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 172
Messenger Issue 172

The Messenger Issue 172

Highlights include:

  • Romaniello, M., Zampieri, S. et al.: Enhanced Data Discovery Services for the ESO Science Archive
  • Leibundgut, B., Hibon, P. et al.: HAWK-I/GRAAL Science Verification
  • Zhang, Z., Romano, D. et al.: ALMA Constrains the Stellar Initial Mass Function of Dusty Starburst Galaxies
  • Wittkowski, M., Humphreys, L.: Report on the ESO Workshop "Imaging of Stellar Surfaces"

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Past Issues
Messenger Issue 192
2024Issue 192
Messenger Issue 191
2023Issue 191
Messenger Issue 190
2023Issue 190
Messenger Issue 189
2022Issue 189
Messenger Issue 188
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Messenger Issue 187
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2018Issue 174
Messenger Issue 173
2018Issue 173
Table of Content No. 172 | 2018
Telescopes and Instrumentation
Romaniello, M., Zampieri, S. et al.
Enhanced Data Discovery Services for the ESO Science Archive
ADS BibCode: 2018Msngr.172....2R
Romaniello, M., Zampieri, S., Delmotte, N., Forchì, V., Hainaut, O., Micol, A., Retzlaff, J., Vera, I., Fourniol, N., Khan, M., Lange, U., Sisodia, D., Stellert, M., Stoehr, F., Arnaboldi, M., Spiniello, C., Mascetti, L., Sterzik, M.
The archive of the La Silla Paranal Observatory is a powerful scientific resource for the ESO astronomical community. It stores both the raw data generated by all ESO instruments and selected processed data. We present new capabilities and user services that have recently been developed in order to enhance data discovery and usage in the face of the increasing volume and complexity of the archive holdings. Future plans to extend the new services to processed data from the Atacama Large Millimeter/submillimeter Array (ALMA) are also discussed.

Leibundgut, B., Hibon, P. et al.
HAWK-I/GRAAL Science Verification
ADS BibCode: 2018Msngr.172....8L
Leibundgut, B., Hibon, P., Kuntschner, H., Opitom, C., Paufique, J., Petr-Gotzens, M., Siebenmorgen, R., Valenti, E., Zanella, A.
Science Verification observations with the High Acuity Wide field K-band Imager (HAWK-I) instrument enhanced by the ground-layer adaptive optics module (GRAAL) were obtained during 4.5 nights from 2 to 6 January 2018. Fourteen projects were selected from a total of 19 submitted proposals. The total time scheduled for these 14 projects was 35.5 hours, which represents a slight oversubscription for the four allocated summer nights. The seven top- ranked projects were completed, three more programmes received some data, one was observed outside the requested constraints, and three projects were not started. The Science Verification nights were affected by various technical problems, mostly unrelated to GRAAL, which resulted in a total loss of 10 hours. Half a night was allocated on 6 January to compensate for some of the lost time. The atmospheric conditions were rather variable with occasionally excellent natural seeing (0.3 arcseconds). The ground layer turbulence fraction varied from 40% to 85% during these nights. The best performance in terms of improved image quality was observed when the ground layer fraction was above 70%, as expected for the system. The image quality in the K filter ranged between 0.2 arcseconds (in excellent conditions) to about 0.5 arcseconds (with mediocre seeing, > 0.8 arcseconds), and a small fraction of ground-layer turbulence. The delivered image quality was very stable, but in some cases an asymmetric point spread function was observed.

Astronomical Science
Zhang, Z., Romano, D. et al.
ALMA Constrains the Stellar Initial Mass Function of Dusty Starburst Galaxies
ADS BibCode: 2018Msngr.172...14Z
Zhang, Z., Romano, D., Ivison, R., Papadopoulos, P., Matteucci, F.
The stellar initial mass function (IMF) is fundamental to all measurements of cosmic star formation, which involves an extrapolation from rare, massive stars (M∗ > 8 M) to the full stellar mass spectrum. Classical determinations of a galaxy’s IMF are limited to ultraviolet, optical and near-infrared wavelengths, and these cannot be adopted for dust- obscured galaxies with intense, ongoing star formation, even in the local Universe. The unprecedented sensi- tivity of the Atacama Large Millimeter/submillimeter Array (ALMA) allows us to detect weak emission from 13CO and C18O isotopologues, which offer a sensitive, relatively dust-free, probe of the IMF. Globally low 13CO/C18O ratios for all our targets — dusty starburst galaxies at redshifts ~ 2–3 — alongside a detailed chemical evolution model imply that stars formed in extreme starburst environments are significantly biased towards massive stars compared to ordinary star-forming spiral galaxies. We have combined information from the coldest interstellar medium (at tens of Kelvins) with the physics of nucleosynthesis in hot stars (at tens of millions of Kelvins), to delineate the formation and evolution of galaxies. This opens up a new window to probe the stellar IMF of galaxies with ALMA and it challenges our understanding of fundamental parameters governing galaxy formation and evolution, such as star formation rates, and the timescales for gas depletion and dust formation.

Ferraro, F., Mucciarelli, A. et al.
MIKiS: the ESO-VLT Multi-Instrument Kinematic Survey of Galactic Globular Clusters
ADS BibCode: 2018Msngr.172...18F
Ferraro, F., Mucciarelli, A., Lanzoni, B., Pallanca, C., Origlia, L., Lapenna, E., Dalessandro, E., Valenti, E., Beccari, G., Bellazzini, M., Vesperini, E., Varri, A., Sollima, A.
Globular clusters are collisional systems, where stars of different masses orbit and mutually interact. They are the best “natural laboratories” in the Universe for studying multi-body dynamics and their (reciprocal) effects on stellar evolution. Although these objects have been studied since the very beginning of modern astrophysics, little is known observationally about their internal kinematics, thus preventing a complete understanding of their dynamical state, and of their formation and evolutionary history. We present the first results from the Very Large Telescope (VLT) Multi- Instrument Kinematic Survey of Galactic globular clusters (MIKiS), which is specifically designed to provide line-of-sight velocities of hundreds of individual stars over the entire radial extension of a selected sample of clusters. The survey allows the first kinematical exploration of the innermost regions of high-density globular clusters. When combined with proper motion measurements, it will provide the full 3D view in velocity-space for each system. Long- running open issues, such as the accurate shapes of the velocity dispersion profiles, the existence of systemic rotation and orbital anisotropy (and thus the level of relaxation), and the controversial presence of intermediate-mass black holes in star clusters can finally be addressed, impacting our understanding of the formation and evolutionary processes of globular clusters and their interactions with the Galactic tidal field.

Paladini, C., Baron, F. et al.
Constraining Convection in Evolved Stars with the VLTI
ADS BibCode: 2018Msngr.172...24P
Paladini, C., Baron, F., Jorissen, A., Le Bouquin, J., Freytag, B., Van Eck, S., Wittkowski, M., Hron, J., Chiavassa, A., Berger, J., Siopis, C., Mayer, A., Sadowski, G., Kravchenko, K., Shetye, S., Kerschbaum, F., Kluska, J., Ramstedt, S.
We used the Precision Integrated-Optics Near-infrared Imaging ExpeRiment (PIONIER) at the Very Large Telescope Interferometer (VLTI) to image the stellar surface of the S-type Asymptotic Giant Branch (AGB) star π1 Gruis. The angular resolution of two milliarcseconds allowed us to observe the surface of this giant star in unprecedented detail. At the observed wavelength the stellar disc appears circular and dust-free. Moreover, the disc is characterised by a few bubbles of a convective nature. We determine the contrast, and the characteristic horizontal length-scale of the convective granules. The latter is determined, for the first time, directly from the image, without involving the usual geometric modelling that has been used in the literature. The measurements fall along empirical scaling relations between stellar parameters and convective sizes, which are determined on the basis of three-dimensional stellar convection models. Our results open up a new era for the characterisation of stellar convection in stars other than the Sun.

Ginski, C., van Holstein, R. et al.
A Planet with a Disc? A Surprising Detection in Polarised Light with VLT/SPHERE
ADS BibCode: 2018Msngr.172...27G
Ginski, C., van Holstein, R., Juhász, A., Benisty, M., Schmidt, T., Chauvin, G., de Boer, J., Wilby, M., Manara, C., Delorme, P., Ménard, F., Muro-Arena, G., Pinilla, P., Birnstiel, T., Flock, M., Keller, C., Kenworthy, M., Milli, J., Olofsson, J., Pérez, L., Snik, F., Vogt, N.
With the Spectro-Polarimetric High- contrast Exoplanet REsearch (SPHERE) instrument at ESO’s Very Large Telescope (VLT) we can study the linear polarisation of directly detected planets and brown dwarfs, to learn about their atmospheres and immediate environments. We summarise here the recent discovery of a low-mass companion in polarised light by Ginski et al. (2018). The object shows an extreme degree of polarisation, indicating the presence of a circumplanetary disc.

Astronomical News
Leibundgut, B., Patat, F.
Report on the ESO Workshop "Planning ESO Observations of Future Gravitational Wave Events"
ADS BibCode: 2018Msngr.172...33L
Leibundgut, B., Patat, F.
Understanding the nature and results of black hole and neutron star mergers has become a hot topic in astrophysics. The combination of gravitational wave and electromagnetic observations of GW170817/GRB 170817A has triggered new and exciting science projects. The timeline for observations of gravitational wave events lies between seconds and days, and coordinated observations of electromagnetic radiation are critical when probing the nature of these events. The great success of the observations of GW170817/GRB 170817A from more than 50 observatories has highlighted the importance of coordination between different instruments and facilities. This two-day workshop focused on what has been learned from ESO observations of GW170817/GRB 170817A, and discussed strategies for coordinating observations of future events.

Wittkowski, M., Humphreys, L.
Report on the ESO Workshop "Imaging of Stellar Surfaces"
ADS BibCode: 2018Msngr.172...35W
Wittkowski, M., Humphreys, L.
There have recently been tremendous advances in observational techniques enabling the resolution of the surfaces of stars other than the Sun. Current VLTI instruments, SPHERE on the VLT, and ALMA, as well as other interferometric facilities, have recently succeeded in resolving stellar surfaces. The workshop aimed to bring together observers specialising in different techniques and wavelength regimes, and theoreticians working on stellar atmospheres and stellar structure. We aimed to organise a focused workshop with ample time devoted to the discussion of recent images of stellar surfaces and their extended atmospheres out to a few stellar radii, as well as observational strategies and the relevant underlying physical processes. The workshop was the first to be held in the seminar room of the new ESO Supernova Planetarium & Visitor Centre, and it was also the first workshop for which the new code of conduct for ESO workshops & conferences was in place

Bianco, A., Bernstein, R. et al.
Report on the Workshop "Dispersing Elements for Astronomy: New Trends and Possibilities"
ADS BibCode: 2018Msngr.172...40B
Bianco, A., Bernstein, R., de Ugarte Postigo, A., Garzon, F., Holland, W., Manescau, A., Navarro, R., Riva, M.
Astronomical spectrographs play an important role in addressing some of the biggest challenges in modern astronomy. One of the most critical components of any spectrograph is its dispersing element, since it determines the resolution and dispersion of the spectrograph, and is typically one of the least efficient optical components of the instrument. The aim of this workshop was to bring together researchers and engineers involved in the design, development and construction of spectroscopic instrumentation, with companies and institutes that produce dispersing elements and associated optical components. The forum provided the opportunity to discuss the scientific needs of future instruments, and to address the technological challenges that will allow the development of new types of dispersing elements in the coming years.

De Breuck, C., Teuben, P. et al.
Report on the ESO–Radionet Workshop "Submillimetre Single-dish Data Reduction and Array Combination Techniques"
ADS BibCode: 2018Msngr.172...42B
De Breuck, C., Teuben, P., Stanke, T.
Single-dish submillimetre facilities provide an essential complement to the Atacama Large Millimeter/submillimeter Array (ALMA) interferometry data, but require a set of special observing techniques and data reduction software that are different from those applied to radio and millimetre facilities. As there has not been a dedicated workshop to inform the ESO user community about these specific aspects, we decided to organise such a workshop, with the generous financial support of Radionet which made the workshop possible.

Boffin, H., Rejkuba, M.
Report on the ESO Workshop "La Silla Paranal Users Workshop"
ADS BibCode: 2018Msngr.172...44B
Boffin, H., Rejkuba, M.
In March, ESO organised the La Silla Paranal Users Workshop, providing current and future users of its observatories with an overview of the available instruments, as well as the most commonly used tools and processes at ESO, from proposal submission to data reduction and data archive. One full day of the event was dedicated to hands- on data reduction tutorials and one-to-one sessions between participants and ESO staff to work jointly on the issues brought up by the participants. The workshop attracted about 50 on-site participants as well as a dozen remote attendees, mostly from Australia.

Selman, F., Melo, C. et al.
Report on the ESO–NEON Observing School at La Silla Observatory
ADS BibCode: 2018Msngr.172...46S
Selman, F., Melo, C., Beccari, G., Boffin, H., Ivanov, V., Sani, E., Schmidtobreick, L., Dennefeld, M., Korhonen, H.
During the two weeks between 19 February and 2 March 2018, the Office for Science at Vitacura and the La Silla Observatory were the hosts of the second ESO/NEON (Network of European Observatories in the North) La Silla Observing School. Thanks to the generous funding from ESO, the Optical Infrared Coordination Network for Astronomy (OPTICON), and the La Silla Observatory, a group of 20 students, consisting of mostly PhD but also some advanced MSc students, from different parts of the world, were guided by five ESO tutors. The students prepared and carried out complex observations, reduced and analysed the data, and finally presented the results to the ESO scientific community at Vitacura. In addition to learning about the observing techniques that were used during the school, the students also attended several lectures covering the current and future capabilities of the Atacama Large Millimeter/submillimeter Array (ALMA), the telescopes at Paranal, and the Extremely Large Telescope (ELT), as well as talks on what makes a good scientific presentation, time management, effective proposal writing, and career choices.

Opitom, C., Harrison, C. et al.
Fellows at ESO
ADS BibCode: 2018Msngr.172...50E
Opitom, C., Harrison, C., Querejeta, M.

Cullum, M.
Raymond Wilson, 1928–2018
ADS BibCode: 2018Msngr.172...53C
Cullum, M.

Personnel Movements
ADS BibCode: 2018Msngr.172...55E