177 research outputs found
Analysis of aircraft microwave measurements of the ocean surface
A data system was developed to process, from calibrated brightness temperature to computation of estimated parameters, the microwave measurements obtained by the NASA CV-990 aircraft during the 1972 Meteorological Expedition. A primary objective of the study was the implementation of an integrated software system at the computing facility of NASA/GSFC, and its application to the 1972 data. A single test case involving measurements away from and over a heavy rain cell was chosen to examine the effect of clouds upon the ability to infer ocean surface parameters. The results indicate substantial agreement with those of the theoretical study; namely, that the values obtained for the surface properties are consistent with available ground-truth information, and are reproducible except within the heaviest portions of the rain cell, at which nonlinear (or saturation) effects become apparent. Finally, it is seen that uncorrected instrumental effects introduce systematic errors which may limit the accuracy of the method
Full-Polarization Observations of OH Masers in Massive Star-Forming Regions: I. Data
We present full-polarization VLBA maps of the ground-state, main-line, 2 Pi
3/2, J = 3/2 OH masers in 18 Galactic massive star-forming regions. This is the
first large polarization survey of interstellar hydroxyl masers at VLBI
resolution. A total of 184 Zeeman pairs are identified, and the corresponding
magnetic field strengths are indicated. We also present spectra of the NH3
emission or absorption in these star-forming regions. Analysis of these data
will be presented in a companion paper.Comment: 111 pages, including 42 figures and 21 tables, to appear in ApJ
Radio Astronomy
Contains research objectives and reports on three research projects.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E)U. S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-0009National Science Foundation (Grant GP-7046)National Aeronautics and Space Administration (Contract NSR-22-009-120)National Aeronautics and Space Administration (Grant NsG-419
Re-analysis of the radio luminosity function of Galactic HII regions
We have re-analyzed continuum and recombination lines radio data available in
the literature in order to derive the luminosity function (LF) of Galactic HII
regions. The study is performed by considering the first and fourth Galactic
quadrants independently. We estimate the completeness level of the sample in
the fourth quadrant at 5 Jy, and the one in the first quadrant at 2 Jy. We show
that the two samples (fourth or first quadrant) include, as well as giant and
super-giant HII regions, a significant number of sub-giant sources. The LF is
obtained, in each Galactic quadrant, with a generalized Schmidt's estimator
using an effective volume derived from the observed spatial distribution of the
considered HII regions. The re-analysis also takes advantage of recently
published ancillary absorption data allowing to solve the distance ambiguity
for several objects. A single power-law fit to the LFs retrieves a slope equal
to -2.23+/-0.07 (fourth quadrant) and to -1.85+/-0.11 (first quadrant). We also
find marginal evidence of a luminosity break at L_knee = 10^23.45 erg s^(-1)
Hz^(-1) for the LF in the fourth quadrant. We convert radio luminosities into
equivalent H_alpha and Lyman continuum luminosities to facilitate comparisons
with extra-galactic studies. We obtain an average total HII regions Lyman
continuum luminosity of 0.89 +/- 0.23 * 10^(53) sec^(-1), corresponding to 30%
of the total ionizing luminosity of the Galaxy.Comment: accepted for publication in Ap
Optical and Infrared Spectroscopy
Contains research objectives and reports on one research project
Radio Astronomy
Contains reports on three research projects, with one broken into two subsections.National Aeronautics and Space Administration (Grant NsG-419)National Aeronautics and Space Administration (Contract NSR-22-009-120)Joint Services Electronics Programs (U.S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E
Radio Astronomy
Contains reports on three research projects.National Aeronautics and Space Administration (Grant NsG-419)National Aeronautics and Space Administration (Contract NSR-22-009-120)Lincoln Laboratory Purchase Order No. 74
New infrared star clusters in the Northern and Equatorial Milky Way with 2MASS
We carried out a survey of infrared star clusters and stellar groups on the
2MASS J, H and K_s all-sky release Atlas in the Northern and Equatorial Milky
Way (350 < l < 360, 0 < l < 230). The search in this zone complements that in
the Southern Milky Way (Dutra et al. 2003a). The method concentrates efforts on
the directions of known optical and radio nebulae. The present study provides
167 new infrared clusters, stellar groups and candidates. Combining the two
studies for the whole Milky Way, 346 infrared clusters, stellar groups and
candidates were discovered, whereas 315 objects were previously known. They
constitute an important new sample for future detailed studies.Comment: Accepted to Astronomy and Astrophysic
Radio Astronomy
Contains reports on five research projects.National Aeronautics and Space Administration (Grant NsG-419)National Aeronautics and Space Administration (Contract NSR-22-009-120)Lincoln Laboratory Purchase Order No. 74
Radio Astronomy
Contains reports on five research projects.National Aeronautics and Space Administration (Grant NsG-419)National Science Foundation (Grant GP-7046)National Aeronautics and Space Administration (Contract NSR-22-009-120)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U, S. Air Force, under Contract DA 28-043-AMC-02536(E)U. S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-000
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