The Ultraviolet Extinction in the $GALEX$ Bands

TL;DR

This study derives the ultraviolet extinction law in GALEX bands by analyzing intrinsic stellar colors and color excess ratios for a large sample of dwarf stars, confirming previous extinction curve results.

Contribution

It provides a new determination of the UV extinction law in GALEX bands using a large stellar sample and intrinsic color analysis, aligning well with established extinction models.

Findings

UV extinction ratios are quantified: $E_{NUV,B}/E_{B,V}=3.77$, $E_{FUV,B}/E_{B,V}=3.39$, $E_{FUV,NUV}/E_{B,V}=-0.38$

Results agree with previous NUV extinction studies and Fitzpatrick (1999) curve for $R_V=3.35$

Analysis of ~25,000 dwarf stars enhances understanding of interstellar dust extinction in UV bands.

Abstract

Interstellar extinction in ultraviolet is the most severe in comparison with optical and infrared wavebands and a precise determination plays an important role in correctly recovering the ultraviolet brightness and colors of objects. By finding the observed bluest colors at given effective temperature and metallicity range of dwarf stars, stellar intrinsic colors, $C^0_{\rm B,V}$, $C^0_{\rm NUV,B}$, $C^0_{\rm FUV,B}$ and $C^0_{\rm FUV,NUV}$, are derived according to the stellar parameters from the LAMOST spectroscopic survey and photometric results from the $GALEX$ and APASS surveys. With the derived intrinsic colors, the ultraviolet color excesses are calculated for about 25,000 A- and F-type dwarf stars. Analysis of the color excess ratios yields the extinction law related to the $GALEX$ UV bands: $E_{{\rm NUV,B}}$/$E_{{\rm B,V}} = 3.77$, $E_{{\rm FUV,B}}$/$E_{{\rm B,V}} = 3.39$, $E_{{\rm FUV,NUV}}$/$E_{{\rm B,V}} = -0.38$. The results agree very well with previous works in the $NUV$ band and in general with the extinction curve derived by Fitzpatrick (1999) for $R_{\rm V}=3.35$.