TY - JOUR

T1 - Shocks and UV radiation around low-mass protostars

T2 - The Herschel-PACS legacy

AU - Karska, Agata

AU - Kaufman, Michael J.

AU - Kristensen, Lars E.

AU - Van Dishoeck, Ewine F.

PY - 2017/1/1

Y1 - 2017/1/1

N2 - 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 × 5 spectra covering the ∼50″ × 50″ field-of-view include rotational transitions of CO, H2O, and OH lines, as well as fine-structure [O I] and [C II] in the ∼50-200 μm range. The CO rotational temperatures are typically ∼300 K, with some sources showing additional components with temperatures as high as ∼1000 K. The H2O / CO and H2O / OH flux ratios are low compared to stationary shock models, suggesting that UV photons may dissociate some H2O and decrease its abundance. Comparison to C shock models illuminated by UV photons show a good agreement between the line emission and the models for pre-shock densities of 105 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.

AB - 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 × 5 spectra covering the ∼50″ × 50″ field-of-view include rotational transitions of CO, H2O, and OH lines, as well as fine-structure [O I] and [C II] in the ∼50-200 μm range. The CO rotational temperatures are typically ∼300 K, with some sources showing additional components with temperatures as high as ∼1000 K. The H2O / CO and H2O / OH flux ratios are low compared to stationary shock models, suggesting that UV photons may dissociate some H2O and decrease its abundance. Comparison to C shock models illuminated by UV photons show a good agreement between the line emission and the models for pre-shock densities of 105 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.

KW - jets

KW - outflows

KW - shocks

KW - Young stellar objects

UR - http://www.scopus.com/inward/record.url?scp=85052727399&partnerID=8YFLogxK

U2 - 10.1017/S1743921317007608

DO - 10.1017/S1743921317007608

M3 - Journal article

AN - SCOPUS:85052727399

VL - 13

SP - 225

EP - 227

JO - Proceedings of the International Astronomical Union

JF - Proceedings of the International Astronomical Union

SN - 1743-9213

IS - S332

ER -