We present the first statistical survey of the properties of the 12 CO(1-0) and 12 CO(3-2) line emission from the nuclei of a nearly complete subsample of 60 infrared (IR) luminous galaxies selected from SCUBA Local Universe Galaxy Survey (SLUGS). This subsample is flux limited at S 60µm ≥ 5.24 Jy with far-IR (FIR) luminosities mostly at L F IR > 10 10 L ⊙ . We compare the emission line strengths of 12 CO(1-0) and (3-2) transitions at a common resolution of 15 ′′ . The measured 12 CO(3-2) to (1-0) line intensity ratios r 31 vary from 0.22 to 1.72 with a mean value of 0.66 for the sources observed, indicating a large spread of the degree of excitation of CO in the sample. These CO data, together with a wide range of data at different wavelengths obtained from the literature, allow us to study the relationship between the CO excitation conditions and the physical properties of gas/dust and star formation in the central regions of galaxies. Our analysis shows that there is a non-linear relation between CO and FIR luminosities, such that their ratio L CO /L F IR decreases linearly with increasing L F IR . This behavior was found to be consistent with the Schmidt Law relating star formation rate to molecular gas content, with an index N = 1.4 ± 0.3. We also find a possible

Aims. We characterize the molecular gas content (ISM cold phase) using CO emission of a redshift-limited subsample of isolated galaxies from the AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies) project in order to provide a comparison sample for studies of galaxies in different environments. Methods. We present the 12 CO(1-0) data for 273 AMIGA galaxies, most of them (n = 186) from our own observations with the IRAM 30 m and the FCRAO 14 m telescopes and the rest from the literature. We constructed a redshift-limited sample containing galaxies with 1500 km s −1 < v < 5000 km s −1 and excluded objects with morphological evidence of possible interaction. This sample (n = 173) is the basis for our statistical analysis. It contains galaxies with molecular gas masses, M H 2 , in the range of ∼10 8 −10 10 M . It is dominated, both in absolute number and in detection rate, by spiral galaxies of type T = 3-5 (Sb-Sc). Most galaxies were observed with a single pointing towards their centers. Therefore, we performed an extrapolation to the total molecular gas mass expected in the entire disk based on the assumption of an exponential distribution. We then studied the relationships between M H 2 and other galactic properties The molecular and the atomic gas masses of our sample show no strong correlation. We find a low mean value, log(M H 2 /M HI ) = −0.7 (for T = 3-5), and a strong decrease in this ratio with morphological type. The molecular gas column density and the surface density of the star formation rate (the Kennicutt-Schmidt law) show a tight correlation with a rough unity slope. We compare the relations of M H 2 with L B and L K found for AMIGA galaxies to samples of interacting galaxies from the literature and find an indication for an enhancement of the molecular gas in interacting galaxies of up to 0.2-0.3 dex.

We have mapped the northern area (30 × 20 ) of a Local Group spiral galaxy M33 in 12 CO(J = 1-0) line with the 45 m telescope at the Nobeyama Radio Observatory. Along with Hα and Spitzer 24 μm data, we have investigated the relationship between the surface density of molecular gas mass and that of star formation rate (SFR) in an external galaxy (Kennicutt-Schmidt law) with the highest spatial resolution (∼80 pc) to date, which is comparable to scales of giant molecular clouds (GMCs). At positions where CO is significantly detected, the SFR surface density exhibits a wide range of over four orders of magnitude, from Σ SFR 10 −10 to ∼10 −6 M yr −1 pc −2 , whereas the Σ H 2 values are mostly within 10-40 M pc −2 . The surface density of gas and that of SFR correlate well at an ∼1 kpc resolution, but the correlation becomes looser with higher resolution and breaks down at GMC scales. The scatter of the Σ SFR -Σ H 2 relationship in the ∼80 pc resolution results from the variety of star-forming activity among GMCs, which is attributed to the various evolutionary stages of GMCs and to the drift of young clusters from their parent GMCs. This result shows that the Kennicutt-Schmidt law is valid only in scales larger than that of GMCs, when we average the spatial offset between GMCs and star-forming regions, and their various evolutionary stages.

For the Antennae interacting galaxy pair, we have obtained high quality, fully sampled 12 CO J=1-0 and 3-2 maps of the regions surrounding the nuclei and the area of overlap between the two galaxies. The maps possess an angular resolution of 15 ′′ or 1.5 kpc, so far the highest resolution maps available at both the J=1-0 and 3-2 transitions. In addition, 12 CO J=2-1 data have been obtained for the positions of the two nuclei as well as in part of the overlap region with 20 ′′ angular resolution. The 12 CO J=1-0, 2-1, 3-2 emission all peak in an off-nucleus region adjacent to where the two disks overlap. Use of the conventional X factor yields ∼ 4 × 10 9 M ⊙ molecular gas mass in the overlap region. It is difficult to understand how such a large amount of molecular gas can be accumulated in this region given the relatively short lifetime of molecular clouds and the limited period of time for this region to form.Line emission at 13 CO J=2-1 and 3-2 is detected at selected points in the two nuclei and the overlap region. Both the 12 CO/ 13 CO J=2-1 and 3-2 integrated intensity ratios are remarkably high in the overlap region. This is the first published case in which such high 12 CO/ 13 CO J=2-1 and 3-2 ratios are found outside a galactic nucleus. Detailed LVG modeling indicates that the 12 CO and 13 CO emission originate in different spatial components. The 12 CO emission may originate within a non-virialized low density gas component with a large velocity gradient. Assuming a CO-to-H 2 abundance ratio of 10 −4 , the X factor given by the LVG model is an order of magnitude lower than the conventional value for molecular clouds in the Milky Way, but it scales inversely as the assumed value for this ratio. Accordingly, we suggest the possibility that the strong CO emission in the overlap region of the Antennae galaxies is associated with increased radiative efficiency, possibly caused by a large velocity dispersion within the individual molecular clouds.A comparison of the CO J=3-2 emission with the SCUBA 850 µm continuum in the Antennae galaxies shows that the CO line emission contributes globally 46% of the 850 µm continuum flux and that the ratio of 12 CO J=3-2 to SCUBA 850 µm flux varies by a factor of two across the system. After correcting for the 12 CO J=3-2 contamination, the dust emission at 850 µm detected by SCUBA is consistent with the thermal emission from a single warm dust component with a mass of 1.7 ×10 7 M ⊙ .

We have developed spectral line On-The-Fly (OTF) observing mode for the Nobeyama Radio Observatory 45-m and the Atacama Submillimeter Telescope Experiment 10-m telescopes. Sets of digital autocorrelation spectrometers are available for OTF with heterodyne receivers mounted on the telescopes, including the focal-plane 5 × 5 array receiver, BEARS, on the 45-m. During OTF observations, the antenna is continuously driven to cover the mapped region rapidly, resulting in high observing efficiency and accuracy. Pointing of the antenna and readouts from the spectrometer are recorded as fast as 0.1 second. In this paper we report improvements made on software and instruments, requirements and optimization of observing parameters, data reduction process, and verification of the system. It is confirmed that, using optimal parameters, the OTF is about twice as efficient as conventional position-switch observing method.