J/A+A/566/A47 Milky Way nuclear star cluster extinction map (Schoedel+, 2014)
Surface brightness profile of the Milky Way's nuclear star cluster.
Schoedel R., Feldmeier A., Kunneriath D., Stolovy S., Neumauer N.
<Astron. Astrophys. 566, A47 (2014)>
=2014A&A...566A..47S 2014A&A...566A..47S
ADC_Keywords: Extinction ; Milky Way ; Infrared sources
Keywords: dust, extinction - Galaxy: center - Galaxy: nucleus -
Galaxy: structure - galaxies: nuclei - infrared: stars
Abstract:
Although the Milky Way Nuclear Star Cluster (MWNSC) was discovered
more than four decades ago, several of its key properties have not
been determined unambiguously up to now because of the strong and
spatially highly variable interstellar extinction toward the Galactic
centre. In this paper we aim at determining the shape, size, and
luminosity/mass of the MWNSC.In order to investigate the properties of
the MWNSC, we use Spitzer/IRAC images at 3.6 and 4.5µm, where
interstellar extinction is at a minimum but the overall emission is
still dominated by stars. We correct the 4.5µm image for PAH
emission with the help of the IRAC 8.0µm map and for extinction
with the help of a [3.6-4.5] colour map. Finally, we investigate the
symmetry of the nuclear cluster and fit it with Sersic, Moffat, and
King models. We present an extinction map for the central
∼300x200pc2 of the Milky Way, as well as a PAH-emission and
extinction corrected image of the stellar emission, with a resolution
of about 0.20pc. We find that the MWNSC appears in projection
intrinsically point-symmetric, that it is significantly flattened,
with its major axis aligned along the Galactic Plane, and that it is
centred on the black hole, Sagittarius A*. Its density follows the
well known approximate ρ∝r-2-law at distances of a few
parsecs from Sagittarius A*, but becomes as steep as about
ρ∝r-3 at projected radii around 5pc. We derive a half
light radius of 4.2±0.4pc, a total luminosity of
LMWNSC,4.5µm=4.1±0.4x107L☉, and a mass of
MMWNSC=2.1±0.4x107M☉. The overall properties of the MWNSC
agree well with the ones of its extragalactic counterparts, which
underlines its role as a template for these objects. Its flattening
agrees well with its previously established rotation parallel to
Galactic rotation and suggests that it has formed by accretion of
material that fell in preferentially along the Galactic Plane. Our
findings support the in situ growth scenario for nuclear clusters and
emphasize the need to increase the complexity of theoretical models
for their formation and for the interaction between their stars and
the central black hole in order to include rotation, axisymmetry, and
growth in recurrent episodes.
Description:
An extinction map at 4.5µm was created from the pixel colours
measured in rebinned images of the Galactic Center in the Spitzer IRAC
Channels 1 (3.6µm) and 2 (4.5µm). The pixel scale is 5
arcseconds per pixel. To convert colours into extinction, an intrinsic
mean stellar colour of [3.6]-[4.5]=-0.15 was assumed and subtracted
from each pixel. Subsequently, the relation
A[4.5]/E([3.6]-[4.5])=1.8±0.2 was used to convert the measured
colour excess to extinction. The unit of the presented maps is
magnitudes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 88 2 List of FITS maps
maps/* . 2 Individual FITS maps (extinction and uncertainty)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 7 F7.5 deg GLON Galactic longitude
8- 15 F8.5 deg GLAT Galactic latitude
17 I1 arcsec/pix Scale [5] Scale of the image
19- 22 I4 --- Nx [1910] Number of pixels along X-axis
23 A1 --- --- [x]
24- 27 I4 --- Ny [1408] Number of pixels along Y-axis
29- 33 I5 Kibyte size [10513] Size of FITS file
35- 44 A10 --- FileName Name of FITS file in subdirectory maps
46- 88 A43 --- Title Title of the file
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Acknowledgements:
Rainer Schoedel, rainer(at)iaa.es
(End) Rainer Schoedel [IAA-CSIC, Spain], Patricia Vannier [CDS] 28-Mar-2014