YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

YouTube video by Institute of Space Sciences (ICE-CSIC)

#PizzaSeminar Title: "X-ray Binary Populations in Galaxies Across Cosmic History" Speaker: Bret D. Lehmer (Department of Physics, University of Arkansas, USA) Studies of the extragalactic Universe, from ultraviolet to infrared wavelengths, have been extremely effective at piecing together a basic picture of how stars in galaxies evolved throughout cosmic history. At X-ray wavelengths, galaxy emission is dominated by hot gas and populations of X-ray binaries, the latter of which consist of black holes and neutron stars accreting material from normal stellar companions. Hot gas in star-forming galaxies traces energetics from young and massive stars and X-ray binaries provide unique and important information regarding the star-formation histories and chemical evolution (metallicities) of their host galaxies. These energetic phenomena have been proposed to play roles in the ionization of nebulae and long-range heating of the intergalactic medium in the early Universe. Furthermore, some X-ray binaries are expected to be predecessors and tracers of the gravitational-wave source populations that are now being detected by LIGO/VIRGO. Using X-ray and multiwavelength observations (e.g., from Chandra, GALEX, Hubble, NuSTAR, Spitzer, Herschel, and other telescopes) of nearby and distant galaxies, as well as large-scale theoretical modeling, we are developing a framework detailing how X-ray binary populations and their host galaxies evolved together over the last 12 billion years (~90%) of cosmic history. In this talk, I will describe some of the exciting new insights from our work, and I will highlight how new data sets, future observational facilities, and improved theoretical modeling will continue to improve our understanding of X-ray binaries, compact objects, and galaxies.

#PizzaSeminar Title: "Unsupervised galaxy classification reveals new evolutionary pathways" Speaker: Malgorzata Siudek, Polish National Agency for Academic Exchange (NAWA) A complete and satisfactory understanding of the processes that led to the formation of all the variety of today’s galaxy types is still beyond our reach. To solve this problem, we need both large datasets reaching high redshifts and novel methodologies for dealing with them. The statistical power of the VIPERS survey, which observed ~90,000 galaxies at intermediate redshifts, and the application of an unsupervised clustering algorithm, allowed us to distinguish between passive galaxies, star-forming galaxies and galaxies hosting active galactic nuclei (AGN), among other types. A follow-up study of their environmental dependence indicates that this classification may actually reflect different galaxy evolutionary paths, revealing for instance a rare population of small and passive red galaxies. In my talk, I will discuss the clustering methodology and emerging scenarios of galaxy evolution.

#PizzaSeminar Title: "Characterizing ASAS-SN core-collapse supernova environments with VLT+MUSE" Speaker: Thallis Pessi, European Southern Observatory (ESO), Universidad Diego Portales (UdP, Chile). The study of supernova (SN) environments is an important method for understanding and constraining the progenitors of the different SN types. In this talk, I will present the analysis of 114 galaxies observed by the All-weather MUse Supernova Integral field Nearby Galaxies survey (AMUSING) that hosted core-collapse supernovae (CCSNe) detected or discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) survey, between 2014 and 2018. This is the largest analysis to date of CCSN host galaxies observed by the MUSE instrument at the Very Large Telescope (VLT). The use of a homogeneous SN sample from ASAS-SN, an untargeted and spectroscopically complete panoramic survey of transients, allowed us to perform a minimally biased statistical analysis of CCSN environments. The talk will describe our sample, the capabilities of the MUSE instrument in investigating SN environments, our main results, and prospects for future projects.

#PizzaSeminar Title: "Visualizing the pulsar population using graph theory" Speaker: Carlos R. García (Institute of Space Sciences, ICE-CSIC) The PPdot-diagram is a cornerstone of pulsar research. It is used in multiple ways for classifying the population, understanding evolutionary tracks, identifying issues in our theoretical reach, and more. However, we have been looking at the same plot for more than five decades. A fresh appraisal may be healthy. Is the PPdot-diagram the most useful or complete way to visualize the pulsars we know? Here we pose a fresh look at the information we have on the pulsar population. First, we use principal component analysis over magnitudes depending on the intrinsic pulsar’s timing properties (proxies to relevant physical pulsar features), to analyse whether the information contained by the pulsar’s period and period derivative is enough to describe the variety of the pulsar population. Even when the variables of interest depend on P and Pdot, we show that PPdot are not principal components. Thus, any distance ranking or visualization based only on P and Pdot is potentially misleading. Next, we define and compute a properly normalized distance to measure pulsar nearness, calculate the minimum spanning tree of the population, and discuss possible applications. The pulsar tree hosts information about pulsar similarities that go beyond P and Pdot, and are thus naturally difficult to read from the P Pdot-diagram. We use this work to introduce the pulsar tree website containing visualization tools and data to allow users to gather information in terms of MST and distance ranking.

#PizzaSeminar Title: "The mass of the interstellar dust reservoir in galaxies" Speaker: Francisca Kemper (Institute of Space Sciences, ICE-CSIC), IEEC, ICREA The evolution of interstellar dust reservoirs, and the evolution of galaxies themselves go hand-in-hand, as the presence of dust alters evolutionary drivers, such as the interstellar radiation field and the star formation history, while at the same time, the dust is being formed and altered by processes taking place in galaxies. However, far-infrared and submillimeter studies have revealed enormous dust masses at high redshifts that are difficult to explain with dust production from evolved stars (the so-called "dust budget problem"), while in the nearby universe there is also a significant mismatch between the dust production rate and the dust mass observed in the interstellar medium of galaxies. I will go over some possible explanations in an attempt to find a way forward towards a solution to this seeming discrepancy.

#PizzaSeminar Title: "Ultraluminous X-ray source populations: observational constraints and theoretical modelling" Speaker: Konstantinos Kovlakas (Institute of Space Sciences, ICE-CSIC) Ultraluminous X-ray sources (ULXs) are thought to be X-ray binary systems exhibiting super-Eddington luminosities. They challenge our understanding of accretion physics at extreme accretion rates, while their nature and evolution has not yet been fully explored. Since ULXs are rare and usually found at large distances, only a few systems have been studied thoroughly, nevertheless providing useful information on their accretion states. On the other hand, having extreme luminosities, numerous ULXs have been detected at different galactic environments, allowing demographic ULX studies to indirectly access the properties of ULXs, but most importantly, to directly explore the formation and evolution of ULX populations via the comparison with binary population synthesis models. In this seminar, we will talk about a census of ULXs designed for this purpose (HECATE-ULX), and a new binary population synthesis code (POSYDON) providing reliable modelling of mass-transfer sequences. We will see how they will be combined with cosmological simulations, giving access to the properties of ULX populations (X-MARCS-THE-SPOT). Furthermore, we will discuss on ULXs as local Universe ionizing sources, and important players in heating the early Universe.

#PizzaSeminar Title: "What Moves the Heavens Above? " Speaker: Enrique Gaztañaga (ICE-CSIC & IEEC,) Aristotle proposed that Aether, a divine substance, moved the heavenly spheres of stars and planets. It took two millennia to discovered that such Aether was just the universal law of Gravity. Yet, according to the current lore, cosmic expansion can not be explained by Gravity. The standard model of cosmology assumes that everything started in a singular Big Bang out of Cosmic Inflation, a mysterious form of modern Aether. But there is no direct evidence that this ever occurred. Measurements of cosmic acceleration also seem to requiere a cosmological constant (Λ), yet another form of such Aether. We will argue instead that these are just indications that our Universe has a finite mass. If this is the case, we live inside a large local Black Hole (BH) Universe (BHU) whose event horizon plays the role of Λ. This BHU has the same metric as the standard cosmology (ΛCDM) . A comoving observer, anywhere inside such BHU, measures the same background as an observer in the standard ΛCDM. This solution to the Λ conundrum opens new questions about the origen of expansion and structure and could also help us understand other recent puzzling observations.