Influence of dust parameters on class II methanol maser pumping

Results of model calculations for class II methanol masers (MMII) are presented. The model of the pumping assumes that an external dust layer provides the source of energy for maser excitation. The dependence of the emergent maser spectrum on the properties of the dust layer is studied. These properties include the chemical composition and sizes of dust grains, the temperature and optical depth of the dust layer. as well as the dilution factor of external dust emission. It is shown that, in order to reproduce the observed patterns of class II methanol maser line ratios, the pumping dust layer should be mostly composed of silicate grains with sizes smaller than 0.01 μ. It is shown that the layer of warm (> 125 K) dust effectively pumps the strongest MMII transitions over a wide range of 30 μ dust opacities (0.01–2) and dilution factors (0.02–0.5).

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The evolutionary status of protostellar clumps hosting class II methanol masers

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa233 ◽

2020 ◽

Vol 493 (2) ◽

pp. 2015-2041 ◽

Cited By ~ 1

Author(s):

B M Jones ◽

G A Fuller ◽

S L Breen ◽

A Avison ◽

J A Green ◽

...

Keyword(s):

Galactic Plane ◽

Dust Emission ◽

Principal Component ◽

Far Infrared ◽

Class Ii ◽

Young Stellar Objects ◽

Galactic Centre ◽

Evolutionary Status ◽

Methanol Maser ◽

Methanol Masers

ABSTRACT The Methanol MultiBeam survey (MMB) provides the most complete sample of Galactic massive young stellar objects (MYSOs) hosting 6.7 GHz class II methanol masers. We characterize the properties of these maser sources using dust emission detected by the Herschel Infrared Galactic Plane Survey (Hi-GAL) to assess their evolutionary state. Associating 731 (73 per cent) of MMB sources with compact emission at four Hi-GAL wavelengths, we derive clump properties and define the requirements of an MYSO to host a 6.7 GHz maser. The median far-infrared (FIR) mass and luminosity are 630 M⊙ and 2500 L⊙ for sources on the near side of Galactic centre and 3200 M⊙ and 10000 L⊙ for more distant sources. The median luminosity-to-mass ratio is similar for both at ∼4.2 L⊙ M⊙−1. We identify an apparent minimum 70 μm luminosity required to sustain a methanol maser of a given luminosity (with $L_{70} \propto L_{6.7}\, ^{0.6}$). The maser host clumps have higher mass and higher FIR luminosities than the general Galactic population of protostellar MYSOs. Using principal component analysis, we find 896 protostellar clumps satisfy the requirements to host a methanol maser but lack a detection in the MMB. Finding a 70 μm flux density deficiency in these objects, we favour the scenario in which these objects are evolved beyond the age where a luminous 6.7 GHz maser can be sustained. Finally, segregation by association with secondary maser species identifies evolutionary differences within the population of 6.7GHz sources.

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A blind survey of the 6.7 GHz methanol maser line

Symposium - International Astronomical Union ◽

10.1017/s0074180900222262 ◽

2002 ◽

Vol 206 ◽

pp. 143-146

Author(s):

Marian Szymczak ◽

Andrzej J. Kus ◽

Grzegorz Hrynek

Keyword(s):

Grid Point ◽

Hii Regions ◽

Triangular Grid ◽

Average Sensitivity ◽

Grid Pattern ◽

Methanol Maser ◽

Peak Flux ◽

Maser Line ◽

Methanol Masers ◽

Ultracompact Hii

A blind survey for 6.7GHz methanol maser emission has been made with the 32 m Toruń radio telescope. The survey consists of 4,800 spectra on an equilateral triangular grid pattern with each grid point separated by 4.4 covering a field of ∼21 deg2 at galactic longitudes 20° to 40° and galactic latitudes ±0°52. The average sensitivity was 1.6 Jy and the spectral resolution was 0.04kms−1. A total of 99 sources were detected, 28 of which were not found during previous searches of IRAS-selected ultracompact HII regions. The peak flux density of new detections is usually lower than 30 Jy. About half of the methanol masers have no IRAS counterparts within a radius of 2. The nature of these sources is unclear.

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Zeeman Effect Observations in Class I Methanol Masers

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319003910 ◽

2018 ◽

Vol 14 (A30) ◽

pp. 140-140

Author(s):

Emmanuel Momjian ◽

Anuj P. Sarma

Keyword(s):

Zeeman Effect ◽

Linear Structure ◽

Class I ◽

Star Forming ◽

Methanol Maser ◽

Star Forming Regions ◽

Splitting Factor ◽

Maser Line ◽

Methanol Masers ◽

Expected Values

AbstractWe report the detection of the Zeeman effect in the 44 GHz Class I methanol maser line toward the star forming region DR21W. The 44 GHz methanol masers in this source occur in a ∼3” linear structure that runs from northwest to southeast, with the two dominant components at each end, and several weaker maser components in between. Toward a 93 Jy maser in the dominant northwestern component, we find a significant Zeeman detection of −23.4 ± 3.2 Hz. If we use the recently published result of Lankhaar et al. (2018) that the F=5-4 hyperfine transition is responsible for the 44 GHz methanol maser line, then their value of z = −0.92 Hz mG−1 yields a line-of-sight magnetic field of Blos =25.4 ± 3.5 mG. If Class I methanol masers are pumped in high density regions with n∼107–8 cm−3, then magnetic fields in these maser regions should be a few to several tens of mG. Therefore, our result in DR21W is certainly consistent with the expected values.Using the above noted splitting factor in past Zeeman effect detections in Class I methanol masers reported by Sarma & Momjian (2011) and Momjian & Sarma (2017) in the star forming regions OMC-2 and DR21(OH) result in Blos values of 20.0 ± 1.2 mG and 58.2 ± 2.9 mG, respectively. These are also consistent with the expected values.

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A Sensitive Search for Predicted Methanol Maser Transitions with the Australia Telescope Compact Array

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2016.48 ◽

2016 ◽

Vol 33 ◽

Cited By ~ 3

Author(s):

A. Chipman ◽

S. P. Ellingsen ◽

A. M. Sobolev ◽

D. M. Cragg

Keyword(s):

Star Formation ◽

Class Ii ◽

High Mass ◽

Mass Star ◽

Radio Telescopes ◽

Methanol Maser ◽

Upper Limit ◽

Methanol Masers ◽

Star Formation Regions ◽

Compact Array

AbstractWe have used the Australia Telescope Compact Array to search for a number of centimetre wavelength methanol transitions which are predicted to show weak maser emission towards star formation regions. Sensitive, high spatial, and spectral resolution observations towards four high-mass star formation regions which show emission in a large number of class II methanol maser transitions did not result in any detections. From these observations, we are able to place an upper limit of ≲ 1300 K on the brightness temperature of any emission from the 31A+–31A−, 17−2–18−3 E (vt = 1), 124–133 A−, 124–133 A+, and 41A+–41A− transitions of methanol in these sources on angular scales of 2 arcsec. This upper limit is consistent with current models for class II methanol masers in high-mass star formation regions and better constraints than those provided here will likely require observations with next-generation radio telescopes.

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44 GHz Methanol Maser Surveys

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312006795 ◽

2012 ◽

Vol 8 (S287) ◽

pp. 133-140

Author(s):

S. E. Kurtz

Keyword(s):

Star Formation ◽

Formation Process ◽

Class Ii ◽

Class I ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Methanol Maser ◽

Star Forming Regions ◽

Methanol Masers

AbstractClass I 44 GHz methanol masers are not as well-known, as common, or as bright as their more famous Class II cousins at 6.7 and 12.2 GHz. Nevertheless, the 44 GHz masers are commonly found in high-mass star forming regions. At times they appear to trace dynamically important phenomena; at other times they show no obvious link to the star formation process. Here, we summarize the major observational efforts to date, including both dedicated surveys and collateral observations. The principal results are presented, some that were expected, and others that were unexpected.

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Exploring the Nature of MMB sources: A Search for Class I Methanol Masers and their Outflows

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318000698 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 317-318

Author(s):

Nichol Cunningham ◽

Gary Fuller ◽

Adam Avison ◽

Shari Breen

Keyword(s):

Massive Star ◽

Class Ii ◽

Class I ◽

Star Forming ◽

Methanol Maser ◽

Star Forming Regions ◽

Methanol Masers ◽

Initial Results ◽

Maser Sources

AbstractWe present the initial results from a class I 44-GHz methanol maser follow-up survey, observed with the MOPRA telescope, towards 272 sources from the Methanol Multi-beam survey (MMB). Over half (∼60%) of the 6.7 GHz class II MMB maser sources are associated with a class I 44-GHz methanol maser at a greater than 5σ detection level. We find that class II MMB masers sources with an associated class I methanol maser have stronger peak fluxes compared to regions without an associated class I maser. Furthermore, as part of the MOPRA follow-up observations we simultaneously observed SiO emission which is a known tracer of shocks and outflows in massive star forming regions. The presence of SiO emission, and potentially outflows, is found to be strongly associated with the detection of class I maser emission in these regions.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307012677 ◽

2007 ◽

Vol 3 (S242) ◽

pp. 125-129

Author(s):

S. N. Longmore ◽

M. G. Burton ◽

P. J. Barnes ◽

T. Wong ◽

C. R. Purcell ◽

...

Keyword(s):

Massive Star ◽

Class Ii ◽

Dynamic State ◽

Continuum Emission ◽

Molecular Gas ◽

Maser Emission ◽

Star Forming ◽

Methanol Maser ◽

Methanol Masers

AbstractMethanol maser emission has proven to be an excellent signpost of regions undergoing massive star formation (MSF). To investigate their role as an evolutionary tracer, we have recently completed a large observing program with the ATCA to derive the dynamical and physical properties of molecular/ionised gas towards a sample of MSF regions traced by 6.7GHz methanol maser emission. We find that the molecular gas in many of these regions breaks up into multiple sub-clumps which we separate into groups based on their association with/without methanol maser and cm continuum emission. The temperature and dynamic state of the molecular gas is markedly different between the groups. Based on these differences, we attempt to assess the evolutionary state of the cores in the groups and thus investigate the role of class II methanol masers as a tracer of MSF.

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0″.4 BIMA Array Mapping of the 107 GHz Methanol Maser in W3(OH)

International Astronomical Union Colloquium ◽

10.1017/s0252921100046029 ◽

1998 ◽

Vol 164 ◽

pp. 379-380

Author(s):

V. I. Slysh ◽

I. E. Val’tts ◽

S. V. Kalenskii ◽

G. M. Larionov ◽

L. G. Mundy

Keyword(s):

Brightness Temperature ◽

Lower Limit ◽

Angular Resolution ◽

Class Ii ◽

Methanol Maser ◽

H Ii Region ◽

Methanol Masers

AbstractUsing A-configuration of the BIMA-array with 0″.4 angular resolution maps were obtained of the 107 GHz methanol line in W3(OH). The 107 GHz masers have their counterparts in another methanol transition at 6.7 GHz. The strongest maser spots are unresolved with the BIMA-array and are less than , which corresponds to the lower limit of the brightness temperature 5×105 K. A model of Class II methanol masers emitted in the extended atmosphere of icy planets orbiting around the O-star which excites H ɪɪ region is proposed.

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Models of class II methanol masers

Symposium - International Astronomical Union ◽

10.1017/s0074180900222353 ◽

2002 ◽

Vol 206 ◽

pp. 179-182 ◽

Cited By ~ 1

Author(s):

Andrej M. Sobolev ◽

Andrei B. Ostrovskii ◽

Alexey V. Malyshev ◽

Dinah M. Cragg ◽

Peter D. Godfrey ◽

...

Keyword(s):

Observational Data ◽

Class Ii ◽

Physical Parameters ◽

Observational Constraints ◽

Line Profiles ◽

Future Studies ◽

Methanol Maser ◽

Methanol Masers

Current models of class II methanol masers are able to describe the brightnesses of the strongest masers and provide a basis for explaining observed line ratios. Determination of the physical parameters in the source requires observational data in many maser transitions. In order to provide observational constraints for models we searched for and detected 7 new methanol masers. This allowed us to constrain the physical parameters of the 3 sources with the greatest number of detected methanol maser lines: W3(OH), NGC6334F, and G345.01 + 1.79. The models accurately account for the fluxes of the bulk of the detected maser lines. Remaining discrepancies most probably reflect the fact that the most prominent components of the different maser lines are formed under different conditions. This is supported by comparison of the line profiles. We outline directions for future studies in the field.

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