Lyalpha EMITTERS IN HIERARCHICAL GALAXY FORMATION. II. ULTRAVIOLET CONTINUUM LUMINOSITY FUNCTION AND EQUIVALENT WIDTH DISTRIBUTION
- Optical and Infrared Astronomy Division, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
- Department of Astronomy, School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
- Faculty of Education, Nagasaki University, Nagasaki 852-8521 (Japan)
We present theoretical predictions of the UV continuum luminosity function (UV LF) and Lyalpha equivalent width (EW) distribution of Lyalpha emitters (LAEs) in the framework of the hierarchical clustering model of galaxy formation. The model parameters for the LAEs were determined by fitting to the observed Lyalpha LF at z = 5.7 in our previous study, and the fit indicates that extinction of Lyalpha photons by dust is significantly less effective than that of UV continuum photons, implying a clumpy dust distribution in the interstellar medium. We then compare the predictions about UV LFs and EW distributions with a variety of observations at zapprox 3-6, allowing no more free parameters and paying careful attention to the selection conditions of LAEs in each survey. We find that the predicted UV LFs and EW distributions are in nice agreement with observed data, and especially, our model naturally reproduces the existence of large EW LAEs (approx> 240 A) without introducing Pop III stars or top-heavy initial mass function. We show that both the stellar population (young age and low metallicity) and extinction by clumpy dust are the keys to reproducing large EW LAEs. The evidence of EW enhancement by clumpy dust is further strengthened by the quantitative agreement between our model and recent observations about a positive correlation between EW and extinction. The observed trend that brighter LAEs in the UV continuum tend to have smaller mean EW is also reproduced, and the clumpy dust plays an important role again for this trend. We suggested in our previous study that the transmission of the intergalactic medium for Lyalpha emission rapidly decreases from z approx 6 to 7 by fitting to Lyalpha LFs, and this evidence is quantitatively strengthened by the comparison with the UV LF and EW distribution at z approx 6.6.
- OSTI ID:
- 21392424
- Journal Information:
- Astrophysical Journal, Vol. 708, Issue 2; Other Information: DOI: 10.1088/0004-637X/708/2/1119; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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