The ACS Nearby Galaxy Survey Treasury

TL;DR

The ANGST survey provides a comprehensive, uniform multi-color photometric dataset of resolved stars in 69 nearby galaxies within 4 Mpc, enabling detailed studies of galaxy properties and stellar populations.

Contribution

This paper introduces the ANGST survey's sample selection, imaging data, data reduction processes, and publicly available photometric catalogs, including distance measurements from the TRGB.

Findings

Photometric catalogs contain over 34 million measurements of more than 14 million stars.

Median 50% completeness reaches magnitudes below the TRGB, enabling detailed stellar population analysis.

Uniform distance measurements derived from the TRGB across the galaxy sample.

Abstract

The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D<4 Mpc). The survey volume encompasses 69 galaxies in diverse environments, including close pairs, small & large groups, filaments, and truly isolated regions. The galaxies include a nearly complete range of morphological types spanning a factor of ~10^4 in luminosity and star formation rate. The survey data consists of images taken with ACS on HST, supplemented with archival data and new WFPC2 imaging taken after the failure of ACS. Survey images include wide field tilings covering the full radial extent of each galaxy, and single deep pointings in uncrowded regions of the most massive galaxies in the volume. The new wide field imaging in ANGST reaches median 50% completenesses of m_F475W=28.0 mag, m_F606W=27.3 mag, and m_F814W=27.3 mag, several magnitudes below the tip of the red giant branch (TRGB). The deep fields reach magnitudes sufficient to fully resolve the structure in the red clump. The resulting photometric catalogs are publicly accessible and contain over 34 million photometric measurements of >14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both the ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.