We present a spectroscopic survey of 318 faint $(R27$, $L\sim0.1L_*)$,
Ly\alpha-emission-selected galaxies (LAEs) at 2.5<z<3. A sample of 32 LAEs
with rest-frame optical spectra from Keck/MOSFIRE are used to interpret the LAE
spectra in the context of their systemic redshifts. We find that the Ly\alpha
emission of LAEs is typically less spectrally extended than among samples of
more luminous continuum-selected galaxies (LBGs) at similar redshifts. Using
the MOSFIRE subsample, we find that the peak of the Ly\alpha line is shifted
by +200 km/s with respect to systemic across a diverse set of galaxies
including both LAEs and LBGs. We also find a small number of objects with
significantly blueshifted Ly\alpha emission, a potential indicator of
accreting gas. The Ly\alpha-to-H\alpha line ratios suggest that the LAEs
have Ly\alpha escape fractions $f_esc,Ly\alpha 30$%,
significantly higher than typical LBG samples. Using redshifts calibrated by
our MOSFIRE sample, we construct composite LAE spectra, finding the first
evidence for metal-enriched outflows in such intrinsically-faint high-redshift
galaxies. These outflows have smaller continuum covering fractions $(f_c
0.3)$ and velocities $(v_ave 100-200$ km/s, $v_max
500$ km/s$)$ than those associated with typical LBGs, suggesting that
gas covering fraction is a likely driver of the high Ly\alpha and
Ly-continuum escape fractions of LAEs. Our results suggest a similar scaling of
outflow velocity with star formation rate as is observed at lower redshifts
$(v_outflow SFR^0.25)$ and indicate that a substantial
fraction of gas is ejected with $v > v_esc$.
Description
[1506.08205] The Spectroscopic Properties of Ly{\alpha}-Emitters at z $\approx$ 2.7: Escaping Gas and Photons from Faint Galaxies
%0 Generic
%1 trainor2015spectroscopic
%A Trainor, Ryan F.
%A Steidel, Charles C.
%A Strom, Allison L.
%A Rudie, Gwen C.
%D 2015
%K cgm emitters lya outflows
%T The Spectroscopic Properties of Ly\alpha-Emitters at z $\approx$ 2.7:
Escaping Gas and Photons from Faint Galaxies
%U http://arxiv.org/abs/1506.08205
%X We present a spectroscopic survey of 318 faint $(R27$, $L\sim0.1L_*)$,
Ly\alpha-emission-selected galaxies (LAEs) at 2.5<z<3. A sample of 32 LAEs
with rest-frame optical spectra from Keck/MOSFIRE are used to interpret the LAE
spectra in the context of their systemic redshifts. We find that the Ly\alpha
emission of LAEs is typically less spectrally extended than among samples of
more luminous continuum-selected galaxies (LBGs) at similar redshifts. Using
the MOSFIRE subsample, we find that the peak of the Ly\alpha line is shifted
by +200 km/s with respect to systemic across a diverse set of galaxies
including both LAEs and LBGs. We also find a small number of objects with
significantly blueshifted Ly\alpha emission, a potential indicator of
accreting gas. The Ly\alpha-to-H\alpha line ratios suggest that the LAEs
have Ly\alpha escape fractions $f_esc,Ly\alpha 30$%,
significantly higher than typical LBG samples. Using redshifts calibrated by
our MOSFIRE sample, we construct composite LAE spectra, finding the first
evidence for metal-enriched outflows in such intrinsically-faint high-redshift
galaxies. These outflows have smaller continuum covering fractions $(f_c
0.3)$ and velocities $(v_ave 100-200$ km/s, $v_max
500$ km/s$)$ than those associated with typical LBGs, suggesting that
gas covering fraction is a likely driver of the high Ly\alpha and
Ly-continuum escape fractions of LAEs. Our results suggest a similar scaling of
outflow velocity with star formation rate as is observed at lower redshifts
$(v_outflow SFR^0.25)$ and indicate that a substantial
fraction of gas is ejected with $v > v_esc$.
@misc{trainor2015spectroscopic,
abstract = {We present a spectroscopic survey of 318 faint $(R\sim 27$, $L\sim0.1L_*)$,
Ly{\alpha}-emission-selected galaxies (LAEs) at 2.5<z<3. A sample of 32 LAEs
with rest-frame optical spectra from Keck/MOSFIRE are used to interpret the LAE
spectra in the context of their systemic redshifts. We find that the Ly{\alpha}
emission of LAEs is typically less spectrally extended than among samples of
more luminous continuum-selected galaxies (LBGs) at similar redshifts. Using
the MOSFIRE subsample, we find that the peak of the Ly{\alpha} line is shifted
by +200 km/s with respect to systemic across a diverse set of galaxies
including both LAEs and LBGs. We also find a small number of objects with
significantly blueshifted Ly{\alpha} emission, a potential indicator of
accreting gas. The Ly{\alpha}-to-H{\alpha} line ratios suggest that the LAEs
have Ly{\alpha} escape fractions $f_{\rm esc,Ly{\alpha}} \approx 30$%,
significantly higher than typical LBG samples. Using redshifts calibrated by
our MOSFIRE sample, we construct composite LAE spectra, finding the first
evidence for metal-enriched outflows in such intrinsically-faint high-redshift
galaxies. These outflows have smaller continuum covering fractions $(f_c
\approx 0.3)$ and velocities $(v_{\rm ave} \approx 100-200$ km/s, $v_{\rm max}
\approx 500$ km/s$)$ than those associated with typical LBGs, suggesting that
gas covering fraction is a likely driver of the high Ly{\alpha} and
Ly-continuum escape fractions of LAEs. Our results suggest a similar scaling of
outflow velocity with star formation rate as is observed at lower redshifts
$(v_{\rm outflow} \sim {\rm SFR}^{0.25})$ and indicate that a substantial
fraction of gas is ejected with $v > v_{esc}$.},
added-at = {2015-06-30T09:22:53.000+0200},
author = {Trainor, Ryan F. and Steidel, Charles C. and Strom, Allison L. and Rudie, Gwen C.},
biburl = {https://www.bibsonomy.org/bibtex/2bd7d8f58ba14bb815d724abff1b768c7/miki},
description = {[1506.08205] The Spectroscopic Properties of Ly{\alpha}-Emitters at z $\approx$ 2.7: Escaping Gas and Photons from Faint Galaxies},
interhash = {63be1881cd3cb2ed55f7c44373de4d1d},
intrahash = {bd7d8f58ba14bb815d724abff1b768c7},
keywords = {cgm emitters lya outflows},
note = {cite arxiv:1506.08205},
timestamp = {2015-06-30T09:22:53.000+0200},
title = {The Spectroscopic Properties of Ly{\alpha}-Emitters at z $\approx$ 2.7:
Escaping Gas and Photons from Faint Galaxies},
url = {http://arxiv.org/abs/1506.08205},
year = 2015
}