196,282 research outputs found
High-resolution UKIRT observations of circumnuclear star formation in M100
We present high-resolution, near-infrared imaging of the circumnuclear region
of the barred spiral galaxy M100 (=NGC 4321), accompanied by near-infrared
spectroscopy. We identify a total of 43 distinct regions in the K-band image,
and determine magnitudes and colours for 41 of them. By comparison with other
near-infrared maps we also derive colour excesses and K-band extinctions for
the knots. Combining the imaging and spectroscopic results, we conclude that
the knots are the result of bursts of star formation within the last 15-25 Myr.
We discuss the implications of these new results for our dynamical and
evolutionary understanding of this galaxy.Comment: 10 pages, 4 figures, uses mn-1.4.sty. Accepted for publication in
Monthly Notices of the Royal Astronomical Societ
Grown-up stars physics with MATISSE
MATISSE represents a great opportunity to image the environment around
massive and evolved stars. This will allow one to put constraints on the
circumstellar structure, on the mass ejection of dust and its reorganization ,
and on the dust-nature and formation processes. MATISSE measurements will often
be pivotal for the understanding of large multiwavelength datasets on the same
targets collected through many high-angular resolution facilities at ESO like
sub-millimeter interferometry (ALMA), near-infrared adaptive optics (NACO,
SPHERE), interferometry (PIONIER, GRAVITY), spectroscopy (CRIRES), and
mid-infrared imaging (VISIR). Among main sequence and evolved stars, several
cases of interest have been identified that we describe in this paper.Comment: SPIE, Jun 2016, Edimbourgh, Franc
An exploration of feature detector performance in the thermal-infrared modality
Thermal-infrared images have superior statistical properties compared with visible-spectrum images in many low-light or no-light scenarios. However, a detailed understanding of feature detector performance in the thermal modality lags behind that of the visible modality. To address this, the first comprehensive study on feature detector performance on thermal-infrared images is conducted. A dataset is presented which explores a total of ten different environments with a range of statistical properties. An investigation is conducted into the effects of several digital and physical image transformations on detector repeatability in these environments. The effect of non-uniformity noise, unique to the thermal modality, is analyzed. The accumulation of sensor non-uniformities beyond the minimum possible level was found to have only a small negative effect. A limiting of feature counts was found to improve the repeatability performance of several detectors. Most other image transformations had predictable effects on feature stability. The best-performing detector varied considerably depending on the nature of the scene and the test
Image Processing for Pathological Visualization in Multitemporal Convoluted TIRI
The convoluted nature of thermal infrared radiation and poor understanding of the physical mechanismsof human emittance, make objective image acquisition and processing protocols prerequisite for meaningful diagnostic specificity. A longitudinal dataset of clinical thermal infrared images was objectively processed to facilitate visualization of osseous stress pathology in the lower limbs.. This paper details processing of 500+ thermal infrared images acquired during a recent three month clinical study into osseous stress pathology in the lower limbs of Australian Army basic trainees. The use ofthermal chroma-keying in segmentation and multitemporal image calibration is demonstrated. The ‘OpenSURF’ implementation of the scale and rotation-invariant interest point detector and escriptor are shown to be performant in registration of multitemporal clinical thermal infrared image data. Thermal ‘signs’ observed in longitudinal images appear to be revealing detectable changes in osseous stress pathophysiology
PhoSim-NIRCam: Photon-by-photon image simulations of the James Webb Space Telescope's Near-Infrared Camera
Recent instrumentation projects have allocated resources to develop codes for
simulating astronomical images. Novel physics-based models are essential for
understanding telescope, instrument, and environmental systematics in
observations. A deep understanding of these systematics is especially important
in the context of weak gravitational lensing, galaxy morphology, and other
sensitive measurements. In this work, we present an adaptation of a
physics-based ab initio image simulator: The Photon Simulator (PhoSim). We
modify PhoSim for use with the Near-Infrared Camera (NIRCam) -- the primary
imaging instrument aboard the James Webb Space Telescope (JWST). This photon
Monte Carlo code replicates the observational catalog, telescope and camera
optics, detector physics, and readout modes/electronics. Importantly,
PhoSim-NIRCam simulates both geometric aberration and diffraction across the
field of view. Full field- and wavelength-dependent point spread functions are
presented. Simulated images of an extragalactic field are presented. Extensive
validation is planned during in-orbit commissioning
Coupling of Optical Lumped Nanocircuit Elements and Effects of Substrates
We present here a model for the coupling among small nanoparticles excited by
an optical electric field in the framework of our optical lumped nanocircuit
theory [N. Engheta, A. Salandrino, and A. Alu Phys. Rev. Lett. 95, 095504
(2005)]. We derive how this coupling affects the corresponding nanocircuit
model by adding controlled sources that depend on the optical voltages applied
on the coupled particles. With the same technique, we can model also the
presence of a substrate underneath nanocircuit elements, relating its presence
to the coupling with a properly modeled image nanoparticle. These results are
of importance in the understanding and the design of complex optical
nanocircuits at infrared and optical frequencies.Comment: 21 pages, 4 figures, under revie
Application of EREP imagery to fracture-related mine safety hazards in coal mining and mining-environmental problems in Indiana
The author has identified the following significant results. This investigation evaluated the applicability of a variety of sensor types, formats, and resolution capabilities to the study of both fuel and nonfuel mined lands. The image reinforcement provided by stereo viewing of the EREP images proved useful for identifying lineaments and for mined lands mapping. Skylab S190B color and color infrared transparencies were the most useful EREP imagery. New information on lineament and fracture patterns in the bedrock of Indiana and Illinois extracted from analysis of the Skylab imagery has contributed to furthering the geological understanding of this portion of the Illinois basin
Time-spliced X-ray Diffraction Imaging
Diffraction imaging of non-equilibrium dynamics at atomic resolution is
becoming possible with X-ray free-electron lasers. However, there are
unresolved problems with applying this method to objects that are confined in
only one dimension. Here I show that one-dimensional coherent diffraction
imaging is possible by splicing together images recovered from different delays
in a time-resolved experiment. This is used to image the time and space
evolution of antiferromagnetic order in a complex oxide heterostructure from
measurements of a resonant soft X-ray diffraction peak. Mid-infrared excitation
of the substrate is shown to lead to a magnetic front that propagates at a
velocity exceeding the speed of sound, a critical observation for the
understanding of driven phase transitions in complex condensed matter
Direct Detection of the Tertiary Component in the Massive Multiple HD 150 136 with VLTI
Massive stars are of fundamental importance for almost all aspects of
astrophysics, but there still exist large gaps in our understanding of their
properties and formation because they are rare and therefore distant. It has
been found that most O-stars are multiples. HD 150 136 is the nearest system to
Earth with >100 M_sol, and provides a unique opportunity to study an extremely
massive system. Recently, evidence for the existence of a third component in HD
150 136, in addition to the tight spectroscopic binary that forms the main
component, was found in spectroscopic observations. Our aim was to image and
obtain astrometric and photometric measurements of this component using long
baseline optical interferometry to further constrain the nature of this
component. We observed HD150136 with the near-infrared instrument AMBER
attached to the ESO VLT Interferometer. The recovered closure phases are robust
to systematic errors and provide unique information on the source asymmetry.
Therefore, they are of crucial relevance for both image reconstruction and
model fitting of the source structure. The third component in HD 150 136 is
clearly detected in the high-quality data from AMBER. It is located at a
projected angular distance of 7.3 mas, or about 13 AU at the line-of-sight
distance of HD 150 136, at a position angle of 209 degrees East of North, and
has a flux ratio of 0.25 with respect to the inner binary. We resolved the
third component of HD 150 136 in J, H and K filters. The luminosity and color
of the tertiary agrees with the predictions and shows that it is also an O
main-sequence star. The small measured angular separation indicates that the
tertiary may be approaching the periastron of its orbit. These results, only
achievable with long baseline near infrared interferometry, constitute the
first step towards the understanding of the massive star formation mechanisms
Radio and IR study of the massive star-forming region IRAS 16353-4636
Context. With the latest infrared surveys, the number of massive protostellar
candidates has increased significantly. New studies have posed additional
questions on important issues about the formation, evolution, and other
phenomena related to them. Complementary to infrared data, radio observations
are a good tool to study the nature of these objects, and to diagnose the
formation stage. Aims. Here we study the far-infrared source IRAS 16353-4636
with the aim of understanding its nature and origin. In particular, we search
for young stellar objects (YSOs), possible outflow structure, and the presence
of non-thermal emission. Methods. Using high-resolution, multi-wavelength radio
continuum data obtained with the Australia Telescope Compact Array, we image
IRAS 16353-4636 and its environment from 1.4 to 19.6 GHz, and derive the
distribution of the spectral index at maximum angular resolution. We also
present new JHKs photometry and spectroscopy data obtained at ESO NTT. 13 CO
and archival HI line data, and infrared databases (MSX, GLIMPSE, MIPSGal) are
also inspected. Results. The radio continuum emission associated with IRAS
16353-4636 was found to be extended (~10 arcsec), with a bow-shaped morphology
above 4.8 GHz, and a strong peak persistent at all frequencies. The NIR
photometry led us to identify ten near-IR sources and classify them according
to their color. We used the HI line data to derive the source distance, and
analyzed the kinematical information from the CO and NIR lines detected.
Conclusions. We have identified the source IRAS 16353-4636 as a new
protostellar cluster. In this cluster we recognized three distinct sources: a
low-mass YSO, a high-mass YSOs, and a mildly confined region of intense and
non-thermal radio emission. We propose the latter corresponds to the terminal
part of an outflow.Comment: To appear in A&A. 10 pages, 8 figure
- …