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

Abstract

The gas cloud G2 that falls toward Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is assumed 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 a possible transient asymmetric structure -such as jets or winds from hot accretion flows -around Sgr A* that might be caused by accretion of material from G2. The interferometric closure phases remained zero within errors during the observation time. We therefore 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 and ≈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 thought to convert magnetic into kinetic energy. Because probably less than 0.2 Jy of the flux from Sgr A* can be attributed to accretion from G2, the effective accretion rate is ηṀ 1.5 × 10 9 kg s −1 ≈ 7.7 × 10 −9 M ⊕ yr −1 for material from G2. Exploiting the relation of kinetic jet power to accretion power of radio galaxies shows that the rate of accretion of matter that is finally deposited in jets is limited toṀ 10 17 kg s −1 ≈ 0.5 M ⊕ yr −1 . Accordingly, G2 appears to be mostly stable against loss of angular momentum and subsequent (partial) accretion at least on timescales 1 yr.

Millimeter VLBI observations of Sgr A* with KaVA and KVN

“…Our multi-epoch results show no significant changes in flux density and size of Sgr A* in 2013-2014. This result is consistent with the one epoch GMVA observation in October 2013 (Park et al 2015) and multi-epoch VLA, SMA, and ALMA observation during 2012-2014 .…”

Fuzzy dark matter black holes and droplets

“…Finally, while finishing this manuscript, we found a paper [93] which is relevant to our work because it shares conclusions similar to those obtained here but by a different method. More precisely, [93] showed by a numerical simulation that if we replace the central supermassive BH by an object made of darkinos, this mass of DM would not only produce the same kinematics for S-stars but can also explain the G2 anomaly [94].…”

Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales

“…If the emission from SgrA * is coming from the footpoints of a MAD-type jet, this is inconsistent with the orientations of the Li et al (2013) jet or Bartko et al (2009) clockwise disk (see extended discussion in Psaltis et al 2015a), but aligned with the preferred axis of the intrinsic emission at 7 mm (Bower et al 2014). Closure phase measurements at 86 GHz already rule out asymmetric jet structures on larger angular scales from a few hundred microarcseconds to a few milliarcseconds (Park et al 2015).…”