85,035 research outputs found
Blind Detections of CO J = 1–0 in 11 H-ATLAS Galaxies at z = 2.1–3.5 with the GBT/Zpectrometer
We report measurements of the carbon monoxide ground state rotational transition (^(12)C^(16)O J = 1-0) with the Zpectrometer ultrawideband spectrometer on the 100 m diameter Green Bank Telescope. The sample comprises 11 galaxies with redshifts between z = 2.1 and 3.5 from a total sample of 24 targets identified by Herschel-ATLAS photometric colors from the SPIRE instrument. Nine of the CO measurements are new redshift determinations, substantially adding to the number of detections of galaxies with rest-frame peak submillimeter emission near 100 μm. The CO detections confirm the existence of massive gas reservoirs within these luminous dusty star-forming galaxies (DSFGs). The CO redshift distribution of the 350 μm selected galaxies is strikingly similar to the optical redshifts of 850 μm-selected submillimeter galaxies in 2.1 ≤ z ≤ 3.5. Spectroscopic redshifts break a temperature-redshift degeneracy; optically thin dust models fit to the far-infrared photometry indicate characteristic dust temperatures near 34 K for most of the galaxies we detect in CO. Detections of two warmer galaxies, and statistically significant nondetections, hint at warmer or molecule-poor DSFGs with redshifts that are difficult to determine from Herschel-SPIRE photometric colors alone. Many of the galaxies identified by H-ATLAS photometry are expected to be amplified by foreground gravitational lenses. Analysis of CO linewidths and luminosities provides a method for finding approximate gravitational lens magnifications μ from spectroscopic data alone, yielding μ ~ 3-20. Corrected for magnification, most galaxy luminosities are consistent with an ultraluminous infrared galaxy classification, but three are candidate hyper-LIRGs with luminosities greater than 10^(13) L_☉
Pwning Level Bosses in MATLAB: Student Reactions to a Game-Inspired Computational Physics Course
We investigated student reactions to two computational physics courses
incorporating several videogame-like aspects. These included use of gaming
terminology such as "levels," "weapons," and "bosses"; a game-style point
system linked to course grades; a self-paced schedule with no deadlines; a
mastery design in which only entirely correct attempts earn credit, but
students can retry until they succeed; immediate feedback via self-test code;
an assignment progression from "minions" (small, focused tasks) to "level
bosses" (integrative tasks); and believable, authentic assignment scenarios.
Through semi-structured interviews and course evaluations, we found that a
majority of students considered the courses effective and the game-like aspects
beneficial. In particular, many claimed that the point system increased their
motivation; the self-paced nature caused them to reflect on their
self-discipline; the possibility and necessity of repeating assignments until
perfect aided learning; and the authentic tasks helped them envision using
course skills in their professional futures.Comment: Accepted for publication in the proceedings of the 2014 Physics
Education Research Conference (PERC
Measurement of the derivative 'ZW' for an oscillating aerofoil
This report presents the results of experimental
measurements of the damping derivative coefficient zw for
constant chord rigid wings of various aspect ratios having
sweepback angles of zero and 450.
The results for the rectangular wings Flow substantial
agreement with the unsteady aerofoil theory developed
by TI.P. Jones $2) The dependence of Zvi upon frequency parameter
is as given by theory and is much less than for two dimensional
flow, but the numerical results are approximately
10 per cent below the theoretical. This is attributed to the
large trailing edge angle 22° of the N.A.C.A. 0020 section
used for the model aerofoils.
The effect of sweepback is to decrease the numerical
value of z , but this effect is much less pronounced, for low
than for high aspect ratios. For aspect ratios 5 and 3
the numerical value is greater than would be given by a factor
of proportionality equal to the cosine of the angle of
sweepback.
The measurements were corrected for tunnel interference
by a method based on the theoretical work of 7.P.Jones.(1
X-ray Emission from the Radio Jet in 3C 120
We report the discovery of X-ray emission from a radio knot at a projected
distance of 25" from the nucleus of the Seyfert galaxy, 3C 120. The data were
obtained with the ROSAT High Resolution Imager (HRI). Optical upper limits for
the knot preclude a simple power law extension of the radio spectrum and we
calculate some of the physical parameters for thermal bremsstrahlung and
synchrotron self-Compton models. We conclude that no simple model is consistent
with the data but if the knot contains small regions with flat spectra, these
could produce the observed X-rays (via synchrotron emission) without being
detected at other wavebands.Comment: 6 pages latex plus 3 ps/eps figures. Uses 10pt.sty and
emulateapj.sty. Accepted for publication in the ApJ (6 Jan 99
Spine-sheath layer radiative interplay in subparsec-scale jets and the TeV emission from M87
Simple one-zone homogeneous synchrotron self-Compton models have severe
difficulties in explaining the TeV emission observed in the radiogalaxy M87.
Also the site of the TeV emission region is uncertain: it could be the
unresolved jet close to the nucleus, analogously to what proposed for blazars,
or an active knot, called HST-1, tens of parsec away. We explore the
possibility that the TeV emission of M87 is produced in the misaligned subpc
scale jet. We base our modelling on a structured jet, with a fast spine
surrounded by a slower layer. In this context the main site responsible for the
emission of the TeV radiation is the layer, while the (debeamed) spine accounts
for the emission from the radio to the GeV band: therefore we expect a more
complex correlation with the TeV component than that expected in one-zone
scenarios, in which both components are produced by the same region. Observed
from small angles, the spine would dominate the emission, with an overall
Spectral Energy Distribution close to those of BL Lac objects with a
synchrotron peak located at low energy (LBLs).Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letter
Static longitudinal aerodynamic characteristics of a hammerhead-shaped Little Joe II - Lunar module model at Mach 0.30 to 1.20
Static longitudinal aerodynamic characteristics of 0.03 scale model of hammerhead-shaped Little Joe II /lunar module suborbital space vehicle/ over Mach number 0.30 to 1.20 rang
Structural parameters for globular clusters in M31 and generalizations for the fundamental plane
The structures of globular clusters (GCs) reflect their dynamical states and
past histories. High-resolution imaging allows the exploration of morphologies
of clusters in other galaxies. Surface brightness profiles from new Hubble
Space Telescope observations of 34 globular clusters in M31 are presented,
together with fits of several different structural models to each cluster. M31
clusters appear to be adequately fit by standard King models, and do not
obviously require alternate descriptions with relatively stronger halos, such
as are needed to fit many GCs in other nearby galaxies. The derived structural
parameters are combined with corrected versions of those measured in an earlier
survey to construct a comprehensive catalog of structural and dynamical
parameters for M31 GCs with a sample size similar to that for the Milky Way.
Clusters in M31, the Milky Way, Magellanic Clouds, Fornax dwarf spheroidal and
NGC 5128 define a very tight fundamental plane with identical slopes. The
combined evidence for these widely different galaxies strongly reinforces the
view that old globular clusters have near-universal structural properties
regardless of host environment.Comment: AJ in press; 59 pages including 16 figure
Impact of flying qualities on mission effectiveness for helicopter air combat, volume 1
A computer simulation to investigate the impact of flying qualities on mission effectiveness is described. The objective of the study was to relate the effects of flying qualities, such as precision of flight path control and pilot workload, to the ability of a single Scout helicopter, or helicopter team, to accomplish a specified anti-armor mission successfully. The model of the actual engagement is a Monte Carlo simulation that has the capability to assess the effects of helicopter characteristics, numbers, tactics and weaponization on the force's ability to accomplish a specific mission against a specified threat as a function of realistic tactical factors. A key feature of this program is a simulation of micro-terrain features and their effects on detection, exposure, and masking for nap-of-the-earth (NOE) flight
X-ray variability in M87
We present the evidence for X-ray variability from the core and from knot A
in the M87 jet based on data from two observations with the Einstein
Observatory High Resolution Imager (HRI) and three observations with the ROSAT
HRI. The core intensity showed a 16% increase in 17 months ('79-'80); a 12%
increase in the 3 years '92 to '95; and a 17% drop in the last half of 1995.
The intensity of knot A appears to have decreased by 16% between 92Jun and
95Dec. Although the core variability is consistent with general expectations
for AGN nuclei, the changes in knot A provide constraints on the x-ray emission
process and geometry. Thus we predict that the x-ray morphology of knot A will
differ significantly from the radio and optical structure.Comment: 9 pages latex plus 6 ps figs. To appear in Monthly Notices of the RA
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