skip to main content

SciTech ConnectSciTech Connect

Title: JET-SHOCKED H{sub 2} AND CO IN THE ANOMALOUS ARMS OF MOLECULAR HYDROGEN EMISSION GALAXY NGC 4258

We present a Spitzer Infrared Spectrograph map of H{sub 2} emission from the nearby galaxy NGC 4258 (Messier 106). The H{sub 2} emission comes from 9.4 ± 0.4 × 10{sup 6} M {sub ☉} of warm molecular hydrogen heated to 240-1040 K in the inner anomalous arms, a signature of jet interaction with the galaxy disk. The spectrum is that of a molecular hydrogen emission galaxy (MOHEG), with a large ratio of H{sub 2} over 7.7 μm polycyclic aromatic hydrocarbon emission (0.37), characteristic of shocked molecular gas. We find close spatial correspondence between the H{sub 2} and CO emission from the anomalous arms. Our estimate of cold molecular gas mass based on CO emission is 10 times greater than our estimate of 1.0 × 10{sup 8} M {sub ☉} based on dust emission. We suggest that the X {sub CO} value is 10 times lower than the Milky Way value because of high kinetic temperature and enhanced turbulence. The H{sub 2} disk has been overrun and is being shocked by the jet cocoon, and much of the gas originally in the disk has been ejected into the galaxy halo in an X-ray hot outflow. We measure a modest star formation rate of 0.08 Mmore » {sub ☉} yr{sup –1} in the central 3.4 kpc{sup 2} that is consistent with the remaining gas surface density.« less
Authors:
; ;  [1]
  1. Infrared Processing and Analysis Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22365767
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 788; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON MONOXIDE; COSMIC DUST; DENSITY; HYDROGEN; JETS; MASS; MILKY WAY; POLYCYCLIC AROMATIC HYDROCARBONS; STAR CLUSTERS; STARS; TURBULENCE; X RADIATION