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Measuring isotopic ratios is a sensitive technique used to obtain information on stellar nucleosynthesis and chemical evolution. We present measurements of the carbon and sulphur abundances in the interstellar medium of the central region of our Galaxy. The selected targets are the +50km/s Cloud and several l.o.s. clouds towards Sgr B2(N). Towards the +50km/s Cloud, we observed the J=2-1 rotational transitions of CS, C34S, 13CS, C33S, and 13C34S, and the J=3-2 transitions of CS and C34S with the IRAM-30m telescope, as well as the J=6-5 transitions of C34S and 13CS with the APEX 12m telescope, all in emission. The J=2-1 rotational transitions of CS, C34S, 13CS, and 13C34S were observed with ALMA in the envelope of Sgr B2(N), with those of CS and C34S also observed in the l.o.s. clouds towards Sgr B2(N), all in absorption. In the +50km/s Cloud we derive a 12C13C isotopic ratio of ~22.1, that leads, with the measured 13CS/C34S line intensity ratio, to a 32S/34S ratio of 16.3+3.0-2.4. We also derive the 32S/34S isotopic ratio more directly from the two isotopologues 13CS and 13C34S, which leads to an independent 32S/34S estimation of 16.3+2.1-1.7 and 17.9+-5.0 for the +50km/s Cloud and Sgr B2(N), respectively. We also obtain a 34S/33S ratio of ~4.3 in the +50 km/s Cloud. Previous studies observed a decreasing trend in the 32S/34S isotopic ratios when approaching the Galactic centre. Our result indicates a termination of this tendency at least at a galactocentric distance of 130-30+60 pc. This is at variance with findings based on 12C/13C, 14N/15N and 18O/17O isotope ratios, where the above-mentioned trend is observed to continue right to the central molecular zone. This can indicate a drop in the production of massive stars at the Galactic centre, in the same line as recent metallicity gradient studies, and opens the work towards a comparison with Galactic and stellar evolution models., Comment: 16 pages, 7 figures, accepted for publication by A&A

We investigate the galaxy population in a field of the Perseus cluster that roughly covers the virial radius of the cluster. The galaxies were selected on Schmidt CCD images in B and H alpha in combination with SDSS images. We present a catalogue of 1294 galaxies. Morphological information was obtained for 90% of the galaxies from the `eyeball' inspection, partly supported by the surface brightness profile analysis. Redshifts were taken from SDSS, literature sources, and own spectroscopic observations and are available for 24% of the catalogues galaxies. The galaxy catalogue is used to derive cluster properties, such as radial profiles, indications of sub-structure, virial mass, and viral radius and to study the cluster galaxy population with regard to morphological types and peculiarities, star formation rates and active galactic nuclei. In addition to the statistical approach, we present brief individual descriptions of 18 cluster galaxies with conspicuous morphological peculiarities. (Abstract modified to match the arXiv format.), Comment: Accepted for publication in A&A

Methanol (CH3OH) is one of the most abundant interstellar molecules, offering a vast number of transitions to be studied, including many maser lines. While the strongest Galactic CH3OH lines, the so-called class II masers, show no indications for the presence of superluminous counterparts in external galaxies, the less luminous Galactic class I sources appear to be different. Here we report class I 36GHz CH3OH 4(-1) - 3(0) E line emission from the nearby galaxies Maffei2 and IC342, measured with the 100-m telescope at Effelsberg at three different epochs within a time span of about five weeks. The 36GHz methanol line of Maffei2 is the second most luminous among the sources detected with certainty outside the Local Group of galaxies. This is not matched by the moderate infrared luminosity of Maffei2. Higher resolution data are required to check whether this is related to its prominent bar and associated shocks. Upper limits for M82, NGC4388, NGC5728 and Arp220 are also presented. The previously reported detection of 36GHz maser emission in Arp220 is not confirmed. Non-detections are reported from the related class I 44GHz methanol transition towards Maffei2 and IC342, indicating that this line is not stronger than its 36GHz counterpart. In contrast to the previously detected 36GHz CH3OH emission in NGC253 and NGC4945, our 36GHz profiles towards Maffei2 and IC342 are similar to those of previously detected non-masing lines from other molecular species. However, by analogy to our Galactic center region, it may well be possible that the 36GHz methanol lines in Maffei~2 and IC~342 are composed of a large number of faint and narrow maser features that remain spatially unresolved. In view of this, a search for a weak broad 36GHz line component would also be desirable in NGC253 and NGC4945., Comment: Accepted by Astronomy & Astrophysics, 8 pages, 1 table, 3 figures, slight changes w.r.t. version 1 due to language editing

NGC 4945 is one of the nearest (~3.8 Mpc; 1" ~ 19 pc) starburst galaxies. ALMA band 3 (3--4\,mm) observations of HCN, HCO+, CS, C3H2, SiO, HCO, and CH3C2H were carried out with ~2" resolution. The lines reveal a rotating nuclear disk of projected size 10" x 2" with position angle ~45 deg, inclination ~75 deg and an unresolved bright central core of size, 31 pages, 29 figures, 6 tables, accepted for publication in A&A; for the draft showing figures with full resolution, see https://gongyan2444.github.io/pdf/Henkel-NGC4945.pdf

Aims: To reveal the morphology, chemical composition, kinematics and to establish the main processes prevalent in the gas at the foot points 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 foot points of a giant molecular loop, in 3-mm range molecular lines. To derive the molecular hydrogen column density, we also observed the $^{13}$CO $(2-1)$ line at 1 mm using the 12-m APEX telescope. From the 3 mm observations 12 molecular species were detected, namely HCO$^+$, HCN, H$^{13}$CN, HNC, SiO, CS, CH$_3$OH, N$_2$H$^+$, SO, HNCO, OCS, and HC$_3$N. Results: Maps revealing the morphology and kinematics of the M$-3.8+0.9$ molecular cloud in different molecules are presented. We identified 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 specie in the GMLs. This indicates that the gas is likely affected by moderate $\sim $ 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 foot points., Comment: Accepted for publication in A&A

Context: The bulk of the Molecular gas in the Central Molecular Zone (CMZ) of the Galactic center region shows warm kinetic temperatures, ranging from $>20$ K in the coldest and densest regions (n$\sim 10^{4-5}$ cm$^{-3}$) up to more than 100 K for densities of about n$\sim 10^3$ cm$^{-3}$. Recently, a more diffuse, hotter ($n \sim 100$ cm$^{-3}$, $T\sim 250$ K) gas component was discovered through absorption observations of H$_3^+$. This component may be widespread in the Galactic center, and low density gas detectable in absorption may be present even outside the CMZ along sightlines crossing the extended bulge of the Galaxy. Aims: We aim to observe and characterize diffuse and low density gas using observations of 3-mm molecular transitions seen in absorption. Methods: Using the Atacama Large (sub)Millimeter Array (ALMA) we observed the absorption against the quasar J1744-312, which is located towards the Galactic bulge region at $(l,b)=(-2{^\circ}.13,-1{^\circ}.0)$, but outside the main molecular complexes. Results: ALMA observations in absorption against the J1744-312 quasar reveal a rich and complex chemistry in low density molecular and presumably diffuse clouds. We detected three velocity components, at $\sim $ 0, $-153$, and $-192$ km s$^{-1}$. The component at $\sim 0$ km s$^{-1}$ could represent gas in the Galactic disk while the velocity components at $-153$, and $-192$ km s$^{-1}$ likely originate from the Galactic bulge. We detected 12 molecules in the survey, but only 7 in the Galactic bulge gas., Accepted for publication in A&A

The chemistry in the central regions of galaxies is expected to be strongly influenced by their nuclear activity. To find the best tracers of nuclear activity is of key importance to understand the processes taking place in the most obscured regions of galactic nuclei. In this work we present multi-line observations of CS, C34S, HNCO and C18O in a sample of 11 bright galaxies prototypical for different types of activity. The 32S/34S isotopic ratio is ~10, supporting the idea of an isotopical 34S enrichment due to massive star formation in the nuclear regions of galaxies. Although C32S and C34S do not seem to be significantly affected by the activity type, the HNCO abundance appears highly contrasted among starburst. We observed HNCO abundance variations of nearly two orders of magnitude. The HNCO molecule is shown to be a good tracer of the amount of molecular material fueling the starburst and therefore can be used as a diagnostics of the evolutionary state of a nuclear starburst., 21 pages, 3 figures, Accepted by ApJ

We present a systematic study of the HNCO, C18O, 13CS, and C34S emission towards 13 selected molecular clouds in the Galactic center region. The molecular emission in these positions are used as templates of the different physical and chemical processes claimed to be dominant in the circumnuclear molecular gas of galaxies. The relative abundance of HNCO shows a variation of more than a factor of 20 amo ng the observed sources. The HNCO/13CS abundance ratio is highly contrasted (up to a factor of 30) between the shielded molecular clouds mostly affected by shocks, where HNCO is released to gas-phase from grain mantles, and those pervaded by an intense UV radiation field, where HNCO is photo-dissociated and CS production favored via ion reactions. We propose the relative HNCO to CS abundance ratio as a highly contrasted diagnostic tool to distinguish between the influence of shocks and/or the radiation field in the nuclear regions of galaxies and their relation to the evolutionary state of their nuclear star formation bursts.

We present high sensitivity observations of the complex organic molecules (COMs) CH3OH, C2H5OH, HCOOCH3, HCOOH and H2CO and of SiO toward the quiescent dark cloud L183 and the molecular outflow L1448-mm. We have not detected C2H5OH, HCOOCH3 and SiO in L183 and in the quiescent gas of L1448-mm. The abundances of CH3OH, H2CO and SiO are enhanced by factors 4-20 in the shock precursor component, and those of CH3OH and SiO by 3 and 4 orders of magnitude in the shocked gas, without substantial changes (< factor of 2) in the abundances of C2H5OH and HCOOCH3 relative to that of CH3OH. The large enhancements of SiO and CH3OH can be explained by the shock ejection of an important fraction of the grain mantle material into gas phase. Our upper limits to the C2H5OH/CH3OH and HCOOCH3/CH3OH ratios are consistent with the rather constant ratios measured in hot cores and Galactic center clouds. However, the upper limits to the HCOOCH3/CH3OH and the HCOOH/CH3OH ratios are at least one order of magnitude smaller than those found in"hot corinos" surrounding low mass protostars. We speculate that the observed abundances of COMs in different objects are consistent with a sort of "universal" grain mantle composition which is locally changed by the processes of low mass star formation., 10 pages, 1 figure. Accepted ApJ Letters

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 AGNs M51, NGC1068, and NGC7469, and the ULIRGs Arp220 and Mrk231. Assuming LTE conditions, we calculated the column densities of 27 molecules and 10 isotopologues. 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. Halpha recombination lines were only found in M82 and NGC253. Vibrationally excited lines of HC3N were only detected in Arp220. 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 starbursts, AGNs and ULIRGs, as well as the differences among galaxies within the same group., Comment: 24 pages, 6 figures, 12 tables. Accepted for publication in Astronomy and Astrophysics

Based on observations of the most abundant sulfur-bearing molecules (H2S, CS, NS, SO, H2CS, OCS, and SO2) carried out with the IRAM 30m telescope and SEST, we present the first analysis of the sulfur chemistry of an extragalactic source, the nuclear region of the starburst galaxy NGC 253. This is the first time that H2S and, tentatively, H2CS are detected towards the nucleus of a starburst galaxy. Source averaged fractional abundances of these molecules are a few 10^-9, except for CS and OCS which are more abundant (10^-8). Sulfur isotopic ratios, 32S/34S~8+-2 and 34S/33S>9, are measured through observations of 13CS, C34S, and C33S. A comparison with the observed relative abundances towards different prototypical Galactic sources suggests that the chemical composition of NGC 253 is similar to that found towards the molecular clouds complexes like Sgr B2 in the nuclear region of the Milky Way. The large overabundance of OCS compared to the predictions of time-dependent sulfur chemistry models supports the idea that OCS is likely injected into the gas phase from the grain mantles by low velocity shocks., Accepted for publication in ApJ. 19 pages, 3 figures

We have used the Atacama Pathfinder Experiment (APEX) 12 m telescope at 218 GHz to observe molecular clouds simultaneously in the JKaKc = 303→202, 322→221, and 321→220 transitions of para-H2CO to determine kinetic temperatures of the dense gas in the central molecular zone of the Galaxy. Gas kinetic temperatures for individual molecular clouds range from 55 to 125 K or even higher. The molecular clouds at high temperatures may be heated by turbulent dissipation and/or cosmic-rays.

A large scale survey of the Galactic center region in the () transition is presented. This survey was obtained with the 1.2 m Southern Millimeter-Wave Telescope (SMWT) at the Cerro Tololo Interamerican Observatory (CTIO) near La Serena, Chile. It covers the region and with a grid spacing of 9, i.e. the sampling is at full FWHP beamwidth. 357 positions were in total observed. After reviewing the instrumentation of the 1.2 m SMWT, the observing techniques, and the methods used in the data reduction, the data of the survey are presented and morphologically described. In addition, data of the HNCO() line are presented, which was also included in the large bandwidth of the spectrometer. measurements performed for comparison purposes are presented and compared with other 12 CO results. The maps of the survey demonstrate that there are great differences between the distribution of the optically thin emission and the usually optically thick emission.

Aims: A large scale survey of the Galactic center region in he 3 mm rotational transitions of SiO, HCO+ and H13CO+ (beamsize ~ 3. 6 arcmin) was conducted to provide an estimate of cloud conditions, heating mechanisms, chemistry and other properties. Methods: Using the NANTEN 4m telescope from Nagoya University, a region between -5.75, Comment: 19 pag main article plus 5 Appendixes. 183 pag full article that can be found at the following address: http://www.iram.es/IRAMES/personal/riquelme/galactic_center_accepted.pdf Accepted for publication in A&A

Ams: We study the 12C/13C isotopic ratio in the disk of the central molecular zone and in the halo to trace gas accretion toward the Galactic center region in the Milky Way. Methods: Using the IRAM 30m telescope, we observe the J=1-0 rotational transition of HCO+, HCN, HNC and their 13C isotopic substitutions in order to measure the 12C/13C isotopic ratio. We observe 9 positions selected throughout the Galactic center region, including clouds at high latitude; locations where the X1 and X2 orbits associated with the barred potential are expected to intersect; and typical Galactic center molecular clouds. Results: We find a systematically higher 12C/13C isotopic ratio (>40) toward the halo and the X1 orbits than for the Galactic center molecular clouds (20-25). Our results point out to molecular gas which has undergone a different degree of nuclear processing than that observed in the gas towards the inner Galactic center region. Conclusions: The high isotopic ratios are consistent with the accretion of the gas from the halo and from the outskirts of the Galactic disk., 8 pages, 2 figures, accepted for publication in A&A

The nuclear regions of many galaxies are not accessible at optical wavelengths and are devoid of HI, but contain large quantities of molecular gas and dust. With recent advances in instrumentation it is now possible to probe the kinematics and physical state of the cool dense interstellar medium, thus providing a new and important tool to investigate the circumnuclear gas in galaxies that are more ‘active’ than our own. The scope of this review is to summarize results related to the subject with an emphasis on observational data. Sects. 1 and 2 present a general introduction, followed by a discussion of molecular mass estimates. In Sect. 3 correlations between nuclear and global galactic properties are discussed. Sects. 4 and 5 summarize observational results for nearby strongly interacting galaxies, properties of molecular bars and rings, and theoretical advances in modelling the data. The main part of the review (Sects. 6–8) describes the kinematics and the physical and chemical properties of the dense gas, including masers, and compares them with the nuclear region of the Galaxy. Molecular gas in distant galaxies and the evolution of active galaxies are discussed in Sect. 9. Some promising avenues for future research are outlined in Sect. 10.

In an interpretation of interstellar, circumstellar, and solar system CNO isotope ratios, we find two scenarios which are free of internal inconsistencies. The first requires that the early solar system was enriched by material from massive stars, leading to enhanced 12C/13C and 18O/17O ratios and to a reduced 14N/15N ratio. The second involves infall of gas onto the galactic disk after the formation of the solar system. Both scenarios require that the bulk of the interstellar 16O, 18O and 15N originates from massive stars (>8M⊙), with 18O and perhaps 15N being destroyed in lower mass stars. 17O is mainly synthesized in stars of intermediate mass while 12C, 13C, and 14N are produced in stars of high and intermediate masses.

Recent results on the molecular gas component in the central regions of galaxies are reviewed. Following the introduction, Sect. 2 discusses the most important tracers of molecular gas mass and describes the detailed spatial distribution of the dense molecular gas component. Sect. 3 summarizes our knowledge on molecular chemistry in external galaxies.

L'etude concerne l'interaction entre les objets stellaires nouvellement formes et le gaz environnant

We report the first detections of SO_2, NS and NO in an extragalactic source, the nucleus of the starburst galaxy NGC 253. Five SO_2 transitions, three groups of hyperfine components of NO and five of NS were detected. All three species show large abundances averaged over the inner 200 pc of NGC 253. With a relative abundance of a few 10^-7, the emission of the NO molecule is similar or even larger than that found in Galactic star forming regions. The derived relative molecular abundances for each molecule have been compared with those of prototypical Galactic molecular clouds. These results seem to confirm that large scale shocks dominate the chemistry of these molecules in the nucleus of NGC 253, ruling out a chemistry dominated by PDRs for the bulk of the gas., Accepted by A&A, 4 pages, 6 figures

Gas masses derived for the bulge regions of the Milky Way and the nearby starburst galaxy NGC 253 using the C18O rotational lines are 5-10 times lower than those from 12CO and a standard X. Also, the distributions of both isotopomers differ. It is suggested that due to the stellar potential, 12CO arises in part from optically thin intercloud gas.

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 (1,1) to (6,6) toward six positions selected throughout the Galactic central disk and halo. We used rotational diagrams and large velocity gradient 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, Comment: accepted for publication in A&A 06/09/2012

We have identified the gas affected by the explosion that created Sgr A East (Sgr A East Core) and show that M-0.13-0.08, the CND and Sgr A East Core — the main molecular features within the 10′ of the Galactic Centre — are physically connected.

Chemical properties of extragalactic molecular clouds are summarized. Column densities, relative abundances, and chemical implications are briefly discussed and references for more detailed studies are given. The need for model calculations is emphasized.

To use a molecule as a diagnostic of a single star forming region, one has to observe it in different transitions. That is especially true for galaxies, where the beam filling factor is small and unknown. From studies of Galactic objects, the CS molecule is a good tracer of dense gas. Toward the IR galaxies NGC 253, IC 342 and M 82, Mauersberger and Henkel (1989) observed the J=2—1, 3=—2 and 5—4 transitions of CS at 3, 2 and 1.3 mm wavelength, repectively. They also measured emission of the isotope C34S, which has an abundance ~ 1/23 that of the main isotope. This study revealed that the H2 densities in the circumnuclear gas exceed 104, and, in the case of NGC 253, 105 cm-3. In all three cases, the distribution of the dense gas traced out by CS follows the CO distribution

We have recently discovered a large-scale (200”) outflow system in the core of OMC-1 (fig. 1), centered about 100” South of IRc2 and extending over some 120” (red lobe) resp. 60” (blue) along a position angle of —31°Schmid-Burgk et al. 1990). The blue lobe which might actually trude into the Ell region M42is poorly defined in CO 2-1, but the red lobe reveals a number of remarkable properties which we summarize here

Observations of the J = 2-1 and J = 5-4 transitions of SiO have been made toward the outflow source about 1.5 arcmin south of Orion-KL, using the IRAM 30-m telescope, with 25- and 13-arcsec resolution, respectively. Additional measurements of the J = 2-1, 3-2, and 5-4 lines of C34S and observations of J = 5-4 and J = 13-12 transitions of CH{sub 3}CN have been made with the 30-m telescope. The SiO data clearly indicate that a separate outflow source exists about 100 arcsec S and 20 arcsec W of the Orion-KL/IRc2 position. 17 refs.

Recently, the authors reported the first detections of HNC, C2H, CN and, perhaps, HC3N toward external galaxies. These detections, as well as that of extragalactic methanol, have been obtained using the 30-m IRAM mm-wave telescope. The previous results are revised in the light of recently available high-resolution CO maps of the respective galaxies. The relative abundances are similar to those found toward warm Galactic molecular clouds.