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.

Too much "pasta" for pulsars to spin down. (arXiv:1304.6546v1 [astro-ph.SR])

Too much "pasta" for pulsars to spin down. (arXiv:1304.6546v1 [astro-ph.SR]):
The lack of X-ray pulsars with spin periods > 12 s raises the question about
where the population of evolved high magnetic field neutron stars has gone.
Unlike canonical radio-pulsars, X-ray pulsars are not subject to physical
limits to the emission mechanism nor observational biases against the detection
of sources with longer periods. Here we show that a highly resistive layer in
the innermost part of the crust of neutron stars naturally limits the spin
period to a maximum value of about 10-20 s. This high resistivity is one of the
expected properties of the nuclear pasta phase, a proposed state of matter
having nucleons arranged in a variety of complex shapes. Our findings suggest
that the maximum period of isolated X-ray pulsars can be the first
observational evidence of the existence of such phase, which properties can be
constrained by future X-ray timing missions combined with more detailed models.

A Massive Pulsar in a Compact Relativistic Binary. (arXiv:1304.6875v1 [astro-ph.HE])

A Massive Pulsar in a Compact Relativistic Binary. (arXiv:1304.6875v1 [astro-ph.HE]):
Many physically motivated extensions to general relativity (GR) predict
significant deviations in the properties of spacetime surrounding massive
neutron stars. We report the measurement of a 2.01 +/- 0.04 solar mass pulsar
in a 2.46-hr orbit with a 0.172 +/- 0.003 solar mass white dwarf. The high
pulsar mass and the compact orbit make this system a sensitive laboratory of a
previously untested strong-field gravity regime. Thus far, the observed orbital
decay agrees with GR, supporting its validity even for the extreme conditions
present in the system. The resulting constraints on deviations support the use
of GR-based templates for ground-based gravitational wave detectors.
Additionally, the system strengthens recent constraints on the properties of
dense matter and provides insight to binary stellar astrophysics and pulsar
recycling.

Does a hadron-quark phase transition in dense matter preclude the existence of massive neutron stars ?. (arXiv:1304.6907v1 [astro-ph.HE])

Does a hadron-quark phase transition in dense matter preclude the existence of massive neutron stars ?. (arXiv:1304.6907v1 [astro-ph.HE]):
We study the impact of a hadron-quark phase transition on the maximum
neutron-star mass. The hadronic part of the equation of state relies on the
most up-to-date Skyrme nuclear energy density functionals, fitted to
essentially all experimental nuclear mass data and constrained to reproduce the
properties of infinite nuclear matter as obtained from microscopic calculations
using realistic forces. We show that the softening of the dense matter equation
of state due to the phase transition is not necessarily incompatible with the
existence of massive neutron stars like PSR J1614-2230.

Radiation driven outflow in active galactic nuclei: the feedback effects of scattered and locally produced photons. (arXiv:1304.4689v1 [astro-ph.HE])

Radiation driven outflow in active galactic nuclei: the feedback effects of scattered and locally produced photons. (arXiv:1304.4689v1 [astro-ph.HE]):
We perform time-dependent, two-dimensional, hydrodynamical, numerical
simulations to study the dynamics of a slowly rotating accretion flow from
sub-pc to pc scales under the irradiation from the central AGN. Compared to
previous work, we improve the calculation of the radiative force due to X-rays.
More importantly, in addition to radiative pressure and radiative
heating/cooling directly from the central AGN, in the momentum equation we also
include the force due to the scattered and locally produced photons. We find
that the accretion flow properties change significantly due to this
"re-radiation" effect. The inflow rate at the inner boundary is reduced, while
the outflow rate at the outer boundary is enhanced by about one order of
magnitude. This effect is more significant when the density at the outer
boundary is higher. The properties of outflows such as velocity, momentum and
energy fluxes, and the ratio of outflow rate and the accretion rate, are
calculated. We find that the efficiency of transferring the radiation power
into the kinetic power of outflow is typically $10^{-3}$, far below the value
of $\sim 0.05$ which is assumed in some cosmological simulations. The effect of
the temperature of the gas at the outer boundary ($T_0$) is investigated. When
$T_0$ is high, the emitted luminosity of the accretion flow oscillates because
of the strong radiative heating. Another question we hope to address by this
work is the so-called "sub-Eddington" puzzle. That is, observations show that
the luminosity of almost all AGNs are sub-Eddington, while theoretically the
luminosity of an accretion flow can easily be super-Eddington. We find that
even when the re-radiation effect is included and outflow does become much
stronger, the luminosity, while reduced, can still be super-Eddington. Other
observational implications and some caveats of our calculations are discusse

Enriching the hot circumgalactic medium. (arXiv:1304.4730v1 [astro-ph.CO])

Enriching the hot circumgalactic medium. (arXiv:1304.4730v1 [astro-ph.CO]):
Models of galaxy formation in a CDM universe predict that massive galaxies
are surrounded by a hot, quasi-hydrostatic circumgalactic corona of slowly
cooling gas, predominantly accreted from the IGM. This prediction is borne out
by the cosmological hydrodynamical simulations of Crain et al., which reproduce
scaling relations between the X-ray and optical properties of nearby disc
galaxies. Such coronae are metal poor, but observations of the X-ray emitting
circumgalactic medium (CGM) of local galaxies typically indicate enrichment to
near-solar iron abundance, potentially signalling a shortcoming in galaxy
formation models. We show here that, while the hot CGM of galaxies formed in
the simulations is metal poor in a mass-weighted sense, its X-ray
luminosity-weighted metallicity is often close to solar. This bias arises
because the soft X-ray emissivity of a typical 0.1 keV corona is dominated by
collisionally-excited metal ions that are synthesised in stars and recycled
into the hot CGM. We find that these metals are ejected primarily by stars that
form in-situ to the main progenitor of the galaxy, rather than in satellites or
external galaxies. The enrichment of the hot CGM therefore proceeds in an
inside-out fashion throughout the assembly of the galaxy: metals are
transported from the central galaxy by SNe-driven winds and convection over
several gigayears, establishing a strong negative radial metallicity gradient.
Whilst metal ions synthesised by stars are necessary to produce the X-ray
emissivity that enables the hot CGM of isolated galaxies to be detected, the
electrons that collisionally excite them are equally important. Since our
simulations indicate that the electron density of hot coronae is dominated by
the metal-poor gas accreted from the IGM, we infer that the hot CGM observed
via X-ray emission is the outcome of both hierarchical accretion and stellar
recycling.

New Limits on 21cm EoR From PAPER-32 Consistent with an X-Ray Heated IGM at z=7.7. (arXiv:1304.4991v2 [astro-ph.CO] UPDATED)

New Limits on 21cm EoR From PAPER-32 Consistent with an X-Ray Heated IGM at z=7.7. (arXiv:1304.4991v2 [astro-ph.CO] UPDATED):
We present new constraints on the 21cm Epoch of Reionization (EoR) power
spectrum derived from 3 months of observing with a 32-antenna,
dual-polarization deployment of the Donald C. Backer Precision Array for
Probing the Epoch of Reionization (PAPER) in South Africa. In this paper, we
demonstrate the efficacy of the delay-spectrum approach to avoiding
foregrounds, achieving over 8 orders of magnitude of foreground suppression (in
mK^2). Combining this approach with a procedure for removing off-diagonal
covariances arising from instrumental systematics, we achieve a best 2-sigma
upper limit of (52 mK)^2 for k=0.11 h Mpc^-1 at z=7.7. This limit falls within
an order of magnitude of the brighter predictions of the expected 21cm EoR
signal level. Using the upper limits set by these measurements, we generate new
constraints on the brightness temperature of 21cm emission in neutral regions
for various reionization models. We show that for several ionization models,
heating of the neutral intergalactic medium (IGM) is necessary to remain
consistent with the constraints we report. Hence, we have suggestive evidence
that by z=7.7, the HI has been warmed from its cold primordial state, probably
by X-rays from high-mass X-ray binaries or mini-quasars.

On the size and location of the X-ray emitting coronae around black holes. (arXiv:1304.4947v1 [astro-ph.HE])

On the size and location of the X-ray emitting coronae around black holes. (arXiv:1304.4947v1 [astro-ph.HE]):
The observation of energetic X-ray emission from black holes, inconsistent
with thermal emission from an accretion disk, has long indicated the presence
of a "corona" around these objects. However, our knowledge of the geometry,
composition, and processes within black hole coronae is severely lacking. Basic
questions regarding their size and location are still a topic of debate. In
this letter, we show that for black holes with luminosities
$L\gtrsim10^{-2}L_{Edd}$ -- characteristic of many Seyferts, quasars, and
stellar-mass black holes (in their brighter states) -- advanced imaging and
timing data strongly favor X-ray emitting regions that are highly compact, and
only a few Gravitational radii above the accretion disk. The inclusion of a
large number of possible systematics uncertainties does not significantly
change this conclusion with our results still suggesting emission from within
$\sim20$\rg\ in all cases. This result favors coronal models wherein most of
the hard X-ray emission derives from magnetic reconnection in the innermost
disk and/or from processes in the compact base of a central, relativistic jet.

The metallicity evolution of low mass galaxies: New constraints at intermediate redshift. (arXiv:1304.4239v1 [astro-ph.CO])

The metallicity evolution of low mass galaxies: New constraints at intermediate redshift. (arXiv:1304.4239v1 [astro-ph.CO]):
We present abundance measurements from 26 emission-line selected galaxies at
z~0.6-0.7. By reaching stellar masses as low as 10^8 M_{\sun}, these
observations provide the first measurement of the intermediate redshift
mass-metallicity (MZ) relation below 10^9 M_{\sun} For the portion of our
sample above M > 10^9 M_{\sun} (8/26 galaxies), we find good agreement with
previous measurements of the intermediate redshift MZ relation. Compared to the
local relation, we measure an evolution that corresponds to a 0.12 dex decrease
in oxygen abundances at intermediate redshifts. This result confirms the trend
that metallicity evolution becomes more significant towards lower stellar
masses, in keeping with a downsizing scenario where low mass galaxies evolve
onto the local MZ relation at later cosmic times. We show that these galaxies
follow the local fundamental metallicity relation, where objects with higher
specific (mass-normalized) star formation rates (SFRs) have lower
metallicities. Furthermore, we show that the galaxies in our sample lie on an
extrapolation of the SFR-M_{*} relation (the star-forming main sequence).
Leveraging the MZ relation and star-forming main sequence (and combining our
data with higher mass measurements from the literature), we test models that
assume an equilibrium between mass inflow, outflow and star formation. We find
that outflows are required to describe the data. By comparing different outflow
prescriptions, we show that momentum driven winds can describe the MZ relation;
however, this model under-predicts the amount of star formation in low mass
galaxies. This disagreement may indicate that preventive feedback from
gas-heating has been overestimated, or it may signify a more fundamental
deviation from the equilibrium assumption.

The COS/UVES Absorption Survey of the Magellanic Stream: II. Evidence for a complex enrichment history of the Stream from the Fairall 9 sightline. (arXiv:1304.4242v1 [astro-ph.GA])

The COS/UVES Absorption Survey of the Magellanic Stream: II. Evidence for a complex enrichment history of the Stream from the Fairall 9 sightline. (arXiv:1304.4242v1 [astro-ph.GA]):
We present a multi-wavelength study of the Magellanic Stream (MS), a massive
gaseous structure in the Local Group that is believed to represent material
stripped from the Magellanic Clouds. We use ultraviolet, optical and radio data
obtained with HST/COS, VLT/UVES, FUSE and GASS to study metal abundances and
physical conditions in the Stream toward the quasar Fairall 9. Line absorption
in the MS is detected from a large number of metal ions and from molecular
hydrogen. From the analysis of unsaturated SII absorption, in combination with
a detailed photoionization model, we obtain a surprisingly high alpha abundance
in the Stream toward Fairall 9 of [S/H]=-0.30pm0.04 (0.5 solar). This value is
5 times higher than what is found along other MS sightlines based on similar
COS/UVES data sets. In contrast, the measured nitrogen abundance is found to be
substantially lower ([N/H]=-1.15pm0.06), implying a very low [alpha/N] ratio of
-0.85 dex. The substantial differences in the chemical composition of the
Magellanic Stream toward Fairall 9 compared to other lines of sight, together
with the presence of dust and molecular gas, point toward a complex enrichment
history of the Magellanic Stream. We favour a scenario, in which the gas was
locally enriched with alpha elements by massive stars in a star-forming region
in the SMC or LMC and then was expelled and/or stripped from the stellar disk
before the delayed nitrogen enrichment from intermediate-mass stars could set
in (abridged).

The Case for Massive, Evolving Winds in Black Hole X-ray Binaries. (arXiv:1304.6091v1 [astro-ph.HE])

The Case for Massive, Evolving Winds in Black Hole X-ray Binaries. (arXiv:1304.6091v1 [astro-ph.HE]):
In the last decade, high-resolution X-ray spectroscopy has revolutionized our
understanding of the role of accretion disk winds in black hole X-ray binaries.
Here I present a brief review of the state of wind studies in black hole X-ray
binaries, focusing on recent arguments that disk winds are not only extremely
massive, but also highly variable. I show how new and archival observations at
high timing and spectral resolution continue to highlight the intricate links
between the inner accretion flow, relativistic jets, and accretion disk winds.
Finally, I discuss methods to infer the driving mechanisms of observed disk
winds and their implications for connections between mass accretion and
ejection processes.

Black hole spin evolution through hydrodynamical cosmological simulations including AGN feedback. (arXiv:1304.4583v1 [astro-ph.CO])

Black hole spin evolution through hydrodynamical cosmological simulations including AGN feedback. (arXiv:1304.4583v1 [astro-ph.CO]):
Supermassive black holes (BH) at the centres of galaxies can rapidly change
their mass and spin by gas accretion and mergers. Using hydrodynamical
cosmological simulations, with prescriptions for BH growth and feedback from
Active Galactic Nuclei, we study the evolution of BH spins and we highlight the
mechanisms responsible for driving the amplitude and the direction of spins as
a function of cosmic time. We find that in the high-redshift universe, galaxies
maintain large values of gas accretion onto BHs. BHs tend to align their spins
with the angular momentum of the surrounding gas and maximise their amplitude.
On the opposite, at low redshift, as BHs get more massive, the contribution
from binary coalescence to the total BH mass growth increases and tends to
decrease the amplitude of spins and change their direction.

Turbulence driven by structure formation in the circum-galactic medium. (arXiv:1304.3465v1 [astro-ph.CO])

Turbulence driven by structure formation in the circum-galactic medium. (arXiv:1304.3465v1 [astro-ph.CO]):
The injection of turbulence in the circum-galactic medium at redshift z = 2
is investigated using the mesh-based hydrodynamic code Enzo and a subgrid-scale
(SGS) model for unresolved turbulence. Radiative cooling and heating by a
uniform Ultraviolet (UV) background are included in our runs and compared with
the effect of turbulence modelling. Mechanisms of gas exchange between galaxies
and the surrounding medium, as well as metal enrichment, are not taken into
account, and turbulence is here driven solely by structure formation (mergers
and shocks). We find that turbulence, both at resolved and SGS scales, impacts
mostly the warm-hot intergalactic medium (WHIM), with temperature between 10^5
and 10^7 K, mainly located around collapsed and shock heated structures, and in
filaments. Typical values of the ratio of turbulent to thermal pressure is 0.1
in the WHIM, corresponding to a volume-weighted average of the SGS turbulent to
thermal Doppler broadening b_t / b_therm = 0.26, on length scales below the
grid resolution of 25 kpc/h. In the diffuse intergalactic medium (IGM), defined
in a range of baryon overdensity \delta\ between 1 and 50, the importance of
turbulence is smaller, but grows as a function of gas density, and the Doppler
broadening ratio is fitted by the function b_t / b_therm = 0.023 \delta^{0.58}.

The ultra-deep XMM survey in the CDFS: X-ray spectroscopy of heavily obscured AGN. (arXiv:1304.3664v1 [astro-ph.CO])

The ultra-deep XMM survey in the CDFS: X-ray spectroscopy of heavily obscured AGN. (arXiv:1304.3664v1 [astro-ph.CO]):
We present selected results on the X-ray spectroscopy of distant, obscured
AGN as obtained with the ultra-deep (~3 Ms) XMM-Newton survey in the Chandra
Deep Field South (CDF-S). One of the primary goals of the project is to
characterize the X-ray spectral properties of heavily obscured and
Compton-thick AGN over the range of redshifts and luminosities that are
relevant in terms of their contribution to the X-ray background. The ultra-deep
exposure, coupled with the XMM detector's spectral throughput, allowed us to
accumulate X-ray spectra for more than 100 AGN to investigate the absorption
distribution up to z~4.

Linking X-ray AGN with dark matter halos: a model compatible with AGN luminosity function and large-scale clustering properties. (arXiv:1304.3717v1 [astro-ph.CO])

Linking X-ray AGN with dark matter halos: a model compatible with AGN luminosity function and large-scale clustering properties. (arXiv:1304.3717v1 [astro-ph.CO]):
Our goal is to find a minimalistic model describing the luminosity function
and large-scale clustering bias of the X-ray selected AGN in the general
framework of the concordance LCDM model. We assume that a simple
population-averaged scaling relation between the AGN X-ray luminosity L_X and
the host dark matter halo mass M_h exists. With such a relation, the AGN X-ray
luminosity function can be computed from the halo mass function. Using for the
latter the concordance LCDM halo mass function, we obtain the M_h-L_X relation
required to match the redshift dependent AGN X-ray luminosity function known
from X-ray observations. We find that with a simple power law scaling M_h
\propto L_X^\Gamma(z), our model can successfully reproduce the observed X-ray
luminosity function. Furthermore, we automatically obtain predictions for the
large-scale AGN clustering amplitudes and their dependence on the luminosity
and redshift, which seem to be compatible with AGN clustering measurements. Our
model also includes the redshift-dependent AGN duty cycle which peaks at the
redshift z ~ 1 and its peak value is consistent with unity, suggesting that on
average there is no more than one AGN per dark matter halo. For a typical X-ray
selected AGN at z ~ 1, our best-fit M_h-L_X scaling implies low Eddington ratio
L_X/L_Edd ~ 10^{-4}-10^{-3} and correspondingly large mass growth e-folding
times, suggesting that the typical X-ray AGN are dominantly fueled via
relatively inefficient 'hot-halo' accretion mode.

The cosmic X-ray background: abundance and evolution of hidden black holes. (arXiv:1304.3665v1 [astro-ph.CO])

The cosmic X-ray background: abundance and evolution of hidden black holes. (arXiv:1304.3665v1 [astro-ph.CO]):
The growth of supermassive black holes across cosmic time leaves a radiative
imprint recorded in the X-ray background (XRB). The XRB spectral shape suggests
that a large population of distant, hidden nuclei must exist, which are now
being revealed at higher and higher redshifts by the deepest surveys performed
by Chandra and XMM.

Our current understanding of the XRB emission in terms of AGN population
synthesis models is here reviewed, and the evolutionary path of nuclear
accretion and obscuration, as emerging from the major X-ray surveys, is
investigated. The role of galaxy merging versus secular processes in triggering
nuclear activity is also discussed in the framework of recent galaxy/black hole
co-evolutionary scenarios. Finally, the limits of current instrumentation in
the detection of the most obscured and distant black holes are discussed and
some possible directions to overcome these limits are presented.

Composition of Low Redshift Halo Gas. (arXiv:1304.3466v1 [astro-ph.CO])

Composition of Low Redshift Halo Gas. (arXiv:1304.3466v1 [astro-ph.CO]):
Halo gas in low-z (z<0.5) >0.1L* galaxies in high-resolution, large-scale
cosmological hydrodynamic simulations is examined with respect to three
components: (cold, warm, hot) with temperatures equal to (<10^5, 10^{5-6},
>10^6)K, respectively. The warm component is compared, utilizing O VI
\lambda\lambda 1032, 1038 absorption lines, to observations and agreement is
found with respect to the galaxy-O VI line correlation, the ratio of O VI line
incidence rate in blue to red galaxies and the amount of O VI mass in
star-forming galaxies. A detailed account of the sources of warm halo gas
(stellar feedback heating, gravitational shock heating and accretion from the
intergalactic medium), inflowing and outflowing warm halo gas metallicity
disparities and their dependencies on galaxy types and environment is also
presented. Having the warm component securely anchored, our simulations make
the following additional predictions. First, cold gas is the primary component
in inner regions, with its mass comprising 50% of all gas within
galacto-centric radius r=(30,150)kpc in (red, blue) galaxies. Second, at
r>(30,200)kpc in (red, blue) galaxies the hot component becomes the majority.
Third, the warm component is a perpetual minority, with its contribution
peaking at ~30% at r=100-300kpc in blue galaxies and never exceeding 5% in red
galaxies. The significant amount of cold gas in low-z early-type galaxies found
in simulations, in agreement with recent observations (Thom et al.), is
intriguing, so is the dominance of hot gas at large radii in blue galaxies.

Novel distance indicator for gamma-ray bursts associated with supernovae. (arXiv:1304.1764v1 [astro-ph.HE])

Novel distance indicator for gamma-ray bursts associated with supernovae. (arXiv:1304.1764v1 [astro-ph.HE]):
Context. It has been proposed that the temporal coincidence of a gamma-ray
burst (GRB) and a type Ib/c supernova (SN) can be explained with the concept of
induced gravitational collapse (IGC), induced by the matter ejected from an SN
Ib/c accreting onto a neutron star (NS). The NS is expected to reach the
critical mass necessary for it to collapse to a black hole (BH) and emit a GRB.
We found a standard luminosity light curve behavior in the late-time X-ray
emission of this subclass of GRBs. Aims. We test if this standard behavior in
the luminosity found in this subclass of GRBs can become a redshift estimator
of these sources. Methods. We selected a sample of GRBs that belong to this
subclass of IGC GRBs associated to an SN (IGC GRB-SN sources). These sources
have an isotropic energy $E_{iso} > 10^{52}$ erg and their cosmological
redshifts are in the range of $z = 0.49-1.261$. We focused on the corresponding
X-ray luminosity light curves. Results. We find that all GRBs of the sample
with measured redshift present a standard luminosity late-time light curve in
the $0.3-10$ keV rest-frame energy range. We used these results to estimate the
GRB redshift of the sample without a measured redshift and found results
consistent with other possible redshift indicators. Conclusions. The standard
late-time X-ray luminosity light curve of all GRBs of the sample shows a common
physical mechanism in this particular phase of the X-ray emission, possibly
related to the creation of the NS from the SN process. This scaling law
moreover represents strong evidence of very low or even absent beaming in this
late phase of the X-ray afterglow emission process. This could be a fundamental
tool for estimating the redshift of GRBs that belong to this subclass of
events. We are currently expanding this subclass of GRBs to further verify the
universal validity of this new redshift estimation method.

BAL QSOs and Extreme UFOs: the Eddington connection. (arXiv:1304.1691v1 [astro-ph.GA])

BAL QSOs and Extreme UFOs: the Eddington connection. (arXiv:1304.1691v1 [astro-ph.GA]):
We suggest a common physical origin connecting the fast, highly ionized winds
(UFOs) seen in nearby AGN, and the slower and less ionized winds of BAL QSOs.
The primary difference is the mass loss rate in the wind, which is ultimately
determined by the rate at which mass is fed towards the central supermassive
black hole (SMBH) on large scales. This is below the Eddington accretion rate
in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143,
but ranges up to $\sim 10-50$ times this in BAL QSOs. For UFOs this implies
black hole accretion rates and wind mass loss rates which are at most
comparable to Eddington, giving fast, highly-ionized winds. In contrast BAL QSO
black holes have mildly super-Eddington accretion rates, and drive winds whose
mass loss rates are significantly super-Eddington, and so are slower and less
ionized. This picture correctly predicts the velocities and ionization states
of the observed winds, including the recently-discovered one in SDSS
J1106+1939. We suggest that luminous AGN may evolve through a sequence from BAL
QSO through LoBAL to UFO-producing Seyfert or quasar as their Eddington factors
drop during the decay of a bright accretion event. LoBALs correspond to a
short-lived stage in which the AGN radiation pressure largely evacuates the
ionization cone, but before the large-scale accretion rate has dropped to the
Eddington value. We show that sub-Eddington wind rates would produce an $M -
\sigma$ relation lying above that observed. We conclude that significant SMBH
mass growth must occur in super-Eddington phases, either as BAL QSOs, extreme
UFOs, or obscured from direct observation.

Outflow vs. Infall in Spiral Galaxies: Metal Absorption in the Halo of NGC 891. (arXiv:1304.0795v1 [astro-ph.CO])

Outflow vs. Infall in Spiral Galaxies: Metal Absorption in the Halo of NGC 891. (arXiv:1304.0795v1 [astro-ph.CO]):
Gas accreting onto a galaxy will be of low metallicity while halo gas due to
a galactic fountain will be of near-solar metallicity. We test these
predictions by measuring the metal absorption line properties of halo gas 5 kpc
above the plane of the edge-on galaxy NGC 891, using observations taken with
HST/STIS toward a bright background quasar. Metal absorption lines of Fe II, Mg
II, and Mg I in the halo of NGC 891 are clearly seen, and when combined with
recent deep H I observations, we are able to place constraints on the
metallicity of the halo gas for the first time. The H I line width defines the
line broadening, from which we model opacity effects in these metal lines,
assuming the absorbing gas is continuously distributed in the halo. The
gas-phase metallicities are [Fe/H] = -1.18 +/- 0.07 and [Mg/H] = -0.23
+0.36/-0.27 (statistical errors) and this difference is probably due to
differential depletion onto grains. When corrected for such depletion using
Galactic gas as a guide, both elements have approximately solar or even
supersolar abundances. This suggests that the gas is from the galaxy disk,
probably expelled into the halo by a galactic fountain, rather than from
accretion of intergalactic gas, which would have a low metallicity. The
abundances would be raised by significant amounts if the absorbing gas lies in
a few clouds with thermal widths smaller than the rotational velocity of the
halo. If this is the case, both the abundances and [Mg/Fe] would be supersolar.

White Paper for Blazar Observations with a GEMS-like X-ray Polarimetry Mission. (arXiv:1303.7158v1 [astro-ph.HE])

White Paper for Blazar Observations with a GEMS-like X-ray Polarimetry Mission. (arXiv:1303.7158v1 [astro-ph.HE]):
In this document, we describe the scientific potential of blazar observations
with a X-ray polarimetry mission like GEMS (Gravity and Extreme Magnetism
SMEX). We describe five blazar science investigations that such a mission would
enable: (i) the structure and the role of magnetic fields in AGN jets, (ii)
analysis of the polarization of the synchrotron X-ray emission from AGN jets,
(iii) discrimination between synchrotron self-Compton and external Compton
models for blazars with inverse Compton emission in the X-ray band, (iv) a
precision study of the polarization properties of the X-ray emission from
Cen-A, (v) tests of Lorentz Invariance based on X-ray polarimetric observations
of blazars. We conclude with a discussion of a straw man observation program
and recommended accompanying multiwavelength observations.

Ripple effects & oscillations in the broad FeKa line as a probe of massive black hole mergers. (arXiv:1303.7206v1 [astro-ph.HE])

Ripple effects & oscillations in the broad FeKa line as a probe of massive black hole mergers. (arXiv:1303.7206v1 [astro-ph.HE]):
(abridged) When a sufficiently massive satellite (or secondary) black hole is
embedded in a gas disk around a (primary) supermassive black hole, it can open
an empty gap in the disk. A gap-opening secondary close to the primary will
leave an imprint in the broad component of the FeKa emission line, which varies
in a unique and predictable manner. If the gap persists into the innermost
disk, the effect consists of a pair of dips in the broad line which ripple
blue-ward and red-ward from the line centroid energy respectively, as the gap
moves closer to the primary. This ripple effect could be unambiguously
detectable and allow an electromagnetic monitoring of massive black hole
mergers as they occur. As the mass ratio of the secondary to primary black hole
increases to q>0.01, we expect the gap to widen, possibly clearing a central
cavity in the inner disk, which shows up in the broad FeKa line component. If
the secondary stalls at >100r_{g} in its in-migration, due to low co-rotating
gas mass, a detectable ripple effect occurs in the broad line component on the
disk viscous timescale as the inner disk drains and the outer disk is dammed.
If the secondary maintains an accretion disk within a central cavity, due to
dam bursting or leakage, a periodic 'see-saw' oscillation effect is exhibited
in the observed line profile. Here we demonstrate the range of ripple effect
signatures potentially detectable with Astro-H and IXO/Athena, and oscillation
effects potentially detectable with XMM or LOFT for a wide variety of merger
and disk conditions. Observations of the ripple effect and periodic
oscillations can be used to provide an early warning of gravitational radiation
emission from the AGN.

Highly Ionized Fe-K Absorption Line from Cygnus X-1 in the High/Soft State Observed with Suzaku. (arXiv:1304.1970v1 [astro-ph.HE])

Highly Ionized Fe-K Absorption Line from Cygnus X-1 in the High/Soft State Observed with Suzaku. (arXiv:1304.1970v1 [astro-ph.HE]):
We present observations of a transient He-like Fe K alpha absorption line in
Suzaku observations of the black hole binary Cygnus X-1 on 2011 October 5 near
superior conjunction during the high/soft state, which enable us to map the
full evolution from the start and the end of the episodic accretion phenomena
or dips for the first time. We model the X-ray spectra during the event and
trace their evolution. The absorption line is rather weak in the first half of
the observation, but instantly deepens for ~10 ks, and weakens thereafter. The
overall change in equivalent width is a factor of ~3, peaking at an orbital
phase of ~0.08. This is evidence that the companion stellar wind feeding the
black hole is clumpy. By analyzing the line with a Voigt profile, it is found
to be consistent with a slightly redshifted Fe XXV transition, or possibly a
mixture of several species less ionized than Fe XXV. The data may be explained
by a clump located at a distance of ~10^(10-12) cm with a density of
~10^((-13)-(-11)) g cm^-3, which accretes onto and/or transits the
line-of-sight to the black hole, causing an instant decrease in the observed
degree of the ionization and/or an increase in density of the accreting matter.
Continued monitoring for individual events with future X-ray calorimeter
missions such as ASTRO-H and AXSIO will allow us to map out the accretion
environment in detail and how it changes between the various accretion states.

Constraints on the Sunyaev-Zel'dovich signal from the Warm Hot Intergalactic Medium from WMAP and SPT data. (arXiv:1304.2901v1 [astro-ph.CO])

Constraints on the Sunyaev-Zel'dovich signal from the Warm Hot Intergalactic Medium from WMAP and SPT data. (arXiv:1304.2901v1 [astro-ph.CO]):
The fraction of ionized gas in the Warm Hot Intergalactic Medium induces
temperature anisotropies on the Cosmic Microwave Background similar to those of
clusters of galaxies. The Sunyaev-Zel'dovich anisotropies due to these low
density, weakly non-linear, baryon filaments can not be distinguished from that
of clusters using frequency information, but they can be separated since their
angular scales are very different. To determine the relative contribution of
the WHIM SZ signal to the radiation power spectrum of temperature anisotropies,
we explore the parameter space of the concordance LCDM model using Monte Carlo
Markov Chains and the Wilkinson Microwave Anisotropy Probe 7yr and South Pole
Telescope data. We find marginal evidence of a contribution by diffuse gas,
with amplitudes of A_WHIM=10-20 muK^2, but the results are also compatible with
a null contribution from the WHIM, allowing to set an upper limit of A_WHIM <
43 muK^2 (95.4% C.L.). The signal produced by galaxy clusters remains at
A_CL=4.5 muK^2, a value similar to what is obtained when no WHIM is included.
From the measured WHIM amplitude we constrain the temperature-density phase
diagram of the diffuse gas, and find it to be compatible with numerical
simulations. The corresponding baryon fraction in the WHIM varies from 0.43 to
0.47, depending on model parameters. Planck data could set tighter constraints
on the temperature-density relation.

Determining neutron star masses and radii using energy-resolved waveforms of X-ray burst oscillations. (arXiv:1304.2330v1 [astro-ph.HE])

Determining neutron star masses and radii using energy-resolved waveforms of X-ray burst oscillations. (arXiv:1304.2330v1 [astro-ph.HE]):
Simultaneous, precise measurements of the mass $M$ and radius $R$ of neutron
stars can yield uniquely valuable information about the still uncertain
properties of cold matter at several times the density of nuclear matter. One
method that could be used to measure $M$ and $R$ is to analyze the
energy-dependent waveforms of the X-ray flux oscillations seen during some
thermonuclear bursts from some neutron stars. These oscillations are thought to
be produced by X-ray emission from hotter regions on the surface of the star
that are rotating at or near the spin frequency of the star. Here we explore
how well $M$ and $R$ could be determined by generating, and analyzing using
Bayesian techniques, synthetic energy-resolved X-ray data that we produce
assuming a future space mission having 2--30 keV energy coverage and an
effective area of 10 m$^2$, such as the proposed \textit{LOFT} or
\textit{AXTAR} missions.

We find that if the hot spot is within 10$^\circ$ of the rotation equator,
both $M$ and $R$ can usually be determined with an uncertainty of about 10% if
there are $10^6$ total counts from the spot, whereas waveforms from spots
within 20$^\circ$ of the rotation pole provide no useful constraints. These
constraints can usually be achieved even if the burst oscillations vary with
time and data from multiple bursts must be used to obtain 10$^6$ counts from
the hot spot. This is therefore a promising method to constrain $M$ and $R$
tightly enough to discriminate strongly between competing models of cold,
high-density matter.

Powering of cool filaments in cluster cores by buoyant bubbles. I. Qualitative model. (arXiv:1304.3168v1 [astro-ph.HE])

Powering of cool filaments in cluster cores by buoyant bubbles. I. Qualitative model. (arXiv:1304.3168v1 [astro-ph.HE]):
Cool-core clusters (e.g., Perseus or M87) often possess a network of bright
gaseous filaments, observed in radio, IR, optical and X-ray bands. We propose
that these filaments are powered by the reconnection of the magnetic field in
the wakes of buoyant bubbles. AGN-inflated bubbles of relativistic plasma rise
buoyantly in the cluster atmosphere, stretching and amplifying the field in the
wake to values of $\beta =8\pi P_{gas}/B^2\sim 1$. The field lines in the wake
have opposite directions and are forced together as the bubble motion stretches
the filament. This setup bears strong similarity to the coronal loops on the
Sun or the Earth magneto-tail. The reconnection process naturally explains both
the required level of local dissipation rate in filaments and the overall
luminosity of filaments. The original source of power for the filaments is the
potential energy of buoyant bubbles, inflated by the central AGN.

The Crab Nebula and the class of Type IIn-P supernovae caused by sub-energetic electron capture explosions. (arXiv:1304.0689v1 [astro-ph.HE])

The Crab Nebula and the class of Type IIn-P supernovae caused by sub-energetic electron capture explosions. (arXiv:1304.0689v1 [astro-ph.HE]):
What sort of supernova gave rise to the Crab Nebula? There are several
indications that the Crab arose from a sub-energetic explosion of an 8-10 Msun
star, this appears to conflict with the high luminosity indicated by historical
observations. This paper shows that several properties of the Crab are best
suited to Type IIn-P explosions (Type IIn spectra with plateau light curves).
These events probably arise from relatively low-energy (1e50 erg) explosions
with low 56Ni yield resulting from electron-capture SNe (ecSNe), but their high
luminosity and Type IIn spectra are dominated by shock interaction with CSM.
After about 120 days, nearly all of the mass in the CSM and ejecta ends up in a
slow dense shell. In the scenario proposed here for SN1054, this thin shell is
accelerated by the growing pulsar wind nebula, producing the complex network of
filaments seen today. There is no need to invoke the invisible fast SN envelope
hypothesized to reside outside the Crab. SNeIIn-P explain several observed
features of the Crab: (1) No blast wave or rapidly expanding SN envelope
outside the filaments, (2) a total mass of 5 Msun swept up in a thin shell, (3)
a high peak luminosity despite the low kinetic energy, and (4) chemical
abundances consistent with an 8-10 Msun star and low 56Ni yield. A number of
other implications are discussed, concerning other plerionic remnants, dust in
the Crab filaments, diversity in the initial masses of SNe IIn, and an
association between ecSNe and SN impostors. This model predicts that if light
echoes from SN1054 are discovered, they will be consistent with a Type IIn-P
spectrum.

AGN feedback in clusters: shock and sound heating. (arXiv:1304.0400v1 [astro-ph.CO])

AGN feedback in clusters: shock and sound heating. (arXiv:1304.0400v1 [astro-ph.CO]):
Observations support the view that feedback, in the form of radio outbursts
from active nuclei in central galaxies, prevents catastrophic cooling of gas
and rapid star formation in many groups and clusters of galaxies. Variations in
jet power drive a succession of weak shocks that can heat regions close to the
active galactic nuclei (AGN). On larger scales, shocks fade into sound waves.
The Braginskii viscosity determines a well-defined sound damping rate in the
weakly magnetized intracluster medium (ICM) that can provide sufficient heating
on larger scales. It is argued that weak shocks and sound dissipation are the
main means by which radio AGN heat the ICM, in which case, the power spectrum
of AGN outbursts plays a central role in AGN feedback.

Stellar Coronae, Solar Flares: a Detailed Comparison of sigma Gem, HR 1099, and the Sun in High-resolution X-rays. (arXiv:1304.0408v1 [astro-ph.SR])

Stellar Coronae, Solar Flares: a Detailed Comparison of sigma Gem, HR 1099, and the Sun in High-resolution X-rays. (arXiv:1304.0408v1 [astro-ph.SR]):
Chandra HETG spectra of the coronally active binary stars sigma Gem and HR
1099 are among the highest fluence observations for such systems taken at high
spectral resolution in x-rays with this instrument. We compare their properties
to solar flare spectra obtained with the Russian CORONAS-F RESIK instrument at
similar resolution in an overlapping bandpass. We emphasize the comparisons of
the 3.3-6.1 A region from solar flare spectra to the corresponding sigma Gem
and HR 1099 spectra. We also model the the HETG spectra from 1.7-25 A to
determine coronal temperatures and elemental abundances. Sigma Gem is a single
lined coronally active long period binary which has a very hot corona. HR 1099
is a similar, but shorter period, double lined system. In the deep exposures we
study emission from some of the weaker species, such as K, Na, and Al, which
have the lowest first ionization potentials (FIP). The solar flare temperatures
reach ~20 MK, comparable to the sigma Gem and HR 1099 coronae. During the
Chandra exposures, sigma Gem was slowly decaying from a flare and its spectrum
is well characterized by a collisional ionization equilibrium plasma with a
broad temperature distribution ranging from 2-60 MK, peaking near 25 MK, but
with substantial emission from 50 MK plasma. We have detected K XVIII and Na XI
emission which allow us to set limits on their abundances. HR 1099 was also in
a flare state but had no detectable K XVIII. These measurements provide new
comparisons of solar and stellar coronal abundances, especially at the lowest
FIP values. The low FIP elements do not show enhancement in the stellar coronae
as they do in the Sun, except for K in sigma Gem. Sigma Gem and HR 1099 differ
in their emission measure distributions but have very similar elemental
abundances.

Collisionless shocks in partly ionized plasma with cosmic rays: microphysics of non-thermal components. (arXiv:1304.0998v1 [astro-ph.HE])

Collisionless shocks in partly ionized plasma with cosmic rays: microphysics of non-thermal components. (arXiv:1304.0998v1 [astro-ph.HE]):
In this review we discuss some observational aspects and theoretical models
of astrophysical collisionless shocks in partly ionized plasma with the
presence of non-thermal components. A specific feature of fast strong
collisionless shocks is their ability to accelerate energetic particles that
can modify the shock upstream flow and form the shock precursors. We discuss
the effects of energetic particle acceleration and associated magnetic field
amplification and decay in the extended shock precursors on the line and
continuum multi-wavelength emission spectra of the shocks. Both Balmer-type and
radiative astrophysical shocks are discussed in connection to supernova
remnants interacting with partially neutral clouds. Quantitative models
described in the review predict a number of observable line-like emission
features that can be used to reveal the physical state of the matter in the
shock precursors and the character of nonthermal processes in the shocks.
Implications of recent progress of gamma-ray observations of supernova remnants
in molecular clouds are highlighted.

Proton-rich nucleosynthesis and nuclear physics. (arXiv:1304.0929v1 [astro-ph.SR])

Proton-rich nucleosynthesis and nuclear physics. (arXiv:1304.0929v1 [astro-ph.SR]):
Although the detailed conditions for explosive nucleosynthesis are derived
from astrophysical modeling, nuclear physics determines fundamental patterns in
abundance yields, not only for equilibrium processes. Focussing on the nu-p-
and the gamma-process, general nucleosynthesis features within the range of
astrophysical models, but (mostly) independent of details in the modelling, are
presented. Remaining uncertainties due to uncertain Q-values and reaction rates
are discussed.

Signatures of an Encounter Between the G2 Cloud and a Jet from Sgr A*. (arXiv:1303.3969v1 [astro-ph.HE])

Signatures of an Encounter Between the G2 Cloud and a Jet from Sgr A*. (arXiv:1303.3969v1 [astro-ph.HE]):
The recent discovery of the G2 cloud of dense, ionized gas on a trajectory
toward Sgr A*, the black hole at the dynamical center of the Galaxy, offers a
unique opportunity to observe an accretion event onto a massive black hole as
well as to probe its immediate environment. Simulations and models predict
increased X-ray and radio variability resulting from increased accretion driven
by drag on an atmosphere of hot, X-ray emitting gas surrounding Sgr A*. Here,
we present X-ray and radio light curves of the emission resulting from the
potential encounter of the G2 cloud with a relativistic jet from Sgr A*. This
interaction would violently shock a portion of the G2 cloud to temperatures
~10^8 K resulting in bright X-ray emission from the dense, shocked gas as it
adiabatically expands. The 2-10 keV luminosity may reach ~10 times the
quiescent X-ray flux of Sgr A*. Approximately 3 solar luminosity is emitted
above 10 keV at the peak of the light curve, with significant softening of the
spectrum occurring as the gas subsequently cools. Observations with NuSTAR
would therefore be able to confirm such an event as well as determine the cloud
speed. At radio wavelengths, the associated synchrotron radio emission may
reach levels of a few Jy, although this is more uncertain due to the efficiency
of converting the shock luminosity to that of electrons accelerated to
relativistic energies.

The space density of magnetic cataclysmic variables. (arXiv:1303.4270v1 [astro-ph.SR])

The space density of magnetic cataclysmic variables. (arXiv:1303.4270v1 [astro-ph.SR]):
We use the complete, X-ray flux-limited ROSAT Bright Survey (RBS) to measure
the space density of magnetic cataclysmic variables (mCVs). The survey provides
complete optical identification of all sources with count rate >0.2/s over half
the sky ($|b|>30^\circ$), and detected 6 intermediate polars (IPs) and 24
polars. If we assume that the 30 mCVs included in the RBS are representative of
the intrinsic population, the space density of mCVs is $8^{+4}_{-2} \times
10^{-7}\,{\rmpc^{-3}}$. Considering polars and IPs separately, we find
$\rho_{polar}=5^{+3}_{-2} \times 10^{-7}\,{\rm pc^{-3}}$ and
$\rho_{IP}=3^{+2}_{-1} \times 10^{-7}\,{\rm pc^{-3}}$. Allowing for a 50%
high-state duty cycle for polars (and assuming that these systems are below the
RBS detection limit during their low states) doubles our estimate of
$\rho_{polar}$ and brings the total space density of mCVs to $1.3^{+0.6}_{-0.4}
\times 10^{-6}\,{\rm pc^{-3}}$. We also place upper limits on the sizes of
faint (but persistent) mCV populations that might have escaped detection in the
RBS. Although the large uncertainties in the $\rho$ estimates prevent us from
drawing strong conclusions, we discuss the implications of our results for the
evolutionary relationship between IPs and polars, the fraction of CVs with
strongly magnetic white dwarfs (WDs), and for the contribution of mCVs to
Galactic populations of hard X-ray sources at $L_X \ga 10^{31} {\rm erg/s}$.
Our space density estimates are consistent with the very simple model where
long-period IPs evolve into polars and account for the whole short-period polar
population. We find that the fraction of WDs that are strongly magnetic is not
significantly higher for CV primaries than for isolated WDs. Finally, the space
density of IPs is sufficiently high to explain the bright, hard X-ray source
population in the Galactic Centre.

X-ray exploration of the outskirts of the nearby Centaurus cluster using Suzaku and Chandra. (arXiv:1303.4240v1 [astro-ph.CO])

X-ray exploration of the outskirts of the nearby Centaurus cluster using Suzaku and Chandra. (arXiv:1303.4240v1 [astro-ph.CO]):
We present Suzaku observations of the Centaurus cluster out to 0.95r200,
taken along a strip to the north west. We have also used congruent Chandra
observations of the outskirts to resolve point sources down to a threshold flux
around 7 times lower than that achievable with just Suzaku data, considerably
reducing the systematic uncertainties in the cosmic X-ray background emission
in the outskirts. We find that the temperature decreases by a factor of 2 from
the peak temperature to the outskirts. The entropy profile demonstrates a
central excess (within 0.5r200) over the baseline entropy profile predicted by
simulations of purely gravitational hierarchical structure formation. In the
outskirts the entropy profile is in reasonable agreement with the baseline
entropy profile from Voit et al., but lies slightly below it. We find that the
pressure profile agrees with the universal pressure profile of Arnaud et al.
but lies slightly above it in the outskirts. The excess pressure and decrement
in entropy in the outskirts appear to be the result of an excess in the
measured gas density, possible due to gas clumping biasing the density
measurements high. The gas mass fraction rises and reaches the mean cosmic
baryon fraction at the largest radius studied. The clumping corrected gas mass
fraction agrees with the expected hot gas fraction and with the simulations of
Young et al. We further the analysis of Walker et al. which studied the shapes
of the entropy profiles of the clusters so far explored in the outskirts with
Suzaku. When scaled by the self similar entropy the Suzaku entropy profiles
demonstrate a central excess over the baseline entropy profile, and are
consistent with it at around r500 . However outside r500 the entropy profiles
tend to lie below the baseline entropy profile.

The IMACS Cluster Building Survey. III. The Star Formation Histories of Field Galaxies. (arXiv:1303.3916v1 [astro-ph.CO])

The IMACS Cluster Building Survey. III. The Star Formation Histories of Field Galaxies. (arXiv:1303.3916v1 [astro-ph.CO]):
Using data from the IMACS Cluster Building Survey and from nearby galaxy
surveys, we examine the evolution of the rate of star formation in field
galaxies from $ z = 0.60$ to the present. Fitting the luminosity function to a
standard Schechter form, we find a rapid evolution of $M_B^*$ consistent with
that found in other deep surveys; at the present epoch $M_B^*$ is evolving at
the rate of $0.38 Gyr^{-1}$, several times faster than the predictions of
simple models for the evolution of old, coeval galaxies. The evolution of the
distribution of specific star formation rates (SSFR) is also too rapid to
explain by such models. We demonstrate that starbursts cannot, even in
principle, explain the evolution of the SSFR distribution. However, the rapid
evolution of both $M_B^*$ and the SSFR distribution can be explained if some
fraction of galaxies have star formation rates characterized by both short rise
and fall times and by an epoch of peak star formation more recent than the
majority of galaxies. Although galaxies of every stellar mass up to
$1.4\times10^{11}\Msun$ show a range of epochs of peak star formation, the
fraction of "younger" galaxies falls from about 40% at a mass of
$4\times10^{10}\Msun$ to zero at a mass of $1.4\times10^{11}\Msun$. The
incidence of younger galaxies appears to be insensitive to the density of the
local environment; but does depend on group membership: relatively isolated
galaxies are much more likely to be young than are group members.

Winds, Clumps, and Interacting Cosmic Rays in M82. (arXiv:1303.4305v1 [astro-ph.HE])

Winds, Clumps, and Interacting Cosmic Rays in M82. (arXiv:1303.4305v1 [astro-ph.HE]):
We construct a family of models for the evolution of energetic particles in
the starburst galaxy M82 and compare them to observations to test the
calorimeter assumption that all cosmic ray energy is radiated in the starburst
region. Assuming constant cosmic ray acceleration efficiency with Milky Way
parameters, we calculate the cosmic-ray proton and primary and secondary
electron/positron populations as a function of energy. Cosmic rays are injected
with Galactic energy distributions and electron-to-proton ratio via type II
supernovae at the observed rate of 0.07/yr. From the cosmic ray spectra, we
predict the radio synchrotron and \gamma-ray spectra. To more accurately model
the radio spectrum, we incorporate a multiphase interstellar medium in the
starburst region of M82. Our model interstellar medium is highly fragmented
with compact dense molecular clouds and dense photoionized gas, both embedded
in a hot, low density medium in overall pressure equilibrium. The spectra
predicted by this one-zone model are compared to the observed radio and
\gamma-ray spectra of M82. Chi-squared tests are used with radio and \gamma-ray
observations and a range of model predictions to find the best-fit parameters.
The best-fit model yields constraints on key parameters in the starburst zone
of M82, including a magnetic field strength of ~250 \mu G and a wind advection
speed in the range of 300-700 km/s. We find that M82 is a good electron
calorimeter but not an ideal cosmic-ray proton calorimeter and discuss the
implications of our results for the astrophysics of the far infrared-radio
correlation in starburst galaxies.

The hard X-ray spectrum of NGC 1365: scattered light, not black hole spin. (arXiv:1303.4309v1 [astro-ph.HE])

The hard X-ray spectrum of NGC 1365: scattered light, not black hole spin. (arXiv:1303.4309v1 [astro-ph.HE]):
Active Galactic Nuclei (AGN) show excess X-ray emission above 10 keV compared
with extrapolation of spectra from lower energies. Risaliti et al. have
recently attempted to model the hard X-ray excess in the type 1.8 AGN NGC 1365,
concluding that the hard excess most likely arises from Compton-scattered
reflection of X-rays from an inner accretion disk close to the black hole.
Their analysis disfavored a model in which the hard excess arises from a high
column density of circumnuclear gas partially covering a primary X-ray source,
despite such components being required in the NGC 1365 data below 10 keV. Using
a Monte Carlo radiative transfer approach, we demonstrate that this conclusion
is invalidated by (i) use of slab absorption models, which have unrealistic
transmission spectra for partial covering gas, (ii) neglect of the effect of
Compton scattering on transmitted spectra and (iii) inadequate modeling of the
expected spectrum of scattered X-rays. The scattered spectrum is geometry
dependent and, for high global covering factors, may dominate above 10 keV. We
further show that, in models of circumnuclear gas, the suppression of the
observed hard X-ray flux by reprocessing may be no larger than required by the
`light bending' model invoked for inner disk reflection, and the expected
emission line strengths lie within the observed range. We conclude that the
time-invariant `red wing' in X-ray spectra is probably caused by continuum
transmitted through and scattered from circumnuclear gas, not by highly
redshifted line emission, and that measurement of black hole spin is not
possible.