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Source-Plane Reconstruction of the Giant Gravitational Arc in A2667: a Candidate Wolf–Rayet Galaxy At

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Source-Plane Reconstruction of the Giant Gravitational Arc in A2667: a Candidate Wolf–Rayet Galaxy At SOURCE-PLANE RECONSTRUCTION OF THE GIANT GRAVITATIONAL ARC IN A2667: A CANDIDATE WOLF–RAYET GALAXY AT z ∼ 1 Shuo Cao, Giovanni Covone, Eric Jullo, Johan Richard, Luca Izzo, Zong-Hong Zhu To cite this version: Shuo Cao, Giovanni Covone, Eric Jullo, Johan Richard, Luca Izzo, et al.. SOURCE-PLANE RE- CONSTRUCTION OF THE GIANT GRAVITATIONAL ARC IN A2667: A CANDIDATE WOLF– RAYET GALAXY AT z ∼ 1. Astronomical Journal, American Astronomical Society, 2015, 149, pp.8. 10.1088/0004-6256/149/1/3. hal-01109685 HAL Id: hal-01109685 https://hal.archives-ouvertes.fr/hal-01109685 Submitted on 26 Jan 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. The Astronomical Journal, 149:3 (8pp), 2015 January doi:10.1088/0004-6256/149/1/3 C 2015. The American Astronomical Society. All rights reserved. SOURCE-PLANE RECONSTRUCTION OF THE GIANT GRAVITATIONAL ARC IN A2667: A CANDIDATE WOLF–RAYET GALAXY AT z ∼ 1 Shuo Cao1,2, Giovanni Covone2,3, Eric Jullo4, Johan Richard5, Luca Izzo6,7, and Zong-Hong Zhu1 1 Department of Astronomy, Beijing Normal University, 100875 Beijing, China; [email protected] 2 Dipartimento di Scienze Fisiche, Universita` di Napoli “Federico II,” Via Cinthia, I-80126 Napoli, Italy 3 INFN Sez. di Napoli, Compl. Univ. Monte S. Angelo, Via Cinthia, I-80126 Napoli, Italy 4 OAMP, Laboratoire d’Astrophysique de Marseille, UMR6110, Traverse du Siphon, F-13012 Marseille, France 5 CRAL, Observatoire de Lyon, Universite Lyon 1, 9 Avenue Ch. Andre, F-69561 Saint Genis Laval Cedex, France 6 Dip. di Fisica, Sapienza Universit‘a di Roma, Piazzale Aldo Moro 5, I-00185 Rome, Italy 7 ICRANet, Piazza della Repubblica 10, I-65122 Pescara, Italy Received 2014 January 23; accepted 2014 August 26; published 2014 December 1 ABSTRACT We present a new analysis of Hubble Space Telescope, Spitzer Space Telescope, and Very Large Telescope imaging and spectroscopic data of a bright lensed galaxy at z = 1.0334 in the lensing cluster A2667. Using this high- resolution imaging, we present an updated lens model that allows us to fully understand the lensing geometry and reconstruct the lensed galaxy in the source plane. This giant arc gives a unique opportunity to view the structure of a high-redshift disk galaxy. We find that the lensed galaxy of A2667 is a typical spiral galaxy with a morphology similar to the structure of its counterparts at higher redshift, z ∼ 2. The surface brightness of the reconstructed source −2 galaxy in the z850 band reveals the central surface brightness I(0) = 20.28 ± 0.22 mag arcsec and a characteristic radius rs = 2.01 ± 0.16 kpc at redshift z ∼ 1. The morphological reconstruction in different bands shows obvious negative radial color gradients for this galaxy. Moreover, the redder central bulge tends to contain a metal-rich stellar population, rather than being heavily reddened by dust due to high and patchy obscuration. We analyze the VIMOS/integral field unit spectroscopic data and find that, in the given wavelength range (∼1800–3200 Å), the combined arc spectrum of the source galaxy is characterized by a strong continuum emission with strong UV absorption lines (Fe ii and Mg ii) and shows the features of a typical starburst Wolf–Rayet galaxy, NGC 5253. More specifically, we have measured the equivalent widths of Fe ii and Mg ii lines in the A2667 spectrum, and obtained similar values for the same wavelength interval of the NGC 5253 spectrum. Marginal evidence for [C iii] 1909 emission at the edge of the grism range further confirms our expectation. Key words: galaxies: clusters: individual (A2667) – gravitational lensing: strong 1. INTRODUCTION was first proposed by Zwicky (1937) and has developed into an important astrophysical tool since the advent of the HST, since Considerable advances have been made over the last 15 yr lensed galaxies are magnified by typically 1–3 mag and spatial to chart and investigate the properties and evolution of disk sizes are correspondingly stretched (Kneib et al. 2005; Bradley galaxies, which may provide insight into the galaxy formation et al. 2008; Zheng et al. 2009). process in a dark-matter-dominated universe. Moreover, it is A magnificent gravitational lensing example is provided by well known that the galaxy stellar disks cannot only be thickened the galaxy cluster A370 at z = 0.375 (Soucail et al. 1987; by interactions with low-mass halos (Benson et al. 2004), but Lynds & Petrosian 1989), showing a giant gravitational arc also be entirely disrupted by the galaxies or by halos with galaxy (z = 0.725; Richard et al. 2010) that has been extensively masses (Koda et al. 2008). Therefore, the environments where analyzed with the multiband HST/ACS images. The galaxy ′′ ′′ these galaxies are located also play a significant role in the basic cluster has a large Einstein radius, θE = 39 ± 2 ,fora observational features of the disk galaxy population. source redshift at z = 2, and strong magnification in the central Hubble Space Telescope (HST) imaging and spectroscopy of region makes A370 one of the best clusters to search for high- high-redshift disk galaxies provide critical diagnostics of their redshift galaxies. The first metallicity gradient measurement for formation and evolution (e.g., Law et al. 2009; Cassata et al. a face-on spiral galaxy at z ∼ 1.5 was also discussed by Yuan 2010). However, there are several observational challenges in et al. (2011), through the analysis of the arc produced by the pursuing the evolution history of disk galaxies beyond z ≃ 1. massive galaxy cluster MACS J1149.5+2223 at z = 0.544. On one hand, observations of low surface brightness galaxies More recently, Sharon et al. (2012) successfully reconstructed at z ≃ 1 are very challenging, thus limiting the size of the the source plane of a bright lensed galaxy at z = 1.7 magnified available data; on the other hand, at high redshift it becomes by the lensing cluster RCS2 032727−132623, using new high- increasingly more difficult to resolve the spatial structure within resolution imaging from HST/Wide Field Camera 3. A similar galaxies, greatly restraining the possibility of understanding rare case was discovered in VIMOS integral field unit (IFU) the exact position where processes (like star formation) occur. spectroscopic observations of the X-ray luminous cluster A2667 Consequently, gravitationally lensing galaxy clusters provide a (z = 0.233). unique and detailed view of the high-redshift universe, allowing The galaxy cluster A2667 is another remarkable example of us to probe the faint population of distant, background galaxies. “gravitational telescope.” It is among the most luminous galaxy This technique, often referred to as “gravitational telescope,” clusters in the X-ray sky (Ebeling et al. 1996), with a regular 1 The Astronomical Journal, 149:3 (8pp), 2015 January Cao et al. X-ray morphology (Newman et al. 2013; Weißmann et al. 2013) The central region of the galaxy cluster was observed with the and a cool core (Covone et al. 2006a). A redshift survey in the VIMOS IFU (Covone et al. 2006b;Grinetal.2007) mounted central acrmin square reveals a unimodal velocity distribution on VLT Melipal, with a field of view of 54′′ × 54′′, fiber size of the member galaxies (Covone et al. 2006b). A2667 shows a 0′′.66, and the low-resolution red grism (R ∼ 250), covering from remarkable giant gravitational arc (Sand et al. 2005) originating about 3900–5300 Å. Covone et al. (2006b) extracted 22 galaxy from a blue star-forming galaxy at z = 1.034 ± 0.005 (Covone spectra and the spatially resolved spectra of 3 lensed images of et al. 2006b), and a system of lensed sources at high redshift the gravitational arc. (Laporte et al. 2011, 2012). Covone et al. (2006b) performed a wide-field integral field spectroscopy survey of the central 3. STRONG LENSING MASS MODEL arcmin square, using the VIMOS IFU, and built a strong lensing model using HST/WFPC2 data. Yuan et al. (2012)usedthis We used the publicly available software LENSTOOL8 (Jullo lensing model to derive the source-plane morphology from the et al. 2007) to compute the best-fit lens model. LENSTOOL archive WFPC2 data. They analyzed Keck II/OSIRIS spatially makes use of a Monte Carlo Markov Chain (MCMC) optimiza- resolved near-infrared (NIR) spectra and found that the higher tion method. [N ii]/Hα ratio in the outer region might be contaminated by a The source galaxy is multiply imaged into three images (A1, significant fraction of shock excitation due to galactic outflows. A2, and A3; see Figure 1)9: two of them (A1 and A2) are In this paper, we extend the previous analysis on the magni- merged, forming the giant gravitational arc located 14′′ northeast fied source of the giant arc in A2667, based on HST/ACS z850 of the brightest cluster galaxy (BCG), while A3 constitutes an imaging data and a set of complementary imaging and spectro- isolated system. The clear mirror symmetry along the giant arc scopic data. We improve the previous lensing model, produce a provides additional constraints on the location of the critical new inversion of the source galaxy, and study in detail the color line at the arc redshift. HST/ACS data allow us to identify gradient in this ∼1 system.
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