MULTINARROWBAND IMAGING - A NEW TECHNIQUE FOR MULTIOBJECT SPECTROPHOTOMETRY

A technique is described which consists of repeated imaging of a field through a series of narrowband filters. Photometry of each image then provides low-resolution spectrophotometry of all detected objects. Fo r faint objects this method is comparable in efficiency to slitless sp ectroscopy, and can cover a larger wavelength range. The principal adv antages of the method are simplicity, accuracy in crowded fields, accu rate sky-subtraction, and the ability to measure many objects simultan eously. In order to investigate the potential of determining galaxy mo rphological type and redshift from multiband data, computer simulation s are performed for a system of 40 bands having central wavelengths eq ually spaced logarithmically from 400 to 1000 nm. Spectral energy dist ributions of various galaxy types are redshifted, multiplied by the fi lter transmission functions, and then degraded by random noise. These simulated data are then compared with model spectral energy distributi ons, sampled with the filters, for a range of Hubble type and redshift , by means of a two-parameter, least-squares analysis. For a signal-to -noise ratio of 10, the rms redshift error is less than 0.02 for all g alaxy types, and the rms error in the morphological type code is less than 0.14. The mean values of these errors are 0.009 and 0.11, respect ively. For a signal-to-noise ratio of 3, the corresponding mean errors are 0.06 and 0.6 for galaxies with redshift z < 0.5, and about half t hese values for galaxies with 0.5 < z < 1.0.