Abstract
Abstract The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. The detection of the molecular 2 pc circumnuclear disk (CND) immediately around the Milky Way SMBH, SgrA*, provides a unique opportunity to study SMBH accretion at subparsec scales. Our new wide-field CS(J = 2 − 1) map toward the Galactic center (GC) reveals multiple dense molecular streamers that originated from the ambient clouds 20 pc further out, and that are connected to the central 2 pc of the CND. These dense gas streamers appear to carry gas directly toward the nuclear region and might be captured by the central potential. Our phase-plot analysis indicates that these streamers show a signature of rotation and inward radial motion with progressively higher velocities as the gas approaches the CND and finally ends up corotating with the CND. Our results might suggest a possible mechanism of gas feeding the CND from 20 pc around 2 pc in the GC. In this paper, we discuss the morphology and the kinematics of these streamers. As the nearest observable Galactic nucleus, this feeding process may have implications for understanding the processes in extragalactic nuclei.
Highlights
The origin of the 2-pc circumnuclear disk (CND) in the Galactic center (GC) has remained unclear in spite of intensive study for the past decades (e.g., Guesten et al 1987; Jackson et al 1993; Amo-Baladron et al 2011; Harris et al 1985; Mezger et al 1989; Etxaluze et al 2011; Lau et al 2013; Wright et al 2001; Montero-Castano et al 2009; Martın et al 2012; Herrnstein & Ho 2002, 2005a; Christopher et al 2005; Requena-Torres et al 2012; Mills et al 2013)
We alternatively propose that the radial motion of the eastern/western streamers may be attributed to the infall toward the CND
We find that the replenishment of the gas accreting onto the CND is on going, we estimate whether this accretion rate is significant to sustain the life time of the CND
Summary
The origin of the 2-pc CND in the GC has remained unclear in spite of intensive study for the past decades (e.g., Guesten et al 1987; Jackson et al 1993; Amo-Baladron et al 2011; Harris et al 1985; Mezger et al 1989; Etxaluze et al 2011; Lau et al 2013; Wright et al 2001; Montero-Castano et al 2009; Martın et al 2012; Herrnstein & Ho 2002, 2005a; Christopher et al 2005; Requena-Torres et al 2012; Mills et al 2013). We call this linear feature “extended western streamer (extW-streamer)” in this paper. The CR is proposed to be elevated disk emission connecting to the extraplanar feature called the polar arc (PA) This CR appears to have no physical association with the CND nor the streamers. The NRO 45-m CS(2-1) data can be found on the following link. https://drive.google.com/open?id=0B87dHJ1XIqjwSVpEdXFKVm01cVU
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