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  • 1
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    The largest molecular cloud complexes in the first galactic quadrant (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The Columbia CO survey of the first Galactic quadrant was used to determine the locations and physical properties of the largest molecular complexes in the inner Galaxy. Within the range of the survey (l = 12-60 deg), 26 complexes were detected with masses greater than 5 x 10 to the 5th solar masses, and roughly several hundred such complexes are deduced to exist throughout the Galaxy within the solar circle. These complexes are the parent objects of much of the Population I in the Galaxy. Distances to most of the complexes were determined kinematically, the distance ambiguity being resolved with the aid of associated H II regions, OB associations, masers, and other early Population I objects. The largest complexes are good tracers of spiral structure, the Sagittarius arm in particular being delineated with unprecedented clarity. A total of 17 large complexes are distributed rather uniformly along a 15 kpc stretch of the arm with a spacing comparable to that of the strings of regularly spaced H Ii regions observed in external galaxies. Power-law relations exist between the line widths and sizes of the complexes and between their densities and sizes. The forms of these relations are in good agreement with those found previously and are extended by roughly an order of magnitude in cloud mass.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 305; 892-908
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  • 2
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    Molecular clouds and star formation in the inner galaxy - A comparison of CO, H II, and far-infrared surveys (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Surveys of the galactic plane over galactic latitudes from -1 degree to +1 degree and galactic longitudes from 12 degrees to 60 degrees are compared in the CO line at 2.6 mm, in the far-infrared (FIR) continuum at 150 micrometers and 250 micrometers, and in the radio continuum and H 110-alpha recombination line at 6 cm. The main purposes are to determine the degree of association between FIR sources, H II regions, and molecular clouds in the first quadrant and to describe and analyze the stellar content of these molecular clouds. Among the conclusions it is noted that most FIR sources coincide with HII regions, and nearly all H II regions coincide with molecular clouds, and that clouds in the inner galaxy are probably several tens of millions of years old and may have been producing O stars for only about the most recent 20 percent of their lives.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 301; 398-422
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  • 3
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    Narrow polarized components in the OH 1612-MHz maser emission from supergiant OH-IR sources (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: High-resolution (300 Hz) OH 1612-MHz spectra of the supergiant OH-IR sources VY CMa, VX Sgr, IRC 10420, and NML Cyg are presented. Linewidths as small as 550 Hz (0.1 km/s) are found for narrow components in the spectra. The present results are consistent with current models for maser line-narrowing and for the physical properties in the OH maser regions. A significant degree of circular polarization is noted in many of the narrow components. The circular polarization suggests the presence of magnetic fields of about 1 mG in the circumstellar envelopes which would be strong enough to influence the outflow from the stars, and which may explain asymmetries found in the circumstellar envelopes.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 225; 491-498
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  • 4
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    CO observations of dark clouds in Lupus (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: C-12O observations covering 170 square degrees toward the southern T Association Lupus have revealed the presence of an extended physically related complex of dark clouds which have recently formed low mass stars. The estimated mass of the clouds (about 30,000 solar masses) is comparable to that of the nearby Ophiuchus dust clouds. The Lupus clouds are projected onto a gap between two subgroups of the Scorpio-Centaurus OB association suggesting that this long accepted subgrouping may require reinterpretation.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 167; 234-238
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  • 5
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    IUE observations of the Seyfert 1.9 galaxy Markarian 423 (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: UV observations of the Seyfert 1.9 galaxy Markarian 423 show a moderately strong UV continuum in the 1200-2000 A region, a strong narrow Lyman-alpha conponent, and no detectable broad lines. This absence of broad UV lines, in conjunction with the steep broad line Balmer decrement, indicates that the gas giving rise to the broad emission lines is significantly reddened. An upper limit on the equivalent width of the broad Lyman-alpha component suggests that the reddening of the broad line region is greater than that of the interstellar continuum, which furnishes evidence of local dust concentration.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 288; L29-L32
    Format: text
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  • 6
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    Star formation in Carina OB1: Observations of a giant molecular cloud associated with the eta Carinae Nebula (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A giant molecular cloud associated with the eta Carinae nebula was fully mapped in CO with the Columbia Millimeter-Wave Telescope at Cerro Tololo. The cloud comples has a mass of roughly 700,000 solar mass and extends about 140 pc along the Galactic plane, with the giant Carina HII region situated at one end of the complex. Clear evidence of interaction between the HII region and the molecular cloud is found in the relative motions of the ionized gas, the molecular gas, and the dust; simple energy and momentum considerations suggest that the HII region is responsible for the observed motion of a cloud fragment. The molecular cloud complex appears to be the parent material of the entire Car OB1 Association which, in addition to the young clusters in the Carine nebula, includes the generally older cluster NGC 3325, NGC 3293, and IC 2581. The overall star formation efficiency in the cloud complex is estimated to be approximately 0.02.
    Keywords: ASTROPHYSICS
    Type: NASA, Washington Star Formation in Galaxies; p 67-70
    Format: application/pdf
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  • 7
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    Molecular clouds and galactic spiral structure (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Two large-scale 2.6 mm CO surveys of the galactic plane, one in the first quadrant (l = 12 to 60 deg, b = -1 to +1 deg), the other in the second (l = 105 to 139 deg, b = -3 to +3 deg), have provided evidence that, contrary to previous findings, molecular clouds constitute a highly specific tracer of spiral structure. Molecular counterparts of five of the classical 21-cm spiral arms have been identified: the Perseus arm, the local arm (including Lindblad's local expanding ring), the Sagittarius arm, the Scutum arm, and the 4-kpc arm. The region between the local arm and the Perseus arm is apparently devoid of molecular clouds, and the interarm regions of the inner Galaxy appear largely so. CO spiral structure implies that the mean lifetime of molecular clouds cannot be greater than 100 million years, the time required for interstellar matter to cross a spiral arm. Conservation of mass then sets a limit on the fraction of the interstellar medium in the form of molecular clouds: it cannot exceed one-half at any distance from the galactic center in the range 4-12 kpc.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 239
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  • 8
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    Molecular clouds in the Carina arm - Large-scale properties of molecular gas and comparison with H I (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Results from the first large-scale survey in the CO (J = 1 - 0) line of the Vela-Carina-Centaurus region of the southern Milky Way are reported. The results demonstrate that molecular clouds in the Galaxy are largely confined to the spiral arms and that CO is therefore an extremely good tracer of the large-scale structure of the system. The Carina arm is the dominant feature in the data. Its abrupt tangent at l of roughly 280 deg and characteristic loop in the (l, v) diagram are unmistakable evidence for CO spiral structure. When the emission is integrated over velocity and latitude, the height of the step seen in the tangent direction indicate that the arm-interarm contrast is at least 13:1.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 315; 122-141
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  • 9
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    Molecular clouds in the Carina arm (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: From a new survey of the 2.6 mm line of CO in the southern Milky Way, 37 molecular clouds were identified along the Carina arm from l = 282 deg to 336 deg with masses generally greater than 10 to the 5th solar mass. The clouds lie approximately every 700 pc along a spiral segment that is nearly 25 kpc long and has a pitch of about 10 deg. The total mass of these clouds is 40 x 10 to the 6th solar mass, or rougly 1 x 10 to the 6th solar mass each on average. The abrupt tangent point in molecular clouds at l = 280 deg and the characteristic loop structure in the l-v diagram are unmistakable evidence of a CO spiral arm in Carina. This arm apparently connects with the northern hemisphere Sagittarius arm to form a single 10 deg spiral which extends more than two-thirds of the way around the Galaxy.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 290; L15-L20
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  • 10
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    A wide latitude CO survey of molecular clouds in the III galactic quadrant (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Molecular clouds in the third galactic quadrant from 180-280 galactic longitude were surveyed in the 115.271 GHz line of CO at an angular resolution of 0.5 deg. In galactic latitude the survey covers from b = -5 to +5 deg, with a few extensions to higher latitudes. A preliminary analysis of the data allowed the determination of distances and masses of at least 30 molecular clouds related to the Perseus arm and to the Cygnus, or outer, arm. The studied clouds are located between 2.5 kpc and 10.7 kpc from the sun with most of the masses between 30,000-700,000 solar masses, and only three up to two million solar masses. The most interesting result comes from the distribution of the clouds distance from the galactic plane that indicates a warp in the arms to which these clouds belong.
    Keywords: ASTROPHYSICS
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