Session 16 - Low Luminosity AGN.
Oral session, Monday, June 10
Union Theater,

[16.04] Relativistic Kinematics of Bipolar Ejecta from AGN (with Application to NGC 4258)

L. M. Ozernoy (CSI/GMU and GSFC/NASA)

The kinematical model of jets/blobs ejected from AGN relativistically with equal velocities in the opposite directions^1 is developed to determine the basic parameters of the model if the redshifts of the two jets/blobs, z_1 and z_2(>z_1), can be measured. The bulk Lorentz factor, \gamma, and the direction of the ejecta, l= \cos i\cos\theta (i being the inclination angle and \theta being the angle between the jet/blob direction and the rotational axis), are found to be \gamma\equiv 1/\sqrt1-\beta^2=1+1øver 2\left(z_1+z_2\right) and l=\left(z_2-z_1\right)/2\gamma\beta, respectively.

Recently, optical redshifts of two ejecta have been measured (presumably for the first time in an extragalactic object) for the two central blobs in NGC 4258 to be z_1=0.398 and z_2=0.653 (ref.^2). The above equations yield \beta=0.755, \gamma=1.525, l=0.111. Assuming, for simplicity, \theta=0, this gives i=83^\circ.6, which should be confronted with the observationally found i=83^\circ\pm 4^\circ (ref.^3). The Doppler, and not an intrinsic (such as gravitational), nature of the blob redshifts, as well as the validity of the relativistic model as a whole can be further tested by measuring the following predicted features of a purely relativistic origin: (i) arm length asymmetry Q=\left(1+\beta\cos i\right)/\left(1-\beta\cos i\right)= 1.18 and (ii) superluminal flying apart of the blobs with the relative velocity v=2\beta c\sin i/\left(1-\beta^2\cos^2 i\right)= 1.49 c. If the blobs observed so far in X-rays and at optical wavelengths also have radio counterparts, VLA observations could reveal their proper motion expected to be as large as 1.3\cdot 10^-2\left(D/7 Mpc \right)^-1 arc sec/yr, where D is the distance to the galaxy.

While a putative central black hole in NGC 4258 with its masing disk offers a general relativity lab, the central blobs turn out to be a special relativity lab (even though i is not small!) Thus the nucleus of this galaxy, as a whole, represents the nearest extragalactic true relativity laboratory.

References: \small ^1Ozernoy, L.M. amp; Sazonov, V.N. 1968, Nature 219, 467; 1969, Ap. Sp. Sci. 3, 395. ^2Burbidge, E.M. 1995, Aamp;A 298, L1. ^3Miyoshi, M. et al. 1995, Nature 373, 127.