Wide-Field Precision Kinematics of the M87 Globular Cluster System. (arXiv:1110.2778v1 [astro-ph.CO])

We present the most extensive combined photometric and spectroscopic study to
date of the enormous globular cluster (GC) system around M87, the central giant
elliptical galaxy in the nearby Virgo cluster. Using observations from DEIMOS
and LRIS at Keck, and Hectospec on the MMT, we derive new, precise radial
velocities for 451 GCs around M87, with projected radii from ~ 5 to 185 kpc. We
combine these measurements with literature data for a total sample of 737
objects, which we use for a re-examination of the kinematics of the GC system
of M87. The velocities are analyzed in the context of archival wide-field
photometry and a novel Hubble Space Telescope catalog of half-light radii,
which includes sizes for 344 spectroscopically confirmed clusters. We use this
unique catalog to identify 18 new candidate ultra-compact dwarfs, and to help
clarify the relationship between these objects and true GCs.

We find much lower values for the outer velocity dispersion and rotation of
the GC system than in earlier papers, and also differ from previous work in
seeing no evidence for a transition in the inner halo to a potential dominated
by the Virgo cluster, nor for a truncation of the stellar halo. We find little
kinematical evidence for an intergalactic GC population. Aided by the precision
of the new velocity measurements, we see significant evidence for kinematical
substructure over a wide range of radii, indicating that M87 is in active
assembly. A simple, scale-free analysis finds less dark matter within ~85 kpc
than in other recent work, reducing the tension between X-ray and optical
results. In general, out to a projected radius of ~ 150 kpc, our data are
consistent with the notion that M87 is not dynamically coupled to the Virgo
cluster; the core of Virgo may be in the earliest stages of assembly.

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A new cosmological distance measure using AGN. (arXiv:1109.4632v1 [astro-ph.CO])

Accurate distances to celestial objects are key to establishing the age and
energy density of the Universe and the nature of dark energy. A distance
measure using active galactic nuclei (AGN) has been sought for more than forty
years, as they are extremely luminous and can be observed at very large
distances. We report here the discovery of an accurate luminosity distance
measure using AGN. We use the tight relationship between the luminosity of an
AGN and the radius of its broad line region established via reverberation
mapping to determine the luminosity distances to a sample of 38 AGN. All
reliable distance measures up to now have been limited to moderate redshift –
AGN will, for the first time, allow distances to be estimated to z~4, where
variations of dark energy and alternate gravity theories can be probed.

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CANDELS: Constraining the AGN-Merger Connection with Host Morphologies at z~2. (arXiv:1109.2588v1 [astro-ph.CO])

Using HST/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared
Deep Extragalactic Legacy Survey (CANDELS), we examine the role that major
galaxy mergers play in triggering active galactic nuclei (AGN) activity at z~2.
Our sample consists of 72 moderate-luminosity (Lx ~ 1E42-1E44 erg/s) AGN at
1.5<z<2.5 that are selected using the 4 Msec Chandra observations in the
Chandra Deep Field South, the deepest X-ray observations to date. Employing
visual classifications, we have analyzed the rest-frame optical morphologies of
the AGN host galaxies and compared them to a mass-matched control sample of 216
non-active galaxies at the same redshift. We find that most of the AGN reside
in disk galaxies (51.4%), while a smaller percentage are found in spheroids
(27.8%). Roughly 16.7% of the AGN hosts have highly disturbed morphologies and
appear to be involved in a major merger or interaction, while most of the hosts
(55.6%) appear relatively relaxed and undisturbed. These fractions are
statistically consistent with the fraction of control galaxies that show
similar morphological disturbances. These results suggest that the hosts of
moderate-luminosity AGN are no more likely to be involved in an ongoing merger
or interaction relative to non-active galaxies of similar mass at z~2. The high
disk fraction observed among the AGN hosts also appears to be at odds with
predictions that merger-driven accretion should be the dominant AGN fueling
mode at z~2, even at moderate X-ray luminosities. Although we cannot rule out
that minor mergers are responsible for triggering these systems, the presence
of a large population of relatively undisturbed disk-like hosts suggests that
secular processes play a greater role in fueling AGN activity at z~2 than
previously thought.

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The Bispectrum of f(R) Cosmologies. (arXiv:1109.2115v1 [astro-ph.CO])

In this paper we analyze a suite of cosmological simulations of modified
gravitational action f(R) models, where cosmic acceleration is induced by a
scalar field that acts as a fifth force on all forms of matter. In particular,
we focus on the bispectrum of the dark matter density field on mildly
non-linear scales. For models with the same initial power spectrum, the dark
matter bispectrum shows significant differences for cases where the final dark
matter power spectrum also differs. Given the different dependence on bias of
the galaxy power spectrum and bispectrum, bispectrum measurements can close the
loophole of galaxy bias hiding differences in the power spectrum.
Alternatively, changes in the initial power spectrum can also hide differences.
By constructing LCDM models with very similar final non-linear power spectra,
we show that the differences in the bispectrum are reduced (<4%) and are
comparable with differences in the imperfectly matched power spectra. These
results indicate that the bispectrum depends mainly on the power spectrum and
less sensitively on the gravitational signatures of the f(R) model. This weak
dependence of the matter bispectrum on gravity makes it useful for breaking
degeneracies associated with galaxy bias, even for models beyond general
relativity.

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Do Anomalous Narrow Line Quasars Cast Doubt on Virial Mass Estimation?. (arXiv:1109.1554v1 [astro-ph.HE])

Anomalous Narrow-Line Quasars (ANLs) are a population of quasars with narrow
H\beta, and sometimes [O III] broader than ~1000 km/s, in total comprising \sim
10-30% (most likely ~25%) of Type I quasars at 0.2 < z < 0.8. We find that
virial masses using the H\beta and Mg II lines systematically differ for ANLs
by an average of as much as 0.5 dex. Because the broad H\beta component width
increases in ANLs but Mg II does not, we might suspect H\beta-based virial
masses for ANLs are wrong but Mg II masses are correct. If this is due to an
outflow reaching the lower-ionization potential H\beta line, C IV masses will
be similarly flawed. However, we cannot be certain of this explanation without
followup work, and may be unable to identify which quasars are ANLs at z > 0.8.
Therefore, it is essential that ANLs be well-understood and well-modeled in
order to allow the use of virial mass estimators on large optical spectroscopic
catalogs, particularly at z < 0.4 and z > 2.0 where only one broad line is
available for use in mass estimation.

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Non-singular Cyclic Cosmology without Phantom Menace. (arXiv:1108.6052v1 [gr-qc])

In this article we review recent developments of cyclic cosmology. A typical
non-singular cyclic model within General Relativity requires a non-conventional
fluid with negative effective energy density, in order to cancel the matter
component and lead to a non-singular bounce. However, the existence of such a
non-conventional fluid usually leads to quantum instabilities and makes the
theory ill-defined. In the present work we follow the alternative way,
obtaining two scenarios of non-singular cyclic cosmological evolutions in the
context of gravitational theories beyond General Relativity. The
degrees-of-freedom examination reveals that these two models are free of the
Phantom Menace. Our analysis illustrates that, if cyclic cosmology describes
overall universe, a theory of gravity beyond Einstein may be expected.

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Jet formation from massive young stars: Magnetohydrodynamics versus radiation pressure. (arXiv:1108.4924v1 [astro-ph.SR])

Observations indicate that outflows from massive young stars are more
collimated during their early evolution compared to later stages. Our paper
investigates various physical processes that impacts the outflow dynamics, i.e.
its acceleration and collimation. We perform axisymmetric MHD simulations
particularly considering the radiation pressure exerted by the star and the
disk. We have modified the PLUTO code to include radiative forces in the
line-driving approximation. We launch the outflow from the innermost disk
region (r < 50 AU) by magneto-centrifugal acceleration. In order to disentangle
MHD effects from radiative forces, we start the simulation in pure MHD, and
later switch on the radiation force. We perform a parameter study considering
different stellar masses (thus luminosity), magnetic flux, and line-force
strength. For our reference simulation – assuming a 30 Msun star, we find
substantial de-collimation of 35 % due to radiation forces. The opening angle
increases from 20 deg to 32 deg for stellar masses from 20 Msun to 60 Msun. A
small change in the line-force parameter ‘alpha’ from 0.60 to 0.55 changes the
opening angle by ~ 8 deg. We find that it is mainly the stellar radiation which
affects the jet dynamics. Unless the disk extends very close to the star, its
pressure is too small to have much impact. Essentially, our parameter runs with
different stellar mass can be understood as a proxy for the time evolution of
the star-outflow system. Thus, we have shown that when the stellar mass (thus
luminosity) increases (with age), the outflows become less collimated.

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The Long-Term Evolution of Double White Dwarf Mergers. (arXiv:1108.4036v1 [astro-ph.HE])

In this paper, we present a model for the long-term evolution of the merger
of two unequal mass C/O white dwarfs (WDs). After the dynamical phase of the
merger, magnetic stresses rapidly redistribute angular momentum, leading to
nearly solid body rotation on a viscous timescale, 1e4-1e8 s, long before
significant cooling can occur. Because of heating during the dynamical and
viscous phases, the less massive WD is transformed into a hot radially extended
envelope supported by thermal pressure and with the majority of the mass having
negligible rotational support. This extended envelope then undergoes
Kelvin-Helmholtz contraction on a thermal timescale of ~1e4 yr; during this
period, the merger remnant radiates near the Eddington limit. Given the double
WD merger rate of a few per 1000 yr, a few dozen of these near-Eddington
sources should exist in a Milky Way-type galaxy.

In our calculations, the contraction of the cooling envelope is relatively
rapid, and the base of the envelope is compressed until off-center convective
C-burning begins. As a result, the long-term evolution of the merger remnant is
similar to that seen in previous calculations, and a collapse to a neutron
star, rather than a Type Ia supernova, is the likely outcome. However, the
physical picture and the dynamical state of the matter in our model differ from
previous work. Furthermore, substantial remaining uncertainties related to the
opacity of the envelope and mass loss during the thermal evolution may
significantly affect our conclusions. Thus, future work within the context of
the physical model presented here is required to better address the potential
of WD mergers as Type Ia supernova progenitors.

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Impact of Protostellar Outflow on Star Formation: Effects of Initial Cloud Mass. (arXiv:1108.3564v1 [astro-ph.SR])

Star formation efficiency controlled by the protostellar outflow in a single
cloud core is investigated by three-dimensional resistive MHD simulations.
Starting from the prestellar cloud core, the star formation process is
calculated until the end of the main accretion phase. In the calculations, the
mass of the prestellar cloud is parameterized. During the star formation, the
protostellar outflow is driven by the circumstellar disk. The outflow extends
also in the transverse direction until its width becomes comparable to the
initial cloud scale, and thus, the outflow has a wide opening angle of >40
degrees. As a result, the protostellar outflow sweeps up a large fraction of
the infalling material and ejects it into the interstellar space. The outflow
can eject at most over half of the host cloud mass, significantly decreasing
star formation efficiency. The outflow power is stronger in clouds with a
greater initial mass. Thus, the protostellar outflow effectively suppresses
star formation efficiency in a massive cloud. The outflow weakens significantly
and disappears in several free-fall timescales of the initial cloud after the
cloud begins to collapse. The natal prestellar core influences the lifetime and
size of the outflow. At the end of the main accretion phase, a massive
circumstellar disk comparable in mass to the protostar remains. Calculations
show that typically, ~30% of the initial cloud mass is converted into the
protostar and ~20% remains in the circumstellar disk, while ~40% is ejected
into the interstellar space by the protostellar outflow. Therefore, a single
cloud core typically has a star formation efficiency of 30-50%.

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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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