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Context.The Carina region is an excellent astrophysical laboratory for studying the feedback mechanisms of newly born, very massive stars within their natal giant molecular clouds (GMCs) at only 2.35 kpc distance.

Aims.We use the Barnard 68 dark globule as a test case for a spherically symmetric PDR model exposed to low-UV radiation fields. With a roughly spherical morphology and an accurately determined density profile, Barnard 68 is ideal for this purpose. The processes governing the energy balance in the cloud surface are studied in detail.

Aims.We present a comparison between independent computer codes, modeling the physics and chemistry of interstellar photon dominated regions (PDRs). Our goal was to understand the mutual differences in the PDR codes and their effects on the physical and chemical structure of the model clouds, and to converge the output of different codes to a common solution.

Context.Characterizing the spatial and velocity structure of molecular clouds is a first step towards a better understanding of interstellar turbulence and its link to star formation.

Aims.The physical conditions and chemical structure in the dark cloud of Barnard 5and its surrounding atomic halo is studied. The impact of the halo on the line emission emerging from the molecular cloud is investigated.Methods.We present observations of the [CI] 3P$_1\rightarrow$3P0transition of neutral carbon and the low-Jtransitions of 12CO and 13CO. The CO maps extend from the core ($A_{\rm v}\ga 7$) to the northern cloud edge and into the halo ($A_{\rm v}\la 1$). They are complemented by deeply integrated [CI] spectra made along a 1D cut of similar extent. Escape probability and photon-dominated region (PDR) models are employed to interpret the observations.Results.12CO and 13CO are detected in the cloud and the halo, while [CI] is detected only toward the molecular cloud. This occurs even though the neutral carbon column density is $\ga$5 times larger than the CO column density in the halo, but it can be understood in terms of excitation. The [CI] excitation is governed by collisions even at the low halo densities, while the CO excitation is dominated by the absorption of line photons emitted by the nearby molecular cloud. The upper limit on the neutral carbon column density in the halo is $6\times 10^{15}$cm-2. The PDR studies show that even small column densities of H2and CO, such as those in the B5halo, can significantly change the [CI] and CO line emission (pre-shielding). Since this effect decreases the [CI] intensity and increases the CO intensity, the largest impact is noted for the [CI]/CO line ratios. For the B5cloud, a PDR model with a molecular hydrogen column density of ~$6\times 10^{19}$cm-2in the halo matches the observed [CI]/CO line ratios best. Models with no pre-shielding, in contrast, suggest high gas densities that are in conflict with independently derived densities. The PDR models with a $\chi<1$demonstrate that the [CI]/CO ratios cannot be attributed solely to a reduced FUV field.

Using MAMBO at the IRAM 30 m telescope we have observed a dense core in the cirrus cloud MCLD 123.5+24.9 in the dust continuum emission at 250 GHz. The core is detected as an elongated filament with an extent of $4.\!'2\times 0.\!'7$, corresponding to 0.18 pc$\times$0.03 pc at an adopted distance of 150 pc. We find a close correlation between the continuum emission and previously observed C18O (1$\to$0) line emission. Using standard dust models we derive hydrogen column densities of up to 1022cm-2. The total mass for the filament is about 0.66 $M_{\odot}$. We also present observations of the HC3N (3$\to$2), (4$\to$3), and (10$\to$9) emission lines obtained with the MPIfR 100 m and the IRAM 30 m telescopes. The distribution is very different from the dust continuum and the C18O (1$\to$0) line emission. HC3N is concentrated in two distinct clumps located at the ends of the filament seen in the other tracers. Based on a LVG analysis of the HC3N transitions we derive column densities of $N({\rm HC_3N})/\Delta v\approx10^{13}$cm-2/kms-1and volume densities of $n({\rm H}_2)\approx10^5$cm-3. We find that the HC3N clumps have masses of 0.13 and 0.19 $M_{\odot}$. Our data demonstrate that the cirrus cloud cores are gravitationally bound, and that they show chemical structure indicating different evolutionary stages within the cloud.

We present a detailed study of the Δ-variance as a method to quantify molecular cloud structure. The Δ-variance was introduced by Stutzki et al. (1998) to analyze the drift behaviour of scalar functions and is used to characterize the spatial structure of observed molecular cloud images. For fractional Brownian motion structures(fBm-fractals), characterized by a power law power spectrum and random phases, the Δ-variance allows to determine the power spectral index β. We present algorithms to determine the Δ-variance for discretely sampled maps and study the influence of white noise, beam smoothing and the finite spatial extent of the maps. We find that for images with $\beta> 3$, edge effects can bias the structure parameters when determined by means of a Fourier transform analysis. In contrast, the Δ-variance provides a reliable estimate for the spectral index β, if determined in the spatial domain. The effects of noise and beam smoothing are analytically represented in a leading order approximation. This allows to use the Δ-variance of observed maps even at scales where the influence of both effects becomes significant, allowing to derive the spectral index βover a wider range and thus more reliably than possible otherwise. The Δ-variance is applied to velocity integrated spectral line maps of several clouds observed in rotational transitions of 12CO and 13CO. We find that the spatial structure of the emission is well characterized by a power law power spectrum in all cases. For linear scales larger than ∼0.5 pc the spectral index is remarkably uniform for the different clouds and transitions observed ($2.5\le\beta\le2.8$). Significantly larger values ($\beta\ga3$) are found for observations made with higher linear resolution toward the molecular cloud MCLD 123.5+24.9 in the Polaris Flare, indicating a smoother spatial structure of the emission at small scales (<0.5 pc).

The beam pattern of a single dish radio telescope is given by the main beam and additional components at larger angles, usually called error beam or stray pattern. The latter have relatively small peak amplitudes (typ. below -25 dB), depending on the rms surface error of the primary reflector. However, because of their large angular extent, they are sensitive to extended sources, and a significant fraction of the observed intensity can result from error beam pick-up. For (sub-)mm observations suffering from error beam pick-up we introduce a new temperature scale for the corrected data, the corrected main beam brightness temperatureTmb,c, which provides a better approximation to the intensity detected by the main beam than the commonly used antenna temperatureand main beam brightness temperature. We consider two different correction methods. The first method uses complementary observations obtained with a smaller telescope. Smeared to the angular resolution of the error beam pattern they provide an estimate of the error beam pick-up in the observations of the large telescope. For the second method, the error beam pick-up is de-convolved from the observed map in Fourier space. The requirements for both correction methods and their advantages and limitations are discussed in detail. Both correction methods require additional observations, unless the full spatial extent of the emission is observed. We find that the de-convolution method is attractive for the correction of fully sampled maps with an angular extent much larger than the error beam pattern. For smaller maps and more sparsely sampled observations, the subtraction method is favorable, because the additional observations with a small telescope are less time consuming.

The goal of the IRAM key-project "Small-scale structure of pre-star forming regions"is to map three nearby ($d\sim 150 {\rm pc}$), quiescent molecular clouds with a high angular and spectral resolution to study the molecular cloud structure down to the smallest linear scales currently accessible by single dish radio telescopes. Here, we give a detailed discussion of the influence and the correction of the error beam pick-up. A new set of corrected data is presented using the beam pattern parameters of the IRAM 30 m telescope recently published by Greve et al. (1998). For the correction we use observations made at lower angular resolution with the KOSMA 3 m telescope. Smeared to the resolution of the error beam, they provide an estimate of the pick-up therein. The error beam pick-up accounts for a significant fraction of the observed intensity in the key-project maps: on average 31% to 50% for the 12CO $J=2\rightarrow$1 maps, 10% to 35% for the 13CO $J=2\rightarrow$1 maps, and 16.5% in the 12CO $J=1\rightarrow$0 map of MCLD 123.5+24.9. In addition, the line profiles are significantly modified by the error beam pick-up. The large data set available with the IRAM key-project allows us to investigate the accuracy of the correction method and its limitations in detail. For the corrected maps, we determine the overall accuracy of the temperature scale to be better than 15% , except for the 13CO $J=2\rightarrow$1 map of MCLD123.5+24.9 and L1512 where we estimate an accuracy of 22% and 18% . The key-project maps presented here and the released maps published by Falgarone et al. (1998) (with the correction done using the previous beam pattern parameters determined by Garcia-Burillo et al. 1993) differ by no more than 10% and only in localized regions. Both data sets and the supplementary observations made with the KOSMA telescope are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/Abstract.htmlThe "error beam problem"is not limited to observations obtained with the IRAM 30 m. Similar beam pattern are found for other large single dish (sub-)mm telescopes, although few quantitative studies exist. In particular, for observations of spatially extended sources, the error beam contribution has to be considered and corrected for if necessary.

Context. Star formation at earlier cosmological times took place in an interstellar medium with low metallicity. The Large Magellanic Cloud (LMC) is ideally suited to study star formation in such an environment. Aims. The physical and chemical state of the ISM in a star forming environment can be constrained by observations of submm and FIR spectral lines of the main carbon carrying species, CO, C?i and C?ii, which originate in the surface layers of molecular clouds illuminated by the UV?radiation of the newly formed, young stars. Methods. We present high-angular resolution sub-millimeter observations in the N159W?region in the LMC obtained with the NANTEN2 telescope of the 12CO?J = 4 ? 3, J = 7 ? 6, and 13CO?J = 4 ? 3 rotational and [C?I] 3P1-3P0and 3P2-3P1fine-structure transitions. The 13CO?J = 4 ? 3 and [C?i]?3P2-3P1transitions are detected for the first time in the LMC. We derive the physical and chemical properties of the low-metallicity molecular gas using an escape probability code and a self-consistent solution of the chemistry and thermal balance of the gas in the framework of a clumpy cloud PDR?model.Results. The separate excitation analysis of the submm CO?lines and the carbon fine structure lines shows that the emitting gas in the N159W?region has temperatures of about 80?K and densities of about 104?cm-3. The estimated C to CO?abundance ratio close to unity is substantially higher than in dense massive star-forming regions in the Milky?Way. The analysis of all observed lines together, including the [C?ii]?line intensity reported in the literature, in the context of a clumpy cloud PDR?model constrains the UV?intensity to about ?? 220 and an average density of the clump ensemble of about 105?cm-3, thus confirming the presence of high density material in the LMC N159W?region.

Context. Studying molecular gas in the central regions of the star burst galaxies NGC?4945 and Circinus enables us to characterize the physical conditions and compare them to previous local and high-z studies.Aims.We estimate temperature, molecular density and column densities of CO?and atomic carbon. Using model predictions we give a range of estimated CO/C abundance ratios.Methods.Using the new NANTEN2 4?m sub-millimeter telescope in Pampa La Bola, Chile, we observed for the first time CO?4?3 and [Ci]?3P1-3P0at the centers of both galaxies at linear scale of 682?pc and 732?pc respectively. We compute the cooling curves of?12CO and 13CO?using radiative transfer models and estimate the physical conditions of CO?and [CI].Results.The centers of NGC?4945 and Circinus are very [Ci]?bright objects, exhibiting [Ci]?3P1-3P0luminosities of 91 and?67?K?km?s-1?kpc2, respectively. The [Ci]?3P1-3P0/CO?4?3 ratio of integrated intensities are large at 1.2 in NGC?4945 and?2.8 in Circinus. Combining previous CO?J= 1-0, 2?1 and 3?2 and 13CO?J= 1-0, 2?1 studies with our new observations, the radiative transfer calculations give a range of densities, n(H2)=103-3 ?104?cm-3, and a wide range of kinetic temperatures, Tkin= 20-100?K, depending on the density. To discuss the degeneracy in density and temperature, we study two representative solutions. In both galaxies the estimated total [CI] cooling intensity is stronger by factors of ~1-3 compared to the total CO?cooling intensity. The CO/C?abundance ratios are?0.2-2, similar to values found in Galactic translucent clouds. Conclusions.Our new observations enable us to further constrain the excitation conditions and estimate the line emission of higher-J CO- and the upper [CI]-lines. For the first time we give estimates for the CO/C abundance ratio in the center regions of these galaxies. Future CO?J= 7-6 and [CI] 2?1 observations will be important to resolve the ambiguity in the physical conditions and confirm the model predictions.

Aims.We aim at deriving the excitation conditions of the interstellar gas as well as the local FUV intensities in the molecular cloud surrounding NGC 3603 to get a coherent picture of how the gas is energized by the central stars.

We report on the initial analysis of Herschel/HIFI carbon monoxide (CO) observations of the Martian atmosphere performed between 11 and 16 April 2010. We selected the (7–6) rotational transitions of the isotopes 13CO at 771 GHz and C18O and 768 GHz in order to retrieve the mean vertical profile of temperature and the mean volume mixing ratio of carbon monoxide. The derived temperature profile agrees within less than 5 K with general circulation model (GCM) predictions up to an altitude of 45 km, however, show about 12–15 K lower values at 60 km. The CO mixing ratio was determined as 980 ±150 ppm, in agreement with the 900 ppm derived from Herschel/SPIRE observations in November 2009.

Comet C/2006 W3 (Christensen) was observed in November 2009 at 3.3 AU from the Sun with Herschel.The PACS instrument acquired images of the dust coma in 70-μm and 160-μm filters and spectra covering several H2O rotational lines. Spectra in the range 450–1550 GHz were acquired with SPIRE. The comet emission continuum from 70 to 672 μm was measured, but no lines were detected. The spectral energy distribution indicates thermal emission from large particles and provides a measure of the size distribution index and dust production rate. The upper limit to the water production rate is compared to the production rates of other species (CO, CH3OH, HCN, H2S, OH) measured with the IRAM 30-m and Nançay telescopes. The coma is found to be strongly enriched in species more volatile than water, in comparison to comets observed closer to the Sun. The CO to H2O production rate ratio exceeds 220%. The dust-to-gas production rate ratio is on the order of 1.

We have obtained the first continuous disk averaged spectrum of Mars from 450 to 1550 Ghz using the Herschel-SPIRE Fourier-transform spectrometer. The spectrum was obtained at a constant resolution of 1.4 GHz across the whole band. The flux from the planet is such that the instrument was operated in “bright source” mode to prevent saturation of the detectors. This was the first successful use of this mode and in this work we describe the method used for observing Mars together with a detailed discussion of the data reduction techniques required to calibrate the spectrum. We discuss the calibration accuracy obtained and describe the first comparison with surface and atmospheric models. In addition to a direct photometric measurement of the planet the spectrum contains the characteristic transitions of 12CO from J 5–4 to J 13–12 as well as numerous H2O transitions. Together these allow the comparison to global atmospheric models allowing the mean mixing ratios of water and 12CO to be investigated. We find that it is possible to match the observed depth of the absorption features in the spectrum with a fixed water mixing ratio of 1×10-4and a 12CO mixing ratio of 9×10-4.

We report on the initial analysis of a Herschel-PACS full range spectrum of Neptune, covering the 51–220 μm range with a mean resolving power of ~3000, and complemented by a dedicated observation of CH4at 120 μm. Numerous spectral features due to HD (R(0) and R(1)), H2O, CH4, and CO are present, but so far no new species have been found. Our results indicate that (i) Neptune's mean thermal profile is warmer by ~3 K than inferred from the Voyagerradio-occultation; (ii) the D/H mixing ratio is (4.5 ±1) × 10-5, confirming the enrichment of Neptune in deuterium over the protosolar value (~2.1 × 10-5); (iii) the CH4mixing ratio in the mid stratosphere is (1.5 ±0.2) × 10-3, and CH4appears to decrease in the lower stratosphere at a rate consistent with local saturation, in agreement with the scenario of CH4stratospheric injection from Neptune's warm south polar region; (iv) the H2O stratospheric column is (2.1 ±0.5) × 1014cm-2but its vertical distribution is still to be determined, so the H2O external flux remains uncertain by over an order of magnitude; and (v) the CO stratospheric abundance is about twice the tropospheric value, confirming the dual origin of CO suspected from ground-based millimeter/submillimeter observations.