A survey for dwarf galaxy remnants around 14 globular clusters in the outer halo

Abstract

We report the results of a systematic photometric survey of the peripheral regions of a sample of 14 globular clusters in the outer halo of the Milky Way at distances d GC > 25 kpc from the Galactic Centre. The survey is aimed at searching for the remnants of the host satellite galaxies where these clusters could originally have been formed before being accreted on to the Galactic halo. The limiting surface brightness varies within our sample, but reaches μ V, lim = 30-32 mag arcsec −2. For only two globular clusters (NGC 7492 and Whiting 1; already suggested to be associated with the Sagittarius galaxy), we detect extended stellar populations that cannot be associated with either the clusters themselves or with the surrounding Galactic field population. We show that the lack of substructures around globular clusters at these Galactocentric distances is still compatible with the predictions of cosmological simulations whereby in the outer halo the Galactic globular cluster system is built up through hierarchical accretion at early epochs.

The outer halo globular cluster system of M31 – III. Relationship to the stellar halo

“…Despite this vast array of indirect evidence, and despite the discovery of abundant substructure and numerous stellar streams criss-crossing the Milky Way's inner halo (e.g., Belokurov et al 2006;Bell et al 2008;Bernard et al 2016;Grillmair & Carlin 2016;Shipp et al 2018;Malhan et al 2018), surveys targeting the outskirts of globular clusters in search of the expected debris from their nowdefunct parent systems have proven largely fruitless (e.g., Carballo-Bello et al 2014Kuzma et al 2016Kuzma et al , 2018Myeong et al 2017;Sollima et al 2018). Indeed, apart from several Sagittarius members, there is no unambiguous example of a Milky Way globular cluster that is embedded in a coherent tidal stream from a disrupted dwarf galaxy.…”

Pal 13: its moderately extended low-density halo and its accretion history

“…The authors mention that details of background subtraction and model-fitting lead to describe Pal 13 as either containing a substantial population of extra-tidal stars, or being considerably more spatially extended than previously thought. Later, Bradford et al (2011) derived a smaller tidal radius of r t = 13.9 ±1.5 from a maximum likelihood method applied to all stars in a color-magnitude diagram (CMD) selection window, while Sollima et al (2018) using the same data set and a different analysis method adopted r lim = 11.2 . More recently, Baumgardt et al (2019) estimated r t = 4.94 by comparing the cluster density profile to a large suite of direct N-body star cluster simulations.…”

Globular Clusters in the Sagittarius stream. Revising members and candidates with Gaia DR2

“…By analogy, additional Sgr GCs may have been lost in the disruption process and may lie immersed in the Sgr stream. Indeed the association of GCs to the Sgr stream was proposed long ago (Fusi Pecci et al 1995, Irwin 1999, Palma et al 2002, and then observationally supported (Bellazzini et al 2003a, Law & Majewski 2010b, at least on a statistical basis (see also, e.g., Bellazzini et al 2003b, Carraro et al 2007, Paust, Wilson & van Belle 2015, Carballo-Bello et al 2017, Sollima et al 2018. In particular Law & Majewski (2010b) discussed in detail the case for the membership or non-membership of new and previously proposed candidates based on their correlation in 3D position and radial velocity with a state-of-the art N-Send offprint requests to: M. Bellazzini body model of the disruption of the Sgr dSph (Law & Majewski 2010a, LM10 hereafter).…”