Recent Talks

List of all the talks in the archive, sorted by date.

Thursday April 20, 2023

How binary stripping affects the late evolution, death, and afterlife of massive stars

Dr. Eva Laplace

HITS, Heidelberg

Abstract

Gravitational-wave observations have revealed the population of stellar remnants from a new angle. Yet their stellar progenitors remain uncertain, in particular in the case of black holes. At least a fraction of these progenitors is believed to form in isolated binary systems. In this talk, I will discuss how binary mass transfer affects the late evolution and final fate of massive stars. The focus will be on stars that transfer their outer layers to a companion star and become binary-stripped. Binary-stripped stars develop systematically different core structures compared to single stars. I will discuss consequences for supernova progenitors, black hole formation, supernova nucleosynthesis, and gravitational-wave observations.

Archived in: Stars - Keywords:binary evolution, stellar evolution

Abstract

Tuesday April 18, 2023

JWST view of Polycyclic Aromatic Hydrocarbons and dust in local active galaxies

Dr. Ismael García Bernete

University of Oxford

Abstract

Nowadays, it is widely accepted that most galaxies undergo an active phase in their evolution. The impact of the energy released by active galactic nuclei (AGN) in the interstellar medium (ISM) of the host galaxy has been proposed as a key mechanism responsible for regulating star formation (SF). The mid-infrared (IR) is the ideal spectral range to investigate the nuclear/circumnuclear regions of AGN since dust extinction is significantly lower compared to the visible range. Furthermore, it provides unique tracers to study the AGN-SF connection such as H2 rotational lines, fine structure lines and Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are also a powerful tool to characterize the ISM in different environments.

Recently, we presented new JWST/MIRI MRS spectroscopy of three Seyfert AGN in which we compare their nuclear PAH emission with that of star-forming regions. This study represents the first of its kind to use sub-arcsecond angular resolution data of local luminous Seyferts (Lbol > 10^44.5 erg/s) with a wide wavelength coverage (4.9-28.1 μm). Our results showed that a suite of PAH features is present in the innermost parts of these Seyfert galaxies. We found that the nuclear regions of AGN lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. Furthermore, we find that the nuclear PAH emission mainly originates in neutral PAHs while, in contrast, PAH emission originating in the star forming regions favours small ionised PAH grains. Therefore, our results provide evidence that the AGN have a significant impact on the ionization state and size of the PAH grains on scales of ~142-245 pc. This is fundamental since PAH bands are routinely used to measure star-formation activity in near and far SF and active galaxies.

Finally, I will summarise our ongoing JWST work within the GATOS (Galactic Activity, Torus and Outflow Survey) collaboration. In particular, I will focus on our recent study about the survival of PAH molecules in AGN-driven outflows.

Archived in: Galaxies - Keywords:Spitzer, spectroscopy, polarimetry, JWST, HST, data reduction, polarization, molecular processes, molecular data, black holes, accretion, accretion discs, polycyclic aromatic hydrocarbon, PAH, outflows, ISM molecules, grains, extinction, dust, supermassive black hole, SMBH, sub-millimetre galaxy, Seyfert galaxies, quasars, jets, intergalactic medium, galaxy evolution, galactic structure, galactic nuclei, emission line quasars, active galaxies, science

Abstract

Thursday April 13, 2023

Women in Astrophysics

Prof. Jocelyn Bell

Oxford University

Abstract

Archived in: - Keywords:science

Abstract

Tuesday April 11, 2023

A new, multi-cloud method to accurately model emission lines in star-forming galaxies

Dr. Amirnezam Amiri

University of Florence and INAF-Arcetri - Italy

Abstract

The abundance of chemical elements across cosmic time provide unique information on the physical processes driving the evolution of galaxies. Current methods for measuring gas-phase metallicities, based on either direct measurements of electron temperature (Te) or calibrations from strong nebular emission line ratios, are based on simplifying assumptions and do not adequately describe the complexity of the emitting regions. We present a new approach based on fitting galaxy spectra with multi-cloud photoionisation models. Unlike current methods, based on comparisons with single-cloud models, our methodology is able to reproduce all observed emission lines to a very high accuracy, down to a few percent, thus allowing for accurate metallicity measurements. We further recover the well known trends between ionization parameter and metallicity, and between the Nitrogen and Oxygen abundances. Our models accurately reproduce the auroral-to-nebular line ratios, while the results of the standard Te method are sometimes very different from the best-fitting model metallity. We finally present newly calibrated metallicity estimators for galaxies based on ratios between strong emission lines.

Archived in: - Keywords:galaxy evolution, galactic abundances

Abstract

Friday March 31, 2023

Seminario de Instrumentación: "Control EST: Requisitos y herramientas de gestión del EST"

Fernando Merlos García

Instituto de Astrofísica de Canarias / EST

Abstract

El Telescopio Solar Europeo (EST), de clase cuatro metros, es un proyecto que se encuentra en su fase de diseño preliminar, previa a la fase de construcción. Con él se pretende aunar y mejorar las prestaciones de los actuales telescopios solares de clase un metro que están operativos. Uno de los principales objetivos en esta fase del proyecto es poder identificar, definir y gestionar los requisitos de cada una de sus disciplinas organizadas en los distintos paquetes de trabajo definidos. En esta charla se pretende mostrar las herramientas utilizadas para llevar a cabo esta importante tarea.

Youtube

https://youtube.com/live/31KKPdG96LI?feature=share

Archived in: - Keywords:

Abstract

Thursday March 30, 2023

Accretion Disc Winds in Low-Mass X-Ray Binary Stars

Dr. Noel Castro Segura

University of Southampton

Abstract

Disc winds and jets are ubiquitous among accreting systems on all scales, from active galactic nuclei (AGN) down to young stellar objects. They represent a key mechanism through which these systems interact with their environment (“feedback") and may be responsible for triggering the mysterious state changes observed in X-ray binary stars (XRBs).

Transient low-mass X-ray binaries (LMXBs), harbouring a black hole or a neutron star, provide us with a natural laboratory for studying the connection(s) between accretion discs, jets and winds. These systems undergo outbursts, during which they brighten dramatically across the whole electromagnetic spectrum. The outbursts typically last hundreds of days, recur on timescales of decades, and reflect a sudden increase in the accretion rate onto the compact object. Over the course of an outburst, LMXBs exhibit two distinct spectral states. These spectral states are thought to be a consequence of different accretion geometries close to the central object.

Remarkably, the two distinct accretion states also appear to produce two distinct types of outflows. Steady compact radio jets are only seen in the hard state, whereas evidence of disc winds originally came in the form of blue-shifted X-ray absorption lines associated with Fe ions detected only during the soft state. However, recent observations of disc winds in the far-UV, optical and NIR lines reveal a multiphase nature of these outflows that may be present across the entire outburst.

I will discuss the current status of disc winds in LMXBs with special emphasis in the latest results from far-UV spectroscopy obtained with the Hubble Space Telescope.

Zoom: https://rediris.zoom.us/j/86826646040?pwd=UmpEZmdKYW90QUpVelFKZitzTzhKUT09
Meeting ID: 868 2664 6040
Passcode: 610738

Youtube: https://youtube.com/live/4-WXSHynTXw?feature=share

Archived in: Stars - Keywords:X-ray binaries, winds , flare stars, X-ray

Abstract

Tuesday March 28, 2023

The galaxy-halo connection in the cosmic web

Drs. Rita Tojeiro

University of St. Andrew

Abstract

Galaxies and the dark matter halos in which they reside are intrinsically connected. That relationship holds information about key processes in galaxy and structure formation. In this talk, I will consider how the galaxy-halo connection depends on position within the cosmic web - the familiar decomposition of large-scale structure in filaments, knots and voids. Simulations demonstrate the various ways in which the cosmic web modulates the growth and dynamics of halos. The extent to which the cosmic web impacts on galaxies is more difficult to establish. For example, galaxies might be sensitive only to the evolution of the host halo, in which case any effect of the cosmic web on galaxies is secondary, and can be inferred from the halo's history. There is evidence, however - from simulations and observations - that the cosmic web also impacts on the evolution of galaxies via the effect it has on the broader gas ecosystem in which they are embedded, as well as through "pre-processing" effects on group scale. So, how should we think of the cosmic web in its role as a transformative agent of galaxies? And what physical processes can we convincingly constrain from observations and simulations? In this talk I highlight recent work that addresses these questions.

Archived in: Cosmology - Keywords:intergalactic medium, galaxy evolution, galactic interactions, large-scale structure, cold dark matter, Machine learning, Data mining, Big data, VISTA, SDSS, COSMOS, science

Abstract

Friday March 24, 2023

Seminario de Instrumentación: "Diseño preliminar de la arquitectura de software de EST"

Ángela Hernández Delgado

Instituto de Astrofísica de Canarias/ EST

Abstract

El Telescopio Solar Europeo (EST), de clase cuatro metros, es un proyecto que se encuentra en su fase de diseño preliminar, previa a la fase de construcción. Con él se pretende aunar y mejorar las prestaciones de los actuales telescopios solares de clase un metro que están operativos. En esta charla se hará un repaso de las herramientas, diagramas, flujo de trabajo utilizado para la definición de los sistemas y subsistemas que abarca el ECS (EST Control System).

Unirse a la reunión Zoom:

https://rediris.zoom.us/j/85762975287
ID de reunión: 857 6297 5287

Youtube:

https://youtube.com/live/h8cpg5yUe9E?feature=share

Archived in: - Keywords:

Abstract

Thursday March 23, 2023

Beyond the Concordance Model with galaxy cluster mass profiles

Dr. Lorenzo Pizzuti

CEICO, Institute of Physics of the Czech Academy of Sciences

Abstract

I present the recent results obtained using the updated version of MG-MAMPOSSt, a code that constrains modified gravity (MG) models viable at cosmological scales using determination of galaxy cluster mass profiles with kinematics and lensing analyses. I will discuss limitations and future developments of this method in view of upcoming imaging and spectroscopic surveys, as well as the possibilities of including X-ray data to break degeneracy among model parameters. Finally I will show preliminary results about the constraints that can be obtained on the inner slope of dark matter profiles when adding the velocity dispersion of the Brightest Central Galaxy (BCG) in the dataset of MG-MAMPOSSt.

Archived in: Cosmology - Keywords:science, cold dark matter, dark energy, dark matter, gravitation

Abstract