Reddening Behaviors of Galaxies in the SDSS Photometric System - AstrophysicsReport as inadecuate

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Abstract: We analyze the behaviors of reddening vectors in the SDSS photometric systemfor galaxies of different morphologies, ages, and redshifts. As seen in otherphotometric systems, the dependence of reddening on the spectral energydistribution SED and the nonlinearity of reddening are likewisenon-negligible for the SDSS system if extinction is significant ~> 1 mag.These behaviors are most significant for the g filter, which has the largestbandwidth-to-central wavelength ratio among SDSS filters. The SDSS colorsinvolving adjacent filters show greater SED-dependence and nonlinearity. Aprocedure for calculating the correct amount of extinction from an observedcolor excess is provided. The relative extinctions between i.e., theextinction law for SDSS filters given by Schlegel et al., which werecalculated with an older version of filter response functions, wouldunderestimate the amount of extinction in most cases by ~5 to 10 % maximum ~20%. We recommend A-A {5500} values of 1.574, 1.191, 0.876, 0.671 and 0.486 forthe u, g, r, i, and z filters, respectively, as a representative extinction lawfor the SDSS galaxies with a small extinction i.e., for cases where thenonlinearity and SED-dependence of the reddening is not important. Thedependence of reddening on redshift at low extinction is the largest for colorsinvolving the g filter as well, which is due to the Balmer break.

Author: Sungsoo S. Kim, Myung Gyoon Lee


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