Other
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992hst..prop.3507f&link_type=abstract
HST Proposal ID #3507
Other
Hst Proposal Id #3507
Scientific paper
We have discovered the least luminous known Seyfert 1 nucleus, in the very nearby (d = 2.6 Mpc), Sd III-IV galaxy NGC 4395. Seyfert 1 nuclei have never before been seen in galaxies of such late Hubble type, and so nearby. The luminosity of the broad H-alpha emission line is a factor of 10 lower than in M81, the previous champion. The blue continuum magnitude of the nucleus is -10, no brighter than a cluster of luminous stars; thus, it is remotely possible that the object itself can be explained by purely stellar phenomena, rather than by accretion onto a black hole. In order to test this hypothesis, and to further explore the unique properties of the active nucleus in NGC 4395, we propose to obtain UV spectra as part of an ongoing multi-wavelength study of this object. Detailed comparisons will be made with the spectra of typical luminous Seyfert 1 nuclei. A search will be made for absorption features produced by hot stars. We will determine whether the continuum has a "big blue bump" (like other type 1 Seyferts), and we will examine various emission-line intensity ratios to see whether a nonstellar photoionizing continuum is required. Since the active nucleus is in a spatially well-resolved galaxy, the spectra will not be contaminated by starlight from a galactic bulge. A direct image of NGC 4395, obtained with the PC, will show whether the active nucleus is a true point source less than 1 pc in size, rather than an extended source (such as a collection of very hot stars).
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