François Hammer

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François Hammer

François Hammer,[1] born on 19 November 1958, is a French astrophysicist. He has been an astronomer at the Paris Observatory since 1987 and was an astronomer attached to the Canada-France-Hawaii Telescope between 1991 and 1992.

He has made several discoveries in the fields of gravitational lensing, cosmology and galaxy formation and structure. He was responsible for the Giraffe spectrograph[2] implemented in 2002 at the Very Large Telescope (VLT). Together with the astronomers Lex Kaper, Per Kjaergaard, Roberto Pallavicini, he was the investigator of the X-shooter[3] spectrograph, implemented in 2009 at the VLT.

Career[edit]

François Hammer studied at the École centrale des arts et manufactures (1980–82), and obtained his PhD in astrophysics in 1986 at the Université Paris-Diderot. He was the founding director of the laboratory "Galaxies, Etoiles Physique et Instrumentation" (GEPI, 2002-2009[4][5]). He was elected[6] at the Scientific Council of the "Institut national des sciences de l'Univers" du centre national de recherches scientifiques (CNRS), first secretary (2011-2013) then president[7] in 2014. As a member of the coordination of the National Committee for Scientific Research (2012-2014), he supported the fundamental research for "Assises de l'Enseignement Supérieur et de la Recherche"[8] as well as the employment of scientists.[9]

He is co-responsible for Franco-Chinese scientific relations in astronomy and astrophysics.

Research[edit]

Hammer established the first gravitational lensing model to explain the giant luminous arcs recently[when?] discovered in galaxy clusters.[10][11] This had led to a new estimate of galaxy cluster masses.

Very few distant galaxies were known in the 80s; together with the astronomers David Crampton, Olivier Le Fèvre and Simon Lilly, Hammer carried out the first spectroscopic survey of a thousand galaxies up to z=1 (Canada-France Redshift Survey). From this, the team discovered that star formation in the Universe had decreased by a factor of ten over the last 8 billion years, a result confirmed using infrared data to account for the dust-enshrouded star formation.[12]

He implemented the first 3D multi-spectroscopy system on an 8- meter class telescope,[13] and invented the new concept of 'morpho-kinematics'[14] to identify the physical processes that govern galaxy formation, by combining the deep morphologies of HST with the 3D spectroscopy performed at the VLT.[15]

Together with colleagues and his students, he discovered that the morphologies of present-day galaxies can be explained by major mergers of gas-rich galaxies, after which the gas is gradually wrapped around the center to form a new disk. This new concept of post-merger disk formation[16][17] indicates that the hierarchical scenario applies to all galaxy types, either spiral or elliptical. Furthermore, this disk rebuilding scenario solves the so-called spin catastrophe by providing large angular momentum to spiral galaxies. In 2007, he showed that the Milky Way is quite exceptional, as it has not been affected by a collision since the earliest epochs.[18] This was confirmed in 2018 by Gaia observations that have identified the remains of a large collision called Gaia-Sausage-Enceladus which took place nearly 10 billion years ago.[19][20]

He produced the most accurate modeling of the large Andromeda galaxy with his colleagues, Yanbin Yang and Jianling Wang. This has shown that Andromeda was the result of a major collision two to three billion years ago,[21][22] explaining the overall properties of the galaxy. He also modeled the large Magellanic Stream of neutral hydrogen,[23] still unexplained since its discovery, 40 years ago.[24] He is currently[when?] researching the origin of dwarf galaxies near the Milky Way, using astrometric data from the Gaia satellite.[25]

Prizes[edit]

Books[edit]

  • Building Galaxies: From The Primordial Universe To The Present, François Hammer et al., (2000)
  • Studying Distant Galaxies: A Handbook Of Methods And Analyses, François Hammer et al., (2016)

Medias and podcasts[edit]

  • C'est pas sorcier, « Mystères de l'Univers », France 3, 2004[27]
  • La Terre au Carré : « La galaxie d'Andromède[28]», France Inter, Mathieu Vidard
  • La méthode scientifique : « Univers jeune : si loin, si proche[29] », France Culture, Nicolas Martin
  • La méthode scientifique : « Galaxie d'Andromède, notre si jeune voisine[30]», France Culture, Nicolas Martin
  • La méthode scientifique : « Fin de l'Univers : et après ?[31]», France Culture, Nicolas Martin
  • Les preuves de la matière sombre aux différentes échelles, Fête de la Science 2019[32]

Notes and references[edit]

  1. ^ "François Hammer - Who's Who". www.whoswho.fr (in French). Retrieved 2022-11-12.
  2. ^ "ESO - The GIRAFFE Spectrograph". www.eso.org. Retrieved 2022-11-12.
  3. ^ information@eso.org. "Most Efficient Spectrograph to Shoot the Southern Skies". www.eso.org. Retrieved 2022-11-12.
  4. ^ CNRS (April 2009). "Bulletin officiel" (PDF). Périodique (in French).
  5. ^ "Délégations de signature BO 12-2002". www.dgdr.cnrs.fr. Retrieved 2022-11-12.
  6. ^ "Note n° 100001ELEC du 9 juillet 2010". www.dgdr.cnrs.fr. Retrieved 2022-11-13.
  7. ^ Conseil scientifique de l'INSU (October 2014). "Recommandations" (PDF). Périodique (in French).
  8. ^ Direction du CNRS et Représentation du Comité National de la Recherche Scientifique (2012-11-17). "Une nouvelle ambition pour la recherche" (PDF). Contribution (in French).
  9. ^ Représentation du Comité de la Recherche Scientifique (C3N) (2014-03-10). "La crise de l'emploi scientifique en France et ses dangers : introduction à l'analyse chiffrée du Conseil Scientifique du CNRS" (PDF). Texte adopté à l'unanimité (in French).{{cite journal}}: CS1 maint: numeric names: authors list (link)
  10. ^ Jim Peebles (2020-06-02). Cosmology's Century: An Inside History of Our Modern Understanding of the Universe. Princeton: Princeton University Press. p. 244.
  11. ^ Francois Hammer (1987-01-01). "A gravitational lensing model of the strange ring-like structure in A370". Proceeding of the Third IAP Workshop: 467–473. Bibcode:1987hrpg.work..467H. Retrieved 2022-11-12.
  12. ^ S. J. Lilly; O. Le Fevre; F. Hammer; David Crampton (1996-03-01). "The Canada-France Redshift Survey: The Luminosity Density and Star Formation History of the Universe to Z approximately 1". The Astrophysical Journal. 460: L1. arXiv:astro-ph/9601050. Bibcode:1996ApJ...460L...1L. doi:10.1086/309975. ISSN 0004-637X. S2CID 18098246. Retrieved 2022-11-12.
  13. ^ information@eso.org. "Multiple Eyes for the VLT - First System of Deployable Multi-Integral Field Units Ready". www.eso.org. Retrieved 2022-11-12.
  14. ^ information@eso.org. "Hubble and ESO's VLT provide unique 3D views of remote galaxies". www.spacetelescope.org. Retrieved 2022-11-12.
  15. ^ François Hammer, Mathieu Puech, Hector Flores, Myriam Rodrigues (November 2016). Studying Distant Galaxies: A Handbook Of Methods And Analyses. World Scientific. ISBN 9781786340566.{{cite book}}: CS1 maint: multiple names: authors list (link)
  16. ^ "ESA Science & Technology - The evolution of the Hubble sequence". sci.esa.int. Retrieved 2022-11-12.
  17. ^ F. Hammer; H. Flores; M. Puech; Y. B. Yang (2009-12-01). "The Hubble sequence: just a vestige of merger events?". Astronomy and Astrophysics. 507 (3): 1313–1326. arXiv:0903.3962. Bibcode:2009A&A...507.1313H. doi:10.1051/0004-6361/200912115. ISSN 0004-6361. S2CID 9355758. Retrieved 2022-11-12.
  18. ^ F. Hammer; M. Puech; L. Chemin; H. Flores (2007-06-01). "The Milky Way, an Exceptionally Quiet Galaxy: Implications for the Formation of Spiral Galaxies". The Astrophysical Journal. 662 (1): 322–334. arXiv:astro-ph/0702585. Bibcode:2007ApJ...662..322H. doi:10.1086/516727. ISSN 0004-637X. S2CID 18002823. Retrieved 2022-11-12.
  19. ^ Vasily Belokurov (2018). "Co-formation of the disc and the stellar halo". Monthly Notices of the Royal Astronomical Society. 478 (1): 611. arXiv:1802.03414. Bibcode:2018MNRAS.478..611B. doi:10.1093/mnras/sty982.
  20. ^ Misha Haywood (2018). "In Disguise or Out of Reach: First Clues about In Situ and Accreted Stars in the Stellar Halo of the Milky Way from Gaia DR2". The Astrophysical Journal. 863 (2): 113. arXiv:1805.02617. Bibcode:2018ApJ...863..113H. doi:10.3847/1538-4357/aad235. S2CID 119392868.
  21. ^ "La nouvelle histoire de la galaxie d'Andromède". France Inter (in French). 2018-02-21. Retrieved 2022-11-12.
  22. ^ F. Hammer; Y. B. Yang; J. L. Wang; R. Ibata (2018-02-01). "A 2-3 billion year old major merger paradigm for the Andromeda galaxy and its outskirts". Monthly Notices of the Royal Astronomical Society. 475 (2): 2754–2767. arXiv:1801.04279. Bibcode:2018MNRAS.475.2754H. doi:10.1093/mnras/stx3343. ISSN 0035-8711. Retrieved 2022-11-12.
  23. ^ F. Hammer; Y. B. Yang; J. L. Wang; R. Ibata (2018-02-01). "A 2-3 billion year old major merger paradigm for the Andromeda galaxy and its outskirts". Monthly Notices of the Royal Astronomical Society. 475 (2): 2754–2767. arXiv:1801.04279. Bibcode:2018MNRAS.475.2754H. doi:10.1093/mnras/stx3343. ISSN 0035-8711. Retrieved 2022-11-12.
  24. ^ Don Mathewson (2012-07-01). "Discovery of the Magellanic Stream". Journal of Astronomical History and Heritage. 15 (2): 100–104. Bibcode:2012JAHH...15..100M. doi:10.3724/SP.J.1440-2807.2012.02.03. ISSN 1440-2807. S2CID 220743599. Retrieved 2022-11-12.
  25. ^ "Gaia reveals that most Milky Way companion galaxies are newcomers to our corner of space". www.esa.int. Retrieved 2022-11-12.
  26. ^ Académie des Sciences et Académie Royale des lettres et des sciences des Pays-Bas (March 2012). "Le prix Descartes-Huygens 2012" (PDF). Communiqué de presse (in French).
  27. ^ "C'est pas sorcier -MYSTERES DE L'UNIVERS". YouTube (in French). Retrieved 2022-11-12.
  28. ^ "La galaxie Andromède". France Inter (in French). 2022-03-22. Retrieved 2022-11-13.
  29. ^ "Univers jeune : si loin, si proche". France Culture (in French). 2020-09-15. Retrieved 2022-11-13.
  30. ^ "Galaxie d'Andromède, notre si jeune voisine". France Culture (in French). 2018-03-06. Retrieved 2022-11-13.
  31. ^ "Fin de l'univers : et après ?". France Culture (in French). 2020-02-25. Retrieved 2022-11-13.
  32. ^ "Les preuves de la matière sombre aux différentes échelles astronomiques". YouTube (in French). Retrieved 2022-11-12.
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