J/A+A/511/A18 NIR observations of stars near SgrA* (Schoedel+, 2010)
Peering through the veil: near-infrared photometry and extinction for the
Galactic nuclear star cluster.
Accurate near infrared H, Ks, and L' photometry and the near-infrared
extinction-law toward the central parsec of the Galaxy.
Schoedel R., Najarro F., Muzic K., Eckart A.
<Astron. Astrophys. 511, A18 (2010)>
=2010A&A...511A..18S 2010A&A...511A..18S
ADC_Keywords: Stars, nearby ; Stars, early-type; Infrared sources;
Photometry, infrared
Keywords: Galaxy: nucleus - dust, extinction - Galaxy: center -
stars: horizontal-branch
Abstract:
The nuclear star cluster of the Galaxy is an important template for
understanding its extragalactic counterparts, which can currently not
be resolved into individual stars. Important drawbacks of observations
of the Galactic center are, however, the presence of strong and
spatially highly variable interstellar extinction and extreme crowding
of the sources, which makes the use of adaptive optics techniques
necessary. Both points pose serious obstacles to precise photometry
that is needed for analyzing the stellar population.
The aims of this work are to provide accurate photometry in multiple
near-infrared broadband filters, to determine the power-law index of
the extinction-law toward the central parsec of the Galaxy, to provide
measurements of the absolute extinction toward the Galactic center,
and finally to measure the spatial variability of extinction on
arcsecond scales.
Description:
The table tablea2.dat contains photometry in the H, Ks, and L'-bands
for stars within a projected distance of approximately 1pc from the
Galaxy's central black hole, Sagittarius A*. The data are based on
observations with the NACO adaptive optics assisted near-infrared
camera at the ESO VLT. Approximate astrometry for the stars is given
relative to Sagittarius A*, as derived from the approximate camera
pixel scale used, 0.027"/pixel, and assuming a 0 degree rotator angle.
We estimate that absolute uncertainties in the astrometric precision
can be as large as 0.1". The J2000.0 position of Sagittarius A* is
(17:45:40.0409, -29:00:28.118) according to Reid & Brunthaler
(2004ApJ...616..872R 2004ApJ...616..872R). The uncertainties of the H, Ks , and
L'-magnitudes in the table are statistical uncertainties. The one
sigma uncertainties of the zero points are not included. They are
0.06mag for the H and Ks filters and 0.15mag for the L'-filter. A
value of 0.00 in either of the H, Ks, or L'-fields means that the star
was not detected with the corresponding filter.
The FITS file AKs_fg6.fit is the extinction map for the Ks-band that
is shown in the upper left panel of Fig. 6 of the original paper. The
value of each pixel in the FITS image corresponds to the extinction in
the Ks-band in magnitudes at the corresponding position. The effective
wavelength is 2.168 micrometer. North is up and east is to the left.
The pixel scale is 0.027" and Sagittarius A* is located at pixel
position (808,611). These values will provide astrometry with an
accuracy of roughly 0.1", a factor about 10 better than the actual
resolution of the extinction map, which is about 1".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea2.dat 57 7738 Stellar positions and magnitudes
AKs_fg6.fits 2880 3557 Ks-band extinction map for the Galactic center
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See also:
J/A+A/433/117 : L- + M-band imaging of the Galactic Center (Viehmann+, 2005)
J/ApJ/642/861 : N-band imaging of the Galactic Center (Viehmann+, 2006)
J/A+A/499/483 : Sources in galactic center NIR observations (Buchholz+, 2009)
J/A+A/502/91 : Proper motions of stars near SgrA* (Schoedel+, 2009)
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq Sequential number
6- 10 F5.2 arcsec Sep Separation from Sagittarius A*
12- 17 F6.2 arcsec oRA Offset from Sagittarius A* in right ascension (1)
19- 24 F6.2 arcsec oDE Offset from Sagittarius A* in declination (1)
26- 30 F5.2 mag Hmag Magnitude in NACO H filter
32- 35 F4.2 mag e_Hmag rms uncertainty in Hmag
37- 41 F5.2 mag Ksmag Magnitude in NACO Ks filter
43- 46 F4.2 mag e_Ksmag rms uncertainty in Ksmag
48- 52 F5.2 mag L'mag Magnitude in NACO L' filter
54- 57 F4.2 mag e_L'mag rms uncertainty in L'mag
--------------------------------------------------------------------------------
Note (1): Offset from Sgr A*, RA=17:45:40.0409, DE=-29:00:28.118, J2000
--------------------------------------------------------------------------------
Acknowledgements:
Rainer Schoedel, rainer(at)iaa.es
History:
* 25-Feb-2010: on-line version
* 26-Mar-2015: fits file corrected
(End) Rainer Schoedel [IAA-CSIC, Spain], Patricia Vannier [CDS] 10-Dec-2009