Missing [C II] emission from early galaxies
Jun 16, 202015 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 499 (2020) 4, 5136-5150
- Published: Nov 21, 2020
e-Print:
- 2006.09402 [astro-ph.GA]
DOI:
- 10.1093/mnras/staa3178 (publication)
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Abstract: (Oxford University Press)
ALMA observations have revealed that [C ii] 158 μm line emission in high-z galaxies is ≈2–3 × more extended than the UV continuum emission. Here we explore whether surface brightness dimming (SBD) of the [C ii] line is responsible for the reported [C ii] deficit, and the large || luminosity ratio measured in early galaxies. We first analyse archival ALMA images of nine z > 6 galaxies observed in both [C ii] and [O iii]. After performing several uv-tapering experiments to optimize the identification of extended line emission, we detect [C ii] emission in the whole sample, with an extent systematically larger than the [O iii] emission. Next, we use interferometric simulations to study the effect of SBD on the line luminosity estimate. About 40 per cent of the extended [C ii] component might be missed at an angular resolution of 0.8 arcsec, implying that || is underestimated by a factor ≈2 in data at low (<7) signal-to-noise ratio. By combining these results, we conclude that || of z > 6 galaxies lies, on average, slightly below the local || relation (Δ^z ^= ^6–9 = −0.07 ± 0.3), but within the intrinsic dispersion of the relation. SBD correction also yields ||, i.e. more in line with current hydrodynamical simulations.- galaxies: evolution
- galaxies: formation
- galaxies: high-redshift
- galaxies: ISM
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