Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts. (arXiv:1303.5080v1 [astro-ph.CO]):
We present constraints on cosmological parameters using number counts as a
function of redshift for a sub-sample of 189 galaxy clusters from the Planck SZ
(PSZ) catalogue. The PSZ is selected through the signature of the
Sunyaev--Zeldovich (SZ) effect, and the sub-sample used here has a
signal-to-noise threshold of seven, with each object confirmed as a cluster and
all but one with a redshift estimate. We discuss the calculation of the
expected cluster counts as a function of cosmological parameters, the
completeness of the sample, and the likelihood construction method. Using a
relation between mass M and SZ signal Y based on comparison to X-ray
measurements, we derive constraints on the power spectrum amplitude sigma_8 and
matter density parameter \Omega_m in a flat LCDM model. We test the robustness
of our estimates and find that possible biases in the Y-M relation and the halo
mass function appear larger than the statistical uncertainties from the cluster
sample. Assuming a bias between the X-ray determined mass and the true mass of
20%, motivated by comparison of the observed mass scaling relations to those
from a set of numerical simulations, we find that
sigma_8(Omega_m/0.27)^0.3=0.78+-0.01, with one-dimensional ranges
sigma_8=0.77+-0.02 and Omega_m=0.29+-0.02. The values of the cosmological
parameters are degenerate with the mass bias, and it is found that the larger
values of sigma_8 and Omega_m preferred by the Planck's measurements of the
primary CMB anisotropies can be accommodated by a mass bias of about 45%.
Alternatively, consistency with the primary CMB constraints can be achieved by
inclusion of processes that suppress power on small scales, such as a component
of massive neutrinos. We place our results in the context of other
determinations of cosmological parameters, and discuss issues that need to be
resolved in order to make progress in this field.
Monday, March 25, 2013
Sunday, March 24, 2013
Planck 2013 results. XXIX. Planck catalogue of Sunyaev-Zeldovich sources. (arXiv:1303.5089v1 [astro-ph.CO])
Planck 2013 results. XXIX. Planck catalogue of Sunyaev-Zeldovich sources. (arXiv:1303.5089v1 [astro-ph.CO]):
We describe the all-sky Planck catalogue of clusters and cluster candidates
derived from Sunyaev--Zeldovich (SZ) effect detections using the first 15.5
months of Planck satellite observations. The catalogue contains 1227 entries,
making it over six times the size of the Planck Early SZ (ESZ) sample and the
largest SZ-selected catalogue to date. It contains 861 confirmed clusters, of
which 178 have been confirmed as clusters, mostly through follow-up
observations, and a further 683 are previously-known clusters. The remaining
366 have the status of cluster candidates, and we divide them into three
classes according to the quality of evidence that they are likely to be true
clusters. The Planck SZ catalogue is the deepest all-sky cluster catalogue,
with redshifts up to about one, and spans the broadest cluster mass range from
(0.1 to 1.6) 10^{15}Msun. Confirmation of cluster candidates through comparison
with existing surveys or cluster catalogues is extensively described, as is the
statistical characterization of the catalogue in terms of completeness and
statistical reliability. The outputs of the validation process are provided as
additional information. This gives, in particular, an ensemble of 813 cluster
redshifts, and for all these Planck clusters we also include a mass estimated
from a newly-proposed SZ-mass proxy. A refined measure of the SZ Compton
parameter for the clusters with X-ray counter-parts is provided, as is an X-ray
flux for all the Planck clusters not previously detected in X-ray surveys.
We describe the all-sky Planck catalogue of clusters and cluster candidates
derived from Sunyaev--Zeldovich (SZ) effect detections using the first 15.5
months of Planck satellite observations. The catalogue contains 1227 entries,
making it over six times the size of the Planck Early SZ (ESZ) sample and the
largest SZ-selected catalogue to date. It contains 861 confirmed clusters, of
which 178 have been confirmed as clusters, mostly through follow-up
observations, and a further 683 are previously-known clusters. The remaining
366 have the status of cluster candidates, and we divide them into three
classes according to the quality of evidence that they are likely to be true
clusters. The Planck SZ catalogue is the deepest all-sky cluster catalogue,
with redshifts up to about one, and spans the broadest cluster mass range from
(0.1 to 1.6) 10^{15}Msun. Confirmation of cluster candidates through comparison
with existing surveys or cluster catalogues is extensively described, as is the
statistical characterization of the catalogue in terms of completeness and
statistical reliability. The outputs of the validation process are provided as
additional information. This gives, in particular, an ensemble of 813 cluster
redshifts, and for all these Planck clusters we also include a mass estimated
from a newly-proposed SZ-mass proxy. A refined measure of the SZ Compton
parameter for the clusters with X-ray counter-parts is provided, as is an X-ray
flux for all the Planck clusters not previously detected in X-ray surveys.
Mass And Radius Constraints Using Magnetar Giant Flare Oscillations. (arXiv:1303.3270v1 [astro-ph.HE])
Mass And Radius Constraints Using Magnetar Giant Flare Oscillations. (arXiv:1303.3270v1 [astro-ph.HE]):
We study crustal oscillations in magnetars including corrections for a finite
Alfv\'en velocity. Our crust model uses a new nuclear mass formula that
predicts nuclear masses with an accuracy very close to that of the Finite Range
Droplet Model. This mass model for equilibrium nuclei also includes recent
developments in the nuclear physics, in particular, shell corrections and an
updated neutron-drip line. We perturb our crust model to predict axial crust
modes and assign them to observed giant flare quasi-periodic oscillation (QPO)
frequencies from SGR 1806-20. The QPOs associated with the fundamental and
first harmonic can be used to constrain magnetar masses and radii. We use these
modes and the phenomenological equations of state from Steiner et al. to find a
magnetar crust which reproduces observations of SGR 1806-20. We find magnetar
crusts that match observations for various magnetic field strengths,
entrainment of the free neutron gas in the inner crust, and crust-core
transition densities. Matching observations with a field-free model we obtain
the approximate values of M =1.35 Msun and R = 11.9 km. Matching observations
using a model with the surface dipole field of SGR 1806-20 (B=2.4x10^15 G) we
obtain the approximate values of M = 1.25 Msun and R = 12.4 km. Without
significant entrainment of the free neutron gas the magnetar requires a larger
mass and radius to reproduce observations. If the crust-core transition occurs
at a lower density the magnetar requires a lower mass and a larger radius to
reproduce observations.
We study crustal oscillations in magnetars including corrections for a finite
Alfv\'en velocity. Our crust model uses a new nuclear mass formula that
predicts nuclear masses with an accuracy very close to that of the Finite Range
Droplet Model. This mass model for equilibrium nuclei also includes recent
developments in the nuclear physics, in particular, shell corrections and an
updated neutron-drip line. We perturb our crust model to predict axial crust
modes and assign them to observed giant flare quasi-periodic oscillation (QPO)
frequencies from SGR 1806-20. The QPOs associated with the fundamental and
first harmonic can be used to constrain magnetar masses and radii. We use these
modes and the phenomenological equations of state from Steiner et al. to find a
magnetar crust which reproduces observations of SGR 1806-20. We find magnetar
crusts that match observations for various magnetic field strengths,
entrainment of the free neutron gas in the inner crust, and crust-core
transition densities. Matching observations with a field-free model we obtain
the approximate values of M =1.35 Msun and R = 11.9 km. Matching observations
using a model with the surface dipole field of SGR 1806-20 (B=2.4x10^15 G) we
obtain the approximate values of M = 1.25 Msun and R = 12.4 km. Without
significant entrainment of the free neutron gas the magnetar requires a larger
mass and radius to reproduce observations. If the crust-core transition occurs
at a lower density the magnetar requires a lower mass and a larger radius to
reproduce observations.
The hottest superfluid and superconductor in the Universe: Discovery and nuclear physics implications. (arXiv:1303.3282v2 [hep-ph] UPDATED)
The hottest superfluid and superconductor in the Universe: Discovery and nuclear physics implications. (arXiv:1303.3282v2 [hep-ph] UPDATED):
We present recent work on using astronomical observations of neutron stars to
reveal unique insights into nuclear matter that cannot be obtained from
laboratories on Earth. First, we discuss our measurement of the rapid cooling
of the youngest neutron star in the Galaxy; this provides the first direct
evidence for superfluidity and superconductivity in the supra-nuclear core of
neutron stars. We show that observations of thermonuclear X-ray bursts on
neutron stars can be used to constrain properties of neutron superfluidity and
neutrino emission. We describe the implications of rapid neutron star rotation
rates on aspects of nuclear and superfluid physics. Finally, we show that
entrainment coupling between the neutron superfluid and the nuclear lattice
leads to a less mobile crust superfluid; this result puts into question the
conventional picture of pulsar glitches as being solely due to the crust
superfluid and suggests that the core superfluid also participates.
We present recent work on using astronomical observations of neutron stars to
reveal unique insights into nuclear matter that cannot be obtained from
laboratories on Earth. First, we discuss our measurement of the rapid cooling
of the youngest neutron star in the Galaxy; this provides the first direct
evidence for superfluidity and superconductivity in the supra-nuclear core of
neutron stars. We show that observations of thermonuclear X-ray bursts on
neutron stars can be used to constrain properties of neutron superfluidity and
neutrino emission. We describe the implications of rapid neutron star rotation
rates on aspects of nuclear and superfluid physics. Finally, we show that
entrainment coupling between the neutron superfluid and the nuclear lattice
leads to a less mobile crust superfluid; this result puts into question the
conventional picture of pulsar glitches as being solely due to the crust
superfluid and suggests that the core superfluid also participates.
Outskirts of Galaxy Clusters. (arXiv:1303.3286v1 [astro-ph.CO])
Outskirts of Galaxy Clusters. (arXiv:1303.3286v1 [astro-ph.CO]):
Until recently, only about 10% of the total intracluster gas volume had been
studied with high accuracy, leaving a vast region essentially unexplored. This
is now changing and a wide area of hot gas physics and chemistry awaits
discovery in galaxy cluster outskirts. Also, robust large-scale total mass
profiles and maps are within reach. First observational and theoretical results
in this emerging field have been achieved in recent years with sometimes
surprising findings. Here, we summarize and illustrate the relevant underlying
physical and chemical processes and review the recent progress in X-ray,
Sunyaev--Zel'dovich, and weak gravitational lensing observations of cluster
outskirts, including also brief discussions of technical challenges and
possible future improvements.
Until recently, only about 10% of the total intracluster gas volume had been
studied with high accuracy, leaving a vast region essentially unexplored. This
is now changing and a wide area of hot gas physics and chemistry awaits
discovery in galaxy cluster outskirts. Also, robust large-scale total mass
profiles and maps are within reach. First observational and theoretical results
in this emerging field have been achieved in recent years with sometimes
surprising findings. Here, we summarize and illustrate the relevant underlying
physical and chemical processes and review the recent progress in X-ray,
Sunyaev--Zel'dovich, and weak gravitational lensing observations of cluster
outskirts, including also brief discussions of technical challenges and
possible future improvements.
Mass profiles of Galaxy Clusters from X-ray analysis. (arXiv:1303.3530v1 [astro-ph.CO])
Mass profiles of Galaxy Clusters from X-ray analysis. (arXiv:1303.3530v1 [astro-ph.CO]):
We review the methods used at the present to reconstruct the mass profiles in
X-ray luminous galaxy clusters. We discuss the limitations and the biases
affecting these measurements and their cosmological implications.
We review the methods used at the present to reconstruct the mass profiles in
X-ray luminous galaxy clusters. We discuss the limitations and the biases
affecting these measurements and their cosmological implications.
Energy Extraction from Spinning Black Holes via Relativistic Jets. (arXiv:1303.3004v1 [astro-ph.HE])
Energy Extraction from Spinning Black Holes via Relativistic Jets. (arXiv:1303.3004v1 [astro-ph.HE]):
It has for long been an article of faith among astrophysicists that black
hole spin energy is responsible for powering the relativistic jets seen in
accreting black holes. Two recent advances have strengthened the case. First,
numerical general relativistic magnetohydrodynamic simulations of accreting
spinning black holes show that relativistic jets form spontaneously. In at
least some cases, there is unambiguous evidence that much of the jet energy
comes from the black hole, not the disk. Second, spin parameters of a number of
accreting stellar-mass black holes have been measured. For ballistic jets from
these systems, it is found that the radio luminosity of the jet correlates with
the spin of the black hole. This suggests a causal relationship between black
hole spin and jet power, presumably due to a generalized Penrose process.
It has for long been an article of faith among astrophysicists that black
hole spin energy is responsible for powering the relativistic jets seen in
accreting black holes. Two recent advances have strengthened the case. First,
numerical general relativistic magnetohydrodynamic simulations of accreting
spinning black holes show that relativistic jets form spontaneously. In at
least some cases, there is unambiguous evidence that much of the jet energy
comes from the black hole, not the disk. Second, spin parameters of a number of
accreting stellar-mass black holes have been measured. For ballistic jets from
these systems, it is found that the radio luminosity of the jet correlates with
the spin of the black hole. This suggests a causal relationship between black
hole spin and jet power, presumably due to a generalized Penrose process.
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