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Past Scientific Seminars
Archivio Seminari Eccezionali

Next Seminar

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OATS-UNI/TS SEMINAR
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Speaker: Elena D'Onghia (Harvard-Center for Astrophys., Cambridge, USA)

Title: Self-Perpetuating Spiral Arms in Disk Galaxies
Date: Wednesday, May 16th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Abstract: The precise nature of spiral structure in galaxies remains uncertain. Recent studies suggest that spiral arms result from interactions between disks and satellite galaxies. Instead, leaving aside the grand bisymmetric spirals, here we consider the possibility that the multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can survive at least in a statistical sense long after the original perturbing influence has been removed. Our findings thus motivate a new interpretation of many phenomena, including disk heating, radial migration, and galaxy pattern speeds.
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Contact: Marisa Girardi (DAUT)

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JOINT ICTP-OATS-SISSA-UNI/TS COLLOQUIUM
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Speaker: Daniel Kunth (Institut d'Astrophysique de Paris - France)

Title: The Lyman emitters along the history of the Universe
Date: Thursday, May 24th, 2012
Time: 15:00
Venue: Villa Bazzoni
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Contact: John Danziger (OATS)

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OATS-UNI/TS SEMINAR
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Speaker: Antonella Garzilli (SISSA - Trieste)

Title: Measuring the intergalactic medium thermal history with wavelets filtering
Date: Wednesday, May 30th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Abstract: We describe our recent measurement of the thermal state of the intergalactic medium (IGM) in the redshift interval z=1.7-3.2 by studying the small-scale fluctuations in the Lyman-alpha forest transmitted flux. We applied a wavelet filtering technique to eighteen high resolution quasar spectra obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES), and compare these data to synthetic spectra drawn from a suite of hydrodynamical simulations in which the IGM thermal state and cosmological parameters are varied. We obtain estimates of the IGM thermal state that are in good agreement with other recent, independent wavelet-based measurements. We also perform a reanalysis of the same data set using the Lyman-alpha forest flux probability distribution function (PDF), which has previously been used to measure the IGM temperature-density relation. We find the constraints obtained from wavelets and the flux PDF are formally consistent with each other, although in agreement with previous studies, the flux PDF constraints favour an isothermal or inverted IGM temperature-density relation. We also perform a joint analysis by combining our wavelet and flux PDF measurements. Our results are consistent with previous observations that indicate there may be additional sources of heating in the IGM at z < 4.
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Contact: Matteo Viel (OATS)

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OATS-UNI/TS SEMINAR
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Speaker: Jochen Weller (LMU, Munich)

Title: Constraining Cosmology with Galaxy Cluster
Date: Wednesday, June 6th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Abstract: I will present how optically selected clusters can constrain cosmological models. This will take full consideration of the maxBCG sample in number counts and power spectrum. I will put constraints from this data set on modifications on gravity. Finally I will give an outlook what we might learn from the Euclid mission with this method.
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Contact: Stefano Borgani (DAUT)

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SEMINARIO ECCEZIONALE
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Speaker: Lucio Crivellari (IASF, Spain)

Title: La teoria euristica della luce di Einstein
Date: Thursday, June 7th, 2012
Time: 11:00
Venue: Villa Bazzoni
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Contact: Paolo Tozzi (OATS)

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OATS-UNI/TS SEMINAR
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Speaker: Massimo Viola (IFA Univ., Edinburgh, UK)

Title: Unbending the light
Date: Wednesday, June 13th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Abstract: Weak gravitational lensing has become in the last decades a very competitive cosmological tool to study the distribution of matter in the universe and to understand the properties of dark matter halos. Measuring lens-induced distortions in noisy galaxy images is however a very challenging task, even more so for the stringent requirements of the upcoming cosmic shear surveys (DES, KIDS, EUCLID): the goal is to measure a 1% variation in galaxy ellipticity with a multiplicative error in the permille range. I will discuss why reaching this precision is extremely difficult and I will present some new methods and ideas to tackle this problem. In the second part of the talk I will discuss about gravitational flexion. It is caused by the derivatives of the gravitational tidal field and it is potentially very important for the analysis of the dark matter distribution in gravitational lenses, such as galaxy clusters or the dark matter haloes of galaxies and to put constraints on the mass scale of dark matter particles. However the measurement of this signal and its interpretation are not trivial. I will critically discuss those aspects and I will present possible solutions.
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Contact: Stefano Borgani (DAUT)

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JOINT ICTP-OATS-SISSA-UNI/TS COLLOQUIUM
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Speaker: Lam Hui

Title: TBD
Date: Thursday, June 21st, 2012
Time: 15:00
Venue: SISSA
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OATS-UNI/TS SEMINAR
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Speaker: M. Murphey

Title: TBD
Date: Wednesday, June 27th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: Paolo Molaro (OATS)

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, September 12th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, September 19th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, September 26th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, October 3rd, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, October 10th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, October 17th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, October 24th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, October 31th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, November 7th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, November 14th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, November 21th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, November 28th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, December 5th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD

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OATS-UNI/TS SEMINAR
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Speaker: TBD

Title: Available
Date: Wednesday, December 12th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Contact: TBD