Strong Ly\${\textbackslash}alpha\$ Emission in an Overdense Region at \$z=6.8\$: A Very Large (\${R}{\textbackslash}sim3\$ physical Mpc) Ionized Bubble in COSMOS?. Endsley, R. & Stark, D. P. arXiv:2112.14779 [astro-ph], December, 2021. arXiv: 2112.14779Paper abstract bibtex Our understanding of reionization has advanced considerably over the past decade, with several results now demonstrating that the IGM transitioned from substantially neutral at \$z=7\$ to largely reionized at \$z=6\$. However, little remains known about the sizes of ionized bubbles at \$z{\textbackslash}gtrsim7\$ as well as the galaxy overdensities which drive their growth. Fortunately, rest-UV spectroscopic observations offer a pathway towards characterizing these ionized bubbles thanks to the resonant nature of Lyman-alpha photons. In a previous work, we presented Ly\${\textbackslash}alpha\$ detections from three closely-separated Lyman-break galaxies at \$z{\textbackslash}simeq6.8\$, suggesting the presence of a large (\$R{\textgreater}1\$ physical Mpc) ionized bubble in the 1.5 deg\${\textasciicircum}2\$ COSMOS field. Here, we present new deep Ly\${\textbackslash}alpha\$ spectra of ten UV-bright (\${\textbackslash}mathrm\{M\}_\{{\textbackslash}mathrm\{UV\}\}{\textasciicircum}\{\} {\textbackslash}leq -20.4\$) \$z{\textbackslash}simeq6.6-6.9\$ galaxies in the surrounding area, enabling us to better characterize this potential ionized bubble. We confidently detect (S/N\${\textgreater}\$7) Ly\${\textbackslash}alpha\$ emission at \$z=6.701-6.882\$ in nine of ten observed galaxies, revealing that the large-scale volume spanned by these sources (characteristic radius \$R = 3.2\$ physical Mpc) traces a strong galaxy overdensity (\$N/{\textbackslash}langle N{\textbackslash}rangle {\textbackslash}gtrsim 3\$). Our data additionally confirm that the Ly\${\textbackslash}alpha\$ emission of UV-bright galaxies in this volume is significantly enhanced, with 40% (4/10) showing strong Ly\${\textbackslash}alpha\$ emission (equivalent width\${\textgreater}\$25 \${\textbackslash}mathrm\{{\textbackslash}mathring\{A\}\}\$) compared to the 8\$-\$9% found on average at \$z{\textbackslash}sim7\$. The median Ly\${\textbackslash}alpha\$ equivalent width of our observed galaxies is also \${\textbackslash}approx\$2\${\textbackslash}times\$ that typical at \$z{\textbackslash}sim7\$, consistent with expectations if a very large (\$R{\textbackslash}sim3\$ physical Mpc) ionized bubble is allowing the Ly\${\textbackslash}alpha\$ photons to cosmologically redshift far into the damping wing before encountering HI.
@article{endsley_strong_2021,
title = {Strong {Ly}\${\textbackslash}alpha\$ {Emission} in an {Overdense} {Region} at \$z=6.8\$: {A} {Very} {Large} (\${R}{\textbackslash}sim3\$ physical {Mpc}) {Ionized} {Bubble} in {COSMOS}?},
shorttitle = {Strong {Ly}\${\textbackslash}alpha\$ {Emission} in an {Overdense} {Region} at \$z=6.8\$},
url = {http://arxiv.org/abs/2112.14779},
abstract = {Our understanding of reionization has advanced considerably over the past decade, with several results now demonstrating that the IGM transitioned from substantially neutral at \$z=7\$ to largely reionized at \$z=6\$. However, little remains known about the sizes of ionized bubbles at \$z{\textbackslash}gtrsim7\$ as well as the galaxy overdensities which drive their growth. Fortunately, rest-UV spectroscopic observations offer a pathway towards characterizing these ionized bubbles thanks to the resonant nature of Lyman-alpha photons. In a previous work, we presented Ly\${\textbackslash}alpha\$ detections from three closely-separated Lyman-break galaxies at \$z{\textbackslash}simeq6.8\$, suggesting the presence of a large (\$R{\textgreater}1\$ physical Mpc) ionized bubble in the 1.5 deg\${\textasciicircum}2\$ COSMOS field. Here, we present new deep Ly\${\textbackslash}alpha\$ spectra of ten UV-bright (\${\textbackslash}mathrm\{M\}\_\{{\textbackslash}mathrm\{UV\}\}{\textasciicircum}\{\} {\textbackslash}leq -20.4\$) \$z{\textbackslash}simeq6.6-6.9\$ galaxies in the surrounding area, enabling us to better characterize this potential ionized bubble. We confidently detect (S/N\${\textgreater}\$7) Ly\${\textbackslash}alpha\$ emission at \$z=6.701-6.882\$ in nine of ten observed galaxies, revealing that the large-scale volume spanned by these sources (characteristic radius \$R = 3.2\$ physical Mpc) traces a strong galaxy overdensity (\$N/{\textbackslash}langle N{\textbackslash}rangle {\textbackslash}gtrsim 3\$). Our data additionally confirm that the Ly\${\textbackslash}alpha\$ emission of UV-bright galaxies in this volume is significantly enhanced, with 40\% (4/10) showing strong Ly\${\textbackslash}alpha\$ emission (equivalent width\${\textgreater}\$25 \${\textbackslash}mathrm\{{\textbackslash}mathring\{A\}\}\$) compared to the 8\$-\$9\% found on average at \$z{\textbackslash}sim7\$. The median Ly\${\textbackslash}alpha\$ equivalent width of our observed galaxies is also \${\textbackslash}approx\$2\${\textbackslash}times\$ that typical at \$z{\textbackslash}sim7\$, consistent with expectations if a very large (\$R{\textbackslash}sim3\$ physical Mpc) ionized bubble is allowing the Ly\${\textbackslash}alpha\$ photons to cosmologically redshift far into the damping wing before encountering HI.},
urldate = {2022-01-05},
journal = {arXiv:2112.14779 [astro-ph]},
author = {Endsley, Ryan and Stark, Daniel P.},
month = dec,
year = {2021},
note = {arXiv: 2112.14779},
keywords = {Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics},
}
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Fortunately, rest-UV spectroscopic observations offer a pathway towards characterizing these ionized bubbles thanks to the resonant nature of Lyman-alpha photons. In a previous work, we presented Ly\\${\\textbackslash}alpha\\$ detections from three closely-separated Lyman-break galaxies at \\$z{\\textbackslash}simeq6.8\\$, suggesting the presence of a large (\\$R{\\textgreater}1\\$ physical Mpc) ionized bubble in the 1.5 deg\\${\\textasciicircum}2\\$ COSMOS field. Here, we present new deep Ly\\${\\textbackslash}alpha\\$ spectra of ten UV-bright (\\${\\textbackslash}mathrm\\{M\\}_\\{{\\textbackslash}mathrm\\{UV\\}\\}{\\textasciicircum}\\{\\} {\\textbackslash}leq -20.4\\$) \\$z{\\textbackslash}simeq6.6-6.9\\$ galaxies in the surrounding area, enabling us to better characterize this potential ionized bubble. We confidently detect (S/N\\${\\textgreater}\\$7) Ly\\${\\textbackslash}alpha\\$ emission at \\$z=6.701-6.882\\$ in nine of ten observed galaxies, revealing that the large-scale volume spanned by these sources (characteristic radius \\$R = 3.2\\$ physical Mpc) traces a strong galaxy overdensity (\\$N/{\\textbackslash}langle N{\\textbackslash}rangle {\\textbackslash}gtrsim 3\\$). Our data additionally confirm that the Ly\\${\\textbackslash}alpha\\$ emission of UV-bright galaxies in this volume is significantly enhanced, with 40% (4/10) showing strong Ly\\${\\textbackslash}alpha\\$ emission (equivalent width\\${\\textgreater}\\$25 \\${\\textbackslash}mathrm\\{{\\textbackslash}mathring\\{A\\}\\}\\$) compared to the 8\\$-\\$9% found on average at \\$z{\\textbackslash}sim7\\$. The median Ly\\${\\textbackslash}alpha\\$ equivalent width of our observed galaxies is also \\${\\textbackslash}approx\\$2\\${\\textbackslash}times\\$ that typical at \\$z{\\textbackslash}sim7\\$, consistent with expectations if a very large (\\$R{\\textbackslash}sim3\\$ physical Mpc) ionized bubble is allowing the Ly\\${\\textbackslash}alpha\\$ photons to cosmologically redshift far into the damping wing before encountering HI.","urldate":"2022-01-05","journal":"arXiv:2112.14779 [astro-ph]","author":[{"propositions":[],"lastnames":["Endsley"],"firstnames":["Ryan"],"suffixes":[]},{"propositions":[],"lastnames":["Stark"],"firstnames":["Daniel","P."],"suffixes":[]}],"month":"December","year":"2021","note":"arXiv: 2112.14779","keywords":"Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics","bibtex":"@article{endsley_strong_2021,\n\ttitle = {Strong {Ly}\\${\\textbackslash}alpha\\$ {Emission} in an {Overdense} {Region} at \\$z=6.8\\$: {A} {Very} {Large} (\\${R}{\\textbackslash}sim3\\$ physical {Mpc}) {Ionized} {Bubble} in {COSMOS}?},\n\tshorttitle = {Strong {Ly}\\${\\textbackslash}alpha\\$ {Emission} in an {Overdense} {Region} at \\$z=6.8\\$},\n\turl = {http://arxiv.org/abs/2112.14779},\n\tabstract = {Our understanding of reionization has advanced considerably over the past decade, with several results now demonstrating that the IGM transitioned from substantially neutral at \\$z=7\\$ to largely reionized at \\$z=6\\$. However, little remains known about the sizes of ionized bubbles at \\$z{\\textbackslash}gtrsim7\\$ as well as the galaxy overdensities which drive their growth. Fortunately, rest-UV spectroscopic observations offer a pathway towards characterizing these ionized bubbles thanks to the resonant nature of Lyman-alpha photons. In a previous work, we presented Ly\\${\\textbackslash}alpha\\$ detections from three closely-separated Lyman-break galaxies at \\$z{\\textbackslash}simeq6.8\\$, suggesting the presence of a large (\\$R{\\textgreater}1\\$ physical Mpc) ionized bubble in the 1.5 deg\\${\\textasciicircum}2\\$ COSMOS field. Here, we present new deep Ly\\${\\textbackslash}alpha\\$ spectra of ten UV-bright (\\${\\textbackslash}mathrm\\{M\\}\\_\\{{\\textbackslash}mathrm\\{UV\\}\\}{\\textasciicircum}\\{\\} {\\textbackslash}leq -20.4\\$) \\$z{\\textbackslash}simeq6.6-6.9\\$ galaxies in the surrounding area, enabling us to better characterize this potential ionized bubble. We confidently detect (S/N\\${\\textgreater}\\$7) Ly\\${\\textbackslash}alpha\\$ emission at \\$z=6.701-6.882\\$ in nine of ten observed galaxies, revealing that the large-scale volume spanned by these sources (characteristic radius \\$R = 3.2\\$ physical Mpc) traces a strong galaxy overdensity (\\$N/{\\textbackslash}langle N{\\textbackslash}rangle {\\textbackslash}gtrsim 3\\$). Our data additionally confirm that the Ly\\${\\textbackslash}alpha\\$ emission of UV-bright galaxies in this volume is significantly enhanced, with 40\\% (4/10) showing strong Ly\\${\\textbackslash}alpha\\$ emission (equivalent width\\${\\textgreater}\\$25 \\${\\textbackslash}mathrm\\{{\\textbackslash}mathring\\{A\\}\\}\\$) compared to the 8\\$-\\$9\\% found on average at \\$z{\\textbackslash}sim7\\$. The median Ly\\${\\textbackslash}alpha\\$ equivalent width of our observed galaxies is also \\${\\textbackslash}approx\\$2\\${\\textbackslash}times\\$ that typical at \\$z{\\textbackslash}sim7\\$, consistent with expectations if a very large (\\$R{\\textbackslash}sim3\\$ physical Mpc) ionized bubble is allowing the Ly\\${\\textbackslash}alpha\\$ photons to cosmologically redshift far into the damping wing before encountering HI.},\n\turldate = {2022-01-05},\n\tjournal = {arXiv:2112.14779 [astro-ph]},\n\tauthor = {Endsley, Ryan and Stark, Daniel P.},\n\tmonth = dec,\n\tyear = {2021},\n\tnote = {arXiv: 2112.14779},\n\tkeywords = {Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics},\n}\n\n","author_short":["Endsley, R.","Stark, D. 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