27/09/06 D. Fenech Jodrell Bank Observatory Supernova Remnants in the Central Starburst Region of M82 EVN Symposium 2006

27/09/06 D. Fenech Jodrell Bank Observatory Introduction M82 is one of the closest starburst galaxies. First radio observations 1972 (Kronberg & Wilkinson 1975). Ref. Tom’s Talk! ~50 known sources in the central kpc, supernova remnants and HII regions. Talk will focus on a few compact sources – VLBI observations. Also discuss VLBI+MERLIN observations!

27/09/06 D. Fenech Jodrell Bank Observatory VLBI VLBI observations have concentrated on four most compact sources – , , and (Pedlar et al. 1999, McDonald et al. 2001, Beswick et al ) These sources remain relatively unresolved in MERLIN observations. Expansion studies of and using EVN observations from 1986 and 1997, as well as global VLBI observations from 1998 and Fifth epoch observed 3 rd March 2005! (global VLBI)

27/09/06 D. Fenech Jodrell Bank Observatory Most compact source in M82. Peak flux decreasing by ~8.5% per year! Bi-polar structure not typical of supernova remnant. Expanding at ~1500km/s Previous epoch Images taken from Beswick et al. MNRAS 369, 1221, 2006

27/09/06 D. Fenech Jodrell Bank Observatory Youngest remnant in M82, first observed in (Kronberg & Wilkinson 1975) Almost complete shell structure. EVN and VLBI observations have followed it’s expansion since Expansion velocity ~10,500km/s Previous epoch Images taken from Beswick et al. MNRAS 369, 1221, 2006

27/09/06 D. Fenech Jodrell Bank Observatory Fit various deceleration parameters to data. Size evolution: D=kT δ (Huang et al. 1994) D size, T is the age, δ is the deceleration parameter. Birth date unknown but can constrain from first detection in Sedov

27/09/06 D. Fenech Jodrell Bank Observatory More VLBI – partial shell structure images. Will study expansion in a similar fashion to

27/09/06 D. Fenech Jodrell Bank Observatory Combination Simultaneous observations of M82 at 1.6GHz using MERLIN seven element array on 3 rd March Successfully combined the two datasets to produce images with angular resolutions from ~5-100 mas Images comparable to MERLIN deep integration observations at 5GHz with angular resolution 35mas. Study size and structure of ~30 remnants at 1.6GHz

27/09/06 D. Fenech Jodrell Bank Observatory MERLIN Deep Integration 5GHz Observations MERLIN observations in April. 8 day deep integration. ~ 175 hours on source. Rms ~ 17μJy beam intended to be comparable to 1992 observations as well as a first epoch to future e- MERLIN observations Observations 2-3 July Rms ~ 46 μJy beam -1

27/09/06 D. Fenech Jodrell Bank Observatory Combination

27/09/06 D. Fenech Jodrell Bank Observatory A Personal Favourite – largest detected remnant in M mas at 5GHz corresponds to ~1.9 pc. Expansion of ~ 5000 km/s 1.6 GHz 5 GHz

27/09/06 D. Fenech Jodrell Bank Observatory Conclusions Confirmed expansion of at 1.6GHz. Continued observations of Observe size and structure of a large number of sources at 1.6 GHz. Detailed comparison of sources at 5 and 1.6 GHz

27/09/06 D. Fenech Jodrell Bank Observatory Background Image Credited to : NASA, ESA, CXC, and JPL-Caltech. Taken from the Hubble Gallery website.

27/09/06 D. Fenech Jodrell Bank Observatory Partial shell structure 110 mas at 5GHz Expansion velocity ~