132,641 research outputs found
Properties of Galaxy Groups in the SDSS: I.-- The Dependence of Colour, Star Formation, and Morphology on Halo Mass
Using a large galaxy group catalogue constructed from the SDSS, we
investigate the correlation between various galaxy properties and halo mass. We
split the population of galaxies in early types, late types, and intermediate
types, based on their colour and specific star formation rate. At fixed
luminosity, the early type fraction increases with increasing halo mass. Most
importantly, this mass dependence is smooth and persists over the entire mass
range probed, without any break or feature at any mass scale. We argue that the
previous claim of a characteristic feature on galaxy group scales is an
artefact of the environment estimators used. At fixed halo mass, the luminosity
dependence of the type fractions is surprisingly weak: galaxy type depends more
strongly on halo mass than on luminosity. We also find that the early type
fraction decreases with increasing halo-centric radius. Contrary to previous
studies, we find that this radial dependence is also present in low mass
haloes. The properties of satellite galaxies are strongly correlated with those
of their central galaxy. In particular, the early type fraction of satellites
is significantly higher in a halo with an early type central galaxy than in a
halo of the same mass but with a late type central galaxy. This phenomenon,
which we call `galactic conformity', is present in haloes of all masses and for
satellites of all luminosities. Finally, the fraction of intermediate type
galaxies is always ~20 percent, independent of luminosity, independent of halo
mass, independent of halo-centric radius, and independent of whether the galaxy
is a central galaxy or a satellite galaxy. We discuss the implications of all
these findings for galaxy formation and evolution.Comment: 28 pages, 15 figures. Submitted for publication in MNRA
Don't Look Back: Robustifying Place Categorization for Viewpoint- and Condition-Invariant Place Recognition
When a human drives a car along a road for the first time, they later
recognize where they are on the return journey typically without needing to
look in their rear-view mirror or turn around to look back, despite significant
viewpoint and appearance change. Such navigation capabilities are typically
attributed to our semantic visual understanding of the environment [1] beyond
geometry to recognizing the types of places we are passing through such as
"passing a shop on the left" or "moving through a forested area". Humans are in
effect using place categorization [2] to perform specific place recognition
even when the viewpoint is 180 degrees reversed. Recent advances in deep neural
networks have enabled high-performance semantic understanding of visual places
and scenes, opening up the possibility of emulating what humans do. In this
work, we develop a novel methodology for using the semantics-aware higher-order
layers of deep neural networks for recognizing specific places from within a
reference database. To further improve the robustness to appearance change, we
develop a descriptor normalization scheme that builds on the success of
normalization schemes for pure appearance-based techniques such as SeqSLAM [3].
Using two different datasets - one road-based, one pedestrian-based, we
evaluate the performance of the system in performing place recognition on
reverse traversals of a route with a limited field of view camera and no
turn-back-and-look behaviours, and compare to existing state-of-the-art
techniques and vanilla off-the-shelf features. The results demonstrate
significant improvements over the existing state of the art, especially for
extreme perceptual challenges that involve both great viewpoint change and
environmental appearance change. We also provide experimental analyses of the
contributions of the various system components.Comment: 9 pages, 11 figures, ICRA 201
Hybrid solutions to the feature interaction problem
In this paper we assume a competitive marketplace where the features are developed by different enterprises, which cannot or will not exchange information. We present a classification of feature interaction in this setting and introduce an on-line technique which serves as a basis for the two novel <i>hybrid</i> approaches presented. The approaches are hybrid as they are neither strictly off-line nor on-line, but combine aspects of both. The two approaches address different kinds of feature interactions, and thus are complimentary. Together they provide a complete solution by addressing interaction detection and resolution. We illustrate the techniques within the communication networks domain
AGN triggering in the infall regions of distant X-ray luminous galaxy clusters at 0.9 < z <~ 1.6
Observational constraints on the average radial distribution profile of AGN
in distant galaxy clusters can provide important clues on the triggering
mechanisms of AGN activity in dense environments and are essential for a
completeness evaluation of cluster selection techniques in the X-ray and
mm-wavebands. The aim of this work is a statistical study with XMM-Newton of
the presence and distribution of X-ray AGN in the large-scale structure
environments of 22 X-ray luminous galaxy clusters in the redshift range 0.9 < z
\lesssim 1.6 compiled by the XMM-Newton Distant Cluster Project (XDCP). To this
end, the X-ray point source lists from detections in the soft-band (0.35-2.4
keV) and full-band (0.3-7.5 keV) were stacked in cluster-centric coordinates
and compared to average background number counts extracted from three
independent control fields in the same observations. A significant full-band
(soft-band) excess of \sim78 (67) X-ray point sources is found in the cluster
fields within an angular distance of 8' (4Mpc) at a statistical confidence
level of 4.0 sigma (4.2 sigma), corresponding to an average number of detected
excess AGN per cluster environment of 3.5\pm0.9 (3.0\pm0.7). The data point
towards a rising radial profile in the cluster region (r<1Mpc) of predominantly
low-luminosity AGN with an average detected excess of about one point source
per system, with a tentative preferred occurrence along the main cluster
elongation axis. A second statistically significant overdensity of brighter
soft-band detected AGN is found at cluster-centric distances of 4'-6' (2-3Mpc),
corresponding to about three times the average cluster radius R200 of the
systems. If confirmed, these results would support the idea of two different
physical triggering mechanisms of X-ray AGN activity in dependence of the
radially changing large-scale structure environment of the distant clusters.Comment: 18 pages, 7 color figures, accepted for publication in Advances in
Astronomy for the special issue 'Seeking for the Leading Actor on the Cosmic
Stage: Galaxies versus Supermassive Black Holes
Considering Side Effects in Service Interactions in Home Automation - An Online Approach
The feature or service interaction problem within home networks is an established topic for the FI community. Interactions between home appliances, services and their environment have been reported previously. Indeed earlier work by the authors introduced a device centric approach which detects undesirable behaviour between appliances and their effects on the environment. However this previous work did not address side-effects between components of the modelled environment. That is some appliances do not only affect the environment through their main function, but may do so also in other ways. For instance, an air conditioner cools the air as its main function, but also decreases the humidity as a side-effect. Here we extend our earlier approach to handle such side effects effectively and discuss previously unreported results
The conservation of the environment in Ecuador's constitution
The 2008 Ecuadorian Constitution is often presented as building on the local traditions of indigenous peoples in order to propose a non-anthropocentric approach to the conservation of the environment, based on the concept of buen vivir. After providing a short introduction on anthropocentric and non-anthropo-centric approaches to the environment, with attention to indigenous worldviews, this article attempts to: analyse the concept of buen vivir, appearing to have unclear boundaries; understand whether or not it is a concept derived from indigenous worldviews; and explore the innovative non-anthropocentric feature of the recognition of rights to the environment. Finally, the article uses the idea of rights of the environment as a key to interpret the fuzzy concept of buen vivir in the most effective way to enhance the conservation of the environment
What May Visualization Processes Optimize?
In this paper, we present an abstract model of visualization and inference
processes and describe an information-theoretic measure for optimizing such
processes. In order to obtain such an abstraction, we first examined six
classes of workflows in data analysis and visualization, and identified four
levels of typical visualization components, namely disseminative,
observational, analytical and model-developmental visualization. We noticed a
common phenomenon at different levels of visualization, that is, the
transformation of data spaces (referred to as alphabets) usually corresponds to
the reduction of maximal entropy along a workflow. Based on this observation,
we establish an information-theoretic measure of cost-benefit ratio that may be
used as a cost function for optimizing a data visualization process. To
demonstrate the validity of this measure, we examined a number of successful
visualization processes in the literature, and showed that the
information-theoretic measure can mathematically explain the advantages of such
processes over possible alternatives.Comment: 10 page
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