000002255 001__ 2255
000002255 005__ 20160701171702.0
000002255 0247_ $$2DOI$$a10.1088/0004-637X/733/1/9
000002255 037__ $$aASTROimport-412
000002255 100__ $$aO'Dell, C. R.
000002255 245__ $$aPhysical Conditions in Barnard's Loop, Components of the Orion-eridanus Bubble, and Implications for the Warm Ionized Medium Component of the Interstellar Medium
000002255 260__ $$c2011
000002255 520__ $$aWe have supplemented existing spectra of Barnard's Loop with high accuracy spectrophotometry of one new position. Cloudy photoionization models were calculated for a variety of ionization parameters and stellar temperatures and compared with the observations. After testing the procedure with recent observations of M43, we establish that Barnard's Loop is photoionized by four candidate ionizing stars, but agreement between the models and observations is only possible if Barnard's Loop is enhanced in heavy elements by about a factor of 1.4. Barnard's Loop is very similar in properties to the brightest components of the Orion-Eridanus Bubble and the warm ionized medium (WIM). We are able to establish models that bound the range populated in low-ionization color-color diagrams (I([S II])/I(Ha) versus I([N II])/I(Ha)) using only a limited range of ionization parameters and stellar temperatures. Previously established variations in the relative abundance of heavy elements render uncertain the most common method of determining electron temperatures for components of the Orion-Eridanus Bubble and the WIM based only on the I([N II])/I(Ha) ratio, although we confirm that the lowest surface brightness components of the WIM are on average of higher electron temperature. The electron temperatures for a few high surface brightness WIM components determined by direct methods are comparable to those of classical bright H II regions. In contrast, the low surface brightness H II regions studied by the Wisconsin Ha Mapper are of lower temperatures than the classical bright H II regions. Based in part on observations obtained at the Cerro Tololo Inter-American Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a Cooperative Agreement with the National Science Foundation. 
000002255 700__ $$a Ferland, G. J.
000002255 700__ $$a Porter, R. L.
000002255 700__ $$a van Hoof, P. A. M.
000002255 773__ $$c9$$i1$$pThe Astrophysical Journal$$v733$$y2011
000002255 85642 $$ahttp://esoads.eso.org/abs/2011ApJ...733....9O
000002255 905__ $$apublished in
000002255 980__ $$aREFERD