# I Galaxy at z=11.1, farthest yet, unusually bright (GN-z11)

1. Mar 4, 2016

### marcus

Measured redshift is z = 11.1
That means at the moment it emitted the light we are receiving from the galaxy, distances were 1/12 their present size.
Technical detail:
http://arxiv.org/abs/1603.00461
A Remarkably Luminous Galaxy at z=11.1 Measured with Hubble Space Telescope Grism Spectroscopy
P. A. Oesch, G. Brammer, P. G. van Dokkum, G. D. Illingworth, R. J. Bouwens, I. Labbe, M. Franx, I. Momcheva, M. L. N. Ashby, G. G. Fazio, V. Gonzalez, B. Holden, D. Magee, R. E. Skelton, R. Smit, L. R. Spitler, M. Trenti, S. P. Willner
(Submitted on 1 Mar 2016)
We present Hubble WFC3/IR slitless grism spectra of a remarkably bright z≳10 galaxy candidate, GN-z11, identified initially from CANDELS/GOODS-N imaging data. A significant spectroscopic continuum break is detected at λ=1.47±0.01 μm. The new grism data, combined with the photometric data, rule out all plausible lower redshift solutions for this source. The only viable solution is that this continuum break is the Lyα break redshifted to zgrism=11.09+0.08−0.12, just ∼400 Myr after the Big Bang. This observation extends the current spectroscopic frontier by 150 Myr to well before the Planck (instantaneous) cosmic reionization peak at z~8.8, demonstrating that galaxy build-up was well underway early in the reionization epoch at z>10. GN-z11 is remarkably and unexpectedly luminous for a galaxy at such an early time: its UV luminosity is 3x larger than L* measured at z~6-8. The Spitzer IRAC detections up to 4.5 μm of this galaxy are consistent with a stellar mass of ∼109 M⊙. This spectroscopic redshift measurement suggests that the James Webb Space Telescope (JWST) will be able to similarly and easily confirm such sources at z>10 and characterize their physical properties through detailed spectroscopy. Furthermore, WFIRST, with its wide-field near-IR imaging, would find large numbers of similar galaxies and contribute greatly to JWST's spectroscopy, if it is launched early enough to overlap with JWST.
Comments: 12 pages, 11 figures, accepted for publication in ApJ

Wide audience account:
http://www.cbsnews.com/news/hubble-space-telescope-finds-most-distant-galaxy-yet/

2. Mar 4, 2016

3. Mar 4, 2016

### marcus

That's an interesting issue to raise. In this case the galaxy is unusually bright allowing spectroscopic determination with "grism" (I suppose that is something like a grating with prism ridges/grooves), seems to involve increased accuracy
"A significant spectroscopic continuum break is detected at λ=1.47±0.01 μm. The new grism data, combined with the photometric data, rule out all plausible lower redshift solutions for this source. The only viable solution is that this continuum break is the Lyα break redshifted to zgrism=11.09+0.08−0.12, just ∼400 Myr after the Big Bang. This observation extends the current spectroscopic frontier..."
To me it seems credible, in this particular case. (Not necessarily in general with photometric estimates of z ~ 10, which we have seen earlier.)

So I'll apply Jorrie's Lightcone calculator to this case:

$${\scriptsize\begin{array}{|c|c|c|c|c|c|}\hline T_{Ho} (Gy) & T_{H\infty} (Gy) & S_{eq} & H_{0} & \Omega_\Lambda & \Omega_m\\ \hline 14.4&17.3&3400&67.9&0.693&0.307\\ \hline \end{array}}$$ $${\scriptsize\begin{array}{|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|} \hline S&T (Gy)&R (Gly)&D_{now} (Gly)&D_{then}(Gly)&V_{now}/c&V_{then}/c \\ \hline 12.100&0.409&0.616&32.174&2.659&2.234&4.317\\ \hline 1.000&13.787&14.400&0.000&0.000&0.000&0.000\\ \hline \end{array}}$$

z=11.1 means a distance expansion ratio of z+1 = 12.1
The time the light was emitted was year 409 million.
The galaxy was then 2.7 billion LY from us, and it is now 32 billion LY from us.
Back then, when it emitted the light we're getting now, it was receding at about 4.3 times speed of light.

Back then the universe' expansion rate was 1/6 % per million years. Do we all see how to get that from the table? And likewise the expansion rate now is 1/144 % per million years. The expansion (i.e. Hubble) rate has come down a lot since then! From 1/6 to 1/144. And as far as we know is on track to keep declining till it levels off at 1/173 (the number given by the cosmological constant, determining the longterm rate)

Last edited: Mar 4, 2016
4. Mar 4, 2016

### Astronuc

Staff Emeritus
Hubble Sees A Galaxy 13.4 Billion Years In The Past, Breaking Distance Record
http://www.npr.org/sections/thetwo-...on-years-in-the-past-breaking-distance-record

Update: https://www.nasa.gov/feature/goddard/2016/hubble-team-breaks-cosmic-distance-record

Last edited: Mar 5, 2016
5. Mar 5, 2016

6. Mar 5, 2016

### marcus

I don't understand your reasoning, Wooly. What "leeway" do you mean? Maybe you would spell out how your reasoning goes?

AFAIK the best estimate of the age of expansion is, in round numbers, 13.8 billion years. (See the 13.787 in the table.)
This little baby galaxy was shining in around year 0.4 billion, or in other words year 400 million.
So the light from it has been traveling 13.4 billion years, on its way to us.
Seems to me to make perfect sense. What don't you like about it?

$${\scriptsize\begin{array}{|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|} \hline S&T (Gy)&R (Gly)&D_{now} (Gly)&D_{then}(Gly)&V_{now}/c&V_{then}/c \\ \hline 12.100&0.409&0.616&32.174&2.659&2.234&4.317\\ \hline 1.000&13.787&14.400&0.000&0.000&0.000&0.000\\ \hline \end{array}}$$

http://sci.esa.int/hubble/57530-hubble-breaks-cosmic-distance-record-heic1604/

Last edited: Mar 5, 2016
7. Mar 5, 2016

### Jonathan Scott

I've previously seen an estimate that the earliest galaxies would have started forming perhaps 400 million years after the big bang, so this seems to be pushing that limit, which is probably what Wooly was concerned about. Even though you call it a "baby" galaxy and it is indeed much smaller than the Milky Way, it still seems a lot brighter than I might have expected from that time.

8. Mar 5, 2016

### marcus

Me too. So this discovery may change our ideas of the processes by which galaxies form. It may contribute to new computer modeling of galaxy formation. And our ideas of how long formation takes once it gets started.
It may (probably will) have a lot of impact on early universe star and protogalaxy models. But it does not necessarily impact on estimates of the age of the universe (time since the start of expansion), does it? What do you think? I think that would be like having the tail wag the dog.

9. Mar 5, 2016

### Staff: Mentor

A grism is the combination of a prism and a diffraction grating, sometimes with the grating engraved into one of the prism's surface.
http://www.stsci.edu/hst/nicmos/design/grisms

Do you know how the usually measure the spectrum of a high-z galaxy? Is it photometrically, or spectroscopically?

10. Mar 5, 2016

### Staff: Mentor

Browsing through the paper, it appears that spectroscopic measurements of high-z galaxies rarely takes place. They apparently use broadband filters to get a rough measurement of redshift in most cases. Not sure if it's because of how dim most sources are, or because of something else.

11. Mar 8, 2016

### Garth

Yet another example of the age problem in the early universe.

From marcus' the second link Hubble Space Telescope finds most distant galaxy yet:
Garth

12. Mar 8, 2016

### Staff: Mentor

Given how little we know about galaxy formation, the fact that this "shouldn't exist" doesn't surprise me much. It seems like every new thing we learn in astronomy and cosmology contradicts some model. Certainly a great time for astronomy!

13. Mar 10, 2016

### grauitate

D'accord!
I have some fear that this galaxy might be quite a normal one.
Viewing through the Hubble 1,6 μm filter, it is observed at 1,6 μm/(11,1+1) = 0,13 μm at that huge distance- i.e. the galaxy shows us its UV-face core, which, regarding the brightness and size, is comparable to normal near-by galaxies, e.g. comparing it with the UV-bulge spot of the Andromeda seen below:

Andromeda-Galaxy in UV: (NASA/Swift/Stefan Immler (GSFC), Erin Grand (UMCP))

Now it can be estimated that the UV-bulge has approx. 1/5 of the diameter of the visible size - for the first this is in accordance with the "small size" spot of approx. 0.5" angle-resolution shown on page 7, fig.6, top right in the paper of Oesch et al.
But through the Spitzer 4,5 μm-filter the galaxy is observed at 4,5/12,1 = 0,37 μm, i. e. at the short end of the VIS-range and astonishingly it appears as large as approx. 2" x 2" in large brightness - this would not be in accordance with a flat universe where the VIS-part of it would appear only in a width of approx. only 0.6...0.8" at that distance (and the UV-part only in a width of 0.1...0.2")

So, these observations (and a lot more e.g. of Oesch and others) are in compliance with a curved, not expanding universe, where far distant objects appear larger and brighter by the integral "lensing" effect of the bulk mass-content (then including its necessarily occurring "dark matter"-effect) of the entire universe.
In such an universe, at least, the persistent conundrum of
would not appear at all.
Again, this is a thesis for suggestion only.

14. Mar 22, 2016

### Darryl

This raises a few questions for me, one is why is gravitational redshift considered to account for the measured redshift, particularly in this case because they start 'unusually bright' so obviously there are a lot of stars there, so it resides in a strong gravity well.

Gravitational red shifts makes more massive objects (like galaxies) redder if observed in a region of lower gravity density, it is also called Einsteinian redshift.
Gravity redshift would mean that the observed redshift is not a measure of distance, but a measure of density (gravity). So deeply redshifted objects have a higher density, and that is why it is 'unusually bright'.

Another point, it is very young, how did it form so quickly?

lastly, Have they measured the ratio of elements from that object?, because if it has elements that can only be produced by second generation stars that is a big problem. How did they get there?

15. Mar 22, 2016

### Jonathan Scott

Try some calculations! The gravitational redshift is roughly the Newtonian potential divided by $c^2$, that is the sum of $-Gm/rc^2$ for each of the nearby sources (where a negative value means a redshift and positive a blue shift).

For a significant gravitational redshift you have to be really close to a huge mass. Even putting a supermassive black hole at the middle of a galaxy doesn't make much difference to the redshift of the rest of the galaxy.

The only way gravitational redshift could be significant is if instead of a galaxy, one is seeing some sort of supermassive stellar object with a highly redshifted surface, which perhaps also lights up nearby material indirectly, causing it to appear to have the same redshift and appear similar to a galaxy. In alternative theories in which black holes do not occur (which are outside the scope of these forums) this is considered a possible explanation of quasars. However, according to General Relativity, such an object would have collapsed into a black hole, so could not have a luminous surface, and any luminosity from further away, for example from a surrounding accretion disk, would only have a small gravitational redshift.

16. Jun 28, 2017

### Maurice Tardif

If the galaxy was at 2,7 billion ly, 13,4 billion year ago, it meen the constant of hubble was very bigger than 72km/s/megaparsec. The more space the photon travel because the expansion are 10,7 billion years that meen the avarage expansion was 239386 km/s for 13,4 billion years.

Today a photon at 2,7 billion years is slow by expansion from a rate of 60000 km/s and at each second, the photon is closer than us and the expansion rate will decrease more and more to become 0 near us. That meen today for a photon from 2,7 billion ly the average expansion rate was lower than 60000 km/s. How do you explaine the average 239386 km/s of gn-z11 photon to reash us from a distance oh 2,7 billion ly?