827 research outputs found
Lessons Learned from Sloan Digital Sky Survey Operations
Astronomy is changing. Large projects, large collaborations, and large
budgets are becoming the norm. The Sloan Digital Sky Survey (SDSS) is one
example of this new astronomy, and in operating the original survey, we put in
place and learned many valuable operating principles. Scientists sometimes have
the tendency to invent everything themselves but when budgets are large,
deadlines are many, and both are tight, learning from others and applying it
appropriately can make the difference between success and failure. We offer
here our experiences well as our thoughts, opinions, and beliefs on what we
learned in operating the SDSS.Comment: Conference Proceedings, SPIE 200
The supernova cosmology cookbook: Bayesian numerical recipes
Theoretical and observational cosmology have enjoyed a number of significant
successes over the last two decades. Cosmic microwave background measurements
from the Wilkinson Microwave Anisotropy Probe and Planck, together with
large-scale structure and supernova (SN) searches, have put very tight
constraints on cosmological parameters. Type Ia supernovae (SNIa) played a
central role in the discovery of the accelerated expansion of the Universe,
recognised by the Nobel Prize in Physics in 2011. The last decade has seen an
enormous increase in the amount of high quality SN observations, with SN
catalogues now containing hundreds of objects. This number is expected to
increase to thousands in the next few years, as data from next-generation
missions, such as the Dark Energy Survey and Large Synoptic Survey Telescope
become available. In order to exploit the vast amount of forthcoming high
quality data, it is extremely important to develop robust and efficient
statistical analysis methods to answer cosmological questions, most notably
determining the nature of dark energy. To address these problems my work is
based on nested-sampling approaches to parameter estimation and model selection
and neural networks for machine-learning. Using advanced Bayesian techniques, I
constrain the properties of dark-matter haloes along the SN lines-of-sight via
their weak gravitational lensing effects, develop methods for classifying SNe
photometrically from their lightcurves, and present results on more general
issues associated with constraining cosmological parameters and testing the
consistency of different SN compilations.Comment: 119 pages, 29 figures, Doctoral Thesis in Theoretical Physics, ISBN
978-91-7447-953-
Working Papers: Astronomy and Astrophysics Panel Reports
The papers of the panels appointed by the Astronomy and Astrophysics survey Committee are compiled. These papers were advisory to the survey committee and represent the opinions of the members of each panel in the context of their individual charges. The following subject areas are covered: radio astronomy, infrared astronomy, optical/IR from ground, UV-optical from space, interferometry, high energy from space, particle astrophysics, theory and laboratory astrophysics, solar astronomy, planetary astronomy, computing and data processing, policy opportunities, benefits to the nation from astronomy and astrophysics, status of the profession, and science opportunities
Astrochemistry of dust, ice and gas: introduction and overview
A brief introduction and overview of the astrochemistry of dust, ice and gas
and their interplay is presented, aimed at non-specialists. The importance of
basic chemical physics studies of critical reactions is illustrated through a
number of recent examples. Such studies have also triggered new insight into
chemistry, illustrating how astronomy and chemistry can enhance each other.
Much of the chemistry in star- and planet-forming regions is now thought to be
driven by gas-grain chemistry rather than pure gas-phase chemistry, and a
critical discussion of the state of such models is given. Recent developments
in studies of diffuse clouds and PDRs, cold dense clouds, hot cores,
protoplanetary disks and exoplanetary atmospheres are summarized, both for
simple and more complex molecules, with links to papers presented in this
volume. In spite of many lingering uncertainties, the future of astrochemistry
is bright: new observational facilities promise major advances in our
understanding of the journey of gas, ice and dust from clouds to planets.Comment: Introductory paper for Faraday Discussions 168 conference, April 201
The Quest for Dual and Binary Supermassive Black Holes: A Multi-Messenger View
The quest for binary and dual supermassive black holes (SMBHs) at the dawn of the multi-messenger era is compelling. Detecting dual active galactic nuclei (AGN) – active SMBHs at projected separations larger than several parsecs – and binary AGN – probing the scale where SMBHs are bound in a Keplerian binary – is an observational challenge. The study of AGN pairs (either dual or binary) also represents an overarching theoretical problem in cosmology and astrophysics. The AGN triggering calls for detailed knowledge of the hydrodynamical conditions of gas in the imminent surroundings of the SMBHs and, at the same time, their duality calls for detailed knowledge on how galaxies assemble through major and minor mergers and grow fed by matter along the filaments of the cosmic web. This review describes the techniques used across the electromagnetic spectrum to detect dual and binary AGN candidates and proposes new avenues for their search. The current observational status is compared with the state-of-the-art numerical simulations and models for formation of dual and binary AGN. Binary SMBHs are among the loudest sources of gravitational waves (GWs) in the Universe. The search for a background of GWs at nHz frequencies from inspiralling SMBHs at low redshifts, and the direct detection of signals from their coalescence by the Laser Interferometer Space Antenna in the next decade, make this a theme of major interest for multi-messenger astrophysics. This review discusses the future facilities and observational strategies that are likely to significantly advance this fascinating field
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