Spiral structure of the Third Galactic Quadrant and the solution to the Canis Major debate

With the discovery of the Sagittarius dwarf spheroidal (Ibata et al. 1994), a galaxy caught in the process of merging with the Milky Way, the hunt for other such accretion events has become a very active field of astrophysical research. The identification of a stellar ring-like structure in Monoceros, spanning more than 100 degrees (Newberg et al. 2002), and the detection of an overdensity of stars in the direction of the constellation of Canis Major (CMa, Martin et al. 2004), apparently associated to the ring, has led to the widespread belief that a second galaxy being cannibalised by the Milky Way had been found. In this scenario, the overdensity would be the remaining core of the disrupted galaxy and the ring would be the tidal debris left behind. However, unlike the Sagittarius dwarf, which is well below the Galactic plane and whose orbit, and thus tidal tail, is nearly perpendicular to the plane of the Milky Way, the putative CMa galaxy and ring are nearly co-planar with the Galactic disk. This severely complicates the interpretation of observations. In this letter, we show that our new description of the Milky Way leads to a completely different picture. We argue that the Norma-Cygnus spiral arm defines a distant stellar ring crossing Monoceros and the overdensity is simply a projection effect of looking along the nearby local arm. Our perspective sheds new light on a very poorly known region, the third Galactic quadrant (3GQ), where CMa is located.Comment: 5 pages, 2 figures. Quality of Fig 1 has been degraded to make it smaller. Original fig. available on request. accepted for publication in MNRAS letter

Modelo de hargreaves-samani ajustado as condições climáticas do estado do Rio de Janeiro para estimativa da evapotranspiração de referência.

Utilizando-se como padrão para determinação da evapotranspiração de referência (ETo) o modelo de Penman-Monteith parametrizado no boletim Nº 56 de irrigação e drenagem da FAO (PM-FAO56) ajustou-se o modelo de Hargreaves-Samani (HS) para as condições climáticas do Estado do Rio de Janeiro. Nas estimativas da ETo foram utilizadas séries climáticas de 10 estações meteorológicas convencionais pertencentes ao Instituto Nacional de Meteorologia. Os valores dos coeficientes do modelo de HS ajustados para o Estado do Rio de Janeiro não variaram significativamente (cv 3,4%), sendo indicado a utilização de um valor médio (0,0116 ± 0,0004) para todo o Estado. O modelo de Hargreaves-Samani ajustado e o original apresentaram elevada precisão (r2 = 0,94) das estimativas de ETo. Contudo, a acurácia das estimativas de ETo foram superiores com o modelo HS ajustado (d = 0,99 e EPE = 0,25 mm d-1) em relação ao original (d = 0,93 e EPE = 0,65 mm d-1)

Variabilidade mesoclimática da chuva no norte e noroeste do estado do Rio de Janeiro.

Resumo: A chuva é um dos elementos climáticos mais importantes. Na quantidade e no período adequado pode trazer benefícios para, por exemplo, a agricultura, mas em situações adversas pode causar prejuízos, como inundações e deslizamentos de terra. Nesse sentido, este estudo analisou a variabilidade climática da altura pluviométrica sazonal nas mesorregiões Norte e Noroeste do estado do Rio de Janeiro. Foram utilizados dados trimestrais de chuva de onze estações hidrológicas. Os métodos da Análise de Regressão e, de Kendall foram utilizados para testar a tendência da altura pluviométrica sazonal. Os resultados mostraram que no verão e inverno foram observadas as maiores e menores tendências significativas da altura pluviométrica, respectivamente. Abstract: Rain is one of the most important climatic elements. In the quantity and at the right time can benefit, for example, agriculture, but in adverse situations can cause damage such as floods and landslides. In this perspective, this study analyzed the climate viability of seasonal rainfall in the North and Northwest mesoregions, from the state of Rio de Janeiro. Quarterly rainfall data from eleven hydrological stations were used. Methods of Regression Analysis and Kendall were used to test the trend of seasonal rainfall. The results showed that in the summer and in the winter the highest and the lowest significant trends in rainfall height were observed, respectively

Anomalous sensitivity to initial conditions and entropy production in standard maps: Nonextensive approach

We perform a throughout numerical study of the average sensitivity to initial conditions and entropy production for two symplectically coupled standard maps focusing on the control-parameter region close to regularity. Although the system is ultimately strongly chaotic (positive Lyapunov exponents), it first stays lengthily in weak-chaotic regions (zero Lyapunov exponents). We argue that the nonextensive generalization of the classical formalism is an adequate tool in order to get nontrivial information about this complex phenomenon. Within this context we analyze the relation between the power-law sensitivity to initial conditions and the entropy production.Comment: 9 pages, 12 figure