Kinematical Clues to the Origin of the Virgo Stellar Stream

Details Kinematical Clues to the Origin of the Virgo Stellar Stream Kinematical Clues to the Origin of the Virgo Stellar Stream

Jan 2012

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21925216y&link_type=abstract

American Astronomical Society, AAS Meeting #219, #252.16

Astronomy and Astrophysics

Astronomy

Scientific paper

Milky Way stellar substructure has been detected in the Virgo constellation (the so-called Virgo Stellar Stream, or VSS; and the possibly associated Virgo Overdensity) using a variety of different stellar tracers over a large (perhaps 100-1000 square degrees) area of sky, but the nature of the overdensities has yet to be determined. Fortuitously, one of Kapteyn's Selected Areas (SAs) making up our deep proper motion survey (Casetti-Dinescu et al. 2006) intersects this structure. Our data in this field, denoted SA 103, span 40x40 arcminutes centered at (RA, Dec) = (178.8, -0.6). We supplemented our proper motions with multifiber spectroscopy. VSS members are selected via kinematics (radial velocities and proper motions), as well as position on the CMD. Theoretical isochrones were fitted to the identified members in the CMD to obtain distance. We find 14 candidates with properties consistent with membership in the VSS (based in part on comparison to previous detections), and use the mean 3-D kinematics of these members to derive an orbit for the VSS debris. We show that Virgo debris is near the pericenter of a high-eccentricity, plunging orbit similar to that found by Casetti-Dinescu et al. (2009) based on one VSS RR-Lyrae star. We explore possible progenitors for the VSS by integrating an orbit with the measured kinematics and comparing this to known Milky Way satellites and stellar substructures. At least three structures (a dwarf galaxy, globular cluster, and at least one diffuse stellar overdensity) are identified whose properties suggest that they may be related to the VSS. An n-body simulation of a Sagittarius-sized dwarf galaxy on our derived orbit produces a remnant with similar properties to the extant VSS detections, supporting the idea that the VSS is the remains of a tidally disrupted dwarf galaxy. Supported by NSF grants AST 09-37523, AST 11-15146, AST 10-09670.

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