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J/A+A/615/A18        NIKA view of two star-forming IRDCs          (Rigby+, 2018)

A NIKA view of two star-forming infrared dark clouds: Dust emissivity variations and mass concentration. Rigby A. J., Peretto N., Adam R., Ade P., Andre P., Aussel H., Beelen A., Benoit A., Bracco A., Bideaud A., Bourrion O., Calvo M., Catalano A., Clark C.J.R., Comis B., De Petris M., Desert F.-X., Doyle S., Driessen E.F.C., Goupy J., Kramer C., Lagache G., Leclercq S., Lestrade J.-F., Macias-Perez J.F., Mauskopf P., Mayet F., Monfardini A., Pascale E., Perotto L., Pisano G., Ponthieu N., Reveret V., Ritacco A., Romero C., Roussel H., Ruppin F., Schuster K., Sievers A., Triqueneaux S., Tucker C., Zylka R. <Astron. Astrophys. 615, A18 (2018)> =2018A&A...615A..18R (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Millimetric/submm sources Keywords: stars: formation - submillimetre: ISM - ISM: clouds - dust, extinction - ISM: structure Abstract: The thermal emission of dust grains is a powerful tool for probing cold, dense regions of molecular gas in the interstellar medium, and so constraining dust properties is key to obtaining accurate measurements of dust mass and temperature. By placing constraints on the dust emissivity spectral index, β, towards two star-forming infrared dark clouds - SDC18.888-0.476 and SDC24.489-0.689 - we aim to evaluate the role of mass concentration in the associated star-formation activity. We exploited the simultaneous 1.2mm and 2.0mm imaging capability of the NIKA camera on the IRAM 30m telescope to construct maps of β for both clouds, and by incorporating Herschel observations, we created H2 column density maps with 13" angular resolution. While we find no significant systematic radial variations around the most massive clumps in either cloud on 0.1 pc scales, their mean β values are significantly different, with {bar}β=2.07±0.09(random)±0.25(systematic) for SDC18.888-0.476 and {bar}β=1.71±0.09(random)±0.25(systematic) for SDC24.489-0.689. These differences could be a consequence of the very different environments in which both clouds lie, and we suggest that the proximity of SDC18.888-0.476 to the W39 HII region may raise β on scales of ∼1pc. We also find that the mass in SDC24.489-0.689 is more centrally concentrated and circularly symmetric than in SDC18.888-0.476, and is consistent with a scenario in which spherical globally-collapsing clouds concentrate a higher fraction of their mass into a single core than elongated clouds that will more easily fragment, distributing their mass into many cores. We demonstrate that β variations towards interstellar clouds can be robustly constrained with high signal-to-noise ratio (S/N) NIKA observations, providing more accurate estimates of their masses. The methods presented here will be applied to the Galactic Star Formation with NIKA2 (GASTON) guaranteed time large programme, extending our analysis to a statistically significant sample of star-forming clouds. Description: The FITS files of the NIKA photometric maps in the 260.0GHz (1.15mm) and 150.0GHz (2.00mm) continuum wavebands towards the two IRDC targets SDC18.888-0.476 and SDC24.489-0.689 have intensity units of Jy/beam. The PSF-matching convolution kernel used in the construction of the NIKA ratio maps is also included. We also include the combined-resolution H2 column density maps, created using the method described in Section 4.1, which have units of cm-2, and were created using dust beta values of 2.07 and 1.71, respectively. Objects: ---------------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------------- 18 27 08.31 -12 41 38.9 SDC18.888-0.476 = SDC G18.888-0.476 18 38 25.25 -07 49 28.9 SDC24.489-0.689 = SDC G24.489-0.689 ---------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 104 7 List of fits files fits/* 0 7 Individual fits files
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- 30 I3 Kibyte size Size of FITS file 32- 53 A22 --- FileName Name of FITS file, in subdirectory fits 55-104 A50 --- Title Title of the FITS file
Acknowledgements: Andrew J. Rigby, RigbyA(at)cardiff.ac.uk
(End) Andrew J. Rigby [Cardiff Univ., UK], Patricia Vannier [CDS] 05-Mar-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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