1. The Role of Parkes in Southern Maser VLBI Simon Ellingsen University of Tasmania

2. Maser Frequencies Major maser transitions observed at Parkes: – Ground state OH (1612,1665,1667,1720 MHz). – Class II methanol (6.7 and 12.2 GHz). – Water 22 GHz. – Excited OH (6030/35 MHz). There are a host of weaker, rarer transitions, including: – Formaldehyde (4830 MHz), other class II (and class I) methanol (9.9, 19.9, 23.1, 25 GHz), other excited OH (4.7 & 13 GHz), ammonia (18 & 23 GHz), CH (3.3 GHz). Science drivers for Parkes Receiver Development: Southern Maser VLBI

3. Size does Matter For spectral lines you can’t increase sensitivity through greater bandwidth. For VLBI the coherence time (typically few-5 min) limits the integration time *. Baselines 25m antenna-Parkes are a factor of 2.5 more sensitive. As the only large aperture in the LBA, Parkes plays an important role (despite being slow and limited in elevation Parkes) Science drivers for Parkes Receiver Development: Southern Maser VLBI * You can extend this through phase referencing, but need a suitable phase reference source within a degree or two.

4. Kinematics As high-intensity, compact spectral line sources masers offer unparalleled insights into the dynamics of the regions where they occur. Science drivers for Parkes Receiver Development: Southern Maser VLBI NGC4258 water megamasers (Herrnstein et al. 1999) Water masers in Cep A (Torrelles et al. (2001)

5. Distances Masers can be used obtain accurate (~10%) distances through trigonometric parallax through much of the Galaxy. Science drivers for Parkes Receiver Development: Southern Maser VLBI Parallax in G232.6+1.0 (Reid et al. 2009a) Reid et al. (2009b)

6. OH Maser Science Measurement of B fields at milliarcsecond resolution through Zeeman splitting. Dynamics and evolution of late-type stars (OH/IR and AGB). The dynamics of interacting Galaxies – OH megamasers. SNR – molecular cloud interactions (1720 MHz OH masers) Science drivers for Parkes Receiver Development: Southern Maser VLBI OH masers in G337.705 Caswell et al. (2011)

7. OH Maser Science Measurement of B fields at milliarcsecond resolution through Zeeman splitting. Dynamics and evolution of late-type stars (OH/IR and post-AGB). The dynamics of interacting Galaxies – OH megamasers. SNR – molecular cloud interactions (1720 MHz OH masers) Science drivers for Parkes Receiver Development: Southern Maser VLBI Late-type star OH37.1-0.8 Amiri et al. (2011)

8. OH Maser Science Measurement of B fields at milliarcsecond resolution through Zeeman splitting. Dynamics and evolution of late-type stars (OH/IR and AGB). The dynamics of interacting Galaxies – OH megamasers. SNR – molecular cloud interactions (1720 MHz OH masers) Science drivers for Parkes Receiver Development: Southern Maser VLBI Moment map of OH megamasers in Arp 220 (Rovilos et al. 2003)

9. Methanol Maser Science Science drivers for Parkes Receiver Development: Southern Maser VLBI Galactic structure and proper motions through trigonometric parallax. The dynamics of very young, high-mass star formation regions – infall, disks etc. Understanding periodicity in young high-mass stars. The methanol maser ring G23.657- 0.127 (Bartkiewicz et al. 2008)

10. Methanol Maser Science Science drivers for Parkes Receiver Development: Southern Maser VLBI Galactic structure and proper motions through trigonometric parallax. The dynamics of very young, high-mass star formation regions – infall, disks etc. Understanding periodicity in young high-mass stars. The periodic methanol maser G9.62+0.20 Goedhart et al. (2005)

11. Water Maser Science Science drivers for Parkes Receiver Development: Southern Maser VLBI The dynamics of AGN at sub- parsec resolutions and geometric distances (water megamasers). Distances and motions of local group Galaxies (e.g. LMC, SMC, M33 etc). Outflows and shocks in both star formation and evolved star systems. The proper motion of water masers in M33 (Brunthaler et al. 2005)

12. Water Maser Science Science drivers for Parkes Receiver Development: Southern Maser VLBI The dynamics of AGN at sub- parsec resolutions and geometric distances (water megamasers). Distances and motions of local group Galaxies (e.g. LMC, SMC, M33 etc). Outflows and shocks in both star formation and evolved star systems. The location of water masers in the LMC (Ellingsen et al. 2010) and SMC (Breen et al. 2013)

13. Water Maser Science Science drivers for Parkes Receiver Development: Southern Maser VLBI The dynamics of AGN at sub-parsec resolutions and geometric distances (water megamasers). Distances and motions of local group Galaxies (e.g. LMC, SMC, M33 etc). Outflows and shocks in both star formation and evolved star systems. SiO (left) and Water (right) masers associated with Orion BN/LN (Greenhill et al. 1998)

14. Conclusions There are a large number of high-profile science projects involving maser VLBI. It is highly desirable for Parkes to be able to cover the 6.7 GHz methanol, 22 GHz water, ground state OH and 12.2 GHz methanol lines (Parkes = Sensitivity) Trigonometric parallax experiments require flexibility in scheduling across the array. The current Parkes receiver availability is sub-optimal. Beware of inherent biases in prioritizing future receiver developments. Science drivers for Parkes Receiver Development: Southern Maser VLBI

15. Beware inherent biases It is important not to focus too heavily on the past when assessing future potential. Research areas which are very well resourced (receivers, back-ends, people and telescope time), are should produce more good science than those which are less well resourced. Science drivers for Parkes Receiver Development: Southern Maser VLBI