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arXiv · 1501.01638

Extinction and nebular line properties of a Herschel-selected lensed dusty starburst AT z=1.027

Nicholas Timmons·Asantha Cooray·Hooshang Nayyeri·Caitlin Casey·Jae Calanog·Brian Ma·Hugo Messias·Maarten Baes·R. Shane Bussmann·Loretta Dunne·Simon Dye·Steve Eales·Hai Fu·R. J. Ivison·Steve Maddox·Michał J. Michałowski·I. Oteo·Dominik A. Riechers·Elisabetta Valiante·Julie Wardlow
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Abstract

We present Hubble Space Telescope (HST) WFC3 imaging and grism spectroscopy observations of the {\it Herschel}-selected gravitationally-lensed starburst galaxy HATLASJ1429-0028. The lensing system consists of an edge-on foreground disk galaxy at $z=0.218$ with a nearly complete Einstein ring of the infrared luminous galaxy at $z=1.027$. The WFC3 spectroscopy with G102 and G141 grisms, covering the wavelength range of 0.8 to 1.7 $μ$m, resulted in detections of H$α$+[NII], H$β$, [SII], and [OIII] for the background galaxy from which we measure line fluxes and ratios. The Balmer line ratio H$α$/H$β$ of $7.5 \pm 4.4$, when corrected for [NII], results in an extinction for the starburst galaxy of $E(B-V)=0.8 \pm 0.5$. The $Hα$ based star-formation rate, when corrected for extinction, is $60 \pm 50$ M$_{\odot}$ yr$^{-1}$, lower than the instantaneous star-formation rate of 390 $\pm$ 90 M$_{\odot}$ yr$^{-1}$ from the total IR luminosity. We also compare the nebular line ratios of HATLASJ1429-0028 with other star-forming and sub-mm bright galaxies. The nebular line ratios are consistent with an intrinsic ultra-luminous infrared galaxy with no evidence for excitation by an active galactic nucleus (AGN). We estimate the metallicity, $12 + log(O/H)$, of HATLASJ1429-0028 to be 8.49 $\pm$ 0.16. Such a low value is below the average relations for stellar mass vs. metallicity of galaxies at $z \sim 1$ for a galaxy with stellar mass of $\sim 2 \times 10^{11}$ M$_{\odot}$. The combination of high stellar mass, lack of AGN indicators, low metallicity, and the high star-formation rate of HATLASJ1429-0028 suggest that this galaxy is currently undergoing a rapid formation.

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Nicholas Timmons, Asantha Cooray, Hooshang Nayyeri, Caitlin Casey, Jae Calanog, Brian Ma, Hugo Messias, Maarten Baes, R. Shane Bussmann, Loretta Dunne, Simon Dye, Steve Eales, Hai Fu, R. J. Ivison, Steve Maddox, Michał J. Michałowski, I. Oteo, Dominik A. Riechers, Elisabetta Valiante, Julie Wardlow. 2015-03-30. Extinction and nebular line properties of a Herschel-selected lensed dusty starburst AT z=1.027. https://doi.org/10.1088/0004-637x%2F805%2F2%2F140

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