Gas conditions of a star-formation selected sample in the first billion years
We present Atacama Large Millimetre/submillimetre Array (ALMA) observations of the [O\(_{\rm III}\)] 88 \(\mu\)m emission of a sample of thirteen galaxies at \(z\) = 6 to 7.6 selected as [C\(_{\rm II}\)]-emitting companion sources of quasars. To disentangle the origins of the luminous Oxygen line in...
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Published in: | arXiv.org 2024-06 |
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Main Authors: | , , , , , , , , , , , , , , , , , , , , , , |
Format: | Article |
Language: | English |
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Online Access: | Get full text |
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Summary: | We present Atacama Large Millimetre/submillimetre Array (ALMA) observations of the [O\(_{\rm III}\)] 88 \(\mu\)m emission of a sample of thirteen galaxies at \(z\) = 6 to 7.6 selected as [C\(_{\rm II}\)]-emitting companion sources of quasars. To disentangle the origins of the luminous Oxygen line in the \(z\) > 6 Universe, we looked at emission-line galaxies that are selected through an excellent star-formation tracer [C\(_{\rm II}\)] with star-formation rates between 9 and 162 M\(_{\odot}\)/yr. Direct observations reveal [O\(_{\rm III}\)] emission in just a single galaxy (L\(_{\rm [O_{\rm III}]}\)/L\(_{\rm [C_{\rm II}]}\) = 2.3), and a stacked image shows no [O\(_{\rm III}\)] detection, providing deep upper limits on the L\(_{\rm [O_{\rm III}]}\)/L\(_{\rm [C_{\rm II}]}\) ratios in the \(z > 6\) Universe (L\(_{\rm [O_{\rm III}]}\)/L\(_{\rm [C_{\rm II}]}\) < 1.2 at 3\({\sigma}\)). While the fidelity of this sample is high, no obvious optical/near-infrared counterpart is seen in the JWST imaging available for four galaxies. Additionally accounting for low-redshift CO emitters, line stacking shows that our sample-wide result remains robust: The enhanced L\(_{\rm [O_{\rm III}]}\)/L\(_{\rm [C_{\rm II}]}\) reported in the first billion years of the Universe is likely due to the selection towards bright, blue Lyman-break galaxies with high surface star-formation rates or young stellar populations. The deep upper limit on the rest-frame 90 \(\mu\)m continuum emission (< 141 \(\mu\)Jy at 3\({\sigma}\)), implies a low average dust temperature (T\(_{\rm dust}\) < 30K) and high dust mass (M\(_{\rm dust}\) ~ 10\(^8\) M\(_{\odot}\)). As more normal galaxies are explored in the early Universe, synergy between JWST and ALMA is fundamental to further investigate the ISM properties of the a broad range of samples of high-\(z\) galaxies. |
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ISSN: | 2331-8422 |