KINEMATICS AND CHEMISTRY OF STARS ALONG THE SAGITTARIUS TRAILING TIDAL TAIL AND CONSTRAINTS ON THE MILKY WAY MASS DISTRIBUTION

Journal Article · Sun Jan 01 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/744/1/25· OSTI ID:22004358

Carlin, Jeffrey L; Majewski, Steven R; Patterson, Richard J ^[1]; Casetti-Dinescu, Dana I; Girard, Terrence M ^[2]

---

1. Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)
2. Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

We present three-dimensional (3D) kinematics of Sagittarius (Sgr) trailing tidal debris in six fields located 70 Degree-Sign -130 Degree-Sign along the stream from the Sgr dwarf galaxy core. The data are from our proper-motion (PM) survey of Kapteyn's Selected Areas, in which we have measured accurate PMs to faint magnitudes in {approx}40' Multiplication-Sign 40' fields evenly spaced across the sky. The radial velocity (RV) signature of Sgr has been identified among our follow-up spectroscopic data in four of the six fields and combined with mean PMs of spectroscopically confirmed members to derive space motions of Sgr debris based on {approx}15-64 confirmed stream members per field. These kinematics are compared to predictions of the Law and Majewski model of Sgr disruption; we find reasonable agreement with model predictions in RVs and PMs along Galactic latitude. However, an upward adjustment of the local standard of rest velocity ({Theta}{sub LSR}) from its standard 220 km s{sup -1} to at least 232 {+-} 14 km s{sup -1} (and possibly as high as 264 {+-} 23 km s{sup -1}) is necessary to bring 3D model debris kinematics and our measurements into agreement. Satisfactory model fits that simultaneously reproduce known position, distance, and RV trends of the Sgr tidal streams, while significantly increasing {Theta}{sub LSR}, could only be achieved by increasing the Galactic bulge and disk mass while leaving the dark matter halo fixed to the best-fit values from Law and Majewski. We derive low-resolution spectroscopic abundances along this stretch of the Sgr stream and find a constant [Fe/H] {approx} -1.15 (with {approx}0.5 dex scatter in each field-typical for dwarf galaxy populations) among the four fields with reliable measurements. A constant metallicity suggests that debris along the {approx}60 Degree-Sign span of this study was all stripped from Sgr on the same orbital passage.

• OSTI ID: 22004358
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 744; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
MASS DISTRIBUTION
MILKY WAY
NONLUMINOUS MATTER
PROPER MOTION
RADIAL VELOCITY
STARS
THREE-DIMENSIONAL CALCULATIONS