Echelle Spectroscopy of Molecular Microjets

This "spectral image" shows the world-leading capabilities of the echelle grating on CGS4. In these data we exchange one spatial dimension for velocity information, by imaging the target through a narrow elongated slit. The slit is just one pixel wide, though over 100 pixels long. By projecting this long, thin image onto a dispersion grating (an echelle in this case) the emission is dispersed horizontally (perpendicular to the slit) to give velocity or "spectral" information at any given location along the slit. In these sample data, the slit has been aligned with a knotty, bipolar jet from a protostar (see for example the image of HH1 in the picture gallery).

The image shows how the velocities of knots of hot molecular gas change with distance from the source of this bipolar jet. The source itself, a newly-formed star, is evident as a horizontal strip in the middle of the image; here we see "continuous" emission - at all velocities - from the source. The knots, however, emit at discreet wavelengths. This emission is doppler shifted to different wavelengths, depending on the velocity of the emitting knot. The blobs in the image therefore represent the knots in the jet. The relative shift of any given blob to the left or right is then a measure of its velocity with respect to the source.

Data courtesy of Chris Davis and Tom Ray