506 research outputs found
Ancillary Testing in Lung Cancer Diagnosis
The pathologic diagnosis of lung cancer historically has relied primarily on morphologic features of tumors in histologic sections. With the emergence of new targeted therapies, the pathologist is called upon increasingly to provide not only accurate typing of lung cancers, but also to provide prognostic and predictive information, based on a growing number of ancillary tests, that may have significant impact on patient management. This review provides an overview of ancillary tests currently used in the pathologic diagnosis of lung cancer, with a focus on immunohistochemistry and molecular diagnostics
Properties of Dark Matter Haloes
An overview is presented of the main properties of dark matter haloes, as we
know them from observations, essentially from rotation curves around spiral and
dwarf galaxies. Detailed rotation curves are now known for more than a thousand
galaxies, revealing that they are not so flat in the outer parts, but rising
for late-types, and falling for early-types. A well established result now is
that most bright galaxies are not dominated by dark matter inside their optical
disks. Only for dwarfs and LSB (Low Surface Brightness galaxies) dark matter
plays a dominant role in the visible regions. The 3D-shape of haloes are
investigated through several methods, that will be discussed: polar rings,
flaring of HI planes, X-ray isophotes.
It is not yet possible with rotation curves to know how far haloes extend,
but tentatives have been made. It will be shown that the dark matter appears to
be coupled to the gas in spirals and dwarfs, suggesting that dark baryons could
play the major role in rotation curves. Theories proposing to replace the
non-baryonic dark matter by a different dynamical or gravity law, such as MOND,
have to take into account the dark baryons, especially since their spatial
distribution is likely to be quite different from the visible matter.Comment: 20 pages, 8 figures, submitted to NewA Reviews, review given at MOND
workshop, Paris, October 200
Radial Mixing in Galactic Disks: The Effects of Disk Structure and Satellite Bombardment
We use a suite of numerical simulations to investigate the mechanisms and
effects of radial migration of stars in disk galaxies like the Milky Way (MW).
An isolated, collisionless stellar disk with a MW-like scale-height shows only
the radial "blurring" expected from epicyclic orbits. Reducing the disk
thickness or adding gas to the disk substantially increases the level of radial
migration, induced by interaction with transient spiral arms and/or a central
bar. We also examine collisionless disks subjected to gravitational
perturbations from a cosmologically motivated satellite accretion history. In
the perturbed disk that best reproduces the observed properties of the MW, 20%
of stars that end up in the solar annulus 7 kpc < R < 9 kpc started at R < 6
kpc, and 7% started at R > 10 kpc. This level of migration would add
considerable dispersion to the age-metallicity relation of solar neighborhood
stars. In the isolated disk models, the probability of migration traces the
disk's radial mass profile, but in perturbed disks migration occurs
preferentially at large radii, where the disk is more weakly bound. The orbital
dynamics of migrating particles are also different in isolated and perturbed
disks: satellite perturbations drive particles to lower angular momentum for a
given change in radius. Thus, satellite perturbations appear to be a distinct
mechanism for inducing radial migration, which can operate in concert with
migration induced by bars and spiral structure. We investigate correlations
between changes in radius and changes in orbital circularity or vertical
energy, identifying signatures that might be used to test models and
distinguish radial migration mechanisms in chemo-dynamical surveys of the MW
disk.Comment: Full resolution paper available at
http://www.astronomy.ohio-state.edu/~bird/bkw11_fullres.pdf . 13 pages, 12
figures; emulate MNRAS format. Accepted for publication in MNRA
The Orbital Structure of Triaxial Galaxies with Figure Rotation
We survey the properties of all orbit families in the rotating frame of a
family of realistic triaxial potentials with central supermassive black holes
(SMBHs). In such galaxies, most regular box orbits (vital for maintaining
triaxiality) are associated with resonances which occupy two-dimensional
surfaces in configuration space. For slow figure rotation all orbit families
are largely stable. At intermediate pattern speeds a significant fraction of
the resonant box orbits as well as inner long-axis tubes are destabilized by
the "envelope doubling" that arises from the Coriolis forces and are driven
into the destabilizing center. Thus, for pattern rotation periods .2 Gyr < Tp <
5 Gyr, the two orbit families that are most important for maintaining
triaxiality are highly chaotic. As pattern speed increases there is also a
sharp decrease in the overall fraction of prograde short-axis tubes and a
corresponding increase in the retrograde variety. At the highest pattern speeds
(close to that of triaxial bars), box-like orbits undergo a sudden transition
to a new family of stable retrograde loop-like orbits, which resemble orbits in
three-dimensional bars, and circulate about the short axis. Our analysis
implies that triaxial systems (with central cusps and SMBHs) can either have
high pattern speeds like fast bars or low patten speeds like triaxial
elliptical galaxies or dark matter halos found in N-body simulations.
Intermediate pattern speeds produce a high level of stochasticity in both the
box and inner long-axis tube orbit families implying that stable triaxial
systems are unlikely to have such pattern speeds.Comment: Version accepted for publication in ApJ, Vol 727, Feb. 1 issue, 201
The Shape of Galaxy Cluster Dark Matter Haloes: Systematics of Its Imprint on Cluster Gas, and Comparison to Observations
(Abridged) We study predictions for galaxy cluster observables that can test
the statistics of dark matter halo shapes expected in a flat LCDM universe. We
present a simple analytical model for the prediction of cluster-scale X-ray
observations, approximating clusters as isothermal systems in hydrostatic
equilibrium, and dark matter haloes as ellipsoids with uniform axial ratios. We
test the model against high-resolution, hydrodynamic cluster simulations to
gauge its reliability. We find that this simple prescription does a good job of
predicting the distribution of cluster X-ray ellipticities compared to the
simulations as long as one focuses on cluster regions that are less sensitive
to recent mergers. Based on this simple model, the distribution of cluster-size
halo shapes expected in the concordance LCDM cosmology implies an X-ray
ellipticity distribution with a mean of 0.32 +- 0.01 and a scatter of 0.14 +-
0.01 for the mass range (1-4)x10^{14} Msun/h. We find it important to include
the mass dependence of halo shape to make comparisons to observational samples
that contain many, very massive clusters. We analyse the systematics of four
observational samples of cluster ellipticities and find that our results are
statistically compatible with observations. In particular, we find remarkably
good agreement between two recent ROSAT samples and LCDM predictions that DO
NOT include gas cooling. We also test how well our analytical model can predict
Sunyaev-Zel'dovich decrement maps and find that it is less successful although
still useful; the model does not perform as well as a function of flux level in
this case because of the changing triaxiality of dark matter haloes as a
function of radial distance. Both this effect and the changing alignment of
isodensity shells of dark matter haloes leave an imprint on cluster gas...Comment: 16 pages, 9 figures; corrected typo (no result affected) submitted to
MNRA
The remnants of galaxy formation from a panoramic survey of the region around M31
In hierarchical cosmological models, galaxies grow in mass through the
continual accretion of smaller ones. The tidal disruption of these systems is
expected to result in loosely bound stars surrounding the galaxy, at distances
that reach times the radius of the central disk. The number,
luminosity and morphology of the relics of this process provide significant
clues to galaxy formation history, but obtaining a comprehensive survey of
these components is difficult because of their intrinsic faintness and vast
extent. Here we report a panoramic survey of the Andromeda galaxy (M31). We
detect stars and coherent structures that are almost certainly remnants of
dwarf galaxies destroyed by the tidal field of M31. An improved census of their
surviving counterparts implies that three-quarters of M31's satellites brighter
than await discovery. The brightest companion, Triangulum (M33), is
surrounded by a stellar structure that provides persuasive evidence for a
recent encounter with M31. This panorama of galaxy structure directly confirms
the basic tenets of the hierarchical galaxy formation model and reveals the
shared history of M31 and M33 in the unceasing build-up of galaxies.Comment: Published in Nature. Supplementary movie available at
https://www.astrosci.ca/users/alan/PANDAS/Latest%20news%3A%20movie%20of%20orbit.htm
Close companions to Brightest Cluster Galaxies: Support for minor mergers and downsizing
We identify close companions of Brightest Cluster Galaxies (BCGs) for the
purpose of quantifying the rate at which these galaxies grow via mergers. By
exploiting deep photometric data from the CFHTLS, we probe the number of
companions per BCG (Nc) with luminosity ratios down to those corresponding to
potential minor mergers of 20:1. We also measure the average luminosity in
companions per galaxy (Lc). We find that Nc and Lc rise steeply with luminosity
ratio for both the BCGs, and a control sample of other bright, red, cluster
galaxies. The trend for BCGs rises more steeply, resulting in a larger number
of close companions. For companions within 50kpc of a BCG, Nc= 1.38+/-0.14 and
Lc=(2.14+/-0.31)x10^(10)L_sun and for companions within 50kpc of a luminosity
matched control sample of non-BCGs, Nc=0.87+/-0.08 and
Lc=(1.48+/-0.20)x10^(10)L_sun. This suggests that the BCGs are likely to
undergo more mergers compared to otherwise comparable luminous galaxies.
Additionally, compared to a local sample of luminous red galaxies, the more
distant sample presented in this study (with redshifts between 0.15-0.39,)
shows a higher Nc, suggesting the younger and smaller BCGs are still undergoing
hierarchical formation. Using the Millennium Simulations we model and estimate
the level of contamination due to unrelated cluster galaxies. The contamination
by interloping galaxies is 50% within projected separations of 50kpc, but
within 30kpc, 60% of identified companions are real physical companions. We
conclude that the luminosity of bound merger candidates down to luminosity
ratios of 20:1 could be adding as much as 10% to the mass of a typical BCG over
0.5Gyr at redshifts of z~0.3.Comment: 10 pages, 7 figures. Accepted and to be published in MNRA
Compact groups in theory and practice -- IV. The connection to large-scale structure
We investigate the properties of photometrically-selected compact groups
(CGs) in the Sloan Digital Sky Survey. In this paper, the fourth in a series,
we focus on understanding the characteristics of our observed CG sample with
particular attention paid to quantifying and removing contamination from
projected foreground or background galaxies. Based on a simple comparison of
pairwise redshift likelihoods, we find that approximately half of compact
groups in the parent sample contain one or more projected (interloping)
members; our final clean sample contains 4566 galaxies in 1086 compact groups.
We show that half of the remaining CGs are associated with rich groups (or
clusters), i.e. they are embedded sub-structure. The other half have spatial
distributions and number-density profiles consistent with the interpretation
that they are either independently distributed structures within the field
(i.e. they are isolated) or associated with relatively poor structures.
Comparisons of late-type and red-sequence fractions in radial annuli show that
galaxies around apparently isolated compact groups resemble the field
population by 300 to 500 kpc from the group centre. In contrast, the galaxy
population surrounding embedded compact groups appears to remain distinct from
the field out beyond 1 to 2 Mpc, consistent with results for rich groups. We
take this as additional evidence that the observed distinction between compact
groups, i.e. isolated vs. embedded, is a separation between different host
environments.Comment: 15 pages, 11 figures. Accepted for publication in MNRA
Barred Galaxies in the Abell 901/2 Supercluster with STAGES
We present a study of bar and host disk evolution in a dense cluster
environment, based on a sample of ~800 bright (MV <= -18) galaxies in the Abell
901/2 supercluster at z~0.165. We use HST ACS F606W imaging from the STAGES
survey, and data from Spitzer, XMM-Newton, and COMBO-17. We identify and
characterize bars through ellipse-fitting, and other morphological features
through visual classification. (1) We explore three commonly used methods for
selecting disk galaxies. We find 625, 485, and 353 disk galaxies, respectively,
via visual classification, a single component S'ersic cut (n <= 2.5), and a
blue-cloud cut. In cluster environments, the latter two methods miss 31% and
51%, respectively, of visually-identified disks. (2) For moderately inclined
disks, the three methods of disk selection yield a similar global optical bar
fraction (f_bar-opt) of 34% +10%/-3%, 31% +10%/-3%, and 30% +10%/-3%,
respectively. (3) f_bar-opt rises in brighter galaxies and those which appear
to have no significant bulge component. Within a given absolute magnitude bin,
f_bar-opt is higher in visually-selected disk galaxies that have no bulge as
opposed to those with bulges. For a given morphological class, f_bar-opt rises
at higher luminosities. (4) For bright early-types, as well as faint late-type
systems with no evident bulge, the optical bar fraction in the Abell 901/2
clusters is comparable within a factor of 1.1 to 1.4 to that of field galaxies
at lower redshifts (5) Between the core and the virial radius of the cluster at
intermediate environmental densities, the optical bar fraction does not appear
to depend strongly on the local environment density and varies at most by a
factor of ~1.3. We discuss the implications of our results for the evolution of
bars and disks in dense environments.Comment: accepted for publication in ApJ, abstract abridged, for high
resolution figures see
http://www.as.utexas.edu/~marinova/STAGES/STAGES_bars.pd
Stellar population gradients in brightest cluster galaxies
We present the stellar population and velocity dispersion gradients for a
sample of 24 brightest cluster galaxies (BCGs) in the nearby Universe for which
we have obtained high quality long-slit spectra at the Gemini telescopes. With
the aim of studying the possible connection between the formation of the BCGs
and their host clusters, we explore the relations between the stellar
population gradients and properties of the host clusters as well as the
possible connections between the stellar population gradients and other
properties of the galaxies. We find mean stellar population gradients (negative
{\Delta}[Z/H]/log r gradient of -0.285{\pm}0.064; small positive {\Delta}log
(age)/log r gradient of 0.069{\pm}0.049; and null {\Delta}[E/Fe]/log r gradient
of -0.008{\pm}0.032) that are consistent with those of normal massive
elliptical galaxies. However, we find a trend between metallicity gradients and
velocity dispersion (with a negative slope of -1.616{\pm}0.539) that is not
found for the most massive ellipticals. Furthermore, we find trends between the
metallicity gradients and K-band luminosities (with a slope of 0.173{\pm}0.081)
as well as the distance from the BCG to the X-ray peak of the host cluster
(with a slope of -7.546{\pm}2.752). The latter indicates a possible relation
between the formation of the cluster and that of the central galaxy.Comment: 23 pages, 18 figures, accepted for publication in MNRAS. arXiv admin
note: text overlap with arXiv:1104.2376v
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