Spring 2023 IfA Colloquia
Talks home
Date
Speaker
Affiliation
IfA Host
Title (click for abstract)
Jan 11 (W)
Zoom
David Kipping
Columbia University
Meech
Jan 18 (W)
IfA Hilo
Olivier Guyon
Subaru Telescope
Bottom
Feb 1 (W)
Judit Szulágyi
ETH Zurich
Williams
Feb 9 (Th)
IfA Hilo
Kevin Wagner
University of Arizona
Bottom
Feb 13 (M)
IfA Hilo
Meng Gu
Carnegie Observatories
Chun
Feb 14 (Tu)
van Saders
Talks are held at 11:45am HST in the IfA Mānoa Auditorium (C-214) unless otherwise noted.
For additional information, please contact Dr. Fabio Bresolin.
Missed a talk? See if there’s a recording at the IfA YouTube channel!
The IfA colloquia are kindly sponsored by the Friends of the IfA.
The Observational Quest for Transiting Exomoons
David Kipping
Assistant Professor, Columbia University
Cool Worlds Lab website
With thousands of known transiting exoplanets, many as small as the Earth, our detection capabilities are beginning to border on that necessary to detect the largest moons found in our solar system. Exomoons would offer new opportunities to understand the origins of planetary systems, as well as potentially playing an important role in the search for life. I will discuss the various methods proposed to identify such objects, the state of our knowledge based on present observations, and the potential for new discoveries via upcoming observations (such as JWST), as well as new methodological developments. The exomoon candidates Kepler-1625b-i and 1708b-i will also be discussed, exploring their current status and follow-up potential. Going forward, it is suggested that the statistical validation of exomoons may enter the fray, akin to many of Kepler’s exoplanets, but JWST could present far more compelling detections should it be used for exomoon hunting.
The Path to Direct Imaging and Spectroscopy of Habitable Exoplanets with Large Ground-based Telescopes
Olivier Guyon
Subaru Telescope/University of Arizona/NINS Astrobiology Center
Direct imaging and spectroscopy of exoplanets is key to characterizing their atmospheres. Current 5-10m class telescopes equipped with adaptive optics and coronagraphy can image young giant gas planets in thermal emission in the near-IR (λ ≳ 1μm). Upcoming 30m class telescope will provide the angular resolution and collecting area to image Earth-size habitable planets in reflected light around nearby stars and probe their atmospheres for signs of biological activity. The best targets will be the nearest M-type stars, for which the planet-to-star reflected light contrast is two orders of magnitude milder than Earth-Sun analogs. I will describe the technical challenges that must be overcome to realize this goal. I will provide an overview of collaborative R&D activities at the Subaru Telescope to advance and prototype technical solutions, and focus on particularly promising approaches.
Machine Learning & Astronomy
Brice Ménard
Professor, Johns Hopkins University
The young field of Machine learning has changed the ways we interact with data. Neural networks have made us appreciate the potential of working with millions of parameters. Interestingly, the vast majority of scientific discoveries today, especially in astronomy, are not based on these new techniques. I will discuss the contrast between these two regimes and I will show how a new intermediate approach can provide promising tools for scientific research. I will show some applications in astrophysics and oceanography.
Planet- and Moon-Formation—Connecting Hydrodynamic Simulations of Planet Formation with Observations
Judit Szulágyi
Computational Astrophysics Group Lead, ETH Zurich
Computational Astrophysics Group website
Planets born in circumstellar disks create various disk substructures, such as gaps, rings, spirals, vortices. Similar structures are observed widely with ALMA, SPHERE and similar instruments. At least some of these disk features are likely due to forming planets, however there are also other mechanisms to explain them. Carrying out high resolution, 3D hydrodynamic simulations with radiative transfer already included, allow us to create realistic “mock observations” or “synthetic images” for a given instrument & telescope combination. These mock observations can be compared with already existing real data, or prepare for future observational proposals. We use them to understand how massive forming planets could be observed with the different instruments, how the planet-disk interactions look like on various wavelengths and what planet-generated features we can observe with the current & near-future instrumentation. I review our findings for near- and mid-infrared, sub-millimeter and radio wavelengths, and identify what are the best wavelengths and instruments for hunting for forming planets.
Transforming the LBTI into a Mid-Infrared Habitable-Zone Exoplanet Imager
Kevin Wagner
NASA Sagan Fellow, University of Arizona
Website
The Large Binocular Telescope Interferometer (LBTI) is a prototype instrument for the next class of large ground-based telescopes. With two 8.4m mirrors on a common mount, the effective imaging resolution of a 23-m telescope can be achieved with Fizeau interferometry. In the mid-infrared (specifically at 10-12 µm), this opens the possibility of imaging the habitable zones of several nearby sun-like stars in the Northern hemisphere–including Tau Ceti and Epsilon Eridani, the two closest single sun-like stars. This talk will describe our technical approach to upgrade the mid-infrared capabilities of LBTI for exoplanet imaging. Our planned upgrades include a new coronagraph designed for dual-aperture observations, and the commissioning of a new class of 10 µm detectors for ground-based astronomy. With these upgrades planned to be completed in the next two years, we anticipate that long (~100 hour) exposures will achieve sensitivity levels sufficient to image nearby habitable-zone super-Earths around Tau Ceti, Epsilon Eridani, and several other stars. With a similar instrument on a 30-m-class telescope, it will be possible to image these same planets in a single night–enabling detailed studies of their orbits and atmospheres.
Exoplanet Imaging: From Planet Formation to Exo-Earths
Kevin Wagner
Sagan Postdoctoral Fellow, University of Arizona
Website
High-contrast imaging has enabled the direct detection of over a dozen young exoplanets. Like the broader population of exoplanets at an earlier stage, the rate of discovery of new directly imaged planets is following a path of exponential growth. Young super-Jovian exoplanets, whose residual heat of recent formation raises their temperature and brightness in the infrared, were the first to be discovered (and on surprisingly wide orbits). Being the case that younger planets are easier to detect, some planets have even been imaged in the midst of their formation–with protoplanetary disks and accreting protoplanets imaged in concert. This talk will review the scientific direction and recent advancements of exoplanet imaging, and then will discuss prospects for the future of the field: in particular imaging exo-Earths around nearby stars. To do this, techniques that were developed in the near-infrared will need to be extended to both shorter wavelengths (for reflected light) and longer wavelengths (for thermal emission). Both are necessary in order to fully characterize nearby Earth-like planets, including fundamental properties such as their temperatures, radii, and albedos. With these properties established, in the next decades it will be possible to observe more intricate details of these nearby planets: such as land covering fractions, atmosphere and cloud properties, and even planetary-scale ecosystems.
The Stellar Initial Mass Function in MASSIVE Early-Type Galaxies
Meng Gu
Postdoctoral Fellow, Carnegie Observatories
Website
The initial mass function (IMF) is fundamental to measuring important galaxy properties such as stellar mass and star formation history. I will present the stellar IMF in the center of nearby early-type galaxies in the MASSIVE survey based on high-quality Magellan/LDSS-3 spectroscopy and detailed stellar population synthesis modeling. I will focus on the relations among stellar IMF, global galaxy properties, and stellar populations and discuss the implications for the physical processes driving the global stellar IMF variation. I will share recent progress in measuring IMF gradients and the relation between IMF and local stellar population properties. I will discuss the implications for star formation histories and mass measurement.
Stellar Populations and Assembly Histories of Early-type Galaxies Near and Far
Meng Gu
Postdoctoral Fellow, Carnegie Observatories
Website
Reconstructing the formation and assembly history of galaxies is critical to astrophysics. Early-type galaxies (ETGs) give us a unique window to achieve this goal. Recent progress in stellar population synthesis (SPS) models has pushed us far beyond the “age and metallicity” era. Detailed element abundance patterns and initial mass function (IMF) extracted from the integrated light of ETGs significantly deepen our understanding of the star formation and assembly history of ETGs, the essential stellar mass measurement, and their dark matter content. I will present stellar population studies of massive galaxies and their surrounding environments, focusing on the scaling relations between stellar mass and stellar population properties from observation and simulation sides with implications for the connection between the environments and the growth and quenching of surrounding galaxies. I will discuss how low surface brightness observation, equipped with modern SPS, can probe galaxy formation and assembly at low mass regimes that are challenging to constrain. I will present novel measurements on the global and local stellar IMF in nearby massive galaxies in the MASSIVE survey. I will preview lookback studies that will soon be feasible with the new facilities, such as the Prime Focus Spectrograph (PFS) and the James Webb Space Telescope (JWST).