Mon. Not. R. Astron. Soc., 425, 2203-2211 (2012/September-3)
VLA imaging of 12CO J = 1-0 and free–free emission in lensed submillimetre galaxies.
THOMSON A.P., IVISON R.J., SMAIL I., SWINBANK A.M., WEISS A., KNEIB J.-P., PAPADOPOULOS P.P., BAKER A.J., SHARON C.E. and VAN MOORSEL G.A.
Abstract (from CDS):
We present a study using the Karl G. Jansky Very Large Array (VLA) of 12CO J = 1-0 emission in three strongly lensed submillimetre-selected galaxies (SMMJ16359, SMMJ14009 and SMMJ02399) at z = 2.5–2.9. These galaxies span LIR= 1011–1013L☉, offering an opportunity to compare the interstellar medium of luminous infrared galaxies and ultraluminous infrared galaxies at high redshift. We estimate molecular gas masses in the range of 2–40 x 109M☉ using a method that assumes canonical underlying brightness temperature (Tb) ratios for star-forming and non-star-forming gas phases and a maximal star formation efficiency. A more simplistic method – using XCO= 0.8 and the measured Tb ratios – yields gas masses twice as high. In SMMJ14009 we find \mi L\mi CO\mn 3\mo –\mn 2\mo '\mo/\mi L\mi CO\mn 1\mo –\mn 0\mo '\mn 0.95=±\mn 0.12, indicative of warm, star-forming gas, possibly influenced by the central active galactic nucleus (AGN). We set a gas mass limit of 3σ < 6 x 108M☉ for the Lyman break galaxy, A2218 #384, located in the same field as SMMJ16359 at z = 2.515. Finally, we use the rest-frame ∼ 115GHz free–free flux densities for SMMJ14009 and SMMJ02399 – measurements tied directly to the photoionization rate of massive stars, and made possible by VLA's bandwidth – to estimate star formation rates (SFRs) of 400–600M☉/yr and to estimate the fraction of LIR due to AGN.
2012 The Authors Monthly Notices of the Royal Astronomical Society 2012 RAS
ISM: molecules - galaxies: active - galaxies: high-redshift - galaxies: ISM - galaxies: starburst - submillimetre: general
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