Exploring the UV spectral range to constrain the evolution of massive galaxies in varying environments and varying redshift

Las galaxias más masivas del Universo local son las galaxias de tipo temprano (del inglés, ETGs) que comprenden las galaxias elípticas y lenticulares. El grueso de sus poblaciones de estrellas son viejas y prácticamente no están formando nuevas estrellas. Su actividad de formación estelar no es lo que llegó a ser en las etapas tempranas del Universo, donde grandes cantidades de gas se transformaron en estrellas. La formación de estrellas se detuvo rápidamente y las ETGs evolucionaron como sistemas rojos y viejos. Cuáles fueron los mecanismos físicos responsables de detener la creación de nuevas estrellas sigue siendo un misterio, aunque se cree que las contribuciones de los núcleos activos de galaxias (del inglés, AGNs) pudieron transformar estos sistemas estelares en objetos evolucionando pasivamente con escasa formación estelar. Las estrellas viejas de las ETGs emiten la mayor parte de su luz en el rango espectral óptico. El óptico, sin embargo, es relativamente insensible a pequeñas fracciones de poblaciones estelares jóvenes, cuya luz domina en el rango ultravioleta (UV). Afortunadamente, el UV es un trazador óptimo de las poblaciones estelares más calientes como las estrellas jóvenes. Estudios fotométricos en el UV han puesto de manifiesto que las ETGs pueden tener formación de estrellas a un ritmo muy bajo. Sin embargo, el rango UV en los espectros de las ETGs no ha sido explorado para determinar sus poblaciones jóvenes. El objetivo de esta tesis es cuantificar estas poblaciones estelares jóvenes de las ETGs masivas usando las líneas de absorción de sus espectros. Hemos usado nuevos modelos de poblaciones estelares para analizar, por primera vez, índices espectrales ópticos y del UV cercano simultáneamente. Comparamos las observaciones con las predicciones de los modelos de dos parametrizaciones de las historias de formación estelar (del inglés, SFH) de las galaxias masivas. Primero hemos investigado si la formación de estrellas residual es una característica común entre la población de ETGs, mediante la suma de miles de espectros de galaxias masivas a un desplazamiento al rojo medio de z~0.4. De estos espectros sumados hemos podido obtener las fracciones de población joven en función de la masa de la galaxia. Hemos encontrado que las ETGs masivas tienen en promedio una fracción de estrellas jóvenes formadas en los últimos 2 mil millones de años por debajo del 1%, y que ésta fracción es mayor para las galaxias menos masivas. Esta tendencia con la masa es consistente con el hecho que las galaxias menos masivas tienen SFH más extendidas en el tiempo que las más masivas. También hemos visto que las galaxias masivas sintéticas de las simulaciones cosmológicas producen demasiadas estrellas de edades intermedias. Esto implica que los procesos para suprimir la formación de estrellas en galaxias masivas y mantenerla suprimida en el tiempo, aun necesitan ser comprendidos. Nuestros resultados ponen rigurosos límites que necesitan ser satisfechos por las simulaciones. Para intentar entender el origen de estas poblaciones jóvenes, hemos analizado espectros resueltos espacialmente para obtener información de dónde están situadas en las galaxias. Para ello, hemos analizado un tipo especial de ETGs: las galaxias más brillantes de los cúmulos de galaxias (del inglés, BCGs). Estas galaxias se encuentran en el centro de los potenciales gravitatorios de los cúmulos de galaxias. Nuestro estudio de 6 BCGs cercanas ha demostrado que sus estrellas jóvenes están en el interior de <2 kpc del centro de las galaxias, es decir, en los núcleos. Las pequeñas fracciones de estrellas jóvenes que encontramos son consistentes con un origen in-situ, es decir, la formación de estrellas residual puede producirse gracias al material reciclado de la muerte de estrellas de generaciones anteriores o del gas inicial residual. Sin embargo, debido a la ubicación de estos objetos, un origen ex-situ a través los efectos y procesos del entorno del no puede ser descartado. Estudiar las componentes estelares jóvenes en galaxias reliquias nos ayuda a entender los orígenes de la formación estelar reciente que detectamos en las galaxias ETGs normales. Estas galaxias reliquias, masivas y compactas, han sobrevivido intactas desde su formación a alto desplazamiento al rojo hasta el Universo local, es decir, sin haber experimentado un crecimiento tanto en tamaño como en masa a través de fusiones e interacciones con otras galaxias. Por ello, hemos estudiado la contribución de las poblaciones jóvenes en la región central de 1 kpc de la galaxia NGC 1277, la galaxia reliquia por excelencia del Universo cercano. Encontramos una población joven que contribuye menos del 1%, similar a los resultados previos, lo que apunta a que la formación estelar reciente encontrada en galaxias masivas ETGs puede estar relacionada con los procesos intrínsecos de las galaxias.Early-type galaxies (ETGs), consisting of ellipticals and lenticulars, are the most massive galaxies in the local Universe. The bulk of their stellar populations are characterised as being old with negligible recent star formation activity, having followed a passive evolution from the high-redshift Universe to the present day. Their star formation activity is not what used to be at the early Universe (z > 2), where large amounts of gas were transformed into stars. Star formation was virtually extinguished in rather short time and ETGs evolved as red and dead objects. The exact physical mechanisms responsible for quenching the star formation in these massive systems at high-redshift is not completely resolved. Although, it is widely considered that AGN feedback could turn these stellar systems into passively evolving objects without significant formation of new stars. There is growing observational and theoretical evidences for a two-phase formation scenario for ETGs. According to this picture, during the first phase the cores of present-day ETGs are formed at z > 2 dissipatively, while in the second phase the outer regions are a result of mergers and accretion. This is supported by a large number of studies that have shown that massive galaxies at z > 2 are more compact than their local counterparts, and have experienced significant growth both in size and, to a lesser degree, in mass. This suggests that these high-z massive compacts are the cores of local ETGs formed at high redshift, while the outer regions are where the accreted material due to dissipationless mergers (i.e. gas-poor) is deposited. This second phase is mostly ”dry”, i.e. does not trigger star formation, at least not in any efficient way. The bulk of the stars in ETGs are ancient and emit much of their light in the optical spectral range. However, the optical is relatively insensitive to small fractions of young stellar populations, whose light dominate the ultraviolet (UV). Studies of the optical range are therefore, biased to the old stellar populations. Fortunately, the UV is an optimal tracer of the hottest stellar populations such as young stars. Photometric studies in the UV have previously suggested that ETGs might have recent low-level star formation. However, the UV window of ETG’s spectra has not been explored for determining the youngest stellar populations. This thesis aims to quantify these young stellar populations by using spectral absorption features of massive ETGs. We exploit state-of-the-art stellar population models based on empirical stellar libraries to analyse, for the first time, observed optical and near-UV line-strength indices simultaneously. We compare observations with model predictions from two assumed simple parameterisations of the star formation history (SFH) of massive galaxies. We first explore if the residual star formation is ubiquitous among the massive ETG population by stacking thousands of galaxy spectra at redshift of z ∼ 0.4. We derive mass fractions of the young stellar component as a function of mass. We find that massive galaxies show, on average, a sub-one percent fraction of young stars formed within the last 2 Gyr, and that this fraction is larger for less massive galaxies. This trend with mass is consistent with the fact that less massive galaxies have more extended SFHs than their more massive counterparts and also may be related to the fact that AGN feedback stops the formation of new stars more efficiently for more massive galaxies. We also find that synthetic massive galaxies from cosmological numerical simulations significantly overproduce both intermediate and young stellar populations. This means that the recipe to quench the star formation in these galaxies, and perhaps to maintain them quenched, still needs to be fully understood. However, the results obtained here put stringent constrains that must be satisfied by these simulations. In order to understand the origin of these young stars, we turned to spatially resolved spectroscopy to tell us precisely where they are located. For this purpose, we analyse a special type of ETGs: the brightest cluster galaxies (BCGs). These galaxies are located in the centres of the gravitational potential wells of galaxy clusters. Our study of 6 nearby BCGs indicate that their young stars are located within < 2 kpc of the galaxy centres, i.e. in their cores. Our findings of small young mass fractions are consistent with being formed in-situ, likely residual star formation from recycled material of dying stars from previous generations. However, due to the particular location of these massive systems, an ex-situ origin through environmental processes can not be ruled out. The study of young stellar components in so-called ”relic galaxies” offers us unique clues to understand the possible origins of the recent star formation that we detect in normal ETGs. These massive compact relic galaxies are thought to have survived untouched since their formation at high-z until the presentday, i.e. without having gone through a second phase that is characterised by a growth in size and mass by accretion. For this purpose, we studied the young stellar contribution in the 1 kpc central region of NGC 1277, a well studied galaxy that is regarded as the prototypical relic galaxy in the nearby Universe. We find a sub-one percent level of young mass fractions, similar to our samples of massive ETGs, which points to intrinsic, in-situ, processes that trigger the formation of these young stars

A widely distributed metalloenzyme class enables gut microbial metabolism of host- and diet-derived catechols.

Catechol dehydroxylation is a central chemical transformation in the gut microbial metabolism of plant- and host-derived small molecules. However, the molecular basis for this transformation and its distribution among gut microorganisms are poorly understood. Here, we characterize a molybdenum-dependent enzyme from the human gut bacterium Eggerthella lenta that dehydroxylates catecholamine neurotransmitters. Our findings suggest that this activity enables E. lenta to use dopamine as an electron acceptor. We also identify candidate dehydroxylases that metabolize additional host- and plant-derived catechols. These dehydroxylases belong to a distinct group of largely uncharacterized molybdenum-dependent enzymes that likely mediate primary and secondary metabolism in multiple environments. Finally, we observe catechol dehydroxylation in the gut microbiotas of diverse mammals, confirming the presence of this chemistry in habitats beyond the human gut. These results suggest that the chemical strategies that mediate metabolism and interactions in the human gut are relevant to a broad range of species and habitats

Dissipative Particle Dynamics with Energy Conservation

The stochastic differential equations for a model of dissipative particle dynamics with both total energy and total momentum conservation in the particle-particle interactions are presented. The corresponding Fokker-Planck equation for the evolution of the probability distribution for the system is deduced together with the corresponding fluctuation-dissipation theorems ensuring that the ab initio chosen equilibrium probability distribution for the relevant variables is a stationary solution. When energy conservation is included, the system can sustain temperature gradients and heat flow can be modeled.Comment: 7 pages, submitted to Europhys. Let

Everything you always wanted to know about SDPD⋆ (⋆but were afraid to ask)

An overview of the smoothed dissipative particle dynamics (SDPD) method is presented in a format that tries to quickly answer questions that often arise among users and newcomers. It is hoped that the status of SDPD is clarified as a mesoscopic particle model and its potentials and limitations are highlighted, as compared with other methods

Does immediate breast reconstruction after mastectomy and neoadjuvant chemotherapy influence the outcome of patients with non-endocrine responsive breast cancer?

Background/Aim: In breast cancer (BC) patients, breast surgery followed by immediate breast reconstruction (IBR) might favour recurrences and metastases due to extensive surgical manipulation. We retrospectively investigated whether IBR after mastectomy and neoadjuvant chemotherapy (NT) influenced the outcome in patients with early and locally advanced oestrogen receptor (ER)-negative BC. Patients and Methods: Between 1995 and 2006, 133 BC patients received NT followed by total mastectomy, 59 of whom underwent IBR. Patients receiving IBR (IBR group) were compared to patients who did not receive IBR (no-IBR group) over a prolonged median follow-up time (8.2 years). Results: Patients receiving IBR were on average younger than patients not receiving IBR (p&lt;0.00I). The percentage of patients with positive clinical nodal status (cN) was 19% in the IBR group and 7% in no-IBR group (p=0.036), whereas patients without 1BR were more frequently diagnosed as clinical T4 (59% vs. 15%, p&lt;0.001). The 5-year cumulative incidence of locoregional recurrences were 14% in the no-IBR group and 21% in the IBR group. The hazard of locoregional events, adjusted for age, clinical T and cN, was significantly greater in the IBR group than in the no-IBR group (hazard ratio (HR)=2.77, p=0.045). The 5-year cumulative incidences of distant metastases were similar in the two groups (p=0.414). Conclusion: IBR following total mastectomy in patients with ER-negative disease after NT is associated with a worse rate of local relapses. More insight in mechanisms of wound healing and extent of surgery is required to further investigate this observation

Logging Affects Fledgling Sex Ratios and Baseline Corticosterone in a Forest Songbird

Silviculture (logging) creates a disturbance to forested environments. The degree to which forests are modified depends on the logging prescription and forest stand characteristics. In this study we compared the effects of two methods of group-selection (“moderate” and “heavy”) silviculture (GSS) and undisturbed reference stands on stress and offspring sex ratios of a forest interior species, the Ovenbird (Seiurus aurocapilla), in Algonquin Provincial Park, Canada. Blood samples were taken from nestlings for corticosterone and molecular sexing. We found that logging creates a disturbance that is stressful for nestling Ovenbirds, as illustrated by elevated baseline corticosterone in cut sites. Ovenbirds nesting in undisturbed reference forest produce fewer male offspring per brood (proportion male = 30%) while logging with progressively greater forest disturbance, shifted the offspring sex ratio towards males (proportion male: moderate = 50%, heavy = 70%). If Ovenbirds in undisturbed forests usually produce female-biased broods, then the production of males as a result of logging may disrupt population viability. We recommend a broad examination of nestling sex ratios in response to anthropogenic disturbance to determine the generality of our findings

Economic and Environmental Impacts of Harmful Non-Indigenous Species in Southeast Asia

10.1371/journal.pone.0071255PLoS ONE88-POLN

A global threats overview for Numeniini populations: synthesising expert knowledge for a group of declining migratory birds

The Numeniini is a tribe of thirteen wader species (Scolopacidae, Charadriiformes) of which seven are near-threatened or globally threatened, including two critically endangered. To help inform conservation management and policy responses, we present the results of an expert assessment of the threats that members of this taxonomic group face across migratory flyways. Most threats are increasing in intensity, particularly in non-breeding areas, where habitat loss resulting from residential and commercial development, aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic native species and climate change) were identified as widely affecting breeding areas. Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation; related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Three priority actions were associated with monitoring and research: to monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites), to deploy tracking technologies to identify migratory connectivity, and to monitor land-cover change across breeding and non-breeding areas. Two priority actions were focused on conservation and policy responses: to identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian - Australasian Flyway), and to implement successful conservation interventions at a sufficient scale across human-dominated landscapes for species’ recovery to be achieved. If implemented urgently, these measures in combination have the potential to alter the current population declines of many Numeniini species and provide a template for the conservation of other groups of threatened species

Stable Isotope Evidence for Dietary Overlap between Alien and Native Gastropods in Coastal Lakes of Northern KwaZulu-Natal, South Africa

Tarebia granifera (Lamarck, 1822) is originally from South-East Asia, but has been introduced and become invasive in many tropical and subtropical parts of the world. In South Africa, T. granifera is rapidly invading an increasing number of coastal lakes and estuaries, often reaching very high population densities and dominating shallow water benthic invertebrate assemblages. An assessment of the feeding dynamics of T. granifera has raised questions about potential ecological impacts, specifically in terms of its dietary overlap with native gastropods.A stable isotope mixing model was used together with gut content analysis to estimate the diet of T. granifera and native gastropod populations in three different coastal lakes. Population density, available biomass of food and salinity were measured along transects placed over T. granifera patches. An index of isotopic (stable isotopes) dietary overlap (IDO, %) aided in interpreting interactions between gastropods. The diet of T. granifera was variable, including contributions from microphytobenthos, filamentous algae (Cladophora sp.), detritus and sedimentary organic matter. IDO was significant (>60%) between T. granifera and each of the following gastropods: Haminoea natalensis (Krauss, 1848), Bulinus natalensis (Küster, 1841) and Melanoides tuberculata (Müller, 1774). However, food did not appear to be limiting. Salinity influenced gastropod spatial overlap. Tarebia granifera may only displace native gastropods, such as Assiminea cf. ovata (Krauss, 1848), under salinity conditions below 20. Ecosystem-level impacts are also discussed.The generalist diet of T. granifera may certainly contribute to its successful establishment. However, although competition for resources may take place under certain salinity conditions and if food is limiting, there appear to be other mechanisms at work, through which T. granifera displaces native gastropods. Complementary stable isotope and gut content analysis can provide helpful ecological insights, contributing to monitoring efforts and guiding further invasive species research