Engineering topics

Solomon, P. M.

Publications and source records attributed to Solomon, P. M..

At least 37 records · Page 2

NASA NTRS1981

Chlorine oxide in the stratospheric ozone layer Ground-based detection and measurement

Stratospheric chlorine oxide, a significant intermediate product in the catalytic destruction of ozone by atomic chlorine, has been detected and measured by a ground-based 204 GHz, millimeter-wave receiver. Data taken at latitude 42 deg N on 17 days between January 10 and February 18, 1980 yield an average chlorine oxide column density of approximately 1.05 x 10 to the 14th/sq cm or approximately 2/3 that of the average of eight in situ balloon flight measurements (excluding the anomalously high data of July 14, 1977) made over the past four years at 32 deg N. Less chlorine oxide below 35 km and a larger vertical gradient than predicted by theoretical models of the stratospheric ozone layer are found.

Parrish, A.↗

NASA NTRS1977

The galactic distribution (in radius and Z) of interstellar molecular hydrogen

Observations of the galactic longitude and latitude distributions of lambda = 2.6 mm CO emission are presented. Analysis of these spectral-line data yields the large-scale distribution of molecular clouds in the galactic disk and their z-distribution out of the disk. Strong maxima in the number of molecular clouds occur in the galactic nucleus and at galactic radii 4 to 8 kpc. The peak at 4 to 8 kpc correlates well with a region of enhanced 100-MeV gamma-ray emissivity. This correlation strongly supports the conclusion that the gamma-rays are produced as a result of cosmic ray interactions in molecular H2 clouds rather than in H(I). The width of the cloud layer perpendicular to the galactic plane between half-density points is 105 plus or minus 15 pc near the 5.5-kpc peak. The total mass of molecular gas in the interior of the galaxy exceeds that of atomic hydrogen and is 30 to the 9th power solar mass based on these observations.

Scoville, N. Z.↗

NASA NTRS1976

The galactic distribution (in radius and Z) of interstellar molecular hydrogen

Observations of the galactic longitude and latitude distributions of gamma = 2.6 mm CO emission are presented. Analysis of this spectral line data yields the large scale distribution of molecular clouds in the galactic disk and their z-distribution out of the disk. Strong maxima in the number of molecular clouds occur in the galactic nucleus and at galactic radii 4-8 kpc. The peak at 4-8 kpc correlates well with a region of enhanced 100 Mev gamma ray emissivity. This correlation strongly supports the conclusion that the gamma rays are produced as a result of cosmic ray interactions in molecular H2 clouds rather than HI. One important implication of this is that the interstellar magnetic field lines to which cosmic rays are confined must therefore not be excluded from these dense clouds. The width of the cloud layer perpendicular to galactic plane between half density points is 105 + or - 15 pc near the 5.5 kpc peak. The total mass of molecular gas in the interior of the galaxy exceeds that of atomic hydrogen.

Scoville, N. Z.↗

NASA NTRS1975

Molecular hydrogen in the Galaxy and galactic gamma rays

Recent surveys of 2.6-cm CO emission and 100-MeV gamma-radiation in the galactic plane reveal a striking correlation suggesting that both emissions may be primarily proportional to the line-of-sight column density of H2 in the inner Galaxy. Both the gamma-ray and CO data suggest a prominent ring or arm consisting of cool clouds of H2 at a galactocentric distance of about 5 kpc with a mean total hydrogen density equivalent to approximately 5 atoms per cu cm. Estimates are made of column densities of H2 at 0 deg galactic longitude and are compared with estimates from infrared and X-ray absorption measurements. These estimates are all consistent, indicating that H2 is far more abundant than H I in the inner Galaxy and is the key to a more satisfactory explanation of the gamma-ray observations than previous suggestions. The importance of H2 in understanding galactic gamma-ray observations is also reflected in the correlation of galactic-latitude distribution of gamma-rays and dense dust clouds. The deduced cosmic-ray distribution inferred from the calculations is similar to that of galactic supernova remnants, suggesting a galactic origin for most cosmic rays.

Stecker, F. W.↗

NASA NTRS1975

Molecular hydrogen in the galaxy and galactic gamma rays

Recent surveys of 2.6 mm CO emission and 100 MeV gamma-radiation in the galactic plane reveal a striking correlation suggesting that both emissions may be primarily proportional to the line-of-sight column density of H2 in the inner galaxy. Both the gamma ray and CO data suggest a prominent ring or arm consisting of cool clouds of H2 at a galactocentric distance of approximately 5 kpc with a mean density of approximately 4 atoms/cu cm. The importance of H2 in understanding galactic gamma ray observations is also reflected in the correlation of galactic latitude distribution of gamma rays and dense dust clouds. A detailed calculation of the gamma ray flux distribution in the 0 deg to 180 deg range using the CO data to obtain the average distribution of molecular clouds in the galaxy shows that most of the enhancement in the inner galaxy is due to pion-decay radiation and the 5 kpc ring plays a major role. Detailed agreement with the gamma ray data is obtained with the additional inclusion of contributions from bremsstrahlung and Compton radiation of secondary electrons and Compton radiation from the intense radiation field near the galactic center.

Stecker, F. W.↗

NASA NTRS1975

Molecular hydrogen in the galaxy and galactic gamma rays

Estimates made of column densities of H2 at galactic longitude equals 0 deg indicate that H2 is far more abundant than HI in the inner galaxy and is the key to an explanation of the gamma-ray observations. This is also reflected in the correlation of galactic longitude and latitude distributions of gamma-rays and molecular clouds. Particularly strong evidence is found from the galactic survey of CO emission at 2.64 mm. The cosmic-ray distribution inferred from the calculations is not uniform but only weakly dependent on the total gas distribution in the inner galaxy.

Stecker, F. W.↗

NASA NTRS1974

Radio and gamma ray evidence for a molecular-arm feature at 5 kpc from the galactic centre

Recent measurements of the galactic CO distribution as evidenced from 2.6 mm radio observations of the CO emission line intensity are correlated with the SAS-2 measurements of galactic gamma ray emission. Both distributions are indicative of a ring-shaped distribution or arm consisting of cool clouds of molecular hydrogen at a galactocentric distance of approximately 5 kpc. The mean density of H2 in this region is estimated to be between 1 and 5 cu cm. Both a galactic and extra-galactic origin of cosmic rays are consistent with the observations, although the presence of dynamical effects and increased star formation at 5 kpc in the dense molecular clouds may be connected with an increase in cosmic-ray production.

Solomon, P. M.↗

NASA NTRS1974

CO and CS in the Orion Nebula

The reported observations were made with an 11-m radio telescope. The CO map considered has a peak near the position of the infrared continuum source. There is little correlation between the CO contours and any optical structure. The CO contours show a pronounced north-south orientation. CS was observed as a representative example of a stable molecule with a higher dipole moment than CO. Questions regarding the structure of Orion A are discussed, giving attention to various models.

Liszt, H. S.↗

NASA NTRS1972

The formation of diatomic molecules in interstellar clouds.

The formation of the classical interstellar molecules CH, CH(+), and CN is investigated, giving attention to the chemistry of moderate-density interstellar clouds. An H I region is considered in the model employed in the study. The major constituents in the region are atoms or ions because of the intensity of the UV radiation field. Aspects of radiative association are discussed together with chemical reactions, the electronic states and optical properties of CH and CH(+), and photodissociation rates.

Solomon, P. M.↗

NASA NTRS1972

C-13O-16/C-12O-18 ratios in nine H II regions.

Investigation of carbon monoxide spectra in sources where the C-12O-18 line is observed at an intensity typically about one-sixth that of the C-13O-16 line. This pair of lines affords the opportunity of studying the relative abundance of their constituents, especially the astrophysically important C-12/C-13 ratio. Data are presented on a total of nine sources which together constitute a reasonable sample of the regions with strong molecular spectra.

Penzias, A. A.↗

NASA NTRS1972

Radiation-pressure-driven mass loss from quasi-stellar objects.

It is shown that radiation pressure acting on the material in the outer envelopes of QSOs will cause mass outflow unless the mass M of the QSO exceeds a critical value Ms. If the QSOs are at cosmological distances, Ms is on the order of 10 to 100 billion solar masses, and otherwise scales according to intrinsic luminosity. Radiation-pressure-driven mass loss could be responsible for the absorption-line spectra observed in many QSOs. If so, the presence of blueshifted absorption lines in some but not all QSOs indicates that typically M is of the same order as Ms. It is also suggested that under radiative acceleration certain ratios of emission-line to absorption-line redshifts may be preferred as a result of a line-locking mechanism. Inferences are made concerning the magnitude of the gravitational component of the redshift. Possible tests of various aspects of the model are discussed.

Mushotzky, R. F.↗

NASA NTRS1972

Survey of molecular lines near the galactic center. I - 6-centimeter formaldehyde absorption in Sagittarius A, Sagittarius B2, and the galactic plane from 359.4 to 2.2 deg galactic longitude.

The data obtained indicate that the formaldehyde is concentrated in distinct clouds to a much greater extent than atomic hydrogen. The findings suggest that most of the mass in these clouds is in the form of molecular hydrogen. The locations of four dominant clouds are reported. The strongest formaldehyde features are apparently associated with the galactic nucleus. Estimates of the hydrogen density in the clouds, based on the assumption of stability and also on a comparison with local dark clouds, indicate a number density in the range from 1000 to 10,000 per cc, and a mass of approximately 500,000 solar masses.

Scoville, N. Z.↗

NASA NTRS1972

Search for interstellar furan and imidazole.

Results are reported on an unsuccessful 6-cm search for the heterocyclic carbon ring molecules furan and imidazole. Upper limits in brightness temperature of 0.25 K or less are found for furan in 11 galactic sources, and of less than 0.1 K for imidazole in Sgr A and Sgr B2.

Dezafra, R. L.↗

NASA NTRS1971

Apparent associations between bright galaxies and quasi-stellar objects.

A comparison of the spatial distribution of the 47 identified QSOs in the 3C and 3CR catalogs with the small-redshift galaxies contained in the Reference Catalog of Bright Galaxies shows that four QSOs with redshift in the range 0.5-1.4 are much closer to bright galaxies than would be expected if the 47 QSOs were distributed randomly. An extensive analysis of the distributions shows that the probability that this is a chance occurrence is less than 0.005. It is also shows that the radio-quiet QSO PHL 1226 lies very close to IC 1746 to which it appears to have a physical connection.

Burbidge, E. M.↗

NASA NTRS1971