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.

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Issue 179
Messenger Issue 179

The Messenger Issue 179

Highlights include:

  • Rix, H.: The 2018 Visiting Committee Report
  • Vernazza, P., Jorda, L. et al.: SPHERE Unveils the True Face of the Largest Main Belt Asteroids
  • Aravena, M., Carilli, C. et al.: The ASPECS Survey: An ALMA Large Programme Targeting the Hubble Ultra-Deep Field

Read the full PDF

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Messenger Issue 191
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2022Issue 188
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2022Issue 187
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Messenger Issue 178
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Table of Content No. 179 | 2020
The Organisation
Rix, H.
The 2018 Visiting Committee Report
ADS BibCode: 2020Msngr.179....3R
Rix, H.
ESO’s activities are externally assessed every few years by a Visiting Committee composed of a panel of senior external experts who report their findings to the ESO Council and Director General. The assessment is based on an extensive set of presentations, reports and interviews with ESO staff conducted during visits to all ESO sites. Here we summarise the report and recommendations produced as a result of the latest Visiting Committee assessment, which took place at the end of 2018 and was presented to the ESO Council in June 2019.

Barcons, X.
Following Up on the Recommendations of the Visiting Committee
ADS BibCode: 2020Msngr.179....5B
Barcons, X.
Like most scientific organisations, ESO periodically invites advice from an external expert panel that assesses the performance of the Organisation, and formulates a number of recommendations. The most recent ESO Visiting Committee travelled to all of the ESO sites in the last months of 2018 and delivered its report to Council in June 2019. The committee, whose composition and mandate had been approved by ESO Council, was constituted by a set of internationally renowned scientists who possess complementary areas of expertise covering all aspects of ESO’s function. I am extremely grateful to all committee members for their hard work and very careful preparation of their report. An extract of the main conclusions and recommendations is presented in the preceding article.

Telescopes and Instrumentation
Schmidtobreick, L., Ageorges, N. et al.
NaCo — The Story of a Lifetime
ADS BibCode: 2020Msngr.179....7S
Schmidtobreick, L., Ageorges, N., Amico, P., Brandner, W., Cerda, S., Cid, C., Close, L., Garces, E., Gillet, G., Girard, J., Guajardo, P., Hau, G., Hummel, W., Jung, Y., Kasper, M., Lidman, C., Lundin, L., Mardones, P., Mawet, D., O’Neal, J., Pompei, E., Schmutzer, R., Silva, K., Smoker, J., Soenke, C., Tacconi-Garman, L., Valenti, E., Valenzuela, J., Velasquez, J., Zins, G.
NaCo was switched off on 2 October 2019, almost 18 years after its first light. The last exposure was of the standard star HD590 as part of the close-out calibrations. To date, 699 papers have been published using NaCo data, including observations of the Galactic centre, direct images of exoplanets orbiting their stars, young stellar objects, brown dwarfs, massive stars, stellar clusters, Solar System objects, SN 1987A and several extragalactic sources. We present a short history of the life and achievements of NaCo from the viewpoint of the Instrument Operation Team, Instrument Scientists, and Instrument Engineers.

Astronomical Science
Vernazza, P., Jorda, L. et al.
SPHERE Unveils the True Face of the Largest Main Belt Asteroids
ADS BibCode: 2020Msngr.179...13V
Vernazza, P., Jorda, L., Carry, B., Hanuš, J., Marsset, M., Viikinkoski, M., Marchis, F., Brož, M., Drouard, A., Fusco, T., Fétick, R., Ferrais, M., HARISSA team
Over the past 2.5 years, we have been carrying out disc-resolved observations of a substantial fraction of all large (D > 100 km) main-belt asteroids, monitoring them at high angular resolution throughout their rotation, and sampling the main compositional classes, using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on the VLT. These observations enable us to characterise the internal structure of our targets from their density as well as their cratering record down to ~ 30 km in diameter. Such information, in turn, places unprecedented constraints on models of the formation of the Solar System and the collisional evolution of the main belt.

Aravena, M., Carilli, C. et al.
The ASPECS Survey: An ALMA Large Programme Targeting the Hubble Ultra-Deep Field
ADS BibCode: 2020Msngr.179...17A
Aravena, M., Carilli, C., Decarli, R., Walter, F., ASPECS collaboration
The ALMA Large Programme ASPECS (The ALMA SPECtroscopic Survey in the UDF) set out to measure the dust and molecular gas content in distant galaxies in the best-studied cosmological deep field, the Hubble Ultra-Deep Field (UDF). Thanks to a unique observing technique, the survey resulted in a full census of gas-rich galaxies in the UDF, yielding dozens of detections in dust continuum and molecular gas emission. Their physical properties could be accurately constrained thanks to the unparalleled wealth of ancillary data, including the most sensitive Hubble Space Telescope (HST) and VLT/MUSE observations. The data confirm that, on average, the gas mass fractions of distant galaxies decreased by an order of magnitude since redshift 2, and that the gas depletion times are ~ 1 Gyr, in approximate agreement with the local value. The ASPECS deep Band 6 continuum map of the field shows that more than 90% of the dust continuum emission in the field has been resolved in individual galaxies. The total CO emission in this well defined cosmological volume is used to constrain the evolution of the cosmic molecular gas density. Together with previous measurements of the evolution of the cosmic densities of stellar mass, star formation rate and atomic gas, these measurements provide quantitative constraints of the gas accretion rate onto the central discs of galaxies.

Pietrzyński, G., Graczyk, D. et al.
The Araucaria Project Establishes the Most Precise Benchmark for Cosmic Distances
ADS BibCode: 2020Msngr.179...24P
Pietrzyński, G., Graczyk, D., Gallenne, A., Gieren, W., Thompson, I., Pilecki, B., Karczmarek, P., Górski, M., Suchomska, K., Taormina, M., Zgirski, B., Wielgórski, P., Nardetto, N., Kervella, P., Bresolin, F., Kudritzki, R., Storm, J., Smolec, R., Narloch, W., Kałuszyński, M., Villanova, S.
In the last 20 years, over the course of the Araucaria project, we have studied 20 very special eclipsing binary systems in the Large Magellanic Cloud (LMC). Based on these systems and our newly calibrated surface brightness–colour relation we have measured a distance to the LMC that is accurate to 1%. This is currently the best benchmark for cosmic distances and it will therefore impact several fields of astrophysics. In particular, it has allowed a determination of the Hubble constant with a precision of 1.9%.

Astronomical News
Patat, F., Primas, F. et al.
ESO’s Peer Review Panel Achieves Gender Balance
ADS BibCode: 2020Msngr.179...30P
Patat, F., Primas, F., Cristiani, S., Gadotti, D., Hoppe, E.
Gender equality, diversity and inclusion are very high on ESO’s agenda, and the organisation has undertaken a number of initiatives in these areas over the past decade (Primas, 2019). The reasons behind these actions are not limited to addressing the issue internally; ESO also aims to raise awareness, with the aim of setting high standards that will motivate members of the scientific community, and hopefully beyond. A diverse and inclusive environment constitutes the most favourable terrain for the growth of ideas, creativity, and the development of original projects — key drivers of success. References Carpenter, J. 2020, PASP, 132, 4503 Patat, F. 2016, The Messenger, 165, 2 Primas, F. 2019, Nature Astronomy, 3, 1075 Reid, I. N. 2014, PASP, 126, 923

Saviane, I., Zoccali, M. et al.
Report on the ESO Workshop "The Galactic Bulge at the Crossroads"
ADS BibCode: 2020Msngr.179...31S
Saviane, I., Zoccali, M., Minniti, D., Geisler, D., Dias, B.
The Galactic bulge is of great interest to researchers working in several different areas and it has seen a surge of interest in recent years; indeed, half of the papers discussed at the meeting were published after 2014. This interest is motivated for several reasons: it is a primary component of the Milky Way, comprising ~ 25% of its stellar mass; and all major stellar populations intersect there, reaching their highest densities, thus making it truly a crossroads. Its formation is intimately related to that of the Milky Way, therefore it offers clues to understanding the structure, formation, and evolution of the Galaxy. A variety of bulge morphologies are seen in the local Universe, so a comparative study of the properties of the Galactic bulge helps with understanding bulge formation in general. Finally, ever more detailed studies of galaxies at high redshift promise to catch Milky Way proxies in their infancy, thus revealing the initial conditions of bulge formation. All of these aspects were reviewed by invited and contributed talks, and in poster sessions.

Saviane, I., Leibundgut, B. et al.
Report on the ESO Workshop "The La Silla Observatory — From Inauguration to the Future"
ADS BibCode: 2020Msngr.179...36S
Saviane, I., Leibundgut, B., Schmidtobreick, L.
This five-day workshop celebrated the achievements of ESO’s first observatory, La Silla, on the occasion of its 50th anniversary. La Silla, officially inaugurated on 25 March 1969, was the culmination of the vision of European astronomers to create a major observatory in the southern hemisphere. In the following decades, La Silla served as a testbed enabling the development of scientific, technical and operational expertise in the European astronomical community, establishing communication channels with the public at large, and working to increase interaction and collaboration with the host country Chile as well as with other astronomical facilities in the Andes mountains. Today, La Silla continues to serve as a superb site hosting the ESO 3.6-metre and NTT telescopes, as well as a number of community-led experiments.

Belfiore, F., Thomas, R. et al.
Fellows at ESO
ADS BibCode: 2020Msngr.179...41E
Belfiore, F., Thomas, R., Navarrete, C.

Personnel Movements
ADS BibCode: 2020Msngr.179...44E