Central Powering of the Largest Lyman-alpha Nebula is Revealed by Polarized Radiation. (arXiv:1108.3332v1 [astro-ph.CO])

High-redshift Lyman-alpha blobs are extended, luminous, but rare structures
that appear to be associated with the highest peaks in the matter density of
the Universe. Their energy output and morphology are similar to powerful radio
galaxies, but the source of the luminosity is unclear. Some blobs are
associated with ultraviolet or infrared bright galaxies, suggesting an extreme
starburst event or accretion onto a central black hole. Another possibility is
gas that is shock excited by supernovae. However some blobs are not associated
with galaxies, and may instead be heated by gas falling into a dark matter
halo. The polarization of the Ly-alpha emission can in principle distinguish
between these options, but a previous attempt to detect this signature returned
a null detection. Here we report on the detection of polarized Ly-alpha from
the blob LAB1. Although the central region shows no measurable polarization,
the polarized fraction (P) increases to ~20 per cent at a radius of 45 kpc,
forming an almost complete polarized ring. The detection of polarized radiation
is inconsistent with the in situ production of Ly-alpha photons, and we
conclude that they must have been produced in the galaxies hosted within the
nebula, and re-scattered by neutral hydrogen.

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Characterization of Seven Ultra-Wide Trans-Neptunian Binaries. (arXiv:1108.2505v1 [astro-ph.EP])

The low-inclination component of the Classical Kuiper Belt is host to a
population of extremely widely-separated binaries. These systems are similar to
other Trans-Neptunian binaries (TNBs) in that the primary and secondary
components of each system are of roughly equal size. We have performed an
astrometric monitoring campaign of a sample of seven wide-separation,
long-period TNBs and present the first-ever well-characterized mutual orbits
for each system. The sample contains the most eccentric (2006 CH69, e=0.9) and
the most widely-separated, weakly bound (2001 QW322, a/Rh~0.22) binary minor
planets known, and also contains the system with lowest-measured mass of any
TNB (2000 CF105, M~1.85E17 kg). Four systems orbit in a prograde sense, and
three in a retrograde sense. They have a different mutual inclination
distribution compared to all other TNBs, preferring low mutual-inclination
orbits. These systems have geometric r-band albedos in the range of 0.09-0.3,
consistent with radiometric albedo estimates for larger solitary
low-inclination Classical Kuiper Belt objects, and we limit the plausible
distribution of albedos in this region of the Kuiper Belt. We find that
gravitational collapse binary formation models produce a similar orbital
distribution to that currently observed, which along with a confluence of other
factors supports formation of the cold Classical Kuiper Belt in situ through
relatively rapid gravitational collapse rather than slow hierarchical
accretion. We show that these binary systems are sensitive to disruption via
collisions, and their existence suggests that the size distribution of TNOs at
small sizes remains relatively shallow.

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Turbulence, Reconnection and Cosmic Rays in Galaxy Clusters. (arXiv:1108.2268v1 [astro-ph.CO])

Recent years have been marked by substantial changes in our understanding of
magnetic turbulence and magnetic reconnection, which, in its turn induced
better understanding of cosmic ray diffusion and acceleration. Current models
of magnetized turbulence are no more ad hoc constructions, but numerically
tested theories. In this very short review we summarize topics presented in two
talks given at the conference and provide a brief sketch of the vast and
rapidly developing field. We discuss how turbulence decreases the efficient
mean free path of the particles in the collisionless plasmas in galaxy clusters
and claim that this makes MHD turbulence description applicable to a wider
range of scales. We discuss the properties of MHD turbulence and its relation
to magnetic reconnection. Finally, we overview how turbulence induces particle
acceleration via second order Fermi process and affects first order Fermi
acceleration in shocks and reconnection regions.

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Mass growth and mergers: direct observations of the luminosity function of LRG satellite galaxies out to z=0.7 from SDSS and BOSS images. (arXiv:1108.1392v1 [astro-ph.CO])

We present a statistical study of the luminosity functions of galaxies
surrounding luminous red galaxies (LRGs) at average redshifts <z>=0.34 and
<z>=0.65. The luminosity functions are derived by extracting source photometry
around the LRGs and subtracting foreground and background contamination using
randomly selected control fields. We show that at both studied redshifts the
average luminosity functions of the LRGs and their satellite galaxies are
poorly fitted by a Schechter function due to a luminosity gap between the
centrals and their most luminous satellites. We utilize a two-component fit of
a Schechter function plus a log-normal distribution to demonstrate that LRGs
are typically brighter than their most luminous satellite by roughly 1.3
magnitudes. This luminosity gap implies that interactions within LRG
environments are typically restricted to minor mergers with mass ratios of 1:4
or lower. The luminosity functions further imply that roughly 35% of the mass
in the environment is locked in the LRG itself, supporting the idea that mass
growth through major mergers within the environment is unlikely. Lastly, we
show that the luminosity gap may be at least partially explained by the
selection of LRGs as the gap can be reproduced by sparsely sampling a Schechter
function. In that case LRGs may represent only a small fraction of central
galaxies in similar mass halos.

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The broad line and gamma-ray luminosity relation in Fermi blazars. (arXiv:1108.0927v1 [astro-ph.HE])

We study the relation between the mass accretion rate, the jet power, and the
black hole mass of blazars. To this aim, we make use of the Sloan Digital Sky
Survey (SDSS) and the 11 months catalog of blazars detected at energies larger
than 100 MeV by the Large Area Telescope (LAT) onboard the Fermi satellite.
This allows to construct a relatively large sample of blazars with information
about the luminosity (or upper limits) of their emission lines used as a proxy
for the strength of the disk luminosity and on the luminosity of the high
energy emission, used as a proxy for the jet power. We find a good correlation
between the luminosity of the broad lines and the gamma-ray luminosity as
detected by Fermi, both using absolute values of the luminosities and
normalising them to the Eddington value. We confirm that the division of
blazars into BL Lacs and Flat Spectrum Radio Quasars (FSRQs) is controlled by
the line luminosity in Eddington units. If this ratio is smaller than 5×10^-4
the object is a BL Lac, while it is a FSRQs for larger values. The transition
appears smooth, but a much larger number of objects is needed to confirm this
point.

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Gamma-ray emission region located in the parsec scale jet of OJ287. (arXiv:1108.0925v1 [astro-ph.HE])

We report on the location of the gamma-ray emission region in flares of the
BL Lacertae object OJ287 at >14pc from the central supermassive black hole. We
employ data from multi-spectral range (total flux and linear polarization)
monitoring programs combined with sequences of ultra-high-resolution 7mm VLBA
images. The correlation between the brightest gamma-ray and mm flares is found
to be statistically significant. The two gamma-ray peaks, detected by
Fermi-LAT, that we report here happened at the rising phase of two
exceptionally bright mm flares accompanied by sharp linear polarization peaks.
The VLBA images show that these mm flares in total flux and polarization degree
occurred in a jet region at >14pc from the innermost jet region. The time
coincidence of the brighter gamma-ray flare and its corresponding mm linear
polarization peak evidences that both the gamma-ray and mm outbursts occur
>14pc from the central black hole. We find two sharp optical flares occurring
at the peak times of the two reported gamma-ray flares. This is interpreted as
the gamma-ray flares being produced by synchrotron self-Compton scattering of
optical photons from the flares triggered by the interaction of moving knots
with a stationary conical shock in the jet.

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Galaxy-Scale Outflows Driven by Active Galactic Nuclei. (arXiv:1107.5579v1 [astro-ph.CO])

We present hydrodynamical simulations of major mergers of galaxies and study
the effects of winds produced by active galactic nuclei (AGN) on interstellar
gas in the AGN’s host galaxy. Motivated by theoretical models and observations
of broad absorption line quasars, the wind has an initial velocity ~ 10,000
km/s and an initial momentum (energy) flux of ~ tau_w L/c (~ 0.01 tau_w L),
with tau_w ~ 1-10. This outflow sweeps up and shock heats the surrounding
interstellar gas, leading to a galaxy-scale outflow with velocities ~ 1000
km/s, peak mass outflow rates comparable to the star formation rate, and a
total ejected gas mass ~ 3 x 10^9 M_sun. Large momentum fluxes, tau_w > 3, are
required for the AGN-driven galactic outflow to suppress star formation and
accretion in the black hole’s host galaxy. We argue that this mechanism of AGN
feedback can produce the high velocity outflows observed in post-starburst
galaxies and the massive molecular and atomic outflows observed in local
ultra-luminous infrared galaxies. Moreover, the outflows from local
ultra-luminous infrared galaxies are inferred to have tau_w ~ 10, comparable to
what we find is required for AGN winds to regulate the growth of black holes
and set the M_BH-sigma relation. We conclude by discussing theoretical
mechanisms that can lead to AGN wind mass-loading and momentum/energy fluxes
large enough to have a significant impact on galaxy formation.

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The Two-Component Radio Luminosity Function of QSOs: Star Formation and AGN. (arXiv:1107.3551v1 [astro-ph.CO])

Despite decades of study, it remains unclear whether there are distinct
radio-loud and radio-quiet populations of quasi-stellar objects (QSOs). Early
studies were limited by inhomogeneous QSO samples, inadequate sensitivity to
probe the radio-quiet population, and degeneracy between redshift and
luminosity for flux-density-limited samples. Our new 6 GHz EVLA observations
allow us for the first time to obtain nearly complete (97%) radio detections in
a volume-limited color-selected sample of 179 QSOs more luminous than M_i = -23
from the Sloan Digital Sky Survey (SDSS) Data Release Seven in the narrow
redshift range 0.2 < z < 0.3. The dramatic improvement in radio continuum
sensitivity made possible with the new EVLA allows us, in 35 minutes of
integration, to detect sources as faint as 20 microJy, or log[L_6 (W/Hz)] ~
21.5 at z = 0.25, well below the radio luminosity, log[L_6 (W/Hz)] ~ 22.5, that
separates star-forming galaxies from radio-loud active galactic nuclei (AGNs)
driven by accretion onto a super-massive black hole. We calculate the radio
luminosity function (RLF) for these QSOs using three constraints: (a) EVLA 6
GHz observations for log[L_6 (W/Hz)] < 23.5, (b) NRAO-VLA Sky Survey (NVSS)
observations for log[L_6 (W/Hz)] > 23.5, and (c) the total number of SDSS QSOs
in our volume-limited sample. We show that the RLF can be explained as a
superposition of two populations, dominated by AGNs at the bright end and star
formation in the QSO host galaxies at the faint end.

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Predicting the Merger Fraction of Lyman alpha Emitters from Redshift z~3 to z~7. (arXiv:1107.2648v1 [astro-ph.CO])

Rapid mass assembly, likely from mergers or smooth accretion, has been
predicted to play a vital role in star-formation in high-redshift Lyman alpha
(Lya) emitters. Here we predict the major merger, minor merger, and smooth
accreting Lya emitter fraction from z \approx 3 to z \approx 7 using a large
dark matter simulation, and a simple physical model that is successful in
reproducing many observations over this large redshift range. The central tenet
of this model, different from many of the earlier models, is that the
star-formation in Lya emitters is proportional to the mass accretion rate
rather than the total halo mass. We find that at z~3, nearly 35% of the Lya
emitters accrete their mass through major (3:1) mergers, and this fraction
increases to about 50% at z \approx 7. This implies that the star-formation in
a large fraction of high-redshift Lya emitters is driven by mergers. Comparing
our predictions with observations, we find that the model predicted fractions
are relatively larger. To investigate this discrepancy, we perform simulated
observations in which we redshift low-z Lya emitters to higher redshifts. These
results suggest that, due to low surface brightness of Lya emitters, with the
current survey depths we are likely to miss > 30 % of merger fraction of Lya
emitters at z~3, and a much larger fraction at higher redshifts. Furthermore,
we find that the predicted merger fraction is also a sensitive function of the
mass-ratio used to define a merger. Thus we predict that future, deeper
observations which use a 3:1 definition of major mergers will find > 30% major
merger fraction of Lya emitters at redshifts > 3.

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An asteroseismic membership study of the red giants in three open clusters observed by Kepler: NGC6791, NGC6819, and NGC6811. (arXiv:1107.1234v1 [astro-ph.SR])

Studying star clusters offers significant advances in stellar astrophysics
due to the combined power of having many stars with essentially the same
distance, age, and initial composition. This makes clusters excellent test
benches for verification of stellar evolution theory. To fully exploit this
potential, it is vital that the star sample is uncontaminated by stars that are
not members of the cluster. Techniques for determining cluster membership
therefore play a key role in the investigation of clusters. We present results
on three clusters in the Kepler field of view based on a newly established
technique that uses asteroseismology to identify fore- or background stars in
the field, which demonstrates advantages over classical methods such as
kinematic and photometry measurements. Four previously identified seismic
non-members in NGC6819 are confirmed in this study, and three additional
non-members are found — two in NGC6819 and one in NGC6791. We further
highlight which stars are, or might be, affected by blending, which needs to be
taken into account when analysing these Kepler data.

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