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arXiv · 1509.06381

Probing the Physical Properties of z=4.5 Lyman Alpha Emitters with Spitzer

Keely D. Finkelstein·Steven L. Finkelstein·Vithal Tilvi·Sangeeta Malhotra·James E. Rhoads·Norman A. Grogin·Norbert Pirzkal·Arjun Dey·Buell T. Jannuzi·Bahram Mobasher·Sabrina Pakzad·Brett Salmon·Junzian Wang
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Abstract

We present the results from a stellar population modeling analysis of a sample of 162 z=4.5, and 14 z=5.7 Lyman alpha emitting galaxies (LAEs) in the Bootes field, using deep Spitzer/IRAC data at 3.6 and 4.5 um from the Spitzer Lyman Alpha Survey, along with Hubble Space Telescope NICMOS and WFC3 imaging at 1.1 and 1.6 um for a subset of the LAEs. This represents one of the largest samples of high-redshift LAEs imaged with Spitzer IRAC. We find that 30/162 (19%) of the z=4.5 LAEs and 9/14 (64%) of the z=5.7 LAEs are detected at >3-sigma in at least one IRAC band. Individual z=4.5 IRAC-detected LAEs have a large range of stellar mass, from 5x10^8 to 10^11 Msol. One-third of the IRAC-detected LAEs have older stellar population ages of 100 Myr - 1 Gyr, while the remainder have ages < 100 Myr. A stacking analysis of IRAC-undetected LAEs shows this population to be primarily low mass (8 -- 20 x 10^8 Msol) and young (64 - 570 Myr). We find a correlation between stellar mass and the dust-corrected ultraviolet-based star-formation rate (SFR) similar to that at lower redshifts, in that higher mass galaxies exhibit higher SFRs. However, the z=4.5 LAE correlation is elevated 4-5 times in SFR compared to continuum-selected galaxies at similar redshifts. The exception is the most massive LAEs which have SFRs similar to galaxies at lower redshifts suggesting that they may represent a different population of galaxies than the traditional lower-mass LAEs, perhaps with a different mechanism promoting Lyman alpha photon escape.

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Keely D. Finkelstein, Steven L. Finkelstein, Vithal Tilvi, Sangeeta Malhotra, James E. Rhoads, Norman A. Grogin, Norbert Pirzkal, Arjun Dey, Buell T. Jannuzi, Bahram Mobasher, Sabrina Pakzad, Brett Salmon, Junzian Wang. 2015-09-21. Probing the Physical Properties of z=4.5 Lyman Alpha Emitters with Spitzer. https://doi.org/10.1088/0004-637x/813/1/78

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