James Webb Space Telescope Feed Post
AGNs and Host Galaxies in COSMOS-Web. I. NIRCam Images, PSF Models and Initial Results on X-ray-selected Broad-line AGNs at 0.35 <= z <= 3.5
Comparison of an F150W mosaic at Observation 047 between the public data release 0.2 by the COSMOS-Web team (top row) and our reduction (bottom row). Mosaics have been smoothed using a Gaussian kernel with a FWHM of 3 pixels. The left column highlights differences in background subtraction and the right column illustrates the removal of artifact features, i.e., wisps (near the bright star at the top of the image) and claws (near the right edge of the image).
Abstract: We present detailed and comprehensive data reduction and point-spread-function (PSF) model construction for all public JWST NIRCam imaging data from the COSMOS-Web treasury program (up to June 2023, totaling 0.28 deg2). We show that the NIRCam PSF has significant short-timescale temporal variations and random spatial variations in all four filters (F115W, F150W, F277W, and F444W). Combining NIRCam with archival HST imaging, we perform multiwavelength AGN+host image decomposition to study the properties of 143 X-ray-selected (Lbol=1043.6-47.2 erg s-1) broad-line AGNs at 0.35?z?3.5. Leveraging the superb resolution, wavelength coverage, and sensitivity of NIRCam, we successfully detect host stellar emission after decomposing the central AGN point source in 142 objects. ~2/3 AGNs are in star-forming galaxies based on the UVJ diagram, suggesting no instantaneous negative AGN feedback. X-ray-selected broad-line AGN hosts follow a similar stellar mass-size relation as inactive galaxies, albeit with slightly smaller galaxy sizes. We find that although major mergers are rare (~7-22%) among the sample, more subtle non-axisymmetric features from stellar bars, spiral arms, and minor mergers are ubiquitous, highlighting the importance of secular processes and minor mergers in triggering AGN activity. For a subsample of 30 AGNs at 1
