Webinars 290

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 265

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Scheduled webinars 07

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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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16/07 - 11:00 am BRT

Justin Myles ( Stanford University )

Title: to be Announced

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23/07 - 11:00 am BRT

Michelle Wangham ( Universidade do Vale do Itajaí )

Title: to be Announced

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30/07 - 11:00 am BRT

Camille Avestruz ( University of Michigan )

Title: to be Announced

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06/08 - 03:00 pm BRT

Ethan Nadler ( Stanford University )

Title: to be Announced

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13/08 - 11:00 am BRT

Dimitrios Tanoglidis ( University of Chicago )

Title: to be Announced

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20/08 - 11:00 am BRT

August Evrard ( University of Michigan )

Title: to be Announced

Past webinars 283


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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.