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Supernova Remnants in M82: VLBI Observations and Expansion Studies

Explore VLBI observations and expansion studies of supernova remnants in the starburst galaxy M82, focusing on compact sources. Detailed analyses, evolution parameters, and comparison at different frequencies discussed.

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Supernova Remnants in M82: VLBI Observations and Expansion Studies

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

  2. 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! D. Fenech Jodrell Bank Observatory

  3. 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 3rd March 2005! (global VLBI) D. Fenech Jodrell Bank Observatory

  4. 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 D. Fenech Jodrell Bank Observatory Previous epoch Images taken from Beswick et al. MNRAS 369, 1221, 2006

  5. 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 D. Fenech Jodrell Bank Observatory Previous epoch Images taken from Beswick et al. MNRAS 369, 1221, 2006

  6. 43.31+59.2 • Fit various deceleration parameters to data. • Size evolution: D=kTδ (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 D. Fenech Jodrell Bank Observatory

  7. 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 D. Fenech Jodrell Bank Observatory

  8. Combination • Simultaneous observations of M82 at 1.6GHz using MERLIN seven element array on 3rd 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 D. Fenech Jodrell Bank Observatory

  9. 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 D. Fenech Jodrell Bank Observatory

  10. Combination D. Fenech Jodrell Bank Observatory

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

  12. 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 D. Fenech Jodrell Bank Observatory

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

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

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