A MegaCam Survey of Outer Halo Satellites. VII. A Single S\'ersic Index v/s Effective Radius Relation for Milky Way Outer Halo Satellites

• Main Authors: Marchi-Lasch, Sebastián, Muñoz, Ricardo R, Santana, Felipe A, Carballo-Bello, Julio A, Chanamé, Julio, Geha, Marla, Simon, Joshua D, Stetson, Peter B, Djorgovski, S. G
• Format: Journal Article
• Language: English
• Published: 23-02-2019
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.1902.08860

In this work we use structural properties of Milky Way's outer halo ($R_G >
25\,\mathrm{kpc}$) satellites (dwarf spheroidal galaxies, ultra-faint dwarf
galaxies and globular clusters) derived from deep, wide-field and homogeneous
data, to present evidence of a correlation in the S\'ersic index v/s effective
radius plane followed by a large fraction of outer halo globular clusters and
satellite dwarf galaxies. We show that this correlation can be entirely
reproduced by fitting empirical relations in the central surface brightness v/s
absolute magnitude and S\'ersic index v/s absolute magnitude parameter spaces,
and by assuming the existence of two types of outer halo globular clusters: one
of high surface brightness (HSB group), with properties similar to inner halo
clusters; and another of low surface brightness (LSB group), which share
characteristics with dwarf spheroidal and ultra-faint dwarf galaxies. Given the
similarities of LSB clusters with dwarf spheroidal and ultra-faint dwarf
galaxies, we discuss the possibility that outer halo clusters also originated
inside dark matter halos and that tidal forces from different galaxy host's
potentials are responsible for the different properties between HSB and LSB
clusters.