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We present a study of the three-dimensional structure of the molecular clouds in the Galactic Centre (GC) using CO emission and OH absorption lines. Two CO isotopologue lines, 12CO(J = 1 → 0) and 13CO(J = 1 → 0), and four OH ground-state transitions, surveyed by the Southern Parkes Large-Area Survey in Hydroxyl, contribute to this study. We develop a novel method to calculate the OH column density, excitation temperature and optical depth precisely using all four OH lines, and we employ it to derive a three-dimensional model for the distribution of molecular clouds in the GC for six slices in Galactic latitude. The angular resolution of the data is 15.5 arcmin, which at the distance of the GC (8.34 kpc) is equivalent to 38 pc. We find that the total mass of OH in the GC is in the range of 2400–5100 M⊚. The face-on view at a Galactic latitude of b = 0° displays a bar-like structure with an inclination angle of 67.5±2.1° with respect to the line of sight. No ring-like structure in the GC is evident in our data, likely due to the low-spatial resolution of the CO and OH maps. [ABSTRACT FROM AUTHOR]

Three bright molecular line sources in G333 have recently been shown to exhibit signatures of infall. We describe a molecular line radiative transfer (RT) modelling process which is required to extract the infall signature from Mopra and Nanten2 data. The observed line profiles differ greatly between individual sources but are reproduced well by variations upon a common unified model where the outflow viewing angle is the most significant difference between the sources. The models and data together suggest that the observed properties of the high-mass star-forming regions such as infall, turbulence and mass are consistent with scaled-up versions of the low-mass case with turbulent velocities that are supersonic and an order of magnitude larger than those found in low-mass star-forming regions. Using detailed RT modelling, we show that the G333 cores are essentially undergoing a scaled-up version of low-mass star formation. This is an extension of earlier work in that the degree of infall and the chemical abundances are constrained by the RT modelling in a way that is not practical with a standard analysis of observational data. We also find high velocity infall and high infall mass rates, possibly suggesting accelerated collapse due to external pressure. Molecular depletion due to freeze-out on to dust grains in central regions of the cores is suggested by low molecular abundances of several species. Strong evidence for a local enhancement of 13C-bearing species towards the outflow cloud cores is discussed, consistent with the presence of shocks caused by the supersonic motions within them. [ABSTRACT FROM AUTHOR]

HESS J1825-137 is a pulsar wind nebula (PWN) whose TeV emission extends across~?1 deg. Its large asymmetric shape indicates that its progenitor supernova interacted with a molecular cloud located in the north of the PWN as detected by previous CO Galactic survey (e.g. Lemiere, Terrier & Djannati-Ataï). Here, we provide a detailed picture of the interstellar medium (ISM) towards the region north of HESS J1825-137, with the analysis of the dense molecular gas from our 7 and 12 mm Mopra survey and the more diffuse molecular gas from the Nanten CO(1-0) and GRS 13CO(1-0) surveys. Our focus is the possible association between HESS J1825-137 and the unidentified TeV source to the north, HESS J1826-130. We report several dense molecular regions whose kinematic distance matched the dispersion measured distance of the pulsar. Among them, the dense molecular gas located at (RA, Dec.) = (18h421h,-13.°282) shows enhanced turbulence and we suggest that the velocity structure in this region may be explained by a cloud.cloud collision scenario. Furthermore, the presence of a H α rim may be the first evidence of the progenitor supernova remnant (SNR) of the pulsar PSR J1826.1334 as the distance between the H α rim and the TeV source matched with the predicted SNR radius RSNR ~ 120 pc. From our ISM study, we identify a few plausible origins of the HESS J1826-130 emission, including the progenitor SNR of PSR J1826-1334 and the PWN G018.5-0.4 powered by PSR J1826-1256. A deeper TeV study however, is required to fully identify the origin of this mysterious TeV source. [ABSTRACT FROM AUTHOR]

We present molecular line imaging observations of three massive molecular outflow sources, G333.6-0.2, G333.1-0.4, and G332.8-0.5, all of which also show evidence for infall, within the G333 giant molecular cloud (GMC). All three are within a beam size (36 arcsec) of IRAS sources, 1.2-mm dust clumps, various masing species, and radio continuum-detected H II regions and hence are associated with high-mass star formation. We present the molecular line data and derive the physical properties of the outflows including the mass, kinematics, and energetics and discuss the inferred characteristics of their driving sources. Outflow masses are of 10-40 M in each lobe, with core masses of the order of 103 M. Outflow size scales are a few tenth of a parsec, time-scales are of several ×104 years, mass-loss rates a few ×10-4 M yr-1. We also find the cores are turbulent and highly supersonic. [ABSTRACT FROM AUTHOR]

ABSTRACT The molecular clouds Lupus 1, 3 and 4 were mapped with the Mopra Telescope at 3 and 12 mm. Emission lines from high-density molecular tracers were detected, i.e. NH3 (1,1), NH3 (2,2), N2H+ (1−0), HC3N (3−2), HC3N (10−9), CS (2−1), CH3OH (20−10)A+ and CH3OH (2−1−1−1)E. Velocity gradients of more than 1 km s−1 are present in Lupus 1 and 3, and multiple gas components are present in these clouds along some lines of sight. Lupus 1 is the cloud richest in high-density cores: eight cores were detected in it, five cores were detected in Lupus 3 and only two in Lupus 4. The intensity of the three species HC3N, NH3 and N2H+ changes significantly in the various cores: cores that are brighter in HC3N are fainter or undetected in NH3 and N2H+ and vice versa. We found that the column density ratios HC3N/N2H+ and HC3N/NH3 change by 1 order of magnitude between the cores, indicating that also the chemical abundance of these species is different. The time-dependent chemical code that we used to model our cores shows that the HC3N/N2H+ and HC3N/NH3 ratios decrease with time, therefore the observed column density of these species can be used as an indicator of the chemical evolution of dense cores. On this basis we classified five out of eight cores in Lupus 1 and one out of five cores in Lupus 3 as very young protostars or pre-stellar cores. Comparing the millimetre core population with the population of the more evolved young stellar objects identified in the Spitzer surveys, we conclude that in Lupus 3 the bulk of the star formation activity has already passed and only a moderate number of stars are still forming. In contrast, in Lupus 1 star formation is ongoing and several dense cores are still in the pre-/protostellar phase. Lupus 4 is at an intermediate stage, with a smaller number of individual objects. [ABSTRACT FROM AUTHOR]

ABSTRACT We present 7 mm Mopra observations of the dense molecular gas towards the W28 supernova remnant (SNR) field, following a previous 12 mm line survey of this region. These observations take advantage of the 7 mm beam size to probe the dense and disrupted gas in the region at ∼1 arcmin scales. Our observations are focused towards the north-eastern (NE) HESS J1801−233 and southern HESS J1800−240 B TeV gamma-ray sources, with slightly less observations towards HESS J1800−240 A and C. Using the CS (1-0) transition we reveal multiple regions of dense gas, cm−3. We report the discovery of dense gas towards HESS J1800−240 C, at the site of a 1720 MHz OH maser. The NE molecular cloud is known to be disrupted; many 1720 MHz OH masers and broad CO line emission are detected at the rim of W28. Here, we reveal this shock interaction region contains generally extended clumpy CS, as well as clumpy SiO and CH3OH emission with broad line profiles. The full width at half maximum (FWHM) of the molecular lines extend up to 18 km s−1 on the W28 side of the NE cloud. The detection of SiO towards maser clumps OH C, D, E and F provides further evidence of the shocked conditions in the NE cloud. Several other lines associated with star formation are also detected towards the southern source, notably the energetic H ii complex G5.89−0.39. The spatial match of dense gas with the TeV emission further supports the cosmic ray (CR) origin for the gamma-rays. We estimate the mass of several extended dense clouds within the field and predict the TeV flux from the dense cloud components. The predicted fluxes are of the order of 10−14 to 10−13 photons cm−2 s−1, which should be detectable and possibly resolved by a future TeV instrument, such as the Cherenkov Telescope Array. [ABSTRACT FROM AUTHOR]

We have undertaken a spectral-line imaging survey of a arcmin area around Sagittarius (Sgr) B2 near the centre of the Galaxy, in the range from 30 to 50 GHz, using the Mopra telescope. The spatial resolution varies from 1.0 to 1.4 arcmin and the spectral resolution varies from 1.6 to 2.7 km s over the frequency range. We present velocity-integrated emission images for 47 lines: 38 molecular lines and nine radio recombination lines. There are significant differences between the distributions of different molecules, in part due to spatial differences in chemical abundance across the complex. For example, HNCO and HOCO are found preferentially in the north cloud, and CHNH near Sgr B2 (N). Some of the differences between lines are due to excitation differences, as shown by the 36.17- and 44.07-GHz lines of CHOH, which have maser emission, compared to the 48.37-GHz line of CHOH. Other major differences in integrated molecular line distribution are due to absorption of the 7-mm free-free continuum emission (spatially traced by the radio recombination line emission) by cool intervening molecular material, causing a central dip in the molecular line distributions. These line distribution similarities and differences have been statistically described by Principal Component Analysis and interpreted in terms of simple Sgr B2 physical components of the cooler, lower density envelope, and dense, hot cores Sgr B2 (N), (M) and (S). [ABSTRACT FROM AUTHOR]

We present 12 mm Mopra observations of dense molecular gas towards the W28 supernova remnant (SNR) field. The focus is on the dense molecular gas towards the TeV gamma-ray sources detected by the HESS telescopes, which likely trace the cosmic rays from W28 and possibly other sources in the region. Using the NH inversion transitions we reveal several dense cores inside the molecular clouds, the majority of which coincide with high-mass star formation and H regions, including the energetic ultracompact H region G5.890.39. A key exception to this is the cloud north-east of W28, which is well known to be disrupted as evidenced by clusters of 1720 MHz OH masers and broad CO line emission. Here we detect broad NH, up to the (9,9) transition, with linewidths up to 16 km s. This broad NH emission spatially matches well with the TeV source HESS J1801233 and CO emission, and its velocity dispersion distribution suggests external disruption from the W28 SNR direction. Other lines are detected, such as HCN and HCN, HO masers, and many radio recombination lines, all of which are primarily found towards the southern high-mass star formation regions. These observations provide a new view on to the internal structures and dynamics of the dense molecular gas towards the W28 SNR field and, in tandem with future higher-resolution TeV gamma-ray observations, will offer the chance to probe the transport of cosmic rays into molecular clouds. [ABSTRACT FROM AUTHOR]

We present molecular-line observations at millimetre, centimetre and infrared wavelengths of the region containing OH(1720 MHz) masers in the supernova remnant (SNR) G349.7+0.2, using the Australia Telescope (AT) Mopra antenna, the Swedish-ESO Submillimeter Telescope, the AT Compact Array and the UNSW Infrared Fabry-Perot narrow-band filter installed on the Anglo-Australian Telescope. Several molecular transitions were observed between 1.6 and 3 mm to constrain the physical parameters of the molecular cloud interacting with the SNR and to investigate the effects of the SNR shock on the gas chemistry. We detected shock-excited near-infrared H emission towards the centre of the SNR, revealing highly clumped molecular gas and a good correlation with published mid-infrared images from the Spitzer Space Telescope. An excellent correlation between the H clumps and OH(1720 MHz) maser positions supports the shock excitation of the OH(1720 MHz) maser emission. Furthermore, we detected OH absorption at 1665 and 1667 MHz which shows a good correlation with the shocked H emission and the masers. We found maser emission at 1665 MHz near the OH(1720 MHz) masers in this SNR, which is found to be associated with a GLIMPSE source SSTGLMC G349.7294+00.1747. We also detected 1665 and 1667 MHz OH masers, and weak 4.8 GHz HCO absorption towards the ultracompact H region IRAS 17147-3725 located to the southeast of the SNR. We found no 4.7- or 6-GHz excited-state OH masers or 6-GHz CHOH maser towards either the SNR or the H region. [ABSTRACT FROM AUTHOR]

We present multimolecular line maps obtained with the Mopra telescope towards the southern giant molecular cloud (GMC) complex G333, associated with the H ii region RCW 106. We have characterized the GMC by decomposing the 3D data cubes withgaussclumps, and investigated spatial correlations among different molecules with principal component analysis (PCA). We find no correlation between clump size and linewidth, but a strong correlation between emission luminosity and linewidth. PCA classifies molecules into high- and low-density tracers, and reveals that HCO+ and N2H+ are anticorrelated. [ABSTRACT FROM AUTHOR]

We are studying the Central Molecular Zone (CMZ) in the inner few degrees around the Galactic Centre, by mapping a large number of 3-mm molecular lines. We have used the 22-m Mopra telescope, with the new capabilities of the 8-GHz bandwidth MOPS digital filter bank. During 2006, we covered a 5 × 5 arcmin² area of the Sagittarius B2 molecular cloud complex, with spectral coverage of nearly all of the range 81.7 to 113.5 GHz with 4 tunings of the broad band mode. We imaged over 50 spectral lines with strong extended emission and around 110 more lines which were weak, or concentrated at the Sgr B2(N) and Sgr B2(M) cores (Jones et al. 2008). We find substantial differences in chemical and physical conditions within the complex. During 2007 we covered the larger region of longitude -0.2 to 0.9 deg. and latitude -0.20 to 0.12 deg., including Sgr A and Sgr B2, in the frequency range 85.3 to 91.3 GHz. This includes lines of C3H2, CH3CCH, HOCO+, SO, H13CN, H13CO+, SO, HN13C, C2H, HNCO, HCN, HCO+, HNC, HC3N, 13CS and N2H+. [ABSTRACT FROM AUTHOR]

We present a fully sampled C18O (1–0) map towards the southern giant molecular cloud (GMC) associated with the H ii region RCW 106, and use it in combination with previous 13CO (1–0) mapping to estimate the gas column density as a function of position and velocity. We find localized regions of significant 13CO optical depth in the northern part of the cloud, with several of the high-opacity clouds in this region likely associated with a limb-brightened shell around the H ii region G333.6−0.2. Optical depth corrections broaden the distribution of column densities in the cloud, yielding a lognormal distribution as predicted by simulations of turbulence. Decomposing the 13CO and C18O data cubes into clumps, we find relatively weak correlations between size and linewidth, and a more sensitive dependence of luminosity on size than would be predicted by a constant average column density. The clump mass spectrum has a slope near −1.7, consistent with previous studies. The most massive clumps appear to have gravitational binding energies well in excess of virial equilibrium; we discuss possible explanations, which include magnetic support and neglect of time-varying surface terms in the virial theorem. Unlike molecular clouds as a whole, the clumps within the RCW 106 GMC, while elongated, appear to show random orientations with respect to the Galactic plane. [ABSTRACT FROM AUTHOR]

Using the Mopra telescope, we have undertaken a 3-mm spectral-line imaging survey of a 5 × 5 arcmin2 area around Sgr B2. We covered almost the complete spectral range from 81.7 to 113.5 GHz, with 2.2 MHz wide spectral channels or and have observed 24 lines, with 0.033 MHz wide, or channels. We discuss the distribution of around 50 lines, and present velocity-integrated emission images for 38 of the lines. In addition, we have detected around 120 more lines, mostly concentrated at the particularly spectral-line-rich Sgr B2(N) source. There are significant differences in molecular emission, pointing to both abundance and excitation differences throughout the region. Seven distinct spatial locations are identified for the emitting species, including peaks near the prominent star-forming cores of Sgr B2(N), (M) and (S) that are seen in infrared (IR)-to-radio continuum images. The other features are a ‘north ridge’ and a ‘north cloud’ to the north of the Sgr B2 N-M-S cores, a ‘south-east peak’ and a ‘west ridge’. The column density, as evident through C18O, peaks at the Sgr B2(N) and (M) cores, where strong absorption is also evident in otherwise generally bright lines such as HCO+, HCN and HNC. Most molecules trace a ridge line to the west of the Sgr B2 N-M-S cores, wrapping around the cores and extending north-east to the north cloud. This is most clearly evident in the species HC3N, CH3CN, CH3OH and OCS. They are found to be closer in distribution to the cooler dust traced by the submillimetre continuum than either the warmer dust seen in the mid-IR or to the radio continuum. The molecule CN, in contrast, is reasonably uniform over the entire region mapped, aside from strong absorption at the positions of the Sgr B2(N) and (M) cores. [ABSTRACT FROM AUTHOR]

We report the results of a blind search for 22-GHz water masers in two regions, covering approximately half a square degree, within the giant molecular cloud associated with RCW 106. The complete search of the two regions was carried out with the 26-m Mount Pleasant radio telescope and resulted in the detection of nine water masers, five of which are new detections. Australia Telescope Compact Array (ATCA) observations of these detections have allowed us to obtain positions with arcsecond accuracy, allowing meaningful comparison with infrared and molecular data for the region. We find that for the regions surveyed there are more water masers than either 6.7-GHz methanol, or main-line OH masers. The water masers are concentrated towards the central axis of the star formation region, in contrast to the 6.7-GHz methanol masers which tend to be located near the periphery. The colours of the GLIMPSE point sources associated with the water masers are similar to those of 6.7-GHz methanol masers, but slightly less red. We have made a statistical investigation of the properties of the 13CO and 1.2-mm dust clumps with and without associated water masers. We find that the water masers are associated with the more massive, denser and brighter 13CO and 1.2-mm dust clumps. We present statistical models that are able to predict those 13CO and 1.2-mm dust clumps that are likely to have associated water masers, with a low misclassification rate. [ABSTRACT FROM AUTHOR]

We present near-infrared and millimetre-line observations of the Tornado nebula (G357.7–0.1). We detected 2.12-μm H2 1–0 S(1) line emission towards the suspected site of interaction with a molecular cloud revealed by the presence of an OH(1720-MHz) maser. The distribution of the H2 emission is well correlated with the non-thermal radio continuum emission from the Tornado, and the velocity of the H2 emission spans over 100 km s−1, which both imply that the H2 emission is shock excited. We also detected millimetre lines from12CO and13CO transitions at the velocity of the maser, and mapped the distribution of the molecular cloud in aregion around the maser. The peak of the molecular cloud aligns well with an indentation in the radio continuum distribution of the nebula, suggesting that the shock of the nebula is being decelerated at this location, which is consistent with the presence of the OH(1720-MHz) maser and shocked H2 emission at that location. [ABSTRACT FROM AUTHOR]

We report the detection of the SiO transition from the massive cold dense core G333.125−0.562. The core remains undetected at wavelengths shorter than 70 μm and has compact 1.2-mm dust continuum. The SiO emission is localized to the core. The observations are part of a continuing multi-molecular line survey of the giant molecular cloud G333. Other detected molecules in the core include 13CO, C18O, CS, , HCN, HNC, CH3OH, , SO, HC3N, NH3, and some of their isotopes. In addition, from NH3 (1,1) and (2,2) inversion lines, we obtain a temperature of 13 K. From fitting to the spectral energy distribution we obtain a colour temperature of 18 K and a gas mass of . We have also detected a 22-GHz water maser in the core, together with methanol maser emission, suggesting that the core will host massive star formation. We hypothesize that the SiO emission arises from shocks associated with an outflow in the cold core. [ABSTRACT FROM AUTHOR]