We present new [OIII] 88-mu m observations of five bright z similar to 7 Lyman-break galaxies spectroscopically confirmed by ALMA through [CII] 158 mu m, unlike recent [OIII] detections where Lyman... Show moreWe present new [OIII] 88-mu m observations of five bright z similar to 7 Lyman-break galaxies spectroscopically confirmed by ALMA through [CII] 158 mu m, unlike recent [OIII] detections where Lyman alpha was used. This nearly doubles the sample of Epoch of Reionization galaxies with robust (5 sigma) [CII] and [OIII] detections. We perform a multiwavelength comparison with new deep HST images of the rest-frame UV, whose compact morphology aligns well with [OIII] tracing ionized gas. In contrast, we find more spatially extended [CII] emission likely produced in neutral gas, as indicated by an [NII] 205-mu m non-detection in one source. We find a correlation between the optical [OIII]+H beta equivalent width and [OIII]/[CII], as seen in local metal-poor dwarf galaxies. cloudy models of a nebula of typical density harbouring a young stellar population with a high-ionization parameter adequately reproduce the observed lines. Surprisingly, however, our models fail to reproduce the strength of [OIII] 88-mu m, unless we assume an alpha/Fe enhancement and near-solar nebular oxygen abundance. On spatially resolved scales, we find [OIII]/[CII] shows a tentative anticorrelation with infrared excess, L-IR/L-UV, also seen on global scales in the local Universe. Finally, we introduce the far-infrared spectral energy distribution fitting code mercurius to show that dust-continuum measurements of one source appear to favour a low dust temperature and correspondingly high dust mass. This implies a high stellar metallicity yield and may point towards the need of dust production or grain-growth mechanisms beyond supernovae. Show less
Holdship, J.; Viti, S.; Martín, S.; Harada, N.; Mangum, J.; Sakamoto, K.; ... ; Werf, P. van der 2021
We present 12CO J = 3→2 maps of NGC 2976 and NGC 3351 obtained with the James Clerk Maxwell Telescope (JCMT), both early targets of the JCMT Nearby Galaxy Legacy Survey (NGLS). We combine the... Show moreWe present 12CO J = 3→2 maps of NGC 2976 and NGC 3351 obtained with the James Clerk Maxwell Telescope (JCMT), both early targets of the JCMT Nearby Galaxy Legacy Survey (NGLS). We combine the present observations with 12CO J = 1→0 data and find that the computed 12CO J = 3→2 to 12CO J = 1→0 line ratio (R31) agrees with values measured in other NGLS field galaxies. We compute the MH2 value and find that it is robust against the value of R31 used. Using H I data from The H I Nearby Galaxy Survey, we find a tight correlation between the surface density of H2 and star formation rate density for NGC 3351 when 12CO J = 3→2 data are used. Finally, we compare the 12CO J = 3→2 intensity with the polycyclic aromatic hydrocarbon (PAH) 8 μm surface brightness and find a good correlation in the high surface brightness regions. We extend this study to include all 25 Spitzer Infrared Nearby Galaxies Survey galaxies within the NGLS sample and find a tight correlation at large spatial scales. We suggest that both PAH 8 μm and 12CO J = 3→2 are likely to originate in regions of active star formation. Show less
