EXTINCTION IN NGC-628 AND NGC-2403 DERIVED FROM PASCHEN AND BALMER LINES

Long-slit spectrophotometry obtained simultaneously in the spectral ra nges lambda lambda 3950-4900 Angstrom and 8000-10500 Angstrom is prese nted for a number of giant extragalactic H II regions (GEHRs) in the s piral galaxies NGC 628 and NGC 2403. These ranges include lines from t he Balmer and Paschen series of hydrogen separated by a wide wavelengt h interval. The Paschen and Balmer lines with special emphasis on the corresponding multiplet lines P delta/H epsilon are used to examine th e dust extinction towards the GEHRs in these galaxies. We find good in ternal consistency for the observed/predicted line ratios used for der ivation of the visual extinction, A(V). Our results for A(V) are in ge neral larger than previously published values based on the H alpha/H b eta ratio with the GEHRs in NGC 628 exhibiting the largest extinction.