Search for: All records

ABSTRACT We report the detection of cold dust in an apparently quiescent massive galaxy (log (M⋆/M⊙) ≈ 11) at z ∼ 2 (G4). The source is identified as a serendipitous 2 mm continuum source in a deep ALMA observation within the field of Q2343-BX610, a z = 2.21 massive star-forming disc galaxy. Available multiband photometry of G4 suggests redshift of z ∼ 2 and a low specific star formation rate (sSFR), log (SFR/M⋆)[yr−1] ≈ −10.2, corresponding to ≈1.2 dex below the z = 2 main sequence (MS). G4 appears to be a peculiar dust-rich quiescent galaxy for its stellar mass (log (Mdust/M⋆) = −2.71 ± 0.26), with its estimated mass-weighted age (∼1–2 Gyr). We compile z ≳ 1 quiescent galaxies in the literature and discuss their age–ΔMS and log (Mdust/M⋆)–age relations to investigate passive evolution and dust depletion scale. A long dust depletion time and its morphology suggest morphological quenching along with less efficient feedback that could have acted on G4. The estimated dust yield for G4 further supports this idea, requiring efficient survival of dust and/or grain growth, and rejuvenation (or additional accretion). Follow-up observations probing the stellar light and cold dust peak are necessary to understand the implication of these findings in the broader context of galaxy evolutionary studies and quenching in the early universe. 

We present ten novel [OIII]λ4363 auroral line detections up toz ∼ 9.5 measured from ultra-deep JWST/NIRSpec MSA spectroscopy from the JWST Advanced Deep Extragalactic Survey (JADES). We leverage the deepest spectroscopic observations taken thus far with NIRSpec to determine electron temperatures and oxygen abundances using the directT_emethod. We directly compare these results against a suite of locally calibrated strong-line diagnostics and recent high-zcalibrations. We find the calibrations fail to simultaneously match our JADES sample, thus warranting a self-consistent revision of these calibrations for the high-zUniverse. We find a weak dependence between R2 and O3O2 with metallicity, thus suggesting these line ratios are inefficient in the high-zUniverse as metallicity diagnostics and degeneracy breakers. We find R3 and R23 are still correlated with metallicity, but we find a tentative flattening of these diagnostics, thus suggesting future difficulties when applying these strong line ratios as metallicity indicators in the high-zUniverse. We also propose and test an alternative diagnostic based on a different combination of R3 and R2 with a higher dynamic range. We find a reasonably good agreement (median offset of 0.002 dex, median absolute offset of 0.13 dex) with the JWST sample at low metallicity, but future investigations are required on larger samples to probe past the turnover point. At a given metallicity, our sample demonstrates higher ionization and excitation ratios than local galaxies with rest-frame EWs(Hβ) ≈200 − 300 Å. However, we find the median rest-frame EWs(Hβ) of our sample to be ∼2× less than the galaxies used for the local calibrations. This EW discrepancy combined with the high ionization of our galaxies does not offer a clear description of [OIII]λ4363 production in the high-zUniverse, thus warranting a much deeper examination into the factors influencing these processes.