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Determinations of Dust Scattering Properties

Interstellar Dust Scattering Properties

From K. D. Gordon 2004, in "Astrophysics of Dust", (ASP Conf. Proceed. 196), ed. A. N. Witt, G. C. Clayton, & B. T. Draine, (ASP: San Francisco), 77

Updated: 28 Nov 2006

This is a tabulation of interstellar dust scattering properties dertermined from observations of various astrophysical objects (eg., DGL, reflection nebulae, etc.). Almost all studies in this field aim to determine the single scattering albedo (a) and scattering phase function asymmetry (g = <cos(α)>) as different wavelengths. While each study is subject to various limitations related to the assumed distribution of dust and stars, the intersection of the studies of different objects should be robust. The tabulation of results is broken up by object type to allow for physical different dust in different regions. In addition, this allows for probes of uncertainies in the different models for different objects.

Object Type	Example Image	a	g
Reflection Nebulae Strengths: Bright Simple Geometries Weaknesses: Emissions (ERE, NIR dust) strong High density regions (R_V > 3.1) Plot Details	from K. Gordon & A. Urban (BVR)
Dark Clouds Strengths: Simple Geometries Emissions (ERE, NIR dust) surpressed Weaknesses: Faint High density regions (R_V > 3.1) Plot Details	from DSS B band
Diffuse Galactic Light Strengths: Diffuse interstellar dust (R_V = 3.1) Weaknesses: Faint Complicated Geometries Plot Details	from Schiminovich et al. 2001

Plot details links to a page describing the studies included in the plot, the radiative transfer model used in each study, and an ascii listing of data plotted.

Critera used for inclusion in plots:

Determine a & g: This requires that specific values be quoted for the two quantities. It is possible for some observations to determine either a or g with only a weak dependence on the other quantity. These studies were acceptable with appropriate uncertainties on the derived quantity. While this criteria means that the large number of early studies which only put limits on a and/or g are neglected, their limits are usually consistent with the values determined from later studies.
Determine uncertainties: The importance of this criteria cannot be understated. The uncertainties tabulated here reflect the range of a & g values allowed by models presented in each study. This sometimes means that multiple models (with different assumptions) have been combined into a single measurement with larger uncertainties than a single model.
Refereed Publication: This ensures that the full details of the work have be presented. In addition to the usual journals (eg., ApJ, AJ, A&A, PASP, MNRAS, etc.), theses are counted as refereed publications.
Not be superseded by other work: A number of studies are superceeded by newer work which usually used better radiative transfer models (especially the case for Diffuse Galactic Light studies). This usually results in significantly different determinations of a & g.