The Ultraviolet Luminosity Density of the Universe from Photometric Redshifts of Galaxies in the Hubble Deep Field

Studies of the Hubble Deep Field (HDF) and other deep surveys have revealed an apparent peak in the ultraviolet (UV) luminosity density, and therefore the star-formation rate density, of the Universe at redshifts 1<z<2. We use photometric redshifts of galaxies in the HDF to determine the comoving UV luminosity density and find that, when errors (in particular, sampling error) are properly accounted for, a flat distribution is statistically indistinguishable from a distribution peaked at z~1.5. Furthermore, we examine the effects of cosmological surface brightness (SB) dimming on these measurements by applying a uniform SB cut to all galaxy fluxes after correcting them to redshift z=5. We find that, comparing all galaxies at the same intrinsic surface brightness sensitivity, the UV luminosity density contributed by high intrinsic SB regions increases by almost two orders of magnitude from z~0 to z~5. This suggests that there exists a population of objects with very high star formation rates at high redshifts that apparently do not exist at low redshifts. The peak of star formation, then, may occur somewhere beyond a redshift z~>5.Comment: 4 pages total, including 3 embedded figures, to appear in the proceedings of the Xth Rencontres de Blois, "The Birth of Galaxies." LaTeX style file include

Variational approach for walking solitons in birefringent fibres

We use the variational method to obtain approximate analytical expressions for the stationary pulselike solutions in birefringent fibers when differences in both phase velocities and group velocities between the two components and rapidly oscillating terms are taken into account. After checking the validity of the approximation we study how the soliton pulse shape depends on its velocity and nonlinear propagation constant. By numerically solving the propagation equation we have found that most of these stationary solutions are stable.Comment: LaTeX2e, uses graphicx package, 23 pages with 8 figure

Estudio de la respuesta de plantas de pepino (Cucumis Sativbus L. CV). Hyclos) a diferentes relaciones NO3/NH4+

En este trabajo se estudia la respuesta de plantas de pepino a diversas relaciones N03-/NH4+ (100/0, 80/20, 60/40, 30/70), al objeto de comprobar el grado de tolerancia de esta especie vegetal a concentraciones crecientes de NH4 + en el medio de cultivo. Las plantas cultivadas con la relación 60/40 presentaron un peso superior a las testigo (100/0). Por el contrario, las sometidas a las relaciones 80/20 y 30/70 ofrecieron una reducción en el crecimiento. A medida que aumenta el aporte de NH4+ disminuye la concentración de Ca, Mg, Mn y B en hoja, de Ca y Mg en raíz y aumenta la concentración de P, K Y Zn en hoja y de Fe, B y Zn en raíz. Finalmente a las plantas de pepino cv. Hyclos no les beneficia el NH4+ cuando la mayor parte del N está como N03- (80/20); les resulta eficaz el catión cuando se suministra en concentraciones casi equivalentes a las de N03-, a la vez que niveles muy altos de NH4+ (70%) causan efectos perjudiciales.STUDY OF CUCUMBER PLANT RESPONSE TO N03- /NH4 + RATIOS Cucumber plants were hydroponically grown in a greenhouse with four N03- /NH/ ratios (100/0, 80/20, 60/40 and 30/70), in order to study their tolerance to NH/ supply. Plants grown in 60/40 N03- /NH/ solution displayed higher weight than N03- treated plants. By contrast, plants grown with N03- /NH/ ratios of 80/20 and 30/70 showed lower growth than plants fed with N03- as the sole source of N. As the proportion of NH/ in the nutrient solution was increased Ca, Mg, Mn and B in the leaf and Ca and Mg in the root decreased, whereas P, K, and Zn concentrations in the leaf and Fe, B and Zn levels in the root increased. Finally, NH/ supplied in low and high concentrations was harmful to cucumber plants cv. Hyclos development, whereas it is really efficient when N03• and NH/ are supplied in about equivalent amounts (60/40)

A z=5.34 Galaxy Pair in the Hubble Deep Field

We present spectrograms of the faint V-drop (V(606) = 28.1, I(814) = 25.6) galaxy pair HDF3-951.1 and HDF3-951.2 obtained at the Keck II Telescope. Fernandez-Soto, Lanzetta, & Yahil (1998) derive a photometric redshift of z(ph) = 5.28 (+0.34,-0.41; 2 sigma) for these galaxies; our integrated spectrograms show a large and abrupt discontinuity near 7710 (+- 5) Angstroms. This break is almost certainly due to the Lyman alpha forest as its amplitude (1 - fnu(short) / fnu(long) > 0.87; 95% confidence limit) exceeds any discontinuities observed in stellar or galaxian rest-frame optical spectra. The resulting absorption-break redshift is z=5.34 (+- 0.01). Optical/near-IR photometry from the HDF yields an exceptionally red (V(606)-I(814)) color, consistent with this large break. A more accurate measure of the continuum depression blueward of Lyman alpha utilizing the imaging photometry yields D(A) = 0.88. The system as a whole is slightly brighter than L*(1500) relative to the z~3 Lyman break population and the total star formation rate inferred from the UV continuum is ~22 h(50)^-2 M(sun) yr^-1 (q(0) = 0.5) assuming the absence of dust extinction. The two individual galaxies are quite small (size scales < 1 h(50)^-1 kpc). Thus these galaxies superficially resemble the Pascarelle etal (1996) ``building blocks''; if they comprise a gravitationally bound system, the pair will likely merge in a time scale ~100 Myr.Comment: 18 pages, 4 figures; accepted to A

Impact exercise strategies in the HRQOL of the sedentary adults

El objetivo del estudio fue analizar la eficacia de diferentes estrategias de intervención del ejercicio físico y relacionarlas con la percepción de la calidad de vida relacionada con la salud (CVRS) en adultos mayores sedentarios. Participaron 100 sujetos, con edades comprendidas entre los 60 y 70 años, que fueron divididos aleatoriamente en cuatro grupos: control, recomendación, prescripción y monitorización. La intervención de ejercicio físico tuvo una duración de 6 meses. Para la valoración de la CVRS se utilizó el cuestionario SF-36. Los grupos monitorización y prescripción obtuvieron los mayores valores en todos los dominios en el análisis intragrupos. La función física y la salud general y mental obtienen los mayores valores significativos entre grupos (p<.05). Entre los grupos prescripción y monitorización no existen diferencias significativas en ninguna dimensión. Sin embargo el grupo de monitorización obtuvo valores superiores en salud mental, no siendo así en salud físicaThe aim of the study was to analyze the effectiveness of different intervention strategies of exercise and relate the perception of quality of life related to health (HRQOL) in sedentary older adults. It involved 100 subjects, aged between 60 and 70, who were randomly divided into four groups: control, recommend, prescribe and monitor. The exercise intervention lasted 6 months. The SF-36 questionnaire was used for the assessment of HRQOL. The monitoring and prescription groups had higher values in all domains in the intragroup analysis. Physical function and health and mental health obtain the highest significant values between groups (p <.05). There are no significant differences at all in any domain among prescription and monitoring groups. However, the monitoring group obtained higher values in mental health, but were not in physical healt

A Seventeen-Year Epidemiological Surveillance Study of Borrelia burgdorferi Infections in Two Provinces of Northern Spain

This paper reports a 17-year seroepidemiological surveillance study of Borrelia burgdorferi infection, performed with the aim of improving our knowledge of the epidemiology of this pathogen. Serum samples (1,179) from patients (623, stratified with respect to age, sex, season, area of residence and occupation) bitten by ticks in two regions of northern Spain were IFA-tested for B. burgdorferi antibodies. Positive results were confirmed by western blotting. Antibodies specific for B. burgdorferi were found in 13.3% of the patients; 7.8% were IgM positive, 9.6% were IgG positive, and 4.33% were both IgM and IgG positive. Five species of ticks were identified in the seropositive patients: Dermacentor marginatus (41.17% of such patients) Dermacentor reticulatus (11.76%), Rhiphicephalus sanguineus (17.64%), Rhiphicephalus turanicus (5.88%) and Ixodes ricinus (23.52%). B. burgdorferi DNA was sought by PCR in ticks when available. One tick, a D. reticulatus male, was found carrying the pathogen. The seroprevalence found was similar to the previously demonstrated in similar studies in Spain and other European countries

An Empirical Limit on Extremely High Redshift Galaxies

We apply the Lyman absorption signature to search for galaxies at redshifts z \~ 6 - 17 using optical and infrared images of the Hubble Deep Field. The infrared images are sensitive to a point source 5 sigma detection threshold of AB(22,000) = 23.8, which adopting plausible assumptions to relate rest-frame ultraviolet flux densities to unobscured star formation rates is easily sufficient to detect the star formation rates expected for massive elliptical galaxy formation to quite high redshifts. For q_0 = 0.5, the infrared images are sensitive to an unobscured star formation rate of 100 h^-2 solar masses per year to redshifts as large as z = 17, and for q_0 = 0, the infrared images are sensitive to an unobscured star formation rate of 300 h^-2 solar masses per year to redshifts as large as z = 14. The primary result of the analysis is that only one extremely high redshift galaxy candidate is identified at the 5 sigma level of significance (and four at the 4 sigma level). This implies a strict upper limit to the surface density of extremely high redshift galaxies of < 1.5 arcmin^-2 to a limiting magnitude threshold AB(22,000) = 23.8. This also implies a strict upper limit to the volume density of extremely high redshift galaxies if (and only if) such galaxies are not highly obscured by dust.Comment: 14 pages, LaTex, 7 figures, to be published in the Astronomical Journa

The evolution of Balmer jump selected galaxies in the ALHAMBRA survey

We present a new color-selection technique, based on the Bruzual & Charlot models convolved with the bands of the ALHAMBRA survey, and the redshifted position of the Balmer jump to select star-forming galaxies in the redshift range 0.5 < z < 1.5. These galaxies are dubbed Balmer jump Galaxies BJGs. We apply the iSEDfit Bayesian approach to fit each detailed SED and determine star-formation rate (SFR), stellar mass, age and absolute magnitudes. The mass of the haloes where these samples reside are found via a clustering analysis. Five volume-limited BJG sub-samples with different mean redshifts are found to reside in haloes of median masses $\sim 10^{12.5 \pm 0.2} M_\odot$ slightly increasing toward z=0.5. This increment is similar to numerical simulations results which suggests that we are tracing the evolution of an evolving population of haloes as they grow to reach a mass of $\sim 10^{12.7 \pm 0.1} M_\odot$ at z=0.5. The likely progenitors of our samples at z$\sim$3 are Lyman Break Galaxies, which at z$\sim$2 would evolve into star-forming BzK galaxies, and their descendants in the local Universe are elliptical galaxies.Hence, this allows us to follow the putative evolution of the SFR, stellar mass and age of these galaxies. From z$\sim$1.0 to z$\sim$0.5, the stellar mass of the volume limited BJG samples nearly does not change with redshift, suggesting that major mergers play a minor role on the evolution of these galaxies. The SFR evolution accounts for the small variations of stellar mass, suggesting that star formation and possible minor mergers are the main channels of mass assembly.Comment: 14 pages, 10 figures. Submitted to A&A. It includes first referee's comments. Abstract abridged due to arXiv requirement

A detailed spectral study of GRB 041219A and its host galaxy

GRB 041219A is one of the longest and brightest gamma-ray bursts (GRBs) ever observed. It was discovered by the INTEGRAL satellite, and thanks to a precursor happening about 300 s before the bulk of the burst, ground based telescopes were able to catch the rarely-observed prompt emission in the optical and in the near infrared bands. Here we present the detailed analysis of its prompt gamma-ray emission, as observed with IBIS on board INTEGRAL, and of the available X-ray afterglow data collected by XRT on board Swift. We then present the late-time multi-band near infrared imaging data, collected at the TNG, and the CFHT, that allowed us to identify the host galaxy of the GRB as an under-luminous, irregular galaxy of about 5x10^9 M_Sun at best fit redshift of z=0.31 -0.26 +0.54. We model the broad-band prompt optical to gamma-ray emission of GRB 041219A within the internal shock model. We were able to reproduce the spectra and light curve invoking the synchrotron emission of relativistic electrons accelerated by a series of propagating shock waves inside a relativistic outflow. On the other hand, it is less easy to simultaneously reproduce the temporal and spectral properties of the infrared data.Comment: 12 pages, 9 figures, accepted for publication in MNRAS, Figure 5 in reduced qualit