471 research outputs found
Testing the photoionization models of powerful radio galaxies: Mixed line-emitting media in 3C 321
The photoionization models for the narrow emission line regions of powerful
radio galaxies have yet to be tested in depth. To this end, we present
high-quality long-slit spectroscopy of the powerful double-nucleus radio galaxy
3C 321. The data have good enough spatial resolution to be able to trace the
variation in emission-line properties on kpc scales. Continuum modelling and
subtraction enables the faint emission line fluxes to be measured in several
regions across the emission line nebula. We plot diagnostic line-ratio diagrams
and compare them with the predictions of various photoionization models,
finding that the data is best fit by models which assume a mixture of optically
thin and thick clouds illuminated by a power-law continuum.
The emission line kinematics, line ratios and deduced physical conditions
show remarkably little variation across the source. We deduce a mean electron
density of 400 +/- 120 cm-3 and a mean temperature of 11500 +/- 1500 K.
Assuming a single population of optically thick line-emitting clouds, we
calculate a mean photoionization parameter of (1.1 +/- 0.5) x 10e-2 and hence a
photoionizing photon luminosity of Q ~ 10e55 -- 10e56 photon/s/sr. This
indicates a central engine as luminous as that of the powerful quasar 3C 273,
yet there is no evidence for such an energetically prolific central engine at
either far-infrared or radio wavelengths. We therefore conclude that the
mixed-media models, which give Q ~ 5 x 10e53 -- 5 x 10e54, represent a more
likely scenario.
As a by-product of the continuum subtraction we infer that young stellar
populations account for ~ 0.4% of the visible stellar mass in the galaxy, and
that these populations are spatially extended.Comment: Accepted for publication in MNRA
Shifting sustainable lifestyle practices and behaviour during times of pandemic disruptive change: Implications for on-going socio-technical transitions
COVID-19 has extensively reshaped lifestyle practices, supply chain dynamics, and climate mitigation efforts. The resulting crises from the pandemic in relation to local and community sustainability practices have not yet been investigated in depth. There is a need to explore the individual characteristics and responses from rapid transitions of lifestyles at various scales. Analysing how the COVID-19 pandemic has shaped and altered sustainable living practices, and the motivations supporting them, has yet to be determined but is crucial to gain further insight to improve management responses to large-scale disruptive change. Presenting empirical findings from semi-structured interviews in New Haven County, Connecticut, this study elucidates the ways in which the lifestyles have been altered and how they responded while specifically highlighting the consequences for behavioural routines and sustainable lifestyle practices. As a result of lockdowns and pandemic mitigation responses, individual sustainability engagement fluctuated with participants shifting dietary, mobility, and energy and food consumption patterns. Specifically, participants emphasised substantial decrease in daily travel during initial phases of the pandemic alongside increased online shopping and energy use at home. Though changes to consumption practices were replaced former habits with unsustainable ones, individuals also noted how they co-opted the pandemic over time to pursue sustainable actions at home. As a macro-level âwindow of opportunityâ and disruptive change, this study illustrates how sustainable lifestyle practices were reshaped; some by choice, some by force, and some reflecting a forced choice. These findings have clear implications for the stability of maintaining sustainable practices influenced by landscape-level shocks
9286 Stars: An Agglomeration of Stellar Polarization Catalogs
This is a revision. The revisions are minor. The new version of the catalog
should be used in preference to the old. The most serious error in the older
version was that was incorrect, being sometimes far too large,
for Reiz and Franco entries; the correct values are all zero for that
reference.
We present an agglomeration of stellar polarization catalogs with results for
9286 stars. We have endeavored to eliminate errors, provide accurate
(arcsecond) positions, sensibly weight multiple observations of the same star,
and provide reasonable distances. This catalog is included as an ASCII file
(catalog.txt) in the source of this submission.Comment: The most serious error in the older version was that
was incorrect, being sometimes far too large, for Reiz and Franco entries;
the correct values are all zero for that reference. 11 pages, no figures.
Accepted for Astronomical Journal. Catalog also available as an ASCII file by
anonymous FTP from ftp://vermi.berkeley.edu/pub/polcat/p14.ou
On the observed distributions of black hole masses and Eddington ratios from radiation pressure corrected virial indicators
The application of the virial theorem to the Broad Line Region of Active
Galactic Nuclei allows Black Hole mass estimates for large samples of objects
at all redshifts. In a recent paper we showed that ionizing radiation pressure
onto BLR clouds affects virial BH mass estimates and we provided empirically
calibrated corrections. More recently, a new test of the importance of
radiation forces has been proposed: the MBH-sigma relation has been used to
estimate MBH for a sample of type-2 AGN and virial relations (with and without
radiation pressure) for a sample of type-1 AGN extracted from the same parent
population. The observed L/LEdd distribution based on virial BH masses is in
good agreement with that based on MBH-sigma only if radiation pressure effects
are negligible, otherwise significant discrepancies are observed. In this paper
we investigate the effects of intrinsic dispersions associated to the virial
relations providing MBH, and we show that they explain the discrepancies
between the observed L/LEdd distributions of type-1 and type-2 AGN. These
discrepancies in the L/LEdd distributions are present regardless of the general
importance of radiation forces, which must be negligible only for a small
fraction of sources with large L/LEdd. Average radiation pressure corrections
should then be applied in virial MBH estimators until their dependence on
observed source physical properties has been fully calibrated. Finally, the
comparison between MBH and L/LEdd distributions derived from sigma-based and
virial estimators can constrain the variance of BLR physical properties in AGN.Comment: Astrophysical Journal Letters, in pres
The highly polarized open cluster Trumpler 27
We have carried out multicolor linear polarimetry (UBVRI) of the brightest
stars in the area of the open cluster Trumpler 27. Our data show a high level
of polarization in the stellar light with a considerable dispersion, from to . The polarization vectors of the cluster members appear to be
aligned. Foreground polarization was estimated from the data of some non-member
objects, for which two different components were resolved: the first one
associated with a dust cloud close to the Sun producing
and degrees, and a second component, the main source of
polarization for the cluster members, originated in another dust cloud, which
polarizes the light in the direction of degrees. From a detailed
analysis, we found that the two components have associated values for the first one, and for the other. Due the
difference in the orientation of both polarization vectors, almost 90 degrees
(180 degrees at the Stokes representation), the first cloud (
degrees) depolarize the light strongly polarized by the second one ( degrees).Comment: 12 Pages, 6 Figures, 2 tables (9 Pages), accepted for publication in
A
STIS Echelle Observations of the Seyfert Galaxy NGC 4151: Physical Conditions in the Ultraviolet Absorbers
We have examined the physical conditions in intrinsic UV-absorbing gas in the
Seyfert galaxy NGC 4151, using echelle spectra obtained with the Space
Telescope Imaging Spectrograph (STIS). We confirm the presence of the kinematic
components detected in earlier GHRS observations as well as a new broad
absorption feature at a radial velocity of -1680 km/s. The UV continuum of NGC
4151 decreased by a factor of 4 over the previous two years, and we argue the
changes in the column density of the low ionization absorption lines associated
with the broad component at -490 km/s reflect the decrease in the ionizing
flux. Most of the strong absorption lines (e.g., N V, C IV, Si IV) from this
component are saturated, but show substantial residual flux in their cores,
indicating that the absorber does not fully cover the source of emission. Our
interpretation is that the unocculted light is due to scattering by free
electrons from an extended region, which reflects continuum, emission lines,
and absorption lines. We have been able to constrain the densities for the
kinematic components based on absorption lines from metastable states of C III
and Fe II, and/or the ratios of ground and fine structure lines of O I,C II,
and Si II. We have generated a set of photoionization models which match the
ionic column densities for each component during the present low flux state and
those seen in previous high flux states with the GHRS and STIS, confirming that
the absorbers are photoionized and respond to the changes in the continuum
flux. We have been able to map the relative radial positions of the absorbers,
and find that the gas decreases in density with distance. None of the UV
absorbers is of sufficiently large column density or high enough ionization
state to account for the X-ray absorption.Comment: 46 pages (Latex), 14 figures (postscript), plus a landscape table
(Latex), to appear in the Astrophysical Journa
Scenarios for the Development of Smart Grids in the UK: Synthesis Report
Building on extensive expert feedback and input, this Research Report describes four smart grid scenarios which consider how the UK' electricity system might develop to 2050. The scenarios outline how political decisions, as well as those made in regulation, finance, technology, consumer and social behaviour, market design or response, might affect the decisions of other actors and limit or allow the availability of future options
The origin of the Narrow Line Region of Mrk 3: an overpressured jet cocoon
We have obtained HST FOC long-slit optical spectroscopy of the Narrow Line
Region of the Seyfert 2 galaxy Mrk 3. In the region cospatial with the
radio-jet the velocity field is highly perturbed and shows two velocity systems
separated by as much as 1700 km/s. We interpret this to be the consequence of
the rapid expansion of a cocoon of hot gas, shocked and heated by the
radio-emitting outflow, which compresses and accelerates the ambient gas. The
NLR itself is essentially a cylindrical shell expanding supersonically. From
the size and velocity of the expanding region, we derive an upper limit to the
radio-source age, ~ 2
E42 erg/s required to inflate the cocoon and estimate that the jet minimum
advance speed is 3 E-3 pc per year. The total kinetic energy of the high
velocity NLR gas can be estimated as ~6 E54 erg, comparable to the total energy
carried by the jet over its lifetime and this quantitatively supports the idea
that the NLR gas is accelerated by the jet. If the advance speed of Mrk 3 is
representative of the Seyfert population then these sources must also be short
lived and probably recurrent. The jet kinetic luminosity of Mrk 3 is between 2
and 3 orders of magnitude smaller than that derived for radio-loud AGNs with
similar emission-line luminosity. On the other hand, the fraction of jet power
dissipated in radio-emission is similar. We speculate that the main distinction
between radio-quiet and radio-loud AGN is ascribed to a difference in jet power
rather than to a different efficiency in synchrotron emission production.Comment: 13 pages, 8 figures, Astrophysical Journal in pres
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