Far-infrared observations of two southern H II regions - RCW 122 and G 351.6-1.3

McBreen, B.; Loughran, L.; Fazio, G. G.; Rengarajan, T. N.

doi:10.1086/113712

Cited by 3 publications

(5 citation statements)

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“…G348.6972−01.0263 lies within part of RCW122, and is definitely radio loud, since Walsh et al (1998) detect even stronger radio emission than we do. Persson et al (1976) calculate a silicate optical depth at of τ 9.7 µm = 3.5 for this region and McBreen et al (1985) calculate A V = 117 and τ 9.7 µm ∼ 6.5 for the whole cloud, so there is certainly significant absorption towards this source. This suggests that the silicate absorption feature, as well as general extinction may play a part in the lower than expected 10.4 µm flux of this source.…”

Section: Comparison With Radio Continuum Observationsmentioning

confidence: 99%

The RMS survey: mid-infrared observations of candidate massive YSOs in the southern hemisphere

Mottram¹,

Hoare²,

Lumsden³

et al. 2007

A&A

106

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Context. The Red MSX Source (RMS) survey is an ongoing effort to return a large, well-selected sample of massive young stellar objects (MYSOs) within our Galaxy. 2000 candidates have been colour-selected from the Mid-course Space Experiment (MSX) point source catalogue (PSC). A series of ground-based follow-up observations are being undertaken in order to remove contaminant objects (ultra-compact HII (UCHII) regions, planetary nebulae (PN), evolved stars), and to begin characterising these MYSOs. Aims. As a part of these follow-up observations, high resolution (∼1 ) mid-IR imaging aids the identification of contaminant objects which are resolved (UCHII regions, PN) as opposed to those which are unresolved (YSOs, evolved stars) as well as identifying YSOs near UCHII regions and other multiple sources. Methods. We present 10.4 µm imaging observations for 346 candidate MYSOs in the RMS survey in the Southern Hemisphere, primarily outside the region covered by the GLIMPSE Spitzer Legacy Survey. These were obtained using TIMMI2 on the ESO 3.6 m telescope in La Silla, Chile. Our photometric accuracy is of order 0.05 Jy, and our astrometric accuracy is 0.8 , which is an improvement over the nominal 2 accuracy of the MSX PSC. Results. Point sources are detected in 64% of our observations, which are expected to be either YSOs or evolved stars. 24% contain only sources of extended emission, which are likely to be either UCHII regions or, in a few cases, PN. This is confirmed by comparison with radio continuum observations. We find that, as expected for a dusty HII region, the strength of 10.4 µm and radio continuum emission is related. The remaining targets (12%) result in non-detections. While for 63% of our targets we detect only one mid-infrared source, 25% show multiple sources. In these cases, our observations will allow the apportioning of the flux from larger beam measurements between the different sources. Within these multiple source targets, we find some point sources on or near UCHII regions. Our improved astrometric information will allow more accurate targeting of spectroscopy, which will be used to identify unresolved sources in cases where it is not clear whether they are YSOs or evolved stars.

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Section: Comparison With Radio Continuum Observationsmentioning

confidence: 99%

The RMS survey: mid-infrared observations of candidate massive YSOs in the southern hemisphere

Mottram¹,

Hoare²,

Lumsden³

et al. 2007

A&A

106

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“…The latter are derived from the 50σ contour level. It is worth mentioning that using the CO map of Gillespie et al (1979), McBreen et al (1985 estimate a total molecular mass of ∼3.4 × 10 5 M . This estimate is a factor of 3.5 lower than the value quoted in Table 1.…”

Section: Large Scale Co Distributionmentioning

confidence: 99%

“…Adopting a distance of 5 kpc, they derived an overall luminosity of 17.3 × 10 5 L . High-resolution (HPBW ∼ 1 ) far-infrared observations of the region were carried out by McBreen et al (1985) [40-250 μm] and Ghosh et al (1989) [120-300 μm]. McBreen et al (1985) resolved RCW 122 in two sources labelled A and B, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Molecular gas associated with RCW 121 and RCW 122

Arnal

Duronea

Testori

2008

A&A

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Aims. We analyse the distribution of the molecular gas towards the region containing the open cluster Havlen-Moffat 1 (HM 1) the Wolf-Rayet stars WR 87, WR 89, and WR 91, and the star forming regions RCW 121 and RCW 122, with the aim of looking for a possible physical relationship among these objects. Methods. We used the carbon monoxide observations carried out at λ ∼ 2.6 mm with the 4 m NANTEN radiotelescope; new flux density determinations derived from already existing radio continuum surveys at 2. 417, 5, 8.35, and 14.35 GHz; continuum flux density determinations available in the literature; and the Midcourse Space Experiment (MSX) and the Improved Reprocessing of the IRAS Survey (IRIS) databases. Results. Adopting a distance of 5 kpc for RCW 121 and RCW 122, we found a giant molecular cloud (GMC) with a linear extent of ∼100 × 20 pc to be associated with galactic star-forming regions. The total mass of this GMC is of the order of 1.2 × 10 6 solar masses and its mean radial velocity is about -15 km s −1 . Within the GMC there are individual molecular gas concentrations, having total molecular masses in the range from 4.6 × 10 4 M (RCW 122 C) to 2.2 × 10 5 M (RCW 122). The CO profiles observed toward the peak of the molecular concentrations are broad, with typical full-width half-maximum around 6 to 7 km s −1 , and show line asymmetries and/or double-peaked shape that change with the observed position within a given CO concentration. An analysis of the MSX and IRAS databases show that each CO concentration has a strong IR counterpart. The dust temperature of these concentrations range from 46 K (RCW 121) to 76 K (RCW 122 C). Their infrared luminosity are a few times 10 5 L . The new radio continuum flux density determinations are in good agreement with previous determinations at other frequencies, and confirm the thermal nature of RCW 121 and RCW 122. Based on the newly-determined 5 GHz flux density, we found that to power these Hii regions, each of them must harbour a sizable number of O type stars. Under the assumption that all the ionizing stars have a O7 V spectral type, at least ∼8 and ∼4 of these stars would be needed to ionize RCW 122 and RCW 121, respectively.

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“…In this Letter, we report measurements of the 3 P 2 → 3 P 1 transition of 12 Ci at 809341.97 MHz and the F = 5/2−3/2, F = 3/2−1/2, and F = 3/2−3/2 components of the equivalent transition of 13 Ci at 809493.7 MHz, 809125.5 MHz, and 809121.3 MHz, respectively, towards three galactic star-froming regions associated with strong IRAS sources and CO emission: G 333.0-0.4, part of the large H ii complex RCW 106 and associated with a molecular cloud with bright CO lines (Gillespie et al 1977;Brand et al 1984) at a distance of 4.2 kpc (Shaver & Goss 1970); NGC 6334 A, a bright FIR continuum region (McBreen et al 1973) associated with a bright PDR (Burton et al 2000;Kraemer et al 2000) located within a giant molecular cloud at a distance of 1.7 kpc (Neckel 1978); and G 351.6-1.3, a luminous (L bol ≈ 10 6 L ) compact H ii region excited by an embedded O/B cluster (McBreen et al 1983) at a distance of 5 kpc (Radhakrishnan et al 1973). These regions were selected because of strong emission in the 3 P 1 → 3 P 0 transition of 12 Ci at 492 GHz (Huang et al 1999) from a list of 30 candidates of galactic H ii regions having strong CO (Brand et al 1984;Henning & Launhardt 1998) and CS (Bronfman et al 1996;Launhardt et al 1998) emission lines.…”

Section: Introductionmentioning

confidence: 99%

¹³C I in high-mass star-forming clouds

Tieftrunk

Jacobs

Martin

et al. 2001

A&A

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Abstract. We report measurements of the 12 C/ 13 C abundance ratio in the three galactic regions G 333.0-0.4, NGC 6334 A and G 351.6-1.3 from observations of the 12 Ci 3 P2 → 3 P1 transition and the hyperfine components of the corresponding 13 Ci transition near 809 GHz. These transitions were observed simultaneously with the CO 7-6 line emission at 806 GHz with the AST/RO telescope located at the South Pole. From a simultaneous fit to the 12 Ci 3 P2 → 3 P1 transition and the HF components of the corresponding 13 Ci transition and an independent estimate of an upper limit to the optical depth of the 12 Ci emission we determine intrinsic 12 Ci/ 13 Ci column density ratios of 23 ± 1 for G 333.0-0.4, 56 ± 14 for NGC 6334 A and 69 ± 12 for G 351.6-1.3. As the regions observed are photon dominated, we argue that the apparent enhancement in the abundance of 13 C towards G 333.0-0.4 may be due to strong isotope-selective photodissociation of 13 CO, outweighing the effects of chemical isotopic fractionation as suggested by models of PDRs. Towards NGC 6334 A and G 351.6-1.3 these effects appear to be balanced, similar to the situation for the Orion Bar region observed by Keene et al. (1998).

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Far-infrared observations of two southern H II regions - RCW 122 and G 351.6-1.3

Cited by 3 publications

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The RMS survey: mid-infrared observations of candidate massive YSOs in the southern hemisphere

The RMS survey: mid-infrared observations of candidate massive YSOs in the southern hemisphere

Molecular gas associated with RCW 121 and RCW 122

¹³C I in high-mass star-forming clouds

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Far-infrared observations of two southern H II regions - RCW 122 and G 351.6-1.3

Cited by 3 publications

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The RMS survey: mid-infrared observations of candidate massive YSOs in the southern hemisphere

The RMS survey: mid-infrared observations of candidate massive YSOs in the southern hemisphere

Molecular gas associated with RCW 121 and RCW 122

13C I in high-mass star-forming clouds

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¹³C I in high-mass star-forming clouds