Colloquia | Instituto de Astrofísica de Andalucía

Present and future of exoplanet research Speaker: Ribas, Ignasi Filiation: ICE-CSIC Date: February, 13th 2025 Abstract: The search for new worlds in the Galaxy in the past three decades has been highly successful and the prospects for the next decade are even brighter. A succession of space missions and ground-based facilities defines a timeline extending well into the 2030s. Many advances on the planet discovery front will come from the PLATO mission, which will find long-period planets and even true Earth analogues, and from the many ongoing and future precise radial velocity instruments from the ground, such as CARMENES and ESPRESSO. A major leap forward is expected regarding exoplanet detailed characterisation. The goal is to understand the nature of the exoplanetary bodies and their formation and evolutionary histories through remote sensing of their atmospheres. JWST is measuring a select sample of key transiting exoplanets while Ariel will take this methodology to the next level by analysing over 1000 planets. And in the farther future, extremely large telescopes or interferometers, both on the ground and in space, should permit the measurement of temperate rocky planet atmospheres and, perhaps, the solid identification of molecules of biological interest, which will truly be a revolutionary finding. In this talk, the state of the art of exoplanet research will be described and the main future exoplanet facilities will be presented and put in context.
Modelling of large-scale magnetic field in low-mass stars Speaker: Guseva, Anna Filiation: Observatoire de Paris Date: January, 30th 2025 Abstract: Recent spectropolarimetric observations of low-mass stars show that large-scale components of their magnetic fields can exhibit cyclic variations or reversals. This magnetic activity affects detection of exoplanets and estimation of their masses, and so its modelling is particularly important. In convective stellar envelopes, magnetic fields are created through dynamo action - systematic stretching and twisting of magnetic field lines by helical convective vortices. It is yet however unclear how low-mass stars, with their strong convective turbulence and relatively slow rotation, are able to maintain coherent large-scale magnetic activity. In this talk, I will discuss the physical mechanisms that allow magnetic flux to accumulate at large scales in both turbulent and strongly stratified models of stellar convection. In such models, a highly turbulent convective layer is formed at the surface while the deep flow interiors remain rotationally constrained. Using direct numerical simulations of such flows, I will show that small-scale magnetic flux, generated by small-scale turbulence in the outer flow regions with low density, is systematically transported into more quiescent inner regions by global magnetic pumping mechanism. Consequently, the dipolarity of the field at the surface of the domain increases both with enhancement of turbulence and stratification. I will also explore the mechanisms of destabilization of magnetic fields resulting in magnetic reversals, and their dynamical interactions with zonal flows; finally, I will discuss the impact of differential rotation on magnetic fields during star formation. Both processes could be responsible for diversity of magnetic topology and activity patterns observed in low-mass stars.
Cosmic chemical evolution: here, there, and everywhere Speaker: Díaz Beltrán, Ángeles Filiation: Universidad Autónoma de Madrid Date: November, 28th 2024 Abstract: Metals play a very important role in star formation and stellar evolution. Amongst other things they control the cooling of the interstellar gas, thus allowing the formation of stars; they affect the radiation transport, through the opacities involved in the different microscopic processes; and they have the most important role in the dust formation and in the mass loss from stars. Metals are formed inside stars. Therefore, it is expected that metal enrichment in the universe should start soon after the formation of the first massive stars that, after a very short life, would return to the interstellar medium (ISM) in explosive events newly synthesised chemical elements, heavier than the primordial hydrogen and helium. It is thought that this ejecta, at some point mixed with the surrounding gas, would help to its cooling and propitiate the appearance of a new generation of stars, hence giving rise to the cycle of cosmic chemical evolution. All this wealth of detail is somehow imprinted in the distribution of abundances in galaxies. The absolute quantities of metals a galaxy (or a region of a galaxy) possesses, the relative abundances of the different elements, and their spatial distribution in a given galaxy are important constraints for the verification of our models and scenarios of the formation and evolution of galaxies.
The tidal arms of open star clusters are much longer than thought, but more difficult to find Speaker: Boffin, Henri Filiation: ESO Date: November, 7th 2024 Abstract: The tidal arms of stellar clusters are an important tool for studying the clusters’ birth conditions, their evolution, coupling, and interaction with the Galactic potential. They also help understand how field stars populate the Milky Way. Thanks to Gaia, much progress has been accomplished in finding the tidal arms of open clusters. I will show here that such arms are much longer than previously observed, and that their identification requires not only a sophisticated analysis of the Gaia catalogue, using the convergent point method and clustering algorithms, but ideally, the use of N-body simulations and the new compact convergent point method. I will highlight recent results about the arms of several open clusters, which extend over several hundreds of parsecs.
Role of Astrophotonics in Astronomy: The MARCOT Pathfinder Speaker: Madhav, Kalaga Filiation: Leibniz Institute for Astrophysics Potsdam (AIP), Germany Date: October, 24th 2024 Abstract: Dr. Kalaga Venu Madhav, a renowned astrophysicist from the Leibniz Institute for Astrophysics Potsdam, will present a colloquium on the role of astrophotonics in astronomy, focusing on the MARCOT Pathfinder project. The talk will cover advancements in astrophotonic technologies and their applications in modern astronomical instrumentation. Dr. Madhav will discuss the development and implementation of photonic devices in telescopes, their impact on observational capabilities, and the prospects of astrophotonics in enhancing our understanding of the universe. This colloquium will provide insights into the innovative technologies driving contemporary astronomical research.
Radio eyes for the Sun, Heliosphere and Ionosphere: Status and plans for the SKAO era. Speaker: Zucca, Pietro Filiation: ASTRON Date: October, 17th 2024 Abstract: The Square Kilometre Array Observatory (SKAO) represents a monumental leap in radio astronomy technology, promising to redefine our understanding of the universe through its unprecedented capabilities. As we stand on the brink of the SKAO era, this talk aims to elucidate the transformative potential of SKAO for solar physics, heliospheric, and ionospheric research. The SKAO's advanced radio telescopes, with their superior angular, spectral, and temporal resolution, are poised to offer new insights into solar activity and its effects on the heliosphere and ionosphere. The deployment of SKAO's facilities, including the pathfinders LOFAR, MWA, and MeerKAT, marks a significant advancement in our ability to monitor solar phenomena and their interactions with the heliosphere and ionosphere. These instruments have already begun to enhance our capabilities for detailed observations and will continue to do so as part of the SKAO network. The integration of these pathfinders with SKAO's infrastructure is expected to improve our understanding of the solar dynamics by enabling high-resolution imaging of solar flares, coronal mass ejections, and other solar events that influence space weather. Furthermore, the SKAO's design considerations for ionospheric calibration and its potential for heliospheric science underscore its role in advancing our knowledge of cosmic ray transport and the structure of the heliosphere. This is crucial for improving models of space weather forecasting and understanding the solar-terrestrial interactions that affect our planet's environment. In summary, the SKAO provides an unparalleled opportunity to explore the Sun, heliosphere, and ionosphere with a level of detail previously unattainable. This talk will discuss the current status of these research areas and outline the future plans for exploiting SKAO's full scientific potential, thereby ushering in a new era of discovery in solar and space sciences.
The next generation of milliarcsecond surveys with SKA-VLBI Speaker: Radcliffe, Jack Filiation: University of Pretoria/University of Manchester Date: October, 3rd 2024 Abstract: Very Long Baseline Interferometry (VLBI), using both SKA-Low and SKA-Mid, is poised to deliver groundbreaking observations with milliarcsecond resolution, surpassing the capabilities of the standard SKA array. VLBI in conjunction with the SKA holds the promise of unlocking profound insights across various astrophysical topics and science working groups. VLBI with the SKA stands to revolutionise our understanding of galaxy evolution and the physics of jet accretion by studying Active Galactic Nuclei (AGN) at low luminosities. Moreover, it is poised to make significant contributions to cosmology, through constraining dark energy and dark matter via gravitational lenses and the study of nuclear water masers. The exploration of the stellar lifecycle, including the temporal evolution of supernova remnants, plus the rapid follow-up of transients (e.g., localising FRBs and tidal disruption events) adds another dimension to the diverse range of science that can be investigated by VLBI with the SKA. SKA-VLBI is set to offer unparalleled astrometric observations capable of measuring proper motions and parallaxes of galactic objects. This capability opens the door to mapping the structure of our Galaxy and testing gravity within binary systems. This overview highlights just a subset of the topics that will be addressed in this presentation, where I will delve into the scientific achievements achievable through VLBI with the SKA and elucidate the operational aspects of SKA-VLBI.
Spectroscopy's Role in Stellar Astrophysics Speaker: Kahraman Aliçavuş, Filiz Filiation: Faculty of Science, Çanakkale Onsekiz Mart University & Astrophysics Research Center and Ulupınar Observatory (Turkey) Date: May, 21st 2024 Abstract: To characterize a star, the stellar fundamental parameters such as mass, radius, metal abundance, and effective temperature should be known. Direct measurements of these parameters, especially for single stars, are quite challenging, and indirect methods are often employed to obtain these characteristics. The most effective method for determining these parameters is spectroscopy, which is an analysis technique of spectra. It allows us to determine the stellar atmospheric parameters such as effective temperature, surface gravity, metallicity, micro turbulence, and rotational velocity values. These parameters play a crucial role in comprehending not only the structure and evolution of stars but also in understanding the evolution of the Milky Way and the chemical evolution of the Universe. Therefore, spectroscopy is a unique tool for a deep understanding of the Universe and its fundamental blocks: stars. To estimate the fundamental atmospheric parameters from spectroscopy there are different methods and this talk will focus on the most prevalent methods used for single and binary B, A, and F-type stars. The presentation will introduce the techniques employed for spectral classification, the determination of atmospheric parameters, the estimation of chemical abundances, the calculation of radial velocity variations in binary systems, and the application of spectral disentangling in binary systems. Furthermore, the impact of spectroscopy on the seismic analysis of pulsating stars will be discussed.
Spatially resolved spectroscopy properties of low-redshift galaxies Speaker: Sebastián, Sánchez Filiation: UNAM, México Date: March, 14th 2024 Abstract: We summarize here some of the results reviewed recently by Sanchez (2020) and Sanchez et al. (2021) comprising the advances in the comprehension of galaxies in the nearby universe based on integral field spectroscopic galaxy surveys. We review our current knowledge of the spatially resolved spectroscopic properties of low-redshift star-forming galaxies (and their retired counterparts) using results from the most recent optical integral field spectroscopy galaxy surveys. We briefly summarize the global spectroscopic properties of these galaxies, discussing the main ionization processes, and the global relations described by the star-formation rates, gas-phase oxygen abundances, and average properties of their stellar populations (age and metallicity) in comparison with the stellar mass. Then, we present the local distribution of the ionizing processes down to kiloparsec scales, and how the global scaling relations found using integrated parameters (like the star-formation main sequence, mass–metallicity relation, and Schmidt–Kennicutt law) have local/resolved counterparts, with the global ones being, for the most part, just integrated/average versions of the local ones. The main conclusions of the most recent explorations are that the evolution of galaxies is mostly governed by local processes but clearly affected by global ones.
Stars and their close-by planets: clues of magnetic interactions Speaker: Lanza, Antonino Francesco Filiation: INAF-Osservatorio Astrofisico di Catania, Via S. Sofia, 78 – 95123 Catania, Italy Date: March, 7th 2024 Abstract: Stars interact with their close-in planets through the gravitational and magnetic fields and with their radiation. After a general introduction to those interactions, I shall review some observational clues of magnetic star-planet interactions considering data obtained in the optical, X-ray, and radio domains. Based on a stellar force-free coronal field or the excitation of Alfven waves by an orbiting planet, some analytical models will be introduced to explore the energetics of the interactions. Some numerical models will be discussed to show their potential and drawbacks in predicting the interactions. The information on stellar magnetic fields that can be derived from magnetic star-planet interactions will be briefly considered and some preliminary results will be presented in the framework of the analytical models.
A new digitized age of SETI – interferometric commensal observations and machine learning Speaker: Ng, Cherry Filiation: Permanent astronomer at Centre National de la Recherche Scientifique (CNRS) in France, under the Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E) Date: March, 5th 2024 Abstract: The search for technosignatures - remotely observable indicators of advanced extraterrestrial life - addresses one of the most profound questions in science: are we alone in the universe as intelligent life? The Breakthrough Listen program is leading the most concerted search for extraterrestrial intelligence (SETI) effort to-date through radio and optical surveys of nearby stars, nearby galaxies and the Milky Way galactic plane, thus representing the best chance the human race has ever had to detect a technosignature. Recently, Breakthrough Listen has partnered with the SETI Institute to develop commensal SETI capabilities on some of the most sensitive radio inteferometers, including the Very Large Array (VLA) and MeerKAT. Interferometric radio telescopes have the advantage of providing a larger field of view, maximizing the SETI survey speed. The VLA search will be operating alongside latter portions of the third epoch of the VLA Sky Survey (VLASS), allowing us to monitor over 1 million nearby stars within the next few years. Moreover, we are developing Machine Learning algorithms that will help reduce the number of false positives. A re-processing of the Green Bank archival SETI data revealed 8 signals-of-interest that were overlooked by previous analyses. In this talk, we will present the latest updates on these projects and conclude with a refreshed outlook on SETI using next generation telescope facilities and machine learning algorithms.
Eyes on the Invisible: Charting New Horizons with the Event Horizon Telescope Speaker: Broderick, Avery Filiation: Perimeter Institute for Theoretical Physics Date: February, 29th 2024 Abstract: The Event Horizon Telescope (EHT) collaboration has captured the first-ever image of a black hole's event horizon in the galaxy M87, and more recently, in the supermassive black hole at the center of our Milky Way, SgrA. These images, consistent with Kerr black holes as described by General Relativity, provide the strongest evidence to date for the existence of supermassive black holes in galaxy nuclei. Notably, the first polarization images of M87 at event horizon scales have revealed a dominant poloidal magnetic field, confirming predictions from general relativistic magnetohydrodynamic simulations and highlighting magnetically arrested disks (MADs) as crucial in black hole accretion and relativistic jet formation processes. These achievements, stemming from EHT’s 2017 inaugural observing campaign, have set the stage for an array of new, exhilarating findings from subsequent campaigns. These include finer details of the emission structure near black holes and pioneering real-time movies of black hole accretion and jet launching, made possible by additional telescopes, enhanced data rates, and improved algorithms. Beyond these remarkable accomplishments, the EHT's journey is just beginning. The next-generation EHT (ngEHT) aims to significantly augment the current array with more stations, multi-frequency simultaneous observations, and extended time coverage. This expansion will dramatically enhance angular resolution, dynamic range, and temporal coverage, solidifying the EHT as a paramount astronomical facility over the next decade, and the only one capable of directly imaging black holes.
MOSAIC: the high multiplex and multi-IFU spectrograph for the ELT Speaker: Sánchez Janssen, Rubén Filiation: STFC-UKRI Date: January, 11th 2024 Abstract: MOSAIC is the planned multi-object spectrograph for the 39m Extremely Large Telescope (ELT). Conceived as a multi-purpose instrument, it offers both high multiplex and multi-IFU capabilities at a range of intermediate to high spectral resolving powers in the visible and the near-infrared. In this talk I will showcase the key science cases that drive the top-level requirements and the adopted instrument architecture. With a planned first light in the early 2030s, MOSAIC will enable unique spectroscopic surveys of the faintest sources, from the oldest stars in the Galaxy and beyond, to the first populations of galaxies that completed the reionisation of the Universe--while simultaneously opening up a wide discovery space and providing enormous synergies with upcoming multi-wavelength facilities (e.g., Euclid, Rubin, Roman, SKA).
Studying star-formation in 'collisional' galaxies with MUSE Speaker: Gomez Gonzalez, Victor Mauricio A. Filiation: Institute for Physics and Astronomy, University Potsdam, Germany Date: November, 30th 2023 Abstract: Galaxies in pre- and post-collisional stages are an excellent laboratory to study the evolution of galaxies, particularly the triggering and suppression of star formation on galactic scales before and after such interactions. In order to analyze the star formation triggered in these systems, we started a series of studies on 'collisional' galaxies with available integral field spectroscopy (IFS) observations. We use Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) observations to study the young star cluster complexes and H ii regions in the Antennae, Cartwheel, and the double-ring collisional galaxy AM 0644-741. MUSE datacubes offer the opportunity to address several problems that are particular to these galaxies, such as studying the ionizing mechanisms and the chemical abundances in the star cluster complexes hosted in the H ii regions. IFS data also offers an opportunity to unveil the presence of populations of Wolf-Rayet stars and the sources of high ionization potential emission lines (e.g., He II 4686) in the nearby universe. We present our recent findings in this seminar.
The transition between super-Earths and sub-Neptunes: Interior and atmosphere modelling of the low-mass planet population Speaker: Acuña, Lorena Filiation: Max Planck Institute for Astronomy Date: November, 23rd 2023 Abstract: Low-mass exoplanets are showing a diversity in their densities, ranging from silicate-dominated super-Earths to volatile-rich sub-Neptunes. We have developed a coupled interior-atmosphere model that estimates the composition and interior structure of super-Earths and sub-Neptunes assuming water and CO2 atmospheres. The applications of the model include the homogenous analysis of a sample of multi-planetary systems, as well as the assessment of the observability of emission spectra for rocky exoplanets with the James Webb Space Telescope. I will explain how their compositions connect to their possible formation site in the protoplanetary disk and their formation mechanisms, including atmospheric escape, and how we can break degeneracies with new atmospheric characterisation data.
The evolution of the accretion process: investigating the protostellar phase to constraints planet formation Speaker: Fiorellino, Eleonora Filiation: Istituto di Astrofisica e Planetologia Spaziali di Roma and Istituto Nazionale di Astrofisica Date: November, 16th 2023 Abstract: The accretion process is responsible for the mass building during the star formation phase, but our knowledge of this phenomenon is still not totally understood. On one side, the magnetospheric accretion scenario describes the accretion on pre-main sequence (Class II/III) low-mass stars. However, most of the material is supposed to be accreted during the earliest stages, i.e. the protostellar phase (Class 0/I), when the forming star and its disk are embedded into a dusty envelope. The presence of the envelope and short lifetimes make the observations of these sources and their analysis challenging, preventing us from testing this and other scenarios during the early stages. On the other hand, the Gaia data alert project is increasing the number of the so-called "eruptive sources'' (FUor, EXors..), which were thought to represent only an exception in the accretion paradigm, suggesting their presence in the stellar mass building to be more important than we thought. In the last decade, thanks to new instruments and analysis techniques, we're starting to unveil the secrets of accretion on low-mass protostars, finding many similarities between these sources and the eruptive stars and finally being able to provide quantitative information about accretion parameters during the overall star formation evolution. In this talk I will present the most recent results about the stellar mass building during the early stages and how they impact the planet formation.
Multi-fluid solar chromosphere Speaker: Khomenko, Elena Filiation: IAC, Spain Date: October, 26th 2023 Abstract: The solar chromosphere is the boundary layer between the interior and exterior of the Sun, routing the origins of the coronal heating. New large-aperture solar telescopes, such as the future 4-meter European Solar Telescope or American DKIST, have among their primary focus observations of chromospheric magnetic fields. The correct interpretation of solar data requires sophisticated theories. The solar chromosphere is made of strongly stratified, weakly ionised and not completely collisionally coupled plasma. On the top of the complexity is the fact that solar photosphere and chromosphere are only partially ionised. The importance of the presence of neutral gas in chromospheric plasma has not been considered to its full extent in the past in the solar physics community. Only now, with the powerful computing techniques that are accessible, we start to be in the position to simulate complex partial ionisation effects and understand their profound consequences. In the recent few years it has been repeatedly demonstrated that processes related to the non-ideal plasma behaviour due to neutrals may be the key ones to solve the problem of chromospheric heating, dynamics and fine structure. In this talk I will describe our recent advances and future ambition in multi-fluid modeling of the solar chromosphere.
Feeding and Feedback: How to Make a Starburst and What that Means for the Host Galaxy Speaker: Levy, Rebecca Filiation: Department of Astronomy/ Steward Observatory University of Arizona Date: October, 19th 2023 Abstract: The cycle of star formation governs the evolution of galaxies. In some local galaxies, the star formation rate in their centers are much higher than other normally star-forming galaxies and may be more similar to galaxies at earlier cosmic times. I present observational results from two archetypal nearby starburst galaxies: NGC253 and M82. First, I will discuss how gas flows to the center of NGC253 along its bar to fuel the extreme burst of star formation. Using very high spatial resolution data from ALMA tracing emission from dust and dense molecular gas, we find that the massive, compact, very young “super” star clusters (SSCs) found in the center of NGC253 are arranged in a ring. Moreover, we find that the SSCs and dense molecular gas are found at the innermost orbit predicted by the barred potential of this galaxy, as expected. I will also show new data on the SSCs in M82 revealed by JWST NIRCam images. Next, I will discuss the detection of massive outflows of molecular gas detected from three of the SSCs in NGC253. These outflows carry a substantial fraction of the gas mass away from the clusters and may stop these clusters from growing even larger. The precise physical mechanism powering these outflows is uncertain, but winds from massive stars and dust-reprocessed radiation pressure are the best candidates - different from lower mass, less extreme star clusters. Finally, I will discuss the result of an extreme burst of star formation on the host galaxy: the central starbursts in both NGC253 and M82 are driving galaxy-scale, multiphase superwinds. Together, these new observations of NGC253 and M82 paint a more complete picture of gas feeding and feedback in extreme star-forming environments and set the stage for JWST observations coming in Cycle 1.
The demographics of small exoplanets Speaker: Luque, Rafael Filiation: University of Chicago Date: October, 9th 2023 Abstract: The diversity of the exoplanet population is beyond our imagination. The more than 5000 known exoplanets vastly differ in mass, size, orbital period, dynamics, and host type. Demographic studies, however, aim to find patterns in the population that inform us about their origin, composition, and evolution. Among these features, perhaps the most surprising is the abundance of planets with no analog in the solar system, also known as sub-Neptunes. In this talk, I will review the state-of-the-art regarding the detection and characterization of such planets and what we know today about their enigmatic nature. A definitive answer, however, seems within reach during this decade thanks to the game-changing observations that will be provided by JWST, PLATO, and ARIEL.
A Light in the Dark - Massive Star Birth Through Cosmic Time Speaker: Tan, Jonathan, C. Filiation: Chalmers University of Technology Date: October, 5th 2023 Abstract: Massive stars are important throughout the universe, but their formation remains poorly understood. I review current understanding of how massive stars form in our Galaxy, in particular examining observational tests of various predictions of Core Accretion and Competitive Accretion theories. Finally, I discuss how massive star formation may have been different in the very early universe and how the first stars may have become supermassive objects to seed the supermassive black holes powering active galactic nuclei.
Extracting stellar populations and (mainly) emission line information out of S-PLUS photometry Speaker: Cid Fernandes, Roberto Filiation: Universidad Federal de Santa Catalina Date: September, 26th 2023 Abstract: We present tests of a new method to simultaneously estimate stellar population and emission line (EL) properties of galaxies out of S-PLUS photometry. The technique uses the AlStar code, updated with an empirical prior which greatly improves its ability to estimate ELs using only the survey's 12 bands. The tests compare the output of (noise-perturbed) synthetic photometry of SDSS galaxies to properties derived from previous (STARLIGHT-based) full spectral fitting and detailed EL analysis. For realistic S/N ratios, stellar population properties are recovered to better than 0.2 dex in masses, mean ages, metallicities and +/-0.2 mag for the extinction. More importantly, ELs are recovered remarkably well for a photometric survey. We obtain input minus output dispersions of 0.05-0.2 dex for the equivalent widths of [OII], [OIII], Hbeta, Halpha [NII] and [SII], and even better for lines stronger than ~ 5 A. These excellent results are achieved by combining two empirical facts into a prior which restricts the EL space available for the fits: (1) Because (for the low redshifts explored here) Halpha and [NII] fall in a single narrow band (J0660), their combined equivalent width is always very well recovered, even when [NII]/Ha comes out miserably wrong. (2) We know from previous EL work (eg., with SDSS) that both W(Ha) and W(Ha+[NII]) correlate strongly with [NII]/Ha, which can be used to tell if a galaxy belongs to the left or right wings in the classical BPT diagnostic diagram. These facts are implemented in the code as constraints which act like an empirical prior, resulting in realistic and reliable EL properties. Example applications to integrated light and spatially resolved data are also presented, including a comparison with independent results obtained with MUSE-based integral field spectroscopy.
Testing black hole structure with very-long-baseline interferometry Speaker: Carballo Rubio, Raúl Filiation: Southern Denmark University Date: September, 21st 2023 Abstract: Black holes hold a tremendous discovery potential, and experiments such as the Event Horizon Telescope and its next generation upgrade could provide important cues about their structure. New physics beyond general relativity can modify the structure of black holes and leave imprints on image features, for instance changing the separation between photon rings or generating additional sets of photon rings. Both cases motivate the study of the detectability of two rings in black hole images. In this talk, I will discuss: (1) the current knowledge about the structure of black holes beyond general relativity, (2) how image features could change due to new physics associated with this modified structure, and (3) the detectability of these features using closure quantities for various telescope arrays.
X-ray polarimetry: a new window to the Universe Speaker: Liodakis, Yannis Filiation: University of Turku & Finish Center for Astronomy with ESO Date: June, 22nd 2023 Abstract: Polarimetry is a very important technique for understanding magnetic fields and high-energy processes in the Universe. While we have been studying polarization in the radio and optical side of the electromagnetic spectrum for decades, what happens at higher energies has, until recently, eluded us. In 2021 NASA finally launched the first X-ray polarimeter, the Imaging X-ray Polarimetry Explorer - IXPE, offering us a completely new window to the Universe, and the tools to study astrophysical systems from a radically different perspective. I will discuss results from IXPE's first two years of observations on a plethora of astrophysical systems from very compact magnetars and X-ray binaries to the biggest black holes in the Universe in radio galaxies and blazars.
The impact of stellar composition: from galactic chemical evolution to planet formation Speaker: Delgado Mena, Elisa Filiation: Universidad de Porto Date: June, 1st 2023 Abstract: The characterization of solar-type stars is fundamental for various fields in astrophysics, including exoplanet detection and the chemical evolution of our Galaxy. In particular, the determination of chemical abundances for stars at different metallicities and ages provides us with a key insight on how and when the various chemical elements were formed within the Galaxy. The chemical trends observed in different parts of the Galaxy (thin disk, thick disk, bulge and halo) also serve to understand how those different populations were formed. On the other hand, knowing the particular characteristics of a given star is essential to be able to detect its hosted planets as well as to characterise their mass, radius, structure and bulk internal composition. The probability of finding planets is clearly related to the chemical makeup of the stars and these planets in turn can have an influence on the stellar composition. In this talk, I will review some of the important advances in these topics.
To be black, or not? Speaker: Bonga, Beátrice Filiation: Institute for Mathematics, Astrophysics and Particle Physics, Radboud University, Nijmegen, The Netherlands Date: May, 25th 2023 Abstract: Observational tests of strong field gravity are improving rapidly. This allows us to test whether the compact objects observed in the sky are truly black holes as described in general relativity or some other "exotic" objects. These tests, however, require exquisite theoretical modeling of black holes as well as their alternatives. This talk will discuss two such examples: the impact of the astrophysical environment on black holes and the stability of black hole alternatives. In particular, I will discuss an astrophysical effect important in extreme mass ratio inspirals (whereby a stellar mass object spirals into a super massive black hole): tidal resonances. If not modeled carefully, these resonances may incorrectly be identified as beyond GR effects. Next, I will show that a popular class of black hole alternatives with membranes are unstable whenever the membrane's pressure and energy density have the same sign.
Pulsar astrophysics in the era of large surveys Speaker: Karastergiou, Aris Filiation: Astrophysics, Dept of Physics, University of Oxford Date: May, 4th 2023 Abstract: History tells us that with new telescopes and new data processing techniques come new discoveries and breakthroughs in pulsar astrophysics. Despite nearly 55 years since their discovery, fundamental open questions remain in almost all areas of research. Examples include the birth properties and environments, the magnetic field configuration and evolution, the interactions of the superfluid interior with the solid crust, the processes of recycling through interactions with binary companions, and many others. I will discuss how these questions can be addressed by current and new surveys. In the process, I will talk about the basic concepts in observational radio pulsar astrophysics, and give examples of phenomena we think we understand and others we know we do not. This will hopefully provide some context and motivation for planned surveys of pulsars with the SKA.
Theoretical models for the formation and evolution of Ultra-Cool Dwarf planetary systems Speaker: Sánchez, Mariana Filiation: University of Leiden Date: April, 25th 2023 Abstract: Rocky planets located in the habitable zones around very low-mass objects are ideal targets for searching for life outside our Solar System. In order to better understand their formation and evolution, N-body simulations are needed. These simulations are developed assuming a star close to the substellar mass limit as the central object. The simulations include tidal and general relativistic effects that incorporate the contraction and evolution of the rotational period of the central object during 100 Myr, as well as interactions of the disk of gas with a sample of protoplanetary embryos during the gas disk lifetime. A very relevant result is that just one of the prescriptions used to treat the interactions between the disk and the sample of embryos allows the survival of a close-in compact planet population of interest, located in the habitable zone of the systems with a wide range of masses from Mars-like up to Earth-like planets and close to orbital period commensurabilities. Moreover, the resulting planets with semi-major axis a < 0.1 au are in agreement with the cumulative distribution of the period ratio of adjacent terrestrial-like exoplanets around stars with masses M < 0.14 Msun (Sanchez et el 2022, https://arxiv.org/pdf/2203). On the other hand, in order to estimate the probability of detection of planetary systems around very low-mass stars, a numerical tool in python was developed. This new tool calculates the changes in stellar flux, radial velocity and proper motion of a sample of stars due to the interaction with their planetary systems. It estimates the probability of detection of planetary systems regarding different samplings and errors associated with a given instrument or survey. A significant result is that the radial velocity method (used by CARMENES) allows a high probability of planetary detection around very low-mass stars (Sanchez et al, in prep).
Gamma rays as cosmic ray tracers: how can CTAO contribute to the cosmic ray physics Speaker: Zanin, Roberta Filiation: Cherenkov Telescope Array Observatory Date: April, 21st 2023 Abstract: Gamma-ray emission produced by interactions of cosmic rays with interstellar matter and radiation fields is a probe of non-thermal particles in galaxies. After decades of instrumental improvements in the field of gamma-ray astronomy, different scales and environments are now accessible and their gamma-ray observations reveal several properties of cosmic rays, especially in our Galaxy. I will provide a short review of the status of the subject and I will also discuss how the next generation of gamma-ray facilities can contribute to the advancement of the topic. In particular, I will focus on the Cherenkov Telescope Array Observatory (CTAO) capabilities. CTAO will be the first proposal-driven observatory in this energy range that will deliver science-ready data to the entire community.
A holistic approach to exoplanet spectroscopy Speaker: Morello, Giuseppe Filiation: IAC Date: April, 13th 2023 Abstract: During the last two decades, multiple observation techniques have enabled the study of exoplanet atmospheres, informing us about their chemical composition, thermal distribution and transport processes. The most successful techniques include low-resolution transit and eclipse spectroscopy, phase curves, and high-resolution Doppler spectroscopy. In all cases, the extraction of the atmospheric signal presents a challenge, being comparable to or smaller than instrumental systematic effects, stellar activity and potentially other astrophysical signals. I will present an overview of data detrending methods and modeling tools that I have developed in recent years, which shed light on the nature of dozens of exoplanetary systems. I will also discuss my ongoing plan to exploit synergies between various types of observation, with an emphasis on leveraging low- and high-resolution spectroscopy. This holistic approach is crucial to maximizing the scientific return of JWST, as well as the upcoming Ariel and PLATO missions.
Investigating the impact of quasar feedback on the central kiloparsecs of galaxies Speaker: Ramos Almeida, Cristina Filiation: IAC Date: March, 23rd 2023 Abstract: Active galactic nuclei (AGN) feedback is the effect that nuclear activity produces in the interstellar and circumgalactic medium of galaxies. Different modes of AGN feedback, which can be broadly divided into radiative/quasar and kinetic/radio, are now considered key processes in the evolution of massive galaxies by regulating black hole and galaxy growth. Indeed, a wealth of observational evidence demonstrates that feedback from supermassive black holes impacts the galaxies and the haloes they inhabit on a wide range of scales: from the central parsecs to hundreds of kpc. What we are still far from understanding is how AGN feedback couples with the host galaxy, which is what ultimately determines its efficiency. The aim of the Quasar Feedback (QSOFEED) project is to answer this question by quantifying the impact of multi-phase quasar-driven outflows on the nuclear regions of galaxies, which have the same dynamical timescales as AGN activity and the outflows that it drives. In this talk I will present recent results from the project based on high angular resolution data from cutting-edge telescopes including the GTC, Gemini, and ALMA, and comparison with tailored hydrodynamical simulations of dense gas.
Dirty Dancing: piercing the dusty environment of merging supermassive black holes Speaker: Guainazzi, Matteo Filiation: ESA/ESTEC Date: January, 30th 2023 Abstract: It is a posit of modern astrophysics that most massive galaxies host a super-massive black hole (millions to billions of times more massive than the Sun). These black holes affect the evolution of galaxies well beyond their gravitational sphere of influence (which does not extend wider than 1/1000th of the typical galaxy linear size). In turn, the evolution of galaxies affects the growth of black holes through, e.g., galaxy merging. Interacting galaxies, or galaxies with multiple (active) nuclei are key laboratories to investigate these processes. While the extragalactic astrophysical community share a broad consensus on each of the above statements taken individually, how these feed-back loops work in the Universe, and the relative importance of various feed-back channels remain largely not understood. Furthermore, the existing samples of dual/binary/multiple active galaxies are remarkably scarce and incomplete. My talk will offer a glimpse of the recent efforts that a group of scientists in the MAGNA ("Multiple AGN Activity"; "Eat" in Roman dialect) collaboration have been undertaking to acquire large observational samples of dual/binary active galactic nuclei, and to use them to inform simulations aiming at predicting the concurrent galaxy/black hole cosmological evolution.