No asymmetric outflows from Sagittarius A* during the pericenter passage of the gas cloud G2

Abstract

The gas cloud G2 falling toward Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is supposed to provide valuable information on the physics of accretion flows and the environment of the black hole. We observed Sgr A* with four European stations of the Global Millimeter Very Long Baseline Interferometry Array (GMVA) at 86 GHz on 1 October 2013 when parts of G2 had already passed the pericenter. We searched for possible transient asymmetric structure -- such as jets or winds from hot accretion flows -- around Sgr A* caused by accretion of material from G2. The interferometric closure phases remained zero within errors during the observation time. We thus conclude that Sgr A* did not show significant asymmetric (in the observer frame) outflows in late 2013. Using simulations, we constrain the size of the outflows that we could have missed to ~2.5 mas along the major axis, ~0.4 mas along the minor axis of the beam, corresponding to approximately 232 and 35 Schwarzschild radii, respectively; we thus probe spatial scales on which the jets of radio galaxies are suspected to convert magnetic into kinetic energy. As probably less than 0.2 Jy of the flux from Sgr A* can be attributed to accretion from G2, one finds an effective accretion rate eta*Mdot < 1.5*10^9 kg/s ~ 7.7*10^-9 Mearth/yr for material from G2. Exploiting the kinetic jet power--accretion power relation of radio galaxies, one finds that the rate of accretion of matter that ends up in jets is limited to Mdot < 10^17 kg/s ~ 0.5 Mearth/yr, less than about 20% of the mass of G2. Accordingly, G2 appears to be largely stable against loss of angular momentum and subsequent (partial) accretion at least on time scales < 1 year.

arXiv comment5 pages, 2 figures, 1 table; A&A Letter, in press (submitted 2015 February 26; accepted 2015 March 31)

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• Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales
• Supermassive dark-matter Q-balls in galactic centers?
• Multiwavelength study of the flaring activity of Sgr A* in 2014 February-April
• Polarized near-infrared light of the Dusty S-cluster Object (DSO/G2) at the Galactic Center
• Ordered magnetic fields around the 3C 84 central black hole
• A Deep Chandra View of A Candidate Parsec-Scale Jet from the Galactic Center Super-massive Black Hole
• Fuzzy dark matter black holes and droplets
• 3D adaptive mesh refinement simulations of the gas cloud G2 born within the disks of young stars in the Galactic Center
• Possible Connection between Dark Matter and Supermassive Black Holes
• Effect of an isotropic outflow from the Galactic centre on the bow-shock evolution along the orbit
• Charged Fuzzy Dark Matter Black Holes