P. M. Solomon

Mass, luminosity, and line width relations of Galactic molecular clouds

The paper presents an analysis of the cloud sizes, velocity line widths, viral masses, and CO luminosities of 273 Galactic molecular clouds which utilizes the higher resolution Massachusetts-Stony Brook Galactic plane CO survey. It is shown that the molecular clouds are in or near viral equilibrium and are not confined by pressure equilibrium with a warm or hot phase of interstellar matter. Allowance is made for the mass-luminosity law in a cloud model consisting of a large number of optically thick clumps in viral equilibrium each with a thermal internal velocity dispersion; the clouds are optically thin at a fixed velocity along the line of sight. 32 references.

The Molecular Interstellar Medium in Ultraluminous Infrared Galaxies

We present observations with the IRAM 30 m telescope of CO in a large sample of ultraluminous IR galaxies out to redshift z = 0.3. Most of the ultraluminous galaxies in this sample are interacting, but not completed, mergers. The CO(1-0) luminosity of all but one of the ultraluminous galaxies is high, with values of log (L

CO excitation and H2 masses of infrared-luminous galaxies

{′}{r CO}

New Observations and a New Interpretation of CO(3-2) in IRAS F10214+4724

-->/K km s-1 pc2) = 9.92 ? 0.12. The extremely small dispersion of only 30% is less than that of the far-infrared luminosity. The integrated CO line intensity is strongly correlated with the 100 ?m flux density, as expected for a blackbody model in which the mid- and far-IR radiation is optically thick. We use this model to derive sizes of the FIR- and CO-emitting regions and the enclosed dynamical masses. Both the IR and CO emission originate in regions a few hundred parsecs in radius. The median value of LFIR

Near-Infrared Spectroscopy and a Search for CO Emission in Three Extremely Luminous IRAS Sources: IRAS F09105+4108, IRAS F15307+3252, and PG 1634+706

{r FIR}

The Molecular Disk in the Cloverleaf Quasar

-->/L

The Star Formation Rate-Dense Gas Relation in Galaxies as Measured by HCN(3-2) Emission

{′}{r CO}

The Massachusetts-Stony Brook Galactic plane CO survey: disk and spiral arm molecular cloud populations

-->=160 L?/K km s-1 pc2, within a factor of 2 or 3 of the blackbody limit for the observed far-IR temperatures. The entire ISM is a scaled-up version of a normal galactic disk with the ambient densities a factor of 100 higher, making even the intercloud medium a molecular region. We compare three different techniques of H2 mass estimation and conclude that the ratio of gas mass to CO luminosity is about a factor of 4 times lower than for giant molecular clouds (GMCs) but that the gas mass is a large fraction of the dynamical mass. Our analysis of CO emission from ultraluminous galaxies reduces the H2 mass from previous estimates of 2-5 ? 1010 M? to 0.4-1.5 ? 1010 M?, which is in the range found for molecular gas-rich spiral galaxies. A collision involving a molecular gas-rich spiral could lead to an ultraluminous galaxy powered by central starbursts triggered by the compression of infalling preexisting GMCs. The extremely dense molecular gas in the center of an ultraluminous galaxy is an ideal stellar nursery for a huge starburst.

Molecular Gas in the Spectacular Ring Galaxy NGC 1144

The CO(2-1) and CO(1-0) emission from four infrared-luminous galaxies, Arp 193, Arp 220, Mrk 231, and VII Zw 31, was mapped with the IRAM 30 m telescope. These maps show the molecular gas is concentrated in the central regions. The CO(2-1)/CO(1-0) brightness temperature ratio for these galaxies is low, 0.6-0.75, indicating the CO is subthermally excited in regions of moderate H2 density, roughly 400/cu cm. The intrinsic CO(1-0) brightness temperatures are inferred to be between 6 and 13 K, even if the gas kinetic temperatures are much higher. For these galaxies, the H2 mass-to-CO luminosity ratio is similar to that measured for giant molecular clouds in the Milky Way molecular ring. 20 refs.

Extraordinary CO luminosity of the far-infrared galaxy VII Zw 31 - a possible proto-galactic disk

New observations with the IRAM interferometer of CO(3-2) from the highly luminous galaxy IRAS F10214+4724 show the source is 15 × ≤09; they display no evidence of any velocity gradient. This size, together with optical and IR data that show the galaxy is probably gravitationally lensed, lead to a new model for the CO distribution. In contrast to many lensed objects, we have a good estimate of the intrinsic CO and far-IR surface brightnesses, so we can derive the CO and far-IR/sub-mm magnifications. The CO is magnified 10 times and has a true radius of 400 pc, and the far-IR is magnified 13 times and has a radius of 250 pc. The true far-IR luminosity is 4-7 × 1012 L☉, and the molecular gas mass is 2 × 1010 M☉. This is nearly an order of magnitude less than previously estimated. Because the far-IR magnification is lower than the mid- and near-IR magnification, the intrinsic spectral energy distribution now peaks in the far-infrared. That is, nearly all the energy of this object is absorbed and reemitted in the far-infrared. In CO luminosity, molecular gas content, CO line width, and corrected far-IR luminosity, 10214+472 is a typical, warm, IR ultraluminous galaxy.