Christine Pulliam
(617) 495-7463


CfA Press Release


TORONTO, Ont.--Smithsonian astronomers will unveiltoday the graphic results of a new global survey ofthe molecular clouds in our galaxy, the Milky Way. Thesurvey was done in the radio band to observe the 115GHz emission line of carbon monoxide (CO), the besttracer of interstellar molecular gas. The study isthe culmination of 20 years of observations by a dozenradio astronomers and 22 Ph.D. students using twosimilar 1.2-meter (4-foot) millimeter-wavetelescopes, one on the grounds of theHarvard-Smithsonian Center for Astrophysics (CfA) inCambridge, Mass., the other at the Cerro TololoInter-American Observatory in Chile.

The large-scale color maps of molecular clouds thatresulted from this study were presented by Drs.Thomas Dame, Dap Hartmann, and Patrick Thaddeus of theCfA at the American Astronomical Society (AAS) meetinghere. The galactic distribution and properties ofmolecular clouds are of interest to astronomersworking in all bands of the electromagnetic spectrumbecause they contain roughly half of all theinterstellar gas and dust and give birth to nearly allof the stars in a spiral galaxy such as ours.

The new maps have 3 to 4 times higher angularresolution (8.7 arcmin) and 5 to 10 times highersensitivity than the only previous complete maps ofthe Milky Way in molecular clouds, which werepresented by Dame and Thaddeus exactly ten years ago,at the January 1987 meeting of the AAS. Theimprovements in resolution and sensitivity are aconsequence of 270,000 new CO spectra obtained overthe past 10 years. As was done 10 years ago, the newmaps have been produced as a wall poster, funded bythe Smithsonian Institution, and distributed at themeeting. As Dame notes, "our original poster stillhangs in many offices and observatories throughout theworld, and the Astrophysical Journal article on whichit is based continues to serve as a useful researchtool for guiding higher- resolution observations andfor putting many smaller-scale studies into a galacticperspective".


Editor's Note: Copies of the new "Milky Way inMolecular Clouds" maps, either as posters, or as 8.5x 11 inch glossies for reproduction, are availablefrom Public Affairs, Smithsonian AstrophysicalObservatory, 60 Garden Street, Cambridge, MA 02138(617-495-7461).

Contact:Tom Dame: 617-495-7334
Public Affairs (Megan Watzke): 617-495-7463

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