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arXiv · 1305.2413

Ultra-faint Ultraviolet Galaxies at z~2 Behind the Lensing Cluster Abell 1689: the Luminosity Function, Dust Extinction and Star Formation Rate Density

Anahita Alavi·Brian Siana·Johan Richard·Daniel P. Stark·Claudia Scarlata·Harry I. Teplitz·William R. Freeman·Alberto Dominguez·Marc Rafelski·Brant Robertson·Lisa Kewley
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Abstract

We identified the z~2 Lyman break galaxies using deep HST ultraviolet (F275W/F336W) imaging of Abell 1689. Because of the imaging depth and the large magnification provided by the cluster, we detect galaxies 100x fainter (-19.5< M_1500 <-13) than previous surveys at this redshift. We are able to calculate the intrinsic sensitivity of the observations as a function of source plane position, allowing determinations of effective volume as a function of luminosity. We fit the faint-end slope of the luminosity function to be alpha = -1.74 +/-0.08, consistent with the values obtained for 2.5 < z < 6. There is no turnover in the luminosity function down to MUV = -13. The trend of increasingly redder UV spectral slopes with luminosity at higher redshifts is observed in our sample, but with redder slopes at all luminosities and average reddening of < E(B - V) >= 0.15. We assume the stars in these galaxies are metal poor (0.2Z_sun) compared to their brighter counterparts (Z_sun), resulting in bluer assumed intrinsic UV slopes and larger derived dust extinction. The total UV luminosity density at z ~ 2 is 4.31x10^26 erg/s/Hz/Mpc^3, more than 70% of which is emitted by galaxies in the luminosity range of our sample. We determine the star formation rate density at z ~ 2 (assuming constant dust extinction correction of 4.2 over all luminosities and a Kroupa IMF) of 0.148 M/yr/Mpc^3, significantly higher than previous determinations because of the additional population of fainter galaxies and the larger dust correction factors.[abridged]

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Anahita Alavi, Brian Siana, Johan Richard, Daniel P. Stark, Claudia Scarlata, Harry I. Teplitz, William R. Freeman, Alberto Dominguez, Marc Rafelski, Brant Robertson, Lisa Kewley. 2013-11-24. Ultra-faint Ultraviolet Galaxies at z~2 Behind the Lensing Cluster Abell 1689: the Luminosity Function, Dust Extinction and Star Formation Rate Density. https://doi.org/10.1088/0004-637x%2F780%2F2%2F143

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