Discovery of a lensed ultrabright submillimeter galaxy at z=2.0439

TL;DR

This paper reports the discovery and detailed analysis of a highly luminous, gravitationally lensed submillimeter galaxy at z=2.0439, with implications for understanding star formation in the early universe.

Contribution

It presents the first identification and multi-wavelength characterization of a bright, lensed SMG similar to the Cosmic Eyelash, expanding the sample of such extreme starburst galaxies.

Findings

Intrinsic luminosity of 1.3 x 10^13 L_sun

Star formation rate estimated between 500-2000 M_sun/yr

Lensing amplification factor of 11±2

Abstract

We report an ultra-bright lensed submillimeter galaxy (SMG) at $z=2.0439$, {\it WISE} J132934.18+224327.3, identified as a result of a full-sky cross-correlation of the {\it AllWISE} and {\it Planck} compact source catalogs aimed to search for bright analogs of the submillimeter galaxy SMMJ2135, the Cosmic Eyelash. Inspection of archival SCUBA-2 observations of the candidates revealed a source with fluxes (S$_{850 \mu m}$= 130 mJy) consistent with the {\it Planck} measurements. The centroid of the SCUBA-2 source coincides within 1 arcsec with the position of the {\it AllWISE} mid-IR source, and, remarkably, with an arc shaped lensed galaxy in {\it HST} images at visible wavelengths. Low-resolution rest-frame UV-optical spectroscopy of this lensed galaxy obtained with 10.4 m GTC reveals the typical absorption lines of a starburst galaxy. Gemini-N near-IR spectroscopy provided a clear detection of H$_{\alpha}$ emission. The lensed source appears to be gravitationally magnified by a massive foreground galaxy cluster lens at $z = 0.44$, modeling with Lenstool indicates a lensing amplification factor of $11\pm 2$. We determine an intrinsic rest-frame 8-1000-$\mu$m luminosity, $L_{\rm IR}$, of $(1.3 \pm 0.1) \times 10^{13}$ $L_\sun$, and a likely star-formation rate (SFR) of $\sim 500-2000$ $M_\sun yr^{-1}$. The SED shows a remarkable similarity with the Cosmic Eyelash from optical-mid/IR to sub-millimeter/radio, albeit at higher fluxes.