Near infrared observations of quasars with extended ionized envelopes

We have observed a sample of 15 and 8 quasars with redshifts between 0.11 and 0.87 (mean value 0.38) in the J and K' bands respectively. Eleven of the quasars were previously known to be associated with extended emission line regions. After deconvolution of the image, substraction of the PSF when possible, and identification of companions with the help of HST archive images when available, extensions are seen for at least eleven quasars. However, average profiles are different from that of the PSF in only four objects, for which a good fit is obtained with an $r^{1/4}$ law, suggesting that the underlying galaxies are ellipticals. Redshifts were available in the literature for surrounding objects in five quasar fields. For these objects, one to five companion galaxies were found. One quasar even belongs to a richness class 1 cluster. Most other quasars in our sample have nearby galaxies in projection which may also be companions. Environmental effects are therefore probably important to account for the properties of these objects.Comment: Accepted for publication in A&A

Integral field spectroscopy of the radio galaxy 3C 171

We have performed integral field spectroscopy of the radio galaxy 3C 171 (redshift z=0.238) with the TIGER instrument at the Canada France Hawaii telescope in the Hbeta-[OIII]4959-5007 wavelength region. We present the reconstructed Hbeta and [OIII] images and compare them to the HST and radio maps. We discuss the variations of the [OIII]/Hbeta line ratio throughout the nebulosity. We also analyze the velocity field in detail, in particular the presence of several components. We find that the kinematics derived with emission lines in the central region (inside 1 arcsec) are compatible with a disk-like rotation of low amplitude (50 km/s). The continuum surface brightness profile follows an r^{1/4} law, suggesting that the underlying galaxy is an elliptical with an effective radius of 15 kpc. We have fit two components in the region centered 2.7 arcsec to the West and of extension 3 arcsec^2. We find that the blueshifted component is an extension of the central part, whereas the second one is redshifted by 600 km/s. In both components, line ratios and FWHM are compatible with the presence of shocks induced by jet-cloud interactions.Comment: 8 pages, 15 figures. Accepted for publication in A&A Main Journal (July, 3rd

Transforming triangulations on non planar-surfaces

We consider whether any two triangulations of a polygon or a point set on a non-planar surface with a given metric can be transformed into each other by a sequence of edge flips. The answer is negative in general with some remarkable exceptions, such as polygons on the cylinder, and on the flat torus, and certain configurations of points on the cylinder.Comment: 19 pages, 17 figures. This version has been accepted in the SIAM Journal on Discrete Mathematics. Keywords: Graph of triangulations, triangulations on surfaces, triangulations of polygons, edge fli

Integrating reproduction and energy metabolism:A round way trip via RF-amide peptides

Reproduction is a process that requires a tight and appropriate metabolic status to ensure the correct development and survival of the offspring. In nature, animals match and anticipate the environmental conditions with their energy supplies and the timing of gestation and delivery. We now know that the control of reproduction, food intake and body weight is centrally located in the hypothalamus. Two specific populations of RF-amide peptide-producing neurons, Kisspeptin and RFRP-3, are upstream to the control of the hypothalamic pituitary gonadal axis. In the last 16 years, these RF-amides have also been implicated in the control of food intake and body weight regulation. We studied the effects of these two peptides on energy metabolism in two animal models: the seasonal reproductive Djungarian hamster and the Wistar rat. Overall, we found clear effects of the RF-amides in the central nervous system on energy metabolism in both species. Djungarian hamsters showed changes in food intake and body weight, mainly in the adipose tissue, whereas the Wistar rats changed their food intake, lipid metabolism and glucose homeostasis. In addition, we showed that the hypothalamic expression of both RF-amides is also influenced by cold environment in rats and that metabolic seasonal adaptations are dampened by an obesogenic diet in the hamsters. With this thesis we confirm that kisspeptin and RFRP-3, originally described for their implication in the control of reproduction, are also involved in the central regulation of energy metabolism, which reinforces our hypothesis that these peptides play a role in the central coordination of reproductive and metabolic functions