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We describe an on-going HST program aimed at determining the relationship between the nuclear black hole mass and bulge mass in spiral galaxies. We have selected a volume limited sample of 54 nearby spiral galaxies for which we already have ground based emission line rotation curves, CCD surface photometry and radio maps. We are now obtaining HST/STIS longslit observations of each of the galaxies in the sample in order to determine the nuclear Hα rotation curve at high (∼ 0.1) spatial resolution. We will use these data to measure the unresolved dark mass concentration at the nucleus of each object. Here we show the first results from observations of objects in the sample.
Photoionization and shock models of the extended emissionline regions (EELRs) in active galaxies demonstrate that the optical emission lines alone are a poor discriminant of the excitation mechanism. Combining optical and UV data provides a discriminant between nuclear photoionization and autoionizing shock models. Hubble Space Telescope UV spectrophotometry of two Seyferts suggests that the EELRs in these objects are probably photoionized by the nucleus.
Since 2010, a program to explore new eclipsing binary systems identified from STEREO photometry has been in progress. Our first results are presented here: light curves and high resolution spectra taken with Coudé spectrograph (National Astronomical Observatory Rozhen) and ARC Échelle spectrometer (ARCES, Apache Point Observatory).
J. Patrick Harrington, Department of Astronomy, University of Maryland, College Park, MD 20742, U.S.A.,
Kazimierz J. Borkowski, Department of Astronomy, University of Maryland, College Park, MD 20742, U.S.A.,
Zlatan Tsvetanov, Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, U.S.A.,
Robin E.S. Clegg, Royal Greenwich Observatory, Madingley Road, Cambridge CB3 OEZ, U.K.
Abell 30 and Abell 78 are the best-known members of a small but important class of planetary nebulae (PNe) which are characterized by H-poor, dusty ejecta. Other members of this group include Abell 58 (V605 Aql), IRAS 18333-2357 (in the globular cluster M22) and IRAS 15154-5258. In these objects the H-poor material is surrounded by an outer envelope of normal composition (except for IRAS 18333-2357, where the ram pressure of the ISM would have stripped off the outer envelope: Borkowski et al. 1993a). Clearly, a secondary ejection of highly processed material has occurred after the loss of the hydrogen envelope of the AGB progenitor. A detailed interpretation was put forward by Iben et al. (1983), who proposed a final helium shell flash after nearly all of the H-rich envelope had been expelled.
The H-poor PNe are important because the composition of the ejecta opens a window upon the final phase of AGB nucleosynthesis and dredge-up, and also because the high dust to gas ratio lets us study the physics of dusty plasmas (e.g., gas heating by photoelectrons from grains: Borkowski & Harrington 1991). Here, however, we wish to point out that at least two of these objects also provide an exceptional opportunity to study mass-loaded flows. Mass-loading occurs when a tenuous, fast wind, as it streams around dense, slow-moving knots, entrains and mixes with bits of the dense material.
Evidence and Implications of Anisotropy in AGN
Ismael Pérez-Fournon, Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain,
Baltasar Vila-Vilaó, Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain,
José A. Acosta-Pulido, Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain,
J. Ignacio González-Serrano, Departamento de Física Teórica, Universidad de Cantabria, Santander, Spain,
Marc Balcells, Observatorio del Roque de los Muchachos, La Palma, Tenerife, Spain,
Andrew S. Wilson, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, U.S.A.,
Zlatan Tsvetanov, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, U.S.A.
We present and discuss the results of long-slit spectroscopic observations of the extended emission line regions (EELR) in NGC4388, a Seyfert 2 galaxy in which extended, off-nuclear broad Hα emission (FWZI ≈ 4000 km s−1) has been reported (Shields & Filippenko 1988). These features have been interpreted as scattered radiation from a Seyfert 1 nucleus that is obscured along our line of sight. Our spectroscopic observations cover a large fraction of the inner part of the EELR, including some of the positions where the presence of broad lines has been claimed. Broad wings in the Hα + [NII] λλ6548, 6583 complex are also present in our data but they can be explained by the superposition of several narrow components. However, we cannot, at present, exclude the possibility that an intrinsically broad component to Hα exists at some locations. The implications of our results for unified models of Seyfert galaxies are briefly discussed.
NGC4388 is a high-inclination Seyfert 2 galaxy with bright EELR (Colina et al. 1987, Pogge 1988, Corbin et al. 1988). Radio observations reveal a double-peaked source close to the apparent optical nucleus and more extended emission aligned roughly perpendicular to the galaxy disk (Stone et al. 1988, Hummel & Saikia 1991). The axis of the cone-like, high-excitation gas is almost perpendicular to the galaxy disk and close to that of the extended radio emission (Pogge 1988, Corbin et al. 1988), suggesting that the EELR are photoionized by nuclear radiation which escapes preferentially along and around the radio axis.
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