J/ApJS/166/567 Radio Molecular lines in infrared dark clouds (Ragan+, 2006)
Molecular line observations of infrared dark clouds: seeking the precursors to
intermediate and massive star formation.
Ragan S.E., Bergin E.A., Plume R., Gibson D.L., Wilner D.J., O'Brien S.,
Hails E.
<Astrophys. J. Suppl. Ser., 166, 567-584 (2006)>
=2006ApJS..166..567R 2006ApJS..166..567R (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Molecular clouds ; Infrared sources
Keywords: ISM: clouds - ISM: molecules - stars: formation
Abstract:
We have identified 41 infrared dark clouds from the 8um maps of the
Midcourse Space Experiment (MSX), selected to be found within 1deg2
areas centered on known ultracompact HII regions. We have mapped these
infrared dark clouds in N2H+ 1->0, CS 2->1, and C18O 1->0
emission using the Five College Radio Astronomy Observatory. The maps
of the different species often show striking differences in
morphologies, indicating differences in evolutionary state and/or the
presence of undetected, deeply embedded protostars. We derive an
average mass for these clouds using N2H+ column densities of
≫2500M☉, a value comparable to that found in previous studies
of high-mass star-forming cores using other mass tracers. The line
widths of these clouds are typically 2.0-2.9km/s. Based on the fact
that they are dark at 8um, compact, and massive, and have large
velocity dispersions, we suggest that these clouds may be the
precursor sites of intermediate- and high-mass star formation.
Description:
We mapped 41 of the sample of MSX dark clouds in emission from C18O
J=1->0 (nu=109.782GHz), CS J=2->1 (nu=97.981GHz), and N2H+ J=1->0
(nu=93.173GHz) using the 14m Five College Radio Astronomy Observatory
(FCRAO). The observations were made in 2002 February, May, and
December using the 16 element focal plane array receiver SEQUOIA.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
regions.dat 30 22 List of HII regions
table1.dat 80 114 Basic properties of the target MSX pre-stellar cores
table2.dat 110 44 Molecular line observations
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See also:
J/ApJ/639/227 : MSX IR dark cloud candidates candidate catalog (Simon+, 2006)
J/ApJ/641/389 : Properties of IR dark cloud candidates cores (Rathborne+ 2006)
Byte-by-byte Description of file: regions.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- HII HII region identification
7 A1 --- --- [=]
9- 26 A18 --- SName Simbad name of the HII region
29- 30 I2 --- Nsources Number of associated sources in table1
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- HII HII region identification
7- 17 A11 --- [RBP2006] Source name
19- 24 F6.3 deg GLON Galactic Longitude
26- 31 F6.3 deg GLAT Galactic Latitude
33- 34 I2 h RAh Hour of Right Ascension (J2000)
36- 37 I2 min RAm Minute of Right Ascension (J2000)
39- 43 F5.2 s RAs Second of Right Ascension (J2000)
45 A1 --- DE- Sign of the Declination (J2000)
46- 47 I2 deg DEd Degree of Declination (J2000)
49- 50 I2 arcmin DEm Arcminute of Declination (J2000)
52- 56 F5.2 arcsec DEs Arcsecond of Declination (J2000)
58- 61 F4.2 arcmin MajAxis Major axis
63- 66 F4.2 arcmin MinAxis Minor axis
68- 72 F5.3 --- BCont Brightness contrast
74- 80 A7 km/s BWidth Bandwidth observed (1)
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Note (1): For observed regions, we give the total velocity range to which
the observations were sensitive. A given object was probed in the same
velocity range for each observed transition.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- [RBP2006] Source name
12 A1 --- m_[RBP2006] [ab] Multiplicity index on source name
14- 17 F4.1 arcmin oRA Difference in Right Ascension
of Molecular Peak from Table 1 position
19- 22 F4.1 arcmin oDE Difference in Declination
of Molecular Peak from Table 1 position
24 A1 --- l_I(N2H+) Upper limit flag on I(N2H+)
25- 28 F4.2 K.km/s I(N2H+) The N2H+ J=1-0 integrated intensity
30- 33 F4.2 K.km/s e_I(N2H+) ? Uncertainty in I(N2H+)
35- 38 F4.1 km/s W(N2H+) ? The N2H+ J=1-0 line width
40- 42 F3.1 km/s e_W(N2H+) ? Uncertainty in W(N2H+)
44- 46 F3.1 km/s V(N2H+) ? The N2H+ J=1-0 LSR velocity
48- 50 F3.1 km/s e_V(N2H+) ? Uncertainty in V(N2H+)
52- 55 F4.2 K.km/s I(C18O) ? The C18O J=1-0 integrated intensity
57- 60 F4.2 K.km/s e_I(C18O) ? Uncertainty in I(C18O)
62- 65 F4.1 km/s W(C18O) ? The C18O J=1-0 line width
67- 69 F3.1 km/s e_W(C18O) ? Uncertainty in W(C18O)
71- 73 F3.1 km/s V(C18O) ? The C18O J=1-0 LSR velocity
75- 77 F3.1 km/s e_V(C18O) ? Uncertainty in V(C18O)
79 A1 --- l_I(CS) Upper limit flag on I(CS)
80- 83 F4.2 K.km/s I(CS) The CS J=2-1 integrated intensity
85- 88 F4.2 K.km/s e_I(CS) ? Uncertainty in I(CS)
90- 94 F5.1 km/s W(CS) ? The CS J=2-1 line width
96- 98 F3.1 km/s e_W(CS) ? Uncertainty in W(CS)
100 A1 --- f_W(CS) [a] Weak CS line (1)
102-104 F3.1 km/s V(CS) ? The CS J=2-1 LSR velocity
106-108 F3.1 km/s e_V(CS) ? Uncertainty in V(CS)
110 A1 --- f_V(CS) [a] Weak CS line (1)
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Note (1): a = Non-detection of CS in single scan. Average of 25 scans
detects a weak line at the 5σ level. The velocity and line
width from this average are provided in the table.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 29-May-2008