Vade Retro Satanas, Insane Galaxies
held between themselves by their small goatees
It's forbidden to see this bridge of matter
ARP 102 or the Dynamics of Galaxies
In the night of the 23/06/95, the NOAO (WIYN
Telescope) takes the photograph of the galaxy pair Arp 102.
This exceptional quality photograph would not probably never have
attracted our attention if we had not had in memory a previous picture
appearing in "Atlas of Peculiar galaxies" of Halton Arp. We
remembered a detail, that there is in the picture of the catalog two
bridges of matter, whereas the picture of the NOAO shows only one
(the one that we distinguishe on the right), but not the one of the left,
that is yet visible in the picture of Arp.
We have first processed the picture of Arp to see if in this
picture, the bridge of matter on the left could be an artifact. We
didn't find anything abnormal. This failure is due, on the one hand,
because it is a monochromatic picture and on the other hand because the
resolution is certainly insufficient, whereas the picture of the NOAO
is a trichromatic high resolution. picture.
California Institute of
Atlas of Peculiar Galaxies.
By Halton Arp
processed then the picture of the NOAO. Below is the result:
The two "bridges of matter" are perfectly visible. There is not
any ambiguousness. And it confirms that which one hardly distinguishes in
the picture of Halton Arp.
- Why the picture published by the NOAO doesn't
show the left bridge of matter ?
- For what technical reason, with means that Arp didn't
certainly have, doesn't this bridge appear here ? We cannot imagine that
one made some Digital Processing to make it disappear. And we have
difficulty again imagining that astronomers didn't "see" this bridge of
We are in the presence of interacting galaxies. Bridges of matter are the
result of mutual gravitational influences of galaxies upon each other.
This hypothesis seems very probable.
We have in this picture:
Near the center of the photograph, a spiral galaxy
whose right arm is strongly stretched and extended outwards, with
the shape of a circular shape. One notices, at its extremity a frontal shock zone that seems to be the source of young stars.
On the left, an elliptic galaxy, linked to the
spiral galaxy by a straight matter bridge.It is impossible, with
this one picture, to say from where is came this matter, nor to say of
what it is made. Its direction movement is not obvious.
We can already deduct that these two bridges of
matter are not of the same kind. The fact that the left bridge is
straight imposes, considering the distance separating the two galaxies,
of the order of 500.000 ly, that these two galaxies didn't have, one in
relation to the other, of perceptiblel angular motion during at least
The redshift of the spiral galaxy is 7182 km/s, The one of the elliptic galaxy is
7250 km/s (Source: Nigel Sharp - NOAO). These very similar redshiftses don't
pose a particular problem. They demonstrate that these two galaxies are
The number of distant galaxies was considerably
multiplied by the Digital processing. It is not trivial.
Here is what the NOAO says about Arp 102
This interesting interacting spiral/elliptical pair
of galaxies was first described in the Catalogue of Peculiar Galaxies,
compiled by Halton Arp in 1966. It is also pair number 508 in Igor
Karachentsev's catalog of binary galaxies. The large spiral galaxy (type
SABb pec) shows long blue tidal tails caused by its interaction with the
southerly elliptical. In fact, this "elliptical" is much the more
interesting galaxy, despite its more nondescript appearance. It is a broad
line radio galaxy with an unresolved core and a sub-parsec VLBI component
at 6cm. It is also an intermediate type Seyfert, meaning it has an active
nucleus, and it shows a double-peaked emission line profile (separation
about 5000 km/s), which is considered to be strong evidence for the
presence of an accretion disk, probably around a central supermassive
In this picture we also see the presence of numerous more distant
background galaxies, showing as clusters of small, diffuse red objects and
scattered diffuse blue objects. These objects are very difficult to detect
and require excellent conditions and superb optics.
Location: 17 18 00 +49 04 (1950.0), constellation of
Distance: approximately 320 million light years
The NOAO hardly extends to the spiral galaxy. It barely makes
allusion to the gravitational interactions between the two galaxies. It
stresses on the elliptic galaxy. That in itself is pretty strange. Is an
elliptic galaxy, even a Seyfert, even with an active core, as exceptional
that that? Why don't they ponder about the system in its whole, on
the pair of galaxies with their filaments of matter, on "bridges of matter
" as says Halton Arp ?
Would not the elliptic galaxy be "active" and "a Seyfert" because it is
in an interactive system, in terms of gravitation and also in terms of
matter exchanges ?
All the same we cannot limit Arp 102 to only one galaxy, and thus
artificially isolate the elliptic galaxy from its global environment.
Let us also note the excessive rotational speed of the "accretion disk" in
the elliptic galaxy (gap of 5000 km/s, i.e. 2500 km/s about). Would
there not be in the core of this galaxy a lens effect, which would
be due to the gradient of matter density, as we already met otherwise some
in certain cores of galaxies (M 87, Einstein Cross) ?
For an unknown reason the two galaxies are, or were, immobilized in space
since, or during, more than 500.000 years. The straight matter bridge,
that links them, shows that. Let's note however that the axis of the jet
is not oriented toward the center of the elliptic galaxy. It could mean
that there exists nevertheless a very slow movement, or that the elliptic
galaxy took regained mobility a while ago.
The Merger of the Milky Way and Andromeda Galaxies - One finds
superb simulations of galaxy interactions there.
Galaxies: Interactions and Induced Star Formation
Kennicutt,Jr. F. Schweizer & J.E. Barnes. -
Springer (available also at
Galaxies et cosmologie - Françoise Combes, Patrick Boissé, Alain
Mazure & Alain Blanchard - Available in all the good bookshops
Dynamique des Galaxies -
(Françoise Combes - Observatoire de Paris).
Dynamics of Galaxy Interactions
by Joshua E. Barnes. Very
complete. High quality simulations.
Introducing BAX: a database for X-ray clusters and groups of
"When looking at this picture no amount of advanced academic education
can substitute for good judgment; in fact it would undoubtedly be an
impediment" (Halton Arp - Seeing Red)
The Brigge of matter of Arp 286: