The dwarf irregular galaxy HIPASS J1131-31 was discovered as a source of HIemission at low redshift in such close proximity of a bright star that we callit Peekaboo. The galaxy resolves into stars in images with Hubble SpaceTelescope, leading to a distance estimate of 6.8+-0.7 Mpc. Spectral opticalobservations with the Southern African Large Telescope reveal HIPASS J1131-31to be one of the most extremely metal-poor galaxies known with the gas-phaseoxygen abundance 12+log(O/H) = 6.99+-0.16 dex via the direct [OIII] 4363 linemethod and 6.87+-0.07 dex from the two strong line empirical methods. The redgiant branch of the system is tenuous compared with the prominence of thefeatures of young populations in the color-magnitude diagram, invitingspeculation that star formation in the galaxy only began in the last few Gyr.

We utilize $\sim17000$ bright Luminous Red Galaxies (LRGs) from the novelDark Energy Spectroscopic Instrument Survey Validation spectroscopic sample,leveraging its deep ($\sim2.5$ hour/galaxy exposure time) spectra tocharacterize the contribution of recently quenched galaxies to the massivegalaxy population at $0.4<z<1.3$. We use Prospector to infer non-parametricstar formation histories and identify a significant population ofpost-starburst galaxies that have joined the quiescent population within thepast $\sim1$ Gyr. The highest redshift subset (277 at $z>1$) of our sample ofrecently quenched galaxies represents the largest spectroscopic sample ofpost-starburst galaxies at that epoch. At $0.4<z<0.8$, we measure the numberdensity of quiescent LRGs, finding that recently quenched galaxies constitute agrowing fraction of the massive galaxy population with increasing lookbacktime. Finally, we quantify the importance of this population amongst massive($\mathrm{log}(M_\star/M_\odot)>11.2$) LRGs by measuring the fraction ofstellar mass each galaxy formed in the Gyr before observation, $f_{\mathrm{1Gyr}}$. Although galaxies with $f_{\mathrm{1 Gyr}}>0.1$ are rare at $z\sim0.4$($\lesssim 0.5\%$ of the population), by $z\sim0.8$ they constitute $\sim3\%$of massive galaxies. Relaxing this threshold, we find that galaxies with$f_\mathrm{1 Gyr}>5\%$ constitute $\sim10\%$ of the massive galaxy populationat $z\sim0.8$. We also identify a small but significant sample of galaxies at$z=1.1-1.3$ that formed with $f_{\mathrm{1 Gyr}}>50\%$, implying that they maybe analogues to high-redshift quiescent galaxies that formed on similartimescales. Future analysis of this unprecedented sample promises to illuminatethe physical mechanisms that drive the quenching of massive galaxies aftercosmic noon.

Surveys with James Webb Space Telescope (JWST) have discovered candidategalaxies in the first 400 Myr of cosmic time. The properties of these distantgalaxies provide initial conditions for understanding early galaxy formationand cosmic reionisation. Preliminary indications have suggested these candidategalaxies may be more massive and abundant than previously thought. However,without spectroscopic confirmation of their distances to constrain theirintrinsic brightnesses, their inferred properties remain uncertain. Here wereport on four galaxies located in the JWST Advanced Deep Extragalactic Survey(JADES) Near-Infrared Camera (NIRCam) imaging with photometric redshifts$z\sim10-13$ subsequently confirmed by JADES JWST Near- Infrared Spectrograph(NIRSpec) observations. These galaxies include the first redshift $z>12$systems both discovered and spectroscopically confirmed by JWST. Using stellarpopulation modelling, we find the galaxies typically contain a hundred millionsolar masses in stars, in stellar populations that are less than one hundredmillion years old. The moderate star formation rates and compact sizes suggestelevated star formation rate surface densities, a key indicator of theirformation pathways. Taken together, these measurements show that the firstgalaxies contributing to cosmic reionisation formed rapidly and with intenseinternal radiation fields.

Finding and characterising the first galaxies that illuminated the earlyUniverse at cosmic dawn is pivotal to understand the physical conditions andthe processes that led to the formation of the first stars. In the first fewmonths of operations, imaging from the James Webb Space Telescope (JWST) havebeen used to identify tens of candidates of galaxies at redshift (z) greaterthan 10, less than 450 million years after the Big Bang. However, none of thesecandidates has yet been confirmed spectroscopically, leaving open thepossibility that they are actually low-redshift interlopers. Here we presentspectroscopic confirmation and analysis of four galaxies unambiguously detectedat redshift 10.3<z<13.2, previously selected from NIRCam imaging. The spectrareveal that these primeval galaxies are extremely metal poor, have massesbetween 10^7 and a few times 10^8 solar masses, and young ages. The dampingwings that shape the continuum close to the Lyman edge are consistent with afully neutral intergalactic medium at this epoch. These findings demonstratethe rapid emergence of the first generations of galaxies at cosmic dawn.