The spectro-astrometry technique is a method for studying the spatial strucutre of astronomical sources on scales well below the normal limit on resolution set by the seeing disk size or the diffraction limit. It relies on the fact that the relative position of a source at two or more wavelengths can be measured to an accuracy limited only be photon statistics, if the measurements are simultaneous.
At the AAT we use the RGO spectrograph with its 82cm camera which gives very good spatial sampling of the seeing profile and take normal long slit spectra at four slit position angles (0, 90, 180, 270 degrees).
The technique is being used for the study of structure in pre-main-sequence stars, where it can be used to detect binary companions and to study the outflows from the stars.
It is also being used to study the
structure of the narrow line region
in active galactic nuclei.
Brannigan, E., Takami, M., Chrysostomou, A., Bailey, J., 2006, On the detection of artefacts in spectro-astrometry, Mon. Not. R. Astr. Soc., 367, 315-322 (ADS)
Takami, M. Bailey, J. Chrysostomou, A. Tamura, M. Terada, H., 2004, Probing AU-scale Structure using Spectro-astrometry, IAU Symp 221, 417 (ADS)
Takami, M., Bailey, J., Chrysostomou, A., 2003, A spectro-astrometric study of southern pre-main sequence stars. Binaries, outflows, and disc structure down to AU scales, Astron. Astrophys., 397, 675-691 (ADS)
Takami, M., Chrysostomou, A., Bailey, J., Gledhill, T. M., Tamura, M., Terada, H., 2003, Hα and HeI emission in the jets of pre-main sequence stars - implications for the heating mechanisms, Astrophys. Space Sci., 287, 143-146 (ADS)
Takami, M., Bailey, J., Gledhill, T. M., Chrysostomou, A., Hough, J. H., 2001, Circumstellar structure of RU Lupi down to au scales, Mon. Not. R. Astr. Soc., 323, 177-187 (ADS)
Bailey, J., 1998, Spectro-astrometry: a new approach to astronomy on small spatial scales, SPIE Proceedings, 3355, 932-939. (ADS)