1. X-ray Binaries in Nearby Galaxies Vicky Kalogera Northwestern University Super Star Clusters Starburst galaxies Ultra-Luminous X-Ray Sources Elliptical galaxies

2. Chandra observations of XRBs - some of the puzzles - How does XRB formation and evolution depend on star-formation history and metallicity ? Do Super Star Clusters form High-Mass XRBs ? What determines the shape of X-Ray Luminosity Functions (XLF) ? Is it due to a blend of different XRB populations ? What is the nature of Ultra-Luminous X-ray Sources (ULX) ?

3. Super-Star Clusters (SSCs) Compact, young analog to globular clusters Found frequently in starburst environments Masses range from ~10 4 to ~10 6 M o Ages range from a few to tens of Myr

4. Kaaret et al. 2004 L x ≥ (0.5-3)x10 36 erg/s Distribution of X-Ray point sources < 1 XRB per cluster!

5. Kaaret et al. 2004 L x ≥ 5x10 35 erg/s Distribution of X-Ray point sources XRBs closely associated with star clusters Median distance ~30-100 pc < 1 XRB per cluster! M82 N5253 N1569 50% Is this all due to Supernova Kicks ?

6. Theoretical XRB Distributions cluster mass: ~5x10 4 M o L X > 5x10 35 erg/s average of 1,000 cluster simulations Significant age dependence < 1 XRB per cluster Models: Population Syntheses of XRBs and Kinematic Orbit Evolution in Cluster Potential Sepinsky et al. 2005, ApJL

7. Conclusions XRB models without cluster dynamics appear in agreement with observations Mean XRB number per SSC < 1 and spatial distribution: M < 10 5 M o and 10-50Myr or more massive and ~50Myr Results do not appear sensitive to binary evolution assumptions, but extended parameter study is needed. Explore role of dynamics for more massive and older clusters Supernova kicks: eject XRBs @ D > 10pc especially for M < 10 5 M o

8. NGC 1569 (post-)starburst galaxy at 2.2Mpc with well-constrained SF history: > ~100Myr-long episode, probably ended 5-10Myr ago, Z ~ 0.25 Z o > older population with continuous SF for ~ 1.5Gyr, Z ~ 0.004 or 0.0004, but weaker in SFR than recent episode by factors of >10 Vallenari & Bomans 1996; Greggio et al. 1998; Aloisi et al. 2001; Martin et al. 2002 courtesy Schirmer, HST courtesy Martin, CXC,NOAO

9. Belczynski, VK et al. 2004, ApJL NGC 1569 XLF modeling Hybrid of 2 populations:  underlying old  starburst young Old: 1.5 Gyr Young: 110 Myr SFR Y/O: 20 Old: 1.5 Gyr Young: 70 Myr SFR Y/O: 20 Old: 1.3 Gyr Young: 70 Myr SFR Y/O: 40

10. Conclusions on Starbursts Current understanding of XRB formation and evolution produces XLF properties consistent with observations Model XLFs can be used to constrain star-formation properties, e.g., age and metallicity Shape of model XLFs appear robust against variations of most binary evolution parameters

11. Ultra-Luminous X-ray Sources  First discovered with Einstein X-ray telescope  Extragalactic sources with L X ≥ 10 39 erg/s  Later observations determined many are off- nuclear & not associated with supernovae  What is the origin of these sources?  Intermediate-Mass Black Holes? (50 - 1000M o )  Strongly Anisotropic XRB emission ?

12. IMBH Binaries ? Cluster core simulations with binary evolution and multi-body dynamical interactions Do IMBH acquire mass-transfering binary companions in cluster cores ? Blecha, Ivanova, VK et al. 2005

13. IMBH Companions Mass distribution Orbital separation distribution

15. Conclusions on IMBH Binaries Optimal IMBH mass range: 100-200 M o MT is relatively rare; highest incidence at 100M o about 3-5% of cluster lifetime with MT IMBH binary MS mass-transferring companions are more common & spend more time in MT BUT ARE THEY ULXs? Blecha, Ivanova, VK et al. 2005

16. Brightest XRBs in Elliptical Galaxies Upper-end XLF slope (L X : from ~0.5 - 2 10 39 erg/s) : footprint of accreting BH mass spectrum modified by probability of XRB detection due to transient mode of accretion Ivanova & VK 2005, ApJ

18. What to Expect in the Future ? For example: * Long-term time monitoring will become possible; identification of X-ray transients and clues to ULX nature * Bigger source samples will allow probing the rare brightest sources and questions of BH formation * Systematic modeling of galaxy samples will reveal sensitivity to SFR and Z …