55 research outputs found
Straylight analyses and mitigation strategies for the ELT METIS instrument
editorial reviewedThe Mid-infrared ELT Imager and Spectrograph (METIS) is one of the three first-generation instruments on the Extremely Large Telescope (ELT). It will provide 20 instrument configurations for direct and high-contrast imaging, medium and high resolution spectroscopy in the wavelength range of 3 - 13μ. The straylight will affect the image contrast and objects recognition thus influencing the final instrument performance. For this reason it should be taken into account and accurately modeled at the design stage. In the present study we consider straylight from the following sources: surface roughness and defects of the optical surfaces, multiple reflections and diffraction, which will all influence the instrument performance. We estimate their influence using a bottom-up modelling approach at the system level and derive the requirements for some critical parameters. Using empirical and analytical models and performing non-sequential raytracing we demonstrate that the target straylight level can be reached in the current design with reasonable specifications on the optical components
Large Interferometer For Exoplanets (LIFE): II. Signal simulation, signal extraction, and fundamental exoplanet parameters from single-epoch observations
peer reviewedContext. The Large Interferometer For Exoplanets (LIFE) initiative is developing the science and a technology road map for an ambitious space mission featuring a space-based mid-infrared (MIR) nulling interferometer in order to detect the thermal emission of hundreds of exoplanets and characterize their atmospheres.
Aims. In order to quantify the science potential of such a mission, in particular in the context of technical trade-offs, an instrument simulator is required. In addition, signal extraction algorithms are needed to verify that exoplanet properties (e.g., angular separation and spectral flux) contained in simulated exoplanet data sets can be accurately retrieved.
Methods. We present LIFEsim, a software tool developed for simulating observations of exoplanetary systems with an MIR space-based nulling interferometer. It includes astrophysical noise sources (i.e., stellar leakage and thermal emission from local zodiacal and exozodiacal dust) and offers the flexibility to include instrumental noise terms in the future. Here, we provide some first quantitative limits on instrumental effects that would allow the measurements to remain in the fundamental noise limited regime. We demonstrate updated signal extraction approaches to validating signal-to-noise ratio (S/N) estimates from the simulator. Monte Carlo simulations are used to generate a mock survey of nearby terrestrial exoplanets and determine to which accuracy fundamental planet properties can be retrieved.
Results. LIFEsim provides an accessible way to predict the expected S/N of future observations as a function of various key instrument and target parameters. The S/Ns of the extracted spectra are photon noise dominated, as expected from our current simulations. Signals from multi-planet systems can be reliably extracted. From single-epoch observations in our mock survey of small (R < 1.5 REarth) planets orbiting within the habitable zones of their stars, we find that typical uncertainties in the estimated effective temperature of the exoplanets are ≲10%, for the exoplanet radius ≲20%, and for the separation from the host star ≲2%. Signal-to-noise-ratio values obtained in the signal extraction process deviate by less than 10% from purely photon-counting statistics-based S/Ns.
Conclusions. LIFEsim has been sufficiently well validated so that it can be shared with a broader community interested in quantifying various exoplanet science cases that a future space-based MIR nulling interferometer could address. Reliable signal extraction algorithms exist, and our results underline the power of the MIR wavelength range for deriving fundamental exoplanet properties from single-epoch observations.Large Interferometer For Exoplanets (LIFE
Spectroscopic time series performance of the Mid-Infrared Instrument on the JWST
We present here the first ever mid-infrared spectroscopic time series
observation of the transiting exoplanet \object{L 168-9 b} with the
Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope. The data were
obtained as part of the MIRI commissioning activities, to characterize the
performance of the Low Resolution Spectroscopy (LRS) mode for these challenging
observations. To assess the MIRI LRS performance, we performed two independent
analyses of the data. We find that with a single transit observation we reached
a spectro-photometric precision of 50 ppm in the 7-8 \micron range at
R=50, consistent with 25 ppm systematic noise. The derived band averaged
transit depth is 524 15 ppm and 547 13 ppm for the two applied
analysis methods, respectively, recovering the known transit depth to within 1
. The measured noise in the planet's transmission spectrum is
approximately 15-20 \% higher than random noise simulations over wavelengths
m. \added{We observed an larger excess
noise at the shortest wavelengths of up to a factor of two, for which possible
causes are discussed.} This performance was achieved with limited in-flight
calibration data, demonstrating the future potential of MIRI for the
characterization of exoplanet atmospheres.Comment: Accepted for publishing in PASP, 21 pages, 10 figure
JWST MIRI flight performance: The Medium-Resolution Spectrometer
The Medium-Resolution Spectrometer (MRS) provides one of the four operating
modes of the Mid-Infrared Instrument (MIRI) on board the James Webb Space
Telescope (JWST). The MRS is an integral field spectrometer, measuring the
spatial and spectral distributions of light across the 5-28 wavelength
range with a spectral resolving power between 3700-1300. We present the MRS's
optical, spectral, and spectro-photometric performance, as achieved in flight,
and we report on the effects that limit the instrument's ultimate sensitivity.
The MRS flight performance has been quantified using observations of stars,
planetary nebulae, and planets in our Solar System. The precision and accuracy
of this calibration was checked against celestial calibrators with well-known
flux levels and spectral features. We find that the MRS geometric calibration
has a distortion solution accuracy relative to the commanded position of 8 mas
at 5 and 23 mas at 28 . The wavelength calibration is accurate
to within 9 km/sec at 5 and 27 km/sec at 28 . The uncertainty in
the absolute spectro-photometric calibration accuracy was estimated at 5.6 +-
0.7 %. The MIRI calibration pipeline is able to suppress the amplitude of
spectral fringes to below 1.5 % for both extended and point sources across the
entire wavelength range. The MRS point spread function (PSF) is 60 % broader
than the diffraction limit along its long axis at 5 and is 15 % broader
at 28 . The MRS flight performance is found to be better than prelaunch
expectations. The MRS is one of the most subscribed observing modes of JWST and
is yielding many high-profile publications. It is currently humanity's most
powerful instrument for measuring the mid-infrared spectra of celestial sources
and is expected to continue as such for many years to come.Comment: 16 pages, 21 figure
Observations of the planetary nebula SMP LMC 058 with the JWST MIRI medium resolution spectrometer
During the commissioning of JWST, the medium-resolution spectrometer (MRS) on the mid-infrared instrument (MIRI) observed the planetary nebula SMP LMC 058 in the Large Magellanic Cloud. The MRS was designed to provide medium resolution (R = λ/Δλ) 3D spectroscopy in the whole MIRI range. SMP LMC 058 is the only source observed in JWST commissioning that is both spatially and spectrally unresolved by the MRS and is a good test of JWST's capabilities. The new MRS spectra reveal a wealth of emission lines not previously detected in this planetary nebula. From these lines, the spectral resolving power (λ/Δλ) of the MRS is confirmed to be in the range R = 4000-1500, depending on the MRS spectral sub-band. In addition, the spectra confirm that the carbon-rich dust emission is from complex hydrocarbons and SiC grains and that there is little to no time evolution of the SiC dust and emission line strengths over a 17-yr epoch. These commissioning data reveal the great potential of the MIRI MRS for the study of circumstellar and interstellar material.</p
MINDS. Abundant water and varying C/O across the disk of Sz 98 as seen by JWST/MIRI
MIRI/MRS on board the JWST allows us to probe the inner regions of
protoplanetary disks. Here we examine the disk around the classical T Tauri
star Sz 98, which has an unusually large dust disk in the millimetre with a
compact core. We focus on the HO emission through both its ro-vibrational
and pure rotational emission. Furthermore, we compare our chemical findings
with those obtained for the outer disk from Atacama Large
Millimeter/submillimeter Array (ALMA) observations. In order to model the
molecular features in the spectrum, the continuum was subtracted and LTE slab
models were fitted. The spectrum was divided into different wavelength regions
corresponding to HO lines of different excitation conditions, and the slab
model fits were performed individually per region. We confidently detect CO,
HO, OH, CO, and HCN in the emitting layers. The isotopologue
HO is not detected. Additionally, no other organics, including
CH, are detected. This indicates that the C/O ratio could be
substantially below unity, in contrast with the outer disk. The HO emission
traces a large radial disk surface region, as evidenced by the gradually
changing excitation temperatures and emitting radii. The OH and CO emission
are relatively weak. It is likely that HO is not significantly
photodissociated; either due to self-shielding against the stellar irradiation,
or UV-shielding from small dust particles. The relative emitting strength of
the different identified molecular features point towards UV-shielding of
HO in the inner disk of Sz 98, with a thin layer of OH on top. The majority
of the organic molecules are either hidden below the dust continuum, or not
present. In general, the inferred composition points to a sub-solar C/O ratio
(<0.5) in the inner disk, in contrast with the larger than unity C/O ratio in
the gas in the outer disk found with ALMA.Comment: Submitted to A&A on May 25 2023. 18 pages, 11 figure
MINDS. The detection of CO with JWST-MIRI indicates abundant CO in a protoplanetary disk
We present JWST-MIRI MRS spectra of the protoplanetary disk around the
low-mass T Tauri star GW Lup from the MIRI mid-INfrared Disk Survey (MINDS) GTO
program. Emission from CO, CO, HO, HCN,
CH, and OH is identified with CO being detected for
the first time in a protoplanetary disk. We characterize the chemical and
physical conditions in the inner few au of the GW Lup disk using these
molecules as probes. The spectral resolution of JWST-MIRI MRS paired with high
signal-to-noise data is essential to identify these species and determine their
column densities and temperatures. The -branches of these molecules,
including those of hot-bands, are particularly sensitive to temperature and
column density. We find that the CO emission in the GW Lup disk is
coming from optically thick emission at a temperature of 400 K.
CO is optically thinner and based on a lower temperature of
325 K, may be tracing deeper into the disk and/or a larger emitting
radius than CO. The derived /
ratio is orders of magnitude higher than previously derived for GW Lup and
other targets based on \textit{Spitzer}-IRS data. This high column density
ratio may be due to an inner cavity with a radius in between the HO and
CO snowlines and/or an overall lower disk temperature. This paper
demonstrates the unique ability of JWST to probe inner disk structures and
chemistry through weak, previously unseen molecular features.Comment: 15 pages, 10 figures. Accepted to ApJ
Atmospheric characterization of terrestrial exoplanets in the mid-infrared: biosignatures, habitability, and diversity
Quanz, S.P. et al.Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for signatures in their atmospheres that indicate biological activity, assess their ability to provide conditions for life as we know it, and investigate their expected atmospheric diversity. None of the currently adopted projects or missions, from ground or in space, can address these goals. In this White Paper, submitted to ESA in response to the Voyage 2050 Call, we argue that a large space-based mission designed to detect and investigate thermal emission spectra of terrestrial exoplanets in the mid-infrared wavelength range provides unique scientific potential to address these goals and surpasses the capabilities of other approaches. While NASA might be focusing on large missions that aim to detect terrestrial planets in reflected light, ESA has the opportunity to take leadership and spearhead the development of a large mid-infrared exoplanet mission within the scope of the “Voyage 2050” long-term plan establishing Europe at the forefront of exoplanet science for decades to come. Given the ambitious science goals of such a mission, additional international partners might be interested in participating and contributing to a roadmap that, in the long run, leads to a successful implementation. A new, dedicated development program funded by ESA to help reduce development and implementation cost and further push some of the required key technologies would be a first important step in this direction. Ultimately, a large mid-infrared exoplanet imaging mission will be needed to help answer one of humankind’s most fundamental questions: “How unique is our Earth?”Open Access funding provided by ETH Zurich. Part of this work has been carried out within the framework of the National Centre of Competence in Research PlanetS supported by the Swiss National Science Foundation. S.P.Q. acknowledges the financial support of the SNSF.Peer reviewe
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
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