Andrew Yee
November 4th 05, 04:27 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-2005/phot-34-05.html
--------------------------------------------------------------
Contact:
Henri Boffin
ESO
Garching, Germany
Phone: +49 89 3209 6222
For immediate release: 4 November 2005
ESO Press Photo 34/05
Cosmic Portrait of a Perturbed Family
ESO PR Photo 34a/05 ESO PR Photo 34b/05
Robert's Quartet NGC 92 in H-alpha
ESO PR Photo 34a/05 shows in amazing details a group of
galaxies known as Robert's Quartet [1]. The image is based
on data collected with the FORS2 multi-mode instrument on
ESO's Very Large Telescope.
Robert's Quartet is a family of four very different galaxies,
located at a distance of about 160 million light-years, close
to the centre of the southern constellation of the Phoenix.
Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered
by John Herschel in the 1830s. NGC 87 (upper right) is an
irregular galaxy similar to the satellites of our Milky Way,
the Magellanic Clouds. NGC 88 (centre) is a spiral galaxy
with an external diffuse envelope, most probably composed of
gas. NGC 89 (lower middle) is another spiral galaxy with two
large spiral arms. The largest member of the system, NGC 92
(left), is a spiral Sa galaxy with an unusual appearance.
One of its arms, about 100,000 light-years long, has been
distorted by interactions and contains a large quantity of
dust.
The quartet is one of the finest examples of compact groups
of galaxies. Because such groups contain four to eight
galaxies in a very small region, they are excellent
laboratories for the study of galaxy interactions and
their effects, in particular on the formation of stars.
Using another set of VLT data also obtained with FORS2,
astronomers [2] were able to study the properties of regions
of active star formation ("HII regions" [3]) in the sister
members of Robert's Quartet. They found more than 200 of
such regions in NGC 92, with a size between 500 and 1,500
light-years (see ESO PR Photo 34b/05). For NGC 87, they
detected 56 HII regions, while the two other galaxies appear
to have far fewer of them. For NGC 88, however, they found
two plume-like features, while NGC 89 presents a ring of
enhanced stellar activity. The system is thus clearly showing
increased star formation activity, most probably as the
result of the interaction between its members. The sisters
clearly belong to a perturbed family.
The quartet has a total visual magnitude of almost 13, i.e.
it is about 600 times fainter than the faintest object that
can be seen with the unaided eye. The brightest member of
the group has a magnitude of about 14. On the sky, the four
galaxies are all within a circle of radius of 1.6 arcmin,
corresponding to about 75,000 light-years.
Technical information: ESO PR Photo 34a/05 is based on images
obtained with the FORS2 multi-mode instrument on ESO's Very
Large Telescope on October 30, 1999, during the commissioning
phase of the instrument. Observations were done in four
different filters : B (8 min exposure), V (4 min), R (3 min)
and I (4 min). The data were extracted from the ESO Science
Archive and processed by Henri Boffin (ESO). The colour image
was finally produced by Kristina Boneva and Haennes Heyer
(ESO). North is up and East is to the left. The field of view
is about 6x6 arcmin. ESO PR Photo 34b/05 is based on data
obtained with the FORS2 instrument on Melipal (UT4) for
E. Pompei and A. Iovino in September 2001. The data were
extracted from the ESO Science Archive and processed by Henri
Boffin (ESO). It is based on 6 images obtained through the
H-alpha filter for a total exposure time of 72 minutes. The
field of view is about 3x3 arcmin.
Notes
[1]: The group of galaxies was known as a Compact Group since
1977 by J.A. Rose, under the designation Rose 34. Robert's
Quartet is also known under the less poetic name of
AM 0018-485 from the Catalogue of Southern Peculiar Galaxies
and Associations, compiled in 1987 by astronomers Halton
"Chip" Arp and Barry Madore. But who is Robert then? As
discovered by Australian amateur astronomer Mike Kerr, Arp
and Madore named Robert's Quartet after Robert Freedman who
generated many of the updated positions of galaxies in the
catalogue. The astronomers clearly had a very good sense of
humour as the catalogue also contains a system of galaxies
called Wendy (ESO 147- 8; for Wendy Freedman) and another
called the Conjugal galaxy (ESO 384- 53)!
[2]: The astronomers are S. Temporin (University of Innsbruck,
Austria), S. Ciroi and P. Rafanelli (University of Padova,
Italy), A. Iovino (INAF-Brera Astronomical Observatory, Italy),
E. Pompei (ESO), and M. Radovich (INAF-Capodimonte Astronomical
Observatory, Italy). (The article describing this result is
available in PDF format at
http://www.ast.cam.ac.uk/%7Esb2004/posters/files/Temporin.pdf)
[3]: The radiation of young hot stars embedded in an
interstellar cloud is able to heat the surrounding gas,
resulting in the apparition of an emission nebula that shines
mostly in the light of ionized hydrogen (H) atoms. Such nebulae
are therefore often referred to as "HII regions". The well-
known Orion Nebula is an outstanding example of that type of
nebula.
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Finland: Ms. Terhi Loukiainen, +358 9 7748 8385
Denmark: Dr. Michael Linden-Vørnle, +45-33-18 19 97
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Prof. Massimo Capaccioli, +39-081-55 75 511
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 the WWW at
http://www.eso.org/outreach/press-rel/
--------------------------------------------------------------
(c) 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-2005/phot-34-05.html
--------------------------------------------------------------
Contact:
Henri Boffin
ESO
Garching, Germany
Phone: +49 89 3209 6222
For immediate release: 4 November 2005
ESO Press Photo 34/05
Cosmic Portrait of a Perturbed Family
ESO PR Photo 34a/05 ESO PR Photo 34b/05
Robert's Quartet NGC 92 in H-alpha
ESO PR Photo 34a/05 shows in amazing details a group of
galaxies known as Robert's Quartet [1]. The image is based
on data collected with the FORS2 multi-mode instrument on
ESO's Very Large Telescope.
Robert's Quartet is a family of four very different galaxies,
located at a distance of about 160 million light-years, close
to the centre of the southern constellation of the Phoenix.
Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered
by John Herschel in the 1830s. NGC 87 (upper right) is an
irregular galaxy similar to the satellites of our Milky Way,
the Magellanic Clouds. NGC 88 (centre) is a spiral galaxy
with an external diffuse envelope, most probably composed of
gas. NGC 89 (lower middle) is another spiral galaxy with two
large spiral arms. The largest member of the system, NGC 92
(left), is a spiral Sa galaxy with an unusual appearance.
One of its arms, about 100,000 light-years long, has been
distorted by interactions and contains a large quantity of
dust.
The quartet is one of the finest examples of compact groups
of galaxies. Because such groups contain four to eight
galaxies in a very small region, they are excellent
laboratories for the study of galaxy interactions and
their effects, in particular on the formation of stars.
Using another set of VLT data also obtained with FORS2,
astronomers [2] were able to study the properties of regions
of active star formation ("HII regions" [3]) in the sister
members of Robert's Quartet. They found more than 200 of
such regions in NGC 92, with a size between 500 and 1,500
light-years (see ESO PR Photo 34b/05). For NGC 87, they
detected 56 HII regions, while the two other galaxies appear
to have far fewer of them. For NGC 88, however, they found
two plume-like features, while NGC 89 presents a ring of
enhanced stellar activity. The system is thus clearly showing
increased star formation activity, most probably as the
result of the interaction between its members. The sisters
clearly belong to a perturbed family.
The quartet has a total visual magnitude of almost 13, i.e.
it is about 600 times fainter than the faintest object that
can be seen with the unaided eye. The brightest member of
the group has a magnitude of about 14. On the sky, the four
galaxies are all within a circle of radius of 1.6 arcmin,
corresponding to about 75,000 light-years.
Technical information: ESO PR Photo 34a/05 is based on images
obtained with the FORS2 multi-mode instrument on ESO's Very
Large Telescope on October 30, 1999, during the commissioning
phase of the instrument. Observations were done in four
different filters : B (8 min exposure), V (4 min), R (3 min)
and I (4 min). The data were extracted from the ESO Science
Archive and processed by Henri Boffin (ESO). The colour image
was finally produced by Kristina Boneva and Haennes Heyer
(ESO). North is up and East is to the left. The field of view
is about 6x6 arcmin. ESO PR Photo 34b/05 is based on data
obtained with the FORS2 instrument on Melipal (UT4) for
E. Pompei and A. Iovino in September 2001. The data were
extracted from the ESO Science Archive and processed by Henri
Boffin (ESO). It is based on 6 images obtained through the
H-alpha filter for a total exposure time of 72 minutes. The
field of view is about 3x3 arcmin.
Notes
[1]: The group of galaxies was known as a Compact Group since
1977 by J.A. Rose, under the designation Rose 34. Robert's
Quartet is also known under the less poetic name of
AM 0018-485 from the Catalogue of Southern Peculiar Galaxies
and Associations, compiled in 1987 by astronomers Halton
"Chip" Arp and Barry Madore. But who is Robert then? As
discovered by Australian amateur astronomer Mike Kerr, Arp
and Madore named Robert's Quartet after Robert Freedman who
generated many of the updated positions of galaxies in the
catalogue. The astronomers clearly had a very good sense of
humour as the catalogue also contains a system of galaxies
called Wendy (ESO 147- 8; for Wendy Freedman) and another
called the Conjugal galaxy (ESO 384- 53)!
[2]: The astronomers are S. Temporin (University of Innsbruck,
Austria), S. Ciroi and P. Rafanelli (University of Padova,
Italy), A. Iovino (INAF-Brera Astronomical Observatory, Italy),
E. Pompei (ESO), and M. Radovich (INAF-Capodimonte Astronomical
Observatory, Italy). (The article describing this result is
available in PDF format at
http://www.ast.cam.ac.uk/%7Esb2004/posters/files/Temporin.pdf)
[3]: The radiation of young hot stars embedded in an
interstellar cloud is able to heat the surrounding gas,
resulting in the apparition of an emission nebula that shines
mostly in the light of ionized hydrogen (H) atoms. Such nebulae
are therefore often referred to as "HII regions". The well-
known Orion Nebula is an outstanding example of that type of
nebula.
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Finland: Ms. Terhi Loukiainen, +358 9 7748 8385
Denmark: Dr. Michael Linden-Vørnle, +45-33-18 19 97
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Prof. Massimo Capaccioli, +39-081-55 75 511
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 the WWW at
http://www.eso.org/outreach/press-rel/
--------------------------------------------------------------
(c) ESO Education & Public Relations Department
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
--------------------------------------------------------------