21,261 research outputs found
Dissecting the quasar main sequence: insight from host galaxy properties
The diverse properties of broad-line quasars appear to follow a well-defined
main sequence along which the optical FeII strength increases. It has been
suggested that this sequence is mainly driven by the Eddington ratio (L/L_Edd)
of the black hole (BH) accretion. Shen & Ho demonstrated with quasar clustering
analysis that the average BH mass decreases with increasing FeII strength when
quasar luminosity is fixed, consistent with this suggestion. Here we perform an
independent test by measuring the stellar velocity dispersion sigma* (hence the
BH mass via the M-sigma* relation) from decomposed host spectra in low-redshift
Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity,
sigma* systematically decreases with increasing FeII strength, confirming that
Eddington ratio increases with FeII strength. We also found that at fixed
luminosity and FeII strength, there is little dependence of sigma* on the broad
Hbeta FWHM. These new results reinforce the framework put forward by Shen & Ho
that Eddington ratio and orientation govern most of the diversity seen in
broad-line quasar properties.Comment: ApJL in press; 5 pages and 4 figure
Precise photoproduction of the charged top-pions at the LHC with forward detector acceptances
We study the photoproduction of the charged top-pion predicted by the top
triangle moose () model (a deconstructed version of the topcolor-assisted
technicolor model) via the processes at the 14 Large Hadron Collider ()
including next-to-leading order () corrections. Our results show
that the production cross sections and distributions are sensitive to the free
parameters and . Typical correction value is and does not depend much on as well as the forward
detector acceptances.Comment: 21pages, 7figures. arXiv admin note: text overlap with
arXiv:1201.4364 by other author
Stable Large-Scale Perturbations in Interacting Dark-Energy Model
It is found that the evolutions of density perturbations on the super-Hubble
scales are unstable in the model with dark-sector interaction proportional
to the energy density of cold dark matter (CDM) and constant equation
of state parameter of dark energy . In this paper, to avoid the
instabilities, we suggest a new covariant model for the energy-momentum
transfer between DE and CDM. Then we show that the the large-scale
instabilities of curvature perturbations can be avoided in our model in the
universe filled only by DE and CDM. Furthermore, by including the additional
components of radiation and baryons, we calculate the dominant non-adiabatic
modes in the radiation era and find that the modes grow in the power law with
exponent at the order of unit.Comment: 14 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:1110.180
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