Harikane, YuichiYuichiHarikaneOuchi, MasamiMasamiOuchiInoue, Akio K.Akio K.InoueMatsuoka, YoshikiYoshikiMatsuokaTamura, YoichiYoichiTamuraBakx, TomTomBakxFujimoto, SeijiSeijiFujimotoMoriwaki, KanaKanaMoriwakiOno, YoshiakiYoshiakiOnoNagao, TohruTohruNagaoTadaki, Ken-ichiKen-ichiTadakiKojima, TakashiTakashiKojimaShibuya, TakatoshiTakatoshiShibuyaEgami, EiichiEiichiEgamiFerrara, AndreaAndreaFerraraGallerani, SimonaSimonaGalleraniHashimoto, TakuyaTakuyaHashimotoKohno, KotaroKotaroKohnoMatsuda, YuichiYuichiMatsudaMatsuo, HiroshiHiroshiMatsuoPallottini, AndreaAndreaPallottiniSugahara, YumaYumaSugaharaVALLINI, LiviaLiviaVALLINI2025-03-122025-03-1220200004-637Xhttp://hdl.handle.net/20.500.12386/36714We present our new Atacama Large Millimeter/Submillimeter Array (ALMA) observations targeting [O III]88 μm, [C II]158 μm, [N II]122 μm, and dust-continuum emission for three Lyman break galaxies at z = 6.0293-6.2037, identified in the Subaru/Hyper Suprime-Cam survey. We clearly detect [O III] and [C II] lines from all of the galaxies at 4.3-11.8σ levels, and identify multi-band dust-continuum emission in two of the three galaxies, allowing us to estimate infrared luminosities and dust temperatures simultaneously. In conjunction with previous ALMA observations for six galaxies at z > 6, we confirm that all the nine z = 6-9 galaxies have high [O III]/[C II] ratios of ${L}_{[{\rm{O}}{\rm{III}}]}/{L}_{[{\rm{C}}{\rm{II}}]}\sim 3\mbox{--}20$, ∼10 times higher than z ∼ 0 galaxies. We also find a positive correlation between the [O III]/[C II] ratio and the Lyα equivalent width (EW) at the ∼90% significance level. We carefully investigate physical origins of the high [O III]/[C II] ratios at z = 6-9 using Cloudy, and find that high density of the interstellar medium, low C/O abundance ratio, and the cosmic microwave background attenuation are responsible to only a part of the z = 6-9 galaxies. Instead, the observed high [O III]/[C II] ratios are explained by 10-100 times higher ionization parameters or low photodissociation region (PDR) covering fractions of 0%-10%, both of which are consistent with our [N II] observations. The latter scenario can be reproduced with a density-bounded nebula with PDR deficit, which would enhance the Lyα, Lyman continuum, and ${{\rm{C}}}^{+}$ ionizing photons escape from galaxies, consistent with the [O III]/[C II]-Lyα EW correlation we find.STAMPAenArticle10.3847/1538-4357/ab94bd2-s2.0-85086878460https://iopscience.iop.org/article/10.3847/1538-4357/ab94bdhttps://api.elsevier.com/content/abstract/scopus_id/850868784602020ApJ...896...93HFIS/05 - ASTRONOMIA E ASTROFISICA