- 4040 - GRAVITATIONAL LENSING - to measure mass? Astronomers are using gravitational lensing to measure mass of a quasar's galaxy. Just as the thickness of a magnefying glass can focus light to magnify a distant object a “concentration of gravity” in a galaxy can focus light coming from a more distant galaxy.
---------- 4040 - GRAVITATIONAL LENSING - to measure mass?
- Astronomers use the
phenomenon of “strong gravitational lensing” to determine with precision the
mass of a galaxy containing a quasar, as well as their evolution in cosmic
time. Knowing the mass of quasar host galaxies provides insight into the
evolution of galaxies in the early universe, for building scenarios of galaxy
formation and black hole development.
-
- The unprecedented
precision and accuracy achieved with gravitational lensing provide a new avenue
for obtaining robust mass estimates in the distant Universe, where conventional
techniques lack precision and are susceptible to biases.
-
- A quasar is a
luminous manifestation of a supermassive black hole that accretes surrounding
matter, sitting at the center of a host galaxy. It is generally difficult to
measure how heavy a quasar's host galaxy is because quasars are very distant
objects, and also because they are so bright that they overshine anything
within their vicinity.
-
- Gravitational
lensing allows astronomers to compute the mass of the lensing object. Thanks to
Einstein's theory of gravitation, we know how massive objects in the foreground
of the night sky, the “gravitational lens”, can bend light coming from
background objects. The resulting strange rings of light are actually
distortions of the background object's light by the gravitational lens.
-
- The Sloan Digital
Sky Survey (SDSS) database was a great place to search for gravitational
lensing quasars candidates. In 2010,
astronomers commissioned time on the Hubble Space Telescope to observe four
candidates of which three showed lensing. Of the three, one stood out due to
its characteristic gravitational lensing rings: SDSS J0919+2720.
-
- The HST image of
“SDSS J0919+2720” shows two bright objects in the foreground that each act as a
gravitational lens, probably two galaxies in the process of merging. The one is
a bright quasar, within a host galaxy too dim to be observed. The bright object
is another galaxy, the main gravitational lens. A faint object on is a
companion galaxy. The characteristic rings are deformed light coming from a
background galaxy.
-
- By carefully
analyzing the gravitationally lensed rings in it is possible to determine the
mass of the two bright objects. Disentangling the masses of the various objects
would have been impossible without the recent development of a wavelet-based lens
modeling technique.
-
- In the local
universe, we observe that the most massive galaxies also host the most massive
black holes at their center. This could suggest that the growth of galaxies is
regulated by the amount of energy radiated by their central black hole and
injected into the galaxy.
-
- Gravitational
lensing events are very rare, with one galaxy in a thousand unveiling the
phenomenon. Since quasars are seen in about one every thousand galaxies a
quasar acting as a lens is one in a million.
-
- The scientists
expect to detect hundreds of these lensing quasars with the ESA-NASA mission
Euclid, to be launched this summer, 2023, with a Falcon-9 SpaceX rocket.
-
June 7, 2023 GRAVITATIONAL LENSING
- to measure mass? 4040
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