J/A+A/609/A123 SABOCA imaging of G304.74+01.32 (Miettinen, 2018)
The Seahorse Nebula: New views of the filamentary infrared dark cloud
G304.74+01.32 from SABOCA, Herschel, and WISE.
Miettinen O.
<Astron. Astrophys. 609, A123 (2018)>
=2018A&A...609A.123M 2018A&A...609A.123M (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Nebulae, dark
Keywords: stars: formation - ISM: clouds - infrared: ISM -
submillimeter: ISM - ISM: individual object: IRDC G304.74+01.32
Abstract:
We aim to determine the occurrence of fragmentation into cores in the
clumps of the filamentary IRDC G304.74+01.32. We also aim to determine
the basic physical characteristics of the clumps and cores in G304.74.
We mapped the G304.74 filament at 350 micron using the SABOCA
bolometer. The new SABOCA data have a factor of 2.2 times higher
resolution than our previous LABOCA 870 micron map of the cloud (9"
versus 19.86"). We also employed the Herschel far-IR and
submillimetre, and WISE IR imaging data available for G304.74. The
WISE data allowed us to trace the IR emission of the YSOs associated
with the cloud. The SABOCA 350 micron data show that G304.74 is
composed of a dense filamentary structure with a mean width of only
0.18±0.05pc. The percentage of LABOCA clumps that are found to be
fragmented into SABOCA cores is 36%±16%, but the irregular
morphology of some of the cores suggests that this multiplicity
fraction could be higher. The WISE data suggest that 65%±18% of the
SABOCA cores host YSOs. The mean dust temperature of the clumps,
derived by comparing the Herschel 250, 350, and 500 micron flux
densities, was found to be 15.0±0.8K. The mean mass, beam-averaged
H2 column density, and H2 number density of the LABOCA clumps are
estimated to be 55±10M☉, (2.0±0.2)x1022cm-2, and
(3.1±0.2)x104cm-3. The corresponding values for the SABOCA cores
are 29±3M☉, (2.9±0.3)x1022cm-2, and
(7.9±1.2)x104cm-3. The G304.74 filament is estimated to be
thermally supercritical by a factor of ≳3.5 on the scale probed by
LABOCA, and by a factor of ≳1.5 for the SABOCA filament. Our data
strongly suggest that the IRDC G304.74 has undergone hierarchical
fragmentation. On the scale where the clumps have fragmented into
cores, the process can be explained in terms of gravitational Jeans
instability. Besides the filament being fragmented, the finding of
embedded YSOs in G304.74 indicates its thermally supercritical state,
although the potential non-thermal (turbulent) motions can render the
cloud a virial equilibrium system on scale traced by LABOCA. The IRDC
G304.74 has a seahorse-like morphology in the Herschel images, and the
filament appears to be attached by elongated, perpendicular
striations. This is potentially evidence that G304.74 is still
accreting mass from the surrounding medium, and the accretion process
can contribute to the dynamical evolution of the main filament. One of
the clumps in G304.74, IRAS 13039-6108, is already known to be
associated with high-mass star formation, but the remaining clumps and
cores in this filament might preferentially form low and
intermediate-mass stars owing to their mass reservoirs and sizes.
Besides the presence of perpendicularly oriented, dusty striations and
potential embedded intermediate-mass YSOs, G304.74 is a relatively
nearby (d∼2.5kpc) IRDC, which makes it a useful target for future star
formation studies. Owing to its observed morphology, we propose that
G304.74 could be nicknamed the Seahorse Nebula. Description: The
SABOCA 350 micron and LABOCA 870 micron dust continuum maps of
G304.74+01.32. The data were reduced using the CRUSH-2 software
Description:
We used the SABOCA bolometer to map the filamentary IRDC G304.74+01.32
in the 350um dust continuum emission. These data were used in
conjunction with our previous LABOCA 870um data (Paper I, Miettinen &
Harju, 2010A&A...520A.102M 2010A&A...520A.102M) for the cloud, and the Herschel far-IR to
submm and WISE near-IR to mid-IR imaging data.
Objects:
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RA (2000) DE Designation(s)
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13 06.6 -61 30 G304.74+01.32 = MSXDC 304.74+01.32
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 84 2 List of fits files
fits/* . 2 Individual fits files
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See also:
J/A+A/542/A101 : 4 Galactic plane fields LABOCA 870um mapping (Miettinen, 2012)
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- 43 A11 --- FileName Name of FITS file, in subdirectory fits
45- 84 A40 --- Title Title of the FITS file
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History:
From Oskari Miettinen, miettinen.oskari(at)gmail.com
Acknowledgements:
I am grateful to the staff at the APEX telescope for performing the
service mode SABOCA and LABOCA observations presented in this paper.
The research presented in this article was funded by the Academy of
Finland under project No. 132291, and the European Union's Seventh
Framework Programme (FP7/2007-2013) under grant agreement 337595 (ERC
Starting Grant, 'CoSMass'). This research has made use of data from
the Herschel Gould Belt survey (HGBS) project
(http://gouldbelt-herschel.cea.fr). The HGBS is a Herschel Key
Programme jointly carried out by SPIRE Specialist Astronomy Group 3
(SAG 3), scientists of several institutes in the PACS Consortium (CEA
Saclay, INAF-IFSI Rome and INAF-Arcetri, KU Leuven, MPIA Heidelberg),
and scientists of the Herschel Science Center (HSC). This publication
makes use of data products from the Wide-field Infrared Survey
Explorer, which is a joint project of the University of California,
Los Angeles, and the Jet Propulsion Laboratory/California Institute of
Technology, funded by the National Aeronautics and Space
Administration. References: Miettinen & Harju, 2010A&A...520A.102M 2010A&A...520A.102M,
LABOCA mapping of the infrared dark cloud MSXDC G304.74+01.32,
Miettinen, 2012A&A...540A.104M 2012A&A...540A.104M, A molecular line study of the
filamentary infrared dark cloud G304.74+01.32
References:
Miettinen & Harju, Paper I 2010A&A...520A.102M 2010A&A...520A.102M
Miettinen, Paper II 2012A&A...540A.104M 2012A&A...540A.104M
(End) Oskari Miettinen [Avarea], Patricia Vannier [CDS] 24-Oct-2017