Calendar

Sep
1
Fri
Colloquium: Isak Wold (Host: Moire Prescott)
Sep 1 @ 3:15 pm – 4:15 pm
Colloquium: Isak Wold (Host: Moire Prescott) @ BX102

A Faint Flux-Limited LAE Sample at z = 0.3

Isak Wold, UT Austin

Observational surveys of Lya emitters (LAEs) have proven to be an efficient method to identify and study large numbers of galaxies over a wide redshift range. To understand what types of galaxies are selected in LAE surveys – and how this evolves with redshift – it is important to establish a low-redshift reference sample that can be directly compared to high-redshift samples.  The lowest redshift where a direct Lya survey is currently possible is at a redshift of z~0.3 via the Galaxy Evolution Explorer (GALEX ) FUV grism data. Using the z~0.3 GALEX sample as an anchor point, it has been suggested that at low redshifts high equivalent width (EW) LAEs become less prevalent and that the amount of escaping Lya emission declines rapidly.  A number of explanations for these trends have been suggested including increasing dust content, increasing neutral column density, and/or increasing metallicity of star-forming galaxies at lower redshifts. However, the published z~0.3 GALEX sample is pre-selected from bright NUV objects.  Thus, objects with strong Lya emission but faint continuum (high-EW LAEs) could be missed.  In this talk, I will present my efforts to re-reduce the deepest archival GALEX FUV grism data and obtain a sample that is not biased against high-EW LAEs.  I will discuss the implications of this new sample on the evolutionary trends listed above.

Mar
28
Wed
Colloquium PhD Thesis Defense: Ethan Dederick
Mar 28 @ 3:15 pm – 4:15 pm
Colloquium PhD Thesis Defense: Ethan Dederick @ Science Hall 109

Seismic Inferences of Gas Giant Planets: Excitation & Interiors

Ethan Dederick, NMSU

Seismology has been the premier tool of study for understanding the interior structure of the Earth, the Sun, and even other stars. In this thesis we develop the framework for the first ever seismic inversion of a rapidly rotating gas giant planet. We extensively test this framework to ensure that the inversions are robust and operate within a linear regime. This framework is then applied to Saturn to solve for its interior density and sound speed profiles to better constrain its interior structure. This is done by incorporating observations of its mode frequencies derived from Linblad and Vertical Resonances in Saturn’s C-ring. We find that although the accuracy of the inversions is mitigated by the limited number of observed modes, we find that Saturn’s core density must be at least 8.97 +/- 0.01 g cm^{-3} below r/R_S = 0.3352 and its sound speed must be greater than 54.09 +/- 0.01 km s^{-1} below r/R_S = 0.2237. These new constraints can aid the development of accurate equations of state and thus help determine the composition in Saturn’s core. In addition, we investigate mode excitation and whether the \kappa-Mechanism can excite modes on Jupiter. While we find that the \kappa-Mechanism does not play a role in Jovian mode excitation, we discover a different opacity driven mechanism, The Radiative Suppression Mechanism, that can excite modes in hot giant planets orbiting extremely close to their host stars if they receive a stellar flux greater than 10^9~erg cm^{-2} s^{-1}. Finally, we investigate whether moist convection is responsible for exciting Jovian modes. Mode driving can occur if, on average, one cloud column with a 1-km radius exists per 6423 km^2 or if ~43 storms with 200 columns, each with a radius of 25 km, erupt per day. While this seems unlikely given current observations, moist convection does have enough thermal energy to drive Jovian oscillations, should it be available to them.

Mar
29
Thu
Colloquium (Joint with Physics): Jim Fuller (Host: Ethan Dederick)
Mar 29 @ 4:00 pm – 5:00 pm
Colloquium (Joint with Physics): Jim Fuller (Host: Ethan Dederick) @ Gardiner Hall 230

Surprising Impacts of Gravity Waves

Jim Fuller, Caltech

Gravity waves are low frequency fluid oscillations restored by buoyancy forces in planetary and stellar interiors. Despite their ubiquity, the importance of gravity waves in evolutionary processes and asteroseismology has only recently been appreciated. For instance, Kepler asteroseismic data has revealed gravity modes in thousands of red giant stars, providing unprecedented measurements of core structure and rotation. I will show how gravity modes (or lack thereof) can also reveal strong magnetic fields in the cores of red giants, and I will demonstrate that strong fields appear to be common within “retired” A stars but are absent in their lower-mass counterparts. In the late phase evolution of massive stars approaching core-collapse, vigorous convection excites gravity waves that can redistribute huge amounts of energy within the star. I will present preliminary models of this process, showing how wave energy redistribution can drive outbursts and enhanced mass loss in the final years of massive star evolution, with important consequences for the appearance of subsequent supernovae.
Apr
2
Mon
Pizza Lunch: Michael Engelhardt (Physics), “The quarks in the proton go round and round …”
Apr 2 @ 12:30 pm – 1:30 pm
Pizza Lunch: Michael Engelhardt (Physics), "The quarks in the proton go round and round ..." @ AY 119

The quarks in the proton go round and round …

Oct
8
Mon
Pizza lunch: Patrick Gaulme
Oct 8 @ 12:30 pm – 1:30 pm
Pizza lunch: Patrick Gaulme @ AY 119

Red giants, eclipsing binaries, and asteroseismology.

Patrick Gaulme, Max Planck Institute for Solar System Research

Nov
5
Mon
Pizza lunch: Heidi Sanchez
Nov 5 @ 12:30 pm – 1:30 pm
Pizza lunch: Heidi Sanchez @ AY 119

The Sunspot Solar Observatory Visitor Center

Heidi Sanchez, Sunspot Solar Observatory, NMSU

Apr
22
Mon
Pizza lunch: Sarah Kovac/David DeColibus
Apr 22 @ 12:30 pm – 1:30 pm
Pizza lunch: Sarah Kovac/David DeColibus @ AY 119

ASTR 598

Apr
29
Mon
Pizza lunch: Kristen Luchsinger
Apr 29 @ 12:30 pm – 1:30 pm
Pizza lunch: Kristen Luchsinger @ AY 119

ASTR 598

Oct
25
Fri
Colloquium: Shun Karato (Host: Jason Jackiewicz)
Oct 25 @ 3:15 pm – 4:15 pm
Colloquium: Shun Karato (Host: Jason Jackiewicz) @ BX102

Solving the Puzzles of the Moon

Shun Karato, Yale University

After 50 years from the first landing of men on the Moon, about 380 kg of samples were collected by the Apollo mission. Chemical analyses of these samples together with a theory of planetary formation led to a “giant impact” paradigm (in mid 1970s). In this paradigm, the Moon was formed in the later stage of Earth formation (not the very late stage, though), when the proto-Earth was hit by an impactor with a modest size (~ Mars size) at an oblique angle. Such an impact is a natural consequence of planetary formation from a proto-planetary nebula. This collision may have kicked out mantle materials from the proto-Earth to form the Moon. This model explains mostly rocky composition of the Moon and the large angular momentum of the Earth-Moon system. High temperatures caused by an impact likely removed much of the volatile components such as water.

However, two recent geochemical observations cast doubt about the validity of such a paradigm. They include (i) not-so-dry Moon suggested from the analysis of basaltic inclusions in olivine, and (ii) the high degree of similarities in many isotopes. The first observation is obviously counter-intuitive, but the second one is also hard to reconcile with the standard model of a giant impact, because many models show that a giant impact produces the Moon mostly from the impactor. In this presentation, I will show how one can solve these puzzles by a combination of physics/chemistry of materials with some basic physics of a giant impact.

Dec
2
Mon
Pizza lunch: ASTR 598 (Farhan and Oana)
Dec 2 @ 12:30 pm – 1:30 pm
Pizza lunch: ASTR 598 (Farhan and Oana) @ AY 119

ASTR 598

Farhan Hasan and Oana Vesa