1,029 research outputs found
Dynamical modelling of luminous and dark matter in 17 Coma early-type galaxies
Dynamical models for 17 Coma early-type galaxies are presented. The galaxy
sample consists of flattened, rotating as well as non-rotating early-types
including cD and S0 galaxies with luminosities between M=-18.79 and M=-22.56.
Kinematical long-slit observations cover at least the major and minor axis and
extend to 1-4 effective radii. Axisymmetric Schwarzschild models are used to
derive stellar mass-to-light ratios and dark halo parameters. In every galaxy
models with a dark matter halo match the data better than models without. The
statistical significance is over 95 percent for 8 galaxies, around 90 percent
for 5 galaxies and for four galaxies it is not significant. For the highly
significant cases systematic deviations between observed and modelled
kinematics are clearly seen; for the remaining galaxies differences are more
statistical in nature. Best-fit models contain 10-50 percent dark matter inside
the half-light radius. The central dark matter density is at least one order of
magnitude lower than the luminous mass density. The central phase-space density
of dark matter is often orders of magnitude lower than in the luminous
component, especially when the halo core radius is large. The orbital system of
the stars along the major-axis is slightly dominated by radial motions. Some
galaxies show tangential anisotropy along the minor-axis, which is correlated
with the minor-axis Gauss-Hermite coefficient H4. Changing the balance between
data-fit and regularisation constraints does not change the reconstructed mass
structure significantly. Model anisotropies tend to strengthen if the weight on
regularisation is reduced, but the general property of a galaxy to be radially
or tangentially anisotropic, respectively, does not change. (abridged)Comment: 31 pages, 34 figures; accepted for publication in MNRA
The supermassive black hole in NGC4486a detected with SINFONI at the VLT
The near-infrared integral field spectrograph SINFONI at the ESO VLT opens a
new window for the study of central supermassive black holes. With a near-IR
spatial resolution similar to HST optical and the ability to penetrate dust it
provides the possibility to explore the low-mass end of the M-sigma relation
(sigma<120km/s) where so far very few black hole masses were measured with
stellar dynamics. With SINFONI we observed the central region of the
low-luminosity elliptical galaxy NGC4486a at a spatial resolution of ~0.1arcsec
in the K band. The stellar kinematics was measured with a maximum penalised
likelihood method considering the region around the CO absorption band heads.
We determined a black hole mass of M_BH=1.25^{+0.75}_{-0.79} x 10^7 M_sun (90%
C.L.) using the Schwarzschild orbit superposition method including the full
2-dimensional spatial information. This mass agrees with the predictions of the
M-sigma relation, strengthening its validity at the lower sigma end.Comment: 7 pages, 7 figures. Accepted by MNRA
The flattening and the orbital structure of early-type galaxies and collisionless N-body binary disk mergers
We use oblate axisymmetric dynamical models including dark halos to determine
the orbital structure of intermediate mass to massive Coma early-type galaxies.
We find a large variety of orbital compositions. Averaged over all sample
galaxies the unordered stellar kinetic energy in the azimuthal and the radial
direction are of the same order, but they can differ by up to 40 percent in
individual systems. In contrast, both for rotating and non-rotating galaxies
the vertical kinetic energy is on average smaller than in the other two
directions. This implies that even most of the rotating ellipticals are
flattened by an anisotropy in the stellar velocity dispersions. Using
three-integral axisymmetric toy models we show that flattening by stellar
anisotropy maximises the entropy for a given density distribution.
Collisionless disk merger remnants are radially anisotropic. The apparent lack
of strong radial anisotropy in observed early-type galaxies implies that they
may not have formed from mergers of disks unless the influence of dissipational
processes was significant.Comment: 14 pages, 8 figures; accepted for publication in MNRA
The central black hole mass of the high-sigma but low-bulge-luminosity lenticular galaxy NGC 1332
The masses of the most massive supermassive black holes (SMBHs) predicted by
the M_BH-sigma and M_BH-luminosity relations appear to be in conflict. Which of
the two relations is the more fundamental one remains an open question. NGC
1332 is an excellent example that represents the regime of conflict. It is a
massive lenticular galaxy which has a bulge with a high velocity dispersion
sigma of ~320 km/s; bulge--disc decomposition suggests that only 44% of the
total light comes from the bulge. The M_BH-sigma and the M_BH-luminosity
predictions for the central black hole mass of NGC 1332 differ by almost an
order of magnitude. We present a stellar dynamical measurement of the SMBH mass
using an axisymmetric orbit superposition method. Our SINFONI integral-field
unit (IFU) observations of NGC 1332 resolve the SMBH's sphere of influence
which has a diameter of ~0.76 arcsec. The sigma inside 0.2 arcsec reaches ~400
km/s. The IFU data allow us to increase the statistical significance of our
results by modelling each of the four quadrants separately. We measure a SMBH
mass of (1.45 \pm 0.20) x 10^9 M_sun with a bulge mass-to-light ratio of 7.08
\pm 0.39 in the R-band. With this mass, the SMBH of NGC 1332 is offset from the
M_BH-luminosity relation by a full order of magnitude but is consistent with
the M_BH-sigma relation.Comment: 15 pages, 12 figures, accepted for publication in MNRA
Regularized orbit models unveiling the stellar structure and dark matter halo of the Coma elliptical NGC 4807
This is the second in a series of papers dedicated to unveil the mass
structure and orbital content of a sample of flattened early-type galaxies in
the Coma cluster. The ability of our orbit libraries to reconstruct internal
stellar motions and the mass composition of a typical elliptical in the sample
is investigated by means of Monte-Carlo simulations of isotropic rotator
models. The simulations allow a determination of the optimal amount of
regularization needed in the orbit superpositions. It is shown that under
realistic observational conditions and with the appropriate regularization
internal velocity moments can be reconstructed to an accuracy of about 15 per
cent; the same accuracy can be achieved for the circular velocity and dark
matter fraction. In contrast, the flattening of the halo remains unconstrained.
Regularized orbit superpositions are applied to a first galaxy in our sample,
NGC 4807, for which stellar kinematical observations extend to 3 Reff. The
galaxy seems dark matter dominated outside 2 Reff. Logarithmic dark matter
potentials are consistent with the data, as well as NFW-profiles, mimicking
logarithmic potentials over the observationally sampled radial range. In both
cases, the derived stellar mass-to-light ratio agrees well with independently
obtained mass-to-light ratios from stellar population analysis. Kinematically,
NGC 4807 is characterized by mild radial anisotropy outside r>0.5 Reff,
becoming isotropic towards the center. Our orbit models hint at either a
distinct stellar component or weak triaxiality in the outer parts of the
galaxy.Comment: 20 pages, 25 figures, accepted for publication in MNRA
MARLUI: Multi-Agent Reinforcement Learning for Adaptive UIs
Adaptive user interfaces (UIs) automatically change an interface to better
support users' tasks. Recently, machine learning techniques have enabled the
transition to more powerful and complex adaptive UIs. However, a core challenge
for adaptive user interfaces is the reliance on high-quality user data that has
to be collected offline for each task. We formulate UI adaptation as a
multi-agent reinforcement learning problem to overcome this challenge. In our
formulation, a user agent mimics a real user and learns to interact with a UI.
Simultaneously, an interface agent learns UI adaptations to maximize the user
agent's performance. The interface agent learns the task structure from the
user agent's behavior and, based on that, can support the user agent in
completing its task. Our method produces adaptation policies that are learned
in simulation only and, therefore, does not need real user data. Our
experiments show that learned policies generalize to real users and achieve on
par performance with data-driven supervised learning baselines
Orbit-Based Dynamical Models of the Sombrero Galaxy (NGC 4594)
We present axisymmetric, orbit-based models to study the central black hole,
stellar mass-to-light ratio, and dark matter halo of NGC 4594 (M104, the
Sombrero Galaxy). For stellar kinematics, we use published high-resolution
kinematics of the central region taken with the Hubble Space Telescope, newly
obtained Gemini long-slit spectra of the major axis, and integral field
kinematics from the SAURON instrument. At large radii, we use globular cluster
kinematics to trace the mass profile and apply extra leverage to recovering the
dark matter halo parameters. We find a black hole of mass M_{\bullet}=(6.6 +/-
0.4) x 10^8 M_{\odot}, and determine the stellar M/L_I=3.4 +/- 0.05
(uncertainties are the 68% confidence band marginalized over the other
parameters). Our best fit dark matter halo is a cored logarithmic model with
asymptotic circular speed V_c=376 +/- 12 km/s and core radius r_c= 4.7 +/- 0.6
kpc. The fraction of dark to total mass contained within the half-light radius
is 0.52. Taking the bulge and disk components into account in our calculation
of \sigma_e puts NGC 4594 squarely on the M-\sigma relation. We also determine
that NGC 4594 lies directly on the M-L relation.Comment: 13 pages, 10 figures, accepted for publication in Ap
Evaluation of strategies to improve efficiency in swine production and minimize pathogen transmission through feed
Doctor of PhilosophyDepartment of Animal Sciences and IndustryJoel C. DeRoucheySteven S. DritzEfficient use of resources is an important goal of modern agriculture. Several approaches to maximize resource utilization in swine production were evaluated including dietary approaches and interventions within the feed manufacturing process to optimize animal health. A total of 7,842 pigs were used over a total of 10 experiments structured in 6 chapters. Chapter 1 evaluated the effects of roller mill configuration on growth performance of nursery and finishing pigs, feed preference, and feed mill throughput. The four experimental treatments included corn ground through a roller mill using two, three, four sets of rolls in a fine-grind configuration, or four sets of rolls in a coarse grind configuration. There was no evidence of differences observed for average daily gain (ADG) or average daily feed intake (ADFI) between roller mill configurations when fed to nursery pigs. However, when given a choice nursery pigs consumed more of the diet containing corn ground through the 2-high roller mill or 4-high coarse configuration compared to corn ground through the 4-high fine configuration. Finally, finishing pigs fed corn ground with the 2-high configuration had greater ADG compared to those fed corn ground using the 3-high configuration. Grinding rate was greatest for the 4-high coarse configuration, while net electricity consumption was lowest for the 2-high configuration and greatest for the 4-high fine configuration. Chapter 2 evaluated the impact of commercial feed additives on the quantification of genetic material and infectivity of swine feed inoculated with porcine epidemic diarrhea virus (PEDV). The combination of essential oils and benzoic acid enhanced degradation of PEDV ribonucleic acid (RNA) in feed but had little impact in spray-dried porcine plasma. In addition, differences in viral stability was observed between feed and spray-dried porcine plasma where PEDV could be detected and remained infectious longer compared to swine feed. Chapter 3 evaluated the impact of flushing feed manufacturing equipment with rice hull flushes following mixing PEDV infected feed. Flushing effectively reduced the quantity of detectible RNA present after mixing a batch of PEDV-positive feed. Furthermore, chemical treatment of rice hulls with formaldehyde or 10% medium chain fatty acid (MCFA) provided additional reduction in RNA detection. Chapters 4 and 5 evaluated the inclusion of added chromium (Cr) in finishing diets. In chapter 4, small differences in ADG and feed efficiency were observed with added Cr. In chapter 5, adding Cr along with Yucca schidigera led to modest changes in performance with the greatest benefit observed with 200 µg/kg Cr and 125 mg/kg Yucca schidigera-based feed grade concentrate. Chapter 6 evaluated the impact of feeding MCFA to nursery pigs and demonstrated improved growth performance, but did not significantly alter fecal microbial composition, and provided residual mitigation activity when inoculated with PEDV following feed storage.
Overall, evaluation of feed manufacturing technologies and various feed additives demonstrates potential to have a significant impact on the efficiency of swine production. Additionally, understanding the role that feed and feed transportation contributes to health of swine populations is critical for maintaining a high health and productive global swine industry
Ionization wave propagation on a micro cavity plasma array
Microcavity plasma arrays of inverse pyramidal cavities have been fabricated
in p-Si wafers. Each cavity acts as a microscopic dielectric barrier discharge.
Operated at atmospheric pressure in argon and excited with high voltage at
about 10 kHz, each cavity develops a localized microplasma. Experiments have
shown a strong interaction of individual cavities, leading to the propagation
of wave-like optical emission structures along the surface of the array. This
phenomenon is numerically investigated using computer simulation. The observed
ionization wave propagates with a speed of about 5 km/s, which agrees well the
experimental findings. It is found that the wave propagation is due to
sequential contributions of a drift of electrons followed by drift of ions
between cavities seeded by photoemission of electrons by the plasma in adjacent
cavities
In vivo molecular imaging of experimental joint inflammation by combined 18F-FDG positron emission tomography and computed tomography
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