Anatomy of a z = 6 Lyman-α emitter down to parsec scales

Authors:
Open Access
Publisher website
Google Scholar
Abstract
We present a detailed JWST/NIRSpec and NIRCam analysis of a gravitationally lensed galaxy (μ = 17 − 21) at a redshift of 6.14 magnified by the Hubble Frontier Field galaxy cluster MACS J0416. The target galaxy is a typical compact and UV-faint (MUV = −17.8) Lyman-α emitter, yet the large magnification allows the detailed characterization of structures on sub-galactic scales (down to a few parsecs). Prominent optical Hα, Hβ, and [OIII]λλ4959, 5007 lines are spatially resolved with the high-spectral-resolution grating (G395H, R 2700), with large equivalent widths, EW(Hβ+O III) ≳ 1000 Å, and elevated ionizing photon production efficiencies, log(ξion/erg−1Hz) = 25.2–25.7. NIRCam deep imaging reveals the presence of compact rest-UV-bright regions along with individual star clusters of Reff = 3 − 8 pc in size and M ∼ 2 ⋅ 105 − 5 ⋅ 106 M⊙ in mass. These clusters are characterized by steep UV slopes, βUV ≲ −2.5, which in some cases are associated with a dearth of line emission, indicating possible leaking of the ionizing radiation, as also supported by a Lyman-α emission peaking at ∼100 km s−1 from the systemic redshift. While the entire system is characterized by low metallicity, ∼0.1 Z⊙, the NIRSpec-IFU map also reveals the presence of a low-luminosity, metal-poor region with Z ≲ 2% Z⊙, which is barely detected in NIRCam imaging; this region is displaced by > 200 pc from one of the brightest structures of the system in UV, and would have been too faint to detect if not for the large magnification of the system.

This publication has 153 references indexed in Scilit: