Blue Jay Photometric catalog ---------------------------- Version: 1.4.0 Last update: Aug 6, 2024 Authors: Amir H. Khoram and the Blue Jay team Contact: amirhossein.khoram@unibo.it This catalog contains photometry for the Blue Jay sample of galaxies in the COSMOS field, measured from observations by the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST). Catalog Description ---------------------------- DATA: This catalog is based on HST mosaics (with a pixel scale of 0.060 arcsec) produced by the 3DHST team, and JWST/NIRCam imaging (with a pixel scale of 0.030 arcsec) obtained by the PRIMER survey. For each target, a cutout of 167x167 pixels was produced in each band. The images in each band are smoothed with a Gaussian kernel to match the spatial resolution in the reddest band of the same telescope: F160W for HST and F444W for JWST (which have very similar spatial resolution). APERTURES: For each galaxy, an elliptical aperture is defined based on the F444W cutout. The aperture is defined using the photutils segmentation map, and adjusting the parameters according to the conditions of each object. Typically, a value of 3 sigma over the background is used to identify the pixels belonging to a source; however for systems with close companions a higher threshold and a smaller number of minimum pixles have been adopted. This aperture is then used for all the other bands. BACKGROUND: In each band, a local background region is defined by taking all the pixels in the cutout, excluding pixels belonging to sources that are detected using a threshold of 2 sigma over the background. The median bkg_m and standard deviation bkg_s are calculated for this sample of pixels. The background flux in the aperture is then calculated as Npix * bkg_m * apcorr, and the error on the background is calculated as bkg_s * sqrt(Npix) * apcorr, where Npix is the number of pixels in the aperture. Note that the local background is reported in the catalog but has NOT been subtracted from the photometry measurements. PHOTOMETRY: Aperture photometry is obtained by summing the flux of all pixels within the aperture. Two types of uncertainty are provided: the nominal error on the aperture flux "apflux_errnominal" is derived from the weight maps and does not account for correlation between pixels; while the error on the aperture flux "apflux_err" is based on the uncertainties in the 3DHST catalog, which were measured using empty apertures, but then rescaled to the aperture size used in this catalog as opposed to the aperture size used by the 3DHST team (see Skelton et al. 2014 for details). For JWST imaging this method is not available, and so the error on the aperture flux is simply equal to the nominal error. APERTURE CORRECTION: To obtain the total photometry we then apply an aperture correction assuming point-like sources. The aperture correction is derived using WebbPSF for the JWST data, and from tables in the official documentation for the ACS and WFC3 instruments onboard HST. Finally, the total error is given by the sum in quadrature of the aperture flux error and the background, followed by the application of the aperture correction. This means that the total uncertainty on the flux reflects any potential systematics due to the presence of local background. MISSING DATA: In a few cases, the JWST/NIRCam imaging is compromised due to detector artifacts, and no measurements are available. Additionally, there are two cases in HST imaging affected by similar issues. Please find the list of these instances below, along with the specific bands in which the artifacts are observed. JWST/NIRCam =========== 11481 —> [ F115W , F150W , F200W] 18769 —> [ F090W , F115W , F150W , F200W] 19945 —> [ F090W , F115W , F150W , F200W] HST ========== 8002 —> [ F140W ] 19342 —> [ F140W ] Catalog Columns ---------------------------- ID galaxy ID from the 3DHST catalog FXXXX_flux total flux in Jy in the FXXXX band FXXXX_flux_err total flux error in Jy in the FXXXX band FXXXX_abmag AB magnitude in the FXXXX band FXXXX_apflux aperture flux in Jy in the FXXXX band FXXXX_apflux_err aperture flux error in Jy in the FXXXX band FXXXX_apflux_errnominal aperture nominal flux error in Jy in the FXXXX band FXXXX_apcorr aperture correction for the FXXXX band FXXXX_bkg local background estimate in Jy in the FXXXX band FXXXX_bkg_err local background error estimate in Jy in the FXXXX band HST_npix number of pixels in the aperture for the HST data HST_ap_a semimajor axis in pixels for the aperture in the HST data HST_ap_b semiminor axis in pixels for the aperture in the HST data HST_ap_theta position angle in degrees for the aperture in the HST data NIRCAM_npix number of pixels in the aperture for the JWST/NIRCam data NIRCAM_ap_a semimajor axis in pixels for the aperture in the NIRCam data NIRCAM_ap_b semiminor axis in pixels for the aperture in the NIRCam data NIRCAM_ap_theta position angle in degree for the aperture in the NIRCam data