Recent Talks

It is often assumed that when stars reach their Eddington limit, strong outflows are initiated, and that this happens only for extreme stellar
masses. I will show that in realistic models of stars up to 500 Msun, the Eddington limit is not reached at the stellar surface. Instead, I will argue that the Eddington limit is exceeded inside the stellar envelope, in hydrogen-rich stars above about 1 ... 30 Msun, and in Wolf-Rayet stars above 7 Msun, with drastic effects for their structure and stability. I will discuss the observational evidence for this, and outline evolutionary consequences.

The epoch of reionization has been predicted to leave an imprint on the star formation histories of dwarf galaxies. I will briefly review theoretical ideas and observational constraints on reionization. I will then discuss the predicted effects on the evolution of dwarf galaxies.
This will be followed by a discussion of tests using star formation histories of nearby dwarf galaxies.

The World Health Organization’s International Agency for Research on Cancer (IARC) on May 31st 2011 classified mobile phone use and other radio-frequency electromagnetic fields as a possible carcinogen (group 2B). This is neither new research nor at odds with previous findings. It does, however, underline the need for further research and precautionary measures to be taken now.
In continuation with the microwave theme the tone is set for a more serious talk about the everyday use of microwave devices and in particular mobile phones. The information that Roger will pass on about the dangers of microwave devices (in a semi-digested state) is important for everyone and will probably be cause for much debate.
There are many opinions filling the internet on this subject. It really is difficult to get a fact based opinion. Either you believe that microwaves are so dangerous we should not be using them at all or you can be led to believe that there is No risk at all.
In this talk Dr Roger Hoyland will present the facts and helpful information that he has found from the most up-to-date research results. He will attempt to give a more rational view of this hot topic!

 Dr Roger Hoyland has been working at the IAC for the last 21 years on the Cosmic Microwave Background Experiments. He started out as a research assistant at Jodrell Bank, University of Manchester, near his home town. His expertise lies in sensitive microwave radiometer design. He has worked on various projects such as the Tenerife Experiments, The Planck Surveyor Mission and The QUIJOTE project.
This talk is for the general public (even if mostly scientific) and aims to explain some of the misunderstandings and myths about microwave devices that we use in our everyday life. There are many YouTube videos about the effects of microwaves but which do you believe? Does your mobile phone really cause interference in an airplane? Can you really destroy your credit card by carrying it next to your mobile? Does the EMP bomb really exist? All this and more…………….
With the help of several live experiments and some audience participation (be prepared!) you will find out the science behind the myths around mobiles, microwave ovens and other microwave devices.
PS: Please bring along your mobile phone if you have one.

In this talk I will present my view on what we know and what we don't know about the so-called secular evolution processes in galaxies. I will focus on the processes that lead to the building of main stellar components in the centre of disc galaxies, and explore how these processes fit in the current cosmological paradigm of galaxy formation and evolution. I will also make an attempt at clarifying misconceptions and discussing outstanding open questions.

I will describe the roles of jets in several quite different astrophysical systems. These include exploding core collapse supernovae, expelling common envelopes, and heating gas in clusters of galaxies. Hot bubbles inflated by jets seem to be a key ingredient in the interaction of jets with the ambient gas. The understanding that jets can efficiently interact with the ambient gas leads to new notions, such as the jittering jets model to explode massive stars, and the grazing envelope evolution(GEE) that can replace the common envelope evolution in some cases.

I will present results from The X-Shooter Lens Survey (XLENS). With XLENS we are unambiguously separate the stellar from the dark-matter content in the internal region of lens early-type galaxies (ETGs) to understand their interplay and to probe directly their formation and dynamical evolution. We combine precise strong gravitational lensing and dynamical constraints on the mass distribution with high signal-to-noise spectroscopy in the entire rest-frame visible to the NIR.In this talk I will present results obtained on a sample of very massive lens ETGs from the SLACS Survey, with velocity dispersions greater than 250 km/s and redshift>0.1.

First I will show how to constrain the low mass end of the Initial Mass Function (IMF)directly from galaxy optical spectra using a new set of non-degenerate optical spectroscopic indices which are strong in cool giants and dwarfs and almost absent in main sequence stars (Spiniello et al., 2014a). I will present unambiguous evidence that the low-mass end of the IMF is not universal. Then, I will demonstrate that the combination of this SSP modelling with a fully self-consistent joint lensing+dynamics analysis (Barnabè et al. 2012) allows us to disentangle IMF slope variations from internal dark-matter variations and, for the first time ever, to contemporary put constrains on the IMF cutoff mass (Barnabè et al., 2013, Spiniello et al., in prep).