9,008 research outputs found
Effects of surface crossing in chemical reactions - The H3/plus/ system
Potential energy surfaces for singlet states of H3/plus
The Velocity Field from Type Ia Supernovae Matches the Gravity Field from Galaxy Surveys
We compare the peculiar velocities of nearby SNe Ia with those predicted by
the gravity fields of full sky galaxy catalogs. The method provides a powerful
test of the gravitational instability paradigm and strong constraints on the
density parameter beta = Omega^0.6/b. For 24 SNe Ia within 10,000 km/s we find
the observed SNe Ia peculiar velocities are well modeled by the predictions
derived from the 1.2 Jy IRAS survey and the Optical Redshift Survey (ORS). Our
best is 0.4 from IRAS, and 0.3 from the ORS, with beta>0.7 and
beta<0.15 ruled out at 95% confidence levels from the IRAS comparison.
Bootstrap resampling tests show these results to be robust in the mean and in
its error. The precision of this technique will improve as additional nearby
SNe Ia are discovered and monitored.Comment: 16 pages (LaTex), 3 postscript figure
The Correlation Between Galaxy HI Linewidths and K' Luminosities
The relationship between galaxy luminosities and rotation rates is studied
with total luminosities in the K' band. Extinction problems are essentially
eliminated at this band centered at 2.1 micron. A template luminosity-linewidth
relation is derived based on 65 galaxies drawn from two magnitude-limited
cluster samples. The zero-point is determined using 4 galaxies with accurately
known distances. The calibration is applied to give the distance to the Pisces
Cluster (60 Mpc) at a redshift in the CMB frame of 4771 km/s. The resultant
value of the Hubble Constant is 81 km/s/Mpc. The largest sources of uncertainty
arises from the small number of zero-point calibrators at this time at K' and
present application to only one cluster.Comment: 13 pages including 5 figures and 2 tables. Accepted for publication
in Astrophysical Journa
A Face-On Tully-Fisher Relation
We construct the first "face-on" Tully-Fisher (TF) relation for 24 galaxies
with inclinations between 16 degrees and 41 degrees. The enabling measurements
are integral-field, echelle spectroscopy from the WIYN 3.5m telescope, which
yield accurate kinematic estimates of disk inclination to 15 degrees. Kinematic
inclinations are of sufficient accuracy that our measured TF scatter of 0.42
mag is comparable to other surveys even without internal-absorption
corrections. Three of four galaxies with significant kinematic and photometric
asymmetries also have the largest deviations from our TF relation, suggesting
that asymmetries make an important contribution to TF scatter. By measuring
inclinations below 40 degrees, we establish a direct path to linking this
scatter to the unprojected structure of disks and making non-degenerate
dynamical mass-decompositions of spiral galaxies.Comment: 13 pages, 3 figures (2 color). Accepted for publication in ApJ
Letter
Who Is Exposed to News? It Depends on How You Measure: Examining Self-Reported Versus Behavioral News Exposure Measures
Despite the importance of news exposure to political outcomes, news consumption is notoriously difficult to measure, and misreporting news exposure is common. In this study, we compare participants' news behaviors measured on a news aggregator website with their self-reported story selection immediately after exposure. We find that both individual and contextual characteristics - especially the presence of political cues in news headlines - influence reporting of news story selection. As a result, the news audience profiles differ using self-reported versus behavioral measures, creating two different pictures of news exposure. More attention is needed to improve news measurement strategies to address misreporting and to improve the accuracy of news audience profiles
The Structure of Dark Matter Haloes in Dwarf Galaxies
Recent observations indicate that dark matter haloes have flat central
density profiles. Cosmological simulations with non-baryonic dark matter
predict however self similar haloes with central density cusps. This
contradiction has lead to the conclusion that dark matter must be baryonic.
Here it is shown that the dark matter haloes of dwarf spiral galaxies represent
a one parameter family with self similar density profiles. The observed global
halo parameters are coupled with each other through simple scaling relations
which can be explained by the standard cold dark matter model if one assumes
that all the haloes formed from density fluctuations with the same primordial
amplitude. We find that the finite central halo densities correlate with the
other global parameters. This result rules out scenarios where the flat halo
cores formed subsequently through violent dynamical processes in the baryonic
component. These cores instead provide important information on the origin and
nature of dark matter in dwarf galaxies.Comment: uuencoded Z-compressed postscript file, 10 pages, 3 figures included,
to appear in ApJ Letter
Empowering Users to Respond to Misinformation about Covid-19
The World Health Organization has declared that misinformation shared on social media about Covid-19 is an “infodemic” that must be fought alongside the pandemic itself. We reflect on how news literacy and science literacy can provide a foundation to combat misinformation about Covid-19 by giving social media users the tools to identify, consume, and share high-quality information. These skills can be put into practice to combat the infodemic by amplifying quality information and actively correcting misinformation seen on social media. We conclude by considering the extent to which what we know about these literacies and related behaviors can be extended to less-researched areas like the Global South
The Principal Axis of the Virgo Cluster
Using accurate distances to individual Virgo cluster galaxies obtained by the
method of Surface Brightness Fluctuations, we show that Virgo's brightest
ellipticals have a remarkably collinear arrangement in three dimensions. This
axis, which is inclined by 10 to 15 degrees from the line of sight, can be
traced to even larger scales where it appears to join a filamentary bridge of
galaxies connecting Virgo to the rich cluster Abell 1367. The orientations of
individual Virgo ellipticals also show some tendency to be aligned with the
cluster axis, as does the jet of the supergiant elliptical M87. These results
suggest that the formation of the Virgo cluster, and its brightest member
galaxies, have been driven by infall of material along the Virgo-A1367
filament.Comment: 8 pages, 4 figures, accepted for publication in ApJ Letter
On the kinematics of the Local cosmic void
We collected the existing data on the distances and radial velocities of
galaxies around the Local Void in the Aquila/Hercules to examine the peculiar
velocity field induced by its underdensity. A sample of 1056 galaxies with
distances measured from the Tip of the Red Giant Branch, the Cepheid
luminosity, the SNIa luminosity, the surface brightness fluctuation method, and
the Tully-Fisher relation has been used for this purpose. The amplitude of
outflow is found to be ~300 km/s. The galaxies located within the void produce
the mean intra-void number density about 1/5 of the mean external number
density of galaxies. The void's population has a lower luminosity and a later
morphological type with the medians: M_B = -15.7^m and T = 8 (Sdm),
respectively.Comment: Version 1. 14 pages, 8 figures, 2 tables. Accepted to Astrophysics,
Volume 54, Issue
Quantifying the value of problem structuring interventions?
We review the current work on measuring and evaluating PSM interventions and return to the paradox of trying to determine a specific monetary value. In an attempt to resolve the paradox, we have borrowed freely from economic theory and constructed a scenario where the question of value can be investigated through the effect that a problem structuring intervention will have on information asymmetry in contract formation. This suggests an avenue of research where the value of problem structuring interventions can be investigated empirically. We discuss the difficulties of research design to investigate this question but also the potential benefits.European Commissio
- …