68 research outputs found
Microlensing Constraints on Broad Absorption and Emission Line Flows in the Quasar H1413+117
We present new integral field spectroscopy of the gravitationally lensed
broad absorption line (BAL) quasar H1413+117, covering the ultraviolet to
visible rest-frame spectral range. We observe strong microlensing signatures in
lensed image D, and we use this microlensing to simultaneously constrain both
the broad emission and broad absorption line gas. By modeling the lens system
over the range of probable lensing galaxy redshifts and using on a new argument
based on the wavelength-independence of the broad line lensing magnifications,
we determine that there is no significant broad line emission from smaller than
~20 light days. We also perform spectral decomposition to derive the intrinsic
broad emission line (BEL) and continuum spectrum, subject to BAL absorption. We
also reconstruct the intrinsic BAL absorption profile, whose features allow us
to constrain outflow kinematics in the context of a disk-wind model. We find a
very sharp, blueshifted onset of absorption of 1,500 km/s in both C IV and N V
that may correspond to an inner edge of a disk-wind's radial outflow. The lower
ionization Si IV and Al III have higher-velocity absorption onsets, consistent
with a decreasing ionization parameter with radius in an accelerating outflow.
There is evidence of strong absorption in the BEL component which indicates a
high covering factor for absorption over two orders of magnitude in outflow
radius.Comment: 29 pages, 8 figure
The distributed co-evolution of an on-board simulator and controller for swarm robot behaviours
We investigate the reality gap, specifically the environmental correspondence of an on-board simulator. We describe a novel distributed co-evolutionary approach to improve the transference of controllers that co-evolve with an on-board simulator. A novelty of our approach is the the potential to improve transference between simulation and reality without an explicit measurement between the two domains. We hypothesise that a variation of on-board simulator environment models across many robots can be competitively exploited by comparison of the real controller fitness of many robots. We hypothesise that the real controller fitness values across many robots can be taken as indicative of the varied fitness in environmental correspondence of on-board simulators, and used to inform the distributed evolution an on-board simulator environment model without explicit measurement of the real environment. Our results demonstrate that our approach creates an adaptive relationship between the on-board simulator environment model, the real world behaviour of the robots, and the state of the real environment. The results indicate that our approach is sensitive to whether the real behavioural performance of the robot is informative on the state real environment. © 2014 Springer-Verlag Berlin Heidelberg
A Visual Guide for Communities Working with Academics on Participatory Research Projects
This illustrated guide is for communities interested in participatory research and engagement with academics as part of participatory projects. It has been written by community members, activists and academics who have been involved in research of this kind. It is intended to provide communities with basic explanations of the background to, and motivations for, participatory research, as well as overviews of the processes of research, the implications that communities should consider when deciding whether or not to participate in projects and the key steps participants can take to minimize risks and maximize benefits. What follows should be regarded only as an introduction to the topic and should be read in combination with more detailed work on specific elements of participatory research outlined in the references list below. While there are many other forms of engagement between communities and academics, such as practice placements, site visits and teaching contributions, this guide deals only with participatory research – a process which can stem from, or provide the basis for, other instances of collaboration. It is freely available online on the website of ‘A Cross-Cultural Working Group on “Good Culture” and Precariousness’ (http://wp.lancs.ac.uk/good-culture/a-guide-for-communities-working-withacademics-on-participatory-research-projects/), a participatory project involving community members from Ashington, Northumberland, and Aboriginal groups around Brisbane, Australia. It was during the development of this broader project that the need for an introductory guide emerged. It is hoped that drawing on those experiences, among others, will help community members and academics to find mutually beneficial means of advancing research capable of improving the lives of those participating in it
The Most Powerful Lenses in the Universe: Quasar Microlensing as a Probe of the Lensing Galaxy
Optical and X-ray observations of strongly gravitationally lensed quasars
(especially when four separate images of the quasar are produced) determine not
only the amount of matter in the lensing galaxy but also how much is in a
smooth component and how much is composed of compact masses (e.g., stars,
stellar remnants, primordial black holes, CDM sub-halos, and planets). Future
optical surveys will discover hundreds to thousands of quadruply lensed
quasars, and sensitive X-ray observations will unambiguously determine the
ratio of smooth to clumpy matter at specific locations in the lensing galaxies
and calibrate the stellar mass fundamental plane, providing a determination of
the stellar . A modest observing program with a sensitive, sub-arcsecond
X-ray imager, combined with the planned optical observations, can make those
determinations for a large number (hundreds) of the lensing galaxies, which
will span a redshift range of Comment: Astro2020 Science White Pape
Latent Stochastic Differential Equations for Modeling Quasar Variability and Inferring Black Hole Properties
Active galactic nuclei (AGN) are believed to be powered by the accretion of
matter around supermassive black holes at the centers of galaxies. The
variability of an AGN's brightness over time can reveal important information
about the physical properties of the underlying black hole. The temporal
variability is believed to follow a stochastic process, often represented as a
damped random walk described by a stochastic differential equation (SDE). With
upcoming wide-field surveys set to observe 100 million AGN in multiple bandpass
filters, there is a need for efficient and automated modeling techniques that
can handle the large volume of data. Latent SDEs are well-suited for modeling
AGN time series data, as they can explicitly capture the underlying stochastic
dynamics. In this work, we modify latent SDEs to jointly reconstruct the
unobserved portions of multivariate AGN light curves and infer their physical
properties such as the black hole mass. Our model is trained on a realistic
physics-based simulation of ten-year AGN light curves, and we demonstrate its
ability to fit AGN light curves even in the presence of long seasonal gaps and
irregular sampling across different bands, outperforming a multi-output
Gaussian process regression baseline.Comment: 10 pages, 5 figures, accepted at the ICLR 2023 Workshop on Physics
for Machine Learnin
The HST Survey of BL Lac Objects: Gravitational Lens Candidates and Other Unusual Sources
We present HST observations of seven unusual objects from the HST ``snapshot
survey'' of BL Lac objects, of which four are gravitational lens candidates. In
three cases a double point sources is observed: 0033+595, with 1.58 arcsec
separation, and 0502+675 and 1440+122, each with arcsec separation.
The last two also show one or more galaxies, which could be either host or
lensing galaxies. If any are confirmed as lenses, these BL Lac objects are
excellent candidates for measuring H via gravitational time delay because
of their characteristic rapid, high amplitude variability. An additional
advantage is that, like other blazars, they are likely superluminal radio
sources, in which case the source plane is mapped out over a period of years,
providing strong additional constraints on the lensing mass distribution. The
fourth gravitational lens candidate is 1517+656, which is surrounded by three
arclets forming an almost perfect ring of radius 2.4 arcsec. If this is indeed
an Einstein ring, it is most likely a background source gravitationally lensed
by the BL Lac object host galaxy and possibly a surrounding group or cluster.
In the extreme case that all four candidates are true lenses, the derived
frequency of gravitational lensing in this BL Lac sample would be an order of
magnitude higher than in comparable quasar samples.
We also report on three other remarkable BL Lac objects: 0138-097, which is
surrounded by a large number of close companion galaxies; 0806+524, whose host
galaxy contains an uncommon arc-like structure; and 1959+650, which is hosted
by a gas rich elliptical galaxy with a prominent dust lane of .Comment: 29 pages in total, 12 figure
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