Calibration of star formation rate tracers for short- and long-lived star formation episodes

To derive the history of star formation in the Universe a set of calibrated star formation rate tracers at different wavelengths is required. The calibration has to consistently take into account the effects of extinction, star formation regime (short or long-lived) and evolutionary state to avoid biases at different redshift ranges. We use evolutionary synthesis models optimized for intense episodes of star formation in order to compute a consistent calibration of the most usual star formation rate tracers at different energy ranges, from X-ray to radio luminosities. Nearly-instantaneous and continuous star formation regimes, and the effect of interstellar extinction are considered, as well as the effect of metallicity on the calibration of the different estimators. A consistent calibration of a complete set of star formation rate tracers is presented, computed for the most usual star-forming regions conditions: evolutionary state, star formation regime, interstellar extinction and initial mass function. We discuss the validity of the different tracers in different star formation scenarios and compare our predictions with previous calibrations of general use. Nearly-instantaneous and continuous star formation regimes must be distinguished. While the Star Formation Strength (\msun) should be used for the former, the more common Star Formation Rate (\msun yr$^{-1}$) is only valid for episodes forming stars at a constant rate during extended periods for time. Moreover, even for the latter, the evolutionary state should be taken into account, since most SFR tracers stabilize only after 100 Myr of evolution.Comment: Accepted for publication in A&A, webtool in http://www.laeff.cab.inta-csic.es/research/sfr/, 19 pages, 10 figures, 14 tables. New version including language style revisio

Rewrite Slatt in python 3

RESUMEN: Las reglas de asociación son objetos matemáticos empleados de forma extensa en disciplinas como la minería de datos, aprendizaje automático y representación del conocimiento, entre otros campos. Slatt es un proyecto de software libre desarrollado por José Luis Balcázar (Universidad Politécnica de Barcelona). Ofrece funcionalidades para el cálculo de reglas de asociación. Para ello, se apoya en implementaciones del algoritmo Apriori para el cálculo de clausuras, el retículo de las clausuras y, entre otras funcionalidades, devuelve las reglas representativas para cualquier elección de los parámetros de soporte y confianza. En este proyecto, se ha mejorado este software utilizando la última versión de Slatt, implementando diferentes algoritmos para: hipergrafos y problemas relacionados con esta estructura de datos; cálculo de clausuras y retículos (lattices); Este trabajo ha requerido la búsqueda y análisis de algoritmos propuestos en la literatura científica sobre los puntos anteriores. El lenguaje de desarrollo será Python3.ABSTRACT: Association rules are mathematical objects used extensively in disciplines such as data mining, machine learning, and knowledge representation, among other fields. Slatt is a free software project developed by José Luis Balcázar (Polytechnic University of Barcelona). It offers functionalities for the calculation of association rules. To do this, it relies on implementations of the a priori algorithm for the calculation of closures, the lattice of closures and, among others functionalities, returns the representative rules for any choice of support and trust parameters. In this project, this software has been improved using as a basis the implementations available in Slatt applied to: hypergraphs and algorithms with application to these objects; calculation of closures and lattices (lattices); This work has required the search and analysis of algorithms proposed in the scientific literature on the previous points. The development language will be Python3, the previous implementation being in Python 2.7Grado en Ingeniería Informátic

On the contribution of ULXs to stellar feedback: an intermediate mass black hole candidate and the population of ULXs in the low-metallicity starburst galaxy ESO 338-4

X-ray radiation from accreting compact objects is an important part of stellar feedback. The metal-poor galaxy ESO 338-4 has experienced vigorous starburst during the last 40 Myr and contains some of the most massive super star clusters in the nearby Universe. Given its starburst age and its star-formation rate, ESO 338-4 is one of the most efficient nearby manufactures of neutron stars and black holes, hence providing an excellent laboratory for feedback studies. We compared X-ray images and spectra obtained by XMM-Newton and Chandra telescopes with integral field spectroscopic VLT MUSE observations in the optical to constrain the nature of strong X-ray emitters. X-ray observations uncover three ultraluminous X-ray sources (ULXs) in ESO 338-4. The brightest among them, ESO 338~X-1, has X-ray luminosity in excess of 10^{40} erg/s. We speculate that ESO 338-4 is powered by accretion on an intermediate-mass (~300Msun) black hole. We show that X-ray radiation from ULXs and hot superbubbles strongly contributes to HeII ionization and general stellar feedback in this template starburst galaxy.Comment: A&A, in pres

Multiwavelength analysis of the Lyman alpha emitting galaxy Haro 2: relation between the diffuse Lyman alpha and soft X-ray emissions

In order to use Lyman alpha (Lya) emission as star formation tracer in cosmological studies, we must understand how the resonant scattering affects the escape fraction of the Lya photons. Thus, high spatial resolution multiwavelength studies of nearby Lya emitters, like Haro 2, are highly needed. For that purpose, we have used Chandra X-ray and HST (UV, optical and NIR) images of Haro 2, and STIS and ground-based spectral images along its major and minor axes, to characterize the Lya emission and the properties of the stellar population. The UV, Ha (Halpha) and FIR luminosities of the Haro 2 nuclear starburst are reproduced using evolutionary synthesis models assuming a young stellar population with ages ~3.5-5.0 Myr, affected by differential interstellar extinctions. The observed X-ray emission is attributed to gas heated by the mechanical energy released by the starburst (soft component) and a Ultra-Luminous X-ray source candidate (hard). Both compact and diffuse Lya components are observed. Whereas Lya is spatially decoupled from Balmer lines emission, Balmer decrement and UV continuum, the diffuse Lya component is spatially correlated with the diffuse soft X-ray emission. Moreover, unlike the compact one, diffuse Lya shows luminosities larger than predicted from Ha, assuming case B recombination and dust extinction as derived from Ha/Hbeta. We propose that, whereas the compact Lya emission is associated to the massive stellar clusters and is affected by outflows and dust extinction, the diffuse Lya originates in gas ionized by the hot plasma responsible for the soft X-ray radiation, as suggested by their spatial correlation and by the measured L(Ha)/LsoftX ratios. Calibration of Lya as star formation rate tracer should therefore include both effects (destruction vs. enhancement) to avoid biases in the study of galaxies at cosmological distances.Comment: Accepted for publication in A&A, 18 pages, 8 figures, 9 tables. If problems with quality of images, see http://www.cab.inta-csic.es/users/otih/haro2-v63.clean.pd

Physical properties and evolutionary state of the Lyman alpha emitting starburst galaxy IRAS 08339+6517

Though Lyman alpha emission (Lya) is one of the most used tracers of massive star formation at high redshift, a correct understanding of radiation transfer effects by neutral gas is required to properly quantify the star formation rate along the history of the Universe. We are embarked in a program to study the properties of the Lya emission (spectral profile, spatial distribution, relation to Balmer lines intensity,...) in several local starburst galaxies. We present here the results obtained for IRAS 08339+6517. Using evolutionary population synthesis models, we have characterized the properties of the starburst (UV continuum, Halpha, total infrared and X-ray emissions, etc.), which transformed 1.4e+8 Mo of gas into stars around 5-6 Myr ago. In addition to the central compact emission blob, we have identified a diffuse Lya emission component smoothly distributed over the whole central area of IRAS 08339+6517. This diffuse emission is spatially decoupled from the UV continuum, the Halpha emission or the Halpha/Hbeta ratio. Both locally and globally, the Lya/Halpha ratio is lower than the Case B predictions, even after reddening correction, with an overall Lya escape fraction of only 4%. We conclude that in IRAS 08339+6517 the resonant scattering of Lya photons by an outflowing shell of neutral gas causes their highly-efficient destruction by dust, which explains the low Lya escape fraction measured. These results stress again the importance of a proper correction of scattering and transfer effects when using Lya to derive the star formation rate in high-redshift galaxies.Comment: Accepted for publication in A&A, 17 pages, 13 figures, 8 tables. If problems with quality of images, see https://cloud.cab.inta-csic.es/public.php?service=files&file=%2Fotih%2Ffiles%2Foti_mas%2Firas%2Firas-v53.ack_referee.pd

Absence of the state in the state in prisons. The limitations of the current penitential readaptation model in Mexico.

Las cárceles en México se caracterizan por permanentes violaciones a los derechos humanos, impunidad, autogobierno, corrupción, violencia y adicciones. El Centro de Análisis de Políticas Públicas México Evalúa (2013, pág. 40) señala que muchas cárceles en México son gobernadas por grupos de internos que luchan por el control de las mismas. Tan solo en 2010, se estima que la violencia en las cárceles dejó un saldo de 400 internos muertos a causa de riñas (University of Pittsburgh, 2014, pág. s/p). En teoría, con la privación de la libertad se busca que quienes han cometido determinados delitos desarrollen las habilidades necesarias para una adecuada reinserción social, es decir, mitigar los factores motivacionales de la comisión delictiva y así evitar la reincidencia, pero el uso excesivo de la cárcel y una intervención ineficiente han provocado que los centros penitenciarios se conviertan en escuelas del crimen