Engineering topics
Publications and source records attributed to Morton, D. C..
The experimental development and evaluation of infrared vidicons for use in solving high precision high flux broadband astronomical problems are discussed. Data cover the EOS, silicon, and doped germanium vidicons. Results are graphed and problems encountered using the vidicons in electrical cameras are reported.
Extensive high-resolution scans with the Copernicus UV spectrometer are combined with available ground-based data on interstellar lines to obtain temperatures, densities, and abundances in H I clouds and H II regions in the direction of zeta Oph. Column densities are obtained for 21 elements in various ionization stages, and upper limits are reported for 5 elements and 11 molecules. Analysis of radial velocities and growth curves indicates that H2, HD, and most neutral atoms are concentrated in one cloud with a heliocentric velocity of -14.4 km/s and that H II regions exist in addition to the Stroemgren sphere. The electron and proton densities are calculated for the -14.4 km/s cloud, and the temperatures required for the populations of the fine-structure levels in the C I ground state and the excited rotational levels of H2 are computed and indicate that the dense cloud must have some associated hotter regions. Relative to hydrogen, most of the elements in the H I clouds are found to be depleted by factors of 3 to 4000 as compared with solar system abundances, and several elements appear to be depleted in the H II regions as well.
With two f-values of C I lines obtained from the spectra of zeta Pup and gamma(2) Vel, it is shown that the interstellar C I spectrum in zeta Oph obeys an optical-depth relation similar to that for Na I, and the relative strengths of 19 multiplets are determined from this relation. The dominant processes which excite neutral carbon are used to calculate populations of the fine-structure levels as functions of the density of H nuclei and the temperature, and evidence is found that the C I lines are formed in the dense cloud in front of zeta Oph at a heliocentric velocity of -14.4 km/s. It is noted that the observed column-density ratios of the neutral carbon fine-structure levels lead to a total H nuclei density of about 220 to 660 per cu cm, while the electron density and observed C(+) abundance indicate a value of 10,000 per cu cm, with a 0.05 pc thick gas layer.
The present work describes high- and low-resolution rocket-ultraviolet spectra of kappa, lambda, tau, and upsilon Scorpii obtained in the range from 1160 to 1880 A. The Si IV resonance lines in tau Sco show asymmetries indicating outward mass motions of up to about 400 km/sec. The suitability of some of the lines observed for indication of luminosity or temperature is discussed. It is pointed out that the intrinsic strength and large changes of the lines of Si III and C IV may permit a more accurate spectral classification of stars between B0 and B3 than has been demonstrated in this same spectral type region using visible spectra.
Extensive Copernicus observations of interstellar absorption lines in front of zeta Oph have been combined with similar ground-based data to give column densities or limits on 26 elements in H I clouds. Compared with solar-system abundances, there is a depletion of most elements relative to hydrogen, except S and Zn, by factors of 3 to 4000. The depletions generally are larger for the higher condensation temperatures.
Report of a new upper limit on interstellar boron in the direction of zeta Oph, obtained by making 25 scans across the B II resonance line at 1362.461 A with the Copernicus satellite. A B/H of about 7.6 times 10 to the negative 11th power or less was found, implying that boron in the interstellar gas is depleted by a factor of about 60 relative to boron in carbonaceous chondrites. These results are related to theories of the formation of grains, and the flux of cosmic rays.-
The observed strengths of interstellar absorption lines of Fe II and Mn II in the spectra of alpha Vir, beta Cen, pi Sco, and zeta Oph along with laboratory f values of some of these lines between 2343 and 2606 A have been used to determine curves of growth for these ions and the f-values of ten lines of Fe II and three lines of Mn II between 1055 and 1261 A. The Fe and Mn abundances are derived.
A table of wavelengths, statistical weights, and excitation energies is given for 944 atomic spectral lines in 221 multiplets whose lower energy levels lie below 0.275 eV. Oscillator strengths were adopted for 635 lines in 155 multiplets from the available experimental and theoretical determinations. Radiation damping constants also were derived for most of these lines. This table contains the lines most likely to be observed in absorption in interstellar clouds, circumstellar shells, and the clouds in the direction of quasars where neither the particle density nor the radiation density is high enough to populate the higher levels. All ions of all elements from hydrogen to zinc are included which have resonance lines longward of 912 A, although a number of weaker lines of neutrals and first ions have been omitted.
Wavelengths and profiles of several absorption lines in the spectrum of the quasar Markarian 132, obtained with the aid of an integrating television sensor, are presented. An attempt is made to derive column densities and internal Doppler velocities by fitting theoretical Voigt profiles to the observed spectra. C IV lines show that the absorption must occur in at least two separate clouds with a relative velocity of 160 km/sec.
The Princeton telescope-spectrometer on the OAO spacecraft Copernicus scans stellar spectra with a resolution of about 0.05 A between 950 and 1450 A, and twice this in first order between 1650 and 3000 A. The pointing during several minutes is steady within .02 sec, and the measured photometric precision in the shorter wavelength range is limited only by the statistics of photon counts, with 14-sec counts of about 1000 on an unreddened B1 star, m(v) = 5.0, at 1100 A. In the 1650-3000 A wavelength range, phototube noise resulting from cosmic rays makes observations difficult on stars fainter than m(v) = 3.0.
A survey of selected spectral regions in five reddened stars is described. A curve-of-growth analysis of abundances indicates that the ratios of Mg, P, Cl, and Mn to hydrogen are less than in the sun by factors of about 4 to 10. Several of the other elements also are depleted in some of the stars.
Interstellar lines have been studied in the unreddened stars lambda Sco, upsilon Sco, alpha Leo, and alpha Eri, which are located between 20 and 150 pc from the sun. The lines are on the linear and saturated Doppler portions of the curve of growth. Preliminary analysis shows that processes producing large amounts of highly ionized species are not dominant. Doubly ionized C, N, Si, and S have been detected, but are all quite weak relative to the singly ionized species. Abundances relative to nitrogen are in the cosmic ratios or slightly lower, with some indication of general depletion of the heavier elements. Hydrogen number densities range from a measured value of 0.22 per cu cm for lambda Sco to a derived value of 0.02 per cu cm for alpha Leo assuming nitrogen to have its solar abundance relative to hydrogen.
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A coude spectrum of the E7 galaxy NGC 7332 with 0.9 A-resolution from 4186 to 4364 A was obtained with the Princeton SEC vidicon television camera and the Hale telescope. Comparisons with spectra of G and K giant stars, numerically broadened for various Maxwellian velocity distributions, give a dispersion velocity in the line of sight of 160 (plus or minus 20) km/sec with the best fit at G8 III. The dispersion appears to be constant within plus or minus 35 km/sec out to 1.4 kpc. After correction for projection, the rotation curve has a slope of 0.18 km/sec per pc at the center and a velocity of 130 km/sec at 1.4 kpc where it is still increasing. For an estimated effective radius of 3.5 kpc enclosing half the light, the virial theorem gives a mass of 140 billion solar masses if the mass-to-light ratio is constant throughout the galaxy.