J/A+A/671/A111 Filaments in the OMC-3 cloud (Juvela+, 2023)
Filaments in the OMC-3 cloud and uncertainties in estimates of
filament profiles.
Juvela M., Mannfors E.
<Astron. Astrophys. 671, A111 (2023)>
=2023A&A...671A.111J 2023A&A...671A.111J (SIMBAD/NED BibCode)
ADC_Keywords: Nebulae ; Extinction ; Interstellar medium ; Infrared sources
Keywords: ISM: clouds - dust, extinction - ISM: structure - stars: formation -
stars: protostars
Abstract:
Filamentary structures are an important part of star-forming
interstellar clouds. The properties of filaments hold clues to their
formation mechanisms and their role in the star-formation process.
We compare the properties of filaments in the Orion Molecular Cloud 3
(OMC-3), as seen in mid-infrared (MIR) absorption and far-infrared
(FIR) dust emission. We also wish to characterise some potential
sources of systematic errors in filament studies.
We calculated optical depth maps of the OMC-3 filaments based on the
MIR absorption seen in Spitzer data and FIR dust emission observed
with Herschel and the ArTeMiS instrument. We then compared the
filament properties extracted from the data. Potential sources of
error were investigated more generally with the help of radiative
transfer models.
The widths of the selected OMC-3 filament segments are in the range
0.03-0.1pc, with similar average values seen in both MIR and FIR
analyses. Compared to the widths, the individual parameters of the
fitted Plummer functions are much more uncertain. The asymptotic
power-law index has typically values p∼3 but with a large scatter.
Modelling shows that the FIR observations can systematically
overestimate the filament widths. The effect is potentially tens of
per cent at column densities above N(H2)∼1022cm-2 but is
reduced in more intense radiation fields, such as the Orion region.
Spatial variations in dust properties could cause errors of similar
magnitude. In the MIR analysis, dust scattering should generally not
be a significant factor, unless there are high-mass stars nearby or
the dust MIR scattering efficiency is higher than in the tested dust
models. Thermal MIR dust emission can be a more significant source of
error, especially close to embedded sources.
The analysis of interstellar filaments can be affected by several
sources of systematic error, but mainly at high column densities and,
in the case of FIR observations, in weak radiation fields. The widths
of the OMC-3 filaments were consistent between the MIR and FIR
analyses and did not reveal any systematic dependence on the angular
resolution of the observations.
Description:
Mid-infrared optical depth of a field in the Orion Molecular Cloud
three (OMC-3). The optical depths were estimated using the absorption
of the background surface brightness that was observed in the Spitzer
satellite 8um data. The FITS images include the optical depth, the
original 8um surface brightness, the background sky brightness used
in the optical depth calculation, and a mask for the main filament
structures.
Objects:
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RA (2000) DE Designation(s)
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05 35 20.00 -05 00 59.9 OMC-3 = OMC 3
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 77 4 List of fits images
fits/* . 4 Individual fits images
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See also:
J/ApJ/566/974 : CHANDRA obs. of YSOs in OMC-2 and OMC-3 (Tsujimoto+, 2002)
J/ApJ/716/893 : Polarisation at 850mu{m} in OMC-2 & OMC-3 (Poidevin+, 2010)
J/MNRAS/514/3024 : Magnetic field of L1495/B211 (Li+, 2022)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 31 I4 Kibyte size Size of FITS file
33- 45 A13 --- FileName Name of FITS file, in subdirectory fits
47- 77 A31 --- Title Title of the FITS file
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Acknowledgements:
Mika Juvela, mika.juvela(at)helsinki.fi
(End) Mika Juvela [Univ. Helsinki], Patricia Vannier [CDS] 23-Jan-2023