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

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 (lt 20 Mo)
• Super Massive Black Holes (gt106 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

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Ultra-Luminous X-ray Sources

• Assuming isotropic X-ray luminosity
• Assuming accretion around a black hole
• LX lt LE
• If isotropy holds, a given L lower limit M

erg s-1
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ULXs - IMBHs

• Applying Eddington
• Stellar mass black holes
• LX lt 1039 erg s-1 MBH 20 Mo
• Intermediate-mass black holes
• LX gt 1039 erg s-1 MBH 20 Mo
• LX lt 1040.5 erg s-1 MBH 250 Mo
• (Miller Colbert 2003)

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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

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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 M16-104 Mo

8
ULXs - IMBHs

• Miller, Fabian
• Miller 2004

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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)

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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,

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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

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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

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Conclusion/utter questions

• Not simple explanation of nature of ULXs (beamed
  outbursts stellar mass BHs, IMBHs)
• Are there IMBH in our Galaxy?