Diffuse Far-ultraviolet Observations of the Taurus Region

Abstract

Diffuse far-ultraviolet (FUV: 1370-1670 A) flux from the Taurus molecular cloud region has been observed with the SPEAR/FIMS imaging spectrograph. An FUV continuum map of the Taurus region, similar to the visual extinction maps, shows a distinct cloud core and halo region. The dense cloud core, where the visual extinction is A_v > 1.5, obscures the background diffuse FUV radiation, while a scattered FUV radiation is seen in and beyond the halo region where A_v < 1.5. The total intensity of H2 fluorescence in the cloud halo is I_{H2} = 6.5 x 10^4 photons cm^{-2} s^{-1} sr^{-1} in the 1370-1670 A wavelength band. A synthetic model of the H2 fluorescent emission fits the present observation best with a hydrogen density n_H = 50 cm^{-3}, H2 column density N(H2) = 0.8 x 10^{20} cm^{-2}, and an incident FUV intensity I_{UV} = 0.2. H2 fluorescence is not seen in the core presumably because the required radiation flux to induce fluorescence is unable to penetrate the core region.

Accepted for ApJL, 4 pages, 3 figures

References in corpus (5)

• The SPEAR Instrument and On-Orbit Performance
• The Spectroscopy of Plasma Evolution from Astrophysical Radiation Mission
• Structure Function Scaling of a 2MASS Extinction Map of Taurus
• Observations of the Diffuse FUV Background with FUSE
• Molecular Hydrogen Emission from the Inner 400 Parsecs of the Galaxy

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