Gene G. Byrd

OJ 287 - binary pair of supermassive black holes

A historical light curve of the BL Lacertae object OJ 287 is constructed in the optical V band using observations between 1890 and the present. The curve exhibits periodic outbursts at intervals of 11.6 yr or 9 yr. The individual outbursts show an initial maximum with decaying submaxima at intervals of about 1 month. It is proposed that these characteristics are caused by a binary in the nucleus of OJ 287, with the binary members having an accretion disk around them. The outbursts at 9-yr intervals would be caused by the tidal action of the companion on the disk of the larger black hole. A computer simulation is used to demonstrate that the inflow into the center of such a disk during the repeated periastron passages of a companion will produce an outburst similar to the ones observed. Based on indirect evidence, probable masses of 5 billion solar and 20 million solar are determined for the two objects. 38 references.

Tidal generation of active spirals and S0 galaxies by rich clusters

Gavazzi and Jaffe found that late-type spiral galaxies in rich clusters are radio sources 10 times more powerful than spirals outside clusters. Gavazzi and Jaffe propose that ram pressure from the cluster medium causes collapse of dense molecular clouds, star formation, and other activity in the spirals disks. Bothun and Dressler similarly explain blue H I poor disk galaxies found in the central regions of the Coma Cluster via ram pressure effects. With computer simulations, it is shown in the present work that the tidal field of the cluster as a whole is physically sufficient to trigger cluster spiral nuclear and disk activity. It is shown that tidally induced collisions of disk gas clouds should be much more effective than ram pressure in causing activity. The observed tendency for disk galaxies in centers of rich clusters to be barred and S0 is explained as due to the cluster tidal field. Metals in the cluster medium would be enhanced by the expulsion of spirals enriched gas via tidally induced activity. 36 refs.

Star Formation Triggering Mechanisms in Dwarf Galaxies: The Far-Ultraviolet, Hα, and H I Morphology of Holmberg II

Far-ultraviolet (FUV), Ha, and H I observations of dwarf galaxy Holmberg II are used to investigate the means by which star formation propagates in galaxies lacking global internal triggering mechanisms such as spiral density waves. The observations trace the interaction between sites of massive star forma- tion and the neutral and ionized components of the surrounding ISM in this intrinsically simple system. Both local and large-scale triggering mechanisms related to massive star formation are seen, suggesting that feedback from massive stars is a microscopic process operating in all galaxies to a certain degree. The data emphasize the importance of local conditions in regulating star formation from evidence such as massive stars inside ionized shells, compact H II regions surrounding aging clusters, and stars formed in chains of progressing age. Surface brightness pro—les show that current activity correlates with the time-averaged level of past star formation at a given radius demonstrating a reliance on local conditions. Large-scale triggering by H I shells is supported by observations of progenitor populations as well as secondary sites of star formation associated with their dense rims. Analysis of the energy available from massive stars inside H I shells indicates that energy deposited into the ISM from supernovae and stellar winds is sufficient to account for the H I morphology. Ages of individual star-forming regions are derived using B ,H a, and FUV photometry and show both older, diUuse FUV regions and younger, compact H II regions. The distribution of ages is reconciled with the H I morphology, showing a clear preference of young regions for areas of dense H I and old regions for H I voids. Global kinematical properties may also play a role in the star formation process since diUerences in the rotation characteristics of the neutral gas disk correlate with diUerences in triggering mechanisms. Large-scale feedback from massive stars is shown to operate in regions that lack diUerential shear in the gas disk. Subject headings: galaxies: dwarfgalaxies: ISMgalaxies: individual (DDO 50) ¨ stars: formationultraviolet: galaxies

Tidal arms are ubiquitous in spiral galaxies

Using a self-gravitating disk galaxy tidal perturbation survey, we find that close passages of unexpectedly small mass perturbers can excite grand design spiral patterns. Conservatively, (perturber mass/galaxy mass)/(perturber distance/galaxy disk radius) 3 must be at least 0.01 to create a grand design pattern for companions passing in the same sense as the disk turns. For example, a direct disk edge grazer only 0.01 of a galaxys mass will excite grand design arms.

A revised history of the local group and a generalized method of timing

Recent measurements suggest that the giant galaxies IC 342 and Maffei 1 are moving so rapidly for their distances that they were close to M31 only 4 billion years ago. If correct, the two-body approximation of Local Group Timing would not be valid. N-body simulations have been carried out to explore how the indicated configuration of four massive bodies might arise, and to study the implications for the mass of local dark matter and the age of the universe. Provided that the total systematic mass is close to 3 × 10 12 solar masses, the high speed of IC 342 and Maffei 1 and the turn around of the motion of M31 with respect to the Milky Way could be explained if IC 342 and Maffei 1 were each members of binaries which successively fell past M31, interacting with M31 strongly and ejecting one component

Binary pairs of supermassive black holes - Formation in merging galaxies

A process in which supermassive binary blackholes are formed in nuclei of supergiant galaxies due to galaxy mergers is examined. There is growing evidence that mergers of galaxies are common and that supermassive black holes in center of galaxies are also common. Consequently, it is expected that binary black holes should arise in connection with galaxy mergers. The merger process in a galaxy modeled after M87 is considered. The capture probability of a companion is derived as a function of its mass. Assuming a correlation between the galaxy mass and the blackholes mass, the expected mass ratio in binary black holes is calculated. The binary black holes formed in this process are long lived, surviving longer than the Hubble time unless they are perturbed by black holes from successive mergers. The properties of these binaries agree with Gaskells (1988) observational work on quasars and its interpretation in terms of binary black holes. 39 refs.

Local dark matter and dark energy as estimated on a scale of ~1 Mpc in a self-consistent way

Context. Dark energy was first detected from large distances on gigaparsec scales. If it is vacuum energy (or Einstein’s Λ), it should also exist in very local space. Here we discuss its measurement on megaparsec scales of the Local Group. Aims. We combine the modified Kahn-Woltjer method for the Milky Way-M 31 binary and the HST observations of the expansion flow around the Local Group in order to study in a self-consistent way and simultaneously the local density of dark energy and the dark matter mass contained within the Local Group. Methods. A theoretical model is used that accounts for the dynamical effects of dark energy on a scale of ∼ 1M pc. Results. The local dark energy density is put into the range 0.8−3.7ρv (ρv is the globally measured density), and the Local Group mass lies within 3.1−5.8 × 10 12 M� . The lower limit of the local dark energy density, about 4/5× the global value, is determined by the natural binding condition for the group binary and the maximal zero-gravity radius. The near coincidence of two values measured

Dark energy domination in the Virgocentric flow

Context. The standard ACDM cosmological model implies that all celestial bodies are embedded in a perfectly uniform dark energy background, represented by Einsteins cosmological constant, and experience its repulsive antigravity action. Aims. Can dark energy have strong dynamical effects on small cosmic scales as well as globally? Continuing our efforts to clarify this question, we now focus on the Virgo Cluster and the flow of expansion around it. Methods. We interpret the Hubble diagram from a new database of velocities and distances of galaxies in the cluster and its environment, using a nonlinear analytical model, which incorporates the antigravity force in terms of Newtonian mechanics. The key parameter is the zero-gravity radius, the distance at which gravity and antigravity are in balance. Results. 1. The interplay between the gravity of the cluster and the antigravity of the dark energy background determines the kinematical structure of the system and controls its evolution. 2. The gravity dominates the quasi-stationary bound cluster, while the antigravity controls the Virgocentric flow, bringing order and regularity to the flow, which reaches linearity and the global Hubble rate at distances ≳15 Mpc. 3. The cluster and the flow form a system similar to the Local Group and its outflow. In the velocity-distance diagram, the cluster-flow structure reproduces the group-flow structure with a scaling factor of about 10; the zero-gravity radius for the cluster system is also 10 times larger. Conclusions. The phase and dynamical similarity of the systems on the scales of 1-30 Mpc suggests that a two-component pattern may be universal for groups and clusters: a quasi-stationary bound central component and an expanding outflow around it, caused by the nonlinear gravity-antigravity interplay with the dark energy dominating in the flow component.

The unusual radio galaxy 3C 288

VLA observations of the radio galaxy 3C 288 at 1.5, 4.9, and 15 GHz are presented. The features revealed in the data include a jet and counterjet near the radio core and faint wings of emission connected to the elongated lobes. The results suggest that the host galaxy is probably the dominant member of a distant cluster. It is found that the larger-scale structure of 3C 288 may be an example of a disturbed secondary-flow pattern. 58 references.

Dark energy and the structure of the Coma cluster of galaxies

Context. We consider the Coma cluster of galaxies as a gravitationally bound physical system embedded in the perfectly uniform static dark energy background as implied by theCDM cosmology. Aims. We ask if the density of dark energy is high enough to affect the structure of a large rich cluster of galaxies? Methods. We use recent observational data on the cluster together with our theory of local dynamical effects of dark energy, including the zero-gravity radius RZG of the local force field as the key parameter. Results. 1) Three masses are defined which characterize the structure of a regular cluster: the matter mass MM, the dark-energy effective mass MDE ( 14 Mpc and should be taken into account when its total mass is derived.