Imaging of four planetary nebulae in the Magellanic Clouds using the Hubble Space Telescope Faint Object Camera

Abstract

Using the Faint Object Camera on-board the Hubble Space Telescope, we have obtained images of four planetary nebulae (PNe) in the Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the LMC. Each nebula was imaged through two narrow-band filters isolating [O III] λ5007 and Hβ, for a nominal exposure time of 1000 s in each filter. Significant detail is evident on the raw images and, after deconvolution using the Richardson-Lucy algorithm, structures as small as 0″.06 are easily discernible. In [O III] , SMC N5 shows a circular ring structure, with a peak-to-peak diameter of 0″.26 and a FWHM of 0″.35, while SMC N2 shows an elliptical ring structure with a peak-to-peak diameter of 0″.26 × 0″.21 (FWHM 0″.40 × 0″.35). The expansion ages corresponding to the observed structures in SMC N2 and N5 are of the order of 3000 yr. Such low ages appear more easy to reconcile with helium-burning rather than hydrogen-burning central star evolutionary tracks. LMC N201 is very compact, with a FWHM of 0″.21 in Hβ. The Type I PN LMC N66 is a multipolar nebula, with the brightest part having an extent of about 2″ and with fainter structures extending over 4″. The [O III] image reveals structures unprecedented for a planetary nebula, w ith several bright knots and faint loops visible outside the two main bright lobes.