The structural properties and star formation history of Leo T from deep LBT photometry

TL;DR

This study uses deep photometry to analyze Leo T, revealing its complex star formation history, structural differences between stellar populations, and minimal tidal disturbance, contributing to understanding dwarf galaxy evolution.

Contribution

It provides detailed insights into the star formation history and structural properties of Leo T using deep LBT photometry, highlighting the presence of multiple stellar populations and their spatial distributions.

Findings

Young stars are more centrally concentrated than old stars.

Star formation in Leo T began over 10 Gyr ago and continued until a few hundred Myr ago.

Leo T shows little evidence of tidal distortion.

Abstract

We present deep, wide-field g and r photometry of the transition type dwarf galaxy Leo T, obtained with the blue arm of the Large Binocular Telescope. The data confirm the presence of both very young (<1 Gyr) as well as much older (>5 Gyr) stars. We study the structural properties of the old and young stellar populations by preferentially selecting either population based on their color and magnitude. The young population is significantly more concentrated than the old population, with half-light radii of 104+-8 and 148+-16 pc respectively, and their centers are slightly offset. Approximately 10% of the total stellar mass is estimated to be represented by the young stellar population. Comparison of the color-magnitude diagram (CMD) with theoretical isochrones as well as numerical CMD-fitting suggest that star formation began over 10 Gyr ago and continued in recent times until at least a few hundred Myr ago. The CMD-fitting results are indicative of two distinct star formation bursts, with a quiescent period around 3 Gyr ago, albeit at low significance. The results are consistent with no metallicity evolution and [Fe/H] ~ -1.5 over the entire age of the system. Finally, the data show little if any sign of tidal distortion of Leo T.