| 1. |
- Alatalo, K., et al.
(författare)
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STRONG FAR-INFRARED COOLING LINES, PECULIAR CO KINEMATICS, AND POSSIBLE STAR-FORMATION SUPPRESSION IN HICKSON COMPACT GROUP 57
- 2014
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 795:2, s. 159-
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Tidskriftsartikel (refereegranskat)abstract
- We present [C II] and [O I] observations from Herschel and CO(1-0) maps from the Combined Array for Research in Millimeter Astronomy (CARMA) of the Hickson compact group HCG 57, focusing on the galaxies HCG 57a and HCG 57d. HCG 57a has been previously shown to contain enhanced quantities of warm molecular hydrogen consistent with shock or turbulent heating. Our observations show that HCG 57d has strong [C II] emission compared to L-FIR and weak CO(1-0), while in HCG 57a, both the [C II] and CO(1-0) are strong. HCG 57a lies at the upper end of the normal distribution of the [C II]/CO and [C II]/FIR ratios, and its far-infrared (FIR) cooling supports a low-density, warm, diffuse gas that falls close to the boundary of acceptable models of a photon-dominated region. However, the power radiated in the [C II] and warm H-2 emissions have similar magnitudes, as seen in other shock-dominated systems and predicted by recent models. We suggest that shock heating of the [C II] is a viable alternative to photoelectric heating in violently disturbed, diffuse gas. The existence of shocks is also consistent with the peculiar CO kinematics in the galaxy, indicating that highly noncircular motions are present. These kinematically disturbed CO regions also show evidence of suppressed star formation, falling a factor of 10-30 below normal galaxies on the Kennicutt-Schmidt relation. We suggest that the peculiar properties of both galaxies are consistent with a highly dissipative, off-center collisional encounter between HCG 57d and 57a, creating ring-like morphologies in both systems. Highly dissipative gas-on-gas collisions may be more common in dense groups because of the likelihood of repeated multiple encounters. The possibility of shock-induced star-formation suppression may explain why a subset of these HCG galaxies has been found previously to fall in the mid-infrared green valley.
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| 2. |
- BarboSá, D., et al.
(författare)
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A sustainable approach to large ICT science based infrastructures: The case for radio astronomy
- 2014
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Ingår i: 2014 IEEE International Energy Conference, ENERGYCON 2014; Dubrovnik; Croatia; 13 May 2014 through 16 May 2014. - 9781479924493 ; , s. 668-674
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Konferensbidrag (refereegranskat)abstract
- Large sensor-based infrastructures for radio astronomy will be among the most intensive data-driven projects in the world, facing very high power demands. The geographically wide distribution of these infrastructures and their associated processing High Performance Computing (HPC) facilities require Green Information and Communications Technologies (ICT): a combination is needed of low power computing, power and byte efficient data storage, local data services, Smart Grid power management, and inclusion of Renewable Energies. Here we outline the major characteristics and innovation approaches to address power efficiency and long-term power sustainability for radio astronomy projects, focusing on Green ICT for science.
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