The Sextet Arcs: a Strongly Lensed Lyman Break Galaxy in the ACS Spectroscopic Galaxy Survey towards Abell 1689

Abstract

We present results of the HST Advanced Camera for Surveys spectroscopic ground-based redshift survey in the field of A1689. We measure 98 redshifts, increasing the number of spectroscopically confirmed objects by sixfold. We present two spectra from this catalog of the Sextet Arcs, images which arise from a strongly-lensed Lyman Break Galaxy (LBG) at a redshift of z=3.038. Gravitational lensing by the cluster magnifies its flux by a factor of ~16 and produces six separate images with a total r-band magnitude of r_625=21.7. The two spectra, each of which represents emission from different regions of the LBG, show H I and interstellar metal absorption lines at the systemic redshift. Significant variations are seen in Ly-alpha profile across a single galaxy, ranging from strong absorption to a combination of emission plus absorption. A spectrum of a third image close to the brightest arc shows Ly-alpha emission at the same redshift as the LBG, arising from either another spatially distinct region of the galaxy, or from a companion galaxy close to the LBG. Taken as a group, the Ly-alpha equivalent width in these three spectra decreases with increasing equivalent width of the strongest interstellar absorption lines. We discuss how these variations can be used to understand the physical conditions in the LBG. Intrinsically, this LBG is faint, ~0.1L*, and forming stars at a modest rate, ~4 solar masses per year. We also detect absorption line systems toward the Sextet Arcs at z=2.873 and z=2.534. The latter system is seen across two of our spectra.

Accepted for publication in ApJ

References in corpus (5)

• 3D Lyman-alpha radiation transfer. I. Understanding Lyman-alpha line profile morphologies
• Galaxies in the Hubble Ultra Deep Field: I. Detection, Multiband Photometry, Photometric Redshifts, and Morphology
• Parametric Strong Gravitational Lensing Analysis of Abell 1689
• A very bright, highly magnified Lyman-break galaxy at z=3.07
• Resolved Spectroscopy of a Gravitationally Lensed L* Lyman-break Galaxy at z~5

Cited by in corpus (9)

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• The Highest Resolution Mass Map of Galaxy Cluster Substructure To Date Without Assuming Light Traces Mass: LensPerfect Analysis of Abell 1689
• Lyman Alpha Emitters in the Hierarchically Clustering Galaxy Formation
• First direct metallicity measurement of a lensed star-forming galaxy at z=1.7
• A Free-Form Lensing Grid Solution for A1689 with New Mutiple Images
• A large H$\alpha$ survey of star formation in relaxed and merging galaxy cluster environments at $z\sim 0.15-0.3$
• Comparisons between isothermal and NFW mass profiles for strong-lensing galaxy clusters
• Observations of the Gas Reservoir around a Star Forming Galaxy in the Early Universe