Presentation title

Class I methanol masers: interferometry and variability Astronomy and Space ScienceMax Voronkov | ASKAP Software scientist CASS Maser workshop - 21 May 2013

Intro: 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 (high & low mass) low-mass: Kalenskii et al., 2011, MNRAS, 405, 613 Common 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 Common masers: 6.7, 12 GHz Rare/weak: 19.9, 23, 28, 85/86, 37/38, 107, 108 GHz Subject ofthis talk

Common 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); Valtts 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 (2011, ApJS, 196, 9) + heaps of unpublished data from Breen, Ellingsen and myself J-1-(J-1)0 E: 36/84 GHz series Single source interferometric papers, e.g. Fish et al.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)Weve completed an ATCA survey at 36 and 44 GHz of all (deeply) southern class I masers known at the time of observations- this survey is the main topic of this presentationData taken with ATCA

G343.12-0.06 (IRAS16547-4247) Some maser spots are associated with the outflow traced by H2 emissionRare masers are confined to a single spot near the brightest H2 knot+ 44 GHz masersx 36 GHz masersThese are new results from the 36/44 GHz ATCA survey

See Voronkov et al. (2006, MNRAS, 373, 411)for more info on the sourceAssociation with expanding HII regions?Class I masers may be associated with ionisation shocks driven by an expanding HII region into surrounding molecular cloud, not just outflows. The analysis was originally based on rare 9.9-GHz masers (see Voronkov et al., 2010, MNRAS, 405, 2471), but 36/44 GHz masers can illustrate it better.

G305.37+0.21Red contours: 18-cm radio-continuum from MAGMOBlue contours: 3-cm spatially filtered radio-continuum (Hindson et al., 2012, MNRAS, 421, 3418)+ 44 GHz masersx 36 GHz masersBackground: 3-colour GLIMPSE imageConcentric circles: 50% sensitivity region at 36 and 44 GHzEvolutionary 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) Biased surveys Association with multiple phenomena Messy environment, e.g. triggered star-formation not clear which generation of stars in the cluster the masers correspond to (as they may be quite offset) There are indications that those class I masers which we know and studied in detail are in relatively evolved sources However, we cannot completely exclude the presence of class I masers at the earliest stagesExpanding HII regions: G348.18+0.48Triggered star-formation around RCW120, see Deharveng et al. 2009, A&A, 496, 177:

Condensation 1 contains a massive deeply embedded core and a number of YSOsExpanding HII regions: G348.18+0.48Deharveng et al. 2009, A&A, 496, 177:

Red rectangle roughly shows the area where the class I methanol maser emission is locatedNo other masers in the immediate vicinity except an H2O maser (single-dish position is the pointing centre, Braz & Scalise, 1982, A&A, 107, 272)

The power of a survey is in numbersATCA 36 and 44 GHz survey Masers reported by Slysh et al. (1994), Valtts et al. (2000) and Ellingsen (2005) which are located south of -35o declination; 71 unique targets in total. Largest interferometric survey to date, the first of this kind in the Southern hemisphere, the first interferometric survey at 36 GHz

Most sources show complex spatial and kinematic structure First, we decomposed all emission into a collection of Gaussians in the spectral domain (each with a position measurement assuming point source) Then, we grouped the Gaussians co-located in both position and velocity within 3 (referred to as groups later on) More than 80% of such groups are simple (i.e. just one Gaussian) In total, there are 740 groups at 36 GHz and 816 groups at 44 GHz Only 291 (or 23%) of them are common groups for both transitions

G333.47-0.16 at 44 and 36 GHzRed: 8.0 m, green: 4.5 m, blue: 3.6 mPositions of masers overlaid on the 3-colour Spitzer IRAC image Extended infrared sources with emission excess at 4.5 m (EGOs) may trace shocked gasAssociation with EGOs -a similar result to that of Cyganowski et al. (2009, ApJ, 702, 1615) + 44 GHz masers 6.7 GHz maserG333.47-0.16 at 44 and 36 GHzRed: 8.0 m, green: 4.5 m, blue: 3.6 mPositions of masers overlaid on the 3-colour Spitzer IRAC image + 44 GHz masers 6.7 GHz maser

Different transitions are highly complementary and are often crucial for the interpretation of morphology.x 36 GHz masers

Velocity match and rest frequenciesAdopted rest frequencies(from Mller et al. 2004)44069.41 0.01 MHz The uncertainty is equivalent to velocity uncertainty of 0.068 km s-1 (about the spectral resolution)36169.265 0.030 MHz The uncertainty is equivalent to velocity uncertainty of 0.24 km s-1Velocity difference: 0.22 0.03 km s-1Suggest: 36169.238 0.011 MHz

Relative flux densities at 36 and 44 GHzFor groups of components emitting at both 36 and 44 GHz:Its rare to have much stronger 36 GHz maserTypically the 44 GHz flux densities are factor of a few higherIn most cases F(36)/F(44)