HubbleSite: The Faintest Galaxy from the Early Universe

[bystander]

The Faintest Galaxy from the Early Universe
NASA | STScI | HubbleSite | JPL | GSFC | 2015 Dec 03

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Astronomers harnessing the combined power of NASA's Hubble and Spitzer space telescopes have found the faintest object ever seen in the early universe. It existed about 400 million years after the big bang, 13.8 billion years ago.

The team has nicknamed the object Tayna, which means "first-born" in Aymara, a language spoken in the Andes and Altiplano regions of South America.

Though Hubble and Spitzer have detected other galaxies that are record-breakers for distance, this object represents a smaller, fainter class of newly forming galaxies that until now have largely evaded detection. These very dim objects may be more representative of the early universe, and offer new insight on the formation and evolution of the first galaxies.

"Thanks to this detection, the team has been able to study for the first time the properties of extremely faint objects formed not long after the big bang," said lead author Leopoldo Infante, an astronomer at Pontifical Catholic University of Chile (Pontificia Universidad Católica de Chile). The remote object is part of a discovery of 22 young galaxies at ancient times located nearly at the observable horizon of the universe. This research is a substantial increase in the number of known very distant galaxies. ...

The new object is comparable in size to the Large Magellanic Cloud (LMC), a diminutive satellite galaxy of our Milky Way. It is rapidly making stars at a rate ten times faster than the LMC. The object might be the growing core of what will likely evolve into a full-sized galaxy. ...

Young Galaxy Candidates in the Hubble Frontier Fields. II. MACS J0416-2403 - Leopoldo Infante et al

• Astrophysical Journal 815(1):18 (2015 Dec 10) DOI: 10.1088/0004-637X/815/1/18
  arXiv.org > astro-ph > arXiv:1510.07084 > 23 Oct 2015

[Ann]

The discovery of the ultra-faint galaxy is very interesting, but I know what I found most amazing about this piece of news. The lensing cluster itself, MACS J0416-2403, is incredible! And so is the Hubble image of it. Just look at how elongated the cluster is, as if it was a textbook illustration of the fact that galaxy clusters tend to line up along huge cosmic filaments. This cluster is lining up its individual members along a filament, too!

And there is a bonanza of lensed galaxies, and I think there are several examples of multiple images of the same galaxy. For example, at about 2.30 there is a red galaxy with two small blue dots to the left of it. To the left and lower left of that red galaxy there is a lineup of four small purple, pink and blue galaxies that appear to be mirror images of each other. In fact the whole Hubble picture is full of objects and arcs that are purple, pink and blue in color, and which might be examples of the same lensed background galaxies.

I'm fascinated by the round, blue galaxy at the end of the long line of massive yellow ellipticals. The blue galaxy appears to be the same size as the yellow ellipticals, so it looks like it could be part of the cluster. But I guess that can't be. The blue galaxy would have an utterly different population of stars even though it would be more or less as massive and as big as the giant ellipticals. It is hard to see how such a configuration of galaxies could come about. Also I find it hard to believe that a very big blue galaxy could be so uniformly blue and so "quiet", with such a "simple" shape. Only a smallish blue galaxy is likely to be shaped like this. So the round blue galaxy is almost certainly a foreground object, and it might even be a yellow galaxy itself. If it is indeed intrinsically yellow, it would look blue compared to the yellow ellipticals because of its much smaller redshift.

In any case, this is an incredible galaxy cluster and an absolutely splendid Hubble image! And the fact that it reveals the faintest galaxy ever discovered in the early universe is certainly a big bonus.

Ann