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Published August 2014 | Published
Journal Article Open

Herschel-ATLAS and ALMA HATLAS J142935.3-002836, a lensed major merger at redshift 1.027

Abstract

Context. The submillimetre-bright galaxy population is believed to comprise, aside from local galaxies and radio-loud sources, intrinsically active star-forming galaxies, the brightest of which are lensed gravitationally. The latter enable studies at a level of detail beyond what is usually possible by the observation facility. Aims. This work focuses on one of these lensed systems, HATLAS J142935.3−002836 (H1429−0028), selected in the Herschel-ATLAS field. Gathering a rich, multi-wavelength dataset, we aim to confirm the lensing hypothesis and model the background source's morphology and dynamics, as well as to provide a full physical characterisation. Methods. Multi-wavelength high-resolution data is utilised to assess the nature of the system. A lensing-analysis algorithm that simultaneously fits different wavebands is adopted to characterise the lens. The background galaxy dynamical information is studied by reconstructing the 3D source plane of the ALMA CO (J:4 → 3) transition. Near-IR imaging from HST and Keck-AO allows to constrain rest-frame optical photometry independently for the foreground and background systems. Physical parameters (such as stellar and dust masses) are estimated via modelling of the spectral energy distribution taking source blending, foreground obscuration, and differential magnification into account. Results. The system comprises a foreground edge-on disk galaxy (at z_(sp) = 0.218) with an almost complete Einstein ring around it. The background source (at zsp = 1.027) is magnified by a factor of μ ~ 8−10 depending on wavelength. It is comprised of two components and a tens-of-kpc-long tidal tail resembling the Antennæ merger. As a whole, the background source is a massive stellar system (1.32_(-0.41)^(+ 0.63) × 10^(11) M_⊙) forming stars at a rate of 394 ± 90  M_⊙ yr^(-1), and it has a significant gas reservoir M_(ISM) = 4.6 ± 1.7 × 10^(10) M_⊙. Its depletion time due to star formation alone is thus expected to be τ_(SF) = M_(ISM)/ SFR = 117 ± 51 Myr. The dynamical mass of one of the components is estimated to be 5.8 ± 1.7 × 10^(10) M_⊙, and, together with the photometric total mass estimate, it implies that H1429−0028 is a major merger system (1:2.8_(-1.5)^(+1.8)).

Additional Information

© 2014 ESO. Received 16 June 2014. Accepted 8 July 2014. Published online 26 August 2014. H.M. acknowledges the support by CONYCIT-ALMA through a post-doc scholarship under the project 31100008. HM acknowledges support by FCT via the post-doctoral fellowship SFRH/BPD/97986/2013 and the programs PTDC/FIS-AST/2194/2012 and PEst-OE/FIS/UI2751/2014. N.N. and R.D. acknowledge support from BASAL PFB-06/2007, Fondecyt 1100540 and Anillo ACT1101. J.A.C. and A.C. acknowledge support from NSF AST-1313319. E.I. acknowledges funding from CONICYT/FONDECYT postdoctoral project N◦:3130504. R.J.I., S.J.M. and L.D. ackowledge support from the European Research Council in the form of Advanced Investigator grant, cosmicism. Y.K.S. acknowledges support by FONDECYT Grant No. 3130470. R.D. acknowledges the support provided by the BASAL centre for Astrophysics and Associated Technologies (CATA) and by FONDECYT N. 1130528. K.R. acknowledges support from the European Research Council Starting Grant SEDmorph (P.I. Wild). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00476.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut fur Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory. We are grateful to the competent staff at the APEX base-camp in Sequitor, Chile and the Z-Spec instrument team. Support for CARMA construction was derived from the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the James S. McDonnell Foundation, the Associates of the California Institute of Technology, the University of Chicago, the states of California, Illinois, and Maryland, and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement, and by the CARMA partner universities. Based in part on observations obtained at the Gemini Observatory (include additional acknowledgement here, see Sect. 1.2), which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). The Herschel-ATLAS is a project with Herschel, 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/. Based in part on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognise and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the US Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. The authors thank the ALMA contact scientist Adam Leroy for the help throughout scheduling block preparation and quality assurance, and the help provided by Alexander J. Conley and Elisabete da Cunha handling, respectively, the mbb_emcee and magphys codes.

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