Past Events in 2018

In my presentation I will give a short introduction to the science of extrasolar planets, in particular the technique of transit, eclipse and phasecurve spectro-photometry.  I will describe my various projects in this emerging field using state of the art spectroscopic and photometric instruments on the largest ground based telescopes, the 'flying telescope' SOFIA (Stratospheric Observatory for Infrared Astronomy) and the Kepler and Hubble space telescopes.

Acetylene (C2H2) is one of the primary building blocks in the formation of larger hydrocarbons, ring molecules and PAHs in the interstellar medium (ISM). This is especially true for the formation of complex organic molecules (important for life) in hot molecular cores, which are the warm, dense regions surrounding massive protostars. Because C2H2 has no permanent dipole moment, it can only be observed via transitions in the mid-infrared (MIR). High spectral resolution is required to resolve the individual ro-vibrational transitions.

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My adventures in infrared astronomy started when I was a grad student in 1965 with the discovery of an infrared-bright object (now known as the Becklin-Neugebauer Object) in the Orion Nebula. In 1966, I made the first measurements of the infrared radiation from the center of the Milky Way Galaxy.

Using long-baseline interferometry, we can beat telescope diffraction and atmospheric turbulence to  image stars and their environments with sub-milli-arcsecond resolution.  The Georgia State University CHARA Array on Mt.

To what extent mass loss and periods of enhanced stellar outflow can influence the terminal state of the most massive stars remains an open question in the fields of stellar physics, chemical enrichment of the Local Universe, and supernova research. For my dissertation, I focus on characterizing the stellar ejecta around supergiants through a combination of observing techniques.

The Arecibo Galaxy Environment Survey (AGES) is using the Arecibo L-band Feed Array to search for and study galaxies and gas clouds in different environments using the 21-cm line of neutral hydrogen. I will discuss the results coming out of AGES, including the Virgo cluster, where we have found a population of dark clouds, analysis of our sample of isolated galaxies, and our newest results from the NGC 7619 field. I will also give an update on the recovery process at Arecibo Observatory following Hurricane Maria in September.

The German REceiver for Astronomy at Terahertz frequencies has been successfully in service onboard SOFIA since 2011. GREAT, with its modular approach, is composed of a group of cryostats containing detectors for different frequency bands between 1.25 and 4.7 THz. Individual cryostats are then grouped in pairs. 4GREAT, a new member of the GREAT constellation, is a four-color single-pixel- detector. Two channels, CH1 and CH2, are implemented using spare flight mixers of Herschel-Heterodyne Instrument for the Far-Infrared: HIFI band 1 (492– 635 GHz) and band 4 (892-1100 GHz).

Meteorites and asteroids preserve information about the early solar system including accretion processes and parent body processes active on asteroids at these early times.  One process of interest is aqueous alteration. This is the chemical reaction between coaccreted water and silicates producing hydrated minerals. Some carbonaceous chondrites have experienced extensive interactions with water through this process.

The last decade has seen revolutionary discoveries of thousands of exoplanets in hundreds of multi-planet systems. It becomes clear that large planets very close to their central stars are surprisingly common. Their presence is incompatible with, and brings serious challenges to old wisdom of planet formation. Nonetheless, the solar system remains our best understood planetary system and the basis of most planet formation models. Therefore, it is of critical importance to place the solar system in proper context to better understand planet formation in general.

My thesis is on three extreme star forming environments in the Large Magellanic Cloud: 30 Doradus, N159, and N79. These three regions are at different evolutionary stage of forming stars. N79 is at a very young stage, just starting its star formation activity. N159 is currently actively forming several massive YSOs. And 30 Doradus has already passed it peak star formation, and several protostars are no longer shrouded by gas and dust, and are starting to be more visible in the optical wavelengths. I analyze the CO molecular gas clouds with ALMA in 30 Doradus, N159, and N79.

Traditionally there are two ways to obtain galaxy spectra with optical fibres: (a) 1000 fibres on 1000 galaxies (b) 1000 fibres on 1 galaxy. The former lacks spatial information, and the latter lacks sample sizes. This decade has seen the development of new instruments that go for the middle ground: 10 fibre bundles of 100 fibres each on 10 galaxies, providing spatial spectroscopy on large samples of near-by galaxies.

On August 17 2017, for the first time, an electromagnetic counterpart to gravitational waves was detected. Two neutron stars merged and lit up the entire electromagnetic spectrum, from gamma-rays to the radio. The infrared signature vividly demonstrates that neutron star mergers are indeed the long-sought production sites that forge heavy elements by r-process nucleosynthesis.

R Sculptoris (R Scl) is a nearby (~270 pc) carbon star with a massive circumstellar shell which is thought to have been produced by a thermal pulse event ∼2000 years ago. We observed R Scl with the Faint Object InfraRed CAMera for the SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, 34.8, and 37.1 μm to study its circumstellar dust emission. Maps of the infrared emission were used to examine the morphology and temperature structure of the spatially extended dust emission.

The heaviest chemical elements in the periodic table are synthesized through the rapid neutron-capture (r-) process but the astrophysical site where r-process nucleosynthesis occurs is still unknown. The best candidate sites are ordinary core-collapse supernovae and mergers of binary neutron stars. Through their stars, 13 billion year old ultra-faint dwarf galaxies preserve a "fossil" record of early chemical enrichment that provides the means to isolate and study clean signatures of individual nucleosynthesis events.

Modern astronomical data sets provide a wealth of data and well-grounded theoretical models describing those data. Our models provide a deeper (multi-level) statistical hierarchy which is allowing researchers to leverage information about the hyper-parameters and hyper-priors in astronomical Bayesian analyses. I will discuss two recent applications of Bayesian Hierarchical Modeling to address how galaxies evolve in clustered environments.

Astronomy at far-infrared and submillimeter wavelengths offers a unique window to study the physical properties of a wide variety of interstellar environments, ranging from the stellar nurseries in our Galaxy to the relativistic jets of faraway blazars. Polarimetric observations in particular can probe the magnetic and turbulent properties of these environments, providing insights into notoriously challenging topics such as the role of magnetic fields in the formation of stars and their planets.

Galactic winds impact ongoing star formation and black hole activity in their hosts and deposit mass and energy into their halos and the intergalactic medium.  Major outstanding questions remain, however, about the precise impact that galactic winds make. In particular, the exact nature of the neutral and molecular gas phases in these winds is still unclear. This seminar will highlight the recent discovery of powerful atomic and molecular winds in nearby galaxies and quantify the role of AGN/quasars in driving these winds.

The Arecibo Observatory celebrated its 50th anniversary in 2013 and continues to do cutting-edge research in radio astronomy, planetary radar, and atmospheric science. Early discoveries include the 33-ms period of the pulsar in the Crab Nebula supernova remnant and the 59-day rotation rate of the planet Mercury. Later discoveries include the first binary pulsar, the first radar maps of Venus, the first megamaser galaxy, the first millisecond pulsar, and the first extrasolar planet.

Several pre-proposal workshops will be held for interested participants. All workshops will be recorded, and the recordings of each workshop will be available once the workshop is complete.

Next Generation SOFIA Science Instrument Call for Proposals Powerpoint slides (6 MB).