Hubble, Gemini Spot ‘Hyperactive’ Stars in Small, Young Galaxies

We all know youngsters are a handful, but this really takes the cake: astronomers have clocked the speeds of stars in infant galaxies at about a million miles an hour, about twice the pace of our Sun’s cruise through the Milky Way.

The small galaxies date to 11 billion years ago, when the universe was just a couple billion years old. Their stars, astronomers say, are buzzing and whirling at head-spinning rates.

Researchers spotted the galaxies with NASA’s Hubble Space Telescope and the 8-meter Gemini South telescope in Chile. Hubble revealed that the galaxies are a fraction the size of most galaxies we see today, and Gemini clocked their speed by using spectroscopy.

The Gemini near-infrared spectroscopic observations required an extensive 29 hours on the sky to collect the extremely faint light from the distant galaxy, which goes by the designation 1255-0.

The results will be published in the August 6, 2009 issue of the journal Nature, with a companion paper in the Astrophysical Journal.

“This galaxy is very small, but the stars are whizzing around as if they were in a giant galaxy that we would find closer to us and not so far back in time,” says Pieter van Dokkum, professor of astronomy and physics at Yale University in New Haven, Connecticut, who led the study.

The researchers say it is difficult to explain how such compact, massive galaxies form, and why they are not seen in the current, local universe. “One possibility is that we are looking at what will eventually be the dense central region of a very large galaxy,” explains team member Marijn Franx of Leiden University in the Netherlands. “The centers of big galaxies may have formed first, presumably together with the giant black holes that we know exist in today’s large galaxies that we see nearby.”

The most massive galaxies we see in the local universe (where we don’t look back in time significantly) that have a mass similar to 1255-0 are typically five times larger than the young compact galaxy. How galaxies grew so much in the past 10 billion years is an active area of research, and understanding the dynamics in these young compact galaxies is a key piece of evidence in eventually solving this puzzle.

To witness the formation of these extreme galaxies, the astronomers plan to observe galaxies even farther back in time with Hubble’s new Wide Field Camera.

Source: Early press release out of the Space Telescope Science Institute (StSci). For illustrations and more information, visit the Hubble Site or the Gemini Observatory online. The ApJ paper doesn’t appear to be published online yet, but check back for the link!

17 Replies to “Hubble, Gemini Spot ‘Hyperactive’ Stars in Small, Young Galaxies”

  1. i’m always fascinated by these ‘views into the past’. our lives are so brief but in the long view the universe seems to have changed so greatly over time. nothing’s static – existence is quite dynamic!

    hope we soon get to see all the way back to the early soup of the universe. wouldn’t it be great to see someone stirring a giant galaxy ladle?

  2. How can we eliminate the possibility that “what we are looking at … [actually IS] … the dense central region of a very large galaxy” just too faint to see at that distance?

  3. @ Manu

    By building an even bigger ‘scope and to take an even longer look at it 😉
    Then you’ll probably some faint sorroundings, which could also be some sort of gas where stars start to be born. Then we could actually see how galaxies were made – and “what came first” (the galaxy or the black hole) 😉

  4. One simple question, if we extrapolate the width of this early galaxy to the width of our Milky Way, how much is the deviation?

  5. Sorry, should have been more specific –

    if we artificially expand the early galaxy to a size comparible to our own galaxy today, how much would the mass-size ratio would deviate?

  6. A ESA Hubblesite press release of the 2008 NICMOS observations can be found here: . The galaxy 1255-0, mentioned in the above article, appears at upper right in the supplied image. Maybe the James Webb Space Telescope (sure doesn’t roll off the tongue like ‘Hubble’) will be able to provide more conclusive deep NIR imaging of these compact galaxies.

  7. I seem to recall seeing a UT article recently that suggested that if we found an an ejected SMBH from a galactic merger that it would probably look like a dense object with stars moving really fast.

    Is this not a dense object with stars moving really fast?

  8. Trippy: I think ejected SMBH’s are too faint to see in our own galactic neighborhood (and hence still theoretical), let alone at that distance (11 billion LY), even with a small swarm of stars floating around it.

  9. Where the bar? This is an ole rending of the Home Galaxy – our galaxy has a big bar in the middle!

  10. These might be the core where galactic glack holes are formed. I am not a galaxy structure maven, but there seem to be a host of questions about how these compact objects evolve into galaxies. Do they by accreting material to form it central black hole in effect evaporate out some material and stars? Or does this over time recruit material towards its outer regions?


  11. Good questions, LBC. and hopefully the new Gemini South observations will further elucidate just what is going on in these systems. Dr. Flimmer brings up a good point, what came first: the BH or stellar accretion that gave rise to SMBHs? 🙂

  12. Lawrence B. Crowell: you don’t know it yet, but you just invented THE name for SMBH: a Glack Hole!
    This is history… ;-)))

  13. Well, well. Sometimes the reminiscence is lazy 😉

    You DON’T want to read the comment section of that article. Trust me, you don’t want to! 😉

    I think, this was the first time I met our good friend Anaconda. I wonder if he really buggered off at last…..

  14. The 2008 paper on these ultracompact, small distant systems makes three interesting observations: 1) these compact systems weigh in at something like 1.7×10^11 Solar masses and do this 2) in a volume of less than radius(R) 0.9kpc = 900 parsec! 3) The van Dokkum et. al. 2008 paper also gives a preliminary median density of 3×10^11 Solar masses/cubic kpc! Authors of the 2008 paper also note that many of the redshifts are photometric redshifts which have hopefully been redetermined by the more precise ultra-long Gemini South direct spectra.

    Any (free) links to that new study, yet ? 🙂

  15. In the new 2009 study, the authors find that these galaxies have extremely low stellar formation rates (SFRs) of 1 to 3 Solar masses/yr and a depleted ISM with which to form new stars. The galaxies are still as massive( even more so) and compact, just not furiously forming stars.

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