Past Pizza Lunches

Número de entradas: 155

10
Enero 2020

White dwarfs as Advanced Physics laboratories: the axion case


Inicio: 12:15h
Ponente: Jordi Isern Vilaboy
Lugar: Alberto Lobo Room

The shape of the luminosity function of white dwarfs (WDLF) is sensitive to the characteristic cooling time and, therefore, it can be used to test the existence of additional sources or sinks of energy such as those predicted by alternative physical theories. However, because of the degeneracy between…
Inicio: 12:15h
Ponente: Jordi Isern Vilaboy
Lugar: Alberto Lobo Room

The shape of the luminosity function of white dwarfs (WDLF) is sensitive to the characteristic cooling time and, therefore, it can be used to test the existence of additional sources or sinks of energy such as those predicted by alternative physical theories. However, because of the degeneracy between the physical properties of white dwarfs and the properties of the Galaxy, the star formation history (SFH) and the IMF, it is almost always possible to explain any anomaly as an artifact introduced by the star formation rate. To circumvent there are at least two possibilities, the analysis of the WDLF in populations with different stories, like disc and halo, and the search of effects not correlated with the SFH. These procedures are illustrated with the case of axions.
17
Diciembre 2019

Especial Christmas Seminar: The 'Climate Emergency': scientific basis, impacts and possible solutions to the first planetary human problem


Inicio: 12:00h
Ponente: Eric Galbraith (Universitat Autònoma de Barcelona (UAB))
Lugar: Alberto Lobo Room

Humanity has been causing environmental problems forever, and has often resolved them with great success. But in the past, these were problems faced by local populations, which were able to coordinate their activities in order to resolve them locally. Climate change is fundamentally different, in that…
Inicio: 12:00h
Ponente: Eric Galbraith (Universitat Autònoma de Barcelona (UAB))
Lugar: Alberto Lobo Room

Humanity has been causing environmental problems forever, and has often resolved them with great success. But in the past, these were problems faced by local populations, which were able to coordinate their activities in order to resolve them locally. Climate change is fundamentally different, in that it is a collective problem played out in the well-mixed global atmosphere, and which can only be addressed through globally-coordinated policy that addresses the majority of our species. Thus far, we have made essentially no tangible progress on this challenge. I will briefly discuss the scientific basis of climate change, including how greenhouse gases work, evidence for natural climate change in the past, and human emissions. I will then review expected impacts of climate change on a range of timescales, focusing on temperatures, food production, sea level rise and ecosystem alterations, as well as the reasons why the impacts will almost certainly exceed expectations. I will then discuss the possible means by which climate change can be mitigated or reversed, and how these might interact with other aspects of human activities and well-being. I will conclude that, although a daunting challenge, the climate emergency may provide the impetus required to develop global policy that could benefit humanity in the long-term.
13
Diciembre 2019

ELGAR: The European Laboratory for Gravitation and Atom-interferometric Research


Inicio: 12:15h
Ponente: Carlos Sopuerta (ICE)
Lugar: Alberto Lobo Conference Room

After the inauguration of Gravitational Wave Astronomy with the first direct detection of Gravitational Waves from a binary black hole coalescence by the Laser Interferometer Gravitational-wave Observatory (LIGO), the race to cover the most relevant parts of the Gravitational-wave spectrum is currently…
Inicio: 12:15h
Ponente: Carlos Sopuerta (ICE)
Lugar: Alberto Lobo Conference Room

After the inauguration of Gravitational Wave Astronomy with
the first direct detection of Gravitational Waves from a binary black
hole coalescence by the Laser Interferometer Gravitational-wave
Observatory (LIGO), the race to cover the most relevant parts of the
Gravitational-wave spectrum is currently at full speed.  Indeed, after
eleven detections  (10 Binary Black Holes and 1 Binary Neutron Star),
the LIGO-Virgo collaboration, operating in the high-frequency band, is
immersed in the third observation run with a lot of new potential
candidates. On the other hand, LISA is the future ESA-L3 mission for
low-frequency gravitational-wave astronomy. Pulsar Timing Arrays,
covering the very-low frequency band, have sensitivities within the
discovery region of the predicted parameter space. And finally, CMB
polarization experiments continue their developments for the ultra-low
frequency band.

Despite these efforts there are still gaps to fill in the gravitational
wave spectrum.  In particular, the deciHertz band is not well covered
neither by the ground-based detectors nor by LISA. In this talk I will
present new efforts to fill the deciHertz band with a new technology,
atom interferometry, and I will talk about the great science that can be
done with the proposed detector ELGAR.

Reference: http://arxiv.org/abs/1911.03701
29
Noviembre 2019

Black hole in globular clusters


Inicio: 12:15h
Ponente: Mark Gieles
Lugar: Alberto Lobo room

Globular clusters (GCs) are the outcome of the earliest phases of star and galaxy formation in the Universe. Their high densities foster the formation and hardening of binary black holes (BHs) that can merge via gravitational wave in-spiral. The contribution of this `dynamical channel' to gravitational…
Inicio: 12:15h
Ponente: Mark Gieles
Lugar: Alberto Lobo room

Globular clusters (GCs) are the outcome of the earliest phases of star and galaxy formation in the Universe. Their high densities foster the formation and hardening of binary black holes (BHs) that can merge via gravitational wave in-spiral. The contribution of this `dynamical channel' to gravitational wave detections - relative to other channels - is not understood, because it sensitively depends on the poorly constrained BH natal kicks and the unknown properties of infant GCs. I will present results of efforts to infer the BH content of Milky Way GCs by comparing dynamical mass models to kinematics and star counts. We find the signal of a BH population in several Milky Way GCs and I will discuss the implications of these findings for the BH merger rate across cosmic time.
22
Noviembre 2019

Magnetic environment and experiments on-board LISA Pathfinder


Inicio: 12:15h
Ponente: Juan Pedro López Zaragoza
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

The differential acceleration measurement between two free-falling test masses on-board LISA Pathfinder is limited in the low frequency regime by force noise applied to the test masses. Several effects can contribute as force noise on the inertial masses and, amongst them, magnetically-induced forces…
Inicio: 12:15h
Ponente: Juan Pedro López Zaragoza
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

The differential acceleration measurement between two free-falling test masses on-board LISA Pathfinder is limited in the low frequency regime by force noise applied to the test masses. Several effects can contribute as force noise on the inertial masses and, amongst them, magnetically-induced forces are precisely one of the effects limiting the performance of the instrument in the milliHertz band. The origin of this disturbance is the coupling of the residual magnetisation and susceptibility of the test masses with the environmental magnetic field. In order to fully understand this term of the noise model, a set of coils and magnetometers are integrated as a part of the LISA Pathfinder diagnostics subsystem.
In this talk we will explain which are the different magnetic experiments we have carried on board LISA Pathfinder in order to extract the magnetic parameters that characterise LISA Pathfinder's test masses. Moreover, we will also give a complete overview of which was the magnetic field on-board the satellite during mission operations and the effects it had on the mission performance. We will finally describe how, by analysing the movement of the test masses during magnetic experiments, we can extract not only information about their magnetic properties, but also about the environment that surrounds them. We also provide the magnetic contribution to the LISA Pathfinder noise budget.
 
15
Noviembre 2019

Apadrina un carolingi


Inicio: 12:30h
Ponente: Serni Ribó (ICE)
Lugar: Alberto Lobo Room

Have you ever found a skeleton in your backyard? Have you ever found four of them? In this presentation I will talk about how four tombs helped me to learn a little bit of history, and how it is to have an archeological site at home. Based on a real story.
Inicio: 12:30h
Ponente: Serni Ribó (ICE)
Lugar: Alberto Lobo Room


Have you ever found a skeleton in your backyard? Have you ever found four of them? In this presentation I will talk about how four tombs helped me to learn a little bit of history, and how it is to have an archeological site at home. Based on a real story.
08
Noviembre 2019

Star formation, polarization, and magnetic fields in the ALMA era


Inicio: 12:15h
Ponente: Chat Hull (National Astronomical Observatory of Japan)
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

New ALMA polarization observations continue to both expand and confound our understanding of the role played by the magnetic field in low-mass star formation.  The sample of very young, Class 0 protostellar sources observed with high resolution and high sensitivity with ALMA is now large enough that…
Inicio: 12:15h
Ponente: Chat Hull (National Astronomical Observatory of Japan)
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

New ALMA polarization observations continue to both expand and confound our understanding of the role played by the magnetic field in low-mass star formation.  The sample of very young, Class 0 protostellar sources observed with high resolution and high sensitivity with ALMA is now large enough that we are beginning to see the same surprising features in multiple sources.  The first of these are magnetic field morphologies that beautifully trace the outflow cavity walls in several objects, suggesting that the outflow has shaped the magnetic field.  The polarization along the cavities is strongly enhanced, and in some cases is co-located with emission from UV-tracing molecules, suggesting that the origin of the enhanced polarization is the strong irradiation of the outflow cavities.  The second, more puzzling set of features are thin structures with well organized magnetic fields that are not associated with outflow cavity walls, and yet have high polarization fractions in spite of being deeply embedded and far from any obvious source of the photons necessary to align the grains.  I will close by discussing recent ALMA observations of polarization toward much more evolved, Class II protoplanetary disks.  In the case of my work on IM Lup (one of these disks): consistent with some (but not all!) polarization observations of other disks, the polarization at Bands 6 and 7 (1.3 mm and 850 microns) appears to be due to scattering by dust grains, thus complicating the search for magnetic fields in these sources.  While on one hand all of these results challenge our understanding of both magnetic grain-alignment and grain growth, they also have the potential to open up new windows into the dust-grain properties and radiation environments in young star-forming sources.
25
Octubre 2019

Recent results from CARMENES


Inicio: 12:15h
Ponente: Juan Carlos Morales Peralta (Institut de Ciències de l'Espai (CSIC-IEEC))
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

The CARMENES spectrograph is surveying around 300 M-dwarf stars to look for exoplanets. About 20 exoplanets have already been announced, and a number of candidates are still under analysis. These discoveries show that there is wider diversity of exoplanets around low-mass stars that initially expected:…
Inicio: 12:15h
Ponente: Juan Carlos Morales Peralta (Institut de Ciències de l'Espai (CSIC-IEEC))
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

The CARMENES spectrograph is surveying around 300 M-dwarf stars to look for exoplanets. About 20 exoplanets have already been announced, and a number of candidates are still under analysis. These discoveries show that there is wider diversity of exoplanets around low-mass stars that initially expected: from rocky Earth-like planets to gas giants like Jupiter. In this talk, I will summarize some of the last CARMENES results, and I will explain in more detail the last discovery we have made of a Jupiter-like planet orbiting a late-type M-dwarf that challenges planet formation models. 
18
Octubre 2019

Tension on the Hubble constant: systematic uncertainties or new physics?


Inicio: 12:15h
Ponente: Isaac Tutusaus Lleixa
Lugar: Sala Alberto Lobo

With the recent increase in precision of our cosmological datasets, measurements of ΛCDM model parameter provided by high- and low-redshift observations started to be in tension. One of the most striking tensions that we have nowadays concerns the value of the expansion rate of the Universe today,…
Inicio: 12:15h
Ponente: Isaac Tutusaus Lleixa
Lugar: Sala Alberto Lobo


With the recent increase in precision of our cosmological datasets, measurements of ΛCDM model parameter provided by high- and low-redshift observations started to be in tension. One of the most striking tensions that we have nowadays concerns the value of the expansion rate of the Universe today, the Hubble constant, which is close to a 5-sigma tension between the measurements derived from the cosmic microwave background and local measurements. There are essentially two different reasons that could explain this tension. Either there are some unaccounted systematic uncertainties on the measurements, or there are new physics on our cosmological model that can change the value derived from high-redshift observations. In the recent literature there are plenty of articles focusing on one of these two options to solve the Hubble constant tension. In this talk I will first give a brief introduction on some of the methods to estimate the value of the Hubble constant. I will then present the results of a recent paper where we try to solve the tension by combining the addition of new physics and the addition of unaccounted systematic uncertainties on type-Ia supernovae data. And I will finish by presenting the most promising ideas that could finally solve the tension.
 
11
Octubre 2019

Stellar Population of galaxies and their evolution


Inicio: 12:15h
Ponente: Helena Domínguez Sánchez (ICE)
Lugar: Alberto Lobo seminar room

In this talk I will present my research trajectory to the ICE. I will review some of the main observed  galaxy properties and relations and how they change across cosmic time. I will summarise some of my contributions to the field, such as the mass function evolution at high-z, star formation rate measurements,…
Inicio: 12:15h
Ponente: Helena Domínguez Sánchez (ICE)
Lugar: Alberto Lobo seminar room

In this talk I will present my research trajectory to the ICE. I will review some of the main observed  galaxy properties and relations and how they change across cosmic time. I will summarise some of my contributions to the field, such as the mass function evolution at high-z, star formation rate measurements, or star formation histories and radial gradients of stellar populations in massive quiescent galaxies. Finally, I will show some of the projects I work on related to machine learning, such as morphological classification of SDSS and DES galaxies, generating synthetic DES images with generative adversarial networks or identification of gravitational lensing and tidal streams.
Institute of Space Sciences (IEEC-CSIC)

Campus UAB, Carrer de Can Magrans, s/n
08193 Barcelona.
Phone: +34 93 737 9788
Email: ice@ice.csic.es
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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