Class I methanol masers in the regions of high-mass star-formation Max Voronkov Software Scientist – ASKAP In collaboration with: Caswell J.L., Ellingsen S.P., Britton T.R., Green J.A., Sobolev A.M. 15 th September 2010

ATCA and CABB All data presented in this talk were obtained with ATCA

Introduction: two classes of methanol masers Class I methanol (CH 3 OH) 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, GHz Class II methanol (CH 3 OH) 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

Some maser spots are associated with an outflow traced by H 2 emission Rare masers are confined to a single spot near the brightest H 2 knot G outflow association

G : high-velocity feature at 36 GHz Red: 8.0 µm, green: 4.5 µm, blue: 3.6 µm Background: Spitzer IRAC data 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 CH 3 OH abundance shocks have to be mild (shock velocities not much more than 10 km/s interaction with moving gas)

G new 23.4 GHz maser First detection of the 23.4 GHz methanol maser in HOPS (PI: Andrew Walsh) towards a single source G HOPS is not sensitive to weak masers (< a few Jy) There is a water maser nearby with unusually large velocity spread/number of components Predicted in models (e.g. Cragg et al. 1992) Followed up with ATCA Initially observed the new maser transition and 7 lines of the 25 GHz maser series Position: 17 h 41 m 20 s o 45’18’’.1 Infrared properties are not exciting 1.3 mJy (12 mm) continuum source ~ 10’’ offset Test 9.9-GHz observations revealed a very strong maser at this frequency (5th found so far) There is at least one more 23.4 GHz maser (in G )

Association with expanding Hii regions? Grayscale: NH 3 (Ho et al. 1986; Garay et al. 1998) Crosses: 9.9 GHz masers Circle: 6.7 GHz maser (Caswell 2010) Contours: 8.6 GHz continuum W33-Met (G ) G ATCA survey for rare 9.9 GHz masers (need higher temperature and density to form) Class I masers may be associated with ionisation shocks

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 G

Summary Class I methanol masers trace shocks caused by various phenomena Outflows, expanding Hii regions, cloud-cloud collisions Rare class I masers trace more energetic shocks Sometimes class I masers are the only available indication of shocks The evolutionary stage with class I masers 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! We report the detection of a high-velocity spectral feature at 36 GHz in G (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. There are 23.4 GHz masers in G and G

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