uses of the combined survey we compare the mass metallicity relation and the distributions of D4000 as a function of stellar mass and redshift for the two fields. The mass-metallicity relations differ by an insignificant 1.6 sigma. For galaxies in the stellar mass range 1.e10 to 1.e11 MSun, the increase in the star-forming fraction with redshift is remarkably similar in the two fields. The seemingly surprising 31-38% difference in the overall galaxy counts in F1 and F2 is probably consistent with the expected cosmic variance given the subtleties of the relative systematics in the two surveys. We also review the Deep Lens Survey cluster detections in the two fields: poorer photometric data for F1 precluded secure detection of the single massive cluster at z = 0.35 that we find in SHELS. Taken together the two fields include 16,055 redshifts for galaxies with R0 <= 20.2 and 20,754 redshifts for galaxies with R <= 20.6. These dense surveys in two well-separated fields provide a basis for future investigations of galaxy properties and large-scale structure.