New Class I methanol masers Max Voronkov Software Scientist – ASKAP In collaboration with: Caswell J.L., Ellingsen S.P., Breen S.L., Britton T.R., Green J.A., Sobolev A.M., Walsh A.J. + some data from Zinchenko I.I. and Salii S.V. 3 February 2012

Data taken with ATCA, ATCA+CABB, Mopra

Introduction: two classes of methanol masers Class I methanol (CH3OH) masers Scattered around YSOs (up to a parsec or so) Many maser spots at arcsec resolution Collisional excitation (e.g. by shocks) Regions of star formation low-mass: Kalenskii et al., 2011, MNRAS, 405, 613 Widespread masers: 36, 44, 84, 95 GHz, … Rare/weak: 9.9, 23.4, series at 25, 104.3 GHz Class II methanol (CH3OH) masers Located in the nearest vicinity of YSOs Usually just one maser spot at the arcsec scale Radiational excitation (by infrared from YSO) Regions of high mass star formation only Widespread masers: 6.7, 12 GHz Rare/weak: 19.9, 23, 28, 85/86, 37/38, 107, 108 GHz Subject of this talk

Methanol maser series Red is class I Green is class II Interestingly, all but one class II maser series go downwards and eventually terminate at the lowest possible level for that particular series Class I masers are more interesting for ALMA

Widespread class I masers J0-(J-1)1 A+: 44/95 GHz series Major published interferometric surveys: Kurtz et al. (2004, ApJS, 155, 149); Cyganowski et al. (2009, ApJ, 702, 1615) Lots of single dish work: e.g. Haschick et al. (1990, ApJ, 354, 556); Slysh et al. (1994, MNRAS, 268, 464); Val’tts et al. (2000, MNRAS, 317, 315); Ellingsen (2005, MNRAS, 359, 1498); Fontani et al. (2010, A&A, 2010, 517A, 56); Chen et al. (2011, ApJS, 196, 9) + heaps of unpublished data from Breen, Ellingsen and myself J-1-(J-1)0 E: 36/84 GHz series Single source interferometric papers, e.g. Fish et al. (2011, ApJ, 729, 14); Voronkov et al. (2010, MNRAS, 408, 133) Single dish work, e.g. Haschick et al. (1989, ApJ, 339, 949); Kalenskii et al. (2001, ARep, 45, 26) + Talk by Stan Kurtz We’ve completed an ATCA survey at 36 and 44 GHz of all (deeply) southern class I masers known at the time of observations - some results are shown later in this presentation

G343.12-0.06 (outflow association) See Voronkov et al. (2006, MNRAS, 373, 411) for more info on the source G343.12-0.06 (outflow association) These are new results from the 36/44 GHz ATCA survey Some maser spots are associated with the outflow traced by H2 emission Rare masers are confined to a single spot near the brightest H2 knot + 44 GHz masers x 36 GHz masers

ATCA 36/44 GHz survey: G333.466-0.164 Red: 8.0 µm, green: 4.5 µm, blue: 3.6 µm Positions of masers overlaid on the 3-colour Spitzer IRAC image Extended infrared sources with emission excess at 4.5 µm (EGOs) may trace shocked gas Association with EGOs -a similar result to that of Cyganowski et al. (2009, ApJ, 702, 1615) + 44 GHz masers  6.7 GHz maser

ATCA 36/44 GHz survey: G333.466-0.164 Red: 8.0 µm, green: 4.5 µm, blue: 3.6 µm Positions of masers overlaid on the 3-colour Spitzer IRAC image Different transitions are highly complementary and are often crucial for the interpretation of morphology. + 44 GHz masers x 36 GHz masers  6.7 GHz maser

What does the theory say about this? Sobolev et al. (2005, IAUS, 227, 174) There are different pumping regimes, each favours a separate transition series. The orientation of maser region w.r.t. the observer has a great influence on the 36/44 GHz flux density ratio (the same is true for the 84/95 GHz flux density ratio) Maser region elongated along the line of sight is stronger at 44 GHz Maser region elongated in the plane of the sky is stronger at 36 GHz We still need to accurately test these predictions on a large sample of sources. Models show quite clearly that rare/weak masers require more restricted range of physical conditions (mainly they need a higher temperature and density)

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) This is not the only such source. So far only blue-shifted high-velocity features were found and only at 36 GHz + 44 GHz masers x 36 GHz masers 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) Voronkov et al. (2010, MNRAS,408, 133)

J2-J1 E (25 GHz) methanol masers Historically, the first methanol maser found in space (Barrett et al., 1971, ApJ, 168, 101) Believed to be rare ATCA survey of known class I maser sites brought up 66 detections out of 102 targets observed (Voronkov et al. 2007, IAUS, 242, 182); the majority are weaker than 1 Jy Now reobserved with CABB - see the poster by Tui Britton There are other detections, e.g. Brogan et al. (2011, ApJ, 739, 16) + talk at this meeting Example of simultaneous 25 GHz spectra with CABB (Wilson et al., 2011, MNRAS, 416, 832)

VLBI observations of the class I masers Early attempts were not very successful Spots were resolved on long baselines Commonly assumed sizes: 10-100 au Ask Karl Menten for more info However, We did not have accurate positions We could not choose the best sources (there were no VLA or ATCA maps yet for a large number of sources) Widespread masers like that at 44 GHz may not be the best targets Observed 10 strongest 25 GHz (J=5&6) masers with LBA in July 2011 Correlated a couple of weeks ago, no results yet As far as I know, VLBI was attempted at 44 GHz with KVN - ask Kee-Tae Kim

Rare 9.9/104 GHz methanol masers These masers belong to J-1-(J-1)-2 E series. 9-1-8-2 E at 9.9 GHz Maser in W33-Met was known from the single dish work of Slysh et al. (1993, ApJ, 413, L133) Sensitive (limits as low as 0.1 Jy) ATCA survey of Voronkov et al. (2010, MNRAS, 405, 2471): two new detections out of 46 new targets observed Two single source papers: Voronkov et al. (2011, MNRAS, 413, 2339 and 2006, MNRAS, 373, 411) 11-1-10-2 E at 104 GHz Single dish surveys: Voronkov et al. (2005, Ap&SS, 295, 217; Voronkov et al. 2007, IAUS, 242, 182) The only additional source is G305.21+0.21 Interferometry - single source G343.12-0.06, Voronkov et al. (2006, MNRAS, 373, 411)

Association with expanding Hii regions? Class I masers may be associated with ionisation shocks driven by an expanding HII region into surrounding molecular cloud This result is currently based on observations of 9.9 GHz masers (need higher temperature and density to form than 36/44 GHz) but should apply to other class I methanol masers as well Another possible example (but it has an outflow as well) See Voronkov et al. (2010, MNRAS, 405, 2471) Crosses: 9.9 GHz masers Open boxes: 6.7 GHz maser (Caswell 2010) Contours: 8.6 GHz continuum Grayscale: Spitzer 4.5µm Grayscale: NH3 (Ho et al. 1986; Garay et al. 1998) G331.13-0.24 W33-Met (G12.80-0.19) G19.61-0.23

Implications for the evolutionary sequence Image credit: Cormac Purcell Ellingsen et al. (2007, IAUS, 242, 213); Breen et al. (2010) 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 There is a notable overlap with OH masers which are not associated with the 6.7 GHz methanol masers

Evolutionary stages traced by class I masers Comparison of different class I transitions is still immature But attempts are made, e.g. Pratap et al. (2008, AJ, 135, 1718) Best to understand first how class I masers fit into common picture based on other maser species (i.e. OH, water, class II methanol) The majority of known class I methanol masers have a class II maser at 6.7 GHz in the vicinity Sample is biased towards a particular evolutionary stage Need blind surveys! But they are hard to do at high frequency Some attempts: MALT45 (Walsh et al.), also ask Gary Fuller Follow-up of Methanol Multi-beam (MMB) 6.7-GHz detections 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 CABB delays slowed the project down Detected 10 masers out of 19 targets despite a very coarse spectral resolution (almost 7 km/s)

G357.97-0.16 - new 23.4 GHz maser First maser in J1-(J-1)2 A- series (J=10) Found in HOPS (unbiased survey at 12mm; PI: Andrew Walsh) towards only one location HOPS is not sensitive to weak masers (< 10 Jy) Predicted in models (e.g. Cragg et al. 1992) as a class I maser Followed up with ATCA Observed the new maser transition + 7 lines of the 25 GHz maser series Also discovered an unusually strong 9.9-GHz maser (and only 5th found so far) There is at least one more 23.4 GHz maser (in G343.12-0.06 - the jet/outflow source shown before) See Voronkov et al. (2011, MNRAS, 413, 2339) for details

G357.97-0.16 - new 23.4 GHz maser Also see a poster by Tui Britton Yellow contour shows 12mm continuum (50% of the peak) Cyan contours show 16cm continuum (observations by CASS summer students A.Dicker, C.-E. Green and D.Compton ) Red: 8.0 µm, green: 4.5 µm, blue: 3.6 µm - IRAC images Squares are class II methanol masers at 6.7 GHz Crosses are water masers Circle shows position of rare class I masers Northern source has an OH maser, the associated H2O maser has a large velocity spread with almost continuous emission across 180 km/s

Class I methanol masers with ALMA Prediction for masers in ALMA bands 6 and 7 based on low-frequency data 36/84 GHz: 8-1-70E at 229, 9-1-80E at 278 GHz, 10-1-90E at 327 GHz e.g., Slysh et al. (2002, ARep, 46, 49); Fish et al. (2011, ApJ, 729, 14) Recent SMA observations of S255 by Zinchenko, Salii, Sobolev et al. 44/95 GHz: 110-101A+ at 250, 120-111A+ at 303, 130-121A+ at 356 GHz 9.9/104 GHz: 14-1-13-2E at 242, 15-1-14-2E at 287, 16-1-15-2E at 331 GHz 23.4 GHz: 141-132A- at 237, 151-142A- at 291, 161-152A- at 346 GHz 25 GHz J2-J1E is a cm-wavelength series, but J2-(J-1)1E gives some mm masers In particular, the 42-31E maser at 218 GHz has been found in S255 These masers correspond to excitation energies of about 300-500 K

Summary Studies of different transitions are very complementary Filling the dots in morphology, high-velocity features, modelling Rare/weak masers (9.9, 23.4, 25 and 104 GHz) trace stronger shocks/ higher temperatures and densities Outflow shocks vs. shocks caused by other mechanisms Some class I masers may be caused by expanding HII regions Implications for maser-based evolutionary sequence 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 Many candidate class I maser transitions can be observed by ALMA G343.12-0.06 and G357.97-0.16 are promising targets - we could even double the number of known maser transitions

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