The NEWFIRM Medium-band Survey: Photometric Catalogs, Redshifts and the Bimodal Color Distribution of Galaxies out to z~3

TL;DR

This paper introduces the NEWFIRM Medium-Band Survey, providing deep NIR photometry, accurate redshifts, and evidence of a bimodal galaxy color distribution up to redshift 3, enhancing understanding of galaxy evolution.

Contribution

It presents a comprehensive NIR medium-band survey with improved photometric redshifts and demonstrates the persistence of galaxy bimodality to higher redshifts than previously known.

Findings

Photometric redshifts with 1-2% accuracy up to z~3.

Bimodal color distribution of galaxies persists to z~3.

Enhanced spectral resolution reduces redshift uncertainties.

Abstract

We present deep near-infrared (NIR) medium-bandwidth photometry over the wavelength range 1-1.8 microns in the All-wavelength Extended Groth strip International Survey (AEGIS) and Cosmic Evolution Survey (COSMOS) fields. The observations were carried out as part of the NEWFIRM Medium-Band Survey (NMBS), an NOAO survey program on the Mayall 4m telescope on Kitt Peak using the NOAO Extremely Wide-Field Infrared Imager (NEWFIRM). In this paper, we describe the full details of the observations, data reduction and photometry for the survey. We also present a public K-selected photometric catalog, along with accurate photometric redshifts. The redshifts are computed with 37 (20) filters in the COSMOS (AEGIS) fields, combining the NIR medium-bandwidth data with existing ultraviolet (UV; Galaxy Evolution Explorer), visible and NIR (Canada-France-Hawaii Telescope and Subaru) and mid-IR (Spitzer/IRAC) imaging. We find excellent agreement with publicly available spectroscopic redshifts, with sigma_z/(1+z)~1-2% for ~4000 galaxies at z=0-3. The NMBS catalogs contain ~13,000 galaxies at z>1.5 with accurate photometric redshifts and rest-frame colors. Due to the increased spectral resolution obtained with the five NIR medium-band filters, the median 68% confidence intervals of the photometric redshifts of both quiescent and star-forming galaxies are a factor of ~2 times smaller when comparing catalogs with medium-band NIR photometry to NIR broadband photometry. We show evidence for a clear bimodal color distribution between quiescent and star-forming galaxies that persists to z~3, a higher redshift than has been probed so far.