We report the discovery of eight optical counterparts of ALFALFAextragalactic objects from DECaLS, five of which are discovered for the firsttime. These objects were flagged as HI emission sources with no opticalcounterparts in SDSS before. Multi-band data reveal their unusual physicalproperties. They are faint and blue ($g-r=-0.35\sim0.55$), with quite lowsurface brightness ($\mu_{\rm g,peak}=24.88\sim26.41\,{\rm mag}/{\rmarcsec}^2$), irregular morphologies, low stellar masses($log_{10}(M_{*}/M_\odot)=5.27\sim7.15$), low star formation rates($SFR=0.21\sim9.24\times10^{-3}\,{M_\odot}\,{\rm yr}^{-1}$), and remarkablyhigh HI-to-stellar mass ratios ($log_{10}(M_{\rm HI}/M_{*}) = 1.72\sim3.22$,except AGC\,215415). They deviate from the scaling relations between HI andoptical properties defined by the ALFALFA sample and the baryonic Tully-Fisherrelation. They agree well with the main sequence of star-forming galaxies butexhibit low star-forming efficiency. Based on their physical properties andenvironments, we speculate that six of these objects may have originated fromtidal processes, while the remaining two appear to have isolated origins. Theymay have had a relatively calm evolutionary history and only begun to formstars recently.

The James Webb Space Telescope (JWST) has discovered a surprising populationof bright galaxies in the very early universe (< 500 Myrs after the Big Bang)that is hard to explain with conventional galaxy formation models and whosephysical properties remain to be fully understood. Insight into the internalphysics of galaxies is captured best via observations of excited-state atomictransitions of ionized gas, but beyond z~7-9, the brightest spectral signaturesare redshifted into the mid-infrared regime, where observations areincreasingly more difficult. Here, we present the first detection of a hydrogenrecombination line (H{\alpha}) and doubly-ionized oxygen ([OIII]4959,5007{\AA})at z>10 using the JWST Mid-Infrared Instrument, MIRI. These detections placethe bright galaxy GHZ2/GLASS-z12 at z=12.33+/-0.02, making it the most distantastronomical object with direct spectroscopic detection of these lines and thebrightest confirmed object at this epoch. These observations provide keyinsights into the conditions of this primeval galaxy, which shows hard ionizingconditions rarely seen in the local Universe and likely driven by compact,young (<30 Myr) star formation. Its oxygen-to-hydrogen abundance is close to atenth of the solar value, indicating a rapid metal enrichment during theearliest phases of galaxy formation. This study confirms the unique conditionsof the brightest and most distant galaxies recently discovered by JWST and thehuge potential of mid-IR observations to characterize these systems, opening arange of new possibilities in the study of the very early Universe.

We spectroscopically confirm the $M_{\rm UV} = -20.5$ mag galaxyGHZ2/GLASS-z12 to be at redshift $z=12.34$. The source was selected via NIRCamphotometry in GLASS-JWST Early Release Science data, providing the firstevidence of a surprising abundance of bright galaxies at $z \gtrsim 10$. TheNIRSpec PRISM spectrum is remarkable and unlike any local analog. It showssignificant detections of N IV, C IV, He II, O III, C III, O II, and Ne IIIlines, and the first detection in a high-redshift object of the O III Bowenfluorescence line at 3133 {\AA} rest-frame. The prominent C IV line withrest-frame equivalent width (EW) $\sim 46$ {\AA} puts GHZ2 in the category ofextreme C IV emitters characterised by hard radiation fields. GHZ2 displays UVlines with EWs that are only found in active galactic nuclei (AGNs) orcomposite objects at low/intermediate redshifts, and UV line-intensity ratiosthat are compatible both with AGNs and star formation in a low-metallicityenvironment. The nondetection of the very high-ionization lines [Ne IV] and [NeV], and the remarkable similarity between GHZ2 and other known C IV emitters,favors a scenario in which the high ionizing output is due to very lowmetallicity, massive stars forming in a dense environment. We estimate ametallicity $\lesssim 0.1 Z/{\rm Z}_{\odot}$, a high ionization parameter logU$>$ -2, a N/O abundance 4--5 times the solar value, and a subsolar C/O ratiosimilar to the recently discovered class of nitrogen-enhanced objects at highredshift. Considering its abundance patterns and the high stellar mass density($10^4$ M$_{\odot}$ pc$^{-2}$), GHZ2 is an ideal formation site for theprogenitors of today's globular clusters. The remarkable brightness of GHZ2makes it a "Rosetta stone" for understanding the physics of galaxy formationwithin just 360 Myr after the Big Bang.