91 research outputs found
Education Law
This article presents a survey of the significant developments in the area of K-12 education law in Virginia from 2012 to the present. After two of the most active legislative and judicial sessions for education policy in recent years, this review can present only a select number of the many education-related statutes and judicial decisions introduced during this time. This survey places a special emphasis on the Virginia General Assembly\u27s recent legislative updates to the Virginia education code. The volume and significance of these updates reflects Governor Robert McDonnell\u27s commitment in 2013 to pursuing a bold education agenda. As Congress begins to seriously consider the reauthorization ofthe Elementary and Secondary Education Act of 1965, however, the education community may need to prepare for additional significant changes to the K-12 school law landscape
Trending Fuel Design Parameters for Competitive Advantage
The primary competitive advantage of commercial nuclear power over other baseload generating sources has been and continues to be the stability of fuel expense. Fuel contributes about 30% of total nuclear production costs and we believe this percentage will rise moderately as non-fuel production costs continue their decline. This places some urgency on seeking and implementing improvements in fuel utilisation by both suppliers and consumers to keep nuclear power competitive. The nuclear operating company as a fuel consumer can evaluate trends over the past operating cycles in its search for improvement in fuel utilisation. Some fuel parameters that have received attention recently are contracting strategies, fuel reliability, and higher exposures for discharged fuel
Photometry using the Infrared Array Camera on the Spitzer Space Telescope
We present several corrections for point source photometry to be applied to
data from the Infrared Array Camera (IRAC) on the Spitzer Space Telescope.
These corrections are necessary because of characteristics of the IRAC arrays
and optics and the way the instrument is calibrated in-flight. When these
corrections are applied, it is possible to achieve a ~2% relative photometric
accuracy for sources of adequate signal to noise in an IRAC image.Comment: 16 pages, 13 figures. Accepted for publication in the Publications of
the Astronomical Society of the Pacifi
Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars
We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z ~ 3, with predictions to z = 7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGNs) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA, and ROSAT data, where available. We discuss how the spectral diversity of quasars influences the determination of bolometric luminosities and accretion rates; assuming the mean SED can lead to errors as large as 50% for individual quasars when inferring a bolometric luminosity from an optical luminosity. Finally, we show that careful consideration of the shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened/obscured AGNs missed by optical surveys as compared to estimates derived from a single mean MIR to optical flux ratio
FIRST-2MASS Red Quasars: Transitional Objects Emerging from the Dust
We present a sample of 120 dust-reddened quasars identified by matching radio
sources detected at 1.4 GHz in the FIRST survey with the near-infrared 2MASS
catalog and color-selecting red sources. Optical and/or near-infrared
spectroscopy provide broad wavelength sampling of their spectral energy
distributions that we use to determine their reddening, characterized by
E(B-V). We demonstrate that the reddening in these quasars is best-described by
SMC-like dust. This sample spans a wide range in redshift and reddening (0.1 <
z < 3, 0.1 < E(B-V) < 1.5), which we use to investigate the possible
correlation of luminosity with reddening. At every redshift, dust-reddened
quasars are intrinsically the most luminous quasars. We interpret this result
in the context of merger-driven quasar/galaxy co-evolution where these reddened
quasars are revealing an emergent phase during which the heavily obscured
quasar is shedding its cocoon of dust prior to becoming a "normal" blue quasar.
When correcting for extinction, we find that, depending on how the parent
population is defined, these red quasars make up < 15-20% of the luminous
quasar population. We estimate, based on the fraction of objects in this phase,
that its duration is 15-20% as long as the unobscured, blue quasar phase.Comment: 21 pages, 17 figures plus a spectral atlas. Accepted for publication
in the Astrophysical Journa
Suppression of Star Formation in NGC 1266
NGC1266 is a nearby lenticular galaxy that harbors a massive outflow of molecular gas powered by the mechanical energy of an active galactic nucleus (AGN). It has been speculated that such outflows hinder star formation (SF) in their host galaxies, providing a form of feedback to the process of galaxy formation. Previous studies, however, indicated that only jets from extremely rare, high power quasars or radio galaxies could impart significant feedback on their hosts. Here we present detailed observations of the gas and dust continuum of NGC1266 at millimeter wavelengths. Our observations show that molecular gas is being driven out of the
nuclear region at Ṁ_(out) ≈ 110M_⊙ yr^(−1), of which the vast majority cannot escape the nucleus. Only 2M_⊙ yr^(−1)
is actually capable of escaping the galaxy. Most of the molecular gas that remains is very inefficient at forming
stars. The far-infrared emission is dominated by an ultra-compact (≾50 pc) source that could either be powered
by an AGN or by an ultra-compact starburst. The ratio of the SF surface density (Σ_(SFR)) to the gas surface
density (Σ_(H2)) indicates that SF is suppressed by a factor of ≈ 50 compared to normal star-forming galaxies if
all gas is forming stars, and ≈150 for the outskirt (98%) dense molecular gas if the central region is is powered
by an ultra-compact starburst. The AGN-driven bulk outflow could account for this extreme suppression by
hindering the fragmentation and gravitational collapse necessary to form stars through a process of turbulent
injection. This result suggests that even relatively common, low-power AGNs are able to alter the evolution of
their host galaxies as their black holes grow onto the M-σ relation
On the Link Between Central Black Holes, Bar Dynamics, and Dark Matter Halos in Spiral Galaxies
The discovery of a relationship between supermassive black hole (SMBH) mass
and spiral arm pitch angle (P) is evidence that SMBHs are tied to the overall
secular evolution of a galaxy. The discovery of SMBHs in late-type galaxies
with little or no bulge suggests that an underlying correlation between the
dark matter halo concentration and SMBH mass (MBH) exists, rather than between
the bulge mass and MBH. In this paper we measure P using a two-dimensional fast
fourier transform and estimate the bar pattern speeds of 40 barred spiral
galaxies from the Carnegie-Irvine Galaxy Survey. The pattern speeds were
derived by estimating the gravitational potentials of our galaxies from Ks-band
images and using them to produce dynamical simulation models. The pattern
speeds allow us to identify those galaxies with low central dark halo
densities, or fast rotating bars, while P provides an estimate of MBH. We find
that a wide range of MBH exists in galaxies with low central dark matter halo
densities, which appears to support other theoretical results. We also find
that galaxies with low central dark halo densities appear to follow more
predictable trends in P versus de Vaucouleurs morphological type (T) and bar
strength versus T than barred galaxies in general. The empirical relationship
between MBH and total gravitational mass of a galaxy (Mtot) allows us to
predict the minimum Mtot that will be observationally measured of our fast bar
galaxies. These predictions will be investigated in a subsequent paper.Comment: 17 pages, 1 table, 11 figures, accepted for publication in MNRA
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