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:
– 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
+ = 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
Great Barriers in High-Mass Star Formation
13-17 September 2010
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
Methanol
Maser
pumping
models
Cragg et
al. (2005)
Great Barriers in High-Mass Star Formation
13-17 September 2010
EGOs
Methanol masers - Science
water
OH
• What can you do with multiple coincident
class II methanol
6.7 GHz
maser transitions?
12.2 GHz
II
– Determine the physical conditionsUCH
at very
high
resolution, by modeling the
observed
ratio of
class
I methanol
the different transitions.
0
1
2
3
4
4
Relative lifetime (x 10 years)
5
– Utilize the presence/absence of different
transitions as an evolutionary clock.
107 GHz methanol masers with ALMA
Methanol
masers in A+
rotational
subspecies :
Class I
Class II
Figure
courtesy of
Maxim
Voronkov.
107 GHz methanol masers with ALMA
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
Caswell et al. (2000)
107 GHz methanol masers with ALMA
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
Conclusions
• ALMA observations of 107 GHz methanol
will allow us to
– Constrain the physical conditions in the masing
regions.
– Constrain evolutionary maser-based clocks.
- “close the loop” on the class II methanol
masers.
107 GHz methanol masers with ALMA