Webinars 309

Since 2011 we promote webinars which are an important aspect of our personnel development. This allows collaborators anywhere in the world to join seminars about the latest developments in several astronomical and technical fields. Webinars are presented in english and announced to a mailing list. Click here if you want to subscribe.

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Speakers 281

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Scheduled webinars 02

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10/12 - 02:00 pm BRT

Peter Nugent ( University of California Berkeley )

The La Silla Schmidt Southern Survey

We are proposing a 5-year public, wide-field, optical survey using an upgraded 20 square degree QUEST Camera on the ESO Schmidt Telescope at the La Silla Observatory in Chile - The La Silla Schmidt Southern Survey (LS4). We will use LBNL fully-depleted CCDs to maximize the sensitivity in the optical up to 1 micron. This survey will complement the Legacy Survey of Space and Time (LSST) being conducted at the Vera C. Rubin Observatory in two ways. First, it will provide a higher cadence than the LSST over several thousand square degrees of sky each night, allowing a more accurate characterization of brighter and faster evolving transients to 21st magnitude. Second, it will open up a new phase-space for discovery when coupled with the LSST by probing the sky between 12-16th magnitude - a region where the Rubin Observatory saturates. In addition, a Target of Opportunity (ToO) program will be able to trigger on Multi-Messenger Astronomy (MMA) events with localization uncertainties up to several hundred sq. deg. in multiple colors very quickly. This project has direct relevance to several cosmology and fundamental physics efforts including: peculiar velocity measurements, and hence fundamental constraints on general relativity, with supernova as standardized candles; gravitational wave standard sirens as probes of the expansion of the Universe and gravity; measurements of the Hubble constant through Type Ia and II-P supernovae; and probes of dark matter through low surface brightness galaxies and intra-cluster light.

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17/12 - 02:00 pm BRT

Željko Ivezić ( University of Washington )

LSST: the greatest movie of all time!

The Legacy Survey of Space and Time (LSST), the first project to be undertaken at the new Vera C. Rubin Observatory, will be the most comprehensive optical astronomical survey ever undertaken. Starting in 2023, Rubin Observatory will obtain panoramic images covering the sky visible from its location in Chile every clear night for ten years. The resulting 60 petabytes of raw image data, essentially a digital color movie of the night sky, will include about 40 billion stars and galaxies, and will be used for investigations ranging from cataloging dangerous near-Earth asteroids to fundamental physics such as characterization of dark matter and dark energy. I will start the presentation with an overview of LSST science drivers and system design, and continue with a construction status report for Rubin Observatory. I will conclude with a brief discussion of a few Big Data challenges posed by LSST dataset.

Past webinars 307


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03/12 - 02:00 pm BRT

Alex Kim ( Berkeley Lab )

Peculiar Velocity Surveys Using Supernovae Discoveries from ZTF-II and the Vera C. Rubin Observatory

The motions of galaxies on top of the Hubble expansion, peculiar velocities, are a probe of clustering and the growth of structure in the Universe. For distance indicators, peculiar velocities manifest themselves as residuals on the Hubble diagram. Ongoing and upcoming wide-field surveys measuring unprecedented numbers of distance indicators, together with improvements in the calibration of Type Ia supernova brightnesses, will provide exquisite precision in the mapping of the peculiar velocity field or more precisely the peculiar distance field. There is an international effort to organize follow-up resources to obtain redshifts, classifications, and distance measurements of transients from DESI, the Zwicky Transient Facility (ZTF), ZTF-II, and the Rubin Observatory in order to produce compelling constraints on the laws of gravity responsible for the growth of structure.

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26/11 - 11:00 am BRT

Peter Hatfield ( University of Oxford )

Probing the Relationship Between Galaxies and their Dark Matter Haloes Over Cosmic Time

Deep wide-field surveys are important data sets for studying galaxy evolution over cosmic time, as both depth and width are needed for probing both sides of the knee of the stellar mass over a range of environments and redshifts. In this talk I will highlight work measuring galaxy environment via non-linear clustering in VISTA surveys as a function of stellar mass over 0.5 < z < 1.7 and modelling these measurements within the HOD phenomenology, in particular finding that environmental dependence of quenching only emerges at z ~1.5. We also measure the clustering of a sample of the most luminous LBGs at z ~6, finding that they are in the densest parts of the early Universe, supporting the claims in Bowler (2014, 2015) that this redshift is the onset of quenching. Collectively these results begin to put time constraints on when the main two pathways for quenching start operating. We validate our results Horizon-AGN, a hydrodynamical cosmological simulation with the volume and resolution necessary to compare with VIDEO and UltraVISTA. We find using mock catalogues that the known physics differences between Horizon-AGN and the real Universe are reflected in clustering measurements, and also study the impact of using photometric redshifts and stellar masses on conclusions. Finally I also highlight new developments in the use of machine learning for calculating photometric redshifts, using the ML code GPz code combined with template based methods.

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19/11 - 11:00 am BRT

Santiago Ismael Ferrero ( University of Oslo )

A Unified Scenario for the Origin of Spiral and Elliptic Galaxy Structural Scaling Laws

Elliptical (E) and spiral (S) galaxies follow tight, but different, scaling laws linking their stellar masses, radii, and characteristic velocities. Mass and velocity, for example, scale tightly in spirals with little dependence on galaxy radius (the “Tully-Fisher relation”; TFR). On the other hand, ellipticals appear to trace a 2D surface in size-mass velocity space (the “Fundamental Plane”; FP). Over the years, a number of studies have attempted to understand these empirical relations, usually in terms of variations of the virial theorem for E galaxies and in terms of the scaling relations of dark matter halos for spirals. We use Lambda Cold Dark Matter (LCDM) cosmological hydrodynamical simulations to show that the observed relations of both ellipticals and spirals arise as the result of (i) a tight galaxy mass-dark halo mass relation, and (ii) the selfsimilar mass profile of CDM halos. In this interpretation, E and S galaxies of given stellar mass inhabit halos of similar mass, and their different scaling laws result from the varying amounts of dark matter enclosed within their luminous radii. This scenario suggests a new galaxy distance indicator applicable to galaxies of all morphologies, and provides simple and intuitive explanations for long-standing puzzles, such as why the TFR is independent of surface brightness, or what causes the “tilt” in the FP. Our results provide strong support for the predictions of LCDM in the strongly non-linear regime, as well as guidance for further improvements to cosmological simulations of galaxy formation.

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12/11 - 11:00 am BRT

Carolina Ödman-Govender ( University of Western Cape )

Socio-economic benefits from astronomy

In this talk, I will explore how scientific excellence can be a tool for development. Using the example of astronomy in South Africa, I will illustrate what major shifts have happened to stimulate science and technology, among others through the development and of a skilled workforce. I will draw examples from the Square Kilometre array project as well as other initiatives and I will describe how we plan socio-economic benefits in future projects.

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29/10 - 02:00 pm BRT

Vivian Miranda ( University of Arizona )

The Connected Universe: Relating Early, Intermediate and Late Universe with cosmological data

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22/10 - 11:00 am BRT

Emir Uzeirbegovic ( University of Hertfordshire )

Eigengalaxies: describing galaxy morphology using principal components in image space

We demonstrate how galaxy morphologies can be represented by weighted sums of \\\\\\\\\\\\\\\"eigengalaxies\\\\\\\\\\\\\\\" and how eigengalaxies can be used in a probabilistic framework to enable principled and simplified approaches in a variety of applications. Eigengalaxies can be derived from a Principal Component Analysis (PCA) of sets of single- or multi-band images. They encode the image space equivalent of basis vectors that can be combined to describe the structural properties of large samples of galaxies in a massively reduced manner. As an illustration, we show how a sample of 10,243 galaxies in the Hubble Space Telescope CANDELS survey can be represented by just 12 eigengalaxies. We show in some detail how this image space may be derived and tested. We also describe a probabilistic extension to PCA (PPCA) which enables the eigengalaxy framework to assign probabilities to galaxies. We present four practical applications of the probabilistic eigengalaxy framework that are particularly relevant for the next generation of large imaging surveys: we (i) show how low likelihood galaxies make for natural candidates for outlier detection (ii) demonstrate how missing data can be predicted (iii) show how a similarity search can be performed on exemplars (iv) demonstrate how unsupervised clustering of objects can be implemented.

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15/10 - 10:00 am BRT

Cyrille Doux ( University of Pennsylvania )

Deblending galaxies with Variational Autoencoders: a joint multi-band, multi-instrument approach

Blending of galaxies has a major contribution in the systematic error budget of weak lensing studies, affecting photometric and shape measurements, particularly for ground-based, deep, photometric galaxy surveys, such as the Rubin Observatory Legacy Survey of Space and Time (LSST). Existing deblenders mostly rely on analytic modelling of galaxy profiles and suffer from the lack of flexible yet accurate models. We propose to use generative models based on deep neural networks, namely variational autoencoders (VAE), to learn probabilistic models directly from data. We train a VAE on images of centred, isolated galaxies, which we reuse, as a prior, in a second VAE-like neural network in charge of deblending galaxies. We train our networks on simulated images including six LSST bandpass filters and the visible and near-infrared bands of the Euclid satellite, as our method naturally generalises to multiple bands and can incorporate data from multiple instruments. We obtain median reconstruction errors on ellipticities and $r$-band magnitude between $\\\\\\\\pm\\\\\\\\num{0.01}$ and $\\\\\\\\pm\\\\\\\\num{0.05}$ respectively in most cases, and ellipticity multiplicative bias of 1.6\\\\\\\\% for blended objects in the optimal configuration. We also study the impact of decentring and prove the method to be robust. This method only requires the approximate centre of each target galaxy, but no assumptions about the number of surrounding objects, pointing to an iterative detection/deblending procedure we leave for future work. Finally, we discuss future challenges about training on real data and obtain encouraging results when applying \\\\\\\\textit{transfer learning}. Our code is publicly available on GitHub.

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08/10 - 02:00 pm BRT

Peregrine McGehee ( College of the Canyons )

Mapping the Milky Way and Beyond

The Legacy Survey of Space and Time [LSST] is an ambitious program undertaken at the Vera C. Rubin Observatory, which is presently under construction on the summit of Cerro Pachon in Chile. Within the LSST there are four main science themes: Understanding Dark Matter and Dark Energy Hazardous Asteroids and the Remote Solar System The Transient Optical Sky The Formation and Structure of the Milky Way The LSST Stars, Milky Way, and Local Volume [SMWLV] science collaboration is focused on that fourth theme concerning the past and present state of the Milky Way Galaxy and its neighbors. During this webinar we will explore the diverse working groups within SWMLV including their science goals and relationships across the broader community.

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01/10 - 09:00 am BRT

Mireia Montes ( The University of New South Wales Sydney )

The Intracluster Light: the missing piece in the galaxy cluster evolution puzzle

There is a huge amount of astrophysical events that remain barely studied due to the lack of large, multiwavelength and deep surveys. These events are those which are very faint and extend over large areas of the sky. For instance, only a handful of galaxy clusters have been observed with enough depth to witness the intracluster light (ICL), a byproduct of interactions between galaxies in clusters. In the course of these interactions, individual stars are stripped from their galaxies and float freely, following the potential of the cluster and forming this diffuse light. Therefore, characterising the ICL is key to understanding the assembly mechanisms occurring inside galaxy clusters. Despite its importance, little is known about this light as it is very difficult to observe due to its low surface brightness. The availability of deep surveys, such as the Hubble Frontier Fields, have expanded our knowledge of the properties, and therefore the origin, of the ICL. In this talk, I will present the latest advances in our understanding of the ICL. I will also talk about the technical challenges of low surface brightness imaging and the possibility to explore the dark matter distribution in galaxy clusters by using this diffuse light.

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24/09 - 12:00 pm BRT

Allison Noble ( Arizona State University )

Dissecting Galaxies in the Heart of Galaxy Clusters over Cosmic Time

A comprehensive understanding of galaxy evolution requires a holistic view into the anatomy of galaxies and the baryonic processes that shape their growth. Using a triad of properties—environment, mass, and time—I will present multi-wavelength studies of the extreme end of these parameters: the rare, dense regions of galaxy clusters; the most massive galaxies in the Universe; and the peak epoch of star formation. I will focus on the first spatially-resolved images and kinematics of molecular gas and star formation within high-redshift clusters, from infalling galaxies to the massive Brightest Cluster Galaxy (BCG) at the heart. Enabled by interferometric observations on the Atacama Large Millimeter Array (ALMA), I will highlight potential evidence for gas stripping and an unexpected channel for stellar mass growth in the centers of galaxy clusters at high redshift. With ALMA, this regime is burgeoning from case studies to a rich field of data science, allowing us to push further back in cosmic time and opening up the potential for many new discoveries.

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17/09 - 11:00 am BRT

Keith Bechtol ( University of Wisconsin-Madison )

View of the Milky Way Stellar Halo from the Dark Energy Survey

The stellar halo of the Milky Way represents only ~1% of the total stellar mass of our Galaxy, but is rich with clues regarding the formation history of the Milky Way, the properties of the first stars and galaxies, and the local distribution of dark matter. The current generation of wide-field optical/NIR imaging surveys including SDSS, DES, Pan-STARRS, Gaia, and HSC-SSP has allowed us to catalog more than a billion individually resolved stars out to the Milky Way viral radius and beyond with precise multiband photometry, proper motions, and light curves for variable stars. These datasets, in combination with follow-up spectroscopy, provide new perspectives on the dynamical and chemical history of the Milky Way and its satellites, and ever more stringent constraints on the fundamental nature of dark matter. I will discuss these topics, with a focus on recent results from the Dark Energy Survey (DES), a 5000 square degree imaging survey of the south Galactic cap to ~24th magnitude in the grizY bands.

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10/09 - 11:00 am BRT

Petar Zecevic ( University of Zagreb )

Using AXS for large-scale astronomical analyses

AXS is a distributed system based on Apache Spark used for fast cross-matching of astronomical catalogs and for doing general analyses of astronomical data. In this talk, Petar will give a short introduction to Apache Spark and AXS and delve into inner workings of AXS and explain what makes it so fast. He will also show a live demo with several examples.

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03/09 - 11:00 am BRT

Kartheik Iyer ( University of Toronto )

Probing the timescales of galaxy evolution with simulations and observations

A diverse range of physical processes are responsible for regulating star formation across galaxies. Understanding their relative contributions to galaxy growth and quenching at different epochs is one of the key questions in galaxy evolution today. Since processes like mergers, winds, and feedback from supernovae and active galactic nuclei (AGN) are thought to have characteristic time-scales, identifying them and studying the strength of SFR fluctuations on these time-scales allows us to disentangle their relative contributions for a population of galaxies. In this talk, I will give a brief summary of current work focusing on (i) establishing a formalism to study the stochasticity of star formation at a given time-scale, (ii) analyzing a variety of cosmological galaxy evolution simulations using this formalism, and (iii) observational methods of reconstructing star formation histories, which yield constraints on the time-scales of galaxy growth, morphological transformations, and quenching. Taken together, simulations and observations leverage the predictive power against observational constraints to obtain a fuller picture of how galaxies evolve over time.

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01/09 - 01:30 pm BRT

Luis F. R. Macedo ( VMware Tanzu )

Bancos de dados para grandes volumes

Análise de dados com grandes volumes de informação sempre foi um desafio computacional. Quando temos um volume de dados acima do que um computador consegue trabalhar de forma razoável temos que partir para soluções de computação distribuída que muitas vezes são complexas e pouco eficientes. O Greenplum Database é um banco de dados paralelo baseado em PostgreSQL que pode administrar petabytes de dados sem a necessidade de hardwares proprietários e com uma familiar interface SQL.

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27/08 - 11:00 am BRT

Matt Hilton ( University of KwaZulu-Natal )

Searching one third of the sky for galaxy clusters using the Atacama Cosmology Telescope

The Atacama Cosmology Telescope (ACT) is a 6m telescope located high in the Chilean Andes that first began observations of the sky at millimetre wavelengths in 2007. Since 2016, ACT has been conducting a high-resolution cosmic microwave background survey over most of the southern sky, using its new receiver: Advanced ACTPol. In this talk, I will present the results of a search for galaxy clusters in all ACT data obtained up to 2018, using the redshift independent Sunyaev-Zel\\\\\\\'dovich (SZ) effect. This allows us to construct an effectively mass-limited cluster sample, and chart the growth of massive structures over the past 10 billion years, regardless of how distant the clusters are. We have assembled a sample of more than 4000 SZ-selected, optically-confirmed clusters with redshift measurements, reaching to redshift 2 - making this larger than all previous SZ-selected cluster samples to date. This was possible thanks to the overlap with new deep, wide area optical surveys such as the Dark Energy Survey, the Hyper Suprime-Cam Strategic Program, and the Kilo Degree Survey. I will give an update on our efforts to improve our knowledge of cluster mass calibration - which is needed to unlock the full statistical power of this cluster sample to constrain cosmological parameters - and briefly describe our follow-up with SALT and MeerKAT, aimed at topics related to galaxy evolution and extended non-thermal emission.

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25/08 - 01:00 pm BRT

Fabio Porto ( Laboratório Nacional de Computação Científica )

Introdução ao Ecosistema e Modelo de Programação no Apache Spark

O processamento de grandes volumes de dados passou a ser a norma no suporte a pesquisas in-silico, como acontece com a eAstronomia. Neste webminar, discutiremos o framework Apache Spark que já vem se tornando uma referência de processamento Big Data. Apache Spark é integrado ao sistema de arquivos distribuídos HDFS para oferecer um ambiente de execução baseada em localidade de dados, com escalabilidade para grande número de nós de computação, e mecanismos de tolerância à falhas. O framework adota o modelo de processamento em memória reduzindo significativamente o custo evolvido em tarefas envolvendo iterações, muito utilizadas em processos baseados em aprendizagem.

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20/08 - 11:00 am BRT

August (Gus) Evrard ( University of Michigan )

Holistic Population Models for Massive Halos and Galaxy Clusters

Advances in cosmological hydrodynamics methods over the past three decades have ridden Moore’s law to establish rich predictive models for population statistics of the dark matter halos that host galaxies, groups, and clusters of galaxies. In this talk, I will first review evidence from multiple simulations teams, each incorporating custom recipes for AGN feedback, for common forms of galaxy occupation statistics — specifically the triad of total stellar mass, central stellar mass, and satellite galaxy count — conditioned on halo mass and redshift. The simulations generally support a multivariate Gaussian form for such features, and the anti-correlation of hot gas and stellar mass fractions seen in such models has recently been confirmed in lensing-mass conditioned statistics of the nearby LoCuSS cluster sample. I’ll close with efficient analytic forms to express multivariate cluster population statistics as halo mixtures to help motivate the coming future of multi-survey, multi-simulation analysis.

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13/08 - 11:00 am BRT

Dimitrios Tanoglidis ( University of Chicago )

Searching for shadows in the dark: Discovering Low Surface Brightness Galaxies in DES

Low-surface-brightness galaxies (LSBGs) are expected to dominate the galaxy population by number and may account for a significant fraction of the dynamical mass budget in the present-day Universe. They are observationally defined as galaxies with central surface brightness fainter than the night sky – thus, by definition, they are objects difficult to detect and study, especially across a wide sky area and different environments. In this talk, I will present the search for LSBGs in the Dark Energy Survey (DES), its challenges, and the resulting galaxy catalog - the largest such catalog so far. I will also touch upon the future directions in the LSBG searches, with a strong emphasis on the development of automated, deep learning-based, pipelines that will be extremely valuable in the advent of future surveys like the planned Legacy Survey of Space and Time (LSST) on the Vera C. Rubin Observatory

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11/08 - 11:00 am BRT

Kyle Chard ( University of Chicago )

funcX: a federated function serving fabric for science

Exploding data volumes and velocities, new computational methods and platforms, and ubiquitous connectivity demand new approaches to computation in the sciences. These new approaches must enable computation to be mobile, so that, for example, it can occur near data, be triggered by events (e.g., arrival of new data), be offloaded to specialized accelerators, or run remotely where resources are available. They also require new design approaches in which monolithic applications can be decomposed into smaller components, that may in turn be executed separately and on the most suitable resources. To address these needs we present funcX—a distributed function as a service (FaaS) platform that enables flexible, scalable, and high performance remote function execution. funcX’s endpoint software can transform existing clouds, clusters, and supercomputers into function serving systems, while funcX’s cloud-hosted service provides transparent, secure, and reliable function execution across a federated ecosystem of endpoints. We motivate the need for funcX with several scientific case studies, present our prototype design and implementation, show optimizations that deliver throughput in excess of 1 million functions per second, and demonstrate, via experiments on two supercomputers, that funcX can scale to more than more than 130,000 concurrent workers.

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06/08 - 11:00 am BRT

Ethan Nadler ( Stanford University )

Constraints on Dark Matter Microphysics from Dwarf Galaxies

As luminous tracers of the smallest halos, dwarf galaxies offer a unique window into the physics of dark matter (DM). The (lack of) a cutoff in the abundance of low-mass halos informs a variety of DM properties, which is crucial given the breadth of theoretical models that have gained popularity following the search for canonical WIMPs. In this talk, we describe recent advances in measuring and modeling small-scale structure tracers, focusing on the population of Milky Way (MW) satellite galaxies. In particular, we combine a state-of-the-art census of the MW satellite population with a rigorous model of the galaxy--halo connection in order to place the strongest astrophysical constraints to date on warm, interacting, and fuzzy DM. We discuss the implications of these constraints for specific DM candidates, including sterile neutrinos and ultra-light axions.

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30/07 - 11:00 am BRT

Camille Avestruz ( University of Michigan )

Simulations for Cluster-Based Cosmology

Observations of galaxy clusters have thus far supported the standard model of cosmology and provided constraints on non-standard models including evolving models of dark energy and modifications of gravity. The statistical power of galaxy clusters is at a golden age, where forthcoming observations will provide data for tens of thousands of galaxy clusters. However, our ability to further use clusters as probes is now limited by how well we measure cluster masses and quantify systematic effects in how we detect and measure galaxy clusters. To calibrate observations and understand underlying astrophysical processes, we need simulations that capture both those relevant astrophysical processes and the diversity within a large sample of galaxy clusters. I will discuss ongoing modeling efforts and software infrastructure development that allows us to best leverage the data in upcoming surveys.

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23/07 - 11:00 am BRT

Michelle Wangham ( Universidade do Vale do Itajaí )

Diretrizes e Boas Práticas para Adequação à LGPD (Guidelines and Best Practices for LGPD compliance)

A Lei Geral de Proteção de Dados (LGPD) altera significativamente o marco normativo referente à proteção dos dados pessoais mantidos por todas as organizações (empresariais e públicas). As corporações que já começaram sua jornada de conformidade têm encontrado inúmeras dificuldades para a construção de suas diretrizes de tratamento de dados pessoais e de políticas para prevenção e mitigação em caso de incidentes. A partir de uma abordagem interativa, analisarei nesta palestra as etapas para adequação à LGPD e as principais dores e desafios da jornada da conformidade. Abordarei um conjunto de diretrizes e boas práticas para proteção de dados que aliem técnicas de segurança cibernética, segurança jurídica e governança corporativa. -- The Brazilian General Data Protection Law significantly changes the regulatory milestone related to personal data protection, adopted by all public and private organizations. The organizations that have already initiated this compliance journey have come across many difficulties in building their guidelines for personal data treatment and preventing and mitigating security incidents. I shall analyze the steps for LGPD compliance and its main challenges from an interactive approach. I shall also discuss a group of best practices to protect personal data that align cybersecurity controls, legal security, and corporate governance. (This talk is in Portuguese)

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16/07 - 11:00 am BRT

Justin Myles ( Stanford University )

Measuring Lensing Survey Redshift Distributions with Self-Organizing Maps

Measuring the distribution of redshifts of galaxies observed by wide-field cosmology surveys like the Dark Energy Survey is an essential component to mapping the matter density field in three dimensions and thus understanding large-scale structure. This problem remains one of the key challenges to achieving state-of-the-art cosmology constraints from lensing surveys. In this talk I will describe sompz , a method for determining redshift distributions and show preliminary results from the application of this method to DES Year 3 data. I will discuss the importance of using deep, many-band photometric information to properly reweight the probability distribution of a set of known, reliable redshifts according to their prevalence in the wide-field survey samples from DES. I will present how Self-Organizing Maps are a flexible tool that facilitate this reweighting procedure by constructing photometric phenotypes that categorize each galaxy sample.

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09/07 - 11:00 am BRT

François Lanusse ( CEA Paris-Saclay )

Merging deep learning with physical models for the analysis of modern cosmological surveys

The upcoming generation of cosmological surveys such as LSST will aim to map the Universe in great detail and on an unprecedented scale. This of course implies new and outstanding challenges at all levels of the scientific analysis. In this talk, I will illustrate how recent advances in Deep Learning, and associated automatic differentiation tools (i.e. TensorFlow), can help us tackle these challenges and rethink our approach to data analysis for cosmological surveys. At the image level, combining physical models of the instrument (which account for noise/PSF) with deep generative models (which account for complex galaxy morphologies) can allow us to solve a range of astronomical inverse problems ranging from deconvolution to deblending galaxy images. At the cosmological analysis level, I will present our efforts to implement N-body simulations directly in TensorFlow, opening the door to a range of novel and efficient inference techniques.

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02/07 - 11:00 am BRT

Pedro Bernardinelli ( University of Pennsylvania )

Characterizing the outer solar system with the Dark Energy Survey

Trans-Neptunian objects (TNOs) are remnants of the formation of the solar system, with their orbits, sizes and colors telling us their dynamical history. I will present an ongoing search for these objects using the Dark Energy Survey (DES), which covered 5000 sq. deg. of the sky between 2012 and 2018 in the grizY bands. Being a cosmology survey, the DES typically images each spot on the sky twice per filter per season, which makes the identification of moving objects challenging. The search, however, is feasible with the use of dedicated algorithms, and has yielded the detection of 316 objects in the first four years of data, with over one hundred newly discovered objects (Bernardinelli et al 2020a, ApJS, 247, 32). I will highlight some of the dynamical properties of these objects, including the sample of extreme TNOs in relation to the Planet 9 hypothesis, which predicts that such objects will be clustered in orbital space, an effect not seen in the DES data when observational biases are considered (Bernardinelli et al 2020b, arXiv:2003.08901). I will conclude by describing the status of the search in the full 6 years of data, where the catalogs are 0.4 mag deeper in completeness, at the expense of ~5x increase in source density.

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25/06 - 12:00 pm BRT

Eve Kovacs ( Argonne National Laboratory )

CosmoDC2: A Synthetic Sky Catalog for LSST

CosmoDC2 is a large synthetic galaxy catalog designed to support precision dark energy science with the Large Synoptic Survey Telescope (LSST). The catalog is based on a trillion-particle, ($4.225$~Gpc)$^3$ box cosmological N-body simulation, the `Outer Rim\\\' run. It covers $440$~deg$^2$ of sky area to a redshift of $z=3$ and matches expected number densities from contemporary surveys to a magnitude depth of 28 in the $r$-band. Each galaxy is characterized by a multitude of galaxy properties including stellar mass, spectral energy distributions, broadband filter magnitudes, host halo information and weak lensing shear. We populate dark-matter halos with galaxies using a new hybrid technique that combines data-based empirical approaches with semi-analytic galaxy modeling. A wide range of observation-based validation tests has been implemented to ensure that cosmoDC2 has sufficient realism to enable the science goals of the analyses planned for the catalog.

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18/06 - 11:00 am BRT

Paul Giles ( University of Sussex )

Galaxy cluster science with XCS and DES

The XMM Cluster Survey (XCS) has analysed the entire XMM public archive with the primary aim of producing a large catalogue of X-ray selected clusters. To date, over 5,000 extended sources have been identified as clusters of galaxies. Most of those have associated redshift and X-ray temperature information. In this talk I will preview the second XCS data release and utilise recent DES data to describe a series of recent science results that include: the evolution and interpretation of various scaling relations (optical richness to T_x; L_x - T_x; M_x - T_x; velocity dispersion - T_x; M_lens - T_x; Y_sz - T_x); the evolution of the red sequence; constraints on modified gravity models. The talk will feature several joint XCS-DES (Dark Energy Survey) results, and outlooks for the future of cluster studies.

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11/06 - 11:00 am BRT

Rachel Amey ( University of Delaware )

Looking Under the Hood of Identity Threat

Increasing national interest in science, technology, engineering, and math (STEM) domains has led to the largest STEM workforce of men and women in the U.S. However, despite current interest, women remain underrepresented. Studies examining the gender gap typically rely on behavioral measures, indexing the thoughts, feelings, and performance of stigmatized individuals in identity threatening STEM contexts. The present work highlights how looking beyond behavioral measures by indexing physiological, cognitive, and environmental factors provides essential insight into why the STEM gender gap remains and how individuals can increase diversity in STEM.

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04/06 - 11:00 am BRT

Carlos Alexandre Wuensche ( INPE )

21 cm cosmology and the BINGO radio telescope

Cosmology in the XXI century is experiencing a \\\\\\\"Golden Age\\\\\\\", with observations and theoretical models contributing to a large-scale description of the Universe. The current view is that it can be well described by the so-called Lambda-CDM model, but some open problems challenge physics and cosmology, including the origin and properties of so-called dark energy. The so-called baryonic acoustic oscillations (BAO), detected for the first time in 2005, are considered one of the most effective probes to understand the properties of dark energy. However, given the implications of these measurements, it is important that they are confirmed at other wavelengths and measured over a wide range of redshifts. The radio band provides a unique and complementary observation window, by emitting 21 cm of neutral hydrogen. The redshifted 21 cm (1420 MHz) emission of the hyperfine transition of neutral hydrogen is measured at lower frequencies, so that the observation frequency is converted directly into information about the source\\\\\\\'s redshift. The BINGO radio telescope (BAO from Integrated Neutral Gas Observations) is a new instrument, designed specifically to observe BAO, mapping a redshift band between 0.13 and 0.45. This seminar will present the basics of 21 cm BAO cosmology, the intensity mapping technique used and describe the current development status of the BINGO radio telescope.

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28/05 - 04:00 pm BRT

Mario Juric ( University of Washington/LSST )

Minimoons to Planet X: Mapping Solar System Populations with ZTF and LSST

The small bodies of the Solar System are a valuable tracer of its present-day structure, its evolution, and ultimately provide clues into the early times of its formation. In the next 5 years, the known sample of all small body populations will grow 10-50x, driven largely by large survey programs. For example, the LSST alone will generate a billion measurements of millions of Solar System objects, with simulations predicting ~100,000 new discoveries of nearby NEOs (Jones et al. 2017), 5.5 million for the main belt, and ~40,000-200,000 for the trans-Neptunian populations (Ivezic et al 2008; Juric et al. 2018). In this talk I will discuss what to expect from this sample, especially in the early years. I\\\'ll briefly overview the LSST and ZTF surveys, and what they are expected to discover (and -- in the case of ZTF -- already have discovered). The talk will discuss the techniques to find small bodies in survey datasets, and places where improved algorithms could significantly increase the yields. I will conclude with an overview the science opportunities this new sample is bringing.

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21/05 - 11:00 am BRT

Rodrigo Boufleur ( ON/LIneA )

ROSA – Rede de Ocultações Sul-Americana

O projeto ROSA tem como objetivo instalar e operar uma rede de telescópios robóticos de 40 cm de abertura, separados por distâncias de aproximadamente 100 km no sentido norte-sul. Inicialmente a rede está projetada para ter 50 telescópios e deverá ser instalada no território brasileiro. Um dos principais objetivos desta rede é a observação de ocultações de estelares por objetos do Sistema Solar com ênfase na região transnetuniana. Estas ocultações deverão ser previstas a partir do refinamento de órbitas obtidas pelas sucessivas observações do telescópio de 8.4 metros de abertura do LSST (Legacy Survey of Space and Time). As ocultações permitem a reconstrução da geometria dos corpos ocultadores e a detecção de possíveis atmosferas, satélites e anéis, informações estas que podem contribuir para o conhecimento da evolução do nosso Sistema Solar. Outro objetivo central da rede é funcionar como suporte para alguns dos 10 milhões de alertas que serão gerados pelo LSST em cada noite de observação. Finalmente, é importante destacar que ela terá um papel ativo no treinamento de estudantes e de futuros professores nas áreas de ciências. Os recursos para o projeto estão sendo solicitados junto a organizações privadas e públicas no exterior e no Brasil.

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14/05 - 11:00 am BRT

Emille Ishida ( Université Clermont Auvergne )

Machine Learning in Astronomy

The availability of large data sets revolutionized many areas of scientific research, astronomy included. The current -- and in many ways already overwhelming -- data paradigm will suffer still another revolution with the advent of the new generation of large astronomical surveys. In this new scenario, the use of automated methods of analysis will be unavoidable. In this talk, I will give a short introduction to the basic principles of machine learning and describe situations where they are traditionally used in astronomical research. I will also present how domain knowledge can be used to optimize results from traditional algorithms by incorporating expert feedback in the learning process.

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07/05 - 11:00 am BRT

Emmanuel Lellouch ( Observatoire de Paris )

The Solar System in the ALMA era

Spectroscopy and radiometry at mm/submm wavelengths has for a long time proven to be a powerful means to study the diversity of Solar System objects (planetary and satellite atmospheres, comets, airless bodies). The operation of ALMA as well as the upgrade of other facilities have provided many new observational results in recent years, addressing a wide range of topics related to either the origin/evolution of these bodies or to the physics of their environments. Submm spectroscopy of comets is a very poweful tool to study the molecular inventory and diversity of comets, their isotopic composition, the nature of cometary activity, the coma physics, and the asteroid/comet relationships. Spectroscopy of planetary atmospheres aims at determining the coupled fields of composition, thermal structure and dynamics, with implication on their energy budgets, and to characterize exogenous input to these atmospheres. Radiometry of satellites and airless small bodies (asteroids and trans-neptunian objects) constrains their surface thermal and emissivity properties, albedo, size, density, with implications for formation mechanisms (e.g. for binary systems). I will review some recent results from ALMA and other mm/submm facilities.

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30/04 - 04:00 pm BRT

J D Prasanna Deshapriya ( Observatoire de Paris )

First results from the OSIRIS-REx’s mission at the asteroid (101955) Bennu

The Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft of the NASA, arrived at the near-Earth asteroid (101955) Bennu in December 2018. Bennu is a primitive asteroid with a low albedo and is spectrally classed under the B-type asteroids, associated to organic-rich hydrated carbonaceous chondrites, that might harbour the pre-biotic chemical constituents, that were fundamental to the origin of life on Earth. The main objective of this space mission is to investigate Bennu using the suite of instrument aboard OSIRIS-REx, in order to select the most safely sampleable and scientifically appealing sample site, acquire loose regolith material from this site and deliver the sample safely to Earth in 2023, for more sophisticated analyses in the terrestrial laboratories. As of now, thorough analyses have led to identifying a primary sampling site as well as a backup site for sampling that is scheduled to take place in this summer. As such, the first results of the mission and a comparison with the knowledge we had about Bennu, prior to the arrival at the asteroid will be presented.

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09/04 - 11:00 am BRT

Marcelo Emilio ( UEPG )

Telescópio PLANETS

Usualmente, obstruções em frente aos espelhos de telescópios limitam a difração e dispersam a luz. Objetos de grande interesse científico como planetas e matéria circunstelar estão próximos a estrelas e frequentemente tem sua observação comprometida ou mesmo impedida pelo espalhamento de luz. É possível, no entanto construir um telescópio sem o suporte secundário e maximizar a faixa dinâmica.Tais telescópios são chamados fora-do-eixo. Eles podem ter contraste muito superior, porque não há obstruções no feixe, como suportes do espelho secundário. Sem obstruções eles permitem observar objetos próximos a estrela.Nessa palestra falaremos sobre o telescópio PLANETS (acronismo em inglês para Luz Polarizada de Atmosferas de Sistemas Extra-Terrestres Próximos), será um telescópio fora-de-eixo de 1,85m de diâmetro que combina várias novas tecnologias e técnicas de instrumentação. Ele será construído em Haleakala, um vulcão de 3.048 metros, na ilha de Maui, Havaí, com “seeing” e clima excelentes.Este telescópio será ideal para coronografia e outras técnicas que requerem um caminho óptico estável. A capacidade única deste telescópio permitirá avanços no estudo de ambientes circunstelares, objetos do sistema solar, atmosferas planetárias, atmosferas de exoplanetas e para o desenvolvimento da instrumentação inovadora. As instituições parceiras são a Universidade Estadual de Ponta Grossa(Brasil), Universidade Tohoku (Japão) e o Instituto Kiepenheuer para Física Solar (KIS, Alemanha).

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02/04 - 11:00 am BRT

Ariel Sanchez ( Max Planck Institute )

Let us bury the prehistoric arguments against using Mpc/h units in cosmology

Thanks to the combined information of baryon acoustic oscillations (BAO) and redshift-space distortions (RSD), anisotropic clustering measurements can probe simultaneously the expansion history of the Universe and the growth of density fluctuations, offering in this way one of the most promising routes to understand the origin of cosmic acceleration. In this talk, I review the standard methodology to obtain these measurements and their information content, using the final results from the Baryon Oscillation Spectroscopic Survey (BOSS) as an example. I also discus the problems and misconceptions caused by the common practice of expressing cosmological measurements in units of Mpc/h.I will discuss how these units has caused critical misconceptions for both the so-called sigma_8tension regarding the consistency between low-redshiftprobes and cosmic microwavebackground data, and the way in which growth-rate estimates inferred from RSD analysesare commonly expressed.

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19/03 - 04:00 pm BRT

Tamara Davis ( University of Queensland )

Chasing Dark Energy

This talk will review the current state of dark energy research and in particular The Australian Dark Energy Survey’s program to measure spectra of tens of thousands of galaxies, thousands of supernovae, and time-lapse spectroscopy of almost 800 AGN. We’ll discuss what we need to do to distinguish between different models of dark energy and prospects of doing that in the next generation of surveys.

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12/03 - 11:00 am BRT

Jo Bovy ( University of Toronto )

The Milky Way in the era of large surveys

For over a hundred years, the Milky Way has been the nexus between many fields of astrophysics, linking together investigations into the formation of planetary systems and stars to studies of galactic evolution, cosmology, and astroparticle physics. Obtaining a detailed understanding of our Galaxy’s structure, formation, and evolution is therefore crucial to the advancement of the whole of astrophysical knowledge. Long thought to be a simple spiral galaxy with a simple disk-plus-bulge structure leading a relatively unperturbed life, the advent of large surveys such as SDSS, Gaia, and soon LSST has breathed new life into the field of galactic structure. I will discuss the new view of the Milky Way—complex, dynamic, and very much in the process of evolving—and what it implies about galaxy formation, galaxy evolution, and the nature of dark matter.

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05/03 - 03:00 pm BRT

Joseph Masiero ( JPL NASA )

NEOWISE tools and techniques

The NEOWISE infrared space telescope has provided an unprecedented set of infrared photometry and astrometry of the entire sky. This includes stars and galaxies, as well as over 150,000 asteroids and comets in our Solar system. I will provide an overview of the data that are publicly available, the tools and techniques that are included to access this data, and some of the results that have been derived from these measurements.