Foreword 1. The wavelet transform 2. Multiresolution support and filtering 3. Deconvolution 4. 1-D signals and Euclidean-based data analysis 5. Geometric registration 6. Disparity analysis and applications in remote sensing 7. Image compression 8. Object detection and point pattern clustering 9. Multiscale vision models Appendix I. Variance stabilisation Appendix II. Software information Acronyms References Index.

Image Processing and Data Analysis: The Multiscale Approach

We determine the most likely values of the free parameters of an N-body model for the Galaxy developed by Fux via a discrete–discrete comparison with the positions on the sky and line-of-sight velocities of an unbiased, homogeneous sample of OH/IR stars. Via Monte Carlo simulation, we find the plausibility of the best-fitting models, as well as the errors on the determined values. The parameters that are constrained best by these projected data are the total mass of the model and the viewing angle of the central bar, although the distribution of the latter has multiple maxima. The other two free parameters, the size of the bar and the (azimuthal) velocity of the Sun, are less well-constrained. The best model has a viewing angle of ∼ 44°, a semimajor axis of 2.5 kpc (corotation radius 4.5 kpc, pattern speed 46 km s−1 kpc−1), a bar mass of 1.7×1010 M⊙ and a tangential velocity of the local standard of rest of 171 km s−1. We argue that the lower values that are commonly found from stellar data for the viewing angle (∼25°) arise when too few coordinates are available, when the longitude range is too narrow or when low latitudes are excluded from the fit. The new constraints on the viewing angle of the Galactic bar from stellar line-of-sight velocities decrease further the ability of the distribution of the bar to account for the observed microlensing optical depth toward Baade’s window: our model reproduces only half the observed value. The signal of triaxiality diminishes quickly with increasing latitude, fading within approximately 1 scaleheight (≲3°). This suggests that Baade’s window is not a very appropriate region in which to sample bar properties.

/pdf/new-constraints-on-a-triaxial-model-of-the-galaxy-2aranx1e7g.pdf

New constraints on a triaxial model of the Galaxy

The available data on the microwave spectrum of the hydroxyl radical are critically reviewed for information applicable to radio astronomy Molecular properties such as the rotational constants, spin‐orbit, spin‐spin and hyperfine coupling constants and centrifugal distortion parameters employed in or derived from the analysis are tabulated All the observed and predicted transitions of 16OH, 16OD, and 18OH below 300 GHz and lower state energy levels less than 4000 cm−1 are presented for the ground vibrational state The laboratory data on 17OH is included, but no predicted transitions are presented due to the limited data available In addition to the transition frequencies the table contains the calculated line strengths and energies of the levels involved in the transition An extensive bibliography of laboratory and astronomical studies of the hydroxyl radical is presented as an aid to workers in both fields

Microwave spectra of molecules of astrophysical interest XII. Hydroxyl radical

We determine the values of parameters of an N-body model for the Galaxy developed by Fux via comparison with an unbiased, homogeneous sample of OH/IR stars. Via Monte-Carlo simulation, we find the plausibilities of the best-fitting models, as well as their errors. The parameters that are constrained best by these projected data are the total mass of the model and the viewing angle of the central Bar, although the distribution of the latter has multiple maxima. The best model has a viewing angle of 44 degrees, semi-major axis of 2.5 kpc, a bar mass of 1.7E10 solar masses and a tangential velocity of the local standard of rest of 171 km/s . We argue that the lower values that are commonly found from stellar data for the viewing angle (around 25 degrees) arise when too few coordinates are available, when the longitude range is too narrow or when low latitudes are excluded from the fit. The new constraints on the viewing angle of the galactic Bar from stellar line-of-sight velocities decrease further the ability of the Bar's distribution to account for the observed micro-lensing optical depth toward Baade's window : our model reproduces only half the observed value. The signal of triaxiality diminishes quickly with increasing latitude, fading within approximately one scaleheight. This suggests that Baade's window is not a very appropriate region to sample Bar properties.

A second argument in this direction was given by several astronomers in the 1950's. It had long been known from the double peaked emission lines observed in the nebulae, that they were expanding. The velocity of expansion is on the average 15 to 20 km s -t, with only exceptional cases differing by more than a factor 2 from this value. Since this nebular material presumably escaped from the central star, the question was asked: which stars have an escape velocity of the order of 20 km s-t? The answer is Red Giants. On considering this answer, other reasons for its correctness became apparent. A red giant actually has the characteristics of an early stage of a PN. Much of its mass is present in a high density core which could easily be the forerunner of the PN central star. Some of its mass is present in the enormous giant atmosphere which could easily become the nebula. It only remained to set the giant atmosphere in motion at the escape velocity. The solution the star has chosen to solve this problem is not yet completely understood. It is clear however that the mass lost by the star to form a PN occurs at a stage prior to its being observed as a PN. Thus the previous stage, whether OH/IR star, Mira variables and other types of red giants will also be discussed.

Evolution of planetary nebulae

USING the 25-m radiotelescope at Dwingeloo, we have recently completed the initial stages of a large scale OH survey. The detailed results will be reported later. The survey is designed to yield an unbiased set of data for all four 18-cm lines of OH.

A very high velocity 1,612-MHz OH source near the galactic centre

A systematic search at 1612 MHz for OH maser sources.

La recherche de la raie d'emission OH a 1612 MHz dans une zone de 1° de rayon autour du centre galactique a permis la detection de 52 sources ponctuelles dont 34 etoiles OH/IR. Bien que la recherche ait ete affectee d'importants effets de selection, on a pu montrer que les etoiles ont une distribution reelle autour du centre galactique identique a celle des geantes rouges, mesurees a 2,4μm. La vitesse radiale moyenne des etoiles varie lineairement avec la longitude dans la direction de la rotation galactique, de Okms −1 a 1=0° a +200 kms −1 a 1=+1°; la dispersion est large, 140 a 160 km −1 . On a deduit la distribution de la masse totale au voisinage du centre a partir de considerations dynamiques

OH/IR stars within one degree of the galactic centre

A systematic search at 1612 MHz for OH maser sources. I - Survey near the Galactic Centre

Utilisation du VLA a 1612 MHz pour etudier la structure de onze etoiles OH/IR, dans leur emission OH. Les etoiles etant a la distance du point tangentiel, leur mesure permet une estimation independante de la distance du centre galactique (9,2±1,2 kpc)

/pdf/vla-line-observations-of-oh-ir-stars-2ngzsllwt9.pdf

VLA line observations of OH/IR stars

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