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J/A+A/284/233 Association of HII regions and IRAS PSC sources (Codella+ 1994) ================================================================================ HII Regions and IRAS PSC sources: the realiability of the association CODELLA C., FELLI M., NATALE V.=1994A&A...284..233C ================================================================================ ADC_Keywords: H II regions ; Infrared sources Keywords: HII regions - radio lines: interstellar - stars: formation infrared: continuum: ISM File Summary: Abstract: The IRAS Point Source Catalogue has been compared with a catalogue of 462 (diffuse) HII regions detected in hydrogen radio recombination lines. To distinguish the true IRAS counterpart of the HII region from chance coincidences the distribution of offset and the position in colour-colour plots as a function of F(60um) are investigated. It is found that sources with F(60um) < 100 Jy have a high probability of being chance coincidences. The far infrared properties of the HII regions are investigated for a subsample of 252 IRAS PSC sources which have a high (> 80%) probability of being true coincidences. The majority satisfy the Wood and Churchwell colour criteria which identify ultracompact HII regions; therefore, these criteria select ultracompact as well as more diffuse HII regions, or, alternatively, diffuse HII and ultracompact HII regions may often be mixed, as predicted by the sequential star formation theory. The luminosity of a single star required to produce the observed HII line emission correlates very well with the far infrared luminosity and is, on the average, higher than the observed value. Consequently, the stars ionizing the extended HII regions can account for the bulk of the observed FIR emission and no contribution from lower mass stars of the cluster is necessary. Keywords: HII regions - radio lines: interstellar - stars: formation - infrared: continuum: ISM -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1 156 252 IRAS properties of HII regions -------------------------------------------------------------------------------- Byte-by-byte Description of file: table1 -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 2 I2 h RAh Right Ascension (1950) 4- 5 I2 min RAm Right Ascension (1950) 7- 10 F4.1 s RAs Right Ascension (1950) 13 A1 --- DE- Declination sign 14- 15 I2 deg DEd Declination (1950) 17- 18 I2 arcmin DEm Declination (1950) 20- 21 I2 arcsec DEs Declination (1950) 26- 32 F7.3 deg GLON Galactic longitude 35- 41 F7.3 deg GLAT Galactic latitude 49- 53 F5.2 kpc d []? Distance 55- 58 I4 pc z []? Height from the galactic plane 65- 75 A11 --- IRAS IRAS name 81 A1 --- l_F12 limit flag on F12 (upper limit) 83- 90 E8.2 Jy F12 IRAS flux density at 12 micron 92 A1 --- l_F25 limit flag on F25 (upper limit) 94-101 E8.2 Jy F25 IRAS flux density at 25 micron 103 A1 --- l_F60 limit flag on F60 (upper limit) 105-112 E8.2 Jy F60 IRAS flux density at 60 micron 114 A1 --- l_F100 limit flag on F100 (upper limit) 116-123 E8.2 Jy F100 IRAS flux density at 100 micron 125 A1 --- l_FIR limit flag on FIR (upper limit) 127-134 E8.2 W/m2 FIR Integrated infrared flux 136 A1 --- l_LFIR limit flag on LFIR (upper limit) 138-145 E8.2 Sun LFIR []? IRAS luminosity 148-156 A9 --- R Remarks: D : double position UCHII: IRAS sources inside the WC box O : observed UCHII region (see text) -------------------------------------------------------------------------------- ================================================================================ (End) Patricia Bauer [CDS] 25-Nov-1993