10,968 research outputs found
Constraints on jet formation mechanisms with the most energetic giant outbursts in MS 0735+7421
Giant X-ray cavities lie in some active galactic nuclei (AGNs) locating in
central galaxies of clusters, most of these cavities are thought to be inflated
by jets of AGNs. The jets can be either powered by rotating black holes or the
accretion disks surrounding black holes, or both. In this work, we choose the
most energetic cavity, MS 0735+7421, with stored energy ~ 10^62 erg, to
constrain the jet formation mechanisms and the evolution of the central massive
black hole in this source. The bolometric luminosity of the AGN in this cavity
is ~ 10^(-5) L_Edd, however, the mean power of the jet required to inflate the
cavity is estimated as ~ 0.02 L_Edd, which implies that the source has
experienced strong outbursts previously. During outbursts, the jet power and
the mass accretion rate should be significantly higher than its present values.
We construct an accretion disk model, in which the angular momentum and energy
carried away by jets is properly included, to calculate the spin and mass
evolution of the massive black hole. In our calculations, different jet
formation mechanisms are employed, and we find that the jets generated with the
Blandford-Znajek (BZ) mechanism are unable to produce the giant cavity with ~
10^62 erg in this source. Only the jets accelerated with the combination of the
Blandford-Payne (BP) and BZ mechanisms can successfully inflate such a giant
cavity, if the magnetic pressure is close to equipartition with the total
(radiation+gas) pressure of the accretion disk. For dynamo generated magnetic
field in the disk, such an energetic giant cavity can be inflated by the
magnetically driven jets only if the initial black hole spin parameter a_0 >
0.95. Our calculations show that the final spin parameter a of the black hole
is always ~ 0:9 - 0.998 for all the computational examples which can provide
sufficient energy for the cavity of MS 0735+7421.Comment: 25 pages, 8 figures, accepted by Ap
Thermodynamics of static dyonic AdS black holes in the -deformed Kaluza-Klein gauged supergravity theory
We study thermodynamical properties of static dyonic AdS black holes in
four-dimensional -deformed Kaluza-Klein gauged supergravity theory, and
find that the differential first law requires a modification via introducing a
new pair of thermodynamical conjugate variables (X, Y). To ensure such a
modification, we then apply the quasi-local ADT formalism developed in Ref.
[20] to calculate the quasi-local conserved charge and identify that the new
pair is precisely the one previously introduced to modify the differential form
of first law.Comment: 13 pages, no figure, elsarticle.cls, updated version to match with
the published pape
Impacts of different SNLS3 light-curve fitters on cosmological consequences of interacting dark energy models
We explore the cosmological consequences of interacting dark energy (IDE)
models using the SNLS3 supernova samples. In particular, we focus on the
impacts of different SNLS3 light-curve fitters (LCF) (corresponding to "SALT2",
"SiFTO", and "Combined" sample). Firstly, making use of the three SNLS3 data
sets, as well as the Planck distance priors data and the galaxy clustering
data, we constrain the parameter spaces of three IDE models. Then, we study the
cosmic evolutions of Hubble parameter , deceleration diagram ,
statefinder hierarchy and , and check whether or
not these dark energy diagnosis can distinguish the differences among the
results of different SNLS3 LCF. At last, we perform high redshift cosmic age
test using three old high redshift objects (OHRO), and explore the fate of the
Universe. We find that, the impacts of different SNLS3 LCF are rather small,
and can not be distinguished by using , , ,
, and the age data of OHRO. In addition, we infer, from the
current observations, how far we are from a cosmic doomsday in the worst case,
and find that the "Combined" sample always gives the largest 2 lower
limit of the time interval between "big rip" and today, while the results given
by the "SALT2" and the "SiFTO" sample are close to each other. These
conclusions are insensitive to a specific form of dark sector interaction. Our
method can be used to distinguish the differences among various cosmological
observations.Comment: 12 pages, 7 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
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