Odin observations of water in molecular outflows and shocks

Abstract

Aims. We investigate the ortho-water abundance in outflows and shocks in order to improve our knowledge of shock chemistry and of the physics behind molecular outflows. Methods. We used the Odin space observatory to observe the H 2 O(1 10 −1 01 ) line. We obtain strip maps and single pointings of 13 outflows and two supernova remnants where we report detections for eight sources. We used RADEX to compute the beam averaged abundances of o-H 2 O relative to H 2 . In the case of non-detection, we derive upper limits on the abundance. Results. Observations of CO emission from the literature show that the volume density of H 2 can vary to a large extent, a parameter that puts severe uncertainties on the derived abundances. Our analysis shows a wide range of abundances reflecting the degree to which shock chemistry affects the formation and destruction of water. We also compare our results with recent results from the SWAS team. Conclusions. Elevated abundances of ortho-water are found in several sources. The abundance reaches values as high as what would be expected from a theoretical C-type shock where all oxygen, not in the form of CO, is converted to water. However, the high abundances we derive could also be due to the low densities (derived from CO observations) that we assume. The water emission may in reality stem from high density regions much smaller than the Odin beam. We do not find any relationship between the abundance and the mass loss rate. On the other hand, there is a relation between the derived water abundance and the observed maximum outflow velocity.

Heavy water around the L1448-mm protostar

“…As an example, H 2 O emission has been detected towards the low-mass protostar NGC 1333-IRAS 4B by different facilities, namely ISO, Odin, SWAS, Spitzer and, very recently, Herschel (Maret et al 2002;Bjerkeli et al 2009;Bergin et al 2003;Franklin et al 1989;Watson et al 2007;Kristensen et al 2010). These observations, with their relatively large apertures, revealed water from different components, namely the protostar, the outflow and the extended ambient medium.…”

Water cooling of shocks in protostellar outflows

“…Following ISO, the SWAS and Odin facilities made it possible to observe the ortho-H 2 Ofundamental line at 557 GHz, providing important constraints on the water abundance and kinematics in the cold outflow gas components (e.g., Franklin et al 2008;Bjerkeli et al 2009). All these facilities, however, had poor spatial resolution (i.e.…”

First spectrally-resolved H2observations towards HH 54

“…The positioning of the slits adopted for VLT/VISIR and CRIRES observations is shown in blue and red. The beam sizes of Herschel H 2 O (2 12 −1 01 ) (magenta circle), CO (15−14) (green, Bjerkeli et al 2014), and SEST CO (2−1) (black, Bjerkeli et al 2009Bjerkeli et al , 2011 are displayed. Offsets are relative to: α J2000 = 12 h 55 m 50. s 3, δ J2000 = −76 • 56 23 (Bjerkeli et al 2011).…”

“…The comparison between H 2 0−0 S(4) at HH 54C1/C2 and H 2 O (2 12 −1 01 ), CO (15−14) (Bjerkeli et al 2014), and CO (2−1) (Bjerkeli et al 2009(Bjerkeli et al , 2011 observations at HH 54B is presented in the lower panel of Fig. 2.…”

“…Caratti o Garatti et al 2006;Ybarra & Lada 2009;Bjerkeli et al 2011). Mid-IR cooling is dominated by pure rotational H 2 lines (Cabrit et al 1999;Giannini et al 2006;Neufeld et al 1998Neufeld et al , 2006 probing warm gas with a mixture of temperatures in the range 400−1200 K. HH 54 was also observed in several lines of CO and H 2 O from space and the ground (Liseau et al 1996;Nisini et al 1996;Bjerkeli et al 2009Bjerkeli et al , 2011.…”