Can galactic outflows explain the properties of Ly-alpha emitters?
A. Orsi, C. Lacey, and C. Baugh. (2011)cite arxiv:1110.5701
Comment: 28 pages, 21 figures, submitted to MNRAS.
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.
Description
[1110.5701] Can galactic outflows explain the properties of Ly-alpha emitters?
%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
}