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We present molecular line and submillimeter dust continuum observations of the Lynds 870 cloud in the vicinity of IRAS 20231+3440. Two submillimeter cores, SMM1 and SMM2, are identified mapping the 870 micron dust continuum and ammonia emission. The total molecular mass is ~70-110 solar mass. The northern core is warmer and denser than the southern one. Molecular outflows are discovered in both cores. In the northern one a significant amount of low velocity (1.3-2.8 km/s) outflowing gas is found, that is hidden in the relatively broad CO lines but that is revealed by the narrower HCO+ spectra. While IRAS 20231+3440 is most likely the exciting star of the northern outflow, the driving source of the southern outflow is not detected by infrared surveys and must be deeply embedded in the cloud core. Large scale (~0.2 pc) infall motion is indicated by blue asymmetric profiles observed in the HCO+ J = 3-2 spectra. Red K_s band YSO candidates revealed by the 2MASS survey indicate ongoing star formation throughout the cloud. The calculated masses and the measured degree of turbulence are also reminiscent of clouds forming groups of stars. The excitation of the molecular lines, molecular abundances, and outflow properties are discussed. It is concluded that IRAS 20231+3440 is a ClassI object, while the southern core most likely contains a Class0 source.
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We present the detection of molecular gas using CO(1-0) line emission and follow up Halpha imaging observations of galaxies located in nearby voids. The CO(1-0) observations were done using the 45m telescope of the Nobeyama Radio Observatory (NRO) and the optical observations were done using the Himalayan Chandra Telescope (HCT). Although void galaxies lie in the most under dense parts of our universe, a significant fraction of them are gas rich, spiral galaxies that show signatures of ongoing star formation. Not much is known about their cold gas content or star formation properties. In this study we searched for molecular gas in five void galaxies using the NRO. The galaxies were selected based on their relatively higher IRAS fluxes or Halpha line luminosities. CO(1--0) emission was detected in four galaxies and the derived molecular gas masses lie between (1 - 8)E+9 Msun. The H$alpha$ imaging observations of three galaxies detected in CO emission indicates ongoing star formation and the derived star formation rates vary between from 0.2 - 1.0 Msun/yr, which is similar to that observed in local galaxies. Our study shows that although void galaxies reside in under dense regions, their disks may contain molecular gas and have star formation rates similar to galaxies in denser environments.
We present the Submillimeter Array observation of the CO J=2-1 transition towards the northern galaxy, ARP 302N, of the early merging system, ARP 302. Our high angular resolution observation reveals the extended spatial distribution of the molecular gas in ARP 302N. We find that the molecular gas has a very asymmetric distribution with two strong concentrations on either side of the center together with a weaker one offset by about 8 kpc to the north. The molecular gas distribution is also found to be consistent with that from the hot dust as traced by the 24 micro continuum emission observed by the Spitzer. The line ratio of CO J=2-1/1-0 is found to vary strongly from about 0.7 near the galaxy center to 0.4 in the outer part of the galaxy. Excitation analysis suggests that the gas density is low, less than 10$^3$ cm$^{-3}$, over the entire galaxy. By fitting the SED of ARP 302N in the far infrared we obtain a dust temperature of $Trm_d$=26-36 K and a dust mass of M$rm _{dust}$=2.0--3.6$times10^8$ M$rm_odot$. The spectral index of the radio continuum is around 0.9. The spatial distribution and spectral index of the radio continuum emission suggests that most of the radio continuum emission is synchrotron emission from the star forming regions at the nucleus and ARP302N-cm. The good spatial correspondance between the 3.6 cm radio continuum emission, the Spitzer 8 & 24 $mu$m data and the high resolution CO J=2-1 observation from the SMA shows that there is the asymmetrical star forming activities in ARP 302N.
Atacama Large Millimeter/submillimeter Array (ALMA) 12CO(J=1-0) observations are used to study the cold molecular ISM of the Cartwheel ring galaxy and its relation to HI and massive star formation (SF). CO moment maps find $(2.69pm0.05)times10^{9}$ M$_{odot}$ of H$_2$ associated with the inner ring (72%) and nucleus (28%) for a Galactic I(CO)-to-N(H2) conversion factor ($alpha_{rm CO}$). The spokes and disk are not detected. Analysis of the inner rings CO kinematics show it to be expanding ($V_{rm exp}=68.9pm4.9$ km s$^{-1}$) implying an $approx70$ Myr age. Stack averaging reveals CO emission in the starburst outer ring for the first time, but only where HI surface density ($Sigma_{rm HI}$) is high, representing $M_{rm H_2}=(7.5pm0.8)times10^{8}$ M$_{odot}$ for a metallicity appropriate $alpha_{rm CO}$, giving small $Sigma_{rm H_2}$ ($3.7$ M$_{odot}$ pc$^{-2}$), molecular fraction ($f_{rm mol}=0.10$), and H$_2$ depletion timescales ($tau_{rm mol} approx50-600$ Myr). Elsewhere in the outer ring $Sigma_{rm H_2}lesssim 2$ M$_{odot}$ pc$^{-2}$, $f_{rm mol}lesssim 0.1$ and $tau_{rm mol}lesssim 140-540$ Myr (all $3sigma$). The inner ring and nucleus are H$_2$-dominated and are consistent with local spiral SF laws. $Sigma_{rm SFR}$ in the outer ring appears independent of $Sigma_{rm H_2}$, $Sigma_{rm HI}$ or $Sigma_{rm HI+H_2}$. The ISMs long confinement in the robustly star forming rings of the Cartwheel and AM0644-741 may result in either a large diffuse H$_2$ component or an abundance of CO-faint low column density molecular clouds. The H$_2$ content of evolved starburst rings may therefore be substantially larger. Due to its lower $Sigma_{rm SFR}$ and age the Cartwheels inner ring has yet to reach this state. Alternately, the outer ring may trigger efficient SF in an HI-dominated ISM.
The molecular gas content of local early-type galaxies is constrained and discussed in relation to their evolution. First, as part of the Atlas3D survey, we present the first complete, large (260 objects), volume-limited single-dish survey of CO in normal local early-type galaxies. We find a surprisingly high detection rate of 22%, independent of luminosity and at best weakly dependent on environment. Second, the extent of the molecular gas is constrained with CO synthesis imaging, and a variety of morphologies is revealed. The kinematics of the molecular gas and stars are often misaligned, implying an external gas origin in over a third of the systems, although this behaviour is drastically diffferent between field and cluster environments. Third, many objects appear to be in the process of forming regular kpc-size decoupled disks, and a star formation sequence can be sketched by piecing together multi-wavelength information on the molecular gas, current star formation, and young stars. Last, early-type galaxies do not seem to systematically obey all our usual prejudices regarding star formation, following the standard Schmidt-Kennicutt law but not the far infrared-radio correlation. This may suggest a greater diversity in star formation processes than observed in disk galaxies. Using multiple molecular tracers, we are thus starting to probe the physical conditions of the cold gas in early-types.
An imaging survey of CO(1-0), HCN(1-0), and HCO$^+$(1-0) lines in the centers of nearby Seyfert galaxies has been conducted using the Nobeyama Millimeter Array and the RAINBOW interferometer. Preliminary results reveal that 3 Seyferts out of 7 show abnormally high HCN/CO and HCN/HCO$^+$ ratios, which cannot occur even in nuclear starburst galaxies. We suggest that the enhanced HCN emission originated from X-ray irradiated dense obscuring tori, and that these molecular line ratios can be a new diagnostic tool to search for ``pure AGNs. According to our HCN diagram, we suggest that NGC 1068, NGC 1097, and NGC 5194 host ``pure AGNs, whereas Seyfert nuclei of NGC 3079, NGC 6764, and NGC 7469 may be ``composite in nature.
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