2013

By Neal Erickson (UMass-Amherst)

UMass and BYU are building a 64 element phased array receiver for use in the focal plane of the GBT, in the frequency range 70-95 GHz. These receivers offer the potential to synthesize up to four times more beams than there are elements, and to measure and correct large scale telescope surface errors.  There are many unique challenges with building such a receiver at short wavelengths, and in applying it at the Gregorian focus.

The talk will discuss the theory of beamforming with the array and the results of simulations of feed efficiency.  This receiver uses cryogenic MMIC amplifiers in the front end followed by room temperature amplification and mixing, requiring several innovations in construction.

These unique features will be described, as well as the layout of the backend beam summing and calibration network.

By David Thilker

Due to recent wide-area surveys conducted by GALEX, Pan-STARRS1, and WISE, plus targeted observations by HST, our generation is afforded the remarkable opportunity to accomplish panchromatic dissection of unprecedented numbers of galaxies in the local universe, even at the scale of individual stars in the nearest objects. Such results may be compared against the emerging view of predecessor objects at high redshift. The broad wavelength coverage of space-based surveys allows the substructure of nearby galaxies to be interpreted meaningfully in terms of realistically complex stellar populations while allowing robust correction for dust obscuration. We will demonstrate our innovative approach to generating a more comprehensive, physically-interpreted view of z ~ 0 galaxy structure via pixel-SED fitting of resolved galaxies. To accomplish such data processing, we have created a successful distributed computing network, enabled by volunteer citizen scientists. Our early work has been focused on visible-light observations from Pan-STARRS1 and SDSS, but we are now in the process of broadening our spectral scope over the UV-IR domain. For thousands of galaxies, we will determine maps of key physical parameters based on UV-IR pixel-SED fitting. We will compute the entire suite of CAS+Gini+M_20 non-parametric morphology indicators from the resulting images of stellar mass (M*) and extinction-free star formation rate (SFR). Further, parametric models of galaxy structure (bulge, disk, bar) will be derived directly using the stellar mass maps. Our overarching science goal is understanding the evolution of galaxies with respect to their position and trajectory in the global (M*, SFR) plane, using maximally orthogonal, quantitative measures of stellar structure and SF modes obtained from our physical parameter maps. We now quantify the z~0 view, but envision that our pixel-SED fitting resource can later be applied to galaxy populations at moderate (LSST+WFIRST) and high z (CANDELS, Frontier fields), even if rest-frame IR bands are unavailable in that case. If time permits, we will provide a brief overview of LEGUS, the Legacy ExtraGalactic UV Survey, which is complementary to our pixel-SED fitting in the sense that it links the ~kpc scale results of our investigation to the constituent stars and clusters at the start of the SF hierarchy.

By Dr Dror Baron – NC State University


Traditional signal acquisition techniques sample band-limited analog signals above the Nyquist rate. Compressed sensing (CS) is based on the revelation that a sparse signal can be reconstructed from a small number of linear projections of the signal. Therefore, CS-based techniques can sample sparse signals at sub-Nyquist rates. Potential applications include broadband analog-to-digital conversion and new kinds of imaging devices.
The focus of our recent research has been on CS algorithms that can reconstruct signals despite not knowing their statistical properties. We will describe algorithms that are universal in the sense that they can adapt to unknown statistics. We will conclude the talk by briefly surveying recent work on a fast parallel algorithm for data compression, which can be used in applications involving high data rates including lossless compression of radio astronomy data.

By: Kevin Bandura (McGill University)

Dark Energy is arguably the greatest mystery in science today.  A promising technique in the pursuit of unraveling the mystery of Dark Energy is 21cm intensity mapping observations. I will discuss observational and instrumentation advances to date.  In particular I will introduce the Canadian Hydrogen Intensity Mapping Experiment (CHIME currently under construction at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, BC. I will detail the novel telescope design concept, details about the correlator, and the current commissioning of the 1/10th scale CHIME pathfinder.