The molecular environment of massive star forming cores associated with Class II methanol maser emission

Longmore, S. N.; Burton, M. G.; Barnes, Peter J.; Wong, Tony; Purcell, Cormac; Ott, J.

doi:10.1017/s1743921307012677

Cited by 3 publications

(3 citation statements)

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“…It can be used to probe the physical conditions of the molecular cloud in which cores are forming and can be used to determine physical conditions of the gas, such as temperature, density and optical depth (cf. Longmore et al 2006). Intriguingly, Longmore et al (these proceedings) report observations where the youngest star formation regions in their sample are devoid of methanol maser emission, traced solely by their NH 3 emission.…”

Section: Future Workmentioning

confidence: 97%

Profiling young massive stars

et al. 2007

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Abstract. We present the results of spectral energy distribution analysis for 162 of the 405 sources reported in the SIMBA survey of . The fits reveal source specific parameters including: the luminosity, mass, temperature, H2 number density, the surface density and the luminosity-to-mass ratio. Each of these parameters are examined with respect to the four classes of source present in the sample. Obvious luminosity and temperature distinctions exist between the mm-only cores and those cores with methanol maser and/or radio continuum emission, with the former cooler and less luminous than the latter. The evidence suggests that the mm-only cores are a precursor to the methanol maser in the formation of massive stars. The mm-only cores comprise two distinct populations distinguished by temperature. Analysis and conclusions about the nature of the cool-mm and warm-mm cores comprising the mm-only population are drawn.

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Section: Future Workmentioning

confidence: 97%

Profiling young massive stars

et al. 2007

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“…Subsequent multiwavelength studies have since derived the large-scale properties (mass, chemical composition, temperature, etc.) of these star-forming cores using the Swedish-ESO 15 m Submillimeter Telescope (SEST), Mopra and Australia Telescope Compact Array (ATCA) telescopes (Hill et al 2005;Purcell et al 2006Purcell et al , 2009Longmore et al 2007bLongmore et al , 2008 and performed a census of the (proto-) stellar populations at infrared wavelengths (Longmore et al 2006(Longmore et al , 2007c. In L07, we selected 21 regions for further study, all of which contained methanol maser emission detected by WBHR98.…”

Section: Introductionmentioning

confidence: 99%

Too large and overlooked? Extended free-free emission towards massive star formation regions

Longmore

Burton

Keto

et al. 2009

Monthly Notices of the Royal Astronomical Society

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We present Australia Telescope Compact Array observations towards six massive star formation regions, which, from their strong 24 GHz continuum emission but no compact 8 GHz continuum emission, appeared good candidates for hypercompact H ii regions. However, the properties of the ionized gas derived from the 19 to 93 GHz continuum emission and H70α+ H57α radio recombination line data show the majority of these sources are, in fact, regions of spatially extended, optically thin free–free emission. These extended sources were missed in the previous 8 GHz observations due to a combination of spatial filtering, poor surface brightness sensitivity and primary beam attenuation. We consider the implications that a significant number of these extended H ii regions may have been missed by previous surveys of massive star formation regions. If the original sample of 21 sources is representative of the population as a whole, the fact that six contain previously undetected extended free–free emission suggests a large number of regions have been mis‐classified. Rather than being very young objects prior to UCH ii region formation, they are, in fact, associated with extended H ii regions and thus significantly older. In addition, inadvertently ignoring a potentially substantial flux contribution (up to ∼0.5 Jy) from free–free emission has implications for dust masses derived from sub‐mm flux densities. The large spatial scales probed by single‐dish telescopes, which do not suffer from spatial filtering, are particularly susceptible and dust masses may be overestimated by up to a factor of ∼2.

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“…The cores in the top and middle plots are well fit by a single temperature model but the single temperature approximation is NH 3 (1,1) linewidths as a reliable indicator of how quiescent the gas is, without worrying about its dependence on the core size (Larson 1981). Figure 4 [from Longmore et al (2007b)] shows NH 3 (1,1) core linewidth vs kinetic temperature. Triangles and crosses show sources with/without methanol maser emission, respectively.…”

Section: Discussionmentioning

confidence: 98%

Determining the relative evolutionary stages of very young massive star formation regions

Longmore,

Burton,

Purcell

et al. 2007

Preprint

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We have recently completed an observing program with the Australia Telescope Compact Array towards massive star formation regions traced by 6.7 GHz methanol maser emission. We found the molecular cores could be separated into groups based on their association with/without methanol maser and 24 GHz continuum emission. Analysis of the molecular and ionised gas properties suggested the cores within the groups may be at different evolutionary stages. In this contribution we derive the column densities and temperatures of the cores from the NH 3 emission and investigate if this can be used as an indicator of the relative evolutionary stages of cores in the sample.The majority of cores are well fit using single-temperature large velocity gradient models, and exhibit a range of temperatures from ∼10 K to >200 K. Under the simple but reasonable assumption that molecular gas in the cores will heat up and become less quiescent with age due to feedback from the powering source(s), the molecular gas kinetic temperature combined with information of the core kinematics seems a promising probe of relative core age in the earliest evolutionary stages of massive star formation.

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The molecular environment of massive star forming cores associated with Class II methanol maser emission

Cited by 3 publications

References 7 publications

Profiling young massive stars

Profiling young massive stars

Too large and overlooked? Extended free-free emission towards massive star formation regions

Determining the relative evolutionary stages of very young massive star formation regions

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