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[en] The first complete mapping of a galaxy has just been carried out. It is the very complex structure of the interstellar gas of the M 33 galaxy which has been revealed with the help of the Zelentchuk telescope in the Soviet Union. Hollow spherical bubbles, with a diameter from 500 to 800 light-year, have been observed
[fr]On vient de realiser la premiere cartographie complete d'une galaxie. La structure complete du gaz interstellaire de la galaxie M 33 a pu etre determinee grace au telescope de Zelentchuk en Union sovietique. La structure de l'hydrogene ionise general a ete recherchee et des bulles spheriques creuses d'un diametre de 500 a 800 annees lumiere ont ete observees
[en] We propose that 14 co-moving groups of stars uncovered by Kounkel & Covey may be related to known nearby moving groups and bridge those and nearby open clusters with similar ages and space velocities. This indicates that known nearby moving groups may be spatially much more extended than previously thought, and some of them might be parts of tidal tails around the cores of known open clusters, reminiscent of those recently found around the Hyades and a handful of other nearby clusters. For example, we find that both the nearby Carina and Columba associations may be linked to Theia 208 from Kounkel & Covey and together form parts of a large tidal tail around the Platais 8 open cluster. The AB Doradus moving group and Theia 301 may form a trailing tidal tail behind the Pleiades open cluster, with hints of a possible leading tidal tail in Theia 369. Similarly, we find that IC 2391 and its tidal tails identified by Meingast et al. may be extended by the nearby Argus association and are possibly further extended by Theia 115. The nearby Octans and Octans-Near associations, as well as Theia 94 and 95, may form a large tidal tail leading the poorly studied Platais 5 open cluster candidate. While a preliminary analysis of Gaia color–magnitude sequences hint that these structures are plausibly related, more observational evidence is still required to corroborate their consistent ages and space velocities. These observations may change our current understanding of nearby moving groups and the different pathways through which they can form. While some moving groups may have formed loosely in extended star formation events with rich spatial structure, others may in fact correspond to the tidal tails of nearby open clusters.
[en] Herein we present a laboratory rotational study of cyanoacetic acid (CH2(CN)C(O)OH), an organic acid as well as a –CN-bearing molecule, which is a candidate molecular system to be detected in the interstellar medium (ISM). Our investigation aims to provide direct experimental frequencies of cyanoacetic acid to guide its eventual astronomical search in low-frequency surveys. Using different jet-cooled rotational spectroscopic techniques in the time domain, we have determined a precise set of the relevant rotational spectroscopic constants, including the 14N nuclear quadrupole coupling constants for the two distinct structures, cis- and gauche-cyanoacetic acid. We believe this work will potentially allow the detection of cyanoacetic acid in the ISM, whose rotational features have remained unknown until now.
[en] Atomic and molecular clouds in the interstellar medium formed through the cooling of regions of hot gas. Here the collapse of a cooling protocloud is investigated: confinement is by an ambient medium rather than gravity. Large-scale thermal and magnetic pressure gradients across the cloud guide the collapse. The hot cloud is kept close to uniform by a short sound-crossing time. Prolate and oblate clouds with criteria for internal shock formation are analysed. Cool discs and filaments are formed from the spheroidal protoclouds. The type of collapse and final sheet column density depends sensitively on the cooling function. Further collapse, if constrained to take place along field lines, then produces cold filamentary structures and striated sheets. (author). 17 refs.; 2 figs
[en] The application of the red-infrared comparison to the Palomar plate 18h 48m + 120 allowed to identify four hitherto unknown planetary nebulae, almost doubling the number of such objects known in this field. Three of these new planetary nebulae are compact, distant and highly obscured objects; by contrast, the fourth appears extended and weak and represents a planetary nebulae in a very late evolutionary phase
[en] We present Gould's Belt (GB) Spitzer IRAC and MIPS observations of the Lupus V and VI clouds and discuss them in combination with near-infrared (2MASS) data. Our observations complement those obtained for other Lupus clouds within the frame of the Spitzer Core to Disk(c2d) Legacy Survey. We found 43 young stellar object (YSO) candidates in Lupus V and 45 in Lupus VI, including two transition disks, using the standard c2d/GB selection method. None of these sources was classified as a pre-main-sequence star from previous optical, near-IR, and X-ray surveys. A large majority of these YSO candidates appear to be surrounded by thin disks (Class III; ∼79% in Lupus V and ∼87% in Lupus VI). These Class III abundances differ significantly from those observed for the other Lupus clouds and c2d/GB surveyed star-forming regions, where objects with optically thick disks (Class II) dominate the young population. We investigate various scenarios that can explain this discrepancy. In particular, we show that disk photoevaporation due to nearby OB stars is not responsible for the high fraction of Class III objects. The gas surface densities measured for Lupus V and VI lie below the star formation threshold (AV ∼ 8.6 mag), while this is not the case for other Lupus clouds. Thus, few Myr older age for the YSOs in Lupus V and VI with respect to other Lupus clouds is the most likely explanation of the high fraction of Class III objects in these clouds, while a higher characteristic stellar mass might be a contributing factor. Better constraints on the age and binary fraction of the Lupus clouds might solve the puzzle but require further observations.
[en] Interstellar dark clouds are the sites of star formation. Their main component, dihydrogen, exists under two states, ortho and para. H2 is supposed to form in the ortho:para ratio (OPR) of 3:1 and to subsequently decay to almost pure para-H2 (OPR ≤ 0.001). Only if the H2 OPR is low enough, will deuteration enrichment, as observed in the cores of these clouds, be efficient. The second condition for strong deuteration enrichment is the local disappearance of CO, which freezes out onto grains in the core formation process. We show that this latter condition does not apply to DCO+, which, therefore, should be present all over the cloud. We find that an OPR ≥ 0.1 is necessary to prevent DCO+ large-scale apparition. We conclude that the inevitable decay of ortho-H2 sets an upper limit of ∼6 million years to the age of starless molecular clouds under usual conditions.