JWST/NIRCam Narrowband Survey of Pa$\beta$ Emitters in the Spiderweb Protocluster at z=2.16

TL;DR

This study uses JWST/NIRCam narrowband imaging to identify and analyze Paβ emitters in the Spiderweb protocluster at z=2.16, revealing candidate members and deriving the luminosity function, advancing understanding of galaxy formation in dense environments.

Contribution

First application of JWST/NIRCam narrowband imaging to detect Paβ emitters in a high-redshift protocluster, providing new insights into galaxy populations and their distribution.

Findings

Identified 24 new Paβ emitter candidates without Hα counterparts.

Derived the Paβ luminosity function with specific normalization and characteristic luminosity.

Found Paβ emitters follow the spatial distribution of known protocluster members.

Abstract

We report the initial result of our Pa$\beta$ 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$\beta$ 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$\beta$ emitter candidates at $z\sim2.16$, and 24 of them do not have H$\alpha$ emitter counterparts. The Pa$\beta$ 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$\alpha$-emitting cluster members are selected as Pa$\beta$ emitters in the current data, albeit the rest fall out of the narrowband selection owing to their small Pa$\beta$ equivalent widths. We derive Pa$\beta$ luminosity function in the Spiderweb protocluster, showing a normalization density of $\log{\phi^\ast}=-2.53\pm0.15$ at a characteristic Pa$\beta$ luminosity of $\log{L^\ast}=42.33\pm0.17$. Furthermore, we examine the possibility of detecting faint line emitters visible only in the narrow-band image, but find no promising candidates.