Thunch

Thunch is a weekly grad-student run seminar series which gives local and visiting scholars, especially students, the opportunity to present their research to a broad audience at the Princeton Department of Astrophysical Sciences. Potential visiting speakers should contact the Thunch Czars, Yue Pan and Zack Andalman.

When: Thursdays at 12 pm (food), 12:15 pm (talk)

Where: Peyton Hall, "grand central" (big room in the center of the building)

What: food + 45 minute talk and discussion

Rules

- Priority goes to students and to those who have not given a talk recently.

- Visiting speakers must be explicitly invited by the department.

- There is no money in Thunch to pay for travel, so visitors need another source of funding.

- Speakers must send a title and abstract to the Thunch Czars at least one week in advance of their talk.

Now you know everything you need to know about Thunch. Join us for good food and good science. Reach out to the Thunch Czars with any questions.

Spring 2024 Upcoming Speakers:

 

Date Name and Institution Title Abstract

February 8th

Benjamin Remy (Princeton University)

Generative modeling for weak lensing inverse problems Gravitational lensing, which is the effect of the distortion of distant galaxy images through the influence of massive matter densities in the line of sight, holds significant promise in addressing questions about dark matter and dark energy. It reflects the distribution of total matter of the Universe and is therefore a promising probe for cosmological models. In the case where these distortions are small, we call it the weak gravitational lensing regime, and a straightforward mapping exists between the matter distribution projected in the line of sight, called mass-map, and the measured lensing effect. However, when attempting to reconstruct dark matter mass-maps under conditions involving missing data and high noise corruption, this linear inverse problem becomes ill-posed and may lack a meaningful solution without additional prior knowledge. In this talk, I will present how to employ recent breakthroughs in the generative modeling literature that enable the modeling of complex distribution in high-dimensional spaces. We propose in particular a novel methodology to solve high-dimensional ill-posed inverse problems, characterizing the full posterior distribution of the problem. By learning the high dimensional prior from cosmological simulations, we demonstrate that we can reconstruct high-resolution 2D mass-maps alongside uncertainty quantification. Additionally, I will present a new method for cosmic shear estimation based on forward modeling of the observations at the pixel level. This represents a new paradigm for weak lensing measurement, as we no longer rely on galaxy shape measurements.
February 15th Lauren Weiss (University of Notre Dame) The Origin of Earth: Lessons from Multi-Planet Systems How did we get here? Are we alone? A fundamental milestone in answering these questions is the origin of Earth, an event that we are just now contextualizing, thanks to the discovery of thousands of exoplanets. Using telescopes, my group is investigating how the thousands of known planetary systems formed, what they reveal about the origin of our solar system, and whether these distant worlds could harbor life. As part of our investigation, we are discovering Earth-sized planets with rocky surfaces amenable to life as we know it. Many of these worlds form in intriguing patterns of regular sizes and orbital spacing. These patterns, which we call “peas in a pod,” are mostly absent from the solar system, but resemble a theorized early generation of solar system planets thought to have been destroyed by Jupiter. Meanwhile, Earth’s extensive surface liquid water, which is a key aspect of its suitability for life, is attributed to the gravitational influence of Jupiter. How was Earth’s water delivered, and can we expect the small, rocky exoplanets we have discovered to be similarly endowed? By combing the cosmos to search for patterns in multi-planet systems and trace the role of Jupiter analogs in providing rocky planets with water, we hope to contextualize the origin of Earth and guide humanity’s next steps in the search for life.
February 22rd Martin Elvis (Harvard) Accelerating the Astro2020 Flagships with Super-Heavy Lift Vehicles The Astro2020 Decadal Report recognized that 21st Century astrophysics required matched coverage across the electromagnetic spectrum. To create that coverage Astro2020 recommended a set of three Great Observatories: X-ray, IR/O/UV, and Mid-Far-IR.
Unfortunately, given the estimated costs and anticipated budget, the first of these (the IR/O/UV flagship) would not launch until 2045. This is a daunting timescale as even JWST with an anticipated lifetime of 20 years will likely be gone by then. Fortunately, there may be a means to speed up the Astro2020 program making use of a new generation of Super-Heavy Lift rockets: SLS, SpaceX Starship, and Blue Origin New Glenn. Each of these vehicles has far greater mass to orbit and payload volume than the present generation of launchers. As a result a broad design space is opened up. It may be possible to use mass and volume to cut the cost of the flagships by billions. Volume is particularly valuable for the IR/O/UV and Mid-Far-IR flagships to avoid the origami-like folding of large mirrors that was necessarily employed for JWST. Instead, the X-ray flagship mass seems to be more important. Discipline will be needed to restrain ourselves from mission creep, going beyond the already ambitious Astro2020 flagship capabilities. If we do, then major savings may cut years from the Astro2020 timeline.
 
February 29th Dom Rowan (Ohio State University) Searching for Non-Interacting Black Holes in the Binary Zoo Characterizing the mass distribution of compact objects is essential for understanding the late-stage evolution of massive stars. The majority of black hole mass measurements come from X-ray binaries and gravitational wave mergers, but the majority of black holes in the Milky Way are expected to instead be either isolated, free-floating systems or in non-interacting binaries. The recent Gaia Focused Product Release contains radial velocity time-series for more than 9,000 long-period photometric variables. We search for binary systems with large radial velocity amplitudes to identify candidates with massive, unseen companions. Eight targets have large binary mass functions f(M) > 1 Msun, three of which are eclipsing binaries. The remaining five show evidence of ellipsoidal modulations. We fit spectroscopic orbit models to the Gaia radial velocities and fit the spectral energy distributions of three targets. For the two systems most likely to host dark companions, J0946 and J1640, we use PHOEBE to fit the ASAS-SN light curves and Gaia radial velocities. The derived companion masses are >3 Msun, but the high Galactic dust extinctions towards these objects limit our ability to rule out main sequence companions or subgiants hotter than the photometric primaries. These systems are similar to other stellar-mass black hole impostors, notably the Unicorn (V723 Mon) and the Giraffe (2M04123153+6738486). While it is possible that J1640 and J0946 are similar examples of stripped giant star binaries, high-resolution spectra can be used to determine the nature of their companions.
March 7th Yubo Su (Princeton University) Merging Binary Black Holes with a Distant Tertiary Companion---Spin and Mass Ratio Dependencies

The LIGO/Virgo/KAGRA (LVK) collaboration has detected 90 compact object mergers to date, most of which are mergers of two black holes. Despite being a great triumph for relativists, these detections also pose a problem for astronomers: how do these binaries form? In the case of binaries consisting of two black holes (black hole binaries; BHBs), the simplest explanation is that they are formed from the large number of massive stellar binaries that we observe. However, this formation channel is both filled with uncertainties and struggles to reproduce certain features of the observed population of merging BHBs. As such, a zoo of alternative formation channels have been proposed, requiring anywhere from 3 gravitationally interacting objects to 10^8. Among these, the three-body channel is attractive for its plausibility (e.g. massive stellar triples are common) and its relative tractability ([semi]-analytical results can be obtained). In this informal talk, I will discuss the dynamics and some predictions of the three-body channel, including a potential application to the unresolved "q-chi_eff" anticorrelation in the LVK data.

March 21st

Pascal Marichalar (French National Center for Scientific Research)

Reserving Mauna Kea for astronomy : a social and political history, from Kuiper to TMT

Intrigued by the recent Thirty Meter Telescope protests on Mauna Kea in Hawai‘i, I launched on a historical study of how astronomy came to the mountain, based on the observatories’ own archives, most of which had never been studied. These documents show the colonial and social underpinnings of how astronomers “discovered” and conquered what Gerard Kuiper heralded in 1964 as “probably the best site in the world – I repeat – in the world, from which to study the Moon, the Planets, the Stars” : how vast tracts of lands were given away for $1 annual leases, how observatories took the place of the islands’ sugarcane plantations and ranches, how the world’s biggest mirrors collided with the environmental and Hawaiian movements. This case study raises the larger question of the responsibility of field scientists toward the sites and communities in which they work.
April 4th Nick Kokron (Princeton University)    
April 11th Kovi Rose (University of Sydney)


 

 
April 18th (double talk) Jamila Pegues (Space Telescope Science Institute)
Kris Pardo (University of Southern California)
 
   
April 25th

Jackie Faherty (American Museum of Natural History)

   

Fall 2023:

September 7th: Andrew Saydjari (Harvard)
September 14th: Samantha Wu (CalTech)
September 21st: Viraj Karambelkar (CalTech)     
September 28th: Fan Zou (Penn State)   
October 5th: Zhuhai Li (CalTech)
October 12th: Prof. Yue Shen (University of Illinois Urbana-Champaign)                 
October 19th: Mor Rozner (Israel Institute of Technology)                          
October 26th: Shangjia Zhang  (University of Nevada)
November 2nd: Teodor Grosu
November 9th:  Hsiang-Chih Hwang (IAS)                           
November 16th: Kishore Patra (Berkeley)
November 30th: Princeton Graduate Students

Spring 2023:

February 16th: Chia-Yu Hu (University of Florida)
February 23rd: Dan Foreman-Mackey (CCA)
March 2nd: Lyla Jung (ANU)
March 16th: Vicente Valenzuela-Villaseca (Princeton University)
March 30th: Roohi Dalal (Princeton)
April 6th: David Velasco (Princeton)
April 13th: Zili Shen (Yale)
April 20th: Sabrina Appel (Rutgers)
May 4th: Ewine van Dishoeck Leiden (Leiden Observatory, the Netherlands)
May 11th: Charlotte Ward (Princeton University)

Fall 2022:

September 15th: Aritra Ghosh (Graduate Student, Yale University)
September 22nd: Thales Gutcke (NASA Hubble Fellow and Lyman Spitzer, Jr. Postdoctoral Fellow, Princeton)
September 29th: Fengwu Sun (Graduate Student, University of Arizona)
October 6th: Yubo Su (Lyman Spitzer Jr. Postdoctoral Fellow, Princeton)
October 13th: Yinhao Wu (Graduate Student, Leicester University)
October 20th: Fall break
October 27th: Lizhong Zhang (Graduate Student, University of California, Santa Barbara)
November 3rd: Oliver Zier (Graduate Student, Max Planck Institute for Astrophysics, Garching, Germany)
November 10th: Chang-Goo Kim (Post-Doctoral Associate Research Scholar, Princeton)
November 17th: Tsun Hin Navin Tsung (Graduate Student, University of California, Santa Barbara)
December 1st: Ore Gottlieb (Rothschild Fellow, CIERA Postdoctoral Fellow, Northwest University)
December 8th: Sihao Cheng (Postdoc Member at the Institute for Advanced Study)

Spring 2022:


February 3rd: Benjamin Crinquand (Post-Doctoral Associate Research Scholar, Princeton)
February 10th: Matthew Coleman (Post-Doctoral Associate Research Scholar, Princeton)
February 17th: Riddhi Bandyopadhyay (Post-Doctoral Associate Research Scholar, Princeton)
February 24th: Alex Gagliano (Pre-Doctoral Fellow, CCA Flatiron)
March 10th: Igor Andreoni (Postdoctoral Fellow, Joint Space-Science Institute)
March 17th: Sihao Cheng (Postdoctoral Fellow, Johns Hopkins University)
March 24th: Keith Hawkins (Assistant Professor, University of Texas at Austin)
March 31th: Frank van den Bosch (Professor of Theoretical Astrophysics, Yale)
April 7th: Mor Rozner (Graduate Student, Technion - Israel Institute of Technology)

April 14th: Sam Yee (Graduate Student, Princeton)

Click here for the latest schedule information

 

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