CCAPP Fellows Symposium 2022

Ashley Ross

The First Year of the Dark Energy Spectroscopic Instrument Survey

The Dark Energy Spectroscopic Instrument has completed the first year of its five year survey. During that year, it successfully measured redshifts for more than 12.5 unique galaxies and quasars, increasing the total known to humans by more than a factor of 4. I will introduce the dataset and how we are using it to improve our knowledge of cosmology.

Naim Goksel Karacayli

Preliminary 1D Lyman-alpha Power Spectrum Results from DESI Early Data

The Lyα forest technique can probe matter in vast volumes far into the past (2 < z < 5) and at smaller scales than galaxy surveys (r < 1 Mpc) through absorption lines in quasar spectra. 1D power spectrum of the Lyα forest (P1D) has emerged as a competitive framework to study new physics, but also has come with various challenges and systematic errors in analysis. In this talk, I will share an analysis overview of DESI’s early data and describe two major challenges, namely determining the quasar continuum and interpreting the spectral extraction algorithm. I will also talk about the metal signal outside the Lyα forest and my proposed model to constrain cosmic ion abundance.

Andrei Cuceu

New Constraints on the Expansion Rate at Redshift 2.3 from the Lyman-α Forest

The Lyman-alpha (Lya) forest is currently one of the most powerful probes of large scale structure (LSS) at high redshift (z > 2). This is made possible by large spectroscopic surveys that measure hundreds of thousands of quasar spectra, such as the Baryon Oscillation Spectroscopic Survey (BOSS) and its successor, extended BOSS (eBOSS). However, 3D correlations of the Lya forest have so far only been used to measure baryon acoustic oscillations (BAO). In this talk, I will present the first ever cosmological analysis of the full shape of the Lya 3D auto-correlation function, and its cross-correlation with quasars. We use Lya correlations measured by eBOSS using data release 16 (DR16), and fit the full shapes of these correlations in order to measure the Alcock-Paczynski (AP) effect. I will start by showing results from a study of a full-shape analysis on a set of one hundred eBOSS mock data sets. This shows that we are able to recover an unbiased measurement of the AP effect from the full shapes of the correlations. After that, I will show results using the real eBOSS DR16 data. Compared to a BAO only analysis, we are able to improve AP constraints by a factor of 2. Finally, I will show how constraints on cosmological parameters are improved by using the full shapes of the Lya correlations.

Peter Taylor

The Covariance of Photometric and Spectroscopic Galaxy Surveys: Implications for Cosmological Parameter Inference

To combine information from photometric and spectroscopic galaxy surveys we must account for the covariance between the two probes. Currently any covariance between the two types of measurements is neglected as existing photometric and spectroscopic surveys largely probe different cosmological volumes. This will cease to be the case as data arrives from next-generation surveys. In this talk I show that although photometric and spectroscopic measurements are covariant on large radial scales the information content of these modes is so so low, that we neglect this covariance when performing cosmological parameter inference

Ryuichiro Hada

Measuring the Lyα Emission Excess Around Quasars with Fiber Spectrograph

The intergalactic medium (IGM) around quasars excessively emits Lyman-alpha (Lyα) photons by being exposed to the quasar's powerful radiation. In particular, the radiation from a local quasar impacts a limited region (called "quasar light echo") characterized by the lifetime, which implies that we can obtain insights into the growth history of quasars by looking into the excess in Lyα emission around quasars. In this talk, I will introduce a statistical method to measure the Lyα emission excess by stacking spectra in galaxy redshift surveys and our simple theoretical model to predict the measurements and then present a forecast for an upcoming spectroscopic survey, the Subaru Prime Focus Spectrograph (PFS).

Chun-Hao To

Challenges and Opportunities of Multi-Probe Cluster Cosmology

Multiple cosmological probes in photometric surveys can measure the cosmic structure. These include cluster abundances and positions, galaxy positions, and weak gravitational lensing shear. In this talk, I will outline a program that combines all these probes to maximize the cosmological science return. Then, using recent results from the Dark Energy Survey as a pathfinder example, I will describe the challenges and opportunities of this program for upcoming large cosmological surveys. I will further present some of the recent progress in tackling these challenges. These include developments of a novel and general sampling scheme that reduces the computational cost of the analysis by more than a factor of 50 and improvements in survey simulations for analysis validation. This talk will be concluded by discussing the prospects of this multi-probe cluster cosmology program in the Rubin Observatory's LSST and CMB-S4 era.

Subhash Bose

Finding Unusual Supernovae from Surveys

Massive stars end their life as energetic core-collapse supernova explosions. They are produced from a wide range of progenitors and environments, and so their observed and physical properties are also diverse. Despite several decades of studies of these objects, various aspects are still poorly understood and highly debated. With the emergence of all-sky and untargeted surveys, we are now able to find several extreme and unusual types of SNe that were previously unknown, and challenge our present understanding which is mostly based on normal types of SNe. So it is important to explore these rare and unusual objects to have a comprehensive picture of the SNe diversity. In this talk I will discuss few such unusual events.

Michael Tucker

Coping with the Transient Onslaught

The past decade has been a boon for discovering and studying astrophysical transients such as supernovae and tidal disruption events. The proliferation of sky surveys has revealed both completely new phenomena and extreme outliers of known events, providing astronomers with crucial insights into the energetic and enigmatic explosions occurring throughout the Universe. I will discuss the Spectral Classification of Astronomical Transients (SCAT) survey which obtains spectrophotometry of astrophysical transients in our search for the interesting and unusual. I will highlight some of our recent results and show how the upcoming DR1 will constrain the next generation of theoretical models.

Amy Sardone

Using Deep HI to Understand the Low Mass End of Dynamic Galaxy Relations

The number of observed low mass galaxies is in conflict with the number predicted by standard cosmological models. Rotation velocities of galaxies provide the observational link to compare the number density of galaxies with a dark matter halo (velocity function). We have used highly sensitive observations of extremely low mass galaxies to extract rotation velocities that encompass diffuse gas in the outskirts of the galaxies. We use these velocities to populate the unconstrained low mass end of the velocity function of galaxies and compare these observations with simulations of dark matter halos. We also use these velocities to populate the low mass end of the Baryonic Tully Fisher Relation, which is currently an unsettled regime in the literature.

Christine Daher

Uncovering Binary Formation Channels in Low-Mass Stars: Evidence for a Regime Change at Teff ~3800 K (M ~ 0.45 M) from APOGEE RV Variability

Given their relative stability over a star's main sequence life, stellar chemical abundances for Fe and α-process elements offer a unique window into the formation mechanisms of low-mass close binaries. We select samples of FV, GV, KV, and M0-5V stars from the seventeenth data release of the APOGEE survey and quantify their radial velocity (RV) variability through the maximum shift in the multi-epoch APOGEE radial velocities. With the fraction of RV variables as a proxy for the close binary fraction, we are able to statistically investigate the interplay between metallicity, effective temperature, and close binary fraction across these samples. In this talk, I will discuss the unique behaviors we observed in each of the spectral types and discuss how these correspond to our current understanding of binary formation channels.

David Martin

Small Stars Flare a lot - but where?

It is well-established that small stars flare more than sun-like stars. What remains to be seen is the latitudinal and longitudinal distribution of these flares. I will demonstrate work done to observed occulted flares in transiting exoplanet and eclipsing binary systems, such that we may place geometric constraints on the flare locations. This has implications for both stellar modelling and the habitability of planets around low-mass stars.

Marshall Johnson

The Atmospheres of Ultra Hot Jupiters at High Resolution

Ultra hot Jupiters (giant planets with temperatures in excess of 2200 K) represent both some of the most extreme planetary environments possible, and some of the most observationally accessible exoplanets. Using ground-based high resolution spectroscopic observations, we can detect the spectroscopic signatures of individual atomic and molecular species in the atmospheres of these planets, and use these data to constrain the atmospheric properties. I will present our observations of ultra hot Jupiters using the PEPSI spectrograph on the LBT, focusing on the exemplar planet KELT-20 b. We have detected the emission spectrum of Fe I in the planetary atmosphere at nearly 17 sigma significance in our data, but fail to detect any other species despite this strong detection. We set limits upon molecular species such as TiO and VO which could cause KELT-20 b's atmospheric inversion, and demonstrate the Ti and V are depleted from the planetary atmosphere. Finally, I will discuss future prospects for learning about these planets' atmospheric dynamics and temporal variability.

Adam Wheeler

Element Abundance of Stars: Problems and Possible Solutions

Element abundances and stellar parameters derived from spectra underpin entire fields of astronomy, from planet formation to galactic chemical evolution. Measuring element abundances requires comparing observed spectra to synthetic models, which involves many physical input quantities (e.g. oscillator strengths, molecular energy levels, broadening parameters), many of which are poorly-constrained. This has lead to a situation where there are large (up to a few 0.1 dex) systematics between and within surveys and analysis pipelines, hindering the use of spectroscopically derived quantities. As large multiplexed surveys deliver stellar spectra by the millions, it's more pressing than every to improve our models. In this talk, I will introduce a new spectral synthesis code, Korg, and discuss ways to improve the physical models underlying elemental abundance measurements.

Sumit Sarbadhicary

Unravelling Supernova Progenitors from Radio Surveys of Supernovae and Supernova

Connecting supernovae with their progenitor stars is a major challenge in astrophysics. Some of the important open questions include: are thermonuclear supernovae mostly explosions of white dwarfs with a main-sequence, evolved giant or white dwarf companion? Is the explosion driven by accretion, merger, or collision with the companion? How often do the white dwarfs explode below the Chandrasekhar limit? For core-collapse supernovae, whose progenitors are massive stars, the precise mass range of stars that explode is presently unclear as a result of uncertainties in binary stellar evolution and the stellar structure of evolved massive stars. I will discuss addressing these topics with two unique strategies: (1) Studying the circumstellar material around the progenitor with radio observations. Radio serves as a clean tracer of circumstellar material produced by mass-loss from the progenitor prior to explosion. I will discuss new ongoing projects to observe radio supernovae very early and very late after the explosion to probe a wide-variety of circumstellar material. (2) Measuring the delay-time distribution of supernovae from supernova remnant surveys and star-formation history maps in the Local Group galaxies, which is a powerful way to constrain the age-distribution of supernova progenitors and directly connect with stellar population model predictions. I will finally discuss the ongoing VLA Local Group Survey — the most sensitive radio survey of six northern star-forming Local Group galaxies — M31, M33, NGC6822, IC10, IC1613, WLM — to uncover the deepest sample of radio supernova remnants, HII regions and atomic ISM in these galaxies, with exciting prospects for progenitor and stellar feedback studies.

William Luszczak

Let's Talk About TXS 0506+056

Past results from the IceCube Collaboration have suggested that the blazar TXS 0506+056 is a potential source of astrophysical neutrinos. However, in the years since there have been numerous updates to event processing and reconstruction, as well as improvements to the statistical methods used to search for astrophysical neutrino sources. This talk will discuss some of these improvements that are relevant for astrophysical neutrino source searches, as well as report an updated significance and neutrino flux fit for the 2014 untriggered neutrino flare candidate that was originally identified at the location of TXS 0506+056.

Takahiro Sudoh

Where are Milky Way's Hadronic PeVatrons?

Observations of the Milky Way at TeV—PeV energies reveal a diffuse flux of hadronic cosmic rays and also point-source emission of gamma rays. If the gamma-ray sources are hadronic cosmic-ray accelerators, they are also neutrino sources. However, no neutrino sources have been detected in the Milky Way. Where are they? We introduce a new population-based approach to probe Milky Way’s hadronic “PeVatrons”, demanding consistency between diffuse and source data on cosmic rays, gamma rays, and neutrinos. We quantify present constraints and future prospects, and discuss the origins of cosmic rays and the nature of gamma-ray sources.

Keith McBride

Isotopic Composition of Light Cosmic Rays with HELIX

The High Energy Light Isotope eXperiment (HELIX) is a balloon-borne mass spectrometer optimized to measure the isotopes of Beryllium in cosmic rays. With high mass resolution, HELIX resolves these isotopes (and those of other light cosmic ray nuclei such as Helium, Lithium, and Boron) at high energies where more precise measurements are needed. These measurements heavily impact our understanding of both Galactic accelerator candidates and cosmic ray propagation. For example, Beryllium isotope measurements at high energy (30 GeV) uniquely probe the cosmic ray propagation halo size in the Milky Way. HELIX directly measures a cosmic ray’s charge, magnetic rigidity, and velocity to identify the isotope. OSU plays a leading role in operations and design of the tracker and magnet subsystems along with the Data Acquisition. I will present a brief overview of HELIX which is aiming for a Long Duration Balloon flight in the upcoming seasons.

Ivan Esteban

Particle Physics at UltraHigh Neutrino Energies

The ultrahigh energy (UHE) range of neutrino physics (above ∼10^7 GeV), as yet devoid of detections, is an open landscape with challenges to be met and discoveries to be made. Many current and future detectors are planned to detect these neutrinos, whose flux is tentatively linked to the UHE Cosmic Ray Flux. Intringuingly, when interacting at Earth UHE neutrinos probe center-of-mass energies higher than anything possible at current colliders. Measurement of the neutrino-nucleus cross section σ would directly probe new physics models. In this talk, I will show how different instruments can measure σ despite the unknown flux, what the required detector resolutions are, what statistics will be needed, and what are the paths for complementarity. We find that with the broad spectrum of upcoming detectors, σ can be measured in the UHE range without prior knowledge about the flux, that presently allowed novel-physics scenarios can be tested even with low statistics, and that this can happen relatively soon.

Jung-Tsung Li

Galactic Cosmic-Ray Propagation in the Inner Heliosphere

A key goal of heliophysics is to understand how cosmic rays propagate in the solar system’s complex, dynamic environment. One observable is solar modulation, i.e., how the flux and spectrum of cosmic rays changes as they propagate inward. We construct an improved force-field model, taking advantage of new measurements of magnetic power spectral density by Parker Solar Probe to predict solar modulation within the Earth’s orbit. We find that modulation of cosmic rays between the Earth and Sun is modest, at least at solar minimum and in the ecliptic plane. Our results agree much better with the limited data on cosmic-ray radial gradients within Earth’s orbit than past treatments of the force-field model. Our predictions can be tested with forthcoming direct cosmic-ray measurements in the inner heliosphere by Parker Solar Probe and Solar Orbiter. They are also important for interpreting the gamma-ray emission from the Sun due to scattering of cosmic rays with solar matter and photons.