Djeffara

La Djeffara est cette vaste plaine du Sud tunisien qui s’étend à l’est du Dahar* et se prolonge en Tripolitaine. Elle est peuplée de semi-nomades en voie de rapide sédentarisation. Les tribus devenues arabophones des Touazin, Khezour et Ouderma, sont regroupées sous le nom d’Ouerghemma. Ces Ouerghemma refoulés dans le Dahar par les « Arabes » sont aujourd’hui en grande partie redescendus dans la plaine en oubliant leur origine berbère. A l’exemple des Djebalia du Dahar, ces pasteurs de la pla..

Antifreeze in the hot core of Orion - First detection of ethylene glycol in Orion-KL

Comparison of their chemical compositions shows, to first order, a good agreement between the cometary and interstellar abundances. However, a complex O-bearing organic molecule, ethylene glycol (CH$_{2}$OH)$_{2}$, seems to depart from this correlation because it was not easily detected in the interstellar medium although it proved to be rather abundant with respect to other O-bearing species in comet Hale-Bopp. Ethylene glycol thus appears, together with the related molecules glycolaldehyde CH$_{2}$OHCHO and ethanol CH$_{3}$CH$_{2}$OH, as a key species in the comparison of interstellar and cometary ices as well as in any discussion on the formation of cometary matter. We focus here on the analysis of ethylene glycol in the nearest and best studied hot core-like region, Orion-KL. We use ALMA interferometric data because high spatial resolution observations allow us to reduce the line confusion problem with respect to single-dish observations since different molecules are expected to exhibit different spatial distributions. Furthermore, a large spectral bandwidth is needed because many individual transitions are required to securely detect large organic molecules. Confusion and continuum subtraction are major issues and have been handled with care. We have detected the aGg' conformer of ethylene glycol in Orion-KL. The emission is compact and peaks towards the Hot Core close to the main continuum peak, about 2" to the south-west; this distribution is notably different from other O-bearing species. Assuming optically thin lines and local thermodynamic equilibrium, we derive a rotational temperature of 145 K and a column density of 4.6 10$^{15}$ cm$^{-2}$. The limit on the column density of the gGg' conformer is five times lower.Comment: 19 pages, 10 figures, A&A accepte

Alfa

On confond habituellement sous le nom de ḥalfa (alfa) deux plantes assez voisines : l’alfa véritable (stipa tenacissima) dont la feuille se replie en demi-gaine et l’épi rappelle un peu celui de l’orge, et le lygée ou sparte « fol alpha» (lygeum spartum), aux dimensions plus réduites, à l’allure plus raide; encore que les gens du Sud tunisien désignent le premier par geddīm et le lygée par ḥalfa. Le premier habite les zones montagneuses et les hauts plateaux ; on le désigne en Tunisie sous le..

Alfa

On confond habituellement sous le nom de ḥalfa (alfa) deux plantes assez voisines : l’alfa véritable (stipa tenacissima) dont la feuille se replie en demi-gaine et l’épi rappelle un peu celui de l’orge, et le lygée ou sparte « fol alpha» (lygeum spartum), aux dimensions plus réduites, à l’allure plus raide; encore que les gens du Sud tunisien désignent le premier par geddīm et le lygée par ḥalfa. Le premier habite les zones montagneuses et les hauts plateaux ; on le désigne en Tunisie sous le..

Beni Snous

Extrait de Géographie de l’Afrique du Nord-Ouest (J. Despois et A. Raynal) Le groupe berbérophone des Beni Snous occupe la Ghaba occidentale, c’est-à-dire l’ensemble des plateaux calcaires de la Haute Tafna à l’ouest-sud-ouest de Tlemcen. La Ghaba est un milieu rude : suffisamment arrosé dans son ensemble (600 à 700 mm) mais froid, avec 10 à 20 chutes de neige par an, des gelées nombreuses, parfois de longues périodes sèches et du siroco. La forêt est plus utile comme pâturage que comme fourn..

Ethylene glycol in comet C/1995 O1 (Hale-Bopp)

We report the detection of ethylene glycol (HOCH_2CH_2OH) in comet C/1995 O1 (Hale-Bopp) from the analysis of archival radio spectra. Its production rate is ≈0.25% that of water, making it one of the most abundant organic molecules in cometary ices. This detection strengthens the similarity between interstellar and cometary material

Beni Snous

Extrait de Géographie de l’Afrique du Nord-Ouest (J. Despois et A. Raynal) Le groupe berbérophone des Beni Snous occupe la Ghaba occidentale, c’est-à-dire l’ensemble des plateaux calcaires de la Haute Tafna à l’ouest-sud-ouest de Tlemcen. La Ghaba est un milieu rude : suffisamment arrosé dans son ensemble (600 à 700 mm) mais froid, avec 10 à 20 chutes de neige par an, des gelées nombreuses, parfois de longues périodes sèches et du siroco. La forêt est plus utile comme pâturage que comme fourn..

The composition of ices in comet C/1995 O1 (Hale-Bopp) from radio spectroscopy - Further results and upper limits on undetected species

From radio spectroscopic observations of comets, more than 22 molecules, radicals and ions, plus several isotopologues, were detected, the majority of them being recently revealed in comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp). Among them, 6 molecules were detected for the first time (Bockelée-Morvan et al. [CITE]) in the course of a spectral survey conducted at radio wavelengths in comet Hale-Bopp with the CSO, the IRAM 30-m telescope and Plateau de Bure interferometer. In addition, many species were searched for unsuccessfully, some of them with stringent upper limits. We present here a review of these observations and further analysis of their results. This include: (i) confirmed detection of acetaldehyde (CH_3CHO); (ii) limits on small molecules such as ketene (H_2CCO) or methanimine (CH_2NH); (iii) limits on the abundance ratios in homologous series such as HC_5N/HC_3N, ethanol/methanol, acetic acid/formic acid; (iv) searches for precursors of key cometary species such as atomic Na and HNC; (v) constraints on more exotic species ranging from water dimer (H_2O)_2 to glycine; (vi) detection of the H_2^(34)S isotopic species and independent observations of HDO and DCN; (vii) limits on several other deuterated species; (viii) limits on several radicals and ions and a tentative detection of the C_2H radical; (ix) the presence of unidentified lines. Typical abundance upper limits of 2–5 x 10^(-4) relative to water are achieved for many species. Better upper limits are obtained for some linear molecules with high dipole moments. But more complex molecules such as dimethyl ether or glycine are poorly constrained. These results should give important clues to the chemical composition of cometary ices, to the formation mechanisms of cometary material, and to the chemical processes which occur in the inner coma