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August[0]=["30","All","HEAP","Jamboree","We ask each of the faculty members, postdocs, and students to submit one slide on their recent or ongoing research or on their research interests. The seminar will be composed of 1-2min talks by everyone (a.k.a. machine gun talks or lightning talks). This provides an opportunity for people to know the current activities in the astronomy and high-energy groups, and it also serves as an introduction of the groups to the newly coming students.","Local","","",""]

September[0]=["06","Kyle Dawson","Utah","Modeling Quasar Spectra for Enhanced Cosmological Studies","The BOSS and eBOSS spectroscopic programs have obtained a sample of more than 200,000 quasars over the high redshift range where absorption by the Lyman-alpha forest is visible to ground-based optical spectroscopy. These quasars were selected to illuminate intervening neutral hydrogen and thus provide a three-dimensional map of the Universe over an interval 1.8 to 3.3 billion years after the Big Bang.  We have successfully measured the Baryon Acoustic Oscillation feature in this distribution of hydrogen highlighted by the Lyman-alpha forest. However, the quasar sample has the potential to provide additional measures of the distance scale and of structures on the largest scales where the initial conditions from inflation preside.  In this talk, I will present the results of our efforts to better understand the physics and diversity of quasars as a step toward expanding the cosmological utility of this sample.","Local","","",""]

September[1]=["13","Rongpu Zhou","Pittsburgh","Galaxy clustering with DESI imaging surveys","Large photometric galaxy surveys such as the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST) rely on photometric redshifts (photo-z's) - redshifts derived from broad-band photometry - as the distance measurement, and accurate photo-z estimation and its optimal utilization are crucial for precision cosmology. In this talk, I will first give a brief overview of photometric redshift in the context of LSST, and then I will present a new method of measuring and modeling galaxy clustering using photo-z's. We select a sample of luminous red galaxies (LRGs) from DECaLS - part of the imaging surveys for the Dark Energy Spectroscopic Instrument (DESI) - and obtain accurate photo-z's using DECaLS grz, WISE W1W2 and galaxy morphology. Rather than measuring the angular correlation function w(theta) in bins of photometric redshift, we measure the projected correlation function wp(rp) between objects in a particular photo-z bin and the entire sample, with a sufficiently large window in the redshift direction to include most physical pairs even in the presence of photometric redshift errors. We model the measured correlation functions in the halo occupation distribution framework with the photo-z error estimates properly incorporated into the analysis. This method maximizes the signal-to-noise in the correlation function measurement and simplifies interpretation compared to a w(theta) analysis. We also discuss other uses of this photo-z dataset such as for improving the selection of spectroscopic targets in DESI.","Kyle Dawson","","",""]

September[2]=["20","Pearl Sandick","Utah","Dark Matter Indirect Detection - Prospects for WIMPs","In this talk, I'll present an overview of dark matter indirect detection, focusing on techniques relevant for weakly interacting massive particle (WIMP) dark matter.  Current and proposed experiments and their ability to probe the identity of WIMP dark matter will be discussed, as well as several unresolved anomalies.  Finally, I'll present some recent work on constructing limits from experimental data using a method that is independent of both the dark matter particle physics and the dark matter astrophysics.","Local","","",""]

September[3]=["27","Paolo Gondolo","Utah","Dark Energy Stars"," I will present a class of time-dependent solutions to Einstein's equations that describe the formation of astrophysical objects with dark energy equation of state p=-rho in a finite central region starting from a configuration with an ordinary equation of state. These solutions have no singularities and do not violate the weak or null energy conditions at any time or position.","Local","","",""]

October[0]=["04","Anson D'Aloisio","UC Riverside","Probing Cosmological Reionization with the Lyman-alpha Forest","When the first galaxies emerged, ~100-500 million years after the Big Bang, their starlight likely reionized and heated the intergalactic hydrogen that had existed since cosmological recombination.    Much is currently unknown about this process, including what spatial structure it had, when it started and completed, and even which sources drove it.  I will discuss what recent Lyman-alpha forest measurements tell us about the reionization process and about structure formation in the first billion years.","Zheng Zheng","","",""]

October[1]=["11","","","No Seminar - Fall Break","","","","",""]

October[2]=["18","Brian Jeffs","BYU","ALPACA: An L-band Wide-field Radio Camera Array Feed for the Arecibo Radio Telescope","NSF has recently funded Brigham Young and Cornell universities to develop an L-band 160 antenna-element phased array feed (PAF) for the Arecibo Radio Telescope in Puerto Rico.  This second-largest radio dish in the world provides exquisite sensitivity for observing some of the faintest and most distant cosmic sources, and is known to the public from appearances in movies like Contact and James Bond: Golden Eye.  This instrument upgrade significantly widens the field of view by digitally forming 40 simultaneous beams on the sky, as compared to one for a conventional single pixel horn feed, or seven for the current ALFA multi-beam array feed.  Telescope performance will be dramatically increased in primary science goals of sky surveys for pulsars, fast radio bursts, and galactic and extragalactic neutral Hydrogen.  A major innovation is that this will be the world's largest fully cryogenically cooled PAF, which will contribute significantly to sensitivity and survey speed.","John Belz","","",""]

October[3]=["25","Sten Hasselquist","Utah","APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy","The Apache Point Observatory Galactic Evolution Experiment provides the opportunity of measuring elemental abundances for C, N, O, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn, Fe, Co, and Ni in vast numbers of stars. We analyze the chemical-abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy (Sgr). This is the largest sample of Sgr stars with detailed chemical abundances, and it is the first time that C, N, P, K, V, Cr, Co, and Ni have been studied at high resolution in this galaxy. We find that the Sgr stars with [Fe/H] &#8819; -0.8 are deficient in all elemental abundance ratios (expressed as [X/Fe]) relative to the Milky Way, suggesting that the Sgr stars observed today were formed from gas that was less enriched by Type II SNe than stars formed in the Milky Way. By examining the relative deficiencies of the hydrostatic (O, Na, Mg, and Al) and explosive (Si, P, K, and Mn) elements, our analysis supports the argument that previous generations of Sgr stars were formed with a top-light initial mass function, one lacking the most massive stars that would normally pollute the interstellar medium with the hydrostatic elements. We then exploit the unique chemical abundance patterns of Sgr to conduct a chemical tagging exercise on the APOGEE data to identify Sgr stream stars in the Milky Way. We find that our chemical tagging method is able to return ~90% Sgr-like members, with half of these stars likely Sgr stream stars, and the other half belonging to the recently characterized &ldquo;accreted halo&rdquo; population. We use the chemical abundance patterns of these stars to draw conclusions about the star formation history of Sgr and of the progenitor of the &ldquo;accreted halo&rdquo; population.","Local","","",""]

November[0]=["01","James Wells","Michigan","Unification and Precision Measurements","The Standard Model of particle physics may yet be unified into a deeper organizing principle. The gauge groups may unify into higher rank gauge group, and the Yukawa couplings might unify into a simplifying symmetry group. The key to assessing these unification prospects is precision measurements and related precision theory. The current status of unification, in its various guises, is discussed from the perspective of precision analysis. In addition, the prospects for further stress-testing the ideas at future experiment and through future theory work are also presented.","Yue Zhao","","",""]

November[1]=["08","John Barentine","Intl Dark Sky Assn","Bright Hopes For Dark Nights: Why And How To Solve The Problem Of Light Pollution","Members of the public are fascinated by space and astronomy, but the public’s ability to the access the night sky around the world is now often significantly impaired by light pollution. Public perception of light pollution as a significant environmental concern is on the rise, and it is perhaps the easiest pollution threat to confront. I will summarize the basics of light pollution and our current understanding how it affects our world. I will then describe the various tools and strategies available to address the problem, including public policies intended to address both the global supply of, and demand for, artificial light at night. I will conclude by arguing for why scientists should care about light pollution, and what they can do to alter the trajectory of the problem and bring it closer to solution.","Anil Seth","","",""]

November[2]=["15","Udara Abeysekara","Utah","New results from HAWC and VERITAS","Very-High-Energy gamma-ray astronomy probes non-thermal, energetic acceleration processes in the Universe. The rapid development of very-high-energy gamma-ray observatories such as HAWC, VERITAS, HESS, and MAGIC expanded the TeV gamma-ray source catalog to more than two hundred sources. The list of known gamma-ray source classes includes active galaxies, supernova remnants, pulsar wind nebulae. VHE observations, in conjunction with observations at other energies/wavelengths as well as particle and now gravitational wave events, allow for an increased understanding of the physics driving these energetic systems. <br> In this talk, I will present recent results from observations using the HAWC and VERITAS observatories. First, I will discuss the HAWC's discovery of gamma-ray emission from SS 433, making it the first known microquasar seen at TeV energies. Another key result from HAWC is resolving the morphology of Geminga supernova remnant. A key result from VERITAS is the detection of gamma-rays from blazar TXS 0506+056 temporally coincident with a neutrino detected by IceCube. Lastly, I will discuss our future observation plans to improve our understanding of these objects.","Local","","",""]

November[3]=["22","","","No Seminar - Thanksgiving Holiday","","","","",""]

November[4]=["29","Tim Linden","OSU","Astrophysical Signatures of Dark Matter Accumulation in Neutron Stars","Over the past few decades, terrestrial experiments have placed increasingly strong limits on the dark matter-nucleon scattering cross-section. However, a significant portion of the standard dark matter parameter space remains beyond our reach. Due to their extreme density and huge gravitational fields, neutron stars stand as optimal targets to probe dark matter-nucleon interactions. For example, over the last few years, the mere existence of Gyr-age neutron stars has placed strong limits on models of asymmetric dark matter. In this talk, I will discuss novel methods that utilize neutron stars to potentially detect dark matter interactions by studying the galactic morphology of neutron stars, as well as the electromagnetic signals that may be produced via neutron star collapse. Intriguingly, these observations can probe extremely generic dark matter models spanning from MeV - PeV energies, including troublesome portions of parameter space such as pure-Higgsino dark matter.","Yue Zhao","","",""]

December[0]=["06","Yuhsin Tsai","Maryland","Anisotropies in the Gravitational Wave Background from Cosmological Phase Transitions","Phase transitions in the early universe can readily create an observable stochastic gravitational wave background. I will argue that such a background necessarily contains anisotropies analogous to those of the cosmic microwave background (CMB) of photons, and that these too may be within reach of proposed gravitational wave detectors. Correlations within the gravitational wave anisotropies and their cross-correlations with the CMB can provide new insights into the mechanism underlying primordial fluctuations, such as multi-field inflation, as well as reveal the existence of non-standard &ldquo;hidden sectors&rdquo; of particle physics in earlier eras.","Yue Zhao","","",""]

December[1]=["13","","","No Seminar - Final Exams","","","","",""]

December[2]=["20","","","Happy Holidays","","","","",""]

December[3]=["27","","","Happy Holidays","","","","",""]

January[0]=["03","","","Happy Holidays","","","","",""]

January[1]=["11","Riccardo DeSalvo","Cal State","The galactic Gold factories, (and Uranium, Lead, Tungsten...)","The detection of gravitational waves (or the lack of them) have brought many new insights in the making of the Universe. We found an excess of black holes, perhaps signaling that the low-metallicity era of the Universe lasted longer than we thought, and maybe they are part of dark matter. We found a source of gamma ray bursts and the process that enriched the interstellar gas with heavy metals and color the stars. We found that Neutron Stars are round to better than one part in a billion, and started measuring their elastic and mechanical dissipation properties, we see how they shred and spew neutron matter when trying not to fall in a black hole and we will measure how nuclear forces help them resist becoming a black hole when they cool off after forming a neutron star too heavy to survive. The question for nuclear physicists will be what is the quark make of Neutron Stars that produce all those properties? We will measure the Hubble constant with unprecedented precision. And who knows what else. The Universe is a strange place indeed.","Stephan LeBohec","Friday Noon",""]

January[2]=["17","Jonathan Trump","UConn","Mapping the Census of Supermassive Black Holes","The past 20 years have revealed that supermassive black holes play an essential role in the formation and growth of galaxies.  But a reliable census of supermassive black holes over cosmic time has remained elusive.  That picture is changing with the advent of two new emphases in astronomical surveys: industrial-scale time-domain monitoring, and massively multiplexed spatially resolved spectroscopy.  The pioneering new SDSS-RM project is now vastly expanding the number of supermassive black holes with reliable mass measurements through time-domain echo-mapping.  Beyond mass, SDSS-RM is also starting to enable the first survey measurements of the other two fundamental black hole quantities: accretion rate and spin.  I will also show how Hubble WFC3 grism spectroscopy spatially resolves a population of nuclear black holes that are otherwise missed due to host galaxy dilution.  CANDELS/3D-HST grism data uniquely reveal the black hole content of low-mass hosts, discriminating between models of black hole formation at cosmic dawn.  I will conclude by looking forward to the next generation of observatories: SDSS-V and LSST for a new time-domain frontier of black hole mass, accretion, and spin, and JWST / CEERS and WFIRST for a new spatially resolved frontier of black hole seeds.","Kyle Dawson","JFB103","",""]

January[3]=["24","Daniel Gruen","Stanford","Cosmology from structure beyond the power spectrum","Gravity produces complex structures in the Universe that inform our understanding of cosmology and astrophysics. Much of this information is contained in non-Gaussian fluctuations of matter density, rather than in the matter power spectrum. I will give an overview of cosmological analyses by the Dark Energy Survey (DES) that are driven by the weak gravitational lensing signals of these non-Gaussian features. My focus will be on results from the full distribution of matter and galaxy density, and from clusters of galaxies. These features allow key tests of our understanding of cosmology and structure formation. They pose significant challenges in modeling, and particularly benefit from connecting photometric surveys with spectroscopy. To fulfill the promise of structure as a decisive test of cosmology, we will thus have to devise new methods of jointly and fully analyzing the unprecedented data collected by upcoming astronomical surveys.","Kyle Dawson","JFB103","",""]

January[4]=["31","Yuan-Sen Ting","IAS","Milky Way, machine learning, big data","Understanding physical processes responsible for the formation and evolution of galaxies like the Milky Way is a fundamental but unsolved problem in astrophysics. Fortunately, most stars are long-lived. As such, using the stars as &ldquo;fossil records&rdquo; (what is known as Galactic archaeology) can offer unparalleled insight into the assembly of galaxies.  In recent years, the landscape of Galactic archaeology is rapidly changing thanks to on-going large-scale surveys (astrometry, photometry, spectroscopy, asteroseismology) which provide a few orders of magnitude more stars than before. In this talk, I will discuss new &ldquo;phenomenological&rdquo; opportunities enabled by large surveys.  I will also discuss how machine-learning tools could leverage the big data about the Milky Way by maximally harnessing information from low-resolution stellar spectra as well as the time-series photometric fluxes of stars.","Kyle Dawson","JFB103","",""]

February[0]=["07","Freeke van de Voort","MPA Garching","Cosmic gas flows: the key to understanding galaxy formation","Galaxies are intimately connected to the environments they live in. The haloes around them contain the gas reservoir from which the galaxies grow, while galactic outflows heat and enrich this circumgalactic medium (CGM) with heavy elements. The elemental abundances of present-day stars are, in part, set by these cosmic gas flows. Most cosmological, hydrodynamical simulations focus their computational effort on the galaxies themselves and treat the CGM more coarsely, which means small-scale structure cannot be resolved. I will discuss how to alleviate this issue by using a new simulation technique that adds uniform spatial refinement within the halo. I will show that increasing the resolution by 2 orders of magnitude results in higher overdensities and strongly affects predicted observables in the CGM. For example, the neutral hydrogen column density is dramatically enhanced, more in line with observations. Additionally, the heavy elements produced by stars are mixed less efficiently in higher resolution simulations. I will use the low-metallicity stars in my simulations to probe the early Milky Way and its satellite galaxies. I will compare my results to observational data and argue whether or not there is sufficient metal mixing for neutron star mergers to be the only source of rapid neutron capture elements in the universe. I will end with a discussion on future developments.","Kyle Dawson","JFB103","",""]

February[1]=["14","Chris Fragile","Charleston","Mysteries of Black Hole Accretion","Black hole accretion has fascinated the general public and been the subject of intense astrophysical study for many decades, yet there are a number of basic questions that still have not been answered. In fact, we seem to be getting to the point where some of the mysteries have been around for so long that many researchers have forgotten about them or at least stopped investing time in trying to solve them. In this talk, I will (re-)introduce the audience to some of these mysteries and mention some of the computational tools and simulations that are being developed to bring fresh insights into the field. Over the course of the talk, I will discuss the unusual behavior of tilted orbits in relativity, strange timing signals (quasi-periodic oscillations) in the light curves of accreting black holes, different states of black hole accretion, and the lingering problems with our &ldquo;standard&rdquo; accretion disk model.","Anil Seth","","",""]

February[2]=["21","Eddie Schlafly","LBNL","Realizing the Full Potential of Large Surveys","Twenty years ago the first digital surveys of the sky were in progress, eventually releasing optical and near-infrared catalogs of hundreds of millions of stars across the sky.  Next-generation photometric and spectroscopic surveys are now underway, detecting ten to a hundred times as many stars and galaxies as these first surveys.  Achieving the cosmological goals of these surveys requires more precise analysis than currently realized.  In this talk, I will discuss three areas in which I have tried to enhance the accuracy obtainable in large surveys.  First, I will present my work to simultaneously model the stars and galaxies in the WISE and DECaPS surveys---each of which contains billions of objects---to address the impact of blending, an increasingly prominent concern.  Second, I will present work characterizing the throughput of surveys like PS1 and DECaLS, where we currently obtain 0.7% repeatability, but a factor of a few improvement is possible through improved modeling of the system.  Finally, I will present improved maps of dust and its properties, mitigating a primary systematic uncertainty in astronomical surveys.  These three areas---modeling, calibration, and astrophysical systematics---present major challenges to next-generation surveys, but likewise provide opportunities for dramatic improvements in the near future.","Kyle Dawson","JFB103","",""]

February[3]=["28","","","No Seminar","","","","",""]

March[0]=["07","Kim Boddy","Johns Hopkins","Searching for Dark Matter Interactions in Cosmology","There is a substantial effort in the physics community to search for dark matter interactions with the Standard Model of particle physics. Collisions between dark matter particles and baryons exchange heat and momentum in the early Universe, enabling a search for dark matter interactions using cosmological observations in a parameter space that is complementary to that of direct detection. In this talk, I will describe the effects of scattering in cosmology and show constraints using Planck 2015 data and SDSS-identified satellites. I will also discuss the implications of late-time scattering during the era of Cosmic Dawn.","Yue Zhao","",""]

March[1]=["14","","","No Seminar - Spring Break","","","","",""]

March[2]=["21","Matthieu Bethermin","Marsielle","Hidden dusty giants in the teenager Universe","Measuring and understanding the star formation history in the Universe in one of key challenges of modern astrophysics. It can be probed using the UV light from young stellar populations. However, the majority of this UV radiation is absorbed by dust and re-remitted in the far-infrared and millimeter domain. The impressive progress of far-infrared and millimeter astronomy in the last decade (e.g., Herschel and ALMA) allowed us to probe the star-formation hidden in the dust clouds in the high-redshift Universe. We found that an important fraction (20-40%) of the star formation budget at z~2 is hosted by dusty galaxies forming stars at a pace 1.5 orders of magnitude higher than the Milky Way (SFR>100 Msun/yr) and it is now clear that very massive and dusty objects exist already as early as z=7. <br> How can these systems host such an impressive star formation so early in the Universe? Their cold gas reservoirs and their efficiency to convert this gas into stars are the key observables to address this question. I will present the latest constraints obtained with ALMA on their interstellar medium (cold gas mass, dense-gas fraction). One of the main results of these study is the presence of incredibly large reservoirs of molecular gas. I will finally explain why it is not so surprising considering the large mass of their host dark-matter halos, which can be constrained through the anisotropies of the cosmic infrared background, i.e. integrated relic emission of all dusty galaxies across cosmic times.","Anil Seth","","",""]

March[3]=["28","Johanna Teske","Carnegie","Characterizing Small Planets From the Ground Up","With the launch in spring 2018 of the Transiting Exoplanet Survey Satellite (TESS), a new phase of exoplanet detection, follow-up, and characterization began. In this talk, I will describe the motivation and methodology behind a new ground-based survey I am leading to study small transiting planets detected by TESS. This survey, combining several different observational techniques, is designed to investigate whether super-Earth (~1-1.6 R_earth) and sub-Neptune (~2-3 R_earth) planets formed in the same way but were sculpted by post-formation processes and so appear different now, or formed differently from the start. The goal of this survey is to double the number of well-characterized small planets known at the start of TESS, while creating an unbiased sample for better constraining the small end of the mass-radius relation. The products of this survey and others like it will feed directly into near-term (JWST, SDSS-V) and longer-term (LUVOIR, HabEx, OST, EELTs) projects intended to measure exoplanet atmospheric compositions, detect evidence of life, and understand how common Earth-like planets are in the Galaxy.","Gail Zasowski","","",""]

April[0]=["04","","","No Seminar","","","","",""]

April[1]=["11","Guido Mueller","Florida","ALPS - the Axion-like particle search","Except for dark energy, dark matter presents probably the largest conundrum in modern science. We appear to be surrounded by a very dilute 'gas' of an unknown substance which appears to only interact gravitationally with the known fermions and bosons we are made of. Speculations about dark matter range from primordial black holes to WIMPs to WISPs. Potential WISP candidates are axion-like particles and hidden sector photons. I will report on ALPS II, a light shining through a wall experiment, which probes the axion- (or hidden sector photon)-two photon Lagrangian directly. ALPS II, located at DESY, uses LIGO technology and strings of HERA magnets for a light shining through a wall experiment and is expected to see first light in late 2020.","Yue Zhao","","",""]

April[2]=["18","Marcel Agueros","Columbia","The evolution of cool dwarf spin rates: Data, models and tensions","Stellar ages are notoriously difficult to measure accurately for main-sequence low-mass stars, severely limiting our ability to address questions ranging from the evolutionary state of exoplanets to the chemical history of the Galaxy. Gyrochronology, which uses stellar rotation as a proxy for age, is a promising solution to this quandary. Unfortunately, however, theoretical calibrations of the age-rotation relation have historically been hampered by the lack of rotational measurements for large numbers of low-mass stars with a wide range of well-known ages. We are still far from being able to describe fully the evolution of rotation for low-mass stars, or from being able to use rotation measurements to estimate accurately the ages of isolated field stars. I will first summarize recent ground-based and space-based work to characterize the rotational behavior of G, K, and M dwarfs in open clusters ranging in age from 125 Myr (the Pleiades) to 3 Gyr (Ruprecht 147), and then compare these data to each other and to models for stellar spin-down in order to appraise our current understanding of the age-rotation relation.","Anil Seth","","",""]

April[3]=["25","","","No Seminar - Final Exams","","","","",""]