Spring 2018

12:40 - 1:30 PM every Thursday, location = 131 A & B Campbell Hall.
  • To volunteer for a 12 minute talk + 4 minutes for questions, send email to Paul Kalas (kalas@berkeley.edu).  
  • This forum is mainly for local scientists of any level to present their work to a broad spectrum of the department, and usually includes one short talk by the astronomy colloquium speaker of the day.  
  • Subjects can include personal scientific research, reporting on other work appearing in journals, education and public outreach efforts, science policy, and professional development issues.
  • It is preferred if speakers bring their own laptop, cable adapter, and pointer.  Presentations may also use the whiteboard.

Bold means confirmed

January 18: 
  • Xander Tielens (Leiden/UCB) -   [CII] 158um square degree survey of Orion
  • Kara Kundert (UCB) -  HYPERION
  • Pieter van Dokuum (Yale) colloq. speaker -  IMF gradients in massive galaxies

January 25:
  • Kareem El-Badry (UCB) -  "Constraining galaxies' gas kinematics from unresolved HI data"
  • Josh Bloom (UC Berkeley) -  A recurrent neural network for classification of unevenly sampled variable stars
  • Katherine de Kleer (Caltech) colloq. speaker -  3D mapping of the Solar System's icy moons with ALMA
February 1:
  • Dave DeBoer (UCB) -  An update on HERA
  • Dan Weisz (UCB) -  “JWST Early Release Science: Resolved Stellar Populations”
  • Mike Wong (UCB)  -  The SNAP Miniature Entry Probe for Uranus (Mission Concept)
February 8:
  • Zack Slepian (UCB) -  A model for embedded stellar core formation in filaments
  • Miguel Zumalacarregui (UCB) -  Gravitational Wave tests of Gravity and Dark Energy
  • Mark Sullivan (Southhampton) colloq. speaker -  The rate of calcium-rich transients in the local universe
February 15:
  • David Khatami (UCB) -  An Unusually Fast and Bright Supernova Caught by Kepler
  • Danny Goldstein (UCB) -  Evidence for Sub-Chandrasekhar Mass Type Ia Supernovae from an Extensive Survey of Radiative Transfer Models
  • Joss Bland-Hawthorn (U. Sydney)  colloq. speaker -  Chemical tagging in ultra faint dwarf galaxies

February 22:
  • Ann Zabludoff (Arizona) colloq. speaker -  Attack of the Lyman-Alpha Blobs
  • Town Hall on the climate survey (Eugene Chiang)
  • Town Hall on the climate survey, cont'd.

March 1:
  • Stephen Ro (UCB) - Launching Winds from Wolf-Rayet Stars
  • Richard Anantua (UCB) -  Sgr A* Emission Parametrizations from GRMHD Simulations
  • Dave Stevenson (Caltech) colloq. speaker -  On the Role of Dissolved Gases in the Atmosphere Retention of Low-Mass Low-Density Planets

March 8:
  • Gibor Basri (UCB) -  A new relation between starspots and stellar rotation
  • Fatima Abdurrahman (UCB) -  First On-Sky Results for Imaka, a Ground Layer Adaptive Optics Instrument
  • Charles Lada (CfA) colloq. speaker -  Relating cloud structure and star formation
March 15:
  • Imke de Pater (UCB) -  ERS observations of the Jovian System as a demonstration of JWST’s capabilities for Solar System science
  • Michelle Myers (UCB) -  GRB Host Galaxies: Providing Snapshots of Stellar Nurseries At Different Redshifts
  • Zach Berta-Thompson (Colorado) colloq. speaker -  Transiting Exoplanet Community JWST Early Release Science Program
March 22:
  • Micah Brush (UCB) -  The two-body problem in academic hiring
  • Elena Massara (UCB) -  WFIRST: The impact of confusing Hβ with [O III] on the determination of the BAO peak
  • Stella Offner (UT Austin)  colloq. speaker -  Toolkits for Turbulence
March 29: UC Berkeley Spring Break

April 5:
  • Elena Giusarma (LBL) -  Exploring neutrino masses with Large Scale Structure
  • Carina Cheng (UCB) -  Updated 21cm Power Spectrum Results from the PAPER Experiment
  • Dimitri Mawet (Caltech) colloq. speaker -  HabEx: The Habitable Exoplanet Observatory

April 12:
  • Shirley Ho (LBNL / CCA) -  Cosmological Analysis with Deep Learning
  • Gina Duggan (Caltech) -  Implications of Barium Abundances for the Chemical Enrichment of Dwarf Galaxies
  • Avishai Dekel (Jerusalem) colloq. speaker -  On the Kennicutt-Schmidt Relation and Supernova Feedback

April 19:  Doctoral Dissertation Seminars (Exit Talks; 20 minutes + 5 minutes for questions)
  • Jason Wang (12:40 - 1:05 PM)
    Title: Footage of Planets in Their Native Habitats or: How I Automated My PhD and Made Some Viral Videos

    My PhD thesis revolves around the Gemini Planet Imager Exoplanet Survey (GPIES), a multi-year survey of 600 stars to image young Jovian exoplanets. I helped commission the instrument and develop the data reduction pipelines for GPIES, including the open-source pyKLIP package which currently supports data from most high-contrast imaging instruments. I also built the Data Cruncher, a real-time, asynchronous, and distributed framework that processes data through multiple data reduction pipelines. The Data Cruncher integrates into a larger data processing architecture that automatically downloads, archives, and processes data in real-time, as well as reprocesses the entire campaign in a single day. I also have been working on measuring the orbits of exoplanets. I developed a technique to obtain precise astrometry of exoplanets that analytically forward models the effects of principal component analysis on the PSF of the planet. I demonstrated one milliarcsecond astrometry with GPI on the exoplanet β Pic b, ruling out a once every 20-year transit of the exoplanet at 10-sigma significance. I'll also show some current work on searching for stable orbits of the four planets in the HR 8799 system using dynamical constraints. To highlight the orbits of these exoplanets, I used a motion interpolation algorithm to create time-lapse videos of these systems. The HR 8799 video went viral, getting over a million views online and making it on to Astronomy Picture of the Day. 

  • Chelsea Harris (4:10 - 4:30 PM) 
Title: "Simulations of Type Ia Supernovae Interacting with Diverse Circumstellar Environments"

In this talk I will discuss the piece of my thesis in which I modeled the interaction of type Ia supernovae (SNe Ia) with circumstellar material (CSM) created by eruptive mass loss episodes like novae. Such an environment is a strong constraint on the yet-unknown progenitor system for these events. The circumstellar environment of SNe can be observed as radiation from the shock of the SN ejecta impacting the CSM, but interpretation requires hydrodynamic and radiation calculations. Before my thesis work, the only utilitarian models available were tailored to wind interaction (for core-collapse supernovae) and ISM interaction (for supernova remnants). These cannot describe the nova shell interaction, rendering observations of such a phenomenon effectively useless and limiting our ability to determine the occurrence rate of such shells. So I simulated the interaction of a SN Ia with low mass and geometrically thin CSM representing a nova shell. I found a new way to place upper limits on CSM density from data at radio frequencies that is simple for anyone to use. I used and extended these models to analyze PTF11kx and critique the use of optical emission lines as CSM density indicators. I joined a collaboration to search for PTF11kx analogs in the near-UV that successfully detected the second known case of delayed interaction in an SN Ia, and used my simulated light curves to constrain its circumstellar environment.

April 26:  Doctoral Dissertation Seminars (Exit Talks; 20 minutes + 5 minutes for questions)
  • Danny Goldstein (12:40 - 1:05 PM):

    Title: Foundations of Strongly Lensed Supernova Cosmology

    In this talk I will present solutions to some problems associated with using strongly gravitationally lensed supernovae (gLSNe) to measure the cosmological parameters.  Chief among these are new methods for finding gLSNe and extracting their time delays in the presence of microlensing. The latter of these results involved performing simulations of radiation transport in supernova atmospheres. I will also talk about how these simulations provided evidence that some Type Ia supernovae come from sub-Chandrasekhar mass progenitors.

  • Kaylan Burleigh (4:10 - 4:35)

            TitleHow much science (Star Formation and Cosmology) can you buy with 10 million CPU hours? 

I will highlight the research in Star Formation and Observational Cosmology I’ve completed over the last six years. High Performance Computing and statistics are the glue that connects these seemingly disparate projects. Stars gain mass by magnetized and supersonically turbulent gas falling onto them. However, the rate of mass gain is not well constrained because such a complicated environment is hard to model, so I performed 3D magnetohydrodynamic simulations to estimate it for a subset of the parameter space. The Dark Energy Spectroscopic Instrument (DESI) will obtain 30M spectra of galaxies to make a sub-percent measurement of the expansion rate of the universe at various times in the past. This sample of 30M galaxies is currently being extracted from multi-wavelength images of the night sky (about 100 TBs), which come from a three-telescope galaxy survey (the Legacy Survey). I will go into technical detail about the imaging pipeline that extracts these galaxies, especially the algorithms and its biases and systematics. I hope to convince you that the science (and software) resulting from my thesis are worth six years of grad school and 10 million CPU hours.

  • Drummond Fielding (4:35 - 5:00)
           Title:  Interplay of Galactic Winds and Circumgalactic Media

            The flow of gas through the circumgalactic medium (CGM) regulates galaxy growth over cosmic time. Observations have recently revealed a complex multi-phase structure in the CGM that has challenged many of the established theories and highlights significant gaps in our understanding of this critical aspect of galaxy formation. The spatial scales relevant to the CGM span a huge range with its structure and evolution determined by small- and large-scale phenomena, such as galactic winds, thermal instability, and cosmological accretion. I will describe my efforts to understand the details and interplay of these multi-scale processes—paying particular attention to the origin and strength of galactic winds—in order to develop a coherent, observationally consistent picture of the CGM.