Transcript Evidence for Intermediate Mass Black Holes and

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 Mo)
 Super Massive Black Holes (>106 Mo)
 Something in between?
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
Ultra-Luminous X-ray Sources
 Assuming isotropic X-ray luminosity
 Assuming accretion around a black hole
LX < LE
LE 
4GMmP
T
 M 
-1
erg
s
1.3 10  
Mo 
If isotropy holds, a given L

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lower limit M
ULXs - IMBHs
Applying Eddington: LE 
4GMmP
T
 M 
1.3 10  
Mo 
 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)
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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 radiusdependent temperature.
 The inferred temperature of the innermost portion
(Tin) is related to MBH:
kTin  M
 14
X-ray Energy Spectra of ULXs
kTin  M
 14
 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
ULXs - IMBHs
 Miller, Fabian
& Miller 2004
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)
Some Problems
 Luminosities need distance determinations
LX  4d FX
2
 Need a counterpart to determine the
distance
 Some sources are not what they seemed

(i.e., D.M. Clark et al 2005)
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,
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
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
Conclusion/utter questions
 Not simple explanation of nature of ULXs
(beamed outbursts stellar mass BHs,
IMBHs)
 Are there IMBH in our Galaxy?