1. 27/09/06 D. Fenech Jodrell Bank Observatory Supernova Remnants in the Central Starburst Region of M82 EVN Symposium 2006

2. 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!

3. 27/09/06 D. Fenech Jodrell Bank Observatory VLBI VLBI observations have concentrated on four most compact sources – 41.95+57.5, 43.31+59.2, 44.01+59.6 and 45.17+61.2. (Pedlar et al. 1999, McDonald et al. 2001, Beswick et al. 2006.) These sources remain relatively unresolved in MERLIN observations. Expansion studies of 41.95+57.5 and 43.31+59.2 using EVN observations from 1986 and 1997, as well as global VLBI observations from 1998 and 2001. Fifth epoch observed 3 rd March 2005! (global VLBI)

4. 27/09/06 D. Fenech Jodrell Bank Observatory 41.95+57.5 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

5. 27/09/06 D. Fenech Jodrell Bank Observatory 43.31+59.2 Youngest remnant in M82, first observed in 1972. (Kronberg & Wilkinson 1975) Almost complete shell structure. EVN and VLBI observations have followed it’s expansion since 1986. Expansion velocity ~10,500km/s Previous epoch Images taken from Beswick et al. MNRAS 369, 1221, 2006

6. 27/09/06 D. Fenech Jodrell Bank Observatory 43.31+59.2 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 1972. Sedov

7. 27/09/06 D. Fenech Jodrell Bank Observatory More VLBI 44.01+59.6 – partial shell structure 45.17+61.2 2005 images. Will study expansion in a similar fashion to 43.31+58.3. 45.17+61.2 44.01+59.6

8. 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 2005. 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

9. 27/09/06 D. Fenech Jodrell Bank Observatory MERLIN Deep Integration 5GHz Observations MERLIN observations in 2002 1-28 April. 8 day deep integration. ~ 175 hours on source. Rms ~ 17μJy beam -1 2002 intended to be comparable to 1992 observations as well as a first epoch to future e- MERLIN observations. 1992 Observations 2-3 July Rms ~ 46 μJy beam -1

10. 27/09/06 D. Fenech Jodrell Bank Observatory Combination

11. 27/09/06 D. Fenech Jodrell Bank Observatory A Personal Favourite 40.68+55.1 – largest detected remnant in M82. 129 mas at 5GHz corresponds to ~1.9 pc. Expansion of ~ 5000 km/s 1.6 GHz 5 GHz

12. 27/09/06 D. Fenech Jodrell Bank Observatory Conclusions Confirmed expansion of 43.31+58.3 at 1.6GHz. Continued observations of 41.95+57.5. Observe size and structure of a large number of sources at 1.6 GHz. Detailed comparison of sources at 5 and 1.6 GHz

13. 27/09/06 D. Fenech Jodrell Bank Observatory Background Image Credited to : NASA, ESA, CXC, and JPL-Caltech. Taken from the Hubble Gallery website.

14. 27/09/06 D. Fenech Jodrell Bank Observatory 39.10+57.3 Partial shell structure 110 mas at 5GHz Expansion velocity ~