J/ApJ/830/17 Galactic Center secondary IR astrometric standards (Boehle+, 2016)
An improved distance and mass estimate for Sgr A* from a multistar orbit
analysis.
Boehle A., Ghez A.M., Schodel R., Meyer L., Yelda S., Albers S.,
Martinez G.D., Becklin E.E., Do T., Lu J.R., Matthews K., Morris M.R.,
Sitarski B., Witzel G.
<Astrophys. J., 830, 17-17 (2016)>
=2016ApJ...830...17B 2016ApJ...830...17B (SIMBAD/NED BibCode)
ADC_Keywords: Positional data ; Proper motions ; Photometry, infrared
Keywords: astrometry; Galaxy: center; Galaxy: fundamental parameters;
infrared: stars; quasars: supermassive black holes;
techniques: high angular resolution
Abstract:
We present new, more precise measurements of the mass and distance of
our Galaxy's central supermassive black hole, Sgr A*. These results
stem from a new analysis that more than doubles the time baseline for
astrometry of faint stars orbiting Sgr A*, combining 2 decades of
speckle imaging and adaptive optics data. Specifically, we improve our
analysis of the speckle images by using information about a star's
orbit from the deep adaptive optics data (2005-2013) to inform the
search for the star in the speckle years (1995-2005). When this new
analysis technique is combined with the first complete re-reduction of
Keck Galactic Center speckle images using speckle holography, we are
able to track the short-period star S0-38 (K-band magnitude=17,
orbital period=19yr) through the speckle years. We use the kinematic
measurements from speckle holography and adaptive optics to estimate
the orbits of S0-38 and S0-2 and thereby improve our constraints of
the mass (Mbh) and distance (Ro) of SgrA*:
Mbh=(4.02±0.16±0.04)x106M☉ and 7.86±0.14±0.04kpc.
The uncertainties in Mbh and Ro as determined by the combined
orbital fit of S0-2 and S0-38 are improved by a factor of 2 and 2.5,
respectively, compared to an orbital fit of S0-2 alone and a factor of
∼2.5 compared to previous results from stellar orbits. This analysis
also limits the extended dark mass within 0.01 pc to less than
0.13x106M☉ at 99.7% confidence, a factor of 3 lower compared
to prior work.
Description:
New high-resolution images of the central ∼10"x10" of our Galaxy were
taken in 2012 and 2013 using the laser guide star AO system on the
Keck II telescope. The images were taken with NIRC2 (PI: Keith
Matthews) in the K' band (2.1um).
The AO observations of this field from 2004 through 2011 have been
previously reported (Ghez+ 2005ApJ...635.1087G 2005ApJ...635.1087G, 2008ApJ...689.1044G 2008ApJ...689.1044G;
Lu+ 2009ApJ...690.1463L 2009ApJ...690.1463L; Yelda et al. 2010, J/ApJ/725/331, 2014,
J/ApJ/783/131; Yelda 2012PhDT........51Y 2012PhDT........51Y).
In addition to the central field, we also take observations designed
to measure the astrometry in the near-infrared (NIR) of a set of seven
SiO masers. Appendix A also provides the resulting absolute astrometry
for the IR secondary standards that are used to combine all the
speckle holography and AO star lists of relative positions together
into a common absolute reference frame (see table 6).
New spectroscopic observations for S0-38 were obtained using the
integral field spectrograph OSIRIS with the laser guide star AO system
on the Keck I telescope on 2013 May 11-13. The S0-38 data were taken
with the K broadband filter (Kbb; 1.965-2.382um).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 70 836 Galactic Center secondary IR astrometric standards
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See also:
J/ApJ/783/131 : Kinematic of stars in Galactic center (Yelda+, 2014)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/ApJ/764/154 : Stellar populations in the central 0.5pc. I. (Do+, 2013)
J/ApJ/725/331 : Astrometry in the Galactic Center (Yelda+, 2010)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/A+A/502/91 : Proper motions of stars near SgrA* (Schoedel+, 2009)
J/ApJ/707/L114 : The orbit of S2 star around Sgr A* (Gillessen+, 2009)
J/ApJ/659/1241 : Stellar variability in Galactic Center (Rafelski+, 2007)
Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Source name, see [GKM98] for the naming
convention (1998ApJ...509..678G 1998ApJ...509..678G)
11- 14 F4.1 mag Kpmag [7.4/15.8] Keck/NIRC2 K' band magnitude
16- 22 F7.2 yr EpIR [2006.96/2011.93] Average time of the IR
positional measurements; decimal years
24- 28 F5.2 arcsec Rad [0.3/18.3] Radius from Sgr A*
30- 36 F7.4 arcsec oRA Offset in Right Ascension from Sgr A*
38- 40 F3.1 mas e_oRA [1/2.5] Uncertainty in oRA (1)
42- 48 F7.4 arcsec oDE Offset in Declination from Sgr A*
50- 52 F3.1 mas e_oDE [1/2] Uncertainty in oDE (1)
54- 57 F4.1 mas/yr pmRA [-9.4/10] Right Ascension proper motion
59- 61 F3.1 mas/yr e_pmRA [0.1/0.8] Uncertainty in pmRA (2)
63- 66 F4.1 mas/yr pmDE [-9/9.2] Declination proper motion
68- 70 F3.1 mas/yr e_pmDE [0.1/1.1] Uncertainty in pmDE (2)
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Note (1): Positional errors include centroiding, alignment, and residual
distortion (1mas) errors, but do not include error in position of
Sgr A* (2.0mas, 1.4mas in RA and Dec, respectively).
Note (2): Velocity errors do not include error in velocity of Sgr A*
(0.13mas/yr, 0.23mas/yr in RA and Dec, respectively).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Jan-2017