1,290 research outputs found
The Intermediate Line Region and the Baldwin Effect
Statistical investigations of samples of quasars have established that
clusters of properties are correlated. The strongest trends among the
ultraviolet emission-line properties are characterized by the object-to-object
variation of emission from low-velocity gas, the so-called ``intermediate-line
region'' or ILR. The strongest trends among the optical emission-line
properties are characterized by the object-to-object variation of the line
intensity ratio of [O III] 5007 to optical Fe II. Additionally, the strength of
ILR emission correlates with [O III]/Fe II, as well as with radio and X-ray
properties. The fundamental physical parameter driving these related
correlations is not yet identified. Because the variation in the ILR dominates
the variation in the equivalent widths of lines showing the Baldwin effect, it
is important to understand whether the physical parameter underlying this
variation also drives the Baldwin effect or is a primary source of scatter in
the Baldwin effect.Comment: 11 pages, to appear in the proceedings of the meeting on "Quasars as
Standard Candles for Cosmology" held on May 18-22, 1998, at La Serena, Chile.
To be published by ASP, editor G. Ferlan
From Service to Experience: Understanding and Defining the Hospitality Business
Failure adequately to define or understand hospitality as a commercial phenomenon has created a fragmented academic environment and a schizophrenia in the industry that has the potential to limit its development as a global industry. This article suggests that, by redefining hospitality as behaviour and experience, a new perspective emerges that has exciting implications for the management of hospitality businesses. A framework to describe hospitality in the commercial domain is proposed. This framework suggests a focus on the hostâguest relationship, generosity, theatre and performance, âlots of little surprisesâ, and the security of strangers â a focus that provides guests with experiences that are personal, memorable and add value to their lives
Spectropolarimetry of PKS 0040-005 and the Orientation of Broad Absorption Line Quasars
We have used the Very Large Telescope (VLT) to obtain spectropolarimetry of
the radio-loud, double-lobed broad absorption line (BAL) quasar PKS 0040-005.
We find that the optical continuum of PKS 0040-005 is intrinsically polarized
at 0.7% with an electric vector position angle nearly parallel to that of the
large-scale radio axis. This result is naturally explained in terms of an
equatorial scattering region seen at a small inclination, building a strong
case that the BAL outflow is not equatorial. In conjunction with other recent
results concerning radio-loud BAL quasars, the era of simply characterizing
these sources as ``edge-on'' is over.Comment: 5 Pages, including 2 PostScript figures. Accepted for publication in
MNRAS letter
Outflows and the Physical Properties of Quasars
We have investigated a sample of 5088 quasars from the Sloan Digital Sky
Survey Second Data Release in order to determine how the frequency and
properties of broad absorptions lines (BALs) depend on black hole mass,
bolometric luminosity, Eddington fraction (L/L_Edd), and spectral slope. We
focus only on high-ionization BALs and find a number of significant results.
While quasars accreting near the Eddington limit are more likely to show BALs
than lower systems, BALs are present in quasars accreting at only a
few percent Eddington. We find a stronger effect with bolometric luminosity,
such that the most luminous quasars are more likely to show BALs. There is an
additional effect, previously known, that BAL quasars are redder on average
than unabsorbed quasars. The strongest effects involving the quasar physical
properties and BAL properties are related to terminal outflow velocity. Maximum
observed outflow velocities increase with both the bolometric luminosity and
the blueness of the spectral slope, suggesting that the ultraviolet luminosity
to a great extent determines the acceleration. These results support the idea
of outflow acceleration via ultraviolet line scattering.Comment: Uses emulateapj.cls, 14 pages including 7 tables and 7 figures.
Accepted for publication in the Astrophysical Journal, Unabridged version of
Table 4 can be downloaded from http://physics.uwyo.edu/agn
H-beta Line Width and the UV-X-ray Spectra of Luminous AGN
The width of the broad H-beta emission line is the primary defining
characteristic of the NLS1 class. This parameter is also an important component
of Boroson and Green's optical Eigenvector 1 (EV1), which links steeper soft
X-ray spectra with narrower H-beta emission, stronger H-beta blue wing,
stronger optical Fe II emission, and weaker [O III] lambda 5007. Potentially,
EV1 represents a fundamental physical process linking the dynamics of fueling
and outflow with the accretion rate. We attempted to understand these
relationships by extending the optical spectra into the UV for a sample of 22
QSOs with high quality soft-X-ray spectra, and discovered a whole new set of UV
relationships that suggest that high accretion rates are linked to dense gas
and perhaps nuclear starbursts. While it has been argued that narrow (BLR)
H-beta means low Black Hole mass in luminous NLS1s, the C IV, lambda 1549 and
Ly alpha emission lines are broader, perhaps the result of outflows driven by
their high Eddington accretion rates. We present some new trends of optical-UV
with X-ray spectral energy distributions. Steeper X-ray spectra appear
associated with stronger UV relative to optical continua, but the presence of
strong UV absorption lines is associated with depressed soft X-rays and redder
optical-UV continua.Comment: Invited talk presented at the Joint MPE,AIP,ESO workshop on NLS1s,
Bad Honnef, Dec. 1999, to appear in New Astronomy Reviews; also available at
http://wave.xray.mpe.mpg.de/conferences/nls1-worksho
Bootstrap data methodology for sequential hybrid model building
A method for modeling engine operation comprising the steps of: 1. collecting a first plurality of sensory data, 2. partitioning a flight envelope into a plurality of sub-regions, 3. assigning the first plurality of sensory data into the plurality of sub-regions, 4. generating an empirical model of at least one of the plurality of sub-regions, 5. generating a statistical summary model for at least one of the plurality of sub-regions, 6. collecting an additional plurality of sensory data, 7. partitioning the second plurality of sensory data into the plurality of sub-regions, 8. generating a plurality of pseudo-data using the empirical model, and 9. concatenating the plurality of pseudo-data and the additional plurality of sensory data to generate an updated empirical model and an updated statistical summary model for at least one of the plurality of sub-regions
- âŠ