Início » Ciência » Webinars » Apresentações » 2015
04/12 - 04:00 pm
Jake VanderPlas
Abstract ⓘ
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Jake VanderPlas
Title
Astrostatistics: Opening the Black Box (University of Washington eScience Institute)
Abstract
The large datasets being generated by current and future astronomical surveys give us the ability to answer questions at a breadth and depth that was previously unimaginable. Yet datasets which strive to be generally useful are rarely ideal for any particular science case: measurements are often sparser, noisier, or more heterogeneous than one might hope. To adapt tried-and-true statistical methods to this new milieu of large-scale, noisy, heterogeneous data often requires us to re-examine these methods: to pry off the lid of the black box and consider the assumptions they are built on, and how these assumptions can be relaxed for use in this new context. In this talk I’ll explore a case study of such an exercise: our extension of the Lomb-Scargle Periodogram for use with the sparse, multi-color photometry expected from LSST. For studies involving RR-Lyrae-type variable stars, we expect this multiband algorithm to push the effective depth of LSST two magnitudes deeper than for previously used methods.
Slides not available
19/11 - 02:00 pm
Erik Tollerud
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Erik Tollerud
Title
The Development of Astropy and Using it to Identify Local Volume Dwarf Galaxies (Space Telescope Science Institute)
Abstract
I will describe the Astropy Project, a community library for Python in Astronomy. I will describe the origins of Astropy, as well as some key aspects of how we develop Astropy. I will further discuss how this (along with other factors) has lead to the explosive growth of the Astropy community since the project’s inception. I will then discuss an effort I have been leading recently to identify nearby (Local Volume) dwarf galaxies, and describe how many of the critical steps were enabled by Astropy and its affiliated packages.
Slides not available
05/11 - 02:00 pm
Robin Ciardullo
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Robin Ciardullo
Title
HETDEX and the Star-Forming Galaxies of the z ~ 2 Universe (Penn State University)
Abstract
In a few months, the Hobby Eberly Telescope Dark Energy Experiment will begin obtaining redshifts for roughly a million Ly-alpha emitting galaxies (LAEs) between 1.9 < z < 3.5. While the main purpose of the project is to study the evolution of Dark Energy, the project will produce an incredible data base for studies of galaxy evolution. In preparation for this, we have been investigating the physical and chemical properties of emission-line galaxies in the z ~ 2 universe, using LAEs discovered from the ground and samples of [O III]-emitting objects identified from space. We show that LAEs are not “low mass, dust-poor galaxies caught in the act of formation”, but instead normal star-forming galaxies with stellar masses that span almost the entire galaxy mass range, from at least 7.5 < log M/Msun < 10.5. We use our z ~ 2 galaxy samples to explore issues such as the relationship between stellar mass and metallicity, the systematics of star-formation rate indicators, the behavior of dust attenuation laws versus stellar mass, and the question of what makes an LAE and LAE.
29/10 - 01:00 pm
Anthony Gonzalez
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Anthony Gonzalez
Title
The Massive and Distant Clusters of WISE Survey (University of Florida)
Abstract
The Massive and Distant Clusters of WISE Survey (MaDCoWS) is a comprehensive program to detect and characterize the most massive galaxy clusters in the Universe at z~1 over the full extragalactic sky. In this talk I will give an overview of the survey and present the status of our search within the PanSTARRS footprint, which has yielded several thousand candidate clusters. I will demonstrate that MaDCoWS is efficiently isolating the cluster population at this epoch, and present recent results from targeted follow-up observations, including confirmation of the second most massive galaxy cluster known at z>1. Finally, I will discuss our ongoing Spitzer program to image nearly 2000 MaDCoWS candidates and discuss potential improvement from incorporation of new data sets.
Slides not available
22/10 - 01:00 pm
Dustin Lang
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Dustin Lang
Title
The DECam Legacy Survey: image reductions using The Tractor (Carnegie Mellon University, University of Waterloo)
Abstract
The Dark Energy Camera (DECam) Legacy Survey is a mid-size survey of about 6000 square degrees of the equatorial sky in g,r,z filters to 2 mags deeper than SDSS. These images overlap millions of spectra from SDSS and BOSS, so should be useful for a variety of science cases. It is a public survey: the raw images have zero proprietary period, and we aim to do public data releases every 6 months. I’ll introduce the survey and the data reduction approach we’re using: a forward-modeling code called the Tractor, which allows us to make simultaneous measurements in images taken in a variety of bands and in a variety of observing conditions, and even from multiple instruments.
Slides not available
15/10 - 10:00 am
Jeremy Tinker
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Jeremy Tinker
Title
The Red Sequence and How It Got That Way (New York University)
Abstract
I will focus on the growth of the red sequence from redshifts 1 to 0, using data from SDSS and COSMOS to isolate the different physical mechanisms that might quench a galaxy and cause it to migrate onto the red sequence. I will use the relationship between galaxies and dark matter halos to quantify the relative contribution to red sequence growth from field galaxies and group galaxies. I will demonstrate that, since z=1, the efficiency of quenching field galaxies is dramatically increasing, while the efficiency of quenching group galaxies is actually slowing down.
Slides not available
01/10 - 11:00 am
Sarah Kendrew
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Sarah Kendrew
Title
Integral field spectroscopy of high-redshift galaxies in the ELT era (Oxford University)
Abstract
High-resolution cosmological simulations are increasingly valuable for preparing surveys and studying the capabilities of future instrumentation. In combination with dedicated instrument simulators and astrophysical modelling methods, data from cosmological simulations can be transformed into realistic observations of a range of astrophysical targets. I’ll present the tools developed to produce observations of a RAMSES simulated star-forming galaxy at z=3 with the E-ELT first light integral field spectrograph HARMONI. Using the data, we investigate how well the properties of the star particle data, in particular the stellar kinematics, can be recovered from the simulated observations. In addition, by adjusting parameters in the instrumental simulation software, we use the simulation data to demonstrate how PSF convolution affects the ability to recover the galaxy’s properties, even for high-resolution adaptive optics-assisted observations. Finally, I’ll discuss future opportunities for extending the work to include more detailed physics, or to larger samples of galaxies.
24/09 - 02:00 pm
Zheng Zheng
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Zheng Zheng
Title
Anisotropic Galaxy Clustering in the Isotropic Universe (University of Utah)
Abstract
Contemporary spectroscopic galaxy surveys (e.g., the Sloan Digital Sky Survey, or SDSS) can map out the distribution of galaxies in the universe in great detail. The clustering of galaxies measured from such surveys has become a powerful probe of cosmology and galaxy formation and evolution. I will talk about the anisotropic patterns seen in galaxy clustering and discuss what we can learn about cosmology and galaxy formation from such anisotropies. I will first talk about a gravitational origin of the anisotropic clustering, known as redshift-space distortion. I will highlight our recent work with SDSS/SDSS-III clustering data on studying the relation between galaxies and dark matter halos and on discovering the difference between galaxy and halo kinematics. Then I will move to a non-gravitational origin of the anisotropic clustering of high-redshift star-forming galaxies, a completely new effect predicted by our recent work from radiative transfer study of such galaxies. I will discuss the profound implications in using such galaxies to study cosmology and physical conditions and environments of galaxies and talk about the current observational status.
17/09 - 10:00 am
Adam Amara
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Adam Amara
Title
Information from Cosmology Experiments and the Latest DES Results (ETH Zürich)
Abstract
Bayesian statistical methods have become common place in cosmology and numerous new experiments have reported posterior results on cosmological parameters. With all of these measurements we can ask basic questions such as: how much have given experiments contributed to our knowledge of the Universe? and are the results from different experiments consistent with each other? In this talk I will present a discussion of relative entropy and how this powerful statistical tool can be used to condense complex results to address these important questions. To demonstrate this tool I will present results from the CMB, before moving to the Dark Energy Survey, for which we have recently published our first cosmology results. In particular I will focus the last part of the talk on the challenges of making precision weak lensing measurements and the prospects for the upcoming data that we are processing now.
10/09 - 10:00 am
Rachel Mandelbaum
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Rachel Mandelbaum
Title
Intrinsic galaxy alignments and the cosmic web (Carnegie Mellon University)
Abstract
The intrinsic shapes of galaxies are not purely random, but rather exhibit coherent alignments (“intrinsic alignments”) with cosmological large-scale structure. Intrinsic alignments include a great deal of information about galaxy formation and evolution in a cosmological context, while also serving as a contaminant to weak gravitational lensing measurements (which assume that all coherent galaxy alignments are due to gravitational lensing). In this talk, I will discuss recent progress in our understanding of galaxy intrinsic alignments on both the observational side and the computational side, using SDSS-III BOSS data and SPH simulations, respectively. Recent work using massive BOSS galaxies has permitted a study of how galaxy intrinsic alignments vary from small scales (within massive halos) to cosmological scales, and how the level of the alignments scales with the galaxy environment (for brightest group galaxies, satellites in groups, and field galaxies). Among these new observational results is the fact that the level of small-scale alignments (<1 Mpc/h) correlates more tightly with the large-scale galaxy bias (from >10 Mpc/h) than with the galaxy luminosity. On the computational side, high-resolution SPH simulations with 100 Mpc/h box sizes are able to make predictions for how galaxy intrinsic alignments scale with galaxy properties, as well as to make verifiable predictions for the intrinsic alignment 2-point correlation functions of massive galaxies that are observed by existing galaxy redshift surveys. I will discuss challenges for using and interpreting simulated intrinsic alignment signals, and the latest results for their comparison with observations, as well as the implications for future weak lensing surveys.
03/09 - 10:00 am
Alex de Oliveira
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Alex de Oliveira
Title
Pluto’s atmosphere from stellar occultations in 2012 and 2013 (Observatório Nacional)
Abstract
Pluto, as well as other objects of the Kuiper belt, is not very subject to the influence of solar radiation, so its atmosphere, provides information about the primordial composition of the protoplanetary cloud. As far as ground based observations are concern, the most effective technique to study Pluto’s atmosphere, is using stellar occultations lightcurves. In this work we present results from two Pluto stellar occultations observed on 18 July 2012 and 04 May 2013, and monitored respectively from five and six sites in South America. Both campaigns involved large telescopes (including the 8.2-m VLT at ESO/Paranal). The high SNR ratios and multi-chord coverage provide amoung the best Pluto atmospheric profiles ever obtained from the ground. We show that a spherically symmetric, clear (no-haze) and pure N2 atmosphere with a unique temperature profile satisfactorily fits the twelve lightcurves provided by the two events. We find, however, a small but significant increase of pressure of 6% (6-sigma level) between the two dates. We provide atmospheric constrains between 1190 km and 1450 km from Pluto’s center, and we determine the temperature profile with accuracy of a few km in vertical scale. This profile provides (assuming no troposphere) a Pluto surface radius of 1190 +/- 5 km, consistent with preliminary values obtained by New Horizons. Currently measured CO abundances are too low to explain an observed negative mesospheric thermal gradient. We explore the possibility of an HCN (recently detected by ALMA) cooling. This model, however, requires largely supersaturated HCN. Zonal winds and vertical compositional variations of the atmosphere are also unable to explain the observed mesospheric trend, leaving the question open. These events are the last useful ground-based occultations recorded before the 29 June 2015 occultation observed from Australia and New Zealand, and before the NASA’s New Horizons flyby of July 2015. This work can serve as a benchmark in the New Horizons context, enabling comparisons between ground-based and space results concerning Pluto’s atmospheric structure and temporal evolution.
27/08 - 10:00 am
Elmer Luque
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Elmer Luque
Title
Search for substructure in the outer Milky-Way halo (Universidade Federal do Rio Grande do Sul)
Abstract
The search for stellar substructures, such as globular clusters, dwarf galaxies and stellar streams, out to the farther fringes of our Galaxy helps us better understand the Milk-Way in many ways: the census of MW satellites and their remnants constrains models of structure formation, the process of mass accretion over time, the Galactic gravitational potential, and the structure and stellar populations of the Galactic Halo. We used a matched-filter technique applied to colour-magnitude data, originally developed by Balbinot et al (2011, MNRAS, 416, 393), to search for new stellar systems on the Dark Energy Survey (DES) first year data based on coadded images (Y1A1). Our goal has been the identification of new clusters and dwarf galaxies. The method was initially improved to be able to detect stellar substructure without prior knowledge of the generating population, using a grid of simulated CMD models instead. It was also validated with the Sloan Digital Sky Survey (SDSS), where we recovered most previously identified faint MW satellites. In this contribution we report on the new satellite candidates identified in the DES Y1A1 and Y2Q1 data. Additionally, we reported the discovery of a new star cluster using the first-year DES data. Finally, the SparSEx code detected new possible candidates for stellar objects in the Y2Q1 data, and the follow-up observations meant to confirm the physical reality of the sparser systems and to better constrain the properties of the richer ones.
Slides not available
20/08 - 10:00 am
Helio Perottoni
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Helio Perottoni
Title
Mapping Triangulum-Andromeda with SDSS. Photometric Cartography (OV UFRJ)
Abstract
The Milky Way was formed in a complex chain of physical processes involving dissipative gravitational collapse, gas flows and galactic mergers. The outer stellar halo is home to a number of substructures that are likely remnants of former interactions of the Galaxy with its dwarf satellites. Triangulum-Andromeda (TriAnd) is one of these halo substructures, found as a debris cloud by Rocha-Pinto et al. (2004) using 2MASS M giants. We analyzed the region of Triangulum-Andromeda using photometric data from the Ninth Data Release of Sloan Digital Sky Survey (SDSS DR9). By comparing the observations with simulations from the TRILEGAL Galactic model we were able to identify and map several scattered overdensities of main sequence stars that seem to be associated with TriAnd over a large area covering ~ 500 deg2. At least two of these excesses may represent new, not previously known, stellar structures, and one of them resembles a faint stellar stream. Our estimates for the their luminosity and total stellar mass (~ 103 to 105 M_sun), for a population having [Fe/H] = -0.46 dex, 8 Gyr and a distance module of 16.3 mag, are compatible with other halo overdensities and with the luminosity of some ultra-faint Milky Way satellites.
13/08 - 10:00 am
Kyoung-Soo Lee
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Kyoung-Soo Lee
Title
Probing the Early Epoch of Massive Cluster Formation (Purdue University)
Abstract
Galaxy clusters serve as unique laboratories to study galaxy formation and cosmology. Nevertheless, little is known about the early stage of cluster formation when the cluster members assembled the bulk of their masses. Long before these galaxies are observed, they shut down star formation and evolved passively since. While this general picture is accepted, the detailed star formation histories of typical cluster galaxies, when/how they shut down star formation, and how these differ from those of field galaxies are not well understood. The biggest challenge has been to identify the sites of massive cluster progenitors (or ‘protoclusters’) at the peak epoch of their formation (z>~3) as such efforts require sampling of very large volumes and adequate imaging/spectroscopy sensitivities to unambiguously determine protocluster membership. Based on the existing data on the recently discovered massive protocluster (total mass >~10^15 Msun, similar to that of the Coma), I will present several observational evidence that suggest that a systematic search for massive protoclusters can be conducted efficiently utilizing several characteristics that mark the protocluster sites and their constituents. Preliminary results on the properties of several confirmed protoclusters, compared to the field, will be discussed.
30/07 - 02:00 pm
Francisco Förster Burón
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Francisco Förster Burón
Title
The High cadence Transient Survey (HiTS): real-time detection of supernovae and other transients with DECam (Universidad de Chile)
Abstract
At the Astroinformatics Laboratory of the Center for Mathematical Modelling (CMM) at the University of Chile and the Millennium Institute for Astronomy (MAS) we have developed a novel transient detection pipeline to be used in real-time with data from the Dark Energy Camera (DECam). DECam is a 520 Megapixel CCD camera with an unprecedented wide angle field of view mounted on the 4m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO). During 5/6 contiguous nights in the 2014/2015 we were able to achieve the real-time data analysis of more than 120/150 square degrees of the sky with a cadence of only 2/1.6 hours. We processed more than 1000 billion pixels in total, leading to the discovery of 30/90 new SNe. We also found thousands of previously unknown asteroids and hundreds of variable stars that can be used to map the structure of the outer parts of the Milky Way.
16/07 - 10:00 am
Tim Eifler
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Tim Eifler
Title
CosmoLike – Preparing for multi-probe cosmological likelihood analyses with Dark Energy Survey data (Jet Propulsion Laboratory)
Abstract
The Dark Energy Survey (DES) has recently completed its second season of observations, now covering the full 5000deg^2 survey footprint at varying depth (23.2-23.4 mag in the i-band). This high quality data set will be extended to a depth of 24 mag i-band during the next 3 years but already today it poses new challenges for the precise modeling of observables of the Universe’s Large-Scale Structure (LSS), and its astrophysical and observational systematics. The tightest constraints on cosmology from DES data will be obtained through a joint analysis of all probes (e.g., weak lensing, galaxy clustering, magnification, cluster masses). Such joint analyses face several difficulties: First, the cosmological information is highly correlated, which requires a joint likelihood including all cross correlations between the individual probes. Second, even more problematic are the correlations of various systematic effects originating from astrophysics and the measurements themselves. In this talk I will give a quick introduction to the DES collaboration and survey. I will then describe the CosmoLike analysis framework that is being developed for a joint likelihood analysis of multiple cosmological probes extracted from DES data. This multi-probe DES analysis is an excellent starting point to prepare for challenges of future data sets from LSST, Euclid, and WFIRST.
Slides not available
09/07 - 10:00 am
Gary Bernstein
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Gary Bernstein
Title
How clear is a cloudless sky? (University of Pennsylvania)
Abstract
Every astronomy student learns how to make photometric measurements with array-camera data by using a flat-field and standard stars. The Sloan and PanStarrs surveys have estimated photometric errors of ~0.01 mag, achieved by a renewed emphasis on using internal consistency to build more accurate models of the instrument response. What physical effects are not properly treated by the standard calibration methods? I’ll show how millimag repeatability is attainable on a given night of DES observations with careful treatments of CCD nonlinearities, pixel-size variations, varying spectral response, and scattered light, that are not part of typical image processing. To tie together all the DES data at millimag level, we have to ask some basic questions: how much does the transparency of the sky vary over time and space on cloudless “photometric” nights? How much does the instrument response change over months or years? I’ll present encouraging results of studies with DES.
25/06 - 10:00 am
Henry McCracken
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Henry McCracken
Title
Galaxies, dark matter haloes and how efficiently galaxies form: new results from the UltraVISTA survey (Institut d’Astrophysique de Paris)
Abstract
In my talk I will present the UltraVISTA survey, an ultra-deep near-infrared survey of the COSMOS field. By combining this data with broad-band and medium-band photometry from Subaru telescope and the Spitzer space telescope, together with a very large number of spectroscopic redshifts, we are able to derive precise photometric redshifts and stellar masses for a very large sample of galaxies in the redshift range 0 < z < 2. We will use this mass-selected sample to investigate the relationship between galaxies and the dark matter haloes which host them over more than half of the age of the universe. We discuss the implications this work has for how efficiently galaxies form stars and what is the fate of satellites galaxies in dark matter haloes. Finally, I will briefly describe the prospects for continuing this study with the latest UltraVISTA / COSMOS data sets which will be publicly available before the end of the year.
11/06 - 11:00 am
Flavia Sobreira
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Flavia Sobreira
Title
DES Large Scale Structure First Results (Fermi National Accelerator Laboratory)
Abstract
In this talk I will present results of galaxy clustering selected from the photometric Science Verification data of the Dark Energy Survey. The SV data corresponds to a period of observations in late 2012 and early 2013 that provided science-quality images for more than 250 sq. deg. at the nominal depth of the survey (iAB ∼ 24). I will put particular emphasis in detailing how we mitigate systematic effects that comes from potential sources as seeing, airmass, sky brightness and also about the behavior of galaxy bias over a broad range of linear scales and its comparison with a CFHTLS sample, showing that the results from both galaxy samples are in very good agreement.
28/05 - 10:00 am
Dante Minniti
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Dante Minniti
Title
Rediscovering the Milky Way with the VVV Survey (UNAB/MAS/CATA Chile)
Abstract
As one of the major surveys of the southern sky, the VISTA telescope at ESO’s Paranal Observatory in Chile is mapping the central regions of the Milky Way in infrared light to search for new and hidden objects. The VVV survey (standing for VISTA Variables in the Via Lactea) returns to the same parts of the sky again and again to spot objects that vary in brightness as time passes. By observing in infrared light, astronomers can see right through the dust-filled central parts of the Milky Way and spot many previously hidden objects. In just this tiny part of one of the VISTA surveys, astronomers have discovered two unknown and very distant Cepheid variable stars. They are the first such stars found that lie in the central plane of the Milky Way beyond its central bulge.
Slides not available
21/05 - 10:00 am
Emmanuel Bertin
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Emmanuel Bertin
Title
The DANCe project: recycling 15 years of archival wide-field data for kinematic studies (Institut d’Astrophysique de Paris)
Abstract
The DANCe (Dynamical Analysis of Nearby ClustErs) project aims at deriving a comprehensive census of the stellar and substellar content of a number of nearby (1 kpc) young (500 Myr) associations. Members are identified based on their kinematics properties, ensuring little contamination from background and foreground sources. I will show how robust individual proper motions can be computed with a precision better than 1 mas/yr by combining thousands of wide-field images downloaded from public archives and covering more than a decade of observations. I will present the first results of the survey and discuss the technical challenges associated with the use of large wide-field image datasets from existing public archives.
Slides not available
28/04 - 02:00 pm
Paolo Giommi
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Paolo Giommi
Title
The ASI Science Data Center: Scientific results and technical activities (ASDC)
Abstract
The ASI Science Data Center (ASDC) is a facility of the Italian Space Agency dedicated to the acquisition, processing, archival and distribution of scientific data from several scientific satellites, 13 of which are currently operational. It operates in the fields of astrophysics, cosmology, solar system exploration, and cosmic-rays. A general overview of the ASDC will be presented together with the description of some on-going activities aimed at establishing a similar facility in Brazil, in cooperation with several Brazilian institutions. Some of the most relevant scientific results, mostly in extragalactic astrophysics will also be presented.
Slides not available
16/04 - 10:00 am
Gail Zasowski
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Gail Zasowski
Title
New Tools for Galactic Archeology from the Milky Way (JHU)
Abstract
One of the critical components for understanding galaxy evolution is understanding the Milky Way Galaxy itself — its detailed structure and chemodynamical properties, as well as fundamental stellar physics, which we can only study in great detail locally. This field is currently undergoing a dramatic expansion to the kinds of large-scale statistical analyses long used by the extragalactic community, among others, thanks in part to the enormous influx of data from multiple large space- and ground-based surveys. I will describe the Milky Way and Local Group in the context of general galaxy evolution and highlight some recent developments in Galactic astrophysics that have strong implications for our understanding of how galaxies form and change across cosmic time. These advances include work done to characterize different elusive phases of the ISM, to describe the resolved bulk stellar properties of the inner disk and bulge, and to map stellar chemical properties and star formation histories throughout the Galactic disk. The rapid progress in these areas promises to continue, with the advent of coming datasets from missions like APOGEE, Gaia, and WFIRST.
Slides not available
09/04 - 11:00 am
David Nidever Nidever
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David Nidever Nidever
Title
Examining Galaxy Formation and Evolution with the Milky Way and Its Satellites (University of Michigan)
Abstract
How galaxies form and evolve remains one of the cornerstone questions in our understanding of the universe on grand scales. The Milky Way and its satellites are a local laboratory for studying the evolution and properties of galaxies of various masses in great detail. I will highlight some recent results from several projects that are providing new insights into the structure and formation history of the Milky Way and the Magellanic Clouds. First, I will discuss some of my work with the SDSS-III/APOGEE data including a recent result that suggests that the early evolution of the MW disk was characterized by stars that shared a similar star formation history and were formed in a well-mixed, turbulent, and molecular-dominated ISM with a short gas consumption timescale. Second, my investigation of the gaseous Magellanic Stream has found that stellar feedback is an important mechanism in its formation and that the Stream is significantly longer than previously thought which has important implications for the interaction history of the MCs with each other and the MW. Finally, in an effort to observationally constrain stellar structure formation on small scales, I have undertaken a multi-faceted photometric and spectroscopic study of the Magellanic Clouds. I will discuss various results from this work including the discovery of remarkably extended stellar components of both the LMC and SMC, reaching distances of ~20 kpc and ~10 kpc from their respective centers. I will also discuss some initial results from SMASH (Survey of the Magellanic Stellar Periphery), a new NOAO community DECam survey that is photometrically mapping the stellar periphery of the Magellanic Clouds for low surface brightness features.
26/03 - 10:00 am
Carlos Frenk
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Carlos Frenk
Title
Cosmology in our Backyard (Durham University)
Abstract
One of the most impressive advances in Physics in the past three decades is the development of the “standard model of cosmology,” LCDM (where L stands for Einstein’s cosmological constant and CDM for cold dark matter). This model accounts for an impressive array of data on the structure of the Universe on large-scale scales, from a few gigaparsecs down to a few megaparsecs. On the scales of galaxies and clusters, however, the model cannot be tested with the same degree of rigour as on larger scales where microwave background radiation data and measures of galaxy clustering provide clean and well-understood diagnostics. Yet, it is precisely on these small scales that the nature of the dark matter manifests itself most clearly. I will discuss theoretical predictions for the small-scale structure of the universe which appear to be discrepant with recent kinematical data for satellite galaxies of the Milky Way. Possible solutions range from the relatively mundane – that the mass of our galaxy is smaller than is often thought – through exotic baryonic processes to the more radical assumption that the dark matter is not what the standard model assumes.
Slides not available
19/03 - 10:30 am
Bob Nichol
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Bob Nichol
Title
Dark Energy Survey Supernova Survey (University of Portsmouth)
Abstract
The Dark Energy Survey (DES) has just completed its second of five years of observations. A key part of DES is a new search for high redshift supernovae; the biggest search for such events ever undertaken. In this talk, I will review DES focusing on this new supernova survey and outline the techniques we are employing to find and classify thousands of supernova-like transient events. In addition to “normal” supernovae, DES has also found a number of interesting transient, especially several examples of a new breed of “superluminous supernovae”. I will discuss these new cosmic explosions and present examples now detected in DES to z>1. I will finish by looking forward to LSST which could find thousands such supernovae.
05/03 - 10:00 am
Richard McMahon
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Richard McMahon
Title
Quasars in formation and in the Epoch of Reionization (University of Cambridge)
Abstract
Sensitive new near infra-red surveys with the VISTA telescope in Chile are allowing us to probe two significant epochs of galaxy and super massive black hole formation; the peak of galaxy and supermassive black hole activity at a redshifts of around 2-3 and the epoch of the first galaxies and supermassive black holes at redshifts above 6. I will review the current status of near IR surveys in the Southern Hemisphere with a focus on the near IR VISTA surveys and the complementary new optical surveys with the VST and the Dark Energy Survey. I will also present recent results from our surveys for z>6 quasars focusing on the new results at z>6.5 including the recent detection of 158micron [CII] cooling line with IRAM and ALMA and the properties of the intergalactic medium at high redsdshift. I will summarise the current status of these surveys and highlight recent scientific results and prospects for the next 3-5 years.
Slides not available
12/02 - 10:00 am
Alessandro Morbidelli
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Alessandro Morbidelli
Title
Solar System formation and evolution (Observatoire de la Côte d’Azur)
Abstract
The discovery of over 1,000 extrasolar planets reveals a huge diversity of planetary system architectures, even when restricting the sample to the sole giant planets. We see many Jovian planets at distances from the parent stars comparable to those of our terrestrial planets or even much smaller (hot Jupiters), as well as on orbits with a variety of eccentricities, ranging up to almost unity. These wild and surprising orbits are usually explained invoking two processes: planet migration and planet instabilities. Then, the question arises on whether our Solar System experienced these processes as well and why its structure looks so different from those of the giant planet extrasolar systems discovered so far. Luckily, we have a huge number of observational constraints that can guide us to reconstruct with some confidence the evolution of the Solar System back to the time of giant planet formation. A non-exhaustive list of constraints is made of: the orbits of the giant planets (non-resonant, partially eccentric and inclined), the Earth/Mars dichotomy (mass ratio, formation timescales), the asteroid belt (depleted, excited, featuring 2 distinct populations partially mixed, accretion within 3My, less than 10Gy-equivalent collisional evolution), Jupiter’s Trojans (extremely strong dynamical excitation, L4/L5 asymmetry), the irregular satellites populations (similar for all giant planets once rescaled to the planet’s Hill radius), the Kuiper belt (complex structure with cold, hot, resonant and scattered populations), the Oort cloud (its large population, compared to the Kuiper belt), the Late Heavy Bombardment of the Moon. I will present a model that can explain the global structure of the Solar System, consistent with all constraints listed above. If this model is correct, it suggests that the specific structure of the Solar System is due to some specific and fortuitous events that happened during its evolution. Changing slightly these events produces, through a chaotic propagation of effects, radically different final systems which cover a wide portion of the observed diversity of planetary systems.
05/02 - 04:00 pm
Eric Bellm
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Eric Bellm
Title
The Dynamic Universe (Caltech)
Abstract
The advent of wide-field synoptic imaging has re-invigorated the venerable field of time domain astronomy. We begin with various science results from the ongoing Palomar Transient Factory (PTF) survey — newborn supernovae, gap transients, orphan afterglows, relativistic explosions and near earth asteroids. Our next-generation survey, the Zwicky Transient Facility (ZTF), provides more than an order of magnitude improvement in survey speed. We describe its design, science goals, and public surveys. Mansi Kasliwal (Carnegie Observatories) Eric Bellm (Caltech)
29/01 - 10:00 am
Christopher Bonnet
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Abstract
×Speaker
Christopher Bonnet
Title
Machine learning for photometric redshifts (Institut de Fisica d’Altes Energies)
Abstract
I will be discussing the current state of machine learning for photometric redshifts from a machine learning standpoint and a astronomy standpoint. This include usage of algorithms, PDF estimation and handling of the photometric errors. I will give an overview of the current status in the DES. I will talk about the pitfalls that we face and the problems we will have to solve if we are wanting to perform precision cosmology with 5-year DES data (or LSST, Euclid).
Slides not available
22/01 - 12:00 pm
François Mignard
Abstract ⓘ
Abstract
×Speaker
François Mignard
Title
The GAIA mission: objectives, principle, status (Observatoire de la Côte d’Azur)
Abstract
A year ago ESA successfully launched the Gaia satellite to survey our Galaxy with astrometry, photometry and spectroscopy. The main goal is to investigate the formation and evolution of the Milky Way through the kinematics and physics of its stars. Astrometry will give the position, proper motion and distances to an unprecedented accuracy down a 20 mag for about 1 billion sources. I will explain how the instruments on-board can achieve this ambitious goal with a scanning satellite and will report on the actual performances as seen after the commissioning phase. Some early achievement will be shown as well to support the claim that Gaia will be a success despite some unexpected hardware problems detected in the early weeks of the mission.
Slides not available