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SUMMARY:JWST\, ALMA\, and Keck Spectroscopic Constraints on the UV Luminos
 ity Functions at z~7-14: Clumpiness and Compactness of the Brightest Galax
 ies in the Early Universe
DTSTART:20260511T123000Z
DTEND:20260511T124500Z
DTSTAMP:20260509T051800Z
UID:indico-event-1822@indico.dfa.unipd.it
DESCRIPTION:Speakers: Michele Catone (Università degli Studi di Padova)\n
 \nWe present a JWST and Atacama Large Millimeter/submillimeter Array (ALMA
 ) detailed study of the interstellar medium properties of high-redshift ga
 laxies. Our JWST/NIRSpec integral field unit spectroscopy targeting three 
 galaxies at z = 6─7 detects key rest-frame optical emission lines\, allo
 wing us to derive [O II] λλ3726\, 3729─based electron densities of ne\
 ,optical ∼ 1000 cm−3 on average and [O III] λ4363─based metallici
 ties of 12+log(O/H)=8.0-8.2 in two galaxies. New ALMA Band 9 and 10 obse
 rvations detect the [O III] 52 μm line in one galaxy but do not in the ot
 hers\, resulting in far-infrared (FIR)-based densities of ne\,FIR ≲ 500
  cm−3 from the [O III] 52 μm/[O III] 88 μm ratio\, systematically low
 er than the optical [O II]-based measurements. These low FIR-based densiti
 es are comparable to those at both z ∼ 0 and z > 6 in the literature\, i
 ncluding JADES-GS-z14-0 at z = 14.18\, suggesting little evolution up to z
  ∼ 14\, in contrast to the increasing trend of optical-based densities w
 ith redshift. By conducting a JWST and ALMA joint analysis using emission 
 lines detected with both telescopes\, we find that the observed FIR [O III
 ] 52 and 88 μm luminosities are too high to be explained by the optical-b
 ased densities at which they would be significantly collisionally de-excit
 ed. Instead\, a two-zone model with distinct high- and low-density regions
  is required to reproduce all observed lines\, indicating that FIR [O III]
  emission arises predominantly from low-density gas\, while the optical [O
  III] and [O II] lines trace both regions. We further demonstrate that the
  direct-Te method can sometimes significantly underestimate metallicities 
 up to 0.8 dex due to the presence of the low-density gas not fully traced 
 by optical lines alone\, highlighting the importance of combining optical 
 and FIR lines to accurately determine gas-phase metallicities in the early
  Universe.\n\n\nhttps://indico.dfa.unipd.it/event/1822/
LOCATION:Aula Rosino (Dipartimento di Fisica e Astronomia - Edificio ex-Ri
 zzato)
URL:https://indico.dfa.unipd.it/event/1822/
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