#PizzaSeminars
Friday at ICE-CSIC means #PizzaSeminar!
These seminars have been going on for 10 years now. We gather at the patio of the institute to eat pizza after the seminar as a nice way of ending the week. Since the last few months, the seminars are a hybrid event and we're happy to see you every Friday at 12 pm online.
Simulation-based inference enables real-time analysis of gravitational waves
The 3D structure of the Milky Way using fast & scalable Gaussian Processes
Outflows in low-power active galaxies, LINERs
CMB anomalies and parity asymmetry
Supernova remnants of massive stars
Thermal analysis & Hypatia
Constraints on the dense matter equation of state from young and cold isolated neutron stars
Improving the Hubble Diagram on Both Axes
Various cosmological parameters such as H0 and S8 measured using Type Ia Supernovae (SNe Ia) have been shown to be in tension with measurements from the early universe. We can improve cosmological parameter measurements and reduce scatter on the Hubble Diagram by focusing on both magnitude scatter by leveraging the near-infrared (NIR) and redshift scatter by leveraging galaxy groups. With the DEHVILS sample, one of the largest uniform NIR samples of SN Ia light curves (LCs), we measure and analyze the reduction in Hubble residual scatter as compared to the optical. Using the low redshift sample from Pantheon+ combined with a new sample from the AAT spectrograph, we obtain and average the redshifts of galaxy groups to correct for peculiar velocities and improve scatter on the Hubble Diagram. With the impending arrival of the Roman Space Telescope, which will observe in the NIR and need a well understood low-redshift anchor SN sample, we encourage further analysis on NIR SN Ia LCs and an increased effort to define more galaxy groups.
Fundamental Physics and Cosmology with the Einstein Telescope
From chirps to gold: colliding neutron stars as a laboratory for extreme physics
The amazing geology and structure of Dimorphos: challenge or opportunity for asteroid deflection?
Who was the first to discover that our Universe expands and that it had an origin?
Strong gravity beyond Einstein's gravity: from "the quantum" to "the cosmo"
General Relativity (GR) is undoubtedly a fascinating theory, which has radically changed the way of understanding space, time and gravitational interactions in Modern Physics. A wide variety of experimental probes, both in terms of sensitivity and number of observations, has allowed GR to be tested in the strong gravitational regime (from gravitational-wave astronomy, electromagnetic counterparts, binary pulsar observations and radio-astronomy, among other channels). Remarkably however, the study of compact objects in GR has motivated the astrophysicist community to ask whether or not similar predictions should also be obtained from modified theories of gravity.
The purpose of this talk is to go through various aspects of gravity in theories beyond GR. Although a large family of theories of gravity has been proposed to address issues such as the nature of the cosmological acceleration, or the non-renormalizability of Einstein’s theory, a pressing question in this context would be: which one/s of them should we really worry about?
We will review two classes of modified theories. The first one, proposed by Petr Hořava in 2009, is a "quantum-motivated" prominent candidate for an ultra-violet completion of GR. This theory aims to understand gravitational interactions at the Planck scale (thus extending Einstein's proposal), but at the cost of giving up Lorentz symmetry. The second one, within the so-called "scalar-tensor" theories, is cosmology-motivated, and it aims to constrain Dark Energy models consistent with observations. After commenting on (some of) the main interesting features within these two different theories, we will comment on recent contributions, some applications and future perspectives.
Snooping around millisecond pulsars: can accretion- and rotation-powered states co-exist?
Cosmological constraints from two- and three-point galaxy clustering
ICE-CSIC María de Maeztu Best paper Awards 2024
Clàudia Soriano: "Magnetic winding and turbulence in ultra-hot Jupiters"
Abstract: While magnetism in exoplanets remains largely unknown, Hot Jupiters have been considered as natural candidates to harbour intense magnetic fields, both due to their large masses which might empower a larger internal dynamo, and, possibly, due to their high energy budgets coming from irradiation. In this work we focus on the latter aspect and perform MHD simulations of a narrow day-side atmospheric column of ultra-hot Jupiters, suitable for very high local temperatures. Due to the high conductivity in this regime, the primary influence is the winding of the magnetic field caused by the intense zonal winds. In our study, we include a forcing that mimics the wind profiles observed in GCMs near the sub-stellar point. As a result, the shear layer generates a toroidal magnetic field, locally reaching few kG, which is supported by meridional currents. Such fields and the sustaining currents do not depend on the internal field, but are all confined in the thin (less than a scale-height) shear layer around 1 bar. Additionally, we add random perturbations that induce turbulent motions, which lead to further (but much smaller) magnetic field generation to a broader range of depths. These results enable the assessment of the atmospheric currents that are induced. Although here we use ideal MHD and the only resistivity comes from the numerical scheme at a fixed resolution, we estimate a-posteriori the amount of Ohmic heat deposited in the outer layers, which could be employed in evolutionary models for Hot Jupiters' inflated radii. We will also include the last updates of the model, which include realistic GCM profiles, non-isothermal profiles as well as real MHD, which make the models applicable for all HJs.
Michele Lenzi: "Black hole greybody factors from Korteweg–de Vries integrals: Theory"
Abstract: The dynamics of perturbed nonrotating black holes (BHs) can be described in terms of master equations of the wave type with a potential. In the frequency domain, the master equations become time-independent Schrödinger equations with no discrete spectrum. It has been recently shown that these wave equations possess an infinite number of symmetries that correspond to the flow of the infinite hierarchy of Korteweg–de Vries (KdV) equations. As a consequence, the infinite set of associated conserved quantities, the KdV integrals, are the same for all the different master equations that we can consider. In this paper we show that the BH scattering reflection and transmission coefficients characterizing the continuous spectrum can be fully determined via a moment problem, in such a way that the KdV integrals provide the momenta of a distribution function depending only on the reflection coefficient. We also discuss the existence and uniqueness of solutions, strategies to solve the moment problem, and finally show the case of the Pöschl-Teller potential where all the steps can be carried out analytically.
Optical technologies for astrophysics, Earth and planetary sciences
A link to the past: Searching for wandering intermediate-mass black holes in the Milky Way
Exploring the Universe with LISA
Meta-materials and Meta-surfaces: Exploring Applications and Research Opportunities in Radio Astronomy
Isolated pulsar population synthesis with simulation-based inference
White dwarf stars in the Gaia era
White dwarf stars are the most common endpoint of stellar evolution. Therefore, these numerous, old and compact objects provide valuable information on the late stages of stellar evolution, the physics of dense plasma and the structure and evolution of our Galaxy. The ESA Gaia space mission has revolutionized this research field, providing multi-band photometry, synthetic spectra, proper motions and parallaxes for these stars. Specifically, this mission has allowed the identification of nearly 360.000 white dwarfs, revealing some unexpected features on the white dwarf sequence in the color-magnitude diagram, and raising new questions on the nature of these stars. Furthermore, this data combined with spectroscopical and spectropolarimetric observations, have provided new information on chemical abundances and magnetic fields of these stars, demanding a thorough understanding of their physical processes. In this talk, I will summarize these questions and I will describe possible explanations for them, on the basis of detailed theoretical evolutionary models and population synthesis studies.
The Magnet alliance: bringing astronomy to the classroom to fight scholar segregation
School segregation is a growing problem throughout Europe that tends to create schools with a very high socioeconomic complexity. We’ll present our experience within the Magnet alliance, in which the Institute of Space Sciences (ICE-CSIC) collaborates in the 2021-2025 period with the Gabriel Castellà i Raich school in Igualada (Barcelona province, Spain). Advised by an expert in didactics, we have co-created with teachers and implemented inquiry-based astronomy activities for 3 to 11 year-old students. The goal is to provide the school with added pedagogical and educational value, which can attract local families, in order to balance the demographics of the student body and promote inclusion in current and future society. In this talk, we will present the activities developed during the first half of the program, plans for the future and lessons learnt.
Explosions of white dwarfs as novae and their role in the origin of Lithium-7 and cosmic rays
Nuclear Physics from Neutron Star Mergers
The ngVLA, its science cases, and the current role of Mexico
The ngVLA, led by the National Radio Astronomy Observatory (NRAO), will be the largest radio interferometer ever built in the northern hemisphere. With more than 200 antennas distributed across the US, Canada, and Mexico, the array will reach spatial resolutions and sensitivities without precedents. The ngVLA will open a new window on the universe through ultra-sensitive imaging of spectral lines and continuum emission with milliarcsecond resolution. We will summarise the main science goals, from the initial conditions of planetary systems to understanding the origin and evolution of black holes. For Galactic science, synergies between ongoing efforts with the current VLA and the ngVLA will be provided, in particular for AGB stars. In the second part of the talk, we will describe the current ngVLA efforts being pursued in Mexico. The MID Array of the ngVLA will provide some of the longest baselines of the new observatory, with a large fraction of those enabled by the antennas in Northern Mexico. We will discuss the work to select the final MID sites in Mexico, including synthetic observations to characterise the array performance. We’ll finalise with the observatory designs that Mexico is leading, such as antenna base foundations, antenna site layouts, and antenna supporting buildings. Finally, we outline the next steps in the coming 2 years, including workshops and conferences.
The wickedly cool and bursting stellar zombies
I will give a very general review on our group's research on neutron stars in a cauldron of boiling multi-band observations and theoretical simulations. I will then report on two recent results: the first related to a new creepy class of periodic radio bursters, and the second to a few super cold rotating jack-o'-lanterns... and how those are changing our understanding of these wicked stellar zombies.
Current flow in pulsar magnetospheres and the role of twist
He will discuss some properties of the axisymmetric force-free pulsar magnetosphere focusing on the inner edge of the current sheet, the so-called Y-point. While it is usually postulated that it is located at the intersection of the equator with the light-cylinder, we propose that it is energetically favourable to be located within the light-cylinder. Should this be the case, the spin-down dipole magnetic field is likely to be an overestimate of the star's actual field. Furthermore, he will discuss the impact of currents flowing within the closed field lines: in this case, the spin-down power is higher than the one corresponding to the dipole field and for sufficiently high twists the field adopts the structure of a split monopole.
B-field Orion Protostellar Survey: Magnetized Envelopes in Orion
B-field Orion Protostellar Survey (BOPS) used ALMA to observe 870 um dust polarization toward 61 young low-mass protostars in the Orion molecular clouds. Its main objective is to investigate the role of B-fields from 400 to several thousands au scales, corresponding to the size of molecular envelopes about the youngest (predominately Class 0) protostars. This survey uniformly probe the B-field structure within the envelopes surrounding the protostars to help remove biases based on resolution and different environments. Both the polarization and outflow were successfully detected emission in 56 sources. In 16 of them the polarization is likely produced by self-scattering, most of these are Class 0, suggesting that grain growth appears to be significant in disks in earlier protostellar phases. For the rest sources, the dust polarization traces the magnetic field, whose morphology can be approximately classified into three categories: standard-hourglass, inverted-hourglass, and spiral-like morphology. Two-fifth of the sources exhibit a mean magnetic field direction approximately perpendicular to the outflow from several hundreds to thousands au scales, but for the rest of protostars, this relative orientation appears to be random, probably due to the complex set of morphologies observed. Furthermore, the protostars are classified into three types based on the velocity gradient traced by C17O (3--2): PerpType (gradient perpendicular to outflow), RandType (gradient randomly aligned with outflow), and UnresType (unresolved gradient, less than 1 km/s/arcsec). In PerpType, field lines are preferentially perpendicular to the outflow, and along the collapsing direction, most of them are inverted-hourglass, suggesting that magnetic field have been overwhelmed by gravity. The spiral-like magnetic fields are associated with sources with large velocity gradients, indicating that the rotation motions is strong enough to twist significantly the field lines. All the sources with a standard-hourglass field morphology show no significant velocity gradient probably due to the strong magnetic braking.
Pulsar science with the MeerKAT radio telescope
Radio pulsars are highly magnetised, fast-rotating neutron stars born from the collapse of massive stars at the end of their life cycle. Pulsar timing is the technique of modelling a pulsar’s rotation down to every single revolution and comparing it with the times of arrival of radio pulses as recorded by telescopes on Earth. When found in binary systems, this technique is used to track the orbital motion of pulsars in their system. This allows us to investigate a wide range of fundamental physics and astrophysics, such as light propagation physics, alternative theories of gravity, equation of state models of neutron stars and binary evolution. The MeerKAT radio telescope in South Africa is currently the most sensitive facility in the Southern Hemisphere, constituting a great leap forward in the search for and study of pulsars in the Southern Sky. In this talk, he highlights recent science results from pulsar observations with MeerKAT and showcase some of the currently ongoing science projects, such as the TRAPUM pulsar surveys and the RelBin pulsar timing programme.
Closing down the observation gap on millisecond to second timescale relativistic X-ray and radio transients
Supporting a culture of public engagement at ICE-CSIC
Astronomy allows us to study the far reaches of the universe but also gives us a different perspective on our planet, showing us its fragility and fostering a sense of global citizenship. In this sense, astronomy is in a unique position to engage citizens on scientific topics, make them reflect on their place in the universe, and encourage their critical thinking. Several studies show that citizens consider that professional scientists are best qualified to explain the impact of scientific and technological developments on society. And even though astronomers are quite involved in public engagement in comparison with scientists in other fields, they often rely on individual endeavours with approaches with little engagement and/or lacking goals for deeper interaction beyond one-off events. In this respect it is important to work together with the institution's communication professionals in our common journey to share the wonders of the universe with society while we establish a culture of public engagement at the institution. In this talk, he will present his thoughts on why public engagement is important, why researchers should get involved and work together with science communication professionals as well as showcase the opportunities we offer through ICE-CSIC's Communication and Outreach Office to participate in communication and public engagement activities.
The MagMAR project: First Results
The process governing the formation of high-mass stars, those exceeding eight solar masses, remains enigmatic, despite their pivotal role in regulating chemical, radiative, and energetic feedback within our galaxy. Of all the pertinent parameters influencing high-mass star formation, the magnetic field stands as a predominantly uncharted territory, its presence inevitable yet exploration limited. Endeavoring to bridge this knowledge gap, the MagMAR project leverages the unparalleled mapping capabilities of ALMA. In this presentation, he will introduce the MagMAR project and showcase its initial results.
Is cosmic expansion really accelerating?
He will show that deceleration (and not acceleration) is the correct interpretation for current measurements of cosmic expansion. The concept of cosmic acceleration, q, that we commonly used is based in the comoving distance. This is a 3D space-like coordinate, which corresponds to distance between events that can not be observed and are not causally related. For a correct interpretation cosmic expansion should be measured using the distance between (4D null) causal events. This is implemented here using a new definition, q_E, for cosmic acceleration. We present a comparison of the two alternative definitions, q_E and q, against data from supernovae (SN) and radial galaxy/QSO clustering (BAO). The standard q analysis reproduces some known tension between SN and BAO, but this tension disappears for q_E, indicating that this definition better fits observations. Data clearly shows that cosmic expansion is decelerating so that cosmic events are trapped inside an Event Horizon, like in the interior of a Black Hole (BH). Rather than a new form of dark energy or modified Gravity, this corresponds to a boundary force that causes friction, i.e. an attractive force, similar to a rubber band that prevents further expansion.