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  • Cambridge University Press (CUP)  (8)
  • 1
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    Online Resource
    SWAG: Survey of Water and Ammonia in the Galactic Center
    Cambridge University Press (CUP) ; 2016
    In:  Proceedings of the International Astronomical Union Vol. 11, No. S322 ( 2016-07), p. 143-144
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 11, No. S322 ( 2016-07), p. 143-144
    Abstract: SWAG (“Survey of Water and Ammonia in the Galactic Center”) is a multi-line interferometric survey toward the Center of the Milky Way conducted with the Australia Telescope Compact Array. The survey region spans the entire ~400 pc Central Molecular Zone and comprises ~42 spectral lines at pc spatial and sub-km/s spectral resolution. In addition, we deeply map continuum intensity, spectral index, and polarization at the frequencies where synchrotron, free-free, and thermal dust sources emit. The observed spectral lines include many transitions of ammonia, which we use to construct maps of molecular gas temperature, opacity and gas formation temperature (see poster by Nico Krieger et al. , this volume). Water masers pinpoint the sites of active star formation and other lines are good tracers for density, radiation field, shocks, and ionization. This extremely rich survey forms a perfect basis to construct maps of the physical parameters of the gas in this extreme environment.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921316011789
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2016
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  • 2
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    SWAG: The Maps
    Cambridge University Press (CUP) ; 2021
    In:  Proceedings of the International Astronomical Union Vol. 17, No. S373 ( 2021-08), p. 52-55
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 17, No. S373 ( 2021-08), p. 52-55
    Abstract: We present maps of the “Survey of Water and Ammonia toward the Galactic center” (SWAG). SWAG was observed over three years (∼550 h) with the Australia Telescope Compact Array (ATCA) and covers the entire Central Molecular Zone (CMZ) at about 26” or ∼1 pc resolution. The observed 21.2–25.6 GHz range contains tens of spectral lines and 4 GHz of continuum. Here, we present some final maps. These include multiple NH 3 lines, radio recombination lines, shock tracers like HNCO and methanol (CH 3 OH), high resolution 22 GHz water masers, and a continuum map. The maps are the foundation for ongoing comprehensive temperature mapping of the CMZ, including the identification of heating mechanisms, the characterization of water maser sources as young stellar objects or AGB stars, as well as chemistry, dynamics, and star formation studies of the ISM in this unique environment.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921323000182
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2021
    detail.hit.zdb_id: 2170724-8
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  • 3
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    The Anomalous Ammonia Spectrum of Arp 220
    Cambridge University Press (CUP) ; 2021
    In:  Proceedings of the International Astronomical Union Vol. 17, No. S373 ( 2021-08), p. 49-51
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 17, No. S373 ( 2021-08), p. 49-51
    Abstract: Ultra-luminous infrared galaxies (ULIRGs) are extreme in many ways. The major mergers trigger star formation at very high rates that cause the ISM to be dominated by infrared (IR) photons. We show the ammonia spectra toward the two cores of Arp 220, the nearest ULIRG, in three Very Large Array (VLA) bands (Ku, K, Ka). Typical decay times of the non-metastable transitions ∼ 100 s and are therefore usually difficult to observe. The FIR excitation of Arp 220, however, shows that non-metastable states are widely populated up to a limiting energy of ∼ 1500 K. We assume that this atypical ammonia spectrum is due to the strong FIR field that re-excites the ammonia molecule on timescales much shorter than the already short decay times. The resulting level population causes a break-down of the typical assumptions made for the use of ammonia as a molecular thermometer.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921323000194
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2021
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  • 4
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    Shock structure and shock heating in the Galactic central molecular zone
    Cambridge University Press (CUP) ; 2013
    In:  Proceedings of the International Astronomical Union Vol. 9, No. S303 ( 2013-10), p. 104-105
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 9, No. S303 ( 2013-10), p. 104-105
    Abstract: We present maps of a large number of dense molecular gas tracers across the central molecular zone of our Galaxy. The data were taken with the CSIRO/CASS Mopra telescope in Large Projects in the 1.3 cm, 7 mm, and 3 mm wavelength regimes. Here, we focus on the brightness of the shock tracers SiO and HNCO, molecules that are liberated from dust grains under strong (SiO) and weak (HNCO) shocks. The shocks may have occurred when the gas enters the bar regions and the shock differences could be due to differences in the moving cloud masses. Based on tracers of ionizing photons, it is unlikely that the morphological differences are due to selective photo-dissociation of the molecules. We also observe direct heating of molecular gas in strongly shocked zones, with high SiO/HNCO ratios, where temperatures are determined from the transitions of ammonia. Strong shocks appear to be the most efficient heating source of molecular gas, apart from high energy emission emitted by the central supermassive black hole Sgr A* and the processes within the extreme star formation region Sgr B2.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921314000283
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2013
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  • 5
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    SWAN: NGC 253's Nucleated Star Bursting Environment
    Cambridge University Press (CUP) ; 2015
    In:  Proceedings of the International Astronomical Union Vol. 11, No. S315 ( 2015-08)
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 11, No. S315 ( 2015-08)
    Abstract: We present the first results from SWAN: “Survey of Water and Ammonia in Nearby galaxies”. Nearby galaxies are conveniently located to probe molecular gas properties on scales of 10 to 200 pc, which are appropriate for the study of Giant Molecular Clouds (GMCs). The resolution of the Very Large Array in D and C configurations corresponds to a few 10s of parsecs in these galaxies. To advance studies of galaxy evolution it is paramount to understand how processes in the molecular Interstellar Medium(ISM) and star formation are linked on these scales. We have observed the metastable transitions of ammonia and the 22GHz water maser line in four nearby galaxies: NGC 253, IC 342, NGC 2146, and NGC 6946 using the VLA. These galaxies were chosen to span an order of magnitude in star formation rate, and a range of galactic ecosystems. We use the ammonia transitions to derive kinetic temperatures, which exposes the heating and cooling balance of the ISM. We then aim to relate these conditions to energetic feedback from star formation as indicated by water masers. Currently, our analysis is focused on NGC 253. NGC 253 is a barred spiral starburst galaxy with a nucleated star formation rate (SFR) of ≈ 3M ⊙ per year. We use a distance of 3.9Mpc for analysis. We have observed ammonia transitions (1,1) to (5,5) and the 22GHz water maser line with a resolution of ≈63pc. We have identified nine regions across the nucleated starburst for study. The ammonia (3,3) line appears to be masing in the centermost 200pc. We have identified two regions of water maser emission. The first region is a minor axis extension, about the center of the galaxy, and is very close to the outflow. By means of these measurements, we gain an understanding of the molecular ISM associated with the nucleated starburst environment in NGC 253.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921316007900
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2015
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  • 6
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    SWAG: Distribution and Kinematics of an Obscured AGB Population toward the Galactic Center
    Cambridge University Press (CUP) ; 2018
    In:  Proceedings of the International Astronomical Union Vol. 14, No. S343 ( 2018-08), p. 485-486
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 14, No. S343 ( 2018-08), p. 485-486
    Abstract: Outflows from AGB stars enrich the Galactic environment with metals and inject mechanical energy into the ISM. Radio spectroscopy can recover both properties through observations of molecular lines. We present results from SWAG: “Survey of Water and Ammonia in the Galactic Center”. The survey covers the entire Central Molecular Zone (CMZ), the inner 3.35° × 0.9° (∼480 × 130 pc) of the Milky Way that contains 5 × 107 M ⊙ of molecular gas. Although our survey primarily targets the CMZ, we observe across the entire sightline through the Milky Way. AGB stars are revealed by their signature of double peaked 22 GHz water maser lines. They are distinguished by their spectral signatures and their luminosities, which reach up to 10 −7 L ⊙ . Higher luminosities are usually associated with Young Stellar Objects located in CMZ star forming regions. We detect a population of ∼600 new water masers that can likely be associated with AGB outflows.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921318007810
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2018
    detail.hit.zdb_id: 2170724-8
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  • 7
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    SWAG Water Masers in the Galactic Center
    Cambridge University Press (CUP) ; 2017
    In:  Proceedings of the International Astronomical Union Vol. 13, No. S336 ( 2017-09), p. 172-175
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 13, No. S336 ( 2017-09), p. 172-175
    Abstract: The Galactic Center contains large amounts of molecular and ionized gas as well as a plethora of energetic objects. Water masers are an extinction-insensitive probe for star formation and thus ideal for studies of star formation stages in this highly obscured region. With the Australia Telescope Compact Array, we observed 22 GHz water masers in the entire Central Molecular Zone with sub-parsec resolution as part of the large SWAG survey: “Survey of Water and Ammonia in the Galactic Center”. We detect of order 600 22 GHz masers with isotropic luminosities down to ~10 −7 L ⊙ . Masers with luminosities of ≳10 −6 L ⊙ are likely associated with young stellar objects. They appear to be close to molecular gas streamers and may be due to star formation events that are triggered at pericenter passages near Sgr A*. Weaker masers are more widely distributed and frequently show double line features, a tell-tale sign for an origin in evolved star envelopes.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921317009322
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2017
    detail.hit.zdb_id: 2170724-8
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  • 8
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    Online Resource
    An ALMA and ATCA Molecular Line Survey Toward Centaurus A
    Cambridge University Press (CUP) ; 2012
    In:  Proceedings of the International Astronomical Union Vol. 8, No. S292 ( 2012-08), p. 251-251
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 8, No. S292 ( 2012-08), p. 251-251
    Abstract: We present Atacama Large Millimeter/submillimeter Array (ALMA) and Australia Telescope Compact Array (ATCA) data of molecular absorption lines toward the bright central core of the prominent, nearby (d ∼ 3.8 Mpc) radio galaxy Centaurus A, at 13, 7, 3, and 1mm wavelengths. The line of sight crosses the prominent dust lane and continues through the disk and eventually through gas that may be very close to the central supermassive black hole. The goal of our survey is to determine the physical conditions of the gas via analyses of molecular line tracers including molecular abundances and excitation conditions that are sensitive to changes in temperature, density, ionization, and shocks. This study allows us to derive the physical processes that are shaping each molecular environment.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921313001269
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2012
    detail.hit.zdb_id: 2170724-8
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