Stellar Density Profiles of Dwarf Spheroidal Galaxies

TL;DR

This study introduces a flexible modeling approach to analyze the stellar density profiles of dwarf spheroidal galaxies, revealing mostly cored profiles with some steepened outer regions, but no clear link to other galaxy features.

Contribution

The paper develops and applies a generalized Plummer profile model to 40 dwarf spheroidals, systematically testing for non-standard profiles and providing new insights into their structure.

Findings

No evidence for cusped central density profiles in studied dSphs.

Detection of steepened outer profiles in several dSphs.

Outer density slopes do not correlate with other galaxy properties.

Abstract

We apply a flexible parametric model, a combination of generalized Plummer profiles, to infer the shapes of the stellar density profiles of the Milky Way's satellite dwarf spheroidal galaxies (dSphs). We apply this model to 40 dSphs using star counts from the Sloan Digital Sky Survey, PanStarrs-1 Survey, Dark Energy Survey, and Dark Energy Camera Legacy Survey. Using mock data, we examine systematic errors associated with modelling assumptions and identify conditions under which our model can identify `non-standard' stellar density profiles that have central cusps and/or steepened outer slopes. Applying our model to real dwarf spheroidals, we do not find evidence for centrally cusped density profiles among the fifteen Milky Way satellites for which our tests with mock data indicate there would be sufficient detectability. We do detect steepened (with respect to a standard Plummer model) outer profiles in several dSphs--Fornax, Leo I, Leo II, and Reticulum II--which may point to distinct evolutionary pathways for these objects. However, the outer slope of the stellar density profile does not yet obviously correlate with other observed galaxy properties.