DRAO Seminar Series Spring 2016

The Milky Way Laboratory

Cara Battersby (CfA SMA Fellow)

Our home Galaxy, the Milky Way, is our closest laboratory for studying physical processes throughout the Universe. Submillimeter observations of the cool, dense gas and dust in our Milky Way provide insights on universal processes including how stars form in both ‘regular’ and ‘extreme’ environments and how gas is organized on galactic scales. On a tour through our Milky Way Laboratory, I will discuss 1) how we can use dense, filamentary molecular clouds, potential “Bones of the Milky Way,” to trace our Galaxy’s spiral structure, 2) how large surveys of our Galaxy have revealed that star clusters continue to accrete significant mass while they are forming, and 3) how observing our extreme, turbulent Galactic Center (the Central Molecular Zone; the inner few hundred parsecs of our Galaxy) can help us learn more about how gas is converted into stars during the peak epoch of cosmic star formation (z~2).

Mass and Geometric Measurements of NANOGrav Binary Millisecond Pulsars

Emmanuel Fonseca (UBC)

Dedicated observations of radio pulsars in binary systems typically yield measurements of deviations from Keplerian motion of the bodies. Careful interpretation of these effects can lead to precise measurements of different types of parameters. A particularly powerful effect is the general-relativistic Shapiro time delay, which quantifies the changing amount of spacetime curvature traversed by the radio pulse as the neutron star orbits its companion. In our talk, we highlight a detailed analysis of observed variations in a sample of 25 millisecond pulsars being observed by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). We measure fifteen significant Shapiro-delay signals—five of which were made for the first time in our study—and derive the binary-component masses and system inclination for these systems from this effect alone. Whenever possible, we use the statistical significance of observed variations as constraints when analyzing the parameters that describe the Shapiro delay, as well as derive other interesting parameters of several pulsar-binary systems. We discuss our measurements in the context of recent studies that probe underlying distributions of the neutron-star mass population delineated by different types of companions.

Status of, and Science with, the Stratospheric Observatory For Infrared Astronomy (SOFIA)

B.-G. Andersson (USRA/SOFIA)

The SOFIA project flies a significantly modified Boeing 747SP, carrying a 2.7m telescope, into the stratosphere 3-4 times a week to perform astronomical observations, primarily in the mid- to far-infrared. The observatory is now in the middle of executing Cycle 4 of its general user observations, employing all the first generation instruments, and covering all areas of astronomy from Solar System studies to extra-galactic astronomy. The Cycle 5 Call for Proposals was released at the end of April, offering all first and second generation instruments, including the FIR polarimeter HAWC+. I will review the status of the project and provide some science highlights from the first few observing cycles.

Why Interstellar Grains Align and Why You Should Care

B.-G. Andersson (USRA/SOFIA)

More than 60 years after the discovery of interstellar polarization we now have a quantitative, empirically tested, theory of grain alignment. This Radiative Alignment Torque (RAT) theory predicts that dust grains are spun up by an anisotropic radiation field, if the wavelength of the light is less than the grain diameter. If the grain is made of a paramagnetic material, it will then align with the magnetic field. A number of specific, observationally testable, predictions follow from the theory, many of which have already been addressed. With a full testing of the theory and quantification of its parameters, polarimetry has the promise to not only allow efficient and reliable tracing of interstellar and interplanetary magnetic fields, but also to provide new and unique probes of the dust and the interstellar environment.

MeerKAT: What’s Happening in Africa?

Russ Taylor (UCT)

MeerKAT, a 64-element array of 13.5-m offset parabolic antennas, is a precursor of the SKA mid-frequency dish array, and following several years of operation as a South African telescope will be incorporated into the SKA phase 1 facility. Construction of MeerKAT is well advanced at the African SKA central site on the South African Karoo plateau. The first 32 elements of MeerKAT will be released for early shared-risk science programs in late 2016, and the full array will be operational in late 2017.

The MeerKAT science program will consist of key-science, legacy-style, Large Survey Projects, plus open time available for new proposals. The Large Survey Projects are direct pathfinder to key science programs being planned for the SKA1-mid. I will present an update on the MeerKAT progress and specifications, the key science programs.