Herschel-ATLAS and ALMA

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 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 Antennae merger. As a whole, the background source is a massive stellar system (1.32 +0.63−0.41 × 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 +1.8 −1.5).

The Strong Gravitationally Lensed Herschel Galaxy HLock01: Optical Spectroscopy Reveals a Close Galaxy Merger with Evidence of Inflowing Gas

“…It is thus no surprise that most high-z close mergers (10 kpc projected separation) have been discovered through the gravitational lensing effect (e.g., Ivison et al 2010b;MacKenzie et al 2014;Messias et al 2014;Rawle et al 2014;Wuyts et al 2014;Spilker et al 2015;Marrone et al 2018), with a few exceptions of unlensed, well separated, SMG-SMG, SMG-QSO or SMG-LBG bright interacting pairs resolved with interferometric observations (e.g., Ivison et al 2002Ivison et al , 2008Smail et al 2003;Salomé et al 2012;Oteo et al 2016;Lu et al 2017;Riechers et al 2017). …”

“…On one hand, almost all ultraluminous galaxies in the local universe are interacting galaxies and mergers (e.g., Farrah et al 2001Farrah et al , 2002Bridge et al 2007;Haan et al 2011). At high-z, a considerable number of SMGs are also found to be galaxy mergers (e.g., Capak et al 2008;Ivison et al 2008Ivison et al , 2013Tacconi et al 2008;Fu et al 2013;Messias et al 2014;Rawle et al 2014;Oteo et al 2016;Riechers et al 2017;Marrone et al 2018), although isolated clumpy gas-rich disk galaxies can also reach extremely large SFRs (e.g., Tacconi et al 2010;Bournaud et al 2014). On the other hand, some authors suggest, based on simulations, that high star formation 1 rates ( M SFRs 1000  ⪆ yr −1 ) in some SMGs are difficult to explain by a merger scenario alone, and propose that the predominant mechanism is smooth accretion of cold gas or infall of gas previously ejected via stellar feedback (e.g., Kereš et al 2005;Dekel et al 2009;Narayanan et al 2015).…”

HerMES: ALMA IMAGING OFHERSCHEL-SELECTED DUSTY STAR-FORMING GALAXIES

“…They cover a wide range in redshift from z 0.5 to z 6 > (Chapman et al 2005;Casey et al 2012a;Riechers et al 2013;Messias et al 2014), with a significant component at z 2 (Casey et al 2012b;Bothwell et al 2013), when they represent the most FIR-luminous objects in existence during this epoch. They are usually signposts of significant overdensities (Daddi et al 2009;Capak et al 2011;compare Robson et al 2014) and likely represent the formative stages of the most massive elliptical galaxies found in the local universe (e.g., Fu et al 2013;Ivison et al 2013).…”

SOFIA/HAWC+ Detection of a Gravitationally Lensed Starburst Galaxy at z = 1.03

“…The de-blending of the foreground lens and background source is discussed in detail in Messias et al (2014). We use the de-blended magnification-corrected photometry for the source to perform SED modeling ( Table 1).…”

“…The brightness enables detections from the optical to radio wavelengths, construction of lens models, and de-blending the source/lens photometry (Calanog et al 2014;Messias et al 2014). Messias et al (2014) presented a detailed analysis of the gas and dust properties, dynamical information, and derive galaxy parameters from SED modeling of J1429-0028. However, a few critical questions remain unaddressed: (1) Is there an energetically important AGN in the system and what is the fractional contribution to the total IR luminosity, if any?…”