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Evidence for Intermediate Mass Black Holes from Ultra-luminous X-Ray Sources

Evidence for Intermediate Mass Black Holes from Ultra-luminous X-Ray Sources. Paola Rodriguez Hidalgo High Energy Astrophysics. Black Hole Masses. Stellar Black Holes (< 20 M o ) Super Massive Black Holes (>10 6 M o ) Something in between?. Intermediate Mass Black Holes.

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Evidence for Intermediate Mass Black Holes from Ultra-luminous X-Ray Sources

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  1. Evidence for Intermediate Mass Black Holes from Ultra-luminous X-Ray Sources Paola Rodriguez Hidalgo High Energy Astrophysics

  2. Black Hole Masses • Stellar Black Holes (< 20 Mo) • Super Massive Black Holes (>106 Mo) • Something in between?

  3. Intermediate Mass Black Holes We are looking fr: MBH ~ 102 - 104 Mo Suggested by: • Ultra-luminous X-Ray Sources (ULXs) • Several globular clusters with excess of dark mass in cores

  4. Ultra-Luminous X-ray Sources • Assuming isotropic X-ray luminosity • Assuming accretion around a black hole LX < LE If isotropy holds, a given L lower limit M erg s-1

  5. ULXs - IMBHs Applying Eddington: • Stellar mass black holes: LX < 1039 erg s-1 ; MBH ~ 20 Mo • Intermediate-mass black holes: LX > 1039 erg s-1 ; MBH ~ 20 Mo LX < 1040.5 erg s-1 ; MBH ~ 250 Mo (Miller & Colbert 2003)

  6. X-ray Energy Spectra of ULXs • Detailed inferences depend on the spectral model used • A popular ULX model is the multi-color disk (MCD) blackbody model: each annulus of the accretion disk radiates as a BB with a radius-dependent temperature. • The inferred temperature of the innermost portion (Tin) is related to MBH:

  7. X-ray Energy Spectra of ULXs • Spectral fit of ULXs requires cool accretion disk temperatures (~100 eV) • Thin disk ULXs correspond to a population of high-state IMBHs with M~16-104 Mo

  8. ULXs - IMBHs • Miller, Fabian & Miller 2004

  9. Is the X-ray Flux isotropic? LE is only applicable if isotropic Looking at their counterparts: • Evidence: diffuse H nebulae found around the X-ray source (i.e. Pakull & Mirioni 200 for NGC 1313) • However, some cases show beaming (Kaaret et al 2003 - associated radio emission)

  10. Some Problems • Luminosities need distance determinations • Need a counterpart to determine the distance • Some sources are not what they seemed (i.e., D.M. Clark et al 2005)

  11. More problems… • If Eddington is not obeyed - ULXs could be outbursts - transient ULXs - super-Eddington emission from accretion disks surrounding stellar mass BHs • In this L range other objects may be confused with ULXs: SNRs, Super-Eddington emission from NS X-ray binaries,

  12. Some facts about ULXs • ULXs do not generally reside in the centers of galaxies • Generally unresolved with Chandra (high spatial resolution ~0”.5) • Many show variability (Fabbiano et al. 2003) • Large majority do not have radio counterparts Hence, ULXs are believed to be powered by accretion onto a compact object

  13. Where do we find ULXs? • Clear correlation between young stellar population and ULXs in a galaxy • ULXs are more numerous in actively star forming galaxies (i.e., the Antennae galaxies) • Also reported in Elliptical galaxies, possibly associated with Globular Clusters (dense environments-ray Energy Spectral ULXs

  14. Conclusion/utter questions • Not simple explanation of nature of ULXs (beamed outbursts stellar mass BHs, IMBHs) • Are there IMBH in our Galaxy?

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