First Results From the Large Binocular Telescope: Deep Photometry of New dSphs

TL;DR

This paper presents deep photometric observations of two newly discovered dwarf spheroidal galaxies in the Local Group using the Large Binocular Telescope, revealing their structure and star formation histories.

Contribution

It provides the first deep photometry and structural analysis of Hercules dSph and the first star formation history for Leo T dSph/dIrr, highlighting their unique properties.

Findings

Hercules is unusually elongated, possibly due to tidal distortion.

Leo T's oldest stars are relatively metal-rich (~ -1.5 [Fe/H]).

First deep photometry for Hercules and star formation history for Leo T.

Abstract

This contribution describes photometry for two Galactic dSphs obtained with the Large Binocular Telescope to a magnitude of ~25.5. Using the Large Binocular Camera, a purpose-built wide-field imager for the LBT, we have examined the structure and star formation histories of two newly-discovered Local Group members, the Hercules dSph and the Leo T dSph/dIrr system. We have constructed a structural map for the Hercules system using three-filter photometry to V ~ 25.5. This is the first deep photometry for this system, and it indicates that Hercules is unusually elongated, possibly indicating distortion due to the Galactic tidal field. We have also derived the first star formation history for the Leo T system, and find that its oldest population of stars (age ~ 13 Gyr) were relatively metal-rich, with [Fe/H] ~ -1.5.