We carried out an unbiased survey for massive dense cores in the giant molecular cloud associated with η Carinae with the NANTEN telescope in 12 CO, 13 CO, and C 18 O J = 1-0 emission lines. We identified 15 C 18 O cores, whose typical line width ∆V comp , radius r, mass M , column density N (H 2 ), and average number density n(H 2 ) were 3.3 km s −1 , 2.2 pc, 2.6×10 3 M ⊙ , 1.3×10 22 cm −2 , and 1.2×10 3 cm −3 , respectively. Two of the 15 cores are associated with IRAS point sources whose luminosities are larger than 10 4 L ⊙ , which indicates that massive star formation is occuring within these cores. Five cores including the two with IRAS sources are associated with MSX point sources. We detected H 13 CO + (J = 1-0) emission toward 4 C 18 O cores, two of which are associated with IRAS and MSX point sources, another one is associated only with an MSX point source, and the other is associated with neither IRAS nor MSX point sources. The core with neither IRAS nor MSX point sources shows the presence of a bipolar molecular outflow in 12 CO (J = 2-1), which indicates that star formation is also occuring in the core, and the other three of the four H 13 CO + detections show wing-like emission. In total, six C 18 O cores out of 15 (= 40%) are experienced star formation, and at least 2 of 15 (= 13 %) are massive-star forming cores in the η Car GMC. We found that massive star formation occurs preferentially in cores with larger N (H 2 ), M , n(H 2 ), and smaller ratio of M vir /M . We also found that the cores in the η Car GMC are characterized by large ∆V and M vir /M on average compared to the cores in other GMCs observed with the same telescope. These properties of the cores may account for the fact that as much as 60-87 % of the cores do not show any signs of massive star formation. We investigated the origin of a large amount of turbulence in the η Car GMC. We found that turbulence injection from stellar winds, molecular outflows, and supernova remnants which originated from stars formed within the GMC, are not enough to explain the existing turbulence. We propose the possibility that the large turbulence was pre-existing when the GMC was formed, and is now dissipating. Mechanisms such as multiple supernova explosions in the Carina flare supershell may have contributed to form a GMC with a large amount of turbulence.

We have surveyed the N 2 H + J=1-0, HC 3 N J=5-4, CCS J N =4 3 -3 2 , NH 3 (J, K) = (1, 1), (2, 2), (3, 3), and CH 3 OH J=7-6 lines toward the 55 massive clumps associated with infrared dark clouds by using the Nobeyama Radio Observatory 45 m telescope and the Atacama Submillimeter Telescope Experiment 10 m telescope. The N 2 H + , HC 3 N, and NH 3 lines are detected toward most of the objects. On the other hand, the CCS emission is detected toward none of the objects. The [CCS]/[N 2 H + ] ratios are found to be mostly lower than unity even in the Spitzer 24 µm dark objects. This suggests that most of the massive clumps are chemically more evolved than the low-mass starless cores. The CH 3 OH emission is detected toward 18 out of 55 objects. All the CH 3 OH-detected objects are associated with the Spitzer 24 µm sources, suggesting that star formation has already started in all the CH 3 OH-detected objects. The velocity widths of the CH 3 OH J K =7 0 -6 0 A + and 7 −1 -6 −1 E lines are broader than those of N 2 H + J=1-0. The CH 3 OH J K =7 0 -6 0 A + and 7 −1 -6 −1 E lines tend to have broader linewidth in the MSX dark objects than in the others, the former being younger or less luminous than the latter. The origin of the broad emission is discussed in terms of the interaction between an outflow and an ambient cloud.

From a 12CO ($J=1 \hbox{--} 0$) survey with the NANTEN telescope, we present a complete catalog of giant molecular clouds (GMCs) in the Large Magellanic Cloud. In total, 107 CO clouds have been identified, 55 of which were detected at more than 3 observed positions. For the 55 clouds, the physical properties, such as size, line-width, virial mass, and CO luminosity, are cataloged. From a statistical analysis of these quantities, we show that GMCs in the LMC are close to gravitational equilibrium. A comparison with H i data indicates that most of the CO clouds are distributed in dense parts of H i gas, whose H i column density is greater than $10^{21} \,\mathrm{cm}^{-2}$. It is notable that the mass ratio of the molecular-to-atomic hydrogen of the lower radial velocity component of gas is $\sim 0.2$, which is a factor of 2 higher than that of the gaseous-disk component, $\sim 0.1$. Molecular clouds are apparently formed efficiently in the parent atomic clouds in the lower velocity component. The CO Arc, which is a few kpc scale ordered structure of CO clouds along the southern optical edge of the galaxy, corresponds well to the the lower velocity component of H i gas.

We present molecular line observations toward the “Pipe Nebula” in the J = 1−0 lines of 12CO, 13CO, and C18O by using “NANTEN” telescope. An area of ∼ 27 deg2 was covered at a 4′ grid spacing with a 2′.7 beam in 12CO. The 12CO velocity-integrated intensity map and channel maps show a filamentary distribution. The total mass of the 12CO- and 13CO-emitting gas is estimated to be ∼ 10000 M⊙ and ∼ 3000 M⊙ , respectively. We have identified 14 C18O cores whose mass is typically ∼ 30 M⊙ . Star formation is active only in the B 59 region. This activity is best demonstrated by a newly detected CO outflow toward the center of B 59. We suggest that the dynamical effects of tau Sco may be responsible for triggering star formation only in the B 59 region. The C18O column density toward B 59 is extremely high compared with the rest of the cloud. This confirms that high C18O column density is a necessary condition of star formation as previously suggested. Although the star-formation efficiency is estimated to be quite low, ≲ 0.1%, except for B 59, the existence of the C18O cores suggests that there is molecular gas that is massive and dense enough to form stars, and that star formation is likely to occur in the near future.

Lyman-alpha emitters are thought to be young, low-mass galaxies with ages of approximately 10(8) yr (refs 1, 2). An overdensity of them in one region of the sky (the SSA 22 field) traces out a filamentary structure in the early Universe at a redshift of z approximately 3.1 (equivalent to 15 per cent of the age of the Universe) and is believed to mark a forming protocluster. Galaxies that are bright at (sub)millimetre wavelengths are undergoing violent episodes of star formation, and there is evidence that they are preferentially associated with high-redshift radio galaxies, so the question of whether they are also associated with the most significant large-scale structure growing at high redshift (as outlined by Lyman-alpha emitters) naturally arises. Here we report an imaging survey of 1,100-microm emission in the SSA 22 region. We find an enhancement of submillimetre galaxies near the core of the protocluster, and a large-scale correlation between the submillimetre galaxies and the low-mass Lyman-alpha emitters, suggesting synchronous formation of the two very different types of star-forming galaxy within the same structure at high redshift. These results are in general agreement with our understanding of the formation of cosmic structure.