J/ApJ/821/44 Star motions in the nuclear cluster of the MW (Fritz+, 2016)
The nuclear cluster of the Milky Way: total mass and luminosity.
Fritz T.K., Chatzopoulos S., Gerhard O., Gillessen S., Genzel R., Pfuhl O.,
Tacchella S., Eisenhauer F., Ott T.
<Astrophys. J., 821, 44-44 (2016)>
=2016ApJ...821...44F 2016ApJ...821...44F (SIMBAD/NED BibCode)
ADC_Keywords: Proper motions ; Radial velocities ; Milky Way ;
Photometry, infrared
Keywords: Galaxy: center; Galaxy: fundamental parameters; proper motions
Abstract:
We obtain the basic properties of the nuclear cluster of the Milky
Way. First, we investigate the structural properties by constructing a
stellar density map of the central 1000" using extinction-corrected
old star counts from VISTA, WFC3/IR, and VLT/NACO data. We describe
the data using two components. The inner, slightly flattened (axis
ratio of q=0.80±0.04) component is the nuclear cluster, while the
outer component corresponds to the stellar component of the
circumnuclear zone. For the nuclear cluster, we measure a half-light
radius of 178±51"∼7±2pc and a luminosity of MKs=-16.0±0.5.
Second, we measure detailed dynamics out to 4pc. We obtain 10351
proper motions from AO data, and 2513 radial velocities from
VLT/SINFONI data. We determine the cluster mass by means of isotropic
spherical Jeans modeling. We fix the distance to the Galactic Center
and the mass of the supermassive black hole. We model the cluster
either with a constant M/L or with a power law. For the latter case,
we obtain a slope of 1.18±0.06. We get a cluster mass within 100" of
M100"=(6.09±0.53|fixR0±0.97|R0)x106M☉ for both
modeling approaches. A model which includes the observed flattening
gives a 47% larger mass (see Chatzopoulos et al. 2015MNRAS.447..948C 2015MNRAS.447..948C).
Our results slightly favor a core over a cusp in the mass profile. By
minimizing the number of unbound stars within 8", we obtain a distance
of R0=8.53-0.15+0.21kpc when using an R0 supermassive black hole
mass relation from stellar orbits. Combining our results, we obtain
M/L=0.51±0.12M☉/L☉,Ks_, which is roughly consistent with a
Chabrier IMF.
Description:
To derive the proper motions and determine the stellar density profile
in the center (Rbox∼20"), we use adaptive optics images with a
resolution of ∼0.080". In the central parsec, we use the same NACO/VLT
images as described in Trippe et al. (2008A&A...492..419T 2008A&A...492..419T) and
Gillessen et al. (2009ApJ...692.1075G 2009ApJ...692.1075G). We add images obtained in
further epochs since then, in the 13mas/pixel scale matching the
Gillessen et al. (2009ApJ...692.1075G 2009ApJ...692.1075G) data set and in the 27mas/pixel
scale extending the Trippe et al. (2008A&A...492..419T 2008A&A...492..419T) data set.
To obtain proper motions outside the central parsec, we use adaptive
optics images covering a larger field of view. These are four epochs
of NACO/VLT images (2004 May 06, 2006 Apr 29, 2011 May 16 and 29), one
epoch of MAD/CAMCAO (2008 Aug 21) at the VLT, and one epoch of
Hokupa'a+Quirc (2000 Jul 02) Gemini North images (see Appendix A).
Most images cover the Ks band.
To obtain the structural properties of the nuclear cluster outside of
the central Rbox=20", we use two additional data sets (HST WFC3/IR
data and the public VISTA Variables in the Via Lactea Survey data
obtained with VIRCAM (Saito et al. 2012A&A...537A.107S 2012A&A...537A.107S)).
To obtain the spectra of the stars, we use data cubes obtained with
the integral field spectrometer SINFONI. We use data with combined
H+K-band (spectral resolution 1500) and K-band (spectral resolution
4000) grating.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table9.dat 72 11024 Radially sorted velocity data
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See also:
J/ApJ/809/143 : K-band spectra of stars within MW central 1pc (Do+, 2015)
J/ApJ/808/106 : NIR spectroscopic obs. in the Galactic Center (Stostad+, 2015)
J/A+A/570/A2 : Spectra and RVs of nuclear stars (Feldmeier+, 2014)
J/A+A/566/A47 : MW nuclear star cluster extinction map (Schoedel+, 2014)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/ApJ/779/L6 : 3D kinematic obs. of stars in Galactic Centre (Do+, 2013)
J/ApJ/764/154 : Stellar populations in the central 0.5pc. I. (Do+, 2013)
J/A+A/549/A57 : Young, massive star candidates in Sgr A* (Nishiyama+, 2013)
J/ApJ/737/73 : Infrared extinction toward the Galactic Centre (Fritz+, 2011)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/ApJ/703/1323 : Spectrosc. of stars in the Galaxy's nuclear cluster (Do+ 2009)
J/ApJ/699/186 : VLA observations of the Galactic center (Zhao+, 2009)
J/A+A/502/91 : Proper motions of stars near SgrA* (Schoedel+, 2009)
J/ApJ/697/1741 : Warped disks of YSOs in Galactic center (Bartko+, 2009)
J/A+A/499/483 : NIR obs. of sources in galactic center (Buchholz+, 2009)
J/ApJ/681/1254 : Radial velocities of stars in the Galactic Center (Zhu+, 2008)
J/ApJ/643/1011 : Early-type stars in the center of the Galaxy (Paumard+, 2006)
J/ApJ/597/323 : Cool stars at the Galactic Center (Blum+, 2003)
J/A+AS/92/43 : OH/IR stars close to Gal. Center in radio (Lindqvist+ 1992)
Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 arcsec Rad [0.1/89.3] Projected radius from Sgr A*
7- 12 F6.2 arcsec oRA Offset in Right Ascension from Sgr A* (1)
14- 19 F6.2 arcsec oDE Offset in Declination from Sgr A* (1)
21- 27 F7.3 mas/yr pmRA [-19.1/15.3]?=0 Proper motion along
Right Ascension
29- 33 F5.3 mas/yr e_pmRA [0.01/10]?=0 Uncertainty in pmRA
35- 41 F7.3 mas/yr pmDE [-14/23.1]?=0 Proper motion along Declination
43- 47 F5.3 mas/yr e_pmDE [0.01/10]?=0 Uncertainty in pmDE
49- 54 F6.1 km/s RVel [-815/520]?=0 Radial velocity
56- 59 F4.1 km/s e_RVel [1/87]?=0 Uncertainty in RVel
61- 65 F5.2 mag Hmag [9.8/23.8]?=0 H band magnitude
68- 72 F5.2 mag Ksmag [8.3/18.6]?=0 Ks band magnitude
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Note (1): The errors of the positions are irrelevantly small for
dynamics purposes.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Jun-2016