2015/03/16 by Michael McCourt, McCourt, Michael, Ann-Marie Madigan +1
Engineering · Physics and Astronomy · #Astrophysical Phenomena and Observations #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Mechanics and Biomechanics Studies
paper · pdf · doi:10.48550/arxiv.1503.04801
openalex publication_date 2015/03/16 · openalex created_date 2022/10/03 · openalex updated_date 2026/07/28
The massive black hole in our galactic center, Sgr A*, accretes only a small\nfraction of the gas available at its Bondi radius. The physical processes\ndetermining this accretion rate remain unknown, partly due to a lack of\nobservational constraints on the gas at distances between ~10 and ~105\nSchwarzschild radii (Rs) from the black hole. Recent infrared observations\nidentify low-mass gas clouds, G1 and G2, moving on highly eccentric, nearly\nco-planar orbits through the accretion flow around Sgr A*. Although it is not\nyet clear whether these objects contain embedded stars, their extended gaseous\nenvelopes evolve independently as gas clouds. In this paper we attempt to use\nthese gas clouds to constrain the properties of the accretion flow at ~103\nRs. Assuming that G1 and G2 follow the same trajectory, we model the small\ndifferences in their orbital parameters as evolution resulting from interaction\nwith the background flow. We find evolution consistent with the G-clouds\noriginating in the clockwise disk. Our analysis enables the first unique\ndetermination of the rotation axis of the accretion flow: we localize the\nrotation axis to within 20 degrees, finding an orientation consistent with the\nparsec-scale jet identified in x-ray observations and with the circumnuclear\ndisk, a massive torus of molecular gas ~1.5 pc from Sgr A*. This suggests that\nthe gas in the accretion flow comes predominantly from the circumnuclear disk,\nrather than the winds of stars in the young clockwise disk. This result will be\ntested by the Event Horizon Telescope within the next year. Our model also\nmakes testable predictions for the orbital evolution of G1 and G2, falsifiable\non a 5-10 year timescale.\n