Katedra Astronomii i Astrofizyki
Wydział Fizyki, Astronomii i Informatyki Stosowanej, Uniwersytet Mikołaja Kopernika

Shocks and UV radiation around low-mass protostars: the Herschel-PACS legacy

Karska Agata, Kaufman Michael J., Kristensen Lars E., van Dishoeck Ewine F.
2017

Far-infrared spectroscopy reveals gas cooling and its underlying heating due to physical processes taking place in the surroundings of protostars. These processes are reflected in both the chemistry and excitation of abundant molecular species. Here, we present the Herschel-PACS far-IR spectroscopy of 90 embedded low-mass protostars from the WISH (van Dishoeck et al. 2011), DIGIT (Green et al. 2013), and WILL surveys (Mottram et al. 2017). The $5\times5$ spectra covering the $\sim50''\times50''$ field-of-view include rotational transitions of CO, H$2$O, and OH lines, as well as fine-structure [O I] and [C II] in the $\sim$50-200 $\mu$m range. The CO rotational temperatures (for $J\mathrm{u}\geq14)$ are typically $\sim$300 K, with some sources showing additional components with temperatures as high as $\sim$1000 K. The H$_2$O / CO and H$_2$O / OH flux ratios are low compared to stationary shock models, suggesting that UV photons may dissociate some H$_2$O and decrease its abundance. Comparison to C shock models illuminated by UV photons shows good agreement between the line emission and the models for pre-shock densities of $10^5$ cm$^{-3}$ and UV fields 0.1-10 times the interstellar value. The far-infrared molecular and atomic lines are the unique diagnostic of shocks and UV fields in deeply-embedded sources.

Słowa kluczowe
Astrophysics - Solar And Stellar Astrophysics