Riccardo Scarpa
Riccardo Scarpa | |
|---|---|
 | |
| Residence | Canary Islands, Spain |
| Nationality | Italian |
| Alma mater | University of Padova |
| Known for | Astronomy, Cosmology, Modified Newtonian dynamics |
| Scientific career | |
| Fields | Astronomy, Astrophysics, Cosmology |
| Institutions | European Southern Observatory Space Telescope Science Institute Instituto de Astrofísica de Canarias Gran Telescopio Canarias |
| Doctoral advisor | Cesare Barbieri, Renato Falomo |
Riccardo Scarpa is an Italian astronomer and astrophysicist working at the Instituto de Astrofísica de Canarias (IAC) as a staff astronomer at the Gran Telescopio Canarias (GTC). He previously served as a staff astronomer at the Paranal Observatory of the European Southern Observatory (ESO) in Chile. His research has centred on active galactic nuclei and the host galaxies of BL Lacertae objects, and on tests of gravity in the weak-acceleration regime, where he is a proponent of Modified Newtonian dynamics (MOND) as an alternative to non-baryonic dark matter.
Biography
Scarpa studied at the University of Padova in Italy, obtaining his laurea doctoral degree in astronomy in 1992 with a thesis titled "Optical spectrophotometry of BL Lacertae objects", supervised by Professor Cesare Barbieri and Dr. Renato Falomo.
After completing his doctorate, he carried out research at the Department of Astronomy of the University of Padova while also teaching mathematics and physics in an Italian high school. During 1994-95 he worked at the University of Padova and at the Space Telescope Science Institute (STScI) in Baltimore as a postdoctoral fellow of the Italian "Ing. Aldo Gini" foundation, and in 1996 he returned to STScI as a University of Padova fellow. From 1997 to 2000 he held a postdoctoral position at STScI, collaborating with C. Megan Urry.
Scarpa subsequently joined the European Southern Observatory as a staff astronomer at the Paranal Observatory in Chile, home of the Very Large Telescope. He later moved to the Instituto de Astrofísica de Canarias in Spain, where he works as a staff astronomer at the 10.4-metre Gran Telescopio Canarias.
Scientific contributions
Much of Scarpa's early work focused on active galactic nuclei, radio galaxies and BL Lacertae objects, studied through both Hubble Space Telescope (HST) imaging and ground-based observations. He contributed to the HST survey of BL Lacertae objects, characterising the morphology and photometric properties of their low-redshift host galaxies. His observational expertise includes optical photometry, HST imaging, and low- and moderate-dispersion spectroscopy. Using the GTC, he has also carried out spectroscopy to determine the redshifts of BL Lac objects and other gamma-ray sources.
Scarpa is known for his work testing Newtonian gravity in the low-acceleration regime. He has argued that non-baryonic dark matter appears to be required in galaxies precisely where the gravitational acceleration produced by ordinary (baryonic) matter falls below a critical value of about a₀ ≈ 1.2 × 10⁻⁸ cm s⁻², the same acceleration scale that characterises Modified Newtonian dynamics. To probe this regime, he and his collaborators have used the internal dynamics of Galactic globular clusters, measuring stellar velocity dispersions with VLT spectra combined with literature data. They reported that the velocity-dispersion profiles of the clusters studied tend to flatten at large radii, where the internal acceleration drops below a₀, rather than following the Keplerian decline expected from Newtonian gravity applied to their visible mass alone.
Because globular clusters are generally believed to contain little or no dark matter, Scarpa has interpreted these results as evidence that the standard understanding of gravity in the weak-acceleration regime may be incomplete, and as support for the MOND phenomenology. He authored an introductory review of Modified Newtonian dynamics presented at the 2005 conference "First Crisis in Cosmology".