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Observations of planetary nebulae with multi-element image sensors

University of British Columbia

Two silicon diode arrays have been used to obtain spectra of the planetary nebula NGC 7027. Relative line intensities (I(H)=100) are determined in the spectral region 5000-9900A. The resolution, good quantum efficiency, and the wide dynamic range available with these detectors permit: i) the resolution of close pairs for which only the blend intensity is presently available, e,.g. Paschen P8 9546 from the [SIII] 9532, and HeII 6683 from HeI 6678. ii) A much closer value of the theoretical ratio for the [SIII] 9069, 9532 lines to be obtained. iii) A better agreement with model predictions for the intensities of the [NII] doublet at 6548, 6584. This planetary was also observed with a 50x50 array through interference filters centered at [OIII] 5007, H 6563, and [SII] 6731. Regions of low and high excitation are determined by inspection of the ratios [SII]/H and [SII]/[OIII]. Variable extinction across the face of the nebula is shown to exist by constructing a two-dimensional map of the color excess E (H – [OIII]). A JPL CCD camera was used to obtain monocromatic images of the planetary nebulae NGC 2440, NGC 3132, and NGC 3242 through interference filters centered at Hβ 4861, H 6563, [NII] 6584, and [SIII] 9532. Two-dimensional data is presented in the form of false-color photographs obtained with a Comtal Imaging System. , This system has the capability of producing images with a brightness resolution of 8 bits per pixel in shades of gray, false or full color. Computer programmes have been written to handle the transfer of data frames from the main computer at UBC to the Comtal Imaging System. A two envelope structure, stratification of the radiation and local density fluctuations are obvious features of the images of NGC 2440, NGC 3132, and NGC 3242. All of them are consistent with an ejection of matter from a central star with non-zero angular momentum. Regions of low and high excitation are determined from the ratios [NII]/H, [SIII]/H, and [SIII]/[NII]. Color excess maps show that variable extinction is also present in these objects. Since the color excess increases outward for all of these objects, the indication is that the dust responsible for this extinction is concentrated more in the outer envelope than in the inner envelope.

Text

2010-03-15

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http://hdl.handle.net/2429/21884

Astronomy

University of British Columbia

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