2,193 research outputs found
Near-IR photometry of disk galaxies: search for nuclear isophotal twist and double bars
We present a near-IR, mainly H band, photometry of 72 nearby disk galaxies.
The main goal of the survey was to search for isophotal twist inside their
nuclear regions. As the twist can be due in some cases to projection effects,
rather than resulting from a dynamical phenomenon, we deproject - under the
simplifying assumption of a 2D geometry - all galaxies whose disk position
angle and inclination are known, the latter not exceeding 75 degrees. We show
the ellipticity, position angle and surface brightness radial profiles, and
discuss how a projection of 2D and 3D bars can distort the isophotes, give an
illusion of a non-existing double bar or mask a real one. We report 15 new
double-barred galaxies and confirm 2 detected previously. We identify 14
additional twists not known before and we also find nuclear triaxial structures
in three SA galaxies. The frequency of Seyferts among galaxies with nuclear
bars or twists is high. As a secondary product, we publish structural
parameters (length and axis ratio) of large-scale bars in order to extend still
scarce data on bars in the near-IR.Comment: 11 pages of text (Astron. & Astroph. LaTeX l-aa macro) with 3
postscript figures, 7 additional pages of non-main-body postscript figures
containing contour and ellipse fitting plots of 72 galaxies; accepted by
Astronomy & Astrophysics Suppl. Se
Nuclear bars and blue nuclei within barred spiral galaxies
Multicolour near IR photometry for a sample of 32 large barred spiral
galaxies is presented. By applying ellipse fitting techniques, we identify
significant isophote twists with respect to the primary bar axis in the nuclear
regions of 70 \%\ of the sample. These twists are identified in galaxies
as late as SBbc and are clearly distinguishable from spiral arm morphology. At
most seven of the galaxies with isophote twists are inferred to possess
secondary (nuclear) bars, the axis ratios of which appear to correlate with
morphological type. The remainder may result from triaxial bulges, or from
oblate bulges misaligned with the primary bar. The near IR colour distributions
in these data show evidence for (red) circumnuclear star forming rings in 4
galaxies. The majority of the sample (19) also possess striking blue nuclear
regions, bluer than typical old stellar populations by 0.3 mag. in (J--H)
and 0.23 mag. in (H--K). Such blue colours do not appear to correlate
with the presence of nuclear rings or pseudo--rings, nor with the activity of
the host galaxy (as determined from emission--line spectroscopic
characteristics). Several mechanisms to explain this blue colour are
considered.Comment: 24 pages plain LaTex( including table captions), 5 tables and 18
figures. Accepted for publication in MNRAS. Paper and tables available via
anonymous ftp://143.167.4.101/pub/papers as sqiid-paper.tex and
table1,2,3.tex, table4.ps, table5.ps. Figures available as postcript upon
request to first Autho
Innovation, the diesel engine and vehicle markets: Evidence from OECD engine patents
This paper uses a patent data set to identify factors fostering innovation of diesel engines between 1974 and 2010 in the OECD region. The propensity of engine producers to innovate grew by 1.9 standard deviations after the expansion of the car market, by 0.7 standard deviations following a shift in the EU fuel economy standard, and by 0.23 standard deviations. The propensity to develop emissions control techniques was positively influenced by pollution control laws introduced in Japan, in the US, and in the EU, but not with the expansion of the car market. Furthermore, a decline in loan rates stimulated the propensity to develop emissions control techniques, which were simultaneously crowded out by increases in publicly-funded transport research and development. Innovation activities in engine efficiency are explained by market size, loan rates and by (Organisation for Economic Cooperation and Development) diesel prices, inclusive of taxes. Price effects on innovation, outweigh that of the US corporate average fuel economy standards. Innovation is also positively influenced by past transport research and development. © 2014 Elsevier Ltd
The evidence for jet-cloud interactions in a sample of high/intermediate-redshift radio galaxies
We present the result obtained from a study, based on long-slit spectroscopy,
of the kinematics and ionization mechanisms of the line-emitting gas for a
sample of four high/intermediate-redshift radio galaxies. In two of the
galaxies (3C352 and 3C435A) the radio sources are of the same scale as the
emission-line regions, whereas in the other two (3C34 and 3C330) the radio
sources are extended on a larger scale than the emission-line structures. We
see evidence for shock-acceleration of the emission-line gas in the extended
regions of all the galaxies, even in the largest radio sources of our sample,
in which the radio hot spots have passed the extended gas of the galaxies. The
extended regions present highly disturbed kinematics (line-splitting and/or
underlying broad components), which are difficult to explain if we do not
consider a strong interaction between the radio-emitting components and the
ambient gas. However, the dominant ionization mechanism of the line-emitting
gas remains uncertain. We have compared the optical diagnostic line ratios of
the galaxies in our sample with both AGN-photoionization and shock-ionization
models. We find a lack of consistency in explaining the main ionization
mechanism of the emission-line gas. This suggest that, if the extended regions
are shock-ionized, some of the assumptions implicit in the shock models may
need to be reconsidered. In addition, we have investigated the nebular
continuum cointribution to the UV excess in the galaxies of our sample. We find
a substantial nebular emission contribution to the UV continuum in all the
cases. However, after the subtraction iof the nebular component, a significant
UV excess remains in the extended nebulae of most of the objects.Comment: 33 pages, 24 figures, accepted for publication in MNRAS. (Abstract
shortened for astro-ph
Using Remote and in situ Observations from TORUS to Investigate a Preexisting Airmass Boundary and its Influence on a Tornadic Supercell on 28 May 2019
During the 2019 field phase of Targeted Observation by Radars and UAS of Supercells (TORUS), a preexisting airmass boundary was sampled on 28 May 2019 in north-central Kansas in close proximity to a tornadic supercell. This work hypothesized that the preexisting airmass boundary was associated with a mesoscale air mass with high theta-E (MAHTE) that favorably interacted with the tornadic supercell to increase the likelihood of tornadogenesis. Observations from TORUS including mobile mesonets, unoccupied aerial vehicles, soundings, and ground-based mobile radar were used along with GOES-16 visible satellite imagery, Kansas mesonet surface stations, and KUEX WSR-88D data to investigate this hypothesis.
Analysis revealed that the preexisting airmass boundary was associated with a synoptic-scale warm front and the cool air mass associated with this boundary had higher moisture compared to the warm side environment resulting in a higher equivalent potential temperature within the cooler air mass. This MAHTE had a boundary-normal width of around 13 km and a vertical depth around 400 m meaning it was truly mesoscale in size. The environment within the MAHTE had similar MLCAPE, greater vertical wind shear, and a lower lifting condensation level than the warm side environment rendering it more favorable for tornadic supercells.
A storm-scale analysis of the evolution of the tornadic supercell, a nontornadic supercell that developed within the MAHTE to the northeast of the tornadic storm, and the preexisting airmass boundary indicated that the preexisting airmass boundary likely interacted with the tornadic supercell in a way that promoted tornadogenesis. The nontornadic supercell also produced at least two outflow boundaries that interacted with the tornadic storm, one of which had a very stable air mass behind it and is hypothesized to have weakened the tornadic supercell.
Advisor: Adam L. Housto
Polarization Profiles of Scattered Emission Lines. II. Upstream Dust Scattering in the HH 1 Jet
Detailed comparisons are made between observations of scattered light
upstream of the head of the HH~1 jet and predictions of simple scattering
models. It is shown that, in order to unambiguously determine the velocity of
the head of the jet (bow shock) with respect to the upstream dust, existing
spectroscopic observations are insufficient and that spectropolarimetric
observations of the scattered light are necessary. Such an independent measure
of the bow shock velocity is important in order to test ``multiple outflow''
theories of Herbig-Haro jets. It is also shown 2that the scattering dust must
have a very forward-throwing scattering phase function
(\langle\cos\theta\rangle\msim 0.7) and slight evidence is found for a
dust-gas ratio that is higher than average.Comment: 11 pages, uuencoded compressed postscript (including 9 figures),
accepted for publication in Ap.J., IAUNAM_contrib.#34
Near-IR Spectropolarimetry of NGC 1088
Original paper can be found at: http://www.astrosociety.org/pubs/cs/035-069.html--Copyright Astronomical Society of the PacificThe current unified model of Seyfert galaxies, as proposed by Antonucci and Miller (1985), has most, if not all, Seyfert 2 galaxies hosting a Seyfert 1 type nucleus in their cores. The broad lines from the type 1 nucleus can be scattered and be seen in the polarized flux spectrum, provided the geometry is correct. Whether the mechanism is electron or dust scattering has been a question of some debate. Since dust would normally have a low scattering efficiency in the infrared, near-IR spectropolarimetry should help in determing the nature of the scatterers. To this end we present the first near-IR spectropolarimetry of NGC 1068 a "Seyfert 2" galaxy in which polarized broad lines have been observed at optical wavelengths
A multi-agent model for assessing electricity tariffs
This paper describes the framework for modelling a multi-agent approach for assessing dynamic pricing of electricity and demand response. It combines and agent-based model with decision-making data, and a standard load-flow model. The multi-agent model described here represents a tool in investigating not only the relation between different dynamic tariffs and consumer load profiles, but also the change in behaviour and impact on low-voltage electricity distribution networks.The authors acknowledge the contribution of the EPSRC Transforming Energy Demand Through Digital Innovation Programme, grant agreement numbers EP/I000194/1 and EP/I000119/1, to the ADEPT project
School to Work: Community Based Transition of 18-21 Year Old Students with Mild Disabilities
A community based service delivery plan was developed to meet the individual transition needs of 18-21 year old students with mild disabilities. The transition service was designed to ease the movement of students into post-secondary community life by providing prepatory experiences and community linkages. Students may receive services in the areas of recreation and leisure, vocational, and independent living activities depending on individual need
- …