The halo of the Milky Way provides a laboratory to study the properties of the shocked hot gas that is predicted by models of galaxy formation. There is observational evidence of energy injection into the halo from past activity in the nucleus of the Milky Way; however, the origin of this energy (star formation or supermassive-black-hole activity) is uncertain, and the causal connection between nuclear structures and large-scale features has not been established unequivocally. Here we report soft-X-ray-emitting bubbles discovered in the first eROSITA all-sky survey image. These 'eROSITA bubbles' extend approximately 14 kiloparsecs above and below the Galactic centre and include a structure in the southern sky analogous to the North Polar Spur. The sharp boundaries of these bubbles trace collisionless and non-radiative shocks, and corroborate the idea that the bubbles are part of a vast Galaxy-scale structure closely related to features seen in γ-rays (aka Fermi bubbles). Large energy injections from the Galactic centre are the most likely cause of both the γ-ray and X-ray bubbles. The latter have an estimated energy of around 10^56 erg, which is sufficient to perturb the structure, energy content and chemical enrichment of the circumgalactic medium of the Milky Way.

Low to intermediate mass stars, as for example the Sun, evolve towards the asymptotic branch of giants (AGBs), showing increased mass loss during their evolution. AGBs are crucial contributors to the chemical enrichment of galaxies because they lose huge amounts of their mass. 

These stars are characterized by:

• large-amplitude variations in radius, brightness, and surface temperature; and

• a high rate of mass loss due to an interaction between pulsation, dust formation, and radiative pressure on the surface.

Their complex dynamics affect measurements and amplify uncertainties on their stellar parameters. Their surfaces are covered by a few large convective cells (with a long life span). These are supported by smaller-scale structures with a shorter duration. The atmosphere above the surface is made up of shock waves, that are produced inside the star and shaped by the top of the convection zone, when these shock waves travel outward. In the presence of light asymmetries, the position of the photocentre does not coincide with the barycentre of the star and changes as the convective pattern changes over time.

The displacement of the photocentre can be explained by numerical simulation, suggesting that the variability related to stellar convection largely explains the Gaia parallax uncertainties. Consequently, parallax variations on Gaia's measurements could be used to extract the fundamental parameters of these stars. With future releases of Gaia, more precise parallax measurements will become available which will hopefully improve these characterisations even further.

In the first part of the seminar, I will talk about an object-by-object comparison between the L-Galaxies semi-analytical model and the IllustrisTNG hydrodynamical simulations. I highlight the similarities and differences, focusing on the properties of galaxies in different environments.

In the second part of my talk, I introduce a local background environment (LBE) estimator to quantify environment, locally, for all galaxies within cosmological simulations. I use the time-evolving LBE of galaxies to develop a method to better account for ram-pressure stripping of gas within the Munich semi-analytical model, L-Galaxies. I calibrate the updated model using a Markov Chain Monte Carlo (MCMC) method and observational constraints from the stellar mass function and quenched fraction of galaxies at z < 2. By comparing to data on galaxy properties in different environments from different surveys (e.g. SDSS, HSC), I demonstrate that the updated model significantly improves the agreement with the quenched fractions and star formation rates of galaxies as a function of stellar mass, halocentric distance, and host halo mass. Overall, in the vicinity of massive haloes, the new model produces higher quenched fractions and stronger environmental dependencies, better recovering observed trends with halocentric distance up to several virial radii. By analysing the actual amount of gas stripped from galaxies in the new model, I show that those in the vicinity of massive haloes lose a large fraction of their hot halo gas prior to their infall. This is likely to influence the correlations between galaxies up to tens of megaparsecs.

The ESO workshop "Ground-Based Thermal Infrared Astronomy – Past, Present and Future" was held on-line from October 12-16, 2020. Originally planned as a traditional in-person meeting at ESO in Garching during April 2020, it was rescheduled and transformed into a fully on-line event due to the COVID-19 pandemic. With 337 participants from 36 countries the workshop was a resounding success, demonstrating the wide interest of the astronomical community in the science goals and toolkit of ground-based thermal infrared astronomy. In this informal discussion we will report on the organization of the workshop and will present some of the science highlights.

Astronomy is a very “open” science by nature — sharing (pr-)eprints, data, and code has a long tradition among astronomers. This is shown by the community’s adoption of platforms like arXiv/astro-ph, Github, and the Astrophysics Source Code Library. Do we actually need “official” open access regulations in astronomy if the community embraces the concept of openness so well anyway? Why is this topic relevant for astronomers?

During the week 19 to 25 October 2020, this year's International Open Access Week takes place. In this informal discussion, we will explain recent developments in open access publishing and explore areas that are still missing on our way to an open science community. In addition, we would like to hear from you what you consider essential in an OA journal.

White dwarf stars are a well-established tool for studying Galactic stellar populations. Two white dwarfs in a tight orbit forming a double white dwarf (DWD) binary offer us an additional messenger - gravitational waves - for exploring the Milky Way and its immediate surroundings.

Gravitational waves produced by DWDs can be detected by the future Laser Interferometer Space Antenna (LISA). I will discuss what we will learn about our Galaxy from the LISA sample of DWDs. In particular, I will demonstrate how well the density distribution of DWDs constrains scale parameters of the Milky Way's bulge, disc and central bar. Finally, I will show that massive Galactic satellites can be seen on gravitational wave sky and I will present which of their properties we will be able to investigate with LISA.

Astronomers offer a unique and important perspective that can help people understand the causes, consequences, and solutions for climate change.  Through the classes we teach and our public outreach we reach large numbers of people.  But we need to recognize that climate change is different than the other topics we teach.  Teaching and communicating climate change is challenging because it spans a wide range of subject areas, from physics to psychology.  It is now clear that understanding the science is not enough.  People largely made decisions about climate change based upon their values and identity.  They therefore need to understand how climate change affects things they care about.

We also need to think about how we do our work.  To avoid the worst consequences of climate change, research indicates that humanity must reduce carbon emissions 50% by 2030, and nearly 100% by 2050.  While a small field, astronomy nonetheless has a significant carbon footprint.  Historically we have relied heavily on travel to do our work.  Fortunately there are many ways in which we can reduce our carbon emissions while actually improving our profession.  We have already seen how remote and queue observing improves the science we do, from conducting observations under appropriate sky conditions to enabling time-sensitive science.  Remote participation online is also becoming more common.  While there will always be value in "face to face" engagement, virtual meetings offer the opportunity for more inclusive and equitable participation.  This is particularly true for those with constraints that restrict travel; e.g., small budgets as well as work and family obligations.  By reducing our footprint we send an important message to the world about the seriousness of the problem.  But if done properly we can also use this as an opportunity to improve our profession.

In my talk I will briefly describe effective methods for talking about climate change with our students and the public.  I will also outline ways in which our profession can reduce our carbon footprint.  I will describe strategies being considered by the American Astronomical Society to meet that goal.

With the discovery of exoplanets, theories of planet formation, structure and evolution (planetology) have to simultaneously explain observations with a huge dynamic range: from exquisitely detailed observations of the atmosphere and structure of planets and minor bodies in our Solar System, to population-wide properties of thousands of exoplanets. For exoplanet observers, the challenge is to present the community with a set of observations that can push our understanding of planet formation further, despite the limited information and limited precision that we can access in exoplanets. I propose to discuss the current contribution of exoplanet sciences to planetology through the simplest measurable quantities (radius and mass), and a possible future avenue to increase that contribution through detailed observations of metals in the atmospheres of ultra-hot Jupiters (T_eq >~ 2200 K), the hottest gaseous giants known.

In particular, I will present the first detection of an atomic species in the emission spectrum of an exoplanet (KELT-9b) realized in a single night of observations with the optical HARPS-N spectrograph, mounted on a 4-meter class telescope (Telescopio Nazionale Galileo). Our detection shows: (1) the unambiguous presence of a thermal inversion in the atmosphere of the planet, constraining its atmospheric structure (2) that, given sufficient precision, it is possible to measure the abundance of metals in a sub-class of exoplanets, the ultra-hot Jupiters. This is a crucial step towards establishing a new set of observational tests of planet formation and evolution theories. In the near future, our technique will be extended to cooler exoplanets. In the era of EELTs and JWST, this kind of measurements could ultimately open a new window on exoplanet formation and evolution.

In this talk I will introduce white dwarfs and discuss the mass distribution of such fascinating objects. We will begin with the first spectroscopic surveys, including the SDSS, and see how our understanding has been improved with the outcome of Gaia.

The EAS 2020 meeting was forced to move online this year. I'll discuss how they decided to go about it and how this worked out, for attendees, session organisers and virtual exhibitors. What worked well and should be kept in post-covid times and what didn't?

We recently organized the e-conference entitled "Assessing uncertainties in Hubble's constant across the Universe", or #H02020, which took place from 22 to 26 June 2020, daily from 12:50 - 15:10 UTC.

Originally planned as an in-person conference to be held at ESO HQ in Garching, #H02020 was moved to the virtual domain in response to the COVID-19 pandemic that led to strict worldwide travel restrictions and a severe reduction in the number of conferences held this early Summer.
With no blueprints for implementation, we decided to risk the experiment of converting a fully planned conference to a live online event spanning 18 time zones using existing infrastructures and free versions of online tools and platforms.

In this informal discussion, I will present how we went about implementing this e-conference, how it was received, and what we have learned in the process.

Given the very positive response received from the community, we hope that others will build and improve upon our setup in order to make e-conferencing an effective, inclusive, and climate-friendly alternative to in-person meetings.

I will give an overview of the fascinating nebulae around one of the closest known symbiotic star R Aquarii.

Among other observational facilities, during the last 40 years, ESO telescopes and researchers, have played a crucial role in understanding the nature of this unique system. 

We have recently reported on the presence and diffusion of weak magnetic fields among the hot stellar populations in Galactic globular clusters. I will try to summarize the results of our survey that led to the identification of both periodic and periodic photometric variability; a twofold manifestation of the often elusive magnetic activity.

Museums (and similar visitor attractions) have experienced unprecedented economic and social consequences in recent times due to the coronavirus. To better understand the status quo and what might come next, the Network of European Museum Organisations (NEMO) launched a survey to map COVID-19’s impact on the museum sector (mostly in Europe). The results are in and the report analyses and documents a sector that, although it is experiencing financial setbacks, is agile and able to adapt to the new normal.
I will present some of the results from this and other studies, whilst also highlighting the impacts on our ESO Supernova.

One of the largest quantitative discrepancies in the local Universe is that population-synthesis models predict between 108 and 109 black holes (BHs) in the Milky Way while only about two dozen have been detected.  Most of the detections were made in X-rays caused by mass accretion from a companion star.  Although the census of accreting BHs is incomplete due to strong extinction of the optical flux of the companions, there must be many X-ray-quiet BHs of which only 2 or 3 (not uncontroversial) examples have been found to date.  This Informal Discussion will be about a hierarchical triple system with a BH in the inner binary.  Since the BH is not accreting, it is just very dull.  However, its relative proximity to Earth (~300 pc) suggests that it is only the tip of a (black) iceberg.  The two luminous components will not also undergo supernova (SN) explosions.  The system may nevertheless be a local example of an architecture sometimes invoked for some GW sources.  Orbital parameters may also give hints at the properties of the SN explosion. 
The underlying paper by Rivinius, Baade, Hadrava, Heida, and Klement appeared in A&A, 637, L3:
https://www.aanda.org/articles/aa/abs/2020/05/aa38020-20/aa38020-20.html

In this talk I will discuss the role played by quasars in the co-evolution of galaxies and black-holes and whether the diversity of quasar colours is explained solely by the AGN unification model or they represent different evolutionary stages. I will present a systematic study on the radio emission of SDSS quasars at low radio frequencies based on a synergy of the LOFAR deep field surveys and multi-wavelength surveys. Intriguingly, we find a large enhancement of radio detections in red quasars when compared to normal quasars and investigate their multi-wavelength SEDs and radio properties in order to characterise the origin of this difference. Our results, together with those from recent high-frequency radio studies, suggest the differences between red and blue quasars do not simply arise from viewing angle effects, but suggest an evolutionary origin.

This exploratory work studies the perception of professional astronomers about the societal impact of astronomy. Ten semi-structured interviews with astronomers from a range of career and cultural backgrounds have been conducted to gain in-depth insight into their opinion about societal impact and their approach in realising it. The results show that the interviewees are aware of the diversity of impacts that astronomical research has. However, they are mostly active in outreach and only a few activities are incorporated into their jobs to achieve an impact on development. There is little contact with stakeholders in industry, policy or other fields, like development. Besides, a structured approach in their personal outreach is lacking, and assessment is only done informally. Despite the limited sample size of this study, the results indicate that a further change is necessary to engage professional astronomers with topics of development and societal impact to create action on the level of individual researchers.

As so often in astronomy, the discovery of the first giant planet in a close orbit around a white dwarf was not the culmination of a carefully crafted master plan, but occurred serendipitously. I will summarise how an initial moment of bewilderment turned into an exciting detective story, and ultimately led to a consistent physical model of the current state, and past evolution of this giant planet. From there, it was only one step further to realise that signatures of giant planets surviving the post-main sequence evolution of their host stars are likely to be common - and will eventually be visible to alien astronomers studying the remains of the solar system.

Success in science correlates strongly with international (airplane) travel. This practice is increasingly at odds with the colleagues who study climate. In order to explore mechanisms to decrease professional air travel, we staged a CArbon REduced (CARE) conference. The CARE model is a hybrid virtual/live conference involving peripheral nuclei of attendees. We will use our conference format to address the issues that must be addressed to make CARE conferencing mainstream. One conclusion is that we will need to re-learn conferencing skills.

In times of crisis, it may help to look back. Inspired by the discussion at the Science Coffee last week, where the autobiographies of famous astronomers in Annual Reviews were mentioned, I decided to take a look at this peculiar literary genre. I found the reading enlightening, at times funny and at times
enraging. I hope to give you some example of what I mean by that. I have chosen to focus on three stories for you: those of James Gunn, Edwin Salpeter and Vera Rubin. The two old men were picked at random, just because they were mentioned at Science Coffee. Vera Rubin is Vera Rubin, so I am sure you will understand why I chose her.

Olivier Hainaut will give a short description of what is a satellite constellation and of why they are useful, then discuss of the current plans by satellite operators (SpaceX, Amazon, Samsung, and many others...). He will show some simulations of the effect on astronomical observations (from naked-eye to ELT), and quantify these effects.

Andrew Williamns will discuss the regulatory situation for these satellite operators, and discuss how the current international treaties could be expanded to protect the night sky.

The ELT telescope is under construction. In this informal discussion we offer a Question and Answer session on the telescope system. Do you have questions about how the primary mirror works, how the segments are made, the shape of the other mirrors, why is M4 deformable, what does M5 do, how many guide probes do we use, what is a phasing station, is the dome really that big, how much does the telescope weigh, how will we point the telescope? Or more?
 

The James Webb Space Telescope, also called Webb or JWST, is a large, space-based observatory, optimized for infrared wavelengths, which will complement and extend the discoveries of the Hubble Space Telescope. It launches in 2021.

It will cover longer wavelengths of light than Hubble and will have greatly improved sensitivity. The longer wavelengths enable JWST to look further back in time to see the first galaxies that formed in the early universe, and to peer inside dust clouds where stars and planetary systems are forming today." -- https://jwst.nasa.gov

In light of the upcoming proposal deadline of the first open call for proposals, I will give an overview about the general capabilities of JWST, its instruments and will give a live demonstration of the various tools (visibility calculator, exposure time calculator, astronomer's proposal tool) that are needed to prepare a JWST proposal.

I will also share some tips and tricks and lessons learnt from preparing our successful JWST Early Release Science Program Q3D (http://www.stsci.edu/jwst/observing-programs/approved-ers-programs/program-1335).

NOTE: Due to the current spread of COVID-19 ESO management decided to cancel all meetings with external participation until the end of March. As such this Informal Discussion will go ahead for ESO staff only.

Over the last decade,  surveys like the SDSS, DES, KiDS, VHS, AllWISE, The Two Micron All Sky Survey, The Sydney University Molonglo Sky Survey, etc, have provided new insights into the physics of objects on all scales from giants early-type galaxies (ETGs) to faint and compact stellar systems, and at all distances from the structure and dynamics of our own galaxy to high-redshift quasars.  

In this informal discussion,  I will start describing few particular scientific problems that can be solved by means of multi-band colors and magnitudes:  object classification, search for strongly lensed quasars, photometric redshifts calculation, identification of high-z galaxies or extremely red objects, focusing in particular on the first two.

I will demonstrate that a wide wavelength coverage is fundamental in these cases and thus introduce the VISTA EXtension to Auxiliary Surveys (VEXAS) project that aims at building the widest and deepest public optical-to-IR photometric and spectroscopic database in the southern hemisphere.

The most dramatic event in the course of a galaxy’s evolution is when it stops forming stars, or quenches. Besides that galaxies quench by internally-driven mechanisms, they also do so as a strong function of their environment - from sparsely populated voids to the densest galaxy clusters. Thanks to large surveys such as SDSS, we have obtained an increasingly clear picture of the particular role of environment in the quenching of galaxies. While this has led to an empirical model that has been successful in describing the basics of galaxy quenching in the local Universe, this model needs to be revised in the more distant (z>~1) Universe. I will first describe where we currently stand in our understanding of environmentally-driven quenching, and then highlight the challenges we face when confronted with data taken of the distant Universe.

In some pre-main-sequence stars such as T Tauri  stars, the short-wavelength (high-energy) flux is stronger than what is  predicted by the rest of the SED, which peaks longwards of the visible.  The most reliable explanation for this excess emission is that these young stars are still accreting from their  protoplanetary disk. Indeed, the release of gravitational energy lets  the accreting gas reach temperatures of 10^5 K or more, while keeping  the stellar photospheric temperature low.

Very recently, such high-energy excess photons from  planets were also detected, in part with high spectral resolution. These  observations are a precious clue to understanding the timescales of  planet formation and the geometry of the accretion.

Back in 2018, the interdisciplinary project "A Global Approach to the Gender Gap in Mathematical and Natural Sciences: How to Measure It, How to Reduce It?” launched a Joint Global Survey to learn about the educational and career paths of scientists and academics with a degree and/or a professional career in STEM. The survey collected more than 30,000 responses, from all over the world and from six different scientific disciplines. After a short introduction to the project, I will highlight and discuss the main results of the Joint Global Survey for the field of astronomy, and compare them to the other research fields and across geographical areas.

The vast majority of all stars, including virtually all known planet hosts (and our own Sun), will end their lives as white dwarfs: small and dense stellar embers.

Planetary system can survive the late evolution of their host star and remnants of these planets can be observed as pollutants in the otherwise pristine atmospheres of some white dwarfs. Spectroscopic observation and accurate modelling of these polluted white dwarf allows to study the bulk composition of rocky exo-planets, a property simply inaccessible by radial velocity and transit observations of planets around main sequence stars. 

I will give a brief overview of the state of the art of this promising field and present some recent exciting results.

First theorized roughly 50 years ago, I will give a brief introduction to the Sunyaev-Zeldovich (SZ) effect, which probe the warm and hot ionized gas in large scale structures at frequencies ~15-500 GHz.  I will then describe how ALMA and the ACA make extremely sensitive but fundamentally limited measurements of the SZ effect, and talk about ways we can improve this in the near future.

The early formation of supermassive black holes a billion years after the Big Bang is challenging our understanding of structure formation at Cosmic Dawn. The growth time for black holes is, indeed, relatively short, with an e-folding time scale of only 45 Myr when accreting at the Eddington limit. This implies that a black hole seed needs to maximally accrete for the entire Cosmic time to reach a mass >10^8 Msun by z~6. However, this is not the only timescale in play. In this presentation I will summarize results from our 3D pan-chromatic view of the first quasars (capitalizing on ALMA, XSHOOTER, and MUSE data) and provide some pencil and paper (or better, chalk and blackboard) estimates on the relevant timescales connecting the inter- and circum-galactic medium, the quasar host galaxy, and the accretion of the central black holes in the most massive galaxies at the dawn of the Universe.