A Quantitative Comparison of the Small Magellanic Cloud, Large Magellanic Cloud, and Milky Way Ultraviolet to Near‐Infrared Extinction Curves

We present an exhaustive, quantitative comparison of all of the knownextinction curves in the Small and Large Magellanic Clouds (SMC and LMC) withour understanding of the general behavior of Milky Way extinction curves. TheR_V dependent CCM relationship and the sample of extinction curves used toderive this relationship is used to describe the general behavior of Milky Wayextinction curves. The ultraviolet portion of the SMC and LMC extinction curvesare derived from archival IUE data, except for one new SMC extinction curvewhich was measured using HST/STIS observations. The optical extinction curvesare derived from new (for the SMC) and literature UBVRI photometry (for theLMC). The near-infrared extinction curves are calculated mainly from 2MASSphotometry supplemented with DENIS and new JHK photometry. For each extinctioncurve, we give R_V = A(V)/E(B-V) and N(HI) values which probe the same dustcolumn as the extinction curve. We compare the properties of the SMC and LMCextinction curves with the CCM relationship three different ways: each curve byitself, the behavior of extinction at different wavelengths with R_V, andbehavior of the extinction curve FM fit parameters with R_V. As has been foundpreviously, we find that a small number of LMC extinction curves are consistentwith the CCM relationship, but majority of the LMC and all of the SMC curves donot follow the CCM relationship. For the first time, we find that the CCMrelationship seems to form a bound on the properties of all of the LMC and SMCextinction curves. This result strengthens the picture of dust extinctioncurves exhibit a continuum of properties between those found in the Milky Wayand the SMC Bar. (abridged)Comment: 18 pages, 10 figures, ApJ in pres