A Dynamically Distinct Stellar Population in the Leading Arm of the Sagittarius Stream

Abstract

We present a chemical and dynamical analysis of the leading arm (LA) and trailing arm (TA) of the Sagittarius (Sgr) stream, as well as for the Sgr dwarf galaxy core (SC), using red giant branch, main-sequence, and RR Lyrae stars from large spectroscopic survey data. The different chemical properties among the LA, TA, and SC generally agree with recent studies and can be understood by a radial metallicity gradient established in the progenitor of the Sgr dwarf, followed by preferential stellar stripping from the outer part of the Sgr progenitor. One striking finding is a relatively larger fraction of low-eccentricity stars ( e 0.6) that the TA stars farther away from the SC are also affected by disturbances from the LMC.

Keywords

• Milky Way dynamics
• Sagittarius dwarf spheroidal galaxy
• Stellar streams
• Dwarf galaxies
• Stellar dynamics
• Stellar abundances