Recent Talks

Very-high-energy (VHE >~100 GeV) gamma rays are absorbed in Earth's
atmosphere and thus cannot be detected directly on Earth. Their fluxes
are also typically too low to efficiently study them with satellite
instruments. A VHE gamma ray entering the atmosphere initiates an
electromagnetic cascade that induces faint flashes of blueish
Cherenkov light. Such flashes can be then detected by Imaging
Atmospheric Cherenkov Telescopes registering images of passage of
individual gamma rays through the atmosphere.
The usage of atmosphere as a part of the detector allows us to achieve
a collection area of gamma rays over two orders of magnitude higher
than the physical size of the detector. But it also introduces
systematic errors connected with the atmosphere's transparency. In
particular, cloud presence during the observations can significantly
affect the data. In this seminar I will cover different methods used
to correct the influence of the clouds. I will show how lack of such a
correction introduces bias in the energy estimation of gamma rays. I
will present how the affected images of showers are degraded and thus
can be confused with background events, lowering the collection area
of the telescope. Finally, I will show a novel method of correcting
the influence of the clouds already at the image level, and discuss
the possibility of measuring the parameters of a cloud directly with
the observations by the Cherenkov telescopes.

Abstract: Solar jets are ubiquitous, sharp-edged collimated plasma ejections that are detected in all layers of the Sun from the photosphere to the corona. Observed as impulsive events, jets can originate in all kinds of solar environments, from active regions to the quiet Sun. Occasionally, these jets interact with large scale solar filaments and can set them into oscillation, sometimes followed by instability and eruption. I will present high spatial, temporal, and spectral resolution observational studies of jets to probe the fundamental physical process behind them and integrate these observations with theoretical models. We use the coordinated observations from space-borne (SDO, IRIS) and ground-based (SST) telescopes. Space-borne telescopes provide the EUV/UV data for the outer atmosphere of the sun (chromosphere, transition region and corona), while ground-based telescopes give access to high resolution data for the inner solar atmosphere (lower chromosphere, photosphere) through H-alpha, Ca II, and Fe I lines. In this way, coordinated observations cover the solar atmosphere in multi-wavelength range from the photosphere to the corona through the chromosphere and transition region.

Current intelligent systems mainly make "predictions". That is, given an input, they estimate the most probable value of the output. These systems have many limitations, they can be easily confused when presented with a different case from their training set and they cannot explain how they arrive to a certain result. Causal models are an alternative to extend the capabilities of current systems; explain the reasons for certain decisions, predict the effect of interventions and imagine alternative situations. In this talk, I will present an introduction to causal models, in particular to causal graphical models. We will see how we can make inferences based on these models: predictions and counterfactuals; as well as learning causal models from data. I will illustrate the application of causal models in various domains: estimation of effective connectivity in the brain, causal modeling of COVID-19, and incorporating causal models in reinforcement learning and its application in robotics. Finally, I will discuss some potential applications of causal modeling in astrophysics.

Gone are the days when we used workstations as our main day to day
computer. Backing-up your data has always been important, but the risks
were much fewer then. Today, when most of us use a laptop as our main
computer, the risks are much higher: added to human error, disk
failures, etc. we have to consider that losing, dropping or getting your
laptop stolen is a real possibility, which brings the added risk of
getting your sensitive data accessed by prying eyes.

In this talk I will share my overall backup plan. While my setting is
likely more complicated than that of most of you, hopefully you can mix
& match the strategies and tools that I use (mainly Borg, but also
Timeshift, Clonezilla, Syncthing, gocryptfs, ...) to suit your needs.

While a complete and thorough backup plan might take some time to
prepare and execute, you shouldn't postpone it. Something is better than
nothing!, and you can start with something very simple, which can be
very easy to implement, and can be improved over time.

CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn) is a low-resolution spectrometer with an instantaneous field-of-view of 18.6, operating in the 130—310 GHz transparent atmospheric window. It is installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5 100 m above sea level. The Fourier transform spectrometer (FTS) contains two focal planes hosting a total of 4 304 kinetic inductance detectors. The FTS interferometric pattern is recorded on the fly while continuously scanning the sky. One of the goals of CONCERTO is to characterize the large-scale structure of the Universe by observing the integrated emission from unresolved galaxies via the line intensity mapping technique. In this presentation, I will introduce the CONCERTO instrument and show some first results.

As the number and variety of communications satellites proliferate in the rapidly accelerating New Space Age, specialists and lay observers alike have weighed the implications of a crowded orbital environment for astronomical research. The satellite launch tempo has recently increased dramatically, but conflict over the safe use of outer space has a much longer history. This talk will focus on similar debates surrounding experimental communications satellites from the late 1950s and early 1960s, notably a controversial test system known as Project West Ford. Astronomers have long acted as environmental watchdogs for outer space even as the power landscape in the international aerospace industry shifted during the decades since West Ford. What lessons might current astronomers take from past conflicts over the integrity of the night sky to address contemporary and future risk?

Pequeñas charlas consecutivas de 5 minutos sobre el trabajo de los becarios de verano en el IAC.

Youtube:

https://youtube.com/live/HrVzwfY33bQ?feature=share

The combination of stellar proper motions measured by the Gaia mission with spectroscopic radial velocities has recently enabled the precise determination of the
orbits of Milky Way stars and globular clusters. The information on their dynamics, coupled with existing chemical information, has allowed us to unravel many unknowns on their
origin and evolution, as well as on the assembly history of the Milky Way itself. In this talk I will present the most recent results on this topic, focusing on how globular
clusters can be superior tracers of the Milky Way build-up, and introducing a project, named CARMA, that aims at using globular cluster ages to characterise the most important
merger events experienced by our Galaxy.

Pequeñas charlas consecutivas de 5 minutos sobre el trabajo de los becarios de verano en el IAC.

Entrar Zoom Reunión
https://rediris.zoom.us/j/89609059257

ID de reunión: 896 0905 9257