The Origin of the Virgo Stellar Substructure
Jeffrey L. Carlin, William Yam, Dana I. Casetti-Dinescu, Benjamin A., Willett, Heidi J. Newberg, Steven R. Majewski, Terrence M. Girard

TL;DR
This study uses kinematic data and simulations to trace the origin of the Virgo stellar substructure, revealing it as tidal debris from a recently disrupted massive dwarf galaxy on an eccentric orbit.
Contribution
It provides the first detailed kinematic analysis of the Virgo substructure and links it to the tidal disruption of a specific progenitor galaxy.
Findings
Virgo substructure is at approximately 14 kpc distance.
The progenitor galaxy was on an eccentric orbit with e ~ 0.8.
The substructure likely originates from a ~10^9 solar mass dwarf galaxy.
Abstract
We present three-dimensional space velocities of stars selected to be consistent with membership in the Virgo stellar substructure. Candidates were selected from SA 103, a single 40x40 arcmin field from our proper motion (PM) survey in Kapteyn's Selected Areas (SAs), based on the PMs, SDSS photometry, and follow-up spectroscopy of 215 stars. The signature of the Virgo substructure is clear in the SDSS color-magnitude diagram (CMD) centered on SA 103, and 16 stars are identified that have high Galactocentric-frame radial velocities (V_GSR > 50 km/s) and lie near the CMD locus of Virgo. The implied distance to the Virgo substructure from the candidates is 14+/-3 kpc. We derive mean kinematics from these 16 stars, finding a radial velocity V_GSR = 153+/-22 km/s and proper motions (mu_alpha*cos(delta), mu_delta) = (-5.24, -0.91)+/-(0.43, 0.46) mas/yr. From the mean kinematics of these…
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