Science Talks

Gokul Srinivasaragavan (U. Maryland): "The Diversity of Massive Stellar Deaths and Relativistic Jets: Unraveling a Cosmic Tandem"

Science Talk • 12:15 PM, November 20th, 2024 • MR-102 and online (Zoom)

We are entering an era in time-domain astronomy where understanding the diversity of relativistic stellar explosions has become more fruitful than ever. Recent time-domain surveys, including the Zwicky Transient Facility (ZTF), have helped discover numerous transients that exist somewhere in the continuum of relativistic stellar explosions, ranging from non-relativistic ordinary broad-lined Type Ic core-collapse...

Alexandra Le Reste (U. Minnesota): "Reionization: Lessons from Observations of Nearby Lyman-Continuum Emitters"

Science Talk • 12:15 PM, November 13th, 2024 • MR-102 and Online on Zoom

The Universe changed drastically during its first billion years as neutral hydrogen gas, which filled the intergalactic space, became ionized. This last major phase transition of the Universe is an important cosmological period known as the Epoch of Reionization. Simulations and observations seem to indicate that primordial galaxies were the main sources of the ionizing UV photons responsible for Reionization. However,...

Isabel Angelo (UCLA): "Searching for Binaries Among Kepler’s Planet Hosts"

Science Talk • 12:15 PM, November 6th, 2024 • MR-102 and online (Zoom)

The Kepler mission discovered the largest sample of planets today, with thousands of confirmed planets that exhibit a diversity of properties and origins. The mission was the first of its kind, and its large sample enabled unprecedented demographic studies of exoplanets. However, Kepler’s large pixels and ~1 kpc distances to most targets means that many apparently single stars have additional stellar companions. As a...

Lado Samushia (Kansas State U.): "Cosmological Constraints from Higher Order Patterns"

Science Talk • 12:15 PM, October 30th, 2024 • Online only (Zoom)

Galaxy surveys provide invaluable information about the composition of the universe and the nature of dark energy and gravity. Unfortunately, the amount of space that we can observe is limited in volume and it is very important that we harness this information as efficiently as possible. I will present recent work by my group on obtaining cosmological constraints from higher order patterns in the observed galaxy...

Steven Giacalone (Caltech): "The Origins of Close-in Brown Dwarfs from the Stellar Obliquity Distribution"

Science Talk • 12:15 PM, October 23rd, 2024 • MR-102 and online (Zoom)

The obliquities of hundreds of planet-hosting stars (i.e., the angles between the stellar spin axes and the planet orbital axes) have been measured over the last decade, providing unique insight into the formations and evolutions of close-in planets. The stellar obliquity distribution can shed similar light on the origins of close-in brown dwarfs (BDs), which are thought to form far from their host stars and migrate...

Farnik Nikakthar (Yale): "DESI Y1 BAO Analysis: Reconstruction of Large-Scale Structures Using Optimal Transport Theory"

Science Talk • 12:15 PM, October 16th, 2024 • MR-102 and online (Zoom)

The universe we observe today is dotted with galaxy clusters separated by vast voids, in sharp contrast to its initial state, which was nearly uniform with only minor density fluctuations. The evolution from this early uniformity to today's complex structure of galaxies is a profound transformation, with many intermediate processes still unexplained. In this talk, I will explore this transformation, focusing on the...

Viraj Karambelkar (Caltech): "Anthropology of Merging Stars - Tracing the Evolution And Impact of Stellar Mergers with Time-Domain Surveys"

Science Talk • 12:15 PM, October 9th, 2024 • MR-102 and online (Zoom),

Most massive stars reside in binary systems where mutual interactions can draw them close enough to merge. These mergers offer insights into key processes like common-envelope evolution, a critical yet poorly-understood phase in the formation of gravitational wave sources. In this talk, I will describe systematic searches for white-dwarf mergers and massive stellar mergers using the Palomar Gattini IR and the Zwicky...

Robert Hurt (Caltech/IPAC): "When Data Is Not Enough: Illustrating Astrophysics for the Public"

Science Talk • 12:15 PM, October 2nd, 2024 • MR-102 and online (Zoom)

Astronomy is a science that easily captures the interest and imagination of the public in no small part due to the sublime beauty of its spectrum- spanning imagery. And yet, the data underlying many significant science results is often only visually meaningful to a particular research community. Because of this, effective public-facing communication frequently relies on science-motivated illustrations to both engage...

Laurie Chu (Caltech/IPAC): "Unlocking the Secrets of Ices in Dense Molecular Clouds: A New Era with JWST"

Science Talk • 12:15 PM, September 25th, 2024 • Online only (Zoom)

Cold (T∼10K), dense (n>10^5 cm^-3) molecular cores are the birthplace of solar-like stars and provide a rich environment for the growth of ices and complex organic molecules (COMs) to form on cold dust grain surfaces. Icy mantles play a key role in building larger planetary bodies. Some evidence suggests these primitive molecules survive the harsh planetary formation process and are incorporated into some of the Solar...

Brandon Hensley (JPL): "The Nature of Dust in the Age of JWST and Prospects for SPHEREx and PRIMA"

Science Talk • 12:15 PM, September 18th, 2024 • MR-102 and online (Zoom)

Observing the emission from dust in galaxies is a window into how they form stars, manufacture heavy elements (i.e., metals), and build complex molecules. I will begin by describing JWST observations of carbon-based molecules called polycyclic aromatic hydrocarbons (PAHs), emphasizing how our understanding of the lifecycle of PAHs is changing with the new data. I will then preview how SPHEREx observations of PAH...

Wonki Lee (Yonsei U.): "Exploring Astrophysics with Cosmic Giants: The Role of Galaxy Cluster Mergers and Radio Relics"

Science Talk • 12:15 PM, September 11th, 2024 • MR-102 and online (Zoom)

Cluster mergers serve as powerful laboratories for cosmology and astrophysics. Radio relics, which are diffuse radio emissions found in the outskirts of merging clusters, are believed to originate from plasma acceleration caused by cluster merger shocks. In this talk, we will demonstrate that cluster mergers exhibiting radio relics provide an ideal laboratory for studying plasma acceleration and the nature of dark...

Mainak Singha (NASA GSFC/CUA): "Unveiling Low-Luminosity AGN (M[BH]=10E4-10E6 Msun) in Reionization-Era Analogs"

Science Talk • 12:15 PM, September 4th, 2024 • MR-102 and online (Zoom)

Recent observations by the James Webb Space Telescope (JWST) have uncovered a substantial population of high-redshift Active Galactic Nuclei (AGN), reigniting the debate over their potential contributions to cosmic reionization. This study leverages archival X-ray data from the Chandra and XMM telescopes to examine 900 galaxies, identified as local analogs to those from the reionization era. These galaxies are notable...

Hakim Atek (IAP, Paris): "The Primordial Universe as Seen by Euclid"

Science Talk • 12:15 PM, June 5th, 2024 • Online only (Zoom)

The Euclid space mission's primary goal is to advance our understanding of dark matter and dark energy by meticulously mapping nearly a third of the entire sky, enabling the identification and study of billions of galaxies to investigate cosmic shear and large-scale structures. With such vast datasets, Euclid supports an important legacy science spanning from nearby galaxies to the early universe. In this presentation,...

Katarina (Dida) Markovic (JPL): "Cosmology with Roman's High Latitude Imaging Survey"

Science Talk • 12:15 PM, May 29th, 2024 • MR-102 and online (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

The past two decades have seen cosmology become a precision science. This decade, the planning for precise measurements of the cosmic expansion and gravitational growth history is culminating in a series of map maker surveys. The Nancy Grace Roman Space Telescope is NASA's flagship to be launched by 2027. This talk will introduce the cosmological concordance model, its recent tensions, and outline how Roman's High...

Thomas Prince/Zachary Vanderbosch (Caltech):"The SDSS-V Open Fiber Call and Data Access for Caltech Scientists"

Science Talk • 12:00 PM, May 22nd, 2024 • In-person in KS-410 , please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

Nikhil Padmanabhan (Yale): "Mapping the Expansion History with DESI Y1 Data"

Science Talk • 12:15 PM, May 15th, 2024 • MR-102 and online (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

I will present the recently released distance measurements from the first year of DESI data using the baryon acoustic oscillation technique. I will review the improvements made in this analysis, highlight our blinded analysis and will emphasize the robustness of the BAO technique. I will then explore the cosmological implications of these results, including a tantalizing hint of time variations in dark energy.

Zachary Slepian (U. Florida): "Searching for Parity Violation with the Galaxy 4-Point Correlation Function"

Science Talk • 12:15 PM, May 8th, 2024 • Online only (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

Recently we have shown that the galaxy 4-point correlation function, which measures an excess of quartets of galaxies over random, is sensitive to parity violation in our Universe's large-scale structure. It is fundamentally 3D and thus has a handedness even after averaging over orientations, in contrast to galaxy pair and triplet correlations. With this new observable we have detected parity violation at high...

Peter Plavchan (George Mason University): "The NASA Landolt Mission"

Science Talk • 12:00 PM, April 29th, 2024 • MR-102

The NASA Landolt mission is a timely PIONEERS program that will provide significant improvement in the accuracy of photometric measurements of absolute stellar fluxes. This will be accomplished with a high accuracy National Institute of Standards and Technology (NIST) calibrated suite of single-mode fiber-fed laser beacons which will be observable from selected ground-based observatory stations. Landolt will improve...

Robert Zellem (JPL): "Masses and Orbits for Planets Likely to be Observed with Ariel/CASE"

Science Talk • 12:15 PM, April 24th, 2024 • MR-102 and online (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

ESA's Ariel mission, with a contribution from NASA's CASE project, will conduct a homogeneous survey of up to 1000 exoplanetary atmospheres to assess the atmospheric demographics and diversity of planets ranging in size from hot-Jupiters to super-Earths. To perform this statistical experiment and derive atmospheric compositions and abundances, the target list must be sufficiently well characterized: transit and eclipse...

Xiaoshan Huang (Caltech): "Pre-Peak Emission in TDEs"

Science Talk • 12:15 PM, April 17th, 2024 • MR-102 and online (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

The tidal disruption of a star by a nearby blackhole can power a bright flare in multiple wavebands, making a class of well-recognized transient events. Understanding the origin of detected emission from such tidal disruption events (TDEs) is particularly interesting. In this talk, I will discuss pre-peak emission mechanisms in TDEs with series of 3D radiation hydrodynamical (RHD) simulations. We found during...

Thomas Lai (Caltech/IPAC): "Probing the Smallest Interstellar Dust Grains with JWST in Different Galaxy"

Science Talk • 12:15 PM, April 10th, 2024 • MR-102 and online (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

Dust around active galactic nuclei (AGN) and star-forming regions offers crucial insights into the physical conditions of the ISM. The advent of sensitive, high-resolution infrared integral-field unit (IFU) spectroscopy in the near- and mid-infrared with the James Webb Space Telescope (JWST) has opened up a tremendous opportunity to study the starburst-AGN connection and dust properties in metal-poor systems in nearby...

Claudia Scarlata (U. Minnesota): "On Galaxies' Circumgalactic Media and Outflows"

Science Talk • 12:15 PM, April 3rd, 2024 • Online only (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

The gas reservoir around galaxies plays a fundamental, while still poorly understood, role in regulating the growth of galaxies, in establishing the scaling relation we observe among galaxies' physical properties as well as in modulating the escape of ionizing radiation from galaxies, and thus their contribution to the reionization process. Particularly at the low mass end of the mass function, where most of the...

Travis Yeager (LLNL): "The MEGASIM: The Multitudinous Earth Greek (not Trojan) Asteroid Simulation: A Study of Orbital Stability and Detectability of Earth Trojan Asteroids"

Science Talk • 12:15 PM, March 27th, 2024 • Online only (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

We present an analysis of lifetimes and resonances of Earth Trojan Asteroids (ETAs) in the MEGASIM data set along with spatial distributions of Earth Trojan Asteroids and assess the detectability of the population in current and next-generation ground-based astronomical surveys. Trojan asteroids co-orbit the Sun with a planet but remain bound to the Lagrange points, L4 (60 deg leading the planet) or L5 (60 deg...

Maxime Devogele (ESA): "Polarimetry as a Tool for Physical Characterization of Potentially Hazardous Near-Earth Objects"

Science Talk • 12:15 PM, March 20th, 2024 • Online only (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

In this talk we will explore the application of polarimetry in planetary defense endeavors. Planetary defense groups all the activities related to the observation and analysis of near-Earth objects (NEOs) to mitigate potential impact risks. The three primary activities within planetary defense include NEO discovery and orbit assessment, physical characterization, and mitigation strategies. Polarimetry, a technique for...

Brian Svoboda (NRAO): "New Frontiers in Spectral Line Modeling: Towards a Bayesian View of Dense Gas in the Milky Way"

Science Talk • 12:15 PM, March 13th, 2024 • Online only (Zoom), please join the Caltech/IPAC Seminar Mailing list at https://lists.ipac.caltech.edu/mailman/listinfo/seminars to obtain more information

Advancements in instrumentation and new generations of astronomical facilities have enabled sensitive, wide-field spectroscopic surveys of the Milky Way. In order for astronomers to draw upon these surveys to advance the study of star formation and the interstellar medium, new spectral line modeling techniques are needed for robust and automated analysis of gas physical properties and kinematics. In this talk I will...