Wei-Hsin Sun 2003/2/9
We are conducting a wide-field, narrow-band northern sky survey with a 3-tube observing system LELIS (Lu-lin Emission Line Imaging Survey), in the 3 most important emission lines in Interstellar Medium (ISM) studies: H£\¡B[OIII]¡Aand [SII]. This survey will provide detailed images and catalogues for the distribution of ISM ¡V including ¡§Supernova Remnants (SNRs)¡¨, ¡§Planetary Nebulae (PNe)¡¨, ¡§Star Formation Regions (SFRs)¡¨, and ¡§HII Regions¡¨. We will carry out flux calibration for all the point sources and extended sources in the target fields. We plan to complete the program in 3 years. By then, the catalogue will be the first CALIBRATED emission line survey of the northern sky in the field of stellar and ISM astrophysics, which will have substantial impact to the researchers in this field. Our research team will first focus on the optical search and multi-wavelength comparison of the optical counterparts of SNRs. This research using the survey data will lay the ground for the theoretical studies on how old, massive stars become supernovae, and how these supernovae interact with the surrounding ISM.
We combine 3 telephoto lens with 11cm diameter on the same equatorial mount for simultaneous observations in 3 emission lines. High QE CCD cameras are mounted at the focal planes of the lens. Same size narrow band interference filters are mounted in the front of the lens to minimize the wavelength shift in fast optical system using interference filters. This tri-color observing system obtains images in 3 lines simultaneously for a target field, removing the errors due to different air mass and transparency from non-simultaneity. This system has already been set up in the PD-10 dome on Lu-Lin mountain for a pilot study of nearly 1 year. There have been two master student theses on ¡§Supernova Remnants¡¨ and ¡§Galaxies in the Local Group¡¨ with the pilot observations. In the pilot study of SNRs, we have already discovered several optical counterparts of radio SNRs which were previously unknown optically. A number of new emission line sources have also been found. From the analysis of the pilot data, we find that this system has an astrometric accuracy at 1 pixel (within 24 arcsec) level on CCD, and a flux accuracy of 0.5%, both good enough to achieve the scientific goals of this sky survey program.