MPA: High Value for Hubble Constant from Two Gravitational Lenses
Posted: Fri Sep 13, 2019 8:57 pm
High Value for Hubble Constant from Two Gravitational Lenses
Mas Planck Institute for Astrophysics | 2019 Sep 13
A Measurement of the Hubble Constant from Angular
Diameter Distances to Two Gravitational Lenses ~ Inh Jee et al
Mas Planck Institute for Astrophysics | 2019 Sep 13
The expansion rate of the Universe today is described by the so-called Hubble constant and different techniques have come to inconsistent results about how fast our Universe actually does expand. An international team led by the Max Planck Institute for Astrophysics (MPA) has now used two gravitational lenses as new tools to calibrate the distances to hundreds of observed supernovae and thus measure a fairly high value for the Hubble constant. While the uncertainty is still relatively large, this is higher than that inferred from the cosmic microwave background.
Gravitational lensing describes the fact that light is deflected by large masses in the Universe, just like a glass lens will bend a light right on Earth. In recent years, cosmologists have increasingly used this effect to measure distances by exploiting the fact that, in a multiple image system, an observer will see photons arriving from different directions at different times due to the difference in optical path lengths for the various images. This measurement thus gives a physical size of the lens, and comparing it to an observed size in the sky gives a geometric distance estimate called the “angular diameter distance”. Such distance measurements in astronomy are the basis for measurements of the Hubble constant...
The team used two strong gravitational lens systems B1608+656 and RXJ1131 (see Figure 1). In each of these systems, there are four images of a background galaxy with one or two foreground galaxies acting as lenses. This relatively simple configuration allowed the scientists to produce an accurate lensing model and thus measure the angular diameter distances to a precision of 12 to 20% per lens. These distances were then applied as anchors to 740 supernovae in a public catalogue (Joint Light-curve Analysis dataset). ...
A Measurement of the Hubble Constant from Angular
Diameter Distances to Two Gravitational Lenses ~ Inh Jee et al
- Science 365(6458):1134 (13 Sep 2019) DOI: 10.1126/science.aat7371