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Molecular line emis...
Molecular line emission in NGC 4945, imaged with ALMA
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- Henkel, C. (author)
- Chinese Academy of Sciences,King Abdulaziz University,Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Muhle, S. (author)
- Universität Bonn,University of Bonn
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- Bendo, G. J. (author)
- University of Manchester
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- Józsa, G. I.G. (author)
- Rhodes University,Universität Bonn,University of Bonn
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- Gong, Y. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG),Chinese Academy of Sciences
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- Viti, Serena (author)
- University College London (UCL)
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- Aalto, Susanne, 1964 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Combes, F. (author)
- LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres, France
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- Burillo, S. G. (author)
- Observatorio Astronómico Nacional (OAN),Spanish National Observatory (OAN)
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- Hunt, L. K. (author)
- Osservatorio Astrofisico di Arcetri,Arcetri Astrophysical Observatory
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- Mangum, J. G. (author)
- National Radio Astronomy Observatory
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- Martin, S. (author)
- Atacama Large Millimeter-submillimeter Array (ALMA),European Southern Observatory Santiago
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- Muller, S. (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Ott, J. (author)
- National Radio Astronomy Observatory Socorro
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- van der Werf, P. (author)
- National Radio Astronomy Observatory Socorro
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- Malawi, A. A. (author)
- King Abdulaziz University
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- Ismail, H. (author)
- King Abdulaziz University
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- Alkhuja, E. (author)
- King Abdulaziz University
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- Asiri, H. (author)
- King Abdulaziz University
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- Aladro, Rebeca, 1979 (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Alves, F. O. (author)
- Universität Bonn,University of Bonn,Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Ao, Y. (author)
- National Astronomical Observatory of Japan
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- Baan, Willem A. (author)
- Netherlands Institute for Radio Astronomy (ASTRON)
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- Costagliola, Francesco, 1981 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Fuller, G. A. (author)
- University of Manchester
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- Greene, J. (author)
- Princeton University
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- Impellizzeri, C. M. V. (author)
- European Southern Observatory Santiago
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- Kamali, F. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Klessen, R. S. (author)
- Ruprecht-Karls-Universität Heidelberg,Heidelberg University
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- Mauersberger, R. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Tang, X. D. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG),Chinese Academy of Sciences
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- Tristram, K. (author)
- European Southern Observatory Santiago
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- Wang, M. (author)
- Chinese Academy of Sciences
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- Zhang, J. S. (author)
- Guangzhou University
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(creator_code:org_t)
- 2018-07-31
- 2018
- English.
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 615
- Related links:
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Abstract
Subject headings
Close
- NGC 4945 is one of the nearest (D ≈ 3.8 Mpc; 1 00 ≈ 19 pc) starburst galaxies. To investigate the structure, dynamics, and composition of the dense nuclear gas of this galaxy, ALMA band 3 (λ ≈ 3−4 mm) observations were carried out with ≈2 00 resolution. Three HCN and two HC + isotopologues, CS, C 3 H 2 , SiO, HCO, and CH 3 C 2 H were measured. Spectral line imaging demonstrates the presence of a rotating nuclear disk of projected size 10 00 × 2 00 reaching out to a galactocentric radius of r ≈ 100 pc with position angle PA = 45 ◦ ± 2 ◦ , inclination i = 75 ◦ ± 2 ◦ and an unresolved bright central core of size <∼ 2 00 . The continuum source, representing mostly free-free radiation from star forming regions, is more compact than the nuclear disk by a linear factor of two but shows the same position angle and is centered 0 00 . 39 ± 0 00 . 14 northeast of the nuclear accretion disk defined by H 2 O maser emission. Near the systemic velocity but outside the nuclear disk, both HCN J = 1 → 0 and CS J = 2 → 1 delineate molecular arms of length >∼ 15 00 ( >∼ 285 pc) on opposite sides of the dynamical center. These are connected by a (deprojected) ≈ 0.6 kpc sized molecular bridge, likely a dense gaseous bar seen almost ends-on, shifting gas from the front and back side into the nuclear disk. Modeling this nuclear disk located farther inside (r <∼ 100 pc) with tilted rings provides a good fit by inferring a coplanar outflow reaching a characteristic deprojected velocity of ≈50 km s −1 . All our molecular lines, with the notable exception of CH 3 C 2 H, show significant absorption near the systemic velocity (≈571 km s −1 ), within the range ≈500-660 km s −1 . Apparently, only molecular transitions with low critical H 2 density (n crit<∼ 10 4 cm −3 ) do not show absorption. The velocity field of the nuclear disk, derived from CH 3 C 2 H, provides evidence for rigid rotation in the inner few arcseconds and a dynamical mass of M tot = (2.1 ± 0.2) × 10 8 M inside a galactocentric radius of 2 00 . 45 (≈45 pc), with a significantly flattened rotation curve farther out. Velocity integrated line intensity maps with most pronounced absorption show molecular peak positions up to ≈1 00 . 5 (≈30 pc) southwest of the continuum peak, presumably due to absorption, which appears to be most severe slightly northeast of the nuclear maser disk. A nitrogen isotope ratio of 14 N/ 15 N ≈ 200-450 is estimated. This range of values is much higher then previously reported on a tentative basis. Therefore, because 15 N is less abundant than expected, the question for strong 15 N enrichment by massive star ejecta in starbursts still remains to be settled.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
- NATURVETENSKAP -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)
- NATURVETENSKAP -- Kemi -- Teoretisk kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences -- Theoretical Chemistry (hsv//eng)
Keyword
- Galaxies: individual: NGC4945
- Nuclear reactions
- Galaxies: starburst
- Nucleosynthesis
- Galaxies: structure
- Radio lines: ISM
- Galaxies: ISM
- Abundances
Publication and Content Type
- art (subject category)
- ref (subject category)
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To the university's database
- By the author/editor
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Henkel, C.
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Muhle, S.
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Bendo, G. J.
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Józsa, G. I.G.
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Gong, Y.
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Viti, Serena
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show more...
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Aalto, Susanne, ...
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Combes, F.
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Burillo, S. G.
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Hunt, L. K.
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Mangum, J. G.
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Martin, S.
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Muller, S.
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Ott, J.
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van der Werf, P.
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Malawi, A. A.
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Ismail, H.
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Alkhuja, E.
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Asiri, H.
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Aladro, Rebeca, ...
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Alves, F. O.
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Ao, Y.
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Baan, Willem A.
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Costagliola, Fra ...
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Fuller, G. A.
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Greene, J.
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Impellizzeri, C. ...
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Kamali, F.
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Klessen, R. S.
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Mauersberger, R.
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Tang, X. D.
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Tristram, K.
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Wang, M.
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Zhang, J. S.
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- About the subject
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- NATURAL SCIENCES
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NATURAL SCIENCES
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and Physical Science ...
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and Astronomy Astrop ...
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- NATURAL SCIENCES
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NATURAL SCIENCES
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and Physical Science ...
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and Atom and Molecul ...
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- NATURAL SCIENCES
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NATURAL SCIENCES
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and Chemical Science ...
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and Theoretical Chem ...
- Articles in the publication
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Astronomy and As ...
- By the university
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Chalmers University of Technology