Recent Talks
List of all the talks in the archive, sorted by date.
Abstract
In this talk, I will present recent results on a new sample of extremely UV-luminous star-forming galaxies at z=2-4 discovered within the 9000deg^2-wide Baryon Oscillation Spectroscopic Survey database of the Sloan Digital Sky Survey. These puzzling sources show apparent magnitudes rivaling those of bright QSOs, but without any hint of AGN activity or being magnified by gravitational lensing. Instead, these sources are characterized by very young stellar populations (~ 10 Myr) and compact morphologies. The two highest-redshift sources in our sample show very high Lyman continuum (LyC, with >13.6 eV) escape fractions, up to fesc(LyC)~90%, being the most powerful ionizing sources identified so far among the star-forming galaxy population, both in terms of the intrinsic LyC photon production rate and escape. With SFRs~1000 Msun/yr, but almost un-obscured, and specific star formation sSFR >50-100 Gyr^-1, these sources are very efficient star-forming galaxies, possibly representing a short-lived phase in the evolution of massive and compact galaxies. I will highlight some unique properties observed in these sources including LyC emission, complex Lyman-alpha profiles, strong wind lines, SEDs, among others. Finally, I discuss the properties of these UV-bright sources in the broad context of galaxy formation and evolution, and possible implications to cosmic reionization.
Abstract
One of the possible ways of creating the supermassive black hole (SMBH) is hierarchical merging scenario. Central SMBHs at interacting and coalescing host-galaxies are observed as SMBH candidates at different separations from hundreds of pc to mpc. One of the strongest SMBHs candidates is ULIRG galaxy NGC6240 which was X-ray spatially and spectroscopically resolved by Chandra. Researching of central SMBHs merging in dense stellar environment allows to retrace their evolution from kpc to mpc scales. The main goal of our dynamical modeling was to reach the gravitational wave (GW) emission regime for the multiple BHs model. We present the direct N-body simulations with up to one million particles and relativistic post-Newtonian corrections for the SMBHs particles up to 3.5PN. From our models we found the upper limit of merging time for NGC6240 central SMBHs is less than ~50 Myr.
Abstract
La creación y uso de modelos es una parte fundamental de la ingeniería. En esta charla se presentará una visión descriptiva de alto nivel sobre los modelos creados para el diseño preliminar del telescopio solar europeo (EST). "Desfilarán" modelos de EST creados con herramientas como Simulink, ANSYS, DASP, Zemax etc. Sin entrar en detalles de implementación, se presentan ejemplos de cómo estos modelos se han usado para tomar algunas decisiones de diseño y una estimación del esfuerzo que ha supuesto la creación de dichos modelos.
Abstract
Bars are prominent features observed in most disc galaxies, having a crucial
within the galaxies, while rotating around the centre at a given angular frequency,
the bar pattern speed.
When formed in an isolated galaxy, a bar is expected to be born as fast rotating
with a bar rotation rate R (a parameter used to describe the bar pattern speed)
equal to 1.0 ≤ R ≤ 1.4. During its evolution, the bar can be slowed through the
exchange of angular momentum with the other components and/or when an efficient
dynamical friction is exerted by the dark matter (DM) halo. In this case, R is
shifted in the slow regime (R > 1.4), while the bar radius and strength are increasing.
On the other hand, ultrafast (UF) bars, with R < 1.0, are physically unstable.
Measuring the bar rotation rate becomes desirable both to investigate the secular
evolution of barred galaxies and to test whether the measured DM distribution matches
that predicted by cosmological simulations in the cold DM framework.
The only model-independent way to recover the bar pattern speed (and derive R) is
the Tremaine-Weinberg (TW) method, nowadays largely applied thanks to the advent
of integral-field spectroscopy: most of the analysed bars are compatible with the
fast regime, while a non-negligible fraction belongs to the unstable UF regime.
As a consequence, the question arises whether these results are biased by an
improper application of the method or instead they come from a not completely
theoretically understanding of the nature of slow/UF bars.
We explore the open questions on bar pattern speed with the TW method by
1. testing the reliability of the TW measurements which led to UF bars
2. pushing further the quest of slow bars applying the TW method to a sample of
dwarf galaxies, the best candidates to host slowly-rotating bars, since they are
commonly thought to host a massive and centrally-concentrated DM halo.
We measure the bar radius from the analysis of the maps tracing the transverse-to-radial
force ratio, showing that UF bars are no longer observed when the correct measurement
of the bar radius is adopted to derive R.
We apply the TW method to dedicated MUSE observations of a sample of 5 dwarf barred
suggests they could have been slowed down by a dense and massive DM halo.
https://rediris.zoom.us/j/88520341620?pwd=RldDYzFzeU8zYzlOckozbjloUmEwZz09
Meeting ID: 885 2034 1620
Passcode: 818629
YouTube: https://youtu.be/8yLu_LHWuxc
Abstract
Most high mass X-ray binaries contain neutron stars as companions to an OB star, while high mass black hole binaries are very rare. We use rapid binary population synthesis to predict the number and properties of OB stars with compact companions, while varying uncertain physics assumptions. We find that synthetic populations which agree with the population properties of Be stars, Wolf-Rayet stars, and neutron stars forecast a large and so far undetected population of massive black hole binaries with orbital periods between a few days and 1000 days. To find or rule out this population is key for quantifying the contribution of isolated binaries to the merging massive black holes found through their gravitational wave emission.
Abstract
With long-term collaboration between Chinese and Spanish astronomical communities, the National Astronomical Observatories of China (NAOC) and Instituto de Astrofísica de Canarias (IAC) co-promoted a meaningful effort in 2016 to develop a high-resolution ultra-stable spectrograph for the Gran Telescopio CANARIAS (GTC) and absorbs the Chinese astronomical community into the GTC partnership. The instrument will enhance the GTC observatory’s capability in exoplanetary research and create more chances for the Chinese astronomical community to explore the universe with the existing largest optical telescope.
In this instrument project, NAOC and Nanjing Institute of Astronomical Optics and Technologies (NIAOT) are jointly responsible for developing a high-resolution spectrograph with competitive capabilities for searching and studying habitable exoplanets. The instrument will provide a hybrid observing function with a high resolution of R≥100000 in the 410–780 nm visible/optical band and R≥20000 in the 310–410 nm near-UV band. In the optical band, the spectrograph will run in an ultra-stable vacuum environment at the Coude room to measure stellar radial velocity. In the near-UV band, the spectrograph near the Nasmyth focus will assist the optical spectrograph to distinguish the signals of stellar radial velocity for high precision RV measurement, and also enable us to observe the celestial objects at the shortest wavelength of 310 nm to investigate the origins of some chemical elements. At present, the project team is working on the preliminary design and aims to complete the first-light observation in 2026.
This talk will introduce in detail the scientific motivation and progress in instrumental design. We look forward to attracting more interests among the audiences and receiving more comments on science and technology. I believe that it would be very helpful to develop a qualified instrument for the GTC. On behalf of the project team, I appreciate all the support from the IAC and the GRANTECAN S. A.
ZOOM
https://rediris.zoom.us/j/86470284286
ID de reunión: 864 7028 4286
YouTube
https://youtu.be/VZMar0vSGMc
Abstract
Since the second half of last century, stellar evolution theory has allowed to
understand the Color Magnitude Diagram of galactic star clusters, so that now
we can explain the distribution of stars in the observed CMDs in terms of the nuclear
evolution of stellar structures and, thus, in terms of cluster age and chemical composition.
In the last decades, however, the impressive amount of data collected by photometric, astrometric,
spectroscopic and asteroseismic surveys is providing a detailed observational framework which
provides at the same time a stringent test and a challenge for the accuracy of the models.
In the same time, these stellar models are a crucial input for asteroseismology as well
as Galactic archeology studies. In this talk, we discuss (some of) the main uncertainties affecting stellar models and
how they critically impact on our capability to reliably unveil the chrono-chemo-dynamical
structure of the Galaxy.
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The seminar will take place in the Aula.
Zoom: https://rediris.zoom.us/j/84304399987?pwd=UmtQb0FhWSs4OXBpUWxUMmhBcFZyUT09
Meeting ID: 843 0439 9987
Passcode: 509451
YouTube: https://youtu.be/7fH2XEXdQlw
Abstract
Unlike the giant planets in the solar system, "hot Jupiter" giant exoplanets are subject to intense stellar irradiation, which drives their atmospheres from ~100 K (in the solar system) to ~1000 to 3000 K. In this talk I will review several aspects of their atmospheric physics and chemistry, with a particular emphasis on the cooler "warm Jupiters" below 1000 K where we expect to see some interesting transitions in atmospheric chemistry and clouds with JWST. I will discuss new JWST spectra and modeling work on 1100 K exoplanet WASP-39b, which will be published in Nature in a few days time, as part of the JWST Early Release Science (ERS) program. The spectra show some expected things but also some very interesting surprises!
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Zoom: https://rediris.zoom.us/j/82072236238?pwd=MWFRSXFnQ0lUN3ZMTzgzTGQxS0ZGUT09
Meeting ID: 820 7223 6238Passcode: 648570
YouTube: https://youtu.be/jbFP6L-7mxo
Abstract
The Oort cloud and the Edgeworth-Kuiper belt are two main reservoirs
that supply new comets to the inner region of the Solar System. Some of
the cometary nuclei demonstrate significant activity at heliocentric
distances beyond 5 au. It is of great interest to determine the reasons
for this. Since 2011 we have provided a comprehensive program of
polarimetric, photometric, and spectral investigations of active distant
comets at the 6-m telescope BTA. We present the results of broadband
polarimetric measurements for seven distant comets C/2011 S1 (LINEAR),
C/2011 R1 (LINEAR), C/2014 A4 (SONEAR), C/2013 V4 (Catalina), C/2012 J1
(Catalina), C/2011 KP36 (Spacewatch), and C/2014 B1 (Schwartz) which
have perihelion distances of more than 3 au. The comets show significant
activity beyond the Jovian orbit. Polarization maps of the comets
demonstrate spatial variations of linear polarization over the coma from
about –2% up to –7% at phase angles from 2 to 20 degrees that may be
related to changes in the physical properties of dust particles. Average
polarization values are significantly higher (in absolute values) than
the typical value of polarization (∼1.5%) observed for the whole coma of
most comets that approach closer to the Sun. Probably dust in distant
comets differs from the dust in short-period comets. We also compare the
polarimetric observational data with the results of numerical modeling
performed early for different types of dust aggregates.
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ZOOM: https://rediris.zoom.us/j/89675933678?pwd=QnptWjNYNzNZQ3V6MFl6SDdjOUFCQT09
Meeting ID: 896 7593 3678
Passcode: 334513
YouTube: https://youtu.be/gjpr7YVmfJA
Abstract
En esta charla haremos un repaso al modelo de desarrollo y puesta en producción del software de control del telescopio NRT, utilizando técnicas y procedimientos basados en la integración contínua de software, el uso de contenedores para ejecución de aplicaciones y la orquestación de servicios con kubernetes.
Youtube
https://youtu.be/8FboV9c5yz4
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