pinecone/core-2020-05-10-deduplication huggingface dataset:
Bulge Formation via Mergers in Cosmological Simulations

The latest generation of cosmological simulations are on the verge of being
able to resolve the structure of bulges for the first time. Hence, we review
the current state of bulge formation in cosmological simulations, and discuss
open questions that can be addressed in the near future by simulators, with a
particular focus on merger-driven bulge growth. Galaxy mergers have long been
assumed to produce classical bulges in disk galaxies. Under this
bulge-formation model, though, the high rates of mergers in Cold Dark Matter
galaxy formation theory predict many more classical bulges than are observed.
Furthermore, simulations of galaxy formation continue to generally produce too
massive of bulges. Feedback offers a promising avenue for reducing
merger-driven bulge growth by maintaining high gas fractions in galaxies and
ejecting low-angular momentum gas driven to the centers of galaxies. After
reviewing the results of relevant research that has been published to date, we
use cosmological simulations to explore the ability of feedback to reduce or
even prevent bulge growth during mergers. In dwarf galaxies, mergers actually
reduce the central concentration of galaxies as the induced burst of star
formation drives out low angular momentum material. This result shows the
potential for feedback to reduce central mass growth. However, we also
demonstrate that it is very difficult for current stellar feedback models to
reproduce the small bulges observed in more massive disk galaxies like the
Milky Way. We argue that feedback models need to be improved, or an additional
source of feedback such as AGN is necessary to generate the required outflows.Comment: The first 5 sections are review, but Section 6 introduces new
  analysis. We demonstrate that mergers prevent bulge formation in low mass
  galaxies. Approximately 15 pages in MNRAS forma
Bulge growth through disk instabilities in high-redshift galaxies

The role of disk instabilities, such as bars and spiral arms, and the
associated resonances, in growing bulges in the inner regions of disk galaxies
have long been studied in the low-redshift nearby Universe. There it has long
been probed observationally, in particular through peanut-shaped bulges. This
secular growth of bulges in modern disk galaxies is driven by weak,
non-axisymmetric instabilities: it mostly produces pseudo-bulges at slow rates
and with long star-formation timescales. Disk instabilities at high redshift
(z>1) in moderate-mass to massive galaxies (10^10 to a few 10^11 Msun of stars)
are very different from those found in modern spiral galaxies. High-redshift
disks are globally unstable and fragment into giant clumps containing 10^8-10^9
Msun of gas and stars each, which results in highly irregular galaxy
morphologies. The clumps and other features associated to the violent
instability drive disk evolution and bulge growth through various mechanisms,
on short timescales. The giant clumps can migrate inward and coalesce into the
bulge in a few 10^8 yr. The instability in the very turbulent media drives
intense gas inflows toward the bulge and nuclear region. Thick disks and
supermassive black holes can grow concurrently as a result of the violent
instability. This chapter reviews the properties of high-redshift disk
instabilities, the evolution of giant clumps and other features associated to
the instability, and the resulting growth of bulges and associated sub-galactic
components.Comment: 37 pages, 9 figures. Invited refereed review to appear in "Galactic
  Bulges", E. Laurikainen, D. Gadotti, R. Peletier (eds.), Springe
Boxy/peanut/X bulges, barlenses and the thick part of galactic bars:
  What are they and how did they form?

Bars have a complex three-dimensional shape. In particular their inner part
is vertically much thicker than the parts further out. Viewed edge-on, the
thick part of the bar is what is commonly known as a boxy-, peanut- or X- bulge
and viewed face-on it is referred to as a barlens. These components are due to
disc and bar instabilities and are composed of disc material. I review here
their formation, evolution and dynamics, using simulations, orbital structure
theory and comparisons to observations.Comment: 21 pages, 7 figures, invited review to appear in "Galactic Bulges",
  E. Laurikainen, R. Peletier, D. Gadotti, (eds.), Springe
Explaining the formation of bulges with MOND

In the cold dark matter (CDM) paradigm, bulges easily form through galaxy
mergers, either major or minor, or through clumpy disks in the early universe,
where clumps are driven to the center by dynamical friction. Also
pseudo-bulges, with a more disky morphology and kinematics, can form more
slowly through secular evolution of a bar, where resonant stars are elevated
out of the plane, in a peanut/box shape. As a result, in CDM cosmological
simulations, it is very difficult to find a bulgeless galaxy, while they are
observed very frequently in the local universe. A different picture emerges in
alternative models of the missing mass problem. In MOND (MOdified Newtonian
Dynamics), galaxy mergers are much less frequent, since the absence of dark
matter halos reduces the dynamical friction between two galaxies. Also, while
clumpy galaxies lead to rapid classical bulge formation in CDM, the inefficient
dynamical friction with MOND in the early-universe galaxies prevents the clumps
to coalesce together in the center to form spheroids. This leads to less
frequent and less massive classical bulges. Bars in MOND are more frequent and
stronger, and have a more constant pattern speed, which modifies significantly
the pseudo-bulge morphology. The fraction of pseudo-bulges is expected to be
dominant in MOND.Comment: 16 pages, 8 figures, invited review to appear in "Galactic Bulges",
  E. Laurikainen, D. Gadotti, R. Peletier (eds.), Springe
Elliptical Galaxies and Bulges of Disk Galaxies: Summary of Progress and
  Outstanding Issues

This is the summary chapter of a review book on galaxy bulges. Bulge
properties and formation histories are more varied than those of ellipticals. I
emphasize two advances: 1 - "Classical bulges" are observationally
indistinguishable from ellipticals, and like them, are thought to form by major
galaxy mergers. "Disky pseudobulges" are diskier and more actively star-forming
(except in S0s) than are ellipticals. Theys are products of the slow
("secular") evolution of galaxy disks: bars and other nonaxisymmetries move
disk gas toward the center, where it starbursts and builds relatively flat,
rapidly rotating components. This secular evolution is a new area of galaxy
evolution work that complements hierarchical clustering. 2 - Disks of
high-redshift galaxies are unstable to the formation of mass clumps that sink
to the center and merge - an alternative channel for the formation of classical
bulges. I review successes and unsolved problems in the formation of
bulges+ellipticals and their coevolution (or not) with supermassive black
holes. I present an observer's perspective on simulations of dark matter galaxy
formation including baryons. I review how our picture of the quenching of star
formation is becoming general and secure at redshifts z < 1. The biggest
challenge is to produce realistic bulges+ellipticals and disks that overlap
over a factor of 10**3 in mass but that differ from each other as observed over
that whole range. Second, how does hierarchical clustering make so many giant,
bulgeless galaxies in field but not cluster environments? I argue that we rely
too much on AGN and star-formation feedback to solve these challenges.Comment: 46 pages, 10 postscript figures, accepted for publication in Galactic
  Bulges, ed. E. Laurikainen, R. F. Peletier, & D. A. Gadotti (New York:
  Springer), in press (2015
The intrinsic shape of galaxy bulges

The knowledge of the intrinsic three-dimensional (3D) structure of galaxy
components provides crucial information about the physical processes driving
their formation and evolution. In this paper I discuss the main developments
and results in the quest to better understand the 3D shape of galaxy bulges. I
start by establishing the basic geometrical description of the problem. Our
understanding of the intrinsic shape of elliptical galaxies and galaxy discs is
then presented in a historical context, in order to place the role that the 3D
structure of bulges play in the broader picture of galaxy evolution. Our
current view on the 3D shape of the Milky Way bulge and future prospects in the
field are also depicted.Comment: Invited Review to appear in "Galactic Bulges" Editors: Laurikainen
  E., Peletier R., Gadotti D. Springer Publishing. 24 pages, 7 figure
An Observational Guide to Identifying Pseudobulges and Classical Bulges
  in Disk Galaxies

In this review our aim is to summarize the observed properties of
pseudobulges and classical bulges. We utilize an empirical approach to studying
the properties of bulges in disk galaxies, and restrict our analysis to
statistical proper- ties. A clear bimodality is observed in a number of
properties including morphology, structural properties, star formation, gas
content & stellar population, and kinematics. As well as summarizing known
methods to identify pseudobulges and classical bulges we also show new results,
including absorption line indices that can be used to identify different bulge
types. We conclude by summarizing those properties that isolate pseudobulges
from classical bulges. Our intention is to describe a practical, easy to use,
list of criteria for identifying bulge types.Comment: Accepted for publication in Springer Review on Bulge
Observed properties of boxy/peanut/barlens bulges

We review the observed morphological, photometric, and kinematic properties
of boxy/peanut (B/P) shape bulges. Nearly half of the bulges in the nearby
edge-on galaxies have these characteristics, which fraction is similar to the
observed bar fraction in Hubble types earlier than Scd. B/P bulges are
generally detected in the edge-on view, but it has been recently demonstrated
that barlenses, which are lens-like structures embedded in bars, are the more
face-on counterparts of the B/P bulges. Multi-component structural
decompositions have shown that B/P/barlens structures are likely to account for
most of the bulge light, including the early-type disks harboring most of the
bulge mass in galaxies. Cool central disks are often embedded in the
B/P/barlens bulges. Barred galaxies contain also dynamically hot classical
bulges, but it is not yet clear to what extent they are really dynamically
distinct structure components, and to what extent stars wrapped into the
central regions of the galaxies during the formation and evolution of bars. If
most of the bulge mass in the Milky Way mass galaxies in the nearby universe
in- deed resides in the B/P-shape bulges, and not in the classical bulges, that
idea needs to be integrated into the paradigm of galaxy formation.Comment: 30 pages (includes 13 figures). Accepted to a book on "Galactic
  Bulges", eds. E. Laurikainen, R.F. Peletier, D.A. Gadotti, Spriger, to appear
  in 201
Nuclear Star Clusters and Bulges

Nuclear star clusters are among the densest stellar systems known and are
common in both early- and late-type galaxies. They exhibit scaling relations
with their host galaxy which may be related to those of supermassive black
holes. These may therefore help us to unravel the complex physical processes
occurring at the centres of galaxies. The properties of nuclear stellar systems
suggest that their formation requires both dissipational and dissipationless
processes. They have stellar populations of different ages, from stars as old
as their host galaxy to young stars formed in the last 100 Myr. Therefore star
formation must be happening either directly in the nuclear star cluster or in
its vicinity. The secular processes that fuel the formation of pseudobulges
very likely also contributes to nuclear star cluster growth.Comment: To appear in "Galactic Bulges", E. Laurikainen, R.F. Peletier, and
  D.A. Gadotti (eds.), Springer Publishin
The Stellar Kinematics of Extragalactic Bulges

Galactic bulges are complex systems. Once thought to be small-scale versions
of elliptical galaxies, advances in astronomical instrumentation (spectroscopy
in particular) has revealed a wealth of photometric and kinematic substructure
in otherwise simple-looking components. This review provides an overview of how
our perspective on galactic bulges has changed over the years. While it is
mainly focused on aspects related to the dynamical state of their stars, there
will be natural connections to other properties (e.g. morphology, stellar
populations) discussed in other reviews in this volume.Comment: Invited Review to appear in "Galactic Bulges" Editors: Laurikainen
  E., Peletier R., Gadotti D. Springer Publishing. 25 pages, 9 figure
The Milky Way Bulge: Observed properties and a comparison to external
  galaxies

The Milky Way bulge offers a unique opportunity to investigate in detail the
role that different processes such as dynamical instabilities, hierarchical
merging, and dissipational collapse may have played in the history of the
Galaxy formation and evolution based on its resolved stellar population
properties. Large observation programmes and surveys of the bulge are providing
for the first time a look into the global view of the Milky Way bulge that can
be compared with the bulges of other galaxies, and be used as a template for
detailed comparison with models. The Milky Way has been shown to have a
box/peanut (B/P) bulge and recent evidence seems to suggest the presence of an
additional spheroidal component. In this review we summarise the global
chemical abundances, kinematics and structural properties that allow us to
disentangle these multiple components and provide constraints to understand
their origin. The investigation of both detailed and global properties of the
bulge now provide us with the opportunity to characterise the bulge as observed
in models, and to place the mixed component bulge scenario in the general
context of external galaxies. When writing this review, we considered the
perspectives of researchers working with the Milky Way and researchers working
with external galaxies. It is an attempt to approach both communities for a
fruitful exchange of ideas.Comment: Review article to appear in "Galactic Bulges", Editors: Laurikainen
  E., Peletier R., Gadotti D., Springer Publishing. 36 pages, 10 figure
Interplay of MLC, gantry and respiratory motion during DCAT delivery

This study investigated the possible interplay effects\ud
arising from the treatment of moving targets using the\ud
dynamic conformal arc therapy (DCAT) technique. Dose from\ud
a modulated test beam was measured, with and without phantom\ud
motion and with and without a 30o arc rotation, using a diode array placed on a sinusoidally moving platform. Measurements were repeated at five different collimator angles (0, 22.5, 45, 67.5 and 90o), at two different dose rates (300 and 600 MU/min). Results showed that the effect of respiratory motion on the measured dose distribution increased slightly when the beams were delivered as arcs, rather than with a static gantry angle, and that this effect increased substantially as the collimator angle was increased from 0o (MLC motion perpendicular to respiratory motion) to 90o (MLC motion parallel to respiratory motion). The dose oscillations arising from interplay between phantom and MLC motion were found to increase in magnitude when the dose rate was increased. These results led to the development of simple recommendations for minimizing the negative effects of motion interplay on DCAT dose distribution
Anatomical modelling of the pregnant radiotherapy patient

This study aimed to take existing anatomical models of pregnant women, currently used for radiation pro-tection and nuclear medicine dose calculations, and adapt them for use in the calculation of fetal dose from external beam radiotherapy (EBRT). The models investigated were ‘KATJA’, which was provided as an MCNPX geometry file, and ‘RPI-P6’, which was provided in a simple, voxelized bina-ry format. In-house code was developed, to convert both mod-els into an `egsphant’ format, suitable for use with DOSXYZnrc. The geometries and densities of the resulting phantoms were evaluated and found to accurately represent the source data. As an example of the use of the phantoms, the delivery of a cranial EBRT treatment was simulated using the BEAMnrc and DOSXYZnrc Monte Carlo codes and the likely out-of-field doses to the fetus in each model was calculated. The results of these calculations showed good agreement (with-in one standard deviation) between the doses calculated in KATJA and PRI-P6, despite substantial anatomical differ-ences between the two models. For a 36 Gy prescription dose to a 233.2 cm3 target in the right brain, the mean doses calcu-lated in a region of interest covering the entire uterus were 1.0 +/- 0.6 mSv for KATJA and 1.3 +/- 0.9 mSv for RPI-P6. This work is expected to lead to more comprehensive studies of EBRT treatment plan design and its effects on fetal dose in the future
Suitability of diodes for point dose measurements in IMRT/VMAT beams

This study investigated a potential source of inaccuracy\ud
for diode measurements in modulated beams; the effect of diode housing asymmetry on measurement results. The possible effects of diode housing asymmetry on the measurement of steep dose gradients were evaluated by measuring 5x5 cm2 beam profiles, with three cylindrical diodes and two commonly used ionization chambers, with each dosimeter positioned in a 3D scanning water tank with its stem perpendicular to the beam axis (horizontal) and parallel to the direction of scanning. The resulting profiles were used to compare the penumbrae measured with the diode stem pointing into (equivalent to a “stem-first” setup) and out of the field (equivalent to a “stem-last” setup) in order to evaluate the effects of dosimeter alignment and thereby identify the effects of dosimeter\ud
asymmetry. The stem-first and stem-last orientations resulted in differences of up to 0.2 mm in the measured 20-80% penumbra widths and differences of up to 0.4 mm in the off axis position of the 90% isodose. These differences, which are smaller than previously reported for older model dosimeters, were apparent in the profile results for both diodes and small volume ionization chambers. As an extension to this study, the practical use of all five dosimeters was exemplified by measuring point doses in IMRT test beams. These measurements showed good agreement (within 2%) between the diodes and the small volume ionization chamber, with all of these dosimeters being able to identify a region 3% under-dosage which was not identified by a larger volume (6 mm diameter) ionization chamber. The results of this work should help to remove some of the barriers to the use of diodes for modulated radiotherapy dosimetry in the future
Use of 3D printed materials as tissue-equivalent phantoms

This study used the specific example of 3D printing with acrylonitrile butadiene styrene (ABS) as a means to investigate the potential usefulness of benchtop rapid prototyping as a technique for producing patient specific phantoms for radiotherapy dosimetry. Three small cylinders and one model of a human lung were produced via in-house 3D printing with ABS, using 90%, 50%, 30% and 10% ABS infill densities. These phantom samples were evaluated in terms of their geometric accuracy, tissue equivalence and radiation hardness, when irradiated using a range of clinical radiotherapy beams. The measured dimensions of the small cylindrical phantoms all matched their planned dimensions, within 1mm. The lung phantom was less accurately matched to the lung geometry on which it was based, due to simplifications introduced during the phantom design process. The mass densities, electron densities and linear attenuation coefficients identified using CT data, as well as the results of film measurements made using megavoltage photon and electron beams, indicated that phantoms printed with ABS, using infill densities of 30% or more, are potentially useful as lung- and tissue-equivalent phantoms for patient-specific radiotherapy dosimetry. All cylindrical 3D printed phantom samples were found to be unaffected by prolonged radiation and to accurately match their design specifications. However, care should be taken to avoid oversimplifying anatomical structures when printing more complex phantoms
Measuring scene detection performance

In this paper we evaluate the performance of scene detection techniques, starting from the classic precision/recall approach, moving to the better designed coverage/overflow measures, and finally proposing an improved metric, in order to solve frequently observed cases in which the numeric interpretation is different from the expected results. Numerical evaluation is performed on two recent proposals for automatic scene detection, and comparing them with a simple but effective novel approach. Experimental results are conducted to show how different measures may lead to different interpretations
Multimodal object recognition using random clustering trees

In this paper, we present an object recognition approach that in addition allows to discover intra-class mo dalities exhibiting high-correlated visual information. Unlike to more conventional approaches based on computing multiple sp ecialized classiers, the proposed approach combines a single classier, Boosted Random Ferns (BRFs), with probabilistic Latent Semantic Analysis (pLSA) in order to recognize an object class and to find automatically the most prominent intra-class appearance mo dalities (clusters) through tree-structured visual words. The proposed approach has b een validated in synthetic and real experiments where we show that the method is able to recognize objects with multiple appearancePeer ReviewedPostprint (author's final draft
Warp propagation in astrophysical discs

Astrophysical discs are often warped, that is, their orbital planes change
with radius. This occurs whenever there is a non-axisymmetric force acting on
the disc, for example the Lense-Thirring precession induced by a misaligned
spinning black hole, or the gravitational pull of a misaligned companion. Such
misalignments appear to be generic in astrophysics. The wide range of systems
that can harbour warped discs - protostars, X-ray binaries, tidal disruption
events, quasars and others - allows for a rich variety in the disc's response.
Here we review the basic physics of warped discs and its implications.Comment: To be published in Astrophysical Black Holes by Haardt et al.,
  Lecture Notes in Physics, Springer 2015. 19 pages, 2 figure
The balance of power: accretion and feedback in stellar mass black holes

In this review we discuss the population of stellar-mass black holes in our
galaxy and beyond, which are the extreme endpoints of massive star evolution.
In particular we focus on how we can attempt to balance the available accretion
energy with feedback to the environment via radiation, jets and winds,
considering also possible contributions to the energy balance from black hole
spin and advection. We review quantitatively the methods which are used to
estimate these quantities, regardless of the details of the astrophysics close
to the black hole. Once these methods have been outlined, we work through an
outburst of a black hole X-ray binary system, estimating the flow of mass and
energy through the different accretion rates and states. While we focus on
feedback from stellar mass black holes in X-ray binary systems, we also
consider the applicability of what we have learned to supermassive black holes
in active galactic nuclei. As an important control sample we also review the
coupling between accretion and feedback in neutron stars, and show that it is
very similar to that observed in black holes, which strongly constrains how
much of the astrophysics of feedback can be unique to black holes.Comment: To be published in Haardt et al. Astrophysical Black Holes. Lecture
  Notes in Physics. Springer 201