337 research outputs found
The Cooperative Participatory Evaluation of Renewable Technologies on Ecosystem Services (CORPORATES)
Publisher PD
The Mid-Infrared Properties of X-ray Sources
We combine the results of the Spitzer IRAC Shallow Survey and the Chandra
XBootes Survey of the 8.5 square degrees Bootes field of the NOAO Deep Wide-
Field Survey to produce the largest comparison of mid-IR and X-ray sources to
date. The comparison is limited to sources with X-ray fluxes >8x10-15 erg
cm-2s-1 in the 0.5-7.0 keV range and mid-IR sources with 3.6 um fluxes brighter
than 18.4 mag (12.3 uJy). In this most sensitive IRAC band, 85% of the 3086
X-ray sources have mid-IR counterparts at an 80% confidence level based on a
Bayesian matching technique. Only 2.5% of the sample have no IRAC counterpart
at all based on visual inspection. Even for a smaller but a significantly
deeper Chandra survey in the same field, the IRAC Shallow Survey recovers most
of the X-ray sources. A majority (65%) of the Chandra sources detected in all
four IRAC bands occupy a well-defined region of IRAC [3.6] - [4.5] vs [5.8] -
[8.0] color-color space. These X-ray sources are likely infrared luminous,
unobscured type I AGN with little mid-infrared flux contributed by the AGN host
galaxy. Of the remaining Chandra sources, most are lower luminosity type I and
type II AGN whose mid-IR emission is dominated by the host galaxy, while
approximately 5% are either Galactic stars or very local galaxies.Comment: Accepted for publication in Ap
SmallSat Solar Axion and Activity X-ray Imager (SSAXI)
Axions are a promising dark matter candidate as well as a solution to the
strong charge-parity (CP) problem in quantum chromodynamics (QCD). We describe
a new mission concept for SmallSat Solar Axion and Activity X-ray Imager
(SSAXI) to search for solar axions or axion-like particles (ALPs) and to
monitor solar activity of the entire solar disc over a wide dynamic range.
SSAXI aims to unambiguously identify X-rays converted from axions in the solar
magnetic field along the line of sight to the solar core, effectively imaging
the solar core. SSAXI also plans to establish a statistical database of X-ray
activities from Active Regions, microflares, and Quiet Sun regions to
understand the origin of the solar corona heating processes. SSAXI employs
Miniature lightweight Wolter-I focusing X-ray optics (MiXO) and monolithic CMOS
X-ray sensors in a compact package. The wide energy range (0.5 - 6 keV) of
SSAXI can easily distinguish spectra of axion-converted X-rays from typical
X-ray spectra of solar activities, while encompassing the prime energy band (3
- 4.5 keV) of axion-converted X-rays. The high angular resolution (30 arcsec
HPD) and large field of view (40 arcmin) in SSAXI will easily resolve the
enhanced X-ray flux over the 3 arcmin wide solar core while fully covering the
X-ray activity over the entire solar disc. The fast readout in the inherently
radiation tolerant CMOS X-ray sensors enables high resolution spectroscopy with
a wide dynamic range in a broad range of operational temperatures. SSAXI will
operate in a Sun-synchronous orbit for 1 yr preferably near a solar minimum to
accumulate sufficient X-ray photon statistics.Comment: 12 pages, 9 figures, 1 table, Presented at the SPIE Optics +
Photonics Conference, August 2019, San Diego, C
Participatory scenario development for environmental management:A methodological framework illustrated with experience from the UK uplands
A methodological framework is proposed for participatory scenario development on the basis of evidence from the literature, and is tested and refined through the development of scenarios for the future of UK uplands. The paper uses a review of previous work to justify a framework based around the following steps: i) define context and establish whether there is a basis for stakeholder engagement in scenario development; ii) systematically identify and represent relevant stakeholders in the process; iii) define clear objectives for scenario development with stakeholders including spatial and temporal boundaries; iv) select relevant participatory methods for scenario development, during initial scenario construction, evaluation and to support decision-making based on scenarios; and v) integrate local and scientific knowledge throughout the process. The application of this framework in case study research suggests that participatory scenario development has the potential to: i) make scenarios more relevant to stakeholder needs and priorities; ii) extend the range of scenarios developed; iii) develop more detailed and precise scenarios through the integration of local and scientific knowledge; and iv) move beyond scenario development to facilitate adaptation to future change. It is argued that participatory scenario development can empower stakeholders and lead to more consistent and robust scenarios that can help people prepare more effectively for future change
Deliberative and non-monetary valuation methods
Abstract There is an increasing interest in methods that can understand our values of ecosystem services in broad and multidimensional way. This chapter discusses a range of deliberative, analytical-deliberative, psychological and interpretive approaches to value the environment. Deliberative methods allow people to ponder, debate and negotiate their values, which can inform, moralise and democratise the valuation process. Analytical-deliberative approaches combine deliberative methods with more formal decision-support tools. Interpretive methods help us understand the narratives of places and what they mean to us as individuals and to our communities and culture. Psychological methods can survey the multi-faceted nature of how ecosystem services contribute to human well-being, and can also investigate our deeper held, 'transcendental' values. The way we approach valuation impacts on the type of values that are highlighted. Embracing values as a pluralistic concept means that, to comprehensively value ecosystem services, we need to embrace a diversity of methods to assess them
The Discovery of a Large Lyman-alpha+HeII Nebula at z~1.67: A Candidate Low Metallicity Region?
We have discovered a ~45 kpc Lya nebula (or Lya ``blob'') at z~1.67 which
exhibits strong, spatially-extended HeII emission and very weak CIV and CIII]
emission. This is the first spatially-extended Lya+HeII emitter observed and
the lowest redshift Lya blob yet found. Strong Lya and HeII-1640 emission in
the absence of metal lines has been proposed as a unique observational
signature of primordial galaxy formation (e.g., from gravitational cooling
radiation or Population III star formation), but no convincing examples of
spatially-extended Lya+HeII emitters have surfaced either in Lya-emitting
galaxy surveys at high redshifts (z > 4) or in studies of Lya nebulae at lower
redshifts. From comparisons with photoionization models, we find that the
observed line ratios in this nebula are consistent with low metallicity gas (Z
< 10^-2 - 10^-3 Z_sun), but that this conclusion depends on the unknown
ionization parameter of the system. The large HeII equivalent width (~37+/-10A)
and the large HeII/Lya ratio (0.12+/-0.04) suggest that the cloud is being
illuminated by a hard ionizing continuum, either an AGN or very low metallicity
stars, or perhaps powered by gravitational cooling radiation. Thus far there is
no obvious sign of a powerful AGN in or near the system, so in order to power
the nebula while remaining hidden from view even in the mid-infrared, the AGN
would need to be heavily obscured. Despite the strong Lya+HeII emission, it is
not yet clear what is the dominant power source for this nebula. The system
therefore serves as an instructive example of how the complexities of true
astrophysical sources will complicate matters when attempting to use a strong
Lya+HeII signature as a unique tracer of primordial galaxy formation.Comment: Accepted for publication in ApJ; emulateapj format, 17 pages, 7
figures, 3 tables; updated coordinate
AEGIS-X: The Chandra Deep Survey of the Extended Groth Strip
We present the AEGIS-X survey, a series of deep Chandra ACIS-I observations
of the Extended Groth Strip. The survey comprises pointings at 8 separate
positions, each with nominal exposure 200ks, covering a total area of
approximately 0.67 deg2 in a strip of length 2 degrees. We describe in detail
an updated version of our data reduction and point source detection algorithms
used to analyze these data. A total of 1325 band-merged sources have been found
to a Poisson probability limit of 4e-6, with limiting fluxes of 5.3e-17
erg/cm2/s in the soft (0.5-2 keV) band and 3.8e-16 erg/cm2/s in the hard (2-10
keV) band. We present simulations verifying the validity of our source
detection procedure and showing a very small, <1.5%, contamination rate from
spurious sources. Optical/NIR counterparts have been identified from the DEEP2,
CFHTLS, and Spitzer/IRAC surveys of the same region. Using a likelihood ratio
method, we find optical counterparts for 76% of our sources, complete to
R(AB)=24.1, and, of the 66% of the sources that have IRAC coverage, 94% have a
counterpart to a limit of 0.9 microJy at 3.6 microns (m(AB)=23.8). After
accounting for (small) positional offsets in the 8 Chandra fields, the
astrometric accuracy of the Chandra positions is found to be 0.8 arcsec RMS,
however this number depends both on the off-axis angle and the number of
detected counts for a given source. All the data products described in this
paper are made available via a public website.Comment: 17 pages, 9 figures. Accepted for publication in ApJS. Data products
are available at http://astro.imperial.ac.uk/research/aegis
Scalable Cross-lingual Document Similarity through Language-specific Concept Hierarchies
With the ongoing growth in number of digital articles in a wider set of
languages and the expanding use of different languages, we need annotation
methods that enable browsing multi-lingual corpora. Multilingual probabilistic
topic models have recently emerged as a group of semi-supervised machine
learning models that can be used to perform thematic explorations on
collections of texts in multiple languages. However, these approaches require
theme-aligned training data to create a language-independent space. This
constraint limits the amount of scenarios that this technique can offer
solutions to train and makes it difficult to scale up to situations where a
huge collection of multi-lingual documents are required during the training
phase. This paper presents an unsupervised document similarity algorithm that
does not require parallel or comparable corpora, or any other type of
translation resource. The algorithm annotates topics automatically created from
documents in a single language with cross-lingual labels and describes
documents by hierarchies of multi-lingual concepts from independently-trained
models. Experiments performed on the English, Spanish and French editions of
JCR-Acquis corpora reveal promising results on classifying and sorting
documents by similar content.Comment: Accepted at the 10th International Conference on Knowledge Capture
(K-CAP 2019
The X-Ray Zurich Environmental Study (X-ZENS). I. Chandra and XMM-Newton observations of active galactic nuclei in galaxies in nearby groups
We describe X-ray observations with Chandra and XMM-Newton of 18 galaxy
groups (M_group ~ 1-6x10^13 Msolar, z~0.05) from the Zurich Environmental Study
(ZENS). We aim to establish the frequency and properties, unaffected by host
galaxy dilution and obscuration, of AGNs in central and satellite galaxy
members, also as a function of halo-centric distance. X-ray point-source
detections are reported for 22 of 177 observed galaxies, down to a limit of
f_(0.5-8 keV) ~ 5x10^-15 erg cm^-2 s^-1, corresponding to a limiting luminosity
of L_(0.5-8 keV)~3x10^40 erg s^-1. With the majority of the X-ray sources
attributed to AGNs of low-to-moderate levels (L/L_Edd>~10^-4), we discuss the
detection rate in the context of the occupation of AGNs to halos of this mass
scale and redshift, and compare the structural/morphological properties between
AGN-active and non-active galaxies of different rank and location within the
group halos. We see a slight tendency for AGN hosts to have either relatively
brighter/denser disks (or relatively fainter/diffuse bulges) than non-active
galaxies of similar mass. At galaxy mass scales <10^11 Msolar, central galaxies
appear to be a factor ~4 more likely to host AGNs than satellite galaxies of
similar mass. This effect, coupled with the tendency for AGNs to reside in
massive galaxies, explains the (weak) trend for AGNs to be preferentially found
in the inner regions of groups, with no detectable trend with halo-centric
distance in the frequency of AGNs within the satellite population. Finally, our
data support other analyses in finding that the rate of decline with redshift
of AGN activity in groups matches that of the global AGN population, indicating
that either AGNs occur preferentially in groups, or that the evolution rate is
independent of halo mass. These trends are of potential importance, and require
X-ray coverage of a larger sample to be solidly confirmed.Comment: 18 pages, 13 figures, submitted to The Astrophysical Journal, this is
a revised version that addresses the referee's comment
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