Riviere Marichalar, P., Merin, B., Kamp, I., Eiroa, C., Montesinos, B. 2016. Herschel-PACS observations of far-IR lines in young stellar objects I. [OI] and H2O at 63 mu m. Astronomy and Astrophysics 594, DOI: 10.1051/0004-6361/201527829
Gas plays a major role in the dynamical evolution of young stellar objects (YSOs). Its interaction with the dust is the key to our understanding planet formation later on in the protoplanetary disc stage. Studying the gas content is therefore a crucial step towards understanding YSO and planet formation. Such a study can be made through spectroscopic observations of emission lines in the far-infrared, where some of the most important gas coolants emit, such as the [OI] P-3(1) -> P-3(2) transition at 63.18 mu m.
Aims. We provide a compilation of observations of far-IR lines in 362 YSOs covering all evolutionary stages, from Class 0 to Class III with debris discs. In the present paper we focus on [OI] and o-H2O emission at 63 mu m.
Methods. We retrieved all the available Herschel-PACS spectroscopic observations at 63 mu m that used the dominant observing mode, the chop-nod technique. We provide measurements of line fluxes for the [OI] P-3(1) -> P-3(2) and o-H2O 8(08) -> 7(17) transitions at 63 mu m computed using different methods. Taking advantage of the PACS IFU, we checked for spatially extended emission and also studied multiple dynamical components in line emission.
Results. The final compilation consists of line and continuum fluxes at 63 mu m for a total of 362 young stellar objects (YSOs). We detect [OI] line emission at 63 mu m in 194 sources out of 362, and line absorption in another five sources. o-H2O was detected in 42 sources. We find evidence of extended [OI] emission in 77 sources, and detect 3 sigma residual emission in 71 of them. The number of sources showing extended emission decays from Class 0 to Class II. We also searched for different components contributing to the line emission, and found evidence for multiple components in 30 sources. We explored correlations between line emission and continuum emission and found a clear correlation between WISE fluxes from 4.6 to 22 mu m and [OI] line emission. We conclude that the observed emission is typically a combination of disc, envelope and jet emission.