%0 Generic %1 Orsi2011 %A Orsi, Alvaro %A Lacey, Cedric G. %A Baugh, Carlton M. %D 2011 %K lyalpha outflows sam %T Can galactic outflows explain the properties of Ly-alpha emitters? %U http://arxiv.org/abs/1110.5701 %X We study the properties of Ly-alpha emitters in a cosmological framework by computing the escape of Ly-alpha photons through galactic outflows. We combine the GALFORM semi-analytical model of galaxy formation with a Monte Carlo Ly-alpha radiative transfer code. The properties of Ly-alpha emitters at 0<z<7 are predicted using two outflow geometries: a Shell of neutral gas and a Wind ejecting material, both expanding at constant velocity. We characterise the differences in the Ly-alpha line profiles predicted by the two outflow geometries in terms of their width, asymmetry and shift from the line centre for a set of outflows with different hydrogen column densities, expansion velocities and metallicities. In general, the Ly-alpha line profile of the Shell geometry is broader and more asymmetric, and the Ly-alpha escape fraction is lower than with the Wind geometry for the same set of parameters. In order to implement the outflow geometries in the semi-analytical model GALFORM, a number of free parameters in the outflow model are set by matching the luminosity function of Ly-alpha emitters over the whole observed redshift range. The models are consistent with the observationally inferred Ly-alpha escape fractions, equivalent width distributions and with the shape of the Ly-alpha line from composite spectra. Interestingly, our predicted UV luminosity function of Ly-alpha emitters and the fraction of Ly-alpha emitters in Lyman-break galaxy samples at high redshift are in partial agreement with observations. Attenuation of the Ly-alpha line by the presence of a neutral intergalactic medium at high redshift could be responsible for this disagreement. We predict that Ly-alpha emitters constitute a subset of the galaxy population with lower metallicities, lower instantaneous star formation rates and larger sizes than the overall population at the same UV luminosity.

@misc{Orsi2011, abstract = { We study the properties of Ly-alpha emitters in a cosmological framework by computing the escape of Ly-alpha photons through galactic outflows. We combine the GALFORM semi-analytical model of galaxy formation with a Monte Carlo Ly-alpha radiative transfer code. The properties of Ly-alpha emitters at 0<z<7 are predicted using two outflow geometries: a Shell of neutral gas and a Wind ejecting material, both expanding at constant velocity. We characterise the differences in the Ly-alpha line profiles predicted by the two outflow geometries in terms of their width, asymmetry and shift from the line centre for a set of outflows with different hydrogen column densities, expansion velocities and metallicities. In general, the Ly-alpha line profile of the Shell geometry is broader and more asymmetric, and the Ly-alpha escape fraction is lower than with the Wind geometry for the same set of parameters. In order to implement the outflow geometries in the semi-analytical model GALFORM, a number of free parameters in the outflow model are set by matching the luminosity function of Ly-alpha emitters over the whole observed redshift range. The models are consistent with the observationally inferred Ly-alpha escape fractions, equivalent width distributions and with the shape of the Ly-alpha line from composite spectra. Interestingly, our predicted UV luminosity function of Ly-alpha emitters and the fraction of Ly-alpha emitters in Lyman-break galaxy samples at high redshift are in partial agreement with observations. Attenuation of the Ly-alpha line by the presence of a neutral intergalactic medium at high redshift could be responsible for this disagreement. We predict that Ly-alpha emitters constitute a subset of the galaxy population with lower metallicities, lower instantaneous star formation rates and larger sizes than the overall population at the same UV luminosity. }, added-at = {2011-10-27T18:30:21.000+0200}, author = {Orsi, Alvaro and Lacey, Cedric G. and Baugh, Carlton M.}, biburl = {https://www.bibsonomy.org/bibtex/2f80f4f2d5af6b9862a608f693913752b/miki}, description = {[1110.5701] Can galactic outflows explain the properties of Ly-alpha emitters?}, interhash = {54036017c450942ebee8819da5450bca}, intrahash = {f80f4f2d5af6b9862a608f693913752b}, keywords = {lyalpha outflows sam}, note = {cite arxiv:1110.5701 Comment: 28 pages, 21 figures, submitted to MNRAS}, timestamp = {2011-10-27T18:30:21.000+0200}, title = {Can galactic outflows explain the properties of Ly-alpha emitters?}, url = {http://arxiv.org/abs/1110.5701}, year = 2011 }