ALMA Imaging of a Galactic Molecular Outflow in NGC 4945
Journal article, 2021
We present the ALMA detection of molecular outflowing gas in the central regions of NGC 4945, one of the nearest starbursts and also one of the nearest hosts of an active galactic nucleus (AGN). We detect four outflow plumes in CO J= 3 - 2 at similar to 0.3 resolution that appear to correspond to molecular gas located near the edges of the known ionized outflow cone and its (unobserved) counterpart behind the disk. The fastest and brightest of these plumes has emission reaching observed line-of-sight projected velocities of over 450 km s(-1) beyond systemic, equivalent to an estimated physical outflow velocity v greater than or similar to 600 km s(-1) for the fastest emission. Most of these plumes have corresponding emission in HCN or HCO + J= 4 - 3. We discuss a kinematic model for the outflow emission where the molecular gas has the geometry of the ionized gas cone and shares the rotation velocity of the galaxy when ejected. We use this model to explain the velocities we observe, constrain the physical speed of the ejected material, and account for the fraction of outflowing gas that is not detected due to confusion with the galaxy disk. We estimate a total molecular mass outflow rate (M) over dot(mol) similar to 20 M-circle dot yr(-1) flowing through a surface within 100 pc of the disk midplane, likely driven by a combination of the central starburst and AGN.
Author
Alberto D. Bolatto
National Radio Astronomy Observatory
University of Maryland
Flatiron Institute
Adam K. Leroy
Ohio State University
Rebecca C. Levy
University of Maryland
David S. Meier
National Radio Astronomy Observatory
New Mexico Institute of Mining and Technology
Elisabeth A. C. Mills
University of Kansas
Todd A. Thompson
Ohio State University
Kimberly L. Emig
National Radio Astronomy Observatory
Sylvain Veilleux
University of Maryland
Juergen Ott
National Radio Astronomy Observatory
Mark Gorski
Astronomy and plasmaphysics 2
Fabian Walter
National Radio Astronomy Observatory
Max Planck Society
Laura A. Lopez
Ohio State University
Laura Lenkic
University of Maryland
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 923 1 83Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.3847/1538-4357/ac2c08