COMPLEX RADIO SPECTRAL ENERGY DISTRIBUTIONS IN LUMINOUS AND ULTRALUMINOUS INFRARED GALAXIES

Journal Article · Tue Sep 20 04:00:00 EDT 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/739/1/L25· OSTI ID:21565459

Leroy, Adam K; Evans, Aaron S; Condon, James ^[1]; Momjian, Emmanuel; Ott, Juergen; Meier, David S ^[2]; Murphy, Eric ^[3]; Armus, Lee; Haan, Sebastian; Mazzarella, Joseph M; Surace, Jason ^[4]; Privon, George C ^[5]; Schinnerer, Eva; Walter, Fabian ^[6]

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1. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States)
2. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
3. Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
4. Spitzer Science Center, California Institute of Technology, MC 314-6, Pasadena, CA 91125 (United States)
5. Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904 (United States)
6. Max Planck Institut fuer Astronomie, Koenigstuhl 17, Heidelberg D-69117 (Germany)

We use the Expanded Very Large Array to image radio continuum emission from local luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in 1 GHz windows centered at 4.7, 7.2, 29, and 36 GHz. This allows us to probe the integrated radio spectral energy distribution (SED) of the most energetic galaxies in the local universe. The 4-8 GHz flux densities agree well with previous measurements. They yield spectral indices {alpha} {approx} -0.67 (where F {sub {nu}}{proportional_to}{nu}{sup {alpha}}) with {+-}0.15 (1{sigma}) scatter, typical of nonthermal (synchrotron) emission from star-forming galaxies. The contrast of our 4-8 GHz data with literature 1.5 and 8.4 GHz flux densities gives further evidence for curvature of the radio SED of U/LIRGs. The SED appears flatter near {approx}1 GHz than near {approx}6 GHz, suggesting significant optical depth effects at lower frequencies. The high-frequency (28-37 GHz) flux densities are low compared to extrapolations from the 4-8 GHz data. We confirm and extend to higher frequency a previously observed deficit of high-frequency radio emission for luminous starburst galaxies.

• OSTI ID: 21565459
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 739; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ELECTROMAGNETIC RADIATION
EMISSION
ENERGY SPECTRA
FLUX DENSITY
GALAXIES
INFRARED RADIATION
LUMINOSITY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
RADIOWAVE RADIATION
SPECTRA