107/108 GHz methanol masers with ALMA

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107/108 GHz methanol masers with ALMA Simon Ellingsen University of Tasmania

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107/108 GHz methanol masers with ALMA. Simon Ellingsen University of Tasmania. Methanol masers – what and where. Methanol masers are empirically divided into two groups: - PowerPoint PPT Presentation

Transcript of 107/108 GHz methanol masers with ALMA

Page 1: 107/108 GHz methanol masers with ALMA

107/108 GHz methanol masers with ALMA

Simon EllingsenUniversity of Tasmania

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Methanol masers – what and where

• Methanol masers are empirically divided into two groups:– Class I masers are associated with outflows and low velocity

shocks, they are collisionally pumped. Strong transitions at 36, 44, 95, 229 GHz.

– Class II masers are exclusively associated with the environment close to very young high-mass stars, they are radiatively pumped. Strong transitions at 6, 12, 107 GHz.

• You frequently find class I and II methanol masers associated with the same object, but not coincident.

• Often multiple class II (or class I) methanol transitions are observed to be coincident spatially and in velocity.

107 GHz methanol masers with ALMA

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Great Barriers in High-Mass Star Formation 13-17 September 2010

+ = 6.7 GHz methanol masers

+ = OH masers

+ = water masers

Green contours = 95 GHz methanol

Black contours = 3cm continuum.

Blue = 3.6 μm

Green = 4.5 μm

Red = 8.0 μm

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Methanol masers - Science

• What can you do with multiple coincident maser transitions?– Determine the physical conditions at very high

resolution, by modeling the observed ratio of the different transitions.

– Utilize the presence/absence of different transitions as an evolutionary clock.

107 GHz methanol masers with ALMA

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Great Barriers in High-Mass Star Formation 13-17 September 2010

Methanol Maser pumping models

Cragg et al. (2005)

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Methanol masers - Science

• What can you do with multiple coincident maser transitions?– Determine the physical conditions at very high

resolution, by modeling the observed ratio of the different transitions.

– Utilize the presence/absence of different transitions as an evolutionary clock.

107 GHz methanol masers with ALMA

water

class I methanol

class II methanol

UCHII

OH

10 2 3 4 5Relative lifetime (x 104 years)

6.7 GHz12.2 GHz

EGOs

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Methanol masers in A+ rotational subspecies :Class IClass II

Figure courtesy of Maxim Voronkov.

107 GHz methanol masers with ALMA

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Low-hanging fruit• The 107 GHz (31-40 A+) methanol

masers are direct analogues of the 6.7 GHz (51-60 A+).

• Approximately 25 107 GHz masers have been detected in previous single-dish searches (e.g. Caswell et al. 2000).

• These look like ideal targets for cycle 0 science :– Intense– Compact– Low frequency

107 GHz methanol masers with ALMA

Caswell et al. (2000)

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Class I masers

• There are a number of relatively strong and common class I transitions in band 3 (84 GHz and 95 GHz).

• Also the 229 GHz transition falls within band 6.

• These are more spatially distributed and may be better targets for later cycles.

107 GHz methanol masers with ALMA

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Conclusions

• ALMA observations of 107 GHz methanol will allow us to– Constrain the physical conditions in the masing

regions.– Constrain evolutionary maser-based clocks.

107 GHz methanol masers with ALMA

- “close the loop” on the class II methanol masers.