Astrophysics Science Division Colloquium Series
Schedule: Spring 2014

Astrophysics Science Division Colloquium Series
Schedule: Spring 2014

Recent schedules:

2013, Fall 2013, Spring 2013, Summer
2012, Fall 2012, Spring  
2011, Fall 2011, Spring  
2010, Fall 2010, Spring  

ASD Colloquia are Tuesdays at 3:45 pm (Meet the Speaker at 3:30 pm)
in Bldg 34, Room W150 unless otherwise noted.


Jan 14 Matt Mountain (STScI) - Why building telescopes is a tremendously human endeavor - what we don't get taught in Graduate School about championing science in projects or in organizations
Host: Harley Thronson
Jan 21 No colloquium (MLK day)
Jan 28 -


Feb 4 Alexander Kashlinsky (GSFC) - Probing the emergence of the Universe from Dark Ages: cosmic infrared background from Spitzer to Euclid
Feb 11 Gerrit Verschuur (University of Memphis) - On the Relationship between Galactic HI Structure and Small-scale Structure in the Cosmic Microwave Background
Feb 18 No colloquium (Presidents day)
Feb 25 Laurens Keek (Georgia Tech) - Taking the temperature of accreting neutron stars with superbursts


Mar 4 Tyler Robinson (NASA ARC) - Exploring Earth as an Exoplanet
(Rescheduled for March 25th)
Mar 11 Warren Skidmore (TMT) - Thirty Meter Telescope: The Next Generation of Ground Based Optical/Infra Red Observatory
Mar 18 Dan Perley (Caltech) - Quantifying High-Redshift Star Formation with Gamma-Ray Bursts: Promises and Perils
Mar 25 Tyler Robinson (NASA ARC) - Exploring Earth as an Exoplanet


Apr 1 Andrea Lommen (Franklin & Marshall) - Pulsar Timing Arrays: No longer a blunt instrument for Gravitational Wave Detection
Apr 8 Jane Rigby (NASA GSFC) - Galaxy Evolution in High Definition, Via Gravitational Lensing
Apr 15 Peter Meszaros (Penn State) - Gamma-Ray Bursts: the Standard Model and Beyond
Apr 22 Ned Wright (UCLA) - [Re]Exploring the Universe with [NEO]WISE
Apr 29 Tony Piro (Caltech) - Connecting the Electromagnetic and Gravitational Wave Skies


May 6 -
May 13 Kim Palladino (MIT/SNOLAB) - Notes from Underground: Direct Dark Matter Searches and Single Phase Liquid Argon Detectors
May 20 Meredith Hughes (Wesleyan) - Planet Formation through Radio Eyes
May 27 Paul McNamara (ESA) - Tracing Einstein's Geodesics in Space: The LISA Pathfinder Mission


June 3 Veronica Dexheimer (Kent State) - Neutron Star Equation of State
June 10 Dave Chuss (GSFC) - The Cosmic Microwave Background and Inflation

Why building telescopes is a tremendously human endeavor - what we don't get taught in Graduate School about championing science in projects or in organizations

Matt Mountain


Tuesday, January 14, 2014

Probing the emergence of the Universe from Dark Ages: cosmic infrared background from Spitzer to Euclid

Alexander Kashlinsky


Tuesday, February 4, 2014


I will review the current theoretical understanding of the first stars and black holes and their potential contributions to the Cosmic Infrared Background (CIB). Intriguing indications of the possible emissions from these objects have been obtained over the last several years from CIB fluctuation measurements using Spitzer/IRAC deep images. The uncovered source-subtracted CIB fluctuations substantially exceed those from remaining known populations. The spatial spectrum of these fluctuations is consistent with populations clustering according to high-z LCDM model. The SED of the CIB fluctuations is blue and consistent with emissions produced by hot objects at high z. Cross-correlation analysis with Chandra X-ray data suggests that the unresolved CIB and CXB are coherent at a remarkably high level implying fractional abundance of black holes, among the emitters of the CIB, which significantly exceeds that in known populations. I will also discuss a new CIB project, LIBRAE (Looking at Infrared Background Radiation Anisotropies with Euclid), planned by NASA and ESA for the future Euclid satellite mission. LIBRAE will identify the net emissions from the first stars era, lead to a better understanding of the condition of intergalactic medium at that epoch, isolate the contributions from the first black holes and shed light on dust content at those times. The project has potentially transformative implications for understanding the emergence of the Universe out of the "Dark Ages".

On the Relationship between Galactic HI Structure and Small-scale Structure in the Cosmic Microwave Background

Gerrit Verschuur

University of Memphis

Tuesday, February 11, 2014


The archive of IRIS, Planck and WMAP data available at the IRSA website of IPAC allows us to look closely at the apparent associations between galactic neutral hydrogen (HI) features and small-scale structure in the CMB found in the WMAP data (previously reported in three ApJ papers). In addition, HI new observations made with the Green Bank Telescope with a resolution of 9 arcmin allow similar associations between HI structure and Planck data to be closely examined.

The talk will demonstrate the complex nature of nearby interstellar HI and its relationship to interstellar cirrus and the small-scale structure in high-frequency continuum emission (purported to be of cosmological origin). It is concluded that serious attention should be paid to the possibility that some or all of the small-scale structure found in WMAP and PLANCK data harbors the signature of a previously unrecognized source of high-frequency continuum emission arising in the Galaxy.

Taking the temperature of accreting neutron stars with superbursts

Laurens Keek

Georgia Tech

Tuesday, February 25, 2014


Hydrogen and helium accreted onto a neutron star is compressed within just a few hours to the point where nuclear fusion starts. This produces explosive events that are frequently observed as Type I X-ray bursts. Many consecutive X-ray bursts create a thick ashes layer that is rich in carbon. Runaway carbon burning is thought to power the powerful but rare superbursts. We show how simulations of carbon burning succesfully explain many of the observed details of one superburst observed by RXTE. Current neutron star theory, however, expects the temperature inside the star to be too low for carbon to ignite. This suggests that new heating as well as cooling processes operate inside neutron stars. We discuss how future missions, such as NICER, can constrain the sources of cooling and heating.

Thirty Meter Telescope: The Next Generation of Ground Based Optical/Infra Red Observatory

Warren Skidmore


Tuesday, March 11, 2014


I will discuss some of the scientific capabilities that the Thirty Meter Telescope will provide and some of the areas of study that will benefit from the TMT's capabilities. I'll describe how the telescope design was developed to support a broad range of observing capabilities and how the observatory is being engineered. Finally I'll describe the avenues through which individuals can actively participate in the project and in planning for a potential TMT/NSF partnership.

Quantifying High-Redshift Star Formation with Gamma-Ray Bursts: Promises and Perils

Dan Perley


Tuesday, March 18, 2014


One of the most exciting broader applications of the study of gamma-ray bursts is in better understanding the star-formation history of the Universe. Long-duration GRBs are produced exclusively by massive, young stars and can be detected beyond z>8, pinpointing a SFR-selected sample of galaxies independent of galaxy luminosity spanning nearly all of cosmic history. On the other hand, GRB selection may introduce new biases, both intrinsic (such as a dependence on metallicity) and observational (the galaxy may be difficult to pinpoint if the GRB afterglow is dust-obscured). I will discuss recent efforts to shine light upon GRBs and their hosts via an ongoing observational campaign designed to robustly evaluate the differences between GRB and star-formation rates and their redshift evolution out to z=3 and beyond. Most dust-obscured GRBs occur in massive, reddened galaxies that systematically differ from the hosts of unobscured GRBs; this population must be carefully accounted for to evaluate the GRB-SFR connection at high redshift. Even so, the GRB host population shows clear differences relative what would be expected from an ideal star-formation tracer out to at least z=2. While GRBs may not serve as pure tracers of star-formation (except, perhaps, at the highest redshifts), they likely instead provide unique insight into the combined evolution of cosmic metal abundance and the star-formation rate across cosmic time.

Exploring Earth as an Exoplanet

Tyler Robinson


Tuesday, March 25, 2014


Earth is our only example of a habitable planet, or a planet capable of maintaining liquid water on its surface. As a result, Earth serves as the archetypal habitable world in conceptual studies of future exoplanet characterization missions, or in studies of techniques for the remote characterization of potentially habitable exoplanets. Pioneering studies of a distant Earth used spatially resolved observations from the Galileo Earth encounters.  However, for the foreseeable future, direct observations of exoplanets will be spatially unresolved, depicting their targets as points of light. As a consequence, characterization techniques will be limited to using disk integrated spectroscopic observations, as well as rotational and orbital light curves. While there are a number of existing observations of the distant Earth that can be used to test our ability to remotely characterize the environment of a habitable exoplanet, such datasets are rare, and are often limited in wavelength range, spectral resolution, temporal coverage, and viewing geometry. As a result, models of Earth's disk-integrated spectrum provide the best means for understanding the appearance of the Pale Blue Dot, and can serve as suitable replacements for data in characterization studies. Most excitingly, the challenges presented by interpreting Earth within the context of an exoplanet offer unique opportunities for collaborations between the Earth sciences and the astronomical sciences, working together to retrieve information from spectra of Earth-like worlds seen at interstellar distances.

Pulsar Timing Arrays: No longer a blunt instrument for Gravitational Wave Detection

Andrea Lommen

Franklin & Marshall

Tuesday, April 1, 2014


The limits that pulsar timing places on the energy density of gravitational waves in the universe are on the brink of limiting models of galaxy formation and have already placed limits on the tension of cosmic strings. Pulsar timing has traditionally focused on stochastic sources, but recent research has demonstrated that pulsar timing will (1) offer a rich variety of information on individual gravitational wave sources including waveform, direction and luminosity distance, (2) test alternative theories of gravity, (3) allow us to observe the same gravitational wave source at two different epochs separated by thousands of years. In other words, pulsar timing is a shrewd and versatile gravitational wave detection instrument.

Galaxy Evolution in High Definition, Via Gravitational Lensing

Jane Rigby


Tuesday, April 8, 2014


In hundreds of known cases, "gravitational lenses" have deflected, distorted, and amplified images of galaxies or quasars behind them. As such, gravitational lensing is a way to "cheat" at studying how galaxies evolve: lensing can magnify galaxies by factors of 10--100 times, transforming them from objects we can barely detect to bright objects we can study in detail. I'll summarize new results from a comprehensive program, using imaging from Hubble and Spitzer, and high-quality spectroscopy from Keck, Magellan, and Hubble, to study how galaxies formed stars at redshifts of 1--3, the epoch when most of the Universe's stars were formed. These results give insight into the process by which galaxies form elements and stars.

Gamma-Ray Bursts: the Standard Model and Beyond

Peter Meszaros

Penn State

Tuesday, April 15, 2014


I will review the recent observational progress on gamma-ray bursts, and the puzzles as well as non-puzzles raised by their intepretation both in terms of the standard model and in terms of recent extensions of this model, including photospheric and hadronic models. I will discuss the physics and issues behind the introduction of such extensions, motivated by the need to address the prompt gamma-ray spectra. I will then discuss the implications of the Icecube TeV neutrino non-detection of either GRB 130427A nor, so far, of the expected cumulative diffuse neutrino flux from many bursts, and its implication for ultra-high energy cosmic rays.

[Re]Exploring the Universe with [NEO]WISE

Ned Wright


Tuesday, April 22, 2014


WISE, the Wide-field Infrared Survey Explorer, surveyed the entire sky in 4 mid-infrared bands at 3.4, 4.6, 12 and 22 microns with vastly greater sensitivity than previous all-sky surveys at these wavelengths. WISE surveyed everything more than 1 AU from the Sun, including asteroids, comets, nearby brown dwarfs and star forming regions both in the Milky Way and in distant galaxies. The 12 and 22 micron channels are very powerful for detecting Ultra-Luminous Infrared Galaxies, and WISE has detected some of the most luminous galaxies in the Universe. The WISE short wavelength channels are very powerful for detecting old cold brown dwarfs, and WISE has detected objects as cool as 300 K. WISE reported 3.75 million asteroid observations to the Minor Planet Center in 2010, and measured the radiometric diameters more than 150,000 objects. WISE has a 40 cm cryogenic telescope, 1024x1024 arrays, a scan mirror to freeze images on the arrays while the spacecraft scans continuously, and takes 47'x47' images every 11 seconds in all four bands from an IRAS/COBE style Sun-synchronous nearly polar low Earth orbit. WISE entered routine survey operations on 14 Jan 2010. It completed full sky coverage on 17 July 2010, and then starting warming up in early August. WISE ran with its 3 shortest bands until the end of September, and then with its two shortest bands until 1 Feb 2011. The AllWISE analysis of the entire WISE dataset keeps track of proper motions and led to the discovery of 3525 new confirmed proper motion obects that had been missed by previous surveys. WISE is now reactivated as NEOWISE-R to search for more Near Earth Objects, and could survey in its two shortest bands for up to 3 more years. As of today more than 70% of the sky has been re-observed.

Connecting the Electromagnetic and Gravitational Wave Skies

Tony Piro


Tuesday, April 29, 2014


The direct detection of gravitational waves in the coming years will open up an entirely new window for studying the Universe. Identifying gravitational and electromagnetic waves from the same events will be crucial for fully utilizing these revolutionary observations. I will summarize recent theoretical efforts to investigate binary coalescences, mergers, gamma-ray bursts, and supernovae from both directions. When there is a clear electromagnetic signal, I will describe unique processes for producing gravitational waves. When there is gravitational wave production, I will explore ways in which these events can be observed with traditional astronomy. These results will highlight what can be learned from such observations, and will help to coordinate efforts between electromagnetic and gravitational wave observers so as to maximize the scientific return.

Notes from Underground: Direct Dark Matter Searches and Single Phase Liquid Argon Detectors

Kim Palladino


Tuesday, May 13, 2014


Evidence for the existence of Dark Matter from astronomical observations abounds, while experimentalists are still in pursuit of a confirmed laboratory 'direct' detection. Currently, contradictory experimental results of allowed signal regions and excluding upper limits exist, which may leave many observers of the field scratching their heads. An overview of the current state of the direct detection field will be provided along with a discussion of new experiments coming online in the near future to shed light on the matter. MiniCLEAN and DEAP-3600 are liquid argon experiments for the direct detection of dark matter under construction at SNOLAB, located 6800 feet underground in an active nickel mine in Sudbury, Ontario. The implications of their unique design will be discussed in the context of the wider search for dark matter.

Planet Formation through Radio Eyes

Meredith Hughes


Tuesday, May 20, 2014


Circumstellar disks provide the raw material and initial conditions for planet formation. Millimeter-wavelength interferometry is a powerful tool for studying gas and dust in planet-forming regions, and it is undergoing an order-of-magnitude leap in sophistication with the advent of the ALMA interferometer that is now in the late stages of construction. I will discuss some ways in which millimeter-wavelength interferometry is being used to study the process of planet formation in circumstellar disks, with particular emphasis on the kinematics of turbulence in protoplanetary disks and the degree to which debris disk structure reflects the dynamics of embedded planetary systems.

Tracing Einstein's Geodesics in Space: The LISA Pathfinder Mission

Paul McNamara


Tuesday, May 27, 2014


LISA Pathfinder is the second of the European Space Agency's Small Missions for Advanced Research and Technology (SMART). The goal of LISA Pathfinder (LPF) is to demonstrate the technologies required for future laser interferometric spaceborne gravitational wave detectors - a variant of which could fulfil the "Gravitational Universe" science theme recently selected for the 3rd Large-class mission of the ESA Cosmic Vision Programme.

The development of the LPF hardware is now complete, and integration and testing of the spacecraft and payload is underway. The delivery of the opto-mechanical heart of the payload is scheduled for later this year, following which the final system tests will be performed. Launch is scheduled for mid-2015, with first results will be available approximately 3 months thereafter.

In this presentation I will describe the LISA Pathfinder mission, highlighting the unique operational aspects under development.

Neutron Star Equation of State

Veronica Dexheimer

Kent State

Tuesday, June 3, 2014


Neutron stars are an ideal laboratory for nuclear and particle physics, since their extremely dense environment cannot be achieved on Earth. I study the composition and equation of state of such stars, more specifically, how exotic particles, e.g. hyperons and quarks, can exist in their interior. I also investigate the effects of strong magnetic fields in such dense environments. This is extremely important, since magnetic fields of the order of 10^15 G can be reached on the surface of neutron stars, and even higher values are expected in their center.

The Cosmic Microwave Background and Inflation

Dave Chuss


Tuesday, June 10, 2014


The March 2014 announcement by the BICEP2 collaboration claimed a detection of the long-sought-after primordial "B-mode" polarization of the cosmic microwave background (CMB). Such a signal is expected to be produced by gravitational waves generated by cosmic inflation, the exponential expansion of the universe in the first ~10-32 seconds that had been postulated in the 1980's as a mechanism to explain the initial conditions of the Big Bang. If this signal is verified, it will have profound implications on our understanding of physical cosmology by providing tangible evidence for inflation and a window into physics at energy scales a trillion times larger than those of the Large Hadron Collider.

The signal claimed by BICEP2 was large enough to be in tension with inflationary limits from WMAP and Planck temperature data. In addition, the knowledge of the Galactic foregrounds in the region of sky measured by BICEP2 is incomplete. Because of this, it is critical to follow up with additional data. Near-future experiments are poised to independently test inflation by measuring the polarization of the cosmic microwave background across a much broader range of angular scales. Specifically, it is critical to measure this signal on large angular scales where the inflationary polarization signal is predicted to be significantly larger than at the degree angular scale to which BICEP2 is sensitive. Goddard is involved in three such experiments. The Cosmology Large Angular Scale Surveyor (CLASS) is a Johns Hopkins University-led ground based telescope array that will survey the CMB from the Atacama Desert in Chile at frequencies below 200 GHz. The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne polarimeter that will survey the CMB at frequencies above 200 GHz. Finally, PIXIE is a Goddard-led space-based mission designed to measure the polarization spectrum of the entire sky from frequencies between 30 GHz and 6 THz.

Jeremy Schnittman
NASA Logo, National Aeronautics and Space Administration