| 1. |
- Font, Joan, et al.
(författare)
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The ratio of pattern speeds in double-barred galaxies
- 2014
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966 .- 1745-3933 .- 1745-3925. ; 444:1, s. l85-L89
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Tidskriftsartikel (refereegranskat)abstract
- We have obtained two-dimensional velocity fields in the ionized gas of a set of eight double-barred galaxies, at high spatial and spectral resolution, using their H alpha emission fields measured with a scanning Fabry-Perot spectrometer. Using the technique by which phase reversals in the non-circular motion indicate a radius of corotation, taking advantage of the high angular and velocity resolution, we have obtained the corotation radii and the pattern speeds of both the major bar and the small central bar in each of the galaxies; there are few such measurements in the literature. Our results show that the inner bar rotates more rapidly than the outer bar by a factor between 3.3 and 3.6.
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| 2. |
- Karlsson, Roland, 1948-, et al.
(författare)
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Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the Sgr A complex
- 2014
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 9:303, s. 97-99
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Tidskriftsartikel (refereegranskat)abstract
- We observed Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the +50 km s−1 cloud (M−0.02−0.07), the circumnuclear disk (CND) and the +20 km s−1 (M−0.13−0.08) cloud in the Sgr A complex with the VLA, Odin and SEST. Strong OH absorption, H2O emission and absorption lines were seen at all three positions. Strong C18O emissions were seen towards the +50 and +20 km s−1 clouds. The CND is rich in H2O and OH, and these abundances are considerably higher than in the surrounding clouds, indicating that shocks, star formation and clump collisions prevail in those objects. A comparison with the literature reveals that it is likely that PDR chemistry including grain surface reactions, and perhaps also the influences of shocks has led to the observed abundances of the observed molecular species studied here. In the redward high-velocity line wings of both the +50 and +20 km s−1 clouds and the CND, the very high H2O abundances are suggested to be caused by the combined action of shock desorption from icy grain mantles and high-temperature, gas-phase shock chemistry. Only three of the molecules are briefly discussed here. For OH and H2O three of the nine observed positions are shown, while a map of the C18O emission is provided. An extensive paper was recently published with Open Access (Karlsson et al. 2013, A&A 554, A141).
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| 3. |
- Piñol-Ferrer, Nuria, 1984-, et al.
(författare)
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Bar pattern speed and position of the circumnuclear ringin NGC 1097
- 2014
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 438:2, s. 971-982
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Tidskriftsartikel (refereegranskat)abstract
- We present the first galactic-scale model of the gas dynamics of the prototype barred Seyfert 1 galaxy NGC 1097. We use large scale FaNTOmM Fabry-Perot interfer-ometric data covering the entire galactic disc and combined the distribution andkinematics maps with high resolution two-dimensional spectroscopy from the Gemini telescope. We build a dynamical model for the gravitational potential by applying the analytic solution to the equations of motion, with in the epicyclic approximation. Our model reproduces all the significant kinematic and structural signatures of thisgalaxy. We find that the primary bar is 7.9±0.6 kpc long and has a pattern speedof 36 ± 2 km s−1 kpc−1. This places the corotation radius at 8.6±0.5 kpc, the outer Lindblad resonance at 14.9±0.9 kpc and two inner Lindblad resonances at 60±5 pcand 2.9±0.1 kpc. These derivations lead to a ratio of the corotation radius over barlength of 1.0–1.2, which is in concordance with simulations of barred galaxies. Our model presents evidence that the circumnuclear ring in this galaxy is not located near any of the resonance radii in this galaxy. The ring might have once formed at the outer inner Lindblad resonance radius, and it has been migrating inward, toward the centre of the galactic gravitational potential.
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