A search for stellar tidal debris of defunct dwarf galaxies around globular clusters in the inner Galactic halo

TL;DR

This study searches for remnants of dwarf galaxies around 23 globular clusters in the Milky Way's inner halo, revealing possible debris in about half of them, including associations with known tidal streams and other stellar structures.

Contribution

It provides the first wide-field photometric survey targeting stellar debris around globular clusters in the inner Galactic halo, identifying potential remnants of progenitor dwarf galaxies.

Findings

Detected underlying stellar populations around ~50% of the clusters.

Identified possible association with the Sagittarius tidal stream in two clusters.

Found evidence of the Hercules-Aquila cloud near NGC7006.

Abstract

In the hierarchical formation scenario in which the outer halo of the Milky Way is the result of the continuous accretion of low-mass galaxies, a fraction of the Galactic globular cluster system might have originated in and been accreted with already extinct dwarf galaxies. In this context, we expect that the remnants of these progenitor galaxies might be still populating the surroundings of those accreted globulars. In this work, we present wide-field photometry of a sample of 23 globular clusters in the Galactocentric distance range 10 < Rg < 40kpc, which we use to search for remnants of their hypothetical progenitor systems. Our deep photometry reveals the presence of underlying stellar populations along the line-of-sight of about half of the globulars included in our sample. Among the detections lying in the footprint of the Sagittarius tidal stream, which we identify via the comparison with its orbit derived from numerical simulations, only Whiting1 and NGC7492 seem to be inmersed in that remnant at a compatible heliocentric distance. We also confirm the existence of a subjacent Main-Sequence feature in the surroundings of NGC1851. A tentative detection of the vast Hercules-Aquila cloud is unveiled in the background of NGC7006.