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

Hugo Messias , Simon Dye , Neil Nagar , Gustavo Orellana , R. Shane Bussmann , Jae Calanog , Helmut Dannerbauer , Hai Fu , Edo Ibar , Andrew Inohara , R. J. Ivison , Mattia Negrello , Dominik A. Riechers , Yun-Kyeong Sheen , James E. Aguirre , Simon Amber , Mark Birkinshaw , Nathan Bourne , Charles M. Bradford , Dave L. Clements , Asantha Cooray , Gianfranco de Zotti , Ricardo Demarco , Loretta Dunne , Stephen Eales , Simone Fleuren , Julia Kamenetzky , Roxana E. Lupu , Steve J. Maddox , Daniel P. Marrone , Michał J. Michałowski , Eric J. Murphy , Hien T. Nguyen , Alain Omont (1) , Kate Rowlands , Dan Smith , Matt Smith , Elisabetta Valiante , Joaquin D. Vieira

1 IAP - Institut d'Astrophysique de Paris

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 z_sp = 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} × 10¹¹ 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 × 10¹⁰ 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 × 10¹⁰ 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).

Mots clés: gravitational lensing: strong; galaxies: ISM; galaxies: kinematics and dynamics; Astrophysics - Astrophysics of Galaxies; Astrophysics - Cosmology and Nongalactic Astrophysics

Domaines: Planète et Univers [physics]

Hugo Messias, Simon Dye, Neil Nagar, Gustavo Orellana, R. Shane Bussmann, et al.. Herschel-ATLAS and ALMA. HATLAS J142935.3-002836, a lensed major merger at redshift 1.027. Astronomy and Astrophysics - A&A, 2014, 568, ⟨10.1051/0004-6361/201424410⟩. ⟨insu-03645350⟩