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| 2. |
- Wahlberg Jansson, Karl
(författare)
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Nu når vi äntligen Pluto
- 2014
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Ingår i: Populär Astronomi. - 1650-7177. ; 14:4, s. 14-19
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- I juli 2015 når NASA-rymdsonden New Horizons till solsystemets mest kända dvärgplanet Pluto. Denna artikel diskuterar vad Pluto egentligen är och vad rymdsonden kommer att hitta.
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| 3. |
- Manzetti, Sergio, 1975-, et al.
(författare)
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Simulating galactical vorticity using a supersymmetric operator
- 2020
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Rapport (populärvet., debatt m.m.)abstract
- Simulations of galactic vorticity require the development of complex systems of equations to generate models that account for the gravity, mass, kinetic, and electromagnetic effects which govern cluster behaviour. In this study, a relationship is outlined through a series of steps, between the Einstein equations, the Ricci equations and the gravitational model of comoslogical bodies. This series of steps are then followed by the generation of a group of equations, including a supersymmetric equation which describes vorticity under the presence of an electromagnetic field for quantized systems. The relationship between the Einstein equations and the equation for quantum vorticity is ultimately the described and we outline the model of galactic vorticity through a nonlinear cluster model, which has direct similarities to the Kosterlitz-Thouless model for vorticity in quasi-ordered systems. The resulting supersymmetric model for describing galactic vorticity we here show suggests that galactic vorticity broke symmetry already at T=0, and by the effect of the galactic halo around the periphery, generates nonlinear vorticity through the shear property of the wavefunction. Most interestingly, this property of the wavefunction, which generates autonomous vorticity by the mere presence of a halo-boundary of the galactic cluster is independent of temperature. We describe by this that the nonlinear relationship between vortices in the cluster leads to a cumulative effect which generates an exchange interaction at the macroscopic level between clusters which is the source of irregular moment of inertia of galaxies, that has been attributed to dark matter. Our theory is thus that galactic rotations are both fueled by the mass of the galaxy by classical physics means as well as the nonlinear vortex interaction between clusters.
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| 4. |
- Mustill, Alexander J
(författare)
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Guide till solsystemets småkroppar
- 2022
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Ingår i: Populär Astronomi. - 1650-7177. ; 2022:4, s. 48-49
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Recension (populärvet., debatt m.m.)abstract
- Review of "Small bodies of the Solar System", Hans Rickman, 2021, World Scientific.
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| 8. |
- Asplund, Martin, et al.
(författare)
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Radiative Transfer in 3D Model Stellar Atmospheres
- 2003
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Ingår i: ASP Conference Proceedings. - 1583811400 ; , s. 197-
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Recently 3D hydrodynamical simulations of stellar surface convection have become feasible thanks to advances in computer technology and efficient numerical algorithms. Available observational diagnostics indicate that these models are highly realistic in describing the topology of stellar granulation and for spectral line formation purposes. The traditional free parameters (mixing length parameters, micro- and macroturbulence) always inherent in standard 1D analyses have thus finally become obsolete. These 3D models can therefore both shed light on the elusive nature of stellar convection as well as be employed in element abundance analyses. In the present contribution we will describe some aspects of the models and possible applications of them in terms of radiative transfer.
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| 9. |
- Atek, Hakim, et al.
(författare)
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On the detectability of Ly-alpha emission in star forming galaxies. The role of dust
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 488:491
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Context: Lyman-alpha (Lyα) radiation is now widely used to investigate the galaxy formation and evolution in the high redshift universe. However, without a rigorous understanding of the processes regulating the Lyα escape fraction, physical interpretations of high-z observations remain questionable. Aims: We examine six nearby star forming galaxies to disentangle the role of the dust from other parameters such as gas kinematics, geometry, and ISM morphology in the obscuration of Lyα. Thereby, we attempt to understand the Lyα escape physics and infer the implications for high-redshift studies. Methods: We use HST/ACS imaging to produce continuum-subtracted Lyα maps, and ground-based observations (ESO/NTT and NOT) to map the Hα emission and the extinction E(B-V) in the gas phase derived from the Balmer decrement Hα/Hβ. Results: When large outflows are present, the Lyα emission does not appear to be correlated with the dust content, confirming the role of the Hi kinematics in the escape of Lyα photons. In the case of a dense, static Hi covering, we observe a damped absorption with a negative correlation between Lyα and E(B-V). We found that the Lyα escape fraction does not exceed 10% in all our galaxies and is mostly about 3% or below. Finally, because of the radiative transfer complexity of the Lyα line, star formation rate based on Lyα luminosity is underestimated with respect to that derived from UV luminosity. Simple reddening correction does not reconcile SFR(Lyα) with the total star formation rate. Conclusions: The dust is not necessarily the main Lyα escape regulatory factor. ISM kinematics and geometry may play a more significant role. The failure of simple dust correction to recover the intrinsic Lyα/Hα ratio or the total star formation rate should prompt us to be more cautious when interpreting high-z observations and related properties, such as SFRs based on Lyα alone. To this end, we propose a more realistic calibration for SFR(Lyα), which accounts for dust attenuation and resonant scattering effects via the Lyα escape fraction.
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| 10. |
- Beckman, John, et al.
(författare)
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The Tremaine-Weinberg method for pattern speeds using H-alpha emission from ionized gas
- 2008
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Ingår i: Formation and Evolution of Galaxy Disks. - : Astronomical Society of the Pacific. - 9781583816622 ; , s. 353-
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Konferensbidrag (populärvet., debatt m.m.)abstract
- The Fabry-Perot interferometer FaNTOmM was used at the 3.6m Canada France Hawaii Telescope and the 1.6m Mont Megantic Telescope to obtain data cubes in H-alpha of 9 nearby spiral galaxies from which maps in integrated intensity, velocity, and velocity dispersion were derived. We then applied the Tremaine-Weinberg method, in which the pattern speed can be deduced from its velocity field, by finding the integrated value of the mean velocity along a slit parallel to the major axis weighted by the intensity and divided by the weighted mean distance of the velocity points from the tangent point measured along the slit. The measured variables can be used either to make separate calculations of the pattern speed and derive a mean, or in a plot of one against the other for all the points on all slits, from which a best fit value can be derived. Linear fits were found for all the galaxies in the sample. For two galaxies a clearly separate inner pattern speed with a higher value, was also identified and measured.
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