An Optimal and Model-Independent Measurement of the Intracluster Pressure Profile I: Methodology and First Applications. (arXiv:1304.6457v1 [astro-ph.CO])

An Optimal and Model-Independent Measurement of the Intracluster Pressure Profile I: Methodology and First Applications. (arXiv:1304.6457v1 [astro-ph.CO]):
We present a statistically-optimal and model-independent method to extract
the pressure profile of hot gas in the intracluster medium (ICM). Using the
thermal Sunyaev-Zeldovich effect, we constrain the mean pressure profile of the
ICM by appropriately considering all primary cosmic microwave background (CMB)
and instrumental noise correlations, while using the maximum resolution and
sensitivity of all frequency channels. As a first application, we analyze CMB
maps of WMAP 9-year data through a study of the Meta-Catalogue of X-ray
detected Clusters of galaxies (MCXC). We constrain the universal pressure
profile out to 4R_500 with 15-sigma confidence, though our measurements are
only significant out to R_200. Using a temperature profile constrained from
X-ray observations, we measure the mean gas mass fraction out to R_200. Within
statistical and systematic uncertainties, our constraints are compatible with
the cosmic baryon fraction and the expected gas fraction in halos. While Planck
multi-frequency CMB data are expected to reduce statistical uncertainties by a
factor of 20, we argue that systematic errors in determining mass of clusters
dominate the uncertainty in gas mass fraction measurements at the level of 20
percent.

ALMA follows streaming of dense gas down to 40 pc from the supermassive black hole in NGC1097. (arXiv:1304.6722v1 [astro-ph.CO])

ALMA follows streaming of dense gas down to 40 pc from the supermassive black hole in NGC1097. (arXiv:1304.6722v1 [astro-ph.CO]):
We present a kinematic analysis of the dense molecular gas in the central 200
parsecs of the nearby galaxy NGC1097, based on Cycle 0 observations with the
Atacama Large Millimeter/sub-millimeter Array (ALMA). We use the HCN(4-3) line
to trace the densest interstellar molecular gas, and quantify its kinematics,
and estimate an inflow rate for the molecular gas. We find a striking
similarity between the ALMA kinematic data and the analytic spiral inflow model
that we have previously constructed based on ionized gas velocity fields on
larger scales. We are able to follow dense gas streaming down to 40 pc distance
from the supermassive black hole in this Seyfert 1 galaxy. In order to fulfill
marginal stability, we deduce that the dense gas is confined to a very thin
disc, and we derive a dense gas inflow rate of 0.09 Msun/yr at 40 pc radius.
Combined with previous values from the Ha and CO gas, we calculate a combined
molecular and ionized gas inflow rate of 0.2 Msun/yr at 40 pc distance from the
central supermassive black hole of NGC1097.

The Column Density Distribution and Continuum Opacity of the Intergalactic and Circumgalactic Medium at Redshift =2.4. (arXiv:1304.6719v1 [astro-ph.CO])

The Column Density Distribution and Continuum Opacity of the Intergalactic and Circumgalactic Medium at Redshift <z>=2.4. (arXiv:1304.6719v1 [astro-ph.CO]):
We present new high-precision measurements of the opacity of the
intergalactic and circumgalactic medium (IGM, CGM) at <z>=2.4. Using Voigt
profile fits to the full Lyman alpha and Lyman beta forests in 15
high-resolution high-S/N spectra of hyperluminous QSOs, we make the first
statistically robust measurement of the frequency of absorbers with HI column
densities 14 < log(NHI) < 17.2. We also present the first measurements of the
frequency distribution of HI absorbers in the volume surrounding high-z
galaxies (the CGM, 300 pkpc), finding that the incidence of absorbers in the
CGM is much higher than in the IGM. In agreement with Rudie et al. (2012), we
find that there are fractionally more high-NHI absorbers than low-NHI absorbers
in the CGM compared to the IGM, leading to a shallower power law fit to the CGM
frequency distribution. We use these new measurements to calculate the total
opacity of the IGM and CGM to hydrogen-ionizing photons, finding significantly
higher opacity than most previous studies, especially from absorbers with
log(NHI) < 17.2. Reproducing the opacity measured in our data as well as the
incidence of absorbers with log(NHI) > 17.2 requires a broken power law
parameterization of the frequency distribution with a break near log(NHI) ~ 15.
We compute new estimates of the mean free path (mfp) to hydrogen-ionizing
photons at z=2.4, finding mfp = 147 +- 15 Mpc when considering only IGM
opacity. If instead, we consider photons emanating from a high-z star-forming
galaxy and account for the local excess opacity due to the surrounding CGM of
the galaxy itself, the mean free path is reduced to mfp = 121 +- 15 Mpc. These
mfp measurements are smaller than recent estimates and should inform future
studies of the metagalactic UV background and of ionizing sources at z~2-3.

Statistical Study of 2XMMi-DR3/SDSS-DR8 Cross-correlation Sample. (arXiv:1304.6497v1 [astro-ph.IM])

Statistical Study of 2XMMi-DR3/SDSS-DR8 Cross-correlation Sample. (arXiv:1304.6497v1 [astro-ph.IM]):
Cross-correlating the XMM-Newton 2XMMi-DR3 catalog with the Sloan Digital Sky
Survey (SDSS) Data Release 8, we obtain one of the largest X-ray/optical
catalogs and explore the distribution of various classes of X-ray emitters in
the multidimensional photometric parameter space. Quasars and galaxies occupy
different zones while stars scatter in them. However, X-ray active stars have a
certain distributing rule according to spectral types. The earlier the type of
stars, the stronger X-ray emitting. X-ray active stars have a similar
distribution to most of stars in the g-r versus r-i diagram. Based on the
identified samples with SDSS spectral classification, a random forest algorithm
for automatic classification is performed. The result shows that the
classification accuracy of quasars and galaxies adds up to more than 93.0%
while that of X-ray emitting stars only amounts to 45.3%. In other words, it is
easy to separate quasars and galaxies, but it is difficult to discriminate
X-ray active stars from quasars and galaxies. If we want to improve the
accuracy of automatic classification, it is necessary to increase the number of
X-ray emitting stars, since the majority of X-ray emitting sources are quasars
and galaxies. The results obtained here will be used for the optical spectral
survey performed by the Large sky Area Multi-Object fiber Spectroscopic
Telescope (LAMOST, also named the Guo Shou Jing Telescope), which is a Chinese
national scientific research facility operated by the National Astronomical
Observatories, Chinese Academy of Sciences.

The Observable Thermal and Kinetic Sunyaev-Zel'dovich Effect in Merging Galaxy Clusters. (arXiv:1304.6088v1 [astro-ph.CO])

The Observable Thermal and Kinetic Sunyaev-Zel'dovich Effect in Merging Galaxy Clusters. (arXiv:1304.6088v1 [astro-ph.CO]):
The advent of high-resolution imaging of galaxy clusters using the
Sunyaev-Zel'dovich Effect (SZE) provides a unique probe of the astrophysics of
the intracluster medium (ICM) out to high redshifts. To investigate the effects
of cluster mergers on resolved SZE images, we present a high-resolution
cosmological simulation of a 1.5E15 M_sun adiabatic cluster using the TreeSPH
code ChaNGa. This massive cluster undergoes a 10:3:1 ratio triple merger
accompanied by a dramatic rise in its integrated Compton-Y, peaking at z =
0.05. By modeling the thermal SZE (tSZ) and kinetic SZE (kSZ) spectral
distortions of the Cosmic Microwave Background (CMB) at this redshift with
relativistic corrections, we produce various mock images of the cluster at
frequencies and resolutions achievable with current high-resolution SZE
instruments. The two gravitationally-bound merging subclusters account for 10%
and 1% of the main cluster's integrated Compton-Y, and have extended merger
shock features in the background ICM visible in our mock images. We show that
along certain projections and at specific frequencies, the kSZ CMB intensity
distortion can dominate over the tSZ due to the large line of sight velocities
of the subcluster gas and the unique frequency-dependence of these effects. We
estimate that a one-velocity assumption in estimation of line of sight
velocities of the merging subclusters from the kSZ induces a bias of ~10%. This
velocity bias is small relative to other sources of uncertainty in
observations, partially due to helpful bulk motions in the background ICM
induced by the merger. Our results show that high-resolution SZE observations,
which have recently detected strong kSZ signals in subclusters of merging
systems, can robustly probe the dynamical as well as the thermal state of the
ICM.

A comprehensive picture of baryons in groups and clusters of galaxies. (arXiv:1304.6061v1 [astro-ph.CO])

A comprehensive picture of baryons in groups and clusters of galaxies. (arXiv:1304.6061v1 [astro-ph.CO]):
(Abridged) Based on XMM-Newton, Chandra and SDSS data, we investigate the
baryon distribution in groups and clusters and its use as a cosmological
constraint. For this, we considered a sample of 123 systems, with total masses
in the mass range M500 = ~ 10^13 - 4 x 10^15 h_70^-1 Msun.

The gas masses and total masses are derived from X-ray data under the
assumption of hydrostatic equilibrium and spherical symmetry. The stellar
masses are based on SDSS-DR8 data. For the 37 systems out of 123 that had both
optical and X-ray data available, we investigated the gas, stellar and total
baryon mass fractions inside r2500 and r500, and the differential gas mass
fraction within the spherical annulus between r2500 and r500, as a function of
total mass. For the other objects, we investigated the gas mass fraction only.
We find that the gas mass fraction inside r2500 and r500 depends on the total
mass.

However, the differential gas mass fraction does not show any dependence on
total mass for systems with M500 > 10^14 Msun. We find that the total baryonic
content increases with cluster mass. This led us to investigate the
contribution of the ICL to the total baryon budget for lower mass systems, but
we find that it cannot account for the difference observed. The gas mass
fraction dependence on total mass observed for groups and clusters could be due
to the difficulty of low-mass systems to retain gas inside the inner region.
Due to their shallower potential well, non-thermal processes are more effective
in expelling the gas from their central regions outwards. Since the
differential gas mass fraction is nearly constant it provides better
constraints for cosmology.

Using our total f_b estimates, our results imply 0.17 < Omega_m < 0.55.

Long-term evolution of the neutron-star spin period of SXP 1062. (arXiv:1304.6022v1 [astro-ph.HE])

Long-term evolution of the neutron-star spin period of SXP 1062. (arXiv:1304.6022v1 [astro-ph.HE]):
The Be/X-ray binary SXP 1062 is of especial interest owing to the large spin
period of the neutron star, its large spin-down rate, and the correlation with
a supernova remnant constraining its age. This makes the source an important
probe for accretion physics. To investigate the long-term evolution of the spin
period and associated spectral variations, we performed an XMM-Newton
target-of-opportunity observation of SXP 1062 during X-ray outburst. Spectral
and timing analysis of the XMM-Newton data was compared with previous studies,
as well as complementary Swift/XRT monitoring and optical spectroscopy with the
SALT telescope. The spin period was measured to be P=(1071.01+-0.16) s on 2012
Oct 14. The X-ray spectrum is similar to that of previous observations. No
convincing cyclotron absorption features are found, constraining the magnetic
field of the neutron star. The high-resolution RGS spectra indicate the
presence of emission lines, which may not completely be accounted for by the
SNR emission. The comparison of multi-epoch optical spectra suggest an
increasing size or density of the decretion disc around the Be star. SXP 1062
showed a net spin-down with an average of (2.27+-0.44) s/yr over a baseline of
915 days.