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Star Formation History of M100: Swift/UVOT

Star Formation History of M100: Swift/UVOT. Alison Newell, Ignacio Ferreras & Mark Cropper Mullard Space Science Laboratory, University College London. Scope of talk. Describe current UV Imaging Surveys M100 (NGC 4321) Describe the data Models of Unresolved Stellar Populations

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Star Formation History of M100: Swift/UVOT

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  1. Star Formation History of M100: Swift/UVOT Alison Newell, Ignacio Ferreras & Mark Cropper Mullard Space Science Laboratory, University College London

  2. Scope of talk • Describe current UV Imaging Surveys • M100 (NGC 4321) • Describe the data • Models of Unresolved Stellar Populations • Further Work

  3. UV Imaging Surveys • Galex • 5 arcsec , FUV, NUV • XMM-OM & Swift UVOT • 2 arcsec, 3 UV + 3 Optical

  4. Gain in spatial resolution – M81 Galex (2 UV colours) Swift-UVOT (3 UV colours)

  5. Swift/UVOT 30 cm modified RC telescope 17x17 arcmin FoV Photon counting detectors 1700 – 6000 Å

  6. OM/UVOT & GALEX filter bandpassesUVOT: UVW2,UVM2,UVW1,UGALEX: FUV,NUV

  7. M100 Basic Properties • Grand design barred Sc Spiral • Nearby, well studied • Central region • Spiral arms • Nearly face-on, ~16 Mpcs • Optical, Hα, CO maps • Spitzer-SINGS • HST – central • GALEX – NUV only • Herschel UVOT 6 colour M100

  8. UVOT Images M100 • Observed 2005 November 5 • UVOT Software – combine and register • Max count rate 1.47 c/s/pixel (B)

  9. Source Detection Process Background • SExtractor – 3σ • UVW2 image used for detections – 1928 Å • Background subtraction complex – stellar emission spiral arms • SF regions: extended, crowded

  10. Photometry Kron elliptical apertures Kron - magnitude Small circular aperture for colours SE Double image mode Large errors on optical images Use SDSS images

  11. SDSS images M100 DR 7 • Observed 2003 January 28, 2004 January 28 • Exposure time 53.9s • 4 separate images • SWARP – combine and register

  12. SDSS Photometry 2 runs, 2 frames 3 arcsec apertures 4 catalogues - amalgamated Removed: Foreground stars Background galaxies

  13. Catalogue • 428 sources with 3 UV colours • ~ 91% have SDSS u,g,r colours, ~ 50% i,z • ~ 2.5 sources per kpc2

  14. Radial Distribution UVW2 Similar for UVM2, UVW1 HII Cepa & Beckman (1996) Sharp edge at 50’’ Sharp fall off at 150 “ Disk edge

  15. Models • Unresolved • 1 px ~ 0.5arcsec ~ 50pc • Age, metallicity, dust • Bruzual & Charlot 2003 models • Simple Stellar Population

  16. C-M Plot

  17. CC plots metallicity UV SDSS

  18. CC plots - dust Degeneracy Model – low dust, young population Cover the UV extent with UVW2 – UVW1 Break degeneracy for older populations

  19. Future work • Comparison with other models • Composite models – more complex analysis • Star formation rate • Radial trends • Comparison with Spitzer SINGS Complementary approach to GALEX

  20. Summary • Swift/UVOT photometry • Described M100 data, some properties • Compared data with Bruzual & Charlot 2003 models • Determined young dust free regions with solar Z • Identified future work

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