A survey of molecular line emission towards ultracompact Hii 
regions

Hatchell, Jennifer; Millar, T. J.; Macdonald, G. H.

doi:10.1051/aas:1998309

Cited by 150 publications

(196 citation statements)

References 24 publications

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“…We also determined the HCO + column density from the column density of H 13 CO + . For this calculation, it was assumed that the carbon-isotope ratio is [ 12 C]/[ 13 C] = 60 (Hatchell et al 1998;Savage et al 2002). This value has been used in several previous studies, e.g., by Bergin et al (1999) in their study of dense cores in Orion (including IRAS 05399) 12 .…”

Section: Notes (A)mentioning

confidence: 99%

A (sub)millimetre study of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2012

A&A

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Context. Studies of dense molecular-cloud cores at (sub)millimetre wavelengths are needed to understand the early stages of star formation. Aims. We aim to further constrain the properties and evolutionary stages of dense cores in Orion B9. The prime objective of this study is to examine the dust emission of the cores near the peak of their spectral energy distributions, and to determine the degrees of CO depletion, deuterium fractionation, and ionisation. Methods. The central part of Orion B9 was mapped at 350 μm with APEX/SABOCA. A sample of nine cores in the region were observed in C 17 O(2−1), H 13 CO + (4−3) (towards 3 sources), DCO + (4−3), N 2 H + (3−2), and N 2 D + (3−2) with APEX/SHFI. These data are used in conjunction with our previous APEX/LABOCA 870-μm dust continuum data. Results. All the LABOCA cores in the region covered by our SABOCA map were detected at 350 μm. The strongest 350 μm emission is seen towards the Class 0 candidate SMM 3. Many of the LABOCA cores show evidence of substructure in the higher-resolution SABOCA image. In particular, we report on the discovery of multiple very low-mass condensations in the prestellar core SMM 6. Based on the 350-to-870 μm flux density ratios, we determine dust temperatures of T dust 7.9−10.8 K, and dust emissivity indices of β ∼ 0.5−1.8. The CO depletion factors are in the range f D ∼ 1.6−10.8. The degree of deuteration in N 2 H + is 0.04−0.99, where the highest value (seen towards the prestellar core SMM 1) is, to our knowledge, the most extreme level of N 2 H + deuteration reported so far. The level of HCO + deuteration is about 1-2%. The fractional ionisation and cosmic-ray ionisation rate of H 2 could be determined only towards two sources with the lower limits of ∼2−6 × 10 −8 and ∼2.6 × 10 −17 −4.8 × 10 −16 s −1 , respectively. We also detected D 2 CO towards two sources. Conclusions. The detected protostellar cores are classified as Class 0 objects, in agreement with our previous SED results. The detection of subcondensations within SMM 6 shows that core fragmentation can already take place during the prestellar phase. The origin of this substructure is likely caused by thermal Jeans fragmentation of the elongated parent core. Varying levels of f D and deuteration among the cores suggest that they are evolving chemically at different rates. A low f D value and the presence of gas-phase D 2 CO in SMM 1 suggest that the core chemistry is affected by the nearby outflow. The very high N 2 H + deuteration in SMM 1 is likely to be remnant of the earlier CO-depleted phase.

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Section: Notes (A)mentioning

confidence: 99%

A (sub)millimetre study of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2012

A&A

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“…Wood et al 1988;Garay et al 1993;Wilner et al 1996;Hatchell et al 1998). This UCHII region presents CH 3 OH and H 2 O maser emission (Codella et al 2004).…”

Section: Introductionmentioning

confidence: 99%

The environs of the ultracompact HII region G45.45+0.06

Paron¹,

Cichowolski²,

Ortega³

2009

A&A

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Aims. G45.45+0.06 is an ultra-compact HII (UCHII) region that has been extensively studied. It is known that G45.45+0.06 is embedded in a complex of UCHII regions, but to date, the surrounding ISM on a larger spatial scale has not been analyzed. Methods. Using data from large-scale surveys, the Two Micron All Sky Survey, GLIMPSE, MIPSGAL, MAGPIS and GRS, we performed a multiwavelength study of a region of about 7 × 7 in the vicinity of G45.45+0.06. Results. We found that the UCHII complex lies on the border of a larger (diameter of ∼3 ) and fainter HII region, which is located at the same distance as G45.45+0.06, ∼8 kpc. In this work, this larger HII region is called G45L. A good morphological correlation is observed between the PDRs and the molecular gas mapped in the 13 CO J = 1−0 and CS J = 2−1 lines, suggesting that G45L may be collecting molecular material. From a near-and mid-IR photometric study, we found three sources, likely O-type stars, that are possibly responsible for the creation of G45L. Additionally, we found several YSO candidates lying preferentially in the molecular shell that surrounds G45L. Our results confirm that the region southeast of the UCHII complex where G45.45+0.06 is embedded and east of G45L is undergoing active star formation. We suggest that G45L has been expanding for about 2 × 10 6 yr and could have triggered the formation of the zero-age main sequence stars that ionize the UCHII region G45.45+0.06. However we cannot discard that both HII regions are coeval.

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“…Comparing these values for a subset of sources for which SO abundances measurements have been made (e.g., Hatchell et al 1998a), generally we find agreement within a factor of a few. Considering the different telescopes and analysis methods employed in these abundance determinations, the agreement is surprisingly good.…”

Section: Discussionmentioning

confidence: 61%

“…Using the H 2 column densities of Hofner et al (2000), Hatchell et al (1998b), and Olmi & Cesaroni (1999) and our SO column densities for 14 sources, we derive SO abundances in the range 0:18 ; 10 À9 Y 4:4 ; 10 À9 . Comparing these values for a subset of sources for which SO abundances measurements have been made (e.g., Hatchell et al 1998a), generally we find agreement within a factor of a few.…”

Section: Discussionmentioning

confidence: 99%

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A Survey of the SO J _K = 1 ₀ –0 ₁ Transition toward Massive Star‐forming Regions

Mateen

Höfner

Araya

2006

ASTROPHYS J SUPPL S

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We present the most extensive survey to date of the SO ground state transition J K ¼ 1 0 Y0 1 (30 GHz). We observed 49 regions of massive star formation with the Max-Planck-Institut für Radioastronomie (MPIf R) 100 m telescope. In addition, the SO J K ¼ 4 3 Y3 2 transition was observed with the IRAM 30 m telescope toward a subsample of seven sources. Emission in the SO J K ¼ 1 0 Y0 1 transition most likely arises from the parsec-scale molecular clumps surrounding ultracompact H ii regions. In general, the SO J K ¼ 1 0 Y0 1 line has a Gaussian shape and appears to be optically thin. We derive SO column densities between 0:58 ; 10 14 and 12 ; 10 14 cm À2 and SO abundances in the range 0:18 ; 10 À9 Y4:4 ; 10 À9 . Our observations show that the SO ground state transition is an effective tool to study massive star-forming clumps, and the data presented in this paper provide a useful supplement for future multitransition SO studies.

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A survey of molecular line emission towards ultracompact Hii regions

Cited by 150 publications

References 24 publications

A (sub)millimetre study of dense cores in Orion B9

A (sub)millimetre study of dense cores in Orion B9

The environs of the ultracompact HII region G45.45+0.06

A Survey of the SO J _K = 1 ₀ –0 ₁ Transition toward Massive Star‐forming Regions

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A survey of molecular line emission towards ultracompact Hii regions

Cited by 150 publications

References 24 publications

A (sub)millimetre study of dense cores in Orion B9

A (sub)millimetre study of dense cores in Orion B9

The environs of the ultracompact HII region G45.45+0.06

A Survey of the SO J K = 1 0 –0 1 Transition toward Massive Star‐forming Regions

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Product

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A Survey of the SO J _K = 1 ₀ –0 ₁ Transition toward Massive Star‐forming Regions