James Webb Space Telescope Feed Post

Date: 5/15/2024

Arxiv: The PSF Smoothing Effect on Concentration-Related Parameters of High Redshift Galaxies in HST and JWST Published: 3/4/2024 4:54:13 PM Updated: 5/14/2024 12:40:19 PM

Paper abstract: We perform a comprehensive investigation of the PSF smoothing effect on themeasurement of concentration-related parameters (C, Gini, M_{20}) of highredshift galaxies in the HST and JWST surveys. Our sample contains massivegalaxies from the CANDELS/EGS survey (0 < z < 2), and the CEERS survey (1 < z <3). The non-parametric concentration-related parameters (C, Gini, M_{20})and the model-dependent parameters (n, Re) of these galaxies are derived fromStatmorph and GALFIT, respectively. We try to evaluate the PSF smoothing effectby comparing the concentration-related parameters to the S\'{e}rsic index inboth observations and mock images. We find that the concentration index isgenerally underestimated, especially for smaller galaxies with higherS\'{e}rsic index (eventually converging to the concentration index of the PSF).However, galaxies with lower S\'{e}rsic index (n <= 1) or larger relativesize are less affected by the PSF smoothing effect. The Gini coefficient andthe absolute M_{20} statistic also show similar behaviour as theconcentration index. Caution should be taken for the possible correction of theconcentration-related parameters, where both the relative size and theS\'{e}rsic index of the galaxy are important. Compared to the HST images, thePSF smoothing is much less severe for images in the CEERS survey due to themuch higher spatial resolution. In fact, it is better to use the S\'{e}rsicindex rather than the non-parametric morphology indicators to trace the lightconcentration for galaxies at high redshifts. From the single S\'{e}rsicmodelling of the HST and JWST images, we also confirm that galaxies at higherredshift are more compact with smaller R_e. The lower mass galaxies are moredisc-like (n~1) compared to the higher mass galaxies that are morespheroid dominated (n~3).