Webinars 260

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 240

201920182017201620152014201320122011 Mostrar Esconder

Scheduled webinars 07

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25/07 - 11:00 am BRT

Bryan Miller ( Gemini Observatory )

New Infrastructure and Processes for Time-Domain Followup

Time domain and multi-messenger astrophysics are rapidly growing and important modes of observational astronomy. The commissioning of LSST and the increasing sensitivity of facilities such as LIGO and IceCube mean that both rapid-response and long-term flexible scheduling capabilities will be essential. Significant effort by a variety of groups is being put into developing the components of a follow-up system for dynamically turning survey alerts into data. This system consists of: 1) brokers that will aggregate, classify, and filter alerts; 2) Target Observation Managers (TOMs) that are used by science teams for prioritizing targets and managing observations and data; and 3) observatory interfaces, schedulers, and facilities along with data reduction software and science archives. These tools will also be beneficial to all users of these facilities. This presentation will review the current status of this developing network with emphasis on the efforts of the Astronomical Event Observatory Network (AEON), a collaboration between Las Cumbres Observatory, NOAO/SOAR, and Gemini, and outstanding issues will be discussed.

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01/08 - 11:00 am BRT

Joe Zuntz ( University of Edinburgh )

LSST/DESC Plans for Computing and Workflow

DESC is the cosmology collaboration for LSST, the Large Synoptic Survey Telescope, which is currently under construction at Cerro Panchon, Chile. Much of DESC\\\'s work is computational, requiring large data processing facilities and tools. I will discuss DESC\\\'s current plans for workflow and processing, starting from the catalogs provided by data management and ending with cosmological constraints

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08/08 - 02:00 pm BRT

Edward Schlafly ( Lawrence Berkeley National Laboratory )

Title: to be Announced

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22/08 - 11:59 pm BRT

Sugata Kaviraj ( University of Hertfordshire )

Title: to be Announced

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29/08 - 10:00 am BRT

Kate Grier ( Ohio State University )

Title: to be Announced

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19/09 - 11:00 am BRT

Matteo Costanzi ( Johann Wolfgang INAF )

Title: to be Announced

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26/09 - 11:00 am BRT

Nathalie Palanque-Delabrouille ( CEA )

Title: to be Announced

Past webinars 253

2019

18
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18/07 - 11:00 am BRT

Henk Hoekstra ( Leiden University )

Weak lensing by large-scale structure as an accurate probe of cosmology and much more!

Weak lensing by large-scale structure is one of the most promising techniques to learn more about the nature of dark energy by mapping the dark matter distribution in the Universe as a function of distance. Weak lensing has also developed into the main tool to determine the masses of collapsed structures, from clusters to galaxies, enabling new studies of scaling relations. I will review the recent progress in this active area of research and discuss the prospects for future projects, such as Euclid.

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11/07 - 11:00 am BRT

Françoise Combes ( Observatoire de Paris )

Molecular tori, black hole fueling and feedback in nearby AGN

Recent molecular line observations with ALMA in several nearby Seyferts have revealed the existence of molecular tori, and the nature of gas flows at 10-20pc scale. At 100pc scale or kpc-scale, previous work on gravitational torques had shown that only about one-third of Seyfert galaxies experienced molecular inflow and central fueling, while in most cases the gas was stalled in rings. At higher resolution, i.e. 10-20pc scale, it is possible now to see in some cases AGN fueling due to nuclear trailing spirals, influenced by the black hole potential. This brings smoking gun evidence for nuclear fueling. In our sample galaxies, the angular resolution of up to 80mas allows us to reach the BH-zone of influence and the BH mass can be derived more directly than with the M-sigma relation.

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04/07 - 11:00 am BRT

Alexandre Le Tiec ( Observatoire de Paris )

Probing the vicinity of the galactic center black hole with LISA

The era of gravitational-wave astronomy was opened in 2015 with the first direct detection by LIGO of gravitational radiation emitted during the coalescence of two 30 Solar mass black holes. The planned Laser Interferometer Space Antenna (LISA) will detect gravitational waves generated during the coalescence of supermassive black hole binaries and the inspiral of stellar mass compact objects into massive black holes. I will present the first fully relativistic study of gravitational radiation from bodies in circular equatorial orbits around the massive black hole at the Galactic Center, Sgr A*. The signal-to-noise ratio in the gravitational wave detector LISA, as well as the time spent in LISA band, have been evaluated for main-sequence stars, brown dwarfs and compact objects. I will argue that Sgr A* is a valuable target for LISA.

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27/06 - 11:00 am BRT

Chihway Chang ( University of Chicago )

Decoding the Universe with Cosmic Surveys

Modern cosmology is built on a robust foundation termed the ΛCDM model. The ΛCDM model has been remarkably successful — it is able to explain a large range of observational data with only six parameters. There are, however, unresolved questions that leave cosmologists unsatisfied: What is Dark Matter? What is Dark Energy? With the increasingly powerful data, is ΛCDM still internally consistent within multiple cosmological probes? In this talk I describe a program where we seek to answer these questions using information in the large-scale structure, as recorded by state-of-the-art cosmological surveys. I will focus on a series of analyses using two-point functions of different cosmic fields and describe ongoing work to go beyond the standard two-point framework.

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13/06 - 11:00 am BRT

Hector Gil-Marin ( Universitat de Barcelona )

Measuring cosmological parameters in the large scale structure through redshift space distortions and Alcock-Paczynski effects

In this talk, I will present an introduction on the concepts of redshift space distortions (RSD) and Alcock-Paczynski (AP) effect and their applicability to measure cosmological parameters, such as the growth of structure or Omega_m, from large scale structure spectroscopic galaxy surveys. As an example, I will present such analyses for BOSS and eBOSS surveys and will review some of the future results for DESI, including both the power spectrum and bispectrum techniques.

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06/06 - 11:00 am BRT

Marika Asgari ( Edinburgh University )

Cosmology with KiDS and cosmic shear

The Kilo Degree Survey (KiDS) is a purpose-built gravitational lensing survey with high quality images and a wide photometric coverage, resulting in very high fidelity data. This dataset, therefore, provides an excellent playground where we can test our methods in preparation for future weak lensing surveys. Already the first KiDS data release (KiDS-450) shows a mild tension with CMB results, which has sparked both skepticism and excitement within the community. One of the major challenges for cosmic shear is the treatment of systematics in the data. Marginalised systematics, currently, comprise a significant portion of the error bars on the estimate of the amount of structures (S_8) inferred from the data. In this talk, I will focus on cosmic shear analysis of the latest KiDS data and compare the cosmological results given different two point statistics and I will go through complications that arise in this kind of analysis and the effect of systematics on the data. I will finally show results from the combination of KiDS and DES cosmic shear data.

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30/05 - 11:00 am BRT

Eva Grebel ( University of Heidelberg )

Dwarf Galaxies - Fossils of Galaxy Evolution

Dwarf galaxies are the most common type of galaxy in the Universe and include the most dark-matter-dominated objects known. They offer intriguing insights into evolutionary processes at low halo masses and low metallicities. Moreover, as survivors of a once much more numerous population of building blocks of larger galaxies, they are key to understanding very early star formation processes. The Local Group and particularly the Milky Way\\\'s dwarf galaxy entourage offer us the unique possibility to compare in detail dwarf and Galactic populations. This is an important step towards quantifying the magnitude and time scales of dwarf contributions to the build-up of the Milky Way and allows us to test predictions of cosmological theories and hierarchical structure formation.

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23/05 - 11:30 am BRT

Fabian Schmidt ( Max Planck Institute - Garching )

New approaches to galaxy clustering

The large-scale clustering of galaxies contains a wealth of information on the geometry and expansion history of the universe, on gravity, and on the initial conditions. In order to extract this information, we need to deal with the complex formation process of galaxies. As a result, current observational constraints are largely based only on the robust BAO feature. However, thanks to significant advances in o ur theoretical understanding of galaxy clustering, we now have a well-defined approach for absorbing all the complicated, incompletely understood physics of galaxy formation into a set of free parameters (the bias parameters and stochastic amplitudes), which opens up considerable additional constraining power. The next challenge to tackle then is how best to connect this theory with data, as delivered by ongoing and future surveys such as BOSS, DESI, and Euclid. In my talk, I will review these developments, and discuss the prospects galaxy clustering as a robust probe of cosmology in the coming decade.

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16/05 - 11:00 am BRT

Katelyn Stringer ( Texas A&M University )

Identifying RR Lyrae in the Dark Energy Survey

RR Lyrae variable stars (RRL) are powerful distance indicators which can be used to locate stellar structures within the Milky Way halo. The Dark Energy Survey (DES), with its large observing footprint and depth, presents a rich opportunity to discover these variables to distances near the edge of the Galactic halo. However, the small number of observations in the DES wide-field survey data (fewer than 20 multiband observations over the first three years) pose a challenge for the traditional RRL detection techniques. In this talk, I will describe the multiband template fitting method and machine learning classifier we developed to identify 5783 RRL candidates in the first three years of DES data. These methods will enable RRL detection in other sparse multiband data sets that are not optimized for time series analyses.

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09/05 - 02:00 pm BRT

Wesley Fraser ( Queen\'s University Belfast )

Colours of the Outer Solar System Origins Survey

The orbital structure of the Kuiper Belt is dynamically excited, with most objects found on highly inclined and eccentric orbits. It is this orbital structure that has provided the main evidence for the early migrations of the gas-giant planets, and the violent dispersal of the outer proto-planetesimal disk. Many observational properties have been used as constraints on numerical efforts to uncover the details of the migratory history, including the detailed orbital distribution of Kuiper Belt Objects (KBOs), and the compositional classes KBOs which are known to correlate with the different orbital classes in which KBOs reside. This chemo-dynamical structure appears to be the result of the dynamical processes experienced by KBOs during the dispersal of the early disk, and the compositional heterogeneity of that disk. As a dynamical tracer however, the chemo-dynamical structure of the Kuiper Belt remains largely untapped. It was around this idea that the Col-OSSOS project was created. The Colours of the Outer Solar System Origins Survey is a large program executing on the Gemini-North and CFHT telescopes aimed to gather high quality optical-NIR colours of ~100 KBOs, in a brightness complete sample, and has designed to overcome various weaknesses of colour surveys that came before it. Col-OSSOS has been running since 2014 and has resulted in many exciting findings to date. With some anecdote about working very closely with Gemini and the excellent work they have done, I will present some of the main results of the Col-OSSOS, including a discussion about what the observed colour distribution informs us of the chemical structure of the early disk. Our results have provided some critical context for a number of otherwise curious objects, including an asteroid found in the Kuiper Belt, Phoebe’s unusual surface, and some odd blue binary KBOs found where no blue objects should be. I will conclude with a cosmogonic history that draws all of these disparate pieces together.

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25/04 - 11:00 am BRT

Bruno Castilho ( LNA )

Desafios da infraestrutura e instrumentação astronômica no Brasil para a próxima década

Nas últimas duas décadas a astronomia optica e infravermelha do Brasil teve um grande crescimento, tanto em número de pessoas quanto em publicações e isto reflete no reconhecimento internacional de nossa comunidade. Este crescimento foi alavancado em boa parte pelo maior acesso a novos telescópios e instrumentação, seja no país seja por acordos internacionais. Em 2020 e 2021 vencem os atuais acordos do SOAR e do Gemini e fazem 10 anos do workshop promovido pelo LNA para avaliar a questão da infraestrutura observacional. Quais são os desafios científicos para a nova década e o que nossa comunidade precisa em termos de instrumentação para poder participar ativamente das respostas a estes desafios? Neste seminário não trazemos as respostas prontas a estas questões, mas sim levantamos a discussão e os pontos a serem discutidos para que toda a comunidade possa participar.

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18/04 - 11:00 am BRT

Paola Dimauro ( Observatoire de Paris )

Is morphology telling us the truth about quenching?

Passive and star forming galaxies have different morphology and structure, suggesting a link between the star formation activity and the formation/growth of internal components. Despite the numerous efforts, the details of how galaxies form and evolve, and in particular the mechanisms responsible of the decreasing/cessation of the star formation and the morphological transformations are still not fully understood. In the talk I will present results we obtained combining the morphology and the star formation activities for galaxies in the CANDELS survey. We first studied structural properties of the four main morphological classes (bulge dominated systems, pure spiral disk dominated, intermediate 2-component and irregular disturbed galaxies) and how their fractions change at different epochs (Huertas-Company et al,2016) to then move forward and analyze in more details the galaxy structure exploring bulge and disk properties and how they correlate with the morphology or the star formation activities of the host galaxies (Dimauro et al, 2018, 2019).

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11/04 - 11:00 am BRT

Hao-Yi Wu ( The Ohio State University )

Probing Cosmic Acceleration with Galaxy Clusters

The acceleration of the Universe is one of the biggest puzzles in physics: is it due to a cosmological constant, dynamical dark energy, or modification of gravity? Galaxy clusters provide a unique opportunity to answer this question. In this talk, I will first discuss how we use cluster abundances to constrain cosmic acceleration, and how weak gravitational lensing effects play a key role in constraining cluster mass. I will then present my research on using simulations to understand cluster weak lensing signals and to accurately model covariance matrices. These results not only mitigate the systematic errors in current cluster surveys but also help the optimization of future ground- and space-based missions.

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04/04 - 11:00 am BRT

Adriano Pieres ( LineA )

Describing the thick disk and halo of the Galaxy as seen by the Dark Energy Survey

In this webinar I will talk about the results of the MWFitting pipeline applied to the stellar content of the DES-Y3 Gold internal release, in a paper about to be published. We fit the thick disk and halo of the Milky Way, simulating the Galaxy with a combination of TRILEGAL models. The stellar density of the thick disk is modeled with an exponential dependence in the radial and vertical directions, and the halo is described as an oblate model with the density of stars decreasing following a radial power law. The pipeline shows robust parameters for those components and the residuals from photometric comparisons attest the excellent job of the method. I detailed the methods applied in the pipeline, the implications of the results, also regarding the upcoming surveys and finally preliminary outcomes with other surveys.

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28/03 - 11:00 am BRT

Jennifer Marshall ( Texas University )

The future of massively multiplexed spectroscopy: the Maunakea Spectroscopic Explorer

Numerous international astronomy reports have recently highlighted the need for fully dedicated, large aperture, massively multiplexed spectroscopy in the optical and near-Infrared wavelength regimes. Such a facility is the most obvious missing link in the emerging network of ground-based observational facilities world-wide. The Maunakea Spectroscopic Explorer (MSE) is a planned 11-m telescope facility designed to fill this scientific gap. MSE is completely dedicated to multi-object optical and near-Infrared spectroscopy of samples of between thousands and millions of astrophysical objects at a range of spectral resolutions. In this talk I will overview the wide-ranging scientific capabilities of the MSE project and review the current design status of this next generation observatory.

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21/03 - 11:00 am BRT

Michael Wood-Vasey ( University of Pittsburgh )

LSST and Data Facilities to Enable Science with Billions of Objects

The Large Synoptic Survey Telescope will open new frontiers in large-scale data analysis in astronomy. In this talk I will discus the opportunities and current implementation of data access and analysis in the LSST Project and in the Dark Energy Science Collaboration. The LSST Science Platform is being built to enable the LSST community to explore the rich and large datasets from from LSST. While the LSP may not be fully operational until the beginning of the LSST Operations in late 2022, development and prototyping efforts are currently underway to understand both the technical scope and user interactions with this ambitious platform. In parallel to the LSST Project construction efforts, the wider LSST scientific community is preparing for LSST. In particular, the Dark Energy Science Collaboration (DESC) was formed to fully exploit the ability of LSST to determine the nature of dark energy. In advance of data from LSST, DESC is preparing a series of Data Challenges to develop and verify scientific and basic data processing pipelines. These data challenges are helping both DESC and the LSST Project explore and understand the opportunities and challenges of exploring terabyte-scale image datasets with catalogs with billions to trillions of entries.

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14/03 - 11:00 am BRT

Brian Yanny ( Fermilab )

The Balrog simulation for DES Years 1-3

We present details of the Balrog object injection and (re)measurement code which is used by DES to determine completeness and biases in detection and measurement of faint stars and galaxies.

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07/03 - 11:00 am BRT

George Beckett ( University of Edinburgh )

UK Ambitions for Astronomy in the LSST Era

The Large Synoptic Survey Telescope promises to revolutionalise many aspects of optical astronomy, most notably dealing with the transient universe. UK-based astronomers have a particular opportunity, since the UK is part of several other significant facilities on a similar timescale--for example, Euclid, 4MOST, and SKA--yielding a possibility to secure leadership in a number of areas, including dark energy, solar system science, and transients. Recognising this, the UK community has formed a consortium with representation from every UK-based astronomy group, to encapsulate its ambitious plans for LSST and to secure funding for a substantial programme of R&D, in the lead up to the beginning of telescope operations in 2022. Through this consortium, LSST:UK has secured data rights for 100 Affiliate PIs (plus the associated 400 Junior Associates), and embarked on an 8-year research and development programme that will yield a UK-based LSST Data Access Centre, tailored to the specific requirements of priority UK astronomy goals. In this talk, I will share highlights from the UK programme to date, including an alert-handling service that is being trialled on the Zwicky Transient Facility, large-scale database ingest and query experiments, toward the 35 billion objects that LSST is predicted to observe, and a fledgling cloud-based deployment of an analysis platform that will be at the heart of the UK DAC. I will also preview the plans for the next phase of work, during 2019--2023, which are likely to involve closer international collaboration on provisioning of data and associated analysis services as well as the finalisation of plans for UK-led User-generated Products, as we transition from the construction to the commissioning phase of LSST.

2018

38

2017

32

2016

35

2015

31

2014

35

2013

31

2012

17

2011

16