Recent Talks

Strongly lensed supernovae are extremely rare and powerful probes that can give insights into high-redshift supernova physics, substructures in massive galaxies, and the expansion rate of the Universe. Currently, the lensed supernova field is at a turning point, as we will go from a handful of present discoveries to several hundreds per year with the advance of the next generation of telescopes. In this talk, I will present the current state of the lensed supernova field and future developments. Beginning with the discovery story of ‘SN Zwicky’, a lensed type Ia supernova found with the Zwicky Transient Facility, I will take you on a visual journey, using beautiful observations to highlight our discoveries about SN Zwicky, its exceptionally light lens galaxy, and implications for stellar microlensing. Finally, we will look ahead at the upcoming Vera Rubin Observatory and how it will help us discover more lensed supernovae and refine our understanding of the Universe’s expansion.

The nature and origin of sub-Neptune-sized planets is arguably the hottest debate in the field of exoplanets nowadays. While absent in the Solar System, they are the most common planet type in the Galaxy. Multiple models (gas dwarfs, water worlds, Hycean planets) appear to explain current observational evidence from mass-radius measurements and demographic analyses. JWST promises to break those degeneracies, but the first results are just getting published. In this talk, I will give an overview of the questions surrounding the origin of the "Radius gap", recent discoveries of benchmark sub-Neptune systems, new developments on the modelling of the internal structure of these planets, and how the ERC-funded project "THIRSTEE" aims to answer the questions surrounding this ubiquitous but mysterious population.

La fabricación aditiva (AM) engloba un conjunto de tecnologías que permiten pasar de un modelo 3D a componentes fabricados, creándolos capa a capa hasta completar la pieza. Entre las ventajas de la AM, las que más se aplican a la instrumentación astronómica son la complejidad y consolidación de las piezas, la adición de funcionalidades, la libertad de diseño y la capacidad de aligerado. El objetivo de esta charla es presentar todo el proceso de obtención de prototipos de espejos metálicos (y cerámicos) desde el inicio: desde el diseño conceptual, hasta los tests sobre las probetas de espejos aligerados.

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.

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.

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

Elemental abundances of Sun-like stars are crucial for understanding the detailed properties of their planets. However, measuring elemental abundances in M stars is challenging due to their faintness and pervasive molecular features in optical spectra. To address this, elemental abundances of Sun-like stars have been proposed to constrain those of M stars by scaling [X/H] with measured [Fe/H] – a practice is yet to be well tested. Here we compile elemental abundances for 43 M dwarfs for 10 major rock-forming elements (Fe, C, O, Mg, Si, Al, Ca, Na, Ni, and Ti) from high-resolution near-infrared stellar surveys (APOGEE, CARMENES and Subaru/IRD). We perform bootstrap-based linear regressions on the M dwarfs to determine the trends of [X/H] vs. [Fe/H] and compare them with GK dwarfs (from GALAH + APOGEE). A 2-sample, multivariate Mahalanobis Distance test is applied to assess the significance of differences in [X/H]—[Fe/H] trends for individual elemental pairs between M and GK dwarfs. The null hypothesis of no significant difference in chemical trends between M and GK dwarfs is strongly rejected for all elements except Si, for which rejection is marginal, and Na and Ni, for which results are inconclusive. This suggests that assuming no difference may lead to biased results and inaccurate constraints on rocky planets around M dwarfs. Therefore, it is crucial for both the stellar and exoplanet communities to recognise these differences. To better understand these differences, we advocate for dedicated modelling techniques for M dwarf atmospheres and more homogeneous abundance analyses. Our statistically constrained trends of [X/H]—[Fe/H] for M dwarfs offer a new constraint on estimating M-dwarf elemental abundances given measured [Fe/H], aiding in detailed characterisation of M dwarf-hosted rocky worlds in the era of JWST, PLATO and ELT.

Cosmic rays interact with astrophysical systems over a broad range of scales. They go hand-in-hand with violent, energetic astrophysical environments, and are an active agent able to regulate the evolution and physical conditions of galactic and circum-galactic ecosystems. Depending on their energy, cosmic rays can also escape from their galactic environments of origin, and propagate into larger-scale cosmological structures. In this talk, I will discuss the impacts of cosmic rays retained in galaxies. I will show that they can deposit energy and momentum, modify the circulation of baryons around galaxies, and have the potential to regulate long-term galaxy evolution. I will highlight some of the astrophysical consequences of contained hadronic and leptonic cosmic rays in and around galaxies, how their influence can be probed using signatures ranging from sub-mm to X-rays and gamma-rays, and the opportunities soon to open-up that will allow us to pin-down the multi-scale effects of cosmic rays in galaxies near and far. I will also discuss what happens to the cosmic rays that escape from galaxies, including their interactions with the magnetized large-scale structures of our Universe, and the fate of distant high-energy cosmic rays that do not reach us on Earth.