J/AJ/148/24 Extinction maps in the bulge from APOGEE (Schultheis+, 2014)
Extinction maps toward the Milky Way bulge: two-dimensional and
three-dimensional tests with APOGEE.
Schultheis M., Zasowski G., Allende Prieto C., Anders F., Beaton R.L.,
Beers T.C., Bizyaev D., Chiappini C., Frinchaboy P.M., Garcia Perez A.E.,
Ge J., Hearty F., Holtzman J., Majewski S.R., Muna D., Nidever D.,
Shetrone M., Schneider D.P.
<Astron. J., 148, 24 (2014)>
=2014AJ....148...24S 2014AJ....148...24S (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Extinction ; Stars, giant
Keywords: dust, extinction - Galaxy: bulge - Galaxy: stellar content -
Galaxy: structure
Abstract:
Galactic interstellar extinction maps are powerful and necessary tools
for Milky Way structure and stellar population analyses, particularly
toward the heavily reddened bulge and in the midplane. However, due to
the difficulty of obtaining reliable extinction measures and distances
for a large number of stars that are independent of these maps, tests
of their accuracy and systematics have been limited. Our goal is to
assess a variety of photometric stellar extinction estimates,
including both two-dimensional and three-dimensional extinction maps,
using independent extinction measures based on a large spectroscopic
sample of stars toward the Milky Way bulge. We employ stellar
atmospheric parameters derived from high-resolution H-band Apache
Point Observatory Galactic Evolution Experiment (APOGEE) spectra,
combined with theoretical stellar isochrones, to calculate
line-of-sight extinction and distances for a sample of more than 2400
giants toward the Milky Way bulge. We compare these extinction values
to those predicted by individual near-IR and near+mid-IR stellar
colors, two-dimensional bulge extinction maps, and three-dimensional
extinction maps. The long baseline, near+mid-IR stellar colors are, on
average, the most accurate predictors of the APOGEE extinction
estimates, and the two-dimensional and three-dimensional extinction
maps derived from different stellar populations along different
sightlines show varying degrees of reliability. We present the results
of all of the comparisons and discuss reasons for the observed
discrepancies. We also demonstrate how the particular stellar
atmospheric models adopted can have a strong impact on this type of
analysis, and discuss related caveats.
Description:
One of four experiments in the Sloan Digital Sky Survey III (SDSS-III;
Eisenstein et al. 2011AJ....142...72E 2011AJ....142...72E), the Apache Point Observatory
Galactic Evolution Experiment (APOGEE; Majewski et al.
2010IAUS..265..480M 2010IAUS..265..480M) is a large-scale, near-IR, high-resolution
(R∼22500) spectroscopic survey of Milky Way stellar populations. The
survey uses a dedicated, 300 fiber, cryogenic spectrograph coupled to
the wide-field, Sloan 2.5m telescope at Apache Point Observatory
(APO). APOGEE observes in the H band (1.5-1.7µm), where extinction
by dust is significantly lower than at optical wavelengths. APOGEE
observes, at high signal-to-noise ratio , about 100000 red giant stars
selected from the 2MASS survey, down to a typical flux limit of
H∼12-14 (Zasowski et al., 2013AJ....146...81Z 2013AJ....146...81Z).
The initial selection for our sample comprises all APOGEE targets from
the first two years of the survey that are located toward the Galactic
bulge: -10°<l<10° and -10°<b<5°, coinciding with the
footprint of the VVV survey extinction map (Gonzalez et al.,
2012A&A...543A..13G 2012A&A...543A..13G). These include data that are part of the latest
SDSS-III Data Release (DR10; Ahn et al., 2014ApJS..211...17A 2014ApJS..211...17A), along
with data not included in that release.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 102 2472 Derived extinction and distances from our
Apache Point Observatory Galactic Evolution
Experiment (APOGEE) sources
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See also:
J/A+A/550/A42 : Extinction map towards the Galactic bulge (Chen+, 2013)
J/AJ/146/133 : Stellar parameters from SDSSIII APOGEE DR10 (Meszaros+, 2013)
J/ApJ/737/73 : Infrared extinction toward the Galactic Centre (Fritz+, 2011)
J/ApJ/707/89 : Variation of mid-IR extinction (Gao+, 2009)
J/A+A/453/635 : Modelling the Galactic Interstellar Extinction
(Marshall+, 2006)
J/MNRAS/338/253 : K extinction near the Galactic Centre (Dutra+, 2003)
J/A+A/349/L69 : Interstellar extinction (Schultheis+, 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [2M]
3- 18 A16 --- 2MASS 2MASS identifier (HHMMSSss+DDMMSSs; J2000)
20- 30 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
32- 42 F11.7 deg DEdeg Declination in decimal degrees (J2000)
44- 49 F6.3 mag AK [-0.24/3.9] Derived Ks band extinction
51- 55 F5.3 mag e_AK [0/0.19] Uncertainty in AK
57- 62 F6.3 kpc Dist [0.4/63] Derived distance
64- 70 F7.3 % e_Dist [0.2/355] Percent uncertainty in Dist
72- 78 F7.3 mag AK1 [0/2.8]?=-99. Rayleigh-Jeans color excess
derived Ks band extinction (1)
80- 86 F7.3 mag AK2 [0/2.4]?=-99. Nidever et al. (2012ApJS..201...35N 2012ApJS..201...35N)
derived Ks band extinction (2)
88- 94 F7.3 mag AK3 [0/2.4]?=-99. Gonzalez et al. 2012A&A...543A..13G 2012A&A...543A..13G
derived Ks band extinction (3)
96-102 F7.3 mag AK4 [0/4.9]?=-99. E(H-Ks) color-excess derived
Ks band extinction (4)
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Note (1): We compare our isochrone-based extinction to the individual stellar
"Rayleigh-Jeans Color Excess" extinction estimates following the method of
Majewski et al. (2011ApJ...739...25M 2011ApJ...739...25M). See Section 4.1 for more details.
Note (2): We compare our isochrone-based extinction to the "all stars, median"
extinction map using the "Rayleigh-Jeans Color Excess" method by Nidever et
al. (2012ApJS..201...35N 2012ApJS..201...35N). With the query scripts provided in that paper,
we retrieved, for each star, the extinction in the 2' pixel closest to the
star's position.
Note (3): We compare our isochrone-based extinction to the extinction map based
on RC stars by Gonzalez et al. (2012A&A...543A..13G 2012A&A...543A..13G). Using the BEAM
calculator Web page (http://mill.astro.puc.cl/BEAM/calculator.php), we
retrieved for each star the extinction in the map's 2' pixel closest to the
star's position.
Note (4): We compare our isochrone-based extinction to the individual stellar
extinction estimates derived from the E(H-Ks) color excess, following Lada
et al. (1994ApJ...429..694L 1994ApJ...429..694L). See Section 4.1 for more details.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 13-Oct-2014