CCAPP is proud to host the 2023 CCAPP Fellows Symposium!
The CCAPP postdoctoral fellows, affiliate fellows, and research staff will present their research in short talks in a hybrid event, in person in PRB 1080 (right off the PRB atrium) and also on Zoom (see link button below). The symposium will take place from 12:30 - 3:00 pm on September 28 and 1:00 - 3:30 pm on September 29, and coffee and snacks will be provided.
The main motivation of the symposium is to have new and present researchers share their research with the rest of CCAPP, and also help the new arrivals to get acquainted with the other members of the departments.
Everyone from CCAPP, the Department of Astronomy, and the Department of Physics is welcome to attend the symposium in person or online. Talks will be geared to a general physics/astronomy audience.
The meeting will be broken up generally by subject, with different sessions focusing on research ranging from supernova to gravitational lensing, neutrino detection, dark matter theory and more. The agenda and abstracts are listed below.
Agenda/Abstracts PDF
Symposium Agenda
ASTRONOMY I |
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12:30 - 12:50 PM |
Adam Wheeler |
Spectral Synthesis for Cool Stars, Brackets Lines, and Empirical Measurement of Stellar Atmospheric Structure |
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12:50 - 1:10 PM |
Christine Daher |
Insight from APOGEE Binaries with White Dwarf Companies |
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1:10 - 1:30 PM |
Michael Tucker |
Error: Donor Star Not Found |
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1:30 PM |
Break |
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ASTROPARTICLE |
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time |
presenter |
Title of talk |
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2:00 - 2:20 PM |
Jung-Tsung Li |
Small-Scale Magnetic Fields are Critical to Shaping Solar Gamma-Ray Emission |
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2:20 - 2:40 PM |
William Luszczak |
Searching for Ultrahigh Energy Neutrinos with PUEO |
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2:40 - 3:00 PM |
Lucas Beaufore |
Measuring Cosmic-Ray Isotopes with the HELIX Ballon |
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ASTRONOMY II |
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Time |
Presenters |
Title of Talk |
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1:00 - 1:20 PM |
Sumit Sarbadhicary |
Where do Stars Explode in the Interstellar Medium? |
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1:20 - 1:40 PM |
Manami Roy |
How do the Satellite Galaxies Gift "Cool" Gas to Their Host? |
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1:40 - 2:00 PM |
Ryuichiro Hada |
Prospects for Constraining the Age and Radiation Geometry of Quasars with Imaging and Spectroscopic Observations |
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2:00 PM |
Break | |
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Abstracts
Adam Wheeler
Spectral synthesis for cool stars, Brackett lines, and empirical measurement of stellar atmospheric structure
I will discuss improvements to Korg, my code to calculate stellar spectra. I'll outline the changes made to extend it's use to cooler (< 4000 K) stars, and demonstrate the difficulty of correct interpolation of model atmospheres, one of the most important physical inputs to the calculations. This places limitations on the applicability of most models to cool stars, a fact which has gone largely unnoticed. I will also discuss recent progress in the modeling of the Brackett series, which are crucial for measuring stellar parameters of warm stars from infrared spectra. Finally, I will demonstrate the possibility of using a fast differentiable synthesis code to constraining atmospheric structure directly from spectra, thus providing an empirical check to 3D radiation-hydrodynamic models.
Christine Daher
Insight from APOGEE Binaries with White Dwarf Companions
Mass transfer in interacting binary stars gives rise to a whole host of fascinating astrophysical phenomena. However, models for the underlying physics have thus far been poorly constrained by available datasets. I will present several ongoing observing programs being undertaken at LCO and WIYN/NEID seeking to bridge this gap with spectroscopic orbital solutions for over a hundred suspected sub-subgiant-white dwarf (SSG-WD) and main-sequence-white dwarf (MS-WD) binaries identified from the APOGEE survey. I will discuss our plans to better understand the formation mechanisms of the SSG-WD systems through joint analysis of their orbital properties and prior spectro-photometric data (e.g. APOGEE, Gaia, and TESS), as well as plans to constrain the mass transfer prescriptions of binary population synthesis codes using the MS-WD binaries.
Michael Tucker
Error: Donor Star Not Found
I will present deep Hubble Space Telescope imaging of the nearby Type Ia supernova 2011fe at an unprecedented 11.5 years after explosion. The supernova itself has faded from view at these extremely late epochs (M_V > 0 mag) and we search for the expected emission from a donor star impacted by the high-speed ejecta. Our non-detection of a companion excludes essentially all Helium-rich stars and further restricts H-rich donors. Our results, in conjunction with previous non-detections of a companion, exclude almost all scenarios requiring a nearby star at the moment of explosion.
Sumit Sarbadhicary
Where do stars explode in the interstellar medium?
The explosions of stars, i.e. supernovae, play a major role in the evolution of galaxies (called feedback) by driving important underlying processes such as galactic outflows, interstellar turbulence, formation of hot gas, acceleration of cosmic rays, cycling of metals and regulation of molecular clouds. How exactly this energy from supernova explosions couple to the multi-phase interstellar gas is not fully understood, and is a major systematic uncertainty in cosmological simulations that remain our primary tools for studying the physics of galaxy formation. In this talk, I will discuss an important but overlooked aspect of this supernova feedback -- the question of where stars explode in interstellar gas. The distribution of densities where stars explode makes a big difference to the predicted star-formation, outflow rates and phase distribution of interstellar gas in simulations. I will specifically focus on how recent high-resolution (1-100 pc-scale) multi-wavelength surveys (e.g. with ALMA, JWST, VLA and Hubble) of the nearest galaxies are providing novel constraints on where stars explode and primarily inject their energy, how this energy couples to the surrounding gas, and how this is an exciting observational probe of feedback physics with upcoming facilities in the next decade.
Ryuichiro Hada
Prospects for constraining the age and radiation geometry of quasars with imaging and spectroscopic observations
Quasar radiation alters the ionization state of the surrounding intergalactic medium (IGM), forming a finite region (called "quasar proximity zone") that is characterized by its age and radiation geometry. This implies that by measuring the variation of Lyman-alpha emission/absorption in the IGM and mapping the quasar proximity zone, we can gain insight into the growth history or radiation mechanism. In this talk, I will present several existing and newly developed methods for probing the proximity zone, intended for use in imaging/spectroscopic surveys, and show results for comparison with or application to recent observational data. I will also discuss the prospects for an ongoing spectroscopic survey, the Dark Energy Spectroscopic Instrument (DESI).
Manami Roy
How do the satellite galaxies gift "cool" gas to their host?
The presence of a cool phase in the outer circumgalactic medium (CGM) of galaxies has sparked extensive debate in the scientific community. While cosmological simulations consistently depict the existence of such cool gas distributions, idealized simulations have thus far struggled to reproduce this phenomenon. One notable missing element in bridging the gap between these two simulation types is the role of satellite galaxies. However, in cosmological simulations, disentangling the contribution of cold gas in the CGM solely from satellite galaxies versus feedback-driven cold clouds or cold filamentary inflows has proven to be a complex challenge.
In our efforts to overcome the limitations of both simulation approaches, we conducted a series of high-resolution idealized simulations featuring Milky Way-type host galaxies with satellite companions. Our primary objective was to explicitly investigate the extent to which satellite galaxies populate the cool phase of their host galaxy's CGM and the underlying processes involved. Our findings reveal that satellite galaxies play a significant role in supplying cold gas to the CGM, both through direct stripping and induced cooling within the mixing layer of the stripped cold gas. Notably, massive satellites, such as the Large Magellanic Cloud (LMC), continue to contribute cold gas to the CGM over extended periods, spanning several billion years. However, low-mass satellites experience rapid gas loss due to their propensity to form small clouds with short cloud-crushing times, rendering them vulnerable to destruction.
Jung-Tsung Li
Small-Scale Magnetic Fields are Critical to Shaping Solar Gamma-Ray Emission
The Sun is a bright gamma-ray source due to hadronic cosmic-ray interactions with solar gas. While it is known that incoming cosmic rays must generally first be reflected by solar magnetic fields to produce outgoing gamma rays, theoretical models have yet to reproduce the observed spectra. In this talk, I will introduce a simplified model of the solar magnetic fields that captures the main elements relevant to gamma-ray production. Despite having no tuning to match gamma-ray data, our model produces a gamma-ray spectrum that reasonably matches Fermi-LAT data at 1–200 GeV and the HAWC data at near 1 TeV. Our study is important for understanding cosmic-ray transport in the solar atmosphere and will lead to insights about solar-surface magnetic fields on the surface of the Sun.
William Luszczak
Searching for Ultrahigh Energy Neutrinos with PUEO
In recent years, significant strides have been made in the field of neutrino astronomy, with the discovery of the TeV/PeV astrophysical neutrino flux by the IceCube collaboration. However due to the limitations of current detectors, the neutrino flux at EeV+ energies has yet to be observed. Probing this energy region is essential for understanding the extreme-energy universe at all distance scales. The Payload for Ultrahigh Energy Observations (PUEO) is a balloon-borne experiment intended to study the ultrahigh energy neutrino regime by utilizing the Askaryan effect to observe neutrino interactions in the Antarctic ice. PUEO builds upon the previously successful Antarctic Impulsive Transient Antenna (ANITA) program, and boasts an improved design that is expected to have world-leading sensitivity to the ultrahigh-energy neutrino flux above 1 EeV. This talk will discuss the science goals, recent developments, and timeline of the PUEO experiment.
Lucas Beaufore
Measuring Cosmic-ray isotopes with the HELIX Balloon
The High Energy Light Isotope eXperiment (HELIX) is a balloon-borne experiment designed to measure the chemical and isotopic abundances of light cosmic-ray nuclei from Z=1 (protons) to Z=10 (Neon). The HELIX payload is a magnet spectrometer, optimized for a measurement of the ratio of the propagation clock isotope Be-10 to stable Be-9 in the cosmic-ray flux. It consists of a high-resolution gas drift chamber tracker placed in the field of a 1 Tesla superconducting magnet, a time-of-flight detector which measures particle charge and velocity at lower energies, and a ring-imaging Cherenkov detector. In its first flight, HELIX will measure the Be isotope fluxes from 0.2 GeV/n to beyond 3 GeV/n with a sufficient mass resolution to individually resolve Be-10 and Be-9. In this talk I will present a brief overview of HELIX, which is currently undergoing integration in preparation for a flight in Spring of 2024.
Andrei Cuceu
Measuring the cosmic expansion rate at high redshift with DESI Lyman-𝛼 forests
The Lyman-alpha (Lya) forest is currently one of the most powerful probes of large-scale structure at high redshift (2 < z < 4). This is made possible by large spectroscopic surveys that measure hundreds of thousands of quasar spectra. The Dark Energy Spectroscopic Instrument (DESI) has finished collecting its first year of data in June 2022. This already comprises the largest ever spectroscopic data set. We are currently in the process of analyzing this data, and deriving the first cosmological constraints from DESI. In this talk, I will show how DESI will take advantage of the Lya forest to comprehensively map the cosmic expansion history between redshifts 2 and 4, and present the current status of the DESI Lya forest Year 1 analysis.
Naim Karacayli
DESI early data: 1D Lyman-alpha forest power spectrum and lessons for Year 1
The one-dimensional power spectrum P1D of the Lya forest provides important information including constraints on warm dark matter models, the sum of the masses of the three neutrino species, and the thermal state of the intergalactic medium. I will present the first measurement of P1D with the quadratic maximum likelihood estimator (QMLE) applied to 54,600 quasars from DESI early data, and an alternative model to measure the cosmic metal properties using P1D redward of the quasar’s Lya emission line (https://arxiv.org/abs/2302.06936). Our analysis demonstrates the percent-level performance of the spectroscopic pipeline noise estimation and the spectrograph resolution matrix with two-dimensional image simulations that we processed with the DESI spectroscopic pipeline. Even though the pipeline is exceptional, noise calibration and spectrograph resolution remain as major sources of systematics. I find that the systematics could double the error bars on cosmological parameters from DESI early data. The statistical power of Year 1 data will demand ever stringent precision.
Peter Taylor
Unsupervised Searches for Parity Violations in Cosmological Fields
Recent measurements of parity-odd modes in galaxy over-density fields provide tantalizing evidence for parity-violations in the large-scale structure of the Universe. If not systematic in origin, this could point novel inflationary physics. Traditional searches for parity violations in large scale structure are limited to low-order numerically tractable summary statistics and theoretical uncertainties in the covariance of the parity-odd modes presents a formidable challenge when trying to quantify the significance of a detection. I present an unsupervised approach which is immune to these difficulties.