Professor Andrew Bunker

Abstract:

The James Webb Space Telescope is discovering increasing numbers of quiescent galaxies 1–2 billion years after the Big Bang, whose redshift, high mass and old stellar ages indicate that their formation and quenching were surprisingly rapid. This fast-paced evolution seems to require that feedback from active galactic nuclei be faster and/or more efficient than previously expected. We present deep Atacama Large Millimeter/submillimeter Array (ALMA) observations of cool molecular gas (the fuel for star formation) in a massive, fast-rotating, quiescent galaxy at z = 3.064, GS-10578. This galaxy hosts an active galactic nucleus, driving neutral-gas outflows with a mass-outflow rate of 60 ± 20 M⊙ yr−1, and it has a star-formation rate of <5.6 M⊙ yr−1. Our data reveal this system to be a distant gas-poor galaxy confirmed with direct CO observations (molecular-gas mass <109.1 M⊙; <0.8% of its stellar mass). Combining Atacama Large Millimeter/submillimeter Array and James Webb Space Telescope observations, we estimate the gas consumption history of this galaxy, showing that it evolved with net-zero gas inflow, that is, the gas consumption by star formation matches the amount of gas this galaxy is missing relative to star-forming galaxies. This could arise both from preventative feedback stopping further gas inflow, which would otherwise refuel star formation or, alternatively, from fine-tuned ejective feedback matching precisely gas inflows. These results show that galaxy quenching is a long-term effect rather than due to a rapid single quasar episode.

Abstract:

The unexpectedly high abundance of galaxies at $z>11$ revealed by JWST has sparked a debate on the nature of early galaxies and the physical mechanisms regulating their formation. The Atacama Large Millimeter/submillimeter Array (ALMA) has begun to provide vital insights on their gas and dust content, but so far only for extreme ‘blue monsters’. Here we present new, deep ALMA observations of JADES-GS-z11-0, a more typical (sub- $L^{*}$ ) $z>11$ galaxy that bridges the discovery space of JWST and the Hubble Space Telescope. These data confirm the presence of the [O III] 88 $\mu$ m line at $4.5\sigma$ significance, precisely at the redshift of several faint emission lines previously seen with JWST/NIRSpec, while the underlying dust continuum remains undetected ( $F_{\nu }<9.0\mathrm{\mu }\mathrm{J}\mathrm{y}$ ), implying an obscured star formation rate (SFR) of ${\mathrm{\text{SFR}}}_{\mathrm{\text{IR}}}\lesssim 6{\mathrm{M}}_{\mathrm{\odot }}\mathrm{y}{\mathrm{r}}^{\mathrm{-}\mathrm{1}}$ and dust mass of $M_{\mathrm{\text{dust}}}\lesssim 1.0\times {10}^6{\mathrm{M}}_{\mathrm{\odot }}$ (all $3\sigma$ ). The accurate ALMA redshift of $z_{\mathrm{\text{[O III]}}}=11.1221\pm 0.0006$ ( $\gtrsim 5\times$ refined over NIRSpec) helps confirm that redshifts measured purely from the Lyman- $\alpha$ break, even spectroscopically, should properly take into account the effects of potential damped Lyman- $\alpha$ absorption (DLA) systems to avoid systematic overestimates of up to $\Delta z\approx 0.5$ . The [O III] 88 $\mu$ m luminosity of $L_{\mathrm{\text{[O III]}}}=(1.1\pm 0.3)\times {10}^8{\mathrm{L}}_{\mathrm{\odot }}$ , meanwhile, agrees well with the scaling relation for local metal-poor dwarfs given the SFR measured by NIRCam, NIRSpec, and MIRI. The spatially resolved MIRI and ALMA emission also underscores that JADES-GS-z11-0 is likely to consist of two low-mass components that are undergoing strong bursts of star formation yet are already pre-enriched in oxygen ( $\sim 30\%$ solar), only 400 Myr after the Big Bang.