Wikipedia

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.

François Hammer

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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