Dark Matter and Cosmic Web Story

by Einasto, Jaan

  Fig. 8.9 Jim Peebles at the void conference, Amsterdam, December 2006 (author’s photo).

  After a long period I visited again the Astrophysical Institute in Potsdam in 1990. This was the start of a continuing collaboration with Potsdamer astronomers, most importantly with Volker Müller and his group. Potsdamer astronomers have been coauthors of most our papers on the large-scale structure of the Universe. Their Institute has better computers, so we have often used N-body simulations made in Potsdam.

  In 2000 a Finnish astronomer from Tuorla Observatory, Pekka Heinamaki, came to us as a postdoc. This was the start of a continuous collaboration with Finnish astronomers. Now we have every year joint Tartu–Tuorla cosmology workshops alternatively in Tuorla and in Tartu. In the last few years astronomers and physicists from other centres have also participated in these workshops, and the topics are now broader from microphysics of the early Universe to the structure and formation of galaxies.

  Fig. 8.10 Bernard Jones at the void conference, Amsterdam, December 2006 (author’s photo).

  During his stay in Garching Gert Hütsi started collaboration with several groups studying the physics of the very early Universe. In Estonia one group in Tallinn, led by Martti Raidal, is also investigating similar problems connected with the nature of dark matter. Now we have started a collaboration with the Martti Raidal team, realised in the form of a joint Center of Excellence.

  In 2006 I was invited to a three-week workshop in Aspen to discuss the void phenomenon and the evolution of galaxies. Volker Müller from Potsdam was also invited, so we rented a car together to drive from Denver airport to Aspen and have the freedom for some excursions in Colorado. This time I took with me my granddaughter Triin. On weekends we had time to look around in mountains around Aspen and Colorado river. The workshop was very interesting, all major problems of the structure of voids were discussed. One problem was: What is the explanation for the absence of even dwarf galaxies in voids? I had thought about this problem for many years already and was able to give a preliminary answer. This problem is discussed elsewhere in this book.

  The discussion of the void problem was continued at a small conference in Amsterdam later in the year. A week before the Amsterdam conference I had the opportunity to visit the Kapteyn Astronomical Institut of Groningen University. This was my first visit to Netherlands after the 1994 IAU General Assembly. I was very happy to have this opportunity, because astronomy in the Netherlands was always for us an example of what can be done in a small country. I had a talk on our work in the seminar. The most accurate and interesting questions were asked by Adriaan Blaauw. I have met Adriaan many times at various conferences, now we met in his home Observatory. After the seminar Adriaan invited me to a tour of North Holland. Next day he drove to the University campus with a brand-new Toyota Camry gasoline/electric hybrid car. We had a trip to the Northern coast of the country with high dams — a large part of the country is located below see level. Figure 8.8 is taken in a gas station where Adriaan added some gasoline to his car.

  Fig. 8.11 Participants of the Kuzmin90 conference in Pulkovo at lunch-time. In the foreground is Alar Toomre, while sitting on the far side is Simon White; August 2007 (author’s photo).

  Next week the void conference took place in Amsterdam, in the main building of the Royal Netherlands Academy of Arts and Sciences. The meeting hall of the Academy had only 50 seats, so participation was very limited. This meeting was also very stimulating; some pictures taken during the breaks are shown in Figs. 8.9 and 8.10.

  Another interesting conference was organised by St. Petersburg astronomers in Pulkovo Observatory in the summer of 2007 on the structure and dynamics of galaxies. With this conference the 90th birthday of Grigori Kuzmin was celebrated. The session devoted to the work and life of Grigori Kuzmin was lead by Alar Toomre. Alar’s own work is a continuation of the theoretical work by Grigori Kuzmin on a new level, using the possibilities of modern computers — galaxy mergers, stability and other similar problems. It was summer time and lunches were served in the garden of the Observatory, as seen in Fig. 8.11. After the sessions in the evenings Russian astronomers gathered to sing old Russian folk songs; one such moment is shown in Fig. 8.12. When summer workshops on astrophysics were held in our Observatory in Tõravere in the Soviet period, participants also used to sit in the evenings around the fireplace and sing Russian songs. One of the enthusiastic and very good singers was Josif Shklovsky.

  Fig. 8.12 Participants of the Kuzmin90 conference at Pulkovo singing Russian folk songs, August 2007 (author’s photo).

  One evening in autumn 2008 I received a phone call from Remo Ruffini. With him we had in the 1980’s very close collaboration, and several of our team members visited Rome, while he and his students visited our Observatory. Now he suggested I become an Adjunct Professor of ICRANet, starting 2009. I accepted the invitation, and since then I spend part of my time in the Pescara center of ICRANet. Also between Tartu Observatory and ICRANet an official agreement of scientific cooperation was signed. Several times I gave lectures to students of his Erasmus Mundus fellowship program.

  8.6 Tartu Observatory and my life in the 2000’s

  8.6.1 Transition years

  Throughout the new independence period right-wing parties had dominated Estonian policy. Free market economy was the major force during the whole transition period. This policy was rather successful, but its possibilities were exhausted by now. Foreign capital had floating in basically due to our low salaries. The basic problem is now — we have too few innovation-oriented enterprises. One reason for this is that during the transition period most young talented people studied soft sciences, such as management and law, because in these fields there were a lot of vacant positions with high salaries. The fraction of young people studying physics and engineering was decreasing.

  These and other actual strategic problems were discussed by the President AcademicAdvisory Board. I was invited to this Board in 1995 by the first President of Estonia after the restoration of independence, Lennart Meri. He organised the work of the Board in a very interesting way. Every year one member of the Board was nominated as the head of the Board, who was responsible for the choice of topics for discussion, helping to find speakers etc. Because members of the Board had different background and interests, the choice of topics was also rather wide. One year I was in this role. My primary idea was to use the experience of Finland in the development of a modern and innovation-friendly society. Here Lennart Meri helped a lot — he had many connections in Finland, so we had as speakers leading specialists from Nokia and Finnish Bank.

  I was invited several times to give talks in the Board, twice during the presidency of Lennart Meri, and twice during the present President Toomas Hendrik Ilves. I discussed several aspects of the innovation, science and education policy of Estonia. Unfortunately the role of the President of Estonia is rather restricted, thus suggestions made by the Advisory Board have basically only a moral value.

  There is a tradition that the President has a reception on Independence Day, February 24. All members of the Estonian Parliament, Government, and diplomatic corpus are invited, as well as numerous active people in every field of the society. I had the honour to be invited several times. Once I was in the reception together with my sister Kersti and her husband Lepo Sumera, a famous Estonian composer, see Fig. 8.13. It is a tradition that at the reception after the talk by the President a concert will be held. This year a composition of Lepo was performed: “Amore et igne” (“With Love and Fire for narrator, mixed chorus and symphony orchestra”). Lepo told me that he has thought for years on how to write music on one of the most important periods of our history, the Christianisation of Estonia in the 13th century. This was the beginning of eight hundred years of dominance of Baltic Barons. Finally he found the form of the composition as a Passion, a modern version of the style used by Johann Sebastian Bach in “St. Matthew Passion” and “St. John Passion”. His composition is based on the text of the “Heinrici
Chronicon Livoniae”, the only surviving document of this event. In this composition the afflictions of the whole nation are described, not those of one person — Jesus Christ.

  Fig. 8.13 In the reception of the President with Kersti and Lepo, February 24, 1998 (author’s photo).

  8.6.2 Center of Excellence

  In the 2000’s our cosmology team got new students and postdocs. Most of them have now finished their theses and continue their work: Antti Tamm, Gert Hütsi, Ivan Suhhonenko, Elmo Tempel, Lauri Juhan Liivamägi. These young collaborators are interested in new problems. One of them, Gert Hütsi, got his PhD degree at the Max Planck Institute of Astrophysics in Garching under the supervision of Rashid Sunyaev. Presently he and Elmo Tempel are actively collaborating with the Martti Raidal group in Tallinn in the study of physical aspects of the dark matter problem.

  We had applied several times in the competition to form a Center of Excellence. The last time we succeeded; the Center was formed together with the Martti Raidal group, and the main goal is to study in more detail the physics of dark matter, using both astronomical as well as experimental physics data. Raidal collaborated closely with CERN, thus we can now look at the problem from the astronomical as well from the physics point of view. A recent result of this collaboration was a joint study of the gamma-ray observations made with the Fermi satellite (Hektor et al., 2013; Tempel et al., 2012b).

  Fig. 8.14 The first picture of the Earth, taken with the onboard camera of ESTCube-1 (ESTCube team).

  In 2007 Estonia became an associated member of European Space Agency. This has motivated our colleagues in Observatory and Tartu University to start a student satellite project1. The practical purpose is to build a small cubic satellite to check the viability of using Solar wind to accelerate satellite motion. The pedagogical goal is to give students real knowledge in the teamwork on international and interdisciplinary level, to learn to build with his/her hands a highly sophisticated and innovative device (the weight of ESTCube-1 is only 1.3 kg). The project involves over a hundred students from Tartu University, Tallinn Technical University, and universities in Finland, Latvia and Germany, as well specialists in various fields working in private enterprises. The satellite was launched on May 7, 2013 form the ESA site at French Guyana. Now radio amateurs from all continents send to Tartu Observatory e-mails that they have received signals from ESTCube-1. The first pictures of the Earth were already taken using the small onboard camera, see Fig. 8.14.

  8.6.3 Egeri

  My mother gave her farm Egeri to the state in 1940. Here our previous lessees and their children lived almost to the end of the Soviet period. However, in the final ten years of this period the last habitants went away, and Egeri was not inhabited. The houses decayed and copses grew. In the last years of the Soviet period a local agronomist purchased from the kolkhoz the ruins of the houses and started to rebuild the main house of the farm.

  In the early 1990’s our Parliament made the decision that all property taken by the Soviet regime can be returned to previous owners. With my brothers and sisters we were the devisees, and had the possibility of initiating the procedure to get the farm back. In 1990 I visited Egeri and discovered that the house was already occupied, so we did not start the procedure to reclaim the farm. However, in 1995 the new owner was ready to sell us the house he had restored. So I did, and we also proceeded to get the whole farm back. Now it is divided between my brothers and sisters. I own a part with the restored house, while the other part is a joint property together with my brothers and sisters.

  With my brother Peeter, his son Laur and my son Indrek we started to restore one additional house. Now it is under a roof, and some rooms inside have been finished. In one of the last winters there was so much snow that the roof of the main house almost collapsed. The next summer was spent repairing the damage. Our experience shows that there is always something to do in the household.

  We have had several times astronomy seminars there. Once the Estonian Astronomical Society had its annual weekly seminar there. Also we have had family gatherings in Egeri. In the summer I spend most of my time in Egeri; about half of my library is there. Internet connection is available, so I can also do my work there.

  It is very quiet there. The next farm is about 2 kilometers away, and there is a large forest surrounding it. There are no city-lights nearby, so the sky is rather dark on a clear night, almost as it is in the mountains. In Egeri I feel at home: here are my roots, my connections to my earlier generations, to my homeland, to the Earth and to the Universe.

  This book is accompanied by a webpage2, which adds some important details to my story. First of all, the webpage contains copies of several papers of the dark matter story in their original form; the official published versions had in some cases omissions or were distorted to follow the referees’ suggestions. The webpage contains several astronomical movies demonstrated in various conferences, both from the early period of the study of the cosmic web, as well as our recent movies based on Sloan Survey.

  In addition, the webpage has my CV in pictures, and the Egeri Story. Both are accompanied by music, my CV by the music of my brother-in-law Lepo Sumera, played by his daughter Kadri-Ann. To express the spirit of the Egeri Story I used one of the best pieces of Bach’s organ music in my music collection, Toccata and Fuga, BWV565, played by the Estonian organist Rolf Uusväli. My grandfather Jaan Lammas, who actually built up the Egeri farm together with his father Wiilip, was an enthusiastic organ player and liked Bach’s music very much.

  In the webpage there is also a movie, prepared by myself on the restoration of Egeri, and on a family gathering in 1999. The family gathering is interesting — the wife of my brother’s son Mart has her roots in Setumaa, a region in South-East Estonia, where the traditions of the ‘regilaul’ are still alive. So during the family gathering she started to sing, as is traditional in family gatherings. Such songs were created and sung during the gathering. They are unique, used only for this particular case.

  My brother Peeter lived several years in Egeri. He is a very talented photographer, and has captured a large number of moments which characterise our feelings and tempers in Egeri. I used a collection of these photos to prepare “Egeri contemplations”. It is accompanied by Johann Sebastian Bach’s music from “Das Wohltemperierte Klavier”. I have in my music collection this Bach’s masterpiece played by five different musicians, including Daniel Barenboim, Svjatoslav Richter and others, played on piano or harpsichord. In my opinion the spirit of the music which best suits my own feelings is reproduced by the Russian pianist Samuel Feinberg’s recording from 1959. I have this rare mono recording on vinyl disks, and transformed it to mp3 files. I found in the web the following description of emotions of the Feinberg play: The way I arrive at it, is that I imagine Feinberg, in Stalin’s relentlessly grim Russia (dead though Stalin was in 1959), undertaking to record this music. There’s something intensely human about pouring your soul out through music like this in the wake of Stalin — perhaps one of the very few allowable ways to finally let your pain and hope and faith in beauty find expression without vanishing into the censor’s office or the Gulag yourself. But even without this historically dubious expatiation, I think that it is exceptionally apparent how much of a labor of love performing this music is for Feinberg. It seems as if the whole of the frailty of human existence is at stake in this recording — which does not mean that it is merely grim. There’s as much light here as sadness, the whole world in fact (from the review by Snow Leopard of Samuel Feinberg playing Bach “Das Wohltemperierte Klavier”).

  1http://www.estcube.eu

  2http://www.aai.ee/~einasto/DarkMatter

  Chapter 9

  Epilogue

  In the spring of 1973 there was a conference on galaxies in Tbilisi, and one evening I walked with Rashid Sunyaev along the Rustaveli avenue discussing our galaxy models with dark halos. Rashid argued that nobody will take our results seriously until some American astronomer confirmed them. Indeed, our exper
ience has confirmed his prediction several times. Our work on the presence of dark matter around galaxies was noticed after Ostriker et al. (1974) got similar results, and Vera Rubin et al. (1978) confirmed flat rotation curves of galaxies; the presence of the cosmic web in the Universe was accepted after the work by Geller & Huchra (1989).

  I have noticed that actually Rashid’s remark has a deeper meaning. People from leading scientific centres, especially Anglo-American ones, have a habit to noticing only the work done in established universities or centres, especially pioneering work. This practice reminds me the tendency in the Soviet period, where it was argued that all major scientific and technical innovations were done by Russian people — the steam machine was invented by Ivan Polzunov, radio by Alexander Popov etc.

  It seems to me that different discoveries may have different characters. Most interesting are unexpected discoveries — one of the best example of such discoveries in cosmology is the discovery of pulsars by Jocelyn Bell and Antony Hewish (Hewish et al., 1968). Of a different type are planned discoveries — some phenomenon is expected and special observational techniques are developed to detect it. Perhaps the best example of such discoveries is the detection of CMB fluctuations by the COBE satellite by Smoot et al. (1992). But there was a surprise here too: the spectrum of the CMB radiation corresponds to a black-body spectrum with extremely high accuracy (Mather et al., 1994). These discoveries have extended enormously our knowledge on the Universe. The smallness of CMB fluctuations and its very accurate black-body spectrum were strong arguments supporting the inflation model of the early Universe, which together changed our paradigm on the evolution of the Universe.