List of all the talks in the archive, sorted by date.
The first Gigayears of our Galactic halo can be probed by using ancient stellar populations as traced by RR Lyrae stars. Today, with the advancement in our knowledge of RR Lyrae properties belonging to the Halo and to Milky Way satellite systems (Globular clusters and dwarf galaxies) we are able
to provide solid constraints on the link between these stellar systems. Here, we present some recent results concerning the Halo formation by using a detailed evolutionary analysis of RR Lyrae stars for which chemical abundances are available.
Cosmological observations (redshifts, cosmic microwave background radiation, abundance of light elements, formation and evolution of galaxies, large-scale structure) find explanations within the standard Lambda-CDM model, although many times after a number of ad hoc corrections. Nevertheless, the expression ‘crisis in cosmology’ stubbornly reverberates in the scientific literature: the higher the precision with which the standard cosmological model tries to fit the data, the greater the number of tensions that arise. Moreover, there are alternative explanations for most of the observations. Therefore, cosmological hypotheses should be very cautiously proposed and even more cautiously received.
There are also sociological and philosophical arguments to support this scepticism. Only the standard model is considered by most professional cosmologists, while the challenges of the most fundamental ideas of modern cosmology are usually neglected. Funding, research positions, prestige, telescope time, publication in top journals, citations, conferences, and other resources are dedicated almost exclusively to standard cosmology. Moreover, religious, philosophical, economic, and political ideologies in a world dominated by anglophone culture also influence the contents of cosmological ideas.
Astrophysical observations at (sub)mm wavelengths (from ~300 micron to ~3mm)
allow us to study the cold and dense material in the Universe, hence probing
the formation of stars and planets, and the interstellar and circumgalactic
medium within galaxies across cosmic time. The current generation of
15m-class single-dish telescopes has delivered some of the first surveys at
(sub)mm wavelengths, allowing to go far beyond the previously optical-biased
view of the Universe. Follow-up observations with interferometers then
revealed in exquisite detail the morphology and kinematics of such (sub)mm
sources. However, it is now clear that without a transformative change in
the capabilities of single-dish facilities in the 2030s, interferometers
will soon become source-starved. The current generation of 15m-class single-
dish telescopes, with their limited fields of view, spatial resolutions, and
sensitivities, can only reveal the "peak of the iceberg" of the (sub)mm
source population, both for Galactic and extragalactic studies. These
limitations cannot be fully mitigated by interferometers, which are all
intrinsically affected by a low mapping speed and by the loss of diffuse
extended signals. The Atacama Large Aperture Submillimeter telescope
(AtLAST) project is a concept for a 50m diameter single dish observatory to
be built near the ALMA site. With its extremely large field of view (the goal
is ~2 degrees), spatial resolution (up to ~1'' at 350 micron) and sensitivity
to both point sources and large-scale structures, AtLAST will be
transformational for all fields of astronomy in the 2030s. In this talk I
will describe the EU Horizon2020-funded project that aims to deliver a
comprehensive design study for such a next-generation single-dish facility.
We present a sample of 734 ultracool dwarfs using LAMOST DR7 spectra, i.e., those having a spectral type of or later than M6, including an L0. All of these red or brown dwarfs are within 360 pc, with a Gaia G magnitude brighter than 19.2 mag, a BP-RP color redder than 2.5 mag and an absolute G magnitude fainter than 9 mag. Their stellar parameters (Teff, log g, and [M/H]) are consistent with being the Galactic thin-disk population, which is further supported by their kinematics using LAMOST radial velocity plus Gaia proper motion and parallax. A total of 77 are detected with the lithium absorption line at 6708 A, signifying youth and substellar nature. We report on their kinematic ages estimated by the velocity dispersion. Thirty five close pairs are identified, of which the binarity of six is discovered for the first time.
With the aim of detecting cosmological gas accretion onto galaxies of the local Universe, we examined the Ha emission in the halo of the 164 galaxies in the field of view of MUSE-Wide (Urrutia+19) with observable Ha (redshift < 0.42). An exhaustive screening of the Ha images led us to select 118 reliable Ha emitting gas clouds. To our surprise, around 38 % of the time the Ha line profile shows a double peak centered at the rest-frame of the corresponding galaxy. We have explored several physical scenarios to explain this Ha emission, among which accretion disks around rogue intermediate mass black holes (IMBHs) fit the observations best. I will describe the data analysis (to discard, e.g, instrumental artifacts and high redshift interlopers), the properties of the Ha emitting clumps (their fluxes, peak separation, and spatial distribution with respect to the central galaxy), and the arguments leading to the IMBH hypothesis rather than other alternatives (e.g., cosmological gas, expanding bubbles, or shocks in the circum galactic medium).
Meeting ID: 841 6348 9744
EST será un telescopio solar de clase 4-metros que se instalará en La Palma. Dos son las principales diferencias respecto a otros telescopios de tamaño similar: al trabajar a cúpula abierta está completamente sometido a las fuerzas producidas por el viento, y al ser solar recibirá una gran cantidad de radicación térmica que debe ser debidamente gestionada. En esta charla se presentarán los estudios preliminares realizados para la selección la solución técnica más prometedora para el M1 Assembly, así como unas pinceladas sobre el diseño preliminar que se está desarrollando a partir de ese concepto.
The first part of this talk will present an overview of the tool "module" and its main commands and flags. "module" provides the dynamic modification of the user’s environment for supporting multiple versions of an application or a library without any conflict. In the second part, we’ll first explain what Python virtual environments are, and describe three actual cases in which they are used. We’ll then illustrate a practical example to install a Python virtual environment, and duplicate it on a different platform.
El Telescopio Solar Europeo (EST) se encuentra actualmente en la fase de diseño preliminar. Uno de los principales objetivos de esta etapa es identificar y definir los requisitos técnicos que guiarán su desarrollo y posterior construcción. En este sentido, las herramientas de modelado y simulación constituyen un elemento clave para la caracterización de prestaciones y la evaluación de distintas alternativas técnicas. El objetivo de esta charla es presentar algunos de los modelos desarrollados por la Oficina de Proyectos de EST para la evaluación de los requisitos dinámicos del telescopio. En concreto, se profundizará en el modelo mecatrónico diseñado para el control del movimiento de los ejes de la estructura.
El seminario se impartirá en el Aula y se anima encarecidamente a asistir presencialmente. Habrá café tecnológico tras la charla, a las 11h30 en la cafetería.
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- Globular clusters as tracers of the Milky Way assembly historyDr. Davide MassariThursday October 5, 2023 - 10:30 GMT+1 (Aula)
- CONCERTO: a breakthrough in the wide field-of-view spectroscopy at millimeter wavelengthsDr. Alessandro FassanoTuesday October 10, 2023 - 12:30 GMT+1 (Aula)