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Young early-type HAeBe stars are still embedded in the molecular clouds in which they formed. They illuminate reflection nebulae, which shape the surrounding molecular cloud and may trigger star formation. They are therefore ideal places to search for ongoing star formation activity. NGC2023 is illuminated by the Herbig Be star HD37903. It is the most massive member of a small young cluster with about 30 PMS stars, several of which are Class I objects that still heavily accrete. It might therefore be expected that they might drive molecular outflows. We examined the whole region for outflows. We analyzed previously published APEX data to search for and characterize the outflows in the NGC2023 region. This is the first systematic search for molecular outflows in this region. Since the outflows were mapped in several CO transitions, we can determine their properties quite well. We have discovered four molecular outflows in the vicinity of NGC2023, three of which are associated with Class I objects. MIR-63, a bright mid-infrared and submillimeter Class I source, is a binary with a separation of 2.4" and drives two bipolar outflows orthogonal to each other. The large southeast-northwest outflow excites the Herbig-Haro flow HH247. MIR-73, a Class I object, which is also a far-infrared source, drives a pole-on outflow. MIR-62 is a Class II object with strong infrared excess and a luminosity of 7 Lsun. It is not detected in the far-infrared. The Class I sources have bolometric luminosities of about 20 Lsun or lower, that is, they are all low-mass stars. One other far-infrared source, MIR-75, may have powered an outflow in the past because it now illuminates an egg-shaped cavity. The four outflow sources are at a similar evolutionary stage, which suggests that their formation may have been triggered by the expanding C II region., Comment: 10 pages,11 figures, accepted for publication in A&A on 12/03/2024

During star formation, the dense gas undergoes significant chemical evolution leading to the emergence of a rich variety of molecules associated with hot cores and hot corinos. The physical and chemical conditions are poorly constrained; the early phases of emerging hot cores in particular represent an unexplored territory. We provide here a full molecular inventory of a massive protostellar core that is proposed to be a precursor of a hot core. We performed an unbiased spectral survey towards the hot core precursor associated with clump G328.2551-0.5321 between 159GHz and 374GHz. To identify the spectral lines, we used rotational diagrams and radiative transfer modelling assuming LTE. We detected 39 species and 26 isotopologues, and were able to distinguish a warm and compact inner region, a colder more extended envelope, and the kinematic signatures of the accretion shocks that have previously been observed with ALMA. We associate most of the emission of the small molecules with the cold gas, while the molecular emission of the warm gas is enriched by complex organic molecules (COMs). We find a high abundance of S-bearing molecules in the cold gas phase suggesting a low sulphur depletion, with a factor of > 1%. We identify nine COMs in the warm gas, four in the cold gas, and four towards the accretion shocks. The high abundances of S-bearing species originating from the undisturbed gas may suggest a contribution from shocked gas at the outflow cavity walls. The molecular composition of the warm gas is similar to that of both hot cores and hot corinos, but the molecular abundances are closer to the values found towards hot corinos than to values found towards hot cores. Considering the compactness of the warm region and its moderate temperature, we suggest that thermal desorption has not been completed towards this object yet, representing an early phase of the emergence of hot cores., Comment: 68 pages, 59 figures. Accepted by A&A after refereeing and language corrections. Abstract abbreviated

Only recently, OD, the deuterated isotopolog of hydroxyl, OH, has become accessible in the interstellar medium; spectral lines from both species have been observed in the supra-Terahertz and far infrared regime. Here we study rotational lines of OD and OH towards 13 Galactic high-mass star forming regions, with the aim to constrain the OD abundance and infer the deuterium fractionation of OH in their molecular envelopes. We used the Stratospheric Observatory for Infrared Astronomy (SOFIA) to observe the $^2\Pi_{3/2}$ $J=5/2-3/2$ ground-state transition of OD at 1.3 THz ($215~\mu$m) and the rotationally excited OH line at 1.84 THz ($163~\mu$m). We also used published high-spectral-resolution SOFIA data of the OH ground-state transition at 2.51 THz ($119.3~\mu$m). Our results show that absorption from the $^2\Pi_{3/2}$ OD $J=5/2-3/2$ ground-state transition is prevalent in the dense clumps surrounding active sites of high-mass star formation. We performed detailed radiative transfer modelling to investigate the OD abundance profile in the inner envelope for a large fraction of our sample. Our modelling suggests that part of the absorption arises from the denser inner parts, while the bulk of it as seen with SOFIA originates in the outer, cold layers of the envelope for which our constraints on the molecular abundance suggest a strong enhancement in deuterium fractionation. We find a weak negative correlation between the OD abundance and the bolometric luminosity to mass ratio, an evolutionary indicator, suggesting a slow decrease of OD abundance with time. A comparison with HDO shows a similarly high deuterium fractionation for the two species in the cold envelopes, which is of the order of 0.48% for the best studied source, G34.26+0.15. Our results are consistent with chemical models that favour rapid exchange reactions to form OD in the dense cold gas., Comment: 20 pages, 14 figures. Accepted by A&A after refereeing and language corrections. Abstract abbreviated

Spectral lines of ammonia, NH3, are useful probes of the physical conditions in dense molecular cloud cores. In addition to advantages in spectroscopy, ammonia has also been suggested to be resistant to freezing onto grain surfaces, which should make it a superior tool for studying the interior parts of cold, dense cores. Here we present high-resolution NH3 observations with the Very Large Array and Green Bank Telescope toward a prestellar core. These observations show an outer region with a fractional NH3 abundance of X(NH3) = (1.975 ± 0.005) × 10-8 (±10% systematic), but it also reveals that, after all, the X(NH3) starts to decrease above a H2 column density of ≈2.6 × 1022 cm-2. We derive a density model for the core and find that the break point in the fractional abundance occurs at the density n(H2) ∼2 × 105 cm-3, and beyond this point the fractional abundance decreases with increasing density, following the power law n -1.1. This power-law behavior is well reproduced by chemical models where adsorption onto grains dominates the removal of ammonia and related species from the gas at high densities. We suggest that the break-point density changes from core to core depending on the temperature and the grain properties, but that the depletion power law is anyway likely to be close to n -1 owing to the dominance of accretion in the central parts of starless cores. © 2022. The Author(s). Published by the American Astronomical Society.

We quantified the effects of stellar feedback in RCW 49 by determining the physical conditions in different regions using the [CII] 158 $\mu$m and [OI] 63 $\mu$m observations from SOFIA, the $^{12}$CO (3-2) observations from APEX and the H$_2$ line observations from Spitzer telescopes. Large maps of RCW 49 were observed with the SOFIA and APEX telescopes, while the Spitzer observations were only available towards three small areas. From our qualitative analysis, we found that the H$_2$ 0-0 S(2) emission line probes denser gas compared to the H$_2$ 0-0 S(1) line. In four regions ("northern cloud", "pillar", "ridge", and "shell"), we compared our observations with the updated PDR Toolbox models and derived the integrated far-ultraviolet flux between 6-13.6 eV ($G_{\rm 0}$), H nucleus density ($n$), temperatures and pressures. We found the ridge to have the highest $G_{\rm 0}$ (2.4 $\times$ 10$^3$ Habing units), while the northern cloud has the lowest $G_{\rm 0}$ (5 $\times$ 10$^2$ Habing units). This is a direct consequence of the location of these regions with respect to the Wd2 cluster. The ridge also has a high density (6.4 $\times$ 10$^3$ cm$^{-3}$), which is consistent with its ongoing star formation. Among the Spitzer positions, we found the one closest to the Wd2 cluster to be the densest, suggesting an early phase of star formation. Furthermore, the Spitzer position that overlaps with the shell was found to have the highest $G_{\rm 0}$ and we expect this to be a result of its proximity to an O9V star., Comment: 18 pages, 12 figures

Revealing the 3D dynamics of HII regions and their associated molecular clouds is important for understanding the longstanding problem as to how stellar feedback affects the density structure and kinematics of the interstellar medium. We employed observations of the HII region RCW 120 in [CII], observed within the SOFIA legacy program FEEDBACK, and the $^{12}$CO and $^{13}$CO (3$\to$2) lines, obtained with APEX. In addition we used HI data from the Southern Galactic Plane Survey. Two radiative transfer models were used to fit the observed data. A line profile analysis with the 1D non-LTE radiative transfer code SimLine proves that the CO emission cannot stem from a spherically symmetric molecular cloud configuration. With a two-layer multicomponent model, we then quantified the amount of warm background and cold foreground gas. There is a deficit of CO emission along the line-of-sight toward the center of the HII region which indicates that the HII region is associated with a flattened molecular cloud. Self-absorption in the CO line may hide signatures of infalling and expanding molecular gas. The [CII] emission arises from an expanding [CII] bubble and from the PDRs. A significant part of [CII] emission is absorbed in a cool (~60-100 K), low-density (<500 cm$^{-3}$) atomic foreground layer with a thickness of a few parsec. We propose that the RCW 120 HII region formed in a flattened molecular cloud and is now bursting out of its parental cloud. The compressed surrounding molecular layer formed a torus around the spherically expanding HII bubble. This scenario can possibly be generalized for other HII bubbles and would explain the observed "flat" structure of molecular clouds associated with HII bubbles. We suggest that the [CII] absorption observed in many star-forming regions is at least partly caused by low-density, cool, HI-envelopes surrounding the molecular clouds.

The [CII] 158$\mu$m fine-structure line is the dominant cooling line of moderate-density photodissociation regions (PDRs) illuminated by moderately bright far-ultraviolet (FUV) radiation fields. We aim to understand the origin of [CII] emission and its relation to other tracers of gas and dust in PDRs. One focus is a study of the heating efficiency of interstellar gas as traced by the [CII] line to test models of the photoelectric heating of neutral gas by polycyclic aromatic hydrocarbon (PAH) molecules and very small grains. We make use of a one-square-degree map of velocity-resolved [CII] line emission toward the Orion Nebula complex, and split this out into the individual spatial components, the expanding Veil Shell, the surface of OMC4, and the PDRs associated with the compact HII region of M43 and the reflection nebula NGC 1977. We employed Herschel far-infrared photometric images to determine dust properties. Moreover, we compared with Spitzer mid-infrared photometry to trace hot dust and large molecules, and velocity-resolved IRAM 30m CO(2-1) observations of the molecular gas. The [CII] intensity is tightly correlated with PAH emission in the IRAC 8$\mu$m band and far-infrared emission from warm dust. The correlation between [CII] and CO(2-1) is very different in the four subregions and is very sensitive to the detailed geometry. Constant-density PDR models are able to reproduce the observed [CII], CO(2-1), and integrated far-infrared (FIR) intensities. We observe strong variations in the photoelectric heating efficiency in the Veil Shell behind the Orion Bar and these variations are seemingly not related to the spectral properties of the PAHs. The [CII] emission from the Orion Nebula complex stems mainly from moderately illuminated PDR surfaces. Future observations with the James Webb Space Telescope can shine light on the PAH properties that may be linked to these variations.

We report SOFIA-upGREAT spectroscopic imaging of the [C II] 158um spectral line, as well as a number of [O I] 63um spectra, across a 67x45 pc field toward the Sgr B region in our Galactic center. The fully-sampled and velocity-resolved [C II] images have 0.55 pc spatial and 1 km/s velocity resolutions. We find that Sgr B extends as a coherent structure spanning some 34 pc along the Galactic plane. Bright [C II] emission encompasses Sgr B1 (G0.5-0.0), the G0.6-0.0 HII region, and passes behind and beyond the luminous star forming cores toward Sgr B2 (G0.7-0.0). Sgr B is a major contributor to the entire Galactic center's [C II] luminosity, with surface brightness comparable to [C II] from the Arches region. [C II], 70um, and 20cm emission share nearly identical spatial distributions. Combined with the lack of [C II] self-absorption, this indicates that these probes trace UV on the near surfaces of more extended clouds visible in CO isotopologues and 160um continuum. Stars from regions of local star formation likely dominate the UV field. Photodissociation regions and HII regions contribute similar amounts of [C II] flux. The extreme star formation cores of Sgr B2 contribute negligible amounts to the total [C II] intensity from the Sgr B region. Velocity fields and association with a narrow dust lane indicate that they may have been produced in a local cloud-cloud collision. The cores are likely local analogs of the intense star formation regions where ideas to explain the "C+ deficit" in ultra-luminous galaxies can be tested., Comment: 22 pages, 13 figures. Accepted for publication in the Astrophysical Journal

Context. The [CII] 158micron far-infrared fine-structure line is one of the dominant cooling lines of the star-forming interstellar medium (ISM). Hence [CII] emission originates in and thus can be used to trace a range of ISM processes. Velocity-resolved large-scale mapping of [CII] in star-forming regions provides a unique perspective of the kinematics of these regions and their interactions with the exciting source of radiation. Aims. We explore the scientific applications of large-scale mapping of velocity-resolved [CII] observations. With the [CII] observations, we investigate the effect of stellar feedback on the ISM. We present the details of observation, calibration, and data reduction using a heterodyne array receiver mounted on an airborne observatory. Results. A square-degree [CII] map with a spectral resolution of 0.3 km/s is presented. The scientific potential of this data is summarized with discussion of mechanical and radiative stellar feedback, filament tracing using [CII], [CII] opacity effects, [CII] and carbon recombination lines, and [CII] interaction with the large molecular cloud. The data quality and calibration is discussed in detail, and new techniques are presented to mitigate the effects of unavoidable instrument deficiencies (e.g. baseline stability) and thus to improve the data quality. A comparison with a smaller [CII] map taken with the Herschel/Heterodyne Instrument for the Far-Infrared (HIFI) spectrometer is presented.

We unveil the stellar wind driven shell of the luminous massive star-forming region of RCW 49 using SOFIA FEEDBACK observations of the [CII] 158 $\mu$m line. The complementary dataset of the $^{12}$CO and $^{13}$CO J = 3 - 2 transitions is observed by the APEX telescope and probes the dense gas toward RCW 49. Using the spatial and spectral resolution provided by the SOFIA and APEX telescopes, we disentangle the shell from a complex set of individual components of gas centered around RCW 49. We find that the shell of radius ~ 6 pc is expanding at a velocity of 13 km s$^{-1}$ toward the observer. Comparing our observed data with the ancillary data at X-Ray, infrared, sub-millimeter and radio wavelengths, we investigate the morphology of the region. The shell has a well defined eastern arc, while the western side is blown open and is venting plasma further into the west. Though the stellar cluster, which is ~ 2 Myr old gave rise to the shell, it only gained momentum relatively recently as we calculate the shell's expansion lifetime ~ 0.27 Myr, making the Wolf-Rayet star WR20a a likely candidate responsible for the shell's re-acceleration., Comment: 31 pages, 17 figures

The Orion Molecular Cloud is the nearest massive-star forming region. Massive stars have profound effects on their environment due to their strong radiation fields and stellar winds. Velocity-resolved observations of the [CII] $158\,\mu\mathrm{m}$ fine-structure line allow us to study the kinematics of UV-illuminated gas. Here, we present a square-degree-sized map of [CII] emission from the Orion Nebula complex obtained by the upGREAT instrument onboard SOFIA, covering the entire Orion Nebula (M42) plus M43 and the nebulae NGC 1973, 1975, and 1977. We compare the stellar characteristics of these three regions with the kinematics of the expanding bubbles surrounding them. The bubble blown by the O7V star $\theta^1$ Ori C in the Orion Nebula expands rapidly, at $13\,\mathrm{km\,s^{-1}}$. Simple analytical models reproduce the characteristics of the hot interior gas and the neutral shell of this wind-blown bubble and give us an estimate of the expansion time of $0.2\,\mathrm{Myr}$. M43 with the B0.5V star NU Ori also exhibits an expanding bubble structure, with an expansion velocity of $6\,\mathrm{km\,s^{-1}}$. Comparison with analytical models for the pressure-driven expansion of H\,{\sc ii} regions gives an age estimate of $0.02\,\mathrm{Myr}$. The bubble surrounding NGC 1973, 1975, and 1977 with the central B1V star 42 Orionis expands at $1.5\,\mathrm{km\,s^{-1}}$, likely due to the over-pressurized ionized gas as in the case of M43. We derive an age of $0.4\,\mathrm{Myr}$ for this structure. We conclude that the bubble of the Orion Nebula is driven by the mechanical energy input by the strong stellar wind from $\theta^1$ Ori C, while the bubbles associated with M43 and NGC 1977 are caused by the thermal expansion of the gas ionized by their central later-type massive stars.

Context. The [CII] 158 {\mu}m far-infrared (FIR) fine-structure line is one of the most important cooling lines of the star-forming interstellar medium (ISM). High spectral resolution observations have shown complex structures in the line profiles of the [CII] emission. Aims. Our aim is to determine whether the complex profiles observed in [^{12}CII] are due to individual velocity components along the line-of-sight or to self-absorption based on a comparison of the [^{12}CII] and isotopic [^{13}CII] line profiles. Methods. Deep integrations with the SOFIA/upGREAT 7-pixel array receiver in M43, Horsehead~PDR, Monoceros~R2, and M17~SW allow for the detection of optically thin [^{13}CII] emission lines, along with the [^{12}CII] emission lines, with a high signal-to-noise ratio. We first derived the [^{12}CII] optical depth and the [CII] column density from a single component model. However, the complex line profiles observed require a double layer model with an emitting background and an absorbing foreground. A multi-component velocity fit allows us to derive the physical conditions of the [CII] gas: column density and excitation temperature. Results. We find moderate to high [^{12}CII] optical depths in all four sources and self-absorption of [^{12}CII] in Mon R2 and M17 SW. The high column density of the warm background emission corresponds to an equivalent Av of up to 41 mag. The foreground absorption requires substantial column densities of cold and dense [CII] gas, with an equivalent Av ranging up to about 13 mag. Conclusions. The column density of the warm background material requires multiple photon-dominated region (PDR) surfaces stacked along the line of sight and in velocity. The substantial column density of dense and cold foreground [CII] gas detected in absorption cannot be explained with any known scenario and we can only speculate on its origins, Comment: 40 pages, 49 figures

We present Atacama Large Millimeter/submillimeter Array maps of the starless molecular cloud core Ophiuchus/H-MM1 in the lines of deuterated ammonia (ortho-NH2 D), methanol (CH3 OH), and sulfur monoxide (SO). The dense core is seen in NH2 D emission, whereas the CH3 OH and SO distributions form a halo surrounding the core. Because methanol is formed on grain surfaces, its emission highlights regions where desorption from grains is particularly efficient. Methanol and sulfur monoxide are most abundant in a narrow zone that follows the eastern side of the core. This side is sheltered from the stronger external radiation field coming from the west. We show that photodissociation on the illuminated side can give rise to an asymmetric methanol distribution but that the stark contrast observed in H-MM1 is hard to explain without assuming enhanced desorption on the shaded side. The region of the brightest emission has a wavy structure that rolls up at one end. This is the signature of Kelvin-Helmholtz instability occurring in sheared flows. We suggest that in this zone, methanol and sulfur are released as a result of grain-grain collisions induced by shear vorticity. © 2020. The American Astronomical Society. All rights reserved.

The IRDC SDC335.579-0.292 (SDC335) is a massive star-forming cloud found to be globally collapsing towards one of the most massive star forming cores in the Galaxy. SDC335 hosts three high-mass protostellar objects at early stages of their evolution and archival ALMA Cycle 0 data indicate the presence of at least one molecular outflow in the region. Observations of molecular outflows from massive protostellar objects allow us to estimate the accretion rates of the protostars as well as to assess the disruptive impact that stars have on their natal clouds. The aim of this work is to identify and analyse the properties of the protostellar-driven molecular outflows within SDC335 and use these outflows to help refine the properties of the protostars. We imaged the molecular outflows in SDC335 using new data from the ATCA of SiO and Class I CH$_3$OH maser emission (~3 arcsec) alongside observations of four CO transitions made with APEX and archival ALMA CO, $^{13}$CO (~1 arcsec), and HNC data. We introduced a generalised argument to constrain outflow inclination angles based on observed outflow properties. We used the properties of each outflow to infer the accretion rates on the protostellar sources driving them and to deduce the evolutionary characteristics of the sources. We identify three molecular outflows in SDC335, one associated with each of the known compact HII regions. The outflow properties show that the SDC335 protostars are in the early stages (Class 0) of their evolution, with the potential to form stars in excess of 50 M$_{\odot}$. The measured total accretion rate onto the protostars is $1.4(\pm 0.1) \times 10^{-3}$M$_{\odot}$ yr$^{-1}$, comparable to the total mass infall rate toward the cloud centre on parsec scales of 2.5$(\pm 1.0) \times 10^{-3}$M$_{\odot}$ yr$^{-1}$, suggesting a near-continuous flow of material from cloud to core scales. [abridged]., Comment: Accepted for publication in A&A. 26 Pages, 17 Figures (+ 4 figures in appendix), 7 Tables, abridged abstract

Supernovae remnants (SNRs) represent a major feedback source from stars on the interstellar medium of galaxies. During the latest stage of supernovae explosions, shock waves produced by the initial blast modify the chemistry of gas and dust, inject kinetic energy in the surroundings, and may alter star formation characteristics. Simultaneously, gamma-ray emission is generated by the interaction between the ambiant medium and the cosmic rays. We study the stellar and interstellar contents of IC443, an evolved shell type SNR at a distance of 1.9 kpc, with an estimated age of 30 kyr. We aim to measure the mass of the gas within the extended G region, which corresponds to the peak of gamma-ray emission detected by VERITAS and Fermi. We performed 10'x10' mapped observations of 12CO and 13CO J=1-0, J=2-1 and J=3-2 pure rotational lines, as well as C18O J=1-0 and J=2-1 obtained with the IRAM-30m and APEX telescopes. We first compared our data with local thermodynamic equilbrium (LTE) models. We estimated the optical depth of each line from the emission of the isotopologues 13CO and C18O. We used the population diagram and large velocity gradient (LVG) assumption to measure the column density, mass, and kinetic temperature of the gas using 12CO and 13CO lines. We used complementary data (stars, gas, and dust at multiple wavelengths) and infrared point source catalogues to search for protostar candidates. Our results emphasize how the mass associated with the ring-like structure and the cloudlet cannot be overlooked when quantifying the interaction of cosmic rays with the dense local medium. Additionally, the presence of numerous possible protostars in the region might represent a fresh source of CR, which must also be taken into account in the interpretation of gamma-ray observations in this region.

NGC 7538 IRS 1 is a very young embedded O star driving an ionized jet and accreting mass with an accretion rate > 10^-4 Msun/year, which is quenching the hypercompact HII region. We use SOFIA GREAT data, Herschel PACS and SPIRE archive data, SOFIA FORCAST archive data, Onsala 20m and CARMA data, and JCMT archive data to determine the properties of the O star and its outflow. IRS 1 appears to be a single O-star with a bolometric luminosity > 1 10^5 Lsun, i.e. spectral type O7 or earlier. We find that IRS 1 drives a large molecular outflow with the blue-shifted northern outflow lobe extending to ~ 280" or 3.6 pc from IRS 1. Near IRS 1 the outflow is well aligned with the ionized jet. The dynamical time scale of the outflow is ~ 1.3 10^5 yr. The total outflow mass is ~ 130 Msun. We determine a mass outflow rate of 1.0 10^-3 Msun/yr, roughly consistent with the observed mass accretion rate. We observe strong high velocity [CII] emission in the outflow, confirming that strong UV radiation from IRS 1 escapes into the outflow lobes and is ionizing the gas. Many O stars may form like low mass stars, but with a higher accretion rate and in a denser environment. As long as the accretion stays high enough to quench the HII region, the star will continue to grow. When the accretion rate drops, the HII region will rapidly start to expand., Comment: 21 pages, 19 figures. Accepted for publication in The Astrophysical Journal

Context. Understanding the dominant heating mechanism in the nuclei of galaxies is crucial to understanding star formation in starbursts (SBs), active galactic nuclei (AGN) phenomena, and the relationship between star formation and AGN activity in galaxies. Analysis of the carbon monoxide (12CO) rotational ladder versus the infrared continuum emission (hereafter, 12CO/IR) in galaxies with different types of activity reveals important differences between them. Aims. We aim to carry out a comprehensive study of the nearby composite AGN-SB galaxy, NGC 4945, using spectroscopic and photometric data from the Herschel satellite. In particular, we want to characterize the thermal structure in this galaxy using a multi-transition analysis of the spatial distribution of the 12CO emission at different spatial scales. We also want to establish the dominant heating mechanism at work in the inner region of this object at smaller spatial scales (200 pc). Methods. We present far-infrared (FIR) and sub-millimeter (sub-mm) 12CO line maps and single spectra (from Jup = 3 to 20) using the Heterodyne Instrument for the Far Infrared (HIFI), the Photoconductor Array Camera and Spectrometer (PACS), and the Spectral and Photometric Imaging REceiver (SPIRE) onboard Herschel, and the Atacama Pathfinder EXperiment (APEX). We combined the 12CO/IR flux ratios and the local thermodynamic equilibrium (LTE) analysis of the 12CO images to derive the thermal structure of the interstellar medium (ISM) for spatial scales raging from 200 pc to 2 kpc. In addition, we also present single spectra of low- (12CO, 13CO and [CI]) and high-density (HCN, HNC, HCO+, CS and CH) molecular gas tracers obtained with APEX and HIFI applying LTE and non-LTE (NLTE) analyses. Furthermore, the spectral energy distribution of the continuum emission from the FIR to sub-mm wavelengths is also presented. Results. From the NLTE analysis of the low- and high-density tracers, we derive gas volume densities (103-106 cm-3) for NGC