Calendar

Mar
13
Mon
Pizza Lunch: Jean McKeever
Mar 13 @ 12:30 pm – 1:30 pm
Pizza Lunch: Jean McKeever @ AY 119

Red Giants in Eclipsing Binary Systems

Jean McKeever

 

Mar
17
Fri
Colloquium: OPEN
Mar 17 @ 3:15 pm – 4:15 pm
Mar
24
Fri
No Colloquium (Spring Break)
Mar 24 @ 3:15 pm – 4:15 pm
Mar
27
Mon
Pizza Lunch: Tom
Mar 27 @ 12:30 pm – 1:15 pm
Pizza Lunch: Tom @ AY 119

Something about CVs so Jason gets a break…. and to bore the rest of you to death.

Mar
28
Tue
Joint Physics/Astronomy Colloquium: William Newman
Mar 28 @ 4:00 pm – 5:00 pm
Joint Physics/Astronomy Colloquium: William Newman @ Gardiner Hall 229, Physics. Dept. | Ames | Iowa | United States

Giant Planet Shielding of the Inner Solar System Revisited: Blending Celestial Mechanics with Advanced Computation

Dr. William Newman, UCLA

The Earth has sustained during the last billion years as many as five catastrophic collisions with asteroids and comets which led to widespread species extinctions. Our own atmosphere was literally blown away 4.5 billion years ago by a collision with a Mars-sized impactor. However, collisions with comets originating in the outer solar system accreted much of the present-day atmosphere. Relatively advanced life on our planet is the beneficiary of a number of impact events during Earth’s history which built our atmosphere without destroying a large fraction of terrestrial life. Using very high precision Monte Carlo integration methods to explore the orbital evolution over hundreds of millions of years followed by the application of celestial mechanical techniques, the presentation will explain directly how Earth was shielded by the combined influence of Jupiter and Saturn, assuring that only 1 in 100,000 potential collisions with the Earth will materialize.

 

Mar
31
Fri
Colloquium PhD Defense: Sean Markert
Mar 31 @ 3:15 pm – 4:15 pm
Colloquium PhD Defense: Sean Markert

THE SIGNAL OF WEAK GRAVITATIONAL LENSING FROM GALAXY
GROUPS AND CLUSTERS,

Dr. S. Markert, NMSU

 

The weak gravitational lensing of galaxy clusters is a valuable tool. The deflection of light around a lens is solely dependent on the underlying distribution of foreground mass, and independent of tracers of mass such as the mass to light ratio and kinematics. As a direct probe of mass, weak lensing serves as an independent calibration of mass-observable relationships. These massive clusters are objects of great interest to astronomers, as their abundance is dependent on the conditions of the early universe, and accurate counts of clusters serve as a test of cosmological model. Upcoming surveys, such as LSST and DES, promise to push the limit of observable weak lensing, detecting clusters and sources at higher redshift than has ever been detected before. This makes accurate counts of clusters of a given mass and redshift, and proper calibration of mass-observable relationships, vital to cosmological studies.
We used M> 10 13.5 h −1 M ⊙ halos from the MultiDark Planck simulation at z∼0.5 to study the behavior of the reduced shear in clusters. We generated 2D maps of convergence and shear the halos using the GLAMER lensing library. Using these maps, we simulated observations of randomly placed background sources, and generate azimuthal averages of the shear. This reduced shear profile, and the true reduced shear profile of the halo, is fit using analytical solutions for shear of the NFW, Einasto, and truncated NFW density profile. The masses of these density profiles are then compared to the total halo masses from the halo catalogs.
We find that fits to the reduced shear for halos extending past ≈ 2 h −1 Mpc are fits to the noise of large scale structure along the line of sight. This noise is largely in the 45 ◦ rotated component to the reduced tangential shear, and is a breakdown in the approximation of g tan ≈g tot required for density profile fitting of clusters. If fits are constrained to a projected radii of < 2 h −1 Mpc, we see massively improved fits insensitive to the amount of structure present along the line of sight.

Apr
3
Mon
Pizza Lunch: Nancy Chanover & James McAteer
Apr 3 @ 12:30 pm – 1:30 pm
Pizza Lunch: Nancy Chanover & James McAteer

The AAS: What Has it Done for You Lately?

Apr
7
Fri
Colloquium: Lauren Waszek (Host: Jason Jackiewicz)
Apr 7 @ 3:15 pm – 4:15 pm
Colloquium: Lauren Waszek (Host: Jason Jackiewicz) @ BX102

The growth of Earth’s inner core: a new technique to constrain seismic properties in its outermost layers

Dr. Lauren Waszek, Department of Physics, NMSU

The inner core displays a hemispherical difference in seismic velocity, attenuation, and anisotropy, which is well-established from seismic studies. Recent observations reveal increasingly complex and regional features. However, geodynamical models generally only attempt to explain the basic east-west asymmetry. Regional seismic features, such as depth-dependence anisotropy or variation in hemisphere boundaries, are difficult to reproduce and relatively poorly constrained by seismic data. Processes to generate these complex features are debated.

The structures of the inner core are suggested to be formed as the inner core grows over time. Thus, the most recently-formed outermost layers likely hold the key to understanding the geodynamical mechanisms generating the inner core properties. Current datasets of the uppermost inner core and inner core boundary are limited by uneven data coverage, however. In the very uppermost inner core, seismic waves arrive with similar travel times and interfere, making measurements difficult.

Despite the uneven coverage of current datasets, we can use them to infer a very slow inner core super-rotation. The first ever global tomographical inversion for the inner core allows us to make regional observations, and map the lateral variation in the hemispherical structures. In the uppermost inner core, we have developed a new waveform modeling technique with synthetic data to separate these seismic phases, allowing us to measure the seismic properties in the very uppermost inner core. This, in combination with geodynamical modeling, will help us determine how the inner core hemispheres and other features are generated.

 

 

 

 

 

 

Tombaugh Observatory Open House
Apr 7 @ 9:00 pm – 10:00 pm
Tombaugh Observatory Open House

9Open to the public.

Faculty member: James McAteer

Graduate students: Jodi Berdis, Caitlin Doughty, Ethan Dederick

Apr
14
Fri
No Colloquium (Spring Holiday)
Apr 14 @ 3:15 pm – 4:15 pm