Cosmic Horseshoe Is Not The Lucky Beacon

Cosmic Horseshoe Is Not The Lucky Beacon

Cosmic horseshoe is not the lucky beacon

A UC Riverside-led team of astronomers use observations of a gravitationally lensed galaxy to measure the properties of the early universe

Although the universe started out with a bang it quickly evolved to a relatively cool, dark place. After a few hundred thousand years the lights came back on and scientists are still trying to figure out why.

Astronomers know that reionization made the universe transparent by allowing light from distant galaxies to travel almost freely through the cosmos to reach us.

However, astronomers don’t fully understand the escape rate of ionizing photons from early galaxies. That escape rate is a crucial, but still a poorly constrained value, meaning there are a wide range of upper and lower limits in the models developed by astronomers.

That limitation is in part due to the fact that astronomers have been limited to indirect methods of observation of ionizing photons, meaning they may only see a few pixels of the object and then make assumptions about unseen aspects. Direct detection, or directly observing an object such as a galaxy with a telescope, would provide a much better estimate of their escape rate.

In a just-published paper, a team of researchers, led by a University of California, Riverside graduate student, used a direct detection method and found the previously used constraints have been overestimated by five times.

“This finding opens questions on whether galaxies alone are responsible for the reionization of the universe or if faint dwarf galaxies beyond our current detection limits have higher escape fractions to explain radiation budget necessary for the reionization of the universe,” said Kaveh Vasei, the graduate student who is the lead author of the study.

It is difficult to understand the properties of the early universe in large part because this was more than 12 billion year ago. It is known that around 380,000 years after the Big Bang, electrons and protons bound together to form hydrogen atoms for the first time. They make up more than 90 percent of the atoms in the universe, and can very efficiently absorb high energy photons and become ionized.

However, there were very few sources to ionize these atoms in the early universe. One billion years after the Big Bang, the material between the galaxies was reionized and became more transparent. The main energy source of the reionization is widely believed to be massive stars formed within early galaxies. These stars had a short lifespan and were usually born in the midst of dense gas clouds, which made it very hard for ionizing photons to escape their host galaxies.

Previous studies suggested that about 20 percent of these ionizing photons need to escape the dense gas environment of their host galaxies to significantly contribute to the reionization of the material between galaxies.

Unfortunately, a direct detection of these ionizing photons is very challenging and previous efforts have not been very successful. Therefore, the mechanisms leading to their escape are poorly understood.

This has led many astrophysicists to use indirect methods to estimate the fraction of ionizing photons that escape the galaxies. In one popular method, the gas is assumed to have a “picket fence” distribution, where the space within galaxies is assumed to be composed of either regions of very little gas, which are transparent to ionizing light, or regions of dense gas, which are opaque. Researchers can determine the fraction of each of these regions by studying the light (spectra) emerging from the galaxies.

In this new UC Riverside-led study, astronomers directly measured the fraction of ionizing photons escaping from the Cosmic Horseshoe, a distant galaxy that is gravitationally lensed. Gravitational lensing is the deformation and amplification of a background object by the curving of space and time due to the mass of a foreground galaxy. The details of the galaxy in the background are therefore magnified, allowing researchers to study its light and physical properties more clearly.

Based on the picket fence model, an escape fraction of 40 percent for ionizing photons from the Horseshoe was expected. Therefore, the Horseshoe represented an ideal opportunity to get for the first time a clear, resolved image of leaking ionizing photons to help understand the mechanisms by which they escape their host galaxies.

The research team obtained a deep image of the Horseshoe with the Hubble Space Telescope in an ultraviolet filter, enabling them to directly detect escaping ionizing photons. Surprisingly, the image did not detect ionizing photons coming from the Horseshoe. This team constrained the fraction of escaping photons to be less than 8 percent, five times smaller than what had been inferred by indirect methods widely used by astronomers.

“The study concludes that the previously determined fraction of escaping ionizing radiation of galaxies, as estimated by the most popular indirect method, is likely overestimated in many galaxies,” said Brian Siana, co-author of the research paper and an assistant professor at UC Riverside.

“The team is now focusing on direct determination the fraction of escaping ionizing photons that do not rely on indirect estimates.”

More Posts from Evisno and Others

8 years ago
Saturn’s Hexagon Is A Hexagonal Cloud Pattern That Has Persisted At The North Pole Of Saturn Since

Saturn’s hexagon is a hexagonal cloud pattern that has persisted at the North Pole of Saturn since its discovery in 1981. At the time, Cassini was only able to take infrared photographs of the phenomenon until it passed into sunlight in 2009, at which point amateur photographers managed to be able to photograph it from Earth. 

The structure is roughly 20,000 miles (32,000 km) wide, which is larger than Earth; and thermal images show that it reaches roughly 60 miles (100 km) down into Saturn’s interior.

Read an explanation of how Saturn’s hexagon works here: [x]

10 years ago
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys
Portraits Of Birds By Laila Jeffreys

Portraits of birds by Laila Jeffreys

11 years ago

(no word to describe this feeling)

Eat Mor Chikin
Eat Mor Chikin
Eat Mor Chikin

eat mor chikin

11 years ago
Window Phone Concept
Window Phone Concept
Window Phone Concept
Window Phone Concept
Window Phone Concept
Window Phone Concept

Window phone concept

Is it a window, is it a phone? No. Actually, it’s Window phone and this is the part where you are saying “Whaaat? What are you talking about?”. The phone is actually a concept with extraordinary features. Surely if this could be actually put into production, it would set a new standard for the term “cool”.

8 years ago
WORKING ON CHRISTMAS: While The Beautiful Earth Looms In The Background, Astronaut Steven Smith Stands

WORKING ON CHRISTMAS: While the beautiful Earth looms in the background, astronaut Steven Smith stands on the mobile foot restraint at the end of the remote manipulator system as he makes repairs to the Hubble Space Telescope, Dec. 24-25, 1999. (NASA)

7 years ago
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void

We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void

“If there weren’t a large cosmic void that our Milky Way resided in, this tension between different ways of measuring the Hubble expansion rate would pose a big problem. Either there would be a systematic error affecting one of the methods of measuring it, or the Universe’s dark energy properties could be changing with time. But right now, all signs are pointing to a simple cosmic explanation that would resolve it all: we’re simply a bit below average when it comes to density.”

When you think of the Universe on the largest scales, you likely think of galaxies grouped and clustered together in huge, massive collections, separated by enormous cosmic voids. But there’s another kind of cluster-and-void out there: a very large volume of space that has its own galaxies, clusters and voids, but is simply higher or lower in density than average. If our galaxy resided near the center of one such region, we’d measure the expansion rate of the Universe to be higher-or-lower than average when we used nearby techniques. But if we measured the global expansion rate, such as via baryon acoustic oscillations or the fluctuations in the cosmic microwave background, we’d actually arrive at the true, average rate.

We’ve been seeing an important discrepancy for years, and yet the cause might simply be that the Milky Way lives in a large cosmic void. The data supports it, too! Get the story today.

10 years ago

W. M. Keck Observatory telescopes logo. December 2, 2014

Image above: A dusty planetary system (left) is compared to another system with little dust in this artist’s conception. Image Credit: NASA/JPL-Caltech. Planet hunters received some good news recently. A...

10 years ago
Merging Galaxies And Droplets Of Starbirth

Merging galaxies and droplets of starbirth

The Universe is filled with objects springing to life, evolving and dying explosive deaths. This new image from the NASA/ESA Hubble Space Telescope captures a snapshot of some of this cosmic movement. Embedded within the egg-shaped blue ring at the centre of the frame are two galaxies. These galaxies have been found to be merging into one and a “chain” of young stellar superclusters are seen winding around the galaxies’ nuclei.

At the centre of this image lie two elliptical galaxies, part of a galaxy cluster known as [HGO2008]SDSS J1531+3414, which have strayed into each other’s paths. While this region has been observed before, this new Hubble picture shows clearly for the first time that the pair are two separate objects. However, they will not be able to hold on to their separate identities much longer, as they are in the process of merging into one.

Finding two elliptical galaxies merging is rare, but it is even rarer to find a merger between ellipticals rich enough in gas to induce star formation. Galaxies in clusters are generally thought to have been deprived of their gaseous contents; a process that Hubble has recently seen in action. Yet, in this image, not only have two elliptical galaxies been caught merging but their newborn stellar population is also a rare breed.

The stellar infants — thought to be a result of the merger — are part of what is known as “beads on a string” star formation. This type of formation appears as a knotted rope of gaseous filaments with bright patches of new stars and the process stems from the same fundamental physics which causes rain to fall in droplets, rather than as a continuous column.

Nineteen compact clumps of young stars make up the length of this “string”, woven together with narrow filaments of hydrogen gas. The star formation spans 100,000 light years, which is about the size of our galaxy, the Milky Way. The strand is dwarfed, however, by the ancient, giant merging galaxies that it inhabits. They are about 330,000 light years across, nearly three times larger than our own galaxy. This is typical for galaxies at the centre of massive clusters, as they tend to be the largest galaxies in the Universe.

The electric blue arcs making up the spectacular egg-like shape framing these objects are a result of the galaxy cluster’s immense gravity. The gravity warps the space around it and creates bizarre patterns using light from more distant galaxies.

Image credit: NASA, ESA/Hubble and Grant Tremblay (European Southern Observatory)

8 years ago
1976 … Space Station Colonies

1976 … space station colonies

by x-ray delta one

7 years ago
We’re Used To Radiation Being Invisible. With A Geiger Counter, It Gets Turned Into Audible Clicks.

We’re used to radiation being invisible. With a Geiger counter, it gets turned into audible clicks. What you see above, though, is radiation’s effects made visible in a cloud chamber. In the center hangs a chunk of radioactive uranium, spitting out alpha and beta particles. The chamber also has a reservoir of alcohol and a floor cooled to -40 degrees Celsius. This generates a supersaturated cloud of alcohol vapor. When the uranium spits out a particle, it zips through the vapor, colliding with atoms and ionizing them. Those now-charged ions serve as nuclei for the vapor, which condenses into droplets that reveal the path of the particle. The characteristics of the trails are distinct to the type of decay particle that created them. In fact, both the positron and muon were first discovered in cloud chambers! (Image credit: Cloudylabs, source)

  • richardotis-blog
    richardotis-blog liked this · 7 years ago
  • iceman6565
    iceman6565 liked this · 8 years ago
  • tori10rambles
    tori10rambles reblogged this · 8 years ago
  • miclnightcity
    miclnightcity liked this · 8 years ago
  • ashynarr
    ashynarr reblogged this · 8 years ago
  • letterpigeon
    letterpigeon reblogged this · 8 years ago
  • trazandrew64-blog
    trazandrew64-blog liked this · 8 years ago
  • nimal0
    nimal0 liked this · 8 years ago
  • kopicetic
    kopicetic liked this · 8 years ago
  • jdr1966
    jdr1966 liked this · 8 years ago
  • freznutz
    freznutz liked this · 8 years ago
  • willmac54
    willmac54 liked this · 8 years ago
  • evisno
    evisno reblogged this · 8 years ago
  • l0stpr0phet
    l0stpr0phet liked this · 8 years ago
  • lunovedi
    lunovedi liked this · 8 years ago
  • thegirldownthelaine
    thegirldownthelaine liked this · 8 years ago
  • amlizard
    amlizard liked this · 8 years ago
  • three-knuckles-deep-blog
    three-knuckles-deep-blog liked this · 8 years ago
  • littlez13
    littlez13 liked this · 8 years ago
  • make-a-noise
    make-a-noise reblogged this · 8 years ago
  • lgniite
    lgniite liked this · 8 years ago
  • forgedbymountains
    forgedbymountains liked this · 8 years ago
  • adamandevedoamerica
    adamandevedoamerica liked this · 8 years ago
  • herkidalpaca
    herkidalpaca reblogged this · 8 years ago
  • herkidalpaca
    herkidalpaca liked this · 8 years ago
  • astrizen
    astrizen reblogged this · 8 years ago
  • roberty340-blog
    roberty340-blog liked this · 8 years ago
  • astronomyandastrophotography
    astronomyandastrophotography reblogged this · 8 years ago
  • boxofboxes
    boxofboxes reblogged this · 8 years ago
  • boxofboxes
    boxofboxes liked this · 8 years ago
  • ubermonkeyfish
    ubermonkeyfish reblogged this · 8 years ago
  • hotdiggityho
    hotdiggityho liked this · 8 years ago
  • space-today
    space-today reblogged this · 8 years ago
  • wolfshank
    wolfshank reblogged this · 8 years ago
  • wolfshank
    wolfshank liked this · 8 years ago
  • storiesnstardust
    storiesnstardust reblogged this · 8 years ago
  • storiesnstardust
    storiesnstardust liked this · 8 years ago
  • mr-top-secret
    mr-top-secret liked this · 8 years ago
  • lunaraether
    lunaraether liked this · 8 years ago
  • gas-on-my-handss
    gas-on-my-handss liked this · 8 years ago
evisno - Majormajor
Majormajor

89 posts

Explore Tumblr Blog
Search Through Tumblr Tags