Galactic Outflows and Evolution of the Interstellar Medium

We present a model to self-consistently describe the joint evolution of starburst galaxies and the galactic wind resulting from this evolution. We combine the population synthesis code Starburst99 with a semi-analytical model of galactic outflows and a model for the distribution and abundances of chemical elements inside the outflows. Starting with a galaxy mass, formation redshift, and adopting a particular form for the star formation rate, we describe the evolution of the stellar populations in the galaxy, the evolution of the metallicity and chemical composition of the interstellar medium (ISM), the propagation of the galactic wind, and the metal-enrichment of the intergalactic medium (IGM). In this paper, we study the properties of the model, by varying the mass of the galaxy, the star formation rate, and the efficiency of star formation. Our main results are the following: (1) For a given star formation efficiency f*, a more extended period of active star formation tends to produce a galactic wind that reaches a larger extent. If f* is sufficiently large, the energy deposited by the stars completely expels the ISM. Eventually, the ISM is being replenished by mass loss from supernovae and stellar winds. (2) For galaxies with masses above 10^11 Msun, the material ejected in the IGM always falls back onto the galaxy. Hence lower-mass galaxies are the ones responsible for enriching the IGM. (3) Stellar winds play a minor role in the dynamical evolution of the galactic wind, because their energy input is small compared to supernovae. However, they contribute significantly to the chemical composition of the galactic wind. We conclude that the history of the ISM enrichment plays a determinant role in the chemical composition and extent of the galactic wind, and therefore its ability to enrich the IGM.Comment: 17 pages, 14 color figures. Accepted for publication in MNRA

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Les essais de François Paré : Une poétique du tourment

Cet article vise à rendre compte des figures exemplaires de la Franco-Amérique présentes dans l’oeuvre de François Paré afin de témoigner de l’évolution de la pensée de l’essayiste. Il s’agira de traiter, dans un premier temps, des plus importantes que l’on retrouve dans son premier essai, Les littérature de l’exiguïté, et, dans un deuxième temps, de celles présentes dans son dernier essai sur le sujet, Le fantasme d’Escanaba, qui prolonge et cherche à dépasser les visées du premier. Conscient des limites de sa notion fondamentale, Paré restreint son corpus dans Le fantasme d’Escanaba pour mettre en lumière les auteurs phares de la Franco-Amérique en laissant de côté les littératures de l’exiguïté de par le monde. Par ailleurs, un des enjeux poétiques du parcours essayistique de Paré devient dans le dernier essai le glissement vers un « je » nostalgique dont le parcours individuel reste intimement lié à son objet d’études. En analysant le panthéon des auteurs marquants pour François Paré, on tentera de mieux circonscrire les convergences, les contradictions et les « dérives obsessionnelles » qui habitent l’essayiste.This article seeks to give an account of the exemplary figures of Franco-America present in the work of François Paré in order to follow the evolution of his thinking as an essayist. Our goal is first to look at key elements of his first essay, Les littératures de l’exiguïté, and, second, to understand his most recent essay on this topic, Le fantasme d’Escanaba, which continues the first and seeks to go beyond it. Aware of the limits of his basic concept, Paré in Le fantasme d’Escanaba restricts his corpus in order to foreground seminal authors of Franco-America, leaving aside the literatures of smallness throughout the world. Another poetic issue raised by Paré’s evolution as an essayist is a shift, apparent in the most recent essay, toward a nostalgic “I” whose individual trajectory remains intimately connected to his object of study. In analysing the pantheon of authors who have had a crucial influence on François Paré, we will attempt to provide a clearer definition of the convergences, contradictions and “obsessive drifts” that inhabit him as an essayist.Este artículo pretende dar cuenta de las figuras ejemplares de la América francohablante presentes en la obra de François Paré, con el fin de mostrar la evolución del pensamiento del ensayista. En un primer tiempo, se trata de ocuparse de las más importantes que aparecen en su primer ensayo, Les littérature de l’exiguïté (Las literaturas de la exigüidad) y, en un segundo tiempo, de las que están presentes en su último ensayo sobre este tema, Le fantasme d’Escanaba (La fantasía de Escanaba), que prolonga y trata de superar las intenciones del primero. Consciente de los límites de su noción fundamental, Paré restringe su corpus en Le fantasme d’Escanaba para poner de relieve a los autores más importantes de la América francohablante, dejando de lado las literaturas de la exigüidad que hay por el mundo. Por otra parte, uno de los retos poéticos del recorrido ensayístico de Paré se transforma, en el último ensayo, en un deslizamiento hacia un ‘yo’ nostálgico cuyo recorrido individual permanece íntimamente vinculado al objeto de sus estudios. Al analizar el panteón de los autores destacados para François Paré, trataremos de circunscribir mejor las convergencias, las contradicciones y las ‘derivas obsesivas’ del ensayista

Crowdsourcing samples in cognitive science

Crowdsourcing data collection with research participants from online labor markets is now well established in cognitive science. We review who is in the crowd and who can be reached by the average laboratory. We discuss reproducibility and review some recent methodological innovations for online experiments. We consider the design of research studies and arising ethical issues. We review how to code experiments for the Web, and what is known about video and audio presentation and the measurement of reaction times. We close with comments about the high levels of experience of many participants and an arising tragedy of the commons