| 1. |
- Baan, Willem A., et al.
(författare)
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Dense gas in luminous infrared galaxies
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 477:3, s. 747-U73
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Tidskriftsartikel (refereegranskat)abstract
- Aims. Molecules that trace the high-density regions of the interstellar medium have been observed in (ultra-) luminous (far-) infrared galaxies, in order to initiate multiple-molecule multiple-transition studies to evaluate the physical and chemical environment of the nuclear medium and its response to the ongoing nuclear activity.Methods. The HCN(1-0), HNC(1-0), HCO+ (1-0), CN(1-0) and CN(2-1), CO(2-1), and CS(3-2) transitions were observed in sources covering three decades of infrared luminosity including sources with known OH megamaser activity. The data for the molecules that trace the high-density regions were augmented with data available in the literature.Results. The integrated emissions of high-density tracer molecules show a strong relation to the far-infrared luminosity. Ratios of integrated line luminosities were used for a first-order diagnosis of the integrated molecular environment of the evolving nuclear starbursts. Diagnostic diagrams display significant differentiation among the sources that relate to the initial conditions and the radiative excitation environment. Initial differentiation was introduced between the FUV radiation field in photon-dominated-regions and the X-ray field in X-ray-dominated-regions. The galaxies displaying OH megamaser activity have line ratios typical of photon-dominated regions.
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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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| 4. |
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| 5. |
- Baan, Willem A., et al.
(författare)
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Dense Molecular Gas in Luminous Infrared Galaxies: Diagnosing the ISM
- 2008
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Ingår i: EAS Publications Series. - : EAS, EDP Sciences. - 1633-4760 .- 1638-1963. ; 31, s. 111-114
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Tidskriftsartikel (refereegranskat)abstract
- The behavior of molecular tracers of the high-density star-forming ISM provides a diagnostics tool for luminous FIR galaxies. All molecules react differently to the physical and chemical environment and their collective behavior is indicative of the excitation of the ISM and its evolutionary state. This paper describes efforts to diagnose the nuclear medium through multiple-molecule studies.
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| 6. |
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