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Session 4 - Low Luminosity AGN and Starburst Galaxies.
Display session, Monday, June 10
Low luminosity, late-type (Scd-Sm) spiral galaxies sometimes contain compact nuclei which appear semi-stellar at ground-based resolutions. Studies of the nature of these nuclei and their relationship to the active nuclei in more luminous galaxies can be undertaken through the use of high-resolution imaging capabilities of the Planetary Camera 2 (PC 2) on the Hubble Space Telescope. Here we present a comparative study of the nuclei of the low-luminosity, late-type spirals NGC 4395 (SAdm) and NGC 4242 (SABdm) using new HST PC 2 images in the F450W and F814W filters in combination with existing multiwavelength data from the literature. The nucleus of NGC 4395 was discovered by Filippenko amp; Sargent (1989; ApJL 342, L11) to be the lowest luminosity Seyfert 1 known. Our new data confirm the existence of slightly extended emission (probably [O \sc iii]) first noted by Filippenko et al. (1993; ApJL, 410, L75) as well as a large filament associated with a possible bi-polar structure. The nucleus of the non-active galaxy NGC 4242 remains a near-stellar object in our PC 2 data. We discuss these results in terms of the starburst and AGN models for the activity in NGC 4395.
Program listing for Monday