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Here we present a sample of 12 massive quiescent galaxy candidates at z ∼ 3 - 4 observed with the James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec). These galaxies were pre-selected from the Hubble Space Telescope imaging and 10 of our sources were unable to be spectroscopically confirmed by ground based spectroscopy. By combining spectroscopic data from NIRSpec with multi-wavelength imaging data from the JWST Near Infrared Camera (NIRCam), we analyse their stellar populations and their formation histories. We find that all of our galaxies classify as quiescent based on the reconstruction of their star formation histories but show a variety of quenching timescales and ages. All our galaxies are massive ( ∼ 0.1 - 1.2 × 10 11 M ⊙ ), with masses comparable to massive galaxies in the local Universe. We find that the oldest galaxy in our sample formed ∼ 1.0 × 10 11 M ⊙ of mass within the first few hundred million years of the Universe and has been quenched for more than a billion years by the time of observation at z ∼ 3.2 ( ∼ 2 billion years after the Big Bang). Our results point to very early formation of massive galaxies requiring a high conversion rate of baryons to stars in the early Universe.

The formation of galaxies by gradual hierarchical co-assembly of baryons and cold dark matter halos is a fundamental paradigm underpinning modern astrophysics 1 , 2 and predicts a strong decline in the number of massive galaxies at early cosmic times 3 – 5 . Extremely massive quiescent galaxies (stellar masses of more than 10 11   M ⊙ ) have now been observed as early as 1–2 billion years after the Big Bang 6 – 13 . These galaxies are extremely constraining on theoretical models, as they had formed 300–500 Myr earlier, and only some models can form massive galaxies this early 12 , 14 . Here we report on the spectroscopic observations with the JWST of a massive quiescent galaxy ZF-UDS-7329 at redshift 3.205 ± 0.005. It has eluded deep ground-based spectroscopy 8 , it is significantly redder than is typical and its spectrum reveals features typical of much older stellar populations. Detailed modelling shows that its stellar population formed around 1.5 billion years earlier in time ( z ≈ 11) at an epoch when dark matter halos of sufficient hosting mass had not yet assembled in the standard scenario 4 , 5 . This observation may indicate the presence of undetected populations of early galaxies and the possibility of significant gaps in our understanding of early stellar populations, galaxy formation and the nature of dark matter. A massive galaxy observed with the JWST indicates that the bulk of its stars formed within the first 500 million years of the Universe.

A massive ancient galaxy with minimal star formation is observed spectroscopically at an epoch when the Universe is less than 2 billion years old, posing a challenge to theories. Galaxies prematurely aged Deep astronomical surveys have provided evidence for groups of massive, quiescent galaxies at high redshifts, but this poses a problem: theoretical models do not account for galaxies that stopped forming stars so early in the history of the Universe. Detecting such galaxies is an observational challenge owing to their negligible rest-frame ultraviolet emission and the need for extremely deep near-infrared surveys—the evidence has so far consisted entirely of coarsely sampled photometry. Karl Glazebrook et al . report spectroscopic confirmation of one of these galaxies at a redshift of 3.717, with a stellar mass of 1.7 × 10 11 solar masses. The absorption line spectrum shows no current star-formation, and the age of the galaxy is derived to be nearly half that of the Universe. The authors suggest that the galaxy formed its stars in an extreme and short starburst within the first billion years of cosmic history, implying that our picture of galaxy formation may need an update. Finding massive galaxies that stopped forming stars in the early Universe presents an observational challenge because their rest-frame ultraviolet emission is negligible and they can only be reliably identified by extremely deep near-infrared surveys. These surveys have revealed the presence of massive, quiescent early-type galaxies 1 , 2 , 3 , 4 , 5 , 6 appearing as early as redshift z  ≈ 2, an epoch three billion years after the Big Bang. Their age and formation processes have now been explained by an improved generation of galaxy-formation models 7 , 8 , 9 , in which they form rapidly at z  ≈ 3–4, consistent with the typical masses and ages derived from their observations. Deeper surveys have reported evidence for populations of massive, quiescent galaxies at even higher redshifts and earlier times, using coarsely sampled photometry. However, these early, massive, quiescent galaxies are not predicted by the latest generation of theoretical models 7 , 8 , 9 , 10 . Here we report the spectroscopic confirmation of one such galaxy at redshift z  = 3.717, with a stellar mass of 1.7 × 10 11 solar masses. We derive its age to be nearly half the age of the Universe at this redshift and the absorption line spectrum shows no current star formation. These observations demonstrate that the galaxy must have formed the majority of its stars quickly, within the first billion years of cosmic history in a short, extreme starburst. This ancestral starburst appears similar to those being found by submillimetre-wavelength surveys 11 , 12 , 13 , 14 . The early formation of such massive systems implies that our picture of early galaxy assembly requires substantial revision.

While quiescent galaxies have comparable amounts of cool gas in their outer circumgalactic medium (CGM) compared to star-forming galaxies, they have significantly less interstellar gas. However, open questions remain on the processes causing galaxies to stop forming stars and stay quiescent. Theories suggest dynamical interactions with the hot corona prevent cool gas from reaching the galaxy, therefore predicting the inner regions of quiescent galaxy CGMs are devoid of cool gas. However, there is a lack of understanding of the inner regions of CGMs due to the lack of spatial information in quasar-sightline methods. We present integral-field spectroscopy probing 10–20 kpc (2.4–4.8 R e ) around a massive quiescent galaxy using a gravitationally lensed star-forming galaxy. We detect absorption from Magnesium (MgII) implying large amounts of cool atomic gas (10 8.4 –10 9.3 M ⊙ with T~10 4 Kelvin), in comparable amounts to star-forming galaxies. Lens modeling of Hubble imaging also reveals a diffuse asymmetric component of significant mass consistent with the spatial extent of the MgII absorption, and offset from the galaxy light profile. This study demonstrates the power of galaxy-scale gravitational lenses to not only probe the gas around galaxies, but to also independently probe the mass of the CGM due to it’s gravitational effect. Quiescent galaxies have similar amount of cool gas to star forming galaxies, yet why galaxies stop forming stars remains an open question. The authors investigate why passive galaxies remain quiescent using a gravitationally lensed background galaxy to probe the faint, diffuse cool gas around a massive quiescent galaxy, and use lensing configuration to constrain the total mass and geometry of this gas reservoir.

Lyα emission, Lyα absorption, and Mg ii absorption are powerful tracers of neutral hydrogen. Hydrogen is the most abundant element in the universe and plays a central role in galaxy formation via gas accretion and outflows, as well as being the precursor to molecular clouds, the sites of star formation. Since 21 cm emission from neutral hydrogen can only be directly observed in the local universe, we rely on Lyα emission, and Lyα and Mg ii absorption to probe the physics that drive galaxy evolution at higher redshifts. Furthermore, these tracers are sensitive to a range of hydrogen densities that cover the interstellar medium, the circumgalactic medium, and the intergalactic medium, providing an invaluable means of studying gas physics in regimes where it is poorly understood. At high-redshift, Lyα emission line searches have discovered thousands of star-forming galaxies out to z = 7. The large Lyα scattering cross-section makes observations of this line sensitive to even very diffuse gas outside of galaxies. Several thousand more high-redshift galaxies are known from damped Lyα absorption lines and absorption by the Mg ii doublet in quasar and GRB spectra. Mg ii, in particular, probes metal-enriched neutral gas inside galaxy haloes in a wide range of environments and redshifts (0.1 < z < 6.3), including the so-called redshift desert. Here, we review what observations and theoretical models of Lyα emission and Lyα and Mg ii absorption have told us about the interstellar, circumgalactic, and intergalactic medium in the context of galaxy formation and evolution.

Observations reveal two gaseous regions with a composition close to that of the universe before the first stars were formed. The existence of everything around us today sometimes seems far removed from the thermonuclear reactions occurring in the interiors of stars and stellar supernovae. These processes are responsible for producing almost all elements heavier than helium and for dispersing these elements throughout the universe. On page 1245 of this issue, Fumagalli et al. ( 1 ) report two gaseous regions that consist of virtually pristine gas (no detected elements heavier than helium) at an epoch where none are expected to exist. These findings demonstrate the nonuniform dispersion of elements throughout the universe, with direct consequences on the formation epoch of first-generation stars.

Here we present a sample of 12 massive quiescent galaxy candidates at $$z\\sim 3-4$$ z∼3-4 observed with the James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec). These galaxies were pre-selected from the Hubble Space Telescope imaging and 10 of our sources were unable to be spectroscopically confirmed by ground based spectroscopy. By combining spectroscopic data from NIRSpec with multi-wavelength imaging data from the JWST Near Infrared Camera (NIRCam), we analyse their stellar populations and their formation histories. We find that all of our galaxies classify as quiescent based on the reconstruction of their star formation histories but show a variety of quenching timescales and ages. All our galaxies are massive ( $$\\sim 0.1-1.2\\times 10^{11}$$ ∼0.1-1.2×1011 M⊙), with masses comparable to massive galaxies in the local Universe. We find that the oldest galaxy in our sample formed $$\\sim 1.0\\times 10^{11}$$ ∼1.0×1011 M⊙ of mass within the first few hundred million years of the Universe and has been quenched for more than a billion years by the time of observation at $$z\\sim 3.2$$ z∼3.2 ( $$\\sim 2$$ ∼2 billion years after the Big Bang). Our results point to very early formation of massive galaxies requiring a high conversion rate of baryons to stars in the early Universe.

In the local (redshift z  ≈ 0) Universe, collisional ring galaxies make up only ~0.01% of galaxies 1 and are formed by head-on galactic collisions that trigger radially propagating density waves 2 – 4 . These striking systems provide key snapshots for dissecting galactic disks and are studied extensively in the local Universe 5 – 9 . However, not much is known about distant ( z  > 0.1) collisional rings 10 – 14 . Here we present a detailed study of a ring galaxy at a look-back time of 10.8 Gyr ( z  = 2.19). Compared with our Milky Way, this galaxy has a similar stellar mass, but has a stellar half-light radius that is 1.5–2.2 times larger and is forming stars 50 times faster. The extended, diffuse stellar light outside the star-forming ring, combined with a radial velocity on the ring and an intruder galaxy nearby, provides evidence for this galaxy hosting a collisional ring. If the ring is secularly evolved 15 , 16 , the implied large bar in a giant disk would be inconsistent with the current understanding of the earliest formation of barred spirals 17 – 21 . Contrary to previous predictions 10 – 12 , this work suggests that massive collisional rings were as rare 11 Gyr ago as they are today. Our discovery offers a unique pathway for studying density waves in young galaxies, as well as constraining the cosmic evolution of spiral disks and galaxy groups. A ring galaxy is found at a look-back time of 10.8 Gyr. The diffuse stellar light outside the star-forming ring, the ring’s radial velocity and a nearby intruder galaxy indicate that this is a collisional ring galaxy.

We have discovered that warm gas flows along galaxy major and minor axes detected out to 200 kpc. Our results are derived from a sample of HST-imaged isolated galaxies with nearby background quasars used to probe their 105K CGM detected in HST/COS UV spectra (traced by Ovi absorption). We constrain the geometry of the gas to reside between 20-40 degrees of the projected major axis and within 60 degrees of the projected minor axis, with little-to-no gas found in between. Furthermore, strong absorption systems tend to be found along the minor axes of star-forming galaxies. All of our results are consistent with the current view of the CGM originating from major axis-fed inflows/recycled gas and from minor axis-driven outflows.

We use high-resolution Keck, VLT, or Hubble Space Telescope spectra of background quasars to examine the kinematic properties of the multiphase, metal-enriched circumgalactic medium in the outskirts of galaxies at 0.08 < z gal < 1.0, focusing on the low-ionization Mgii and high-ionization Ovi doublets. The absorption kinematics of low-ionization gas in the circumgalactic medium depend strongly on the star formation activity and the location about the host galaxy, where the largest velocity dispersions are associated with blue, face-on galaxies probed along the minor axis. Conversely, high-ionization gas kinematics are independent of galaxy star formation activity and orientation.