Judith J. Perry

Discovery of extended Faraday rotation compatible with spiral structure in an intervening galaxy at Z = 0.395 - New observations of PKS 1229 - 021

The damped Lyα and 21 cm absorption-line quasar PKS 1229-021 (z=1.038) has been mapped in detail with the VLA at seven frequencies, with polarimetry. It has a radio jet, whose rotation measure distribution at 0″.46 shows a clear and strong «oscillation» over its length, which is ∼35h 65 kpc at the absorption-line redshift of 0.395. This new, extended, intervenor probe combined with the optical absorption spectrum, well studied by Briggs and coworkers, suggests that the intervenor at z=0.395 is a «bisymmetric magnetic field» spiral galaxy, possibly similar to M81

Symbiotic starburst–black hole active galactic nuclei – I. Isothermal hydrodynamics of the mass‐loaded interstellar medium

Compelling evidence associates the nuclei of active galaxies and massive starbursts. The symbiosis between a compact nuclear starburst stellar cluster and a massive black hole can self-consistently explain the properties of active nuclei. The young stellar cluster has a profound effect on the most important observable properties of active galaxies through its gravity, and by mass injection through stellar winds, supernovae and stellar collisions. This mass loss, injected throughout the nucleus, creates a hot nuclear interstellar medium (nISM). The cluster both acts as an optically thin fuel reservoir and enriches the nISM with the products of nucleosynthesis. The nISM flows under gravitational and radiative forces until it leaves the nucleus or is accreted on to the black hole or accretion disc. The radiative force exerted by the black hole–accretion disc radiation field is not spherically symmetric. This results in complex flows in which regions of inflow can coexist with high Mach number outflowing winds and hydrodynamic jets. We present two-dimensional hydrodynamic models of such nISM flows, which are highly complex and time-variable. Shocked shells, jets and explosive bubbles are produced, with bipolar winds driving out from the nucleus. Our results graphically illustrate why broad-emission-line studies have consistently failed to identify any simple, global flow geometry. The real structure of the flows is inevitably yet more complex. The structure of these nISM flows is principally determined by two dimensionless quantities. The first is the magnitude of the stellar cluster velocity dispersion relative to the sound speed in the nISM. These speeds measure the gravitational and thermal energies in the nISM respectively, and, therefore, whether the gas is initially bound or escapes in a thermal wind. The second parameter is the Mach number of the ill-collimated nISM flow which is driven away from the central black hole. We discuss a two-parameter classification based on this observation which, in future papers, we will relate to empirical classifications. The interplay between the nucleus and the wider galaxy depends critically on the exchange of radiative and mechanical energy. The outbound mechanical energy transfer is governed by the nuclear stellar cluster. Active galactic nuclei will only be understood once the symbiotic relationships between the black hole, the stellar cluster and the galaxy are considered. It is impossible to treat correctly any isolated component. Our conceptually simple and self-consistent symbiotic model explains the observed complexity of active galaxies without ad hoc measures.

Magnetic field strengths in high-redshift galaxies - Can the galactic dynamo be tested?

The hypothesis that the population of strong H I absorption systems is responsible for a significant excess Faraday rotation measure in quasars is discussed, and it is concluded that the case is unproved, in contrast to a recent analysis by Wolf et al. (1991). The limitations and pitfalls inherent in attempts to derive firm magnetic field strengths from the existing integrated rotation measures of quasars are discussed, and it is shown that although it is premature to use integrated quasar rotation measures to either confirm or rule out particular mechanisms of magnetic field amplification in galaxy disks, the present observations may call for reexamination of current theories of large-scale magnetic field generation. The sources of rotation measure in the double quasar 0957+561 are also discussed.

The jet rotation measure distribution and the optical absorption system near the z=1.953 quasar 3C 191

A subarcsec-resolution map of the Faraday rotation of an extended high-redshift quasar, 3C 191, is presented. 3C 191 has strong optical absorption at z(abs) = about z(em) and a large integrated rotation measure. It is shown that the extraordinarily large rotation measure along the jet is unlikely to be intrinsic to the jet but rather probably arises in the absorbing system at z(abs) = 1.945. 16 refs.

3 C 191 revisited - Circumquasar shells and radio jets

The quasar 3C 191 is reexamined in the light of recent rotation measure (RM) observations by Kronberg et al. (1990) and recent He II emission data, and an updated model for the intrinsic formation of the narrow shell of this object is developed. It is argued that the extraordinarily high rotation measure in the jet of this quasar is produced by an intrinsic absorption line system at z(abs) = 1.9453, which has a thin shell configuration produced as a wind from the quasar central regions sweeps up interstellar in an elliptical host galaxy. 28 refs.

Starburst–black hole QSO model II: Broad absorption lines

Supernovae provide a natural connection between the production of broad absorption lines (BAL) and the HIL, in the symbiosis between a black hole and a nuclear stellar cluster. Ejecta velocities are very similar to those observed in the absorption line troughs. The frequency of occurrence of BAL QSOs is similar to the covering factors (≊5–10%) inferred for HIL production (Perry & Dyson7,8). We argue that the BAL is produced in the small (≊0.1) fraction of supernova ejecta which is shock heated to only low temperatures when the supernova blast wave and the shock moving back into the ejecta move at low velocities relative to each other (during the initial phase of the interaction). Suppression of red‐shifted absorption lines arises because supernova debris moving toward the central source is slowed down much more rapidly by the wind than is material moving away. Absorption trough velocity variations should occur over time scales characteristically of tens of years; however, line structure and line strength ...

Starburst–black hole QSO model I: Broad emission lines and the central luminosity

QSOs in galactic nuclei can be modeled using a massive black hole, a nuclear starburst stellar cluster, an accretion disc and an interstellar medium. The symbiosis of the starburst and black hole self‐consistently explains the production of the bolometric luminosity and the lines. The ISM contains both inflow, which fuels the black hole and accretion disc, and a wind. This system leads naturally to a two component broad emission line region (BELR). High ionization lines (the HIL) are emitted by wind gas which has cooled after shocking against supernovae in the starburst cluster (Perry & Dyson7). the HIL velocity reflects a combination of the wind speed and the Keplerian velocity of the supernovae which is hypersonic with respect to the second speed (cs≊400 km s−1) in the Compton heated wind. Low ionization lines (LIL) are emitted from the accretion disc surface: the disc rotational velocity produces their line widths (Collin‐Souffrin, Dyson, McDowell & Perry1).

Wolf-Rayet stars in Active Galactic Nuclei

Starbursts, black holes and AGN have strong observational links, as discussed elsewhere in these proceedings. Perry & Dyson (1985 (PD), see also Perry 1994) studied the role of shocks around supernovae and stellar wind bubbles in the nuclei of active galaxies. Both the ejecta and the ambient ISM are initially shocked to high temperatures. PD found that while the shocked gas is maintained at high pressure by ram pressure, it cools rapidly, to then produce the observed optical and UV emission lines. The mass supply rate from the nuclear starburst, inferred from the strength of the emission lines, tallies well with that required by an accreting black hole to generate the observed luminosity. A symbiosis between a starburst stellar cluster and an accreting black hole naturally generates the observational features associated with QSOs. Wolf-Rayet stars are an important constituent of such metal-rich starburst clusters. In clusters with metal abundances typical of galactic nuclei, the WR phase is responsible for a substantial fraction of the mass loss from massive stars. The high metallicity of the gas in WR winds promotes Bremsstrahlung and line emission, so shocked WR ejecta will be seen preferentially in such nuclei. In particular, Seyfert nuclei are sufficiently small that supernovae will be infrequent, and those that do occur will run rapidly through them. Therefore stellar wind sources of shocked gas will dominate. WR stars may also have important consequences for the abundances of line-emitting gas in all AGN, particularly in producing high metal abundances in cool gas at the early cosmic times to which AGN are now observed. The strong neon lines seen in the UV (Hamann et ale 1998) are also suggestive of the importance of mass input by WR stars. Compared to well-studied WR/OB binaries, WR bow-shocks in AGN will be rather larger, and the WR ejecta flowing through them will be on the margins of cooling. The external radiation field in AGN serves both to enhance the cooling of the shocked gas somewhat, and also to irradiate any gas which cools in the bow-shock and hence to enhance its line emission. Stevens et ale (1992) found that strongly cooling shocks were highly unstable, but classified shocks with tcool/tdyn == X ~ 1 as effectively adiabatic. In the Figure, a simulation of a WR bow-shock with a marginally-cooling WR wind is shown. Gas which shocks at the apex maintains its small angular momentum

Line Forming Regions in Active Galaxies and Their Nuclei

The spectra of active galaxies and their nuclei are rich in emission and absorption line features. A major aim of present research is the development of self-consistent hydrodynamic models for the production of the line-forming regions. We here review such modelling and stress the central role played by shock phenomena induced by winds and explosions on scales ranging from the circumstellar to the intergalactic.

Flows and shocks in active galaxies and their nuclei

Observations of active galactic nuclei imply that shocks must be an essential and important part of their structure. We outline the basic observations, and discuss those features which must be addressed by any physical model of active nuclei. These features, in particular the observed spectrum of strong emission and absorption lines, lead naturally to the conclusion that shocks are present. The velocity widths of these lines, which range from hundreds to many thousands of kilometres per second, are most readily explained by models in which shocks play an important role in the generation of cool gas. The extreme parameters of the shocks in and around active nuclei provide a unique application for the physics discussed in this meeting.