Far infrared CO and H${}_2$O emission in intermediate-mass protostars

Abstract

Intermediate-mass young stellar objects (YSOs) provide a link to understand how feedback from shocks and UV radiation scales from low to high-mass star forming regions. Aims: Our aim is to analyze excitation of CO and H${}_2$O in deeply-embedded intermediate-mass YSOs and compare with low-mass and high-mass YSOs. Methods: Herschel/PACS spectral maps are analyzed for 6 YSOs with bolometric luminosities of $L_{\mathrm{bol}}\sim 10^2-10^3$ $L_{\odot }$. The maps cover spatial scales of $\sim 10^4$ AU in several CO and H${}_2$O lines located in the $\sim 55-210$ $\mu$m range. Results: Rotational diagrams of CO show two temperature components at $T_{\mathrm{rot}}\sim 320$ K and $T_{\mathrm{rot}}\sim 700-800$ K, comparable to low- and high-mass protostars probed at similar spatial scales. The diagrams for H${}_2$O show a single component at $T_{\mathrm{rot}}\sim 130$ K, as seen in low-mass protostars, and about $100$ K lower than in high-mass protostars. Since the uncertainties in $T_{\mathrm{rot}}$ are of the same order as the difference between the intermediate and high-mass protostars, we cannot conclude whether the change in rotational temperature occurs at a specific luminosity, or whether the change is more gradual from low- to high-mass YSOs. Conclusions: Molecular excitation in intermediate-mass protostars is comparable to the central $10^3$ AU of low-mass protostars and consistent within the uncertainties with the high-mass protostars probed at $3\cdot 10^3$ AU scales, suggesting similar shock conditions in all those sources.

Accepted to Astronomy & Astrophysics. 4 pages, 5 figures, 3 tables

References in corpus (3)

• The Effects of Radiative Transfer on Low-Mass Star Formation
• Herschel Far-Infrared Spectral-mapping of Orion BN/KL Outflows: Spatial distribution of excited CO, H2O, OH, O and C+ in shocked gas
• Shockingly low water abundances in Herschel / PACS observations of low-mass protostars in Perseus

Cited by in corpus (6)

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• The importance of radiative pumping on the emission of the H_2O submillimeter lines in galaxies
• Velocity-resolved high-J CO emission from massive star-forming clumps
• Far-infrared line emission from the outer Galaxy cluster Gy 3-7 with SOFIA/FIFI-LS: Physical conditions and UV fields