673 research outputs found
Polling bias and undecided voter allocations: US Presidential elections, 2004 - 2016
Accounting for undecided and uncertain voters is a challenging issue for
predicting election results from public opinion polls. Undecided voters typify
the uncertainty of swing voters in polls but are often ignored or allocated to
each candidate in a simple, deterministic manner. Historically this may have
been adequate because the undecided were comparatively small enough to assume
that they do not affect the relative proportions of the decided voters.
However, in the presence of high numbers of undecided voters, these static
rules may in fact bias election predictions from election poll authors and
meta-poll analysts. In this paper, we examine the effect of undecided voters in
the 2016 US presidential election to the previous three presidential elections.
We show there were a relatively high number of undecided voters over the
campaign and on election day, and that the allocation of undecided voters in
this election was not consistent with two-party proportional (or even)
allocations. We find evidence that static allocation regimes are inadequate for
election prediction models and that probabilistic allocations may be superior.
We also estimate the bias attributable to polling agencies, often referred to
as "house effects".Comment: 32 pages, 9 figures, 6 table
The He abundance in the metal-deficient blue compact dwarf galaxies Tol 1214-277 and Tol 65
We present high-quality Keck telescope spectroscopic observations of the two
metal-deficient blue compact dwarf (BCD) galaxies Tol 1214-277 and Tol 65.
These data are used to derive the heavy-element and helium abundances. We find
that the oxygen abundances in Tol 1214-277 and Tol 65 are the same,
12+logO/H=7.54+/-0.01, or Zsun/24, despite the different ionization conditions
in these galaxies. The nitrogen-to-oxygen abundance ratio in both galaxies is
logN/O=-1.64+/-0.02 and lies in the narrow range found for the other most
metal-deficient BCDs. We use the five strongest HeI emission lines 3889, 4471,
5876, 6678 and 7065, to correct self-consistently their intensities for
collisional and fluorescent enhancement mechanisms and to derive the He
abundance. Underlying stellar absorption is found to be important for the HeI
4471 emission line in both galaxies, being larger in Tol 65. The weighted He
mass fractions in Tol 1214-277 and Tol 65 are respectively Y=0.2458+/-0.0039
and 0.2410+/-0.0050 when the three HeI emission lines, 4471, 5876 and 6678, are
used, and are, respectively, 0.2466+/-0.0043 and 0.2463+/-0.0057 when the HeI
4471 emission line is excluded. These values are in very good agreement with
recent measurements of the He mass fraction in others of the most
metal-deficient BCDs by Izotov and coworkers. We find that the combined effect
of the systematic uncertainties due to the underlying HeI stellar absorption
lines, ionization and temperature structure of the HII region and collisional
excitation of the hydrogen emission lines is likely small, not exceeding ~2%
(the error is 2sigma). Our results support the validity of the standard big
bang model of nucleosynthesis.Comment: 22 pages, 3 Postscript figures, accepted for publication in the
Astrophysical Journa
Relativistic positioning: four-dimensional numerical approach in Minkowski space-time
We simulate the satellite constellations of two Global Navigation Satellite
Systems: Galileo (EU) and GPS (USA). Satellite motions are described in the
Schwarzschild space-time produced by an idealized spherically symmetric non
rotating Earth. The trajectories are then circumferences centered at the same
point as Earth. Photon motions are described in Minkowski space-time, where
there is a well known relation, Coll, Ferrando & Morales-Lladosa (2010),
between the emission and inertial coordinates of any event. Here, this relation
is implemented in a numerical code, which is tested and applied. The first
application is a detailed numerical four-dimensional analysis of the so-called
emission coordinate region and co-region. In a second application, a GPS
(Galileo) satellite is considered as the receiver and its emission coordinates
are given by four Galileo (GPS) satellites. The bifurcation problem (double
localization) in the positioning of the receiver satellite is then pointed out
and discussed in detail.Comment: 16 pages, 9 figures, published (online) in Astrophys. Space Sc
The Metallicity of the Redshift 4.16 Quasar BR2248-1242
We estimate the metallicity in the broad emission-line region of the redshift
z=4.16 quasar, BR2248-1242, by comparing line ratios involving nitrogen to
theoretical predictions. BR2248-1242 has unusually narrow emission lines with
large equivalent widths, thus providing a rare opportunity to measure several
line-ratio abundance diagnostics. The combined diagnostics indicate a
metallicity of ~2 times solar. This result suggests that an episode of vigorous
star formation occurred near BR2248-1242 prior to the observed z=4.16 epoch.
The time available for this enrichment episode is only ~1.5 Gyr at z=4.16 (for
H_{0}=65 km s^-1 Mpc^-1, Omega_{m}=0.3 and Omega_Lambda ~< 1). This evidence
for high metallicities and rapid star formation is consistent with the expected
early-epoch evolution of dense galactic nuclei.Comment: 8 pages, 3 figures. Prepared in AAStex. Submitted to the
Astrophysical Journal Revised version: added 1 referenc
KECK HIRES Spectroscopy of APM 08279+5255
With an optical R-band magnitude of 15.2, the recently discovered z=3.911 BAL
quasar APM 08279+5255 is an exceptionally bright high redshift source. Its
brightness has allowed us to acquire a high signal-to-noise ratio (~100), high
resolution (~6 km/s) spectrum using the HIRES echelle spectrograph on the 10-m
Keck I telescope. Given the quality of the data, these observations provide an
unprecedented view of associated and intervening absorption systems. Here we
announce the availability of this spectrum to the general astronomical
community and present a brief analysis of some of its main features.Comment: 21 pages including 5 figures. Accepted for publication by PAS
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