70 research outputs found
Perceptual Context in Cognitive Hierarchies
Cognition does not only depend on bottom-up sensor feature abstraction, but
also relies on contextual information being passed top-down. Context is higher
level information that helps to predict belief states at lower levels. The main
contribution of this paper is to provide a formalisation of perceptual context
and its integration into a new process model for cognitive hierarchies. Several
simple instantiations of a cognitive hierarchy are used to illustrate the role
of context. Notably, we demonstrate the use context in a novel approach to
visually track the pose of rigid objects with just a 2D camera
The Destructive Action of IL-1α and IL-1β in IDDM is a Multistage Process: Evidence and Confirmation by Apoptotic Studies, Induction of Intermediates and Electron Microscopy
Galaxy Luminosity Functions to z~1: DEEP2 vs. COMBO-17 and Implications for Red Galaxy Formation
The DEEP2 and COMBO-17 surveys are used to study the evolution of the
luminosity function of red and blue galaxies to . Schechter function
fits show that, since , dims by 1.3 mag per unit redshift
for both color classes, of blue galaxies shows little change, while
for red galaxies has formally nearly quadrupled. At face value, the
number density of blue galaxies has remained roughly constant since ,
whereas that of red galaxies has been rising. Luminosity densities support both
conclusions, but we note that most red-galaxy evolution occurs between our data
and local surveys and in our highest redshift bin, where the data are weakest.
We discuss the implications of having most red galaxies emerge after
from precursors among the blue population, taking into account the properties
of local and distant E/S0s. We suggest a ``mixed'' scenario in which some blue
galaxies have their star-formation quenched in gas-rich mergers, migrate to the
red sequence with a variety of masses, and merge further on the red sequence in
one or more purely stellar mergers. E/S0s of a given mass today will have
formed via different routes, in a manner that may help to explain the
fundamental plane and other local scaling laws.Comment: Submitted to ApJ. 73 pages, 12 figures. Part II of a two-paper
series. The entire paper is available as a single postscript file at:
http://www.ucolick.org/~cnaw/paper2_submitted.ps.g
Host galaxy colour gradients and accretion disc obscuration in AEGIS z~1 X-ray-selected active galactic nuclei
We describe the effect of AGN light on host galaxy optical and UV-optical
colours, as determined from X-ray-selected AGN host galaxies at z~1, and
compare the AGN host galaxy colours to those of a control sample matched to the
AGN sample in both redshift and stellar mass. We identify as X-ray-selected
AGNs 8.7 +4/-3 per cent of the red-sequence control galaxies, 9.8 +/-3 per cent
of the blue-cloud control galaxies, and 14.7 +4/-3 per cent of the green-valley
control galaxies. The nuclear colours of AGN hosts are generally bluer than
their outer colours, while the control galaxies exhibit redder nuclei. AGNs in
blue-cloud host galaxies experience less X-ray obscuration, while AGNs in
red-sequence hosts have more, which is the reverse of what is expected from
general considerations of the interstellar medium. Outer and integrated colours
of AGN hosts generally agree with the control galaxies, regardless of X-ray
obscuration, but the nuclear colours of unobscured AGNs are typically much
bluer, especially for X-ray luminous objects. Visible point sources are seen in
many of these, indicating that the nuclear colours have been contaminated by
AGN light and that obscuration of the X-ray radiation and visible light are
therefore highly correlated. Red AGN hosts are typically slightly bluer than
red-sequence control galaxies, which suggests that their stellar populations
are slightly younger. We compare these colour data to current models of AGN
formation. The unexpected trend of less X-ray obscuration in blue-cloud
galaxies and more in red-sequence galaxies is problematic for all AGN feedback
models, in which gas and dust is thought to be removed as star formation shuts
down. [See paper for full abstract.]Comment: Accepted to MNRAS. 19 pages, 14 figures, 1 table; table, four figures
(4, 6, 11, 13) revised to reflect corrected values for one of our objects;
results unchange
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SN 2018fif: The explosion of a large red supergiant discovered in its infancy by the Zwicky transient facility
High-cadence transient surveys are able to capture supernovae closer to their first light than ever before. Applying analytical models to such early emission, we can constrain the progenitor stars’ properties. In this paper, we present observations of SN 2018fif (ZTF 18abokyfk). The supernova was discovered close to first light and monitored by the Zwicky Transient Facility (ZTF) and the Neil Gehrels Swift Observatory. Early spectroscopic observations suggest that the progenitor of SN 2018fif was surrounded by relatively small amounts of circumstellar material compared to all previous cases. This particularity, coupled with the high-cadence multiple-band coverage, makes it a good candidate to investigate using shock-cooling models. We employ the SOPRANOS code, an implementation of the model by Sapir & Waxman and its extension to early times by Morag et al. Compared with previous implementations, SOPRANOS has the advantage of including a careful account of the limited temporal validity domain of the shock-cooling model as well as allowing usage of the entirety of the early UV data. We find that the progenitor of SN 2018fif was a large red supergiant with a radius of R = 744.0-+128.0183.0 R☉ and an ejected mass of Mej = 9.3-+5.80.4 M☉. Our model also gives information on the explosion epoch, the progenitor’s inner structure, the shock velocity, and the extinction. The distribution of radii is double-peaked, with smaller radii corresponding to lower values of the extinction, earlier recombination times, and a better match to the early UV data. If these correlations persist in future objects, denser spectroscopic monitoring constraining the time of recombination, as well as accurate UV observations (e.g., with ULTRASAT), will help break the extinction/radius degeneracy and independently determine both
A retrospective cohort study in patients with tractional diseases of the vitreomacular interface (ReCoVit)
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