J/ApJ/764/154 Stellar populations in the central 0.5pc. I. (Do+, 2013)
Stellar populations in the central 0.5 pc of the galaxy.
I. A new method for constructing luminosity functions and surface-density
profiles.
Do T., Lu J.R., Ghez A.M., Morris M.R., Yelda S., Martinez G.D.,
Wright S.A., Matthews K.
<Astrophys. J., 764, 154 (2013)>
=2013ApJ...764..154D 2013ApJ...764..154D
ADC_Keywords: Milky Way ; Stars, late-type ; Stars, early-type ;
Spectra, infrared
Keywords: Galaxy: center; infrared: stars; stars: early-type;
stars: luminosity function, mass function;
techniques: high angular resolution; techniques: spectroscopic
Abstract:
We present new high angular resolution near-infrared spectroscopic
observations of the nuclear star cluster surrounding the Milky Way's
central supermassive black hole. Using the integral-field spectrograph
OSIRIS on Keck II behind the laser-guide-star adaptive optics system,
this spectroscopic survey enables us to separate early-type (young,
4-6Myr) and late-type (old, >1Gyr) stars with a completeness of 50%
down to K'=15.5mag, which corresponds to ∼10M☉ for the
early-type stars. This work increases the radial extent of reported
OSIRIS/Keck measurements by more than a factor of three from 4" to 14"
(0.16 to 0.56pc), along the projected disk of young stars. For our
analysis, we implement a new method of completeness correction using a
combination of star-planting simulations and Bayesian inference. We
assign probabilities for the spectral type of every source detected in
deep imaging down to K'=15.5mag using information from spectra,
simulations, number counts, and the distribution of stars. The
inferred radial surface-density profiles,
Σ(R)∝R-Γ, for the young stars and late-type
giants are consistent with earlier results
(Γearly=0.93±0.09, Γlate=0.16±0.07). The late-type
surface-density profile is approximately flat out to the edge of the
survey. While the late-type stellar luminosity function is consistent
with the Galactic bulge, the completeness-corrected luminosity
function of the early-type stars has significantly more young stars at
faint magnitudes compared with previous surveys with similar depth.
This luminosity function indicates that the corresponding mass
function of the young stars is likely less top-heavy than that
inferred from previous surveys.
Description:
Near-IR integral-field spectra of the Galactic center were obtained
between 2007 and 2011 using the OH-Suppressing Infrared Imaging
Spectrograph (OSIRIS). The primary observations for this work
constitute a survey through the narrowband filter Kn3 (2.121-2.220um).
This includes both observations initially reported in Do et al. (2009,
J/ApJ/703/1323) and Do (2010, PhD thesis, Univ. California, Los
Angeles) and new 2010-2011 observations, which increase the radial
extent of this survey by more than a factor of three from 4" to 14"
(0.16 to 0.56pc; see Figure 2).
Photometric observations for the individual stars in the central
parsec of the Galaxy were conducted using the K'-band (K') filter at
λ0=2.12um (Δλ=0.35um). Observations were taken
in 2006, 2008, and 2010 with the NIRC2 instrument (PI: K. Matthews).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 76 219 OSIRIS observations of late-type stars
table3.dat 76 67 OSIRIS observations of early-type stars
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See also:
J/ApJ/737/73 : Infrared extinction toward the Galactic Centre (Fritz+, 2011)
J/ApJ/725/331 : Astrometry in the Galactic Center (Yelda+, 2010)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/A+A/499/483 : NIR obs. of sources in galactic center (Buchholz+, 2009)
J/ApJ/703/1323 : Spectro. of stars in the Galaxy's nuclear cluster (Do+ 2009)
J/ApJ/697/1741 : Warped disks of YSOs in Galactic center (Bartko+, 2009)
J/ApJ/643/1011 : Early-type stars in the center of the Galaxy (Paumard+, 2006)
J/A+A/457/637 : UBVJHK synthetic phot. of Galactic O stars (Martins+, 2006)
J/A+A/426/81 : Kinematic analysis of the Minispiral (Paumard+, 2004)
J/ApJ/597/323 : Cool stars at the Galactic Center (Blum+, 2003)
J/ApJS/107/281 : Atlas of hot, luminous stars at 2 microns (Hanson+ 1996)
J/ApJ/470/864 : JHKL photometry of the Galactic Center (Blum+, 1996)
J/AJ/110/2788 : JHK photometry for Galactic bulge stars (Tiede+ 1995)
J/A+AS/97/587 : JHK photometry of Galactic center stars (Ruelas-Mayorga+ 1993)
Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Star name (SNN-NNN or IRSNNWW)
9 A1 --- f_Name [d] Status changed from Do et al. 2009 (1)
11- 15 F5.2 mag K'mag [9.5/16] K'-band magnitude (2)
17- 20 F4.2 mag e_K'mag [0.01/0.4]? K'mag uncertainty
22- 26 F5.2 mag K'mag0 [9.2/16] K'-band magnitude corrected for
differential extinction (2)
28- 32 F5.2 arcsec RAoff Right ascension offset from Sgr A*
34- 38 F5.2 arcsec DEoff Declination offset from Sgr A*
40- 44 F5.2 arcsec Rad [0.1/13.3] Projected radius (R)
46- 52 F7.2 --- Epoch [2003/2010] Epoch in decimal years
54- 58 F5.2 0.1nm EW ? Equivalent width of NaI (late-type stars)
or of Brγ (early-type stars)
60- 64 F5.2 0.1nm e_EW ? EW uncertainty
66- 67 I2 --- Nobs [1/24]? Number of observations (3)
69- 71 I3 --- S/N [5/149]? Signal to noise ratio (4)
73- 76 A4 --- Field Field designation
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Note (1):
d = Identified as early-type in Do et al. 2009 (J/ApJ/703/1323), but now as
late-type. See Appendix A for more details.
Note (2): K'-band filter at λ0=2.12µm, {DeltA}λ=0.35µm.
The correction for differential extinction uses AKs=2.7 from
Schoedel et al. 2010 (J/A+A/511/A18) (see Appendix C)
Note (3): Each observation has an integration time of 900s.
Note (4): Signal-to-noise ratio per pixel calculated between 2.212 and 2.218um.
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History:
From electronic version of the journal
References:
Lu et al. Paper II. 2013ApJ...764..155L 2013ApJ...764..155L
Jia et al. Paper III. 2023ApJ...949...18J 2023ApJ...949...18J Cat. J/apJ/949/18
(End) Emmanuelle Perret [CDS] 27-Oct-2014