Calendar

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

Title

Dr. Lauren Waszek, Department of Physics, NMSU

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
10
Mon
Pizza Lunch: Laurel Farris
Apr 10 @ 12:30 pm – 1:30 pm
Pizza Lunch: Laurel Farris @ AY 119

Determining the size of coronal bright points using cross-correlation methods

Laurel Farris

 

Apr
14
Fri
No Colloquium (Spring Holiday)
Apr 14 @ 3:15 pm – 4:15 pm
Apr
21
Fri
Colloquium: George Becker (Host: Kristian Finlator)
Apr 21 @ 3:15 pm – 4:15 pm
Colloquium: George Becker (Host: Kristian Finlator) @ BX102

George Becker

Apr
28
Fri
Colloquium: Cameron Hummels (Host: Chris Churchill)
Apr 28 @ 3:15 pm – 4:15 pm
Colloquium: Cameron Hummels (Host: Chris Churchill) @ BX102

Dr. Cameron Hummels (Caltech)

Galaxy Evolution via Simulations

Abstract: TBA

 

May
5
Fri
Colloquium PhD Defense: Jacob Vander Vliet
May 5 @ 2:00 pm – 3:00 pm
Colloquium PhD Defense: Jacob Vander Vliet @ BX102

HydroART Simulations of Galaxies: Filaments and Halos

Tombaugh Observatory Open House
May 5 @ 9:00 pm – 10:00 pm
Tombaugh Observatory Open House

Open to the public.

Faculty member: Jon Holtzman

Graduate students: Laurel Farris, Drew Chojnowski

 

http://whatsouttonight.com/Resources/2016SepSkyWOT.pdf