H2O Masers in the Galactic Plane. II. Longitudes 260° to 326°

Caswell, J. L.; Batchelor, R.; Forster, J. R.; Wellington, K. J.

doi:10.1071/ph890331

Cited by 40 publications

(59 citation statements)

References 6 publications

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“…Two water masers have been reported (Braz & Epchtein 1983;Caswell et al 1989) as well as a class II methanol maser (Chan et al 1996;Walsh et al 1997). Associated with the water masers, CS emission has been found (Zinchenko et al 1995) with an estimated mass of 1320 M .…”

Section: Rcw 34mentioning

confidence: 98%

Sequential Star Formation in RCW 34: A Spectroscopic Census of the Stellar Content of High-Mass Star-Forming Regions

Bik

Puga

Waters

et al. 2010

ApJ

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In this paper, we present VLT/SINFONI integral field spectroscopy of RCW 34 along with Spitzer/IRAC photometry of the surroundings. RCW 34 consists of three different regions. A large bubble has been detected in the IRAC images in which a cluster of intermediate-and low-mass class II objects is found. At the northern edge of this bubble, an H ii region is located, ionized by 3 OB stars, of which the most massive star has spectral type O8.5V. Intermediate-mass stars (2-3 M ) are detected of G-and K-spectral type. These stars are still in the premain-sequence (PMS) phase. North of the H ii region, a photon-dominated region is present, marking the edge of a dense molecular cloud traced by H 2 emission. Several class 0/I objects are associated with this cloud, indicating that star formation is still taking place. The distance to RCW 34 is revised to 2.5 ± 0.2 kpc and an age estimate of 2 ± 1 Myr is derived from the properties of the PMS stars inside the H ii region. Between the class II sources in the bubble and the PMS stars in the H ii region, no age difference could be detected with the present data. The presence of the class 0/I sources in the molecular cloud, however, suggests that the objects inside the molecular cloud are significantly younger. The most likely scenario for the formation of the three regions is that star formation propagated from south to north. First the bubble is formed, produced by intermediate-and low-mass stars only, after that, the H ii region is formed from a dense core at the edge of the molecular cloud, resulting in the expansion similar to a champagne flow. More recently, star formation occurred in the rest of the molecular cloud. Two different formation scenarios are possible. (1) The bubble with the cluster of low-and intermediate-mass stars triggered the formation of the O star at the edge of the molecular cloud, which in its turn induces the current star formation in the molecular cloud. (2) An external triggering is responsible for the star formation propagating from south to north.

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Section: Rcw 34mentioning

confidence: 98%

Sequential Star Formation in RCW 34: A Spectroscopic Census of the Stellar Content of High-Mass Star-Forming Regions

Bik

Puga

Waters

et al. 2010

ApJ

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“…These results are consistent with the literature values provided by P11 and N02 (log 10 N H 2 ∼ 22.6-23 cm −2 ), as well as with the density values found for the star-formation activity at the edges of H ii regions (Urquhart et al 2009). The strong radiation front generated by NGC 3603 YC is likely ionizing the MM1 and MM2 pillar heads, which in turn are the sites of strong star-formation processes (P11, NS03), as also supported by the methanol and water maser emissions (Caswell et al 1989;de Pree et al 1999).…”

Section: Temperature and Density Mapsmentioning

confidence: 99%

HERSCHELFAR-IR OBSERVATIONS OF THE GIANT H II REGION NGC 3603

Cecco

Faustini

Paresce

et al. 2015

ApJ

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We observed the giant H ii region around the NGC 3603 YC with the five broad bands (70, 160, 250, 350, 500 μm) of the SPIRE and PACS instruments, on board the Herschel Space Observatory. Together with what is currently known of the stellar, atomic, molecular, and warm dust components, this additional and crucial information should allow us to better understand the details of the star-formation history in this region. The main objective of the investigation is to study, at high spatial resolution, the distribution and main physical characteristics of the cold dust. By reconstructing the temperature and density maps, we found, respectively, a mean value of 36 K and log 10 N H = 22.0 ± 0.1 cm −2 . We carried out a photometric analysis detecting 107 point-like sources, mostly confined to the north and south of the cluster. By comparing our data with spectral energy distribution models, we found that 35 sources are well represented by young stellar objects in early evolutionary phases, from Class 0 to Class I. The Herschel detections also provided far-IR counterparts for 4 H 2 O masers and 11 objects previously known from mid-IR observations. The existence of so many embedded sources confirms the hypothesis of intense and ongoing star-formation activity in the region around NGC 3603 YC.

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“…The final known site, M9 (G291.284-0.716), exhibits a single intense maser at a velocity of −130 km s −1 and with a linewidth of 4.8 km s −1 . We measure an intensity of 670 Jy in contrast to the earlier value of 945 Jy (Caswell et al 1989), perhaps reflecting a real decrease in the intensity over the intervening time. We note that this maser feature falls on the edge of our bandpass, which may make the flux density measurement unreliable.…”

Section: H 2 O Masersmentioning

confidence: 99%

Multi-generation massive star-formation in NGC 3576

Purcell

Minier

Longmore

et al. 2009

A&A

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Context. Recent 1.2-mm continuum observations have shown the giant H II region NGC 3576 to be embedded in the centre of an extended filamentary dust-cloud. The bulk of the filament away from the H II region contains a number of clumps seen only at (sub-)millimetre wavelengths. Infrared and radio observations of the central star cluster have uncovered evidence of sequential starformation leading us to believe that the adjacent clumps may host massive protostellar objects at a very early stage of evolution. Aims. We have investigated the physical and chemical conditions in the dusty clumps with the goal of characterising their star-forming content. Methods. We have used the Australia Telescope Compact Array (ATCA) to image the cloud for the NH 3 (1,1), (2,2) and (4,4) transitions, 22 GHz H 2 O masers, and 23 GHz continuum emission. The 70-m Tidbinbilla dish was used to estimate the total integrated intensity of NH 3 . We also utilised the 22-m Mopra antenna to map the region for the molecular lines 13 CO (1 -0), C 18 O (1 -0), HCO + (1 -0), H 13 CO + (1 -0), CS (1 -0) and N 2 H + (1 -0). Results. Emission from dense molecular gas follows the morphology of the 1.2-mm dust emission, except towards the central ionised region. The H II region is observed to be expanding into the molecular cloud, sweeping up a clumpy shell of gas, while the central star cluster is dispersing the molecular gas to the east. Analysis of the NH 3 data indicates that temperature and linewidth gradients exist in the western arm of the filament. Temperatures are highest adjacent to the central H II region, indicating that the embedded cluster of young stars there is heating the gas. Six new H 2 O masers were detected in the arms of the filament, all associated with NH 3 emission peaks, confirming that star-formation has begun within these cores. Core masses range from 5 to 516 M and most appear to be gravitationally bound. Complementary results by André et al. (2008) imply that seven cores will go on to form massive stars between 15 and 50 M . The large scale velocity structure of the filament is smooth, but at least one clump shows the signature of inward gas motions via asymmetries in the NH 3 (1,1) line profiles. The same clump exhibits an enhanced abundance of N 2 H + , which coupled with an absence of CO indicates depletion onto the dust grain surface. Conclusions. The HII region at the heart of NGC 3576 is potentially triggering the formation of massive stars in the bulk of the associated cloud.

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H2O Masers in the Galactic Plane. II. Longitudes 260° to 326°

Cited by 40 publications

References 6 publications

Sequential Star Formation in RCW 34: A Spectroscopic Census of the Stellar Content of High-Mass Star-Forming Regions

Sequential Star Formation in RCW 34: A Spectroscopic Census of the Stellar Content of High-Mass Star-Forming Regions

HERSCHELFAR-IR OBSERVATIONS OF THE GIANT H II REGION NGC 3603

Multi-generation massive star-formation in NGC 3576

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