scholarly journals New constraints on the HR 8799 planetary system from mid-infrared direct imaging

2019 ◽  
Vol 491 (2) ◽  
pp. 1795-1799
Author(s):  
D J M Petit dit de la Roche ◽  
M E van den Ancker ◽  
M Kissler-Patig ◽  
V D Ivanov ◽  
D Fedele
Keyword(s):  
Near Infrared ◽  
Planetary System ◽  
Mass Limit ◽  
Atmospheric Models ◽  
Subtraction Technique ◽  
Direct Imaging ◽  
Point Spread ◽  
Spread Function ◽  
Additional Constraints ◽  
Better Than

ABSTRACT Direct imaging is a tried and tested method of detecting exoplanets in the near-infrared (IR), but has so far not been extended to longer wavelengths. New data at mid-IR wavelengths (8–20 μm) can provide additional constraints on planetary atmospheric models. We use the VLT Imager and Spectrometer for the mid-IR (VISIR) instrument on the VLT to detect or set stringent limits on the 8.7 μm flux of the four planets surrounding HR 8799, and to search for additional companions. We use a novel circularized point spread function subtraction technique to reduce the stellar signal and obtain instrument limited background levels and obtain optimal flux limits. The BT SETTL isochrones are then used to determine the resulting mass limits. We find flux limits between 0.7 and 3.3 mJy for the J8.9 flux of the different planets at better than 5σ level and derive a new mass limit of 30 MJup for any objects beyond 40 au. While this work has not detected planets in the HR 8799 system at 8.7 μm, it has found that an instrument with the sensitivity of VISIR is sufficient to detect at least four known hot planets around close stars, including β Pictoris b (1700 K, 19 pc), with more than 5σ certainty in 10 h of observing time in the mid-IR.

Near-infrared fundus imaging system with light illumination from an electronic contact lens

2022 ◽  
Vol 15 (2) ◽  
pp. 027001
Author(s):  
Yang Cui ◽  
Taiki Takamatsu ◽  
Koichi Shimizu ◽  
Takeo Miyake
Keyword(s):  
Contact Lens ◽  
Near Infrared ◽  
Imaging System ◽  
Low Cost ◽  
Light Illumination ◽  
Fundus Images ◽  
Fundus Imaging ◽  
Point Spread ◽  
Spread Function ◽  
Dependent Point

Abstract As for the diagnosis and treatment of eye diseases, an ideal fundus imaging system is expected to be portability, low cost, and high resolution. Here, we demonstrate a non-mydriatic near-infrared fundus imaging system with light illumination from an electronic contact lens (E-lens). The E-lens can illuminate the retinal and choroidal structures for capturing the fundus images when voltage is applied wirelessly to the lens. And we also reconstruct the images with a depth-dependent point-spread function to suppress the scattering effect that eventually visualizes the clear fundus images.

scholarly journals Companion Detection Limits with Adaptive Optics Coronagraphy

2004 ◽  
Vol 202 ◽  
pp. 99-102
Author(s):  
B. R. Oppenheimer ◽  
R. G. Dekany ◽  
M. Troy ◽  
T. Hayward ◽  
B. Brandl
Keyword(s):  
Adaptive Optics ◽  
Focal Plane ◽  
Near Infrared ◽  
Dynamic Range ◽  
Infrared Camera ◽  
Nearby Star ◽  
Point Spread ◽  
Spread Function ◽  
Adaptive Optics System ◽  
Circular Disks

We present a study of the Palomar Adaptive Optics System and the PHARO near infrared camera in coronagraphic mode. The camera provides two different focal plane occulting masks–opaque circular disks 0.43 and 0.97″ across. Three different pupil plane apodizing masks (Lyot masks) are also provided. The six different combinations of Lyot mask and focal plane mask suppress differently the point spread function of a bright star centered on the focal plane mask. We obtained images of the bright nearby star Gliese 614 with all six different configurations in the K filter. We measured the dynamic range achievable with these configurations. Within 2.5″, the dynamic range is at least 8 magnitudes at the 5σ level and as high as 12 in a 1 s exposure. This represents a substantial gain over similar techniques without adaptive optics.

scholarly journals Deep point spread function photometric catalog of the VVV survey data

2019 ◽  
Vol 632 ◽  
pp. A85
Author(s):  
M. Zhang ◽  
J. Kainulainen
Keyword(s):  
Point Spread Function ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Galactic Plane ◽  
High Reliability ◽  
Point Spread ◽  
Deep Point ◽  
Spread Function ◽  
Local Crowding ◽  
Source Number

Context. The Vista Variables in the Vía Láctea (VVV) survey has performed a multi-epoch near-infrared imaging of the inner Galactic plane. High-fidelity photometric catalogs are needed to utilize the data. Aims. We aim at producing a deep, point spread function (PSF) photometric catalog for the VVV survey J-,H-, and Ks-band data. Specifically, we aim to take advantage of multiple epochs of the survey to reach high limiting magnitudes. Methods. We developed an automatic PSF-fitting pipeline based on the DaoPHOT algorithm and performed photometry on the stacked VVV images in J,  H, and Ks bands. Results. We present a PSF photometric catalog in the Vega system that contains about 926 million sources in the J,  H, and Ks filters. About 10% of the sources are flagged as possible spurious detections. The 5σ limiting magnitudes of the sources with high reliability are about 20.8, 19.5, and 18.7 mag in the J,  H, and Ks bands, respectively, depending on the local crowding condition. Our photometric catalog reaches on average about one magnitude deeper than the previously released PSF DoPHOT photometric catalog and includes less spurious detections. There are significant differences in the brightnesses of faint sources between our catalog and the previously released one. The likely origin of these differences is in the different photometric algorithms that are used; it is not straightforward to assess which catalog is more accurate in different situations. Our new catalog is beneficial especially for science goals that require high limiting magnitudes; our catalog reaches such high magnitudes in fields that have a relatively uniform source number density. Overall, the limiting magnitudes and completeness are different in fields with different crowding conditions.

scholarly journals Direct imaging of haloes and truncations in face-on nearby galaxies

2015 ◽  
Vol 11 (S317) ◽  
pp. 39-44
Author(s):  
J. H. Knapen ◽  
S. P. C. Peters ◽  
P. C. van der Kruit ◽  
I. Trujillo ◽  
J. Fliri ◽  
...  
Keyword(s):  
Point Spread Function ◽  
Spiral Galaxies ◽  
Surface Photometry ◽  
Direct Imaging ◽  
Point Spread ◽  
Deep Imaging ◽  
Spread Function ◽  
Stellar Halo ◽  
Nearby Galaxies ◽  
Proper Analysis

AbstractWe use ultra-deep imaging from the IAC Stripe 82 Legacy Project to study the surface photometry of 22 nearby, face-on to moderately inclined spiral galaxies. The reprocessed and co-added SDSS/Stripe 82 imaging allows us to probe down to 29–30 r′-mag/arcsec2 and thus reach into the very faint outskirts of the galaxies. We find extended stellar haloes in over half of our sample galaxies, and truncations in three of them. The presence of stellar haloes and truncations is mutually exclusive, and we argue that the presence of a stellar halo can hide a truncation. We find that the onset of the halo and the truncation scales tightly with galaxy size. We highlight the importance of a proper analysis of the extended wings of the point spread function (PSF), finding that around half the light at the faintest levels is from the inner regions of a galaxy, though not the nucleus, re-distributed to the outskirts by the PSF. We discuss implications of this effect for future deep imaging surveys, such as with the LSST.

scholarly journals Searching for the near-infrared counterpart of Proxima c using multi-epoch high-contrast SPHERE data at VLT

2020 ◽  
Vol 638 ◽  
pp. A120 ◽  
Author(s):  
R. Gratton ◽  
A. Zurlo ◽  
H. Le Coroller ◽  
M. Damasso ◽  
F. Del Sordo ◽  
...  
Keyword(s):  
Near Infrared ◽  
Planetary System ◽  
Orbital Motion ◽  
Signal To Noise Ratio ◽  
Orbital Plane ◽  
Radial Velocities ◽  
Random Fluctuation ◽  
Direct Imaging ◽  
Imaging Detection

Context. Proxima Centauri is the closest star to the Sun and it is known to host an Earth-like planet in its habitable zone; very recently a second candidate planet was proposed based on radial velocities. At quadrature, the expected projected separation of this new candidate is larger than 1 arcsec, making it a potentially interesting target for direct imaging. Aims. While identification of the optical counterpart of this planet is expected to be very difficult, successful identification would allow for a detailed characterization of the closest planetary system. Methods. We searched for a counterpart in SPHERE images acquired over four years through the SHINE survey. In order to account for the expected large orbital motion of the planet, we used a method that assumes the circular orbit obtained from radial velocities and exploits the sequence of observations acquired close to quadrature in the orbit. We checked this with a more general approach that considers Keplerian motion, called K-stacker. Results. We did not obtain a clear detection. The best candidate has signal-to-noise ratio (S∕N) = 6.1 in the combined image. A statistical test suggests that the probability that this detection is due to random fluctuation of noise is <1%, but this result depends on the assumption that the distribution of noise is uniform over the image, a fact that is likely not true. The position of this candidate and the orientation of its orbital plane fit well with observations in the ALMA 12 m array image. However, the astrometric signal expected from the orbit of the candidate we detected is 3σ away from the astrometric motion of Proxima as measured from early Gaia data. This, together with the unexpectedly high flux associated with our direct imaging detection, means we cannot confirm that our candidate is indeed Proxima c. Conclusions. On the other hand, if confirmed, this would be the first observation in imaging of a planet discovered from radial velocities and the second planet (after Fomalhaut b) of reflecting circumplanetary material. Further confirmation observations should be done as soon as possible.

scholarly journals Towards the analysis of JWST exoplanet spectra: the effective temperature in the context of direct imaging

2019 ◽  
Vol 490 (2) ◽  
pp. 2086-2090
Author(s):  
Jean-Loup Baudino ◽  
J Taylor ◽  
P G J Irwin ◽  
R Garland
Keyword(s):  
Wavelength Range ◽  
Effective Temperature ◽  
Best Practice ◽  
Atmospheric Models ◽  
Direct Imaging ◽  
Current State ◽  
James Webb Space Telescope ◽  
Crucial Parameter ◽  
Current Modelling ◽  
Better Than

ABSTRACT The current sparse wavelength range coverage of exoplanet direct imaging observations, and the fact that models are defined using a finite wavelength range, lead both to uncertainties on effective temperature determination. We study these effects using blackbodies and atmospheric models and we detail how to infer this parameter. Through highlighting the key wavelength coverage that allows for a more accurate representation of the effective temperature, our analysis can be used to mitigate or manage extra uncertainties being added in the analysis from the models. We find that the wavelength range coverage will soon no longer be a problem. An effective temperature computed by integrating the spectroscopic observations of the James Webb Space Telescope will give uncertainties similar to, or better than, the current state–of–the–art, which is to fit models to data. Accurately calculating the effective temperature will help to improve current modelling approaches. Obtaining an independent and precise estimation of this crucial parameter will help the benchmarking process to identify the best practice to model exoplanet atmospheres.

scholarly journals Region-Based Partial Volume Correction Techniques for PET Imaging: Sinogram Implementation and Robustness

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Mike Sattarivand ◽  
Jennifer Armstrong ◽  
Gregory M. Szilagyi ◽  
Maggie Kusano ◽  
Ian Poon ◽  
...  
Keyword(s):  
Partial Volume Correction ◽  
Emission Tomography ◽  
Partial Volume ◽  
Volume Correction ◽  
Noise Characteristics ◽  
Point Spread ◽  
Positron Emission ◽  
Spread Function ◽  
3D Pet ◽  
Better Than

Background/Purpose. Limited spatial resolution of positron emission tomography (PET) requires partial volume correction (PVC). Region-based PVC methods are based on geometric transfer matrix implemented either in image-space (GTM) or sinogram-space (GTMo), both with similar performance. Although GTMo is slower, it more closely simulates the 3D PET image acquisition, accounts for local variations of point spread function, and can be implemented for iterative reconstructions. A recent image-based symmetric GTM (sGTM) has shown improvement in noise characteristics and robustness to misregistration over GTM. This study implements the sGTM method in sinogram space (sGTMo), validates it, and evaluates its performance. Methods. Two 3D sphere and brain digital phantoms and a physical sphere phantom were used. All four region-based PVC methods (GTM, GTMo, sGTM, and sGTMo) were implemented and their performance was evaluated. Results. All four PVC methods had similar accuracies. Both noise propagation and robustness of the sGTMo method were similar to those of sGTM method while they were better than those of GTMo method especially for smaller objects. Conclusion. The sGTMo was implemented and validated. The performance of the sGTMo in terms of noise characteristics and robustness to misregistration is similar to that of the sGTM method and improved compared to the GTMo method.

PERFORMANCE OF BLIND DECONVOLUTION IN OPTOACOUSTIC TOMOGRAPHY

2011 ◽  
Vol 04 (04) ◽  
pp. 385-393 ◽  
Author(s):  
THOMAS JETZFELLNER ◽  
VASILIS NTZIACHRISTOS
Keyword(s):  
Point Spread Function ◽  
Near Infrared ◽  
Blind Deconvolution ◽  
Photoacoustic Imaging ◽  
Reconstructed Image ◽  
Optoacoustic Tomography ◽  
Point Spread ◽  
Spread Function ◽  
Old Mice ◽  
Unknown Point

In this paper, we consider the use of blind deconvolution for optoacoustic (photoacoustic) imaging and investigate the performance of the method as means for increasing the resolution of the reconstructed image beyond the physical restrictions of the system. The method is demonstrated with optoacoustic measurement obtained from six-day-old mice, imaged in the near-infrared using a broadband hydrophone in a circular scanning configuration. We find that estimates of the unknown point spread function, achieved by blind deconvolution, improve the resolution and contrast in the images and show promise for enhancing optoacoustic images.

scholarly journals Deciphering Quasar Millilensing – How to Distinguish Between Dark and Luminous Lenses

2007 ◽  
Vol 3 (S244) ◽  
pp. 368-369
Author(s):  
Heidi Lietzen ◽  
Chris Flynn ◽  
Erik Zackrisson ◽  
Pasi Nurmi
Keyword(s):  
Dark Matter ◽  
Point Spread Function ◽  
Dwarf Galaxy ◽  
Host Galaxy ◽  
Dark Matter Halos ◽  
Direct Imaging ◽  
Point Spread ◽  
Spread Function

AbstractDwarf-galaxy sized dark matter halos may be detectable when a bright background source is gravitationally lensed on scales of milliarcseconds. Such effects can be caused by dark galaxies as well as luminous ones. Here we discuss conditions for detecting a luminous lensing object through direct imaging, via measurements of the point spread function (PSF) to subtract the quasar from the image, revealing the quasar host galaxy and any luminous lens. The technique applies to both types of millilensing effect, i.e. magnification and image splitting. We show that luminous dwarf-galaxy lenses should be detectable with this method up to redshifts z~0.2.

scholarly journals Night-light Image Restoration Method Based on Night Scattering Model for Luojia 1-01 Satellite

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3761 ◽  
Author(s):  
Bu ◽  
Xu ◽  
Zhang ◽  
Zhang
Keyword(s):  
Single Point ◽  
Remote Sensing Images ◽  
Initial Value ◽  
Light Image ◽  
Point Spread ◽  
Spread Function ◽  
Restoration Method ◽  
Restoration Model ◽  
Degradation Problem ◽  
Better Than

Aiming at solving the degradation problem of Luojia 1-01 night-light remote sensing images, the main reason for the “glow” phenomenon was analyzed. The APSF (Atmospheric Point Spread Function) template of night-light image was obtained from atmospheric source scattering. The template was used as the initial value in the regularization restoration model in this paper. Experiments were carried out using single point and regional images. The results demonstrate that the estimated APSF and restoration results of the method are better than those from other methods, and the image quality is improved after restoration.

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