A Very Large Array Survey of Luminous Extranuclear Star-forming Regions in Luminous Infrared Galaxies in GOALS

Creators: Linden, S. T.; Song, Y.; Evans, A. S.; Murphy, E. J.; Armus, L.; Barcos-Muñoz, L.; Larson, K.; Díaz-Santos, T.; Privon, G. C.; Howell, J.; Surace, J. A.; Charmandaris, V.; Vivian, U.; Medling, A. M.; Chu, J.; Momjian, E.

Abstract

We present the first results of a high-resolution Karl G. Jansky Very Large Array imaging survey of luminous and ultra-luminous infrared galaxies (U/LIRGs) in the Great Observatories All-sky LIRG Survey. From the full sample of 68 galaxies, we have selected 25 luminous infrared galaxies (LIRGs) that show resolved extended emission at sufficient sensitivity to image individual regions of star formation activity beyond the nucleus. With wideband radio continuum observations, which sample the frequency range from 3 to 33 GHz, we have made extinction-free measurements of the luminosities and spectral indicies for a total of 48 individual star-forming regions identified as having deprojected galactocentric radii (r_G ) that lie outside the 13.2 μm core of the galaxy. The median 3–33 GHz spectral index and 33 GHz thermal fraction measured for these "extranuclear" regions is −0.51 ± 0.13 and 65% ± 11%, respectively. These values are consistent with measurements made on matched spatial scales in normal star-forming galaxies, and suggests that these regions are more heavily dominated by thermal free–free emission relative to the centers of local U/LIRGs. Further, we find that the median star formation rate derived for these regions is ~1 M⊙ yr^(−1), and when we place them on the sub-galactic star-forming main sequence of galaxies (SFMS), we find they are offset from their host galaxies' globally averaged specific star formation rates. We conclude that while nuclear starburst activity drives LIRGs above the SFMS, extranuclear star formation still proceeds in a more extreme fashion relative to what is seen in local spiral galaxies.

Additional Information

© 2019 The American Astronomical Society. Received 2019 January 25; revised 2019 June 5; accepted 2019 June 6; published 2019 August 13. S.T.L. was supported by the NRAO Grote Reber Dissertation Fellowship. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities Inc. A.S.E. and Y.S. were supported by NSF grant AST 1816838. G.C.P. acknowledges support from the University of Florida. A.S.E. was also supported by the Taiwan, ROC, Ministry of Science and Technology grant MoST 102-2119-M-001-MY3. T.D.-S. acknowledges support from ALMA-CONICYT project 31130005 and FONDECYT regular project 1151239. Portions of this work were performed at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1066293. This work was partially supported by a grant from the Simons Foundation. Finally, this research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Attached Files

Published - Linden_2019_ApJ_881_70.pdf

Accepted Version - 1906.05182.pdf

Files

1906.05182.pdf

Files (21.6 MB)

Name	Size	Download all
1906.05182.pdf md5:813c7c8196eda074806755c491a857f7	15.3 MB	Preview Download
Linden_2019_ApJ_881_70.pdf md5:9bd91f70da21e46406589df4e75afa53	6.2 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes