Hot and dense water in the inner 25 AU of SVS13-A

In the context of the ASAI (Astrochemical Surveys At IRAM) project, we carried out an unbiased spectral survey in the millimeter window towards the well known low-mass Class I source SVS13-A. The high sensitivity reached (3-12 mK) allowed us to detect at least 6 HDO broad (FWHM ~ 4-5 km/s) emission lines with upper level energies up to Eu = 837 K. A non-LTE LVG analysis implies the presence of very hot (150-260 K) and dense (> 3 10^7 cm-3) gas inside a small radius ($\sim$ 25 AU) around the star, supporting, for the first time, the occurrence of a hot corino around a Class I protostar. The temperature is higher than expected for water molecules are sublimated from the icy dust mantles (~ 100 K). Although we cannot exclude we are observig the effects of shocks and/or winds at such small scales, this could imply that the observed HDO emission is tracing the water abundance jump expected at temperatures ~ 220-250 K, when the activation barrier of the gas phase reactions leading to the formation of water can be overcome. We derive X(HDO) ~ 3 10-6, and a H2O deuteration > 1.5 10-2, suggesting that water deuteration does not decrease as the protostar evolves from the Class 0 to the Class I stage.Comment: MNRAS Letter

A primordial origin for molecular oxygen in comets: a chemical kinetics study of the formation and survival of O₂ ice from clouds to discs

Molecular oxygen has been confirmed as the fourth most abundant molecule in cometary material (O2/H2O ∼ 4 per cent) and is thought to have a primordial nature, i.e. coming from the interstellar cloud from which our Solar system was formed. However, interstellar O2 gas is notoriously difficult to detect and has only been observed in one potential precursor of a solar-like system. Here, the chemical and physical origin of O2 in comets is investigated using sophisticated astrochemical models. Three origins are considered: (i) in dark clouds; (ii) during forming protostellar discs; and (iii) during luminosity outbursts in discs. The dark cloud models show that reproduction of the observed abundance of O2 and related species in comet 67P/C-G requires a low H/O ratio facilitated by a high total density (≥105 cm−3), and a moderate cosmic ray ionization rate (≤10−16 s−1) while a temperature of 20 K, slightly higher than the typical temperatures found in dark clouds, also enhances the production of O2. Disc models show that O2 can only be formed in the gas phase in intermediate disc layers, and cannot explain the strong correlation between O2 and H2O in comet 67P/C-G together with the weak correlation between other volatiles and H2O. However, primordial O2 ice can survive transport into the comet-forming regions of discs. Taken together, these models favour a dark cloud (or ‘primordial’) origin for O2 in comets, albeit for dark clouds which are warmer and denser than those usually considered as Solar system progenitors

Nouvelle découverte d'empreintes laissées par des dinosaures dans la formation des couches rouges (bassin de Cuzco-Sicuani, Sud du Pérou) : conséquences stratigraphiques et tectoniques

La découverte d'empreintes laissées par le dinosaures vers le sommet de la formation des Couches Rouges permet de préciser la stratigraphie du Sud du Pérou. La durée de la sédimentation continentale du bassin de Cuzco-Sicuani n'excéderait pas 20 Ma (santonien - paléocène) et non plus 45 Ma, comme cela était jusqu'à présent admis. Le bassin d'avant-pays de Cuzco-Sicuani est caractérisé par une déformation synsédimentaire essentiellement compressive pendant toute la durée de la sédimentation des "Couches Rouges". En conséquence, une durée équivalente à celle de cette sédimentation peut être retenue pour ces événements tectoniques qui marquent ici le début de la surrection de la chaîne andine. La phase péruvienne, traditionnellement placée vers 85 Ma, représenterait ainsi le début de ces événements tectoniques. (Résumé d'auteur

Genetic connectivity of the coral-eating sea star Acanthaster planci during the severe outbreak of 2006&8211;2009 in the Society Islands, French Polynesia

Occasional population outbreaks of the crown-of-thorns sea star, Acanthaster planci, are a major threat to coral reefs across the Indo-Pacific. The presumed association between the serial nature of these outbreaks and the long larval dispersal phase makes it important to estimate larval dispersal; many studies have examined the population genetic structure of A. planci for this purpose using different genetic markers. However, only a few have focused on reef-scale as well as archipelago-scale genetic structure and none has used a combination of different genetic markers with different effective population sizes. In our study, we used both mtDNA and microsatellite loci to examine A. planci population genetic structure at multiple spatial scales (from <2 km to almost 300 km) within and among four islands of the Society Archipelago, French Polynesia. Our analysis detected no significant genetic structure based on mtDNA (global FST = &#8722;0.007, P = 0.997) and low levels of genetic structure using microsatellite loci (global FST = 0.006, P = 0.005). We found no significant isolation by distance patterns within the study area for either genetic marker. The overall genetically homogenized pattern found in both the mitochondrial and nuclear loci of A. planci in the Society Archipelago underscores the significant role of larval dispersal that may cause secondary outbreaks, as well as possible recent colonization in this area

The census of interstellar complex organic molecules in the Class I hot corino of SVS13-A

We present the first census of the interstellar Complex Organic Molecules (iCOMs) in the low-mass Class I protostar SVS13-A, obtained by analysing data from the IRAM-30m Large Project ASAI (Astrochemical Surveys At IRAM). They consist of an high-sensitivity unbiased spectral survey at the 1mm, 2mm and 3mm IRAM bands. We detected five iCOMs: acetaldehyde (CH$_3$CHO), methyl formate (HCOOCH$_3$), dimethyl ether (CH$_3$OCH$_3$), ethanol (CH$_3$CH$_2$OH) and formamide (NH$_2$CHO). In addition we searched for other iCOMs and ketene (H$_2$CCO), formic acid (HCOOH) and methoxy (CH$_3$O), whose only ketene was detected. The numerous detected lines, from 5 to 37 depending on the species, cover a large upper level energy range, between 15 and 254 K. This allowed us to carry out a rotational diagram analysis and derive rotational temperatures between 35 and 110 K, and column densities between $3\times 10^{15}$ and $1\times 10^{17}$ cm$^{-2}$ on the 0."3 size previously determined by interferometric observations of glycolaldehyde. These new observations clearly demonstrate the presence of a rich chemistry in the hot corino towards SVS13-A. The measured iCOMs abundances were compared to other Class 0 and I hot corinos, as well as comets, previously published in the literature. We find evidence that (i) SVS13-A is as chemically rich as younger Class 0 protostars, and (ii) the iCOMs relative abundances do not substantially evolve during the protostellar phase.Comment: 24 pages, MNRAS in pres

Deuterated water in the solar-type protostars NGC 1333 IRAS 4A and IRAS 4B

Aims. The aim of this paper is to study deuterated water in the solar-type protostars NGC1333 IRAS4A and IRAS4B, to compare their HDO abundance distribution with other star-forming regions, and to constrain their HDO/H2O ratios. Methods. Using the Herschel/HIFI instrument as well as ground-based telescopes, we observed several HDO lines covering a large excitation range (Eup/k=22-168 K) towards these protostars and an outflow position. Non-LTE radiative transfer codes were then used to determine the HDO abundance profiles in these sources. Results. The HDO fundamental line profiles show a very broad component, tracing the molecular outflows, in addition to a narrower emission component and a narrow absorbing component. In the protostellar envelope of NGC1333 IRAS4A, the HDO inner (T>100 K) and outer (T<100 K) abundances with respect to H2 are estimated at 7.5x10^{-9} and 1.2x10^{-11}, respectively, whereas, in NGC1333 IRAS4B, they are 1.0x10^{-8} and 1.2x10^{-10}, respectively. Similarly to the low-mass protostar IRAS16293-2422, an absorbing outer layer with an enhanced abundance of deuterated water is required to reproduce the absorbing components seen in the fundamental lines at 465 and 894 GHz in both sources. This water-rich layer is probably extended enough to encompass the two sources as well as parts of the outflows. In the outflows emanating from NGC1333 IRAS4A, the HDO column density is estimated at about (2-4)x10^{13} cm^{-2}, leading to an abundance of about (0.7-1.9)x10^{-9}. An HDO/H2O ratio between 7x10^{-4} and 9x10^{-2} is derived in the outflows. In the warm inner regions of these two sources, we estimate the HDO/H2O ratios at about 1x10^{-4}-4x10^{-3}. This ratio seems higher (a few %) in the cold envelope of IRAS4A, whose possible origin is discussed in relation to formation processes of HDO and H2O.Comment: 16 pages, 13 figure