Molecular line emission in NGC 4945, imaged with ALMA
Henkel, C.1,2,3; Muehle, S.4; Bendo, G.5,6; Jozsa, G. I. G.4,7,8; Gong, Y.1,9,10; Viti, S.11; Aalto, S.12; Combes, F.13; Garcia-Burillo, S.14; Hunt, L. K.15; Mangum, J.16; Martin, S.17,18; Muller, S.12; Ott, J.19; van der Werf, P.19; Malawi, A. A.2; Ismail, H.2; Alkhuja, E.2; Asiri, H. M.2; Aladro, R.1; Alves, F.4,21; Ao, Y.22; Baan, W. A.23; Costagliola, F.12; Fuller, G.5; Greene, J.24; Impellizzeri, C. M. V.17; Kamali, F.1; Klessen, R. S.25,28; Mauersberger, R.1; Tang, X. D.1,3,26; Tristram, K.17; Wang, M.9,10; Zhang, J. S.27
Corresponding AuthorHenkel, C.(
AbstractNGC 4945 is one of the nearest (D approximate to 3.8 Mpc; 1" approximate to 19 pc) starburst galaxies. To investigate the structure, dynamics, and composition of the dense nuclear gas of this galaxy, ALMA band 3 (lambda approximate to 3-4mm) observations were carried out with approximate to 2" resolution. Three HCN and two HCO+ isotopologues, CS, C3H2, SiO, HCO, and CH3C2H were measured. Spectral line imaging demonstrates the presence of a rotating nuclear disk of projected size 10" x 2" reaching out to a galactocentric radius of r 100 pc with position angle PA = 45 degrees +/- 2 degrees, inclination i = 75 degrees +/- 2 degrees and an unresolved bright central core of less than or similar to 2" size 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".39 +/- 0".14 northeast of the nuclear accretion disk defined by H2O 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 greater than or similar to 15" (greater than or similar to 285 pc) on opposite sides of the dynamical center. These are connected by a (deprojected) approximate to 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 less than or similar to 100 pc) with tilted rings provides a good fit by inferring a coplanar outflow reaching a characteristic deprojected velocity of approximate to 50 km s(-1). All our molecular lines, with the notable exception of CH3C2H, show significant absorption near the systemic velocity (approximate to 571 km s(-1)), within the range approximate to 500-660 km s(-1). Apparently, only molecular transitions with low critical H-2 density (n(crit) less than or similar to 10(4) cm(-3)) do not show absorption. The velocity field of the nuclear disk, derived from CH3C2H, provides evidence for rigid rotation in the inner few arcseconds and a dynamical mass of M-tot = (2.1 +/- 0.2) x 10(8) M-circle dot inside a galactocentric radius of 2".45 (approximate to 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 approximate to 1".5 (approximate to 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 N-14/N-15 approximate to 200-450 is estimated. This range of values is much higher then previously reported on a tentative basis. Therefore, because N-15 is less abundant than expected, the question for strong N-15 enrichment by massive star ejecta in starbursts still remains to be settled.
Keywordgalaxies: starburst galaxies: structure galaxies: ISM nuclear reactions nucleosynthesis abundances galaxies individual: NGC4945 radio lines: ISM
Indexed BySCI
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000440418800004
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Cited Times:7[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorHenkel, C.
Affiliation1.Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany
2.King Abdulaziz Univ, Fac Sci, Astron Dept, POB 80203, Jeddah 21589, Saudi Arabia
3.Chinese Acad Sci, Xinjiang Astron Observ, Urumqi 830011, Peoples R China
4.Univ Bonn, Argelander Inst Astron, Hugel 71, D-53121 Bonn, Germany
5.Univ Manchester, Ctr Astrophys, Jodrell Bank, Oxford Rd, Manchester M13 9PL, Lancs, England
6.Univ Manchester, UK ALMA Reg Ctr Node, Oxford Rd, Manchester M13 9PL, Lancs, England
7.SKA South Africa, SARAO, Pk Rd, ZA-7405 Pinelands, South Africa
8.Rhodes Univ, RARG, RATT, POB 94, ZA-6140 Grahamstown, South Africa
9.Chinese Acad Sci, Purple Mt Observ, Nanjing 210008, Jiangsu, Peoples R China
10.Chinese Acad Sci, Key Lab Radio Astron, Nanjing 210008, Jiangsu, Peoples R China
11.UCL, Dept Phys & Astron, Gower St, London WC1E 6BT, England
12.Chalmers Univ Technol, Onsala Observ, Dept Earth & Space Sci, S-43992 Onsala, Sweden
13.UPMC Sorbonne Univ, PSL Univ, CNRS, LERMA,Observ Paris,Coll France, Paris, France
14.OAN IGN, Observ Madrid, Alfonso XII 3, Madrid 28014, Spain
15.INAF Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy
16.Natl Radio Astron Observ, 520 Edgemont Rd, Charlottesville, VA 22903 USA
17.European Southern Observ, Alonso de Cordova 3107,Vitacura Casilla 763 0355, Santiago, Chile
18.Joint ALMA Observ, Alonso de Cordova 3107,Vitacura Casilla 763 0355, Santiago, Chile
19.Natl Radio Astron Observ, POB O,1003 Lopezville Rd, Socorro, NM 87801 USA
20.Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands
21.Max Planck Inst Extraterr Phys, Giessenbachstr 1, D-85748 Garching, Germany
22.Natl Astron Observ Japan, 2-21-1 Osawa, Mitaka, Tokyo 1818588, Japan
23.Netherlands Inst Radioastron ASTRON, NL-7991 PD Dwingeloo, Netherlands
24.Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA
25.Heidelberg Univ, Zentrum Astron, Inst Theoret Astrophys, Albert Ueberle Str 2, D-69120 Heidelberg, Germany
26.Chinese Acad Sci, Key Lab Radio Astron, Urumqi 830011, Peoples R China
27.Guangzhou Univ, Ctr Astrophys, Guangzhou 510006, Guangdong, Peoples R China
28.Heidelberg Univ, Interdisziplinares Zentrum Wissens, Neuenheimer Feld 205, D-69120 Heidelberg, Germany
Recommended Citation
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Henkel, C.,Muehle, S.,Bendo, G.,et al. Molecular line emission in NGC 4945, imaged with ALMA[J]. ASTRONOMY & ASTROPHYSICS,2018,615:29.
APA Henkel, C..,Muehle, S..,Bendo, G..,Jozsa, G. I. G..,Gong, Y..,...&Zhang, J. S..(2018).Molecular line emission in NGC 4945, imaged with ALMA.ASTRONOMY & ASTROPHYSICS,615,29.
MLA Henkel, C.,et al."Molecular line emission in NGC 4945, imaged with ALMA".ASTRONOMY & ASTROPHYSICS 615(2018):29.
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