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Title:
Stellar Populations and Radiative Transfer of Lyman Alpha Galaxies
Authors:
Finkelstein, Steven L.; Rhoads, J. E.; Malhotra, S.; Pirzkal, N.; Wang, J.; Grogin, N.
Affiliation:
AA(Arizona State Univ), AB(Arizona State Univ), AC(Arizona State Univ), AD(Space Telescope Science Institute), AE(University of Science and Technology of China, China), AF(Arizona State Univ)
Publication:
American Astronomical Society Meeting 210, #103.04; Bulletin of the American Astronomical Society, Vol. 38, p.230
Publication Date:
05/2007
Origin:
AAS
Bibliographic Code:
2007AAS...21010304F

Abstract

From stellar population modeling of z 4.5 Lyman alpha emitting galaxies (LAEs), we find that they are in general a young (t 10 Myr), low mass (M 108 MSun) subset of galaxies. We detected 22 LAE candidates in two or more broadband filters (g', r', i' and z') in the Large Area Lyman Alpha (LALA) survey Cetus Field with the MMT. These objects had calculated rest-frame equivalent widths (EWs) ranging from 5-800 Å. By comparing broad and narrow-band colors of these galaxies to stellar population models, we determined their ages and stellar masses. The highest EW objects were found to have an average age of 4 Myr, consistent with ongoing star formation. The lowest EW objects showed an age of 40 - 200 Myr, consistent with the expectation that larger numbers of old stars are causing low EWs. We found masses ranging from 2 x 107 MSun for the youngest objects in the sample to 2 x 109 MSun for the oldest.

While young stellar populations are the generally accepted cause of the large Lyα EW in these objects, it is possible that dust effects could produce large EWs in older populations. This could occur if the ISM were sufficiently clumpy such that the continuum photons would suffer attenuation, while the Lyα photons would be resonantly scattered by the clumps, eventually escaping. We investigate this radiative transfer scenario with our second sample, which consists of six LAE candidates in the GOODS CDF-S, selected at z 4.5 with Hα narrow-band imaging obtained at CTIO. We will present results of stellar population studies of these objects, constraining their rest-frame UV with HST and their rest-frame optical with Spitzer.

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