A non ambiguous definition of stellar radial velocity (RV) is non trivial. Early comparison between astrometric and spectroscopic RVs revealed only a qualitative agreement and hint to potential quantitative differences between them. We compare for the first time in detail spectroscopic and astrometric RVs for stars of the Hyades open cluster.

Astrometric RVs are available for the Hyades’ stars, based on Hipparcos and on the first Gaia data release. We obtained HARPS spectra for a large sample of Hyades stars, and we homogeneously analysed them, either by applying a zero point correction deduced from solar observations and equal for all stars, or by correcting each star for the convective shifts in the stellar atmosphere computed theoretically from 3D atmospheric models. After cleaning the sample from binaries, RV variables, and outliers, 71 stars remained.

The distribution of the RV difference (spectroscopic – astrometric) is skewed and possibly double-peaked, and it depends on the star right ascension. This is consistent with the Hyades cluster rotating at 43±10 m s−1pc−1.We find that the spectroscopic radial velocities published in literature have a mean offset of 689 m s−1.We detect in the two single cluster giants clearly Gravitational Redshift in perfect agreement with predictions.The mean difference between spectroscopic and astrometric RV is of −33 m s−1 and the median is of −16 m s−1 when considering the Gaia-based RVs (corrected for cluster rotation) and the theoretical spectroscopic RV corrections, and of −85 m s−1 and +48 m s−1 when considering the Hipparcos and the empirically determined zero correction.  Thus it is possible to reach accurate RV measurements.

We finally discuss the phenomena that can influence the astrometri and spectroscopic RVs, such as cluster expansion, stellar activity, general relativity, Galactic potential; clusters within the reach of current telescopes are expected to show differences of several hundreds m s−1, depending on their position in the Galaxy, but will not have precise enough astrometric RV.

Cataclysmic variables (CVs) are interacting binaries composed of a white dwarf undergoing stable mass transfer from (usually) a low-mass main sequence star and they are expected to exist in non-negligible numbers in globular clusters (GCs) that are natural laboratories for testing theories of stellar dynamics and evolution. In the first part of this talk, I will describe two methods for investigating CVs in GCs, which are direct N-body integrations and Monte Carlo approach. I will then explain why the Monte Carlo approach is the most convenient for investigating exotic objects in GCs. In the second part, I will present the main aspects related to our understanding regarding GC CV populations based on the analysis of MOCCA (Hypki & Giersz 2013) numerical simulations performed by Belloni et al. (2016,2017a,2017b) and Hong et al. (2017). Emphasis will be given to the main differences in present-day CV properties due to dynamics in comparison with CVs in non-crowded environments. Finally, I will discuss how good are the agreements with respect to recent searches for CV candidates in four specific GCs, namely NGC 6397 (Cohn et al. 2010), Omega Cen (Cool et al. 2013), NGC 6752 (Lugger et al. 2017), and 47 Tuc (Rivera-Sandoval et al., sub. to MNRAS).

At the heart of interpreting starlight, infrared and radio continuum (all typically dominated by massive stars) in terms of star-formation rate (SFR) and stellar mass in individual galaxies or averaged over cosmological volumes, the stellar initial mass function (IMF) is often described as a nearly-universal function in the Galaxy and nearby galaxies. Classical determinations of the IMFin local galaxies are traditionally made at ultraviolet, optical and near-infrared wavelengths that cannot be adopted for dust-obscured galaxies, and even more so in distant starbursts selected at submillimetre (rest-framefar-infrared) wavelengths, exactly the type of galaxies for which galaxy evolution models often predict an IMF biased towards massive stars.  We bring along the state-of-the-art chemical evolution models with well-calibrated stellar yields, time-delay effects, and various star formation history, combine with abundances of carbon and oxygen isotopologues measured in molecular gas,opening up an unexpected new gate of exploring the IMFs in dust-rich galaxies,especially for those in the early Universe. We will also  discuss the physical origins for the top-heavy IMF in starburst systems, presenting our new ALMA results in a few strongly lensed dusty starbursts at high redshift, and compare them with different types of local galaxies.

Ultra-diffuse galaxies (UDGs) are a class of low surface brightness (LSB) galaxies with stellar masses typical of dwarfs (M*~10^7-10^8) and large sizes (Rh>1.5kpc) for their luminosity. UDGs are ubiquitous and abundant in nearby galaxy clusters, but their formation mechanism is still unclear. I will review the recent proposals and show that a scenario in which UDGs represent the tail into the LSB regime of the abundant dwarf galaxy populationreproduces their abundance and size-distribution in clusters. I will also expand on an effort to assess the richness of their GC systems. This has shown that most Coma LSB galaxies have GC abundances that are in line with what expected for their stellar mass. A small fraction of systems, however, displays ‘over-abundant’ GC systems. Interestingly, not all of the latter are extended, implying that the physical mechanisms responsible for the large sizes of the UDGs and for the enhanced GC abundances of some cluster dwarfs are not identical.

We will share our experience of teaching at the West African International Summer School for Young Astronomers, held in Ghana this summer and Nigeria in 2015. We will summarize the obstacles faced by West African physics students in pursuing a career in science, and explore how we as professional astronomers could contribute to improving the situation.

We will informally discuss the recently announced kilonova event associated with the gravitational wave GW 170817, with particular emphasis on the ePESSTO collaboration paper.

Lithium, fragile and scarce, sensitive and primitive, is one of the most complicated elements in astrophysics. Its abundance in stars, in both the main sequence phase and the giant branch phase, has plagued our current understanding of cosmology, stellar evolution, and metal sources of the interstellar medium. I will discuss problems and puzzles that Li introduces in astrophysics, including cosmological Li problem, Li-rich giants problem, Li problem in the Sun, nucleosynthesis of Li production, and Interstellar Li content, then focus on the Galactic Li evolution.

It is generally accepted that the distribution in colour and magnitude (temperature and luminosity) of the Pre MainSequence (PMS) objects in the Orion Nebula Cluster (ONC) shows an intrinsic spread. At least two are the interpretations of such observed spread:1) a genuine spread of the ages of few Myr, inconsistent with that of a coeval stellar population and in agreement with a star formation activity lasting between 1.5 and 3.5 Myr; 2) the spread in temperature and luminosity is a consequence of the accretionhistory taking place at the early stages of the formation of the stars. Recent results obtainedwith multi-band optical photometry with OmegaCAM@VST indicate the presenceof 3 discrete populations of PMS in the ONC. I will discuss how discreteness might prompt a revised look at the formation mode and early evolution of stars in the ONC.

Due to the limitations of current astronomical instrumentation and data reduction techniques, the Ultra-Low Surface Brightness (ULSB) universe,  which lies over two orders of magnitude below that of the sky background , is one of the last niche that remains to be explored in observational parameter space. So far, the first pioneering observations using small telescopes and telephoto lens have revealed  a wealth of stellar tidal streams and shells, diffuse stellar systems and a possible hitherto unknown type of galaxies (ultra-diffuse galaxies) whose properties could be  different from those at brighter levels. In this talk, I'll discuss this topic and our deep exploration of the interaction of the Magellanic Clouds using telephoto lens.

We would like to discuss with you the time allocation process at ESO – how does (should) it support the scientific goals of the community? We will briefly review the outcomes of the Time Allocation Working Group, look at what other observatories are doing (HST, Gemini, …) and present fun facts about request statistics and OPC gradings.

First of all, I shall give an overview on the research status about stellar magnetic activity and exoplanetary systems at Yunnan Observatories. Then, some more detailed results derived during recent years will be introduced. For stellar activity, I shall talk about the study on chromospheric and photospheric activities by using high-resolution spectroscopy, magnetic field by using Zeeman Doppler imaging method. For exoplanetary systems, I shall introduce the study on wide field transit survey project, TTV follow-up observations. Finally, the prospects in the near future will be given.

We present a tomographic method allowing to recover the velocity field at different optical depths in a stellar atmosphere. It is based on the computation of the contribution function to identify the depth of formation of spectral lines in order to construct numerical spectral masks probing different optical depths.
These masks are cross-correlated with observed spectra to extract information about the average shape of lines forming at a given optical depth and to derive the velocity field projected on the line of sight. We apply this method to time-series of spectra of the red supergiant star mu Cep and derive velocities
in different atmospheric layers. The main results will be discussed during the talk.

Luminous and ultra luminous infrared galaxies (LIRGs and ULIRGs) are one of the most extreme systems in the local universe, showing star formation rates of up to a few 100 solar masses per year. They produce the bulk of their luminosity in the infrared due to a combination of starburst, and/or AGN activity, and overwhelming amount of dust. Due to the latter, understanding the physics of these extreme environments becomes challenging. Radio and sub millimeter continuum may be the key in such extreme environments, presenting an unobscured view of the ongoing star formation. I will present results on a sample of 22 local U/LIRGs that have been observed at 33 GHz with the upgraded Very Large Array (Barcos-Muñoz+17). We observed them with the four different array configurations of the VLA allowing us to resolve the cores of these sources, but also recover the total 33 GHz emission. I will discuss the implications of the derived physical parameters obtained from the observed radio continuum emission. These include optically thin regimes, star formation scaling relation (KS relation), and maximal starbursts scenario. Finally, I will describe new high-resolution ALMA observations on Arp 220 and discuss on the synergy between these observations and the ones from the VLA described above.

While the Solar System planets are on nearly circular (e~0.06) and coplanar (i~3 deg) orbits, the first several hundred extrasolar planets discovered using the Radial Velocity technique are commonly on eccentric orbits (e~0.3). This raises a fundamental question: Are the Solar System and its formation special? The Kepler mission has found thousands of transiting planets, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the LAMOST observations, we measure the eccentricity distributions for a large and homogeneous Kepler planet sample. We observe an eccentricity dichotomy, a common orbital pattern and the prevalence of near-circular orbits for planets inside and outside the Solar System, which provide insights to answer the above fundamental question.

Rich clusters of galaxies generally have an extended population of intergalactic stars stripped off the member galaxies over the past Hubble time.  For clusters closer than ~200 Mpc or so, an extremely effective way to search for this Intracluster Medium is by identifying the intergalactic globular clusters (IGCs) within the cluster.  I will describe some new results of this type for the Perseus cluster, a system about 75 Mpc distant that is as rich as Coma or Virgo.

The VLTI has an array angular resolution of about 1.2 mas in the near-IR H-band. This allows us to image the surfaces of stars other than the sun. In the past, optical interferometry in general and the VLTI in particular have been focusing on model fitting. With a steady progress on observation efficiency and accuracy, the VLTI is now producing images of stars of different kinds. I will discuss the basics and recent progress on the technique at aperture synthesis imaging at the VLTI, and will present a variety of very recent imaging results  and their astrophysical interpretation. Some of these results are just published, others are currently under review or in preparation. They include mostly red giants and supergiants, asymptotic giant branch stars, but also other types. While I will focus on imaging at the VLTI, I will briefly mention the context of other techniques that have the power to resolve stellar surfaces. Finally, we are preparing an ESO workshop on stellar imaging for 2018, and if time allows we will discuss ideas for that workshop.

In this informal discussion I will show why the study of the chemical
complexity of the interstellar medium is highly interesting and can be a
powerful tool for scientists working on different fields. Some spoilers:

1) We are chemistry. We already know that chemistry in the interstellar
medium is able to form complex organic molecules (COMs) of great importance to
astrobiology. The unprecedented sensitivity of current telescopes is allowing us to
detect for the first time in the ISM a rich variety of molecules,
including some families with high astrobiological interest (sugars,
phosphorus-bearing species, isocyanates …), which could play a central
role in prebiotic chemistry and directly linked to the origin of life.

2) Chemical complexity is, by definition, COMPLEX. The processes leading
the formation of COMs in space are highly complicated. That´s why a
proper study requires a multidisciplinary approach, which not only
involves astrophysicists, but also chemists, spectroscopists,
biologists, geologists, laboratory works and theoretical chemical
modelling. Therefore, only a joint effort will help us to understand how
the chemical complexity could growth until giving rise to Life.

3) It is the perfect time to explore this topic thanks the advent of
very powerful telescopes as ALMA.
Astrochemistry is still in its infancy, so new exciting opportunities
are now in front of us.

4) Even if you are not interested at all in the origin of life (?)...
you can learn a lot thanks to the variety of molecules that we can
detect in space. Different molecules and chemical reactions trace very
different enviroments and conditions of the interstellar medium, and
hence they are a very useful tool to derive physical and dinamical
parameters (densities, temperatures, evolutionary stages,
infall, rotation...) of your favourite sources, not only in our Galaxy
but also in external galaxies.

ESO, together with CERN, is an observer in the H2020 GENERA (Gender Equality Network in the European
Research Area) project, which aims at continuing, monitoring and improving the Gender Equality Plans (GEPs)
of research and funding institutions/agencies in the field of physics. The ultimate ambitious goal is to develop
and support gender-inclusive organizational structures and customized GEPs.

One aspect of the GENERA project is the organization of Gender in Physics Days (GiPD), one per each country
represented in the project. So far, this initiative has proven to be an efficient mean to quickly gather an overview of what has already been done, what works and what does not. ESO, CERN and NordForsk have contributed to this by organizing a GiPD focused on the challenges that intra-governmental organizations (e.g., EIROforum) normally face in terms of GEPs. One part of this special event was dedicated to early career scientists and their expectations in terms of GEPs, in preparation of which I had carried out a small poll among ESO students and fellows.

During this informal discussion, I will share a few highlights from the ESO/CERN/NordForsk GiPD and discuss
the outcome of our ESO poll of early career scientists.

AGN feedback is often invoked in simulations to reproduce observed properties such as the massive end of galaxy mass functions. While efforts have been underway during the past decade to unviel the feedback effects at both low and high redshift, a direct observational evidence is still elusive in literature. I will discuss our current efforts on this front for high redshift galaxies using optical and near infrared IFU, single slit and sub-mm spectroscopic observations with WiFeS, SINFONI, XSHOOTER, and ALMA. Such a diverse set of high quality multiwavelength dataset sets the stage to understand how AGN affects the ionized as well as molecular gas content of the host galaxy. Some of the key questions addressed in this discussion are: Are ionized outflows in high redshift galaxies driven by AGNs or star formation? What are the level of uncertainties in these outflow models and how to reduce them?  Are such AGN outflows capable of affecting the molecular gas content in the host galaxy?

In order to study kinematics of galaxies, one uses spectroscopic observations, which provide us with the line-of-sight velocity component only. What about the two other velocity components? Can we get a handle on them for external galaxies, where proper motions are too small to detect? I will show that if a galaxy contains a feature with a mirror symmetry, like a bar, then from the observed line-of-sight velocity one can recover two velocity components in its disc, assuming that the vertical velocity is zero. What can we learn from having at hand these two velocity components? I will be glad to hear your ideas, but I will also present what I've got thus far: the estimate of dark matter contribution in central parts of galaxies, and the evaluation of pattern speed of the bar.

First, I will briefly talk about and advertise the "recently" established astrochemistry department of MPE. Paola Caselli has taken up the role as one of the directors of MPE about three years ago, almost exact to date (1st of April, no joke). I will explain the organizational structure and the various topics in which the CAS group is involved in. I will then continue to informally discuss how chemistry on microscopic dust grains can impact the evolution of interstellar clouds on parsec scales, and vice versa, and how this may eventually influence star formation. I will delve into the thermal balance of translucent and molecular clouds, discuss the importance of the dust temperature, mention the issues when digging into the finer details of surface chemistry, and perhaps present some "fresh from the oven" models of the chemical-magnetic interplay. This discussion is expected to be highly interactive, and the steering of the topic of discussion in a preferred direction is up to you.

The physical origin of different properties of high versus low-redshift star-forming galaxies in the [OIII]/Hβ-[NII]/Hα-plane is still controversially debated. I will present recent theoretical progress on this topic. Specifically, we first model the nebular emission from different sources of ionizing radiation, namely young stars, AGN and post-AGB stars. We then couple these same models with new sets of cosmological hydrodynamic zoom-in simulations of massive galaxies. I will then discuss how this approach can help disentangle the galaxy properties that drive the redshift evolution of the optical line-ratios, focusing on the [OIII]/Hβ ratio.

Symbiotic stars (SySt) are long-period interacting binaries composed of a hot compact star --generally a white dwarf-- an evolved giant star, and a tangled network of gas and dust nebulae. Inspired by the fact that SySt are a promising  channel to supernovae Ia, it is clearly of prime relevance to determine their  population. We discovered a number of SySt in the Local Group galaxies, while using imaging techniques to search for planetary nebulae. Most of them showing a particular  emission line that is almost exclusive of symbiotic systems, the O VI Raman scattered line at 6825A. In this opportunity I will discuss the first results of our pilot project of an innovative technique to search for SySt, which --if proved to work--, will be far more efficient them those commonly used.

ePOD is the link between ESO and the outside world - the media, the public, local communities, decision makers etc. I will briefly explain what the department does and how it works - tasks including news production, print products, images and videos. I will also talk about more about its role for astronomers - how you can get involved and how it can help you to publicise your work. There should be lots of time for questions.

A chance to find out all you want to know about the ESO Supernova! What is the progress? When will it open? What will be offered? How can you get involved? Why are we bothering? And any other questions you might have are welcome.

The key process of gas accretion is fundamental in understanding the formation and evolution of galaxies throughout the cosmic history. While there are a few indirect observational evidences supporting the presence of gas accretion its direct detection in individual galaxies remains challenging. As the inflowing gas is diffuse the best tool to probe it directly lies in absorption-line spectroscopy. I will introduce the common absorption-line techniques generally used to search for the inflowing gas into galaxies. Furthermore, I discuss the recent observational claims for the possible detections of gas accretion in galaxies based on absorption line spectroscopy.

The different statistical approaches to hypothesis testing will be reviewed, and contrasted to what we do in physics.  The recent claims of discoveries (Higgs Boson, Gravitational Waves) and non-discoveries (superluminal neutrinos) will be analyzed and used to generate discussion on how to formulate the hypothesis testing question.

In 1926, Hubble showed that galaxies can be classified in three different groups depending on their shape: ellipticals, spirals, and irregulars. The Milky Way is a barred spiral galaxy. However, due to our position in the Galaxy, the exact structure of the Milky Way is still under debate, i.e. the number and position of the spiral arms, the rotation curve, or the shape of the bar. To determine the Galactic structure, distance measurements to the spiral arms are needed. In the optical, the satellite mission Gaia is measuring the distance to billions of stars. At radio wavelengths, very long baseline interferometry observations of maser sources in star forming regions yield parallactic distances to the spiral arms. I will present first results of the Bar and Spiral Structure Legacy (BeSSeL) survey, a Very Long Baseline Array Key Science project, which will determine the distances to several hundreds of star forming regions. On the basis of these measurements, we are able to pinpoint the spiral arms and determine the structure of our Galaxy.

Recent investigations on the effect of cosmic rays on our most used/cherished/calibrated  H2 gas tracer, namely the CO molecule, showed that even modest enhancements of the CR energy density (factors of 10-100 x Galactic) can wipe out CO throughout the volume of Milky-Way type Giant Molecular Clouds, leaving it intact only in their high-density regions (n>=10^{4} cm^{-3}). This is bad news for gas-rich disk galaxies in the Early Universe with even modestly enhanced SF rates.  Not all is lost though, as another tracer is left in the wake of the CR-induced destruction of CO.