High dispersion spectroscopy of two A supergiant systems in the Small Magellanic Cloud with novel properties

We present the results of a spectroscopic investigation of two novel variable bright blue stars in the SMC, OGLE004336.91-732637.7 (SMC-SC3) and the periodically occulted star OGLE004633.76-731204.3 (SMC-SC4), whose photometric properties were reported by Mennickent et al. (2010). High-resolution spectra in the optical and far-UV show that both objects are actually A + B type binaries. Three spectra of SMC-SC4 show radial velocity variations, consistent with the photometric period of 184.26 days found in Mennickent et al. 2010. The optical spectra of the metallic lines in both systems show combined absorption and emission components that imply that they are formed in a flattened envelope. A comparison of the radial velocity variations in SMC-SC4 and the separation of the V and R emission components in the Halpha emission profile indicate that this envelope, and probably also the envelope around SMC-SC3, is a circumbinary disk with a characteristic orbital radius some three times the radius of the binary system. The optical spectra of SMC-SC3 and SMC-SC4 show, respectively, HeI emission lines and discrete Blue Absorption Components (BACs) in metallic lines. The high excitations of the HeI lines in the SMC-SC3 spectrum and the complicated variations of FeII emission and absorption components with orbital phase in the spectrum of SMC-SC4 suggests that shocks occur between the winds and various static regions of the stars' co-rotating binary-disk complexes. We suggest that BACs arise from wind shocks from the A star impacting the circumbinary disk and a stream of former wind-efflux from the B star accreting onto the A star. We dub these objects prototype of a small group of Magellanic Cloud wind-interacting A + B binaries.Comment: To be published in MNRA

SARCS strong lensing galaxy groups: I - optical, weak lensing, and scaling laws

We present the weak lensing and optical analysis of the SL2S-ARCS (SARCS) sample of strong lens candidates. The sample is based on the Strong Lensing Legacy Survey (SL2S), a systematic search of strong lensing systems in the photometric Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). The SARCS sample focuses on arc-like features and is designed to contain mostly galaxy groups. We briefly present the weak lensing methodology that we use to estimate the mass of the SARCS objects. Among 126 candidates, we obtain a weak lensing detection for 89 objects with velocity dispersions of the Singular Isothermal Sphere mass model ranging from 350 to 1000 km/s with an average value of 600km/s, corresponding to a rich galaxy group (or poor cluster). From the galaxies belonging to the bright end of the group's red sequence (M_i<-21), we derive the optical properties of the SARCS candidates. We obtain typical richnesses of N=5-15 galaxies and optical luminosities of L=0.5-1.5e+12 Lsol (within a radius of 0.5 Mpc). We use these galaxies to compute luminosity density maps, from which a morphological classification reveals that a large fraction of the sample are groups with a complex light distribution, either elliptical or multimodal, suggesting that these objects are dynamically young structures. We finally combine the lensing and optical analyses to draw a sample of 80 most secure group candidates, i.e. weak lensing detection and over-density at the lens position in the luminosity map, to remove false detections and galaxy-scale systems from the initial sample. We use this reduced sample to probe the optical scaling relations in combination with a sample of massive galaxy clusters. We detect the expected correlations over the probed range in mass with a typical scatter of 25% in the SIS velocity dispersion at a given richness or luminosity, making these scaling laws interesting mass proxie

MS 2053.7-0449: Confirmation of a bimodal mass distribution from strong gravitational lensing

We present the first strong lensing study of the mass distribution in the cluster MS 2053-04 based on HST archive data. This massive, X-ray luminous cluster has a redshift z=0.583, and it is composed of two structures that are gravitationally bound to each other. The cluster has one multiply imaged system constituted by a double gravitational arc. We have performed a parametric strong lensing mass reconstruction using NFW density profiles to model the cluster potential. We also included perturbations from 23 galaxies, modeled like elliptical singular isothermal sphere, that are approximately within 1'x1' around the cluster center. These galaxies were constrained in both the geometric and dynamical parameters with observational data. Our analysis predicts a third image which is slightly demagnified. We found a candidate for this counter-image near the expected position and with the same F702W-F814W colors as the gravitational arcs in the cluster. The results from the strong lensing model shows the complex structure in this cluster, the asymmetry and the elongation in the mass distribution, and are consistent with previous spectrophotometric results that indicate that the cluster has a bimodal mass distribution. Finally, the derived mass profile was used to estimate the mass within the arcs and for comparison with X-ray estimates.Comment: To be published in ApJ (accepted

Colaboración con la empresa en la formación de alumnos de ingeniería [Collaboration with the company in the training of engineering students]

En este trabajo se muestra una experiencia llevada a cabo para mejorar la formación de los alumnos de ingeniería a base de involucrar en dicha formación a las empresas del entorno. Esta actividad está basada en la metodología PBL (Aprendizaje basado en proyectos). La colaboración de las empresas se basa en la oferta de trabajos para asignaturas concretas. Estos trabajos se realizan en grupo y son tutorizados, tanto por la empresa como por el profesorado de la asignatura. La colaboración con el entorno empresarial de la Universidad supone no solamente un incremento en las competencias propias de la asignatura sino también en las competencias transversales (capacidad de trabajo en equipo, capacidad de comunicación, toma de decisiones consensuadas, etc.), así como una mejora importante de cara a la empleabilidad de los alumnos. Esta actividad se está desarrollando desde el curso 1998-99 y con resultados plenamente satisfactorios, por lo que actualmente se utiliza en más asignaturas de nuestra Universidad. [This paper describes an experiment to improve the training of engineering students based on the involvement of companies from the environment of the university. The PBL (Project-Based Learning) methodology is at the foundation of this activity. The collaboration of the companies is based on their offer of work for specific subjects. The projects are done in groups and the students have both an academic and a company supervisor. Collaborating with these companies improves the competences inherent to the subject, but also transversal competences like teamwork capacity, communication skills or consensual decision-making; it also increases the employability of the students. This activity has been developed since 1998-99 with satisfactory results, so it is currently used in more subjects of our University.

Are Type, Frequency, and Daily Time Equally Valid Estimators of Support Needs in Children With Intellectual Disability? A Multitrait?Multimethod Analysis of the Supports Intensity Scale for Children (SIS-C)

ABSTRACT: Support needs represent the intensity of support required by a person with a disability in order to take part in the activities related to normative human functioning. The Supports Intensity Scale for Children (SIS-C) is possibly the most promising tool for assessing and designing individualized support programs in children with intellectual disability. The SIS-C measures support needs across 61 activities, each one assessed along three methods: type of support, frequency, and daily time during which support is to be given. We investigated the impact of method effects in the SIS-C through a bifactor approach to the analysis of multitrait?multimethod matrices. The results suggest that neither intensity nor frequency scales produced method effects that significantly distorted the measurement of support needs. However, the daily support time method had substantial undesirable effects on five of the seven subscales of support needs. Considerations about support needs assessment and future modifications of the scale are discussed.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Work on this research was funded by the Spanish Ministry of the Economy and Competitiveness (R&D Projects, PSI2012- 36278), and the Autonomous Community of Castile and Leon (R&D Projects, SA120U13)

A hot Jupiter transiting a mid-K dwarf found in the pre-OmegaCam Transit Survey

We describe the pre-OmegaTranS project, a deep survey for transiting extra-solar planets in the Carina region of the Galactic Disk. In 2006-2008 we observed a single dense stellar field with a very high cadence of ~2min using the ESO Wide Field Imager at the La Silla Observatory. Using the Astronomical Wide-field System for Europe and the Munich Difference Imaging Analysis pipeline, a module that has been developed for this project, we created the light curves of 16000 stars with more than 4000 data points which we searched for periodic transit signals using a box-fitting least-squares detection algorithm. All light curves are publicly available. In the course of the pre-OmegaTranS project we identified two planet candidates - POTS-1b and POTS-C2b - which we present in this work. With extensive follow-up observations we were able to confirm one of them, POTS-1b, a hot Jupiter transiting a mid-K dwarf. The planet has a mass of 2.31+-0.77M_Jup and a radius of 0.94+-0.04R_Jup and a period of P=3.16d. The host star POTS-1 has a radius of 0.59+-0.02R_Sun and a mass of 0.70+-0.05M_Sun. Due to its low apparent brightness of I=16.1mag the follow-up and confirmation of POTS-1b was particularly challenging and costly.Comment: 18 pages, 23 figures, accepted for publication in MNRA

Serious limitations of the QTL/Microarray approach for QTL gene discovery

<p>Abstract</p> <p>Background</p> <p>It has been proposed that the use of gene expression microarrays in nonrecombinant parental or congenic strains can accelerate the process of isolating individual genes underlying quantitative trait loci (QTL). However, the effectiveness of this approach has not been assessed.</p> <p>Results</p> <p>Thirty-seven studies that have implemented the QTL/microarray approach in rodents were reviewed. About 30% of studies showed enrichment for QTL candidates, mostly in comparisons<b/> between congenic and background strains. Three studies led to the identification of an underlying <it>QTL </it>gene. To complement the literature results, a microarray experiment was performed using three mouse congenic strains isolating the effects of at least 25 biometric QTL. Results show that genes in the congenic donor regions were preferentially selected. However, within donor regions, the distribution of differentially expressed genes was homogeneous once gene density was accounted for. Genes within identical-by-descent (IBD) regions were less likely to be differentially expressed in chromosome 2, but not in chromosomes 11 and 17. Furthermore, expression of <it>QTL </it>regulated in <it>cis </it>(<it>cis </it>eQTL) showed higher expression in the background genotype, which was partially explained by the presence of single nucleotide polymorphisms (SNP).</p> <p>Conclusions</p> <p>The literature shows limited successes from the QTL/microarray approach to identify <it>QTL </it>genes. Our own results from microarray profiling of three congenic strains revealed a strong tendency to select <it>cis-</it>eQTL over <it>trans-</it>eQTL. IBD regions had little effect on rate of differential expression, and we provide several reasons why IBD should not be used to discard eQTL candidates. In addition, mismatch probes produced false <it>cis-</it>eQTL that could not be completely removed with the current strains genotypes and low probe density microarrays. The reviewed studies did not account for lack of coverage from the platforms used and therefore removed genes that were not tested. Together, our results explain the tendency to report QTL candidates as differentially expressed and indicate that the utility of the QTL/microarray as currently implemented is limited. Alternatives are proposed that make use of microarray data from multiple experiments to overcome the outlined limitations.</p

Internal kinematics of spiral galaxies in distant clusters III. Velocity fields from FORS2/MXU spectroscopy

(Abridged) We study the impact of cluster environment on the evolution of spiral galaxies by examining their structure and kinematics. Rather than two-dimensional rotation curves, we observe complete velocity fields by placing three adjacent and parallel FORS2 MXU slits on each object, yielding several emission and absorption lines. The gas velocity fields are reconstructed and decomposed into circular rotation and irregular motions using kinemetry. To quantify irregularities in the gas kinematics, we define three parameters: sigma_{PA} (standard deviation of the kinematic position angle), Delta phi (the average misalignment between kinematic and photometric position angles) and k_{3,5} (squared sum of the higher order Fourier terms). Using local, undistorted galaxies from SINGS, these can be used to establish the regularity of the gas velocity fields. Here we present the analysis of 22 distant galaxies in the MS0451.6-0305 field with 11 members at z=0.54. In this sample we find both field (4 out of 8) and cluster (3 out of 4) galaxies with velocity fields that are both irregular and asymmetric. We show that these fractions are underestimates of the actual number of galaxies with irregular velocity fields. The values of the (ir)regularity parameters for cluster galaxies are not very different from those of the field galaxies, implying that there are isolated field galaxies that are as distorted as the cluster members. None of the deviations in our small sample correlate with photometric/structural properties like luminosity or disk scale length in a significant way. Our 3D-spectroscopic method successfully maps the velocity field of distant galaxies, enabling the importance and efficiency of cluster specific interactions to be assessed quantitatively.Comment: accepted for publication in A&A, high resolution version available at http://www.astro.rug.nl/~kutdemir/papers

Characterizing SL2S galaxy groups using the Einstein radius

We analyzed the Einstein radius, $\theta_E$, in our sample of SL2S galaxy groups, and compared it with $R_A$ (the distance from the arcs to the center of the lens), using three different approaches: 1.- the velocity dispersion obtained from weak lensing assuming a Singular Isothermal Sphere profile ($\theta_{E,I}$), 2.- a strong lensing analytical method ($\theta_{E,II}$) combined with a velocity dispersion-concentration relation derived from numerical simulations designed to mimic our group sample, 3.- strong lensing modeling ($\theta_{E,III}$) of eleven groups (with four new models presented in this work) using HST and CFHT images. Finally, $R_A$ was analyzed as a function of redshift $z$ to investigate possible correlations with L, N, and the richness-to-luminosity ratio (N/L). We found a correlation between $\theta_{E}$ and $R_A$, but with large scatter. We estimate $\theta_{E,I}$ = (2.2 $\pm$ 0.9) + (0.7 $\pm$ 0.2)$R_A$, $\theta_{E,II}$ = (0.4 $\pm$ 1.5) + (1.1 $\pm$ 0.4)$R_A$, and $\theta_{E,III}$ = (0.4 $\pm$ 1.5) + (0.9 $\pm$ 0.3)$R_A$ for each method respectively. We found a weak evidence of anti-correlation between $R_A$ and $z$, with Log$R_A$ = (0.58$\pm$0.06) - (0.04$\pm$0.1)$z$, suggesting a possible evolution of the Einstein radius with $z$, as reported previously by other authors. Our results also show that $R_A$ is correlated with L and N (more luminous and richer groups have greater $R_A$), and a possible correlation between $R_A$ and the N/L ratio. Our analysis indicates that $R_A$ is correlated with $\theta_E$ in our sample, making $R_A$ useful to characterize properties like L and N (and possible N/L) in galaxy groups. Additionally, we present evidence suggesting that the Einstein radius evolves with $z$.Comment: Accepted for publication in Astronomy & Astrophysics. Typos correcte

Dark matter-baryons separation at the lowest mass scale: the Bullet Group

We report on the X-ray observation of a strong lensing selected group, SL2S J08544-0121, with a total mass of $2.4 \pm 0.6 \times 10^{14}$ $\rm{M_\odot}$ which revealed a separation of $124\pm20$ kpc between the X-ray emitting collisional gas and the collisionless galaxies and dark matter (DM), traced by strong lensing. This source allows to put an order of magnitude estimate to the upper limit to the interaction cross section of DM of 10 cm$^2$ g$^{-1}$. It is the lowest mass object found to date showing a DM-baryons separation and it reveals that the detection of bullet-like objects is not rare and confined to mergers of massive objects opening the possibility of a statistical detection of DM-baryons separation with future surveys.Comment: 5 pages, 3 figures. Accepted for publication in MNRAS Letters. Typos correcte