J/A+A/499/483 NIR observations of sources in galactic center (Buchholz+, 2009)
Composition of the galactic center star cluster: Population analysis from
adaptive optics narrow band spectral energy distributions.
Buchholz R.M., Schoedel R., Eckart A.
<Astron. Astrophys. 499, 483 (2009)>
=2009A&A...499..483B 2009A&A...499..483B
ADC_Keywords: Stars, nearby ; Stars, early-type ; Infrared sources ;
Photometry, infrared
Keywords: Galaxy: center - stars: early-type - stars: late-type -
infrared: stars
Abstract:
We present the results of a study that uses AO assisted observations
obtained at the ESO VLT in the NIR H-band and 7 intermediate bands
covering the NIR K-band. A comparison of the resulting SEDs with a
blackbody of variable extinction then allows us to determine the
presence and strength of a CO absorption feature to distinguish
between early and late type stars. This new method is suitable for
classifying K giants (and later), as well as B2 main sequence (and
earlier) stars that are brighter than 15.5mag in the K band in the
central parsec. Extremely red objects and foreground sources can also
be reliably removed from the sample. Several results, such as the
shape of the KLF and the spatial distribution of both early and late
type stars, confirm and extend previous works. The distribution of the
early type stars can be fitted with a steep power law
(beta1"=-1.49±0.12), alternatively with a broken power law,
beta1-10"=-1.08±0.12, beta10-20"=-3.46±0.58, since we find a
drop in the early type density at ∼10". We also detect early type
candidates outside of 0.5pc in significant numbers for the first time.
The late type density function shows an inversion in the inner 6",
with a power-law slope of betaR<6"=0.17±0.09. The late type KLF
has a power-law slope of 0.30±0.01, closely resembling the KLF
obtained for the bulge of the Milky Way. The early type KLF has a much
flatter slope of (0.14±0.02). Our results agree best with an in-situ
star formation scenario.
Description:
This table provides the positions and apparent magnitudes, as well as
the extinctions and classifications as they were determined with our
new method. Please note that it is not possible with this method to
determine the exact spectral type of a source. Early and late type
candidates have been further separated into sub-groups based on the
confidence level of the classification. Quality 1 denotes the highest
confidence here, quality 3 the lowest.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
typelist.dat 37 5914 Positions, magnitudes, types and extinctions
for sources in the Galactic center
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See also:
J/A+AS/97/587 : Galactic center stars JHK photometry (Ruelas-Mayorga+ 1993)
J/AJ/106/2291 : UBV photometry toward Galactic Center (Reed 1993)
J/A+AS/139/231 : Early-type stars towards the Galactic Centre (Dufton+, 1999)
J/ApJ/470/864 : JHKL photometry of the Galactic Center (Blum+, 1996)
J/A+A/373/608 : Early-type stars towards Galactic Center. II (Dufton+, 2001)
J/MNRAS/348/1439 : OGLE II Galactic center proper motions (Sumi+, 2004)
J/ApJ/642/861 : N-band imaging of the Galactic Center (Viehmann+, 2006)
Byte-by-byte Description of file: typelist.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq Source identification number
7- 12 F6.2 arcsec xpos Relative position towards Sgr A* (1)
14- 19 F6.2 arcsec ypos Relative position towards Sgr A* (1)
21- 25 F5.2 arcsec Rp Projected distance to Sgr A*
27- 30 F4.1 --- Kmag Apparent magnitude in the K band at 2.18um
32- 34 F3.1 --- AK Extinction at 2.18um
36- 37 A2 --- Type Type (2)
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Note (1): SgrA* J2000 position: 17:45:40.0409-29:00:28.118
Note (2): Type as follows:
E1 = Early type candidate quality 1
E2 = Early type candidate quality 2
E3 = Early type candidate quality 3
L1 = Late type candidate quality 1
L2 = Late type candidate quality 2
N = Noisy SED
FG = Foreground source
R = Strongly reddened source
FT = Source too faint for classification
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Acknowledgements:
Rainer M. Buchholz, buchholz(at)ph1.uni-koeln.de
(End) R.M. Buchholz [Univ. zu Koeln, Germany], P. Vannier [CDS] 26-Mar-2009