Internal Dust in Gaseous Nebulae

Abstract

view Abstract Citations (101) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Internal Dust in Gaseous Nebulae Mathis, John S. Abstract The emergent flux from spherical nebulae is presented as a function of optical depth and albedo of internal isotropically scattering particles Several different structures of the emission and absorption, including emission-free shells, are considered. In color-color plots, the tracks of increasing optical depth are remarkably insensitive to the geometry of the nebula. For some proposed interstellar particles, such as graphite with and without coatings of ice and hydrogen, the paths in a color-color plot are about the same for both internal and external dust, although the optical depth associated with a given point is about twice as great for internal as for external extinction. The assumption that all dust is external when observed line ratios are corrected for extinction leads to the correct line ratios but may give serious underestimates of the total extinction. In the Orion Nebula, the intensity and color of the scattered light are consistent with about 1.8 mag of internal extinction and 0.35 mag of external extinction. Some planetary nebulae would require impossibly large amounts (several magnitudes) of extinction within the ionized region to explain the Balmer decrement. Nuclei of Seyfert galaxies must be surrounded by shells of dust outside the emission regions, since their colors are more reddened than even infinite optical depth in internal dust can provide. Publication: The Astrophysical Journal Pub Date: January 1970 DOI: 10.1086/150308 Bibcode: 1970ApJ...159..263M full text sources ADS | data products SIMBAD (6) NED (2)