|Shock treatment: breaking the degeneracy on the origin of water emission in protostars
|What is the origin of the high excitation, mid-IR water lines in protostars? Two separate shock mechanisms have been proposed: (i) an envelope-disk accretion shock at the protostellar disk surface and (ii) shocks in outflows. Past studies with Spitzer IRS data have been unable to conclusively rule out either scenario, despite extensive study in recent literature. Doing so for a sample of the earliest protostars would further our understanding of envelope-disk-protostar dynamics and perhaps inform us of the state of a protostellar disk just after formation. From our high resolution Spitzer IRS survey of 80 protostars in nearby star forming regions, we have assembled a sample of protostars in which strong, high excitation water lines are detected. To resolve the question of the origin of water emission, we propose full PACS spatial resolution mapping in the range spectroscopy mode of one of the most luminous water emitters in our sample. From the PACS maps we will be able to test each shock mechanism in two ways. First, we will investigate the spatial correlation between the peaks of the water emission, continuum emission, and outflow tracers such as the [OI], CO (J &amp;gt; 21), and OH lines. Significant spatial offset between the water emission and the continuum, and the spatial coincidence of water emission with outflow lines would rule out envelope-disk accretion shocks. Second, we will model the combined set of PACS and IRS water lines using a large grid of non-LTE models to derive the density and temperature of the water-emitting gas. High density (n&amp;gt;1.0E+10 cm^-3), low temperature (T virgul 200 K) solutions would favor envelope-disk accretion shocks, while low density (n&amp;lt; 1.0E+6 cm^-3), high temperature (T &amp;gt; 1000virgulK) solutions would favor the outflow shocks origin of water.
|Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
|Publisher And Registrant
|European Space Agency
|European Space Agency, 2013, OT2_mpuravan_2, SPG v14.2.0. https://doi.org/10.5270/esa-qgsn8tn