Doubts about the z = 10 galaxy of Roser Pello

[marcus]

several months back some PF people were discussing
the finding of a z = 10 galaxy by a French team led by
Roser Pello

Now three Anglo-Saxons at the Imperial College have
reluctantly expressed doubts: they have tried to find the
reported Lyman Alpha line and did not see it.

S. J. Weatherley, S. J. Warren, T. S. R. Babbedge
Reanalysis of the spectrum of the z=10 galaxy
http://arxiv.org/abs/astro-ph/0407150

If one sets aside the finding of Pello's group, then I suppose
the highest redshift observed for a galaxy or equally well a quasar
would be roughly 6.5.
does someone know what the current maximum would be, not
counting the one z = 10?

I am still hoping that Pello is right.

[Chronos]

z=6.5 is the uncontested observed leader, last I heard. z=10 is a bit uncomfortable. z=8 is closer to the theoretical limit, as I recall.

New and Improved.

In February 2004, HST and Keck found a galaxy with a redshift of at least 6.6 and possibly as high as 7.0 near the cluster Abell 2218.
http://www.usatoday.com/news/science/2004-02-15-farthest-galaxy_x.htm

In March 2004, NASA reseased HST images of galaxies thought to have originated between 400 and 800 million years after BB. Redshifts estimated to be as high as Z=12. [I havent found confirmation of actual measured redshifts, so it appears 7.0 is still the 'official' champ for now.
http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/07/text/

[Chronos]

I was trying to figure out where I got the notion of z=8 is an observational llimit. I have this maddening tendency to remember obscure things but not where they came from. After revisting just about every web site I've been to for the past couple months, I got lucky and found it.

http://astrophysics.phys.cmu.edu/~jbp/past6.pdf

z~8 is well hidden in this very interesting paper. I assumed the authors were ascribing z~8 as a limit to optically detectable ionization sources [e.g. galaxies].

[meteor]

The reply of Roser Pello:
http://arxiv.org/abs/astro-ph/0407194

[Chronos]

Interesting paper, thanks for the post meteor.

[meteor]

As a sidenote, this recent discovered galaxy with z=6.54, I think that is actually the third most distant known object, after the protogalaxy with z=10 of R. Pello and the galaxy with z=7 discovered in the first half of 2004
http://xxx.lanl.gov/abs/astro-ph/0407409

[turbo]

When the Large Binocular Telescope comes on line, it will not only have tremendous light-gathering power, but with the adaptive optics and the separation of the primary mirrors, it will have a huge advantage in resolution over other ground-based and orbiting telescopes. It will be hampered by the absorption of some wavelengths by the atmosphere, but it's resolution will revolutionize observational astronomy. I predict that it will be used to discover faint objects so heavily redshifted that (if redshift = cosmological distance) they will grossly violate the best-guess 13.7Gy Big-Bang envelope. When this happens, we should be prepared for a messy backlash. It should be interesting times, (in the sense of the old Chinese curse).

[Chronos]

There is no upper limit for the value of z. At 13.7 Gy, the value of z approaches infinity. The current 'best guess' observational limit is z ~ 1000 [the universe is opaque much beyond that]. Aside from the CMB [possibly], it is highly unlikely we will ever see anything near that. It is even more improbable we will observe objects with z values that exceed infinity.

[turbo]

There is no upper limit for the value of z. At 13.7 Gy, the value of z approaches infinity. The current 'best guess' observational limit is z ~ 1000 [the universe is opaque much beyond that]. Aside from the CMB [possibly], it is highly unlikely we will ever see anything near that. It is even more improbable we will observe objects with z values that exceed infinity.

The problem arises not simply when an object with high z is observed. The problems arise when objects are observed with sufficiently high z to make it unlikely that they could have formed within the 13.7Gy (with our current heirarchical model of galaxy formation and our current understanding of redshift). That is why finding a large luminous galaxy with z~10 could be troubling. Pello claims that the team that failed to confirm the redshift failed to analyze the data properly and that the high redshift is confirmable with the right techniques. We'll see...

[tbabbedge]

Although a galaxy a z=10 has important implications, this 'detection' is near-IR spectrsocopy, which is very difficult to reduce correctly due noise issues etc. You might be interested in these two papers (now both peer-reviewed and published/in press) which both fail to confirm any detection of the z=10 galaxy.
A reanalysis of Pello's data: http://arxiv.org/abs/astro-ph/0407150
Indepedent observations: http://arxiv.org/abs/astro-ph/0409485

[ohwilleke]

I was trying to figure out where I got the notion of z=8 is an observational llimit. I have this maddening tendency to remember obscure things but not where they came from. After revisting just about every web site I've been to for the past couple months, I got lucky and found it.

http://astrophysics.phys.cmu.edu/~jbp/past6.pdf

z~8 is well hidden in this very interesting paper. I assumed the authors were ascribing z~8 as a limit to optically detectable ionization sources [e.g. galaxies].

The link seems to be broken.