Calendar

Nov
6
Fri
Colloquium: John Wisniewski
Nov 6 @ 3:15 pm – 4:15 pm
Colloquium:  John Wisniewski @ BX102

Diagnosing the SEEDS of Planet Formation

John Wisniewski, University of Oklahoma

Circumstellar disks provide a useful astrophysical diagnostic of the formation and early evolution of exoplanets. It is commonly believed that young protoplanetary disks serve as the birthplace of planets, while older debris disks can provide insight into the architecture of exoplanetary systems. In this talk, I will discuss how one can use high contrast imaging techniques to spatially resolve nearby circumstellar disk systems, and how this imagery can be used to search for evidence of recently formed planetary bodies. I will focus on results from the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) project, as well as some ongoing follow-up work.

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.

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

Sep
9
Fri
Colloquium Thesis Proposal: Lauren Kahre
Sep 9 @ 3:15 pm – 4:15 pm
Colloquium Thesis Proposal: Lauren Kahre @ Biology Annex 102

Extinction mapping with LEGUS

Lauren Kahre

The study of star formation and galaxy evolution in nearby galaxies depends on obtaining accurate stellar photometry in those galaxies. However, dust in the galaxies hinders our ability to obtain accurate stellar photometry, particularly in star-forming galaxies that have the highest concentrations of dust. This proposal presents a thesis project to develop a method for generating extragalactic extinction maps using photometry of massive stars from the Hubble Space Telescope. This photometry spans nearly 50 galaxies observed by the Legacy Extragalactic Ultraviolet Survey (LEGUS). The derived extinction maps can be used to correct other stars and Halpha maps (from the Halpha LEGUS) for extinction, and will be used to constrain changes in the dust-to-gas ratio across the galaxy sample and in different star formation rate, metallicity and morphological environments. Previous studies have found links between galaxy metallicty and the dust-to-gas mass ratio. The relationship between these two quantities can be used to constrain chemical evolution models.

Selected galaxies will also be compared to IR-derived dust maps for comparison to recent M31 results from Dalcanton et al. (2015) which found a minimum factor of 2 inconsistency between their extinction-derived maps and emission-derived maps from Draine et al. (2014).

Sep
20
Tue
Colloquium Thesis Proposal: Ethan Dederick
Sep 20 @ 3:00 pm – 4:00 pm
Colloquium Thesis Proposal: Ethan Dederick @ Science Hall 310

Utilizing Planetary Oscillations to Constrain the Interior Structure of the Jovian Planets

Ethan Dederick

Seismology has been the premier tool of study for understanding the
interior structure of the Earth, the Sun, and even other stars. Yet in this
thesis proposal, we wish to utilize these tools to understand the interior
structure of the Jovian planets, Saturn in particular. Recent observations
of spiral density structures in Saturn’s rings caused by its oscillations
have provided insight into which modes exist within Saturn and at what
frequencies. Utilizing these frequencies to compare to probable mode can-
didates calculated from Saturn models will also us to ascertain the interior
profiles of state variables such as density, sound speed, rotation, etc. Using
these profiles in a Saturn model, coupled with tweaking the interior struc-
ture of the model, i.e. the inclusion of stably stratified regions, should
allow us to explain which modes are responsible for the density structures
in the rings, as well as predict where to look to find more such structures.
In doing so, we will not only have a much greater understanding of Sat-
urn’s interior structure, but will have constructed a method that can also
be applied to Jupiter once observations of its mode frequencies become
available. In addition, we seek to explain if moist convection on Jupiter is
responsible for exciting its modes. We aim to do this by modeling Jupiter
as a 2D harmonic oscillator. By creating a resonance between moist con-
vective storms and Jovian modes, we hope to match the expected mode
energies and surface displacements of Jupiter’s oscillations.

Oct
10
Mon
Pizza Lunch: Laura Mayorga
Oct 10 @ 12:30 pm – 1:30 pm
Pizza Lunch: Laura Mayorga @ AY 119

Title: Proto-BD disks and the Kavli Summer Program in Astrophysics

Laura Mayorga

 

Mar
2
Thu
Colloquium: Jack Burns (Host: Nancy Chanover)
Mar 2 @ 3:15 pm – 4:15 pm
Colloquium: Jack Burns (Host: Nancy Chanover) @ Domenici Hall Room 106

Cosmology from the Moon: The Dark Ages Radio Explorer (DARE)

Dr. Jack Burns, University of Colorado Boulder

In the New Worlds, New Horizons in Astronomy & Astrophysics Decadal Survey, Cosmic Dawn was singled out as one of the top astrophysics priorities for this decade. Specifically, the Decadal report asked “when and how did the first galaxies form out of cold clumps of hydrogen gas and start to shine—when was our cosmic dawn?” It proposed “astronomers must now search the sky for these infant galaxies and find out how they behaved and interacted with their surroundings.” This is the science objective of DARE – to search for the first stars, galaxies, and black holes via their impact on the intergalactic medium (IGM) as measured by the highly redshifted 21-cm hyperfine transition of neutral hydrogen (HI). DARE will probe redshifts of 11-35 (Dark Ages to Cosmic Dawn) with observed HI frequencies of 40-120 MHz. DARE will observe expected spectral features in the global signal of HI that correspond to stellar ignition (Lyman-α from the first stars coupling with the HI hyperfine transition), X-ray heating/ionization of the IGM from the first accreting black holes, and the beginning of reionization (signal dominated by IGM ionization fraction). These observations will complement those expected from JWST, ALMA, and HERA. We propose to observe these spectral features with a broad-beam dipole antenna along with a wide-band receiver and digital spectrometer. We will place DARE in lunar orbit and take data only above the farside, a location known to be free of human-generated RFI and with a negligible ionosphere. In this talk, I will present the mission concept including initial results from an engineering prototypes which are designed to perform end-to-end validation of the instrument and our calibration techniques. I will also describe our signal extraction tool, using a Markov Chain Monte Carlo technique, which measures the parameterized spectral features in the presence of substantial Galactic and solar system foregrounds.

 

Jun
27
Tue
Colloquium PhD Defense: Laura Mayorga
Jun 27 @ 2:30 pm – 3:30 pm
Colloquium PhD Defense: Laura Mayorga @ Domenici Hall 102

The Orbital and Planetary Phase Variations of Jupiter-Sized Planets: Characterizing Present and Future Giants

Laura Mayorga, NMSU

It is commonly said that exoplanet science is 100 years behind planetary science. While we may be able to travel to an exoplanet in the future, inferring the properties of exoplanets currently relies on extracting as much information as possible from a limited dataset. In order to further our ability to characterize, classify, and understand exoplanets as both a population and as individuals, this thesis makes use of multiple types of observations and simulations.

Firstly, direct-imaging is a technique long used in planetary science and is only now becoming feasible for exoplanet characterization. We present our results from analyzing Jupiter’s phase curve with Cassini/ISS to instruct the community in the complexity of exoplanet atmospheres and the need for further model development. The planet yields from future missions may be overestimated by today’s models. We also discuss the need for optimal bandpasses to best differentiate between planet classes.

Secondly, photometric surveys are still the best way of conducting population surveys of exoplanets. In particular, the Kepler dataset remains one of the highest precision photometric datasets and many planetary candidates remain to be characterized. We present techniques by which more information, such as a planet’s mass, can be extracted from a transit light curve without expensive ground- or space-based follow-up observations.

Finally, radial-velocity observations have revealed that many of the larger “planets” may actually be brown dwarfs. To understand the distinction between a brown dwarf and an exoplanet or a star, we have developed a simple, semi-analytic viscous disk model to study brown dwarf evolutionary history. We present the rudimentary framework and discuss its performance compared to more detailed numerical simulations as well as how additional physics and development can determine the potential observational characteristics that will differentiate between various formation scenarios.

Exoplanet science has already uncovered a plethora of previously unconsidered phenomenon. To increase our understanding of our own planet, as well as the other various possible end cases, will require a closer inspection of our own solar system, the nuanced details of exoplanet data, refined simulations, and laboratory astrophysics.

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