Quenching Star Formation in the Green Valley: The Mass Flux at Intermediate Redshifts

We have obtained several hundred very deep spectra with DEIMOS/Keck in order to estimate the galactic mass flux density at intermediate redshifts (0.6 < z < 0.9) from the ”blue cloud” to the red sequence across the so-called ”green valley”, the intermediate region in the color-magnitude plot between those two populations. We use spectral indices (specifically D_n (4000) and H_(δ,A)) to determine star formation histories. Together with an independent measurement of number density of galaxies in each bin of the color-magnitude plot, one can infer the rate at which galaxies from a given sample are transiting through that bin. Measuring this value for all magnitude values, studies at lower redshift determined that the mass flux density in the green valley is comparable to both the mass build-up rate of the red sequence and the mass loss rate from the blue cloud. We show preliminary results for our intermediate redshift sample

Lyman Break Analogs: Constraints on the Formation of Extreme Starbursts at Low and High Redshift

Lyman Break Analogs (LBAs), characterized by high far-UV luminosities and surface brightnesses as detected by GALEX, are intensely star-forming galaxies in the low-redshift universe ($z\sim 0.2$), with star formation rates reaching up to 50 times that of the Milky Way. These objects present metallicities, morphologies and other physical properties similar to higher redshift Lyman Break Galaxies (LBGs), motivating the detailed study of LBAs as local laboratories of this high-redshift galaxy population. We present results from our recent integral-field spectroscopy survey of LBAs with Keck/OSIRIS, which shows that these galaxies have the same nebular gas kinematic properties as high-redshift LBGs. We argue that such kinematic studies alone are not an appropriate diagnostic to rule out merger events as the trigger for the observed starburst. Comparison between the kinematic analysis and morphological indices from HST imaging illustrates the difficulties of properly identifying (minor or major) merger events, with no clear correlation between the results using either of the two methods. Artificial redshifting of our data indicates that this problem becomes even worse at high redshift due to surface brightness dimming and resolution loss. Whether mergers could generate the observed kinematic properties is strongly dependent on gas fractions in these galaxies. We present preliminary results of a CARMA survey for LBAs and discuss the implications of the inferred molecular gas masses for formation models.Comment: To appear in the proceedings of IAU Symposium 277, "Tracing the Ancestry of Galaxies on the Land of our Ancestors", eds. C. Carignan, K.C. Freeman, and F. Combe

Quenching Star Formation at Intermediate Redshifts: Downsizing of the Mass Flux Density in the Green Valley

The bimodality in galaxy properties has been observed at low and high redshifts, with a clear distinction between star-forming galaxies in the blue cloud and passively evolving objects in the red sequence; the absence of galaxies with intermediate properties indicates that the quenching of star formation and subsequent transition between populations must happen rapidly. In this paper, we present a study of over 100 transiting galaxies in the so-called green valley at intermediate redshifts (z ~ 0.8). By using very deep spectroscopy with the DEIMOS instrument at the Keck telescope we are able to infer the star formation histories of these objects and measure the stellar mass flux density transiting from the blue cloud to the red sequence when the universe was half its current age. Our results indicate that the process happened more rapidly and for more massive galaxies in the past, suggesting a top-down scenario in which the massive end of the red sequence is forming first. This represents another aspect of downsizing, with the mass flux density moving toward smaller galaxies in recent times

The kinematics of ionized gas in lyman-break analogs at z ~ 0.2

We present results for 19 “Lyman-break analogs” observed with Keck/OSIRIS with an adaptive-optics-assisted spatial resolution of less than 200 pc. We detect satellites/companions, diffuse emission, and velocity shear, all with high signal-to-noise ratios. These galaxies present remarkably high velocity dispersion along the line of sight (~70 km s^(−1)), much higher than standard star-forming spirals in the low-redshift universe. We artificially redshift our data to z ~ 2.2 to allow for a direct comparison with observations of high-z Lyman-break galaxies and find striking similarities between both samples. This suggests that either similar physical processes are responsible for their observed properties, or, alternatively, that it is very difficult to distinguish between different mechanisms operating in the low- versus high-redshift starburst galaxies based on the available data. The comparison between morphologies in the UV/optical continuum and our kinemetry analysis often shows that neither is by itself sufficient to confirm or completely rule out the contribution from recent merger events. We find a correlation between the kinematic properties and stellar mass, in that more massive galaxies show stronger evidence for a disk-like structure. This suggests a co-evolutionary process between the stellar mass buildup and the formation of morphological and dynamical substructure within the galaxy

Molecular gas properties of UV-bright star-forming galaxies at low redshift

Lyman break analogues (LBAs) are a population of star-forming galaxies at low redshift (z ∼ 0.2) selected in the ultraviolet (UV). These objects present higher star formation rates and lower dust extinction than other galaxies with similar masses and luminosities in the local universe. In this work, we present results from a survey with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) array to detect CO(1–0) emission in LBAs, in order to analyse the properties of the molecular gas in these galaxies. Our results show that LBAs follow the same Schmidt–Kennicutt law as local galaxies. On the other hand, they have higher gas fractions (up to 66 per cent) and faster gas depletion time-scales (below 1 Gyr). These characteristics render these objects more akin to high-redshift star-forming galaxies. We conclude that LBAs are a great nearby laboratory for studying the cold interstellar medium in low-metallicity, UV-bright compact star-forming galaxies

Quenching or Bursting:the Role of Stellar Mass, Environment, and Specific Star Formation Rate to z ~ 1

Using a novel approach, we study the quenching and bursting of galaxies as a function of stellar mass (M∗), local environment (Σ), and specific star-formation rate (sSFR) using a large spectroscopic sample of ∼ 123,000 GALEX/SDSS and ∼ 420 GALEX/COSMOS/LEGA-C galaxies to z ∼ 1. We show that out to z ∼ 1 and at fixed sSFR and local density, on average, less massive galaxies are quenching, whereas more massive systems are bursting, with a quenching/bursting transition at log(M∗/M⊙) ∼ 10.5-11 and likely a short quenching/bursting timescale (ﰁ 300 Myr). We find that much of the bursting of star-formation happens in massive (log(M∗/M⊙) ﰀ 11), high sSFR galaxies (log(sSFR/Gyr−1) ﰀ -2), particularly those in the field (log(Σ/Mpc−2) ﰁ 0; and among group galaxies, satellites more than centrals). Most of the quenching of star-formation happens in low-mass (log(M∗/M⊙) ﰁ 9), low sSFR galaxies (log(sSFR/Gyr−1) ﰁ -2), in particular those located in dense environments (log(Σ/Mpc−2) ﰀ 1), indicating the combined effects of M∗ and Σ in quenching/bursting of galaxies since z ∼ 1. However, we find that stellar mass has stronger effects than environment on recent quenching/bursting of galaxies to z ∼ 1. At any given M∗, sSFR, and environment, centrals are quenchier (quenching faster) than satellites in an average sense. We also find evidence for the strength of mass and environmental quenching being stronger at higher redshift. Our preliminary results have potential implications for the physics of quenching/bursting in galaxies across cosmic time

Estimation of the potential impact of dengue vaccination on clinical outcomes in Brazil

ABSTRACT Objective: The aim of the current analysis was to measure the public health impact of dengue vaccination in Brazil using a published transmission dynamics model. Methods: We adapted a mathematical model that represented the transmission dynamics of the four dengue fever serotypes in humans and in the mosquito. This compartmental model represents the known characteristics of dengue transmission dynamics: host-vector interactions, immunological interactions between all four dengue serotypes, age structure of the population, levels of specific transmission by age, seasonality of the disease, and growth of the human and vector population. Results: Our mathematical model showed a 22% (CI95%: 9-37) reduction of all cases of dengue fever for a smaller scenario (routine vaccination at 9 years old and catch-up campaign to 10 years of age) and 81% (CI95%: 67-89) in the largest scenario (routine vaccination at 9 years old and catch-up campaign to 40 years of age) over a 5-year period. For the 10-year impact, we estimated a 22% (CI95%: 12-39) reduction in the smaller scenario, and a 92% (CI95%: 80-95) reduction in the larger scenario. This reduction in the number of cases would lead to significant decrease in the number of hospitalizations. Up to 233,509 (CI95%: 148,534 -331,849) and 739,378 (CI95%: 604,386 -894,072) hospitalizations would be prevented over a 5-year and 10-year period, respectively, with the larger vaccination program. Conclusion: This analysis indicates that, within expected variations, a national dengue vaccination program in Brazil would lead to significant public health benefits by reducing dengue infections and hospitalizations. RESUMO Objetivo: O objetivo da análise é medir o impacto na saúde pública com vacinação da dengue no Brasil, utilizando um modelo dinâmico de transmissão publicado. Método: Adaptamos modelo matemático que representa a dinâmica de transmissão dos quatro sorotipos da dengue em humanos e no mosquito. O modelo é determinístico, compartimental, para representar as características conhecidas da dinâmica de transmissão da dengue: interações hospedeiro-vetor; interações imunológicas entre os quatro sorotipos de dengue; estrutura etária da população; níveis de transmissão específicas por idade; sazonalidade da doença e o crescimento da população de humanos e vetores. Resultado: Nosso modelo matemático estimou em 22% (IC95%: 9-37) de redução dos casos de dengue para o cenário mais conservador (rotina aos 9 anos e campanha de vacinação até 10 anos) e 81% (IC95%: 67-89) no cenário mais liberal (rotina aos 9 anos e campanha de vacinação até 40 anos) ao longo de 5 anos. Para o impacto de 10 anos, estimou-se 22% (IC95%: 12-39) de redução no cenário de mais conservador e 92% (IC95%: 80-95) de redução no cenário mais liberal. Esta redução dos casos leva a redução significativa do número de hospitalizações. Até 233,509 (CI95%: 148,534 -331,849) e 739,378 (CI95%: 604,386 -894,072) internações poderiam ser salvas em 5 e 10 anos, respectivamente para período com o programa mais liberal de vacinação. Conclusão: A análise indica que, dentro de variações esperadas, um programa de vacinação nacional contra dengue no Brasil teria um benefício significativo para saúde pública, reduzindo infecções e internações de dengue. Palavras-chave: dengue, modelagem, vacinação Recebido em: 05/12/2015. Aprovado para publicação em: 14/01/2016

Remoção de matéria orgânica natural em águas usando cavitação hidrodinâmica e peróxido de hidrogênio (CH-H2O2)

The presence of natural organic matter (NOM) in water does not present direct risk to the human body or to the environment. However, its presence along with other pollutants can lead to countless issues and damage human health and the environment. The hydrodynamic cavitation (HC) phenomenon started being used in the early 21st century as a process capable of treating supply-water and wastewater based on pollutant and pathogen degradation. Process effectiveness increases when it is combined to chemical agents, creating an advanced oxidation process (AOP). Although several studies have presented broaden applications for the HC process, its use for NOM removal from supply-water was not yet assessed; therefore, it remains a gap in scientific knowledge. The aim of the current study is to assess HC potential in NOM removal. In order to do so, the experiments were carried out in bench scale hydrodynamic cavitation system operated at batch model within 15-min duration period-of-time. In addition, decantation experiments (24-h period-of-time) were performed in order to check HC influence on molecules found in reaction medium after the exposure of NOM to the phenomenon. NOM was produced by a synthetic humic acid (HA) matrix at fixed concentration of 100 ppm. In total, 16 experiments were carried out; each experiment was featured by the following pair: pH (2.6, 3.0, 3.5 and 5.5) and hydrogen peroxide (0, 1, 5 and 30 mL). The best removal efficiencies (34%-36%) were observed in the most acidic pH ranges (2.6-3.0) at H2O2 concentration of 15mL. Results have presented high NOM removal efficiency (approximately 90%) after decantation at the most acidic pH ranges, as well. It can be explained by the fact that hydrodynamic cavitation in acid solution can break molecular structures suspended in the liquid medium, which favors decantation. Based on the present study, hydrodynamic cavitation with hydrogen peroxide addition can remove NOM from water; moreover, pH control is an essential factor for process development.A presença de matéria orgânica natural (MON) em águas não apresenta riscos diretos relacionados ao seu contato com o organismo humano e nem mesmo ao meio ambiente. Entretanto, sua presença, em conjunto a outros poluentes, pode acarretar inúmeros problemas e danos à saúde humana e ao meio ambiente. O fenômeno de cavitação hidrodinâmica (CH) passou a ser utilizado no início do século XXI como um processo capaz de realizar o tratamento de águas de abastecimento ou residuárias a partir da degradação de poluentes e patógenos. A efetividade do processo aumenta quando aliado à adição de agentes químicos no meio reacional, configurando um processo oxidativo avançado (POA). Por mais que diversos trabalhos apresentem amplas aplicações para o processo de CH, sua utilização para remoção de MON de águas de abastecimento ainda não foi avaliada e, portanto, apresenta-se como uma lacuna no conhecimento científico. O objetivo deste trabalho é avaliar o potencial da CH em remover MON. Para tanto, os experimentos foram realizados em um sistema de cavitação hidrodinâmica, em escala de bancada, operado em modo batelada com duração de 15 minutos. Adicionalmente, experimentos de decantação (período de 24 horas) foram conduzidos com intuito de verificar a influência da CH sobre as moléculas presentes no meio reacional após exposição ao fenômeno. A MON foi constituída por uma matriz de ácido húmico (AH) sintética à uma concentração fixa de 100 ppm. No total foram realizados 16 experimentos, no qual cada experimento foi caracterizado pelo par: pH (2,6; 3,0; 3,5; e 5,5) e peróxido de hidrogênio (0; 1; 15 e 30 mL). As melhores eficiências de remoção (34-36%) foram encontradas para faixas de pH mais ácidas (2,6-3,0), para uma concentração de 15 mL de H2O2. Após decantação, os resultados apresentaram uma elevada eficiência de remoção de MON (aproximadamente 90%), também para faixas de pH mais ácidas. Isso pode ser explicado pelo fato de que, em soluções ácidas, a cavitação hidrodinâmica consegue romper estruturas moleculares suspensas no meio líquido, favorecendo a decantação. Este estudo mostrou que a cavitação hidrodinâmica aliada a peróxido de hidrogênio é capaz de remover MON presentes em águas e que o controle do pH é fator crucial para o desempenho do processo

Exploring glycoside hydrolases and accessory proteins from wood decay fungi to enhance sugarcane bagasse saccharification

Abstract\ud \ud Background\ud Glycoside hydrolases (GHs) and accessory proteins are key components for efficient and cost-effective enzymatic hydrolysis of polysaccharides in modern, biochemically based biorefineries. Currently, commercialized GHs and accessory proteins are produced by ascomycetes. However, the role of wood decay basidiomycetes proteins in biomass saccharification has not been extensively pursued. Wood decay fungi degrade polysaccharides in highly lignified tissues in natural environments, and are a promising enzyme source for improving enzymatic cocktails that are designed for in vitro lignocellulose conversion.\ud \ud \ud Results\ud GHs and accessory proteins were produced by representative brown- and white-rot fungi, Laetiporus sulphureus and Pleurotus ostreatus, respectively. Concentrated protein extracts were then used to amend commercial enzymatic cocktails for saccharification of alkaline-sulfite pretreated sugarcane bagasse. The main enzymatic activities found in the wood decay fungal protein extracts were attributed to endoglucanases, xylanases and β-glucosidases. Cellobiohydrolase (CBH) activities in the L. sulphureus and P. ostreatus extracts were low and nonexistent, respectively. The initial glucan conversion rates were boosted when the wood decay fungal proteins were used to replace half of the enzymes from the commercial cocktails. L. sulphureus proteins increased the glucan conversion levels, with values above those observed for the full load of commercial enzymes. Wood decay fungal proteins also enhanced the xylan conversion efficiency due to their high xylanase activities. Proteomic studies revealed 104 and 45 different proteins in the P. ostreatus and L. sulphureus extracts, respectively. The enhancement of the saccharification of alkaline-pretreated substrates by the modified enzymatic cocktails was attributed to the following protein families: GH5- and GH45-endoglucanases, GH3-β-glucosidases, and GH10-xylanases.\ud \ud \ud Conclusions\ud The extracellular proteins produced by wood decay fungi provide useful tools to improve commercial enzyme cocktails that are currently used for the saccharification of alkaline-pretreated lignocellulosic substrates. The relevant proteins encompass multiple glycoside hydrolase families, including the GH5- and GH45-endoglucanases, GH3-β-glucosidases, and GH10-xylanases.The authors thank J.M. Silva and J.C. Tavares for technical assistance. This work\ud was supported by FAPESP (contract numbers 08/56256-5 and 2014/06923-6),\ud CNPq (contract numbers 442333/2014-5; 310186/2014-5 and 140796/2013-\ud 4), and CAPES. We gratefully acknowledge the provision of time on the MAS\ud and NGS facilities (LNBio and CTBE, respectively) at the National Center for\ud Research in Energy and Materials (CNPEM).\ud The work was supported by Fundação de Amparo à Pesquisa do Estado de\ud São Paulo (FAPESP), contract numbers 08/56256-5 and 2014/06923-6, and by\ud Conselho Nacional de Pesquisa (CNPq), contract numbers 442333/2014-5;\ud 310186/2014-5, 140796/2013-4

Bar properties as a function of wavelength: a local baseline with S4G for high-redshift studies

The redshift evolution of bars is an important signpost of the dynamic maturity of disc galaxies. To characterize the intrinsic evolution safe from band-shifting effects, it is necessary to gauge how bar properties vary locally as a function of wavelength. We investigate bar properties in 16 nearby galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G) at ultraviolet, optical, and mid-infrared wavebands. Based on the ellipticity and position angle profiles from fitting elliptical isophotes to the two-dimensional light distribution, we find that both bar length and ellipticity – the latter often used as a proxy for bar strength – increase at bluer wavebands. Bars are 9 per cent longer in the B band than at 3.6 μm. Their ellipticity increases typically by 8 per cent in the B band, with a significant fraction (>40 per cent) displaying an increase up to 35 per cent. We attribute the increase in bar length to the presence of star-forming knots at the end of bars: these regions are brighter in bluer bands, stretching the bar signature further out. The increase in bar ellipticity could be driven by the apparent bulge size: the bulge is less prominent at bluer bands, allowing for thinner ellipses within the bar region. Alternatively, it could be due to younger stellar populations associated with the bar. The resulting effect is that bars appear longer and thinner at bluer wavebands. This indicates that band-shifting effects are significant and need to be corrected for high-redshift studies to reliably gauge any intrinsic evolution of the bar properties with redshift