Of Systems of Galaxies

IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. PS-14, NO. 6, DECEMBER 1986 763 Evolution of the Plasma Universe: II. The Formation of Systems of Galaxies ANTHONY L. PERATT, SENIOR MEMBER, IEEE Abstract-The model of the plasma universe, inspired by totally un- and the formation of stars within the dusty galactic plas- expected phenomena observed with the advent and application of fully mas [2]-[4]. three-dimensional electromagnetic particle-in-cell simulations to filamentary plasmas, consists of studying the interaction between field- Although the gravitational force is weaker than the aligned current-conducting, galactic-dimensioned plasma sheets or fil- electromagnetic force by 39 orders of magnitude, gravi- aments (Birkeland currents). In a preceding paper, the evolution of tation is one of the dominant forces in astrophysics when the interaction spanned some 108_109 years, where simulational ana- electromagnetic forces neutralize each other, as is the case logs of synchrotron-emitting double radio galaxies and quasars were when large bodies form [5]. Indicative of the analogy of discovered. This paper reports the evolution through the next 109-5 x 109 years. In particular, reconfiguration and compression of tenuous forces for the motion of electrons and ions in the electro- cosmic plasma due to the self-consistent magnetic fields from currents magnetic field and the motion of large bodies in the grav- conducted through the filaments leads to the formation of elliptical, itational field is the ease with which a plasma model may peculiar, and barred and normal spiral galaxies. The importance of be changed to a gravitational model. This transformation the electromagnetic pinch in producing condense states and initiating requires only a change of sign in the (electrostatic) poten- gravitational collapse of dusty galactic plasma to stellisimals, then stars, tial is discussed. Simulation data are directly compared to galaxy mor- calculation such that like particles attract instead of phology types, synchrotron flux, Hi distributions, and fine detail struc- repel, followed by setting the charge-to-mass ratio equal ture in rotational velocity curves. These comparisons suggest that to the square root of the gravitational constant (a gravi- knowledge obtained from laboratory, simulation, and magnetospheric tational model cannot be simply changed to an electro- plasmas offers not only to enhance our understanding of the universe, magnetic model as the full set of Maxwell's equations are but also to provide feedback information to laboratory plasma exper- iments from the unprecedented source of plasma data provided by the required in the latter). plasma universe. The basic model of the plasma universe, inspired by the observation that most cosmic plasmas are filamentary in I. INTRODUCTION structure [6], consists of studying the interaction between T HE evolution of cosmic plasma from a current-conducting galactic-dimensioned plasma fila- filamentary ments field state to the development of double radio sources and aligned along magnetic lines (Birkeland currents, [1]). Although the entire filamental ex- quasars was investigated in the first part to this sequel circuit is paper (Paper I) [1]. The time frame pected to be hundreds of megaparsecs in length and is of this study, based probably no less upon scaling simulation parameters to galactic complex than the magnetospheric current dimen- distribution near sions, spanned some 108_109 years. In this paper (Paper Earth, only a fraction of the circuit is II), the evolution for the next 1-5 x simulated. The fraction of the length corresponds to a lo- 109 years under the cal that is influence of electromagnetic forces acting on the plasma region capable of interacting with an adjacent is investigated. local region in a neighboring filament. Strictly speaking, the The importance of electromagnetic forces in galactic neighboring regions in adjacent filaments are double and stellar layers since the model consists of a parallel electric field evolution derives from the fact that the uni- in verse is largely matter in its plasma state. each of the pinched plasma filaments [7]. Because of The observed the axial E stars are composed of plasmas, as are the interstellar and field, electrons within the pinch are acceler- interplanetary media and the ated along the filament producing strong currents and also outer atmospheres of planets. radiating The neutral HI regions in galaxies are also plasma al- away energy in the form of synchrotron radia- though the degree of ionization is tion at radio, optical, and X-ray wavelengths. probably only 10-4. It Both the intra- and intergalactic media then consist of is the purpose of this paper to continue the investi- plasma, leading to the coinage of the term "plasma uni- gation of the dynamics of the denser interacting plasmas verse." Electromagnetic forces can then be expected to pinched within the filaments by means of the electromag- play a crucial role in the development of the plasma uni- netic and gravitational force laws. That this is possible is verse including both the formation of systems of galaxies due largely to the advent of the particle simulation of dy- namic systems in three dimensions on large computers, allowing the computation of up to many millions of Manuscript received June 6, 1986; revised July 17, 1986. charge The author is with the Los Alamos National Laboratory, Los Alamos, and mass particles according to their respective force laws. NM 87545. This approach to the study of cosmic plasma is labeled IEEE Log Number 8610914. "gravito-electrodynamic" [8]. 0093-3813/86/1200-0763$01.00 © 1986 IEEE 764 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. PS-14, NO. 6, DECEMBER 1986 Galaxy 3C465 Cyg A TABLE I PROPERTIES OF SYNCHROTRON-EMITTING GALACTIC RADIO SOURCES Cen A 3C452 -2 Source Power W/Hz Geometry and Dimension Red-Shift. z double radio galaxies, 1026 1029 two extended radio lobes separated 0.01-1.8 quasars tens of Kpc to tens of Mpc; oftentimes 0.3-3.8 -4 a central component is present ellipncals 1023 1026 kiloparsecs to decaparsecs -6 cD giant ellipticals with very extended haloes N bright nucleus surrounded 0120E -8 by faint nebulosity I Quasars tO24.5 break in RLF 1026 Seyfert-like spectra -10 _ Seyfert spirals elementary spirals of a few 0.02-0.09 tens of kpc extent; most acfive nuclei. -12 K spirals <lo23 two radio components: -IOKpc 0.003-0.5 coincident with spiral disk, .Kpc (Andromeda -14 nuclear region. is blue- shifted) 20 22 24 26 28 1021.3 break in RLF Log P(1.4 GHz) - W Hz-' our Fig. 1. The radio luminosity function of galaxies and quasars at the pres- an order of magnitude greater than the power of Gal- ent cosmological epoch (adapted from Fanti and Perola [10]). axy) the power comes principally from spiral galaxies. In the region 102 -1023 W/Hz, an overlap of spiral and The gross radio properties of galaxies are reviewed in elliptical galaxies occurs. The "ellipticals" are in fact a Section II. Section III describes a transistion through the hybrid class, containing bona fide ellipticals along with N following sequence of cosmic objects: double radio gal- galaxies (a bright nucleus surrounded by a faint nebulos- axy to radioquasar; radioquasar to radioquiet quasi-stel- ity) to that of cD galaxies (giant ellipticals with very ex- lar objects (QSO's) [9]; radioquiet QSO's to peculiar and tended radio "halos"). Noteworthy in Fig. 1 is a "break" Seyfert spiral galaxies; and peculiar and Seyfert galaxies in synchrotron power from ellipticals at 1024.5 W/Hz and to normal and barred galaxies. The various classifications another at 1021.3 W/Hz for spirals. of elliptical and spiral galaxies are discussed in Sections The size of the radio-emitting regions in galaxies spans IV and V, respectively. The importance of electromag- a very wide range. At powers larger than about 1023 netic effects in describing both the bulk- and fine-detail W/Hz at 1.4 GHz the radio emission is generally domi- structure in the velocity curves of spiral galaxies is also nated by an extended component, whose size goes from reported in Section V. Multiple interacting galaxies are tens of kiloparsecs (e.g., Cyg A) to tens of megaparsecs studied in Section VI. The chemical composition and the (e.g., 3C236). Often a very compact central radio com- distribution of neutral hydrogen in galaxies is discussed ponent is present, whose power ranges from 1022 up to in Section VII. Section VIII covers the Alfven-Carlqvist 1025 W/Hz, and which may be seen to vary with time. model for star formation in pinched plasma filaments Extended and central radio components are typically found while Section IX reports the extension of three-dimen- also in quasars. sional electromagnetic particle simulation techniques to At powers less than about 1023 W/Hz the size of the include gravitational forces with the formation of stars. radio region in elliptical galaxies is generally measured in kiloparsecs and often reduces to a compact central com- II. GROSS RADIO PROPERTIES OF GALAXIES ponent. In spiral galaxies, the next stage of a suggested The radio power L of galaxies, integrated from 10 MHz epochological sequence in Fig. 1, the situation is differ- to 100 GHz, ranges from about 1030 to about 1038 W, and ent. Apart from the radical change in morphology be- relative to their optical luminosity from less than 10-6 to tween elliptical and spiral, the spiral galaxies have not about 1 [10], [11]. The distribution in power is described only a compact nuclear component (of radio dimension by means of the radio luminosity function (RLF), which between 0.1 and 1 kpc) but also a component of size - 10 represents the number of radio-emitting galaxies per unit kpc coincident with the spiral disk.

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