Library: Astronomy & Space Science

Adaptive optics (AO) corrects distortions created by atmospheric turbulence and delivers diffraction-limited images on ground-based telescopes. The vastly improved spatial resolution and sensitivity has been utilized for studying everything from the magnetic fields of sunspots upto the internal dynamics of high-redshift galaxies. This thesis about AO science from small and large telescopes is divided into two parts: Robo-AO and magnetar kinematics. In the first part, I discuss the construction and performance of the world’s first fully autonomous visible light AO system, Robo-AO, at the Pal...

In 2005, Palla & Baraffe proposed that brown dwarfs and very low mass stars (less than 0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated oscillation periods of 1-4 hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1-15 million year age range. Furthermore, several previous reports of short-period variability have suggested that deuterium-burning pulsation is in fact at work in young clusters. For my dissertation, I develo...

For centuries, we have known that our dynamic universe is adorned by cosmic fireworks: energetic and ephemeral beacons of light from a single star that are a million (nova) to a billion (supernova) times brighter than our sun. However, it had been an age-old conundrum that the brightest nova is approximately 1000 times fainter than the faintest supernova; why should nature leave such a wide "gap"? In search of an answer, I undertook three systematic surveys for my thesis. Since I was looking for transients fainter, faster and rarer than supernovae, I focused my search on galaxies in the loc...

The evolution, ages and masses of neutron stars are the fundamental threads that make pulsars accessible to other sub-disciplines of astronomy and physics. A realistic and accurate determination of these indirectly probed features play an important role in understanding a very broad range of astrophysical processes that are, in many cases, not empirically accessible otherwise. For the majority of pulsars, the only observables are the rotational period, and its derivative which gives the rate of change in the spin. I start with calculating the joint P-Pdot distributions of millisecond pulsar...

Asteroids are diverse and numerous solar system objects, from the large number of objects in the main asteroid belt to the relatively small near-Earth population. Understanding their physical properties is essential to understanding the evolution of the solar system, and asteroid morphology is a complex field in its own right. The histories of individual asteroids, and particularly near-Earth objects, reflect continuous interaction among their shapes, rotation states, and orbits due to the effects of radiation pressure. Radar astronomy has provided detailed information on the orbits, sizes,...

According to astrophysical theory, magnetic fields should play an important role in the structure and dynamics of the interstellar medium. While astronomical observations confirm this directly, the observational record is sparse. This is because magnetic fields can only be measured via polarimetric methods, and most of these methods can only provide an indirect inference of the magnetic field strength. The Zeeman effect, however, is the only method by which in situ measurements of astrophysical magnetic fields can be made. The spectral signature of Zeeman splitting is imprinted in t...

We present the results of a large-area survey for millisecond pulsars (MSPs) at moderately high galactic latitudes with the 64 m Parkes radio telescope, along with follow-up timing and optical studies of the newly-discovered pulsars and several others. Major results include the first precise measurement of the mass of a fully recycled pulsar and measurement of orbital period decay in a double neutron star binary system allowing a test of general relativity along with improved measurements of the neutron star masses. In a survey of approx. 4,150 square degrees, we discovered 26 previously unkn...

Over the past few years, long-duration gamma-ray bursts (GRBs), including the subclass of X-ray flashes (XRFs), have been revealed to be a rare variety of Type Ibc supernova (SN Ibc). While all these events result from the death of massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those of ordinary Type Ibc SNe by many orders of magnitude. The observed diversity of stellar death corresponds to large variations in the energy, velocity, and geometry of the explosion ejecta. Using multi-wavelength (radio, optical, X-ray) observations of the nearest GRBs, XRFs, and...

We examine the census of star-forming galaxies and their extinction properties at redshift z~2, when a large fraction of the stellar mass in the universe formed. We find a good agreement between the X-ray, radio, and de-reddened UV estimates of the average star formation rate (SFR) for our sample of z~2 galaxies of ~50 Msun/yr, indicating that the locally calibrated SFR relations appear to be statistically valid from redshifts 1.5<z<3.0. Spitzer MIPS data are used to assess the extinction properties of individual star-forming galaxies, and we find that the rest-frame UV slope of most...

As late as 1995, the anticipated widespread population of primeval galaxies remained at large, lurking undetected at unknown redshifts, with undiscovered properties. We present results from our efforts to detect and characterize primeval galaxies by their signature high-redshift Lyman-alpha emission lines utilizing two observational techniques: serendipitous slit spectroscopy and narrowband imaging. By pushing these techniques to their utmost limits, we probe the Lyman-alpha-emitting galaxy population out to redshifts as high as z = 6.5. Galaxies at this epoch reside in a universe which is ...