Structural parameters of 11 faint Galactic globular clusters derived with 2MASS

TL;DR

This study derives structural parameters for 11 faint Galactic globular clusters using 2MASS data, addressing field-star contamination and fitting King profiles to understand their properties.

Contribution

It provides the first detailed structural analysis of these faint clusters, expanding the known parameter space of Galactic globular clusters.

Findings

Most clusters are consistent with Palomar-like low-mass, loose structures.

Field-star decontamination is crucial for accurate parameter estimation.

Derived parameters align with those of similar low-mass globular clusters.

Abstract

The determination of structural parameters of 11 faint Galactic globular clusters that, in most cases, had not been previously studied in this context. The clusters are IC1257, Lynga7, Terzan4, Terzan10, BH176, ESO452-SC11, ESO280-SC08, 2MASS-GC01, 2MASS-GC02, GLIMPSE-C01 and AL3, which are projected not far from the central region of the Galaxy. Field-star contamination is significant in the colour-magnitude diagrams. Stellar radial number-density and surface-brightness profiles are built with 2MASS photometry that, for the present clusters, corresponds basically to giant-branch stars. Field-star decontamination is essential for clusters in dense fields. With decontaminated photometry we also compute the total MV of four such globular clusters, using M4 as a template. King-like functions are fitted to the radial profiles, from which the core, half-light, half-star count and tidal radii are derived, together with the concentration parameter. Parameters derived here are compared to the equivalent ones of other Galactic globular clusters available in the literature. Structural parameters and luminosity of most of the faint globular clusters dealt with in this paper are consistent with those of Palomar-like (low-mass and loose structure) globular clusters. This work helps to improve coverage of the globular cluster parameter space.