Oral Presentation

Inside-out growth of star formation within galaxies in the Spiderweb protocluster at z~2 revealed by JWST narrow-band imaging

Author(s): Michiru Maruyama(University of Tokyo), Tadayuki Kodama(Tohoku University), Yusei Koyama(NAOJ), Rhythm Shimakawa(Waseda University)

Presenter: Michiru Maruyama (the University of Tokyo)

We investigate the spatial extent of star-forming regions within galaxies in the Spiderweb protocluster at z = 2.16 using JWST/NIRCam narrowband (F405N) and medium-band (F410M) imaging with high spatial resolution to isolate Paβ emission line map. By combining stacking analyses and individual galaxy profile fitting, we explore whether galaxies form inside-out — with current star formation more extended than the stellar continuum. From a sample of 37 Paβ-emitting galaxies, we perform mass- and sSFR-binned stacking and find that more massive or moderately star-forming galaxies show Paβ emission more extended than continuum light, while low-mass or intensely star-forming galaxies display comparable extents. The Sérsic profile fitting of 27 individual galaxies further reveals that in 15 galaxies, Paβ emission is more spatially extended than the continuum, though with substantial scatter and uncertainties. These findings support the inside-out growth scenario at z ~ 2 and suggest that the spatial structure of star formation is influenced by both stellar mass and evolutionary stage. Our work highlights the power of JWST in resolving high-redshift galaxy internal structures and provides new insights into early cluster galaxy formation.