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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 1450 K, 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 V ~ 45 km/s, well separated from the quasi-thermal emission near 60 km/s. These features were absent 25 years ago and show a velocity drift of about +0.2 km/s/yr. 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 km/s component of the (9,6) maser line is found to be strongly linearly polarized. 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., Accepted for publication in Astronomy & Astrophysics, 11 pages, 12 postscript figures, 1 table

In previous articles, we described how electromagnetic waves emitted from objects in the sky are collected by the ALMA antennas (Anatomy of ALMA), and how they are combined in order to produce images. Before these images can be processed, they are picked up by the antennas and concentrated by the large main mirror and a smaller secondary mirror in the so called focal point of each antenna. In order to process the data they must be first converted to electromagnetic waves of a lower frequency and amplified. This is the role of the ALMA receivers. In principle they work like a normal AM receiver, but at much higher frequencies. Here we describe how they work and what makes them special.

Here we will discuss which calibrations are needed, how to perform them and how the calibration affect ALMA observations. This first part concentrates on aspects related to a single antenna, namely antenna pointing (including the antenna metrology), focusing, and the amplitude calibration, we also mention the bandpass calibration for single measurements.

We study the disk-halo interaction, in the context of orbits and Giant Molecular loops (GMLs) in the Galactic center (GC) region. We present a large scale survey in the central kpc in SiO(J=2-1), HCO$^+$(J=1-0) and H$^{13}$CO$^+$ (J=1-0), observations in 3mm lines toward a region in two clumps M+5.3-0.3 and M-3.8+0.9 placed in the foot point of two molecular loops, and observations toward selected positions, to trace accretion of the gas from the halo, Proceedings of the Galactic Center Workshop 2009, Shanghai. To be published in the Astronomical Society of the Pacific Conference Series

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., 25 pages, 5 figures, Accepted for publication in ApJ

We present the first unbiased molecular line survey towards an extragalactic source, namely the nuclear region of the starburst galaxy NGC 253. The scan covers the frequency band from 129.1 to 175.2 GHz, i.e. most of the 2mm atmospheric window. We identify 111 spectral features as transitions from 25 different molecular species. Eight of which (three tentatively) are detected for the first time in the extragalactic interstellar medium. Among these newly detected species, we detected the rare isotopomers 34SO and HC18O+. Tentative detections of two deuterated species, DNC and N2D+, are reported for the first time from a target beyond the Magellanic Clouds. Additionally, three hydrogen recombination lines are identified, while no organic molecules larger than methanol are detected. Column densities and rotation temperatures are calculated for all the species, including an upper limit to the ethanol abundance. A comparison of the chemical composition of the nuclear environment of NGC 253 with those of selected nearby galaxies demonstrates the chemical resemblance of IC 342 and NGC 4945 to that of NGC 253. On the other hand, the chemistries characterizing NGC 253 and M 82 are clearly different. We also present a comparison of the chemical composition of NGC 253 with those observed in Galactic prototypical sources. The chemistry of NGC 253 shows a striking similarity with the chemistry observed toward the Galactic center molecular clouds, which are thought to be dominated by low-velocity shocks. This resemblance strongly suggests that the heating in the nuclear environment of NGC 253 is dominated by the same mechanism as that in the central region of the Milky Way., Comment: Accepted for publication in ApJS

The J=2-1 and 3-2 rotational lines of the rare isotopomer C36S and the J=5-4 and 6-5 transitions of Si36S were detected in the carbon star IRC+10216 (CW Leo). These are the first detections of 36S bearing molecules in a star and the first spectroscopic detection of Si36S. From a comparison of 34S and 36S bearing isotopomers, th 34S/36S isotopic ratio is 107(+-15). This value is comparable to values in the interstellar medium of the inner Galactic disk (115) but is smaller than the solar value of 288 (Ding et al. 2001). The increase of the 36S abundance relative to 34S only qualitatively follows model predictions of a low mass AGB star. Quantitative agreement of the observed 34S/36S ratio with the stellar models can be reached if the age of IRC+10216 and Galactic chemical evolution are taken into account. Other less likely possibilities are the presence of considerable inhomogeneities in the interstellar medium and either IRC+10216 or the Sun started with a peculiar 36S abundance. Other production mechanisms potentially capable of enhancing the Galactic interstellar medium are discussed. From the observed line density toward IRC+10216 and toward Galactic star forming regions, we estimate the confusion limit toward those sources.

12CO 1-0,2-1,4-3,7-6, and 13CO 1-0, 2-1, and 3-2 line was mapped with angular resolutions of 13" - 22" toward the nuclear region of starburst galaxy M82. The difference of lobe spacings in submillimeter (~15") and millimeter (~26") lines indicates the presence of a `low' and a `high' CO excitation component. An LVG excitation analysis of the submillimeter lines leads to inconsistencies, since area and volume filling factors are almost the same, resulting in cloud sizes along the lines-of-sight that match the entire size of the M82 starburst region. Nevertheless, LVG column densities agree with estimates derived from the dust emission in the far infrared and at submillimeter wavelengths. Accounting for high UV fluxes and variations in kinetic temperature and assuming that the observed emission arises from photon dominated regions (PDRs) resolves the problems related to an LVG treatment of the radiative transfer. 12CO/13CO line intensity ratios > 10 indicate that the bulk of the CO emission arises in UV-illuminated diffuse cloud fragments of small column density and sub-parsec cloud sizes with area filling factors >> 1. Thus CO arises from quite a different gas component than the classical high density tracers. The dominance of such a diffuse molecular interclump medium also explains observed high [CI}/CO line intensity ratios. PDR models do not allow a determination of the relative abundances of 12CO to 13CO. Ignoring magnetic fields, the CO gas appears to be close to the density limit for tidal disruption. A warm diffuse ISM not only dominates the CO emission in the starburst region of M82 but is also ubiquitous in the central region of our Galaxy, where tidal stress, cloud-cloud collisions, shocks, high gas pressure, and high stellar densities may all contribute to the formation of a highly fragmented molecular debris., 20 pages, 12 figures, Accepted for publiation in A&A

Multiline observations of C18O and SiO isotopomers toward 33 molecular peaks in the Galactic center region, taken at the SEST, JCMT and HHT telescopes, are presented. The C18O presumably traces the total H_2 column density, while the SiO traces gas affected by shocks and high temperature chemistry. The J =2-1 line of SiO is seen only in few regions of the Galactic disk. This line is easily detected in all Galactic center sources observed. A comparison of the strength of the rare isotopomers 29SiO and 30SiO to the strength of the main isotopomer 28SiO implies that the J = 2-1 transition of 28SiO is optically thick. The 29Si/30Si isotope ratio of 1.6 in the Galactic center clouds is consistent with the terrestrial value. Large Velocity Gradient models show that the dense component (n_(H_2) > 10^4cm-3) in typical molecular cores in the Galactic center is cool (TKIN ~ 25K), contrary to what is usually found in Giant Molecular Clouds in the disk, where the densest cores are the hottest. High kinetic temperatures, > 100K, known to exist from NH_3 studies, are only present at lower gas densities of a few 10^3cm-3, where SiO is highly subthermal. Assuming that C18O traces all of the molecular gas, it is found that in all cases but one, SiO emission is compatible with arising in gas at higher density that is (presently) relatively cool. The relative abundance of SiO is typically 10^-9, but differs significantly between individual sources. It shows a dependence on the position of the source within the Galactic center region. High abundances are found in those regions for which bar potential models predict a high likelihood for cloud-cloud collisions. These results can be used to relate the amount of gas that has encountered shocks within the last ~ 10^6 years to the large scale kinematics in the inner ~500pc of the Galaxy., Accepted for publication by Astronomy & Astrophysics Main Journal; 14 pages, 5 Figs. included, aa.cls and psfig used

$^{12}$C$/^{13}$C line intensity ratios have been derived from several carbon-bearing molecules to confine the range of carbon and oxygen isotope abundance ratios toward the nuclear regions of two infrared bright galaxies. The most stringent limits are obtained from CN mm-wave emission lines. Supplementary measurements toward the Galactic center region indicate that overall I(12CN)/I(13CN) line intensity ratios are giving lower limits to the corresponding 12C/13C abundance ratio. Toward M 82 and IC 342, we find 12C/13C > 40 and >30. Therefore the smaller 12C/13C ratio of our own Galactic center region (25) may not be typical for central regions of galaxies which are more luminous in the infrared. The 12C/13C limits and data from various isotopic species of CO also infer 16O/18O abundance ratios of > 90 and > 125 for M 82 and IC 342, respectively. From the I(HC14N)/I(HC15N) line intensity ratio, 14N/15N > 100 is derived for M 82., 8 pages, including three figures, To appear in A&A Main Journal, further comments: please contact Yi-nan Chin (einmann@biaa.sinica.edu.tw)

The large scale structure and physics of molecular gas in the Galactic center region is discussed based on the analysis of a 9' resolution survey of the Galactic center region in the J=1->0 line of C^18O. Emphasis is placed on the comparison with ^12CO(1--0) data. The line shapes of C^18O(1--0) and ^12CO(1--0) differ significantly. The ratio of the intensities of the two isotopomers in the Galactic center region is generally higher than the value of ~15 expected from the ``Standard Conversion Factor'' (SCF) of ^12CO integrated line intensity to H_2 column density. In our data, this ratio is in the range from 30 to 200, mostly ~60 to 80. From LVG calculations, we estimate that the large scale ^12CO(1--0) emission in the Galactic center region is of moderate or low optical depth. Higher optical depths are restricted to very limited regions. We estimate H_2 densities and kinetic temperatures for different ranges of intensity ratios. A considerable amount of molecular mass is in a widespread molecular gas component with low densities and high kinetic temperatures. The total molecular mass is found to be (3^+2_-1) 10^7 M_{sun}. We show that the SCF is not valid toward the Galactic bulge. It overestimates the H_2 column density by an order of magnitude because the assumptions required for this factor are not fulfilled for a significant fraction of the molecular gas. Therefore, also one cannot apply a modified conversion factor to the Galactic center region since the N(H_2)/I(^12CO) ratio is highly variable and cannot be represented by a universal constant. Results from external galaxies indicate that the ^12CO emission is generally not a suitable tracer of H_2 masses in galactic bulges., 20 pages, 8 postscript figures; accepted for publication in A&A Main Journal; uses laa.sty and psfig_laa.sty

Multilevel observations of formaldehyde (H_2CO) and methanol (CH_3OH) toward the nearby spiral galaxies NGC 253, Maffei 2, IC 342, M 82 and NGC 6946 are presented. H_2CO was detected in all galaxies (tentatively in NGC 6946). CH_3OH was detected in all objects with the notable exception of M 82. H_2CO line intensity ratios point out differences in gas density both between galaxies and within the central regions of individual objects. Model calculations show that the bulk of the gas emitting H_2CO in NGC 253 is at a density of ~10^4 cm^-3 , while the H_2CO lines in M 82 and IC 342 trace two different, spatially separated gas components with densities of, 12 Pages, A&A latex (l-aa.sty), 5 figures included with psfig; Accepted by Astronomy and Astrophysics Main Journal

The first detection of a $^{36}$S-bearing molecule in interstellar space is reported. The $J$=$2-1$ and $3-2$ transitions of C$^{36}$S have been observed toward eight Galactic molecular hot cores. From a comparison with other optically thin isotopic species of CS, the abundance ratio of $^{34}$S/$^{36}$S is 115$(\pm 17)$. This is smaller than the solar system ratio of 200 and supports the idea that $^{36}$S is, unlike the other stable sulfur isotopes, a purely secondary nucleus that is produced by s-process nucleosynthesis in massive stars., 4 pages uuencoded gzip-compressed .tar file including two figures, To appear in A&A Letter

The first definite discoveries of extragalactic deuterium are reported. DCO$^+$ has been detected in three and DCN has been measured in one star-forming region of the Large Magellanic Cloud (LMC). While the HCO$^+$/DCO$^+$ abundance ratios are found to be 19 $\pm$ 3, 24 $\pm$ 4, and 67 $\pm$ 18 for N113, N44BC and N159HW, respectively, a HCN/DCN abundance ratio of 23 $\pm$ 5 is obtained for N113. These results are consistent with a gas temperature of about 20\,K and a D/H ratio of about $1.5 \times 10^{-5}$, consistent with that observed in the Galaxy. If the cloud temperature is closer to 30\,K, then a D/H ratio is required to be up to an order of magnitude larger. Because this ratio provides a lower limit to the primordial D/H ratio, it indicates that the baryon mass density alone is unable to close the universe., Comment: 4 pages uuencoded gzip-compressed .tar file including one figures, To appear in A&A Letter, further comments: please contact Yi-nan Chin (einmann@biaa21.biaa.sinica.edu.tw)

The (J,K) = (1,1), (2,2), (3,3), and (4,4) inversion lines of ammonia (NH3) have been detected toward the nuclear 40'' sized bar of the nearby spiral galaxy Maffei 2. The relative intensities of the ammonia lines are characterized by a rotational temperature of 85 K. This is higher than rotational temperatures measured toward IC342 and most Galactic Center clouds, implying kinetic temperatures of at least 100 K. Since the kinetic temperature of the gas is larger than that of the dust, NH3 is tracing a particularly dense warm gas component that is heated by young massive stars, cloud-cloud collisions, or ion-slip heating in the nuclear starburst. The gas north of the nucleus (V(LSR} = -80 km/s) is more highly excited than the gas further south (+6 km/s). This asymmetry might be related to a pronounced morphological distortion that is observed in the north-eastern part of the galaxy., 4 pages, Latex file, 2 Postscript Figures, aa.cls and psfig.sty stylefiles included. Accepted to Astronomy and Astrophysics Letters