Physical properties of the Sh2-104 HII region as seen by Herschel

Abstract

Context. Sh2-104 is a Galactic Hii region with a bubble morphology, detected at optical and radio wavelengths. It is considered the first observational confirmation of the collect-and-collapse model of triggered star-formation. Aims. We aim to analyze the dust and gas properties of the Sh2-104 region to better constrain its effect on local future generations of stars. In addition, we investigate the relationship between the dust emissivity index β and the dust temperature, T_(dust). Methods. Using Herschel PACS and SPIRE images at 100, 160, 250, 350 and 500 μm we determine T_(dust) and β throughout Sh2-104, fitting the spectral energy distributions (SEDs) obtained from aperture photometry. With the SPIRE Fourier-transform spectrometer (FTS) we obtained spectra at different positions in the Sh2-104 region. We detect J-ladders of ^(12)CO and ^(13)CO, with which we derive the gas temperature and column density. We also detect proxies of ionizing flux as the [N_(II)] ^3P_1−^3P_0 and [C_I] ^3P_2−^3P_1 transitions. Results. We find an average value of β ~ 1.5 throughout Sh2-104, as well as a T_(dust) difference between the photodissociation region (PDR, ~25K) and the interior (~40K) of the bubble. We recover the anti-correlation between β and dust temperature reported numerous times in the literature. The relative isotopologue abundances of CO appear to be enhanced above the standard ISM values, but the obtained value is very preliminary and is still affected by large uncertainties.

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