Calendar

Oct
20
Fri
Colloquium: Benjamin Oppenheimer (Host: Kristian Finlator)
Oct 20 @ 3:15 pm – 4:15 pm
Colloquium: Benjamin Oppenheimer (Host: Kristian Finlator) @ BX102

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.

 

 

Oct
23
Mon
Pizza Lunch: Kristian Finlator
Oct 23 @ 12:30 pm – 1:30 pm
Pizza Lunch: Kristian Finlator @ AY 119

Vastly Improved Simulations of the Hydrogen Reionization Epoch: Too Much for One Paper?

Nov
6
Mon
Pizza Lunch: Ethan Dederick
Nov 6 @ 12:30 pm – 1:30 pm
Pizza Lunch: Ethan Dederick @ AY 119

Cool Science Results

Nov
9
Thu
Special Pizza Lunch: Jane Rigby
Nov 9 @ 1:00 pm – 2:00 pm
Special Pizza Lunch: Jane Rigby @ AY 119

Galaxy Evolution in High Definition Via Gravitational Lensing

Dr. Jane Rigby

Deputy Project Scientist for JWST, NASA Goddard Space Flight Center

Abstract: In hundreds of known cases, “gravitational lenses” have deflected, distorted, and amplified images of galaxies or quasars behind them.  As such, gravitational lensing is a way to “cheat” at studying how galaxies evolve:  lensing can magnify galaxies by factors of 10–100 times, transforming them from objects we can barely detect to bright objects we can study in detail.   For such rare objects, we are studying how galaxies formed stars at redshifts of 1–4, the epoch when most of the Universe’s stars were formed. For lensed galaxies, we can obtained spectral diagnostics that are currently unavailable for the distant universe, but will become routine with next-generation telescopes.

In particular, I’ll discuss MEGaSaURA, The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas, which comprises high signal-to-noise, medium spectral resolution (R~3300) spectra of 15 extremely bright gravitationally lensed galaxies at redshifts of 1.6<z<3.6.   The sample, drawn from the SDSS Giant Arcs Survey, are many of the brightest lensed galaxies known.  The MEGaSaURA spectra reveal a wealth of spectral diagnostics: absorption from the outflowing wind; nebular emission lines that will be key diagnostics for JWST, GMT, and TMT; and photospheric absorption lines and P Cygni profiles from the massive stars that power the outflow.

Nov
10
Fri
Colloquium: Jane Rigby (Host: Moire Prescott)
Nov 10 @ 3:15 pm – 4:15 pm
Colloquium: Jane Rigby (Host: Moire Prescott) @ BX102

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.

Nov
13
Mon
Pizza Lunch: James Lewis
Nov 13 @ 12:30 pm – 1:30 pm
Pizza Lunch: James Lewis @ AY 119

Multivariate Analysis of the CGM

Nov
17
Fri
Colloquium: Larisza Krista (Host: James McAteer)
Nov 17 @ 3:15 pm – 4:15 pm

The statistical study of solar dimmings and their eruptive counterparts

Larisza Krista, Cu/CIRES, NOAA/NCEI

Picture1Results 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.

BIO

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.

 

 

Nov
27
Mon
Pizza Lunch: Rachel Marra and Trevor Picard
Nov 27 @ 12:30 pm – 1:30 pm
Pizza Lunch: Rachel Marra and Trevor Picard @ AY 119

ASTR 598 Talk

Dec
1
Fri
Colloquium: Laura Keating (Host: Kristian Finlator)
Dec 1 @ 3:15 pm – 4:15 pm
Colloquium: Laura Keating (Host: Kristian Finlator) @ BX102

Colloquium Title

Colloquium Speaker Name, Affiliation

Abstract text

Dec
4
Mon
Pizza Lunch: Karen Kinemuchi
Dec 4 @ 12:30 pm – 1:30 pm
Pizza Lunch: Karen Kinemuchi @ AY 119

Life at Apache Point Observatory