paper

Far-infrared Herschel SPIRE spectroscopy of lensed starbursts reveals physical conditions of ionised gas

arXiv:1807.07080 · doi:10.1093/mnras/sty2082

Abstract

The most intensively star-forming galaxies are extremely luminous at far-infrared (FIR) wavelengths, highly obscured at optical and ultraviolet wavelengths, and lie at . We present a programme of FIR spectroscopic observations with the SPIRE FTS and photometric observations with PACS, both on board , towards a sample of 45 gravitationally lensed, dusty starbursts across . In total, we detected 27 individual lines down to 3-, including nine 158-m lines with confirmed spectroscopic redshifts, five possible lines consistent with their far-infrared photometric redshifts, and in some individual sources a few 88-m, 52-m, 145-m, 63-m, 122-m, and OH 119-m (in absorption) lines. To derive the typical physical properties of the gas in the sample, we stack all spectra weighted by their intrinsic luminosity and by their 500-m flux densities, with the spectra scaled to a common redshift. In the stacked spectra, we detect emission lines of 158-m, 122-m, 88-m, 52-m, 63-m, and the absorption doublet of OH at 119-m, at high fidelity. We find that the average electron densities traced by the and lines are higher than the average values in local star-forming galaxies and ULIRGs, using the same tracers. From the and ratios, we find that the emission is likely dominated by the photo-dominated regions (PDR), instead of by ionised gas or large-scale shocks.

arXiv comment39 pages, 19 figures, Accepted for publication in MNRAS. For extra pptx slides prepared for this work, please see http://www.eso.org/~zzhang/download/FTS_SMG_survey_ZhiyuZhang.pdf

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