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Young X-ray source populations in M81 and other galaxies

Young X-ray source populations in M81 and other galaxies. Andreas Zezas Harvard-Smithsonian Center for Astrophysics In collaboration with: K. Gazeas, J. Huchra, J. Gallagher, M. Mutchler, Z. Levay. X-ray source populations.

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Young X-ray source populations in M81 and other galaxies

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  1. Young X-ray source populations in M81 and other galaxies Andreas Zezas Harvard-Smithsonian Center for Astrophysics In collaboration with: K. Gazeas, J. Huchra, J. Gallagher, M. Mutchler, Z. Levay

  2. X-ray source populations • There is evidence for a common XLF describing different XRB populations (e.g. Grimm etal 2002) • Theoretical population synthesis models indicate evolution of the populations and their XLFs (e.g. Belczynski etal 2002) • Observational results show evidence for changes between HMXB and LMXB populations - but little is known about variations within each population. • Star-forming galaxies address the evolution of HMXBs • Spiral galaxies address the evolution of HMXBs and LMXBs.

  3. Soria & Wu 2002 Grimm etal 2006 Spiral galaxies There is strong evidence for changing populations in star-forming galaxies (arms, bulge, inter-arm regions) However, little is known about the properties of those X-ray sources.

  4. M81 : A case study Nearby (3.6 Mpc) grand design spiral galaxy Detect the bulk of active X-ray binaries Identify optical counterparts Detect early type (OB) stars Resolve star-clusters, and measure structural parameters

  5. Swartz etal 2003 Tennant etal 2000 Gordon etal 2004 M81 profile Extensively studied Optical : several stellar generations (6-600Myr, >1Gyr; e.g. Chandar etal 2001) Radio : Radio SNRs (Kaufman etal 1987) Infrared : Obscured star-formation (Gordon etal 2004, Willner etal 2004) X-rays : Deep exposures (PI D. Swartz) and monitoring campaign (PI D. Pooley) Several populations of X-ray sources Prime target to study star-formation and its relation to X-ray binary populations

  6. Description of the Chandra observations 13 ACIS-S pointings (PI D. Pooley) Cover ~50% of D25 Exposure : ~10-15ksec Detection limit : ~1037erg/s in each pointing (21037 erg/s @ 90% compl.) ~61035 erg/s in combined exposure (4 1036 erg/s @ 90% compl.)

  7. Chandra observations : First results 50-60 sources in each pointing 120 sources in coadded exposure (~35 backgr. sources)

  8. Average Lx Coadded Lx Zezas etal 2007 Zezas etal 2007 A caveat Photometry on coadded exposures underestimates luminosity of faint sources

  9. Chandra observations : First results XLFs do not vary Consistent with results from the Antennae and other star-forming galaxies

  10. HST observations HST-ACS BVI imaging of entire galaxy Combination of P10540 (I-band; PI J. Huchra) and P10584 (BV-bands; PI A. Zezas) Total of 29 ACS fields (24+39 orbits) B,V-band exposure : 1200 sec (~27 mag at S/N=10) I-band exposure : 1650 sec (~27 mag at S/N=10) Goal : Detect all star-clusters, and bulk of OB stars

  11. Bulge and inner disk

  12. First results

  13. Comparison with Chandra • Chandra-HST astrometric registration : < 0.4” • Very high chance coincidence rate • Cross-corelate with different source types • OB stars • Giants /supergiants

  14. Comparison with Chandra a ~ 0.75

  15. NGC4214 NGC5253 Older Young NGC1569 Star-forming galaxies We find indication for different XLFs associated with different stellar populations • Antennae • Starburst sequence NGC 1569 NGC 4214 NGC 5253

  16. Future plans • Derive the spatially resolved star-formation history of M81 • Classify X-ray sources, compare populations with local star-formation history • Compare with predictions from X-ray binary population synthesis models (Belczynski etal, 2007) • Compare properties of different X-ray source populations • Compare results with other galaxies

  17. Large scale structure OB associations, star-clusters, globular clusters HII regions Inner bulge dust lanes Background galaxies

  18. Comparison with Chandra : XLFs of different source populations Select X-ray sources based on their position on the CMD Spatial distribution of OB sources, unidentified sources. XLF of source populations

  19. Nuclear region HII regions OB associations Background galaxies

  20. First results : HST

  21. Data analysis • Data preparation (drizzle, cleaning etc) • Astrometric registration with SDSS (0.3” rms) • Detection limits : • ~ 27 mag at S/N = 10 • ~ 27.5 mag at S/N = 5 • Covers the bulk of OB main sequence stars

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