Browsing by Subject "galaxies: interactions"

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    Open Access
    CO in Hickson compact group galaxies with enhanced warm H 2 emission: Evidence for galaxy evolution?
    (2014) Lisenfeld, U; Appleton, P N; Cluver, M E; Guillard, P; Alatalo, K; Ogle, P
    Context. Galaxies in Hickson Compact Groups (HCGs) are believed to experience morphological transformations from blue, star-forming galaxies to red, early-type galaxies. Galaxies with a high ratio between the luminosities of the warm H2 to the 7.7 μm PAH emission (so-called Molecular Hydrogen Emission Galaxies, MOHEGs) are predominantly in an intermediate phase, the green valley. Their enhanced H2 emission suggests that the molecular gas is affected in the transition.
  • Thumbnail Image
    Item
    Open Access
    Constraining AGN triggering mechanisms through the clustering analysis of active black holes
    (2016) Gatti, M; Shankar, F; Bouillot, V; Menci, N; Lamastra, A; Hirschmann, M; Fiore, F
    The triggering mechanisms for active galactic nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disc instabilities (DIs). Using an advanced semi-analytic model (SAM) of galaxy formation, coupled to accurate halo occupation distribution modelling, we investigate the imprint left by each separate triggering process on the clustering strength of AGN at small and large scales. Our main results are as follows: (i) DIs, irrespective of their exact implementation in the SAM, tend to fall short in triggering AGN activity in galaxies at the centre of haloes with
  • Thumbnail Image
    Item
    Open Access
    Herschel observations of Hickson compact groups of galaxies: Unveiling the properties of cold dust
    (2014) Bitsakis, T; Charmandaris, V; Appleton, P N; Díaz-Santos, T; Le Floc’h, E; da Cunha, E; Alatalo, K; Cluver, M
    We present a Herschel far-IR and sub-mm study of a sample of 120 galaxies in 28 Hickson Compact Groups. Fitting their UV to sub-mm spectral energy distributions with the model of da Cunha et al. (2008), we accurately estimate the dust masses, luminosities and temperatures of the individual galaxies. We find that nearly half of the late-type galaxies in dynamically "old" groups, those with more than 25% of early-type members and redder UV-optical colours, have also significantly lower dust-to-stellar mass ratios compared to those of actively star-forming galaxies of the same mass found both in HCGs and the field. Examining their dust-to-gas mass ratios we conclude that dust was stripped out of these systems as a result of the gravitational and hydrodynamic interactions, experienced due to previous encounters with other group members. About 40% of the early-type galaxies (mostly lenticulars), in dynamically "old" groups, display dust properties similar to those of the UV-optical red late-type galaxies. Given their stellar masses, star formation rates and UV-optical colours, we suggest that red late-type and dusty lenticular galaxies represent transition populations between blue star-forming disk galaxies and quiescent early-type ellipticals. [...ABRIDGED...] Our deep Herschel observations also allow us to detect the presence of diffuse cold intragroup dust in 4 HCGs. We also find that the fraction of 250micron emission which is located outside of the main bodies of the red late-type galaxies as well as of the dusty lenticulars is 15-20% of their integrated emission at this band. All these findings are consistent with an evolutionary scenario in which gas dissipation, shocks and turbulence in addition to tidal interactions, shape the evolution of galaxies in compact groups.
  • Thumbnail Image
    Item
    Open Access
    HI deficiency in the galaxy cluster ACO 3627: ATCA observations in the Great Attractor region
    (2001) Vollmer, B; Cayatte, V; van Driel, W; Henning, P A; Kraan-Korteweg, R C; Balkowski, C; Woudt, P A; Duschl, W J
    ATCA 21 cm H
  • Thumbnail Image
    Item
    Open Access
    HI in group interactions: HCG 44
    (2017) Hess, Kelley M; Cluver, M E; Yahya, Sahba; Leisman, Lukas; Serra, Paolo; Lucero, Danielle M; Passmoor, Sean S; Carignan, Claude
    Extending deep observations of the neutral atomic hydrogen (H I) to the environment around galaxy groups can reveal a complex history of group interactions which is invisible to studies that focus on the stellar component. Hickson Compact Group 44 (HCG 44) is a nearby example, and we have combined H I data from the Karoo Array Telescope, Westerbork Synthesis Radio Telescope, and Arecibo Legacy Fast ALFA survey, in order to achieve high column density sensitivity (N _{H {I}}
  • Thumbnail Image
    Item
    Open Access
    Mid-infrared dust in two nearby radio galaxies, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36)
    (2016) Duah Asabere, B; Horellou, C; Jarrett, T H; Winkler, H
    Context. Most radio galaxies are hosted by giant gas-poor ellipticals, but some contain significant amounts of dust, which is likely to be of external origin.