J/PASJ/51/791 Molecular clouds in southern HII regions (Yamaguchi+ 1999)
Molecular clouds and star formation in the southern HII regions
Yamaguchi R., Saito H., Mizuno N., Mine Y., Mizuno A., Ogawa H., Fukui Y.
<Publ. Astron. Soc. Jap., 51, 791 (1999)>
=1999PASJ...51..791Y 1999PASJ...51..791Y
ADC_Keywords: H II regions ; Molecular clouds ; Infrared sources
Keywords: ISM: H II regions - ISM: molecules - radio lines: ISM -
stars: early-type - stars: formation
Abstract:
We have carried out extensive 13CO(J=1-0) observations toward
23 southern H II regions associated with bright-rimmed clouds. In
total, 95 molecular clouds have been identified to be associated with
the H II regions. Among the 95, 57 clouds are found to be associated
with 204 IRAS point sources which are candidates for young stellar
objects. There is a significant increase of star-formation efficiency
on the side facing to the H II regions; the luminosity-to-mass ratio,
defined as the ratio of the stellar luminosity to the molecular cloud
mass, is higher by an order of magnitude on the near side of the H II
regions than that on the. far side. This indicates that molecular gas
facing to the H II regions is more actively forming massive stars
whose luminosity is ~>103L☉. In addition, the number density
of the IRAS point sources increases by a factor of 2 on the near side
of the H II regions compared with on the far side. These results
strongly suggest that the active formation of massive stars on the
near side of the H II regions is due to the effects of the H II
regions, such as the compression of molecular material by the
ionization/shock fronts. For the whole Galaxy, we estimate that the
present star-formation rate under such effects is at least
0.2-0.4M☉/yr, corresponding to a few 10% by mass.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 73 28 Observed H II regions
refs.dat 71 24 References
table2.dat 67 104 Observed properties of 13CO clouds
table3.dat 53 104 Physical properties of 13CO clouds
table4.dat 14 204 Associated IRAS point sources
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See also:
VII/20 : Catalogue of HII Regions (Sharpless 1959)
J/A+A/284/233 : Association of HII regions & IRAS PSC sources (Codella+ 1994)
J/A+AS/133/29 : Molecular line survey towards UC HII (Hatchell+ 1998)
J/A+AS/131/319 : HII regions catalogue (Petit+ 1998)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- HII HII region
13- 19 A7 arcmin Size Size (NN or NNNxNNN) in arcmin (1)
21- 31 A11 --- Star Exciting star
32 A1 --- n_Star [+] +: the earliest star probably contributing
to ionization
34- 42 A9 --- SpType MK spectral type
44- 47 F4.2 kpc Dist ? Distance
49- 54 A6 --- r_Dist References for distance and exciting star (2),
in refs.dat file
55- 74 A20 --- RelObj Related objects
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Note (1): References for size:
S = Sharpless (1959, Cat. VII/20)
RCW = Rodgers et al. (1960, Cat. VII/216)
Cum Nebula = Chanot and Sivan (1983A&A...121...19C 1983A&A...121...19C)
Others = Brand et al. (1986A&AS...65..537B 1986A&AS...65..537B)
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 22 A19 --- BibCOde BibCode
24- 43 A20 --- Aut Author's name
50- 72 A23 --- Com Comments
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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- 2 I2 --- [YSM99] [1-95] Sequential number
4- 13 A10 --- Cloud Cloud name
15- 20 F6.2 deg GLON Galactic longitude
22- 27 F6.2 deg GLAT Galactic latitude
29- 30 I2 h RAh Right ascension (1950)
32- 33 I2 min RAm Right ascension (1950)
35- 38 F4.1 s RAs Right ascension (1950)
40 A1 --- DE- Declination sign (1950)
41- 42 I2 deg DEd Declination (1950)
44- 45 I2 arcmin DEm Declination (1950)
47- 48 I2 arcsec DEs Declination (1950)
50- 52 F3.1 K TR* Peak antenna temperature (1)
54- 56 F3.1 km/s DV FWHM line width (1)
58- 62 F5.1 km/s Vlsr LSR velocity (1)
64- 67 F4.1 K.km/s Int Velocity-integrated intensity (1)
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Note (1): Observed properties at the peak position of molecular clouds.
The typical rms noise fluctuations are 0.35K at a velocity
resolution of 0.1km/s with 4-12s integration.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- [YSM99] [1-95] Sequential number
4- 7 F4.2 --- tau ? Optical depth
9- 13 F5.2 10+21cm-2 N(H2) H2 column density
15- 17 F3.1 km/s DVc ? FWHM line width computed from gaussian fit
19- 22 F4.2 kpc Dist ? Distance to the molecular cloud
24- 27 F4.1 pc Rad ? Size of the molecular cloud
29- 34 I6 solMass Mass ? Molecular cloud mass
36- 50 A15 ---- HII Associated HII regions
52- 53 I2 --- IPS ? Number of cold IRAS points sources
listed in table4
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- [YSM99] [1-95] Sequential number
4- 13 A10 --- IRAS Associated IRAS point source
14 A1 --- m_IRAS [A] Multiplicity index on IRAS name
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History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Vannier [CDS] 31-May-2005