JWST/NIRCam Narrowband Survey of Pa${\hat{I}}^2$ Emitters in the Spiderweb Protocluster at z=2.16

Abstract

We report the initial result of our Pa${\hat{I}}^2$ narrowband imaging on a protocluster with the JWST Near Infrared Camera (NIRCam). As NIRCam enables deep narrowband imaging of rest-frame NIR lines at $z>1$, we target one of the most studied protoclusters, the Spiderweb protocluster at $z=2.16$, in which previous studies have confirmed more than a hundred member galaxies. The NIRCam F405N narrowband filter covers in Pa${\hat{I}}^2$ line the protocluster redshift given by known protocluster members, allowing the search for new member candidates. The weight-corrected color-magnitude diagram obtained 57 sources showing narrowband excesses, 41 of which satisfy further color selection criteria for limiting the sample to Pa${\hat{I}}^2$ emitter candidates at $z\sim 2.16$, and 24 of them do not have H$\hat{I}\pm$ emitter counterparts. The Pa${\hat{I}}^2$ emitter candidates appear to follow the spatial distribution of known protocluster members; however, follow-up spectroscopic confirmation is required. Only 17 out of 58 known H$\hat{I}\pm$-emitting cluster members are selected as Pa${\hat{I}}^2$ emitters in the current data, albeit the rest fall out of the narrowband selection owing to their small Pa${\hat{I}}^2$ equivalent widths. We derive Pa${\hat{I}}^2$ luminosity function in the Spiderweb protocluster, showing a normalization density of $\log \ddot{I}{•}^{\ast }=-2.53\pm 0.15$ at a characteristic Pa${\hat{I}}^2$ luminosity of $\log L^{\ast }=42.33\pm 0.17$. Furthermore, we examine the possibility of detecting faint line emitters visible only in the narrow-band image, but find no promising candidates.

19 pages, 12 figures, 2 tables; Accepted for publication in ApJ