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Aims. We aim to reveal the morphology, chemical composition, kinematics, and to establish the main processes prevalent in the gas at the footpoints of the giant molecular loops (GMLs) in the Galactic center region. Methods. Using the 22-m Mopra telescope, we mapped the M-3.8+0.9 molecular cloud, placed at the footpoints of a GML, in 3-mm range molecular lines. To derive the molecular hydrogen column density, we also observed the 13CO(2 - 1) line at 1 mm using the 12-m APEX telescope. From the 3 mm observations 12 molecular species were detected, namely HCO+, HCN, H13CN, HNC, SiO, CS, CH3OH, N2H+, SO, HNCO, OCS, and HC3N. Results. Maps revealing the morphology and kinematics of the M-3.8+0.9 molecular cloud in different molecules are presented. We identify six main molecular complexes. We derive fractional abundances in 11 selected positions of the different molecules assuming local thermodynamical equilibrium. Conclusions. Most of the fractional abundances derived for the M-3.8+0.9 molecular cloud are very similar over the whole cloud. However, the fractional abundances of some molecules show significant difference with respect to those measured in the central molecular zone (CMZ). The abundances of the shock tracer SiO are very similar between the GMLs and the CMZ. The methanol emission is the most abundant species in the GMLs. This indicates that the gas is likely affected by moderate ~30 km s-1 or even high velocity (50 km s-1) shocks, consistent with the line profile observed toward one of the studied position. The origin of the shocks is likely related to the flow of the gas throughout the GMLs towards the footpoints. [ABSTRACT FROM AUTHOR]

Aims. We aim to better understand the imprints that the nuclear activity in galaxies leaves in the molecular gas. Methods. We used the IRAM 30m telescope to observe the frequency range ∼[86-116] GHz towards the central regions of the starburst galaxies M83, M82, and NGC253, the galaxies hosting an active galactic nucleus (AGN) M51, NGC1068, and NGC7469, and the ultra-luminous infrared galaxies (ULIRGs) Arp 220 and Mrk 231. Assuming local thermodynamic equilibrium (LTE), we calculated the column densities of 27 molecules and 10 isotopologues (or their upper limits in case of non-detections). Results. Among others, we report the first tentative detections of CH3CHO, HNCO, and NS in M82 and, for the first time in the extragalactic medium, HC5N in NGC253. Hα recombination lines were only found in M82 and NGC253. Vibrationally excited lines of HC3N were only detected in Arp 220. CH3CCH emission is only seen in the starburst-dominated galaxies. By comparison of the fractional abundances among the galaxies, we looked for the molecules that are best suited to characterise the chemistry of each group of galaxies (starbursts, AGNs and ULIRGs), as well as the differences among galaxies within the same group. Conclusions. Suitable species for characterising and comparing starburst galaxies are CH3OH and HNCO as tracers of large-scale shocks, which dominate early to intermediate starburst stages, and CH3CCH, c-C3H2, and HCO as tracers of UV fields, which control the intermediate-to-old or post starburst phases. M83 shows signs of a shock-dominated environment. NGC253 is characterised by both strong shocks and some UV fields. M82 stands out for its bright photo-dissociated region tracers, which indicate an UV fielddominated environment. Regarding AGNs, the abundances of HCN and CN (previously claimed as enhanced in AGNs) in M51 are similar to those in starburst galaxies, while the HCN/HCO+ ratio is high in M51 and NGC1068, but not in NGC7469.We did not find a correlation between the HCN/CS ratio (recently claimed as a possible starburst/AGN discriminator) and the AGN activity. However, a high enough spatial resolution to separate their circumnuclear disks from the surrounding star-forming regions is needed to find molecular abundance trends in AGNs. High abundances of H13CN and HC3N, as well as a similarity between the column densities of 13CO and C18O, are representative of the molecular interstellar medium in the ULIRGs. Furthermore, the chemistry of Arp 220 points towards a more starburst-dominated environment, while that of Mrk 231 more resembles the AGNs of our sample. [ABSTRACT FROM AUTHOR]

We used the Atacama Pathfinder Experiment (APEX) 12 m telescope to observe the JKAKc = 303 → 202, 322 → 221, and 321 → 220 transitions of para-H2CO at 218 GHz simultaneously to determine kinetic temperatures of the dense gas in the central molecular zone (CMZ) of our Galaxy. The map extends over approximately 400 ± 80 (±100 ± 20 pc2) along the Galactic plane with a linear resolution of 1.2 pc. The strongest of the three lines, the H2CO (303 → 202) transition, is found to be widespread, and its emission shows a spatial distribution similar to ammonia. The relative abundance of para-H2CO is 0.5-1.2 ± 10-9, which is consistent with results from lower frequency H2CO absorption lines. Derived gas kinetic temperatures for individual molecular clouds range from 50K to values in excess of 100 K. While a systematic trend toward (decreasing) kinetic temperature versus (increasing) angular distance from the Galactic center (GC) is not found, the clouds with highest temperature (Tkin > 100 K) are all located near the nucleus. For the molecular gas outside the dense clouds, the average kinetic temperature is 65 ± 10 K. The high temperatures of molecular clouds on large scales in the GC region may be driven by turbulent energy dissipation and/or cosmic-rays instead of photons. Such a non-photon-driven thermal state of the molecular gas provides an excellent template for the more distant vigorous starbursts found in ultraluminous infrared galaxies (ULIRGs). [ABSTRACT FROM AUTHOR]

With the 100-m telescope at Effelsberg, 19 ammonia (NH3) maser lines have been detected toward the prominent massive star forming region W51-IRS2. Eleven of these inversion lines, the (J, K) = (6, 2), (5, 3), (7, 4), (8, 5), (7, 6), (7, 7), (9, 7), (10, 7), (9, 9), (10, 9), and (12, 12) transitions, are classified as masers for the first time in outer space. All detected masers are related to highly excited inversion doublets. The (5, 4) maser originates from an inversion doublet ∼340 K above the ground state, while the (12, 12) transition, at ∼1450K, is the most highly excited NH3 maser line so far known. Strong variability is seen not only in ortho- but also in para-NH3 transitions. Bright narrow emission features are observed, for the first time, in (mostly) ortho-ammonia transitions, at VLSR ∼ 45 km s-1, well separated from the quasi-thermal emission near 60 km s-1. These features were absent ∼25 years ago and show a velocity drift of about +0.2 kms-1 yr-1. The component is likely related to the SiO maser source in W51-IRS2 and a possible scenario explaining the velocity drift is outlined. The 57 kms-1 component of the (9, 6) maser line is found to be strongly linearly polarised. Maser emission in the (J, K) to (J + 1, K) inversion doublets is strictly forbidden by selection rules for electric dipole transitions in the ground vibrational state. However, such pairs (and even triplets with (J + 2, K)) are common toward W51-IRS2. Similarities in line widths and velocities indicate that such groups of maser lines arise from the same regions, which can be explained by pumping through vibrational excitation. The large number of NH3 maser lines in W51-IRS2 is most likely related to the exceptionally high kinetic temperature and NH3 column density of this young massive star forming region. [ABSTRACT FROM AUTHOR]

Aims. We study the molecular composition of the interstellar medium (ISM) surrounding an active galactic nucleus (AGN), by making an inventory of molecular species and their abundances, to establish a chemical differentiation between starburst galaxies and AGN. Methods. We used the IRAM-30m telescope to observe the central 1.5-2 kpc region of NGC 1068, covering the frequencies between 86.2 GHz and 115.6 GHz. Using Boltzmann diagrams, we calculated the column densities of the detected molecules. We used a chemical model to reproduce the abundances found in the AGN, to determine the origin of each detected species, and to test the influence of UV fields, cosmic rays, and shocks on the ISM. Results. We identified 24 different molecular species and isotopologues, among which HC3N, SO, N2H+, CH3CN, NS, 13CN, and HN13C are detected for the first time in NGC1068. A comparison of the abundances in the nuclear regions of NGC1068, M82, and NGC253 allowed us to establish a chemical differentiation between starburst galaxies and AGN. Two abundant species in starburst galaxies, H2CO and CH3CCH, are not detected in NGC1068, probably because they are destroyed by UV fields or shocks. On the other hand, species such as CN, SiO, HCO+, and HCN, are enhanced by cosmic ray radiation fields. We obtained the upper limits to the isotopic ratios 12C/13C = 49, 16O/18O = 177, and 32S/34S = 5. These ratios are much lower in this AGN than in starburst galaxies. Our chemical models suggest that the chemistry in the nucleus of NGC1068 is strongly influenced by cosmic rays, although high values of both cosmic rays and far ultraviolet (FUV) radiation fields also explain the observations well. C-shocks can explain the abundances of C2H and H2CO, but do not strongly affect the abundances of the other detected species. Conclusions. The gas in the nucleus of NGC 1068 has a different chemical composition than starburst galaxies. The distinct physical processes dominating galaxy nuclei (e.g. C-shocks, UV fields, X-rays, cosmic rays) leave clear imprints in the chemistry of the gas, which allow the nucleus activity to be characterised by its molecular abundances. [ABSTRACT FROM AUTHOR]

Context. It is well known that the kinetic temperatures, Tkin, of the molecular clouds in the Galactic center region are higher than in typical disk clouds. However, the Tkin of the molecular complexes found at higher latitudes towards the giant molecular loops in the central region of the Galaxy is so far unknown. The gas of these high-latitude molecular clouds (hereafter referred to as "halo clouds") is located in a region where the gas in the disk may interact with the gas in the halo in the Galactic center region. Aims. To derive Tkin in the molecular clouds at high latitude and understand the physical process responsible for the heating of the molecular gas both in the central molecular zone (the concentration of molecular gas in the inner ∼500 pc) and in the giant molecular loops. Methods. We measured the metastable inversion transitions of NH3 from (J, K) = (1, 1) to (6, 6) toward six positions selected throughout the Galactic central disk and halo. We used rotational diagrams and large velocity gradient (LVG) modeling to estimate the kinetic temperatures toward all the sources. We also observed other molecules like SiO, HNCO, CS, C34S, C18O, and 13CO, to derive the densities and to trace different physical processes (shocks, photodissociation, dense gas) expected to dominate the heating of the molecular gas. Results. We derive for the first time Tkin of the high-latitude clouds interacting with the disk in the Galactic center region. We find high rotational temperatures in all the observed positions. We derive two kinetic temperature components (∼150 K and ∼40 K) for the positions in the central molecular zone, and only the warm kinetic temperature component for the clouds toward the giant molecular loops. The fractional abundances derived from the different molecules suggest that shocks provide the main heating mechanism throughout the Galactic center, also at high latitudes. [ABSTRACT FROM AUTHOR]