Past Pizza Lunches

Number of entries: 153

04
November 2016

Shedding light on the initial conditions for the formation of disks and multiple systems: interferometric studies of Class 0 protostars


Start: 12:00h
Speaker: Maury, Anaëlle (Service d'Astrophysique, CEA, Saclay (France))
Place: Sala Alberto Lobo

One of the main challenges to the formation of stars is the angular momentum problem: the gas contained in a typical star-forming core must reduce its specific angular momentum by 5 to 10 orders of magnitude to form a typical star such as our Sun, or else centrifugal forces will soon balance gravity…
Start: 12:00h
Speaker: Maury, Anaëlle (Service d'Astrophysique, CEA, Saclay (France))
Place: Sala Alberto Lobo

One of the main challenges to the formation of stars is the angular momentum problem: the gas contained in a typical star-forming core must reduce its specific angular momentum by 5 to 10 orders of magnitude to form a typical star such as our Sun, or else centrifugal forces will soon balance gravity and prevent inflow, accretion and the growth of the protostellar embryo. Early analytical analysis proposed that the formation of large (r > 100 AU) centrifugally supported disks would allow to dissipate angular momentum and therefore solve the angular momentum problem. However, we still don't know how the angular momentum is distributed and evolves in protostellar envelopes during the youngest phases of low-mass star formation. From pilot observations, we recently argued that the small disk sizes at the Class 0 stage are in favor of a magnetically-regulated angular momentum scenario for the formation of low-mass protostars and their disks. I will present new insights obtained thanks to the detailed analysis of millimeter observations of protostellar envelopes probing the envelope density, structure and kinematics from the small scales (50 AU) to large scales (5000 AU) obtained with the Plateau de Bure interferometer (PdBI) and the IRAM 30m telescope in the framework of the CALYPSO program. I will present statistical results putting constraints on disk properties in our CALYPSO sample of Class 0 protostars and connect our results to other datasets obtained with both the SMA, CARMA and ALMA interferometers, including a short discussion on the role of magnetic braking during the formation of solar-type stars.
28
October 2016

Supernovae in the Dark Energy Survey


Start: 12:00h
Speaker: Francisco Javier Castander Serentill (ICE/CSIC-IEEC)
Place: Alberto Lobo seminar room

The nature of dark energy is one of the greatest unsolved problems in physics today. Its existence was inferred from observations of exploding stars known as Type Ia supernovae (SNe Ia). These SNe Ia are standardizable candles that are excellent cosmological tools for probing dark energy through…
Start: 12:00h
Speaker: Francisco Javier Castander Serentill (ICE/CSIC-IEEC)
Place: Alberto Lobo seminar room

The nature of dark energy is one of the greatest unsolved problems in physics today. Its existence was inferred from observations of exploding stars known as Type Ia supernovae (SNe Ia). These SNe Ia are standardizable candles that are excellent cosmological tools for probing dark energy through the distance-redshift relation. The Dark Energy Survey (DES) Supernova Program is repeatedly observing 30 square degrees within the full 5000-square-degree DES footprint and has discovered thousands of SNe Ia, in addition to many other types of SNe. DES has recently recently started Year 4 of observations. In this talk, I will review the work of the DES supernova group.
21
October 2016

The extremely compact and magnetic leftovers of the biggest explosions in the Universe


Start: 12:00h
Speaker: Nanda Rea (CSIC-IEEC)
Place: Sala Alberto Lobo

I will review the characteristics of the biggest explosions we witness (almost daily) in the Universe, from radio, infrared, optical, X-rays to gamma-rays. Most of these explosions (sometimes so powerful to affect Earth atmosphere and comunications) are connected with the formation and evolution of…
Start: 12:00h
Speaker: Nanda Rea (CSIC-IEEC)
Place: Sala Alberto Lobo

I will review the characteristics of the biggest explosions we witness (almost daily) in the Universe, from radio, infrared, optical, X-rays to gamma-rays. Most of these explosions (sometimes so powerful to affect Earth atmosphere and comunications) are connected with the formation and evolution of compact objects: neutron stars and black holes, the dead-end of very massive stars. Neutron stars, often observed as pulsars, are by far the strongest magnets, the most precise clocks, as well as the most dense (almost nuclear) state of matter we know of in the Universe, representing the only laboratories to test our understanding of the physics under such extremes regimes. The exact physics behind the formation of these extreme magnetic fields and their large scale dipolar ordering is still mostly unkown, however in recent years, the discovery of magnetic flares from pulsars allegedly believed to be quiet and mostly rotational powered, as well as advances in MHD simulations of field formation and evolution, have greatly enlarged our understanding of these extreme sources, and their explosive events.    
14
October 2016

From disks to planets through the astrochemical lens


Start: 12:00h
Speaker: Ilsedore L. Cleeves (Hubble postdoc fellow, Harvard-Smithsonian Center for Astrophysics)
Place: Sala Alberto Lobo

During the first few Myr of a young, Sun-like star's life, it is encircled by a disk made up of molecular gas, dust, and ice. These materials form the building blocks for future planetary systems. Improvements in observational spatial resolution and sensitivity have allowed us to characterize the…
Start: 12:00h
Speaker: Ilsedore L. Cleeves (Hubble postdoc fellow, Harvard-Smithsonian Center for Astrophysics)
Place: Sala Alberto Lobo

During the first few Myr of a young, Sun-like star's life, it is encircled by a disk made up of molecular gas, dust, and ice. These materials form the building blocks for future planetary systems. Improvements in observational spatial resolution and sensitivity have allowed us to characterize the protoplanetary disk environment in great detail. Recent interferometric observations with both the Submillimeter Array (SMA) and the Atacama Large Millimeter/Submillimeter Array (ALMA) have shed light on disks' chemical composition and the structure of their rocky/solid and gaseous components, which together feed young terrestrial and gas giant planets. I will discuss recent results and new puzzles regarding our understanding of protoplanetary disk chemical and structural evolution, along with future avenues to detect individual young planets forming in situ.
07
October 2016

Proxima Centauri b: our nearest neighbor


Start: 12:00h
Speaker: Ignasi Ribas Canudas
Place: Sala Alberto Lobo. ICE

A major astronomical discovery was announced several weeks ago, namely a potentially habitable planet around Proxima Centauri, the nearest star to the Sun. The finding of Proxima b has great impact to astronomy since it will allow us to learn a lot about the evolution of Earth-like planets and, maybe,…
Start: 12:00h
Speaker: Ignasi Ribas Canudas
Place: Sala Alberto Lobo. ICE

A major astronomical discovery was announced several weeks ago, namely a potentially habitable planet around Proxima Centauri, the nearest star to the Sun. The finding of Proxima b has great impact to astronomy since it will allow us to learn a lot about the evolution of Earth-like planets and, maybe, it will offer the possibility of studying a habitable planet (perhaps even inhabited!) in unbeatable conditions. In this talk, I will explain the details of the discovery, our contribution to understand the habitability of Proxima b and some future perspectives.
17
June 2016

EARLY X- AND GAMMA-RAY EMISSION FROM THE RECURRENT NOVAE RS OPH AND V745 SCO


Start: 12:00h
Speaker: Laura Delgado Pardo (Institut de Ciències de l'Espai (CSIC-IEEC))
Place: Alberto Lobo Conference Room (Campus UAB, Institut de Ciències de l'Espai, C/ de Can Magrans s/n)

Nova explosions can be sources of high-energy gamma-ray photons. This emission is produced by π0 decay and/or Inverse Compton, which is a consequence of particle, p and e-, acceleration. The strong shock between matter ejected by the white dwarf and the circumstellar medium is responsible for this process.…
Start: 12:00h
Speaker: Laura Delgado Pardo (Institut de Ciències de l'Espai (CSIC-IEEC))
Place: Alberto Lobo Conference Room (Campus UAB, Institut de Ciències de l'Espai, C/ de Can Magrans s/n)

Nova explosions can be sources of high-energy gamma-ray photons. This emission is produced by π0 decay and/or Inverse Compton, which is a consequence of particle, p and e-, acceleration. The strong shock between matter ejected by the white dwarf and the circumstellar medium is responsible for this process. Particle acceleration in a nova was predicted for the first time in the 2006 outburst of RS Ophiuchi. Up to now, the Fermi/LAT satellite has detected seven nova explosions in the high energy range, five classical novae and two symbiotic recurrent novae. Our aim is to understand the acceleration process through the analysis of contemporaneous X-ray emission. We present the analysis of X-ray observations of the recurrent novae RS Oph and V745 Sco the first days after the outburst. We have studied XMM-Newton’s observations of RS Oph early after its 2006 outburst. Furthermore, we have analysed X-ray observations of V745 Sco simultaneous to gamma-ray Fermi/LAT detection. This study gives a global picture of the evolution of the nova the first days after its outburst and its relationship with particle acceleration.
10
June 2016

Extragalactic Novae: A brief history and a recent highlight


Start: 12:00h
Speaker: Martin Henze
Place: Sala Alberto Lobo (ICE)

The first detections of extragalactic Classical Novae (CNe), found on photographic-plate images of the Andromeda galaxy (M31) taken in 1909, preceded the Great Debate and the insight that there exist other “island universes” besides our own. Over the following century, extragalactic novae played…
Start: 12:00h
Speaker: Martin Henze
Place: Sala Alberto Lobo (ICE)

The first detections of extragalactic Classical Novae (CNe), found on photographic-plate images of the Andromeda galaxy (M31) taken in 1909, preceded the Great Debate and the insight that there exist other “island universes” besides our own. Over the following century, extragalactic novae played an active part in the astronomical controversies of the time: from being instrumented on both sides of the Great Debate, through applications as standard candles for building the cosmic distance ladder, to their currently discussed relevance as progenitors for the highly important type Ia supernovae (SNe Ia). I will present a brief history of these developments in the first part of my talk. The second part will focus on the recent highlight discovery of the best SN Ia progenitor candidate known to date: the M31 recurrent nova M31N 2008-12a. With eight eruptions in the last eight years its eruption frequency is unparalleled.  All data and models are consistent with a WD mass close to the Chandrasekhar limit and a high accretion rate. For the first time, we can conduct statistical studies of repeated eruptions in an individual nova. I will present new results from the recent 2015 eruption and discuss them in the context of the known eruption history.
27
May 2016

On the fragmentation of the Orion Molecular Cloud 1n.


Start: 12:00h
Speaker: Paula Stella Teixeira (University of Vienna)
Place: ICE - Carrer Can Magrans S/N (Sala Alberto Lobo)

The filamentary structure of molecular clouds may play an important role in setting the initial mass function. Observational studies of filament fragmentation may help us understand how important that role is. The Orion Molecular Cloud is an active star forming region that is an ideal target for…
Start: 12:00h
Speaker: Paula Stella Teixeira (University of Vienna)
Place: ICE - Carrer Can Magrans S/N (Sala Alberto Lobo)

The filamentary structure of molecular clouds may play an important role
in setting the initial mass function. Observational studies of filament
fragmentation may help us understand how important that role is. The
Orion Molecular Cloud is an active star forming region that is an ideal
target for such a study. I will present our latest results on an SMA
1.3mm continuum study of the OMC 1 northern filament. We discovered 24
new compact sources, ranging in mass from 0.1 to 2.3M?, and in size from
400 to 1300au. The masses of these sources are similar to those of the
SMA protostars in OMC 3 (Takahashi et al. 2013), but their typical sizes
and densities are lower by a factor of ten. Most of these sources are
thus likely in the Class 0 evolutionary phase. The spatial analysis of
these sources reveal two characteristic length scales: 30' (0.06pc) and
6" (2500au). We analyze different physical processes to determine the
origin of these scales. We find that turbulence and the magnetic field
are not dominant in the fragmentation of OMC1n, however, both spatial
scales are largely consistent with the local Jeans gravitational length.
20
May 2016

NEW INSIGHTS ON THE PHYSICS OF TYPE IA SUPERNOVAE OBTAINED FROM THEIR GAMMA-RAY EMISSION


Start: 12:30h
Speaker: Jordi Isern Vilaboy
Place: Sala Alberto Lobo (ICE building)

Type Ia supernovae are thought to be the outcome of the thermonuclear explosion of a carbon/oxygen white dwarf in a close binary system. Their optical light curve is powered by thermalized gamma-rays produced by the radioactive decay of $^{56}$Ni, the most abundant isotope present in the debris. Gamma-rays…
Start: 12:30h
Speaker: Jordi Isern Vilaboy
Place: Sala Alberto Lobo (ICE building)

Type Ia supernovae are thought to be the outcome of the thermonuclear explosion of a carbon/oxygen white dwarf in a close binary system. Their optical light curve is powered by thermalized gamma-rays produced by the radioactive decay of $^{56}$Ni, the most abundant isotope present in the debris. Gamma-rays escaping the ejecta can be used as a diagnostic tool for studying the structure of the exploding star and the characteristics of the explosion. The fluxes of the 56Ni lines and the continuum obtained by INTEGRAL from SN2014J in M82, the first ever gamma-detected SNIa, around the time of the maximum of the optical light curve strongly suggest the presence of a non-spherical plume of 56Ni in the outermost layers moving at high velocities and receding from the observer. If this interpretation were correct, it could have important consequences on our current understanding of the physics of the explosion and on the nature of the systems that explode.
13
May 2016

Looking for rain using GPS radio occultations


Start: 12:30h
Speaker: Ramon Padullés Rulló
Place: Sala Alberto Lobo (ICE - Carrer Can Magrans S/N)

The use of Global Positioning System (GPS) Radio Occultations (RO) for climate and weather monitoring has grown a lot during the last decade, becoming a key instrument for weather forecasting and modeling. GPS RO are nowadays fully operational implemented, and provide their retrievals in near real…
Start: 12:30h
Speaker: Ramon Padullés Rulló
Place: Sala Alberto Lobo (ICE - Carrer Can Magrans S/N)

The use of Global Positioning System (GPS) Radio Occultations (RO) for climate and weather
monitoring has grown a lot during the last decade, becoming a key instrument for
weather forecasting and modeling. GPS RO are nowadays fully operational implemented,
and provide their retrievals in near real time. A new concept to further exploit the
capabilities of the RO technique with the aim of detecting rain was devised in the ICE
and will be tested on board the spanish satellite PAZ in the near future. In this talk, I will briefly explain the concepts beyond GPS and its applications, focused
in the aspects that are important for the radio occultation technique. I will go throught
the RO concept, and the Radio Occultations and Heavy Precipitation on PAZ (ROHP-PAZ) experiment
will be introduced.  
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