Consejo Superior de Investigaciones Científicas   Instituto de Astrofísica de Andalucía   Excelencia Severo Ochoa   HR Excellence in Research   Presidencia española de la Unión Europea
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, 7th 2024
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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, 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
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
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
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
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.