2,187 research outputs found
Why does Low-Luminosity AGN Fueling Remain an Unsolved Problem?
Despite many years of effort, observational studies have not found a strong
correlation between the presence of any proposed fueling mechanism and
low-luminosity AGN. After a discussion of the mass requirements for fueling, I
summarize this observational work and provide a number of hypotheses for why
the nature of AGN fueling has remained unresolved. In particular, I stress the
potential importance of the increasing number of candidate fueling mechanisms
with decreasing mass accretion rate, the relevant spatial scales for different
fueling mechanisms, and the lifetime of an individual episode of nuclear
accretion. The episodic AGN lifetime is a particularly relevant complication if
it is comparable to or shorter than the time that the responsible fueling
mechanisms are observationally detectable. I conclude with a number of
relatively accessible areas for future investigation.Comment: 7 pages, 2 figures. Invited review to appear in "The Interplay among
Black Holes, Stars and ISM in Galactic Nuclei," Proc. IAU 222 (Gramado,
Brazil), eds. Th. Storchi Bergmann, L.C. Ho, H.R. Schmit
The harmonic map and Killing fields for self-dual SU(3) Yang-Mills equations
Using symbolic computations, the unique metric in the space of fields, required to describe self-dual SU(3) Yang-Mills equations by a harmonic map, is determined. Moreover the complete Lie algebra of Killing fields for this metric is established
The Giant Branches of Open and Globular Clusters in the Infrared as Metallicity Indicators: A Comparison with Theory
We apply the giant branch slope-[Fe/H] relation derived by Kuchinski et al.
[AJ, 109, 1131 (1995)] to a sample of open clusters. We find that the slope of
the giant branch in K vs. (J-K) color-magnitude diagrams correlates with [Fe/H]
for open clusters as it does for metal-rich globular clusters but that the open
cluster data are systematically shifted to less negative values of giant branch
slope, at constant [Fe/H]. We use isochrone models to examine the theoretical
basis for this relationship and find that for a given value of [Fe/H], the
slope of the relationship remains constant with decreasing population age but
the relation shifts to less negative values of giant branch slope with
decreasing age. Both of these theoretical predictions agree with the trends
found in the data. Finally, we derive new coefficients for the giant branch
slope-[Fe/H] relation for specific members of 3 populations, metal-rich
globular clusters, bulge stars and open clusters.Comment: 16 pages including 3 figures (AASTEX), AJ Accepted, also available at
http://www.astronomy.ohio-state.edu/~martini/pubs.htm
MORE THAN SMART: A Framework to Make the Distribution Grid More Open, Efficient and Resilient
This paper is the result of a series of workshops with industry, government and nonprofit leaders focused on helping guide future utility investments
and planning for a new distributed generation system. The distributed grid is the final stage in the delivery of electric power linking electricity
sub-stations to customers. To date, no state has initiated a comprehensive effort that includes the planning,
design-build and operational requirements for large
scale integration of DER into state-wide distributed
generation systems. This paper provides a framework and guiding principles for how to initiate such a
system and can be used to implement California law
AB 327 passed in 2013 requiring investor owned
utilities to submit a DER plan to the CPUC by July
2015 that identifies their optimal deployment
locations
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