4,466 research outputs found
EXPLANATION OF THE BASIC FORMULA PRICE PROVISIONS OF THE PROPOSED RULE
An important segment of milk marketing order reform involves replacing the current BFP. This working paper explains the background of the BFP issue, the options considered and the provisions of the proposed rule as related to the BFP issue.Marketing,
Discovery of dumbbell-shaped Cs*He_n exciplexes in solid He 4
We have observed several new spectral features in the fluorescence of cesium
atoms implanted in the hcp phase of solid helium following laser excitation to
the 6P states. Based on calculations of the emission spectra using
semiempirical Cs-He pair potentials the newly discovered lines can be assigned
to the decay of specific Cs*He exciplexes: an apple-shaped CsHe and a dumbbell-shaped CsHe exciplex with
a well defined number of bound helium atoms. While the former has been
observed in other enviroments, it was commonly believed that exciplexes with
might not exist. The calculations suggest CsHe to be
the most probable candidate for that exciplex, in which the helium atoms are
arranged on a ring around the waist of the dumbbell shaped electronic density
distribution of the cesium atom.Comment: 4 pages, 4 figure
Red Quasars and Quasar Evolution: the Case of BALQSO FIRST J155633.8+351758
We present the first near-IR spectroscopy of the z=1.5 radio-loud BALQSO
FIRST J155633.8+351758. Both the Balmer decrement and the slope of the
rest-frame UV-optical continuum independently suggest a modest amount of
extinction along the line of sight to the BLR (E(B-V)~0.5 for SMC-type screen
extinction at the QSO redshift). The implied gas column density along the line
of sight is much less than is implied by the weak X-ray flux of the object,
suggesting that either the BLR and BAL region have a low dust-to-gas ratio, or
that the rest-frame optical light encounters significantly lower mean column
density lines of sight than the X-ray emission. From the rest-frame UV-optical
spectrum, we are able to constrain the stellar mass content of the system.
Comparing the maximal stellar mass with the black hole mass estimated from the
bolometric luminosity of the QSO, we find that the ratio of the black hole to
stellar mass may be comparable to the Magorrian value, which would imply that
the Magorrian relation is already in place at z=1.5. However, multiple factors
favor a much larger black hole to stellar mass ratio. This would imply that if
the Magorrian relation characterizes the late history of QSOs, and the
situation observed for F1556+3517 is typical of the early evolutionary history
of QSOs, central black hole masses develop more rapidly than bulge masses.
[ABRIDGED]Comment: 23 pages, 4 embedded postscript figures; Accepted for publication in
The Astronomical Journal, December 200
X-ray properties of the Parkes sample of flat-spectrum radio sources: dust in radio-loud quasars?
We investigate the X-ray properties of the Parkes sample of flat-spectrum
radio sources using data from the ROSAT All-Sky Survey and archival pointed
PSPC observations. In total, 163 of the 323 sources are detected. For the
remaining 160 sources 2 sigma upper limits to the X-ray flux are derived. We
present power-law photon indices for 115 sources, which were either determined
with a hardness ratio technique or from direct fits to pointed PSPC data. For
quasars, the soft X-ray photon index is correlated with redshift and with radio
spectral index. Webster et al. (1995) discovered many sources with unusually
red optical continua among the quasars of this sample and interpreted this
result in terms of extinction by dust. Although the X-ray spectra in general do
not show excess absorption, we find that low-redshift optically red quasars
have significantly lower soft X-ray luminosities on average than objects with
blue optical continua. The difference disappears for higher redshifts, as is
expected for intrinsic absorption by cold gas associated with the dust.
Alternative explanations are briefly discussed. We conclude, however, that dust
does play an important role in some of the radio-loud quasars with red optical
continua.Comment: 21 pages, 13 figures, to appear in MNRA
Detection of x-rays from galaxy groups associated with the gravitationally lensed systems PG 1115+080 and B1422+231
Gravitational lenses that produce multiple images of background quasars can
be an invaluable cosmological tool. Deriving cosmological parameters, however,
requires modeling the potential of the lens itself. It has been estimated that
up to a quarter of lensing galaxies are associated with a group or cluster
which perturbs the gravitational potential. Detection of X-ray emission from
the group or cluster can be used to better model the lens. We report on the
first detection in X-rays of the group associated with the lensing system PG
1115+080 and the first X-ray image of the group associated with the system
B1422+231. We find a temperature and rest-frame luminosity of 0.8 +/- 0.1 keV
and 7 +/- 2 x 10^{42} ergs/s for PG 1115+080 and 1.0 +infty/-0.3 keV and 8 +/-
3 x 10^{42} ergs/s for B1422+231. We compare the spatial and spectral
characteristics of the X-ray emission to the properties of the group galaxies,
to lens models, and to the general properties of groups at lower redshift.Comment: Accepted for publication in ApJ. 17 pages, 5 figures. Minor changes
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