James Webb Space Telescope Feed Post
Harvard ADS: Anatomy of a z=6 Lyman-{\alpha} emitter down to parsec scales: extreme UV slopes, metal-poor regions and possibly leaking star clusters
Paper abstract: We present a detailed JWST/NIRSpec and NIRCam analysis of a gravitationally-lensed galaxy (\rm \mu=17-21) at redshift 6.14 magnified by the Hubble Frontier Field galaxy cluster MACS J0416. The target galaxy is overall a typical compact and UV-faint (\rm M_{UV}=-17.8) Lyman-\alpha emitter; yet, the large magnification allows the detailed characterisation of structures on sub-galactic (down to few parsec) scales. Prominent optical \rm H\alpha, \rm H\beta and [OIII]\lambda\lambda4959,5007 lines are spatially resolved with the high spectral resolution grating (G395H, R~2700), with large equivalent widths, EW(\rm H\beta+[OIII])\gtrsim1000 \AA, and elevated ionising photon production efficiencies \rm log(\xi_{ion}/erg^{-1}Hz)=25.2-25.7. NIRCam deep imaging reveals the presence of compact rest-UV bright regions along with individual star clusters of sizes \rm R_{eff}=3-8~pc and masses \rm M~2\cdot10^5-5\cdot10^{6}~M_\odot These clusters are characterised by steep UV slopes, \rm\beta_{UV}<~-2.5, in some cases associated with a dearth of line emission, indicating possible leaking of the ionising radiation, as also supported by a Lyman-\rm \alpha emission peaking at \rm ~100~km~s^{-1} from the systemic redshift. While the entire system is characterised by low-metallicity, ~0.1~Z_\odot, the NIRSpec-IFU map also reveals the presence of a low-luminosity, metal-poor region with \rm Z<~2\%~Z_\odot, barely detected in NIRCam imaging; this region is displaced by \rm >200~pc from one of the UV brightest structures of the system, and it would have been too faint to detect if not for the large magnification of the system.