Empirical extinction coefficients for the GALEX, SDSS, 2MASS and WISE passbands

Abstract

By using the 'standard pair' technique of pairing stars of almost nil and high extinction but otherwise with almost identical stellar parameters from the Sloan Digital Sky Survey (SDSS), and combining this information with photometry from the SDSS, Galaxy Evolution Explorer (GALEX), Two Micron All Sky Survey (2MASS) and Wide-field Infrared Survey Explorer (WISE) photometry ranging from the far ultraviolet (UV) to the mid-infrared (mid-IR), we measure dust reddening in the FUV - NUV, NUV - u, u - g, g - r, r - i, i - z, z - J, J - H, H - Ks, Ks - W1 and W1 - W2 colours for thousands of Galactic stars. The measurements, together with the E(B - V) values given by Schlegel et al., allow us to derive the observed, model-free reddening coefficients for these colours. The results are compared with previous measurements and with the predictions of various Galactic reddening laws. We find that (i) the dust reddening map of Schlegel et al. overestimates E(B - V) by about 14 per cent, consistent with the recent work of Schlafly et al. and Schlafly & Finkbeiner; (ii) after accounting for the d fferences in reddening normalization, the newly deduced reddening coefficients for colours FUV - NUV, NUV - u, u - g, g - r, r - i, i - z, z - J, J - H and H - Ks differ by respectively -1640, 15.5, 12.6, -0.8, 3.4, -0.7, 3.5, 2.5 and 1.4 per cent from the predictions of the Fitzpatrick reddening law for an assumed total-to-selective extinction ratio R(V) = 3.1, and by respectively -1730, 13.0, 8.1, 10.0, 8.0, -13.5, -1.7, -6.7 and -17.1 per cent from the predictions of the CCM reddening law; and (iii) all the new reddening coefficients, except those for NUV - u and u - g, favour the R(V) = 3.1 Fitzpatrick reddening law over the R(V) = 3.1 CCM and O'Donnell reddening laws. Using the Ks-band extinction coefficient predicted by the R(V)=3.1 Fitzpatrick lawand the observed reddening coefficients, we deduce new extinction coefficients for the FUV, NUV, u, g, r, i, z, J, H, W1 and W2 passbands. We recommend that the new reddening and extinction coefficients should be used in the future and that the Fitzpatrick reddening law in the UV should probably be updated. We stress, however, that the FUV- and NUV-band coefficients should be used with caution, given their relatively largemeasurement uncertainties. Finally, potential applications of the 'standard pair' technique with the upcoming LAMOST Galactic surveys are discussed. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.