Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

The gamma-ray binary LS I +61 303 is composed of a Be star and a compact companion orbiting in an eccentric orbit. Variable flux modulated with the orbital period of ~26.5 d has been detected from radio to very high-energy gamma rays. In addition, the system presents a superorbital variability of the phase and amplitude of the radio outburst with a period of ~4.6 yr. We present optical photometric observations of LS I +61 303 spanning ~1.5 yr and contemporaneous Halpha equivalent width (EW Halpha) data. The optical photometry shows, for the first time, that the known orbital modulation suffers a positive orbital phase shift and an increase in flux for data obtained 1-yr apart. This behavior is similar to that already known at radio wavelengths, indicating that the optical flux follows the superorbital variability as well. The orbital modulation of the EW Halpha presents the already known superorbital flux variability but shows, also for the first time, a positive orbital phase shift. In addition, the optical photometry exhibits a lag of ~0.1-0.2 in orbital phase with respect to the EW Halpha measurements at similar superorbital phases, and presents a lag of ~0.1 and ~0.3 orbital phases with respect noncontemperaneous radio and X-ray outbursts, respectively. The phase shifts detected in the orbital modulation of thermal indicators, such as the optical flux and the EW Halpha, are in line with the observed behavior for nonthermal indicators, such as X-ray or radio emission. This shows that there is a strong coupling between the thermal and nonthermal emission processes in the gamma-ray binary LS I +61 303. The orbital phase lag between the optical flux and the EW Halpha is naturally explained considering different emitting regions in the circumstellar disk, whereas the secular evolution might be caused by the presence of a moving one-armed spiral density wave in the disk.Comment: 4 pages, 3 figures, accepted for publication in A&A (this version matches the published version

Properties of Galaxy Groups in the SDSS: II.- AGN Feedback and Star Formation Truncation

Successfully reproducing the galaxy luminosity function and the bimodality in the galaxy distribution requires a mechanism that can truncate star formation in massive haloes. Current models of galaxy formation consider two such truncation mechanisms: strangulation, which acts on satellite galaxies, and AGN feedback, which predominantly affects central galaxies. The efficiencies of these processes set the blue fraction of galaxies as function of galaxy luminosity and halo mass. In this paper we use a galaxy group catalogue extracted from the Sloan Digital Sky Survey (SDSS) to determine these fractions. To demonstrate the potential power of this data as a benchmark for galaxy formation models, we compare the results to the semi-analytical model for galaxy formation of Croton et al. (2006). Although this model accurately fits the global statistics of the galaxy population, as well as the shape of the conditional luminosity function, there are significant discrepancies when the blue fraction of galaxies as a function of mass and luminosity is compared between the observations and the model. In particular, the model predicts (i) too many faint satellite galaxies in massive haloes, (ii) a blue fraction of satellites that is much too low, and (iii) a blue fraction of centrals that is too high and with an inverted luminosity dependence. In the same order, we argue that these discrepancies owe to (i) the neglect of tidal stripping in the semi-analytical model, (ii) the oversimplified treatment of strangulation, and (iii) improper modeling of dust extinction and/or AGN feedback. The data presented here will prove useful to test and calibrate future models of galaxy formation and in particular to discriminate between various models for AGN feedback and other star formation truncation mechanisms.Comment: 16 pages, 5 figures, submitted to MNRA

Aplicación de la genética en la identificación de enfermedades infecciosas bucodentales

La genética ha supuesto una gran revolución en la identificación de seres vivos a través de análisis de ADN. Actualmente se investiga la pos1bilidad de aplicarla en el estudio de nuestros antepasados, desde el hombre prehistórico. En el ámbito de la odontologfa se vislumbran nuevas perspectivas en el estudio de la patologfa infecciosa, gracias a estos avances en biologfia molecular. El presente trabajo pretende repasar cuál ha sido esta patología infecciosa en el hombre del pasado y cuáles son Jos métodos de análisis genético que penniten estudiarla. Fundamentalmente, las infecciones bucodentales del hombre prehistórico se resumen en caries y patología periodontal. La RCP (reacción en cadena de la polimerasa) es la técnica que ha revolucionado la ingeniería genética, pues permite obtener copias del ADN para poder ser analizado y, con ello, ofrece un diagnóstico específico de la etiología de las enfermedades infecciosas, lográndose una identificación más precisa que con el cultivo o con la inmunohistoquímica de las bacterias, hongos y virus que conviven en el medio oral

L’impacte de la cabra (Capra hircus) sobre el teix (Taxus baccata) a l’illa de Mallorca

[cat] El teix Taxus baccata a les Balears es troba únicament a la Serra de Tramuntana, està protegit com d’Especial Protecció i és objecte d’un Pla de Maneig executat per la Conselleria de Medi Ambient del Govern de les Illes Balears. La forta pressió de les cabres Capra hircus, incrementada els darrer decennis per l’abandonament de les finques i l’agricultura, és una amenaça que fa perillar el futur del teix. El present treball completa i revisa l’inventari de teixos naturals a la Serra i avalua el seu estat de conservació en funció del grau d’afectació per les cabres assilvestrades. Un 70% dels teixos silvestres pateixen impactes visibles provocats per les cabres. Tot i que la majoria de teixos es trobem empenyalats, la gran majoria (un 84%) pateix un grau d’afectació moderat; el 14% restant presenta una afectació greu, amb una clara amenaça per a la seva supervivència. Els teixos menys afectats són els més difícilment accessibles, i no hi ha cap opció de que puguin créixer amb normalitat a un lloc on arribin les cabres. Ara que ja no es talla ni es permeten les cremes descontrolades, el teix podria tenir unes poblacions més nombroses, tot i que les elevades temperatures estivals i la disminució de les precipitacions, com a conseqüència del canvi climàtic, podrien esdevenir un factor limitant. Avui, però, el principal factor limitant no natural que afecta les poblacions de teix a Mallorca és la pressió que exerceixen les cabres assilvestrades les quals, en molts de casos, poden arribar a provocar la mort dels exemplars.[eng] The yew Taxus baccata in the Balearic Islands is only in the Serra de Tramuntana. It is under Special Protection category and is object of a Management Plan executed by the Balearic Environmental Administration. The strong pressure of goats Capra hircus, increased over the last decades due to the abandonment of farms and agriculture, is a threat that endangers yews future. The present report completes and reviews the inventory of natural yews in the Serra and evaluates its state of conservation based on the degree of involvement by the wild goats. 70% of natural yews suffer visible impacts caused by goats. Although most yews are in cliffs, the vast majority (84%) suffers a moderate degree of threat; the remaining 14% have a serious affectation, with a clear threat to their survival. The least-affected yews are the most difficult to reach, and there is no option to grow normally on a goat's place. Now that neither the cutting of yew or the uncontrolled burning are not allowed, the yew tree could have larger populations, although the high summer temperatures and the decrease of the precipitations, as a consequence of the climate change, could become a limiting factor. Today, however, the main unnatural limiting factor affecting yew populations in Mallorca is the pressure exerted by feral goats which, in many cases, may cause the death of specimens

Cosmological constraints from the cluster contribution to the power spectrum of the soft X-ray background. New evidence for a low sigma_8

We use the X-ray power spectrum of the ROSAT all-sky survey in the R6 band (approximately 0.9-1.3 keV) to set an upper limit on the galaxy cluster power spectrum. The cluster power spectrum is modelled with a minimum number of robust assumptions regarding the structure of the clusters. The power spectrum of ROSAT sets an upper limit on the Omega_m-sigma_8 plane which excludes all the models with sigma_8 above sigma_8 = 0.5/(Omega_m^0.38) in a flat LCDM universe. We discuss the possible sources of systematic errors in our conclusions, mainly dominated by the assumed L_x-T relation. Alternatively, this relation could be constrained by using the X-ray power spectrum, if the cosmological model is known. Our conclusions suggest that only models with a low value of sigma_8 (sigma_8 < 0.8 for Omega_m = 0.3) may be compatible with our upper limit. We also find that models predicting lower luminosities in galaxy clusters are favoured. Reconciling our cosmological constraints with these arising by other methods might require either a high entropy floor or wide-spread presence of cooling flows in the low-redshift clusters.Comment: 14 pages, 19 plots (2 as gif files). MNRAS submitte

INTEGRAL and XMM-Newton observations towards the unidentified MeV source GRO J1411-64

The COMPTEL unidentified source GRO J1411-64 was observed by INTEGRAL, and its central part, also by XMM-Newton. The data analysis shows no hint for new detections at hard X-rays. The upper limits in flux herein presented constrain the energy spectrum of whatever was producing GRO J1411-64, imposing, in the framework of earlier COMPTEL observations, the existence of a peak in power output located somewhere between 300-700 keV for the so-called low state. The Circinus Galaxy is the only source detected within the 4$\sigma$ location error of GRO J1411-64, but can be safely excluded as the possible counterpart: the extrapolation of the energy spectrum is well below the one for GRO J1411-64 at MeV energies. 22 significant sources (likelihood $> 10$) were extracted and analyzed from XMM-Newton data. Only one of these sources, XMMU J141255.6-635932, is spectrally compatible with GRO J1411-64 although the fact the soft X-ray observations do not cover the full extent of the COMPTEL source position uncertainty make an association hard to quantify and thus risky. The unique peak of the power output at high energies (hard X-rays and gamma-rays) resembles that found in the SED seen in blazars or microquasars. However, an analysis using a microquasar model consisting on a magnetized conical jet filled with relativistic electrons which radiate through synchrotron and inverse Compton scattering with star, disk, corona and synchrotron photons shows that it is hard to comply with all observational constrains. This and the non-detection at hard X-rays introduce an a-posteriori question mark upon the physical reality of this source, which is discussed in some detail