BLACK HOLES: FROM STARS TO GALAXIES – ACROSS THE RANGE OF MASSES

Felix Mirabel

European Southern Observatory. Chile

(on leave from CEA. France)

• In last decade there have been overwhelming evidences

for the existence of BHs as stellar remnants in binaries,

as supermassive objects at the centers of galaxies, and

possibly, as intermediate-mass compact objects in

ultraluminous X-ray sources.

• BHs are real physical entities that play an important role

in several areas of modern astrophysics

STELLAR BLACK HOLES• Compact objects in stellar binaries with mass functions greater than 4.• ~20 known out of a total population that could be as large as 100 million.

• Is there a real gap for MBH = 2.2 - 4 M ?• Why in the Milky Way has not been found a stellar BH with MBH >18 M ?• Is this due to poor statistics or to the metal content of BH progenitors ?• Are BHs always form in energetic supernovae as suggested by the

chemical composition of some donors, or could they also be form directly ?• Does explosion vs. implosion depend on the mass of the collapsing core ?

• The observation of GRBs of long duration should shed light for our understanding of the mechanisms of stellar-mass black hole formation.

Synergy needed

SUPERMASSIVE BLACK HOLES• Dynamics is the most direct method to determine the masses of compact

objects, and therefore, the best evidence for their existence.• First dynamic evidence by the motion of H2O masers in NGC 4258.• Best dynamic evidence by the motion of stars around the dormant BH of

3-4 x 106 M at the center of our Galaxy.• Presence of a cluster of massive stars distributed along randomly

inclined disks of 0.04 pc and 0.5 pc radii.• This cluster seems to have been formed in situ and its study may open

new horizons for our understanding of the formation of massive BHs and its relation with massive formation of stars in galactic centers.

• SMBHs are ubiquitous. Their mass is proportional to that of the bulge.• The most massive are at z > 6 and must have assembled in t < 109 yr.• Lower mass SMBHs formed more slowly by mergers at z < 3.• The peak accretion rate took place at z~0.7 as the peak IR background. • Due to gravitational recoil SMBHs could be off center and running away.

HOW WERE SMBHs FORMED ?

BHs OF INTERMEDIATE MASS

• Possible existence of BHs with M > 100 M in ULXs because of X-ray spectra properties, QPOs, and injected energy in surrounding nebulae. Furthermore, stellar BHs show luminosity saturation.

• The luminosity of ULXs fits the luminosity function of BHXRBs.

• No dynamic evidence found so far by the motion of satellite objects.• No hyper-luminous stellar BH such as SS433 or GRS 1915+105 has

been found in our Galaxy hosting an IMBHs. Upper limit is M ~ 20 M

• Why in our Galaxy -where the determination of the mass functions is possible-, no IMBH is found ?

• IMBHs may be there but are difficult to identify.

ANALOGOUS PHENOMENA IN BHs ACROSS THE RANGE OF MASSES

• Accretion-ejection coupling in microquasars and quasars (e.g. 3C120).• Analogous time lags in adiabatically expanding clouds in quasi-periodic

flares of Sgr A* and microquasars. Rotating blobs or jets ? • At low accretion rates the power is dominated by synchrotron, compact,

flat spectrum jets, and universal correlations are being found.• In high accretion states there are non-relativistic outflows with masses

as large as 30% the accreting mass.• The joint action of massive outflows and jets heat and blow away the

surrounding medium (ISM/IGM). Solve the cooling flow problem.• Bended disks re-direct the jets. This geometry could account for the

unified model of AGN, and the large fraction of obscured AGN. • Inflow of mass & jet collimation close to the BH in terms of the

gravitational radius can be zoomed with better angular resolution in SMBH than in stellar-mass BHs.

BHs AS PROBES OF GRAVITY IN THE STRONG-FIELD REGIME

• Much of the radiation emerges within 6 Rg

• BHs are determined by mass, spin and electric charge. THE SPIN CAN BE DERIVED FROM: • X-ray flux and temperature.• Skewed fluorescence iron lines.• QPOs of maximum fix frequency.

BH ASTROPHYSICS IS TODAY IN SIMILAR SITUATION AS STELLAR ASTROPHYSICS IN THE FIRST DECADES OF THE XX CENTURY.

EMPIRICAL CORRELATIONS PRECEEDS THE PHYSICAL UNDERSTANDING OF STARS AND BHs.

Thank to G. Matt, V. Karas and the local support !

&

have a good trip back home !