Breaking the Self-Similarity of Galaxy Formation: A Circumgalactic Medium Perspective
Benjamin Oppenheimer, University of Colorado Boulder
If you could see a dark matter halo directly without knowing the scale, you probably could not distinguish a Milky Way halo from a cluster-sized halo. However, if you look at the galaxies, you would likely see a dominant spiral galaxy in the former and a many quenched and quenching galaxies in the latter. The study of galaxy formation aims to understand how very different galaxies form in dark matter halos of different masses. I will argue for the importance of understanding the gaseous baryons in this context. In contrast to the hot intracluster medium detected in emission in clusters, the circumgalactic medium (CGM) has to be probed by absorption lines toward background quasars and tells a vastly different and complicated story. I will demonstrate, with the aid of hydrodynamic simulations, how the CGM is multi-phase (with cool ~10^4 K clouds embedded in a hot, ambient medium), plus how non-equilibrium ionization processes altering the heavy element ions we probe in spectra. The next frontiers in the CGM require understanding the dynamics encoded not only in absorption line spectra of the UV, but in the X-ray via emission and absorption.
Science with the James Webb Space Telescope
Jane Rigby, NASA/GSFC
NASA’s James Webb Space Telescope (JWST) will have revolutionary capabilities and sensitivity for imaging and spectroscopy from 0.7 to 28 micron. JWST should make major scientific advances across astrophysics, including the physics of reionization, galaxy formation and assembly, planetary science, and extrasolar planets. In anticipation of a scheduled launch in 2019, JWST Cycle 1 Guest Observer proposals will be due in spring of 2018. I will review the scientific capabilities of the telescope, the integration and test program, and how observers will plan observations and analyze JWST data.
The statistical study of solar dimmings and their eruptive counterparts
Larisza Krista, Cu/CIRES, NOAA/NCEI
Results are presented from analyzing the physical and morphological properties of 154 dimmings (transient coronal holes) and the associated flares and coronal mass ejections (CMEs). Each dimming in the catalog was processed with the semi-automated Coronal Dimming Tracker (CoDiT) using Solar Dynamics Observatory AIA 193 Å observations and HMI magnetograms. Instead of the typically used difference images, the transient dark regions were detected “directly” in extreme ultraviolet (EUV) images. This allowed us to study dimmings as the footpoints of CMEs—in contrast with the larger, diffuse dimmings seen in difference images that represent the projected view of the rising, expanding plasma. Studying the footpoint-dimming morphology allowed us to better understand the CME structure in the low corona. While comparing the physical properties of dimmings, flares, and CMEs, the relationships between the different parts of this complex eruptive phenomenon were identified: larger dimmings were found to be longer-lived, which suggests that it takes longer to “close down” large open magnetic regions. During their growth phase, smaller dimmings were found to acquire a higher magnetic flux imbalance (i. e., become more unipolar) than larger dimmings. Furthermore, the EUV intensity of dimmings (indicative of local electron density) was found to correlate with how much plasma was removed and how energetic the eruption was. Studying the morphology of dimmings (single, double, fragmented) also helped identify different configurations of the quasi-open magnetic field.
Dr Larisza Krista received an MSc degree in astrophysics in 2007 from Eotvos Lorand University, in Budapest, Hungary. She did her PhD at Trinity College Dublin (Ireland) as a Government of Ireland Scholar, on “The Evolution and Space Weather Effects of Solar Coronal Holes”. She moved to Boulder in 2011 to accept a research scientist position at CU/CIRES in residence at NOAA/SWPC. She has also been a long-term scientific visitor at the High Altitude Observatory, where she collaborates with Dr Scott McIntosh. Her main interests involve the evolution of open solar magnetic field regions over the solar cycle as well as the related heliospheric structures and geomagnetic effects.