TY - JOUR
T1 - Lyman-alpha spectroscopy of extreme [O iii] emitting galaxies at z 2-3
T2 - implications for Lyα visibility and LyC leakage at z > 6
AU - Tang, Mengtao
AU - Stark, Daniel P.
AU - Chevallard, Jacopo
AU - Charlot, Stéphane
AU - Endsley, Ryan
AU - Congiu, Enrico
N1 - Publisher Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2021/5/1
Y1 - 2021/5/1
N2 - Spectroscopic observations of massive z > 7 galaxies selected to have extremely large [O iii] + H β equivalent width (EW ∼1500 Å) have recently revealed large Ly α detection rates, in contrast to the weak emission seen in the general population. Why these systems are uniquely visible in Ly α at redshifts where the intergalactic medium (IGM) is likely significantly neutral is not clear. With the goal of better understanding these results, we have begun a campaign with MMT and Magellan to measure Ly α in galaxies with similar [O iii] + H β EWs at z 2-3. At these redshifts, the IGM is highly ionized, allowing us to clearly disentangle how the Ly α properties depend on the [O iii] + H β EW. Here, we present Ly α EWs of 49 galaxies at z = 2.2-3.7 with intense [O iii] + H β line emission (EW = 300-3000 Å). Our results demonstrate that strong Ly α emission (EW >20 Å) becomes more common in galaxies with larger [O iii] + H β EW, reflecting a combination of increasingly efficient ionizing photon production and enhanced transmission of Ly α. Among the galaxies with the most extreme [O iii] + H β emission (EW ∼1500 Å), we find that strong Ly α emission is not ubiquitous, with only 50 per cent of our population showing Ly α EW >20 Å. Our data suggest that the range of Ly α strengths is related to the observed ellipticity, with those systems that appear edge-on or elongated having weaker Ly α emission. We use these results to interpret the anomalous Ly α properties seen in z > 7 galaxies with extreme [O iii] + H β emission and discuss implications for the escape of ionizing radiation from these extreme line emitting galaxies.
AB - Spectroscopic observations of massive z > 7 galaxies selected to have extremely large [O iii] + H β equivalent width (EW ∼1500 Å) have recently revealed large Ly α detection rates, in contrast to the weak emission seen in the general population. Why these systems are uniquely visible in Ly α at redshifts where the intergalactic medium (IGM) is likely significantly neutral is not clear. With the goal of better understanding these results, we have begun a campaign with MMT and Magellan to measure Ly α in galaxies with similar [O iii] + H β EWs at z 2-3. At these redshifts, the IGM is highly ionized, allowing us to clearly disentangle how the Ly α properties depend on the [O iii] + H β EW. Here, we present Ly α EWs of 49 galaxies at z = 2.2-3.7 with intense [O iii] + H β line emission (EW = 300-3000 Å). Our results demonstrate that strong Ly α emission (EW >20 Å) becomes more common in galaxies with larger [O iii] + H β EW, reflecting a combination of increasingly efficient ionizing photon production and enhanced transmission of Ly α. Among the galaxies with the most extreme [O iii] + H β emission (EW ∼1500 Å), we find that strong Ly α emission is not ubiquitous, with only 50 per cent of our population showing Ly α EW >20 Å. Our data suggest that the range of Ly α strengths is related to the observed ellipticity, with those systems that appear edge-on or elongated having weaker Ly α emission. We use these results to interpret the anomalous Ly α properties seen in z > 7 galaxies with extreme [O iii] + H β emission and discuss implications for the escape of ionizing radiation from these extreme line emitting galaxies.
KW - cosmology: observations
KW - galaxies: evolution
KW - galaxies: formation
KW - galaxies: high-redshift
UR - http://www.scopus.com/inward/record.url?scp=85120767698&partnerID=8YFLogxK
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U2 - 10.1093/mnras/stab705
DO - 10.1093/mnras/stab705
M3 - Article
AN - SCOPUS:85120767698
SN - 0035-8711
VL - 503
SP - 4105
EP - 4117
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -