J/ApJ/784/170 The SEGUE K giant survey. II. Distances of 6036 stars (Xue+, 2014)
The SEGUE K giant survey. II. A catalog of distance determinations for the SEGUE
K giants in the galactic halo.
Xue X.-X., Ma Z., Rix H.-W., Morrison H.L., Harding P., Beers T.C.,
Ivans I.I., Jacobson H.R., Johnson J., Lee Y.S., Lucatello S.,
Rockosi C.M., Sobeck J.S., Yanny B., Zhao G., Allende Prieto C.
<Astrophys. J., 784, 170 (2014)>
=2014ApJ...784..170X 2014ApJ...784..170X (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, halo ; Stars, K-type ; Stars, giant ;
Abundances, [Fe/H] ; Radial velocities ; Stars, distances ;
Photometry, SDSS
Keywords: galaxies: individual (Milky Way) - Galaxy: halo -
stars: distances - stars: individual (K giants)
Abstract:
We present an online catalog of distance determinations for 6036 K
giants, most of which are members of the Milky Way's stellar halo.
Their medium-resolution spectra from the Sloan Digital Sky
Survey/Sloan Extension for Galactic Understanding and Exploration are
used to derive metallicities and rough gravity estimates, along with
radial velocities. Distance moduli are derived from a comparison of
each star's apparent magnitude with the absolute magnitude of
empirically calibrated color-luminosity fiducials, at the observed
(g-r)0 color and spectroscopic [Fe/H]. We employ a probabilistic
approach that makes it straightforward to properly propagate the
errors in metallicities, magnitudes, and colors into distance
uncertainties. We also fold in prior information about the
giant-branch luminosity function and the different metallicity
distributions of the SEGUE K-giant targeting sub-categories. We show
that the metallicity prior plays a small role in the distance
estimates, but that neglecting the luminosity prior could lead to a
systematic distance modulus bias of up to 0.25mag, compared to the
case of using the luminosity prior. We find a median distance
precision of 16%, with distance estimates most precise for the least
metal-poor stars near the tip of the red giant branch. The precision
and accuracy of our distance estimates are validated with observations
of globular and open clusters. The stars in our catalog are up to
125kpc from the Galactic center, with 283 stars beyond 50kpc, forming
the largest available spectroscopic sample of distant tracers in the
Galactic halo.
Description:
SDSS and its extensions use a dedicated 2.5m telescope to obtain ugriz
imaging and resolution (defined as R=λ/Δλ)∼2000
spectra for 640 (SDSS spectrograph) or 1000 (BOSS spectrograph)
objects over a 7deg2 field. Sloan Extension for Galactic
Understanding and Exploration (SEGUE), one of the key projects
executed during SDSS-II and SDSS-III, obtained some 360000 spectra of
stars in the Galaxy, selected to explore the nature of stellar
populations from 0.5kpc to 100kpc (Yanny et al. 2009, cat.
J/AJ/137/4377; and C. M. Rockosi et al., in preparation). Data from
SEGUE is a significant part of the ninth SDSS public data release
(DR9; Ahn et al. 2012, cat. V/139).
The SEGUE project obtained spectra for a large number of different
stellar types: 18 for SEGUE-1 (see Yanny et al. 2009, cat.
J/AJ/137/4377, for details) and 11 for SEGUE-2 (C. M. Rockosi et al.
in preparation). Three of these target types were specifically
designed to detect K giants: these are designated "l-color K giants",
"red K giants", and "proper-motion K giants." The K-giant targets from
these three categories all have 0.5<(g-r)0<1.3, 0.5<(u-g)0<3.5,
and proper motions smaller than 11mas/yr.
We present a catalog containing the distance moduli, observed
information, and SEGUE Stellar Parameter Pipeline (SSPP) atmospheric
parameters for 6036 SEGUE K giants (see Table4). For each object in
the catalog, we also list some of the basic observables such as (R.A.,
decl.), extinction-corrected apparent magnitudes and dereddened
colors, as well as the information obtained from the
spectra--heliocentric radial velocities plus SSPP atmospheric
parameters. In addition, we provide the Bayesian estimates of the
distance moduli, distances to the Sun, Galactocentric distances, the
absolute magnitudes and their uncertainties, along with the distance
moduli at (5%, 16%, 50%, 84%, 95%) confidence of L(DM).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 19 1000 Interpolated fiducial
table4.dat 158 6036 List of 6036 K giants selected from SDSS DR9
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See also:
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/ApJ/738/79 : SDSS-DR8 BHB stars in the Milky Way's halo (Xue+, 2011)
J/ApJ/731/4 : Galactic halo as seen by the CFHTLS (Sesar+, 2011)
J/AJ/141/90 : SEGUE stellar parameter pipeline. V. (Lee+, 2011)
J/AJ/141/89 : SEGUE stellar parameter pipeline. IV. (Smolinski+, 2011)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/AJ/136/2070 : SEGUE stellar parameter pipeline. III. (Allende Prieto+, 2008)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/ApJ/684/1143 : BHB candidates in the Milky Way (Xue+, 2008)
J/AJ/125/2502 : Spectral indices of Galactic halo (Morrison+, 2003)
J/AJ/100/1191 : Giants DDO photometry (Morrison+, 1990)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 F5.3 mag g-r [0.3/1.4] Extinction-corrected color index
(g-r)0
7- 12 F6.3 mag rMag [-3.4/3] Absolute magnitude in r band (Mr)
14- 19 F6.3 [-] [Fe/H] [-2.4/0.4] Metallicity
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 8 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
10- 17 F8.4 deg DEdeg Declination in decimal degrees (J2000)
19- 24 F6.3 mag rmag [13.8/19.6] Extinction-corrected r band
magnitude (r0)
26- 30 F5.3 mag e_rmag [0.037/0.053] Error in rmag (Δr0) (1)
32- 36 F5.3 mag g-r [0.5/1.3] The (g-r) color index after
extinction correction (g-r)0
38- 42 F5.3 mag e_g-r [0.018/0.044] Error in g-r
(Δ(g-r)0) (1)
44- 49 F6.1 km/s HRV [-506.5/419.4] Heliocentic radial velocity
51- 54 F4.1 km/s e_HRV [0.5/15.1] Error in HRV
56- 59 I4 K Teff [4025/5691] Effective temperature (SSPP) (2)
61- 65 F5.2 [-] [Fe/H] [-3.6/0.32] Metallicity (SSPP) (2)
67- 70 F4.2 [-] e_[Fe/H] [0.1/0.23] Error in [Fe/H] (3)
72- 75 F4.2 [cm/s2] logg [0.18/3.5] Log of the surface gravity
(SSPP) (2)
77- 81 F5.2 mag DMpeak [13.1/20.4] Distance modulus at peak of
distance modulus likelihood (DMpeak) (4)
83- 87 F5.2 mag DM05 [12.2/20.3] Distance modulus at 5% confidence
of distance modulus likelihood (DM5%) (4)
89- 93 F5.2 mag DM16 [12.6/20.3] Distance modulus at 16% confidence
of distance modulus likelihood (DM16%) (4)
95- 99 F5.2 mag DM50 [13/20.4] Distance modulus at 50% confidence
of distance modulus likelihood (DM50%) (4)
101-105 F5.2 mag DM84 [13.5/20.5] Distance modulus at 84% confidence
of distance modulus likelihood (DM84%) (4)
107-111 F5.2 mag DM95 [13.7/20.6] Distance modulus at 95% confidence
of distance modulus likelihood (DM95%) (4)
113-116 F4.2 mag eDM [0.05/0.76] Error in distance modulus estimate
(ΔDM) (5)
118-122 F5.2 mag rMag [-3.2/1.2] Absolute magnitude in r band
(Mr) (6)
124-127 F4.2 mag e_rMag [0.07/0.8] Error in rMag (ΔMr)
129-134 F6.2 kpc Dist [4.2/120.3] Distance to Sun (d) (6)
136-140 F5.2 kpc e_Dist [0.5/16.6] Error in Dist (Δd)
142-147 F6.2 kpc Rgc [4.79/125.1] Distance to Galactic center
(rGC) (6)
149-153 F5.2 kpc e_Rgc [0/16.47] Error in Rgc (ΔrGC)
155-158 F4.2 --- pRGB [0.45/1] Chance of being clearly on the
Red-Giant Branch (RGB), above the level of
the Horizontal Branch (HB) (PaboveHB) (7)
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Note (1): Corrected for measurement errors on the photometry and reddening
(see Section 2).
Note (2): SDSS DR9 delivers estimates of Teff, logg, [Fe/H], and [α/Fe]
from an updated and improved version of the SEGUE Stellar Parameter
Pipeline (SSPP; Lee et al. 2008AJ....136.2022L 2008AJ....136.2022L; Lee et al. 2008,
cat. J/AJ/136/2050; Allende Prieto et al. 2008, cat. J/AJ/136/2070;
Smolinski et al. 2011, cat. J/AJ/141/89; Lee et al. 2011,
cat. J/AJ/141/90). The errors for Teff and log(g) are published in SDSS
DR9, so we recommend readers to download them directly from CasJob.
Note (3): Derived from Signal-to-Noise ratio (S/N), which is calibrated using
cluster data plus repeat observations, as described in detail in Morrison
et al. (in preparation).
Note (4): Distance moduli are derived from a comparison of each star's apparent
magnitude with the absolute magnitude of empirically calibrated
color-luminosity fiducials, at the observed (g-r)0 color and
spectroscopic [Fe/H]. See Section 3 in the text for more details. DMpeak
is the best estimate of the distance modulus for the K giant.
Note (5): Calculated from (DM84%-DM16%)/2.
Note (6): Calculated from DMpeak, assuming R☉=8.0kpc
(i.e., rMag=rmag-DMpeak, d=10((DM+5)/5)).
Note (7): See Section 3.4 in the text for further details.
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History:
From electronic version of the journal
References:
Janesh et al., Paper III 2016ApJ...816...80J 2016ApJ...816...80J, cat. J/ApJ/816/80
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 03-Aug-2016