22,353 research outputs found
A New Component in the Radio Continua of PNe
A byproduct of experiments designed to map the CMB is the recent detection of a new component of foreground galactic emission. The anomalous foreground at 10–30 GHz, unexplained by traditional emission mechanisms, correlates with 100 mum dust emission, and is thus presumably due to dust.Is the anomalous foreground ubiquitous in the Galaxy? I will present evidence obtained with the CBI and SIMBA+SEST supporting the existence of the new component in the ISM at large, and in specific objects, in the form of a 31 GHz excess over free-free emission in PNe
Extracting quantum dynamics from genetic learning algorithms through principal control analysis
Genetic learning algorithms are widely used to control ultrafast optical
pulse shapes for photo-induced quantum control of atoms and molecules. An
unresolved issue is how to use the solutions found by these algorithms to learn
about the system's quantum dynamics. We propose a simple method based on
covariance analysis of the control space, which can reveal the degrees of
freedom in the effective control Hamiltonian. We have applied this technique to
stimulated Raman scattering in liquid methanol. A simple model of two-mode
stimulated Raman scattering is consistent with the results.Comment: 4 pages, 5 figures. Presented at coherent control Ringberg conference
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Dynamic stability of a flexible booster subjected to a gimbled, periodically-varying end thrust Technical memorandum no. 104
Dynamic structural behavior of large rocket booster synthesized by two thin-walled cylinders and subjected to periodically varying end thrus
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Lithium and carbon isotopic fractionations between the alteration assemblages of Nakhla and Lafayette
Nakhla and Lafayette delta 7Li values for samples and extracts (4.1-14.2�) are consistent with brine evaporation. Relatively 13C-poor siderite in Lafayette suggests more than one carbon source was sampled
An Empirically Based Calculation of the Extragalactic Infrared Background
Using the excellent observed correlations among various infrared wavebands
with 12 and 60 micron luminosities, we calculate the 2-300 micron spectra of
galaxies as a function of luminosity. We then use 12 micron and 60 micron
galaxy luminosity functions derived from IRAS data, together with recent data
on the redshift evolution of galaxy emissivity, to derive a new, empirically
based IR background spectrum from stellar and dust emission in galaxies. Our
best estimate for the IR background is of order 2-3 nW/m^2/sr with a peak
around 200 microns reaching 6-8 nW/m^2/sr. Our empirically derived background
spectrum is fairly flat in the mid-IR, as opposed to spectra based on modeling
with discrete temperatures which exhibit a "valley" in the mid-IR. We also
derive a conservative lower limit to the IR background which is more than a
factor of 2 lower than our derived flux.Comment: 14 pages AASTeX, 2 .ps figures, the Astrophysical Journal, in pres
First Season QUIET Observations: Measurements of Cosmic Microwave Background Polarization Power Spectra at 43 GHz in the Multipole Range 25 ≤ ℓ ≤ 475
The Q/U Imaging ExperimenT (QUIET) employs coherent receivers at 43 GHz and 94 GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile, to measure the anisotropy in the polarization of the cosmic microwave background (CMB). QUIET primarily targets the B modes from primordial gravitational waves. The combination of these frequencies gives sensitivity to foreground contributions from diffuse Galactic synchrotron radiation. Between 2008 October and 2010 December, over 10,000 hr of data were collected, first with the 19 element 43 GHz array (3458 hr) and then with the 90 element 94 GHz array. Each array observes the same four fields, selected for low foregrounds, together covering ≈1000 deg^2. This paper reports initial results from the 43 GHz receiver, which has an array sensitivity to CMB fluctuations of 69 μK√s. The data were extensively studied with a large suite of null tests before the power spectra, determined with two independent pipelines, were examined. Analysis choices, including data selection, were modified until the null tests passed. Cross-correlating maps with different telescope pointings is used to eliminate a bias. This paper reports the EE, BB, and EB power spectra in the multipole range ℓ = 25-475. With the exception of the lowest multipole bin for one of the fields, where a polarized foreground, consistent with Galactic synchrotron radiation, is detected with 3σ significance, the E-mode spectrum is consistent with the ΛCDM model, confirming the only previous detection of the first acoustic peak. The B-mode spectrum is consistent with zero, leading to a measurement of the tensor-to-scalar ratio of r = 0.35^(+1.06)_(–0.87). The combination of a new time-stream "double-demodulation" technique, side-fed Dragonian optics, natural sky rotation, and frequent boresight rotation leads to the lowest level of systematic contamination in the B-mode power so far reported, below the level of r = 0.1
The COINS Sample - VLBA Identifications of Compact Symmetric Objects
We present results of multifrequency polarimetric VLBA observations of 34
compact radio sources. The observations are part of a large survey undertaken
to identify CSOs Observed in the Northern Sky (COINS). Compact Symmetric
Objects (CSOs) are of particular interest in the study of the physics and
evolution of active galaxies. Based on VLBI continuum surveys of ~2000 compact
radio sources, we have defined a sample of 52 CSOs and CSO candidates. In this
paper, we identify 18 previously known CSOs, and introduce 33 new CSO
candidates. We present continuum images at several frequencies and, where
possible, images of the polarized flux density and spectral index distributions
for the 33 new candidates and one previously known but unconfirmed source. We
find evidence to support the inclusion of 10 of these condidates into the class
of CSOs. Thirteen candidates, including the previously unconfirmed source, have
been ruled out. Eleven sources require further investigation. The addition of
the 10 new confirmed CSOs increases the size of this class of objects by 50%.Comment: 24 pages, incl 8 figures. Accepted for publication in ApJ. Figure
quality degraded in the interests of space, full gzipped PS version also
available at http://www.ee.nmt.edu/~apeck/papers
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