2,936 research outputs found
Experimental and Predicted Longitudinal and Lateral-Directional Response Characteristics of a Large Flexible 35 Degree Swept-Wing Airplane at an Altitude of 35,000 Feet
Measured and predicted dynamic response characteristics of a large flexible swept-wing airplane to control surface inputs are presented for flight conditions of 0.6 to 0.85 Mach number at an altitude of 35,000 feet. The report is divided into two parts. The first part deals with the response of the airplane to elevator control inputs with principal responses contained in a band of frequencies including the longitudinal short-period mode and several symmetrical structural modes. The second part deals with the response of the airplane to aileron and rudder control inputs with principal responses contained in a band of frequencies including the dutch roll mode, the rolling mode, and three antisymmetrical structural modes
Using Cluster Abundances and Peculiar Velocities to Test the Gaussianity of the Cosmological Density Field
(Abridged) By comparing the frequency of typical events with that of unusual
events, one can test whether the cosmological density distribution function is
consistent with the normally made assumption of Gaussianity. To this end, we
compare the consistency of the tail-inferred (from clusters) and measured
values (from large-scale flows) of the rms level of mass fluctuations for two
distribution functions: a Gaussian, and a texture (positively-skewed) PDF.
Averaging the recent large-scale flow measurements, we find that observations
of the rms and the tail at the 10 h^-1 Mpc scale disfavor a texture PDF at ~1.5
sigma in all cases. However, taking only the most recent measurement of the
rms, that from Willick et al. (1997b), the comparison disfavors textures for
low Omega_0=0.3, and disfavors Gaussian models if Omega_0=1 (again at ~1.5
sigma). Predictions for evolution of high temperature clusters can also be made
for the models considered, and strongly disfavor Omega_0=1 in Gaussian models
and marginally disfavor Omega_0=1 in texture models. Only Omega_0=0.3 Gaussian
models are consistent with all the data considered.Comment: 34 pg incl. 8 embedded figures, LaTeX, aaspp4.sty, submitted to Ap
Mass Profiles of the Typical Relaxed Galaxy Clusters A2199 and A496
We present maps and radial profiles of the gas temperature in the nearby
galaxy clusters A2199 and A496, which have the most accurate ASCA spectral data
for all hot clusters. These clusters are relaxed and can provide reliable X-ray
mass measurements under the assumption of hydrostatic equilibrium. The cluster
average temperatures corrected for the presence of cooling flows are 4.8+-0.2
keV and 4.7+-0.2 keV (90% errors), respectively. Outside the central cooling
flow regions, the radial temperature profiles are similar to those of the
majority of nearby relaxed clusters. They are accurately described by
polytropic models with gamma=1.17+-0.07 for A2199 and gamma=1.24+-0.09 for
A496. We use these polytropic models to derive accurate total mass profiles.
Within r=0.5/h Mpc, which corresponds to a radius of overdensity 1000, the
total mass values are 1.45+-0.15 10^14 /h Msun and 1.55+-0.15 10^14 /h Msun.
These values are 10% lower than those obtained assuming constant temperature.
The values inside a gas core radius (0.07-0.13/h Mpc) are a factor of >1.5
higher than the isothermal values. The gas mass fraction increases with radius
(by a factor of 3 between the X-ray core radius and r_1000) and at r_1000
reaches values of 0.057+-0.005 and 0.056+-0.006 h^-3/2 for the two clusters,
respectively. Our mass profiles within r_1000 are remarkably well approximated
by the NFW "universal" profile. Since A2199 and A496 are typical relaxed
clusters, the above findings should be relevant for most such systems. In
particular, the similarity of the temperature profiles in nearby clusters
appears to reflect the underlying "universal" dark matter profile. The upward
revision of mass at small radii will resolve most of the discrepancy between
the X-ray and strong lensing mass estimates. (Abridged)Comment: Latex, 9 pages, 6 figures, uses emulateapj.sty. Submitted to Ap
The Large-scale and Small-scale Clustering of Lyman-Break Galaxies at 3.5 < z< 5.5 from the GOODS survey
We report on the angular correlation function of Lyman-break galaxies (LBGs)
at z~4 and 5 from deep samples obtained from the Great Observatories Deep
Origins Survey (GOODS). Similar to LBGs at z~3, the shape of w(theta) of the
GOODS LBGs is well approximated by a power-law with slope beta~0.6 at angular
separation theta > 10 arcsec. The clustering strength of z~4, 5 LBGs also
depends on the rest-frame UV luminosity, with brighter galaxies more strongly
clustered than fainter ones, implying a general correlation between halos' mass
and LBGs' star-formation rate. At smaller separations, w(theta) of deep samples
significantly exceeds the extrapolation of the large-scale power-law fit,
implying enhanced spatial clustering at scales r < 1 Mpc. We also find that
bright LBGs statistically have more faint companions on scales theta < 20
arcsec than fainter ones, showing that the enhanced small-scale clustering is
very likely due to sub-structure, namely the fact that massive halos can host
multiple galaxies. A simple model for the halo occupation distribution and the
CDM halo mass function reproduce well the observed w(theta). The scaling
relationship of the clustering strength with volume density and with redshift
is quantitatively consistent with that of CDM halos. A comparison of the
clustering strength of three samples of equal luminosity limit at z ~ 3, 4 and
5 shows that the LBGs at z~5 are hosted in halos about one order of magnitude
less massive than those in the lower redshift bins, suggesting that
star-formation was more efficient at higher-redshift.Comment: replaced with the version accepted for publication in ApJ. 46 pages,
10 figures; minor changes to text, one subsection adde
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