Showing papers by "Michael Meyer published in 2012"

FIRST LIGHT LBT AO IMAGES OF HR 8799 bcde AT 1.6 AND 3.3 μm: NEW DISCREPANCIES BETWEEN YOUNG PLANETS AND OLD BROWN DWARFS*

Abstract: As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study the physical properties of several planets in parallel. In this paper, we image all four of the HR 8799 planets at H band and 3.3 {mu}m with the new Large Binocular Telescope adaptive optics system, PISCES, and LBTI/LMIRCam. Our images offer an unprecedented view of the system, allowing us to obtain H and 3.3 {mu}m photometry of the innermost planet (for the first time) and put strong upper limits on the presence of a hypothetical fifth companion. We find that all four planets are unexpectedly bright at 3.3 {mu}m compared to the equilibrium chemistry models used for field brown dwarfs, which predict that planets should be faint at 3.3 {mu}m due to CH{sub 4} opacity. We attempt to model the planets with thick-cloudy, non-equilibrium chemistry atmospheres but find that removing CH{sub 4} to fit the 3.3 {mu}m photometry increases the predicted L' (3.8 {mu}m) flux enough that it is inconsistent with observations. In an effort to fit the spectral energy distribution of the HR 8799 planets, we construct mixtures of cloudy atmospheres, which are intended to represent planets covered by clouds of varying opacity.more » In this scenario, regions with low opacity look hot and bright, while regions with high opacity look faint, similar to the patchy cloud structures on Jupiter and L/T transition brown dwarfs. Our mixed-cloud models reproduce all of the available data, but self-consistent models are still necessary to demonstrate their viability.« less

First Light LBT AO Images of HR 8799 bcde at 1.65 and 3.3 Microns: New Discrepancies between Young Planets and Old Brown Dwarfs

Abstract: As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study the physical properties of several planets in parallel. In this paper, we image all four of the HR 8799 planets at H-band and 3.3 microns with the new LBT adaptive optics system, PISCES, and LBTI/LMIRCam. Our images offer an unprecedented view of the system, allowing us to obtain H and 3.3$ micron photometry of the innermost planet (for the first time) and put strong upper-limits on the presence of a hypothetical fifth companion. We find that all four planets are unexpectedly bright at 3.3 microns compared to the equilibrium chemistry models used for field brown dwarfs, which predict that planets should be faint at 3.3 microns due to CH4 opacity. We attempt to model the planets with thick-cloudy, non-equilibrium chemistry atmospheres, but find that removing CH4 to fit the 3.3 micron photometry increases the predicted L' (3.8 microns) flux enough that it is inconsistent with observations. In an effort to fit the SED of the HR 8799 planets, we construct mixtures of cloudy atmospheres, which are intended to represent planets covered by clouds of varying opacity. In this scenario, regions with low opacity look hot and bright, while regions with high opacity look faint, similar to the patchy cloud structures on Jupiter and L/T transition brown-dwarfs. Our mixed cloud models reproduce all of the available data, but self-consistent models are still necessary to demonstrate their viability.

EChO - Exoplanet Characterisation Observatory

Abstract: A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO -the Exoplanet Characterisation Observatory- is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. EChO will build on observations by Hubble, Spitzer and groundbased telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. EChO will simultaneously observe a broad enough spectral region -from the visible to the mid-IR- to constrain from one single spectrum the temperature structure of the atmosphere and the abundances of the major molecular species. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules to retrieve the composition and temperature structure of planetary atmospheres. The target list for EChO includes planets ranging from Jupiter-sized with equilibrium temperatures Teq up to 2000 K, to those of a few Earth masses, with Teq ~300 K. We have baselined a dispersive spectrograph design covering continuously the 0.4-16 micron spectral range in 6 channels (1 in the VIS, 5 in the IR), which allows the spectral resolution to be adapted from several tens to several hundreds, depending on the target brightness. The instrument will be mounted behind a 1.5 m class telescope, passively cooled to 50 K, with the instrument structure and optics passively cooled to ~45 K. EChO will be placed in a grand halo orbit around L2. We have also undertaken a first-order cost and development plan analysis and find that EChO is easily compatible with the ESA M-class mission framework.

The JWST Fine Guidance Sensor (FGS) and Near-Infrared Imager and Slitless Spectrograph (NIRISS)

Abstract: The Fine Guidance Sensor (FGS) is one of the four science instruments on board the James Webb Space Telescope (JWST). FGS features two modules: an infrared camera dedicated to fine guiding of the observatory and a science camera module, the Near-Infrared Imager and Slitless Spectrograph (NIRISS) covering the wavelength range between 0.7 and 5.0 μm with a field of view of 2.2' X 2.2'. NIRISS has four observing modes: 1) broadband imaging featuring seven of the eight NIRCam broadband filters, 2) wide-field slitless spectroscopy at a resolving power of rv150 between 1 and 2.5 μm, 3) single-object cross-dispersed slitless spectroscopy enabling simultaneous wavelength coverage between 0. 7 and 2.5 μm at Rrv660, a mode optimized for transit spectroscopy of relatively bright (J > 7) stars and, 4) sparse aperture interferometric imaging between 3.8 and 4.8 μm enabling high­ contrast ("' 10-4) imaging of M < 8 point sources at angular separations between 70 and 500 milliarcsec. This paper presents an overview of the FGS/NIRISS design with a focus on the scientific capabilities and performance offered by NIRISS.

FGF receptors 1 and 2 are key regulators of keratinocyte migration in vitro and in wounded skin

Abstract: Efficient wound repair is essential for the maintenance of the integrity of the skin. The repair process is controlled by a variety of growth factors and cytokines, and their abnormal expression or activity can cause healing disorders. Here, we show that wound repair is severely delayed in mice lacking fibroblast growth factor receptors (FGFR) 1 and 2 in keratinocytes. As the underlying mechanism, we identified impaired wound contraction and a delay in re-epithelialization that resulted from impaired keratinocyte migration at the wound edge. Scratch wounding and transwell assays demonstrated that FGFR1/2-deficient keratinocytes had a reduced migration velocity and impaired directional persistence owing to inefficient formation and turnover of focal adhesions. Underlying this defect, we identified a significant reduction in the expression of major focal adhesion components in the absence of FGFR signaling, resulting in a general migratory deficiency. These results identify FGFs as key regulators of keratinocyte migration in wounded skin.

On-sky operations and performance of LMIRcam at the Large Binocular Telescope

Abstract: The L/M-band (3−5 μm) InfraRed Camera (LMIRcam) sits at the combined focal plane of the Large Binocular Telescope Interferometer (LBTI), ultimately imaging the coherently combined focus of the LBT’s two 8.4-meter mirrors. LMIRcam achieved first light at the LBT in May 2011 using a single AO-enabled 8.4-meter aperture. With the delivery of LBT’s final adaptive secondary mirror in Fall of 2011, dual-aperture AO-corrected interferometric fringes were realized in April 2012. We report on the performance of these configurations and characterize the noise performance of LMIRcam’s HAWAII-2RG 5.3-μm cutoff array paired with Cornell FORCAST readout electronics. In addition, we describe recent science highlights and discuss future improvements to the LMIRcam hardware.

EX Lupi FROM QUIESCENCE TO OUTBURST : EXPLORING THE LTE APPROACH IN MODELING BLENDED H2O AND OH MID-INFRARED EMISSION

Abstract: We present a comparison of archival Spitzer spectra of the strongly variable T Tauri EX Lupi, observed before and during its 2008 outburst. We analyze the mid-infrared emission from gas-phase molecules thought to originate in a circumstellar disk. In quiescence the emission shows a forest of H2O lines, highly excited OH lines, and the Q branches of the organics C2H2, HCN, and CO2, similar to the emission observed toward several T Tauri systems. The outburst emission shows instead remarkable changes: H2O and OH line uxes increase, new OH, H 2, and Hi transitions are detected, and organics are no longer seen. We adopt a simple model of a single-temperature slab of gas in local thermal equilibrium, a common approach for molecular analyses of Spitzer spectra, and derive the excitation temperature, column density, and emitting area of H2O and OH. We show how model results strongly depend on the selection of emission lines tted, and that spectrally-resolved observations are essential for a correct interpretation of the molecular emission from disks, particularly in the case of water. Using H2O lines that can be approximated as thermalized to a single temperature, our results are consistent with a column density decrease in outburst while the emitting area of warm gas increases. A rotation diagram analysis suggests that the OH emission can be explained with two temperature components, which remarkably increase in column density in outburst. The relative change of H2O and OH emission suggests a key role for UV radiation in the disk surface chemistry.

Science Opportunities with the Near-IR Camera (NIRCam) on the James Webb Space Telescope (JWST)

Abstract: The Near-Infrared Camera (NIRCam) on the James Webb Space Telescope (JWST) offers revolutionary gains in sensitivity throughout the 1-5 m region. NIRCam will enable great advances in all areas of astrophysics, from the composition of objects in our own Kuiper Belt and the physical properties of planets orbiting nearby stars to the formation of stars and the detection of the youngest galaxies in the Universe. NIRCam also plays an important role in initial alignment of JWST and the long term maintenance of its image quality. NIRCam is presently undergoing instrument Integration and Test in preparation for delivery to the JWST project. Key near-term milestones include the completion of cryogenic testing of the entire instrument; demonstration of scientific and wavefront sensing performance requirements; testing of replacement H2RG detectors arrays; and an analysis of coronagraphic performance in light of

The SAFARI imaging spectrometer for the SPICA space observatory

Abstract: The Japanese SPace Infrared telescope for Cosmology and Astrophysics, SPICA, will provide astronomers with a long awaited new window on the universe. Having a large cold telescope cooled to only 6K above absolute zero, SPICA will provide a unique environment where instruments are limited only by the cosmic background itself. A consortium of European and Canadian institutes has been established to design and implement the SpicA FAR infrared Instrument SAFARI, an imaging spectrometer designed to fully exploit this extremely low far infrared background environment provided by the SPICA observatory. SAFARI’s large instantaneous field of view combined with the extremely sensitive Transition Edge Sensing detectors will allow astronomers to very efficiently map large areas of the sky in the far infrared – in a square degree survey of a 1000 hours many thousands of faint sources will be detected, and a very large fraction of these sources will be fully spectroscopically characterised by the instrument. Efficiently obtaining such a large number of complete spectra is essential to address several fundamental questions in current astrophysics: how do galaxies form and evolve over cosmic time?, what is the true nature of our own Milky Way?, and why and where do planets like those in our own solar system come into being?

METIS: the thermal infrared instrument for the E-ELT

Abstract: The ‘Mid-infrared ELT Imager and Spectrograph’ (METIS) will be the third instrument on the European Extremely Large Telescope (E-ELT). METIS will provide diffraction limited imaging in the atmospheric L/M and N-band from 3 to 14 μm over an 18˝×18˝ field of view, as well as high contrast coronagraphy, medium-resolution (R ≤ 5000) long slit spectroscopy, and polarimetry. In addition, an integral field spectrograph will provide a spectral resolution of R ~ 100,000 at L/M band. Focusing on highest angular resolution and high spectral resolution, METIS will deliver unique science, in particular in the areas of exo-planets, proto-planetary-disks and high-redshift galaxies, which are illustrated in this paper. The reduction of the E-ELT aperture size had little impact on the METIS science case. With the recent positive developments in the area of detectors, the METIS instrument concept has reached a high level of technology readiness. For some key components (cryogenic chopping mirror, immersed grating, sorption cooler and cryogenic derotator) a development and test program has been launched successfully.

Exoplanet characterisation observatory

Abstract: A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO – the Exoplanet Characterisation Observatory – is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. The use of passive cooling, few moving parts and well established technology gives a low-risk and potentially long-lived mission. EChO will build on observations by Hubble, Spitzer and groundbased telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. However, EChO’s configuration and specifications are designed to study a number of systems in a consistent manner that will eliminate the ambiguities affecting prior observations. EChO will simultaneously observe a broad enough spectral region – from the visible to the mid-infrared – to constrain from one single spectrum the temperature structure of the atmosphere, the abundances of the major carbon and oxygen bearing species, the expected photochemically-produced species and magnetospheric signatures. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules and retrieve the composition and temperature structure of planetary atmospheres. The target list for EChO includes planets ranging from Jupiter-sized with equilibrium temperatures Teq up to 2000 K, to those of a few Earth masses, with Teq ∼300 K. The list will include planets with no Solar System analog, such as the recently discovered planets GJ1214b, whose density lies between that of terrestrial and gaseous planets, or the rocky-iron planet 55 Cnc e, with day-side temperature close to 3000 K. As the number of detected exoplanets is growing rapidly each year, and the mass and radius of those detected steadily decreases, the target list will be constantly adjusted to include the most interesting systems. We have baselined a dispersive spectrograph design covering continuously the 0.4–16μm spectral range in 6 channels (1 in the visible, 5 in the InfraRed), which allows the spectral resolution to be adapted from several tens to several hundreds, depending on the target brightness. The instrument will be mounted behind a 1.5 m class telescope, passively cooled to 50 K, with the instrument structure and optics passively cooled to ∼45 K. EChO will be placed in a grand halo orbit around L2. This orbit, in combination with an optimised thermal shield design, provides a highly stable thermal environment and a high degree of visibility of the sky to observe repeatedly several tens of targets over the year. Both the baseline and alternative designs have been evaluated and no critical items with Technology Readiness Level (TRL) less than 4 to 5 have been identified. We have also undertaken a first-order cost and development plan analysis and find that EChO is easily compatible with the ESA M-class mission framework.

An end-to-end instrument model for the proposed E-ELT instrument METIS

Abstract: The optimal performance of an instrument relies critically on accurate performance estimates during its design phase. They need to be modeled to give the science and engineering teams a preview of the performance of the instrument, to guide the design process, to prove the capabilities of the instrument and to prepare science ready software tools before the instrument is operational. METIS, the Mid-infrared E-ELT Imager, is an instrument concept for the E-ELT that covers the thermal infrared wavelengths from 2:9 – 14 μm (L, M and N band). It contains a diffraction limited imager and an integral field high resolution spectrograph. The instrument consists of two independent units, the imager and the spectrograph, and is entirely encased in a cryostat to maintain the stable low temperatures required for good performance at mid-infrared wavelengths. METIS was identified in the instrument roadmap as the third instrument for the E-ELT, after two first light instruments. Because in the mid-infrared the Earth's atmosphere and the telescope mirrors radiate and produce a very high thermal background, it is crucial to develop techniques and mechanisms to measure and reduce this background, to achieve the desired performance of an E-ELT. To demonstrate the capabilities of METIS, years before the actual instrument is built and can be tested, we are developing an end-to-end instrument model, which will simulate the full capacity of METIS. The structure of the model and first results of the performance evaluation are shown.

The Exoplanet Characterization Observatory (EChO): performance model EclipseSim and applications

Abstract: We present EclipseSim, a radiometric model for exoplanet transit spectroscopy that allows easy exploration of the fundamental performance limits of any space-based facility aiming to perform such observations. It includes a library of stellar model atmosphere spectra and can either approximate exoplanet spectra by simplified models, or use any theoretical or observed spectrum, to simulate observations. All calculations are done in a spectrally resolved fashion and the contributions of the various fundamental noise sources are budgeted separately, allowing easy assessment of the dominant noise sources, as a function of wavelength. We apply EclipseSimto the Exoplanet Characterization Observatory (EChO), a proposed mission dedicated to exoplanet transit spectroscopy that is currently in competition for the M3 launch slot of ESA’s cosmic vision programme. We show several case studies on planets with sizes in the super-Earth to Jupiter range, and temperatures ranging from the temperate to the ≈1500 K regime, demonstrating the power and versatility of EChO. EclipseSim is publicly available ∗ .

Designing the METIS adaptive optics system

Abstract: METIS, the Mid-infrared E-ELT Imager and Spectrometer is foreseen to be the third instrument on the European Extremely Large Telescope (E-ELT) and the only instrument to provide high sensitivity mid-IR imaging and spectroscopy to the E-ELT. In order to reach the maximum resolution and sensitivity, an adaptive optics system is required. Since the operational wavelength of METIS is the longest of all E-ELT instruments and the field is relatively small, the complexity of the AO system is significantly reduced, both in required speed as well as order of the AO system. Adaptive Optics has been demonstrated to deliver consistently high performance for the current generation of 6-10 meter class telescopes at mid-infrared wavelengths, and similar performance is expected for METIS on the E-ELT. But in order to provide a reliable system on the E-ELT, several effects which have a minor impact on 6-8 meter class telescopes will need to be investigated for their impact on METIS AO. These effects include refractivity, atmospheric composition variations, but also the operation in a complex operational environment given by both METIS as well as the E-ELT. In this paper we describe the scientific requirements on the METIS AO system, the specific issues related to Adaptive Optics in the mid-IR and expected performance of the METIS AO system on the E-ELT.

Conceptual phase A design of a cryogenic shutter mechanism for the SAFARI flight instrument

Abstract: We present a conceptual design for a cryogenic optical mechanism for the SAFARI instrument. SAFARI is a long wavelength (34-210 micron) Imaging Fourier Transform Spectrometer (FTS) to fly as an ESA instrument on the JAXA SPICA mission projected to launch in 2021. SPICA is a large 3m class space telescope which will have an operating temperature of less than 7K. The SAFARI shutter is a single point of failure flight mechanism designed to operate in space at a temperature of 4K which meets redundancy and reliability requirements of this challenging mission. The conceptual design is part of a phase A study led by ETH Institute for Astronomy and conducted by RUAG Space AG.

Is Mars Sample Return Required Prior to Sending Humans to Mars

Abstract: Prior to potentially sending humans to the surface of Mars, it is fundamentally important to return samples from Mars. Analysis in Earth's extensive scientific laboratories would significantly reduce the risk of human Mars exploration and would also support the science and engineering decisions relating to the Mars human flight architecture. The importance of measurements of any returned Mars samples range from critical to desirable, and in all cases these samples will would enhance our understanding of the Martian environment before potentially sending humans to that alien locale. For example, Mars sample return (MSR) could yield information that would enable human exploration related to 1) enabling forward and back planetary protection, 2) characterizing properties of Martian materials relevant for in situ resource utilization (ISRU), 3) assessing any toxicity of Martian materials with respect to human health and performance, and 4) identifying information related to engineering surface hazards such as the corrosive effect of the Martian environment. In addition, MSR would be engineering 'proof of concept' for a potential round trip human mission to the planet, and a potential model for international Mars exploration.

Visible/infrared spectrometer for EChO

Abstract: The Exoplanet Characterisation Observatory (EChO) is a medium class mission candidate within ESA's Cosmic Vision 2015-2025 program on space science. EChO will be equipped with a visible to infrared spectrometer covering the wavelength range from 0.4 - 11 μm (goal: 16 μm) at a spectral resolving power between 30 and 300 in order to characterize the atmospheres of known transiting extrasolar planets ranging from Hot Jupiters to Super Earths. In this paper we will present first results from the dedicated study of the EChO science payload carried out by our EChO Instrument Consortium during the assessment phase of the mission.

An integrated 1-5 micron test bench for the characterization of cryogenic optical elements

Abstract: We report on the final design and current status of a 1-5 micron infrared test bench at the ETH Zurich Institute for Astronomy. This facility will enable us to characterize infrared optics, both reflective and transmissive, at cryogenic operating temperatures for both ground- and space-based applications. A focus of our lab is to facilitate the detection and characterization of extra-solar planets. The test bench is designed to characterize a range of spectrally dispersive and diffraction suppression optics such as filters, grisms, gratings, as well as both focal and pupil plane coronagraphs. The test bench is built around a 2048x2048 HAWAII-2RG detector from Teledyne Imaging Systems. The optical bench is envisioned to operate down to 30 K. “First light” is expected in the second half of 2012. We outline the status of the project, and describe the capabilities of the test bench in detail in order to alert potential collaborators to this new capability.