Início » Ciência » Webinars » Apresentações » 2017
07/12 - 11:00 am
Roberto Vieira Martins
Abstract ⓘ
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Roberto Vieira Martins
Title
The discovery of a ring around the dwarf planet Haumea (ON)
Abstract
In our solar system, five bodies are currently classified as dwarf planets. Recent stellar occultation revealed a dense ring around the Trans-Neptunian dwarf planet Haumea. Exception made to the giant planets, this is the second body known to have a ring. The formation of stable rings around small bodies is difficult to explain and, in the case of Haumea, that has the shape of a very elongated ellipsoid and a fast rotation, it is even more surprising. I will show how the discovery was possible, the procedures used to obtain the physical data of Haumea, and what are the possible origins of the ring.
23/11 - 11:00 am
Antonella Palmese
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Antonella Palmese
Title
DECam and DES perspective of GW170817: optical counterpart search and properties of the host galaxy (Fermilab)
Abstract
In the occasion of the exciting discovery of the electromagnetic counterpart of the GW170817 gravitational wave event, the Dark Energy Survey collaboration produced a series of studies covering different aspects of the event. In this talk, I will present the Dark Energy Survey gravitational wave follow up program and how observations of the GW170817 host galaxy can provide information about the formation of the binary neutron star that merged, producing the gravitational wave signal.
16/11 - 10:00 am
Marcel Popescu
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Marcel Popescu
Title
Compositional mapping of minor planets population using near-infrared data (Observatório de Paris)
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09/11 - 12:00 pm
Alexandre Refregier
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Alexandre Refregier
Title
Cosmological Weak Lensing (ETH Zurich)
Abstract
Weak gravitational lensing is a unique technique to map the distribution of dark matter in the universe. It is also a sensitive probe of large scale structures in the universe and cosmological parameters. I will first briefly describe the principles of weak lensing. I will then review the current observational status of this field, highlighting several new measurements especially from the ongoing Dark Energy Survey (DES). I will then discuss the status of tensions between cosmological probes and results for a new integrated approach to combine them.
01/11 - 04:00 pm
Rebecca Bernstein
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Rebecca Bernstein
Title
The Giant Magellan Telescope: Science and Status (Carnegie Institution for Science)
Abstract
In the last four centuries, ground based telescopes have provided some of the key discoveries that have driven our understanding of both astronomy and fundamental physics. In the coming decade, a new generation of ground- and space-based observatories will come on line, providing unprecedented potential for new discoveries in all areas of astrophysics and cosmology, from exoplanets and life to the birth of the first stars and galaxies at the edge of the visible universe. In this talk, I will provide an overview of the design and status of the Giant Magellan Telescope (GMT), which is a 25.4m diameter, optical/infrared telescope that is being built in northern Chile by an international collaboration of research institutions. It will provide a factor of three gain in angular resolution and an order of magnitude increase in collecting area relative to the previous generation of 8m telescopes. I will focus on some of the unique capabilities the GMT will provide in the coming decades.
30/10 - 01:00 pm
Marcelle Soares
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Marcelle Soares
Title
Observation of a Gravitational Wave Emitting Neutron Star Merger with the Dark Energy Camera (Brandeis University)
Abstract
Motivated by the exciting prospect of new wealth of information arising from the first observations of gravitational and electromagnetic radiation from the same astrophysical phenomena, the Dark Energy Survey (DES) has performed a broad range follow-up program for LIGO/Virgo events using the Dark Energy Camera (DECam). In this talk, I present the discovery of the optical transient associated with the neutron star merger GW170817 using DECam and discuss its implications for the emerging field: multi-messenger cosmology with gravitational waves and optical data.
19/10 - 11:00 am
Johnny Greco
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Johnny Greco
Title
Searching for low-surface-brightness Galaxies with the Hyper Suprime-Cam Survey (Princeton University)
Abstract
Low-surface-brightness galaxies (LSBGs) are a significant component of the galaxy population, which provide a unique testing ground for theoretical predictions of galaxy and star formation, stellar feedback processes, and the distribution and nature of dark matter. However, their defining characteristic—central surface brightnesses that are fainter than the night sky—makes them difficult to detect and study, leading to their underrepresentation in previous optical surveys and biasing our view of the full galaxy population. I will present a new view of these elusive galaxies from the Hyper Suprime-Cam (HSC) Survey, a 300-night imaging survey using the 8.2-meter Subaru Telescope on Mauna Kea. After giving an overview of the HSC Survey, I will present our source-detection pipeline and initial catalog of LSBGs within the first ~200 deg^2 of the survey, which will grow to 1400 deg^2 upon survey completion. Our LSBG catalog will facilitate follow-up efforts (which we have already started) to study the physical properties and number densities of these galaxies as a function of environment. Pushing such studies to lower surface brightnesses will be necessary to form a more complete census of the galaxy population, which will ultimately provide one of the strongest tests of the standard LCDM framework.
05/10 - 02:00 pm
Daniel Gruen
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Daniel Gruen
Title
The bright and the dark side of gravitational lensing (Stanford University)
Abstract
The Dark Energy Survey has combined analyses of galaxy clustering and weak gravitational lensing two-point correlation functions in its first year (Y1) of observations. This combination of measurements provides information on the amplitude of density fluctuations (S8=0.794+0.029-0.027) and the dark energy equation of state (w=-0.80+0.20-0.22) that is competitive with Planck CMB data. I will review these results, with a focus on the technical advances on shape measurement and photometric redshifts that facilitated them. I will also show preliminary results from novel work, called density tomography, that studies overdense and underdense lines of sight separately. The latter constrains the joint 1pt-PDF of matter density and galaxy count, sensitive also to higher order moments and galaxy stochasticity. This provides additional information and, by comparing the full shape of the PDF to predictions, a non-parametric test of gravity.
28/09 - 11:00 am
Ting Li
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Ting Li
Title
Constraining the Nature of Dark Matter with Milky Way\'s Nearest Neighbors (Fermilab)
Abstract
The census of Milky Way satellite galaxies provides crucial tests of both galaxy formation models and the broader Cold Dark Matter paradigm. Over two-dozens of new Milky Way satellite candidates have been discovered in the last two years, primarily in data from the Dark Energy Survey (DES). These discoveries double the number of known Milky Way satellite galaxies, leading a huge advance in solving the missing satellite problem. Furthermore, many of these newly discovered dwarf galaxies are excellent targets for providing constraints on WIMP dark matter cross section and MACHO dark matter abundance. In this talk, I will present the latest discoveries of the Milky Way satellite galaxies in DES and show some initial results from a spectroscopic campaign on these satellite candidates using 4-8 meter class telescopes in the southern hemisphere.
21/09 - 10:00 am
Alberto Molino
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Alberto Molino
Title
CLASH: Accurate Photometric Redshifts with 14 HST bands in Massive Galaxy Cluster Cores (USP)
Abstract
In this talk, i would like to present the new accurate photometric redshifts for galaxies observed by the Cluster Lensing and Supernova survey with Hubble (CLASH). CLASH observed 25 massive galaxy cluster cores with the Hubble Space Telescope in 16 filters spanning 0.2 - 1.7 m. Photometry in such crowded fields is challenging. Compared to our previously released catalogs, we make several improvements to the photometry, including smaller aper- tures, ICL subtraction, PSF matching, and empirically measured uncertainties. We further improve the Bayesian Photometric Redshift (BPZ) estimates by adding a redder elliptical template and by inflating the photometric uncertainties of the brightest galaxies. The resulting photometric redshift accuracies are dz/(1+z) ∼ 0.8%, 1.0%, 1.5%, 2.0%, and 2.2% for galaxies with I-band F814W AB magnitudes < 18, 20, 22, 23, and 25, respectively. These results are consistent with our expectations. They improve on our previously reported accuracies by a factor of 3 at the bright end and 60% at the faint end. Our catalogs include 1295 spectroscopic redshifts, including 561 confirmed cluster members. We also provide stellar mass estimates. Finally, we include lensing magnification estimates of background galaxies based on our public lens models. The catalogs of all 25 CLASH clusters are available via MAST. The analysis techniques developed here will be useful in other surveys of crowded fields, including the Frontier Fields and surveys carried out with J-PAS and JWST.
15/09 - 02:00 pm
Michel Aguena
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Michel Aguena
Title
Constructing a pipeline to constrain cosmology with galaxy clusters (USP)
Abstract
Galaxy cluster are the largest gravitationally bound structures in the Universe. Mapping the abundance and spacial distribution of clusters we can trace the underlying dark matter field, and extract cosmological information such the history of expansion of the Universe and the growth of perturbation. However, in order to use galaxy clusters as cosmological probe, we have to consider observational effects, i. e. the selection function and the relation between the dark matter halo mass and a proxy. In this webinar, I will present the main steps to construct a cluster cosmology pipeline developed during my PhD.
31/08 - 11:00 am
Pierluigi Cerulo
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Pierluigi Cerulo
Title
Galaxy Transformations in the Most Massive Clusters (Universidad de Concepción)
Abstract
Slides not available
28/08 - 04:00 pm
Rogério Rosenfeld
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Rogério Rosenfeld
Title
Dark Energy Survey results from the first year of observations (UNESP)
Abstract
Slides not available
24/08 - 02:00 pm
Julian Bautista
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Julian Bautista
Title
Measuring baryon acoustic oscillations at z=2.3 with SDSS DR12 Lyman-alpha forests (University of Utah)
Abstract
27/07 - 11:00 am
Rachel Mandelbaum
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Rachel Mandelbaum
Title
Science with the Hyper Suprime-Cam survey (Carnegie Mellon University)
Abstract
Hyper Suprime-Cam (HSC) is an imaging camera mounted at the Prime Focus of the Subaru 8.2-m telescope operated by the National Astronomical Observatory of Japan on the summit of Maunakea in Hawaii. A consortium of astronomers from Japan, Taiwan and Princeton University is carrying out a three-layer, 300-night, multiband survey from 2014-2019 with this instrument. In this talk, I will focus on the HSC survey Wide Layer, which will cover 1400 square degrees in five broad bands (grizy), to a 5 sigma point-source depth of r~26. We have covered 240 square degrees of the Wide Layer in all five bands, and the median seeing in the i band is 0.60 arcseconds. This powerful combination of depth and image quality makes the HSC survey unique compared to other ongoing imaging surveys. In this talk I will describe the HSC survey dataset and the completed and ongoing science analyses with the survey Wide layer, including galaxy studies, strong and weak gravitational lensing, but with an emphasis on weak lensing. I will demonstrate the level of systematics control, the potential for competitive cosmology constraints, some early results, and describe some lessons learned that will be of use for other ongoing and future lensing surveys.
20/07 - 02:00 pm
Joe deRose
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Joe deRose
Title
Simulating the Dark Energy Survey: Catalogs to Cosmology (Stanford University)
Abstract
Using measurements of the matter power spectrum and the geometry of the universe at the surface of last scattering from CMB experiments we can make precise predictions for the amplitude of matter fluctuations at low redshift. Current galaxy surveys will be able to test these predictions so long as cosmologists are able to overcome the complex systematics associated with measuring cosmology using galaxies. In this talk I will overview the current analysis that one such galaxy survey, the Dark Energy Survey (DES), is pursuing with their first year of data. In particular, I will highlight the role that cosmological simulations have played in the analysis both in developing algorithms and in testing systematics mitigation techniques. I will conclude by discussing future prospects and challenges that will face simulators for upcoming analyses.
13/07 - 03:00 pm
Michael Strauss
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Michael Strauss
Title
The properties of the highest-redshift quasars (Princeton University)
Abstract
There are now over 200 quasars known with redshifts above 5.5. I will discuss the search for these highest-redshift objects with various wide-field surveys. In many ways, the physical properties of high-redshift quasars are remarkably similar to those at lower redshift, even as quasars become increasingly rare at early cosmic epochs. Remarkably, the properties of the quasar host galaxies can be studies using submm observations of the dust continuum and molecular lines in the interstellar medium of these objects, which demonstrates that these objects are often embedded in extreme starbursting galaxies. Dust obscuration is another theme in quasar studies; an appreciable fraction of the growth of black holes may be hidden at optical wavelengths by dust. I will describe searches for obscured quasars at high redshift and low, and studies of their demographics and physical properties.
29/06 - 11:00 am
Bruno Sicardy
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Bruno Sicardy
Title
Exploring the Solar System using stellar occultations in the Gaia era (Université Pierre et Marie Curie)
Abstract
Stellar occultations occur when a planetary body passes in front of a star. The spatial resolution depends on acquisition rate, reaching kilometric levels. Those events permit, among others, the detection of tenuous atmospheres (nbar level) and the discovery of new ring systems. We have developed in the last decades new calculation tools and new technological devices (fast cameras) in order to use stellar occultations for exploring the Solar Sytem beyond Neptune. Some highlights will be presented, in particular, the monitoring of Pluto\\\'s atmosphere and the surprising discovery of rings around an asteroid-like object, Chariklo. Up to now, the main limitation of the method has been the prediction accuracy, typically 40 milliarcsec (mas) projected on the sky, corresponding to some 500 to 1,500 km projected on Earth, depending on the body. This lead to large time dedicated to astrometry, tedious logistical issues, and more often than not, mere miss of the event. The Gaia catalog, with sub-mas accuracy, hugely improves both the star positions and ephemerides of the bodies, resulting in accuracies of ~10 km for the shadow track on Earth. Thus campaigns will be much more carefully planned, with success rate approaching 100%, weather permitting. Scientific perspectives will be presented, e.g. central flashes caused by Pluto’s or Triton\\\'s atmosphere may reveal hazes and winds near the surface, grazing occultations will show topographic features on remote bodies, allowing geological studies, occultations by Chariklo’s rings will unveil dynamical features such as resonances with nearby satellites or proper mode “breathing”. New atmospheres and rings will probably be discovered.
22/06 - 09:00 am
Antonino Troja
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Antonino Troja
Title
Angular Polyspectra in Cosmology: LSS Bispectrum and CMB Trispectrum (University of Milan)
Abstract
Polyspectra represent one of the strongest tool in cosmology in order to derive information. The lowest order polyspectra, bispectrum and trispectrum, corresponding to the Fourier transform of the three- and four-points correlation function respectively, have been used in the past decades to derive information about the primordial physics of the Universe, as well as improving the results of the power spectrum only analysis. When we deal with spherical field, such as the Cosmic Microwave Background radiation (CMB), the Fourier transform is replaced by the Harmonic decomposition, performed using the Spherical Harmonics, i.e. the orthonormal basis of all the functions defined on the sphere, and the angular polyspectra are developed from the harmonic coefficients. Many models and estimators of angular polyspectra were developed, but there is still room for new ones. I will discuss of the spherical mathematical framework as well as the derivation and results of angular bispectrum of the Large Scale Structure (LSS) and the Needlet trispectrum of the CMB. The former case represent one of the first attempt made in order to constrain cosmological parameters using the bispectrum of the galaxy projected field along the line of sight. In the latter case, I\\\'ll show a new basis-like wavelet system in order to construct a strong estimator when the spherical field presents masked region, the Needlet system, with which it is possible to build a new estimator for the trispectrum.
01/06 - 11:00 am
Dominika Wylezalek
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Dominika Wylezalek
Title
Observational signatures of AGN feedback (Johns Hopkins University)
Abstract
While many compelling models of AGN feedback exist, there is no clear data-driven picture of how winds are launched, how they propagate through the galaxy and what impact they have on the galactic gas. Recent work suggests that AGN luminosity plays an important role. In my talk, I will present results from several projects that focus on understanding the power, reach and impact of feedback processes exerted by AGN of different power. I will first describe recent efforts in our group of relating feedback signatures in powerful quasars to the specific star formation rate in their host galaxies, where our results are consistent with the AGN having a `negative\' impact through feedback on the galaxies\' star formation history. Feedback signatures seem to be best observable in gas-rich galaxies where the coupling of the AGN-driven wind to the gas is strongest, in agreement with recent simulations. But how and where does this quenching happen? Is it accomplished through the mechanical action of jets or through nuclear winds driven by radiation pressure? In the second part of my presentation, I will show that AGN signatures and AGN-driven winds can be easily hidden and not be apparent in the integrated spectrum of a galaxy hosting a low/intermediate-luminosity AGN. Using data from the new SDSS-IV MaNGA survey, we have developed a new AGN selection algorithm tailored to IFU data and we are uncovering a much more nuanced picture of AGN activity allowing us to discover AGN signatures at large distances from the galaxy center. This implies that large IFU surveys, such as the SDSS-IV MaNGA survey, might uncover many previously unknown AGN and feedback signatures related to them. Outflows and feedback from low- and intermediate-luminosity AGN might have been underestimated in the past but can potentially significantly contribute to the AGN/host-galaxy self-regulation.
25/05 - 11:00 am
Helena Dominguez-Sanchez
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Helena Dominguez-Sanchez
Title
Star Formation Histories of Massive Quiescent Galaxies at z > 1 (Observatoire de Paris/University of Pennsylvania)
Abstract
Three billion years after the big bang (at redshift z = 2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation. How were the lives of these galaxies so they died so fast? In this talk, I will present recent results on the Star Formation Histories (SFHs) of a sample of ~ 100 quiescent massive (log M > 10 solar masses) galaxies at z=1.0 - 1.5, inferred from the analysis of spectro-photometric data from the SHARDS and HST/WFC3 G102-G141 surveys of the GOODS-N field. The data are compared to stellar population models assuming different SFHs, with the goal of determining 4 basic physical properties of red quiescent galaxies at high-z: their age, star formation timescale (tau), metallicity, and extinction. Thanks to the spectral resolution of the SHARDS plus G102 and G141 data, we are able to measure spectral features related to the age of the galaxies (MgUV and D4000), which allow us to break the typical age-tau, age extinction degeneracies with great confidence. We find that the derived SFHs for our MQGs are consistent with the slope and the location of the Main Sequence of star-forming galaxies (MS) at z > 1.2, when these galaxies were 0.5--1.0~Gyr old. According to the derived SFH, all of the MQGs experienced a Luminous Infrared Galaxy (LIRG) phase during typically ~500~Myr and roughly half of them went through ULIRG phase for ~100 Myr. I will also briefly introduce other projects I am involved in, including stellar population gradients of local ETGs with the MANGA survey and morphological classification of galaxies using Deep Learning.
18/05 - 02:00 pm
Eric Huff
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Eric Huff
Title
Weak Lensing: the Next Generation (Jet Propulsion Laboratory - Caltech)
Abstract
Weak gravitational lensing is one of the most challenging cosmological measurements, and the difficulty of its extraction is driving much of the design of the big cosmological surveys. Significant progress has been made in the last few years, however, and it is likely that the coming generation of large imaging surveys will be limited only by sample size, and not by systematic measurement errors. As a result, it is now useful to think about new sources of lensing signal that are not accessible to WFIRST or LSST. I will talk about current challenges, and explain why I think the lensing shear calibration problem is now (mostly) solved. I will then describe how wide-field galaxy kinematics may open a promising new avenue for cosmological measurement, and discuss one possible way of obtaining them at the necessary scale.
11/05 - 11:00 am
Peter Nugent
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Peter Nugent
Title
The Palomar Transient Factory (University of California Berkeley)
Abstract
Astrophysics is transforming from a data-starved to a data-swamped discipline, fundamentally changing the nature of scientific inquiry and discovery. New technologies are enabling the detection, transmission, and storage of data of hitherto unimaginable quantity and quality across the electromagnetic, gravity and particle spectra. The observational data obtained during this decade alone will supersede everything accumulated over the preceding four thousand years of astronomy. Currently there are 4 large-scale photometric and spectroscopic surveys underway, each generating and/or utilizing hundreds of terabytes of data per year. Some will focus on the static universe while others will greatly expand our knowledge of transient phenomena. Maximizing the science from these programs requires integrating the processing pipeline with high-performance computing resources. These are coupled to large astrophysics databases while making use of machine learning algorithms with near real-time turnaround. Here I will present an overview of one of these programs, the Palomar Transient Factory (PTF). I will cover the processing and discovery pipeline we developed at LBNL and NERSC for it, several of the great discoveries made during the 7 years of observations, and where we are headed with a new facility, Zwicky Transient Facility starting August 2017, which will be an order of magnitude faster.
04/05 - 10:00 am
Ravi Sheth
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Ravi Sheth
Title
Estimating the BAO scale (University of Pennsylvania)
Abstract
The Baryon Acoustic Peak oscillations imprint a characteristic length scale on the galaxy 2-point correlation function. This scale is related to, but distinct from, the local maximum of the correlation function on ~100 Mpc/h scales. In contrast to the local maximum, this scale is not affected by nonlinear effects to sub-percent precision. I will discuss how to estimate this scale, and the result of applying this analysis to the LOWZ and CMASS samples from the Twelfth Data Release (DR12) of the Baryon Oscillation Spectroscopic Survey (BOSS) collaboration.
27/04 - 10:00 am
Roberto de Propris
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Roberto de Propris
Title
The New Bulge (University of Turku)
Abstract
The Milky Way is the quintessential example of a spiral galaxy and the only one whose stellar populations can be studied in detail. In particular, the bulge is the only resolved elliptical-like stellar system that we can observe, despite the extremely high foreground extinction and crowding. It has long been known that our Galaxy is a barred spiral and that our bulge belongs to the class of boxy/peanut shaped pseudobulges. We have completed the first radial velocity survey of the Southern bulge, using a total of nearly 10,000 M giants as tracers. Our study clearly shows that the entirety of the Galactic bulge is consistent with the stellar bar and no spheroidal component. We also present the first results of a new survey to probe the inner and oldest regions of the galaxy with RR Lyrae.
20/04 - 10:00 am
Fabien Lacasa
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Fabien Lacasa
Title
Super-sample covariance (University of Geneva)
Abstract
Current and future galaxy surveys are reaching a high signal-to-noise regime, with the detection of clusters down to low masses and the measurement of galaxy clustering and weak lensing down to small scales. In this very regime, super-sample covariance (SSC) becomes the dominant source of statistical errors, for the Large Scale Structure observables that we use to improve our cosmological understanding of the universe. I will start with a pedagogical introduction of SSC in the case of cluster counts, where the effect is usually called sample (co)variance, before examining the precision of several analytical approximations designed in the flat sky limit. Then I will present how to predict SSC for an arbitrary survey geometry, as required by surveys such as DES, LSST or Euclid with a wide coverage far from the flat sky limit. I will show that SSC is poorly estimated with classical internal covariance methods relying on the data itself, such as bootstrap or jackknife. It is also poorly estimated from subsampling a given simulation, unless said simulation is considerably larger than the survey. The latter being a challenge for future surveys covering a large portion of the observable universe such as Euclid or LSST. Beyond cluster counts, SSC also affects galaxy clustering and weak-lensing and couples observables together, thus being a particular challenge for probe combination. I will briefly explore the link between SSC and recent advances on the theoretical (soft limits and consistency relations) and simulation (separate universes) fronts, before making the case for analytical prediction of SSC as the way forward for analysis of large surveys.
06/04 - 11:00 am
Bruno Merín
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Bruno Merín
Title
ESASky: a new science-driven data portal for the XXI century (European Space Astronomy Centre)
Abstract
ESASky is a science-driven discovery portal for all ESA space astronomy missions. The first public release of ESASky features interfaces for sky exploration and for single and multiple targets searches. Using the application requires no prior-knowledge of any of the missions involved and gives users world-wide simplified access to high-level science-ready public data products from space-based Astronomy missions, plus a number of ESA-produced source catalogues. HST data, metadata and products were some of the first to be accessible through ESASky. I will highlight the latest feature that we have developed, which allows the user to project onto the sky the footprints of the JWST instruments, at any chosen position and orientation. This tool has been developed to aid JWST astronomers when they are defining observing proposals. We aim to include other missions and instruments and to expand ESASky\\\\\\\'s functionalities in the future. I will demo the tool and ask for feedback on how to make it more useful.
30/03 - 03:00 pm
Ewa Deelman
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Ewa Deelman
Title
Challenges of Managing Scientific Workflows: The Pegasus Workflow Management System (University of Southern California)
Abstract
Scientific workflows allow researchers to declaratively describe potentially complex applications that are composed of individual computational components. Workflows also include a description of the data and control dependencies between the components. This talk will describe example workflows in various science domains including astronomy, bioinformatics, earthquake science, gravitational-wave physics, and others. It will examine the challenges faced by workflow management systems when executing complex workflows in distributed and high-performance computing environments. In particular the talk will describe the Pegasus Workflow Management System developed at USC/ISI (http://pegasus.isi.edu). Pegasus bridges the scientific domain and the execution environment by automatically mapping high-level workflow descriptions onto distributed resources. As part of this process, Pegasus may transform the workflow based on the workflow properties and the target architecture. The talk will describe the optimizations and techniques developed and used within the Pegasus system to efficiently manage data and computations across heterogeneous computing environments. Pegasus can execute workflows on a laptop, a campus cluster, grids, and clouds. It can handle workflows with a single task or millions of tasks and has been used to manage workflows accessing and generating Terabytes of data. The talk will also look at the challenges and opportunities that upcoming computing systems bring to workflow management systems.
23/03 - 10:00 am
Rossana Ruggeri
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Rossana Ruggeri
Title
Measuring Redshift Space Distortion in deep redshift surveys (University of Portsmouth)
Abstract
Forthcoming galaxy redshift surveys are motivated, to a large extent, by obtaining galaxy clustering measurements to accurately quantify the observed acceleration in the expansion of the Universe. It is to be hoped that these observations will reveal insight into the physical mechanism responsible for the cosmic acceleration, be it a new scalar field currently contributing to the energy budget of the Universe as Dark Energy, modification of gravitational laws on cosmological scales, or an unknown alternative to the Standard Cosmological Model. The statistical precision afforded by forthcoming surveys including DESI and Euclid is impressive and will push at least an order of magnitude beyond current measurements. However this promised low statistical errors will only be realised with the development of new, fast, analysis methods that reduce potential systematic problems to low levels. We present an efficient method for measuring the evolution of the growth of structure using Redshift Space Distortions (RSD), that removes the need to make measurements in redshift shells. We provide sets of galaxy-weights that cover a wide range in redshift, but are optimised to provide differential information about cosmological evolution. These are derived to optimally measure the coefficients of a parameterisation of the redshift-dependent matter density, which provides a framework to measure deviations from the concordance LCDM cosmology, allowing for deviations in both geometric and/or growth. We test the robustness of the weights by comparing with alternative schemes and investigate the impact of galaxy bias.
16/03 - 10:00 am
Paolo Tanga
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Paolo Tanga
Title
Gaia and the asteroid population: a revolution on Earth, coming from space (Observatoire de la Côte d\'Azur)
Abstract
The ESA Gaia mission is performing since summer 2014 an all-sky survey of all sources brighter than V~20. Most of them are stars (more than one billion), but many Solar System object are also present: 350,000 asteroids, some TNOs, comets and planetary satellites. The main science driver of Gaia is provided by the unprecedented astrometric accuracy and the physical characterization by spectro-photometry for all sources. For the Solar System, these data represent the richest homogeneous survey available, providing access to an incredible variety of properties and potentially leading to major breakthroughs in asteroid science. Also, Gaia stellar astrometry in general is going to heavily impact ground-based observations, as a completely new calibration of the sky is accessible. Some simple exploitations of the first intermediate data release published in September 2016, already show the improvements brought to ground-based astrometry of asteroids, and demonstrate the completely renewed role of stellar occultations, an impressive tool of exploration whose efficiency is being multiplied by a large factor.