Jet‐ and Wind‐driven Ionized Outflows in the Superbubble and Star‐forming Disk of NGC 3079

Abstract

Hubble Space Telescope WFPC2 images are presented that span the inner ~19 kpc diameter of the edge-on galaxy NGC 3079; they are combined with optical, emission-line imaging spectrophotometry and VLA images of radio polarization vectors and rotation measures. Ionized gas filaments within 9 kpc diameter project up to 3 kpc above the disk, with the brightest forming the ≈1 kpc diameter superbubble. They are often resolved into strands ≈03 (25 pc) wide, which emerge from the nuclear CO ring as five distinct streams with large velocities and velocity dispersions (FWHM ≈ 450 km s-1). The brightest stream emits ≈10% of the superbubble Hα flux and extends for 250 pc along the axis of the VLBI radio jet to one corner of the base of the superbubble. The other four streams are not connected to the jet, instead curving up to the vertical ≈0.6 kpc above the galaxy disk, then dispersing as a spray of droplets each with ≈103 M☉ of ionized gas (the volume filling factor f > 3 × 10-3). Shredded clumps of disk gas form a similar structure in hydrodynamical models of a galaxy-scale wind. The pattern of magnetic fields and the gaseous kinematics also suggest that a wind of mechanical luminosity Lw ≈ 1043 ergs s-1 has stagnated in the galaxy disk at a radius of ~800 pc, has flared to larger radii with increasing height as the balancing interstellar medium pressure reduces above the disk, and has entrained dense clouds into a mushroom vortex above the disk. Hα emissivity of the filaments limits densities to ne > 4.3f-1/2 cm-3, hence kinetic energy and momentum to (0.4-5) × 1055 ergs and (1.6-6) × 1047 dyne s, respectively; the ranges result from uncertain space velocities. A prominent star-forming complex elsewhere in the galaxy shows a striking spray of linear filaments that extend for hundreds of parsecs to end in unresolved bullets.