Dark-ages Reionization and Galaxy Formation Simulation XX. The Ly\${\textbackslash}alpha\$ IGM transmission properties and environment of bright galaxies during the Epoch of Reionization. Qin, Y., Wyithe, J. S. B., Oesch, P. A., Illingworth, G. D., Leonova, E., Mutch, S. J., & Naidu, R. P. Technical Report August, 2021. Publication Title: arXiv e-prints ADS Bibcode: 2021arXiv210803675Q Type: article
Dark-ages Reionization and Galaxy Formation Simulation XX. The Ly\${\textbackslash}alpha\$ IGM transmission properties and environment of bright galaxies during the Epoch of Reionization [link]Paper  abstract   bibtex   
The highly neutral inter-galactic medium (IGM) during the Epoch of Reionization (EoR) is expected to suppress Ly\${\textbackslash}alpha\$ emission with damping-wing absorption, causing nearly no Ly\${\textbackslash}alpha\$ detection from star-forming galaxies at \$z\{{\textbackslash}sim\}8\$. However, spectroscopic observations of the 4 brightest galaxies (\$\{{\textbackslash}rm H\}_\{160\}\{{\textbackslash}sim\}25\$ mag) at these redshifts do reveal prominent Ly\${\textbackslash}alpha\$ line, suggesting locally ionised IGM. In this paper, we explore the Ly\${\textbackslash}alpha\$ IGM transmission and environment of bright galaxies during the EoR using the Meraxes semi-analytic model. We find brighter galaxies to be less affected by damping-wing absorption as they are effective at ionizing surrounding neutral hydrogen. Specifically, the brightest sources (\$\{{\textbackslash}rm H\}_\{160\}\{{\textbackslash}lesssim\}25.5\$ mag) lie in the largest ionized regions in our simulation, and have low attenuation of their Ly\${\textbackslash}alpha\$ from the IGM (optical depth \$\{{\textless}\}1\$). Fainter galaxies (25.5 mag\$\{{\textless}\}\{{\textbackslash}rm H\}_\{160\}\{{\textless}\}27.5\$ mag) have transmission that depends on UV luminosity, leading to a lower incidence of Ly\${\textbackslash}alpha\$ detection at fainter magnitudes. This luminosity-dependent attenuation explains why Ly\${\textbackslash}alpha\$ has only been observed in the brightest galaxies at \$z\{{\textbackslash}sim\}8\$. Follow-up observations have revealed counterparts in the vicinity of these confirmed \$z\{{\textbackslash}sim\}8\$ Ly\${\textbackslash}alpha\$ emitters. The environments of our modelled analogues agree with these observations in the number of nearby galaxies, which is a good indicator of whether Ly\${\textbackslash}alpha\$ can be detected among fainter galaxies. At the current observational limit, galaxies with \$\{{\textbackslash}ge\}2\$–5 neighbours within \$2'\{{\textbackslash}times\}2'\$ are \$\{{\textbackslash}sim\}2\$–3 times more likely to show Ly\${\textbackslash}alpha\$ emission. JWST will discover an order of magnitude more neighbours, revealing \$\{rsim\}50\$ galaxies in the largest ionizing bubbles and facilitating direct study of reionization morphology.
@techreport{2021arXiv210803675Q,
	title = {Dark-ages {Reionization} and {Galaxy} {Formation} {Simulation} {XX}. {The} {Ly}\${\textbackslash}alpha\$ {IGM} transmission properties and environment of bright galaxies during the {Epoch} of {Reionization}},
	url = {https://ui.adsabs.harvard.edu/abs/2021arXiv210803675Q},
	abstract = {The highly neutral inter-galactic medium (IGM) during the Epoch of Reionization (EoR) is expected to suppress Ly\${\textbackslash}alpha\$ emission with damping-wing absorption, causing nearly no Ly\${\textbackslash}alpha\$ detection from star-forming galaxies at \$z\{{\textbackslash}sim\}8\$. However, spectroscopic observations of the 4 brightest galaxies (\$\{{\textbackslash}rm H\}\_\{160\}\{{\textbackslash}sim\}25\$ mag) at these redshifts do reveal prominent Ly\${\textbackslash}alpha\$ line, suggesting locally ionised IGM. In this paper, we explore the Ly\${\textbackslash}alpha\$ IGM transmission and environment of bright galaxies during the EoR using the Meraxes semi-analytic model. We find brighter galaxies to be less affected by damping-wing absorption as they are effective at ionizing surrounding neutral hydrogen. Specifically, the brightest sources (\$\{{\textbackslash}rm H\}\_\{160\}\{{\textbackslash}lesssim\}25.5\$ mag) lie in the largest ionized regions in our simulation, and have low attenuation of their Ly\${\textbackslash}alpha\$ from the IGM (optical depth \$\{{\textless}\}1\$). Fainter galaxies (25.5 mag\$\{{\textless}\}\{{\textbackslash}rm H\}\_\{160\}\{{\textless}\}27.5\$ mag) have transmission that depends on UV luminosity, leading to a lower incidence of Ly\${\textbackslash}alpha\$ detection at fainter magnitudes. This luminosity-dependent attenuation explains why Ly\${\textbackslash}alpha\$ has only been observed in the brightest galaxies at \$z\{{\textbackslash}sim\}8\$. Follow-up observations have revealed counterparts in the vicinity of these confirmed \$z\{{\textbackslash}sim\}8\$ Ly\${\textbackslash}alpha\$ emitters. The environments of our modelled analogues agree with these observations in the number of nearby galaxies, which is a good indicator of whether Ly\${\textbackslash}alpha\$ can be detected among fainter galaxies. At the current observational limit, galaxies with \$\{{\textbackslash}ge\}2\$--5 neighbours within \$2'\{{\textbackslash}times\}2'\$ are \$\{{\textbackslash}sim\}2\$--3 times more likely to show Ly\${\textbackslash}alpha\$ emission. JWST will discover an order of magnitude more neighbours, revealing \$\{rsim\}50\$ galaxies in the largest ionizing bubbles and facilitating direct study of reionization morphology.},
	urldate = {2021-09-07},
	author = {Qin, Yuxiang and Wyithe, J. Stuart B. and Oesch, Pascal A. and Illingworth, Garth D. and Leonova, Ecaterina and Mutch, Simon J. and Naidu, Rohan P.},
	month = aug,
	year = {2021},
	note = {Publication Title: arXiv e-prints
ADS Bibcode: 2021arXiv210803675Q
Type: article},
	keywords = {Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics},
}

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