Radiation, winds, and jets from the active nucleus of a massive galaxy can interact with its interstellar medium, and this can lead to ejection or heating of the gas. This terminates star formation in the galaxy and stifles accretion onto the black hole. Such active galactic nuclei (AGN) feedback can account for the observed proportionality between the central black hole and the host galaxy mass. Direct observational evidence for the radiative or quasar mode of feedback, which occurs when AGN are very luminous, has been difficult to obtain but is accumulating from a few exceptional objects. Feedback from the kinetic or radio mode, which uses the mechanical energy of radio-emitting jets often seen when AGN are operating at a lower level, is common in massive elliptical galaxies. This mode is well observed directly through X-ray observations of the central galaxies of cool core clusters in the form of bubbles in the hot surrounding medium. The energy flow, which is roughly continuous, heats the hot intraclu...

Observational Evidence of Active Galactic Nuclei Feedback

We quantify the importance of mass accretion during AGN phases in the growth of supermassive black holes (BH) by comparing the mass function of black holes in the local universe with that expected from AGN relics, which are black holes grown entirely with mass accretion during AGN phases. The local BH mass function (BHMF) is estimated by applying the well-known correlations between BH mass, bulge luminosity and stellar velocity dispersion to galaxy luminosity and velocity functions. We find that different correlations provide the same BHMF only if they have the same intrinsic dispersion. The density of supermassive black holes in the local universe which we estimate is ρBH = 4.6 +1.9 −1.4 h 2.7 × 10 5 M⊙ Mpc −3 . The relic BHMF is derived from the continuity equation with the only assumption that AGN activity is due to accretion onto massive BH’s and that merging is not important. We find that the relic BHMF at z = 0 is generated mainly at z 10 9 M⊙ but can become as large as ∼ 10 9 yr for the lowest acceptable ǫ and λ values.

Local supermassive black holes, relics of active galactic nuclei and the X-ray background

High resolution X-ray spectroscopy of the hot gas in galaxy clusters has shown that the gas is not cooling to low temperatures at the predicted rates of hundreds to thousands of solar masses per year. X-ray images have revealed giant cavities and shock fronts in the hot gas that provide a direct and relatively reliable means of measuring the energy injected into hot atmospheres by active galactic nuclei (AGN). Average radio jet powers are near those required to offset radiative losses and to suppress cooling in isolated giant elliptical galaxies, and in larger systems up to the richest galaxy clusters. This coincidence suggests that heating and cooling are coupled by feedback, which suppresses star formation and the growth of luminous galaxies. How jet energy is converted to heat and the degree to which other heating mechanisms are contributing, e.g., thermal conduction, are not well understood. Outburst energies require substantial late growth of supermassive black holes. Unless all of the ∼10 62 erg required to suppress star formation is deposited in the cooling regions of clusters, AGN outbursts must alter large-scale properties of the intracluster medium.

Heating Hot Atmospheres with Active Galactic Nuclei

Part I. Astronomical Background: 1. High energy astrophysics - an introduction 2. The stars and stellar evolution 3. The galaxies 4. Clusters of galaxies Part II. Physical Processes: 5. Ionisation losses 6. Radiation of accelerated charged particles and bremsstrahlung of electrons 7. The dynamics of charged particles in magnetic fields 8. Synchrotron radiation 9. Interactions of high energy photons 10. Nuclear interactions 11. Aspects of plasma physics and magnetohydrodynamics Part III. High Energy Astrophysics in our Galaxy: 12. Interstellar gas and magnetic fields 13. Dead stars 14. Accretion power in astrophysics 15. Cosmic rays 16. The origin of cosmic rays in our galaxy 17. The acceleration of high energy particles Part IV. Extragalactic High Energy Astrophysics: 18. Active galaxies 19. Black holes in the nuclei of galaxies 20. The vicinity of the black hole 21. Extragalactic radio sources 22. Compact extragalactic sources and superluminal motions 23. Cosmological aspects of high energy astrophysics Appendix References Index.

High Energy Astrophysics

A significant fraction of nearby galaxies show evidence of weak nuclear activity unrelated to normal stellar processes. Recent high-resolution, multiwavelength observations indicate that the bulk of this activity derives from black hole accretion with a wide range of accretion rates. The low accretion rates that typify most low-luminosity active galactic nuclei induce significant modifications to their central engine. The broad-line region and obscuring torus disappear in some of the faintest sources, and the optically thick accretion disk transforms into a three-component structure consisting of an inner radiatively inefficient accretion flow, a truncated outer thin disk, and a jet or outflow. The local census of nuclear activity supports the notion that most, perhaps all, bulges host a central supermassive black hole, although the existence of active nuclei in at least some late-type galaxies suggests that a classical bulge is not a prerequisite to seed a nuclear black hole.

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Nuclear Activity in Nearby Galaxies

Results of an investigation of the X-ray properties of quasars conducted using the Einstein Observatory (HEAO 2) are reported. The positions, fluxes and luminosities of 35 known quasars were observed by the Einstein high-resolution imaging detector and the imaging proportional counter. Assuming optical redshifts as valid distance indicators, 0.5-4.5 keV X-ray luminosities ranging from 10 to the 43rd to 10 to the 47 ergs/sec are obtained, with evidence of very little cold gas absorption. Flux variability on a time scale of less than 10,000 sec is observed for the quasar OX 169, which implies a mass between 8 x 10 to the 5th and 2 x 10 to the 8th solar masses for the black hole assumed to be responsible for the emission. Preliminary results of the quasar survey also indicate that quasars contribute significantly to the diffuse X-ray background.

X-ray studies of quasars with the Einstein Observatory. II

A method for determining luminosity functions incorporating both flux measurements and flux upper limits, with applications to the average X-ray to optical luminosity ratio for quasars

We report the results of 0.5--3.0 keV X-ray observations of the central region of the Perseus cluster carried out with the Imaging Proportional Counter and High Resolution Imager aboard the Einstein Observatory. In addition to the very extended thermal cluster emission and a sharply peaked component at NGC 1275 previously known, the high resolution image reveals a point source coincident with the optical nucleus of NGC 1275. The 0.5--3.0 keV luminosity of the compact source is approx.10/sup 44/ ergs s/sup -1/.

Soft X-ray images of the central region of the Perseus cluster

The first image of an X-ray burst was recorded with the HRI detector at the Einstein Observatory while observing the globular cluster Terzan 2. The burst was coincident with a persistent X-ray source located near the center of the cluster (thus confirming an earlier suggested identification) and reached a peak luminosity exceeding 5 x 10 to the 38th (d/10 kpc) squared. After a rapid rise to peak luminosity, a double-peaked spectral variation was observed over the next approximately 20 s with anticorrelated changes in the apparent emission region radius and temperature derived from blackbody (and modified blackbody) spectral fits. A shell or disk geometry, which undergoes adiabatic expansion and contraction, may be implied for the burst emission region. Alternatively, Comptonization is required. It is also shown that the peak burst luminosity must exceed the Eddington limit.

Time-resolved imaging and spectral studies of an X-ray burst from the globular cluster Terzan

The properties of very low luminosity active galactic nuclei are not well studied, and, in particular, their possible contribution to the diffuse X-ray background is not known. In the present investigation, an X-ray luminosity function for the range from 10 to the 39th to 10 to the 42.5th ergs/s is constructed. The obtained X-ray luminosity function is integrated to estimate the contribution of these very low luminosity active galaxies to the diffuse X-ray background. The construction of the X-ray luminosity function is based on data obtained by Keel (1983) and some simple assumptions about optical and X-ray properties.

A. M. Soltan

Papers

X-ray studies of quasars with the Einstein Observatory. II

A method for determining luminosity functions incorporating both flux measurements and flux upper limits, with applications to the average X-ray to optical luminosity ratio for quasars

Soft X-ray images of the central region of the Perseus cluster

Time-resolved imaging and spectral studies of an X-ray burst from the globular cluster Terzan

Very low luminosity active galaxies and the X-ray background