Three new H2O masers in the vicinity of NGC 6357 and NGC 6334

Sakellis, S.; Taylor, Morgan; Taylor, Keith; Vaile, R. A.; Han, Tao

doi:10.1086/131375

Cited by 9 publications

(7 citation statements)

References 3 publications

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“…It flared from a peak of 35 Jy in 2003 to 700 Jy in 2004. It appears to be the same maser that was first reported by Sakellis et al (1984) with a peak flux density of 346 Jy. The first source is solitary with no other maser counterpart and offset by more than 40 arcsec.…”

Section: Individual Sourcessupporting

confidence: 76%

Water masers accompanying OH and methanol masers in star formation regions

Breen¹,

Caswell²,

Ellingsen³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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The Australia Telescope Compact Array has been used to measure positions with arcsecond accuracy for 379 masers at the 22-GHz transition of water. The principal observation targets were 202 OH masers of the variety associated with star formation regions (SFRs) in the Southern Galactic plane. At a second epoch, most of these targets were observed again, and new targets of methanol masers were added. Many of the water masers reported here are new discoveries and others had been reported, with position uncertainties exceeding 10 arcsec, from Parkes telescope single-dish observations many years ago.Variability in the masers is often acute, with very few features directly corresponding to those discovered two decades ago. Within our current observations, less than a year apart, spectra are often dissimilar, but positions at the later epoch, even when measured for slightly different features, mostly correspond to the detected maser site measured earlier, to within the typical extent of the whole site, of a few arcseconds.The precise water positions show that approximately 79 per cent (160 of 202) of the OH maser sites show coincident water maser emission, the best estimate yet obtained for this statistic; however, there are many instances where additional water sites are present offset from the OH target, and consequently less than half of the water masers coincide with a 1665-MHz ground-state OH maser counterpart. Our less uniform sample of methanol targets is not suitable for a full investigation of their association with water masers, but we are able to explore differences between the velocities of peak emission from the three species and quantify the typically larger deviations shown by water maser peaks from systemic velocities.Clusters of two or three distinct but nearby sites, each showing one or several of the principal molecular masing transitions, are found to be common. We also report the detection of ultracompact H II regions towards some of the sites. In combination with an investigation of correlations with IR sources from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) catalogue, these comparative studies allow further progress in the use of the maser properties to assign relative evolutionary stages in star formation to individual sites.

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Section: Individual Sourcessupporting

confidence: 76%

Water masers accompanying OH and methanol masers in star formation regions

Breen¹,

Caswell²,

Ellingsen³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…It contains a single O5 star, and several B stars and embedded IR sources, but no indication of current star formation can be found (Felli et al 1990;Massi et al 1997). G353.2+0.7, which is also a FIR peak, does not contain early-type stars (Felli et al 1990;Massi et al 1997), but it hosts the only water maser found in NGC 6357 (Sakellis et al 1984). However, Persi et al (1986) identifies this water maser source as an evolved late M star.…”

Section: Observational Overview Of Ngc 6357 and Pismis 24mentioning

confidence: 99%

An X‐Ray Census of Young Stars in the Massive Southern Star‐forming Complex NGC 6357

Wang

Townsley

Feigelson

et al. 2007

ASTROPHYS J SUPPL S

140

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We present the first high spatial resolution X-ray study of the massive star-forming region NGC 6357, obtained in a 38 ks Chandra/ACIS observation. Inside the brightest constituent of this large H ii region complex is the massive open cluster Pismis 24. It contains two of the brightest and bluest stars known, yet remains poorly studied; only a handful of optically bright stellar members have been identified. We investigate the cluster extent and initial mass function and detect $800 X-ray sources with a limiting sensitivity of $10 30 ergs s À1 ; this provides the first reliable probe of the rich intermediate-mass and low-mass population of this massive cluster, increasing the number of known members from optical study by a factor of $50. The high-luminosity end ( log L h ½2Y8 keV ! 30:3 ergs s À1 ) of the observed X-ray luminosity function in NGC 6357 is clearly consistent with a power-law relation as seen in the Orion Nebula Cluster and Cepheus B, yielding the first estimate of NGC 6357's total cluster population, a few times the known Orion population. We investigate the structure of the cluster, finding small-scale substructures superposed on a spherical cluster with 6 pc extent, and discuss its relationship to the nebular morphology. The long-standing L X À 10 À7 L bol correlation for O stars is confirmed. Twenty-four candidate O stars and one possible new obscured massive YSO or Wolf-Rayet star are presented. Many cluster members are estimated to be intermediate-mass stars from available infrared photometry (assuming an age of $1 Myr), but only a few exhibit K-band excess. We report the first detection of X-ray emission from an evaporating gaseous globule at the tip of a molecular pillar; this source is likely a B0YB2 protostar.

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“…A water maser discovered in the star formation region NGC 6357 showed strong emission centred at velocity −52 km s −1 (Sakellis et al 1984). We will refer to it by its Galactic coordinates as 353.273+0.641.…”

Section: Introductionmentioning

confidence: 99%

Water maser 353.273+0.641, the prime example of a class dominated by a blueshifted outflow

Caswell¹,

Phillips²

2008

Monthly Notices RAS

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The Galactic site 353.273+0.641 shows maser emission at both the 22-GHz transition of water and the 6.668-GHz transition of methanol. We argue that the methanol maser establishes the site as most likely a newly forming massive star, and the narrow velocity range of this emission establishes a reliable systemic velocity. The water maser shows weak emission at this systemic velocity and much stronger emission at a velocity blueshifted by 50 km s −1 . It is a second excellent example (joining 291.270−0.719) of what must now be regarded as an emerging distinct class of massive young stellar objects showing dominant blueshifted water maser outflows. We also present new data for 351.243+0.671 that strengthen its claim to be yet another member. There appears to be no complementary class of water maser dominated by redshifted outflows. The mechanism that favours dominant blueshifted outflows in preference to redshifted outflows needs further exploration.

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Three new H2O masers in the vicinity of NGC 6357 and NGC 6334

Cited by 9 publications

References 3 publications

Water masers accompanying OH and methanol masers in star formation regions

Water masers accompanying OH and methanol masers in star formation regions

An X‐Ray Census of Young Stars in the Massive Southern Star‐forming Complex NGC 6357

Water maser 353.273+0.641, the prime example of a class dominated by a blueshifted outflow

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