J/A+A/614/A65 VISION II. VISTA Orion A survey (Meingast+, 2018)
VISION - Vienna Survey in Orion. II. Infrared extinction in Orion A.
Meingast S., Alves J., Lombardi M.
<Astron. Astrophys., 614, A65 (2018)>
=2018A&A...614A..65M 2018A&A...614A..65M (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Photometry, infrared ; Surveys
Keywords: ISM: clouds - ISM: structure - dust, extinction -
methods: data analysis - methods: statistical
Abstract:
We have investigated the shape of the extinction curve in the infrared
up to ∼25µm for the Orion A star-forming complex. The basis of this
work is near-infrared data acquired with the Visual and Infrared
Survey Telescope for Astronomy, in combination with Pan-STARRS and
mid-infrared Spitzer photometry. We obtain colour excess ratios for
eight passbands by fitting a series of colour-colour diagrams. The
fits are performed using Markov chain Monte Carlo methods, together
with a linear model under a Bayesian formalism. The resulting colour
excess ratios are directly interpreted as a measure of the extinction
law. We show that the Orion A molecular cloud is characterized by flat
mid-infrared extinction, similar to many other recently studied
sightlines. Moreover, we find statistically significant evidence that
the extinction law from ∼1µm to at least ∼6µm varies across the
cloud. In particular, we find a gradient along galactic longitude,
where regions near the Orion Nebula Cluster show a different
extinction law compared to L1641 and L1647, the low-mass star-forming
sites in the cloud complex. These variations are of the order of only
3% and are most likely caused by the influence of the massive stars on
their surrounding medium. While the observed general trends in our
measurements are in agreement with model predictions, both
well-established and new dust grain models are not able to fully
reproduce our infrared extinction curve. We also present a new
extinction map featuring a resolution of 1' and revisit the
correlation between extinction and dust optical depth. This analysis
shows that cloud substructure, which is not sampled by background
sources, affects the conversion factor between these two measures. In
conclusion, we argue that specific characteristics of the infrared
extinction law are still not well understood, but Orion A can serve as
an unbiased template for future studies.
Description:
The given file corresponds to the extinction map presented in the
paper at a resolution of 1 arcmin. It contains four FITS extensions:
(1) Extinction map in units of Ak (mag)
(2) The variance of the computed extinction
(3) The number of sources used to compute the extinction in each pixel
(4) Source kernel density after adjustment with the NICEST.
Objects:
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RA (2000) DE Designation(s)
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05 37 51.78 -06 40 07.9 Orion A = NAME Orion A
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 118 4 Information of fits file extensions
fits/* . 1 Fits file
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See also:
J/A+A/587/A153 : VISION I. VISTA Orion A Survey (Meingast+, 2016)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [G]
2- 10 F9.5 deg GLON Galactic longitude
11- 19 F9.5 deg GLAT Galactic latitude
21- 24 I4 --- Nx Number of pixels along X-axis
26- 28 I3 --- Ny Number of pixels along Y-axis
30- 33 I4 Kibyte size Size of FITS file extension
35 I1 --- Ext [1/4] Extension number
37- 55 A19 --- FileName Name of FITS file, in subdirectory fits
57-118 A62 --- Title Title of the FITS file extension
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Acknowledgements:
Stefan Meingast, stefan.meingast(at)univie.ac.at
Joao Alves, joao.alves(at)univie.ac.at
References:
Meingast et al., Paper I 2016A&A...587A.153M 2016A&A...587A.153M, Cat. J/A+A/587/A153
(End) Stefan Meingast [Univ. Vienna], Patricia Vannier [CDS] 15-Jan-2019