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J/ApJ/428/693    Rosette Nebula and Maddalena Cloud structures (Williams+ 1994)

Determining structure in molecular clouds. Williams J.P., De Geus E.J., Blitz L. <Astrophys. J. 428, 693 (1994)> =1994ApJ...428..693W (SIMBAD/NED BibCode)
ADC_Keywords: Nebulae ; Morphology Keywords: ISM: clouds - ISM: individual (Rosette Nebula, Maddalena Cloud) - ISM: structure - methods: analytical - stars: formation Abstract: We describe an automatic, objective routine for analyzing the clumpy structure in a spectral line position-position-velocity data cube. The algorithm works by first contouring the data at a multiple of the rms noise of the observations, then searches for peaks of emission which locate the clumps, and then follows them down to lower intensities. No a priori clump profile is assumed. By creating simulated data, we test the performance of the algorithm and show that a contour map most accurately depicts internal structure at a contouring interval equal to twice the rms noise of the map. Blending of clump emission leads to small errors in mass and size determinations and in severe cases can result in a number of clumps being misidentified as a single unit, flattening the measured clump mass spectrum. The algorithm is applied to two real data sets as an example of its use. The Rosette molecular cloud is a "typical" star-forming cloud, but in the Maddalena molecular cloud high-mass star formation is completely absent. Comparison of the two clump lists generated by the algorithm show that on a one-to-one basis the clumps in the star-forming cloud have higher peak temperatures, higher average densities, and are more gravitationally bound than in the non star-forming cloud. Collective properties of the clumps, such as temperature-size-line-width-mass relations appear very similar, however. Contrary to the initial results reported in a previous paper (Williams & Blitz, 1993ApJ...405L..75W), we find that the current, more thoroughly tested analysis finds no significant difference in the clump mass spectrum of the two clouds. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 46 88 Clumps in the Rosette molecular cloud table3a.dat 39 53 Clumps in the Maddalena molecular cloud: region 1 (RA=6h46m50s, DE=-4°31'14") table3b.dat 39 39 Clumps in the Maddalena molecular cloud: region 2 (RA=6h43m39s, DE=-3°30'23")
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 I2 --- RMC [1/95]+ Clump number ([WDB94] RMC NN in Simbad) 4- 10 F7.3 deg GLON Peak galactic longitude 12- 17 F6.3 deg GLAT Peak galactic latitude 19- 22 F4.1 km/s Vpeak Peak velocity 24- 26 F3.1 K Tpeak Peak temperature 28- 31 F4.2 pc DR Equivalent circular radius (1) 33- 36 F4.2 km/s FWHM Line width (1) 38- 41 I4 solMass Mlte Clump masses (2) 43- 46 I4 solMass Mvir Virial mass (3)
Note (1): Data corrected for beam size as described in Appendix A Note (2): Clump masses, derived from the integrated 13CO luminosity assuming LTE, τ13<0.5, NH2/N13CO=4.8x105, and Tex=20K. Includes an additional factor of 1.4 for helium. Note (3): Virial mass, assuming an inverse-square power-law density profile (see Appendix A)
Byte-by-byte Description of file: table3a.dat table3b.dat
Bytes Format Units Label Explanations
1- 2 I2 --- MMC [1/58]+ Clump number (1) 4- 6 I3 arcmin oRApeak Offset from right ascension (2) 8- 10 I3 arcmin oDEpeak Offset from declination (2) 12- 15 F4.1 km/s Vpeak Peak velocity 17- 19 F3.1 K Tpeak Peak temperature 21- 24 F4.2 pc DR Equivalent circular radius (3) 26- 29 F4.2 km/s FWHM Line width (3) 31- 34 I4 solMass Mlte Clump masses (4) 36- 39 I4 solMass Mvir Virial mass (5)
Note (1): table3a.dat: [WDB94] MMC-1 NN in Simbad table3b.dat: [WDB94] MMC-2 NN in Simbad Note (2): For table3a.dat, RA=6h46m50s, DE=-4°31'14" For table3b.dat, RA=6h43m39s, DE=-3°30'23"Note (3): Data corrected for beam size as described in Appendix A Note (3): Data corrected for beam size as described in Appendix A Note (4): Clump masses, derived from the integrated 13CO luminosity assuming LTE, τ13<0.5, NH2/N13CO=4.8x105, and Tex=10K. Includes an additional factor of 1.4 for helium. Note (5): Virial mass, assuming an inverse-square power-law density profile (see Appendix A)
History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 12-Oct-1998
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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