Re-Assembling the Sagittarius Dwarf Galaxy

TL;DR

This paper reconstructs the stellar debris of the Sagittarius dwarf galaxy to estimate its original luminosity and dark matter halo mass, revealing it was somewhat fainter than the Small Magellanic Cloud with a halo mass around 10^10 solar masses.

Contribution

It provides a detailed reassembly of Sagittarius debris to estimate the galaxy's original luminosity and dark matter halo mass using observational data and cosmological models.

Findings

Luminosity range of 9.6-13.2 x10^7 solar luminosities

Progenitor's dark matter halo mass approximately 10^10 solar masses

Debris contains about 70% of the original light

Abstract

What is the mass of the progenitor of the Sagittarius (Sgr) dwarf galaxy? Here, we reassemble the stellar debris using SDSS and 2MASS data to find the total luminosity and likely mass. We find that the luminosity is in the range 9.6-13.2 x10^7 solar luminosities or M_V ~ -15.1 - 15.5, with 70% of the light residing in the debris streams. The progenitor is somewhat fainter than the present-day Small Magellanic Cloud, and comparable in brightness to the M31 dwarf spheroidals NGC 147 and NGC 185. Using cosmologically motivated models, we estimate that the mass of Sgr's dark matter halo prior to tidal disruption was ~10^10 solar masses.