Deviations from the infrared-radio correlation in massive, ultracompact starburst galaxies

Authors

Grayson C. Petter, Dartmouth College
Amanda A. Kepley, National Radio Astronomy Observatory
Ryan C. Hickox, Dartmouth College
Gregory H. Rudnick, University of Kansas
Christy A. Tremonti, University of Wisconsin-Madison
Aleksandar M. Diamond-Stanic, Bates CollegeFollow
James E. Geach, University of Hertfordshire
Alison L. Coil, Center for Astrophysics & Space Sciences
Paul H. Sell, University of Florida
John Moustakas, Siena College
David S.N. Rupke, Rhodes College
Serena Perrotta, Center for Astrophysics & Space Sciences
Kelly E. Whalen, Dartmouth College
Julie D. Davis, University of Wisconsin-Madison

Publication Title

Astrophysical Journal

Document Type

Article

Department or Program

Physics and Astronomy

Publication Date

10-2020

Keywords

Compact galaxies (285), E+A galaxies (424), Galaxy evolution (594), Galaxy mergers (608), Luminous infrared galaxies (946), Radio astronomy (1338), Radio continuum emission (1340), Star formation (1569), Starburst galaxies (1570), Stellar feedback (1602)

Abstract

Feedback through energetic outflows has emerged as a key physical process responsible for transforming star-forming galaxies into the quiescent systems observed in the local universe. To explore this process, this paper focuses on a sample of massive and compact merger remnant galaxies hosting high-velocity gaseous outflows (IvI ≳103 km s-1), found at intermediate redshift (z ∼ 0.6). From their mid-infrared emission and compact morphologies, these galaxies are estimated to have exceptionally large star formation rate (SFR) surface densities (ΣSFR ∼ 103M⊙ yr-1 kpc-2), approaching the Eddington limit for radiation pressure on dust grains. This suggests that star formation feedback may be driving the observed outflows. However, these SFR estimates suffer from significant uncertainties. We therefore sought an independent tracer of star formation to probe the compact starburst activity in these systems. In this paper, we present SFR estimates calculated using 1.5 GHz continuum Jansky Very Large Array observations for 19 of these galaxies. We also present updated infrared (IR) SFRs calculated from WISE survey data. We estimate SFRs from the IR to be larger than those from the radio for 16 out of 19 galaxies by a median factor of 2.5. We find that this deviation is maximized for the most compact galaxies hosting the youngest stellar populations, suggesting that compact starbursts deviate from the IR-radio correlation. We suggest that this deviation stems either from free-free absorption of synchrotron emission, a difference in the timescale over which each indicator traces star formation, or exceptionally hot IR-emitting dust in these ultra-dense galaxies.

Comments

Original version is available from the publisher at: https://doi.org/10.3847/1538-4357/abb19d

Recommended Citation

Petter, G. C., Kepley, A. A., Hickox, R. C., Rudnick, G. H., Tremonti, C. A., Diamond-Stanic, A. M., Geach, J. E., Coil, A. L., Sell, P. H., Moustakas, J., Rupke, D. S. N., Perrotta, S., Whalen, K. E., & Davis, J. D. (2020). Deviations from the Infrared-radio Correlation in Massive, Ultracompact Starburst Galaxies. The Astrophysical Journal, 901(2), 138–.