Artists
impression of the power of background galaxies to measure the size of
gas clouds as compared to the conventional method of using quasars. The
plane to the far right shows the background galaxy and overlaid in the
center of the galaxy is a bright white light representing a quasar. The
DLA gas cloud is shown at the center of the plane in between the galaxy
and Earth. The blue/white narrow beam indicates the small area of the
DLA gas cloud probed by quasars, the wider red cone of light indicates
the large area of the DLA probed by galaxies, which is a 100
million-fold increase in area.
Credit: Adrian Malec (Swinburne University) and Marie Martig (Max Planck Institute for Astronomy, Heidelberg)
MAUNAKEA, Hawaii – Using the world’s largest
telescopes, researchers discovered ancient cold gas clouds larger than
galaxies in the early Universe. The discovery was announced today at a
press conference at the 227th meeting of the American Astronomical
Society in Orlando, Florida.
The discovery, led by Associate
Professor Jeff Cooke, Swinburne University of Technology, and Associate
Professor John O’Meara, St. Michael’s College, has helped solve a
decades-old puzzle on the nature of gas clouds, known as damped Lyman
alpha systems, or DLAs.
Cooke and O’Meara realized that finding
DLA gas clouds in the line of sight to background galaxies would enable
measurements of their size by determining how much of the galaxy they
cover.
“Our new method first identifies galaxies that are more
likely to have intervening DLA gas clouds and then searches for them
using long, deep exposures on the powerful Keck Observatory 10m
telescopes on Maunakea and deep data from the VLT 8m telescopes in
Chile,” Cooke said. “The technique is timely as the next generation of
giant 30m telescopes will be online in several years and are ideal to
take advantage of this method to routinely gather large numbers of DLAs
for study.”
DLA clouds contain most of the cool gas in the
Universe and are predicted to contain enough gas to form most of the
stars we see in galaxies around us today, like the Milky Way. However,
this prediction has yet to be confirmed.
DLAs currently have
little ongoing star formation, making them too dim to observe directly
from their emitted light alone. Instead, they are detected when they
happen to fall in the line of sight to a more distant bright object and
leave an unmistakeable absorption signature in the background object’s
light.
Previously, researchers used quasars as the background
objects to search for DLAs. Although quasars can be very bright, they
are rare and are comparatively small, only a fraction of a light year
across, whereas galaxies are quite common and provide a 100 million-fold
increase in area to probe DLAs.
“Using the galaxy technique,
DLAs can be studied in large numbers to provide a 3-D tomographic
picture of distribution of gas clouds in the early Universe and help
complete our understanding of how galaxies formed and evolved over
cosmic time,” O’Meara said.
The W. M. Keck Observatory operates
the largest, most scientifically productive telescopes on Earth. The
two, 10-meter optical/infrared telescopes near the summit of Maunakea on
the Island of Hawaii feature a suite of advanced instruments including
imagers, multi-object spectrographs, high-resolution spectrographs,
integral-field spectrographs and world-leading laser guide star adaptive
optics systems.
Keck Observatory is a private 501(c) 3 non-profit
organization and a scientific partnership of the California Institute
of Technology, the University of California and NASA.
Media
Steve Jefferson
Communication Officer
W. M. Keck Observatory
sjefferson@keck.hawaii.edu
Science
Jeff Cooke
Swinburne University
jcooke@astro.swin.edu.au
John O’Meara
St. Michael’s College
jomeara@smcvt.edu
Source: W.M. Keck Observatory
