Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 2016 | Published + Submitted
Journal Article Open

Comparing [C II] , HI, and CO Dynamics of Nearby Galaxies

Abstract

The H I and CO components of the interstellar medium (ISM) are usually used to derive the dynamical mass M_(dyn) of nearby galaxies. Both components become too faint to be used as a tracer in observations of high-redshift galaxies. In those cases, the 158 μm line of atomic carbon ([C II]) may be the only way to derive M_(dyn). As the distribution and kinematics of the ISM tracer affects the determination of M_(dyn), it is important to quantify the relative distributions of H I, CO, and [C II]. H Iand CO are well-characterized observationally, however, for [C II] only very few measurements exist. Here we compare observations of CO, H I, and [C II] emission of a sample of nearby galaxies, drawn from the HERACLES, THINGS, and KINGFISH surveys. We find that within R_(25), the average [C II] exponential radial profile is slightly shallower than that of the CO, but much steeper than the H Idistribution. This is also reflected in the integrated spectrum ("global profile"), where the [C II] spectrum looks more like that of the CO than that of the H I. For one galaxy, a spectrally resolved comparison of integrated spectra was possible; other comparisons were limited by the intrinsic line-widths of the galaxies and the coarse velocity resolution of the [C II] data. Using high-spectral-resolution SOFIA [C II] data of a number of star forming regions in two nearby galaxies, we find that their [C II] linewidths agree better with those of the CO than the H I. As the radial extent of a given ISM tracer is a key input in deriving M_(dyn) from spatially unresolved data, we conclude that the relevant length-scale to use in determining M_(dyn) based on [C II] data, is that of the well-characterized CO distribution. This length scale is similar to that of the optical disk.

Additional Information

© 2016 The American Astronomical Society. Received 2015 December 3; accepted 2016 April 28; published 2016 August 4. W.J.G.d.B. was supported by the European Commission (grant FP7-PEOPLE-2012-CIG #333939). Beyond the Peak research has been supported by a NASA/JPL grant (RSA 1427378). J.D.S. gratefully acknowledges visiting support from the Alexander von Humboldt Foundation and the Max Planck Institute für Astronomie. A.D.B. and R.H.C. acknowledge support from grants USRA-SOF020098, NSF-AST0955836, and NSF-AST1412419, as well as visiting support from the Humboldt Foundation. This work is based in part on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). Financial support for this work was provided by NASA.

Attached Files

Published - aj_152_2_51.pdf

Submitted - 1604.08777v1.pdf

Files

1604.08777v1.pdf
Files (5.1 MB)
Name Size Download all
md5:83eafae4d88fe4855a38e221ffb4fa0d
3.3 MB Preview Download
md5:ac57b29e754adf0143a87e47de4b80db
1.8 MB Preview Download

Additional details

Created:
August 20, 2023
Modified:
October 20, 2023