JADES: Resolving the Stellar Component and Filamentary Overdense Environment of HST-Dark Submillimeter Galaxy HDF850.1 at z=5.18

HDF850.1 is the brightest submillimeter galaxy (SMG) in the Hubble Deep Field. It is known as a heavily dust-obscured star-forming galaxy embedded in an overdense environment at z=5.18. With nine-band NIRCam images at 0.8-5.0 µm obtained through the JWST Advanced Deep Extragalactic Survey (JADES), we detect and resolve the rest-frame UV-optical counterpart of HDF850.1, which is split into two components because of heavy dust obscuration in the center. The southern component leaks UV and Hα photons, bringing the galaxy ~100 times above the empirical relation between infrared excess and UV continuum slope (IRX-β_UV). The northern component is higher in dust attenuation and thus fainter in UV and Hα surface brightness. We construct a spatially resolved dust attenuation map from the NIRCam images, which matches well with the dust continuum emission obtained through millimeter interferometry. The whole system hosts a stellar mass of 10^11.0±0.3 M_sun and SFR of 10^2.6±0.3 M_sun/yr, placing the galaxy at the massive end of the star-forming main sequence at this epoch. Moreover, combining with the public NIRCam slitless spectroscopic observations at 3.9-5 µm, we confirm 108 galaxies at z=5.17-5.30 in the GOODS-N field through Hα emission, of which only eight were known before the JWST observations. Four galaxy groups are identified within filamentary overdense structures over a comoving volume of 16×18×64 Mpc³, which hosts another luminous SMG at z=5.30 (GN10). Our results highlight the capability of JWST/NIRCam in resolving the dust-obscured stellar component and large-scale environment of high-redshift galaxies through imaging and spectroscopy.