J/A+A/649/A83 Milky Way nuclear disk KMOS survey (Fritz+, 2021)
A KMOS survey of the nuclear disk of the Milky Way.
I: Survey design and metallicities.
Fritz T.K., Patrick L.R., Feldmeier-Krause A., Schoedel R., Schultheis M.,
Gerhard O., Nandakumar G., Neumayer N., Nogueras-Lara F., Prieto M.A.
<Astron. Astrophys. 649, A83 (2021)>
=2021A&A...649A..83F 2021A&A...649A..83F (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Surveys ; Stars, giant ; Abundances, [Fe/H] ;
Effective temperatures ; Radial velocities ; Spectra, infrared ;
Photometry, infrared
Keywords: Galaxy: nucleus - Galaxy: abundances -
Galaxy: kinematics and dynamics - catalogs - infrared: stars -
techniques: spectroscopic
Abstract:
In the central few degrees of the bulge of the Milky Way there is a
flattened structure of gas, dust, and stars, known as the central
molecular zone, that is similar to nuclear disks in other galaxies. As
a result of extreme foreground extinction, we possess only sparse
information about the (mostly old) stellar population of the nuclear
disk.
In this work we present our KMOS spectroscopic survey of the stars in
the nuclear disk reaching the old populations. To obtain an unbiased
data set, we sampled stars in the full extinction range along each
line of sight. We also observed reference fields in neighboring
regions of the Galactic bulge. We describe the design and execution of
the survey and present first results.
We obtain spectra and five spectral indices of 3113 stars with a
median S/N of 67 and measure radial velocities for 3051 stars.
Of those, 2735 sources have sufficient S/N to estimate temperatures
and metallicities from indices. We derive metallicities using the
CO 2-0 and Na I K-band spectral features, where we derive our own
empirical calibration using metallicities obtained with
higher-resolution observations.We use 183 giant stars for calibration
spanning in metallicity from -2.5 to 0.6dex and covering temperatures
of up to 5500K. The derived index based metallicities deviate from
the calibration values with a scatter of 0.32dex. The internal
uncertainty of our metallicities is likely smaller. We use these
metallicity measurements, together with the CO index, to derive
effective temperatures using literature relations. We publish the
catalog in this paper. Our data set complements Galactic surveys such
as Gaia and APOGEE for the inner 200pc radius of the Milky Way, which
is not readily accessible by those surveys owing to extinction. We
will use the derived properties in future papers for further analysis
of the nuclear disk.
Description:
Table D1 shows the calibrator stars used for the derivation of our
metallicity relation. Besides the names and metallicity from the
literature, we also include the line indices measured by us and the
derived metallicities.
Table E1 includes all successfully observed stars.
A successfully observed star is defined as having a measured
line-of-sight velocity and/or at least S/N>10.
The table lists the following properties:
Our identification number, coordinates, magnitudes in H, K, and when
also available, in the J (Nishiyama et al. 2013ApJ...769L..28N 2013ApJ...769L..28N) and
IRAC bands (Churchwell et al. 2009PASP..121..213C 2009PASP..121..213C). If there is no
good match or no detection, the magnitude value is set as -999.999.
From our spectroscopy we present the overall S/N, the barycentric
line-of-sight velocity and its error, the line indices of
Brackett-gamma, NaI, CaI, CO 2-0, H2O and their errors caused by
S/N. For all stars with a CO based temperature, we also include the
metallicity, its random error term and metallicity value when we omit
KMOS/APOGEE or SINFONI (Thorsbro et al., 2020ApJ...894...26T 2020ApJ...894...26T) for the
calibration. For all stars we include the effective temperature with
its random error. For stars without CO absorption (T>6000K), the
temperature estimate is more uncertain as also visible in the error.
For all stars we show an estimate of the intrinsic H-K color and of
the extinction ordering parameter ext-order. We also provide the
ripples flags. Values that could not be provided are set to -999.999.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tabled1.dat 73 183 Properties of calibrator stars
tablee1.dat 263 3065 Properties of stars successfully observed by
the survey
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See also:
II/295 : Spitzer IRAC survey of the galactic center (Ramirez+, 2008)
J/A+A/549/A57 : Young, massive star candidates in Sgr A* (Nishiyama+, 2013)
Byte-by-byte Description of file: tabled1.dat
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Bytes Format Units Label Explanations
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1- 26 A26 --- Name Target Name
29- 34 F6.3 [-] [Fe/H]lit Literature metallicity
36 I1 --- r_[Fe/H] Source of metallicity (1)
38- 44 A7 --- Inst Instrument used for the spectrum
46 I1 --- r_Inst [3]? Source of spectrum (2)
48- 55 F8.5 0.1nm EWNa Na equivalent width
57- 64 F8.4 0.1nm EWCO CO equivalent width
66- 73 F8.5 [-] [Fe/H] Metallicity estimate
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Note (1): Source of metallicity as follows:
1 = Ahumada et al. (2020ApJS..249....3A 2020ApJS..249....3A)
2 = Arentsen et al. (2019A&A...627A.138A 2019A&A...627A.138A, Cat. J/A+A/627/A138)
4 = Magrinini et al. (2010A&A...523A..11M 2010A&A...523A..11M, Cat. J/A+A/523/A11)
5 = Thorsbro et al. (2020ApJ...894...26T 2020ApJ...894...26T)
Note (2): 3 indicates that the spectrum is from Gonneau et al.
(2020A&A...634A.133G 2020A&A...634A.133G, Cat. J/A+A/634/133), the rest are own spectra.
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Byte-by-byte Description of file: tablee1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID1 Identification number 1
5- 6 I2 --- ID2 Identification number 2
8 I1 --- ID3 Identification number 3
10- 18 F9.5 deg RAdeg Right ascension (J2000.0)
20- 28 F9.5 deg DEdeg Declination (J2000.0)
30- 37 F8.5 deg GLON [] Galactic longitude
39- 46 F8.5 deg GLAT Galactic latitude
48- 55 F8.3 mag Jmag ?=-999.999 J-band magnitude, from
Nishiyama et al., 2013ApJ...769L..28N 2013ApJ...769L..28N)
57- 62 F6.3 mag Hmag H-band magnitude, from Nishiyama et al.,
2013ApJ...769L..28N 2013ApJ...769L..28N)
64- 69 F6.3 mag Kmag K-band magnitude, from Nishiyama et al.,
2013ApJ...769L..28N 2013ApJ...769L..28N)
71- 78 F8.3 mag 3.6mag ?=-999.999 IRAC [3.6]-band magnitude,
from Churchwell et al., 2009PASP..121..213C 2009PASP..121..213C
80- 87 F8.3 mag 4.5mag ?=-999.999 IRAC [4.5]-band magnitude
from Churchwell et al., 2009PASP..121..213C 2009PASP..121..213C
89- 96 F8.3 mag 5.8mag ?=-999.999 IRAC [5.8]-band magnitude
from Churchwell et al., 2009PASP..121..213C 2009PASP..121..213C
98-105 F8.3 mag 8.0mag ?=-999.999 IRAC [8.0]-band magnitude
from Churchwell et al., 2009PASP..121..213C 2009PASP..121..213C
107-113 F7.3 --- S/N Signal to noise ratio
115-122 F8.3 km/s vlos Barycentric line of sight velocity
124-131 F8.3 km/s e_vlos ?=-999.999 Error of barycentric line of
sight velocity
133-137 F5.3 --- H20 ?=-999.999 H20 index
139-143 F5.3 --- e_H20 Error of H20 index
145-151 F7.3 0.1nm EWBrg Brackett gamma equivalent width
153-157 F5.3 0.1nm e_EWBrg Error of Brackett gamma equivalent width
159-165 F7.3 0.1nm EWNa Na equivalent width
167-171 F5.3 0.1nm e_EWNa Error of Na equivalent width
173-179 F7.3 0.1nm EWCa Ca equivalent width
181-186 F6.3 0.1nm e_EWCa Error of Ca equivalent width
188-194 F7.3 0.1nm EWCO CO equivalent width
196-201 F6.3 0.1nm e_EWCO Error of CO equivalent width
203-210 F8.3 [-] [Fe/H] ?=-999.999 Metallicity
212-219 F8.3 [-] e_[Fe/H] ?=-999.999 Metallicity error
221-228 F8.3 [-] [Fe/H]a ?=-999.999 Alternative metallicity
without using Thorsbro sample
230-237 F8.3 [-] [Fe/H]b ?=-999.999 Alternative metallicity
without using KMOS/APOGEE sample
239-243 I5 K Teff Effective temperature
245-248 I4 K e_Teff Error of effective temperature
250-255 F6.3 mag (H-K)0 Intrinsic H-K color index
257-261 F5.3 --- Ext-order Extinction ordering parameter
263 I1 --- Ripples [0/1] Spectral ripples flag
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Acknowledgements:
Tobias K. Fritz, tobias.k.fritz(at)gmail.com
(End) Patricia Vannier [CDS] 05-Mar-2021