Tracing Sagittarius Structure with SDSS and SEGUE Imaging and Spectroscopy

TL;DR

This study demonstrates that the Sagittarius dwarf tidal stream can be effectively traced using red K/M-giant stars selected from SDSS data, with spectroscopic confirmation and calibration to RR Lyrae distances, revealing detailed structure and new features.

Contribution

The paper introduces a method to trace the Sagittarius stream with K/M-giant stars from SDSS, calibrated to RR Lyrae distances, and identifies a new low-metallicity tidal stream.

Findings

Confirmed velocities of M giants and BHB stars match previous observations.

Estimated stellar densities along tidal tails to aid future modeling.

Detected an additional low-metallicity tidal stream near the Sgr trailing tail.

Abstract

We show that the Sagittarius dwarf tidal stream can be traced with very red K/M-giant stars selected from SDSS photometry. A subset of these stars are spectroscopically confirmed with SEGUE and SDSS spectra, and the distance scale of 2MASS and SDSS M giants is calibrated to the RR Lyrae distance scale. The absolute g band magnitude of the K/M-giant stars at the tip of the giant branch is M_g=-1.0. The line-of-sight velocities of the M giant and BHB stars that are spatially coincident with the Sgr dwarf tidal stream are consistent with those of previous authors, reinforcing the need for new models that can explain all of the Sgr tidal debris stream observations. We estimate stellar densities along the tidal tails that can be used to help constrain future models. The K/M-giant, BHB, and F-turnoff stars in the lower surface brightness tidal stream that is adjacent to the main leading Sgr dwarf tidal tail have velocities and metallicities that are similar to those of the stars in the leading tidal tail. The ratio of K/M giants to BHBs and BHBs to F-turnoff stars are also similar for both branches of the leading tidal tail. We show that there is an additional low-metallicity tidal stream near the Sgr trailing tidal tail.