http://www.researchonline.mq.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:730 We demonstrate that artificial bipolar structure can be detected using spectro-astrometry when the point spread function (PSF) of a point source suffers distortion in a relatively wide slit. Spectro-astrometry is a technique which allows us to probe the spatial structure of astronomical sources on milliarcsec (mas) scales making it possible to detect close binaries and to study the geometry and kinematics of outflowing gas on scales much smaller than the seeing or the diffraction limit of the telescope. It is demonstrated that a distorted PSF, caused by tracking errors of the telescope or unstable active optics during an exposure, can induce artificial signals which may be misinterpreted as a real spectro-astrometric signal. Using simulations, we show that these may be minimized by using a narrow slit relative to the seeing. Spectra should be obtained at antiparallel slit position angles (e.g. 0° and 180°) for comparison in order to allow artificial signatures to be identified. 2010-01-27T23:24:48.969Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:995 We present infrared echelle spectroscopy of three Herbig-Haro (HH) driving sources (SVS 13, B5-IRS 1, and HH 34 IRS) using Subaru IRCS. The large diameter of the telescope and wide spectral coverage of the spectrograph allowed us to detect several H₂ and [Fe II] lines in the H and K bands. These include H₂ lines arising from v = 1-3 and J = 1-11 , and [Fe II] lines with upper level energies of E/k = (1.1-2.7) × 10⁴ K. For all objects the outflow is found to have two velocity components: (1) a high-velocity (−70 to −130 km s⁻¹) component (HVC), seen in [Fe II] or H₂ emission and associated with a collimated jet; and (2) a low-velocity (−10 to −30 km s⁻¹) component (LVC), which is seen in H₂ emission only and is spatially more compact. Such a kinematic structure resembles optical forbidden emission line outflows associated with classical T Tauri stars, whereas the presence of H₂ emission reflects the low-excitation nature of the outflowing gas close to these protostars. The observed H₂ flux ratios indicate a temperature of (2-3) × 10³ K and a gas density of 10⁵ cm⁻³ or more, supporting shocks as the heating mechanism. B5-IRS 1 exhibits faint extended emission associated with the H₂-LVC, in which the radial velocity slowly increases with distance from the protostar (by ~20 km s⁻¹ at ~500 AU). This is explained as warm molecular gas entrained by an unseen wide-angled wind. The [Fe II] flux ratios indicate electron densities to be ~10⁴ cm⁻³ or greater, similar to forbidden-line outflows associated with classical T Tauri stars. Finally, the kinematic structure of the [Fe II] emission associated with the base of the B5-IRS 1 and HH 34 IRS outflows is shown to support disk-wind models. 2010-01-27T23:21:37.674Z ]]>