3D-HST GRISM SPECTROSCOPY OF A GRAVITATIONALLY LENSED, LOW-METALLICITY STARBURST GALAXY AT z=1.847

作者：Brammer Gabriel B^*; Sanchez Janssen Ruben; Labbe Ivo; da Cunha Elisabete; Erb Dawn K; Franx Marijn; Fumagalli Mattia; Lundgren Britt; Marchesini Danilo; Momcheva Ivelina; Nelson Erica; Patel Shannon; Quadri Ryan; Rix Hans Walter; Skelton Rosalind E; Schmidt Kasper B; van der Wel Arjen; van Dokkum Pieter G; Wake David A; Whitaker Katherine E

来源：Astrophysical Journal Letters, 2012, 758(1): L17.

DOI：10.1088/2041-8205/758/1/L17

• galaxies: dwarf
• galaxies: formation
• galaxies: high-redshift
• galaxies: starburst

We present Hubble Space Telescope (HST) imaging and spectroscopy of the gravitational lens SL2SJ02176-0513, a cusp arc at z = 1.847. The UV continuum of the lensed galaxy is very blue, which is seemingly at odds with its redder optical colors. The 3D-HSTWFC3/G141 near-infrared spectrum of the lens reveals the source of this discrepancy to be extremely strong [OIII]lambda 5007 and H beta emission lines with rest-frame equivalent widths of 2000 +/- 100 and 520 +/- 40 angstrom, respectively. The source has a stellar mass similar to 10(8) M-circle dot, sSFR similar to 100 Gyr(-1), and detection of [OIII]lambda 4363 yields a metallicity of 12 + log (O/H) = 7.5 +/- 0.2. We identify local blue compact dwarf analogs to SL2SJ02176-0513, which are among the most metal-poor galaxies in the Sloan Digital Sky Survey. The local analogs resemble the lensed galaxy in many ways, including UV/optical spectral energy distribution, spatial morphology, and emission line equivalent widths and ratios. Common to SL2SJ02176-0513 and its local counterparts is an upturn at mid-IR wavelengths likely arising from hot dust heated by starbursts. The emission lines of SL2SJ02176-0513 are spatially resolved owing to the combination of the lens and the high spatial resolution of HST. The lensed galaxy is composed of two clumps with combined size r(e) similar to 300 pc, and we resolve significant differences in UV color and emission line equivalent width between them. Though it has characteristics occasionally attributed to active galactic nuclei, we conclude that SL2SJ02176-0513 is a low-metallicity star-bursting dwarf galaxy. Such galaxies will be found in significant numbers in the full 3D-HST grism survey.

• 出版日期2012-10-10