Seminari dell’ Osservatorio Astronomico di Palermo “G.S. Vaiana” (15 e 30 Ottobre 2015)

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Seminari dell’ Osservatorio Astronomico di Palermo “G.S. Vaiana”

(15 e 30 Ottobre 2015)


Gio 15 October 2015, 15.30

Ven 16 30 October 2015, 15.30   (N.B. Il seminario è stato procrastinato al 30 ottobre 2015)

Calendar-Time15 e 30 Ottobre 2015, ore 15.30 map-8Osservatorio Astronomico “G.S. Vaiana”, Piazza del Parlamento 1,  Palermo
Partecipazione libera senza registrazione business_contacticon-webapp+39 091 233 111,

“Simulating the formation of galaxies”

Pierluigi Monaco (Università degli Studi di Trieste) – Gio 15 Ottobre 2015, 15.30
Simulating the formation of galaxies in a cosmological context, starting from small Gaussian perturbations in the linear regime as given by the concordance LambdaCDM model, is a challenge both from the physical and the numerical point of view. In recent years there has been a breakthrough in our ability of reproducing spiral galaxies with extended disks and limited or negligible bulges, and now simulations of small but significant cosmological volumes (~100 Mpc) can produce galaxy populations with realistic properties. However, a true ab-initio approach is hampered by the wide range of scales that needs to be taken into account, given the importance of energetic feedback from massive stars and their SNe. With resolution limited to ~kpc scales, many important processes must be taken into account through suitable sub-resolution models. I will present results from a simulation program that we are carrying on in Trieste, discuss the potentialities and limits of this approach, and highlight what we can expect in the near future.

“Fine structure and flickering of coronal loops: new diagnostics of coronal heating” 

Edris Tajfirouze (Università degli Studi di Palermo) – Ven 16 30 Ottobre 2015, 15.30
Evidence for some super-hot plasma (> 4 MK) has been found in the core of active region loops. This is a signature of impulsive heating (nano-flaring). We study the EUV light curves in one or a few pixels with a model of multi-stranded coronal loop. Each strand is pulse-heated. In the hypothesis of an energy distribution of the heat pulses, we first generate a grid of strand models with different heating rates, and then we combine them randomly to generate simulated light curves similar to the observed ones. We make 10000 realisations for each set of model parameters (the power law index of the energy distribution, the duration of the heat pulse, the number of strands) and compare them to the observed light curves to find the best one by means of an artificial intelligence system (Probabilistic Neural Network, PNN). Cross-Correlation is used as a cross-check. We find that a shallow (but not flat) distribution of short-duration pulses in a relatively high number of strands (1000) best describes the observed data. A space-resolved loop model with these parameters predicts different fluctuations of the emission from the bottom to the top of the loop: we compare with observation.

INAF – Osservatorio Astronomico di Palermo “Giuseppe Salvatore Vaiana”

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