JACQUELINE BERGERON (1942-2024)
Photography of Jacqueline Bergeron, taken at IAP on May 24, 2007.Credit: Jean Mouette
Jacqueline Bergeron, born in Marseille on January 28, 1942, died in Paris on December 20, 2024, aged 82, after facing with great courage for almost three years the consequences of a stroke that left her hemiplegic. She was Director of Research emeritus at the CNRS.
Jacqueline became an internationally-renowned astrophysicist at an early age. At the very beginning of her career, she tackled theoretical topics concerning microscopic processes in dilute media ionized by high-energy rays (intergalactic media in particular), notably during several stays abroad, during which she rubbed shoulders with such great names in astrophysics as M. Rees, E. Salpeter, J. Gunn, W. Sargent and K. Thorne. Her interests shifted first to the observation of active nuclei and their surroundings, then to the gas halos surrounding galaxies and the intergalactic medium.
From the 1980s onwards, she was heavily involved in the using and design of several major astronomical facilities, in several wavelength domains: visible, UV and X-rays. She was always on the lookout for decisive observations to make or new topics to address, and discovered the first absorbing galaxy on a quasar line of sight in 1985.
In parallel to this prolific scientific activity, impressive in terms of the knowledge involved and of the diversity of observation techniques used, Jacqueline held many and sometimes very heavy responsibilities, mainly at international level (General Secretary of the IAU, Associate Director for Science at ESO, member of numerous committees and working groups).
Jacqueline's death leaves a great void. We will greatly miss her energy, her very broad vision of astrophysics and the acuity of her opinions.
Jacqueline Bergeron's career
After studying at the ESPCI, Jacqueline spent her entire career at the CNRS, first as a Research Associate in 1969, then as “Chargée de Recherche” (1975) and “Directrice de Recherche” (1985).
In this photo, taken in the summer of 1970, bringing together members of the Institute of Astronomy in Cambridge (UK) and visitors of the time, Jacqueline can be seen on the far left of the second row, next to Jean Audouze and many great names in astrophysics.Credit: Edward Leigh
She joined Evry Schatzman's group at the IAP in 1967, coming from Saclay, where she had defended her master thesis (“thèse de 3ème cycle”) on the “Possibilities of existence of the intergalactic medium” in 1968. From this time onwards, she made brief stays abroad, collaborating with several English and American researchers: J. Felten at Cambridge (UK, 1969 - 1970), then E. Salpeter at Cornell University (USA, 1971).
In 1967, she began a very fruitful collaboration with Suzy Collin-Zahn - first at the IAP, then at the Observatoire de Paris-Meudon - on the behavior of cosmic rays in the interstellar medium and their impact on the heating of the medium and the emission induced in the ultraviolet and X-ray domains, and more generally on the microscopic heating processes in hot dilute media and the visible line spectra emitted by these media. This led her to defend a PhD thesis in February 1972 entitled “Étude des milieux dilués hors équilibre thermodynamique”, once more under the supervision of Evry Schatzman (thesis committee: E. Schatzman, J.C. Pecker, J. Lequeux, S. Collin-Zahn).
Suzy describes this period in the following terms: “Quickly, Jacqueline showed an incredible ability to tackle and publish several subjects at the same time. A hard worker, she had fundamental contributions in each of them. She was very generous with young people, eager to make known all the subjects related to cosmology and quasars, and this soon led her to give courses and numerous seminars.”
Jacqueline then made two more stays abroad as an Assistant Professor (Cornell University in 1973 - 1974, Caltech in 1974 - 1975). From 1976 to 1980, she was a long-term visitor at ESO, invited by its then director Lo Woltjer. Her activities there were mainly devoted to observing and analyzing the emission line spectra of quasars and dwarf or irregular galaxies.
In 1980, she returned to the IAP, where she spent most of her career. She then took advantage of the new IUE satellite and of observations made at ESO to determine the properties of active nuclei. In the mid-1980s, her work shifted to the study of the gaseous halos surrounding galaxies (now known as the “circumgalactic medium”), revealed by absorption lines detected in the spectra of quasars, located far in the background and simply used as light sources. These activities led her to collaborate with several IAP researchers, including D. Kunth, P. Petitjean and P. Boissé.
In 1985, using ESO's 3.60m telescope, she identified for the first time a galaxy whose gaseous halo or disk is responsible for an absorption line system detected in a quasar spectrum[1]. This was a major discovery that had a profound impact on the development of observational cosmology. At the same time, she was studying, with F. Durret at the IAP, the properties of extended ionized envelopes around active galaxies, and was pursuing various theoretical and modeling projects related to these different topics.
Paradoxically, spectroscopy of quasars in the visible with large ground-based telescopes provides more readily information on the distant Universe than on the near Universe, which requires observations in the UV range. The Hubble Space Telescope helped to bridge this gap, and Jacqueline Bergeron became the French leader of an important key program (initiated by J. Bahcall and his collaborators from 1993 onwards), which brought many essential results, particularly on the intergalactic medium of the near Universe.
Similarly, some ten years later, Jacqueline led a major quasar spectroscopic observation program as part of a wide-ranging collaboration, taking advantage of the excellent performance of the UVES high-resolution spectroscope mounted on the VLT in Paranal. This federative project allowed them to address many aspects of quasar absorption line systems in intergalactic and circumgalactic environments, as well as in the disks of distant galaxies (z > 2). These absorption systems provide unique information on gas properties such as kinematics, heavy element abundance and the presence of dust associated with gas. The data generated by this major program led to numerous scientific breakthroughs.
Since the 1990s, Jacqueline had been involved in numerous studies of high redshift quasars, in collaboration with A. Omont, Sophia Yu Dai, C. Willott and P. Petitjean. In addition to the search for quasars at z > 6 in CFHT surveys, these studies mainly concerned star formation in host galaxies, combining: i) submillimeter and infrared emission measured by the Herschel and Spitzer space observatories; and ii) millimeter and submillimeter emission in the continuum and CO and C+ lines, observed with the IRAM and ALMA telescopes; These studies led to some observational firsts, notably of ordinary galaxies at z > 6 with ALMA.
After having actively contributed to the preparation of the European XMM-Newton mission as “Mission Scientist”, she became a member of the time allocation committee for the same mission, and participated in the exploitation of deep surveys with G. Hasinger and his collaborators. Still in the field of X-rays, she took part in the Chandra mission surveys, in collaboration with R. Giacconi and his team.
In this photograph, taken on February 8, 2013 during the traditional IAU cocktail party, we see the three French astronomers who served as IAU General Secretary: J.C. Pecker (1964-1967), J. Bergeron (1991-1994) and T. Montmerle (2012-2015). Credit: DR
In addition to her many first-rate scientific achievements, Jacqueline took on numerous responsibilities for the French, European and worldwide community. Between 1991 and 1994, she was General Secretary of the IAU, in a highly complex context due to the break-up of the USSR (December 1991), while the President of the IAU, A. Boyarchuk, was Soviet and I. Appenzeller Assistant General Secretary. During her term, she made a major contribution to the development of IAU structures (leading to the creation of the Divisions) and to the format of General Assemblies, making them more attractive by including purely scientific symposia. Jacqueline was the second astrophysicist, after Edith Müller (1976-1979), to take on the responsibility of General Secretary of the IAU.
In 1994, she was recruited as Associate Director for Science at ESO (Munich) for seven years, during the mandates of Riccardo Giacconi and Catherine Cesarsky at the head of ESO.
Xavier Barcons, ESO's current Director General, underlines the very important role she played at the time: “I first met Jacqueline Bergeron at a workshop on QSO absorption lines at the STScI in Baltimore back in 1987. The HST Key Project on Lyman-alpha absorption lines at low z was in full swing, with Jacqueline in a stellar role. I saw in Jacqueline an admirable and immensely active scientist, very well connected and always passionate (and at times strongly opinionated) about her work. Passion for science was probably the most visible attribute that she would irradiate at all times.
We met again several times in different astronomy environments, in particular in X-ray astronomy. We were both supporters of ESA’s XMM-Newton observatory, and we served there in several committees. Jacqueline carried lots of knowledge about AGN physics, on which she had worked both in the US and in Europe. She was always willing to share her knowledge and engage on a scientific discussion. The very open way she had to interact with colleagues made that a very easy and positive experience.
I was aware that she had spent a long time at ESO, but it was only since I became ESO DG that I realized the profound legacy and impact that she left at ESO. I would like to underline that the role of the Directorate for Science that we have today at ESO is largely a testimony of the actions and structures that Jacqueline put in place at ESO during her term as Associate Director of Science in the 1990s.
Astronomy in general, and ESO in particular, owes a lot to Jaqueline. Her dedication has left an important legacy.”
Bruno Leibundgut (Director of Science at ESO) elaborates on Jacqueline's major contribution: “Jacqueline Bergeron joined ESO as a long-term scientific visitor between 1976 and 1980 on a personal invitation by Lo Woltjer. She spent her time in the science group located at the ESO technical offices at CERN in Geneva. In 1994 she returned as the Associate Director for Science, a position that was newly created to establish a scientific framework within ESO. In this role, Jacqueline advised the ESO Director General, Riccardo Giacconi, on scientific matters. Jacqueline also initiated and implemented important changes that prepared ESO for the VLT, ALMA and future facilities. She implemented the ESO faculty and defined an internal promotion structure for ESO scientists. The scientific activities were brought together into the Office for Science, present both in Garching and in Vitacura supporting all astronomers working at ESO. The Office for Science also represented an important link between ESO and its community. Following the recommendations of a working group organized by Jacqueline, ESO re-introduced large observing programmes in a format that is still used today. Jacqueline reformed the ESO Fellowship programme and extended it to positions in Vitacura. She introduced the fourth year for ESO Fellows working in Chile to be spent at an astronomy department in an ESO Member State, enabling the young researchers to re-integrate into the European community. Jacqueline had an extremely beneficial influence on young researchers, including junior staff, in promoting their research and enabling them to develop their careers. Her sincere and honest assessments were of great value to many ESO astronomers. Her vision of a strong research-oriented staff providing input into the construction and usage of ESO facilities has proven extremely successful and helped establish ESO as a leader in ground-based astronomy.”
Over the past 20 years, Jacqueline played a leading role in the ASTRONET network of European astronomy funding agencies, whose mission was to make recommendations on European astronomy facilities for the 2020 decade. She chaired one of the four working groups, “How do galaxies form and evolve?” of the first Science Vision report published in 2007. She co-chaired the group of the same name that drafted the revision of this report in 2012. Finally, she co-chaired the working group on 2-4m class telescopes, which published its report in 2010. She was also a member of the ESO-ELT working group which ran from 2005 to 2012, and which produced, among other things, the ELT Design Reference Mission published in 2011.
Photography of Jacqueline Bergeron taken in Munich on the occasion of ESO's 50th anniversary celebration, September 4, 2012. Credit: M. McCaughrean (ESA/ESO)
Jacqueline was also a member of the ESO French Committee for many years (2002 - 2016). She served on numerous time allocation committees (for HST, XMM, CFHT, ESO telescopes, ALMA), selection committees for several prizes (Gruber Foundation, EAS Tycho Brahe Prize), the ERC funding committee, and evaluation and visiting committees for several laboratories and agencies abroad (Germany, Portugal).
At the IAP, Jacqueline played an important role in training young people in research by supervising internships and theses, and for many years she supervised the foreign visitor program.
Last but not least, Jacqueline was always keen to promote the role of women in research.
Beyond the brilliant results she achieved throughout her career, Jacqueline made a remarkable contribution to the discipline, through her global vision of extragalactic topics, her vast experience of astrophysical observations in several spectral domains, and her inexhaustible energy in driving projects forward. We are deeply grateful to her.
Awards received by Jacqueline Bergeron
Nomination to the Légion d'Honneur in 2001.
Prix Claude Berthault from the Académie des Sciences in 2010.
Layout: Jean Mouette
January 2025