New high resolution interferometer data of 10 IR ultraluminous galaxies shows the molecular gas is in rotating nuclear rings or disks with radii 300 to 800 pc. Most of the CO flux comes from a moderate-density, warm, intercloud medium rather than self-gravitating clouds. Gas masses of ~ 5 x 10^9 Msun, 5 times lower than the standard method are derived from a model of the molecular disks. The ratio of molecular gas to dynamical mass, is M_gas/M_dyn ~ 1/6 with a maximum ratio of gas to total mass surface density of 1/3. For the galaxies VIIZw31, Arp193, and IRAS 10565+24, there is good evidence for rotating molecular rings with a central gap. In addition to the rotating rings a new class of star formation region is identified which we call an Extreme Starburst. They have a characteristic size of only 100 pc., about 10^9 Msun of gas and an IR luminosity of ~3 x 10^11 Lsun. Four extreme starbursts are identified in the 3 closest galaxies in the sample Arp220, Arp193 and Mrk273. They are the most prodigious star formation events in the local universe, each representing about 1000 times as many OB stars as 30 Doradus. In Arp220, the CO and 1.3 mm continuum maps show the two ``nuclei'' embedded in a central ring or disk and a fainter structure extending 3 kpc to the east, normal to the nuclear disk. There is no evidence that these sources really are the pre-merger nuclei. They are compact, extreme starburst regions containing 10^9 Msun of dense molecular gas and new stars, but no old stars. Most of the dust emission and HCN emission arises in the two extreme starbursts. The entire bolometric luminosity of Arp~220 comes from starbursts, not an AGN. In Mrk231, the disk geometry shows that the molecular disk cannot be heated by the AGN; the far IR luminosity of Mrk~231 is powered by a starburst, not the AGN. (Abridged)Comment: 97 pages Latex with aasms.sty, including 29 encapsulated Postscript figures. Figs 18 and 23 are GIFs. 31 figures total. Text and higher quality versions of figures available at http://sbastk.ess.sunysb.edu/www/RINGS_ESB_PREPRINT.html To be published in Ap. J., 10 Nov. 199

We present CO observations of a large sample of ultraluminous IR galaxies out to z = 0.3. Most of the galaxies are interacting, but not completed mergers. All but one have high CO(1-0) luminosities, log(Lco [K-km/s-pc^2]) = 9.92 +/- 0.12. The dispersion in Lco is only 30%, less than that in the FIR luminosity. The integrated CO intensity correlates Strongly with the 100 micron flux density, as expected for a black body model in which the mid and far IR radiation are 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/Lco = 160 Lsun/(K-km/s-pc^2), within a factor of two of the black body limit for the observed FIR temperatures. The entire ISM is a scaled up version of a normal galactic disk with densities a factor of 100 higher, making even the intercloud medium a molecular region. Using three different techniques of H2 mass estimation, we conclude that the ratio of gas mass to Lco is about a factor of four lower than for Galactic molecular clouds, but that the gas mass is a large fraction of the dynamical mass. Our analysis of CO emission reduces the H2 mass from previous estimates of 2-5e10 Msun to 0.4-1.5e10 Msun, 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 GMC's.Comment: 34 pages LaTeX with aasms.sty, 14 Postscript figures, submitted to ApJ Higher quality versions of Figs 2a-f and 7a-c available by anonymous FTP from ftp://sbast1.ess.sunysb.edu/solomon/

We report the detection of the CO 4-3, 6-5, 9-8, 10-9, and 11-10 lines in the Broad Absorption Line quasar APM 08279+5255 at z = 3.9 using the IRAM 30 m telescope. We also present IRAM PdBI high spatial resolution observations of the CO 4-3 and 9-8 lines, and of the 1.4 mm dust radiation as well as an improved spectrum of the HCN(5-4) line. Unlike CO in other QSO host galaxies, the CO line SED of APM 08279+5255 rises up to the CO(10-9) transition. The line fluxes in the CO ladder and the dust continuum fluxes are best fit by a two component model, a "cold" component at ∼65 K with a high density of n(H 2 ) = 1 × 10 5 cm −3 , and a "warm", ∼220 K component with a density of 1 × 10 4 cm −3 . We show that IR pumping via the 14 µm bending mode of HCN is the most likely channel for the HCN excitation. From our models we find, that the CO(1-0) emission is dominated by the dense gas component which implies that the CO conversion factor is higher than usually assumed for high-z galaxies with α ≈ 5 M (K km s −1 pc 2 ) −1 . Using brightness temperature arguments, the results from our high-resolution mapping, and lens models from the literature, we argue that the molecular lines and the dust continuum emission arise from a very compact (r ≈ 100−300 pc), highly gravitationally magnified (m = 60−110) region surrounding the central AGN. Part of the difference relative to other high-z QSOs may therefore be due to the configuration of the gravitational lens, which gives us a high-magnification zoom right into the central 200-pc radius of APM 08279+5255 where IR pumping plays a significant role for the excitation of the molecular lines.

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The Hubble Deep Field (HDF) is a region in the sky that provides one of the deepest multi-wavelength views of the distant universe and has led to the detection of thousands of galaxies seen throughout cosmic time 1 . An early map of the HDF at a wavelength of 850 microns that is sensitive to dust emission powered by star formation revealed the brightest source in the field, dubbed HDF850.1 2 . For more than a decade, this source remained elusive and, despite significant efforts, no counterpart at shorter wavelengths, and thus no redshift, size or mass, could be identified 3-7 . Here we report, using a millimeter wave molecular line scan, an unambiguous redshift determination for HDF850.1 of z=5.183. This places HDF850.1 in a galaxy overdensity at z~5.2 in the HDF, corresponding to a cosmic age of only 1.1 Gyr after the Big Bang. This redshift is significantly higher than earlier estimates 3,4,6,8 and higher than most of the >100 sub-millimeter bright galaxies identified to date. The source has a star formation rate of 850 M sun yr -1 and is spatially resolved on scales of 5 kpc, with an implied dynamical mass of ~1.3x10 11 M sun , a significant fraction of which is present in the form of molecular gas. Despite our accurate redshift and position, a counterpart arising from starlight remains elusive.We have obtained a full frequency scan of the 3 mm band towards the HDF using the IRAM Plateau de Bure Interferometer (PdBI). The observations covered the frequency range from 80-115 GHz in 10 frequency settings at uniform sensitivity and at a resolution (~2.3") that is a good match to galaxy sizes at high redshift. They resulted in the detection of two lines of Carbon Monoxide (CO), the most common tracer for molecular gas at high redshift 9 , at 93.20 GHz and 111.84 GHz at the position of HDF850.1. Identifying these lines with the J=5 and J=6 rotational transitions of CO gives a redshift for HDF850.1 of z=5.183. This redshift was then unambiguously confirmed by the PdBI detection of the 158 μm line of ionized carbon ([CII], redshifted to 307.38 GHz), one of the main cooling lines of the star-forming interstellar medium. Stacking of other molecules covered by our frequency scan that trace higher volume densities did not lead to a detection (see Supplementary Information). Subsequently, the J=2 line of CO has also been detected using the NRAO Jansky Very Large Array (Jansky VLA) at 37.29 GHz. The observed [CII] and CO spectra towards HDF850.1 are shown in Fig. 1.The beamsize of our CO observations (~2.3", 15 kpc at z=5.183) is too large to spatially resolve the molecular gas emission in HDF850.1. However the [CII] and underlying continuum observations (~1.2" x 0.8") show that the source is extended (hitherto, the interstellar medium has been spatially resolved only in extremely rare quasar host galaxies at such high redshift 10 ). A single Gaussian fit yields a deconvolved size of 0.9±0.3", or 5.7±1.9 kpc at the redshift of the source. Fig. 2 shows the maps of total [CII] emission (left) as well as the red-and blue-...