Recent Talks

The Atacama Large Millimetre/submillimetre Array (ALMA), the world's most powerful radio facility, is embarking on its most ambitious upgrade since its conception: the Wideband Sensitivity Upgrade (WSU). The WSU consists of an increase of the instantaneous spectral bandwidth by up to a factor of four, while retaining full spectral resolution over the full bandwidth. In addition, an upgrade of the full signal chain will translate in increases in sensitivity. In this talk, I will discuss the major scientific discoveries made with ALMA during the 10+ years of operations, I will present the WSU and its challenges and will conclude with the science that will be enabled once the WSU is delivered.

The instrumentation for gamma-ray astronomy has advanced tremendously during the last two decades. The study of the most violent environments in the Universe has opened a new window to understand the frontier of physics, exploring processes that are beyond the capabilities of Earth-based laboratories to replicate. In this talk, I will review the different strategies and instrumentation for gamma-ray astronomy, and report some of the most exciting observations from this rapidly evolving field. Among all instruments, the talk will be somewhat biased towards scientific results obtained with MAGIC, which is located on the Canary Island of La Palma, and has been at the forefront of gamma-ray astronomy since 2003, participating in multiple multiwavelength and multimessenger observational campaigns.

Canon is using its in-house ultra-precision cutting machines to provide the market with new optical devices for spectroscopy, including the world's first CdZnTe and InP immersion gratings and IFUs. They are used in the VLT and ELT instruments of Europe/ESO and in the instruments of the US/KECK and DKIST. The advantage of high-precision cutting is that surface roughness of less than 1 nm RMS can be obtained by cutting alone, so if the shape can be fabricated by cutting, it becomes an optical device. Since no post-processing such as polishing is required, optical devices with fine and sharp structures can be fabricated, and machined image slicers are a major advance in IFUs.
In my presentation, I will introduce the performance of our original cutting machine and the devices we have fabricated.

Segunda tanda de las charlas de instrumentación de los becarios de verano.

Supermassive black holes (SMBHs) in Active Galactic Nuclei (AGN) play a key role in the formation of galaxies and large-scale structure, but the triggering and impact of AGN feedback across scales and the origin of the observed SMBH–galaxy connection remain major open questions owing to the multi-scale and multi-physics nature of the problem. AGN feedback can also profoundly affect the properties and spatial distribution of baryons on scales that contain a large amount of cosmological information.  Current and upcoming cosmological surveys will provide unprecedented data to constrain the fundamental cosmological parameters, but uncertainties in galaxy formation physics remain a major theoretical obstacle to extract information from cosmological experiments.  In this talk, I will present new simulation techniques that are pushing the frontiers of galaxy formation modeling towards (1) the smallest scales, developing physically predictive models of SMBH accretion and feedback explicitly at sub-pc resolution in a full cosmological context and (2) the largest scales, using thousands of large-volume simulations exploring a wide range of sub-grid feedback implementations to train machine learning algorithms that can maximize the extraction of information from cosmological surveys while marginalizing over uncertainties in galaxy formation physics.  I will demonstrate the feasibility of these orthogonal approaches to address fundamental problems and discuss their potential to advance the fields of galaxy evolution and cosmology.

Zoom link: https://rediris.zoom.us/j/95949230133?pwd=xxXArEDCwNg4iXt4f5vUiCGvUFC9ph.1

Massive stars are real cosmic engines, and they have a large impact onto our Universe from early times on. Unfortunately, their evolution is still uncertain in many aspects, even on the main sequence. To check and improve corresponding predictions (needed, e.g., in galaxy simulations as sub-grid physics), various efficiency factors for internal processes such as core-envelope mixing need to be calibrated, by means of observational constraints. To this end, the measurement of chemical abundances, in particular for C,N,O, is a primary tool. Compared to low and intermediate mass stars and also to massive Red Supergiants, these measurements (by means of quantitative spectroscopy) are much more complex, since particularly deviations from LTE and the presence of inhomogeneous winds affect the observed line-strengths, and lead to significant uncertainties in the derived abundance values. In this talk, I will discuss these problems at hand of specific examples, summarize important results of the current state of the art, and provide a quick outlook what's next to come (within a collaboration with IAC-members).

Zoom link: https://rediris.zoom.us/j/98925990368?pwd=LJDIa3HSX4zIHM74vimXTwiabfrreN.1

In the first two years of scientific operations of JWST, three results have emerged, closely related to each other: an unexpected large abundance of bright galaxies at z>9 as well as AGN at z>5, and the existence of some dust even in the confirmed galaxies at the highest redshifts, with large contents present in some particular sources known as little red dots up to at least z~9. I will discuss the details and reliability of these results based on some of the recent work published by the MIRI European and US GTO, the CEERS, and the JADES-SMILES teams.

25 years ago, a seminal letter was published in Nature where it was concluded that the enigmatic linear polarization signal observed in the solar sodium D1 line implies that the quiet solar chromosphere is practically unmagnetized, in contradiction with other observational inferences and plasma physics arguments. This became known as the paradox of the solar sodium D1 polarization, which has puzzled theoretical physicists for many years, even leading some scientists to question the established quantum theory of radiation-matter interaction. In this talk I will briefly discuss the theoretical basis for this intriguing paradox and present its resolution in terms of a radiative transfer investigation published in Physical Review Letters. The observed linear polarization pattern across the sodium D2 and D1 lines can be reproduced to a remarkable degree in the presence of magnetic fields in the gauss range, if one accounts for the variations in the anisotropy of the solar radiation field over the small spectral interval spanned by the various hyperfine structure components of the sodium D2 and D1 lines. In addition, I will present the results of a series of radiative transfer investigations focused on the D lines of other alkali species, namely K I and Ba II, discussing their interest for probing the magnetism of the solar chromosphere.

Primera tanda de las charlas de instrumentación de los becarios de verano.

As a measure to fight global climate change, legislation is essentially terminating coal mining in Germany. In order to help with the necessary transformation of the economy, the federal government has set aside a total of 40 billion Euros for investment into new infrastructure in the affected regions. The state of Saxony decided to use a significant fraction of these funds to create two major research centers -- in essence to invest in brains, and not only in concrete and steel. As a result of a two-stage competition, the proposal of a group of astrophysicists has won a grant of 1.4 billion Euros to create, over a period of 15 years, the Deutsches Zentrum für Astrophysik (DZA). 
The talk will explain the structure of the institute, the current status, and the main focus on (1) fundamental research in Astrophysics, (2) technology development, and (3) big data & eScience. As for technology development, several examples will be presented that are intended to exploit the regional strength in semiconductor and photonics industry, e.g. CMOS sensors, photonic integrated circuits, photonic lanterns, etc.
In a second part of the talk, I will make a connection from the intended DZA engagement in novel detector technologies to the future WST: perhaps the next big project of ESO once the ELT has been finished. I will briefly touch upon the concept of the telescope, and report on the science case about resolved stellar populations that was developed in collaboration with IAC and others, and published recently as part of the WST White Paper (Mainieri+2024).