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J/ApJ/644/990    Sub-mm clumps at 450 and 850µm in M17    (Reid+, 2006)

High-mass star formation. II. The mass function of submillimeter clumps in M17. Reid M.A., Wilson C.D. <Astrophys. J., 644, 990-1005 (2006)> =2006ApJ...644..990R
ADC_Keywords: Interstellar medium ; Millimetric/submm sources Keywords: ISM: individual (M17) - ISM: structure - methods: data analysis - stars: formation - submillimeter Abstract: We have mapped a 5.5x5.5pc portion of the M17 massive star-forming region in both 850 and 450µm dust continuum emission using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). The maps reveal more than 100 dusty clumps with deconvolved linear sizes of ∼0.05-0.2pc and masses of ∼0.8-120M, most of which are not associated with known mid-infrared point sources. Fitting the clump mass function with a double power law gives a mean power-law exponent of αhigh=-2.4±0.3 for the high-mass power law, consistent with the exponent of the Salpeter stellar mass function. We show that a lognormal clump mass distribution with a peak at 4M produces as good a fit to the clump mass function as does a double power law. This 4M peak mass is well above the peak masses of both the stellar initial mass function and the mass function of clumps in low-mass star-forming regions. Despite the difference in intrinsic mass scale, the shape of the M17 clump mass function appears to be consistent with the shape of the core mass function in low-mass star-forming regions. Thus, we suggest that the clump mass function in high-mass star-forming regions may be a scaled up version of that in low-mass regions, instead of its extension to higher masses. Description: We used the Submillimeter Common-User Bolometer Array on the James Clerk Maxwell Telescope (JCMT) to map an approximately 12'x12' (5.5x5.5pc) region of M17. The data were acquired on the nights of 2003 March 17 and April 16 with a total on-source integration time of about 5hr. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 95 121 Properties of the 850um Clumps table2.dat 95 101 Properties of the 450um Clumps
See also: J/ApJ/625/891 : Sub-mm clumps at 450 and 850µm in NGC 7538 (Reid+, 2005) Byte-by-byte Description of file: table[12].dat
Bytes Format Units Label Explanations
1- 7 A7 --- [RW2006b] Name SNN NNN (1) 8 A1 --- m_[RW2006b] [ABC] Multiplicity index for clump (1) 9 A1 --- n_[RW2006b] [e] Note on Name (2) 11- 12 I2 h RAh Right ascension (J2000) 14- 15 I2 min RAm Right ascension (J2000) 17- 20 F4.1 s RAs Right ascension (J2000) 22 A1 --- DE- Declination sign (J2000) 23- 24 I2 deg DEd Declination (J2000) 26- 27 I2 arcmin DEm Declination (J2000) 29- 30 I2 arcsec DEs Declination (J2000) 32- 35 F4.2 pc Reff Effective radius 37- 41 F5.2 Jy Speak Peak flux density at 850um for table1 and 450um for table2, in Jy/beam 43- 46 F4.2 Jy e_Speak rms uncertainty on Speak (3) 48- 52 F5.2 Jy Sint Integrated flux density at 850um for table1 and 450um for table2 54- 58 F5.2 Jy e_Sint rms uncertainty on Sint (3) 60- 63 F4.2 --- alpha ?=- Spectral index (only in table1) (4) 65- 67 I3 K Td ?=- Dust temperature (only in table1) (5) 69- 74 F6.2 solMass M(30K) ?=- Mass calculated with fixed Td (Td=30K) 76- 80 F5.2 solMass e_M(30K) ? rms uncertainty on M(30K) (3) 82- 87 F6.2 solMass M(Td) ?=- Mass calculated with estimated Td (only in table1) 89- 93 F5.2 solMass e_M(Td) ? rms uncertainty on M(Td) (3) (only in table1) 95 I1 --- Npsc Number of MSX point sources contained within the clump's 0.5Speak contour
Note (1): Names in Simbad are [RW2006b] SMM NNN in table1 and [RW2006b] SMM NNNA in table2. The names of the 450um clumps have been set to reflect the names of the 850um clumps in which their peaks appear. Thus, clumps SMM 21A-21C are the three 450um clumps whose peaks appear within the boundaries of 850um clump SMM 21. Note (2): "e" denotes a clump to which corrections for free-free emission have been applied in the calculation of the spectral index, dust temperature, and masses. The free-free correction has not been applied to the peak and integrated fluxes listed here. Note (3): The uncertainties stated in this table are composed of the uncertainties in the gain calibration, the sky opacities, and the corrections due to the error beam. These uncertainties are typically significantly larger than the random measurement errors associated with the rms flux of the map. The exception is the peak flux, where the random error of sigma=0.027Jy/beam (table1) or sigma=0.32Jy/beam (table2) dominates the systematic error for the clumps with lower peak fluxes. Note (4): The systematic uncertainty in the spectral index, alpha, is 13%. These systematic uncertainties, which are composed of the uncertainties in the gain calibration and sky opacities, dominate the random errors on the spectral index. Note (5): See Sect. 3.2 for a discussion of the uncertainties in the temperatures. Temperatures are omitted where high spectral index makes them incalculable or where no reliable spectral index can be calculated (see text). All of the temperatures above 40K should be considered highly uncertain, indicating only that a clump is probably hot.
History: From electronic version of the journal
(End) Patricia Vannier [CDS] 02-Oct-2007
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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