| 1. |
- Baan, Willem, et al.
(författare)
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Multimolecular studies of Galactic star-forming regions
- 2014
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 445:4, s. 3331-3344
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Tidskriftsartikel (refereegranskat)abstract
- Molecular emission-line observations of isolated Galactic star-forming regions are used to model the physical properties of the molecular interstellar medium in these systems. Observed line ratios are compared with the results predicted by models that incorporate gas-phase chemistry and the heating by stellar radiation and non-radiative feedback processes. The line ratios of characteristic tracer molecules may be interpreted using the contributions of two distinct components: a cold (40-50 K) and high-density (105-105.5 cm(-3)) photon-dominated region (PDR) with a nominal UV flux density and a warm (similar to 300 K) mechanical heating-dominated region (MHDR) with a slightly lower density (10(4.5)-10(5) cm(-3)). The relative contributions of these structural components are used to model the observed line ratios. Ionized species may be better modelled by adopting an increase of the cosmic ray flux towards the Galactic Centre and the sulphur abundance should depleted by a factor of 200-400 relative to solar values. The line ratios of the Galactic sample are found to be very similar to those of the integrated signature of prominent (ultra) luminous IR Galaxies. The PDRs and MHDRs in the isolated Galactic regions may be modelled with slightly higher mean densities than in extragalactic systems and a higher MHDR temperature resulting from non-radiative mechanical heating. Multimolecular studies are effective in determining the physical and chemical properties of star formation regions by using characteristic line ratios to diagnose their environment. The addition of more molecular species will reduce the existing modelling redundancy.
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| 2. |
- Loenen, A. F., et al.
(författare)
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Extragalactic Chemistry: HCN, HNC, and HCO+ : M. , W. A. Baan, and R.
- 2008
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Ingår i: EAS Publications Series. - : EAS, EDP Sciences. - 1633-4760 .- 1638-1963. ; 31, s. 183-185
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Tidskriftsartikel (refereegranskat)abstract
- High- and low-density tracer molecules have been observed in (Ultra-) Luminous Infrared Galaxies in order to initiate multi-molecule multi-transition studies to evaluate the physical and chemical environment of the nuclear medium and the ongoing nuclear activity. The data, augmented with data available in the literature, are presented in Baan et al. (2007), which also presents a first order analysis. Here, we present the chemical analysis of the J=1–0 transition lines of HCN, HNC, and HCO+.
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| 3. |
- Loenen, A. F., et al.
(författare)
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Mechanical feedback in the molecular ISM of luminous IR galaxies
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 488:1, s. L5-L8
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Tidskriftsartikel (refereegranskat)abstract
- Aims. Molecular emission lines originating in the nuclei of luminous infra-red galaxies are used to determine the physical properties of the nuclear ISM in these systems.Methods. A large observational database of molecular emission lines is compared with model predictions that include heating by UV and X-ray radiation, mechanical heating, and the effects of cosmic rays.Results. The observed line ratios and model predictions imply a separation of the observed systems into three groups: XDRs, UV-dominated high-density ( $n \geq 10^5$ cm-3) PDRs, and lower-density ( n = 104.5 cm-3) PDRs that are dominated by mechanical feedback.Conclusions. The division of the two types of PDRs follows naturally from the evolution of the star formation cycle of these sources, which evolves from deeply embedded young stars, resulting in high-density ( $n \geq 10^5$ cm-3) PDRs, to a stage where the gas density has decreased ( n = 104.5 cm-3) and mechanical feedback from supernova shocks dominates the heating budget.
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