Are Little Blue Dots in a Hubble Frontier Fields Precursors to Globular Clusters?

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In 2012, a Hubble Space Telescope Frontier Fields module (aka. Hubble Deep Fields Initiative 2012) strictly kicked off. The purpose of this plan was to investigate a faintest and many detached galaxies in a Universe regulating a gravitational lensing technique, so advancing a believe of early star formation. By 2017, a Frontier Field module wrapped up, and a tough work of examining all a information it collected began.

One of a some-more engaging finds within a Frontier Fields information has been a find of low mass galaxies with high star arrangement rates. After examining a “parallel fields” for Abell 2744 and MACS J0416.1-2403 – dual star clusters complicated by a module – a span of astronomers remarkable a participation of what they impute to as “Little Blue Dots” (LBDs), a anticipating that has implications for star arrangement and globular clusters.

The investigate that sum their commentary recently seemed online underneath a pretension “Little Blue Dots in a Hubble Space Telescope Frontier Fields: Precursors to Globular Clusters?“. The investigate group consisted of Dr. Debra Meloy Elmegreen – a highbrow of astronomy during Vassar College – and Dr. Bruce G. Elmegreen, an astronomer with a IBM Research Division during a T.J. Watson Research Center in Yorktown Heights.

The star clusters Abell 2744, MACS J0416.1-2403, MACS J0717.5+3745, MACS J1149.5+2223, Abell S1063, Abell 370. Credit: NASA, ESA, STScI, and a HFF team

To put it simply, a Frontier Fields module used a Hubble Space Telescope to observe 6 large star clusters during visual and near-infrared wavelengths – with a Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3), respectively. These large galaxies were used to increase and widen images of remote galaxies located behind them that were differently too gloomy for Hubble to see directly (aka. gravitational lensing).

While one of these Hubble cameras would demeanour during a star cluster, a other would concurrently perspective an adjacent patch of sky. These adjacent rags are famous as “parallel fields”, differently gloomy regions that yield some of a deepest looks into a early Universe. As Dr. Bruce Emelgreen told Universe Today around email:

“The purpose of a HFF module is to take low images of 6 regions of a sky where there are clusters of galaxies, given these clusters increase credentials galaxies by a gravitational lens effect. In this way, we can see serve than usually with approach imaging of a sky alone. Many galaxies have been complicated regulating this magnification technique. The clusters of galaxies are critical given they are large mass concentrations that make clever gravitational lenses.”

This 6 star clusters used for a consequence of a plan enclosed Abell 2744, MACS J0416.1-2403 and their together fields, a latter of that were a focal indicate in this study. These and a other clusters were used to find galaxies that existed usually 600 to 900 years after a Big Bang. These galaxies and their particular parallels had already been cataloged regulating mechanism algorithms that automatically found galaxies in a images and dynamic their properties.

Images of a MACS J0416.1–2403 and Abell 2744 star clusters, taken as partial of a Hubble Frontier Fields program. Credit: NASA/ESA/HST Frontier Fields group (STScI)

As a investigate twin go on to explain in their study, new large-scale low surveys have enabled studies of smaller galaxies during aloft redshifts. These embody “green peas” – luminous, compress and low mass galaxies with high specific star arrangement rates – and even lower-mass “blueberries”, small starburst galaxies that are a gloomy prolongation of a immature peas that also uncover heated rates of star formation.

Using a aforementioned catalogues, and examining a together fields for Abell 2744 and MACS J0416.1-2403, a group went looking for other examples of low-mass galaxies with high star arrangement rates. The purpose of this was to magnitude a properties of these dwarf galaxies, and to see if any of their positions accorded with where globular clusters are famous to have formed.

What they found was what they referred to as “Little Blue Dots” (LBSs), that are even lower-mass versions of “blueberries”. As Dr. Debra Elmegreen told Universe Today around email:

“When we was examining a images (there are about 3400 galaxies rescued in any field), we beheld occasional galaxies that seemed as small blue dots, that was really intriguing given of Bruce’s prior fanciful work on dwarf galaxies. The published catalogs enclosed redshifts and star arrangement rates and masses for any galaxy, and it turns out a small blue dots are low mass galaxies with really high star arrangement rates for their mass.”

The stars in a globular star cluster Messier 79 demeanour a lot like a snowstorm in a sleet creation in this NASA Hubble Space Telescope image. Credits: NASA and ESA, Acknowledgment: S. Djorgovski (Caltech) and F. Ferraro (University of Bologna)

These galaxies didn’t uncover structure, so Debra and Bruce built a images of galaxies into 3 opposite redshift ranges of sequence (which worked out to about 20 galaxies each) to emanate deeper images. “Still they showed no structure or gloomy extended outdoor disk,” pronounced Debra, “so they are during a extent of resolution, with normal sizes of 100-200 parsecs (about 300-600 light years) and masses of a few million times a mass of a sun.”

In a end, they dynamic that within these LBDs, star arrangement rates were really high. They also remarkable that these dwarf galaxies were really young, being reduction than 1% a age of a Universe during a time that they were observed. “So a small galaxies usually formed,: pronounced Bruce, “and their star arrangement rates are high adequate to comment for a globular clusters, maybe one in any LBD, when a star bursts in them breeze down after a few tens of million years.”

For years, Debra and Bruce have been looking for dwarf galaxies that have high rates of star formation. Back in 2012, Bruce published a paper that suggested that a globular clusters that circuit a Milky Way (and many other galaxies) shaped in dwarf galaxies during a early Universe. These dwarf galaxies would have given been acquired by incomparable galaxies like a own, and a clusters are radically their remnants.

Globular clusters are radically large star clusters that circuit around a Milky Way Halo. They are typically around 1 million Solar masses and are done adult of stars that are really aged – somewhere on a sequence of 10 to 13 billion years. Beyond a Milky Way, many appear in common orbits and in a Andromeda Galaxy, some even seem connected by a tide of stars.

Color perspective of M31 (The Andromeda Galaxy), with M32 (a satellite galaxy) shown to a reduce left. Credit and copyright: Terry Hancock.

As Bruce explained, his is a constrained evidence for a speculation that globular clusters shaped from dwarf galaxies in a early Universe:

“This suggests that a metal-poor globular clusters are a unenlightened ruins of small galaxies that got prisoner by bigger galaxies, like a Milky Way, and ripped detached by tidal forces. This thought for a start of halo globular clusters goes behind several decades… It would be usually a metal-poor one that are like this, that are about half a total, given dwarf galaxies are steel bad compared to large galaxies, and they were also some-more steel bad in a early universe.”

This investigate has many implications for a bargain of how a Universe evolved, that was a arch aim of a Hubble Frontier Fields program. By examining objects in a early Universe, and last their properties, scientists are means to establish how a structures that we are informed with currently – i.e. stars, galaxies, clusters, etc. – truly came from.

These same studies also concede scientists to make prepared guesses about where a Universe is going and what will turn of those same structures millions or even billions of years from now. In short, meaningful where we’ve been lets us envision where we are headed!

Further Reading: arXiv

Source: Universe Today, created by Matt Williams.

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