JWST/NIRCam Coronagraphy: Commissioning and First On-Sky Results

TL;DR

This paper reports on the commissioning and initial on-sky performance of JWST's NIRCam coronagraphy mode, demonstrating its ability to detect faint objects near bright sources and comparing real data with simulations.

Contribution

It presents the first on-sky results of JWST's NIRCam coronagraphy, including performance verification and successful detection of a faint white dwarf companion.

Findings

Successful detection of HD 114174 B at 3.35μm with high contrast

Achievement of excellent coronagraphic suppression performance

Effective target acquisition with all five NIRCam masks

Abstract

In a cold and stable space environment, the James Webb Space Telescope (JWST or "Webb") reaches unprecedented sensitivities at wavelengths beyond 2 microns, serving most fields of astrophysics. It also extends the parameter space of high-contrast imaging in the near and mid-infrared. Launched in late 2021, JWST underwent a six month commissioning period. In this contribution we focus on the NIRCam Coronagraphy mode which was declared "science ready" on July 10 2022, the last of the 17 JWST observing modes. Essentially, this mode will allow to detect fainter/redder/colder (less massive for a given age) self-luminous exoplanets as well as other faint astrophysical signal in the vicinity of any bright object (stars or galaxies). Here we describe some of the steps and hurdles the commissioning team went through to achieve excellent performances. Specifically, we focus on the Coronagraphic Suppression Verification activity. We were able to produce firm detections at 3.35$\mu$m of the white dwarf companion HD 114174 B which is at a separation of $\simeq$ 0.5" and a contrast of $\simeq$ 10 magnitudes ($10^{4}$ fainter than the K$\sim$5.3 mag host star). We compare these first on-sky images with our latest, most informed and realistic end-to-end simulations through the same pipeline. Additionally we provide information on how we succeeded with the target acquisition with all five NIRCam focal plane masks and their four corresponding wedged Lyot stops.