Calendar

Oct
30
Fri
Colloquium: Sergio Rodriguez
Oct 30 @ 3:15 pm – 4:15 pm
Colloquium: Sergio Rodriguez @ BX102

BOSS DR12 survey: Clustering of galaxies and Dark Matter Haloes

Sergio Rodriguez, UAM, Madrid and Cal. Berkeley

BOSS SDSS-III is the largest redshift survey for the large scale structure and a powerful sample for the study of the low redshift Baryonic Acoustic Oscillations. We combine the features of the survey, such as, geometry, angular incompleteness and stellar mass incompleteness, with the BigMultiDark cosmological simulation to do a study of the distribution of galaxies in the dark matter halos. Using this large N-Body simulation and the halo abundance matching technique, we found a remarkably good agreement with the 2-point and 3-point statistics of the data.

Dec
4
Fri
Colloquium: Brian Jackson
Dec 4 @ 3:15 pm – 4:15 pm
Colloquium:  Brian Jackson @ BX102

On the Edge: Exoplanets with Orbital Periods Shorter Than a Peter Jackson Movie

Brian Jackson, Boise State Univeristy

From wispy gas giants to tiny rocky bodies, exoplanets with orbital periods of several days and less challenge theories of planet formation and evolution. Recent searches have found small rocky planets with orbits reaching almost down to their host stars’ surfaces, including an iron-rich Mars-sized body with an orbital period of only four hours. So close to their host stars that some of them are actively disintegrating, these objects’ origins remain unclear, and even formation models that allow significant migration have trouble accounting for their very short periods. Some are members of multi-planet system and may have been driven inward via secular excitation and tidal damping by their sibling planets. Others may be the fossil cores of former gas giants whose atmospheres were stripped by tides.

In this presentation, I’ll discuss the work of our Short-Period Planets Group (SuPerPiG), focused on finding and understanding this surprising new class of exoplanets. We are sifting data from the reincarnated Kepler Mission, K2, to search for additional short-period planets and have found several new candidates. We are also modeling the tidal decay and disruption of close-in gaseous planets to determine how we could identify their remnants, and preliminary results suggest the cores have a distinctive mass-period relationship that may be apparent in the observed population. Whatever their origins, short-period planets are particularly amenable to discovery and detailed follow-up by ongoing and future surveys, including the TESS mission.

Mar
4
Fri
Colloquium: Gail Zasowski (Host: Drew Chojnowski)
Mar 4 @ 3:15 pm – 4:15 pm
Colloquium:  Gail Zasowski  (Host: Drew Chojnowski) @ BX102

New Tools for Galactic Archaeology from the Milky Way

Gail Zasowski, John Hopkins University

One of the critical components for understanding galaxy evolution is understanding the Milky Way Galaxy itself — its detailed structure and chemodynamical properties, as well as fundamental stellar physics, which we can only study in great detail locally.  This field is currently undergoing a dramatic expansion towards the kinds of large-scale statistical analyses long used by the extragalactic and other communities, thanks in part to an enormous influx of data from space- and ground-based surveys.  I will describe the Milky Way and Local Group in the context of general galaxy evolution and highlight some recent developments in Galactic astrophysics that take advantage of these big data sets and analysis techniques.  In particular, I will focus on two diverse approaches: one to characterize the distribution and dynamics of the carbon-rich, dusty diffuse ISM, and one to map the resolved bulk stellar properties of the inner disk and bulge.  The rapid progress in these areas promises to continue, with the arrival of data sets from missions like SDSS, Gaia, LSST, and WFIRST.

Apr
8
Fri
Colloquium PhD Defense: Meredith Rawls
Apr 8 @ 3:00 pm – 4:00 pm
Colloquium PhD Defense: Meredith Rawls @ BX102

Red Giants in Eclipsing Binaries as a Benchmark for Asteroseismology

Meredith Rawls, NMSU

May
31
Tue
Colloquium PhD Defense: Diane Feuillet
May 31 @ 3:00 pm – 4:00 pm
Colloquium PhD Defense: Diane Feuillet @ Dominici106

Ages and Abundance of Local Stellar Populations

Diane Feuillet, NMSU

Aug
26
Fri
Colloquium PhD Defense: Kyle Uckert
Aug 26 @ 3:15 pm – 4:15 pm
Colloquium PhD Defense: Kyle Uckert @ BX102

Characterization of Biosignatures within Geologic Samples Analyzed using a Suite of in situ Techniques

Kyle Uckert, NMSU   

Abstract:
I investigated the biosignature detection capabilities of several in situ techniques to evaluate their potential to
detect the presence of extant or extinct life on other planetary surfaces. These instruments included: a laser desorption
time-of- flight mass spectrometer (LD-TOF-MS), an acousto-optic tunable filter (AOTF) infrared (IR) point spectrometer, a
laser-induced breakdown spectrometer (LIBS), X-ray diffraction (XRD)/X-ray fluorescence (XRF), and scanning electron
microscopy (SEM)/energy dispersive X-Ray spectroscopy (EDS). I measured the IR reflectance spectra of several speleothems
in caves in situ to detect the presence of biomineralization. Microorganisms (such as those that may exist on other solar
system bodies) mediate redox reactions to obtain energy for growth and reproduction, producing minerals such as
carbonates, metal oxides, and sulfates as waste products. Microbes occasionally become entombed in their mineral
excrement, essentially acting as a nucleation site for further crystal growth. This process produces minerals with a
crystal lattice distinct from geologic precipitation, detectable with IR reflectance spectroscopy. Using a suite of
samples collected from three subterranean environments, along with statistical analyses including principal component
analysis, I measured subsurface biosignatures associated with these biomineralization effects, including the presence of
trace elements, morphological characteristics, organic molecules, and amorphous crystal structures.

I also explored the optimization of a two-step LD-TOF-MS (L2MS) for the detection of organic molecules and other
biosignatures. I focused my efforts on characterizing the L2MS desorption IR laser wavelength dependence on organic
detection sensitivity in an effort to optimize the detection of high mass (≤100 Da) organic peaks. I analyzed samples
with an IR reflectance spectrometer and an L2MS with a tunable desorption IR laser whose wavelength range (2.7 – 3.45
microns) overlaps that of our IR spectrometer (1.6 – 3.6 microns), and discovered a IR resonance enhancement effect. A
correlation between the maximum IR absorption of organic functional group and mineral vibrational transitions – inferred
from the IR spectrum – and the optimal IR laser configuration for organic detection using L2MS indicates that IR
spectroscopy may be used to inform the optimal L2MS IR laser wavelength for organic detection. This work suggests that a
suite of instruments, particularly LD-TOF-MS and AOTF IR spectroscopy, has strong biosignature detection potential on a
future robotic platform for investigations of other planetary surfaces or subsurfaces.

Jan
27
Fri
Colloquium: Bryan Butler (Host: Nancy Chanover)
Jan 27 @ 3:15 pm – 4:15 pm
Colloquium: Bryan Butler (Host: Nancy Chanover) @ BX 102

Observations of Solar System Bodies with the VLA and ALMA

Dr. Bryan Butler, NRAO

Observations of solar system bodies at wavelengths from submm to meter wavelengths provide important and unique information about those bodies. Such observations probe to depths unreachable at other wavelengths – typically of order 10-20 wavelengths for bodies with solid surfaces, and as deep as tens of bars for those with thick atmospheres (the giant planets). In the past five years, two instruments have been commissioned which have revolutionized the ability to make very sensitive, high-resolution observations at these wavelengths: the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/Submillimeter Array (ALMA). I will present a discussion of results over the past five years from observations from both the VLA and ALMA. These include observations of the atmospheres of all of the giant planets, the rings of Saturn, and the surfaces of many icy bodies in the outer solar system. I will also present plans for the Next Generation Very Large Array (ngVLA), the next step for millimeter to centimeter wavelength interferometry.

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.