Sascha Patrick Quanz


Last Name

Quanz

First Name

Sascha Patrick

ORCID

0000-0003-3829-7412

Organisational unit

09680 - Quanz, Sascha Patrick / Quanz, Sascha Patrick

Search Results

Publications 1 - 10 of 264
  • Atmospheric retrievals of terrestrial planets with future space missions
    Item type: Other Conference Item
    Alei, Eleonora; Konrad, Björn; Angerhausen, Daniel; et al. (2022)
    EPSC Abstracts
    From the White Paper series within the ESA “Voyage 2050” process [1] and the US Astro 2020 Decadal [2], it is clear that the astronomical community is going to focus on investigating temperate, terrestrial exoplanets to understand their potential habitability and search for atmospheric signatures of biospheres. Various concepts for future space missions have been proposed, from a large IR/O/UV (LUVOIR/HabEx-like) space mission for studies in reflected light [3, 4], to the mid-infrared nulling interferometer LIFE (Large Interferometer for Exoplanets), to characterize the thermal portion of the planetary spectrum [5, 6]. Their goal is to constrain the bulk parameters, atmospheric structure and composition, and the surface conditions of dozens of terrestrial exoplanets. Atmospheric retrieval studies are essential to define the potential of future missions, determine the technical requirements, as well as to validate the analysis pipelines. It is also relevant at this stage to quantify any synergy among the various instruments, in order to identify compelling science cases whose characterization would be enhanced by observation in multiple wavelength ranges. Bayesian retrieval routines are the key to a statistically robust analysis of a measured atmospheric spectrum. The Bayesian retrieval method builds on iteratively fitting a parametric model for the planet spectrum to the observed spectrum to get estimates on the composition of the planet’s atmosphere and its structure. Such a method can be useful to quantify the amount of information that can be extracted from an observed spectrum, depending on its quality (in terms of resolution, signal-to-noise ratio, observing time, and wavelength range). Retrieval studies are currently being performed in order to determine the requirements for the upcoming missions. In this talk, I will summarize the main results of the latest atmospheric retrieval studies that were performed during the studies of some future space mission concepts.
  • Detecting Atmospheric CO₂ Trends as Population-level Signatures for Long-term Stable Water Oceans and Biotic Activity on Temperate Terrestrial Exoplanets
    Item type: Journal Article
    Hansen, Janina; Angerhausen, Daniel; Quanz, Sascha Patrick; et al. (2025)
    The Astrophysical Journal
    Identifying key observables is essential for enhancing our knowledge of exoplanet habitability and biospheres, as well as improving future mission capabilities. While currently challenging, future observatories such as the Large Interferometer for Exoplanets (LIFE) will enable atmospheric observations of a diverse sample of temperate terrestrial worlds. Using thermal emission spectra that represent conventional predictions of atmospheric CO₂ variability across the habitable zone (HZ), we assess the ability of the LIFE mission—as a specific concept for a future space-based interferometer—to detect CO₂ trends indicative of the carbonate–silicate (Cb–Si) weathering feedback, a well-known habitability marker and potential biological tracer. Therefore, we explore the feasibility of differentiating between CO₂ trends in biotic and abiotic planet populations. We create synthetic exoplanet populations based on geochemistry-climate predictions and perform retrievals on simulated thermal emission observations. The results demonstrate the robust detection of population-level CO2 trends in both biotic and abiotic scenarios for population sizes as small as 30 exo-Earth candidates (EECs) and the lowest assessed spectrum quality in terms of signal-to-noise ratio, S/N = 10, and spectral resolution, R = 50. However, biased CO₂ partial pressure constraints hinder accurate differentiation between biotic and abiotic trends. If these biases were corrected, accurate differentiation could be achieved for populations with ≥100 EECs. We conclude that LIFE can effectively enable population-level characterization of temperate terrestrial atmospheres and detect CO₂ trends driven by the Cb–Si cycle as habitability indicators. Nevertheless, the identified biases underscore the importance of testing atmospheric characterization performance against the broad diversity expected for planetary populations.
  • The interior diversity of terrestrial-type exoplanets: constrained with devolatilized stellar abundances and mass-radius measurements
    Item type: Other Conference Item
    Wang, Haiyang; Quanz, Sascha Patrick; Yong, David; et al. (2022)
    EPSC Abstracts
    A major goal in the discovery and characterization of exoplanets is to identify terrestrial-type worlds that are similar to (or otherwise distinct from) our Earth. The combination of mass-radius measurements and host stellar abundances has been proposed to constrain the interiors of small (rocky) exoplanets. In this work, we advocate the importance of using devolatilized stellar abundances, instead of uncorrected stellar abundances, to further reduce degeneracies in modelling the interiors of rocky exoplanets. We apply an empirical devolatilization model to a selected sample of 13 planet-hosting Sun-like stars, for which high-precision photospheric abundances have been available. With the resultant devolatilized stellar composition (i.e. the model planetary bulk composition), as well as other constraints including mass and radius, we model the detailed mineralogy and interior structure of hypothetical, habitable-zone terrestrial planets (‘exo-Earths’) around these stars. Model output shows that most of these exo-Earths are expected to have broadly Earth-like composition and interior structure, consistent with conclusions derived independently from analysis of polluted white dwarfs. Investigating the empirical devolatilization model at its extremes as well as varying planetary mass and radius (within the terrestrial regime) reveals potential diversities in the interiors of terrestrial planets. By considering (i) high-precision stellar abundances, (ii) devolatilization, and (iii) planetary mass and radius holistically, this work represents essential steps to explore the detailed mineralogy and interior structure of terrestrial-type exoplanets, which in turn are fundamental for a quantitative understanding of planetary long-term evolution including the interior-atmosphere interactions.
  • Resolving the Planet-Hosting Inner Regions of the LkCa 15 Disk
    Item type: Journal Article
    Thalmann, Christian; Janson, M.; Garufi, A.; et al. (2016)
    The Astrophysical Journal Letters
  • Large Interferometer For Exoplanets (LIFE): V. Diagnostic potential of a mid-infrared space interferometer for studying Earth analogs
    Item type: Journal Article
    Alei, Eleonora; Konrad, Björn; Angerhausen, Daniel; et al. (2022)
    Astronomy & Astrophysics
    Context. An important future goal in exoplanetology is to detect and characterize potentially habitable planets. Concepts for future space missions have already been proposed: from a large UV-optical-infrared space mission for studies in reflected light, to the Large Interferometer for Exoplanets (LIFE) for analyzing the thermal portion of the planetary spectrum. Using nulling interferometry, LIFE will allow us to constrain the radius and effective temperature of (terrestrial) exoplanets, as well as provide unique information about their atmospheric structure and composition. Aims. We explore the potential of LIFE for characterizing emission spectra of Earth at various stages of its evolution. This allows us (1) to test the robustness of Bayesian atmospheric retrieval frameworks when branching out from a modern Earth scenario while still remaining in the realm of habitable (and inhabited) exoplanets, and (2) to refine the science requirements for LIFE for the detection and characterization of habitable, terrestrial exoplanets. Methods. We performed Bayesian retrievals on simulated spectra of eight different scenarios, which correspond to cloud-free and cloudy spectra of four different epochs of the evolution of the Earth. Assuming a distance of 10 pc and a Sun-like host star, we simulated observations obtained with LIFE using its simulator LIFESIM, considering all major astrophysical noise sources. Results. With the nominal spectral resolution (R = 50) and signal-to-noise ratio (assumed to be S/N = 10 at 11.2 μm), we can identify the main spectral features of all the analyzed scenarios (most notably CO2, H2O, O3, and CH4). This allows us to distinguish between inhabited and lifeless scenarios. Results suggest that O3 and CH4 in particular yield an improved abundance estimate by doubling the S/N from 10 to 20. Neglecting clouds in the retrieval still allows for a correct characterization of the atmospheric composition. However, correct cloud modeling is necessary to avoid biases in the retrieval of the correct thermal structure. Conclusions. From this analysis, we conclude that the baseline requirements for R and S/N are sufficient for LIFE to detect O3 and CH4 in the atmosphere of an Earth-like planet with an O2 abundance of around 2% in volume mixing ratio. Doubling the S/N would allow a clearer detection of these species at lower abundances. This information is relevant in terms of the LIFE mission planning. We also conclude that cloud-free retrievals of cloudy planets can be used to characterize the atmospheric composition of terrestrial habitable planets, but not the thermal structure of the atmosphere. From the inter-model comparison performed, we deduce that differences in the opacity tables (caused by, e.g., a different line wing treatment) may be an important source of systematic errors.
  • The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems. IV. NIRISS Aperture Masking Interferometry Performance and Lessons Learned
    Item type: Journal Article
    Sallum, Steph; Ray, Shrishmoy; Kammerer, Jens; et al. (2024)
    The Astrophysical Journal Letters
    We present a performance analysis for the aperture masking interferometry (AMI) mode on board the James Webb Space Telescope Near Infrared Imager and Slitless Spectrograph (JWST/NIRISS). Thanks to self-calibrating observables, AMI accesses inner working angles down to and even within the classical diffraction limit. The scientific potential of this mode has recently been demonstrated by the Early Release Science (ERS) 1386 program with a deep search for close-in companions in the HIP 65426 exoplanetary system. As part of ERS 1386, we use the same data set to explore the random, static, and calibration errors of NIRISS AMI observables. We compare the observed noise properties and achievable contrast to theoretical predictions. We explore possible sources of calibration errors and show that differences in charge migration between the observations of HIP 65426 and point-spread function calibration stars can account for the achieved contrast curves. Lastly, we use self-calibration tests to demonstrate that with adequate calibration NIRISS F380M AMI can reach contrast levels of ∼9–10 mag at ≳λ/D. These tests lead us to observation planning recommendations and strongly motivate future studies aimed at producing sophisticated calibration strategies taking these systematic effects into account. This will unlock the unprecedented capabilities of JWST/NIRISS AMI, with sensitivity to significantly colder, lower-mass exoplanets than lower-contrast ground-based AMI setups, at orbital separations inaccessible to JWST coronagraphy.
  • Combining high-contrast imaging and radial velocities to constrain the planetary architectures of nearby stars
    Item type: Journal Article
    Boehle, Anna; Quanz, Sascha Patrick; Lovis, Christophe; et al. (2019)
    Astronomy & Astrophysics
  • ERIS: revitalising an adaptive optics instrument for the VLT
    Item type: Conference Paper
    Davies, Richard I.; Esposito, Simone; Schmid, Hans Martin; et al. (2018)
    Proceedings of the Conference on Ground-Based and Airborne Instrumentation for Astronomy VII
  • METIS: The Mid-infrared ELT Imager and Spectrograph
    Item type: Journal Article
    Brandl, Bernhard; Bettonvil, Felix; van Boekel, Roy; et al. (2021)
    The Messenger
    The Mid-infrared ELT Imager and Spectrograph (METIS) will provide the Extremely Large Telescope (ELT) with a unique window to the thermal- and mid-infrared (3–13 µm). Its single-conjugate adaptive optics (SCAO) system will enable high contrast imaging and integral field unit (IFU) spectroscopy (R ~ 100 000) at the diffraction limit of the ELT. This article describes the science drivers, conceptual design, observing modes, and expected performance of METIS.
  • The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems V: Do Self-Consistent Atmospheric Models Represent JWST Spectra? A Showcase With VHS 1256 b
    Item type: Working Paper
    Petrus, Simon; Whiteford, Niall; Patapis, Polychronis; et al. (2023)
    arXiv
    The unprecedented medium-resolution (R=1500-3500) near- and mid-infrared (1-18um) spectrum provided by JWST for the young (120-160Myr) low-mass (12-20MJup) L-T transition (L7) companion VHS1256b has opened new avenues for the in-depth characterization of substellar object atmospheres. In this study, we present a comprehensive analysis of this dataset utilizing a forward modelling approach. We explore five distinct atmospheric models, each aiming to encompass diverse physical and chemical phenomena proposed to happen in cool atmospheres in a self-consistent way. Our aim is to assess their performance in estimating key atmospheric parameters: Teff, log(g), [M/H], C/O, gamma, fsed, and R. To achieve this, we apply our Bayesian framework, ForMoSA, employing an optimized nested sampling algorithm for model-data comparison. Our findings reveal that each parameter's estimate is significantly influenced by factors such as the wavelength range considered, the spectral features used, the signal-to-noise ratio, and the model chosen for the fit. The observed parameter dispersion may be attributed to systematic error in the models, resulting from their difficulties in accurately replicating the complex atmospheric structure of VHS1256b, notably the complexity of its clouds and dust distribution. To propagate the impact of these systematic uncertainties on our atmospheric property estimates, we introduce innovative fitting methodologies based on independent fits performed on different spectral windows. We finally derived a Teff consistent with the spectral type of the target, considering its young age, which is confirmed by our estimate of log(g). Despite the exceptional data quality, attaining robust estimates for chemical abundances [M/H] and C/O, often employed as indicators of formation history, remains challenging with estimates dispersed on the entire range explored by the model grids.
Publications 1 - 10 of 264