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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 (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) for the cloud, and the Herschel far-IR to submm and WISE near-IR to mid-IR imaging data. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 13 06.6 -61 30 G304.74+01.32 = MSXDC 304.74+01.32 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 84 2 List of fits files fits/* 0 2 Individual fits files
See also: J/A+A/542/A101 : 4 Galactic plane fields LABOCA 870um mapping (Miettinen, 2012) Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
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
History: From Oskari Miettinen, miettinen.oskari(at) 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 ( 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, LABOCA mapping of the infrared dark cloud MSXDC G304.74+01.32, Miettinen, 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 Miettinen, Paper II 2012A&A...540A.104M
(End) Oskari Miettinen [Avarea], Patricia Vannier [CDS] 24-Oct-2017
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