Star-forming Clumps in Local Luminous Infrared Galaxies

January 2020 • 2020ApJ...888...92L

Authors • Larson, K. L. • Díaz-Santos, T. • Armus, L. • Privon, G. C. • Linden, S. T. • Evans, A. S. • Howell, J. • Charmandaris, V. • U, V. • Sanders, D. B. • Stierwalt, S. • Barcos-Muñoz, L. • Rich, J. • Medling, A. • Cook, D. • Oklopĉić, A. • Murphy, E. J. • Bonfini, P.

Abstract • We present HST narrowband near-infrared imaging of Paα and Paβ emission of 48 local luminous infrared galaxies (LIRGs) from the Great Observatories All-Sky LIRG Survey. These data allow us to measure the properties of 810 spatially resolved star-forming regions (59 nuclei and 751 extranuclear clumps) and directly compare their properties to those found in both local and high-redshift star-forming galaxies. We find that in LIRGs the star-forming clumps have radii ranging from ∼90 to 900 pc and star formation rates (SFRs) of ∼1 × 10-3 to 10 M yr-1, with median values for extranuclear clumps of 170 pc and 0.03 M yr-1. The detected star-forming clumps are young, with a median stellar age of 8.7 Myr, and have a median stellar mass of 5 × 105 M. The SFRs span the range of those found in normal local star-forming galaxies to those found in high-redshift star-forming galaxies at z = 1-3. The luminosity function of the LIRG clumps has a flatter slope than found in lower-luminosity, star-forming galaxies, indicating a relative excess of luminous star-forming clumps. In order to predict the possible range of star-forming histories and gas fractions, we compare the star-forming clumps to those measured in the MassiveFIRE high-resolution cosmological simulation. The star-forming clumps in MassiveFIRE cover the same range of SFRs and sizes found in the local LIRGs and have total gas fractions that extend from 10% to 90%. If local LIRGs are similar to these simulated galaxies, we expect that future observations with ALMA will find a large range of gas fractions, and corresponding star formation efficiencies, among the star-forming clumps in LIRGs.


IPAC Authors


Lee Armus

Senior Scientist

David Cook

Assistant Scientist