SQuIGGL⃗E: Spatially resolved NIRSpec Paα reveals that the most CO-luminous, z∼0.7 post-starburst galaxies exhibit falling---but still active---star formation behind optically thick dust

@misc{setton2026squiggle,
  title = {{SQuIGG$\vecL$E: Spatially resolved NIRSpec Pa$α$ reveals that the most CO-luminous, $z\sim0.7$ post-starburst galaxies exhibit falling---but still active---star formation behind optically thick dust}},
  author = {David J. Setton and Jenny E. Greene and Rachel Bezanson and Katherine A. Suess and Justin S. Spilker and Vincenzo R. D'Onofrio and Elia Cenci and Robert Feldmann and Alex J. Geiger and Andy D. Goulding and Mariska Kriek and Anika Kumar and Yuanze Luo and Desika Narayanan and Margaret E. Verrico and Pengpei Zhu},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.31307},
  eprint = {2609.31307},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.31307},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - SQuIGGL⃗E: Spatially resolved NIRSpec Paα reveals that the most CO-luminous, z∼0.7 post-starburst galaxies exhibit falling---but still active---star formation behind optically thick dust
AU  - David J. Setton
AU  - Jenny E. Greene
AU  - Rachel Bezanson
AU  - Katherine A. Suess
AU  - Justin S. Spilker
AU  - Vincenzo R. D'Onofrio
AU  - Elia Cenci
AU  - Robert Feldmann
AU  - Alex J. Geiger
AU  - Andy D. Goulding
AU  - Mariska Kriek
AU  - Anika Kumar
AU  - Yuanze Luo
AU  - Desika Narayanan
AU  - Margaret E. Verrico
AU  - Pengpei Zhu
PY  - 2026
DA  - 2026/09/25
PB  - arXiv
DO  - 10.48550/arxiv.2609.31307
UR  - https://arxiv.org/abs/2609.31307
AB  - One of the fundamental uncertainties in the study of galaxies at the interface between star formation and quiescence--post-starburst galaxies--is their instantaneous star formation rate. While these galaxies appear quiescent in the rest UV-optical, many of the youngest systems are highly CO luminous, implying dense molecular gas, and potentially star formation. However, their instantaneous star formation rates have proved elusive, as measurements with rest-optical emission lines or UV-to-IR SED fitting yield order-of-magnitude uncertainty. Here, we present JWST/NIRSpec G395M/170LP integral field spectroscopy of the three most CO-luminous massive galaxies in the SQuIGGL⃗E survey, spatially resolving Paα/Brγ/Brβ to map the dust-corrected star formation rate. We find that these galaxies host star formation rates of 27−80 M_⊙ yr^−1, though ∼30−40% of the emission may arise from non-star-forming ionization (AGN or shocks), implied by high [FeII]/Paα in central spaxels. We also find effective A_Paα∼1 and individual ∼700 pc spaxels with A_Paα∼2, implying significant dust obscuration of nebular regions that contribute little to the rest-optical lines. These galaxies are not consistent with total quiescence; the measured star formation rates place these galaxies on or above the main sequence. However, their star formation rates \textit{are} significantly lower (∼0.5−1 dex) than the peak star formation rates inferred from spectrophotometric fitting. We propose that the CO luminous post-starburst phase represents the last gasp of star formation in galaxies on the rapid quenching pathway, and that dust-obscured star formation, outflows, and (speculatively) an uncertain CO-to-H2 conversion reconcile their gas exhaustion with observed timescales of fading.
ER  -