A stellar stream around the spiral galaxy Messier 61 in Rubin First Look imaging

TL;DR

Rubin First Look imaging of Virgo reveals the first stellar stream around a non-MW spiral, extending about $50\,\mathrm{kpc}$ north of M61. The authors characterize the stream morphology and perform aperture photometry, deriving a $g$-band surface-brightness profile, colors, and a stellar mass of about $2\times 10^{8} M_\odot$ with a total luminosity of about $9\times 10^{7} L_{g,\odot}$. They infer a progenitor halo mass of roughly $8\times 10^{10} M_\odot$ and discuss its possible role in triggering M61's bar, starburst, and AGN activity, drawing analogies to the Sagittarius stream. The result demonstrates Rubin's ability to reveal extended low-surface-brightness substructures in external galaxies and foreshadows a bounty of accretion features in the upcoming LSST Deep imaging.

Abstract

We present the first stellar stream discovered with the Vera C. Rubin Observatory, around spiral galaxy M61 (NGC 4303) in Virgo First Look imaging. The stream is narrow, radially-oriented in projection, and ~50 kpc long. It has g-band surface brightness (SB) mu_g ~ 28 AB mag arcsec^-2, color g-z ~ 1.0, and stellar mass M_* ~ 2x10^8 M_Sun. This dwarf galaxy interaction may have provoked the M61 starburst, and foreshadows the bounty of accretion features expected in the ten-year Rubin Legacy Survey of Space and Time (LSST).

Figures (1)

• Figure 1: M61 in Rubin. (a): 50 kpc stream extends Northward. (b): Zoom-in on plume North-end, showing complex structure. (c): Image-stretch highlighting lower-SB features. Apparent plumes $\sim$ 20--30 kpc out on the disk-periphery ( arrows) will require confirmation with the full dataset. Image credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA.