Characterization in the laboratory of VISIR, the mid-infrared imager and spectrometer for the VLT

Lagage, Pierre-Olivier; Pel, J. W.; Claret, A.; Damstra, S.; Dubreuil, Didier; Durand, G.; Elswijk, Eddy; Galdemard, Philippe; Jong, Arie N. de; Kroes, Gabby; Lyraud, C.; Pantin, É.; Pragt, J.; Rio, Y.; Schoenmaker, Anton; Authier, M.; Belorgey, J.; Gournay, J.F.; Lortholary, M.; Lussignol, Y.; Veyssière, C.

doi:10.1117/12.461101

Cited by 16 publications

(13 citation statements)

References 2 publications

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“…VLT/VISIR (2006): Thermal images were obtained by ESO's Very Large Telescope (VLT) UT-3 (Melipal) mid-infrared camera/spectrometer (VISIR, Lagage et al, 2004) in September 2006, and presented by Orton et al (2007). In this analysis we use an 18.7-µm image from 01:44-03:47 UT on September 2, 2006; and images at 17.6 µm (01:55-03:13 UT), 8.6 µm (06:53-07:40 UT) and 12.3 µm (03:16-03:36 UT) from September 3, 2006.…”

Section: Sources Of Imaging Datamentioning

confidence: 99%

Neptune at summer solstice: Zonal mean temperatures from ground-based observations, 2003–2007

Fletcher

Pater²,

Orton

et al. 2014

Icarus

108

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• ). Our aim was to analyse imaging and spectroscopy from multiple different sources using a single self-consistent radiative-transfer model to assess the magnitude of seasonal variability. Globally-averaged stratospheric temperatures measured from methane emission tend towards a quasi-isothermal structure (158-164 K) above the 0.1-mbar level, and are found to be consistent with spacecraft observations of AKARI. This remarkable consistency, despite very different observing conditions, suggests that stratospheric temporal variability, if present, is < ±5 K at 1 mbar and < ±3 K at 0.1 mbar during this solstice period. Conversely, ethane emission is highly variable, with abundance determinations varying by more than a factor of two (from 500 to 1200 ppb at 1 mbar). The retrieved C 2 H 6 abundances are extremely sensitive to the details of the T (p) derivation, although the underlying cause of the variable ethane emission remains unidentified. Stratospheric temperatures and ethane are found to be latitudinally uniform away from the south pole (assuming a latitudinally-uniform distribution of stratospheric methane), with no large seasonal hemispheric asymmetries evident at solstice. At low and mid-latitudes, comparisons of synthetic Voyager-era images with solstice-era observations suggest that tropospheric zonal temperatures are unchanged since the Voyager 2 encounter, with cool mid-latitudes and a warm equator and pole. A re-analysis of Voyager/IRIS 25-50 µm mapping of tropospheric temperatures and para-hydrogen disequilibrium (a tracer for vertical motions) suggests a symmetric meridional circulation with cold air rising at mid-latitudes (sub-equilibrium para-H 2 conditions) and warm air sinking at the equator and poles (super-equilibrium para-H 2 conditions). The most significant atmospheric changes have occurred at high southern latitudes, where zonal temperatures retrieved from 2003 images suggest a polar enhancement of 7-8 K above the tropopause, and an increase of 5-6 K throughout the 70 − 90• S region between 0.1 and 200 mbar. Such a large perturbation, if present in 1989, would have been detectable by Voyager/IRIS in a single scan despite its long-wavelength sensitivity, and we conclude that Neptune's south polar cyclonic vortex increased in strength significantly from Voyager to solstice.

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Section: Sources Of Imaging Datamentioning

confidence: 99%

Neptune at summer solstice: Zonal mean temperatures from ground-based observations, 2003–2007

Fletcher

Pater²,

Orton

et al. 2014

Icarus

108

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“…In this Letter we present the first millimeter and mid-infrared observations of the Uranian ring system, obtained in 2017 and 2018 with ALMA at three wavelengths (Band 3; 3.1 mm, Band 4: 2.1 mm, Band 6: 1.3 mm) and the VISIR instrument (Lagage et al 2004) Q2 filter (18.72 µm) on the Very Large Telescope (VLT). In contrast to images at visible/near-infrared wavelengths, which show the rings in reflected sunlight, our ALMA and VISIR images detect thermal emission from the rings, a component that has never before been imaged.…”

Section: Introductionmentioning

confidence: 99%

Thermal Emission from the Uranian Ring System

Molter

Pater

Roman

et al. 2019

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The narrow main rings of Uranus are composed of almost exclusively centimeter-to meter-sized particles, with a very small or nonexistent dust component; however, the filling factor, composition, thickness, mass, and detailed particle size distribution of these rings remain poorly constrained. Using millimeter (1.3 -3.1 mm) imaging from the Atacama Large (sub-)Millimeter Array and midinfrared (18.7 µm) imaging from the Very Large Telescope VISIR instrument, we observed the thermal component of the Uranian ring system for the first time. The ring is detected strongly and can be seen by eye in the images; the other main rings are visible in a radial (azimuthally-averaged) profile at millimeter wavelengths. A simple thermal model similar to the NEATM model of near-Earth asteroids is applied to the ring to determine a ring particle temperature of 77.3 ± 1.8 K. The observed temperature is higher than expected for fast-rotating ring particles viewed at our observing geometry, meaning that the data favor a model in which the thermal inertia of the ring particles is low and/or their rotation rate is slow. The ring displays a factor of 2-3 brightness difference between periapsis and apoapsis, with 49.1 ± 2.2% of sightlines through the ring striking a particle. These observations are consistent with optical and near-infrared reflected light observations, confirming the hypothesis that micron-sized dust is not present in the ring system.

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“…Here we report on the science verification results from VISIR, the MIR instrument at the VLT (Lagage et al 2004). We exploit VISIR's capabilities to study a sample of bright, nearby spirals and compare the observations with both radiative transfer models and radio-interferometric maps.…”

Section: Introductionmentioning

confidence: 99%

Nuclear activity in nearby galaxies

Siebenmorgen¹,

Haas

Pantin

et al. 2008

A&A

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Aims. Dust enshrouded activity can be studied ideally by mid-infrared (MIR) observations. To explore the active galactic nuclei (AGN) versus star forming origin of the nuclear MIR emission of galaxies, observations of high spatial resolution are required. We report on 11.3 μm observations with VISIR at the VLT, which reach 0.35 spatial resolution (FWHM). Methods. During the scientific verification of VISIR, we observed a sample of 36 nearby galaxies with a range of optically classified nuclear activity: 17 black hole driven AGN, 10 starbursts (SB), and 9 quiescent spirals. Results. 16 objects out of 17 AGN are detected and unresolved, 5 out of 10 SB are detected and resolved with structured emission up to a few arcsec, while for 5 targets out of 10 SB and all 9 quiet nuclei low upper limits are provided. The morphology of the resolved SB nuclei is similar to that observed at radio frequencies. The compactness of AGN and the extent of SB nuclei is consistent with the predictions of radiative transfer models and Spitzer spectra observed at much lower spatial resolution than with VISIR. We introduce the nuclear MIR surface brightness, S , as a quantitative measurement for AGN and SB activity. Although one is unable to distinguish between AGN and SB activity using the nuclear MIR surface brightness derived from 4 m class telescopes, our data indicate that, out to a distance of 100 Mpc, the MIR surface brightness acquired by 8 m class telescopes can differentiate AGN from SB behavior.

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Characterization in the laboratory of VISIR, the mid-infrared imager and spectrometer for the VLT

Cited by 16 publications

References 2 publications

Neptune at summer solstice: Zonal mean temperatures from ground-based observations, 2003–2007

Neptune at summer solstice: Zonal mean temperatures from ground-based observations, 2003–2007

Thermal Emission from the Uranian Ring System

Nuclear activity in nearby galaxies

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