European
Southern
Observatory

The Messenger

The Messenger is ESO’s journal for science and technology. It serves as a link between ESO and its broad astronomical community by providing information about scientific, technical, and other developments. It also delivers relevant news about astronomy and astrophysics to a broader public, including policy-makers, government officials, journalists, teachers, and amateur astronomers, as well as to interested scientists from other fields.

The Messenger is published twice per year and is available for free download as a PDF here and via the digital publishing platform Scribd.

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Issue 178
Messenger Issue 178

The Messenger Issue 178

Highlights include:

  • Vernet, E., Cirasuolo, M. et al.: ELT M4 — The Largest Adaptive Mirror Ever Built
  • GRAVITY Collaboration, Abuter, R. et al.: Spatially Resolving the Quasar Broad Emission Line Region
  • GRAVITY Collaboration: GRAVITY and the Galactic Centre
  • Wittkowski, M., Bladh, S. et al.: Precision Monitoring of Cool Evolved Stars: Constraining Effects of Convection and Pulsation
  • Davies, C., Hone, E. et al.: Spatially Resolving the Innermost Regions of the Accretion Discs of Young, Low-Mass Stars with GRAVITY
  • Dong, S., Mérand, A. et al.: When the Stars Align — the First Resolved Microlensed Images
  • GRAVITY Collaboration: Hunting Exoplanets with Single-Mode Optical Interferometry
  • Manara, C., Harrison, C. et al.: The ESO Summer Research Programme 2019

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Table of Content No. 178 | 2019
Telescopes and Instrumentation
Vernet, E., Cirasuolo, M. et al.
ELT M4 — The Largest Adaptive Mirror Ever Built
More...
ADS BibCode: 2019Msngr.178....3V
Authors:
Vernet, E., Cirasuolo, M., Cayrel, M., Tamai, R., Kellerer, A., Pettazzi, L., Lilley, P., Zuluaga, P., Diaz Cano, C., Koehler, B., Biancat Marchet, F., Gonzalez, J., Tuti, M., The ELT Team
Abstract:
The Extremely Large Telescope (ELT) is at the core of ESO’s vision to deliver the largest optical and infrared telescope in the world. Continuing our series of Messenger articles describing the optical elements of the ELT, we focus here on the quaternary mirror (M4), a true technological wonder; it is the largest deformable mirror ever made. In combination with M5, M4 is vital to delivering the sharp (diffraction-limited) images needed for science by correcting for atmospheric turbulence and the vibrations of the telescope itself. Here we describe the main characteristics of M4, the challenges and complexity involved in the production of this unique adaptive mirror, and its manufacturing status.

Kasper, M., Arsenault, R. et al.
NEAR: First Results from the Search for Low-Mass Planets in α Cen
More...
ADS BibCode: 2019Msngr.178....5K
Authors:
Kasper, M., Arsenault, R., Käufl, U., Jakob, G., Leveratto, S., Zins, G., Pantin, E., Duhoux, P., Riquelme, M., Kirchbauer, J., Kolb, J., Pathak, P., Siebenmorgen, R., Soenke, C., Fuenteseca, E., Sterzik, M., Ageorges, N., Gutruf, S., Kampf, D., Reutlinger, A., Absil, O., Delacroix, C., Maire, A., Huby, E., Guyon, O., Klupar, P., Mawet, D., Ruane, G., Karlsson, M., Dohlen, K., Vigan, A., N’Diaye, M., Quanz, S., Carlotti, A.
Abstract:
ESO, in collaboration with the Breakthrough Initiatives, has modified the VLT mid-infrared imager VISIR to greatly enhance its ability as a planet finder. It has conducted a 100-hour observing campaign to search for low-mass planets around both components of the binary a Centauri, part of the closest stellar system to the Earth. Using adaptive optics and high-performance coronagraphy, the instrument reached unprecedented contrast and sensitivity allowing it to see Neptune-sized planets in the habitable zone, if present. The experiment allowed us to characterise the current limitations of the instrument. We conclude that the detection of rocky planets similar to Earth in the habitable zone of the a Centauri System is already possible with 8-metre-class telescopes in the thermal infrared.

Arnaboldi, M., Delmotte, N. et al.
Report on Status of ESO Public Surveys and Current Activities
More...
ADS BibCode: 2019Msngr.178...10A
Authors:
Arnaboldi, M., Delmotte, N., Gadotti, D., Hilker, M., Hussain, G., Mascetti, L., Micol, A., Petr-Gotzens, M., Rejkuba, M., Retzlaff, J., Spiniello, C., Leibundgut, B., Romaniello, M.
Abstract:
This report on the status of the ESO Public Surveys includes a brief overview of their legacy value and scientific impact. Their legacy is ensured by their homogeneity, sensitivity, large sky coverage in multiple filters, large number of targets, wavelength coverage and spectral resolution, which make them useful for the community at large, extending beyond the scientific goals identified by the survey teams. In May 2019, as almost all first-generation imaging and spectroscopic surveys completed their observations and second- generation imaging surveys got well underway, the Public Survey Panel reviewed the scientific impact of these projects. The review was based on a quantitative assessment of the number of refereed publications from the survey teams and archive users. It included the number of citations, the number of data releases and statistics on access to archive data by the user community. The ESO Users Committee also discussed the availability and usage of ESO Public Survey data by the community during their yearly meeting in April 2019. We describe the status of these projects with respect to their observing plans, highlight the most recent data releases and provide links to the resulting science data products.

Ivanov, V., Coccato, L. et al.
MUSE Spectral Library
More...
ADS BibCode: 2019Msngr.178...17I
Authors:
Ivanov, V., Coccato, L., Neeser, M., Selman, F., Pizzella, A., Dalla Bontà, E., Corsini, E., Morelli, L.
Abstract:
Empirical stellar spectral libraries have applications in both extragalactic and stellar studies. We have assembled the MUSE Spectral Library (MSL), consisting of 35 high-quality spectra of stars covering the Hertzsprung–Russell diagram, and verified the continuum shape of our spectra with synthetic broadband colours. We also report indices from the Lick system, derived from the new observations. Our data demonstrate that integral field units (IFUs) are excellent tools for building spectral libraries with reliable continuum shapes that can be used as templates for extragalactic studies.

GRAVITY Science
GRAVITY Collaboration, Abuter, R. et al.
Spatially Resolving the Quasar Broad Emission Line Region
More...
ADS BibCode: 2019Msngr.178...20A
Authors:
GRAVITY Collaboration, Abuter, R., Accardo, M., Adler, T., Amorim, A., Anugu, N., Ávila, G., Bauböck, M., Benisty, M., Berger, J., Bestenlehner, J., Beust, H., Blind, N., Bonnefoy, M., Bonnet, H., Bourget, P., Bouvier, J., Brandner, W., Brast, R., Buron, A., Burtscher, L., Cantalloube, F., Caratti o Garatti, A., Caselli, P., Cassaing, F., Chapron, F., Charnay, B., Choquet, É., Clénet, Y., Collin, C., Coudé du Foresto, V., Davies, R., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., de Wit, W., Dexter, J., de Zeeuw, T., Dougados, C., Dubus, G., Duvert, G., Ebert, M., Eckart, A., Eisenhauer, F., Esselborn, M., Eupen, F., Fédou, P., Ferreira, M., Finger, G., Förster Schreiber, N., Gao, F., García Dabó, C., Garcia Lopez, R., Garcia, P., Gendron, É., Genzel, R., Gerhard, O., Gil, J., Gillessen, S., Gonté, F., Gordo, P., Gratadour, D., Greenbaum, A., Grellmann, R., Grözinger, U., Guajardo, P., Guieu, S., Habibi, M., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Hönig, S., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Hummel, C., Jakob, G., Janssen, A., Jimenez Rosales, A., Jochum, L., Jocou, L., Kammerer, J., Karl, M., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Kishimoto, M., Klarmann, L., Klein, R., Köhler, R., Kok, Y., Kolb, J., Koutoulaki, M., Kulas, M., Labadie, L., Lacour, S., Lagrange, A., Lapeyrère, V., Laun, W., Lazareff, B., Le Bouquin, J., Léna, P., Lenzen, R., Lévêque, S., Lin, C., Lippa, M., Lutz, D., Magnard, Y., Maire, A., Mehrgan, L., Mérand, A., Millour, F., Mollière, P., Moulin, T., Müller, A., Müller, E., Müller, F., Netzer, H., Neumann, U., Nowak, M., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Peterson, B., Petrucci, P., Pflüger, A., Pfuhl, O., Phan Duc, T., Pineda, J., Plewa, P., Popovic, D., Pott, J., Prieto, A., Pueyo, L., Rabien, S., Ramírez, A., Ramos, J., Rau, C., Ray, T., Riquelme, M., Rodríguez-Coira, G., Rohloff, R., Rouan, D., Rousset, G., Sanchez-Bermudez, J., Schartmann, M., Scheithauer, S., Schöller, M., Schuhler, N., Segura-Cox, D., Shangguan, J., Shimizu, T., Spyromilio, J., Sternberg, A., Stock, M., Straub, O., Straubmeier, C., Sturm, E., Suárez Valles, M., Tacconi, L., Thi, W., Tristram, K., Valenzuela, J., van Boekel, R., van Dishoeck, E., Vermot, P., Vincent, F., von Fellenberg, S., Waisberg, I., Wang, J., Wank, I., Weber, J., Weigelt, G., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yang, P., Yazici, S., Ziegler, D., Zins, G.
Abstract:
The angular resolution of the Very Large Telescope Interferometer (VLTI) and the excellent sensitivity of GRAVITY have led to the first detection of spatially resolved kinematics of high velocity atomic gas near an accreting super- massive black hole, revealing rotation on sub-parsec scales in the quasar 3C 273 at a distance of 550 Mpc. The observations can be explained as the result of circular orbits in a thick disc configuration around a 300 million solar mass black hole. Within an ongoing Large Programme, this capability will be used to study the kinematics of atomic gas and its relation to hot dust in a sample of quasars and Seyfert galaxies. We will measure a new radius-luminosity relation from spatially resolved data and test the current methods used to measure black hole mass in large surveys.

GRAVITY Collaboration
An Image of the Dust Sublimation Region in the Nucleus of NGC 1068
More...
ADS BibCode: 2019Msngr.178...24E
Authors:
GRAVITY Collaboration
Abstract:
The superb resolution of the Very Large Telescope Interferometer (VLTI) and the unrivalled sensitivity of GRAVITY have allowed us to reconstruct the first detailed image of the dust sublimation region in an active galaxy. In the nearby archetypal Seyfert 2 galaxy NGC 1068, the 2 µm continuum emission traces a highly inclined thin ring-like structure with a radius of 0.24 pc. The observed morphology challenges the picture of a geometrically and optically thick torus.

GRAVITY Collaboration
GRAVITY and the Galactic Centre
More...
ADS BibCode: 2019Msngr.178...26E
Authors:
GRAVITY Collaboration
Abstract:
On a clear night, our home galaxy, the Milky Way, is visible as a starry ribbon across the sky. Its core is located in the constellation of Sagittarius, approximately where the bright glow is interrupted by the darkest dust filaments. There, hidden, lies a massive black hole. To peer through the obscuring clouds and see the stars and gas near the black hole we use GRAVITY. The main GRAVITY results are the detection of gra- vitational redshift, the most precise mass- distance measurement, the test of the equivalence principle, and the detection of orbital motion near the black hole.

GRAVITY Collaboration
Spatially Resolved Accretion-Ejection in Compact Binaries with GRAVITY
More...
ADS BibCode: 2019Msngr.178...29E
Authors:
GRAVITY Collaboration
Abstract:
The GRAVITY instrument at the Very Large Telescope Interferometer has led to the first spatially resolved observations of X-ray binaries at scales comparable to the binary orbit, providing unprecedented spatial information on their accretion-ejection mechanisms. In particular, observations of the hypercritical accretor SS433 have revealed a variety of spatial structures at the heart of this exotic microquasar, including bipolar outflows, super-Keplerian equatorial outflows and extended baryonic jets photoionised by collimated ultraviolet radiation.

GRAVITY Collaboration
Images at the Highest Angular Resolution with GRAVITY: The Case of η Carinae
More...
ADS BibCode: 2019Msngr.178...31E
Authors:
GRAVITY Collaboration
Abstract:
The main goal of an interferometer is to probe the physics of astronomical objects at the highest possible angular resolution. The most intuitive way of doing this is by reconstructing images from the interferometric data. GRAVITY at the Very Large Telescope Interferometer (VLTI) has proven to be a fantastic instrument in this endeavour. In this article, we describe the reconstruction of the wind-wind collision cavity of the massive binary η Car with GRAVITY across two spectral lines: HeI and Brγ.

Wittkowski, M., Bladh, S. et al.
Precision Monitoring of Cool Evolved Stars: Constraining Effects of Convection and Pulsation
More...
ADS BibCode: 2019Msngr.178...34W
Authors:
Wittkowski, M., Bladh, S., Chiavassa, A., de Wit, W., Eriksson, K., Freytag, B., Haubois, X., Höfner, S., Kravchenko, K., Paladini, C., Paumard, T., Rau, G., Wood, P.
Abstract:
Mass loss from cool evolved stars is an important ingredient of the cosmic matter cycle, enriching the Universe with newly formed elements and dust. However, physical processes that are not considered in current models represent uncertainties in our general understanding of mass loss. Time-series of interferometric data provide the strongest tests of dynamical processes in the atmospheres of these stars. Here, we present a pilot study of such measurements obtained with the GRAVITY instrument on the Very Large Telescope Interferometer.

GRAVITY Collaboration
Multiple Star Systems in the Orion Nebula
More...
ADS BibCode: 2019Msngr.178...36E
Authors:
GRAVITY Collaboration
Abstract:
GRAVITY observations reveal that most massive stars in the Orion Trapezium cluster live in multiple systems. Our deep, milliarcsecond-resolution interferometry fills the gap at 1–100 astronomical units (au), which is not accessible to traditional imaging and spectroscopy, but is crucial to uncovering the mystery of high-mass star formation.The new observations find a significantly higher companion fraction than earlier studies of mostly OB associations. The observed distribution of mass ratios declines steeply with mass and follows a Salpeter power-law initial mass function. The observations therefore exclude stellar mergers as the dominant formation mechanism for massive stars in Orion.

GRAVITY Collaboration
Probing the Discs of Herbig Ae/Be Stars at Terrestrial Orbits
More...
ADS BibCode: 2019Msngr.178...38E
Authors:
GRAVITY Collaboration
Abstract:
More than 4000 exoplanets are known to date in systems that differ greatly from our Solar System. In particular, inner exoplanets tend to follow orbits around their parent star that are much more compact than that of Earth. These systems are also extremely diverse, covering a range of intrinsic properties. Studying the main physi- cal processes at play in the innermost regions of the protoplanetary discs is crucial to understanding how these planets form and migrate so close to their host. With GRAVITY, we focused on the study of near-infrared emission of a sample of young intermediate- mass stars, the Herbig Ae/Be stars.

GRAVITY Collaboration
Spatially Resolving the Inner Gaseous Disc of the Herbig Star 51 Oph through its CO Ro-vibration Emission
More...
ADS BibCode: 2019Msngr.178...40E
Authors:
GRAVITY Collaboration
Abstract:
Near-infrared interferometry gives us the opportunity to spatially resolve the circumstellar environment of young stars at sub-astronomical-unit (au) scales, which a standalone telescope could not reach. In particular, the sensitivity of GRAVITY on the VLTI allows us to spatially resolve the CO overtone emission at 2.3 microns. In this article, we present a new method of using the model of the CO spectrum to reconstruct the differential phase signal and extract the geometry and size of the emitting region.

Davies, C., Hone, E. et al.
Spatially Resolving the Innermost Regions of the Accretion Discs of Young, Low-Mass Stars with GRAVITY
More...
ADS BibCode: 2019Msngr.178...43D
Authors:
Davies, C., Hone, E., Kluska, J., Kreplin, A.
Abstract:
Low-mass, young stars — the T Tauri stars — make up the majority of young stellar objects. They have been relatively unexplored with optical long baseline interferometry owing to the cooler temperatures of their stellar photospheres which makes them fainter and more compact than the more frequently studied intermediate mass, young stars — the Herbig Ae/Be stars. With its greater flux sensitivity, GRAVITY has allowed us to explore T Tauri stars at high angular resolution in unprecedented detail. Here we present highlights from two such studies.

Dong, S., Mérand, A. et al.
When the Stars Align — the First Resolved Microlensed Images
More...
ADS BibCode: 2019Msngr.178...45D
Authors:
Dong, S., Mérand, A., Delplancke-Ströbele, F., Gould, A., Zang, W.
Abstract:
Using GRAVITY, we have resolved the two images of a microlensed source star for the first time, more than a century after Einstein first predicted that such image splitting could be caused by the gravity of another (lens) star along the line of sight to the source. We have measured the angular Einstein radius (almost exactly half the image separation) to be 1.87 milliarcseconds, with a precision of just 30 microarcseconds. The measurement also yields the direction of the relative motion of the lens with respect to the source. These results, combined with other, so-called microlens parallax measurements, yield the lens mass and distance. While this lens is an ordinary luminous star, the same technique could be applied in the future to measure the mass and distance of completely dark objects, such a black hole. In fact, while black holes in binaries have been found from X-ray and LIGO gravitational-wave observations, and are likely to be found in the future by Gaia astrometry, gravitational microlensing is the only known way to find isolated black holes. Our detection using GRAVITY on the VLTI opens the path to such measurements of isolated black hole masses.

GRAVITY Collaboration
Hunting Exoplanets with Single-Mode Optical Interferometry
More...
ADS BibCode: 2019Msngr.178...47E
Authors:
GRAVITY Collaboration
Abstract:
The GRAVITY instrument was primarily conceived for imaging and astrometry of the Galactic centre. However, its sensitivity and astrometric capabilities have also enabled interferometry to reach a new domain of astrophysics: exoplanetology. In March 2019, the GRAVITY collaboration published the first spectrum and astrometry of an exoplanet obtained by optical interferometry. In this article, we show how this observation is paving the way to even more exciting discoveries — finding new planets, and characterising their atmospheres.

Astronomical News
Christensen, L., Horálek, P.
Light Phenomena Over ESO’s Observatories IV: Dusk and Dawn
More...
ADS BibCode: 2019Msngr.178...51C
Authors:
Christensen, L., Horálek, P.
Abstract:
Several interesting atmospheric phenomena take place during dusk and dawn, associated with the setting and rising of the Sun and Moon. Here, the most important of these are discussed in the context of ESO observing sites. This is the fourth article in a series about a range of light phenomena that can be experienced at ESO observatories

Manara, C., Harrison, C. et al.
The ESO Summer Research Programme 2019
More...
ADS BibCode: 2019Msngr.178...57M
Authors:
Manara, C., Harrison, C., Zanella, A., Agliozzo, C., Anderson, R., Arrigoni Battaia, F., Belfiore, F., van der Burg, R., Chen, C., Facchini, S., Fensch, J., Jethwa, P., Kokotanekova, R., Lelli, F., Miotello, A., Pala, A., Querejeta, M., Rubin, A., Wylezalek, D., Watkins, L.
Abstract:
For the first time ever, a summer research programme was organised at ESO Garching. Seven students, enrolled in universities all around the world, were selected from more than 300 applicants. They each spent six weeks from June to August 2019 carrying out a scientific project under the supervision of teams of ESO Fellows and postdocs, while engaging in the scientific life of ESO. The students carried out research in different fields of astronomy, from comets to high-redshift galaxies and from pulsating stars to protoplanetary discs. In this report we present the programme and describe the main outcomes of the projects.

Boffin, H., Jerabkova, T. et al.
Report on the ESO Workshop "Artificial Intelligence in Astronomy"
More...
ADS BibCode: 2019Msngr.178...61B
Authors:
Boffin, H., Jerabkova, T., Mérand, A., Stoehr, F.
Abstract:
In July 2019, ESO hosted one of the first international workshops on artificial intelligence in astronomy, with the double aims of presenting the current landscape of methods and applications in astronomy and preparing the next generations of astronomers to embark on these fields. In addition to a wide range of review and contributed talks, as well as posters, the ~ 150 attendees could learn the techniques through several dedicated tutorials.

Vieser, W., Johnston, T. et al.
Report on the IAU Conference "Astronomy Education — Bridging Research & Practice"
More...
ADS BibCode: 2019Msngr.178...63V
Authors:
Vieser, W., Johnston, T., Salimpour, S.
Abstract:
Astronomy education contributes to the spread of scientific literacy among successive generations, helping to attract students into science, technology, engineering and mathematics (STEM) subjects and potentially also into astronomy research. Although the field of research into astronomy education has grown significantly, the sustainable transfer from research institutes into the classroom is lacking. The goal of this conference was to bring together all stakeholders — teachers, educators and researchers — to communicate and discuss their various needs in order to effectively bridge the gap between astronomy education research and its practical application.

Kokotanekova, R., Facchini, S. et al.
Fellows at ESO
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ADS BibCode: 2019Msngr.178...67E
Authors:
Kokotanekova, R., Facchini, S., Hartke, J.

ESO
In Memoriam Cristian Herrera González
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ADS BibCode: 2019Msngr.178...70E
Authors:
ESO

ESO
Personnel Movements
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ADS BibCode: 2019Msngr.178...71E
Authors:
ESO

Patat, F.
Erratum: The Distributed Peer Review Experiment
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ADS BibCode: 2019Msngr.178Q..71E
Authors:
Patat, F.