Azimuthal and Kinematic Segregation of Neutral and Molecular Gas in Arp 118: The Yin-Yang Galaxy NGC 1144

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dc.creatorAppleton, P. N.
dc.creatorCharmandaris, V.
dc.creatorGao, Yu
dc.creatorJarrett, T.
dc.creatorBransford, M. A.
dc.date2002-11-27
dc.date.accessioned2026-07-07T10:31:28Z
dc.date.available2026-07-07T10:31:28Z
dc.descriptionWe present new high-resolution HI observations of the disk of the collisional infrared luminous (L$_{\rm IR}=2.2\times10^{11}$ L$_{\sun}$) galaxy NGC 1144, which reveal an apparent large-scale azimuthal and kinematic segregation of neutral hydrogen relative to the molecular gas distribution. Even among violently collisional galaxies, the CO/HI asymmetry in NGC 1144 is unusual, both in the inner regions, and in the outer disk. We suggest that we are observing Arp 118 at a special moment, shortly after a high-speed collision between NGC 1144 and its elliptical companion NGC 1143. HI emission with an average molecular fraction f$_{mol}$ $<$ 0.5 is observed on one side (NW) of the rotating disk of NGC 1144, while the other side (SE) is dominated by dense molecular complexes in which f$_{mol}$ is almost unity. The interface region between the warm-- and cool--cloud dominated regions, lies on a deep spiral-like dust-lane which we identify as a shock-wave responsible for the relative shift in the dominance of HI and H$_2$ gas. A strong shock being fed by diffuse HI clouds with unusually large ($>$ 400 km s$^{-1}$) rotational velocities can explain: 1) the CO/HI asymmetries, 2) a large velocity jump (185 km s$^{-1}$) across the arm as measured by HI absorption against a radio bright continuum source which straddles the arm, and 3) the asymmetric distribution of star formation and off-nuclear molecular gas resulting from likely streaming motions associated with the strong-shock. The new results provide for the first time a coherent picture of Arp 118's many peculiarities, and underlines the potentially complex changes in the gas-phase that can accompany large gravitational perturbations of gas-rich galaxies.
dc.description20 pages, two tables, 9 Figures
dc.identifierhttps://arxiv.org/abs/astro-ph/0211585
dc.identifierhttp://arxiv.org/abs/astro-ph/0211585
dc.identifierAstrophys.J.586:112-122,2003
dc.identifierdoi:10.1086/367635
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/178419
dc.subjectAstrophysics
dc.titleAzimuthal and Kinematic Segregation of Neutral and Molecular Gas in Arp 118: The Yin-Yang Galaxy NGC 1144
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