Jet-Gas Interactions in Markarian 78. I. Morphology and Kinematics

Abstract

We present a detailed study of the Seyfert 2 galaxy Markarian 78, using continuum and emission-line images and multiaperture spectra from the Hubble Space Telescope (HST) and a deep 3.6 cm VLA image. Our overall aim is to study the interaction between the radio source and the emission-line gas, since ground-based data already indicate the presence of a strong bipolar jet-driven flow. First, in the wider context, Mrk 78 is probably a post-merger system, with a nuclear dust lane, approximate r 1/4 continuum profile, and highly extended asymmetric gas distribution. The [O iii] and radio images both show complex structures with many similarities but also important differences. A careful comparison shows convincing morphological evidence for jet-gas interaction: (1) the western inner radio jet terminates and flares at the position of a bright [O iii] knot; (2) the weaker eastern radio jet changes direction as it encounters a large [O iii] knot; (3) most [O iii] features appear limb brightened on the upstream side, and flared on the downstream side; and (4) in the outer regions the radio components tend to lie between or adjacent to [O iii] knots, indicating the radio and line emitting phases do not easily interpenetrate. In addition to evidence of jet-gas interaction, two features indicate the importance of a central ionizing radiation field: an inner fanlike structure to the east, with a straight kinematically quiet northern edge; and an approximately fanlike extended narrow-line region to the west, lying well outside the radio source. The [O iii] line profiles from 10 Faint Object Spectrograph apertures provide further kinematic insight into the jet-gas interaction. (1) On the eastern side, where the radio source is deflected, the [O iii] profile contains a highly redshifted component ($700 km s À1) that is also narrow (FWHM 200 km s À1), indicating significant coherent gas acceleration with almost no induced turbulence. (2) At this location, the [O iii] profile is also double, suggesting lateral expansion away from a jet axis, as it burrows into the cloud complex. (3) In contrast, the bright western inner knot, which seems to disrupt the inner radio jet, has essentially undisturbed kinematics. (4) Across the outer complex western region, gas velocities are higher in the region center, decrease at the leading edge and may be highest where radio flows ''blow out'' of the region. Overall, morphology and kinematics suggest the western side is best described as an initially disrupted jet that then fills, accelerates, and leaks out of a complex incomplete ''bubble'' of ionized gas. The eastern side is best described as a large centrally illuminated fanlike gas structure that is penetrated, accelerated, and ultimately deflects the radio source. We use these different regions to construct a plausible evolutionary sequence: Initially, a dense (molecular?) cloud enters the jet flow and disrupts it (inner western knot); as time passes, the jet begins to penetrate, accelerate, and ablate the cloud (eastern knot complex); conti...

STORM IN A “TEACUP”: A RADIO-QUIET QUASAR WITH ≈10 kpc RADIO-EMITTING BUBBLES AND EXTREME GAS KINEMATICS

“…The radio bubbles of the "Teacup" AGN (see Figure 6) are reminiscent of several of the large-scale ( 1-10 kpc) radio structures observed in local Seyfert galaxies (i.e., lowluminosity AGNs), which are often associated with optical emission-line regions and disturbed ionized gas (e.g., Capetti et al 1996;Colbert et al 1996;Falcke et al 1998;Ferruit et al 1999;Whittle & Wilson 2004;Hota & Saikia 2006;Kharb et al 2006). Furthermore, the morphology of the large-scale arc of ionized gas in the Teacup AGN (Figure 6) is analogous to some local starburst galaxies and AGNs that host "super bubbles," or arcs/filaments of optical emission lines (e.g., Heckman et al 1990;Veilleux et al 1994Veilleux et al , 2001Veilleux et al , 2005Capetti et al 1996;Ferruit et al 1999;Whittle & Wilson 2004; also see the analogous radio-loud AGNs in van Breugel et al 1985 andHatch et al 2013).…”

CHANDRAX-RAY ANDHUBBLE SPACE TELESCOPEIMAGING OF OPTICALLY SELECTED KILOPARSEC-SCALE BINARY ACTIVE GALACTIC NUCLEI. I. NATURE OF THE NUCLEAR IONIZING SOURCES

“…Detecting two stellar components alone (e.g., Fu et al 2011a;Rosario et al 2011) is not a sufficient condition for identifying binary AGNs, as the double-peaked profile could be caused by NLR gas kinematics around a single AGN in a merger. Neither is detecting spatial offsets between the emission-line components alone (e.g., Gerke et al 2007;Comerford et al 2009a;Barrows et al 2012) a sufficient condition, even though most double-peaked AGNs show spatial offsets on kpc scales between the two velocity components (Shen et al 2011a;Fu et al 2012;Comerford et al 2012), because such spatial offsets are also expected and commonly observed in single AGNs due to the spatial extent of the NLR, as demonstrated by Fischer et al (2011) in Mrk 78 (see also Whittle & Wilson 2004).…”

Radio continuum of galaxies with H2O megamaser disks: 33 GHz VLA data

“…The narrow line region (NLR) of this galaxy is affected by a strong jet-gas interaction, and spectroscopic observations have shown that its narrow emission lines are double peaked (Sargent 1972;Adams 1973). Based on optical and 3.6 cm VLA images, Whittle & Wilson (2004) suggested that Mrk 78 is a post-merger system, with a highly extended asymmetric gas distribution and a nuclear dust lane. The radio nucleus lies within this highly obscuring dust lane (Whittle & Wilson 2004).…”