Oral Presentation

The Second Galactic Center Black Hole?; Possible Detection of Accreting Ionized Gas onto the IRS13E

Author(s): Masato Tsuboi, Yoshimi Kitamura (ISAS/JAXA), Takahiro Tsutsumi (NRAO), Makoto Miyoshi (NAOJ), Kenta Uehara (the University of Tokyo), Ryosuke Miyawaki (J.F. Oberlin University), Atsushi Miyazaki (Japan Space Forum)

Presenter: Masato Tsuboi (Institute of Space and Astronautical Science, JAXA)

We found an ionized gas with a very wide velocity width (wider than 500 km/s) toward the Galactic Center IRS13E complex with ALMA. The IRS 13E complex is a very intriguing IR object identified within 0.2 pc from Sgr A*. Although the complex should be disrupted by the strong tidal force of Sgr A*, the main member stars seem to be physically bound. Then one of the possible speculations is that a dark mass, like an intermediate mass black hole (IMBH) in the complex prevents its disruption. We analyzed the DDT observation of the Galactic Center with ALMA and obtained the channel maps with very high resolution (0.4”x0.3”) and very high sensitivity (0.8 mJy/beam) in Hydrogen recombination line, H30a. The ionized gas associated with the IRS 13E is very compact (smaller than 0.4”). The enclosed mass is estimated to be 10^4-5 Mo from the compactness and the wide velocity width. This mass is enough to bound the main member stars. However, the mass apparently conflicts with the upper limit mass of the IMBH around Sgr A* which has been derived by the long-term VLBA astrometry.