Andrew Yee[_1_]
January 28th 07, 05:58 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/outreach/press-rel/pr-2006/pr-45-06.html
----------------------------------------------------------------------------
Contacts:
Olivier Le Fre
Laboratoire d'Astrophysique de Marseille, France
Phone: +33 4 91 05 59 85
Christian Marinoni
Centre de Physique Thrique, Marseille, France
Phone: +33 4 91 26 95 35
For Immediate Release: 6 December 2006
ESO Science Release 45/06
Do Galaxies Follow Darwinian Evolution?
VLT Survey Provides New Insight into Formation of Galaxies
Using VIMOS on ESO's Very Large Telescope, a team of French and Italian
astronomers have shown the strong influence the environment exerts on the
way galaxies form and evolve. The scientists have for the first time charted
remote parts of the Universe, showing that the distribution of galaxies has
considerably evolved with time, depending on the galaxies' immediate
surroundings. This surprising discovery poses new challenges for theories of
the formation and evolution of galaxies.
The 'nature versus nurture' debate is a hot topic in human psychology. But
astronomers too face similar conundrums, in particular when trying to solve
a problem that goes to the very heart of cosmological theories: are the
galaxies we see today simply the product of the primordial conditions in
which they formed, or did experiences in the past change the path of their
evolution?
In a large, three-year long survey carried out with VIMOS [1], the Visible
Imager and Multi-Object Spectrograph on ESO's VLT, astronomers studied more
than 6,500 galaxies over a wide range of distances to investigate how their
properties vary over different timescales, in different environments and for
varying galaxy luminosities [2]. They were able to build an atlas of the
Universe in three dimensions, going back more than 9 billion years.
This new census reveals a surprising result. The colour-density relation,
that describes the relationship between the properties of a galaxy and its
environment, was markedly different 7 billion years ago. The astronomers
thus found that the galaxies' luminosity, their initial genetic properties,
and the environments they reside in have a profound impact on their
evolution.
"Our results indicate that environment is a key player in galaxy evolution,
but there's no simple answer to the 'nature versus nurture' problem in
galaxy evolution," said Olivier Le Fre from the Laboratoire d'Astrophysique
de Marseille, France, who coordinates the VIMOS VLT Deep Survey team that
made the discovery. "They suggest that galaxies as we see them today are the
product of their inherent genetic information, evolved over time, as well as
complex interactions with their environments, such as mergers."
Scientists have known for several decades that galaxies in the Universe's
past look different to those in the present-day Universe, local to the Milky
Way [3]. Today, galaxies can be roughly classified as red, when few or no
new stars are being born, or blue, where star formation is still ongoing.
Moreover, a strong correlation exists between a galaxy's colour and the
environment it resides in: the more sociable types found in dense clusters
are more likely to be red than the more isolated ones.
By looking back at a wide range of galaxies of a variety of ages, the
astronomers were aiming to study how this peculiar correlation has evolved
over time.
"Using VIMOS, we were able to use the largest sample of galaxies currently
available for this type of study, and because of the instrument's ability to
study many objects at a time we obtained many more measurements than
previously possible," said Angela Iovino, from the Brera Astronomical
Observatory, Italy, another member of the team.
The team's discovery of a marked variation in the 'colour-density'
relationship, depending on whether a galaxy is found in a cluster or alone,
and on its luminosity, has many potential implications. The findings suggest
for example that being located in a cluster quenches a galaxy's ability to
form stars more quickly compared with those in isolation. Luminous galaxies
also run out of star-forming material at an earlier time than fainter ones.
They conclude that the connection between galaxies' colour, luminosity and
their local environment is not merely a result of primordial conditions
'imprinted' during their formation -- but just as for humans, galaxies'
relationship and interactions can have a profound impact on their evolution.
A high resolution image and its caption is available on this page:
http://www.eso.org/outreach/press-rel/pr-2006/phot-45-06.html
More information
Results from this study are published in volume 458 (1) of Astronomy &
Astrophysics, "The VIMOS VLT Deep Survey: The build-up of the colour-density
relation", by O. Cucciati et al. The paper is available from the A&A web
site.
The Survey team consists of O. Cucciati, A. Iovino, L. Guzzo, S. Temporin
(INAF-Observatory of Brera, Italy), C. Marinoni (Centre de Physique Thrique,
Marseille, France), O. Ilbert, B. Maranno, A. Bongiorno (University of
Bologna, Italy), O. Le Fre, A. Pollo, L. Tresse, V. Le Brun, C. Adami, S.
Arnouts, A. Mazure, S. de la Torre (CNRS-Universitde Provence, France), S.
Bardelli, G. Zamorani, A. Cappi, E. Zucca, M. Bolzonella, P. Ciliegi, R.
Merighi, L. Pozzetti (INAF-Observatory of Bologna, Italy), P. Franzetti, B.
Meneux, M. Scodeggio, D. Bottini, B. Garilli, D. Maccagni, S. Foucaud, D.
Vergani (IASF-INAF, Italy), H.J. McCracken, Y. Mellier (Institut
d'Astrophysique de Paris, France), L. Scaramella, A. Zanichelli, G.
Vettolani, M. Bondi, L. Gregorini (IRA-INAF, Italy), J.P. Picat, T. Contini,
I. Gavignaud, R. Pello, F. Lamareille, G. Mathez, D. Rizzo (Institut
d'Astrophysique de l'Observatoire Midi-Pyrens), M. Arnaboldi, M. Radovich,
G. Busarello, P. Merluzzi, V. Ripepi (Observatory of Capodimonte, Italy), S.
Charlot (MPIA, Germany) and S. Paltani (Integral Science Data Centre,
Switzerland)
INAF has also made a press release available in Italian.
Notes
[1] The Visible Multi-Object Spectrograph VIMOS is a multi-mode instrument
on Melipal, the third Unit Telescope of the Very Large Telescope array at
ESO's Paranal Observatory. In operation since 2003, VIMOS can provide both
images and astronomical spectra at visible wavelengths over wide fields of
view. In its multi-object mode, it can record up to 1,000 spectra at a time.
[2] The VIMOS VLT Deep Survey (VVDS) is a breakthrough spectroscopic survey
which will provide, when finished, a complete picture of galaxy and
structure formation over a very broad redshift range (0 < z < 5), over
sixteen square degrees of the sky in four separate fields.
[3] Because of the time taken for light to reach an observer on Earth over
the vast distances of the cosmos, astronomers studying distant galaxies are
in fact observing conditions in the Universe's past. The region closer to
Earth, local to our own Milky Way Galaxy, is thus often referred to as the
'present-day' Universe.
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Finland: Ms. Riitta Tirronen, +358 9 7748 8369
Denmark: Dr. Michael Linden-Vnle, +45-33-18 19 97
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: Ms. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
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
----------------------------------------------------------------------------
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/outreach/press-rel/pr-2006/pr-45-06.html
----------------------------------------------------------------------------
Contacts:
Olivier Le Fre
Laboratoire d'Astrophysique de Marseille, France
Phone: +33 4 91 05 59 85
Christian Marinoni
Centre de Physique Thrique, Marseille, France
Phone: +33 4 91 26 95 35
For Immediate Release: 6 December 2006
ESO Science Release 45/06
Do Galaxies Follow Darwinian Evolution?
VLT Survey Provides New Insight into Formation of Galaxies
Using VIMOS on ESO's Very Large Telescope, a team of French and Italian
astronomers have shown the strong influence the environment exerts on the
way galaxies form and evolve. The scientists have for the first time charted
remote parts of the Universe, showing that the distribution of galaxies has
considerably evolved with time, depending on the galaxies' immediate
surroundings. This surprising discovery poses new challenges for theories of
the formation and evolution of galaxies.
The 'nature versus nurture' debate is a hot topic in human psychology. But
astronomers too face similar conundrums, in particular when trying to solve
a problem that goes to the very heart of cosmological theories: are the
galaxies we see today simply the product of the primordial conditions in
which they formed, or did experiences in the past change the path of their
evolution?
In a large, three-year long survey carried out with VIMOS [1], the Visible
Imager and Multi-Object Spectrograph on ESO's VLT, astronomers studied more
than 6,500 galaxies over a wide range of distances to investigate how their
properties vary over different timescales, in different environments and for
varying galaxy luminosities [2]. They were able to build an atlas of the
Universe in three dimensions, going back more than 9 billion years.
This new census reveals a surprising result. The colour-density relation,
that describes the relationship between the properties of a galaxy and its
environment, was markedly different 7 billion years ago. The astronomers
thus found that the galaxies' luminosity, their initial genetic properties,
and the environments they reside in have a profound impact on their
evolution.
"Our results indicate that environment is a key player in galaxy evolution,
but there's no simple answer to the 'nature versus nurture' problem in
galaxy evolution," said Olivier Le Fre from the Laboratoire d'Astrophysique
de Marseille, France, who coordinates the VIMOS VLT Deep Survey team that
made the discovery. "They suggest that galaxies as we see them today are the
product of their inherent genetic information, evolved over time, as well as
complex interactions with their environments, such as mergers."
Scientists have known for several decades that galaxies in the Universe's
past look different to those in the present-day Universe, local to the Milky
Way [3]. Today, galaxies can be roughly classified as red, when few or no
new stars are being born, or blue, where star formation is still ongoing.
Moreover, a strong correlation exists between a galaxy's colour and the
environment it resides in: the more sociable types found in dense clusters
are more likely to be red than the more isolated ones.
By looking back at a wide range of galaxies of a variety of ages, the
astronomers were aiming to study how this peculiar correlation has evolved
over time.
"Using VIMOS, we were able to use the largest sample of galaxies currently
available for this type of study, and because of the instrument's ability to
study many objects at a time we obtained many more measurements than
previously possible," said Angela Iovino, from the Brera Astronomical
Observatory, Italy, another member of the team.
The team's discovery of a marked variation in the 'colour-density'
relationship, depending on whether a galaxy is found in a cluster or alone,
and on its luminosity, has many potential implications. The findings suggest
for example that being located in a cluster quenches a galaxy's ability to
form stars more quickly compared with those in isolation. Luminous galaxies
also run out of star-forming material at an earlier time than fainter ones.
They conclude that the connection between galaxies' colour, luminosity and
their local environment is not merely a result of primordial conditions
'imprinted' during their formation -- but just as for humans, galaxies'
relationship and interactions can have a profound impact on their evolution.
A high resolution image and its caption is available on this page:
http://www.eso.org/outreach/press-rel/pr-2006/phot-45-06.html
More information
Results from this study are published in volume 458 (1) of Astronomy &
Astrophysics, "The VIMOS VLT Deep Survey: The build-up of the colour-density
relation", by O. Cucciati et al. The paper is available from the A&A web
site.
The Survey team consists of O. Cucciati, A. Iovino, L. Guzzo, S. Temporin
(INAF-Observatory of Brera, Italy), C. Marinoni (Centre de Physique Thrique,
Marseille, France), O. Ilbert, B. Maranno, A. Bongiorno (University of
Bologna, Italy), O. Le Fre, A. Pollo, L. Tresse, V. Le Brun, C. Adami, S.
Arnouts, A. Mazure, S. de la Torre (CNRS-Universitde Provence, France), S.
Bardelli, G. Zamorani, A. Cappi, E. Zucca, M. Bolzonella, P. Ciliegi, R.
Merighi, L. Pozzetti (INAF-Observatory of Bologna, Italy), P. Franzetti, B.
Meneux, M. Scodeggio, D. Bottini, B. Garilli, D. Maccagni, S. Foucaud, D.
Vergani (IASF-INAF, Italy), H.J. McCracken, Y. Mellier (Institut
d'Astrophysique de Paris, France), L. Scaramella, A. Zanichelli, G.
Vettolani, M. Bondi, L. Gregorini (IRA-INAF, Italy), J.P. Picat, T. Contini,
I. Gavignaud, R. Pello, F. Lamareille, G. Mathez, D. Rizzo (Institut
d'Astrophysique de l'Observatoire Midi-Pyrens), M. Arnaboldi, M. Radovich,
G. Busarello, P. Merluzzi, V. Ripepi (Observatory of Capodimonte, Italy), S.
Charlot (MPIA, Germany) and S. Paltani (Integral Science Data Centre,
Switzerland)
INAF has also made a press release available in Italian.
Notes
[1] The Visible Multi-Object Spectrograph VIMOS is a multi-mode instrument
on Melipal, the third Unit Telescope of the Very Large Telescope array at
ESO's Paranal Observatory. In operation since 2003, VIMOS can provide both
images and astronomical spectra at visible wavelengths over wide fields of
view. In its multi-object mode, it can record up to 1,000 spectra at a time.
[2] The VIMOS VLT Deep Survey (VVDS) is a breakthrough spectroscopic survey
which will provide, when finished, a complete picture of galaxy and
structure formation over a very broad redshift range (0 < z < 5), over
sixteen square degrees of the sky in four separate fields.
[3] Because of the time taken for light to reach an observer on Earth over
the vast distances of the cosmos, astronomers studying distant galaxies are
in fact observing conditions in the Universe's past. The region closer to
Earth, local to our own Milky Way Galaxy, is thus often referred to as the
'present-day' Universe.
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Finland: Ms. Riitta Tirronen, +358 9 7748 8369
Denmark: Dr. Michael Linden-Vnle, +45-33-18 19 97
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: Ms. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
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
----------------------------------------------------------------------------
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
----------------------------------------------------------------------------