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Published May 21, 2015 | Published + Submitted
Journal Article Open

A multiwavelength exploration of the [C II]/IR ratio in H-ATLAS/GAMA galaxies out to z = 0.2

Abstract

We explore the behaviour of [C ii] λ157.74 μm forbidden fine-structure line observed in a sample of 28 galaxies selected from ∼ 50 deg^2 of the Herschel-Astrophysical Terahertz Large Area Survey survey. The sample is restricted to galaxies with flux densities higher than S160 μm > 150 mJy and optical spectra from the Galaxy and Mass Assembly survey at 0.02 < z < 0.2. Far-IR spectra centred on this redshifted line were taken with the Photodetector Array Camera and Spectrometer instrument on-board the Herschel Space Observatory. The galaxies span 10 < log(L_(IR)/L_⊙) < 12 (where L_(IR) ≡ L_(IR)[8-1000 μm]) and 7.32.5 × 10^(−3) with respect to those showing lower ratios. In particular, those with high ratios tend to have: (1) L_(IR) <10^(11) L_⊙; (2) cold dust temperatures, T_d < 30 K; (3) disc-like morphologies in r-band images; (4) a Wide-field Infrared Survey Explorer colour 0.5 ≲ S_(12 μm)/S_(22 μm) ≲ 1.0; (5) low surface brightness Σ_(IR) ≈ 10^(8–9) L_⊙ kpc^(−2), (6) and specific star formation rates of sSFR ≈0.05–3 Gyr^(−1). We suggest that the strength of the far-UV radiation fields (〈G_O〉) is main parameter responsible for controlling the [C _(ii)]/IR ratio. It is possible that relatively high 〈G_O〉 creates a positively charged dust grain distribution, impeding an efficient photoelectric extraction of electrons from these grains to then collisionally excite carbon atoms. Within the brighter IR population, 11 < log(L_(IR)/L_⊙) < 12, the low [C_( ii)]/IR ratio is unlikely to be modified by [C _(ii)] self-absorption or controlled by the presence of a moderately luminous AGN (identified via the BPT diagram).

Additional Information

© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 February 24. Received 2015 February 17. In original form 2014 October 17. First published online April 2, 2015. EI acknowledges funding from CONICYT FONDECYT postdoctoral project No: 3130504. RJI, LD and SM acknowledge support from the European Research Council in the form of Advanced Investigator programme, COSMICISM. CF acknowledges funding from CAPES (proc. 12203-1). We would like to thank the anonymous referee for the helpful comments. The Herschel-ATLAS is a project with Herschel, which is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. The H-ATLAS website is http://www.h-atlas.org/. PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAF-IFSI/OAA/OAP/OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), and CICYT/MCYT (Spain). GAMA is a joint European-Australasian project based around a spectroscopic campaign using the Anglo-Australian Telescope. The GAMA input catalogue is based on data taken from the Sloan Digital Sky Survey and the UKIRT Infrared Deep Sky Survey. Complementary imaging of the GAMA regions is being obtained by a number of independent survey programs including GALEX MIS, VST KiDS, VISTA VIKING, WISE, H-ATLAS, GMRT and ASKAP providing UV to radio coverage. GAMA is funded by the STFC (UK), the ARC (Australia), the AAO, and the participating institutions. The GAMA website is http://www.gama-survey.org/. This work has been developed thanks to TOPCAT software (Taylor 2005).

Attached Files

Published - MNRAS-2015-Ibar-2498-513.pdf

Submitted - 1503.01128v1.pdf

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