INPA

Rebecca Canning (Stanford) - Understanding Active Galactic Nuclei (AGN) in the most massive cosmic laboratories
2018-04-20 12:00 - 13:00 (America/Los_Angeles) | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Supermassive Black Holes (SMBHs) lurk in the centers of all massive galaxies, a fraction of these SMBHs are actively accreting and this can result in powerful outbursts which have important consequences for galaxy formation and evolution. However, the conditions under which a SMBH becomes active and the manner in which it interacts with its environment are not well understood. Clusters of galaxies offer us wonderful cosmic laboratories in which we can observe these processes. I will discuss what observations of these massive galaxy clusters can tell us about the role of AGN feedback in both maintaining a delicate balance between heating and cooling and in searching for a casual link between SMBHs and galaxy co-evolution and detail the Cluster AGN Topography Survey which is undertaking a census of SMBH activity in massive galaxy clusters.

Heidi Newberg (RPI) - Dwarf galaxies and dark matter in the Milky Way
2018-04-17 17:00 - 18:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
In the past fifteen years, dozens of tidal streams of stars pulled from dwarf galaxies and globular clusters have been discovered in the Milky Way’s stellar halo. Recently, it has been discovered that as the dwarf galaxies fall into our galaxy they perturb the stars in the disk, causing wavelike disturbances that are seen in the densities and velocities of disk stars. These disturbances could be driving force behind spiral structure in galaxies. MilkyWay@home is a petaFLOPS scale volunteer computing platform that is mapping the densities of stars in the larger tidal streams in the stellar halo and using that information to measure the mass and density profile of both the stars and the dark matter in the progenitor dwarf galaxies, using only information from the stars in the tidal streams. Eventually, MilkyWay@home will fit the shape of the Galactic potential using tidal streams.

Helion Mas du Bourboux ( University of Utah) - Baryonic Acoustic Oscillations in SDSS and DESI using the intergalactic medium absorption
2018-04-13 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
We present the measurement of the Baryonic Acoustic Oscillation (BAO) scale from the correlation between absorption in the intergalactic medium and the positions of galaxies and quasars in the SDSS data and in the desi simulations.
We use the absorption by neutral Hydrogen and by Magnesium-II observed in quasar spectra to trace the underlying matter density fluctuations. Combined with galaxies and quasars, these two tracers allow to measure the 3d cross-correlation of matter from a redshift of z = 0.5 up to a redshift of z = 2.4.

Vincent Fischer (UC Davis) - Accelerator Neutrino Neutron Interaction Experiment (ANNIE)
2018-04-06 12:00 - 13:00
The next generation of large scale neutrino detectors, such as DUNE or Hyper-Kamiokande, will heavily rely on a precise understanding of neutrino-nucleus interactions to reach their goal of measuring leptonic CP violation. Accounting for and reconstructing all final state particles, especially neutrons, created upon such interactions is thus crucial. This is the goal of the ANNIE experiment: Measuring the neutron abundance in the final state of neutrino-nucleus interactions in the energy domain relevant for oscillation experiments. With a volume of about 30 tons of pure water doped with gadolinium to enhance neutron tagging efficiency, ANNIE will provide a measurement of the neutron yield of neutrino interactions as a function of the neutrino energy in the well-characterized Booster Neutrino Beam at Fermilab. The modularity of ANNIE will allow it to perform the very first live test of a novel kind of photodetectors called LAPPDs (Large Area Picosecond Photodetectors) in a neutrino detector to reconstruct neutrino interaction vertices through precision timing measurement. This seminar will describe the design and construction of the experiment, along with the background measurement results from Phase~I and the plans for Phase~II.

Dr. Leila Haegel (University of the Balearic Islands, Spain) - Testing general relativity with gravitational waves
2018-03-26 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Gravitational waves have been directly detected by the LIGO experiment in 2015. Since then, five black holes and one neutron star binaries merging have been observed during the two observational runs. The measured signals already provided a large amount of physical results, from the mass distribution of stellar-masses black holes to the short gamma-ray burst mechanisms through measurement of the expansion rate of the Universe and tests of general relativity. Both detection and analysis of gravitational waves rely on the simulation of the expected signal to be extracted from the noise. As the exact computation of gravitational waveforms is a computationally expensive resource, physicists are building phenomenological models. I will review the process of designing such models as well as their impact on the physics extracted from the signals.

Krista Lynne Smith (Stanford) - A New Regime of Optical Variability in AGN: Light Curves from Exoplanet Satellites
2018-03-23 12:00 - 13:00
The optical light curves of AGN provide a unique window into the conditions and behavior within the accretion disk. The development of a specialized pipeline for AGN science with the unparalleled photometry of exoplanet-hunting satellites allows us to explore new optical variability phenomena. Such data provide an opportunity for direct comparison with X-ray light curves, and promise to inform models of both accretion physics and the relationship between X-ray and optical emitting regions in the central engine. These data will be critical in learning how to interpret AGN light curves from upcoming large variability surveys like LSST. Finally, exoplanet mission data have enormous future promise for a multifaceted understanding of accretion processes, including blazar jets and quasi-periodic oscillations.

Ana Bonaca (Harvard-CfA) - What are the tidal streams constraining?
2018-03-16 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Cold stellar streams, remnants of tidally disrupted globular clusters, have been employed as exquisite tracers of dark matter in the Milky Way. Because of their different positions in phase space, different ages, and different levels of observational scrutiny, different streams tell us different things about the Galaxy. We employ a Cramer–Rao or Fisher-matrix approach to understand the quantitative information content in the known streams. In simple, static, analytic models of the Milky Way, streams on eccentric orbits contain the most information about the dark-matter shape. For any individual stream, there are near-degeneracies between dark-matter halo properties and parameters describing the Galactic bulge, disk and the stream progenitor itself, but we find that simultaneous fitting of multiple streams ought to constrain all parameters to a precision of a few percent. At this level, simulated dark matter halos deviate from analytic parametrizations, so we chart the way forward by discussing constraints streams place on more flexible models of the Galactic gravitational potential.

Giorgia Pollina - Unveiling cosmic voids in large-scale structure surveys: the impact of tracer bias
2018-03-09 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The large-scale structure of the Universe can only be observed directly via luminous tracers of the underlying matter density field. However, luminous tracers, such as galaxies, do not precisely mirror the clustering statistic of the bulk of the cold dark matter distribution: their correlation function (or power spectrum) is biased and depends on various properties of the tracers themselves. Although on small scales this bias is an unestablished function of space and time, on very large scales it results in a constant offset in the clustering amplitude, known as linear bias. In this talk we focus on the bias of luminous objects within and around cosmic voids, enormous under-dense regions of the Universe that occupy the vast majority of its volume. As a remarkable result, we find that, within voids, the relation between matter and galaxy density is always linear and determined by a multiplicative constant. Furthermore, the value of this constant decreases with the increase of the size of voids and asymptotes to the linear bias. This result opens to the possibility of using such simple relation in other voids studies, allowing to extend our theoretical understanding of voids (typically defined as depressions in the matter density field) to voids that are identified using galaxies as tracers of the matter density. Ultimately we aim to test these findings with observations, using the Dark Energy Survey data currently available.

Andre Walker-Loud (LBNL) - Lattice QCD for Neutrinoless Double Beta Decay
2018-03-02 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
In recent years, lattice QCD has matured to the stage where it is now routine for calculations to be performed at or near the physical pion mass, with fully controlled extrapolations to the continuum and infinite volume limits. These calculations are predominantly related to flavor physics and heavy quark physics. The application of lattice QCD to nuclear physics is beset by a number of additional challenges which make them exponentially more expensive, prohibiting the same success so far for low-energy nuclear processes. Algorithmic improvements and the computing power of the next generation supercomputers promises an era in which we will be able to make rigorous, fully controlled calculations of basic nuclear properties. I will briefly introduce lattice QCD and describe the challenges in applying it to basic nuclear physics. I will then highlight some recent results and outline a strategy for connecting complex, exotic phenomena such as neutrinoless double beta decay to the fundamental theory of nuclear strong interactions, Quantum Chromodynamics. aim to test these findings with observations, using the Dark Energy Survey data currently available.

Dan Wilkins (Stanford) - Seeing to the Event Horizons of Supermassive Black Holes
2018-02-23 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
From the reflection and reverberation of X-rays off the innermost regions of AGN accretion discs, a three-dimensional picture is starting to emerge of the extreme environments around supermassive black holes in which intense X-ray emission is produced and jets are launched at close to the speed of light.

Recent advances in the analysis of the X-ray emission and its variability in AGN, observed by the great X-ray observatories, coupled with general relativistic ray tracing simulations, have revealed vast amounts of information about the extreme environments in the immediate vicinity of the black hole event horizon. The effects of general relativity on the reflected emission can be exploited to pinpoint the location of reflection in the strong gravitational field, while time delays in the X-ray echoes off the accretion disc enable the structure of the innermost regions to be mapped.

We discover how the X-ray emitting corona evolves on long and short timescales, giving rise to orders of magnitude variation in luminosity as well as the processes the corona can undergo during transient events, most notably the collimation and ejection of portions of the corona during X-ray flares, reminiscent of the aborted launching of a jet. The latest X-ray reverberation studies are revealing, for the first time, structure within the corona including a persistent collimated core akin to the base of a jet, even in radio-quiet sources, alongside a second component associated with the accretion disc itself.

This gives us important insight into the small-scale processes close to the event horizon that enable supermassive black holes to power some of the most luminous objects in the Universe, launch vast jets and play their important role in the formation of structure in the Universe.

Samuele Sangiorgio (Lawrence Livermore National Laboratory) - Neutrinoless Double Beta Decay with nEXO: Experiment Concept, R&D, and Sensitivity
2018-02-16 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double beta (0νββ) decay whose observation would imply lepton number violation and confirm the existence of elementary Majorana fermions. nEXO searches for 0νββ in 136 Xe with a target half-life sensitivity of approximately 10 28 years using 5×10 3 kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the 136Xe mass, the monolithic and homogeneous configuration of the active medium, and the multi-parameter measurements of the interactions enabled by the time projection chamber. This seminar will introduce nEXO’s detector concept, present the R&D activities, and discuss the anticipated performance based upon demonstrated realizable background rates.

Special - Danielle Leonard (CMU) - Measuring the scale-dependence of intrinsic alignments using multiple shear estimates
2018-02-12 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The next generation of cosmological surveys promises significant advancements in the field of weak gravitational lensing. As such, it is crucial that relevant systematic effects such as the intrinsic alignment of galaxies are well-understood. I will discuss a new method for measuring the scale-dependence of the intrinsic alignment contamination to the galaxy-galaxy lensing signal, which takes advantage of multiple shear estimates applied to the same data set. For a galaxy-galaxy lensing measurement which uses LSST sources and DESI lenses, the signal-to-noise on the intrinsic alignment signal measured by our method is forecast to improve on an existing method (Blazek et al. 2012) by a factor of >2, for optimally chosen pairs of shear estimates.

Wing Yan Ma (Imperial College London) - Recent Neutrino Oscillation Results from T2K
2018-02-09 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
T2K is a long baseline neutrino experiment situated in Japan. A muon neutrinos and antineutrinos beam is produced and fired 295km across the country and observed using the 50 kTon Super Kamiokande detector. By studying how many of these neutrinos have oscillated into different flavours and whether the oscillations occur differently for antineutrinos we have sensitivity to CP violation in the neutrino sector. I will present the latest results of the neutrino oscillation measurements using data collected up to May 2017, including new limits on the CP violating parameter δCP.

Jason Bono (Fermilab) - Muon Anomalies and Their Future Investigations
2018-02-02 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The muon is 200 times heavier than the electron and still lighter than any hadron, which make it’s interactions, at once, potentially sensitive to undiscovered phenomena, and predictable to high precision within the Standard Model. The muon’s ease of production, natural polarization and self analyzing decay, and comparatively long lifetime also allow for extremely high precision measurements of fundamental constants and interactions. Muons thus offer a unique probe to search for physics beyond the Standard Model.
This discussion will first elaborate on some of the experimental and theoretical niceties of the muon, and briefly look at the particle from a historical perspective, emphasizing a few of the many important roles that it’s played in piecing together our current understanding of particle physics. We will then look at a variety of anomalies in experiments using muons, which, taken together may suggest the possibility of sensitivity to new physics within reach of future experiments, some of which will also be looked at. Topics include recent developments in the proton radius puzzle, the muon anomalous magnetic moment, hints of lepton flavor non-universality in B decays, and searches for charged lepton flavor violation. For fun, a recent discovery in the Great Pyramid of Giza using muon tomography will also be discussed.

Elizabeth Wills (Drexel) - Probing Cosmic Ray Anisotropy in the Northern Hemisphere with Atmospheric Neutrinos
2018-01-26 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Cosmic Rays have remained an enigma for over a hundred years since their discovery. This talk focuses on a well-measured, yet similarly elusive feature; an unexplained structure in arrival direction spanning many energies and angular scales. This talk introduces a new way of exploring Cosmic Ray Anisotropy: observation through secondary neutrinos. Studying the cosmic rays’ neutral daughter particles with pointing capabilities, like neutrinos, could shed new light. This can be done at two levels; a source which produces cosmic rays must also produce high energy astrophysical neutrinos, and low energy atmospheric neutrinos are made when the cosmic rays interact with the atmosphere. This analysis focuses on atmospheric neutrinos detected by IceCube, a Cherenkov detector instrumenting a kilometer cubed of glacial ice at the South Pole. IceCube has studied the anisotropy and its energy dependence in the Southern sky using atmospheric muons.

Using IceCube and a high-acceptance dataset of atmospheric neutrinos created for this analysis, we are nearing the sensitivity threshold to observe the phenomenon in atmospheric neutrinos arriving from the Northern Hemisphere. This analysis focuses on energy ranges that correspond to the spatially-consistent lower energy features of the dipole structure. Due to the statistical limitations of the neutrino dataset in comparison to the cosmic ray datasets, we also introduce new methods for detecting signal along with the standard multipole analysis methods. These include a 1D relative intensity fit to determine the amplitude and phase of the dipole, and a 2D binned log-likelihood analysis focusing on searching for observed anisotropy maps from the Tibet collaboration. Future hope for the work is to create a single-detector all-sky map of the anisotropy, minimizing systematical difficulties combining datasets from separate collaborations.

Bjoern Lehnert (Carleton University) - Dark Matter Search with DEAP-3600 and the Importance of Rare Nuclear Decay Searches
2018-01-23 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The DEAP-3600 experiment is searching for dark matter with a single phase liquid argon (LAr) target, located at SNOLAB. For a background-free exposure of 3000 kg·yr, the projected sensitivity to the spin-independent WIMP-nucleon cross section at 100 GeV/c2 WIMP mass is 1e-46 cm2. The construction and filling of DEAP-3600 was completed in 2016 and the experiment is currently taken physics data. Recently, the first results of an initial commissioning data set were presented which could successfully demonstrate the detector performance and resulted in the leading limit on the WIMP-nucleon spin-independent cross section for argon.
In the first part of this seminar I will present the DEAP-3600 experiment and its recent results with an emphasis on radioactive backgrounds. In the second part of the seminar I will briefly describe a few recent investigations of rare beta and double beta decay processes such as 36Ar, 39Ar and 42Ar with DEAP but also other isotopes with gamma-spectroscopy setups. I will illustrate their importance in the context of radioactive backgrounds in other low background experiments and in the context of understanding nuclear structure. Especially the better understanding of nuclear models and their intrinsic parameters is needed to obtain more reliable nuclear matrix elements e.g. for neutrinoless double beta decay processes in order to connect the observed half-life to the the effective Majorana neutrino mass.

Hirotaka Ito - Numerical Simulations of Photospheric Emission from Collapsar Jets
2018-01-12 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
We explore the photospheric emission from a relativistic jet breaking out
from a massive stellar envelope based on relativistic hydrodynamical simulations and post- process radiation transfer calculations in three dimensions. It is shown that structures developed within the jet during its propagation have a significant imprint on the resulting emission. Particularly, we show that the viewing angle dependence of the emission properties caused by the lateral structure naturally reproduces the observed correlation between the peak energy and luminosity (Yonetoku relation). We also show that the emission possesses non-negligible degree of polarization.

Marco Salathe (LBL) - GRETA R&D
2017-12-15 12:00 - 13:00

Anna Zsigmond - GERDA neutrinoless double beta decay experiment
2017-12-08 08:00 - 17:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA

Yuan Mei (LBL) - TPC without charge multiplication: a CMOS direct readout towards neutrinoless double-beta decay and other applications
2017-12-01 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
High-pressure gaseous TPCs provide a unique combination of excellent energy resolution, event tracking for background discrimination, and scalability, which are ideal for neutrinoless double-beta decay searches. We are developing a pixelated charge readout plane filled with an array of CMOS sensors to harness the power of such a TPC. Each CMOS sensor has an exposed metal patch for direct charge collection and integrates charge sensitive amplifiers as well as signal processing and digitization/data transmission circuitry. The electronic noise is suppressed to a level that the required signal-to-noise ratio is achieved without the need of charge multiplication. It provides competitive energy resolution while improves on tracking capability, stability, and scalability compared to alternative readout schemes. Moreover, ions drifting in the gas can be read directly since the otherwise prohibitive ion avalanche is unnecessary. It enables the use of alternative gases and double-beta decay candidate isotopes such as $^{82}$SeF$_6$ gas, in which only ion drifting is possible. With modest modifications, the readout plane could be used in liquid noble gas and organic liquid TPCs for a broad range of applications. The design and the progress of the first prototype will be presented.

Holiday
2017-11-24 08:00 - 17:00

Katelin Schutz (UCB) - Excluding a thin dark matter disk in the Milky Way with Gaia DR1: Resurrecting the Dinosaurs
2017-11-10 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
If a component of the dark matter has dissipative interactions, it could collapse to form a thin dark disk in our Galaxy coincident with the baryonic disk. It has been suggested that dark disks could explain a variety of observed phenomena, including mass extinction events due to periodic comet impacts. Using the first data release from the Gaia space observatory, I will present the results of a search for a dark disk via its effect on stellar kinematics in the Milky Way. I will discuss our strong new limits that disfavor the presence of a thin dark matter disk and present updated measurements on the total matter density in the solar neighborhood.

Noah Kurinsky (Stanford) - Pushing to Low Mass with SuperCDMS SNOLAB: New Developments in Ultra-Low Threshold Dark Matter Detectors
2017-11-03 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
In the last few years, the dark matter field has bifurcated into experiments focused on wimp-scale dark matter with massive liquid noble detectors and experiments focused on so-called ‘hidden sectors’ dark matter, pushing small detectors to much lower energy resolutions. Low-mass dark matter searches, focusing on single eV-scale energy deposits, are sensitive to different backgrounds than their higher-threshold counterparts, including but not limited to infrared emissions from the experimental environment and low-rate cosmogenic contamination in the target materials. The traditional paradigm of 2-phase detectors used to discriminate between electronic and nuclear recoils is no longer effective, both because of experimental limitations and kinematic constraints. The low-mass reach of SuperCDMS SNOLAB is based on the idea of moving from a phonon+charge readout to a charge-mediated phonon readout; introducing degeneracy between our separate detection channels to achieve lower thresholds. In this talk I will discuss the theory behind the CDMS-HV detector technology and present exciting results from prototype detectors run at test facilities in the CDMS collaboration. I will then discuss the science reach given these results, and explore future directions with this technology.I will describe our development of a convolutional neural network (CNN) to learn to search for and characterize absorption lines in quasar spectra. Specifically, the algorithm discovers and measures the redshift and Hydrogen column density of damped Lya systems (DLAs). These systems dominate the neutral hydrogen gas of the universe, trace the interstellar medium of distant galaxies, and offer cosmological constraints on the build up of gas and heavy elements across cosmic time. I will discuss the lessons learned employing CNN techniques on large spectral datasets and the prospects for future analysis.

Xavier Prochaska (UCSD) - Deep Learning of Quasar Spectra
2017-10-27 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
I will describe our development of a convolutional neural network (CNN) to learn to search for and characterize absorption lines in quasar spectra. Specifically, the algorithm discovers and measures the redshift and Hydrogen column density of damped Lya systems (DLAs). These systems dominate the neutral hydrogen gas of the universe, trace the interstellar medium of distant galaxies, and offer cosmological constraints on the build up of gas and heavy elements across cosmic time. I will discuss the lessons learned employing CNN techniques on large spectral datasets and the prospects for future analysis.

Prabhat (NERSC at LBL) - Deep Learning for Science
2017-10-20 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Deep Learning has revolutionized the fields of computer vision, speech recognition and control systems. Can Deep Learning (DL) work for scientific problems? This talk will explore a variety of DOE/LBL applications that are currently benefiting from Deep Learning. We will review classification and regression problems in astronomy, cosmology, neuroscience, genomics and high-energy physics. We will outline several short and long-term challenges at the frontier of DL research, and speculate about the future of DL for data-intensive science.

Michael Walther (UCSB) - New Constraints on Thermal Evolution in the IGM from the Small Scale Lyα Forest Power Spectrum
2017-10-13 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The line-of-sight power spectrum (P_F(k)) of the Ly-α forest has proven to be a valuable tool for doing cosmological observations. It also not only allows to constrain cosmological parameters, but enables us to measure the thermal state of the IGM at redshifts z>1.8. While at large scales (k<0.02 s/km) P_F(k) has been accurately measured using the large number (10^3-10^5) of quasar sightlines from SDSS and BOSS, there are much less spectra available at smaller scales (larger k). Prior power spectrum measurements from high-resolution data only used several times less (QSO) spectra in our redshift range about 15 years ago whereas a few hundred became available in the meantime. We therefore performed a new measurement using 74 quasar sightlines with 1.8<z<3.4 significantly improving the precision of the small-scale P_F(k). Using this additional precision on small scales combined with the BOSS measurements on large scales enables us to accurately constrain the thermal cutoff scale of the IGM set by a combination of temperature broadening of Ly-α forest lines, and ‘Jeans’ smoothing due to baryonic pressure support. We perform an MCMC analysis based on Gaussian process based techniques for interpolation between a grid of high-resolution hydrodynamical simulations and using our new high-resolution dataset, the BOSS data, a recent X-SHOOTER analysis, and a previous HIRES/MIKE analysis at higher redshifts. This allows us to measure thermal evolution in the IGM from z=5.4 to z=1.8 showing a suggestive peak at z~3.3 that might be attributed to He reionization. These constraints will help solving the existing discrepancies in the IGM thermal evolution between different works using different techniques as existing degeneracies between different thermal parameters in the existing measurements can be broken in our analysis.and can be used to place limits on possible exotic sources of heating. Additionally a better knowledge of thermal evolution will also lead to better constraints of e.g. the nature of dark matter or neutrino masses by breaking degeneracies in those measurements and thereby improve our knowledge of the underlying cosmology.

Marie Lau (UC Santa Cruz) - Quasars Probing Quasars: the Circumgalactic Medium Surrounding z ~ 2 Quasars
2017-10-06 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Understanding the circumgalactic medium–the gaseous halo surrounding a galaxy, is an integral part to understanding galaxy evolution. The z ~ 2-3 universe is interesting as this is when the star formation rate and AGN activity peak. My work concludes the decade-long Quasars Probing Quasars survey designed for studying massive galaxy formation and quasar feedback. I use background quasar sightlines that pass close to foreground quasars to study the circumgalactic medium of quasar-host galaxies in absorption. My sample of 149 quasar pairs involve spectra taken with 17 different optical and near IR instruments. I present results on the statistical and physical properties of the quasar circumgalactic medium. My results pose challenges for cosmological hydrodynamic simulations to produce a substantial cool gas reservoir surrounding quasars, that is also enriched and exhibits extreme kinematics.

I will discuss other science goals that can be facilitated using the spectral databases and absorption-line analysis tools built. If there is interest, I will show preliminary results on a peculiar tidal disruption event and evidence for deep internal mixing in red giants.

Stephen Portillo (Harvard) - Improved Source Detection in Crowded Fields using Probabilistic Cataloging
2017-09-29 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Cataloging is challenging in crowded fields because sources are extremely covariant with their neighbors and blending makes even the number of sources ambiguous. We present the first optical probabilistic stellar catalog, cataloging a crowded (~0.1 sources per pixel) Sloan Digital Sky Survey r band image from M2. Probabilistic cataloging returns an ensemble of catalogs inferred from the image and thus can capture source-source covariance and deblending ambiguities. By comparing to a traditional catalog of the same image and a Hubble Space Telescope catalog of the same region, we show that our catalog ensemble better recovers sources from the image. It goes more than a magnitude deeper than the traditional catalog while having a lower false discovery rate brighter than 20th magnitude. Future telescopes will be more sensitive, and thus more of their images will be crowded. We detail our efforts to extend probabilistic cataloging to galaxies, making the method applicable to the data that will be collected in the Large Synoptic Survey Telescope era.

Yury Kolomensky (LBNL) - New results from the CUORE experiment
2017-09-22 12:00 - 13:00

Oliver Just (RIKEN)​ - Modeling remnants of neutron-star mergers and core-collapse supernovae
2017-09-15 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Neutron-star mergers and core-collapse supernovae are promising events to herald a new era of multi-messenger astronomy, as they release substantial amounts of energy in gravitational waves, neutrinos, and electromagnetic emission. Moreover, these events are connected to long-standing physics questions related to, e.g., heavy-element nucleosynthesis, gamma-ray bursts, and the nuclear equation of state. However, while offering a unique laboratory to investigate matter and spacetime under extreme conditions, these events are particularly difficult to model theoretically, one of the most challenging, but equally important ingredients being the neutrino transport. The latter is not only responsible for cooling the compact remnant and heating its surroundings, but it may also have a major leverage on the nucleosynthesis conditions in the ejecta and the eventual launch of a polar jet. In this talk I will review the current state-of-the-art in modeling mergers and core-collapse supernovae and present some recent results that we obtained from numerical simulations.
