Faster-Than-Expected Expansion of the Universe Supported by Results from Cosmic Lensing Research

January 27,  2017
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)

An international team of astronomers, including Kavli IPMU Project Researcher Alessandro Sonnenfeld, has used galaxies as giant gravitational lenses to make an independent measurement of how fast the Universe is expanding. Led by Sherry Suyu, the Max Planck @TUM professor at the Technical University Munich and Max Planck Institute for Astrophysics, Germany, the team used the NASA/ESA Hubble Space Telescope, the Subaru Telescope, and other telescopes in space and on the ground to study five galaxies [1].

The study arrived at an independent measurement of the Hubble constant—a fundamental quantity that describes the rate at which the Universe is expanding [2]. The new results are entirely independent and agree with other measurements of the Hubble constant in the local Universe, measurements that used as their reference points Cepheid variable stars and supernovae.

However, the findings from Suyu and her team, as well as those from the Cepheids and supernovae, differed from those made previously by the ESA Planck satellite—in the latter case, measurement of the Hubble constant was made for the early Universe by observing the cosmic microwave background. While the Planck measurements agree with our current understanding of the cosmos, the results emanating from measurements for the local Universe disagree with currently accepted theoretical models of the Universe.

“The expansion rate of the Universe is now starting to be measured in different ways with such high precision that actual discrepancies may possibly point towards new physics beyond our current knowledge of the Universe,” explained Suyu, who carried out much of her research when she was affiliated to Academia Sinica Intitute of Astronomy and Astrophysics, Taiwan .

The study looked at massive galaxies located between Earth and distant quasars, which are very luminous galaxy cores. Due to strong gravitational lensing, huge masses of galaxies bend light emerging from more distance quasars, thereby creating multiple images of the background quasars, with some of them smeared into extended arcs [3]. Light from the images formed of background quasars follow paths that are of different length because the distortions caused by galaxies to the fabric of space are not perfectly spherical. What is more, the lensing of galaxies and quasars are not perfectly aligned.  

As the brightness of quasars changes over time, different images can be seen at different times, the lag between them depending on the lengths of the paths the light has taken. Such delays are directly related to the value of the Hubble constant. The team was able to measure the Hubble constant with precision (3.8 percent) [4] by using accurate measurements of the time delays between the multiple images, in addition to utilizing computer models.

Kavli IPMU’s Sonnenfeld said: “The idea of measuring the Hubble constant using time delays between lensed images of quasars has been around for over fifty years, but it is only recently that such measurements have become possible, thanks to the efforts of our collaboration. The next goal will be to increase the number of lenses used for the analysis. The Subaru Telescope is playing an important role in the hunt for new gravitational lenses.”

Notes

[1] Alongside the Subaru Telescope, the study used the NASA/ESA Hubble Space Telescope, the Keck TelescopeESO’s Very Large Telescope, the Gemini Telescope, the Victor M. Blanco Telescope, the Canada-France-Hawaii telescope and the NASA Spitzer Space Telescope. In addition, data from the Swiss 1.2-metre Leonhard Euler Telescope and the MPG/ESO 2.2-metre telescope were used.

[2] The gravitational lensing time-delay method that the astronomers used here to achieve a value for the Hubble constant is especially important owing to its near-independence of the three components our Universe consists of: normal matter, dark matter and dark energy. Though not completely separate, the method is only weakly dependent on these.

[3] Gravitational lensing was first predicted by Albert Einstein more than a century ago. All matter in the Universe warps the space around itself, with larger masses producing a more pronounced effect. Around very massive objects, such as galaxies, light that passes close by follows this warped space, appearing to bend away from its original path by a clearly visible amount. This is known as strong gravitational lensing.

[4] The H0LiCOW team determined a value for the Hubble constant of 71.9±2.7 kilometres per second per Megaparsec. In 2016, scientists using Hubble measured a value of 73.24±1.74 kilometres per second per Megaparsec. In 2015, the ESA Planck Satellite measured the constant with the highest precision so far and obtained a value of 66.93±0.62 kilometres per second per Megaparsec.

Paper Details:

Journal: 
This research was presented in a series of papers to appear in the Monthly Notices of the Royal Astronomical Society.

Link to science papers: H0LiCOW I*, H0LiCOW II**, H0LiCOW III***, H0LiCOW IV, H0LiCOW V and H0LiCOW VI (* , **, and *** are pending publication)

Authors:
S. H. Suyu (Max Planck @TUM professor at the Technical University Munich and Max Planck Institute for Astrophysics, Germany; Academia Sinica Institute of Astronomy and Astrophysics, Taiwan), V. Bonvin (Laboratory of Astrophysics, EPFL, Switzerland), F. Courbin (Laboratory of Astrophysics, EPFL, Switzerland), C. D. Fassnacht (University of California, Davis, USA), C. E. Rusu (University of California, Davis, USA), D. Sluse (STAR Institute, Belgium), T. Treu (University of California, Los Angeles, USA), K. C. Wong (National Astronomical Observatory of Japan, Japan; Academia Sinica Institute of Astronomy and Astrophysics, Taiwan), M. W. Auger (University of Cambridge, UK), X. Ding (University of California, Los Angeles, USA; Beijing Normal University, China), S. Hilbert (Exzellenzcluster Universe, Germany; Ludwig-Maximilians-Universität, Munich, Germany), P. J. Marshall (Stanford University, USA), N. Rumbaugh (University of California, Davis, USA), A. Sonnenfeld (Kavli IPMU, The University of Tokyo, Japan; University of California, Los Angeles, USA; University of California, Santa Barbara, USA), M. Tewes (Argelander-Institut für Astronomie, Germany), O. Tihhonova (Laboratory of Astrophysics, EPFL, Switzerland), A. Agnello (ESO, Garching, Germany), R. D. Blandford (Stanford University, USA), G. C.-F. Chen (University of California, Davis, USA; Academia Sinica Institute of Astronomy and Astrophysics, Taiwan), T. Collett (University of Portsmouth, UK), L. V. E. Koopmans (University of Groningen, The Netherlands), K. Liao (University of California, Los Angeles, USA), G. Meylan (Laboratory of Astrophysics, EPFL, Switzerland), C. Spiniello (INAF – Osservatorio Astronomico di Capodimonte, Italy; Max Planck Institute for Astrophysics, Garching, Germany) and A. Yıldırım (Max Planck Institute for Astrophysics, Garching, Germany)

Researcher contact: 
Sherry Suyu

Max Planck Institute for Astrophysics
Garching, Germany

Tel: +49 89 30000 2015

Email: suyu@mpa-garching.mpg.de

 

Vivien Bonvin

Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatory of Sauverny
Versoix, Switzerland

Tel: +41 22 3792420

Email: vivien.bonvin@epfl.ch

 

Frederic Courbin

Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatory of Sauverny
Versoix, Switzerland

Tel: +41 22 3792418

Email: frederic.courbin@epfl.ch

Local contact:
Alessandro Sonnenfeld
Project Researcher
Kavli Institute for the Physics and Mathematics of the Universe
The University of Tokyo
Kashiwa-no-ha, Kashiwa
277-8583, Japan
Tel: +81-04-7136-5980
E-mail: alessandro.sonnenfeld_at_ipmu.jp*
*Change “_at_” to @ in the email

 

John Amari
Kavli IPMU press office
Kavli Institute for the Physics and Mathematics of the Universe
The University of Tokyo
Kashiwa-no-ha, Kashiwa
277-8583, Japan
Tel: +81-04-7136-5980
E-mail: press_at_ipmu.jp*
*Change “_at_” to @ in the email

Useful links:

Hubble Space Telescope.

Subaru Telescope press release.

Images of Hubble

Hubblecast 70: Peering around cosmic corners

H0LiCOW video on recent results

H0LiCOW cooperation