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arXiv:0704.3426
(cross-list from hep-th) [ps,
pdf, other] :
Title: Large Nongaussianity from Nonlocal Inflation
Authors:
N.
Barnaby, J.M.
Cline
We study the
possibility of obtaining large nongaussian signatures in the Cosmic
Microwave
Background in a general class of single-field nonlocal hill-top
inflation models. We estimate the
nonlinearity parameter f_{NL} which characterizes nongaussianity in
such models and show that
large nongaussianity is possible. For the recently proposed p-adic
inflation model we find that
f_{NL} ~ 120 when the string coupling is order unity. We show that
large nongaussianity is also
possible in a toy model with an action similar to those which arise in
string field theory.
arXiv:0704.2783
[ps, pdf, other] :
Title: Nonlinear Evolution of Baryon Acoustic Oscillations
Authors:
M.
Crocce, R.
Scoccimarro
Comments: 18 pages, 8 figures, submitted to Phys. Rev. D
We study the nonlinear evolution of the baryon acoustic signature in
the dark matter power
spectrum and correlation function using renormalized perturbation
theory (RPT). In a previous
paper we showed that RPT successfully predicts the damping of acoustic
oscillations; here we
extend our calculation to the enhancement of power due to
mode-coupling, showing that this
typically leads to percent-level shifts in the acoustic peak of the
two-point correlation function.
We present predictions for this shift as a function of redshift; these
should be considered as a
robust lower limit to the more realistic case that includes in addition
redshift distortions and
galaxy bias. We show that these nonlinear effects occur at very large
scales, leading to a
breakdown of linear theory at scales much larger than commonly thought.
We discuss why
virialized halo profiles are not responsible for these effects, which
can be understood from basic
physics of gravitational instability. Our results are in excellent
agreement with numerical
simulations, and can be used as a starting point for modeling these
effects in future
observations. To meet this end, we suggest a simple physically
motivated model to correct for
the shifts caused by mode-coupling.
arXiv:0704.3377 [ps, pdf, other] :
Title: Halo-model signatures from 380,000 SDSS Luminous Red
Galaxies with photometric redshifts
Authors:
Chris
Blake, Adrian
Collister, Ofer
Lahav
Comments: 14 pages, 10 figures, accepted by MNRAS
We analyze the
small-scale clustering in "MegaZ-LRG", a large photometric-redshift
catalogue of
Luminous Red Galaxies extracted from the imaging dataset of the Sloan
Digital Sky Survey.
MegaZ-LRG, presented in a companion paper, spans the redshift range 0.4
< z < 0.7 with an
r.m.s. redshift error dz ~ 0.03(1+z), covering 5,914 deg^2 to map out a
total cosmic volume
2.5 h^-3 Gpc^3. In this study we use 380,000 photometric redshifts to
measure significant
deviations from the canonical power-law fit to the angular correlation
function in a series of
narrow redshift slices, in which we construct volume-limited samples.
These deviations are
direct signatures of the manner in which these galaxies populate the
underlying network of dark
matter haloes. We cleanly delineate the separate contributions of the
"1-halo" and "2-halo"
clustering terms and fit our measurements by parameterizing the halo
occupation distribution
N(M) of the galaxies. Our results are successfully fit by a "central"
galaxy contribution with a
"soft" transition from zero to one galaxies, combined with a power-law
"satellite" galaxy
component, the slope of which is a strong function of galaxy
luminosity. The large majority of
galaxies are classified as central objects of their host dark matter
haloes rather than satellites
in more massive systems. The effective halo mass of MegaZ-LRG galaxies
lies in the range
log_10 (M_eff / h^-1 M_sol) = 13.7 - 14.0 (depending on luminosity,
assuming large-scale
normalization sigma_8 = 0.8). Our results confirm the usefulness of the
halo model for gaining
physical insight into the patterns of galaxy clustering.
arXiv:0704.3437
[ps, pdf, other] :
Title: Stellar kinematics in the remote Leo II dwarf spheroidal
galaxy -- Another brick in the wall
Authors:
A.Koch,
J.T.
Kleyna, M.I.
Wilkinson, E.K.
Grebel, G.F.
Gilmore, N.W.
Evans, R.F.G.
Wyse, D.R.
Harbeck
Comments: 17 pages, 10 figures, accepted for publication in the AJ
We present the projected velocity dispersion profile for the remote
(d=233kpc) Galactic dwarf
spheroidal (dSph) galaxy Leo II, based on 171 discrete stellar radial
velocities that were
obtained from medium-resolution spectroscopy using the FLAMES/GIRAFFE
spectrograph at the
European Southern Observatory, Chile. The dispersion profile of those
stars with good
membership probabilities is essentially flat with an amplitude of
6.6+-0.7 km/s over the full
radial extent of our data, which probe to the stellar boundary of this
galaxy. We find no evidence
of any significant apparent rotation or velocity asymmetry which
suggests that tidal effects
cannot be invoked to explain Leo II's properties. From basic mass
modeling, employing Jeans'
equation, we derive a mass out to the limiting radius of (2.7+-0.5)
10^7 Msun and a global
mass to light ratio of 27-45 in solar units, depending on the adopted
total luminosity. A cored
halo profile and a mild amount of tangential velocity anisotropy is
found to account well for Leo
II's observed kinematics, although we cannot exclude the possibility of
a cusped halo with
radially varying velocity anisotropy. All in all, this galaxy exhibits
dark matter properties which
appear to be concordant with the other dSph satellites of the Milky
Way, namely a halo mass
profile which is consistent with a central core and a total mass which
is similar to the common
mass scale seen in other dSphs.
arXiv:0704.3271
[ps, pdf, other] :
Title: Constraining Models of Neutrino Mass and Neutrino
Interactions with the Planck Satellite
Authors:
Alexander
Friedland, Kathryn
M. Zurek, Sergei
Bashinsky
Comments: 25 pages, 16 figures
In several classes of particle physics models -- ranging from the
classical Majoron models, to
the more recent scenarios of late neutrino masses or Mass-Varying
Neutrinos -- one or more of
the neutrinos are postulated to couple to a new light scalar field. As
a result of this coupling,
neutrinos in the early universe instead of streaming freely could form
a self-coupled fluid, with
potentially observable signatures in the Cosmic Microwave Background
and the large scale
structure of the universe. We re-examine the constraints on this
scenario from the presently
available cosmological data and investigate the sensitivity expected
from the Planck satellite. In
the first case, we find that the sensitivity strongly depends on which
piece of data is used. The
SDSS Main sample data, combined with WMAP and other data, disfavors the
scenario of three
coupled neutrinos at about the 3.5$\sigma$ confidence level, but also
favors a high number of
freely streaming neutrinos, with the best fit at 5.2. If the matter
power spectrum is instead
taken from the SDSS Large Red Galaxy sample, best fit point has 2.5
freely streaming
neutrinos, but the scenario with three coupled neutrinos becomes
allowed at $2\sigma$. In
contrast, Planck alone will exclude even a single self-coupled neutrino
at the $4.2\sigma$
confidence level, and will determine the total radiation at CMB epoch
to $\Delta N_\nu^{eff} =
^{+0.5}_{-0.3}$ ($1\sigma$ errors). We investigate the robustness of
this result with respect
to the details of Planck's detector. This sensitivity to neutrino
free-streaming implies that Planck
will be capable of probing a large region of the Mass-Varying Neutrino
parameter space. Planck
may also be sensitive to a scale of neutrino mass generation as high as
1 TeV.
arXiv:0704.3131
[ps, pdf, other] :
Title: Observing high redshift galaxy clusters through lensing of
the Ostriker-Vishniac effect
Authors:
J.M.
Diego, D.
Herranz
Comments: Submiteed to MNRAS
In this paper we study the possibility of detecting lensing signals in
high-resolution and high-
sensitivity CMB experiments. At scales below 1 arcmin, the CMB
background is dominated by the
Sunyaev-Zel'dovich effect in clusters and by Ostriker-Vishniac effect
distortions elsewhere.
Assuming the Sunyaev-Zel'dovich component in clusters can be removed,
we focus on the
Ostriker-Vishniac effect and study the possibility of its detection
while paying special attention to
contaminants, such as instrumental noise and point sources. After
designing an optimal filter for
this particular lensing signal we explore the signal-to-noise ratio for
different scenarios varying
the resolution of the experiment, its sensitivity, and the level of
contamination due to point
sources. Our results show that the next generation of experiments
should be able to do new and
exciting science through the lensing effect of the Ostriker-Vishniac
background.
arXiv:0704.3064
[ps, pdf, other] :
Title: Diffuse cosmic gamma-rays at 1-20 MeV: A trace of the dark
matter?
Authors:
Kyle
Lawson, Ariel
R.Zhitnitsky
Comments: 11 pages, 1 figure
Several independent observations of the galactic core suggest hitherto
unexplained sources of
energy. The most well known case is the 511 keV line which has proven
very difficult to explain
with conventional astrophysical positron sources. A similar, but less
well known mystery is the
excess of gamma-ray photons detected by COMPTEL across a broad energy
range 1-20 MeV.
Such photons are found to be very difficult to produce via known
astrophysical sources. We
show in this work that dark matter in the form of dense antimatter
droplets provides a natural
explanations for the observed flux of gamma-rays in the 1-20 MeV range.
We argue thatsuch
photons must always accompany the 511 keV line as they produced by the
same mechanism
within our framework. We calculate the spectrum and intensity of the
1-20 MeV gamma-rays,
and find it to be consistent with the COMPTEL data.
arXiv:0704.3031 [pdf] :
Title: The Cornell Caltech Atacama Telescope
Authors:
Simon
J. E. Radford, Riccardo
Giovanelli, Thomas
A. Sebring, Jonas
Zmuidzinas
Cornell University, the California Institute for Technology, and the
Jet Propulsion Laboratory are
jointly studying the construction of a 25 m diameter telescope for
submillimeter astronomy on a
high mountain in northern Chile. This Cornell Caltech Atacama Telescope
(CCAT) will combine
high sensitivity, a wide field of view, and a broad wavelength range to
provide an unprecedented
capability for deep, large area, multi-color submillimeter surveys to
complement narrow field,
high resolution studies with ALMA. CCAT observations will address
fundamental themes in
contemporary astronomy, notably the formation and evolution of
galaxies, the nature of the
dark matter and dark energy that comprise most of the content of the
universe, the formation of
stars and planets, the conditions in circumstellar disks, and the
conditions during the early
history of the Solar system. The candidate CCAT site, at 5600 m in
northern Chile, enjoys superb
observing conditions. To accommodate large format bolometer cameras,
CCAT is designed with
a 20 arcmin field of view. CCAT will incorporate closed loop active
control of its segmented
primary mirror to maintain a half wavefront error of 10 mum rms or
less. Instrumentation
under consideration includes both short (650 mum-200 mum) and long (2
mm-750 mum)
wavelength bolometer cameras, direct detection spectrometers, and
heterodyne receiver arrays.
The University of Colorado, a Canadian university consortium, and the
UK Astronomy Technology
Centre on behalf of the UK community are pursuing participation in the
CCAT consortium. When
complete early in the next decade, CCAT will be the largest and most
sensitive facility of its
class as well as the highest altitude astronomical facility on Earth.
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