Twin Explosions In Gigantic Dusty Potato Crisp (Forwarded)

ESO Education and Public Relations Dept.

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Text with all links and the photos are available on the ESO
Website at URL:

http://www.eso.org/outreach/press-re.../pr-17-06.html
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For immediate release: 11 May 2006

ESO Press Photo 17/06

Twin Explosions In Gigantic Dusty Potato Crisp

ESO's Very Large Telescope, equipped with the multi-mode FORS
instrument, took an image of NGC 3190, a galaxy so distorted that
astronomers gave it two names. And as if to prove them right, in
2002 it fired off, almost simultaneously, two stellar explosions,
a very rare event.

This beautiful edge-on spiral galaxy with tightly wound arms and
a warped shape that makes it resemble a gigantic potato crisp lies
in the constellation Leo ('the Lion') [1] and is approximately 70
million light years away. It is the dominant member of a small
group of galaxies known as Hickson 44, named after the Canadian
astronomer, Paul Hickson. In addition to NGC 3190 [2], Hickson 44
consists of one elliptical and two spiral galaxies. These are,
however, slightly out of the field of view and therefore not
visible here.

In 1982, Hickson published a catalogue of over 400 galaxies found
in compact, physically-related groups of typically 4 to 5 galaxies
per group (see the image of Robert's Quartet in ESO PR Photo 34/05
as another example). Such compact groups allow astronomers to
study how galaxies dynamically affect each other, and help them
test current ideas on how galaxies form. One idea is that compact
groups of galaxies, such as Hickson 44, merge to form a giant
elliptical galaxy, such as NGC 1316 (see ESO PR 17/00).

Indeed, signs of tidal interactions are visible in the twisted
dust lane of NGC 3190. This distortion initially misled astronomers
into assigning a separate name for the southwestern side, NGC 3189,
although NGC 3190 is the favoured designation.

NGC 3190 has an 'Active Galactic Nucleus', and as such, the bright,
compact nucleus is thought to host a supermassive black hole.

In March 2002, a new supernova (SN 2002bo) was found in between the
'V' of the dust lanes in the southeastern part of NGC 3190. It was
discovered independently by the Brazilian and Japanese amateur
astronomers, Paulo Cacella and Yoji Hirose. SN 2002bo was caught
almost two weeks before reaching its maximum brightness, allowing
astronomers to study its evolution. It has been the subject of
intense monitoring by a world-wide network of telescopes. The
conclusion was that SN 2002bo is a rather unusual Type Ia supernova
[3]. The image presented here was taken in March 2003, i.e. about
a year after the maximum of the supernova which is 50 times fainter
on the image than a year before.

While observing SN 2002bo in May 2002, a group of Italian astronomers
discovered another supernova, SN 2002cv, on the other side of NGC
3190. Two supernovae of this type appearing nearly simultaneously in
the same galaxy is a rare event, as normally astronomers expect only
one such event per century in a galaxy. SN 2002cv was best visible
at infrared wavelengths as it was superimposed on the dust lane of
NGC 3190, and therefore hidden by a large quantity of dust. In fact,
this supernova holds the record for the most obscured Type Ia event.

The image was obtained with a total exposure time of 14 minutes only.
Yet, with the amazing power of the Very Large Telescope, it reveals
a large zoo of galaxies of varying morphologies. How many can you
find?

A high resolution image and its caption is available at
http://www.eso.org/outreach/press-re...hot-17-06.html

Notes

[1] The constellation 'Leo' represents the Lion. Many ancient
civilisations, e.g. Sumerian, Babylonian, Persian, Syrian, Greek,
all identified this constellation as a lion. In Greek Mythology,
the first of Hercules' twelve tasks was to slay the Nemean lion
and bring back its skin.

[2] 'NGC' stands for 'New General Catalogue' (of nebulae and
clusters) that was published in 1888 by J.L.E. Dreyer in the
'Memoirs of the Royal Astronomical Society'.

[3] Type Ia supernovae are believed to result from the explosion of
old stars known as 'white dwarfs' -- the endpoint of most low mass
stars such as our Sun. However, a white dwarf only explodes when
its mass reaches a certain critical value (about 1.4 times the
mass of our Sun). The general consensus is that this critical mass
can only be attained if the white dwarf has a nearby companion
star from which it can gain matter. Their generally uniform
properties combined with their intrinsic brightness means that
Type Ia supernovae can be used to measure relative distances (see
ESO PR 21/98). They have been used to infer that the Universe is
currently accelerating.

SN 2002bo has been extensively studied by Benetti et al. (2004,
MNRAS, 348, 261), while SN 2002cv has been described by Di Paola
et al. (2002, A&A, 393, L21).

Technical Information: ESO PR Photo 17/06 is based on data
extracted from the ESO Science Archive. It is a colour composite
based on images obtained on 26 March 2003 with FORS1 on UT2
(Kueyen) in four filters (B, V, R and I) for a total exposure
time of 14 minutes. The observations were done in the framework of
a programme aiming at studying the physics of Type Ia supernovae.
The field of view is 6.15 x 5 arcminutes. North is up and East is
to the left. The data extraction from the archive, data reduction
and final colour processing of the image was done by Henri Boffin
(ESO).

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-Vørnle, +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, benacchio @ inaf.it
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

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