Deep Field North, Deep Field South

Anyone qualified, I'd like an estimate of distance from a far away
North Deep Field object - to a South Deep Field object. How far
apart might they be, and one can't see the other, I presume...
Regards, Newbie Terry S.

TerryS wrote:
Anyone qualified, I'd like an estimate of distance from a far away
North Deep Field object - to a South Deep Field object. How far
apart might they be, and one can't see the other, I presume...
Regards, Newbie Terry S.

I'll take the opportunity to be a bit didactic (my license is on
file...). If we restrict ourselves to spectroscopic redshifts,
with at least one emission line matching the redshift that
makes sense for the object's colors (photometric redshift),
we find the following.
For the HDF north, the Hawaii group at
http://www.ifa.hawaii.edu/~cowie/tts/tts.html
gives the highest spectroscopic redshift as 3.18 (wow, that's out of
date, but I'll leave it in to reduce more arcane searches).

On the HDF-S, the WWW data collections seemed to have moved around
ahead of the links from STScI, so I did an ADS abstract search
on "Hubble Deep Field South VLT spectroscopic redshifts galaxies"
which netted a highest value of z=6.5 from slitless spectropscopy
and several near z=5. A similar search on the HDF-N from the litarature
shows similar objects at z=4-7 in this field, but the full paper
hasn't been published yet with exact numbers. The Team Keck results
(Astron J) include objects to z=3.6 in the HDF and surrounding
regions.

So, to convert these to light-travel distances, one can use
Ned Wright's calculator at
http://www.astro.ucla.edu/~wright/CosmoCalc.html
and take the light-travel times. Using the default WMAP
cosmological parameters, this gives
travel time since z=3.6 11.88 Gyr
6.5 12.8 Gyr

Clearly these objects couldn't have seen each other yet, although by
how much depends on the history of cosmic expansion. This defintiion
of distance is the one I find the most natural, having something
to do with the path the light actually took through the expanding
Universe (rather than "how far is it now?" or a luminosity- or
angular-size-based distance).

The other detail to throw in is that the HDF-N and -S aren't quite
opposite on the sky; the HDF is at 12h 36m 49.4000s +62d 12' 58.000"
while the HDF-S is centered near 22h 32m 56.22s -60d 33' 02.69
making their directions about 150 degrees apart rather than 180.

Bill Keel

ËKeel" wrote in message ...
(regarding Terrys question posed and answered by E Keel, thanks BK..

I'll take the opportunity to be a bit didactic (my license is on
file...). If we restrict ourselves to spectroscopic redshifts,
with at least one emission line matching the redshift that
makes sense for the object's colors (photometric redshift),
we find the following.
For the HDF north, the Hawaii group at
http://www.ifa.hawaii.edu/~cowie/tts/tts.html
gives the highest spectroscopic redshift as 3.18 (wow, that's out of
date, but I'll leave it in to reduce more arcane searches).

On the HDF-S, the WWW data collections seemed to have moved around
ahead of the links from STScI, so I did an ADS abstract search
on "Hubble Deep Field South VLT spectroscopic redshifts galaxies"
which netted a highest value of z=6.5 from slitless spectropscopy
and several near z=5. A similar search on the HDF-N from the litarature
shows similar objects at z=4-7 in this field, but the full paper
hasn't been published yet with exact numbers. The Team Keck results
(Astron J) include objects to z=3.6 in the HDF and surrounding
regions.

So, to convert these to light-travel distances, one can use
Ned Wright's calculator at
http://www.astro.ucla.edu/~wright/CosmoCalc.html
and take the light-travel times. Using the default WMAP
cosmological parameters, this gives
travel time since z=3.6 11.88 Gyr
6.5 12.8 Gyr

Clearly these objects couldn't have seen each other yet, although by
how much depends on the history of cosmic expansion. This defintiion
of distance is the one I find the most natural, having something
to do with the path the light actually took through the expanding
Universe (rather than "how far is it now?" or a luminosity- or
angular-size-based distance).

The other detail to throw in is that the HDF-N and -S aren't quite
opposite on the sky; the HDF is at 12h 36m 49.4000s +62d 12' 58.000"
while the HDF-S is centered near 22h 32m 56.22s -60d 33' 02.69
making their directions about 150 degrees apart rather than 180.

Bill Keel

Thanks for the followup. Interesting that the Hubble Deep Fields
are similar, but not in redshift listings. Oh well. And, yes, I know
they don't exist as they appear, at least anymore, on a real-time
basis. And, yes they're not 180 apart, but it's the best we've got.
Poses me a new question.. Maybe near the beginning of our
available knowledge, they were close enough to see each other.
Kind of like a possibility that everything is centered around a
POINT, but the Point is on the outside, and all else that happens
is influenced from outside the "point"? eh? Speculating.
Terry S, Not a PhD, but avid astonomy-physics fan. Thanks Terry Swanets
Santa Rosa CA.

once again, from Terry S,
Thanks again Dr. Keel, HDFN, HDFS-
If those places that we saw as they were,
10-14 BYL ago, away, have long since
vanished, or transformed into other venues,
And since moved further away, as predicted?
Are they still near the POINT? which would
make them close to another at that TIME we
saw their images? If closer to the outer shell
of such a (multidimensional edge)- They must
have been close at some time. Now, new
matter (or unknown matter or non matter),
Still is flowing in. We are inside a dark
thing bigger than anyone can imagine,
or image.. FWIT.. Regards, Terry Swanets