The Relation between Galaxy Activity and the Dynamics of Compact Groups of Galaxies

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Interaction between the Galaxies IC 2163 and NGC 2207

VLA HI observations of the interacting pair IC 2163/NGC 2207 are presented. The velocity and structural anomalies of IC 2163 agree with predictions of N-body galaxy encounter simulations if IC 2163 recently underwent a strong, prograde, in-plane encounter with NGC 2207. The velocity disturbances in NGC 2207 suggests that the main tidal force on NGC 2207 was perpendicular to the disk of NGC 2207

H I Recycling: Formation of Tidal Dwarf Galaxies

Original paper can be found at: http://www.astrosociety.org/pubs/cs/222-252.html--Copyright Astronomical Society of the PacificGalactic collisions trigger a number of phenomena, such as transportation inward of gas from distances of up to kiloparsecs from the center of a galaxy to the nuclear region, fueling a central starburst or nuclear activity. The inverse process, the ejection of material into the intergalactic medium by tidal forces, is another important aspect and can be studied especially well through detailed HI observations of interacting systems. These studies have shown that a large fraction of the gaseous component of colliding galaxies can be expelled. Part of this tidal debris might fall back, be dispersed throughout the intergalactic medium or re-condense to form a new generation of galaxies: the so-called tidal dwarf galaxies. The latter are nearby examples of galaxies in formation. The properties of these recycled objects, and different ways to identify them, are reviewed here

VLA HI imaging of the Low Surface Brightness dwarf galaxy DDO47

Original paper can be found at: http://www.astrosociety.org/pubs/cs/156-194.html--Copyright Astronomical Society of the PacificWe present high resolution VLA-observations of the nearby Low Surface Brightness Galaxy DDO 47. This object shows many hole-like structures in its neutral interstellar medium. The majority of the detected H I-shells are found to be expanding. Their origin is therefore believed to be due to stellar winds of the most massive stars and their subsequent supernova (SN type II) explosions within regions of recent star formation

Molecular Gas in Tidal Dwarf Galaxies: On-going Galaxy Formation

We investigate the process of galaxy formation as can be observed in the only currently forming galaxies -- the so-called Tidal Dwarf Galaxies, hereafter TDGs -- through observations of the molecular gas detected via its CO (Carbon Monoxide) emission. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of gas and a {\it bona fide} galaxy. We have now detected CO in 9 TDGs with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few $10^8 M_\odot$. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular gas masses is observed, in accord with the transformation of HI into H$_2$. Although uncertainties are still large for individual objects as the geometry is unknown, we find that the "dynamical" masses of TDGs, estimated from the CO line widths, do not seem to be greater than the "visible" masses (HI + H$_2$ + a stellar component), i.e., TDGs require no dark matter. We provide evidence that TDGs are self-gravitating entities, implying that we are witnessing the ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas, which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component.Comment: 8 pages 4 figures, to be published in: Proceedings of the IAU Symposium 217: Recycling Intergalactic and Interstellar Matte

Spitzer Space Telescope IRAC and MIPS observations of the interacting galaxies Ic 2163 and NGC 2207: clumpy emission

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CO Observations of the Interacting Galaxy Pair NGC 5394/95

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