Hydroxyl Emission Research Articles

The 18 centimeter OH emission of IC 4553 (Arp 220)

view Abstract Citations (40) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The 18 Centimeter OH Emission of IC 4553 (Arp 220) Baan, Willem A. ; Haschick, Aubrey D. Abstract All transitions of hedroxyl have been found in emission in IC 4553 (Arp 220). The line shapes have been decomposed and interpreted in terms of three distinct emission regions: one region at the systemic velocity of the galaxy, and a second at a 334 km/s higher velocity. A third region represents a nuclear outflow with a terminal velocity of approximately 700 km/s. The emission lines for the region I are the strongest and originate in a molecular disk surrounding the nucleus of the galaxy. The infalling foreground region II is thought to be rather extended and has a very prominennt 1612 MHz line. The line ratios of regions I and II are quite different indicating that, although the primary pump for both regions is the infrared radiation field, there are differences in the (secondary) excitation conditions. Regions I and II may represent the two nuclei of the galaxies, which make up the merging IC 4553. The excitation of region III is collisional. Publication: The Astrophysical Journal Pub Date: July 1987 DOI: 10.1086/165356 Bibcode: 1987ApJ...318..139B Keywords: Centimeter Waves; Emission Spectra; Galactic Nuclei; Galactic Rotation; Gas Dynamics; Hydroxyl Emission; Astronomical Spectroscopy; Interstellar Matter; Molecular Clouds; Radial Velocity; Radio Spectra; Astrophysics; GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 4553; GALAXIES: INTERNAL MOTIONS; GALAXIES: NUCLEI; INTERSTELLAR: MOLECULES full text sources ADS | data products SIMBAD (1) NED (1)

Observations of comet Giacobini-Zinner at the 1.667 GHz OH line

view Abstract Citations (5) References (3) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of Comet Giacobini-Zinner at the 1.667 GHz OH Line Galt, J. Abstract Comet Giacobini-Zinner was observed during an 18 day interval just prior to its perihelion passage. The 1.667 GHz OH line appeared in absorption, as expected, but showed large intensity fluctuations from day to day. Comparisons are made with subsequent observations of comet Halley. Publication: The Astronomical Journal Pub Date: July 1987 DOI: 10.1086/114461 Bibcode: 1987AJ.....94..174G Keywords: Absorption Spectra; Astronomical Spectroscopy; Giacobini-Zinner Comet; Hydroxyl Emission; Line Spectra; Halley'S Comet; Periodic Variations; Radiant Flux Density; COMETS; GIACOBINI-ZINNER; OBSERVATIONS; ABSORPTION; INTENSITY; SPECTRA; COMPARISONS; EARTH-BASED OBSERVATIONS; WAVELENGTHS; RADIO WAVES; DATA; Astronomy; Comets; COMETS full text sources ADS |

Study of the H42-alpha (86 GHz) recombination line in W3(OH)

view Abstract Citations (39) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Study of the H42 alpha (86 GHz) Recombination Line in W3(OH) Welch, Wm. J. ; Marr, J. Abstract The authors have observed the H42α recombination line at 86 GHz in the compact H II region W3(OH). The central velocity of the line is -45.6±1.0 km s-1, only 1.3 km s-1 from the measured mean velocity of the OH masers in front of the region. It is argued that the OH masers are not in free-fall onto the central O star, as suggested in 1980 by Reid et al. The width of the line is 27.3±1.5 km s-1, too small to fit the model proposed in 1983 by Berulis and Erschov of a shell expanding at 18 km s-1. Publication: The Astrophysical Journal Pub Date: June 1987 DOI: 10.1086/184905 Bibcode: 1987ApJ...317L..21W Keywords: H Alpha Line; Hydroxyl Emission; Interstellar Masers; Recombination Reactions; Stellar Envelopes; H Ii Regions; Radial Velocity; Spectral Line Width; Astrophysics; MASERS; NEBULAE: H II REGIONS; STARS: CIRCUMSTELLAR SHELLS full text sources ADS | data products SIMBAD (1)

On the contribution of interstellar extinction to the 10 micron dust feature in OH/IR stars

view Abstract Citations (44) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Contribution of Interstellar Extinction to the 10 Micron Dust Feature in OH/IR Stars Volk, Kevin ; Kwok, Sun Abstract The IRAS Low Resolution Spectra of 467 sources with the 10 micron dust feature are analyzed. The strengths of the dust feature are determined by the ratio of the flux at 9.7 micron to the fitted continuum level. Color temperatures are derived from the fluxes of the four IRAS photometric bands after correcting for the effect of the 10 micron feature on the fluxes of the 12 micron band. A definite correlation between the strength of the feature and the color temperature of the continuum is found, implying that the 10 micron dust feature is largely circumstellar in origin. A reexamination of the strength of the silicate feature for seven of the OH/IR star used by Gehrs and colleagues in 1985 has failed to reproduce the optical depth-distance relationship found by these authors. It is concluded that interstellar extinction does not play a major role in the formation of the 10 micron absorption feature. Publication: The Astrophysical Journal Pub Date: April 1987 DOI: 10.1086/165167 Bibcode: 1987ApJ...315..654V Keywords: Cosmic Dust; Hydroxyl Emission; Infrared Absorption; Infrared Stars; Interstellar Extinction; Stellar Envelopes; Infrared Astronomy Satellite; Stellar Color; Stellar Temperature; Astrophysics; INFRARED: SOURCES; INTERSTELLAR: GRAINS; STARS: CIRCUMSTELLAR SHELLS full text sources ADS | data products SIMBAD (467) NED (1)

Monitoring the 1.667 GHz OH line in Comet Halley

view Abstract Citations (13) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Monitoring the 1.667 GHz OH Line in Comet Halley Galt, J. Abstract From October 5, 1985 to March 26, 1986 and again from April 30 to May 29, the 1.667 GHz OH line in Comet Halley was observed almost continuously with the Dominion Radio Astrophysical Observatory's 25.6 m antenna and a digital autocorrelation spectrometer. Spectra covered the velocity range + or - 5.6 km/s with a resolution of 0.18 km/s. A Gaussian curve was fitted to each daily averaged spectrum to determine peak flux, width, and velocity of the line whenever signal-to-noise ratio permitted. A plot of peak line flux against time shows frequent outbursts superimposed on the slow variations predicted by Schloerb and Gerard (1985). In at least two instances, bursts of enhanced emission lasting about six days rose above the predicted levels. Several spectra show asymmetries which could be attributed to anisotropic release of gas. Publication: The Astronomical Journal Pub Date: March 1987 DOI: 10.1086/114357 Bibcode: 1987AJ.....93..747G Keywords: Halley'S Comet; Hydroxyl Emission; Radio Spectra; Gas Jets; Line Spectra; Radiant Flux Density; Ultrahigh Frequencies; COMETS; HALLEY; HYDROXYL RADICAL; EARTH-BASED OBSERVATIONS; ASTRONOMY; RADIO METHODS; SPECTROMETRY; SPECTRA; PROCEDURE; FLUX; BURSTS; GASES; EMISSIONS; WATER; PRODUCTION RATES; DISTRIBUTION; DENSITY; COMAE; SYMMETRY; ANISOTROPY; DATA REDUCTION; Astronomy; Comets; COMETS full text sources ADS |

Pumping the stellar hydroxyl maser

view Abstract Citations (27) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Pumping the Stellar Hydroxyl Maser Dickinson, Dale F. Abstract IRAS far-IR flux data for 163 OH maser stars were analyzed to quantify the contributions 35 and 53 microns inversions make to pumping of the hydroxyl maser. The 35 microns transition is from the 3,3 ground state to the 1,5 rotationally excited level and subsequent decay; the 53 microns transition is a change from the ground state to the 1,3 excited level and relaxation. The stars examined included Mira, short period semi-regular and long-period semi-regular variables. Both transition lines had rough parity in contributing to the approximately 8 percent pumping efficiency at 1612 MHz. However, the individual contributions of the lines could not be determined for the stellar population studied. Publication: The Astrophysical Journal Pub Date: February 1987 DOI: 10.1086/164978 Bibcode: 1987ApJ...313..408D Keywords: Hydroxyl Emission; Infrared Spectra; Interstellar Masers; Late Stars; Mira Variables; Far Infrared Radiation; Semiregular Variable Stars; Stellar Spectrophotometry; Astrophysics; INFRARED: SOURCES; MASERS; STARS: LATE-TYPE; STARS: VARIABLES full text sources ADS |

The winter anomaly in the ionospheric D-region—some numerical calculations

This paper reports on results of numerical calculations for conditions under which the anomalously high absorption of radio waves appears and disappears at middle atmosphere heights, having characteristic time constants of about 24 h. In the calculations we have solved a system of equations which are self-consistent in a one-dimensional approximation and govern the temperature and neutral and ion composition behaviour in the height range 40–150 km. The values of the turbulent transfer coefficient and turbulent energy dissipation rate were calculated for the case of the anomalous absorption commencement, using experimental data pertaining to the vertical structure of the wind and temperature field. The results derived from numerical calculations involving evidence of turbulent processes were used to interpret some characteristic properties of neutral and charged particles, temperature and densities for day-time conditions with anomalously high absorption. The lack of experimental data on winds and temperature throughout the height range under study for the dates with normal absorption forced us to use indirect measurements in making assumptions about the vertical profile of the turbulent transfer coefficient and the values of the turbulent dissipation rate. The results thus obtained agree with measurements of electron density, temperature and hydroxyl emission intensity (the hydrogen content decreases as the conditions change from anomalous to normal). There are, however, discrepancies between calculated and measured atomic oxygen densities.

OH/IR stars. V - Sources near the galactic center

view Abstract Citations (13) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS OH/IR stars. V. Sources near the galactic center. Jones, T. J. ; Hyland, A. R. Abstract Infrared observations of 15 OH/IR stars within 30arcmin of the galactic center are reported. The luminosities range from a few ×103L_sun; up to, but not exceeding, the AGB limit (≡6×104L_sun;). This suggests a range in main-sequence progenitors from ≡1 to 9 M_sun; with no clear evidence for massive core-burning supergiants. The infrared and maser properties of this sample are similar to the less extreme (bluer) OH/IR stars found in surveys of the galactic plane. Less than half of the stars near the galactic center have luminosities below 104L_sun;, in contrast to the authors' expectations that they would dominate the statistics. Publication: The Astronomical Journal Pub Date: October 1986 DOI: 10.1086/114213 Bibcode: 1986AJ.....92..805J Keywords: Galactic Nuclei; Hydroxyl Emission; Infrared Stars; Milky Way Galaxy; Astronomical Photometry; Color; Stellar Luminosity; Astrophysics full text sources ADS | data products SIMBAD (2)

OH masers in short-period Mira and semiregular variable stars

view Abstract Citations (17) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS OH masers in short-period Mira and semiregular variable stars. Dickinson, D. F. ; Turner, B. E. ; Jewell, P. R. ; Benson, P. J. Abstract The authors have made a systematic search in all four OH lines for maser emission from the short-period Mira variables and the known short-period semiregular maser stars. R Ceti was detected in the main lines, the first short-period (166 days) Mira ever found in OH. None of the short-period Miras searched showed water emission. The authors also present spectra of three SiO detections made in a very limited sample of the short-period Mira variables. Six new OH lines were detected in the semiregular variables; all are Type I stars devoid of any satellite line emission. Both classes of star are weak OH emitters and there is a relative lack of circumstellar material as evidenced by the modest infrared excess shown in the 2.2 - 11 μ color index. These facts are probably related and lend support to the idea that far-infrared radiation is the primary OH maser pump in these stars. Publication: The Astronomical Journal Pub Date: September 1986 DOI: 10.1086/114193 Bibcode: 1986AJ.....92..627D Keywords: Hydroxyl Emission; Interstellar Masers; Mira Variables; Semiregular Variable Stars; Stellar Spectrophotometry; Far Infrared Radiation; Line Spectra; Silicon Oxides; Astrophysics full text sources ADS | data products SIMBAD (102)

The brightness distribution of OH around Comet Halley

view Abstract Citations (16) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Brightness Distribution of OH around Comet Halley de Pater, I. ; Palmer, P. ; Snyder, L. E. Abstract The first successful VLA observations of OH emission from any comet have been made for comet Halley. In 1985 November, 120 arcsec and 60 arcsec resolution images of the brightness distribution of the 1667 MHz line were obtained. The 120 arcsec image shows that the peak of the OH emission is displaced 40 arcsec to the west and 80 arcsec to the south. The 60 arcsec image shows that the emission is concentrated in 'clumps', which surround a 'hole' in the OH emission. The hole may be the first direct observation of OH maser quenching in the inner cometary coma. The clumps of OH emission can best be explained by bow shock excitation or by large ice fragments broken off the cometary nucleus. Publication: The Astrophysical Journal Pub Date: May 1986 DOI: 10.1086/184665 Bibcode: 1986ApJ...304L..33D Keywords: Astronomical Spectroscopy; Brightness Distribution; Halley'S Comet; Hydroxyl Emission; Astronomical Maps; Bow Waves; Comet Heads; Interstellar Masers; Shock Waves; COMETS; HALLEY; BRIGHTNESS; DISTRIBUTION; HYDROXYL RADICAL; EMISSIONS; EARTH-BASED OBSERVATIONS; COMAE; BOW SHOCK; ICE; FRAGMENTS; OUTGASSING; Astrophysics; Comets; COMETS; MOLECULAR PROCESSES full text sources ADS |

New OH observations of the supergiant IRC +10420

view Abstract Citations (20) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS New OH Observations of the Supergiant IRC +10420 Lewis, B. M. ; Terzian, Y. ; Eder, J. Abstract The left and right circularly polarized spectra of the supergiant IRC +10420 are presented. The current intensity of the object's +55 km/s feature in the 1612 and 1665 MHz lines is discussed. The 1665 MHz feature is weakening while its 1612 MHz feature is growing more quickly than before. These observations are consistent with a linear growth of the mean flux from the two lines, which originate from the same excited level. The decreasing intensity of the 1665 MHz feature may be due to conversion of 1665 MHz photons from a thriving maser to 1612 MHz photons in the saturated outer layers, as the maser's column length grows outward. Publication: The Astrophysical Journal Pub Date: March 1986 DOI: 10.1086/184629 Bibcode: 1986ApJ...302L..23L Keywords: Hydroxyl Emission; Interstellar Masers; Line Spectra; Stellar Spectrophotometry; Supergiant Stars; Interstellar Matter; Stellar Envelopes; Astrophysics; INTERSTELLAR: MOLECULES; MASERS; STARS: CIRCUMSTELLAR SHELLS full text sources ADS | data products SIMBAD (1)

Zeeman splitting of 18 centimeter OH lines toward Cassiopeia A and other sources

view Abstract Citations (43) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Zeeman Splitting of 18 Centimeter OH Lines toward Cassiopeia A and Other Sources Heiles, C. ; Stevens, M. Abstract Zeeman splitting of the OH absorption lines has been detected toward Ori B, W22, and Cas A. For W22, the derived magnetic field strength is -11 micro-G. For Ori B, the inferred magnetic field strength is consistent in magnitude, but not in direction, with the 38 micro-G derived previously by Crutcher and Kazes (1983, 1985); the field is positive and therefore points away from the observer. For Cas A, the average field in four velocity components is +9 micro-G, in the same direction as, but weaker than, the field strengths measured in single-dish H I data. They are considerably weaker than the field strengths in less dense H I clumps that are associated with the OH clumps. This circumstance raises serious interpretive difficulties. Publication: The Astrophysical Journal Pub Date: February 1986 DOI: 10.1086/163903 Bibcode: 1986ApJ...301..331H Keywords: Hydroxyl Radicals; Interstellar Gas; Interstellar Magnetic Fields; Line Spectra; Molecular Clouds; Zeeman Effect; Absorption Spectra; Cassiopeia A; Centimeter Waves; Field Strength; Hydroxyl Emission; Astrophysics; INTERSTELLAR: MAGNETIC FIELDS; INTERSTELLAR: MOLECULES; NEBULAE: INDIVIDUAL NAME: CASSIOPEIA A; ZEEMAN EFFECT full text sources ADS | data products SIMBAD (10)

Effects of the law for nongravitational forces on the precession model of comet Encke

view Abstract Citations (12) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Effects of the law for nongravitational forces on the precession model of comet Encke Sekanina, Z. Abstract The precession model for P/Encke formulated by Whipple and Sekanina (1979) is re-examined in the light of the recent measurements of the OH and H production rates, which according to A'Hearn et al. (1985) indicate that the comet's visual light curve cannot be employed to approximate the variations with time in the nongravitational force that is being exerted on the nucleus by the comet's outgassing. The optimized precession solution derived here with the use of the A'Hearn et al. production law is shown to require unacceptably small nucleus dimensions and to offer an inferior fit to observed variations in the orientation of the comet's preperihelion fan-shaped coma. It is concluded that the Whipple-Sekanina model remains the best available precession solution for this comet. Publication: The Astronomical Journal Pub Date: February 1986 DOI: 10.1086/114022 Bibcode: 1986AJ.....91..422S Keywords: Astronomical Models; Encke Comet; Gravitational Effects; Precession; Comet Nuclei; Hydrogen; Hydroxyl Emission; Light Curve; Outgassing; Perihelions; Water; Astrophysics full text sources ADS |

Circular polarization of astrophysical masers due to overlap of Zeeman components

view Abstract Citations (47) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Circular Polarization of Astrophysical Masers Due to Overlap of Zeeman Components Deguchi, S. ; Watson, W. D. Abstract Calculational methods are presented and utilized in an idealized case to evaluate the polarization due to the overlap of Zeeman components that arises in the radiation from astrophysical masers. The essential simplicity of this previously unrecognized effect is a compelling argument in its favor as the basic cause for the strong, net circular polarization of the OH masers. Observations can then be interpreted to yield an estimate for the strength of the magnetic fields in the masing regions, even when Zeeman pairs cannot be identified as is usually the situation. Magnetic fields of approximately a milligauss or greater are inferred to be common in the masing gas associated with regions of star formation. This estimate should be considerably more general than the specific assumptions of the present calculation. Publication: The Astrophysical Journal Pub Date: January 1986 DOI: 10.1086/184594 Bibcode: 1986ApJ...300L..15D Keywords: Circular Polarization; Computational Astrophysics; Hydroxyl Emission; Interstellar Masers; Stellar Evolution; Zeeman Effect; Magnetic Field Configurations; Spectral Line Width; Astrophysics; MASERS; POLARIZATION full text sources ADS |

Far-infrared emission lines of CO and OH in the Orion-KL molecular shock

view Abstract Citations (98) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Far-infrared emission lines of CO and OH in the Orion-KL molecular shock. Watson, D. M. ; Genzel, R. ; Townes, C. H. ; Storey, J. W. V. Abstract Observations of far infrared rotational emission lines which arise in the shocked gas associted with Orion-Kl are presented, including detections of the CO J = 34 yields 33, J = 31 yields 30, J = 26 yields 25, and OH2 PI(3/2) JP = 7/2(-) yields 5/2(+) emission lines, as well as improved measurements of the CO J = 22 yields 21 and OH2 PI(3/2) J = 5/2 yields 3/2 lines. These lines are observed to have velocity widths of Del V approx. 20 to 30 km/sec, somewhat less than either the 2 micro H2 lines or the high velocity plateau component of the millimeter wave CO lines seen in this object. An H2 column density of aprox. 3 x 10 to the 21st power, a total mass of approx. 1 solar mass and characteristic temperature and density T approx. 750 K and approx. 2 x 10 to the 6th power per cu cm can be derived from the CO intensities. The density is too low by at least an order of magnitude for the observed infrared H2 and far infrared CO emission to be accounted for by a purely hydrodynamic shock, and support is lent to hydromagnetic shock models. From the present measurements, the relative abundance of CO is estimated to be CO H2 = 1.2 x .0001, corresponding to 20 percent of the cosmic abundance of C existing in the form of CO. The average relative abundance of OH in the shocked gas is O/H2 or = 5 x 10 to the -7th power. An upper limit to the intensity of the HD J - 1 yields 0 line is used to derive an upper limit of tau or = 3 for the D/H relative abundance in the Orion cloud core. Publication: The Astrophysical Journal Pub Date: November 1985 DOI: 10.1086/163612 Bibcode: 1985ApJ...298..316W Keywords: Carbon Dioxide; Far Infrared Radiation; Hydroxyl Emission; Line Spectra; Molecular Clouds; Orion Nebula; Interstellar Gas; Interstellar Matter; Nebulae; Astrophysics full text sources ADS | data products SIMBAD (1)

The fourth OH megamaser - Markarian 273

view Abstract Citations (23) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The fourth OH megamaser : Markarian 273. Baan, W. A. ; Haschick, A. D. ; Schmelz, J. T. Abstract A fourth OH megamaser has been found in the luminous IR galaxy Mrk 273 (= U08696). The characteristics of this masing galaxy are similar to those of the other powerful extragalactic masers in NGC 3690, IC 4553, and Mrk 231. The 1667 MHz line luminosity of Mrk 273 is 335 L solar luminosities. The IR photon-to-OH photon conversion efficiency is calculated for all OH megamasers and is found to be close to 1 percent. Publication: The Astrophysical Journal Pub Date: November 1985 DOI: 10.1086/184565 Bibcode: 1985ApJ...298L..51B Keywords: Hydroxyl Emission; Infrared Radiation; Interstellar Masers; Seyfert Galaxies; Emission Spectra; Line Spectra; Radial Velocity; Astrophysics full text sources ADS | data products SIMBAD (7) NED (4)

Relation between bright nights and meteoritic showers

From examination of published data, we find a strong correlation between the "bright-night" phenomenon and meteoritic showers. We show how the N atoms and nitric oxide molecules produced along meteor trails give a continuous emission due to NO2, the enhancement of which is at the origin of bright nights. At the same time the hydroxyl emission is enhanced.

A search for 18-cm OH emission from Comet Crommelin

view Abstract Citations (3) References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A search for 18-cm OH emission from Comet Crommelin Deich, W. T. S. ; Cordes, J. M. ; Terzian, Y. Abstract The Arecibo radiotelescope was used to scan for OH 18-cm line emissions from the Comet Crommelin as a trial for 3 arcsec resolution observations of Halley's Comet. The instrument was centered on the 1665 and 1667 MHz bands during intervals in January and February 1984. No detection of the OH 1665 and 1667 MHz lines was made above a 3-sigma limit of 9 mJy; and no detection of continuum emission at 18 cm was made above a 3-sigma level of 5 mJy. Publication: The Astronomical Journal Pub Date: February 1985 DOI: 10.1086/113742 Bibcode: 1985AJ.....90..373D Keywords: Astronomical Spectroscopy; Comets; Hydroxyl Emission; Radio Astronomy; Centimeter Waves; Line Spectra; COMETS; CROMMELIN; EMISSIONS; HYDROXEL RADICAL?; OBSERVATIONS; ASTRONOMY; OPTICAL PROPERTIES; SPECTRA; DATA; ANALYSIS; Astrophysics; Comets full text sources ADS |

OH/IR stars within 50 parsecs of the Galactic center

view Abstract Citations (54) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS OH/IR stars within 50 parsecs of the galactic center. Winnberg, A. ; Baud, B. ; Matthews, H. E. ; Habing, H. J. ; Olnon, F. M. Abstract A search for OH/IR stars close to the Galactic center has been initiated using the VLA at 18 cm. Thirty-three stars were found in a 34 x 34 arcmin field centered on Sgr A West. The strong concentration toward the galactic plane and the bulk rotation around the nucleus reported by Habing et al. in 1983 in a 2 deg field around the Galactic center are confirmed, but the random motion with a dispersion of 60 km/s in the radial direction is less than half the value found by them. The circumstellar shell expansion velocities are higher than found at larger distances from the Galactic center, suggesting a relatively more massive population of stars near the nucleus or a more efficient conversion of radiation pressure to bulk motion of the circumstellar gas. The OH/IR stars are strongly concentrated toward the continuum source Sgr A West, suggesting a pronounced increase in the density of stars toward the Galactic center. Publication: The Astrophysical Journal Pub Date: April 1985 DOI: 10.1086/184456 Bibcode: 1985ApJ...291L..45W Keywords: Galactic Nuclei; Hydroxyl Emission; Infrared Stars; Interstellar Masers; Milky Way Galaxy; Star Distribution; Gas Expansion; Radial Velocity; Stellar Envelopes; Astrophysics full text sources ADS | data products SIMBAD (3)

2(11)-2(12) formaldehyde emission from DR 21(OH)

view Abstract Citations (36) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS 2 11-2 12 formaldehyde emission from DR 21 (OH). Johnston, K. J. ; Henkel, C. ; Wilson, T. L. Abstract The first interferometric measurements have been made of the 2(11)-2(12) K-doublet line of ortho-H2CO for a source near the site of the OH/H2O maser source denoted as DR 21(OH) or W75(S). The precise location of the emission, its extent, and the physical conditions in the region are determined. The emission is consistent with quasi-thermal excitation and displays two peaks with brightness temperatures of 2 K or higher separated by 9 arcsec. The overall convolved FWHP size of the region is 18 arcsec by 6 arcsec or less. Assuming that the doublet emission requires an H2 density of a million per cubic centimeter, the total mass is between 6 and 150 solar masses. The mass in the absorption region is roughly five solar masses. Publication: The Astrophysical Journal Pub Date: October 1984 DOI: 10.1086/184371 Bibcode: 1984ApJ...285L..85J Keywords: Emission Spectra; Formaldehyde; Hydroxyl Emission; Interstellar Masers; Molecular Clouds; Radio Sources (Astronomy); Astronomical Maps; Hydrogen Clouds; Mass Distribution; Very Long Base Interferometry; Astrophysics full text sources ADS | data products SIMBAD (1)