James Webb Space Telescope Feed Post

JWST/NIRCam Detection of the Fomalhaut C Debris Disk in Scattered Light

Left: NIRCam F356W detection of the Fomalhaut C debris disk in scattered light resulting from the MCRDI procedure (Section 4). The image has been smoothed by a gaussian kernel with FWHM of 6.7 pixels (3× the PSF FWHM). The inner software mask has a radius of 1.''5 and covers the region of significant residual speckle noise. Logarithmically-spaced black contours are drawn above the maximum for the color stretch to show the peak location of the bright south-western background source. Right: As the image on the left, but with silver contours showing the 1–5s levels for the ALMA detection of the disk reported in Cronin-Coltsmann et al. (2021). The gold arrows extend from the locations of the two assumed background sources modeled in Cronin-Coltsmann et al. (2021), showing their expected displacement due to the proper motion of Fomalhaut C (Gaia Collaboration et al., 2022). Both predicted positions are consistent with sources detected in the 2022 NIRCam data, supporting their identity as unassociated background objects. Abstract: Observations of debris disks offer important insights into the formation and evolution of planetary systems. Though M dwarfs make up approximately 80% of nearby stars, very few M-dwarf debris disks have been studied in detail -- making it unclear how or if the information gleaned from studying debris disks around more massive stars extends to the more abundant M dwarf systems. We report the first scattered-light detection of the debris disk around the M4 star Fomalhaut C using JWST's Near Infrared Camera (NIRCam; 3.6 µm and 4.4 µm). This result adds to the prior sample of only four M-dwarf debris disks with detections in scattered light, and marks the latest spectral type and oldest star among them. The size and orientation of the disk in these data are generally consistent with the prior ALMA sub-mm detection. Though no companions are identified, these data provide strong constraints on their presence - with sensitivity sufficient to recover sub-Saturn mass objects in the vicinity of the disk. This result illustrates the unique capability of JWST for uncovering elusive M-dwarf debris disks in scattered light, and lays the groundwork for deeper studies of such objects in the 2--5 µm regime.