Parsec‐Scale Properties of Markarian 501

Abstract

We present the results of a high angular resolution study of the BL Lac object Markarian 501 in the radio band. We consider data taken at 14 different epochs, ranging between 1.6 and 22 GHz in frequency, and including new Space VLBI observations obtained on 2001 March 5 and 6 at 1.6 and 5 GHz. We study the kinematics of the parsec-scale jet and estimate its bulk velocity and orientation with respect to the line of sight. Limb-brightened structure in the jet is clearly visible in our data, and we discuss its possible origin in terms of velocity gradients in the jet. Quasi-simultaneous, multiwavelength observations allow us to map the spectral index distribution and to compare it to the jet morphology. Finally, we estimate the physical parameters of the parsec-scale jet.

On the magnetization of BL Lac jets

“…We recall here that the existence of the postulated structure in BL Lac jets (and FRI radiogalaxies) is supported by a variety of observational and phenomenological arguments (e.g. Chiaberge et al 2000, Giroletti et al 2004, Piner & Edwards 2014, Nagai et al 2014) and also by numerical simulations (e.g. Rossi et al 2008).…”

Observational Properties of Jets in Active Galactic Nuclei

“…The presence of this structure very near to the central core as in M87 (Junor et al, 1999) and Mkn 501 (Giroletti et al 2004) is in favour of a jet intrinsic property in the inner region (as discussed by Meier, 2003), whereas a jet velocity decrease due to the ISM is likely to be present in an intermediate region (from the pc to the kpc scale).…”

“…At parsec resolution it is one of the best observed radio sources. In a recent paper Giroletti et al 2004 show a clear evidence of a limb-brightened jet structure visible at a distance < 1 mas from the core up to 50-100 mas from the core.…”

Variation of bulk Lorentz factor in AGN jets due to Compton rocket in a complex photon field

“…In this framework, Ghisellini et al (2005) explain the rapid variability of the TeV emission without requiring huge Doppler factors, and Tavecchio & Ghisellini (2014) are able to reproduce the SED of NGC 1275. Recent observations (Giovannini et al 1999;Swain et al 1998;Giroletti et al 2004) also bring evidence of such structures.…”