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The BN/KL region in the Orion molecular cloud is an archetype for the study of the formation of stars much more massive than the Sun. This region contains luminous young stars and protostars but, like most star-forming regions, is difficult to study in detail because of the obscuring effects of dust and gas. Our basic expectations are shaped to some extent(More)
The image of the emission surrounding the black hole in the center of the Milky Way is predicted to exhibit the imprint of general relativistic (GR) effects, including the existence of a shadow feature and a photon ring of diameter ∼50 μas. Structure on these scales can be resolved by millimeter-wavelength very long baseline interferometry. However,(More)
I calculate the statistics of correlation of two digitized noiselike signals: drawn from complex Gaussian distributions, sampled, quantized, correlated, and averaged. Averaged over many such samples, the correlation r approaches a Gaussian distribution. The mean and variance of r fully characterize the distribution of r. The mean corresponds to the(More)
Observations of radio signals from distant pulsars provide a valuable tool for investigation of interstellar turbulence. The time shapes of the signals are the result of pulse broadening by the fluctuating electron density in the interstellar medium. While the scaling of the shapes with the signal frequency is well understood, the observed anomalous scaling(More)
We have made the first VLBI synthesis images of the H 2 O maser emission associated with the central engine of the Seyfert galaxy NGC 1068. Emission extends about ±300 km s −1 from the systemic velocity. Images with submilliarcsecond angular resolution show that the red-shifted emission lies along an arc to the northwest of the systemic emission. (The(More)
Attaining the limit of sub-microarcsecond optical resolution will completely revolutionize fundamental astrometry by merging it with relativistic gravitational physics. Beyond the sub-microarcsecond threshold , one will meet in the sky a new population of physical phenomena caused by primordial gravitational waves from early universe and/or different(More)
We describe the expected distribution of intensity for a scintillating source of finite size observed through a scattering medium, including systematic and instrumental effects. We describe measurements of the size of the Vela pulsar, using this technique. 1. Theoretical Background Waves from a pointlike source observed through a scattering medium will(More)
Gravitational waves affect the observed direction of light from distant sources. At telescopes, this change in direction appears as periodic variations in the apparent positions of these sources on the sky; that is, as proper motion. A wave of a given phase, traveling in a given direction, produces a characteristic pattern of proper motions over the sky.(More)
We present measurements of the size of the Vela pulsar in 3 gates across the pulse, from observations of the distribution of intensity. We calculate the effects on this distribution of noise in the observing system, and measure and remove it using observations of a strong continuum source. We also calculate and remove the expected effects of averaging in(More)