J/A+A/570/A2 Spectra and radial velocities of nuclear stars (Feldmeier+, 2014)
Large scale kinematics and dynamical modelling of the Milky Way nuclear star
cluster.
Feldmeier A., Neumayer N., Seth A., Schodel R., Lutzgendorf N.,
de Zeeuw P.T., Kissler-Patig M., Nishiyama S., Walcher C.J.
<Astron. Astrophys. 570, A2 (2014)>
=2014A&A...570A...2F 2014A&A...570A...2F
ADC_Keywords: Stars, nearby ; Radial velocities ; Spectra, infrared
Keywords: Galaxy: nucleus - Galaxy: kinematics and dynamics
Abstract:
Within the central 10pc of our Galaxy lies a dense cluster of stars.
This nuclear star cluster forms a distinct component of the Galaxy,
and similar nuclear star clusters are found in most nearby spiral and
elliptical galaxies. Studying the structure and kinematics of nuclear
star clusters reveals the history of mass accretion and growth of
galaxy nuclei and central massive black holes.
Because the Milky Way nuclear star cluster is at a distance of only 8
kpc, we can spatially resolve the cluster on sub-parsec scales. This
makes the Milky Way nuclear star cluster a reference object for
understanding the formation of all nuclear star clusters.
Description:
We used the near-infrared long-slit spectrograph ISAAC (VLT) in a
drift-scan to observe the central ∼9.5pcx8pc of our Galaxy, and
six fields of ∼4.6pcx0.6pc each along the Galactic plane in the
K-band. We use this data set to extract spectra from individual stars
brighter than Ks=11.5, and construct an integral-field map of the
central field. We also measure radial velocities and CO bandhead
strengths of 1,375 spectra from individual stars. The table
mw_star.dat contains the position of the stars (in RA and DEC), the
Ks- and H-band magnitudes as measured from Skrutskie et al.
2006AJ....131.1163S 2006AJ....131.1163S (2MASS catalogue, Cat. VII/233), and Nishiyama et
al. 2006ApJ...638..839N 2006ApJ...638..839N (SIRIUS catalogue), the radial velocity and
the formal velocity uncertainty measured from the CO lines, the CO
index of the spectrum, and the signal-to-noise. For stars with no or
weak CO lines, we set the radial velocity, velocity uncertainty, and
CO index to NaN (---) values. The velocity uncertainty was measured with
Monte Carlos simulations. Based on a comparison with previous studies,
we estimate the real velocity uncertainty to be at least 5km/s. Due to
the drift scan technique, the sampling was 2.22"x0.148", therefore the
single stellar spectra can be contaminated with other stars and the
velocity uncertainties are underestimated in some cases. The file
mw_star.fits contains the same information as the table mw_star.dat,
together with the extracted spectra. The file mw_cube.fits is the data
cube of the central ∼9.5pcx8pc field.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
mw_star.dat 66 1375 List of extracted spectra with measured radial
velocities and CO indices in the Milky Way
nuclear star cluster observed on 2012-07-04
list.dat 192 2 List of fits files
fits/* . 2 Individual fits files
sp/* . 1375 Spectra as ascii files, from fits/mw_star.fits
(added at CDS)
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
Byte-by-byte Description of file: mw_star.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/1375] Row number
6- 14 F9.5 deg RAdeg Right ascension (J2000)
16- 24 F9.5 deg DEdeg Declination (J2000)
26- 30 F5.2 mag Kmag K-band magnitude
32- 36 F5.2 mag Hmag H-band magnitude
38- 43 A6 --- Source Source catalog: 2Mass (II/246)
or Sirius (2006ApJ...638..839N 2006ApJ...638..839N)
45- 50 F6.1 km/s RV [-343/292]?=- Radial velocity
52- 56 F5.1 km/s e_RV [0.1/142]?=- Formal uncertainty of RV
58- 61 F4.2 mag COmag [0.01/0.52]?=- CO index (1)
63- 66 F4.1 --- S/N [7/63] signal-to-noise
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Note (1): the CO index is defined as COmag=-2.5log(Fa/Fc), where
Fa is is the mean flux at the first CO absorption line (2.2885-2.2925um)
corrected for radial velocity, and Fc is the continuum.
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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- 9 F9.5 deg RAdeg ? Right ascension of center (J2000)
10- 18 F9.5 deg DEdeg ? Declination of center (J2000)
20- 23 F4.2 arcsec/pix Scale ? Scale of the images
25- 27 I3 --- Nx [108]? Number of pixels along X-axis
28 A1 --- --- [x]
29- 30 I2 --- Ny [95]? Number of pixels along Y-axis
31 A1 --- --- [x]
32- 35 I4 --- Nz [1024]? Number of slices
37- 43 F7.1 0.1nm blambda ? Lower value of wavelength interval
(for datacube)
45- 49 I5 0.1nm Blambda ? Upper value of wavelength interval
(for datacube)
51- 57 F7.5 0.1nm dlambda ? Wavelength resolution (for datacube)
59- 63 I5 Kibyte size Size of the FITS file
65- 76 A12 --- FileName Name of the FITS file in subdirectory fits
78-192 A115 --- Title Title of the file
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 8 F8.6 um lambda [2.288/2.412] Wavelength, in µm
10- 21 E12.6 --- Flux Corresponding flux
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Acknowledgements:
Anja Feldmeier, afeldmei(at)eso.org
(End) Patricia Vannier [CDS] 15-Jul-2014