Past Pizza Lunches

Number of entries: 155

19
May 2017

Clustering of halos in Lagrangian Space


Start: 12:00h
Speaker: Kwan Chuen Chan
Place: Sala Alberto Lobo

To extract cosmological information from galaxy surveys, the galaxy bias must be understood. As galaxies are hosted within halos, we often take the more tractable step by first studying halo formation and its bias. The most popular theoretical approach to model halo formation and its bias starts in Lagrangian…
Start: 12:00h
Speaker: Kwan Chuen Chan
Place: Sala Alberto Lobo

To extract cosmological information from galaxy surveys, the galaxy bias must be understood. As galaxies are hosted within halos, we often take the more tractable step by first studying halo formation and its bias. The most popular theoretical approach to model halo formation and its bias starts in Lagrangian space, i.e. the initial condition. In this talk I will first review the modelling of the Lagrangian halos in a pedagogical manner. I then present some of the progress on the smoothing window for the Lagrangian halos and the Lagrangian bias consistency relations, which enable us to extract the halo formation physics from the clustering properties.
12
May 2017

Singularities in cosmology: theory and observations


Start: 12:00h
Speaker: Diego Sáez-Chillón Gómez
Place: Sala de Conferencias Alberto Lobo

As pointed by the observations, the Universe expansion is increasing its speed. Nevertheless, how this acceleration works is still a mystery that has been called dark energy. On the other hand, General Relativity contains inherently singularities, which refer to singular points of the spacetime, i.e.…
Start: 12:00h
Speaker: Diego Sáez-Chillón Gómez
Place: Sala de Conferencias Alberto Lobo

As pointed by the observations, the Universe expansion is increasing its speed. Nevertheless, how this acceleration works is still a mystery that has been called dark energy. On the other hand, General Relativity contains inherently singularities, which refer to singular points of the spacetime, i.e. geodesically incomplete spacetimes according to the usual definitions by Hawking and Ellis. Over the last years, some proposed dark energy models drive the universe towards one of these future "singularities", near which the laws of physics lose their validity. In this talk, I will review and show the physical features of these singularities and present a new one that encompasses all the future singularities. Then, I will present several phenomenological parameterizations of the Hubble expansion rate to model different types of singularities and use SN Ia, BAO and H(z) data to constrain how far in the future the singularity may be, and how good the models are in comparison with the concordance model in cosmology.
05
May 2017

The gravitational capture of compact objects with supermassive black holes


Start: 12:00h
Speaker: (Institut de Ciències de l'Espai (CSIC-IEEC))
Place: Sala Alberto Lobo (ICE building, Campus UAB)

One of the most interesting sources of gravitational waves for space-borne missions is the inspiral of compact objects on to a massive black hole (MBH), commonly referred to as an "extreme-mass ratio inspiral". The small object, typically a stellar black hole, emits significant amounts of GW along…
Start: 12:00h
Speaker: (Institut de Ciències de l'Espai (CSIC-IEEC))
Place: Sala Alberto Lobo (ICE building, Campus UAB)

One of the most interesting sources of gravitational waves for space-borne missions is the inspiral of compact objects on to a massive black hole (MBH), commonly referred to as an "extreme-mass ratio inspiral". The small object, typically a stellar black hole, emits significant amounts of GW along each orbit in the detector bandwidth. In my talk I will review the most significant advances in our understanding of the astrophysics of this process. In particular, I will present new rates and the confirmation that EMRIs formed via two-body relaxation dominate them. I will also show that, contrary to those formed below a hundreth of a parsec via resonant relaxation, two-body relaxation EMRIs are not blocked.
28
April 2017

CosmoHub on Hadoop: a web portal to analyze and distribute massive cosmological data


Start: 12:00h
Speaker: Jorge Carretero (PIC )
Place: Sala Alberto Lobo (ICE building, Campus UAB)

We present CosmoHub, a web platform to perform interactive analysis of massive cosmological data without any SQL knowledge. CosmoHub is built on top of Apache Hive, which is an Apache Hadoop ecosystem component, which facilitates reading, writing, and managing large datasets.   CosmoHub is…
Start: 12:00h
Speaker: Jorge Carretero (PIC )
Place: Sala Alberto Lobo (ICE building, Campus UAB)

We present CosmoHub, a web platform to perform interactive analysis of massive cosmological data without any SQL knowledge. CosmoHub is built on top of Apache Hive, which is an Apache Hadoop ecosystem component, which facilitates reading, writing, and managing large datasets.   CosmoHub is hosted at the Port de Informació Científica (PIC) and currently provides support to several international cosmology projects such as the Euclid space ESA mission, the Dark Energy Survey (DES), the Physics of the Accelerated Universe (PAU) and the Marenostrum Institut de Ciències de l'Espai Simulations (MICE). More than two billion objects, from public and private data, as well as observed and simulated data, are available among all projects. In the last three an a half years more than 400 users have produced about 1500 custom catalogs occupying 2TB in compressed format.

CosmoHub allows users to access value-added data, to load and explore pre-built datasets and to create their own custom datasets through a guided process. All those datasets can be interactively explored using an integrated visualization tool which includes 1D histogram and 2D heatmap plots. In our current implementation, online analysis of datasets of a billion objects can be done in less than 25 seconds. Finally, all those datasets can be downloaded in three different formats: CSV.BZ2, FITS and ASDF.
21
April 2017

LISA: Past, Present, and Future


Start: 12:00h
Speaker: Carlos Sopuerta
Place: Sala de Conferencies Alberto Lobo

The Laser Interferometer Space Antenna is a mission concept for a space-based gravitational-wave observatory that is very likely going  to be adopted by the European Space Agency for its future third L-class mission.  In this talk I will briefly go through the history of this mission, its main features…
Start: 12:00h
Speaker: Carlos Sopuerta
Place: Sala de Conferencies Alberto Lobo

The Laser Interferometer Space Antenna is a mission concept for a space-based gravitational-wave observatory that is very likely going  to be adopted by the European Space Agency for its future third L-class mission.  In this talk I will briefly go through the history of this mission, its main features and the powerful science program that can be carried out.  
07
April 2017

Science with the Upgraded SMA in the Next Decade


Start: 12:00h
Speaker: Ramprasad Rao (ASIAA / SMA Hawaii)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

The Submillimeter Array (SMA) is in the process of upgrading its system -- both the front end receivers as well as the correlator over the next 3 years which should significantly improve on the existing sensitivity as well as spectral bandwidth. We expect that this upgrade will usher in a new era…
Start: 12:00h
Speaker: Ramprasad Rao (ASIAA / SMA Hawaii)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

The Submillimeter Array (SMA) is in the process of upgrading its
system -- both the front end receivers as well as the correlator over
the next 3 years which should significantly improve on the existing
sensitivity as well as spectral bandwidth. We expect that this upgrade
will usher in a new era of discoveries in submillimeter astronomy in
Hawaii. In this brief talk, I will present an overview of the
instrument upgrades and focus on some of the key science cases.
31
March 2017

An introduction to cosmological simulations


Start: 12:00h
Speaker: Linda Blot (IEEC-CSIC)
Place: Sala Alberto Lobo

Numerical simulations have a very important role in cosmology, as they allow to study the gravitational interactions that shape the large scale structure of the Universe in regimes that are not accessible to analytical methods. In this talk I will describe the ingredients that go into a cosmological…
Start: 12:00h
Speaker: Linda Blot (IEEC-CSIC)
Place: Sala Alberto Lobo

Numerical simulations have a very important role in cosmology, as they allow to study the gravitational interactions that shape the large scale structure of the Universe in regimes that are not accessible to analytical methods. In this talk I will describe the ingredients that go into a cosmological simulation and the specific challenges that such simulations pose. Finally I will present a few applications for present-day cosmology.
24
March 2017

Understanding the first magnetar nebula


Start: 12:00h
Speaker: Diego F. Torres (Institute for Space Science (IEEC/CSIC))
Place: Barcelona

A wind nebula, generating extended and bright X-ray emission, was recently detected surrounding Swift 1834.9-0846. This is  the first magnetar for which such a wind nebula was found. Soon after this discovery, claims were made arguing that such a nebula could only be produced by a transfer of magnetic…
Start: 12:00h
Speaker: Diego F. Torres (Institute for Space Science (IEEC/CSIC))
Place: Barcelona

A wind nebula, generating extended and bright X-ray emission, was recently detected surrounding Swift 1834.9-0846. This is  the first magnetar for which such a wind nebula was found. Soon after this discovery, claims were made arguing that such a nebula could only be produced by a transfer of magnetic energy into particle acceleration, thus being different in nature to all others pulsar wind nebulae (PWNe) known. Here, we investigate whether there is a plausible scenario where the PWN can be sustained without the need of advocating for additional sources of energy other than rotational. We do this by using a detailed radiative and dynamical code that studies the evolution of the nebula and its particle population in time. We find new effects related to the reverberation processes in nebulae of pulsars of low spin-down power, the most important of which is the appearance of adiabatic heating being increasingly dominant over the escape of particles as reverberation goes by. We show that Swift 1834.9-0846's nebula can be explained as being rotationally-powered, as all other known PWNe are, if it is currently being compressed by the environment. The need of reverberation naturally explains why this is the only magnetar nebula detected, and provides estimates for Swift 1834.9-0846's age.
17
March 2017

Breaking the Habit - The peculiar 2016 eruption of the remarkable recurrent nova in M31


Start: 12:00h
Speaker: Martin Henze
Place: Sala de Conferencies Alberto Lobo

Since its discovery in 2008, the Andromeda galaxy nova M31N 2008-12a has been observed in eruption every single year. This makes it the most extreme object in the new class of Rapidly Recurring Novae (RRN) - objects which show repeated eruptions within a ten-year time span. Such frequent eruptions indicate…
Start: 12:00h
Speaker: Martin Henze
Place: Sala de Conferencies Alberto Lobo

Since its discovery in 2008, the Andromeda galaxy nova M31N 2008-12a has been observed in eruption every single year. This makes it the most extreme object in the new class of Rapidly Recurring Novae (RRN) - objects which show repeated eruptions within a ten-year time span. Such frequent eruptions indicate the presence of high mass accretion onto a white dwarf which is close to the Chandrasekhar mass limit, thereby making RRN promising candidates for the progenitors of type-Ia supernovae. The previous three eruptions of M31N 2008-12a have displayed remarkably homogeneous multi-wavelength properties. In contrast, the delayed 2016 eruption (in December last year) showed significant deviations from this pattern. In this talk, I will discuss the observational results and possible interpretations on the physics and evolution of the system.
10
March 2017

Accrete, accrete, accrete… Bang! (and repeat): The Remarkable Recurrent Novae


Start: 12:00h
Speaker: Matt Darnley (Liverpool John Moores University)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

Classical Novae are powered by thermonuclear eruptions on the surface of accreting white dwarfs. By definition, Recurrent Novae are any such systems where two or more eruptions have been witnessed. The recurrents typically contain high-mass white dwarfs and are, as such, among the leading Type…
Start: 12:00h
Speaker: Matt Darnley (Liverpool John Moores University)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

Classical Novae are powered by thermonuclear eruptions on the surface of accreting white dwarfs. By definition, Recurrent Novae are any such systems where two or more eruptions have been witnessed. The recurrents typically contain high-mass white dwarfs and are, as such, among the leading Type Ia Supernova progenitor candidates. In this talk I will present the results of the first extragalactic surveys for Recurrent Novae and their own progenitor systems – both of which had unexpected findings. I will also introduce a remarkable subset of recurrent novae — the ‘rapid recurrents’ with inter-eruption timescales shorter than a decade and discuss their potential connection with SNe Ia.
Institute of Space Sciences (IEEC-CSIC)

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08193 Barcelona.
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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya