1,387 research outputs found
The Kormendy relation of massive elliptical galaxies at z~1.5. Evidence for size evolution ?
We present the morphological analysis based on HST-NIC2 (0.075 arcsec/pixel)
images in the F160W filter of a sample of 9 massive field (> 10^{11} M_\odot)
galaxies spectroscopically classified as early-types at 1.2<z<1.7. Our analysis
shows that all of them are bulge dominated systems. In particular, 6 of them
are well fitted by a de Vaucouleurs profile (n=4) suggesting that they can be
considered pure elliptical galaxies. The remaining 3 galaxies are better fitted
by a Sersic profile with index 1.9<n<2.3 suggesting that a disk-like component
could contribute up to 30% to the total light of these galaxies. We derived the
effective radius R_e and the mean surface brightness within R_e of our
galaxies and we compared them with those of early-types at lower redshifts. We
find that the surface brightness of our galaxies should get fainter by
2.5 mag from z~1.5 to z~0 to match the surface brightness of the local
ellipticals with comparable R_e, i.e. the local Kormendy relation. Luminosity
evolution without morphological changes can only explain half of this effect,
as the maximum dimming expected for an elliptical galaxy is ~1.6 mag in this
redshift range. Thus, other parameters, possibly structural, may undergo
evolution and play an important role in reconciling models and observations.
Hypothesizing an evolution of the effective radius of galaxies we find that R_e
should increase by a factor 1.5 from z~1.5 to z~0.Comment: Accepted for publication in MNRAS, 15 pages, 8 figure
Refraction corrected transmission imaging based on BĂ©zier curves: first results with KIT 3D USCT
AbstractThe computational complexity of wave-based image ultrasound transmission reconstructionsis very high especially in 3D. Hence, ray-based approximations are often used. Bent rayapproaches like the fast marching method are time-consuming in comparison to the straightray approximation. The B Ìezier curve technique for refraction approximation, introduced byPerez-Liva et al., could be a compromise between computational effort and image quality. Inthis work, the method was extended to 3D and an evaluation on two 3D datasets was carriedout. The first dataset was simulated with the k-wave toolbox, with hemispherically arrangedemitters and receivers and a sound speed inhomogeneity. With a mean squared error of 9.98m/s the method produces similar results as the fast marching method (11.85 m/s). The objectsize is represented better in comparison to the straight ray method. Applied to real data ofthe KIT 3D USCT both methods performed similarly. The object size was better preservedusing bent ray methods. The B Ìezier bent ray method shows first promising results in 3D asit leads to similar results than the fast marching method
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A Philosophical Perspective of Art
The underlying problem of the thesis is elucidating the relationship between the art object and philosophy. The thesis is organized into an introduction and four chapters. The introduction poses the need for a philosophical approach to the art object, and the phenomological method is briefly described. The first chapter defines and describes two basic structures found in the art object. The second chapter probes into the ontological structure of the art object in terms of form and media. The third chapter focuses on the relation of form and media evident in personal art works. The fourth chapter summarizes the content of preceding chapters and describes the relationship between the art object and the phenomological method, and discusses the significance of this relationship to philosophy and mankind
Seismic Response to Injection Well Stimulation in a High-Temperature, High-Permeability Reservoir
Fluid injection into the Earth's crust can induce seismic events that cause damage to local infrastructure but also offer valuable insight into seismogenesis. The factors that influence the magnitude, location, and number of induced events remain poorly understood but include injection flow rate and pressure as well as reservoir temperature and permeability. The relationship between injection parameters and injection-induced seismicity in high-temperature, high-permeability reservoirs has not been extensively studied. Here we focus on the Ngatamariki geothermal field in the central TaupĆ Volcanic Zone, New Zealand, where three stimulation/injection tests have occurred since 2012. We present a catalog of seismicity from 2012 to 2015 created using a matched-filter detection technique. We analyze the stress state in the reservoir during the injection tests from first motion-derived focal mechanisms, yielding an average direction of maximum horizontal compressive stress (SHmax) consistent with the regional NE-SW trend. However, there is significant variation in the direction of maximum compressive stress (Ï1), which may reflect geological differences between wells. We use the ratio of injection flow rate to overpressure, referred to as injectivity index, as a proxy for near-well permeability and compare changes in injectivity index to spatiotemporal characteristics of seismicity accompanying each test. Observed increases in injectivity index are generally poorly correlated with seismicity, suggesting that the locations of microearthquakes are not coincident with the zone of stimulation (i.e., increased permeability). Our findings augment a growing body of work suggesting that aseismic opening or slip, rather than seismic shear, is the active process driving well stimulation in many environments
Modified-release prednisone for polymyalgia rheumatica: a multicentre, randomised, active-controlled, double-blind, parallel-group study.
Objective: To assess the efficacy and safety of modified-release (MR) versus immediate-release (IR) prednisone in newly diagnosed glucocorticoid (GC)-na\uefve patients with polymyalgia rheumatica (PMR). Methods: Patients were randomised to double-blind MR prednisone (taken at approximately 22:00) or IR prednisone (taken in the morning), 15 mg/day for 4 weeks. The primary end point was complete response rate ( 6570% reduction in PMR visual analogue scale, duration of morning stiffness and C reactive protein (CRP) (or CRP < 2
7 upper limit of normal (ULN))) at week 4. Non-inferiority was decided if the lower 95% confidence limit (MR vs IR prednisone) was above -15%. 400 patients were planned but only 62 were enrolled due to difficulties in recruiting GC-na\uefve patients with PMR with CRP 652
7ULN. Results: The percentage of complete responders at week 4 was numerically greater for MR prednisone (53.8%) than for IR prednisone (40.9%). Non-inferiority of MR versus IR prednisone was not proven in the primary analysis on the per protocol population (N=48; treatment difference: 12.22%; 95% CI -15.82% to 40.25%). However, sensitivity analysis on the full analysis population showed an evident trend favouring MR prednisone (N=62; treatment difference: 15.56%; 95% CI -9.16% to 40.28%). Adverse events were generally mild and transient with no unexpected safety observations. Conclusions: The study showed a clear trend for favourable short-term efficacy of MR prednisone versus IR prednisone in early treatment of PMR. Further studies are warranted
Extremely compact massive galaxies at z~1.4
The optical rest-frame sizes of 10 of the most massive
(~5x10^{11}h_{70}^{-2}M_sun) galaxies found in the near-infrared MUNICS survey
at 1.2<z<1.7 are analysed. Sizes were estimated both in the J and K' filters.
These massive galaxies are at least a factor of 4_{-1.0}^{+1.9} (+-1 sigma)
smaller in the rest-frame V-band than local counterparts of the same stellar
mass. Consequently, the stellar mass density of these objects is (at least) 60
times larger than massive ellipticals today. Although the stellar populations
of these objects are passively fading, their structural properties are rapidly
changing since that redshift. This observational fact disagrees with a scenario
where the more massive and passive galaxies are fully assembled at z~1.4 (i.e.
a monolithic scenario) and points towards a dry merger scenario as the
responsible mechanism for the subsequent evolution of these galaxies.Comment: 5 pages, 2 figures, 1 table, accepted for publication in MNRAS
letter
Properties of Galaxies in and around Voids
Two surveys for intrinsically faint galaxies towards nearby voids have been
conducted at the MPI f\"ur Astronomie, Heidelberg. One selected targets from a
new diameter limited () catalog with morphological criteria while
the other used digitized objective prism Schmidt plates to select mainly HII
dwarf galaxies. For some 450 galaxies, redshifts and other optical data were
obtained. We studied the spatial distribution of the sample objects, their
luminosity function, and their intrinsic properties. Most of the galaxies
belong to already well known sheets and filaments. But we found about a dozen
highly isolated galaxies in each sample (nearest neighborhood distance ). These tend to populate additional structures and are not
distributed homogeneously throughout the voids. As our results on 'void
galaxies' still suffer from small sample statistics, I also tried to combine
similar existing surveys of nearby voids to get further hints on the larger
structure and on the luminosity function of the isolated galaxies. No
differences in the luminosity function of sheet and void galaxies could be
found. The optical and infrared properties of both samples are in the normal
range for samples dominated by late-type dwarfs. Follow-up HI studies show that
the isolated dwarfs in both samples have unusual high amount of neutral gas for
a given luminosity.Comment: 10 pages, 4 figures, latex, to appear in the proceedings of the
'Ringberg workshop on Large Scale Structure', hold Sep. 23-28, 199
A Stellar Population Gradient in VII Zw 403 - Implications for the Formation of Blue Compact Dwarf Galaxies
We present evidence for the existence of an old stellar halo in the Blue
Compact Dwarf galaxy VII Zw 403. VII Zw 403 is the first Blue Compact Dwarf
galaxy for which a clear spatial segregation of the resolved stellar content
into a "core-halo" structure is detected. Multicolor HST/WFPC2 observations
indicate that active star formation occurs in the central region, but is
strikingly absent at large radii. Instead, a globular-cluster-like red giant
branch suggests the presence of an old (> 10 Gyr) and metal poor
(=-1.92) stellar population in the halo. While the vast majority of
Blue Compact Dwarf galaxies has been recognized to possess halos of red color
in ground-based surface photometry, our observations of VII Zw 403 establish
for the first time a direct correspondence between a red halo color and the
presence of old, red giant stars. If the halos of Blue Compact Dwarf galaxies
are all home to such ancient stellar populations, then the fossil record
conflicts with delayed-formation scenarios for dwarfs.Comment: Accepted for publication in the Ap
MScMS-II: an innovative IR-based indoor coordinate measuring system for large-scale metrology applications
According to the current great interest concerning large-scale metrology applications in many different fields of manufacturing industry, technologies and techniques for dimensional measurement have recently shown a substantial improvement. Ease-of-use, logistic and economic issues, as well as metrological performance are assuming a more and more important role among system requirements. This paper describes the architecture and the working principles of a novel infrared (IR) optical-based system, designed to perform low-cost and easy indoor coordinate measurements of large-size objects. The system consists of a distributed network-based layout, whose modularity allows fitting differently sized and shaped working volumes by adequately increasing the number of sensing units. Differently from existing spatially distributed metrological instruments, the remote sensor devices are intended to provide embedded data elaboration capabilities, in order to share the overall computational load. The overall system functionalities, including distributed layout configuration, network self-calibration, 3D point localization, and measurement data elaboration, are discussed. A preliminary metrological characterization of system performance, based on experimental testing, is also presente
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