On the calibration of the COBE/IRAS dust emission reddening maps

DUTRA, C. M.; AHUMADA, A. V.; CLARIÁ, J. J.; BICA, E.; BARBUY, B.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2003 vol. 408 p. 287 - 295

0004-6361

In this work we study the spectral properties (3600-6800 Å) of the nuclear region of early-type galaxies at low (|b|<25deg), intermediate (including surroundings of the Magellanic Clouds) and high (South Polar Cap) Galactic latitudes. We determine the E(B-V) reddening values of the galaxies by matching their continuum distribution with respect to those of reddening-free spectral galaxy templates with similar stellar populations. We also compare the spectroscopic reddening value of each galaxy with that derived from 100 mu m dust emission (E(B-V)FIR) in its line of sight, and we find that there is agreement up to E(B-V)=0.25. Beyond this limit E(B-V)FIR values are higher. Taking into account the data up to E(B-V) ~ 0.7, we derive a calibration factor of 0.016 between the spectroscopic E(B-V) values and Schlegel et al.´s (cite{Schlegel1998}) opacities. By combining this result with an AK extinction map built within ten degrees of the Galactic centre using Bulge giants as probes (Dutra et al. cite{Dutra2003}), we extended the calibration of dust emission reddening maps to low Galactic latitudes down to |b|=4deg and E(B-V)= 1.6 (AV ~ 5). According to this new calibration, a multiplicative factor of ~0.75 must be applied to the COBE/IRAS dust emission reddening maps.