New high-resolution maps with the IRAM Interferometer of the redshifted [C II] 158 micron line and the 0.98mm dust continuum of HDF850.1 at z = 5.185 show the source to have a blueshifted northern component and a redshifted southern component, with a
projected separation of 0.3 arcsec, or 2 kpc. We interpret these components as primordial galaxies that are merging to form a larger galaxy. We think it is the resulting merger-driven starburst that makes HDF850.1 an ultraluminous infrared galaxy, with an L(IR) of 1E13 Lsun. The observed line and continuum brightness temperatures and the constant line-to-continuum ratio across the source imply (1) high [C II] line optical depth, (2) a [C II] excitation temperature of the same order as the dust temperature, and (3) dust continuum emission that is nearly optically thick at 158 microns. These conclusions for HDF850.1 probably also apply to other high-redshift submillimeter galaxies and quasar hosts in which the [C II] 158 micron line has been detected, as indicated by their roughly constant [C II]-to-158 micron continuum ratios, in sharp contrast to the large dispersion in their [C II]-to-FIR luminosity ratios. In brightness temperature units, the [C II] line luminosity is about the same as the predicted CO(1-0) luminosity, implying that the [C II] line can also be used to estimate the molecular gas mass, with the same assumptions as for CO.
The radio-quiet quasar BR1202-0725 (z=4.695) is a remarkable source with a bright Northwest (NW) companion detected at submm and radio wavelengths but invisible in the optical. In the absence of amplification by gravitational lensing, BR1202-0725 wou
ld be the most luminous binary CO and FIR source in the Universe. In this paper, we report observations with the IRAM Plateau de Bure interferometer of BR1202-0725 in the redshifted emission of the CO(5-4) and (7-6) lines, the [C I](3P2-3P1) line, a high angular resolution (0.3 x 0.8 arcsec) 1.3 mm map of the rest-frame, far-IR dust continuum, and a search for the CO(11-10) line. We compare these results with recent ALMA data in the [C II] line. Both the quasar host galaxy and its NW companion are spatially resolved in the molecular line emission and the dust continuum. The CO profile of the NW companion is very broad with a full width at half maximum of 1000 +/- 130 km/s, compared to 360 +/- 40 km/s for the quasar host galaxy to the Southeast (SE). The difference in linewidths and center velocities, and the absence of any lens candidate or arc-like structure in the field, at any wavelength, show that the obscured NW galaxy and the SE quasar host galaxy cannot be lensed images of the same object. Instead, we find morphological and kinematic evidence for sub-structures in both the NW and SE sources. We interpret these results as strong indications that the BR1202-0725 complex is a group of young, interacting, and highly active starburst galaxies.
We report on sensitive observations of the CO(7-6) and CI(2-1) transitions in the z=2.79 QSO host galaxy RXJ0911.4+0551 using the IRAM Plateau de Bure interferometer (PdBI). Our extremely high signal to noise spectra combined with the narrow CO line
width of this source (FWHM = 120 km/s) allows us to estimate sensitive limits on the space-time variations of the fundamental constants using two emission lines. Our observations show that the CI and CO line shapes are in good agreement with each other but that the CI line profile is of order 10% narrower, presumably due to the lower opacity in the latter line. Both lines show faint wings with velocities up to +/-250 km/s, indicative of a molecular outflow. As such the data provide direct evidence for negative feedback in the molecular gas phase at high redshift. Our observations allow us to determine the observed frequencies of both transitions with so far unmatched accuracy at high redshift. The redshift difference between the CO and CI lines is sensitive to variations of dF/F with F=alpha^2/mu where alpha is the fine structure constant and mu the proton-to-electron mass ratio. We find dF/F=6.9 +/-3.7 x 10^-6 at a lookback time of 11.3 Gyr, which within the uncertainties, is consistent with no variations of the fundamental constants.
Using the IRAM 30m telescope and the Plateau de Bure interferometer we have detected the ctwo and the CO 3$-$2, 4$-$3, 6$-$5, 7$-$6 transitions as well as the dust continuum at 3 and 1.2 mm towards the distant luminous infrared galaxy IRAS F10214+472
4 at $z=2.286$. The ctwo line is detected for the first time towards this source and IRAS F10214+4724 now belongs to a sample of only 3 extragalactic sources at any redshift where both of the carbon fine structure lines have been detected. The source is spatially resolved by our ctwo observation and we detect a velocity gradient along the east-west direction. The CI line ratio allows us to derive a carbon excitation temperature of 42$^{+12}_{-9}$ K. The carbon excitation in conjunction with the CO ladder and the dust continuum constrain the gas density to $n(hh)$ = $10^{3.6-4.0}$ cm$^{-3}$ and the kinetic temperature to $Trm_{kin}$ = 45--80 K, similar to the excitation conditions found in nearby starburst galaxies. The rest-frame 360 $mu$m dust continuum morphology is more compact than the line emitting region, which supports previous findings that the far infrared luminosity arises from regions closer to the active galactic nucleus at the center of this system.
