The jet/wind outflow in Centaurus A: a local laboratory for AGN feedback

Abstract

We present new radio and optical images of the nearest radio galaxy Centaurus A and its host galaxy NGC 5128. We focus our investigation on the northern transition region, where energy is transported from the ∼5 kpc (∼5 arcmin) scales of the Northern Inner Lobe (NIL) to the ∼30 kpc (∼30 arcmin) scales of the Northern Middle Lobe (NML). Our Murchison Widefield Array observations at 154 MHz and our Parkes radio telescope observations at 2.3 GHz show diffuse radio emission connecting the NIL to the NML, in agreement with previous Australia Telescope Compact Array observations at 1.4 GHz. Comparison of these radio data with our widefield optical emission line images show the relationship between the NML radio emission and the ionised filaments that extend north from the NIL, and reveal a new ionised filament to the east, possibly associated with a galactic wind. Our deep optical images show clear evidence for a bipolar outflow from the central galaxy extending to intermediate scales, despite the non-detection of a southern radio counterpart to the NML. Thus, our observational overview of Centaurus A reveals a number of features proposed to be associated with AGN feedback mechanisms, often cited as likely to have significant effects in galaxy evolution models. As one of the closest galaxies to us, Centaurus A therefore provides a unique laboratory to examine feedback mechanisms in detail.

LOFAR view of NGC 3998, a sputtering AGN

“…α ∼ 0.7). Also in these two objects, the spectral index is quite homogeneous across the lobes with no trend that could be connected with the ageing of the electrons (see Brienza et al 2018 andMorganti et al 1999;McKinley et al 2018 for B2 0258+35 and Centaurus A respectively). In B2 0258+35 the spectral index of the lobes does not show any significant curvature up to 6.6 GHz, suggesting even tighter requirements for the reacceleration of the electrons in the lobes.…”

“…In Centaurus A, a low-surface brightness, large-scale jet connecting the bright central part with the large-scale lobes has been found (Morganti et al 1999;McKinley et al 2018). This structure would ensure that the supplies of energy from the central galaxy to the lobes is still occurring (even if at low rate as suggested by their low surface brightness).…”

Duty cycle of the radio galaxy B2 0258+35

“…A few sources, for example, show some inner and outer lobes with a very high surface brightness contrast as observed in B2 0258+35 and for this reason are claimed to be restarted radio galaxies. Among these there are the radio galaxy associated with NGC 3998 (∼20 kpc, Frank et al 2016), the source 4C 29.30 (∼600 kpc, Jamrozy et al 2007), the misaligned DDRG 3C293 (190 kpc, Joshi et al 2011;Machalski et al 2016), the source Mrk 6 (7.5 kpc, Kharb et al 2006) and the well-known radio galaxy Centaurus A (∼200 kpc, McKinley et al 2018;Morganti et al 1999). Moreover, we note some similarity with the famous radio galaxies M87 (e.g.…”

The Extraordinary Linear Polarisation Structure of the Southern Centaurus A Lobe Revealed by ASKAP

“…Morganti, 2010 andrefs. therein, also Tingay &Lenc, 2009;Neff et al, 2015;Wykes et al, 2015b;McKinley et al, 2018), MHD instabilities (Wykes et al, 2014), astrophysical shocks and particle acceleration processes (e.g. Croston et al, 2009;Crockett et al, 2012;Wykes et al, 2015a), and more.…”

“…Cen A's radio emission is complex and structured on all scales at which it has been observed (e.g. see Junkes et al, 1993;Israel, 1998;Morganti et al, 1999;Ojha et al, 2010;Feain et al, 2011;Müller et al, 2014;McKinley et al, 2018). It is precisely this structure that has given us important insights into as varied a set of astrophysical processes as jet launching and collimation (e.g.…”