Paper: astro-ph/0602029
Date: Thu, 2 Feb 2006 20:02:50 GMT (217kb)
Title: Multi-scale simulations of merging galaxies with supermassive black
holes
Authors: Lucio Mayer (ETH Zurich), Stelios Kazantzidis (KICP Chicago), Piero
Madau (UC Santa Cruz), Monica Colpi (Universita' Milano-Bicocca), Thomas
Quinn (University of Washington), James Wadsley (McMaster University)
Comments: 7 pages, 3 Figures, extended version of the contributed paper to
appear in the Proceedings of the Conference "Relativistic Astrophysics and
Cosmology - Einstein's Legacy" held in Munich, Germany, November 7-12 2005
\\
We present the results of the first multi-scale N-Body+SPH simulations of
merging galaxies containing central supermassive black holes (SMBHs) and having
a spatial resolution of only a few parsecs. Strong gas inflows associated with
equal-mass mergers produce non-axisymmetric nuclear disks with masses of order
$10^9 M_{\odot}$, resolved by about $10^6$ SPH particles. Such disks have sizes
of several hundred parsecs but most of their mass is concentrated within less
than $50$ pc. We find that a close SMBH pair forms after the merger. The
separation of the two SMBHs then shrinks further owing to dynamical friction
against the predominantly gaseous background. The orbits of the SMBHs decay
down to the minimum resolvable scale in a few million years for an ambient gas
temperature and density typical of a region undergoing a starburst. These
results suggest the initial conditions necessary for the eventual coalescence
of the two holes arise naturally from the merging of two equal-mass galaxies
whose structure and orbits are consistent with the predictions of the
$\Lambda$CDM model. Our findings have important implications for planned
gravitational wave detection experiments such as {\it LISA}.
\\ (
http://arXiv.org/abs/astro-ph/0602029 , 217kb)
Paper: astro-ph/0602043
Date: Thu, 2 Feb 2006 13:58:56 GMT (21kb)
Title: The Source of Mass Accreted by the Central Black Hole in Cooling Flow
Clusters
Authors: Noam Soker (Technion, Israel)
Comments: Submitted to MNRAS
\\
This paper reports the study of the cold-feedback heating in cooling flow
clusters. In the cold-feedback model the mass accreted by the central black
hole originates in non-linear over-dense blobs of gas residing in an extended
region (r ~ 5-30 kpc); these blobs are originally hot, but then cool faster
than their environment and sink toward the center. The intra-cluster medium
(ICM) entropy profile must be shallow for the blobs to reach the center as cold
blobs. I build a toy model to explore the role of the entropy profile and the
population of dense blobs in the cold-feedback mechanism. The mass accretion
rate by the central black hole is determined by the cooling time of the ICM,
the entropy profile, and the presence of inhomogeneities. The mass accretion
rate determines the energy injected by the black hole back to the ICM. These
active galactic nucleus (AGN) outbursts not only heat the ICM, but also change
the entropy profile in the cluster and cause inhomogeneities that are the seeds
of future dense blobs. Therefore, in addition to the ICM temperature (or
energy), the ICM entropy profile and ICM inhomogeneities are also ingredients
in the feedback mechanism.
\\ (
http://arXiv.org/abs/astro-ph/0602043 , 21kb)
Paper: astro-ph/0602047
Date: Thu, 2 Feb 2006 19:16:54 GMT (223kb)
Title: Strangeness in Compact Stars
Authors: Fridolin Weber (San Diego State University), Andreu Torres i Cuadrat
(Universitat Autonoma de Barcelona), Alexander Ho (San Diego State
University), Philip Rosenfield (San Diego State University)
Comments: 26 pages, 13 figures, 29th Johns Hopkins Workshop on current problems
in particle theory: Strong Matter in the Heavens
\\
Astrophysicists distinguish between three different types of compact stars.
These are white dwarfs, neutron stars, and black holes. The former contain
matter in one of the densest forms found in the Universe. This feature,
together with the unprecedented progress in observational astronomy, makes such
stars superb astrophysical laboratories for a broad range of exciting physical
studies. This article studies the role of strangeness for compact star
phenomenology. Strangeness is carried by hyperons, mesons, H-dibaryons, and
strange quark matter, and may leave its mark in the masses, radii, cooling
behavior, surface composition and the spin evolution of compact stars.
\\ (
http://arXiv.org/abs/astro-ph/0602047 , 223kb)