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http://inaoe.repositorioinstitucional.mx/jspui/handle/1009/1022| Comparison of ¹³CO line and far-infrared continuum emission as a diagnostic of dust and molecular gas physical conditions: III. systematic effects and scientific implications | |
| WILLIAM FRANK WALL | |
| Acceso Abierto | |
| Atribución-NoComercial-SinDerivadas | |
| Far-infrared continuum data from the COBE/DIRBE instrument were combined with Nagoya 4-m ¹³CO J = 1 → 0 spectral line data to infer the multiparsec-scale physical conditions in the OrionA and B molecular clouds, using 140 μm/240 μm dust color temperatures and the 240 μm/¹³CO J = 1 → 0 intensity ratios. In theory, the ratio of far-IR, submillimeter, or millimeter continuum to that of a ¹³CO (or C¹⁸O) rotational line can place reliable upper limits on the temperature of the dust and molecular gas on multi-parsec scales; on such scales, both the line and continuum emission are optically thin, resulting in a continuum-to-line ratio that suffers no loss of temperature sensitivity in the high-temperature limit as occurs for ratios of CO rotational lines or ratios of continuum emission in different wavelength bands. Two-component models fit the Orion data best, where one has a fixedtemperature and the other has a spatially varying temperature. The former represents gas and dust towards the surface of the clouds that are heated primarily by a very large-scale (i.e. ∼ 1 kpc) interstellar radiation field. The latter represents gas and dust at greater depths into the clouds and are shielded from this interstellar radiation field and heated by local stars. The inferred physical conditions are consistent with those determined from previously observed maps of ¹²CO J = 1 → 0 and J = 2 → 1 that cover the entire OrionA and B molecular clouds. The models require that the dust-gas temperature difference is 0±2K. If this surprising result applies to much of the Galactic ISM, except in unusual regions such as the Galactic Center, then there are a number implications. These include dust-gas thermal coupling that is commonly factors of 5 to 10 stronger than previously believed, Galactic-scale molecular gas temperaturas closer to 20K than to 10K, an improved explanation for the N(H₂)/I(CO) conversión factor (a full discussion of this is deferred to a later paper), and ruling out at least one dust grain alignment mechanism. The simplest interpretation of the models suggests that about 40–50% of the Orion clouds are in the form of cold (i.e. ∼ 3-10K) dust and gas, although alternative explanations are not ruled out. These alternatives include the contribution to the 240 μm continuum by dust associated with atomic hydrogen and reduced ¹³CO abundance towards the clouds’ edges. | |
| Monthly notices of the royal astronomical society | |
| 2007 | |
| Artículo | |
| Inglés | |
| Estudiantes Investigadores Público en general | |
| Wall, W. F., (2007). Comparison of ¹³CO line and far-infrared continuum emission as a diagnostic of dust and molecular gas physical conditions: III. systematic effects and scientific implications, Monthly notices of the royal astronomical society, Vol.377(2): 556-570 | |
| ASTRONOMÍA Y ASTROFÍSICA | |
| Versión aceptada | |
| acceptedVersion - Versión aceptada | |
| Aparece en las colecciones: | Artículos de Astrofísica |
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