J/A+A/593/A7 NH and AV Towards YSOs in the ONC (Hasenberger+, 2016)
Gas absorption and dust extinction towards the Orion Nebula Cluster.
Hasenberger B., Forbrich, J., Alves J., Wolk S.J., Meingast S.,
Getman K.V., Pillitteri I.
<Astron. Astrophys. 593, A7 (2016)>
=2016A&A...593A...7H 2016A&A...593A...7H (SIMBAD/NED BibCode)
ADC_Keywords: Extinction ; Infrared sources ; X-ray sources ; YSOs
Keywords: dust, extinction - X-ray: ISM - infrared: ISM -
stars: pre-main sequence
Abstract:
We characterise the relation between the gas and dust content of the
interstellar medium towards young stellar objects in the Orion Nebula
Cluster. X-ray observations provide estimates of the absorbing
equivalent hydrogen column density NH based on spectral fits.
Near-infrared extinction values are calculated from intrinsic and
observed colour magnitudes (J-H) and (H-Ks) as given by the VISTA
Orion A survey. A linear fit of the correlation between column density
and extinction values AV yields an estimate of the NH/AV ratio. We
investigate systematic uncertainties of the results by describing and
(if possible) quantifying the influence of circumstellar material as
well as the adopted extinction law, X-ray models, and elemental
abundances on the NH/AV ratio. Assuming a Galactic extinction law with
R_V=3.1 and solar abundances by Anders et al. (1989), we deduce an
NH/AV ratio of (1.39±0.14)*1021cm-2.mag-1^ for Class III
sources in the Orion Nebula Cluster, where the given error does not
include systematic uncertainties. This ratio is consistent with
similar studies in other star-forming regions and approximately 31%
lower than the Galactic value. We find no obvious trends in the
spatial distribution of NH/AV ratios. Changes in the assumed
extinction law and elemental abundances are demonstrated to have a
relevant impact on deduced AV and NH values, respectively. Large
systematic uncertainties associated with metal abundances in the Orion
Nebula Cluster represent the primary limitation for the deduction of a
definitive NH/AV ratio and the physical interpretation of these
results.
Description:
Column density (NH) and extinction (AV) values are presented for a
sample of YSO sources in the ONC. Near-infrared colours based on the
VISION (Meingast et al., 2016A&A...587A.153M 2016A&A...587A.153M) catalogue were employed
to calculate extinction values using the NICER algorithm (Lombardi et
al., 2001A&A...377.1023L 2001A&A...377.1023L) and assuming RV=3.1. Column densities were
adopted from the COUP (Getman et al., 2005, Cat. J/ApJS/160/319)
catalogue. In addition to NH and AV, the following quantities are
provided: JHK_s magnitudes, taken from the VISION catalogue; spectral
types, adopted from the catalogue by Hillenbrand et al. (2013, Cat.
J/AJ/146/85); intrinsic near-infrared colours, deduced from spectral
types and data by Scandariato et al. (2012A&A...545A..19S 2012A&A...545A..19S); and the
YSO classification, based on the classification by Megeath et al.
(2012, Cat. J/AJ/144/192). 1-Sigma error estimates are given for all
quantities in the table.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 130 239 Catalog
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See also:
J/ApJS/160/319 : COUP: observations and source lists (Getman+, 2005)
J/AJ/144/192 : Orion A and B Spitzer survey. I. YSO catalog (Megeath+, 2012)
J/AJ/146/85 : Spectral types of 1576 stars in ONC (Hillenbrand+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- COUP COUP identification number
6- 12 F7.4 deg RAdeg Right Ascension (J2000) (1)
14- 20 F7.4 deg DEdeg Declination (J2000) (1)
22- 24 F3.1 10+22cm-2 NH Column density (1)
26- 29 F4.1 10+22cm-2 e_NH Error of NH
31- 46 A16 --- VISION VISION identification number
48- 53 F6.3 mag Jmag J magnitude from VISION (2)
55- 59 F5.3 mag e_Jmag Error of J magnitude (2)
61- 66 F6.3 mag Hmag H magnitude from VISION (2)
68- 72 F5.3 mag e_Hmag Error of H magnitude (2)
74- 79 F6.3 mag Ksmag K_s magnitude from VISION (2)
81- 85 F5.3 mag e_Ksmag Error of Ks magnitude (2)
87- 88 A2 --- SpType Spectral type
90- 94 F5.3 mag (J-H)0 Intrinsic (J-H) magnitude
96-100 F5.3 mag e_(J-H)0 Error on (J-H)_0
102-106 F5.3 mag (H-Ks)0 Intrinsic (H-K_s) magnitude
108-112 F5.3 mag e_(H-Ks)0 Error on (H-Ks)0
114-119 F6.3 mag AV Extinction for RV=3.1 (3)
121-125 F5.3 mag e_AV Error on AV
127-130 A4 --- Class YSO Classification (4)
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Note (1): From Getman et al. (2005ApJS..160..319G 2005ApJS..160..319G)
Note (2): From Meingast et al. (2016A&A...587A.153M 2016A&A...587A.153M)
Note (3): Extinction values for RV=5.5 can be calculated by multiplication
with the factor 1.18.
Note (4): Possible classifications are as follows:
p = protostar
d = disc star
cl3 = Class III source
uncl = unclassified
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Acknowledgements:
Birgit Hasenberger, birgit.hasenberger(at)univie.ac.at
(End) B. Hasenberger [Univ. of Vienna, Austria], P. Vannier [CDS] 22-Jul-2016