Webinars 254

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.

Search icon

Speakers 235

201920182017201620152014201320122011 Mostrar Esconder

Scheduled webinars 05

Edit iconRemove icon

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.

Edit iconRemove icon

04/07 - 11:00 am BRT

Alexandre Le Tiec ( Observatoire de Paris )

Title: to be Announced

Edit iconRemove icon

11/07 - 11:00 am BRT

Françoise Combes ( Observatoire de Paris )

Molecular tori, black hole fueling and feedback in nearby AGN

Edit iconRemove icon

18/07 - 11:00 am BRT

Henk Hoekstra ( Leiden University )

Title: to be Announced

Edit iconRemove icon

25/07 - 11:00 am BRT

Bryan Miller ( Gemini Observatory )

Title: to be Announced

Past webinars 249


Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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).

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.

Edit iconRemove icon

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.