LEDA 84446 With Another Voorwerpjes

Rick,

amazing image to capture such elusive objects. I would also go for the green
signal here as this is the "special feature" of these objects.

Stefan


"WA0CKY" schrieb im Newsbeitrag ...


LEDA 84446 is a rather obscure small outlying member of the ABELL 2040
galaxy cluster about 620 million light-years distant. It is located in
the very southeast corner of Bootes. The galaxies along the bottom edge
of the image are in Virgo while those on the eastern edge are in Serpens
Caput so this small field of about 0.2 square degrees includes three
constellations. LEDA 84446 is about 60,000 light-years across but at
its distance only about 20" of arc across. it is classified as S0/a and
as a narrow emission line galaxy. It is also sometimes called SDSS
1510+07.

So why did I take such a insignificant galaxy? It turns out to be one
of a handful of galaxies known to contain voorwerpjes as they are
called. I had to try and see if I could pick up these green objects
recently imaged by the HST. They are thought to be illuminated gas
clouds outside the galaxy that were left by a galaxy digested by the
main galaxy. The illumination coming from a quasar that has since died
down to where the galaxy is now just NELG class but the light path from
the quasar to the cloud then to us is longer so we are seeing the light
echo left by this now quiescent black hole. Most of the voorwerpjes are
seen around NELG (Narrow Emission Line Galaxies). Though only a very
few NELG have voorwerpjes.

The green color is more a result of LRGB filters as the true color is
somewhat bluer than seen here. This is because the light from the
voorwerpjes is red shifted just enough that instead of falling in the
overlap of the green and blue filters it falls entirely in the green
filter. The HST uses tunable filters for both the oxygen I seen as
green and red for H alpha. Since that is out of my passband I didn't
even try for it. The included HST image maps the oxygen to green and the
hydrogen to red. As I had no way to isolate the hydrogen and my camera
sees the green emission far more strongly than the red of H alpha by
almost a 2:1 ratio I see even the red portion in the HST image as green.
Also since it was the faint green I was interested in I used more time
on the green data allowing it to be pulled out of the noise better than
the red. I should have paid more attention to the HST image and put
some extra time in on the red filter but didn't.

Seeing was better than it has been much of the last year the night I
took this but still far below what I used to get a few nights of the
year. Still it helped to bring out the southern green band.

While the galaxy and several others, mostly on the eastern half of my
image are members of the Abell 2040 galaxy cluster most, especially
those to the lower right are members of the more distant Abell 2028
galaxy cluster that's about 1.03 billion light-years distant. It is
centered in the lower right corner. With two overlapping galaxy
clusters this makes for a very cluttered annotated image. Fortunately
there were no asteroids in the field at the time to add to the clutter.

14" LX200R @ f/10, L=4x10' RB=2x10' G=6x10', STL-11000XM, Paramount ME

Besides my usual image at 1" per pixel and annotated image the cropped
image is at my full resolution of 0.5" per pixel. I've also included
the HST image of this voorwerpjes.

Rick


--
WA0CKY