|
FAQ
What is Munch?
|
NOTE SPECIAL
DAY AND TIME! NOON, TUESDAY!
Cluster Mass Estimators from CMB Temperature and Polarization
Lensing astro-ph/0701276
Authors:
Wayne
Hu, Simon
DeDeo (KICP, UChicago), Chris
Vale (FNAL)
Comments: 8 pages, 5 figures, invited original contribution to
gravitational lensing focus issue, New Journal of Physics
Upcoming Sunyaev-Zel'dovich surveys are expected to return ~10^4
intermediate
mass clusters at high redshift. Their average masses must be known to
same
accuracy as desired for the dark energy properties. Internal to the
surveys,
the CMB potentially provides a source for lensing mass measurements
whose
distance is precisely known and behind all clusters. We develop
statistical
mass estimators from 6 quadratic combinations of CMB temperature and
polarization fields that can simultaneously recover large-scale
structure and
cluster mass profiles. The performance of these estimators on idealized
NFW
clusters suggests that surveys with a ~1' beam and 10uK' noise in
uncontaminated temperature maps can make a ~10sigma detection, or
equivalently
a ~10% mass measurement for each 10^3 set of clusters. With internal or
external acoustic scale E-polarization measurements, the ET cross
correlation
estimator can provide a stringent test for contaminants on a first
detection at
\~1/3 the significance. For surveys that reach below 3muK', the EB
cross
correlation estimator should provide the most precise measurements and
potentially the strongest control over contaminants.
Black Hole
Spectacular! 4 papers, plus inks in the popular press:
http://news.yahoo.com/s/space/20070107/sc_space/smallgalaxypacksmassiveblackhole
http://news.yahoo.com/s/space/20070103/sc_space/scientistsspotblackholeinunlikelyplace
http://news.yahoo.com/s/space/20070109/sc_space/blackholetripletsspotted
The Binary Nucleus in VCC 128: A Candidate Supermassive Black
Hole in a Dwarf Elliptical Galaxy astro-ph/0609792 (suggested by Robyn)
Authors:
Victor
P. Debattista (University of Washington, Brooks Fellow), Ignacio
Ferreras (King's College London), Anna
Pasquali (Max-Planck-Institut fur Astronomie), Anil
Seth (University of Washington)
Sven
De Rijcke (Universiteit Gent), Lorenzo
Morelli (Pontificia Universidad Catolica de Chile)
Comments: Accepted to ApJL, 4 pages, 3 figures. Uses emulateapj
{\it Hubble Space Telescope} (\hst) Wide Field Planetary Camera 2 ({\it
WFPC2}) images of the Virgo Cluster dwarf elliptical galaxy VCC 128
reveal an
apparently double nucleus. The two components, which are separated by
$\sim 32$
pc in projection, have the same magnitude and color. We present a
spectrum of
this double nucleus and show that it is inconsistent with one or both
components being emission-line background objects or foreground stars.
The most
likely interpretation is that, as suggested by \citet{lauer_etal_96}
for the
double nucleus in NGC 4486B, we are seeing a nuclear disk surrounding a
supermassive black hole. This is only the second time an early-type
dwarf
(dE/dSph) galaxy has been suggested to host a SMBH.
A black hole in a globular cluster
astro-ph/0701310
Authors:
Thomas
J. Maccarone (University of Southampton)
Arunav
Kundu, Stephen
E. Zepf (Michigan State University)
Katherine
L. Rhode (Wesleyan University and Yale University)
Comments: 11 pages, 1 figure, to appear in 11 January edition of
Nature. Has already appeared in online advance publications section of
Nature. DOI: 10.1038/nature05434
Journal-ref: Nature (2007), 445, 183-185
DOI: 10.1038/nature05434
Globular star clusters contain thousands to millions of old stars
packed
within a region only tens of light years across. Their high stellar
densities
make it very probable that their member stars will interact or collide.
There
has been considerable debate about whether black holes should exist in
these
star clusters. Some theoretical work suggests that dynamical processes
in the
densest inner regions of globular clusters may lead to the formation of
black
holes of ~1,000 solar masses. Other numerical simulations instead
predict that
stellar interactions will eject most or all black holes that form in
globular
clusters. Here we report the X-ray signature of an accreting black hole
in a
spectroscopically-confirmed globular cluster in the Virgo Cluster giant
elliptical galaxy NGC 4472. This object has an X-ray luminosity of
about
4*10^39 ergs/sec, making it brighter than any non-black hole object can
be in
an old stellar population. The X-ray luminosity varies by a factor of 7
in a
few hours, ruling out the possibility that the object is several
neutron stars
superposed.
Discovery of a Probable Physical Triple Quasar
astro-ph/0701155
Authors:
S.G.
Djorgovski, F.
Courbin, G.
Meylan, D.
Sluse, D.J.
Thompson, A.
Mahabal, E.
Glikman
Comments: Submitted to ApJL, LaTeX, 13 pages, 4 eps figures, all
included
We report the discovery of the first known probable case of a physical
triple
quasar (not a gravitational lens). A previously known double system, QQ
1429-008 at z = 2.076, is shown to contain a third, fainter QSO
component at
the same redshift within the measurement errors. Deep optical and IR
imaging at
the Keck and VLT telescopes has failed to reveal a plausible lensing
galaxy
group or a cluster, and moreover, we are unable to construct any viable
lensing
model which could lead to the observed distribution of source positions
and
relative intensities of the three QSO image components. Furthermore,
there are
hints of differences in broad-band spectral energy distributions of
different
components, which are more naturally understood if they are physically
distinct
AGN. Therefore, we conclude that this system is most likely a physical
triple
quasar, the first such close QSO grouping known at any redshift. The
projected
component separations in the restframe are ~ 30 - 50 kpc for the
standard
concordance cosmology, typical of interacting galaxy systems. The
existence of
this highly unusual system supports the standard picture in which
galaxy
interactions lead to the onset of QSO activity.
Black Hole Cross Section at the Large Hadron Collider
hep-ph/0609055 (suggested by Mark)
Authors:
Douglas
M. Gingrich
Comments: 28 pages, 9 figures, LaTeX; added references, corrected
typos, expanded discussion
Black hole production at the Large Hadron Collider (LHC) was first
discussed
in 1999. Since then, much work has been performed in predicting the
black hole
cross section. In light of the start up of the LHC, it is now timely to
review
the state of these calculations. We review the uncertainties in
estimating the
black hole cross section in higher dimensions. One would like to make
this
estimate as precise as possible since the predicted values, or lower
limits,
obtain for the fundamental Planck scale and number of extra dimensions
from
experiments will depend directly on the accuracy of the cross section.
Based on
the current knowledge of the cross section, we give a range of lower
limits on
the fundamental Planck scale that could be obtained at LHC energies.
Can large-scale structure probe CMB-constrained
non-Gaussianity?
astro-ph/0701131 (suggested by Emiliano)
Authors:
X.
Kang, P.
Norberg, J.
Silk
Comments: 5 Pages, 5 Figures; accepted for publication in MNRAS
The first year Wilkinson Microwave Anisotropy Probe (WMAP) set
quantitative
constraints on the amplitude of any primordial non-Gaussianity. We run
a series
of dark matter-only N-body simulations with the WMAP constraints to
investigate
the effect of the presence of primordial non-Gaussianity on large scale
structures. The model parameters can be constrained using the
observations of
protoclusters associated with Ly-$\alpha$ emitters at high redshift ($2
\leq z
\leq 4$), assuming the galaxy velocity bias can be modelled properly.
High
redshift structure formation potentially provides a more powerful test
of
possible primordial non-Gaussianity than does the CMB, albeit on
smaller
scales. Another constraint is given by the local galaxy density
probability
distribution function (PDF), as mapped by the 2 degree Field Galaxy
Redshift
Survey (2dFGRS). The PDF of 2dFGRS \lstar galaxies is substantially
higher than
the standard model predictions and requires either a non-negligible
bias
between galaxy and dark matter on $\sim 12$~\hmpc scales or a stronger
non-Gaussianity than allowed by the WMAP year one data. The latter
interpretation is preferred since second-order bias corrections are
negative.
With a lower normalisation of the power spectrum fluctuations,
sigma_8=0.74, as
favoured by the WMAP 3 year data, the discrepancy between the Gaussian
model
and the data is even larger.
Dark matter from late decays and the small-scale structure
problems hep-ph/0701007
(suggested by Dan)
Authors:
Torsten
Bringmann, Francesca
Borzumati, Piero
Ullio
Comments: 15 pages revtex4 style; 10 figures
The generation of dark matter in late decays of quasi-stable massive
particles has been proposed as a viable framework to address the excess
of
power found in numerical N-body simulations for cold dark matter
cosmologies.
We identify a convenient set of variable to illustrate which
requirements need
to be satisfied in any generic particle physics model to address the
small
scale problems and fulfill other astrophysical constraints. We
re-examine the
role of gravitinos and Kaluza-Klein gravitons in this context and find
them
disfavoured as a solution to the small-scale problems in case they are
DM
candidates generated in the decay of thermally produced WIMPs. We
propose
right-handed sneutrinos and right-handed Kaluza-Klein neutrinos as
alternatives. We find that they are viable dark matter candidates, but
that
they can contribute to a solution of the small scale problems only in
case the
associated Dirac neutrino mass term appears as a subdominant
contribution in
the neutrino mass matrix.
Dark energy from cosmological neutrino
condensation
astro-ph/0701212 (suggested by Scott)
Authors:
H. J.
de Vega
Comments: 25 pages, 2 figures
We show here that cosmological neutrino condensation provides a
continuous
energy distribution able to reproduce the observed dark energy. The
neutrino
evolution is solved as a field theory initial value problem in
cosmological
spacetime for times after neutrino decoupling. Physical quantities are
subtracted in order to eliminate ultraviolet divergences. The
subtractions
respect the symmetries of the theory and we normalize them such that
the
physical quantities are zero in Minkowski space-time.The lightest
neutrino mass
has to be 0.0033 eV for Dirac neutrinos [and 0.0039 eV for Majorana
neutrinos]
in order to reproduce the observed dark energy.The two heavier
neutrinos should
annihilate with their respective anti-neutrinos in the time scale of
the age of
the universe. We find a dark matter equation of state with a
logarithmic
dependence in the redshift w(z) = -1 - 1/\{3 [21.8 - log(1+z)]} and
w(0) =
-1.015...These formulas only depend on the ratio of the neutrino
temperatures
at decoupling and today. Dark energy arises from neutrino condensation
in FRW
cosmological space-time in an analogous way to the Casimir effect in
Minkowski
space-time with non-trivial boundaries.
Hints of Isocurvature Perturbations in the Cosmic Microwave
Background astro-ph/0611917 (suggested by Pasquale)
Authors: Reijo
Keskitalo (HIP and Helsinki U.), Hannu
Kurki-Suonio (Helsinki U.), Vesa
Muhonen (HIP and Helsinki U.), Jussi
Valiviita (ICG, Portsmouth)
Comments: 4 pages, 2 figures, revtex4 format
Report-no: HIP-2006-52/TH, ICG 06/43
The improved data on the cosmic microwave background
(CMB) anisotropy
allows
a better determination of the adiabaticity of the primordial
perturbation.
Interestingly, we find that the CMB favors a significant contribution
of a
primordial isocurvature mode where the entropy perturbation is
positively
correlated with the primordial curvature perturbation and has a large
spectral
index (n_iso ~ 3). With 4 additional parameters we obtain a better fit
to the
CMB data by \Delta\chi^2 = 9.4 compared to an adiabatic model. At more
than 95%
C.L., the nonadiabatic contribution to the CMB temperature variance is
nonzero;
indeed positive. For the best-fit model it is 4%.
|
|