Latest talks

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


carlos_allende_190116s
Wednesday January 16, 2019
Dr. Carlos Allende
IAC

Abstract

The High Optical Resolution Spectrograph (HORuS), is now ready for operation on Gran Telescopio Canarias (GTC). HORuS is mainly a recyled instrument, largely based on components from UES, which was available at the WHT in the 90's. HORuS offers single-object R=25,000 spectroscopy with broad spectral coverage (380-700 nm, with gaps in the red). A 3x3 integral field unit (IFU) covering 4.4 arcsec2 gathers the light on the focal plane into optical fibers that later align to form a pseudo-slit at the entrance of the spectrograph.
The science fibers can be illuminated with light from calibration lamps. On the detector, with the IFU acting as an image slicer, monochromatic light spreads over hundreds of pixels, enabling the possibility of achieving, for very bright targets, signal-to-noise ratios per resolution element of several thousand in a single exposure. For fainter targets (12<V<16), readout noise is minimized by on-chip binning 8 (spatial) x 2 (spectral). From direct comparison of spectra of the same targets, the combined efficiency of HORuS+GTC is about 40% lower than UVES+VLT. For a V=7 star, the signal-to-noise per resolution element in a 900-seconds integration is about 1500 at 525 nm.


jose_fernandez-trincado_190115s
Tuesday January 15, 2019
Dr. J. G. Fernández-Trincado
Universidad de Atacama, Copiapó, Chile

Abstract

APOGEE contains more than hundred thousands new giant stars. This enabled
us to collected an unprecedented and homogeneous sample of giant stars with
light-element abundance variations similar to observed in “
*second-generation*” globular cluster stars. If they are really former
members of dissolved globular clusters, stars in these groups should show
some of the basic SG-like chemical patterns known for stars currently
belonging to the Milky Way globular clusters, such as depletion in C and O
together with N and Al enrichments. Here, I will present the results of an
updated census of *SG-like* stars from a near-infrared manual analysis
using the Brussels Automatic Stellar Parameter (BACCHUS) code to provide
the abundances of C, N, O, Mg, Si, Al, Fe, Ce and Nd for every line of
possible cluster member stars, which they migrate to the disk, halo and
bulge as unbound stars, and become part of the general stellar population
of the Milky Way. By combining wide-field time-series photometry with
APOGEE-2S spectroscopy data, we are in a good position to put the big
picture together. The VVV survey have produced a large variability dataset
towards the Milky Way bulge and disk, including data in the near-IR (J and
Ks). These data will allow us to place constraints on the “polluters" that
are responsible for the chemical peculiarities, with candidates including
TP-AGB stars, binary mass transfer, accretion of material from the winds of
AGB stars, etc.  A cross match between VVV sources and APOGEE targets is
ongoing.


Johan_Knapen_190108s
Tuesday January 8, 2019
Dr. Johan Knapen
IAC

Abstract

We present the discovery of a small 0.2'' (60 pc) radius kinematically decoupled core, as well as an outflow jet, in the archetypical AGN-starburst "composite" galaxy NGC 7130 from integral field data obtained with the adaptive optics-assisted MUSE-NFM instrument on the VLT. Correcting the already good natural seeing at the time of our science verification observations with the four-laser GALACSI AO system we reach an unprecedented spatial resolution of around 0.15''. We confirm the existence of star-forming knots arranged in an 0.58'' (185 pc) radius ring around the nucleus, previously observed from UV and optical  Hubble Space Telescope and CO(6-5) ALMA imaging. We determine the position of the nucleus as the location of a peak in gas velocity dispersion. A plume of material extends towards the NE from the nucleus until at least the edge of our FOV at 2'' (640 pc) radius which we interpret as an outflow jet originating in the AGN. The plume is not visible morphologically, but is clearly characterised in our data by emission lines ratios characteristic of AGN emission, enhanced gas velocity dispersion, and distinct non-circular gas velocities. Its orientation is roughly perpendicular to line of nodes of the rotating host galaxy disk. An 0.2''-radius circumnuclear area of positive and negative velocities indicates a tiny inner disk, which can only be seen after combining the integral field spectroscopic capabilities of MUSE with adaptive optics.


annalisa_pillepich_181220s
Thursday December 20, 2018
Dr. Annalisa Pillepich
MPIA Heidelberg

Abstract

I will describe the numerical efforts to simulate galaxies with the moving-mesh code AREPO across an unprecedented range of halo masses, environments, evolutionary stages and cosmic times. In particular, I will focus on the IllustrisTNG project (www.tng-project.org <http://www.tng-project.org>), a series of three gravity+magnetohydrodynamics cosmological volumes of 50, 100, and 300 Mpc a side, respectively, in a LCDM cosmology. With these, we are capable of both resolving the inner structures of galaxies as small as the classical dwarfs of the Milky Way, as well as of sampling the large scale structure of the Universe with thousands among massive groups and clusters of galaxies. I will discuss what is explicitly and empirically solved in gravity+magnetohydrodynamics simulations for galaxy formation in a cosmological context and what is required and what it means to “successfully” reproduce populations of galaxies which resemble the real ones. I will therefore show novel insights allowed by the new simulations, ranging from the assembly of the most massive structures in the Universe, to the effects of baryons of the phase-space properties of dark matter and to the changes in the star-formation activity and morphological mix of galaxies at early epochs.


olga_maryeva_181213s
Thursday December 13, 2018
Olga Maryeva
Astronomical Institute of Czech Academy of Sciences

Abstract

Massive stars (with masses higher than 30 M) undergo the mass loss during their whole lifes. During hydrogen burning in their cores massive stars demonstrate fast winds with velocity about V∞=2500 km/s and relatively low mass-loss rate about 10 -7-10-6 M/year. At the same time, after the end of core hydrogen burning stars become less stable and mass-loss rate increases, stars move to the stage of Luminous Blue variable (LBV). LBVs are relatively short evolutionary stage in life of massive stars, during which they lose significant amount of mass through strong stellar winds and occasional giant eruptive events. As a result, they shed their outer layers and eventually become hydrogen-deficient Wolf–Rayet stars. Massive stars with 25-40 Mreach LBV stage after being red supergiants i.e. reaching cool end on Hertzsprung– Russell diagram, more massive stars became LBV right after blue supergiants phase. Consideration of the initial mass function leads to conclusion that LBV stars are extremely rare and there should be no more than a few dozens such objects in the Galaxy. Detection of LBV- like shells may be considered an indication of that their associated stars are massive and evolved. Searches for such shells using the infrared surveys resulted in the discovery of many dozens of such shells, while follow-up spectroscopy of their central stars led to the discovery of dozens of new candidates to LBVs. In the talk I will tell about properties of nebula around post-LBV star GR290 and about estimated parameters of couple of stars with LBV-like shells, and discuss that at least in some cases the envelope loss occurs before LBV stage.

Frantisek_Duris_181210s
Monday December 10, 2018
Frantisek Duris
Comenius University in Bratislava

Abstract

In this talk, I will briefly introduce Slovak instrument AMOS - all-sky meteor orbit system. We designed and developed a GUI tool for calculating and visualizing trajectories of meteors in Earth's atmosphere and Solar system from multiple-station observations. The current version of the program includes calculation of 1) atmospheric trajectory and velocity, 2) Solar system trajectory, 3) photometric mass, 4) dark flight and impact, 5) Monte Carlo simulation of errors. The program is written in Lazarus/Object Pascal and can be run under Windows as well as Linux systems. Numerical simulations and graphical outputs are produced in R.
In the second part of the talk, I will discuss the python-based photometry pipeline by Mommert (2017) for reducing 4-colour MuSCAT2 images. We implemented several modifications to significantly increase the number of successfully reduced images. I will discuss how the modifications combine data through colors as well as time to obtain more results.


Chiara_Feruglio_181204s
Tuesday December 4, 2018
Dr. Chiara Feruglio
INAF Observatory of Trieste

Abstract

Why did galaxies stop forming stars? Why do black holes in galactic nuclei have masses proportional to bulge masses? What are the physical mechanisms leading the transition from gas-rich, star-forming galaxies, to red gas-deprived passive galaxies? Theoretical models predict that AGN should play a major role in this co-evolution, by driving super winds that are eventually able to remove gas from galaxies, thus quenching star-formation and preventing them from over growing.  
Today’s flagship Instruments - like ALMA and MUSE/VLT - allow to routinely detect AGN-driven massive winds, and to spatially resolve and measure their main parameters. AGN driven galactic winds seem a widespread feature in AGN host galaxies in the local universe, with mounting numbers also in the distant universe.  
But questions arise about their net impact on the surrounding ISM, on the relative importance of quenching versus stimulating star-formation, on the removal of the gas reservoirs from the disks of the host galaxies. 
Do we really understand the interplay of these AGN super-winds with the ISM of the host galaxy, and -perhaps more importantly- with the entire AGN/host galaxy/circum-galactic medium (CGM) ecosystem? I will discuss both observational and theoretical recent results on this topic - and highlight possible strategies to progress. 


ruben_fechiani_181203s
Monday December 3, 2018
Rubén Fedriani
Dublin Institute for Advanced Studies (DIAS)

Abstract

In contrast with low-mass young stellar objects (LMYSOs), very little is known about high-mass YSOs (HMYSOs). Latest results indicate that HMYSOs might be born in a similar way as LMYSOs, i.e., through disc accretion and jet ejection. HMYSOs are deeply embedded in their parent cloud and are at kpc distance, hindering direct imaging of their accretion discs. Jets then become essential to understand the physical properties of the central source. High-resolution near-IR VLT instruments allow us to study HMYSO jets down to au scales and compare them with the low-mass regime. In this talk, I will present VLT/ISAAC, SINFONI, and CRIRES results on two HMYSOs. Spectro-astrometry is used to retrieve information about the jet down to mas scales (~tens of au at kpc distance). High-resolution spectroscopy allows us to retrieve the kinematic and dynamic properties of the massive jets. Additionally, HST imaging in the [FeII] shows the jet structure close to the star. Finally, these properties are compared with low-mass jets, suggesting that the formation of HMYSOs might be a scaled-up version of their low-mass counterparts, and their properties scale with mass.


Klaus_Strassmeier_181130s
Friday November 30, 2018
Prof. Klaus G. Strassmeier
AIP

Abstract

The demand of high-res spectroscopy had seen a tremendous increase after the discovery of exoplanets. Such instruments are now among the standard equipment of nearly every observatory. The latest addition in the zoo is PEPSI, the new bench-mounted fiber-fed and stabilized “Potsdam Echelle Polarimetric and Spectroscopic Instrument” for the 11.8m Large Binocular Telescope (LBT). It covers the entire optical wavelength range from 383 to 914 nm in three exposures at resolutions of either R=λ/Δλ=50,000, 130,000 or 250,000. As of this year, the R=130,000 mode can also be used with two dual-beam Stokes IQUV polarimeters and as such provides another unique capability besides the ultra-high resolution mode. It is also fiber linked to a disk-integration solar telescope and the Vatican Observatory's 1.8m VATT. In this talk I introduce the instrument and focus on first data and results in order to "feel the taste". Among the first targets were the Sun and solar twins, Gaia benchmark stars, Jupiter's Io, planet-host stars with hot Jupiters as well as stars with Earth-sized planets, novae, the ISM, and much more.


Fernando_Buitrago_181128s
Wednesday November 28, 2018
Fernando Buitrago
Institute of Astrophysics and Space Sciences (IA)

Abstract

There are galaxies that remain untouched since the ancient
Universe. These unique objects, the so-called relic galaxies, are several times
more massive than our Milky Way but with much smaller sizes, and
containing very old (>10 Gyr) stellar populations. For the very few of
them already found and analysed (most of them by our IAC colleagues),
they seem to host "too heavy" central
super massive black holes, also displaying an overabundance of low mass
versus high mass stars and retaining their primeval morphologies and
kinematics. How did they survive until the present day? Simulations
predict that they reside in galaxy overdensities whose large internal
random motions prevent galaxies from merging. However, we have not yet
determined observationally neither the environments these galaxies
inhabit nor how many there are (their number densities). We make use
of the GAMA survey, that allows us to conduct a complete
census of this elusive galaxy population, because of its large area and
spectroscopic completeness. After inspecting 180 square degrees of the sky
using the deepest photometric images available, we identified 29
massive ultracompact galaxies in the nearby Universe (0.02 < z < 0.3),
that are true windows to the ancient Universe. I will present the first paper
about this exceptional sample, describing their properties and
highlighting the fact that while some galaxies seem to be satellites
of bigger objects, others are not located in clusters, at odds with the
theoretical expectations.



Upcoming talks

  • Astro-African memories
    Dr. Cristina Martínez Lombilla
    Thursday January 17, 2019 - 10:30  (Aula)
  • TBD
    Beatriz Villarroel
    Thursday January 24, 2019 - 10:30  (Aula)

Featured talks