5,452 research outputs found
The First Public Release of South Pole Telescope Data: Maps of a 95 deg^2 Field from 2008 Observations
The South Pole Telescope (SPT) has nearly completed a 2500 deg^2 survey of the southern sky in three frequency bands. Here, we present the first public release of SPT maps and associated data products. We present arcminute-resolution maps at 150 GHz and 220 GHz of an approximately 95 deg^2 field centered at R.A. 82°.7, decl. –55°. The field was observed to a depth of approximately 17 μK arcmin at 150 GHz and 41 μK arcmin at 220 GHz during the 2008 austral winter season. Two variations on map filtering and map projection are presented, one tailored for producing catalogs of galaxy clusters detected through their Sunyaev-Zel'dovich effect signature and one tailored for producing catalogs of emissive sources. We describe the data processing pipeline, and we present instrument response functions, filter transfer functions, and map noise properties. All data products described in this paper are available for download at http://pole.uchicago.edu/public/data/maps/ra5h30dec-55 and from the NASA Legacy Archive for Microwave Background Data Analysis server. This is the first step in the eventual release of data from the full 2500 deg^2 SPT survey
Analysis of the Copenhagen Accord pledges and its global climatic impacts‚ a snapshot of dissonant ambitions
This analysis of the Copenhagen Accord evaluates emission reduction pledges by individual countries against the Accord's climate-related objectives. Probabilistic estimates of the climatic consequences for a set of resulting multi-gas scenarios over the 21st century are calculated with a reduced complexity climate model, yielding global temperature increase and atmospheric CO2 and CO2-equivalent concentrations. Provisions for banked surplus emission allowances and credits from land use, land-use change and forestry are assessed and are shown to have the potential to lead to significant deterioration of the ambition levels implied by the pledges in 2020. This analysis demonstrates that the Copenhagen Accord and the pledges made under it represent a set of dissonant ambitions. The ambition level of the current pledges for 2020 and the lack of commonly agreed goals for 2050 place in peril the Accord's own ambition: to limit global warming to below 2 °C, and even more so for 1.5 °C, which is referenced in the Accord in association with potentially strengthening the long-term temperature goal in 2015. Due to the limited level of ambition by 2020, the ability to limit emissions afterwards to pathways consistent with either the 2 or 1.5 °C goal is likely to become less feasibl
Some photometer results obtained on the NASA 1969 Airborne Auroral Expedition
The spectral features measured by a photometer onboard the Convair 990 Galileo, during the Auroral Expedition are given in tables. The measurements given cover flights 3 to 15
Cosmological forecast of the 21-cm power spectrum using the halo model of reionization
The 21-cm power spectrum of reionization is a promising probe for cosmology
and fundamental physics. Exploiting this new observable, however, requires fast
predictors capable of efficiently scanning the very large parameter space of
cosmological and astrophysical uncertainties. In this paper, we introduce the
halo model of reionization (HMreio), a new analytical tool that combines the
halo model of the cosmic dawn with the excursion-set bubble model for
reionization, assuming an empirical correction factor to deal with overlapping
ionization bubbles. First, HMreio is validated against results from the
well-known semi-numerical code 21cmFAST, showing a good overall agreement for
wave-modes of h/Mpc. Based on this result, we perform a
Monte-Carlo Markov-Chain (MCMC) forecast analysis assuming mock data from
1000-hour observations with the low-frequency part of the Square Kilometre
Array (SKA) observatory. We simultaneously vary the six standard cosmological
parameters together with seven astrophysical nuisance parameters quantifying
the abundance and spectral properties of sources. Depending on the assumed
theory error, we find very competitive constraints on cosmological parameters.
In particular, it will be possible to conclusively test current cosmological
tensions related to the Hubble parameter (-tension) and the matter
clustering amplitude (-tension). Furthermore, the sum of the neutrino
masses can be strongly constrained, making it possible to determine the
neutrino mass hierarchy at the percent confidence level. However,
these goals can only be achieved if the current modelling uncertainties are
substantially reduced to below percent.Comment: 18 pages, 8 figures, comments welcom
BEoRN: A fast and flexible framework to simulate the epoch of reionisation and cosmic dawn
In this study, we introduce BEoRN (Bubbles during the Epoch of Reionisation
Numerical Simulator), a publicly available Python code that generates
three-dimensional maps of the 21-cm signal from the cosmic dawn and the epoch
of reionisation. Built upon N-body simulation outputs, BEoRN populates haloes
with stars and galaxies based on a flexible source model. It then computes the
evolution of Lyman- coupling, temperature, and ionisation profiles as a
function of source properties, and paints these profiles around each source
onto a three-dimensional grid. The code consistently deals with the overlap of
ionised bubbles by redistributing photons around the bubble boundaries, thereby
ensuring photon conservation. It accounts for the redshifting of photons and
the source look-back effect for the temperature and Lyman- coupling
profiles which extend far into the intergalactic medium to scales of order 100
cMpc. We provide a detailed description of the code and compare it to results
from the literature. After validation, we run three different benchmark models
based on a cosmological N-body simulation. All three models agree with current
observations from UV luminosity functions and estimates of the mean ionisation
fraction. Due to different assumptions regarding the small-mass stellar-to-halo
relation, the X-ray flux emission, and the ionising photon escape fraction, the
models produce unique signatures ranging from a cold reionisation with deep
absorption trough to an emission-dominated 21-cm signal, broadly encompassing
the current uncertainties at cosmic dawn. The code BEoRN is publicly available
at https://github.com/cosmic-reionization/BEoRN
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