Performance of near-infrared high-contrast imaging methods with JWST from commissioning

Abstract

The James Webb Space Telescope (JWST ) will revolutionize the field of high-contrast imaging and enable both the direct detection of Saturn-mass planets and the characterization of substellar companions in the mid-infrared. While JWST will feature unprecedented sensitivity, angular resolution will be the key factor when competing with ground-based telescopes. Here, we aim to characterize the performance of several extreme angular resolution imaging techniques available with JWST in the 3-5 µm regime based on data taken during the instrument commissioning. Firstly, we introduce custom tools to simulate, reduce, and analyze JWST NIRCam and MIRI coronagraphy data and use these tools to extract companion detection limits from on-sky NIRCam round and bar mask coronagraphy observations. Secondly, we present on-sky JWST NIRISS aperture masking interferometry (AMI) and kernel phase imaging (KPI) observations from which we extract companion detection limits using the publicly available fouriever tool. Scaled to a total integration time of one hour and a target of the brightness of AB Dor (W1 ≈ 4.4 mag, W2 ≈ 3.9 mag), we find that NIRISS AMI and KPI reach contrasts of ∼ 7-8 mag at ∼ 70 mas and ∼ 9 mag at ∼ 200 mas. Beyond ∼ 250 mas, NIRCam coronagraphy reaches deeper contrasts of ∼ 13 mag at ∼ 500 mas and ∼ 15 mag at ∼ 2 arcsec. While the bar mask performs ∼ 1 mag better than the round mask at small angular separations 0.75 arcsec, it is the other way around at large angular separations 1.5 arcsec. Moreover, the round mask gives access to the full 360 deg field-of-view which is beneficial for the search of new companions. We conclude that already during the instrument commissioning, JWST high-contrast imaging in the L-and M-bands performs close to its predicted limits and is a factor of ∼ 10 times better at large separations than the best ground-based instruments operating at similar wavelengths despite its > 2 times smaller collecting area.

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

“…The way PID 1441 was carried out is explained in greater details in Kammerer et al 2022 (this conference): 16 HD 114174 (with its WD companion, observable in June/July 2022) was set to be our "science scene"/star (Obs 1 & 2 for MASK335R, Obs 5 & 6 for MASKLWB with 2 rolls). 3 reference stars were carefully chosen (all main sequence G stars in the long baseline interferometry calibrator catalog to avoid multiplicity, all within K∼5.0 and 5.2): HD 111733, HD 115640, HD 116249 (all observed with a 9-point small grid dither "SGD" 21 pattern) respectively at an angular distance of 5.3 • , 4.6 • and 11.9 • from HD 114174 which would allow to explore difference time and pitch angle (solar elongation) baselines.…”

“…Performance of the LW bar mask MASKLWB are good as well and reported in Kammerer et al 2022 (this conference). 16…”

“…spaceKLIP is an agile community version of coron3 based on the very successful and popular pyKLIP. It is in active development 16 and has many functionalities that we are not describing in this work: forward modeling of point sources and disks, simultaneous astrometry and photometry using a Monte-Carlo approach, etc.…”

The Near Infrared Imager and Slitless Spectrograph for the James Webb Space Telescope -- IV. Aperture Masking Interferometry

“…This overlaps with NIR-Cam's coronagraphic IWA, so could help tie in NIRISS AMI mode observations with NIR-Cam's coronagraphic ones. First results from commissioning are reported in Kammerer et al (2022) and a detailed description and performance analysis of the NIRISS KPI observing mode can be found in the NIRISS V paper (Kammerer et al 2022, accepted). The fainter NIRISS KPI targets do not overlap with ground-based ExAO targets, but are, for example, uniquely suited to an as-yet unexplored search space of binary and multiple ultra-cool dwarf stars.…”

The Near Infrared Imager and Slitless Spectrograph for JWST -- V. Kernel Phase Imaging and Data Analysis

“…At these separations, classical highcontrast imaging techniques such as coronagraphy are typically superior to KPI. The NIRISS full pupil images considered for the KPI analysis here do only have a native size of 80 by 80 pixels and we are using a constant window radius of r = 15 pixels for them resulting in a field-of-view of ∼ 2 arcsec, which is more than sufficient for the region where NIRISS KPI is superior to NIRCam coronagraphy (Kammerer et al 2022). The diagnostic plot of the windowing step is shown in Figure 4.…”