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THE MASSACHUSETTS-STONY BROOK GALACTIC PLANE CARBON MONOXIDE SURVEY: OBSERVATIONS, GALACTIC STRUCTURE, AND CLOUD IDENTIFICATION (RADIO ASTRONOMY, MOLECULAR, GALAXY)

DAN PERCIVAL CLEMENS, University of Massachusetts Amherst

Abstract

The observing parameters for a galactic plane CO survey consisting of 40,551 spectra with 301 km s('-1) coverage at 1 km s('-1) resolution are presented. The mostly 3 x 3' sky sampling with a 45" beam enables detection of virtually all galactic clouds larger than 10-20 pc in the northern plane. Using these data and published HI, HII region, and globular cluster data, a rotation curve for the north- ern disk was determined. Large-scale streaming motions with characteristic velocities of 5 km s('-1) and wavelengths of 2 kpc are identified. Small-scale cloud-cloud motions have rms velocities of 3 (+OR-) 1 km s('-1) over lengths larger than 150 pc. The LSR is found to have an azimuthal peculiar velocity of 7 (+OR-) 1.5 km s('-1) with respect to the molecular cloud system.^ A combination of appropriate (L,V) binning and cluster analysis were used to extract near and far-side emission parameters from the different angular width components present in latitude emission profiles. The face-on distribution of molecular hydrogen derived is dominated by the molecular ring feature. Lesser, extended features are also present outside the ring. The scale height of the molecular layer is roughly 120 pc (FWHM) from 4 to 9 kpc radius, smaller interior to 4 kpc, and much larger beyond 10 kpc.^ An automated cloud identification system was developed and used on the entire CO survey data set. Cloud blending problems, which are severe at the 2 K boundary level used, were circumvented for model clouds and a selected region of the survey around L = 36(DEGREES) by use of cluster analysis-based unblending program. The 112 clouds found in the select region using the automated means are compared to those found by Stark in a subset of this region using ('13)CO. The agreement between the clouds found is good. The slopes of the mass and diameter spectra for these ('12)CO clouds (N (TURN) M('-0.88(+OR-)0.13), N (TURN) D('-1.33(+OR-)0.26)) are flatter than published values and may reflect galactic positional dependencies. ^

Subject Area

Astronomy

Recommended Citation

CLEMENS, DAN PERCIVAL, "THE MASSACHUSETTS-STONY BROOK GALACTIC PLANE CARBON MONOXIDE SURVEY: OBSERVATIONS, GALACTIC STRUCTURE, AND CLOUD IDENTIFICATION (RADIO ASTRONOMY, MOLECULAR, GALAXY)" (1985). Doctoral Dissertations Available from Proquest. AAI8517090.
https://scholarworks.umass.edu/dissertations/AAI8517090

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