The many faces of LINER-like galaxies: a WISE view

We use the SDSS and WISE surveys to investigate the real nature of galaxies defined as LINERs in the BPT diagram. After establishing a mid-infrared colour W2-W3 = 2.5 as the optimal separator between galaxies with and without star formation, we investigate the loci of different galaxy classes in the W_{Ha} versus W2-W3 space. We find that: (1) A large fraction of LINER-like galaxies are emission-line retired galaxies, i.e galaxies which have stopped forming stars and are powered by hot low-mass evolved stars (HOLMES). Their W2-W3 colours show no sign of star formation and their Ha equivalent widths, W_{Ha}, are consistent with ionization by their old stellar populations. (2) Another important fraction have W2-W3 indicative of star formation. This includes objects located in the supposedly `pure AGN' zone of the BPT diagram. (3) A smaller fraction of LINER-like galaxies have no trace of star formation from W2-W3 and a high W_{Ha}, pointing to the presence of an AGN. (4) Finally, a few LINERs tagged as retired by their W_{Ha} but with W2-W3 values indicative of star formation are late-type galaxies whose SDSS spectra cover only the old `retired' bulge. This reinforces the view that LINER-like galaxies are a mixed bag of objects involving different physical phenomena and observational effects thrusted into the same locus of the BPT diagram.Comment: Accepted for publication in MNRAS; 9 pages, 6 figure

Late Winter Dietary Overlap among Greater Rheas and Domestic Herbivores on the Argentinean Flooding Pampa

This study evaluates the dietary overlap among greater rheas (Rhea americana L.) sheep and cattle in the Flooding Pampa, Buenos Aires, Argentina during late winter, when is observed the lowest forage availability. The work was carried out with the following forage classes (FC): warm and cool season grasses and forbs (legumes and no-legumes). Diet botanical composition was estimated by microanalysis of faeces. Principal Component Analysis and Kulcyznsky´s index of similarity were used for data analysis. Rhea populations selected diets with higher forb percentages. On the contrary, vegetation structure and their own morpho-physiology conditioned cattle to diets almost exclusively gramineous. Although forbs were more consumed by sheep than by cattle, they do not represent a major portion of sheep diets. In the Flooding Pampa grasslands, the probability of competition for forage between greater rheas and sheep is intermediate, and that between rheas and cattle is low

A class of surfaces with planar lines of curvature

En este articulo estudiamos superficies parametrizadas por líneas de curvatura. Obtenemos una caracterización de una clase de superficies con líneas de curvatura planas, esta caracterización depende de ciertas funciones holomorfas. Presentamos una clase de superficies con dos familias de líneas de curvatura planas, esta clase incluye las superficies de Dupin. También damos algunos ejemplos explícitos.In this paper we study surfaces parameterized by lines of curvature. We obtain a characterization of a class of surfaces with planar lines of curvature, this characterization depend on certain holomorphic function. We present a class of surfaces with two family of planar lines of curvature, this class of surfaces includes the Dupin surfaces. Also, we give explicit examples

Nuclear activity and star formation properties of Seyfert 2 galaxies

In order to characterize the amount of recent or ongoing stellar formation in the circumnuclear region of active galaxies on a statistically sound basis, we have studied the stellar component of the nuclear spectra in three different samples of galaxies, namely Seyfert 2 galaxies (hereafter S2G), star-forming galaxies (SFG) and passive normal galaxies (NG), i.e., no emission lines observed, using Sloan Digital Sky Survey data (SDSS) (Adelman-McCarthy, 2008). The stellar component of the observed spectra has been extracted using STARLIGHT (Cid Fernandes et al., 2004), which fits an observed spectrum with a model (template) spectrum obtained by combining a library of pre-defined simple stellar populations spectra, with distinct ages and metallicities. The resulting template spectra for the different samples of galaxies have been compared to determine the features of the stellar emission component and to evaluate the presence and intensity of the star formation in the nuclear regions of different families of galaxies. From a first qualitative analysis it results that the shape of the Spectral Energy Distribution (SED) of S2G and NG is very similar, while that of SFG is characterized by a strong blue excess. The presence of the 4000 A break in the spectra of S2G and NG together with the lack of a strong blue continuum clearly indicate the absence of ongoing star formation in the circumnuclear regions of S2G and obviously of NG. Anyway traces of a recent star formation history are evident in the spectra of S2G galaxies, which show a 4000 A break systematically shallower than in NG.Comment: Proceeding of the VII Serbian Conference on Spectral Line Shapes in Astrophysic

On the nature of the near-UV extended light in Seyfert galaxies

We study the nature of the extended near-UV emission in the inner kiloparsec of a sample of 15 Seyfert galaxies which have both near-UV (F330W) and narrow band [OIII] high resolution Hubble images. For the majority of the objects we find a very similar morphology in both bands. From the [OIII] images we construct synthetic images of the nebular continuum plus the emission line contribution expected through the F330W filter, which can be subtracted from the F330W images. We find that the emission of the ionised gas dominates the near-UV extended emission in half of the objects. A further broad band photometric study, in the bands F330W (U), F547M (V) and F160W (H), shows that the remaining emission is dominated by the underlying galactic bulge contribution. We also find a blue component whose nature is not clear in 4 out of 15 objects. This component may be attributed to scattered light from the AGN, to a young stellar population in unresolved star clusters, or to early-disrupted clusters. Star forming regions and/or bright off-nuclear star clusters are observed in 4/15 galaxies of the sample.Comment: 23 pages, 6 figures, 3 tables; accepted for publication in MNRA

A Simple and Inexpensive Method to Gain Diatom Absolute Abundances from Permanent Mounts in Hydrobiological and Paleoecological Research

Here, we describe and discuss a method based on microscopical field of view (FOV) area to estimate diatom absolute abundances (densities or concentrations), and we statistically verify its reliability, also comparing it to another commonly used method (microspheres). To test the new method, we purposely performed replicate counts, both with the FOV and with the microsphere method, on both subfossil and recent material (samples) from mires. Intraclass correlation (ICC) revealed a high degree of agreement between the measurements obtained for the replicates with each of the two methods, suggesting that both are reliable for measuring diatom valve concentrations. However, the FOV consistently overestimated diatom absolute abundances, as compared to the microsphere method, and the ICC value used to assess the reliability of the two methods combined suggested that the two methods cannot be used interchangeably. The FOV method is relatively simple, has a lower cost, wider applicability, higher resolution, and warrants compatibility with existing datasets. However, there may also be drawbacks, such as the potential for sample distortion during the concentration process. Therefore, it is important to carefully evaluate the strengths and limitations of the different methods before adopting one for specific research or applied questions

Stellar population analysis on local infrared-selected galaxies

To study the stellar population of local infrared galaxies, which contain star-forming galaxies, composite galaxies, LINERs, and Seyfert 2s. We also want to find whether infrared luminosity and spectral class have any effects on their stellar populations. The sample galaxies are selected from the main galaxy sample of SDSS-DR4 and then cross-correlated with the IRAS-PSCz catalog. We fit our spectra (stellar absorption lines and continua) using the spectral synthesis code STARLIGHT on the base of the templates of Simple Stellar Population and the spectra of star clusters.Among the 4 spectral classes, LINERs present the oldest stellar populations, and the other 3 sub-samples all present substantial young and intermediate age populations and very few old populations. The importance of young populations decreases from star-forming, composite, Seyfert 2 to LINER. As to different infrared luminosity bins, ULIGs & LIGs (log($L_{IR}/L_{\odot})\geq$11) present younger populations than starbursts and normal galaxies. However, the dominant contributors to mass are old populations in all sample galaxies. The fittings by using the spectra of star clusters with different ages and metallicities as templates also give consistent results. The dominated populations in star-forming and composite galaxies are those with metallicity $Z=0.2Z_\odot$, while LINERs and Seyfert 2s are more metal-rich. The normal galaxies are more metal-rich than the ULIGs & LIGs and starbursts for the star-forming galaxies within different infrared luminosity bins. Additionally, we also compare some synthesis results with other parameters obtained from the MPA/JHU catalog.Comment: 13 pages, 11 figures, accepted for publication by A&

Feminine Identities

The first four essays in this volume all focus on issues of gender in the works of different English authors and thinkers. Shorter versions of each of these essays were formerly presented as papers in an autonomous section of the Research and Educational Programme on Studies of Identity at the XXth Meeting of the Portuguese Association of Anglo-American Studies (Póvoa de Varzim, 1999) and published in the proceedings of the conference. The second cluster of essays in this volume — two of which (Jennie Wang’s and Teresa Cid’s) were first presented, in shorter versions, at the joint ASA/CAAS Conference (Montréal, 1999) — addresses the work of American women variously engaged in contexts of cultural diversity and grappling with the ideas of what it means to be an American and a woman, particularly in the twentieth century. These essays approach, from different angles, the definitional quandaries and semantic difficulties encountered when speaking about the self and the United States and provide, in one way or another, a sort of feminine rewriting of American myths and history.Fundação para a Ciência e a Tecnologi