Very-long-baseline radio interferometry (VLBI) observations of gamma-ray blazars: results from millimeter-VLBI observations.

Abstract

VLBI observations of the extremely y-bright blazar PKS 0528+134 at 8, 22, 43, and 86 GHz reveal a strongly bent one-sided-core jet structure with at least three moving and two apparently stationary jet components. At the highest observing frequencies the brightest and most compact jet component (the VLBI core) is unresolved with an upper limit to its size of '50 microarcsec corresponding to "0.2 parsec [Ho = 100 km s'l Mpc-1 (megaparsec-1), qo = 0.5, where Ho is Hubble constant and qo is the deceleration parameter]. Two 86-GHz VLBI observations performed in 1993.3 and 1994.0 reveal a new jet component emerging with superluminal speed from the core. Linear back-extrapolation of its motion yields strong evidence that the ejection of this component is related to an outburst in the millimeter regime and a preceding intense flare of the y-flux density observed in early 1993. This and the radio/optical "light curves" and VLBI data for two other sources (S5 0836+710 and 3C 454.3) suggest that the observed y-radiation might be Dopplerboosted and perhaps is closely related to the physical processes acting near the "base" of the highly relativistic jets observed in quasars.The high-redshift blazar PKS 0528+134 (redshift z = 2.07), recently attracted special attention due to its extreme brightness and pronounced variability in the y-ray regime (1, 2). Previous very-long-baseline radio interferometry (VLBI) observations at 8 GHz and 22 GHz revealed a core jet morphology, extending several milli-arcseconds (mas) to the north (3) [1 mas corresponds to =4 parsecs (pc), assuming a cosmological origin of the redshift of the source, and Ho = 100 km s-l Mpc-1, qo = 0.5 where Ho is the Hubble constant and qo is the deceleration parameter] with at least one superluminally moving jet component (4). It was also suggested that at least part of the radio variability observed at centimeter wavelengths might be due to refractive interstellar scattering (4).With their high angular resolution, VLBI observations at millimeter wavelengths allow detection of new jet components shortly after their "birth" in the immediate vicinity of the hypothetical central black hole, tracing their motion from several tens to several hundreds of micro-arcseconds (,uas) core separations (5, 6). These central regions of VLBI jets are synchrotron self-absorbed at longer wavelengths and therefore cannot directly be imaged at centimeter wavelengths. RESULTSIn May 1992, the blazar 0528+134 was observed at 43 GHz within a global VLBI observing campaign with eight stationsThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.participating. Despite a somewhat limited ,v-coverage (6), the source could be imaged for the first time at 43 GHz, and several distinct jet components were found. These components are also seen in a 22-GHz VLBI map obtained 6 months later (4). In Fig. 1 both images (43 GHz and 22 GHz)...

Morphology of high-luminosity compact radio sources.

“…I. K. Pauliny-Toth, J.A.Z., and G. Nicolson (unpublished results) found from observations during 1983-1990 that the jet in the quasar 3C 454.3 is curved, confirmed by observations at 3 mm (27). A correlation between curvature and velocity changes is also observed in 3C 84 (28,29) at high frequencies, with components accelerating from <O.lc to -0.25c.…”

“…Although a number of apparent correlations between flux variations and emergence of VLBI components have been reported, their relationship remains unclear (27,57).…”

“…One of these appears to be related to a y-ray/millimeter flare (27). In the quasar 1928+738, there appears to be a transition zone at about 4-6 mas from the core-similar to the case of 3C 345-separating two jet regions with different apparent component speeds: at separations from the core smaller than 4 mas, speeds of about 4c were measured (43), whereas between 6 and 18 mas from the core, the speeds were 6-7c (44).…”

“…27, and references therein). The correlation between y-ray outbursts and superluminal motion may suggest the existence of relativistic y-ray jets (i.e., within as close as a few light-days to the central engine in such objects).…”

Szupernagy tömegű fekete lyuk kettősökre utaló jelek rádió-hangos aktív galaxismagok jeteiben

“…A VLBI megfigyelések elvégzésével lehetővé válik az AGN jetek morfológiájának részletes vizsgálata. Az AGN jetek gyakran mutatnak erős gör-bületet szub-parszektől egészen megaparszekes skálákig (például [114,115,4,218,42,182]). Az értekezés szempontjából a parszek-skálájú görbületek fontosak, hiszen a fény véges terjedési sebessége miatt az emberi időskálán észlelhető periodicitások ezen a térbeli skálán jelennek meg.…”