I. Kazes

OH Zeeman observations of dark clouds

We have made measurements with the Green Bank 43 m telescope of the Zeeman effect in the 1665 and 1667 MHz lines of OH toward dark clouds. The typical 1 σ sensitivity was 3 μG. The only certain detection of a magnetic field was toward B1, for which we measured a line-of-sight component |B|cos θ=−19.1±3.9 μG. Comparison with our earlier measurement of the field toward B1 with the Arecibo telescope provided evidence for a 40% enhancement in field strength between the molecular envelope and core of the B1 cloud, which is consistent with quasi-static contraction of the cloud driven by ambipolar diffusion. Because the Zeeman effect is only sensitive to the line-of-sight component of the magnetic field, a statistical analysis of the detection and upper limits was necessary

Detection of the CN Zeeman Effect in Molecular Clouds

Observations of the Zeeman effect in the 3 mm lines of CN have been carried out with the 30 m IRAM telescope toward seven dense molecular clouds. Detections were achieved toward the Orion Molecular Cloud 1 (OMC1), toward two cores in the DR21OH molecular cloud, and probably toward the M17SW molecular cloud. The line-of-sight magnetic field strengths inferred are Blos(OMC1)=-0.36±0.08, Blos(DR21OH1)=-0.36±0.10, Blos(DR21OH2)=-0.71±0.12, and Blos(M17SW)=-0.33±0.14 mG. The theoretical implications of these results are discussed.

The Magnetic Fields in the Ophiuchus and Taurus Molecular Clouds

We discuss the significance of previously published OH Zeeman effect measurements of the magnetic field in the ρ Oph cloud (L1688) and also a new OH Zeeman effect measurement for the dark cloud core TMC-1C, the latter obtained with the Arecibo telescope. Results for both of these clouds, like previously published OH Zeeman results for other dark clouds, show that the line-of-sight field strength |B||| ≤ 10 μG. The ρ Oph cloud is significantly higher in column density than other clouds studied, and recent H I Zeeman effect observations have revealed B|| ≈ +10 μG in the H I self-absorption region in front of the cloud. The low values of B derived from the OH Zeeman effect may indicate that OH poorly samples the dense gas in the ρ Oph cloud, or else that the cloud is in a state of supercritical collapse. The TMC-1C cloud core may have formed via ambipolar diffusion in a manner similar to recent modeling of dark cloud Barnard 1.

A Dual-Transition Survey of CO in the Coma Cluster of Galaxies

We present CO (1–0) and (2–1) observations of 33 galaxies in the Coma/Abell 1367 supercluster made with the IRAM 30 m telescope. In addition, we observed four of the galaxies with the 15 m JCMT, at CO (2–1). The indicative molecular gas mass correlates strongly with the dust mass, and a stronger relationship is seen between the far-infrared and CO surface brightnesses than between the simple luminosities. Comparison of CO (2–1) spectra from IRAM and JCMT allows an estimate of the size of the CO emission region, which varies between 10% and 100% of the size of the optical disk, contrary to earlier estimates that the CO is contained within the optical half-light radius. There is a slight suggestion that starburst galaxies have a lower ratio of brightness temperatures, Tb(2–1)/Tb(1–0), than other galaxies.

The Tully-Fisher relation for the CO line

The question addressed here is whether linewidths measured in CO emission can be used in the Tully-Fisher relation as a substitute or supplement to H I line widths. To answer this question we have observed a test sample of galaxies in the Coma-A1367 supercluster using the IRAM 30 m telescope to measure CO line widths for comparison with 21 cm line widths from the Arecibo telescope. The galaxies were selected to span a very broad range of H I line widths (113-575 km s −1 ) and to have simple, two-horned line shapes at 21 cm

The magnetic field in the vicinity of S106

Studies of the Zeeman effect in the 18 cm OH absorption lines toward the bipolar nebula S106 yield a line-of-sight field strength of 137 + or - 17 microG. This field is probably associated with the inner regions of a flared disk of molecular gas surrounding the H II region. The field is strong enough to have important dynamical effects upon the molecular disk, including possible magnetic braking. The field strength is comparable to those envisioned in magnetic acceleration mechanisms for bipolar outflows. 39 references.

Detection of the OH Zeeman effect toward Orion A

The Zeeman effect in the 18 cm OH absorption spectrum of Orion A is detected. From this effect, a line-of-sight magnetic field strength of - 125 + or - 20 is derived. At the same position, an H I Zeeman effect equivalent to a magnetic field of - 49 + or - 4 micro-G is found. Thus, the magnetic field in the molecular gas toward Orion A is significantly stronger than that in the atomic gas, contrary to the recent determination for the Cas A line of sight. Densities in the atomic and molecular regions toward Orion A are estimated and it is found that for this region the data are consistent with B proportional to n exp kappa, kappa = 0.3. 23 references.

Distance Measurement of Galaxies to a Redshift of-0.1 Using the CO-Line Tully-Fisher Relation

We report on the first results of a long-term project to derive distances of galaxies at cosmological distances by applying the CO-line width-luminosity relation. We have obtained deep CO-line observations of galaxies at redshifts up to 29,000 km/s using the Nobeyama 45-m mm-wave Telescope, and some supplementary data were obtained by using the IRAM 30-m telescope. We have detected the CO line emission for several galaxies, and used their CO line widths to estimate the absolute luminosities using the line-width-luminosity relation. In order to obtain photometric data and inclination correction, we also performed optical imaging observations of the CO-detected galaxies using the CFHT 3.6-m telescope at high resolution. The radio and optical data have been combined to derive the distance moduli and distances of the galaxies, and Hubble ratios were estimated for these galaxies. We propose that the CO line width-luminosity relation can be a powerful method to derive distances of galaxies to redfhift of z = 0.1 and to derive the Hubble ratio in a significant volume of the universe. Key words: Cosmology - Galaxies: general - Distance scale - CO line

The Smallest Sizes of Diffuse Interstellar Clouds

By observing the difference in optical depths between absorption spectra toward the two components of double sources, the variations in opacity over lengths of less than 0.1 up to 10 pc inside diffuse interstellar clouds were measured. Significant variations were detected on scales larger than about 0.2 pc, but not less. This may represent the minimum size for diffuse cloud structure. By comparing the variations of Gaussian fitted line parameters, it was found that variations in the internal velocity field of diffuse clouds explain the data better than tiny independent cloudlets.