Ambilateral collimation study of the twin-jets in NGC 1052

Abstract

Context. With the increase in the sensitivity and resolution of radio interferometry within recent years, the study of the collimation and acceleration region of extragalactic jets in active galactic nuclei (AGN) has come into focus. Whereas a large fraction of AGN jets show a change from parabolic to conical collimation profile around the Bondi radius, there is a small number of sources that display a deviation from this standard picture, including the radio galaxy NGC 1052. Aims. We study the jet width profile, which provides valuable information about the interplay between the central engine and accretion disk system and the formation, acceleration, and collimation of the jets. Methods. We observed the double-sided, low-radio-power active galaxy NGC 1052 at six frequencies with the VLBA in 2017 and at 22 GHz with RadioAstron in 2016. These data are combined with archival 15, 22, and 43 GHz multi-epoch VLBA observations. From ridge-line fitting we obtained width measurements along the jet and counter-jet which were fitted with single and broken power laws. Results. We find a clear break point in the jet collimation profile at ∼104 RS (Schwarzschild radii). Downstream of the break, the collimation is conical with a power-law index of 1.0 − 1.2 (cylindrical 0; parabolic 0.5; conical 1) for both jets. On the other hand, the upstream power-law index of 0.36 for the approaching jet is neither cylindrical nor parabolic, and the value of 0.16 for the receding jet suggests this latter is close-to cylindrical. For both jets we find a large opening angle of ∼30° at a distance of ∼103 RS and well-collimated structures with an opening angle of < 10° downstream of the break. Conclusions. There are significant differences between the upstream collimation profiles of the approaching (eastern) and receding (western) jets. Absorption or scattering in the surrounding torus as well as an accretion wind may mimic a cylindrical profile. We need to increase the observing frequencies, which do not suffer from absorption, in order to find the true jet collimation profile upstream of 104 RS.

Exploring the disk-jet connection in NGC 315

“…All distances are expressed with respect to the 43 GHz core, assumed to coincide with the actual position of the black hole. This assumption is supported by previous observational results, showing that the mm-core in radio galaxies lies very close (< 100𝑅 S ) to the true position of the central black hole (e.g., Hada et al 2011;Baczko et al 2022).…”

Dual-high-frequency VLBI study of blazar-jet brightness-temperature gradients and collimation profiles

“…In the case of M87, Asada & Nakamura (2012) showed that such a geometry transition can be observed in the vicinity of the Bondi-sphere (Russell et al 2015) where the external medium is expected to change its pressure gradient. More recent works also found these transitions in several different sources, NGC 6251 (Tseng et al 2016), NGC 4261 (Nakahara et al 2018), NGC 1052 (Nakahara et al 2020;Baczko et al 2022), NGC 315 (Boccardi et al 2021;Park et al 2021) and 1H0323+342 (Hada et al 2018). In the cases of M87 (Mertens et al 2016;Hada et al 2018;Park et al 2019), NGC 315 (Park et al 2021) and 1H0323+342 (Hada et al 2018) the jets also show accelerating jet components near the geometry-transition zones.…”

“…In this study we made use of the orthogonal distance regression (ODR) as used in Baczko et al (2016), Baczko et al (2019) and Baczko et al (2022) in order to fit the smoothly broken power law in the geometry transition sources. For the discussion in this paper, we use the least square implementation in scipy with the trust-region reflective algorithm in order to fit the smoothly broken power law which allows us to set bounds on each parameter which we get from the numerical method when searching for a possible break in geometry in each jet.…”

“…There are different ways this function can be fit to data. Baczko et al (2022) deploy the orthogonal distance regression while Casadio et al (2021) use a gnuplot implementation of the Levenberg-Marquardt algorithm. In this work we use scipy (Virtanen et al 2020) in order to fit the smoothly broken power law with a classical least square method.…”

Jets in radio galaxies and quasars: an observational perspective

“…An interesting example is the lowionisation nuclear emission line region (LINER) galaxy NGC1052 with twin-jets. Baczko et al (2022) find that both jets are conical downstream of a break in the jet collimation profile at 10 4 R s . However upstream of the jets, the jet collimation profile is neither cylindrical nor parabolic for the approaching jet and close to cylindrical for the receding one.…”