Radial Stellar Age Gradients in 42 Local Volume Dwarf Galaxies
9 affiliations
- 1Rutgers, the State University of New Jersey
- 2Eureka Scientific Inc.
- 3Space Telescope Science Institute
- 4University of Utah
- 5Indiana University
- 6Dartmouth College
- 7Raytheon
- 8University of Arizona
- 9West Virginia University
Abstract
We present radial stellar age gradients measured from star formation histories (SFHs) fit to resolved color–magnitude diagrams (CMDs) of 42 Local Volume dwarfs (6 ≲ Log M ⋆ / M ⊙ ≲ 9), spatially divided into elliptical annuli. Ages in each annulus are quantified using τ ₉₀ and τ ₅₀ , the lookback times to form 90% and 50% of the cumulative stellar mass. We find that radial age gradients are uncorrelated with environment, but gradients in τ ₉₀ are significantly correlated ( p -values ≲ 0.001) with lifetime galaxy-wide (“global”) SFHs, in agreement with two independent cosmological zoom-in simulations. For radial gradients of τ ₅₀ , simulation predictions differ. We demonstrate that given our large ( N = 42) and diverse observational sample, the strength of an observed correlation with global SFH is an actionable parameter to discriminate between different simulations with differing stellar feedback prescriptions. Overall, our results support predictions that dwarfs form inside-out like their more massive counterparts, with a combination of feedback-driven outward radial stellar migration and increasing birth radii for young stellar populations yielding present-day stellar age gradients ranging from outside-in to flat. In addition, the lack of a correlation between τ ₅₀ gradients and global SFH argues against recent star formation in radially outflowing gas. We also discuss the impact of differences between our observational sample and samples available in the latest simulations, highlighting areas for future investigation.
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- ELVES-Dwarf. II. A Systematic Search for Satellite Systems of Dwarf Galaxies in the Local Volume
BibTeX
@article{cohen2026radial,
title = {{Radial Stellar Age Gradients in 42 Local Volume Dwarf Galaxies}},
author = {Roger E. Cohen and Kristen B. W. McQuinn and O. Grace Telford and Liese van Zee and Laura Congreve Hunter and Andrew E. Dolphin and Suchindram Dasgupta},
journal = {The Astrophysical Journal},
year = {2026},
month = nov,
doi = {10.3847/1538-4357/ae93a9},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/ae93a9},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Radial Stellar Age Gradients in 42 Local Volume Dwarf Galaxies
AU - Roger E. Cohen
AU - Kristen B. W. McQuinn
AU - O. Grace Telford
AU - Liese van Zee
AU - Laura Congreve Hunter
AU - Andrew E. Dolphin
AU - Suchindram Dasgupta
PY - 2026
DA - 2026/11/02
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae93a9
UR - https://iopscience.iop.org/article/10.3847/1538-4357/ae93a9
AB - We present radial stellar age gradients measured from star formation histories (SFHs) fit to resolved color–magnitude diagrams (CMDs) of 42 Local Volume dwarfs (6 ≲ Log M ⋆ / M ⊙ ≲ 9), spatially divided into elliptical annuli. Ages in each annulus are quantified using τ ₉₀ and τ ₅₀ , the lookback times to form 90% and 50% of the cumulative stellar mass. We find that radial age gradients are uncorrelated with environment, but gradients in τ ₉₀ are significantly correlated ( p -values ≲ 0.001) with lifetime galaxy-wide (“global”) SFHs, in agreement with two independent cosmological zoom-in simulations. For radial gradients of τ ₅₀ , simulation predictions differ. We demonstrate that given our large ( N = 42) and diverse observational sample, the strength of an observed correlation with global SFH is an actionable parameter to discriminate between different simulations with differing stellar feedback prescriptions. Overall, our results support predictions that dwarfs form inside-out like their more massive counterparts, with a combination of feedback-driven outward radial stellar migration and increasing birth radii for young stellar populations yielding present-day stellar age gradients ranging from outside-in to flat. In addition, the lack of a correlation between τ ₅₀ gradients and global SFH argues against recent star formation in radially outflowing gas. We also discuss the impact of differences between our observational sample and samples available in the latest simulations, highlighting areas for future investigation.
SN - 1538-4357
SN - 0004-637X
ER -