Andrew Yee[_1_]
May 14th 08, 09:25 PM
ESO Education and Public Relations Dept.
----------------------------------------------------------------------------
Text with all links and the photos are available on the ESO Website at URL:
http://www.eso.org/public/outreach/press-rel/pr-2008/pr-13-08.html
----------------------------------------------------------------------------
Contacts:
Cedric Ledoux and Pasquier Noterdaeme
ESO, Chile
Phone: +56 2 463 30 56 or +56 55 43 53 11
Patrick Petitjean
Institut d'Astrophysique de Paris, France
Phone: +33 1 44 32 81 50
Raghunathan Srianand
Inter University Centre for Astronomy and Astrophysics
Pune, India
Phone: +91 20 569 1414 (ext 320)
Dr. Henri Boffin
ESO Press Officer
Phone: +49 89 3200 6222
Valentina Rodriguez
ESO Press Officer in Chile
Phone: +56 2 463 3123
For Immediate Release: 13 May 2008
ESO Science Release 13/08
A Molecular Thermometer for the Distant Universe
First accurate measurement of the temperature of the cosmic background at an
early epoch
Astronomers have made use of ESO's Very Large Telescope to detect for the
first time in the ultraviolet the carbon monoxide molecule in a galaxy
located almost 11 billion light-years away, a feat that had remained elusive
for 25 years. This detection allows them to obtain the most precise
measurement of the cosmic temperature at such a remote epoch.
The team of astronomers [1] aimed the UVES spectrograph on ESO's VLT for
more than 8 hours at a well-hidden galaxy whose light has taken almost 11
billion years to reach us, that is about 80% of the age of the Universe.
The only way this galaxy can be seen is through the imprint its interstellar
gas leaves on the spectrum of an even more remote quasar [2]. "Quasars are
here only used as a beacon in the very distant Universe. Interstellar clouds
of gas in galaxies, located between the quasars and us on the same line of
sight, absorb parts of the light emitted by the quasars. The resulting
spectrum consequently presents dark 'valleys' that can be attributed to
well-known elements and possibly molecules," explains Raghunathan Srianand
(Pune, India), who led the team making the observations.
Thanks to the power of the VLT and a very careful selection of the target --
the target was selected among about ten thousands quasars -- the team was
able to discover the presence of normal and deuterated molecular hydrogen
(H2, HD) and carbon monoxide (CO) molecules in the interstellar medium of
this remote galaxy. "This is the first time that these three molecules have
been detected in absorption in front of a quasar, a detection that has
remained elusive for more than a quarter century," says Cedric Ledoux (ESO),
member of the team.
The same team had already broken the record for the most distant detection
of molecular hydrogen in a galaxy that we see as it was when the Universe
was less than 1.5 billion years old (see ESO 16/06).
The interstellar gas is the reservoir from which stars form and, as such, is
an important component of galaxies. Furthermore, because the formation and
the state of molecules are very sensitive to the physical conditions of the
gas, which in turn depend on the rate at which stars are formed, the
detailed study of the chemistry of the interstellar medium is an important
tool to understand how galaxies form.
Based on their observations, the astronomers showed that the physical
conditions prevailing in the interstellar gas in this remote galaxy are
similar to what is seen in our Galaxy, the Milky Way.
But most importantly, the team was able to measure with the best ever
precision the temperature of the cosmic background radiation in the remote
Universe [3]. "Unlike other methods, measuring the temperature of the cosmic
background using the CO molecule involves very few assumptions," declares
co-author Pasquier Noterdaeme.
If the Universe was formed in a 'Big Bang', as most astrophysicists infer,
the glow of this primeval fireball should have been warmer in the past. This
is exactly what is found by the new measurements. "Given the current
measured temperature of 2.725 K, one would expect that the temperature 11
billion years ago was about 9.3 K," says co-author Patrick Petitjean. "Our
unique set of VLT observations allows us to deduce a temperature of 9.15 K,
plus or minus 0.7 K, in excellent agreement with the theory."
"We believe our analysis pioneers interstellar chemistry studies at high
redshift and demonstrates that it is possible, together with the detection
of other molecules such as HD or CH, to use interstellar chemistry to tackle
important cosmological issues," adds Srianand.
The results described here have been presented in a Letter to the Editor in
Astronomy and Astrophysics ("First detection of CO in a high-redshift damped
Lyman-alpha system", by R. Srianand et al.).
Notes
[1]: The team is composed of Raghunathan Srianand (IUCAA, Pune, India),
Pasquier Noterdaeme and Cedric Ledoux (ESO), and Patrick Petitjean (IAP,
France). The same team already made the first measurement of the temperature
of the cosmic microwave background radiation, at a time when the Universe
was only about 2.5 billion years old, also using UVES on the VLT (see ESO
27/00). At that time, they could only measure a temperature in the range
between 6 and 14 K.
[2]: Quasars are extraordinarily luminous objects in the distant Universe,
thought to be powered by supermassive black holes at the heart of galaxies.
A single quasar could be a thousand times brighter than an entire galaxy of
a hundred billion stars, and yet this remarkable amount of energy originates
from a volume smaller than our Solar System.
[3]: One of the fundamental predictions of the Hot Big Bang theory for the
creation of the Universe is the existence of the Cosmic Microwave Background
Radiation (CMBR). This relic radiation of the primeval fireball was
discovered in 1964 by means of radio observations by American physicists
Arno A. Penzias and Robert W. Wilson, who were rewarded with the Nobel Prize
in 1978. Precision measurements by the COBE and WMAP satellites later showed
that this ancient radiation fills the Universe, with a present-day
temperature of slightly less than 3 degrees above absolute zero (2.725
Kelvin, or -270.4 degree Celsius). A particular prediction of the Big Bang
theory is that the Universe cools when expanding, the temperature scaling
with the dilution factor of the Universe (1 + redshift). At the redshift of
the galaxy (2.41837), one would thus expect a temperature of 2.725 x (1 +
2.41837) = 9.315 K or -263.835 degree Celsius.
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Czech Republic: Pavel Suchan, +420 267 103 040
Denmark: Dr. Michael Linden-Vornle, +45-33-18 19 97
Finland: Ms. Riitta Tirronen, +358 9 7748 8369
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Dr. Leopoldo Benacchio, +39-347-230 26 51
The Netherlands: Dr. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
Spain: Dr. Miguel Mas-Hesse, +34918131196
Sweden: Dr. Jesper Sollerman, +46-8-55 37 85 54
Switzerland: Dr. Martin Steinacher, +41-31-324 23 82
United Kingdom: Mr. Peter Barratt, +44-1793-44 20 25
USA: Dr. Paola Rebusco, +1-617-308-2397
----------------------------------------------------------------------------
ESO Press Information is available on Receive email notification
the WWW at about important news from
http://www.eso.org/outreach/press-rel/ ESO - subscribe to the
ESO-NEWS Mailing List.
----------------------------------------------------------------------------
Copyright ESO Education & Public Relations Department
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
----------------------------------------------------------------------------
----------------------------------------------------------------------------
Text with all links and the photos are available on the ESO Website at URL:
http://www.eso.org/public/outreach/press-rel/pr-2008/pr-13-08.html
----------------------------------------------------------------------------
Contacts:
Cedric Ledoux and Pasquier Noterdaeme
ESO, Chile
Phone: +56 2 463 30 56 or +56 55 43 53 11
Patrick Petitjean
Institut d'Astrophysique de Paris, France
Phone: +33 1 44 32 81 50
Raghunathan Srianand
Inter University Centre for Astronomy and Astrophysics
Pune, India
Phone: +91 20 569 1414 (ext 320)
Dr. Henri Boffin
ESO Press Officer
Phone: +49 89 3200 6222
Valentina Rodriguez
ESO Press Officer in Chile
Phone: +56 2 463 3123
For Immediate Release: 13 May 2008
ESO Science Release 13/08
A Molecular Thermometer for the Distant Universe
First accurate measurement of the temperature of the cosmic background at an
early epoch
Astronomers have made use of ESO's Very Large Telescope to detect for the
first time in the ultraviolet the carbon monoxide molecule in a galaxy
located almost 11 billion light-years away, a feat that had remained elusive
for 25 years. This detection allows them to obtain the most precise
measurement of the cosmic temperature at such a remote epoch.
The team of astronomers [1] aimed the UVES spectrograph on ESO's VLT for
more than 8 hours at a well-hidden galaxy whose light has taken almost 11
billion years to reach us, that is about 80% of the age of the Universe.
The only way this galaxy can be seen is through the imprint its interstellar
gas leaves on the spectrum of an even more remote quasar [2]. "Quasars are
here only used as a beacon in the very distant Universe. Interstellar clouds
of gas in galaxies, located between the quasars and us on the same line of
sight, absorb parts of the light emitted by the quasars. The resulting
spectrum consequently presents dark 'valleys' that can be attributed to
well-known elements and possibly molecules," explains Raghunathan Srianand
(Pune, India), who led the team making the observations.
Thanks to the power of the VLT and a very careful selection of the target --
the target was selected among about ten thousands quasars -- the team was
able to discover the presence of normal and deuterated molecular hydrogen
(H2, HD) and carbon monoxide (CO) molecules in the interstellar medium of
this remote galaxy. "This is the first time that these three molecules have
been detected in absorption in front of a quasar, a detection that has
remained elusive for more than a quarter century," says Cedric Ledoux (ESO),
member of the team.
The same team had already broken the record for the most distant detection
of molecular hydrogen in a galaxy that we see as it was when the Universe
was less than 1.5 billion years old (see ESO 16/06).
The interstellar gas is the reservoir from which stars form and, as such, is
an important component of galaxies. Furthermore, because the formation and
the state of molecules are very sensitive to the physical conditions of the
gas, which in turn depend on the rate at which stars are formed, the
detailed study of the chemistry of the interstellar medium is an important
tool to understand how galaxies form.
Based on their observations, the astronomers showed that the physical
conditions prevailing in the interstellar gas in this remote galaxy are
similar to what is seen in our Galaxy, the Milky Way.
But most importantly, the team was able to measure with the best ever
precision the temperature of the cosmic background radiation in the remote
Universe [3]. "Unlike other methods, measuring the temperature of the cosmic
background using the CO molecule involves very few assumptions," declares
co-author Pasquier Noterdaeme.
If the Universe was formed in a 'Big Bang', as most astrophysicists infer,
the glow of this primeval fireball should have been warmer in the past. This
is exactly what is found by the new measurements. "Given the current
measured temperature of 2.725 K, one would expect that the temperature 11
billion years ago was about 9.3 K," says co-author Patrick Petitjean. "Our
unique set of VLT observations allows us to deduce a temperature of 9.15 K,
plus or minus 0.7 K, in excellent agreement with the theory."
"We believe our analysis pioneers interstellar chemistry studies at high
redshift and demonstrates that it is possible, together with the detection
of other molecules such as HD or CH, to use interstellar chemistry to tackle
important cosmological issues," adds Srianand.
The results described here have been presented in a Letter to the Editor in
Astronomy and Astrophysics ("First detection of CO in a high-redshift damped
Lyman-alpha system", by R. Srianand et al.).
Notes
[1]: The team is composed of Raghunathan Srianand (IUCAA, Pune, India),
Pasquier Noterdaeme and Cedric Ledoux (ESO), and Patrick Petitjean (IAP,
France). The same team already made the first measurement of the temperature
of the cosmic microwave background radiation, at a time when the Universe
was only about 2.5 billion years old, also using UVES on the VLT (see ESO
27/00). At that time, they could only measure a temperature in the range
between 6 and 14 K.
[2]: Quasars are extraordinarily luminous objects in the distant Universe,
thought to be powered by supermassive black holes at the heart of galaxies.
A single quasar could be a thousand times brighter than an entire galaxy of
a hundred billion stars, and yet this remarkable amount of energy originates
from a volume smaller than our Solar System.
[3]: One of the fundamental predictions of the Hot Big Bang theory for the
creation of the Universe is the existence of the Cosmic Microwave Background
Radiation (CMBR). This relic radiation of the primeval fireball was
discovered in 1964 by means of radio observations by American physicists
Arno A. Penzias and Robert W. Wilson, who were rewarded with the Nobel Prize
in 1978. Precision measurements by the COBE and WMAP satellites later showed
that this ancient radiation fills the Universe, with a present-day
temperature of slightly less than 3 degrees above absolute zero (2.725
Kelvin, or -270.4 degree Celsius). A particular prediction of the Big Bang
theory is that the Universe cools when expanding, the temperature scaling
with the dilution factor of the Universe (1 + redshift). At the redshift of
the galaxy (2.41837), one would thus expect a temperature of 2.725 x (1 +
2.41837) = 9.315 K or -263.835 degree Celsius.
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Czech Republic: Pavel Suchan, +420 267 103 040
Denmark: Dr. Michael Linden-Vornle, +45-33-18 19 97
Finland: Ms. Riitta Tirronen, +358 9 7748 8369
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Dr. Leopoldo Benacchio, +39-347-230 26 51
The Netherlands: Dr. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
Spain: Dr. Miguel Mas-Hesse, +34918131196
Sweden: Dr. Jesper Sollerman, +46-8-55 37 85 54
Switzerland: Dr. Martin Steinacher, +41-31-324 23 82
United Kingdom: Mr. Peter Barratt, +44-1793-44 20 25
USA: Dr. Paola Rebusco, +1-617-308-2397
----------------------------------------------------------------------------
ESO Press Information is available on Receive email notification
the WWW at about important news from
http://www.eso.org/outreach/press-rel/ ESO - subscribe to the
ESO-NEWS Mailing List.
----------------------------------------------------------------------------
Copyright ESO Education & Public Relations Department
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
----------------------------------------------------------------------------