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arXiv · 1508.07373

The Most Massive Ultra-Compact Dwarf Galaxy in the Virgo Cluster

Chengze Liu·Eric W. Peng·Elisa Toloba·J. Christopher Mihos·Laura Ferrarese·Karla Alamo-Martínez·Hong-Xin Zhang·Patrick Côté·Jean-Charles Cuillandre·Emily C. Cunningham·Puragra Guhathakurta·Stephen Gwyn·Gregory Herczeg·Sungsoon Lim·Thomas H. Puzia·Joel Roediger·Rubén Sánchez-Janssen·Jun Yin
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Abstract

We report on the properties of the most massive ultra-compact dwarf galaxy (UCD) in the nearby Virgo Cluster of galaxies using imaging from the Next Generation Virgo Cluster Survey (NGVS) and spectroscopy from Keck/DEIMOS. This object (M59-UCD3) appears to be associated with the massive Virgo galaxy M59 (NGC 4621), has an integrated velocity dispersion of 78 km/s, a dynamical mass of $3.7\times10^8 M_\odot$, and an effective radius ($R_e$) of 25 pc. With an effective surface mass density of $9.4\times10^{10} M_\odot/kpc^2$, it is the densest galaxy in the local Universe discovered to date, surpassing the density of the luminous Virgo UCD, M60-UCD1. M59-UCD3 has a total luminosity of $M_{g'}=-14.2$ mag, and a spectral energy distribution consistent with an old (14 Gyr) stellar population with [Fe/H]=0.0 and [$α$/Fe]=+0.2. We also examine deep imaging around M59 and find a broad low surface brightness stream pointing towards M59-UCD3, which may represent a tidal remnant of the UCD progenitor. This UCD, along with similar objects like M60-UCD1 and M59cO, likely represents an extreme population of tidally stripped galaxies more akin to larger and more massive compact early-type galaxies than to nuclear star clusters in present-day dwarf galaxies.

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Chengze Liu, Eric W. Peng, Elisa Toloba, J. Christopher Mihos, Laura Ferrarese, Karla Alamo-Martínez, Hong-Xin Zhang, Patrick Côté, Jean-Charles Cuillandre, Emily C. Cunningham, Puragra Guhathakurta, Stephen Gwyn, Gregory Herczeg, Sungsoon Lim, Thomas H. Puzia, Joel Roediger, Rubén Sánchez-Janssen, Jun Yin. 2015-08-28. The Most Massive Ultra-Compact Dwarf Galaxy in the Virgo Cluster. https://doi.org/10.1088/2041-8205%2F812%2F1%2Fl2

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