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BOSS Quasars Unveil a New Era in the Expansion History of the Universe

Light from distant quasars (dots at left) is partially absorbed as it passes through clouds of hydrogen gas. A “forest” of hydrogen absorption lines in an individual quasar’s spectrum (inset) pinpoints denser clumps of gas along the line of sight, and the spectra are collected by the telescope’s spectrograph (square at right). Before BOSS, the Sloan Digital Sky Survey had collected spectra from 10 times fewer quasars (yellow dots) per square degree of sky in the accessible redshift range, which corresponds to about 10 billion years ago. By measuring the spectra from many more quasars in this range (red dots), BOSS can reconstruct a three-dimensional map of the otherwise invisible gas, revealing the large-scale structure of the early universe. (Illustration by Zosia Rostomian, LBNL; Nic Ross, BOSS Lyman-alpha team, LBNL; and Springel et al, Virgo Consortium and Max Planck Institute for Astrophysics) (Click for best resolution)

By collecting tens of thousands of quasar spectra, the Baryon Oscillation Spectroscopic Survey (BOSS) has measured the large-scale structure of the early universe for the first time. Like backlights in the fog, the quasars illuminate clouds of hydrogen gas along the line of sight. No other technique can reach back over 10 billion years to probe structure at a time when the expansion of the universe was still decelerating and dark energy was yet to turn on.

Berkeley Lab Sensors Enable First Light for the Dark Energy Camera

The focal plane of the Dark Energy Camera, mounted on the Victor Blanco 5-meter telescope at Cerro Tololo, consists of 62 large Berkeley Lab CCDs with exceptionally high sensitivity to the near infrared end of the spectrum. (Photos Roger Smith, NOAO, AURA, NSF; Blanco webcom; Fermilab; Roy Kaltschmidt, Lawrence Berkeley National Laboratory)

Mounted on a telescope high in the Andes, the Dark Energy Camera (DECam) saw first light September 12. DECam’s half-billion-pixel focal plane is made of Berkeley Lab CCDs, descended from sensors developed for high-energy physics by Berkeley Lab scientists and engineers. Highly sensitive to the near-infrared region of the spectrum, Berkeley Lab CCDs are an essential component of the most powerful dark-energy survey instrument yet made.

The First Public Data Release from BOSS, the Baryon Oscillation Spectroscopic Survey


Now freely available to the public: spectroscopic data from over half a million galaxies up to 7 billion light years away, over a hundred thousand quasars up to 11.5 billion light years away, and tens of thousands of stars and other astronomical objects in the Sloan Digital Sky Survey’s Data Release 9. This data is just the first year and a half of observation by BOSS, the Baryon Oscillation Spectroscopic Survey led by Berkeley Lab scientists. BOSS is the largest spectroscopic survey ever made to measure the evolution of large-scale galactic structure.

Clocking an Accelerating Universe: First Results from BOSS

For each 15-minute exposure of a small region of the sky, technicians plug a thousand optical fibers by hand into a plate that fits at the focal plane of the 2.5-meter Sloan Telescope. Each fiber feeds the light of an individual galaxy to BOSS’s advanced spectrogram.

First spectroscopic results from BOSS, the Baryon Oscillation Spectroscopic Survey, give the most detailed look yet at the time when dark energy turned on. Over six billion light years distant, halfway back to the big bang, the expanding universe slipped from the grasp of matter’s mutual gravitational attraction. Dark energy took over, and expansion began to accelerate. BOSS is the largest component of the third Sloan Digital Sky Survey, led by scientists from Berkeley Lab.

Calculating What’s in the Universe from the Biggest Color 3-D Map


Berkeley Lab scientists and their colleagues in the Sloan Digital Sky Survey have used visual data from nearly a million galaxies to derive the most accurate calculation yet of how matter clumps together – from a time when the universe was only half its present age until now. The results yield cosmic rulers to measure how the universe has expanded and to determine how much dark matter, dark energy, and even hard-to-detect neutrinos it contains.

Clearest Picture Yet of Dark Matter Points the Way to Better Understanding of Dark Energy

Teams from Fermilab and Berkeley Lab used galaxies from wide-ranging SDSS Stripe 82, a tiny detail of which is shown here, to plot new maps of dark matter based on the largest direct measurements of cosmic shear to date.

Two teams at Fermilab and Berkeley Lab have independently made the largest direct measurements of the invisible scaffolding of the universe, using the gravitational lensing effect known as “cosmic shear” to build maps of the distribution of dark matter. Their methods show that surveys with ground-based telescopes can measure cosmic shear with enough accuracy to aid in better understanding the mysterious space-stretching effects of dark energy.

Measuring the Distant Universe in 3-D

BOSS is extending the existing Sloan Digital Sky Survey map of the universe based on galaxies, center, into the realm of intergalactic gas in the distant universe, using the light from bright quasars (blue dots). (Sloan Digital Sky Survey)

The biggest 3-D map of the distant universe ever made, showing the distribution of intergalactic clouds of gas by using light from 14,000 galaxy-eating black holes over 10 billion light years away, has been announced by the Baryon Oscillation Spectroscopic Survey (BOSS), the largest survey in the third Sloan Digital Sky Survey. The result proves that the technique, never attempted before, can be used to study dark energy in the early universe.