Poster Presentation

Detection of cool gas around a quiescent galaxy at z=4 by JWST

Author(s): Po-Feng Wu, National Taiwan University

Presenter: Po-Feng Wu (National Taiwan University)

The unprecedented sensitivity of JWST in the IR allows us to discover and characterize galaxies at high redshift. Obtaining restframe UV and optical continuum spectra of z>3 galaxies would take dozens of hours on large ground-based telescopes but only a few hours on JWST. Absorption-line spectroscopy and characterization of high-redshift quiescent galaxies become possible.

I will present the first detection of cool gas around a massive quiescent galaxy at z=4 with JWST NIRSpec. This galaxy has no measurable H_beta or [OII] emission, indicating that the star formation rate is less than 1/10 of the star formation main sequence at z=4. Modeling the restframe optical absorption lines shows that the last major star formation event was at ~500 Myrs before observation. Clear [Mg II] and [Fe II] absorptions present in the restframe UV spectrum cannot be fully attributed to stellar absorption, indicating absorption by cool gas surrounding the quiescent galaxy. Combining the absorption strengths from cool gas and the metallicity measured from stellar absorption, we could estimate the hydrogen column density. This case demonstrates a viable way to probe the gas content surrounding high-z quiescent galaxies.