First measurements of 15N fractionation in N2H+ toward high-mass star forming cores

We report on the first measurements of the isotopic ratio 14N/15N in N2H+ toward a statistically significant sample of high-mass star forming cores. The sources belong to the three main evolutionary categories of the high-mass star formation process: high-mass starless cores, high-mass protostellar objects, and ultracompact HII regions. Simultaneous measurements of 14N/15N in CN have been made. The 14N/15N ratios derived from N2H+ show a large spread (from ~180 up to ~1300), while those derived from CN are in between the value measured in the terrestrial atmosphere (~270) and that of the proto-Solar nebula (~440) for the large majority of the sources within the errors. However, this different spread might be due to the fact that the sources detected in the N2H+ isotopologues are more than those detected in the CN ones. The 14N/15N ratio does not change significantly with the source evolutionary stage, which indicates that time seems to be irrelevant for the fractionation of nitrogen. We also find a possible anticorrelation between the 14N/15N (as derived from N2H+) and the H/D isotopic ratios. This suggests that 15N enrichment could not be linked to the parameters that cause D enrichment, in agreement with the prediction by recent chemical models. These models, however, are not able to reproduce the observed large spread in 14N/15N, pointing out that some important routes of nitrogen fractionation could be still missing in the models.Comment: 2 Figures, accepted for publication in ApJ

Ammonia observations in the LBV nebula G79.29+0.46. Discovery of a cold ring and some warm spots

The surroundings of Luminous Blue Variable (LBV) stars are excellent laboratories to study the effects of their high UV radiation, powerful winds, and strong ejection events onto the surrounding gas and dust. The LBV G79.29+0.46 powered two concentric infrared rings which may interact with the infrared dark cloud (IRDC) G79.3+0.3. The Effelsberg 100m telescope was used to observe the NH_3 (1,1), (2,2) emission surrounding G79.29+0.46 and the IRDC. In addition, we observed particular positions in the (3,3) transition toward the strongest region of the IRDC. We report here the first coherent shell-like structure of dense NH_3 gas associated with an evolved massive star. The shell, two or three orders of magnitude more tenuous than the IRDC, is well traced in both ammonia lines, and surrounds the ionized nebula. The NH_3 emission in the IRDC is characterized by a low and uniform rotational temperature (T_rot ~ 10 K) and moderately high opacities in the (1,1) line. The rest of the observed field is spotted by warm or hot zones (T_rot > 30 K) and characterized by optically thin emission of the (1,1) line. The NH_3 abundances are about 10^{-8} in the IRDC, and 10^{-10}-10^{-9} elsewhere. The warm temperatures and low abundances of NH_3 in the shell suggest that the gas is being heated and photo-dissociated by the intense UV field of the LBV star. An outstanding region is found to the south-west (SW) of the LBV star within the IRDC. The NH_3 (3,3) emission at the centre of the SW region reveals two velocity components tracing gas at temperatures > 30K. The northern edge of the SW region agrees with the border of the ring nebula and a region of continuum enhancement; here, the opacity of the (1,1) line and the NH_3 abundance do not decrease as expected in a typical clump of an isolated cold dark cloud. This strongly suggests some kind of interaction between the ring nebula and the IRDC.Comment: 15 pages, 13 figures, accepted by A&A. Note the change of title with respect to previous versio

Resolving the chemical substructure of Orion-KL

The Kleinmann-Low nebula in Orion (Orion-KL) is the nearest example of a high-mass star-forming environment. For the first time, we complemented 1.3 mm Submillimeter Array (SMA) interferometric line survey with IRAM 30 m single-dish observations of the Orion-KL region. Covering a 4 GHz bandwidth in total, this survey contains over 160 emission lines from 20 species (25 isotopologues), including 11 complex organic molecules (COMs). At a spatial resolution of 1200 AU, the continuum substructures are resolved. Extracting the spectra from individual substructures and providing the intensity-integrated distribution map for each species, we studied the small-scale chemical variations in this region. Our main results are: (1) We identify lines from the low-abundance COMs CH3COCH3 and CH3CH2OH, as well as tentatively detect CH3CHO and long carbon-chains C6H and HC7N. (2) We find that while most COMs are segregated by type, peaking either towards the hot core (e.g., N-bearing species) or the compact ridge (e.g., O-bearing species like HCOOCH3 and CH3OCH3), while the distributions of others do not follow this segregated structure (e.g., CH3CH2OH, CH3OH, CH3COCH3). (3) We find a second velocity component of HNCO, SO2, 34SO2, and SO lines, which may be associated with a strong shock event in the low-velocity outflow. (4) Temperatures and molecular abundances show large gradients between central condensations and the outflow regions, illustrating a transition between hot molecular core and shock-chemistry dominated regimes. Our observations of spatially resolved chemical variations in Orion-KL provide the nearest reference source for hot molecular core and outflow chemistry, which will be an important example for interpreting the chemistry of more distant HMSFRs.Comment: 51 pages, 17 figures, accepted on 12 March 2015 Dashed lines in Figure 10 of the published paper was missin

The Spanish Constitution of 1978: Legislative Competence of the Autonomous Communities in Civil Law Matters

The Spanish Constitution of 1978 had to deal with the issues that emerged with the advent of a democratic regime following the death of General Francisco Franco in 1975. Political pluralism, the relationship between church and state, and the official language of the Spanish state were among the dilemmas facing the Constitutional Commission. Yet the historically sensitive issue of the autonomy of the Spanish regions proved to be the most troublesome. Title VIII of the Constitution provides a political compromise in resolution of this issue although scholars and politicians, including some constitutional draftsmen, have criticized the ambiguity of this title. This study focuses on article 149, paragraph 1, section 8 of the Spanish Constitution and the legislative powers granted therein to the autonomous regions in matters of civil law. Not only should it provide some insight into one of the most perplexing clauses of the founding document of post-Franco Spain, but, moreover, it should prove to be an enlightening case study of the interaction between politics and law in the uneasy relationship between Madrid and the present and aspiring autonomous regions of Spain

The coalescent structure of Galton-Watson trees in varying environments

We investigate the genealogy of a sample of k particles chosen uniformly without replacement from a population alive at a large time n in a critical discrete-time Galton-Watson process in a varying environment (GWVE). We will show that subject to an explicit deterministic time-change involving only the mean and variances of the varying offspring distributions, the sample genealogy always converges to the same universal genealogical structure; it has the same tree topology as Kingman's coalescent, and the coalescent times of the k-1 pairwise mergers look like a mixture of independent identically distributed times. Our approach uses k spine particles and a change of measure $\mathbf{Q}_n^{(e,k, \theta)}$ under which the spines form a uniform sample without replacement at time n, as required, but additionally there is k-size biasing and discounting at rate $\theta$ by the population size at time n. We give a forward in time construction for the process with k spines under $\mathbf{Q}_n^{(e,k, \theta)}$ where the k size-biasing provides a great deal of structural independence that enables explicit calculations, and the discounting means that no additional offspring moment assumptions are required. Combining the special properties of $\mathbf{Q}_n^{(e,k, \theta)}$ together with the Yaglom theorem for GWVE, plus a suitable time-change that encodes variation within the environment, we then undo the k-size biasing and discounting to recover the limiting genealogy for a uniform sample of size k in the GWVE. Our work extends the spine techniques developed in Harris, et. al [Annals of Applied Probability, 2020] and complements recent work by Kersting [Proceedings of the Steklov Institute of Mathematics, 2022] which describes the genealogy of the entire extant population in the GWVE in the large time limi

The recent abrupt increase in the precipitation rate, as seen in a ultra-centennial series of precipitation

The authors analyse the ultra-centennial series (1833- 1995) of daily total amounts of precipitation recorded in the Genoa University’s Meteorological Observatory and the precipitation annual rates, investigating any relationship with the recent occurrences of exceptional rainfall. Among the principal results there is a constant decrease in the number of rainy days since the first records and a significative jump of precipitation rate since 1950. The application of the Gumbel method to the Return Time of the Annual Maximum (AM) series, owing to the recent anomalous variations of Annual Maximum daily precipitation (mmO24 h), has revealed an increase of heavy rainfall in the last thirty years. Moreover, the return times of these events are remarkably shortened