skip to main content

Title: KECK OBSERVATIONS OF THE GALACTIC CENTER SOURCE G2: GAS CLOUD OR STAR?

We present new observations and analysis of G2-the intriguing red emission-line object which is quickly approaching the Galaxy's central black hole. The observations were obtained with the laser guide star adaptive optics systems on the W. M. Keck I and II telescopes (2006-2012) and include spectroscopy (R {approx} 3600) centered on the hydrogen Br{gamma} line as well as K' (2.1 {mu}m) and L' (3.8 {mu}m) imaging. Analysis of these observations shows the Br{gamma} line emission has a positional offset from the L' continuum. This offset is likely due to background source confusion at L'. We therefore present the first orbital solution derived from Br{gamma} line astrometry, which, when coupled with radial velocity measurements, results in a later time of closest approach (2014.21 {+-} 0.14), closer periastron (130 AU, 1600 R{sub s}), and higher eccentricity (0.9814 {+-} 0.0060) compared to a solution using L' astrometry. It is shown that G2 has no K' counterpart down to K' {approx} 20 mag. G2's L' continuum and the Br{gamma} line emission appears unresolved in almost all epochs, which implies that the bulk of the emission resides in a compact region. The observations altogether suggest that while G2 has a gaseous component that is tidallymore » interacting with the central black hole, there is likely a central star providing the self-gravity necessary to sustain the compact nature of this object.« less
Authors:
; ; ; ; ; ; ;  [1] ;  [2] ;  [3] ;  [4]
  1. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)
  2. Dunlap Institute for Astronomy and Astrophysics, University of Toronto, Toronto, Ontario, M5S 3H4 (Canada)
  3. Institute for Astronomy, University of Hawaii, Hilo, HI 96720 (United States)
  4. Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22136605
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 773; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; BLACK HOLES; EMISSION; GALAXIES; GRAVITATION; HYDROGEN; RADIAL VELOCITY; SPECTROSCOPY; STARS; TELESCOPES