Professor Andrew Bunker

Abstract:

We report the discovery of a substantial sodium doublet (Na D λλ5890, 5896)—traced neutral outflow in the quiescent galaxy JADES-GS-206183 at z = 1.317. Its JWST/NIRSpec-Microshutter Array spectrum shows a deep, blueshifted Na D absorption, revealing a neutral outflow with vout=828−49+79kms−1 and a mass outflow rate of log(Ṁout/M⊙yr−1)=2.40−0.16+0.11 . This outflow rate exceeds that of any neutral outflows identified beyond z ∼ 1 by the same line and is comparable with those in local galaxies with intensive star formation (SF) or luminous active galactic nuclei (AGN). JADES-GS-206183 is also a peculiar quiescent galaxy with a spiral+bar morphology, high dust attenuation (AV = 2.27 ± 0.23 mag). Paschen α (Paα) emission from the FRESCO NIRCam grism confirms its low star formation rate (SFRPaα = 10.78 ± 0.55 M⊙ yr−1), placing it 0.5 dex below the main sequence ( log(sSFRyr−1)=−10.2 ). Despite the systematics introduced by different SF history priors, the spectral energy distribution modeling, combining Hubble Space Telescope-to-NIRCam photometry with the Very Large Telescope/MUSE spectrum, suggests that JADES-GS-206183 experienced an older episode of SF 0.5–2 Gyr ago and a possible rejuvenation within the recent ∼10 Myr. Moreover, rest-frame optical lines indicate that the current AGN activity of JADES-GS-206183, if present, is also weak. Even though we tentatively detect a broad component of the Hα line, it likely traces an ionized outflow rather than an AGN. The results demonstrate that the Na D outflow in JADES-GS-206183 is highly unlikely to be driven by current SF or nuclear activity. Instead, it may represent a long-lasting fossil outflow from past AGN activity, potentially cotriggered with the early phase of rejuvenation.

Abstract:

Recent photometric surveys with James Webb Space Telescope (JWST) have revealed a significant population of mysterious objects with red colours, compact morphologies, frequent signs of active galactic nucleus (AGN) activity, and negligible X-ray emission. These ‘little red dots’ (LRDs) have been explored through spectral and photometric studies, but their nature is still under debate. As part of the BlackTHUNDER survey, we have observed UNCOVER_20466, one of the most distant LRDs known (), with the JWST/NIRSpec Integral Field Unit (IFU). Previous JWST/NIRCam and JWST/NIRSpec MSA observations of this source revealed its LRD nature, as well as the presence of an AGN. Using our NIRSpec IFU data, we confirm that UNCOVER_20466 is an LRD (based on spectral slopes and compactness) that contains an overmassive black hole. However, our observed Balmer decrements do not suggest strong dust attenuation, resulting in a lower -based bolometric luminosity and () than previously found. This source lies on local relations between and , suggesting that this could be a progenitor of the core of a lower-redshift galaxy. We explore the possible evolution of this source, finding evidence for substantial black hole accretion in the past and a likely origin as a heavy seed at high redshift (). emission is strongly detected, implying . The extremely high / ratio is indicative of not only AGN photoionization and heating, but also extremely high densities (), suggesting that this black hole at such high redshift may be forming in an ultra-dense protogalaxy.