The paper deals with with the on-sky performance of the pyramid wavefront sensor-based Adaptive Optics (AO) systems. These wavefront sensors are of great importance, being used in all first light AO ...systems of the ELTs (E-ELT, GMT, and TMT), currently in design phase. In particular, non-common path aberrations (NCPAs) are a critical issue encountered when using an AO system to produce corrected images in an associated astronomical instrument. The AO wavefront sensor (WFS) and the supported scientific instrument typically use a series of different optical elements, thus experiencing different aberrations. The usual way to correct for such NCPAs is to introduce a static offset in the WFS signals. In this way, when the AO loop is closed the sensor offsets are zeroed and the deformable mirror converges to the shape required to null the NCPA. The method assumes that the WFS operation is linear and completely described by some pre-calibrated interaction matrix. This is not the case for some frequently used wavefront sensors like the Pyramid sensor or a quad-cell Shack-Hartmann sensor. Here we present a method to work in closed-loop with a pyramid wavefront sensor, or more generally a non-linear WFS, introducing a wavefront offset that remains stable when AO correction quality changes due to variations in external conditions like star brightness, seeing, and wind speed. The paper details the methods with analytical and numerical considerations. Then we present results of tests executed at the LBT telescope, in daytime and on sky, using the FLAO system and LUCI2 facility instrument. The on-sky results clearly show the successful operation of the method that completely nulls NCPA, recovering diffraction-limited images with about 70% Strehl ratio in H band in variable seeing conditions. The proposed method is suitable for application to the above-mentioned ELT AO systems.
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Using the adaptive optics system of the Large Binocular Telescope, we have obtained near-infrared camera PISCES images of the inner shell of the nebula around the luminous blue variable star P Cygni ...in the Fe ii emission line at 1.6435 μm. We have combined the images in order to cover a field of view of about 20 arcsec around P Cygni, thus providing the high-resolution (0.08 arcsec) two-dimensional spatial distribution of the inner shell of the P Cygni nebula in Fe ii. We have identified several nebular emission regions that are characterized by a signal-to-noise ratio > 3. A comparison of our results with those available in the literature shows full consistency with the findings of Smith & Hartigan, which are based on radial velocity measurements, and relatively good agreement with the extension of emission nebula in N ii λ6584 found by Barlow et al. We have clearly also detected extended emission inside the radial distance R = 7.8 arcsec and outside R = 9.7 arcsec, which are the nebular boundaries proposed by Smith & Hartigan. New complementary spectroscopic observations are planned in order to measure radial velocities and to derive the three-dimensional distribution of the P Cygni nebula.
We have performed H and K sub(s) band observations of the planetary system around HR 8799 using the new AO system at the Large Binocular Telescope and the PISCES Camera. The excellent instrument ...performance (Strehl ratios up to 80% in H band) enabled the detection of the innermost planet, HR 8799e, at H band for the first time. The H and K sub(s) magnitudes of HR 8799e are similar to those of planets c and d, with planet e being slightly brighter. Therefore, HR 8799e is likely slightly more massive than c and d. We also explored possible orbital configurations and their orbital stability. We confirm that the orbits of planets b, c and e are consistent with being circular and coplanar; planet d should have either an orbital eccentricity of about 0.1 or be non-coplanar with respect to b and c. Planet e can not be in circular and coplanar orbit in a 4:2:1 mean motion resonances with c and d, while coplanar and circular orbits are allowed for a 5:2 resonance. The analysis of dynamical stability shows that the system is highly unstable or chaotic when planetary masses of about 5 M sub(J) for b and 7 M sub(J) for the other planets are adopted. Significant regions of dynamical stability for timescales of tens of Myr are found when adopting planetary masses of about 3.5, 5, 5, and 5 M sub(J) for HR 8799b, c, d, and e respectively. These masses are below the current estimates based on the stellar age (30 Myr) and theoretical models of substellar objects.
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The new 8.4 m LBT adaptive secondary AO system, with its novel pyramid wavefront sensor, was used to produce very high Strehl (> ~75% at 2.16 mu m) near-infrared narrowband (Br gamma : 2.16 mu m and ...FeII: 1.64 mu m) images of 47 young (~1 Myr) Orion Trapezium theta super(1) Ori cluster members. The inner ~41 x 53" of the cluster was imaged at spatial resolutions of ~0".050 (at 1.64 mu m). A combination of high spatial resolution and high S/N yielded relative binary positions to ~0.5 mas accuracies. Including previous speckle data, we analyze a 15 year baseline of high-resolution observations of this cluster. We are now sensitive to relative proper motions of just ~0.3 mas yr super(-1) (0.6 km s super(-1) at 450 pc); this is a ~7 x improvement in orbital velocity accuracy compared to previous efforts. We now detect clear orbital motions in the theta super(1) Ori B sub(2)B sub(3) system of 4.9 + or - 0.3 km s super(-1) and 7.2 + or - 0.8 km s super(-1) in the theta super(1) Ori A sub(1)A sub(2) system (with correlations of P.A. versus time at >99% confidence). All five members of the theta super(1) Ori B system appear likely a gravitationally bound "mini-cluster." The very lowest mass member of the theta super(1) Ori B system (B sub(4); mass ~0.2 M sub(middot in circle)) has, for the first time, a clearly detected motion (at 4.3 + or - 2.0 km s super(-1); correlation = 99.7%) w.r.t. B sub(1). However, B sub(4) is most likely in a long-term unstable (non-hierarchical) orbit and may "soon" be ejected from this "mini-cluster." This "ejection" process could play a major role in the formation of low-mass stars and brown dwarfs.
Context. The formation of OB-type stars up to (at least) 140 M⊙ can be explained via disk-mediated accretion and in fact growing observational evidence of disk-jet systems is found in high-mass ...star-forming regions. Aims. With the present observations we wish to investigate at sub-arcsecond resolution the jet structure close to the well studied high-mass protostar IRAS 20126+4104, which is known to be surrounded by a Keplerian disk. Methods. Adaptive optics imaging of the 2.2 μm continuum and H2 and Brγ line emission have been performed with the Large Binocular Telescope, attaining an angular resolution of ~90 mas and an astrometric precision of ~100 mas. Results. While our results are consistent with previous K-band images by other authors, the improved (by a factor ~3) resolution allows us to identify a number of previously unseen features, such as bow shocks spread all over the jet structure. Also, we confirm the existence of a bipolar nebulosity within 1′′ from the protostar, prove that the emission from the brightest, SE lobe is mostly due to the H2 line, and resolve its structure. Conclusions. Comparison with other tracers such as masers, thermal molecular line emission, and free-free continuum emission proves that the bipolar nebulosity is indeed tracing the root of the bipolar jet powered by the deeply embedded protostar at the center of the Keplerian disk.
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Adaptive optics at short wavelengths Agapito, Guido; Arcidiacono, Carmelo; Quirós-Pacheco, F. ...
Experimental astronomy,
11/2014, Volume:
37, Issue:
3
Journal Article
Peer reviewed
The First Light Adaptive Optics (FLAO) system has been successfully commissioned at the Large Binocular Telescope. It delivers extreme adaptive optics performance using bright natural guide stars ...reaching 90 % Strehl Ratios in H-band. Observations with current adaptive optics systems are limited to the near infrared wavelengths, in these bands the diffraction limited resolution of the largest ground-based telescopes (8–10 meter class) is comparable to the one of the much smaller Hubble Space Telescope that observes in the visible bands. This study aims to demonstrate the feasibility of an adaptive optics system designed to achieve very high order correction at visible wavelengths (0.5 to 0.8
μ
m
) with significant sky coverage. Upgrading the FLAO design with a low noise CCD relaxes the reference magnitude limit needed to achieve greater performance. In particular, we demonstrate that a gain of 1–2 magnitudes is possible by upgrading the wavefront sensor with a very low read out noise CCD. For future AO systems, in addition to low noise CCDs, deformable (secondary) mirrors with a higher actuator density will be able to move the high order correction capability from the near infrared to the visible wavelengths (Strehl Ratio of 80 % in
R
(0.7
μ
m
), 60 % in
V
(0.5
μ
m
)). We investigate, by means of numerical simulation, the gain in imaging performance obtained at Near Infrared, Visible, and UV wavelengths. The results of these simulations have been used to derive the empirical relation between Strehl Ratio and magnitude of the reference star and we then use this relationship to perform a detailed sky coverage analysis based on astronomical catalog data. The detailed simulations of the Point Spread Functions allow us to compute Ensquared Energy and Strehl Ratio for the magnitude working range of such an Adaptive Optics system. We present the results of the instrumental isoplanatic angle determination. We then used these values to compute the relationship between correction level and the off-axis angle from the reference star. The Strehl Ratio relationship with the reference magnitude and the angular distance provides the information needed to perform the sky-coverage analysis, which demonstrates that the designed system is able to provide V and R bands correction on a not negligible few percent of the sky.
We present deep near-infrared J, K sub(s) photometry of the old, metal-poor Galactic globular cluster M15 obtained with images collected with the LUCI1 and PISCES cameras available at the Large ...Binocular Telescope (LBT). We show how the use of First Light Adaptive Optics (FLAO) system coupled with the PISCES camera allows us to improve the limiting magnitude by ~2 mag in K sub(s). By analyzing archival Hubble Space Telescope data, we demonstrate that the quality of the LBT/PISCES color-magnitude diagram is fully comparable with analogous space-based data. The smaller field of view is balanced by the shorter exposure time required to reach a similar photometric limit. We investigated the absolute age of M15 by means of two methods: (i) by determining the age from the position of the main-sequence turnoff (MSTO), and (ii) by the magnitude difference between the MSTO and the well-defined knee detected along the faint portion of the MS. We derive consistent values of the absolute age of M15, that is, 12.9 + or - 2.6 Gyr and 13.3 + or - 1.1 Gyr, respectively.
We have performed H and KS band observations of the planetary system around HR 8799 using the new AO system at the Large Binocular Telescope and the PISCES Camera. The excellent instrument ...performance (Strehl ratios up to 80% in H band) enabled the detection of the innermost planet, HR 8799e, at H band for the first time. The H and KS magnitudes of HR 8799e are similar to those of planets c and d, with planet e being slightly brighter. Therefore, HR 8799e is likely slightly more massive than c and d. We also explored possible orbital configurations and their orbital stability. We confirm that the orbits of planets b, c and e are consistent with being circular and coplanar; planet d should have either an orbital eccentricity of about 0.1 or be non-coplanar with respect to b and c. Planet e can not be in circular and coplanar orbit in a 4:2:1 mean motion resonances with c and d, while coplanar and circular orbits are allowed for a 5:2 resonance. The analysis of dynamical stability shows that the system is highly unstable or chaotic when planetary masses of about 5 MJ for b and 7 MJ for the other planets are adopted. Significant regions of dynamical stability for timescales of tens of Myr are found when adopting planetary masses of about 3.5, 5, 5, and 5 MJ for HR 8799b, c, d, and e respectively. These masses are below the current estimates based on the stellar age (30 Myr) and theoretical models of substellar objects.
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FMFMET, NUK, UL, UM, UPUK
Adaptive optics at short wavelengths Agapito, Guido; Arcidiacono, Carmelo; Quiros-Pacheco, F ...
Experimental astronomy,
11/2014, Volume:
37, Issue:
3
Journal Article
Peer reviewed
The First Light Adaptive Optics (FLAO) system has been successfully commissioned at the Large Binocular Telescope. It delivers extreme adaptive optics performance using bright natural guide stars ...reaching 90 % Strehl Ratios in H-band. Observations with current adaptive optics systems are limited to the near infrared wavelengths, in these bands the diffraction limited resolution of the largest ground-based telescopes (8-10 meter class) is comparable to the one of the much smaller Hubble Space Telescope that observes in the visible bands. This study aims to demonstrate the feasibility of an adaptive optics system designed to achieve very high order correction at visible wavelengths (0.5 to 0.8 mu m) with significant sky coverage. Upgrading the FLAO design with a low noise CCD relaxes the reference magnitude limit needed to achieve greater performance. In particular, we demonstrate that a gain of 1-2 magnitudes is possible by upgrading the wavefront sensor with a very low read out noise CCD. For future AO systems, in addition to low noise CCDs, deformable (secondary) mirrors with a higher actuator density will be able to move the high order correction capability from the near infrared to the visible wavelengths (Strehl Ratio of 80 % in R (0.7 mu m), 60 % in V (0.5 mu m)). We investigate, by means of numerical simulation, the gain in imaging performance obtained at Near Infrared, Visible, and UV wavelengths. The results of these simulations have been used to derive the empirical relation between Strehl Ratio and magnitude of the reference star and we then use this relationship to perform a detailed sky coverage analysis based on astronomical catalog data. The detailed simulations of the Point Spread Functions allow us to compute Ensquared Energy and Strehl Ratio for the magnitude working range of such an Adaptive Optics system. We present the results of the instrumental isoplanatic angle determination. We then used these values to compute the relationship between correction level and the off-axis angle from the reference star. The Strehl Ratio relationship with the reference magnitude and the angular distance provides the information needed to perform the sky-coverage analysis, which demonstrates that the designed system is able to provide V and R bands correction on a not negligible few percent of the sky.
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