This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.

Finding and characterising the first galaxies that illuminated the early Universe at cosmic dawn is pivotal to understand the physical conditions and the processes that led to the formation of the first stars. In the first few months of operations, imaging from the James Webb Space Telescope (JWST) has been used to identify tens of candidates of galaxies at redshift (z) greater than 10 less than 450 million years after the Big Bang. However, none of such candidates has yet been confirmed spectroscopically, leaving open the possibility that they are actually low-redshift interlopers. Here we present spectroscopic confirmation and analysis of four galaxies unambiguously detected at redshift 10.3≤z≤13.2, previously selected from NIRCam imaging. The spectra reveal that these primeval galaxies are metal poor, have masses between of order ~10 7 -10 8 solar masses, and young ages. The damping wings that shape the continuum close to the Lyman edge provide the first constraints on neutral Hydrogen fraction of the intergalactic medium to be obtained from normal star-forming galaxies. These findings demonstrate the rapid emergence of the first generations of galaxies at cosmic dawn.The opening act of galaxy formation in the first billion years after the Big Bang sets in motion the physics of galaxy formation and evolution that shapes galaxy properties across cosmic time. Galaxies forming at these times may be the seeds of the much more massive and mature galaxies in the local Universe. Theoretical models and cosmological simulations differ greatly in their predictions of the physical properties and abundance of the first galaxies. The theoretical pictures depend strongly on assumptions about the physical processes at play in

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We present JADES JWST/NIRSpec spectroscopy of GN-z11, the most luminous candidate z > 10 Lyman break galaxy in the GOODS-North field with M UV = −21.5. We derive a redshift of z = 10.603 (lower than previous determinations) based on multiple emission lines in our low and medium resolution spectra over 0.8 − 5.3 µm. We significantly detect the continuum and measure a blue rest-UV spectral slope of β = −2.4. Remarkably, we see spatially-extended Lyman-α in emission (despite the highly-neutral IGM expected at this early epoch), offset 555 km s −1 redward of the systemic redshift. From our measurements of collisionally-excited lines of both low-and high-ionization (including [O ii] λ3727, [Ne iii] λ3869 and C iii] λ1909) we infer a high ionization parameter (log U ∼ −2). We detect the rarely-seen N iv] λ1486 and N iii] λ1748 lines in both our low and medium resolution spectra, with other high ionization lines seen in low resolution spectrum such as He ii (blended with O iii]) and C iv (with a possible P-Cygni profile). Based on the observed rest-UV line ratios, we cannot conclusively rule out photoionization from AGN. The high C iii]/He ii ratios, however, suggest a likely star-formation explanation. If the observed emission lines are powered by star formation, then the strong N iii] λ1748 observed may imply an unusually high N/O abundance. Balmer emission lines (Hγ, Hδ) are also detected, and if powered by star formation rather than an AGN we infer a star formation rate of ∼ 20 − 30 M yr −1 (depending on the IMF) and low dust attenuation. Our NIRSpec spectroscopy confirms that GN-z11 is a remarkable galaxy with extreme properties seen 430 Myr after the Big Bang.

Context. Arp220 is the nearest and prototypical ultra-luminous infrared galaxy; it shows evidence of pc-scale molecular outflows in its nuclear regions and strongly perturbed ionised gas kinematics on kpc scales. It is therefore an ideal system for investigating outflow mechanisms and feedback phenomena in detail. Aims. We investigate the feedback effects on the Arp220 interstellar medium (ISM), deriving a detailed picture of the atomic gas in terms of physical and kinematic properties, with a spatial resolution that had never before been obtained (0.56″, i.e. ∼210 pc). Methods. We use optical integral-field spectroscopic observations from VLT/MUSE-AO to obtain spatially resolved stellar and gas kinematics, for both ionised ([N II]λ6583) and neutral (Na IDλλ5891, 96) components; we also derive dust attenuation, electron density, ionisation conditions, and hydrogen column density maps to characterise the ISM properties. Results. Arp220 kinematics reveal the presence of a disturbed kpc-scale disc in the innermost nuclear regions as well as highly perturbed multi-phase (neutral and ionised) gas along the minor axis of the disc, which we interpret as a galactic-scale outflow emerging from the Arp220 eastern nucleus. This outflow involves velocities up to ∼1000 km s−1 at galactocentric distances of ≈5 kpc; it has a mass rate of ∼50 M⊙ yr−1 and kinetic and momentum power of ∼1043 erg s−1 and ∼1035 dyne, respectively. The inferred energetics do not allow us to distinguish the origin of the outflows, namely whether they are active galactic nucleus- or starburst-driven. We also present evidence for enhanced star formation at the edges of – and within – the outflow, with a star-formation rate SFR ∼ 5 M⊙ yr−1 (i.e. ∼2% of the total SFR). Conclusions. Our findings suggest the presence of powerful winds in Arp220: They might be capable of heating or removing large amounts of gas from the host (“negative feedback”) but could also be responsible for triggering star formation (“positive feedback”).