The formation of stellar clusters is one of the biggest issues in Astronomy. In our Galaxy, the currently formedclusters are only open clusters; no “young” globular clusters have been observed. On the other hand, in the LMC,stellar clusters called “populous clusters” are found to be forming at present. Comparative studies of young starsas well as the properties of giant molecular clouds both in our Galaxy and LMC are therefore of vital importance.We present here the statistical comparison of the distribution of YSOs with that of CO molecular clouds detected bythe NANTEN CO survey throughout the entire galaxy. The Spizter/SAGE dataset provides the most comprehensive and complete knowledgeon how and where the YSOs are distributed in the LMCs for the first time. The distribution of SAGE sources with a coldspectrum shows good correlation with that of molecular clouds, indicating that these sources are good candidates for YSOs.

We discuss some implications of our recent detection of extragalactic H3 O+: the location of the gas in M 82, the origin of energetic radiation in M 82, and the possible feedback effects of star formation on the cosmic ray flux in galaxies.

The behavior of molecular tracers of the high-density star-formingISM provides a diagnostics tool for luminous FIR galaxies. Allmolecules react differently to the physical and chemicalenvironment and their collective behavior is indicative of theexcitation of the ISM and its evolutionary state. This paperdescribes efforts to diagnose the nuclear medium throughmultiple-molecule studies.

Large-scale shocks propagate in the interstellar medium of starburst and active galaxies, driven by the same mechanisms that regulate the evolution of the star formation and AGN episodes. The imprints of shocks in the chemical composition of the molecular gas provide useful means to identify those mechanisms and to asses their effects. We review some recent and on-going studies of the molecular gas chemistry in the nearby star-forming galaxies IC 342, NGC 253 and M 82, based on the well known shock tracer silicon monoxide (SiO). When mapped at high–spatial resolution the SiO emission reveals substantial differences among these galaxies. In particular, the location of shocks and their dominant driver are in correspondence with the evolutionary stage of the starburst episode. Complementary observations of other tracers of shock chemistry, like methanol (CH3OH), help us to improve the characterization of the shock mechanisms. We also present the first high-resolution observations of the SiO emission in the Seyfert 2 galaxy NGC 1068.

Dwarf galaxies are currently enjoying wide popularity as more sensitive telescopes are able to unveil their dust emission properties in the mid-infrared to submillimetre wavelengths. Once thought to be an insignificant component of their ISM, the dust in dwarf galaxies can now be studied in greater detail with ISO and Spitzer and soon, Herschel, as well as new ground-based submillimetre telescopes. The mid-infrared to millimetre spectral energy distributions reveal global dust properties which look to be different from more metal-rich starburst galaxies, or our own Galaxy: a) deficit of PAHs; b) abundant very small grains; c) excess submillimetre emission that has been interpreted as very cold (<10 K) dust, thus containing up to 50% of the dust mass of the galaxies. The molecular clouds, and the morphology of the ISM appear to differ dramatically. These properties can be explained by the low metallicity environments and the young massive star formation activity, supernovae activity and chemical abundances.

Almost all properties of a photodissociation region (PDR) depend on its metallicity. The heating and cooling efficiencies that determine the temperature of the gas and dust, the dust composition, as well as the elemental abundances that influence the chemical structure of the PDR are just three examples that demonstrate the importance of metallicity effects in PDRs. PDRs are often associated with sites of star formation. If we want to understand the star formation history of our own Galaxy and of distant low-metallicity objects we need to understanding how metallicity acts on PDR physics and chemistry.

Dust models have been applied to interpret the IR emission from65 galaxies in the SINGS galaxy survey, allowing dust masses, PAH fractions,and starlight intensities to be determined. The dust models reproduce theglobal SEDs without requiring “cold” (T $\lesssim$ 12 K) dust. The bulk of theIR emission appears to be radiated by dust in the diffuse ISM,with starlight intensities similar to the intensity in the solar neighborhood.A fraction fPDR of the IR emission is radiated by dust in regions ofhigh starlight intensities (e.g., PDRs), with median fPDR = 0.08.The dust composition is characterized by qPAH, the fraction ofthe dust mass contributed by PAHs with <103 C atoms.Galaxies with metallicities Z/Z๏ < 0.2 tend to have qPAH $\lesssim$ 0.01, but galaxies with Z/Z๏ > 0.4 have qPAH = 0.02 - 0.05.Over the entire sample, with Z/Z๏ ranging from 0.1 to 1, theobservations are consistent with a constant fraction of interstellarmetals being in dust, with Mdust/MH ≈ 0.01(Z/Z๏).

Variations in the diffuse infrared emission from the Galactic plane areinvestigated in the framework of the present dust model. It is shown that observations are interpreted in terms of superposition ofemission from dust grains in various radiation field intensities. The superposition model can also be applied successfully to observations ofthe Large Magellanic Cloud as well as of external galaxies. Infrared spectroscopy of gaseous species provides information onthe elemental compositionsof interstellar dust grains. Recent observations indicatethat part of silicon atoms reside in rather volatile components other thansilicates, which may call for reconsideration of major components of interstellar dust grains. Latest observations with Spitzer and AKARI in a wide spectral rangewill further improve our understanding of the interstellar medium.

We report the first detection of a mid-J isotopic CO line from an external galaxy. We detected the 13CO (6-5) line from the starburst nucleus of NGC 253. The line is suprisingly bright with an integrated intensity 7% of the 12CO (6-5) line, indicating optical depth in the 12CO line. Our LVG modeling shows that a single warm(T ~ 120 K), dense (n ~ 104cm-3) component emits most of the 12CO and 13CO line emission from J = 2-1 through J = 7-6. The CO(1-0) line comes from an additional lower excitation envelope. About 60% of the total molecular gas mass within 70 pc of the nucleus is in the warm, dense component. We show that stellar far-UV photons or X-ray photons from a nuclear source are unlikely to be the primary sources of the gas heating. The most likely sources of heat are cosmic rays from the nuclear starburst or microturbulence within molecular clouds.


We have begun a survey of the [CI] 370 μm fine structure line and of mid-J CO line emission from ULIRGs and starburst galaxies using our grating spectrometer ZEUS on the CSO. Here we present observations from six ULIRGs: Mrk 231, Zw 049.057, NGC 6240, Arp 299, Arp 220, and IRAS 17208. The CO (6-5)/FIR ratio in ULIRGs appears to be lower for ULIRGs than for LIRGs. Comparing the CO SEDs of the ULIRGs shows the necessity of obtaining CO rotational transitions up to at least J = 7 to properly constrain LVG models.

We report the detection of the 158 μm [CII] line from the LIR ~ 1014 L๏ galaxy FSC 10026+4949 at z = 1.12. This is the first detection of [CII] from the z = 1-3 epoch of enhanced starformation. The L[CII]/LFIR ratio is 1.3 × 10-3, larger than the ratio typically seen in local ULIRGs, but similar to that measured in normal and starburst galaxies. This high ratio implies that the UV fields powering the far-infrared emission are of only modest intensity, and that FSC 10026+4949 may be undergoing a galaxy-wide starburst.

We adopted a Galactic model of massive star forming regions (Viti & Williams 1999; Viti et al. 2001) to predict the possible range of chemical abundances of more than 200 species in extragalactic star forming regions. We find that hot core molecules should be detectable in external active galaxies out to high redshift. We present a summary of this study as well as observations of typical tracers of extragalactic hot cores to confirm the modelling work. We detected for the first time the CS(7-6) line in the center of M 82 and we provide the first detection of CS taken in the Antennae (NGC 4038).

We have performed a comparison between the molecular gas emission and the mid IR dust component emission distributions in a sample of nearby galaxies. We have compared CO maps at high spatial resolution, from Wilson et al. (2000), Bayet et al. (2004, 2006) and from Kramer et al. (2005), with the emission distributions of ionised and neutral PAHs (PAH+; PAH0) and of very small grains (VSGs), obtained using signal processing methods as explained in Berné et al. (2007a) and Rapacioli et al. (2005).In M 82, we have also compared the dust emission maps with dense gas tracer maps (HCO and H13CO+ data from García-Burillo et al. 2002) as well as with shock tracer maps (SiO data from García-Burillo et al. 2001).

We present observations of five 12CO and 13CO lines in NGC 2024, including the first velocity resolved observations of lines above 1 THz in this object (J = 13–12). We analysed the observations using radiative transfer codes and derived a more consistent model of this complex source. We found that the high-J CO emission stems from a dense (n ~ 106 cm-3) and hot (~300 K) component, located at the interface of the H II region and the molecular cloud.

Studying molecular gas in the central regions of the star burst galaxies NGC 4945 and Circinus enables us to characterize the physical conditions in these starbursts and compare them with previous studies of local and high-z galaxies. Using the new NANTEN2 4 m sub-millimeter telescope on Pampa La Bola, Chile, we observed for the first time CO 4–3 and [CI] 1–0 at the centers of both galaxies at linear scales of about 700 pc. We find that the centers of NGC 4945 and Circinus are very [CI] bright objects, exhibiting [CI] 1–0 luminosities of 91 and 67 K km s-1 kpc2, respectively. The [CI] 1–0/CO 4–3 integrated intensity rations show high values of about 1.2 in NGC 4945 and 2.8 in Circinus. In both galaxies, the estimated total [CI] cooling intensity of both fine structure transitions is stronger by factors of ~1–3 compared to the total CO cooling intensity. The CO/C abundance ratios are 0.2–2. Similarly low values are found in Galactic translucent clouds (Mookerjea et al. 2006).

We present studies of polarized cloud emission that are in progress at theHelsinki University Observatory. Two projects are concerned with FIR/sub-mmdust polarization, one based on collapse models of protostellar cores, theother on 3D MHD simulations of larger clouds. We also examine the Zeemansplitting and the relations between the derived average magnetic field and theactual field strengths.

We performed mid- to far-IR observations of 20 nearby dusty elliptical galaxies with AKARI and Spitzer. We have detected PAHs and extended dust emission from many of our sample galaxies.

High- and low-density tracer molecules have been observed in (Ultra-) Luminous Infrared Galaxies in order to initiatemulti-molecule multi-transition studies to evaluate the physical and chemical environment of the nuclear medium and the ongoing nuclear activity. The data, augmented with data available in the literature, are presented in Baan et al. (2007), which also presents a first order analysis. Here, we present the chemical analysis of the J = 1–0 transition lines of HCN, HNC, and HCO+.

Astronomical observations at sub-millimetre wavelengths are limited either by the angular resolution of the telescope or by the sensitivity and field of view of the detector array. New generation of radio telescopes, such as the APEX 12-m telescope on Chajnantor plateau in Chile, can overcome these limitations if they are equipped with large detector arrays made of thousands of sensitive bolometer pixels. Instrumentation developments undertaken at CEA and based on the all silicon technology of CEA/Leti are able to provide such large detector arrays. The ArTeMiS project at CEA Saclay, in partnership with IAS, IAP and CRTBT, consists in developing a 4000-pixel bolometer camera for ground-based telescopes that operates in atmospheric windows at 200–450 μm (Talvard et al. 2006, SPIE, 6275).

We demonstrate the diagnostic value of para-formaldehyde (p-H2CO) as a tracer of the density and the temperature of the molecular gas in external galaxies 
using the prototypical starburst galaxy M 82 as an example. 
We also report the discovery of the methanol line CH3OH(42 → 31, E) from M 82.