An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS), I. Overview

TL;DR

DUSTiNGS is a Spitzer survey of 50 nearby dwarf galaxies aiming to identify dust-producing evolved stars across a wide metallicity range, providing valuable statistical insights into stellar evolution and dust production in low-metallicity environments.

Contribution

This paper presents the design, data, and preliminary results of the DUSTiNGS survey, a comprehensive infrared study of dust-producing stars in nearby dwarf galaxies, highlighting dust formation at low metallicity.

Findings

Detection of dust-producing AGB stars in 8 galaxies with metallicities as low as [Fe/H] = -1.9.

Survey achieves >75% completeness at the tip of the Red Giant Branch.

Evidence that dust production occurs even in low-metallicity dwarf galaxies.

Abstract

Nearby resolved dwarf galaxies provide excellent opportunities for studying the dust-producing late stages of stellar evolution over a wide range of metallicity (-2.7 < [Fe/H] < -1.0). Here, we describe DUSTiNGS (DUST in Nearby Galaxies with Spitzer): a 3.6 and 4.5 micron post-cryogen Spitzer Space Telescope imaging survey of 50 dwarf galaxies within 1.5 Mpc that is designed to identify dust-producing Asymptotic Giant Branch (AGB) stars and massive stars. The survey includes 37 dwarf spheroidal, 8 dwarf irregular, and 5 transition-type galaxies. This near-complete sample allows for the building of statistics on these rare phases of stellar evolution over the full metallicity range. The photometry is >75% complete at the tip of the Red Giant Branch for all targeted galaxies, with the exception of the crowded inner regions of IC 10, NGC 185, and NGC 147. This photometric depth ensures that the majority of the dust-producing stars, including the thermally-pulsing AGB stars, are detected in each galaxy. The images map each galaxy to at least twice the half-light radius to ensure that the entire evolved star population is included and to facilitate the statistical subtraction of background and foreground contamination, which is severe at these wavelengths. In this overview, we describe the survey, the data products, and preliminary results. We show evidence for the presence of dust-producing AGB stars in 8 of the targeted galaxies, with metallicities as low as [Fe/H] = -1.9, suggesting that dust production occurs even at low metallicity.