When native species become invasive: the case of bamboos in fragmented forests of Southern Brazil.

ESA 2013. Abstract. COS 29-2

Detection of Additional Members of the 2003 EL61 Family via Infrared Spectroscopy

We have acquired near-infrared spectra of Kuiper belt objects 2003 UZ117, 2005 CB79 and 2004 SB60 with NIRC on the Keck I Telescope. These objects are dynamically close to the core of the 2003 EL61 collisional family and were suggested to be potential fragments of this collision by Ragozzine and Brown (2007). We find that the spectra of 2003 UZ117 and 2005 CB79 both show the characteristic strong water ice absorption features seen exclusively on 2003 EL61, its largest satellite, and the six other known collisional fragments. In contrast, we find that the near infrared spectrum of 2004 SB60 is essentially featureless with a fraction of water ice of less than 5%. We discuss the implications of the discovery of these additional family members for understanding the formation and evolution of this collisional family in the outer solar system.Comment: 9 Pages, 2 figure

Quaoar: A Rock in the Kuiper belt

Here we report WFPC2 observations of the Quaoar-Weywot Kuiper belt binary. From these observations we find that Weywot is on an elliptical orbit with eccentricity of 0.14 {\pm} 0.04, period of 12.438 {\pm} 0.005 days, and a semi-major axis of 1.45 {\pm} 0.08 {\times} 104 km. The orbit reveals a surpsingly high Quaoar-Weywot system mass of 1.6{\pm}0.3{\times}10^21 kg. Using the surface properties of the Uranian and Neptunian satellites as a proxy for Quaoar's surface, we reanalyze the size estimate from Brown and Trujillo (2004). We find, from a mean of available published size estimates, a diameter for Quaoar of 890 {\pm} 70 km. We find Quaoar's density to be \rho = 4.2 {\pm} 1.3 g cm^-3, possibly the highest density in the Kuiper belt.Comment: 11 pages, 2 figures, accepted for publication in ApJ letters

Variação da habilidade combinatória em população restauradora para o desenvolvimento de genitores de híbridos de arroz.

Baseia-se na exploração da macho-esterilidade genética utilizada na população restauradora em processo de seleção recorrente

Sputtering of Oxygen Ice by Low Energy Ions

Naturally occurring ices lie on both interstellar dust grains and on celestial objects, such as those in the outer solar system. These ices are continu- ously subjected to irradiation by ions from the solar wind and/or cosmic rays, which modify their surfaces. As a result, new molecular species may form which can be sputtered off into space or planetary atmospheres. We determined the experimental values of sputtering yields for irradiation of oxygen ice at 10 K by singly (He+, C+, N+, O+ and Ar+) and doubly (C2+, N2+ and O2+) charged ions with 4 keV kinetic energy. In these laboratory experiments, oxygen ice was deposited and irradiated by ions in an ultra high vacuum chamber at low temperature to simulate the environment of space. The number of molecules removed by sputtering was observed by measurement of the ice thickness using laser interferometry. Preliminary mass spectra were taken of sputtered species and of molecules formed in the ice by temperature programmed desorption (TPD). We find that the experimental sputtering yields increase approximately linearly with the projectile ion mass (or momentum squared) for all ions studied. No difference was found between the sputtering yield for singly and doubly charged ions of the same atom within the experimental uncertainty, as expected for a process dominated by momentum transfer. The experimental sputter yields are in good agreement with values calculated using a theoretical model except in the case of oxygen ions. Preliminary studies have shown molecular oxygen as the dominant species sputtered and TPD measurements indicate ozone formation.Comment: to be published in Surface Science (2015

Visible spectroscopy of the new ESO Large Program on trans-Neptunian objects and Centaurs: final results

A second large programme (LP) for the physical studies of TNOs and Centaurs, started at ESO Cerro Paranal on October 2006 to obtain high-quality data, has recently been concluded. In this paper we present the spectra of these pristine bodies obtained in the visible range during the last two semesters of the LP. We investigate the spectral behaviour of the TNOs and Centaurs observed, and we analyse the spectral slopes distribution of the full data set coming from this LP and from the literature. We computed the spectral slope for each observed object, and searched for possible weak absorption features. A statistical analysis was performed on a total sample of 73 TNOs and Centaurs to look for possible correlations between dynamical classes, orbital parameters, and spectral gradient. We obtained new spectra for 28 bodies, 15 of which were observed for the first time. All the new presented spectra are featureless, including 2003 AZ84, for which a faint and broad absorption band possibly attributed to hydrated silicates on its surface has been reported. The data confirm a wide variety of spectral behaviours, with neutral--grey to very red gradients. An analysis of the spectral slopes available from this LP and in the literature for a total sample of 73 Centaurs and TNOs shows that there is a lack of very red objects in the classical population. We present the results of the statistical analysis of the spectral slope distribution versus orbital parameters. In particular, we confirm a strong anticorrelation between spectral slope and orbital inclination for the classical population. A strong correlation is also found between the spectral slope and orbital eccentricity for resonant TNOs, with objects having higher spectral slope values with increasing eccentricity.Comment: 11 pages, 9 figure