La Freccia Rossa: An IR-dark cloud hosting the Milky Way intermediate-mass black hole candidate

Abstract

The dynamics of the high-velocity compact molecular cloud CO-0.40-0.22 have been interpreted as evidence for a $\sim 10^5{M}_{\odot }$ black hole within 60 pc of Sgr A*. Recently, Oka et al. have identified a compact millimetre-continuum source, CO-0.40-0.22*, with this candidate black hole. Here we present a collation of radio and infrared data at this location. ATCA constraints on the radio spectrum, and the detection of a mid-infrared counterpart, are in tension with an Sgr A*-like model for CO-0.40-0.22* despite the comparable bolometric to Eddington luminosity ratios under the IMBH interpretation. A protostellar-disk scenario is, however, tenable. CO-0.40-0.22(*) is associated with an arrowhead-shaped infrared-dark cloud (which we call the Freccia Rossa). Radio-continuum observations reveal a candidate HII region associated with the system. If the $V_{\mathrm{LSR}}\approx 70$ km s${}^{-1}$ systemic velocity of CO-0.40-0.22 is common to the entire Freccia Rossa system, we hypothesise that it is the remnant of a high-velocity cloud that has plunged into the Milky Way from the Galactic halo.

6 pages, 3 figures, submitted to MNRAS Letters

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• Hunting for wandering massive black holes
• An energetic high-velocity compact cloud: CO$-$0.31+0.11
• Weighing the IMBH candidate CO-0.40-0.22* in the Galactic Centre
• Central X-ray point-sources found to be abundant in low-mass, late-type galaxies predicted to contain an intermediate-mass black hole
• An Unusual Transient in the Extremely Metal-Poor Galaxy SDSS J094332.35+332657.6 (Leoncino Dwarf)