A 4~Kpc Molecular Gas Lane in Cygnus A

Abstract

We present the discovery of a 4 kpc molecular gas lane in the Cygnus A host galaxy, using ALMA CO 2-1 observations. The gas lane is oriented roughly perpendicular to the projected radio jet axis. The CO emission generally follows the clumpy dust lanes seen in HST I-band images. The total molecular gas mass is $30\times 10^8$ M${}_{\odot }$ for Milky Way type clouds, and $3.6\times 10^8$ M${}_{\odot }$ for starburst conditions. There is a velocity change from the northern to southern CO peaks of about $\pm 175$~km~s${}^{-1}$, and an apparently smooth velocity gradient between the peaks, although the emission in the central region is weak. In the inner $\sim 0.5"$ projected distance from the radio core, comparison of the CO velocities to those observed for H${}_2$ 2.1218 $\mu$m emission shows higher velocities for the vibrationally excited warm molecular gas than the cooler CO 2-1 line emitting gas at similar projected radii. A possible explanation for these different projected velocities at a given radius is that the cooler CO gas is distributed in a clumpy ring at radius $\sim 1.5"$ to $2"$, while the warm H${}_2$ 2.12$\mu$m emitting gas is interior to this ring. Of course, the current data cannot rule-out a clumpy, amorphous molecular gas distribution linearly distributed perpendicular to the radio jet axis. We consider surface brightness properties on scales down to $\sim 265$~pc, and discuss the Cygnus A results in the context of other radio galaxies with CO emission.

5 Figures, 23 pages, 2 tables, accepted for publication in the ApJ

References in corpus (8)

• Cold molecular gas in the Perseus cluster core - Association with X-ray cavity, Halpha filaments and cooling flow -
• Deep and narrow CO absorption revealing molecular clouds in the Hydra-A brightest cluster galaxy
• Disentangling the Circumnuclear Environs of Centaurus A: III. An Inner Molecular Ring, Nuclear Shocks and the CO to warm H2 interface
• Discovery of a Luminous Radio Transient 460 pc from the Central Supermassive Black Hole in Cygnus A
• Simulations of the merging cluster of galaxies Cygnus A
• Subaru Spectroscopy and Spectral Modeling of Cygnus A
• ALMA Observations of the Molecular Gas in the Elliptical Galaxy NGC3557
• Evidence for a TDE origin of the radio transient Cygnus A-2

Cited by in corpus (1)

• Jet-driven shocks and turbulence in radio-loud Active Galactic Nuclei observed with JWST MIRI/MRS