Stellar population analysis of two ellipticals

The spatial distributions of the mean luminosity-weighted stellar age, metallicity, and alpha/Fe ratio along both photometric axes of two nearby elliptical galaxies have been obtained using Lick index measurements on long slit spectra in order to reconstruct the star formation history in their kinematically distinct subsystems. Lick indexes were compared with those of single-aged stellar population (SSP) models. A population synthesis method was also applied in order to help disentangling the age-metallicity degeneracy. The stars characteristics are associated with their kinematics: they are older and alpha-enhanced in the not rotating bulge of NGC 1052 and counter rotating core of NGC 7796, while they show a strong spread of alpha/Fe and age along the rotating disk of NGC 1052 and an outwards radial decreasing of them outside the core of NGC 7796.Comment: 2 pages, to appear in the Proceedings of IAU Symposium 241 "Stellar populations as building blocks of galaxies", A. Vazdekis & R. Peletier, ed

The lenticular galaxy NGC3607: stellar population, metallicity and ionised gas

In this work we derive clues to the formation scenario and ionisation source of the lenticular galaxy NGC 3607 by means of metallicity gradients, stellar population and emission lines properties. We work with long-slit spectroscopy from which we (i) study the radial distribution of the equivalent widths of conspicuous metallic absorption features, (ii) infer on the star-formation history (with a stellar population synthesis algorithm), and (iii) investigate the ionisation source responsible for a few strong emission lines. Negative radial gradients are observed for most of the absorption features of NGC 3607. Compared to the external parts, the central region has a deficiency of alpha elements and higher metallicity, which implies different star-formation histories in both regions. At least three star formation episodes are detected, with ages within 1-13 Gyr. The dynamical mass and the $Mg_2$ gradient slope are consistent with mergers being important contributors to the formation mechanism of NGC 3607. Emission-line ratios indicate the presence of a LINER at the centre of NGC 3607. Contribution of hot, old stars to the gas ionisation outside the central region is detected. Evidence drawn from this work suggest small mergers as important contributors to the formation of NGC 3607, a scenario consistent with the star-formation episodes.Comment: 10 pages, 11 figs; accepted for publication in A&

Counterintuitive transitions between crossing energy levels

We calculate analytically the probabilities for intuitive and counterintuitive transitions in a three-state system, in which two parallel energies are crossed by a third, tilted energy. The state with the tilted energy is coupled to the other two states in a chainwise linkage pattern with constant couplings of finite duration. The probability for a counterintuitive transition is found to increase with the square of the coupling and decrease with the squares of the interaction duration, the energy splitting between the parallel energies, and the tilt (chirp) rate. Physical examples of this model can be found in coherent atomic excitation and optical shielding in cold atomic collisions

On the topology of adiabatic passage

We examine the topology of eigenenergy surfaces characterizing the population transfer processes based on adiabatic passage. We show that this topology is the essential feature for the analysis of the population transfers and the prediction of its final result. We reinterpret diverse known processes, such as stimulated Raman adiabatic passage (STIRAP), frequency-chirped adiabatic passage and Stark-chirped rapid adiabatic passage (SCRAP). Moreover, using this picture, we display new related possibilities of transfer. In particular, we show that we can selectively control the level which will be populated in STIRAP process in Lambda or V systems by the choice of the peak amplitudes or the pulse sequence

Panchromatic Averaged Stellar Populations: PaasP

We study how the spectral fitting of galaxies, in terms of light fractions derived in one spectral region translates into another region, by using results from evolutionary synthesis models. In particular, we examine propagation dependencies on Evolutionary Population Synthesis (EPS, {\sc grasil}, {\sc galev}, Maraston and {\sc galaxev}) models, age, metallicity, and stellar evolution tracks over the near-UV---near infrared (NUV---NIR, 3500\AA\ to 2.5\mc) spectral region. Our main results are: as expected, young ($t \lesssim$ 400 Myr) stellar population fractions derived in the optical cannot be directly compared to those derived in the NIR, and vice versa. In contrast, intermediate to old age ($t \gtrsim$ 500 Myr) fractions are similar over the whole spectral region studied. The metallicity has a negligible effect on the propagation of the stellar population fractions derived from NUV --- NIR. The same applies to the different EPS models, but restricted to the range between 3800 \AA\ and 9000 \AA. However, a discrepancy between {\sc galev}/Maraston and {\sc grasil}/{\sc galaxev} models occurs in the NIR. Also, the initial mass function (IMF) is not important for the synthesis propagation. Compared to {\sc starlight} synthesis results, our propagation predictions agree at $\sim$95% confidence level in the optical, and $\sim$85% in the NIR. {\bf In summary, spectral fitting} performed in a restricted spectral range should not be directly propagated from the NIR to the UV/Optical, or vice versa. We provide equations and an on-line form ({\bf Pa}nchromatic {\bf A}veraged {\bf S}tellar {\bf P}opulation - \paasp) to be used for this purpose.Comment: 13 pages and 10 figures. Accepted by MNRA

Manejo de plantas daninhas em arroz irrigado pelo método intermitente de irrigação.

Este trabalho teve por objetivo avaliar as espécies de plantas que se estabelecem e a eficiência do controle de arroz-daninho e capim-arroz em lavoura de arroz irrigado por inundação intermitente, comparativamente à inundação contínua, bem como o reflexo desses métodos de irrigação sobre o desempenho produtivo da lavoura de arroz.ODS

The elliptical galaxy NGC 5044: Stellar population and ionized gas

In this work we investigate the stellar population, metallicity distribution and ionized gas in the elliptical galaxy NGC 5044, using long-slit spectroscopy and a stellar population synthesis method. We found differences in the slope of metal-line profiles along the galaxy which suggests an enhancement of alpha elements, particularly towards the central region. The presence of a non-thermal ionization source, such as a low-luminosity AGN and/or shock ionization, is implied by the large values of the ratio (N II])Ha observed in all sampled regions. However, the emission lines observed in the external regions indicate the presence of an additional ionization source, probably hot, post-AGB stars.Comment: Accepted by A&

The elliptical galaxies NGC 1052 and NGC 7796: stellar populations and abundance alpha/Fe ratio

Context: The spatial distribution of the stellar populations inside a spheroidal system and their kinematical properties supply important informations about the formation process. Aims: We have performed a detailed stellar population analysis using long slit spectroscopic observations up to almost one effective radius of two different early-type galaxies of low density regions of the local Universe: NGC 1052, a E4 Liner prototype of a loose group that has a stellar rotating disc, and NGC 7796, a E1 of the field which shows a kinematically distinct core. The mean luminosity-weighted stellar age, metallicity, and alpha/Fe ratio along both photometric axes of them have been obtained in order to reconstruct the star formation history in their kinematically distinct subsystems. Methods: We have measured Lick indices and computed their radial gradients. They were compared with the predicted ones of simple stellar population models. We have also applied a stellar population synthesis. Results: The star characteristics are associated with their kinematics: they are older and alpha-enhanced in the bulge of NGC 1052 and core of NGC 7796, while they show a strong spread of alpha/Fe and age along the disc of NGC 1052 and an outwards radial decreasing of them outside the core of NGC 7796. The age variation is possibly connected to the alpha/Fe one. Conclusions: Both galaxies were formed by processes in which the star formation occurred firstly at the bulge (NGC 1052) and nucleus (NGC 7796) 12-15 Gyr ago on short timescales (0.1-1 Gyr) providing an efficient chemical enrichment by SN-II. In the disc of NGC 1052, there is some spread of age and formation timescales around its stars. In NGC 7796, the star formation timescale had some outwards radial increasing along both axes.Comment: 26 pages, 27 figures, accepted for publication in A&

Comparison of DNA histograms by standard flow cytometry and image cytometry on sections in Barrett's adenocarcinoma

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to compare DNA histograms obtained by standard flow cytometry (FC) and high fidelity image cytometry on sections (ICS) in normal gastrointestinal mucosa and Barrett's adenocarcinoma (BAC).</p> <p>Methods</p> <p>Archival formalin-fixed paraffin-embedded tissue blocks of 10 normal controls from 10 subjects and 42 BAC tissues from 17 patients were examined. DNA FC was performed using standard techniques and ICS was carried out by Automated Cellular Imaging System (ACIS). DNA ploidy histograms were classified into diploid with peak DNA index (DI) at 0.9–1.1, and aneuploid with peak DI > 1.1. DI values of aneuploid peaks were determined. Additionally, for DNA ICS, heterogeneity index (HI) representing DNA content heterogeneity, and histograms containing cells with DI > G2 were also identified.</p> <p>Results</p> <p>All control samples were diploid by both FC and ICS analyses. In BAC, FC showed diploid peaks in 29%, diploid peaks with additional aneuploid or tetraploid peaks in 57%, and 14% of the samples, respectively. In contrast, ICS showed aneuploid peaks in all the cases with peak DI > 1.25; 37 cases had peak DI between 1.25 and 2.25; and 5 cases had peak DI > 2.25. HI values (mean ± SD) were 11.3 ± 1.1 in controls and 32.4 ± 8.5 in BAC (p < 0.05). Controls had no G2 exceeding cells. However, 19/37 (51%) of the cases with primary peak DI < 2.25 had cells exceeding 9N.</p> <p>Conclusion</p> <p>ICS detects DNA aneuploidy in all BAC samples while FC missed the diagnosis of aneuploidy in 29%. In addition, ICS provides more information on HI and G2 exceeding rates.</p