Class I methanol masers and shocks Max Voronkov Software Scientist – ASKAP In collaboration with: Caswell J.L., Ellingsen S.P., Britton T.R., Green J.A., Sobolev A.M. 8 July 2010

Introduction: two classes of methanol masers Class I methanol (CH3OH) masers Collisional excitation (e.g. by shocks) Regions of star formation (possibly low-mass ones as well) Usually offset from YSOs (up to a parsec) Many maser spots scattered over tens of arcsec Widespread masers: 36, 44, 84, 95 GHz Rare/weak: 9.9, 23.4, series at 25, 104.3 GHz Class II methanol (CH3OH) masers Radiational excitation (by infrared from YSO) Regions of high mass star formation only Located at the nearest vicinity of YSOs Usually just one maser spot at the arcsec scale Widespread masers: 6.7, 12 GHz Rare/weak: 19.9, 23, 85/86, 37/38, 107, 108 GHz Subject of this talk

Class I methanol masers in outflows

G309.38-0.13: high-velocity feature at 36 GHz Background: Spitzer IRAC data Red: 8.0 µm, green: 4.5 µm, blue: 3.6 µm Excess of 4.5 µm may be a signature of Shocks (Extented Green Objects) Red contours: peak of the 36 GHz emission in the cube Circles/crosses: maser spots Garay et al. (2002): to increase CH3OH abundance shocks have to be mild (shock velocities not much more than 10 km/s interaction with moving gas)

Search for 9.9 GHz methanol masers These masers need higher than average temperatures and densities to form This is one of the rare class I masers Only two sources were known prior to this work Two new detections out of 48 targets observed Detection limits as low as 0.1 Jy ATCA observations (pre-CABB) 6A and 6C arrays Continuum at 8.6 GHz as a by-product Spectral resolution 0.12 km/s Obtained absolute positions for masers

Sources detected at 9.9 GHz Grayscale: 4.5 µm (above) and NH3 (below) (Ho et al. 1986; Garay et al. 1998) Crosses: 9.9 GHz masers Circles: 6.7 GHz masers (Phillips et al. 1998; Caswell 2010) Contours: 8.6 GHz continuum (from Phillips et al. 1998 for G331.13) Ellipse: Extended Green Object (EGO)

Implications for the evolutionary sequence Image credit: Cormac Purcell Image credit: Simon Ellingsen Ellingsen (2006): class I masers tend to be deeply embedded younger. More than one phenomenon may be responsible for the class I masers Stage with class I masers is likely to outlast 6.7 GHz (class II) masers Whether class I masers can precede class II masers is unclear A notable overlap with OH masers which are not associated with the 6.7 GHz methanol masers is expected

Search for methanol masers towards OH The majority of class I methanol masers were found towards known class II masers at 6.7 GHz Biased towards a particular evolutionary stage Need blind surveys! Blind surveys are impeded by the lack of a widespread low frequency class I maser (lowest sensible is 36 GHz!) Search for class I methanol masers in old OH-selected SFR Search for 44 GHz class I methanol masers towards OH masers not detected at 6.7 GHz in the Parkes Methanol Multibeam survey Unfortunately delays of CABB zoom mode implementation slowed the project down

Search for methanol masers towards OH The majority of class I methanol masers were found towards known class II masers at 6.7 GHz Biased towards a particular evolutionary stage Need blind surveys! Blind surveys are impeded by the lack of a widespread low frequency class I maser (lowest sensible is 36 GHz!) Search for class I methanol masers in old OH-selected SFR Search for 44 GHz class I methanol masers towards OH masers not detected at 6.7 GHz in the Parkes Methanol Multibeam survey Unfortunately delays of CABB zoom mode implementation slowed the project down

Observations without zooms Coarse spectral resolution of 1 MHz = 6.8 km/s at 44 GHz Not sensitive to weak masers (weaker than tens of Jy) Can’t measure flux density and radial velocity accurately Observed 19 OH masers which didn’t show up in MMB Detected 10 methanol masers at 44 GHz (even without zooms!) New 44 GHz maser G307.808-0.456

Summary We report the detection of a high-velocity spectral feature at 36 GHz in G309.38-0.13 (off by about 30 km s-1 from the peak velocity) This is the largest velocity offset reported so far for a class I methanol maser source associated with a single molecular cloud. Class I methanol masers may be caused by expanding HII regions This is in addition to the outflow scenario Applies to all class I maser transitions, not just to 9.9 GHz The evolutionary stage with the class I maser activity is likely to outlast the stage when the 6.7-GHz methanol masers are present overlap in time with the stage when the OH masers are active Search for the class I methanol masers at 44 GHz towards OH masers not associated with the 6.7 GHz masers was very successful The detection rate exceeds 50% even without zoom modes!

Thank you Australia Telescope National Facility Max Voronkov Contact Us Phone: 1300 363 400 or +61 3 9545 2176 Email: enquiries@csiro.au Web: www.csiro.au Australia Telescope National Facility Max Voronkov Software Scientist (ASKAP) Phone: 02 9372 4427 Email: maxim.voronkov@csiro.au Web: http://www.narrabri.atnf.csiro.au/~vor010 Thank you