1,756 research outputs found
VLBI Imaging of Water Maser Emission from the Nuclear Torus of NGC 1068
We have made the first VLBI synthesis images of the H2O maser emission
associated with the central engine of the Seyfert galaxy NGC 1068. Emission
extends about +/-300 km/s from the systemic velocity. Images with
submilliarcsecond angular resolution show that the red-shifted emission lies
along an arc to the northwest of the systemic emission. (The blue-shifted
emission has not yet been imaged with VLBI.) Based on the maser velocities and
the relative orientation of the known radio jet, we propose that the maser
emission arises on the surface of a nearly edge-on torus, where physical
conditions are conducive to maser action. The visible part of the torus is
axially thick, with comparable height and radius. The velocity field indicates
sub-Keplerian differential rotation around a central mass of about 1e7 Msun
that lies within a cylindrical radius of about 0.65 pc. The estimated
luminosity of the central engine is about 0.5 of the Eddington limit. There is
no detectable compact radio continuum emission near the proposed center of the
torus (T_B< 5e6 K on size scales of about 0.1 pc), so that the observed
flat-spectrum core cannot be direct self-absorbed synchrotron radiation.Comment: 12 pages, 4 figures. To appear in ApJ Part 2. Also available at
http://www.physics.ucsb.edu/~vlbiweb
Visitors' Interpretive Strategies at Wolverhampton Art Gallery
Making Meaning in Art Museums is one of two research projects on the theme of art museums and interpretive communities. The first was published as Making Meaning 1:Visitors' Interpretive Strategies at Wolverhampton Art Gallery (RCMG 2001). Making Meaning in Art Museums 2 is the second of two research projects on the theme of art museums and interpretive communities. The Long Gallery at the Nottingham Castle Museum and Art Gallery was selected as the research site for this second study. Both studies have explored the ways in which visitors talked about their experience of a visit to the art museum-both what they said about the paintings and the whole of the visit.The research questions on which this project is based are: What interpretive strategies and repertories are deployed by art museum visitors? Can distinct interpretive communities be identified? What are the implications for the communication policies within art museums? This research is an ethnographic study, using qualitative methods.This research project was funded through a grant from the Arts and Humanities Research Boar
Powerful Water Masers in Active Galactic Nuclei
Luminous water maser emission in the 6_(16)-5_(23) line at 22 GHz has been
detected from two dozen galaxies. In all cases the emission is confined to the
nucleus and has been found only in AGN, in particular, in Type 2 Seyferts and
LINERs. I argue that most of the observed megamaser sources are powered by
X-ray irradiation of dense gas by the central engine. After briefly reviewing
the physics of these X-Ray Dissociation Regions, I discuss in detail the
observations of the maser disk in NGC 4258, its implications, and compare
alternative models for the maser emission. I then discuss the observations of
the other sources that have been imaged with VLBI to date, and how they do or
do not fit into the framework of a thin, rotating disk, as in NGC 4258.
Finally, I briefly discuss future prospects, especially the possibility of
detecting other water maser transitions.Comment: 45 pages, 16 figures. Refereed and greatly expanded version of my
review talk at the ASA meeting in Lorne, July 2001. To appear in Proceedings
of the Astronomical Society of Australi
Sexual interest as performance, intellect and pathology: a critical discursive case study of dacryphilia
The present study depicts the case of a straight, 25 year old, Romanian woman Angela M, who is an individual with a sexual interest in dacryphilia (i.e. she derives sexual pleasure and arousal from crying and/or tears). Asynchronous email interviews were carried out with Angela M between January 2013 and February 2013 as part of a wider study into dacryphilia. Angela M’s interview transcripts comprised rich textual accounts that often made reference to cultural phenomena. Therefore, we apply critical discursive psychology to her data and identify the interpretative repertoires, subject positions, and ideological dilemmas that she uses to construct and negotiate her sexual identity. Our analysis suggests that Angela M draws predominantly upon two interpretative repertoires that construct her sexual interest in dacryphilia both as a performance and as an intellectual activity. However, some tensions exist within these interpretative repertoires, which Angela M negotiates by also constructing her sexual interest as a pathology. We explore the implications of the analysis with reference to postmodern theory and the historical context of a psychiatric tradition that pathologises non-normative sexual interests
Angular Momentum Transfer in the Binary X-ray Pulsar GX 1+4
We describe three presentations relating to the X-ray pulsar GX 1+4 at a
workshop on magnetic fields and accretion at the Astrophysical Theory Centre,
Australian National University on 1998, November 12-13. Optical and X-ray
spectroscopy indicate that GX 1+4 is seen through a cloud of gravitationaly
bound matter. We discuss an unstable negative feedback mechanism (originally
proposed by Kotani et al, 1999), based on X-ray heating of this matter which
controls the accretion rate when the source is in a low X-ray luminosity state.
A deep minimum lasting ~6 hours occurred during observations with the RXTE
satellite over 1996, July 19-21. The shape of the X-ray pulses changed
remarkably from before to after the minimum. These changes may be related to
the transition from neutron star spin-down to spin-up which occurred at about
the same time. Smoothed particle hydrodynamic simulations of the effect of
adding matter with opposite angular momentum to an existing disc, show that it
is possible for a number of concentric rings with alternating senses of
rotation to co-exist in a disc. This could provide an explanation for the
step-like changes in Pdot which are observed in GX 1+4. Changes at the inner
boundary of the disc occur at the same timescale as that imposed at the outer
boundary. Reversals of material torque on the neutron star occur at a minimum
in L_X.Comment: 10 pages, 5 figures; accepted for publication by PAS
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