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  • richardmitnick 4:59 pm on December 9, 2014 Permalink | Reply
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    From Frontier Fields: “Mapping Mass in a Frontier Fields Cluster” 

    Frontier Fields
    Frontier Fields

    December 9, 2014
    Tracy Vogel

    The Frontier Fields project’s examination of galaxy cluster MACS J0416.1-2403 has led to a precise map that shows both the amount and distribution of matter in the cluster. MACS J0416.1-2403 has 160 trillion times the mass of the Sun in an area over 650,000 light-years across.

    The mass maps have a two-fold purpose: they identify the location of mass in the galaxy clusters, and by doing so make it easier to characterize lensed background galaxies.

    m
    Mass map of galaxy cluster MCS J0416.1–2403
    The galaxy clusters under observation in Frontier Fields are so dense in mass that their gravity distorts and bends the light from the more-distant galaxies behind them, creating the magnifying effect known as gravitational lensing. Astronomers use the lensing effect to determine the location of concentrations of mass in the cluster, depicted here as a blue haze. Credit: ESA/Hubble, NASA, HST Frontier Fields

    Astronomers use the distortions of light caused by mass concentrations to pinpoint the distribution of mass within the cluster, including invisible dark matter. Weakly lensed background galaxies, visible in the outskirts of the cluster where less mass accumulates, may be stretched into slightly more elliptical shapes or transformed into smears of light. Strongly lensed galaxies, visible in the inner core of the cluster where greater concentrations of mass occur, can appear as sweeping arcs or rings, or even appear multiple times throughout the image. And as a dual benefit, as the clusters’ mass maps improve, it becomes easier to identify which galaxies are strongly lensed, and which galaxies are farther away.
    Stronger lensing produces greater distortions. Astronomers can work backwards from the distortions to pinpoint the greater concentrations of mass responsible for producing such altered images.

    s
    Stronger lensing produces greater distortions. Astronomers can work backwards from the distortions to pinpoint the greater concentrations of mass responsible for producing such altered images. Credit: A. Feild (STScI)

    The depth of the Frontier Fields images allows astronomers to see extremely faint objects, including many more strongly lensed galaxies than seen in previous observations of the cluster. Hubble identified 51 new multiply imaged galaxies around this cluster, for instance, quadrupling the number found in previous surveys. Because the galaxies are multiples, that means almost 200 strongly lensed images appear in the new observations, allowing astronomers to produce a highly constrained map of the cluster’s mass, inclusive of both visible and dark matter.

    The dark matter aspect is particularly intriguing. Because these types of Frontier Fields analyses create extremely precise maps of the locations of dark matter, they provide the potential for testing the nature of dark matter. Learning where dark matter concentrates in massive galaxy clusters can give clues to how it behaves and changes. And as the mass maps become more precise, astronomers are better able to determine the distance of the lensed galaxies.

    In order to obtain a complete picture of MACS J0416.1-2403’s mass, astronomers will also need to include weak lensing measurements. Follow up observations will include further Frontier Fields imaging, as well as X-ray measurements of hot gas and spectroscopic redshifts to break down the total mass distribution into dark matter, gas, and stars.

    See the full article here.

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    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

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  • richardmitnick 6:03 pm on November 16, 2014 Permalink | Reply
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    From Frontier Fields: “Gravitational Forensics: Astronomers Discover a Distant Galaxy in the Frontier Fields” 

    Frontier Fields
    Frontier Fields

    November 12, 2014
    Dr. Brandon Lawton

    The first Hubble Frontier Fields observations of a galaxy cluster and adjacent parallel field are complete, and interesting results are starting to arrive from astronomers. In this post, we explore how astronomers used the tools available to them to piece together the discovery of a very distant galaxy.

    The Discovery

    A team of international astronomers, led by Adi Zitrin of the California Institute of Technology in Pasadena, Calif., have discovered a very distant galaxy observed to be multiply lensed by the foreground Abell 2744 galaxy cluster. The light from this distant galaxy was distorted into three images and magnified via gravitational lensing of Abell 2744. This magnification provided the astronomers with a means to detect the incredibly faint galaxy with Hubble.

    a2744
    Abell 2744, nicknamed Pandora’s Cluster. The galaxies in the cluster make up less than five percent of its mass. The gas (around 20 percent) is so hot that it shines only in X-rays (coloured red in this image). The distribution of invisible dark matter (making up around 75 percent of the cluster’s mass) is coloured here in blue.
    Date 22 June 2011
    Source HubbleSite
    Author NASA, ESA, J. Merten (Institute for Theoretical Astrophysics, Heidelberg/Astronomical Observatory of Bologna), and D. Coe (STScI)

    Astronomers are interested in finding these very distant galaxies because they represent an early stage of galaxy formation that occurred just after the Big Bang. Light from this galaxy has been traveling for quite some time. We are seeing this galaxy as it existed when the universe was only about 500 million years old. For context, the current age of the universe is around 13.8 billion years old.

    Like visitors to a nursery, astronomers can see this baby galaxy is much smaller than present-day adult galaxies. In fact, they measure it to be about 500 times smaller than our own Milky Way galaxy. This baby galaxy is estimated to be forming new stars at a rate of one star every three years. That is about 1/3 the current rate of star formation of our own Milky Way, but keep in mind that this infant galaxy is much smaller than the present-day Milky Way. This baby galaxy is not just small but also a lightweight. It has the mass, in stars, of only about 40 million suns. Compare that to the Milky Way, which has a mass of several hundred billion suns. It is also one of the intrinsically faintest distant galaxies ever discovered.

    The three lensed images of the baby galaxy are highlighted in the composite image below.

    im
    Credit: NASA, ESA, A. Zitrin (California Institute of Technology, Pasadena), and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (Space Telescope Science Institute, Baltimore, Md.) Shown is the discovery of a high redshift galaxy candidate, triply lensed by Abell 2744. The high redshift galaxy candidate’s lensed images are labeled as a, b, and c.

    This is now one of only a small handful — about 10 — of galaxies we have discovered at such great distances. The way the team discovered this distant galaxy is, perhaps, as interesting as the galaxy itself. The team of astronomers used a traditional color-based method for determining that the galaxy is a candidate for being a distant, baby galaxy. They then followed up with a pioneering new technique to confirm the distance via the geometry of gravitational lensing.

    Using Colors to Find Candidate Distant Galaxies

    Why do we think that the galaxy is very far away? Astronomers used Hubble’s filters to capture the light from this baby galaxy in several different colors. The intensity of light coming from the galaxy at different colors can give an estimate of the galaxy’s cosmological redshift. Cosmological redshift, commonly denoted by the letter “z,” is a number that signifies how reddened a galaxy is due to the expansion of space. A distance can be estimated once a cosmological redshift is measured. Larger cosmological redshifts correspond to larger distances.

    Adi Zitrin and his collaborators initially found the distant galaxy (labeled “a” in the figure above) by noticing that it remained when they were looking for only the reddest galaxies. Remember, a galaxy may appear red if its light is redshifted due to the expansion of the universe. The farther the galaxy, the longer its light has to traverse the expanding universe, getting more and more stretched (redshifted) along the way. Astronomers are particularly interested in finding a population of galaxies with large cosmological redshifts — values of z around 10 or greater — because they represent some of the earliest galaxies to form after the Big Bang.

    From the colors of the galaxy found in box ‘a,’ the team estimated that the galaxy has a redshift greater than 4, with 95% confidence. In fact, the colors of the galaxy in box ‘a’ highly favored a galaxy around z=10, but they could not discount that what they were measuring was an intrinsically red galaxy at a lower redshift, around a z=2. How do we sort this out?

    Deciphering the Geometry of Abell 2744′s Gravitational Lens

    Astronomers can do better, and these astronomers have shown that with knowledge of how mass is distributed in the foreground galaxy cluster, it is possible to distinguish between higher redshift and lower redshift background galaxies. Thus, with updated maps of the mass distribution of the Abell 2744 galaxy cluster, astronomers created more precise mathematical models of how light from a more distant galaxy behaves as it passes around the galaxy cluster’s warped space.

    The geometry of a gravitational lens is such that the more distant a background galaxy behind the galaxy cluster, the farther from the center of the galaxy cluster we observe the distorted and magnified, lensed versions of the galaxy. This is portrayed in the graphic below, where two lensed versions of the more distant, highly redshifted, red galaxy appears on the sky at larger apparent distances from the central, foreground, lensing galaxy cluster.

    2
    Credit: Courtesy of Dr. Dan Coe (STScI). Shown here is an illustration of how the multiple lensing of a background galaxy will show its maximum magnification depending on its distance to the foreground galaxy cluster. More distant galaxies will be lensed such that we observe them further from the center of the galaxy cluster.

    Astronomers can use the computed geometry of gravitational lensing to ascertain the cosmological redshift of the lensed galaxy based on its observed positions relative to the foreground galaxy cluster. If multiple images of the lensed galaxy appear nearby the cluster, it is at a lower redshift. If the multiple images of the lensed galaxy appear more separated from the cluster, it is at a larger redshift.

    Finding the Multiple Images of a Distant Lensed Galaxy

    With the updated mathematical models of the gravitational lensing by Abell 2744, Adi Zitrin and his team could follow up and look for multiply lensed images of the one potentially distant galaxy they had found, labeled “a” in the image at top. The mathematical models give them positions on the sky to look for the lensed siblings of galaxy ‘a’ for various redshifts. If the distant galaxy is at a relatively low redshift, multiply lensed images will appear nearer the cluster. If the distant galaxy is at a high redshift, multiply lensed images will appear farther from the cluster.

    With the computational tools and mathematical knowledge available to them, the team discovered the lensed versions of galaxy “a” at positions that match a high-redshift solution. In the figure below, they marked the locations of the lensed images, labeled “B” and “C”, along with their best mathematical estimates of redshift for each of them (labeled along the blue- and green-colored redshift lines). What is labeled as the initially discovered candidate galaxy “a” in the image at top is now labeled as “A” in the image below.
    Credit: Adi Zitrin et al. 2014. Shown here are the expected positions of the three lensed versions of the newly discovered high redshift galaxy candidate, based on mathematical models of the gravitational lensing from Abell 2744. Galaxy lens A, B, and C are all in positions that match high redshift solutions in the models, i.e. redshifts of around 8 or greater.

    3
    Credit: Modified from Adi Zitrin et al., ApJ, 793 (2014). Shown here are the expected positions of the three lensed versions of the newly discovered high-redshift galaxy candidate, based on mathematical models of the gravitational lensing from Abell 2744. The multiply-lensed positions of the galaxy, labeled “A”, “B”, and “C,” match the high-redshift solution in the models, i.e., redshifts of around 8 or greater.

    This is but a taste of how astronomers will use the Frontier Fields to combine exquisite imaging with updated mathematical models to detect and study some of the first galaxies to form after the Big Bang. We are just at the beginning of collecting the baby pictures of galaxies in our universe. Stay tuned as we detect more baby galaxies from the dawn of time!

    Looking to the Future

    The galaxy presented here is one of the least luminous high-redshift galaxies ever detected. This bodes very well for finding future baby galaxies in the Frontier Fields. We also expect that studies of the galaxy clusters themselves, via the new data in the Frontier Fields, will lead to more accurate mass distribution maps and more accurate mathematical models of how light from distant galaxies are gravitationally lensed and magnified.

    This really is a new age in using humankind’s most sophisticated telescopes with nature’s lenses to probe deeper into our cosmic past than ever before. Stay tuned for more results from the Frontier Fields.

    See the full article here.

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    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

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  • richardmitnick 4:52 pm on October 29, 2014 Permalink | Reply
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    From Frontier Fields: “Light Detectives: Using Color to Estimate Distance” 

    Frontier Fields
    Frontier Fields

    October 28, 2014
    Dr. Brandon Lawton

    Distances are notoriously difficult to measure in astronomy. Astronomers use many methods for estimating distances, but the farther away an object is, the more uncertain the results. Cosmological distances, distances on the largest scales of our universe, are the most difficult to estimate. To measure the distances to the farthest galaxies, those gravitationally lensed by massive foreground galaxy clusters, astronomers really have their work cut out for them.

    If a massive stellar explosion, known as a supernova, happens to go off in a galaxy and we catch it, then we can use the “standard candle” method of computing the distance to the galaxy. Supernovae are expected to be discovered in the Frontier Fields, but not at the numbers that will help us find distances to most of the galaxies in the images. Without these standard candles, astronomers must use other means to estimate distances.

    A Spectrum is Worth a Thousand Pictures

    One of the more accurate methods for measuring the distance to a distant galaxy involves obtaining a spectrum of the galaxy. Getting a galaxy’s spectrum basically means taking the light from that galaxy and breaking it up into its component colors, much like a prism breaks up white light into the rainbow of visible colors. By comparing the brightness of light at each component color, a spectrum can give us a wealth of information. This can include detailed information about a galaxy’s composition, temperature, and how fast it is moving relative to us. Because the universe is expanding, we observe most galaxies, and all distant galaxies, to be moving away from us.

    When looking at a distant galaxy’s spectrum, the expansion of the universe causes the component colors in the spectrum to be stretched to longer wavelengths. For visible light, red has the longest wavelengths, which leads to the term ‘redshift’. This cosmological redshift can be accurately measured from a spectrum. Astronomers then use mathematical models of the expansion rate of our universe to convert the measured redshift into an estimate of distance. Larger values of redshift correspond to larger distances.

    This video, developed by the Office of Public Outreach at the Space Telescope Science Institute, gives a demonstration of how light is redshifted as it travels through the expanding universe. Here, the lightbulb stands in place of a galaxy. As the universe expands, it stretches the light traveling through the universe, increasing the light’s wavelength. As the wavelength increases, it becomes more red. Light traveling longer distances through the universe will be stretched/reddened more than light traveling short distances. This is why astronomers use instruments sensitive to redder light, including infrared light, when they attempt to observe the light from very distant galaxies. Watch this video on Youtube.

    Larger redshifts not only correspond to larger distances, but they also correspond to earlier times in our universe’s history. This is because light takes time to travel to us from these distant galaxies. The more distant the galaxy, the longer the light has been traveling before we intercept it with sensitive telescopes, like Hubble.

    Assuming typical contemporary mathematical models, the universe is about 13.8 billion years old. Galaxies at a redshift of 1 are seen as they existed when the universe was about 6 billion years old. Galaxies at a redshift of 3 are seen as they existed when the universe was about 2 billion years old. Galaxies at a redshift of 6 are seen as they existed when the universe was about 1 billion years old. Galaxies at a redshift of 10 are seen as they existed when the universe was only about 500 million years old.

    It is notoriously difficult to obtain a spectrum of a very distant galaxy. They are very faint, and an accurate spectrum relies on obtaining a lot of light. One is, after all, taking what little light you get and breaking it up further into the component colors, meaning that you start with little light and get out even less light at each component color. Getting enough light to take an accurate spectrum of a distant galaxy requires very lengthy observations with sensitive telescopes. This is not always feasible.

    Redshifts measured via spectra are called spectroscopic redshifts. Many of the nearer galaxies in Abell 2744 have measured spectroscopic redshifts. There will likely be many follow-up observations from ground- and space-based observatories to obtain spectra of many of the fainter and more distant galaxies in the Frontier Fields. So stay tuned!
    I Can’t Obtain a Spectrum! What to do?

    If you do not have a spectrum, are there other ways to estimate the redshift and distance to a galaxy? Yes! Just take a look at the galaxy’s colors.

    All Hubble images are taken with filters. Blue filters allow Hubble’s instruments to capture only blue light, red filters allow Hubble’s instruments to capture only red light, and so on. By comparing a galaxy’s brightnesses in these different colors, astronomers can estimate the distance to the galaxy. The redder the color, the more likely the galaxy is to be redshifted, and thus, farther away.

    This technique of using color to estimate redshift is called photometric redshift. The following two primary methods are used for estimating a photometric redshift:

    compare the colors of your high-redshift galaxy candidate to a set of typical galaxy color templates at various redshifts, or
    compare the colors of your high-redshift galaxy candidate to a set of galaxies with measured spectroscopic redshifts and, utilizing specialized software, compute the most likely redshift for your galaxy.

    In the first case, the photometric redshift comes from the best match between the observed high-redshift candidate colors and the colors of the template galaxies. The template galaxy colors stem from observations of galaxies that tend to be relatively close but are then mathematically reddened over a range of redshift values.

    In the second case, astronomers use a set of observed galaxies whose redshifts have been measured spectroscopically, as explained in the prior section. This set contains galaxies at various redshifts. They then use machine-learning algorithms to compare the colors of this set of galaxies with the colors of the target high-redshift galaxy candidate. The software selects the most likely redshift.

    Whichever method is used, astronomers are careful to give confidence levels in their calculations. For the computation of photometric redshift, there is typically an uncertainty of around a few percent for high-quality data. In addition, there is the lingering issue of whether the high-redshift galaxy candidate is truly redshifted, or if it is a nearer galaxy that is intrinsically redder. It is not uncommon to read results where astronomers find a galaxy with a probable high photometric redshift and a less probable low photometric redshift, or vice versa.

    shif
    Credit: Adapted from Adi Zitrin, et al., 2014. Shown is a high-redshift galaxy candidate in Hubble’s observations of Abel 2744, discovered using filters. Dark regions represent light in these images. Notice how the galaxy drops out of the image in the bluest filters. This is a hint that the galaxy may be significantly redshifted.

    Many of the first results for the Frontier Fields utilize photometric redshifts. In the absence of spectra, photometric redshifts are the next best thing to obtaining estimates of distances for large samples of galaxies. They are readily computed from the current Frontier Fields data.

    See the full article, with video, here.

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

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  • richardmitnick 7:37 am on October 25, 2014 Permalink | Reply
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    From Frontier Fields: “First Galaxy Field Complete: Abell 2744″ 

    Frontier Fields
    Frontier Fields

    October 23, 2014
    Tony Darnell

    This past summer, the Hubble Frontier Fields team completed observations of the first cluster on its list: Abell 2744! The second set of observations — astronomers call them epochs — consisted of 70 orbits and marks the completion of the first Frontier Fields galaxy cluster. During this set, Hubble’s Advanced Camera for Surveys (ACS) was pointed at the main galaxy cluster and studied the visible-light portions of the spectrum, while the Wide Field Camera 3 (WFC3) looked at the parallel field in the infrared.

    NASA Hubble ACS
    ACS

    NASA Hubble WFC3
    WFC3

    Remember that Hubble will visit each field multiple times, with Hubble oriented such that one set of observations will point WFC3 at the cluster and ACS at a parallel field adjacent to the cluster (that’s one epoch). The telescope will then come back and do another set of observations with the cameras switched: ACS pointing at the cluster and WFC3 pointing to the parallel field (that’s the second one).

    The Frontier Fields team does this to allow for complete wavelength coverage in both infrared and visible light for the galaxy cluster and the parallel field.

    The first epoch, completed in November 2013, consisted of 87 orbits. This brings the total amount of time Hubble looked at this cluster to 157 orbits.

    a2744
    Final mosaic of the Frontier Fields galaxy cluster Abell 2744. This image is the culmination of both epochs totaling 157 Hubble orbits. The numbers prefixed with “F” are the Hubble filters used by the ACS and WFC3 cameras to take the image. The scale bar of 30″ is approximately 2% the angular size of the full moon as seen from Earth – very small! Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

    Final mosaic of the Frontier Fields galaxy cluster Abell 2744. This image is the culmination of both epochs totaling 157 Hubble orbits. The numbers prefixed with “F” are the Hubble filters used by the ACS and WFC3 cameras to take the image. The scale bar of 30″ is approximately 2% the angular size of the full moon as seen from Earth – very small!
    Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

    par
    Parallel field of Frontier Field Abell 2744

    This is the completed composite mosaic of the Parallel Fields observed with galaxy cluster Abell 2744.
    Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

    See? Epic! Er, I mean epoch.

    Once the second epoch was completed, some of the faintest galaxies ever seen were measured for the first time. Astronomers have been working on these images since their release, and we are anxiously awaiting to hear what they find.

    See the full article here.

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

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  • richardmitnick 10:58 am on July 24, 2014 Permalink | Reply
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    From NASA/ESA Hubble: “New mass map of a distant galaxy cluster is the most precise yet” 

    NASA Hubble Telescope

    Hubble

    24 July 2014
    Mathilde Jauzac
    Durham University, Institute for Computational Cosmology
    Durham, United Kingdom
    Tel: +33 6 52 67 15 39 (France)
    Cell: +44 7445 218614 (UK)
    Email: mathilde.jauzac@dur.ac.uk

    Jean-Paul Kneib
    École Polytechnique Fédérale de Lausanne, Observatoire de Sauverny
    Versoix, Switzerland
    Tel: +41 22 3792473
    Cell: +33 695 795 392
    Email: jean-paul.kneib@epfl.ch

    Stunning new observations from Frontier Fields

    Astronomers using the NASA/ESA Hubble Space Telescope have mapped the mass within a galaxy cluster more precisely than ever before. Created using observations from Hubble’s Frontier Fields observing programme, the map shows the amount and distribution of mass within MCS J0416.1–2403, a massive galaxy cluster found to be 160 trillion times the mass of the Sun. The detail in this mass map was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing.

    imasge

    Measuring the amount and distribution of mass within distant objects in the Universe can be very difficult. A trick often used by astronomers is to explore the contents of large clusters of galaxies by studying the gravitational effects they have on the light from very distant objects beyond them. This is one of the main goals of Hubble’s Frontier Fields, an ambitious observing programme scanning six different galaxy clusters — including MCS J0416.1–2403, the cluster shown in this stunning new image.

    Large clumps of mass in the Universe warp and distort the space-time around them. Acting like lenses, they appear to magnify and bend light that travels through them from more distant objects.

    Despite their large masses, the effect of galaxy clusters on their surroundings is usually quite minimal. For the most part they cause what is known as weak lensing, making even more distant sources appear as only slightly more elliptical or smeared across the sky. However, when the cluster is large and dense enough and the alignment of cluster and distant object is just right, the effects can be more dramatic. The images of normal galaxies can be transformed into rings and sweeping arcs of light, even appearing several times within the same image. This effect is known as strong lensing, and it is this phenomenon, seen around the six galaxy clusters targeted by the Frontier Fields programme, that has been used to map the mass distribution of MCS J0416.1–2403, using the new Hubble data.

    “The depth of the data lets us see very faint objects and has allowed us to identify more strongly lensed galaxies than ever before,” explains Mathilde Jauzac of Durham University, UK, and Astrophysics & Cosmology Research Unit, South Africa, lead author of the new Frontier Fields paper. “Even though strong lensing magnifies the background galaxies they are still very far away and very faint. The depth of these data means that we can identify incredibly distant background galaxies. We now know of more than four times as many strongly lensed galaxies in the cluster than we did before.”

    Using Hubble’s Advanced Camera for Surveys, the astronomers identified 51 new multiply imaged galaxies around the cluster, quadrupling the number found in previous surveys and bringing the grand total of lensed galaxies to 68. Because these galaxies are seen several times this equates to almost 200 individual strongly lensed images which can be seen across the frame. This effect has allowed Jauzac and her colleagues to calculate the distribution of visible and dark matter in the cluster and produce a highly constrained map of its mass.

    NASA Hubble ACS
    Hubble ACS

    “Although we’ve known how to map the mass of a cluster using strong lensing for more than twenty years, it’s taken a long time to get telescopes that can make sufficiently deep and sharp observations, and for our models to become sophisticated enough for us to map, in such unprecedented detail, a system as complicated as MCS J0416.1–2403,” says team member Jean-Paul Kneib.

    By studying 57 of the most reliably and clearly lensed galaxies, the astronomers modelled the mass of both normal and dark matter within MCS J0416.1-2403. “Our map is twice as good as any previous models of this cluster!” adds Jauzac.

    The total mass within MCS J0416.1-2403 — modelled to be over 650 000 light-years across — was found to be 160 trillion times the mass of the Sun. This measurement is several times more precise than any other cluster map, and is the most precise ever produced. By precisely pinpointing where the mass resides within clusters like this one, the astronomers are also measuring the warping of space-time with high precision.

    “Frontier Fields’ observations and gravitational lensing techniques have opened up a way to very precisely characterise distant objects — in this case a cluster so far away that its light has taken four and a half billion years to reach us,” adds Jean-Paul Kneib. “But, we will not stop here. To get a full picture of the mass we need to include weak lensing measurements too. Whilst it can only give a rough estimate of the inner core mass of a cluster, weak lensing provides valuable information about the mass surrounding the cluster core.”

    The team will continue to study the cluster using ultra-deep Hubble imaging and detailed strong and weak lensing information to map the outer regions of the cluster as well as its inner core, and will thus be able to detect substructures in the cluster’s surroundings. They will also take advantage of X-ray measurements of hot gas and spectroscopic redshifts to map the contents of the cluster, evaluating the respective contribution of dark matter, gas and stars [5].

    Combining these sources of data will further enhance the detail of this mass distribution map, showing it in 3D and including the relative velocities of the galaxies within it. This paves the way to understanding the history and evolution of this galaxy cluster.

    The results of the study will be published online in Monthly Notices of the Royal Astronomical Society on 24 July 2014.

    NASA’s Chandra X-ray Observatory was used to obtain X-ray measurements of hot gas in the cluster and ground based observatories provide the data needed to measure spectroscopic redshifts.

    NASA Chandra Telescope
    NASA/Chandra

    Frontier Fields Mast

    The international team of astronomers in this study consists of M. Jauzac (Durham University, UK and Astrophysics & Cosmology Research Unit, South Africa); B. Clement (University of Arizona, USA); M. Limousin (Laboratoire d’Astrophysique de Marseille, France and University of Copenhagen, Denmark); J. Richard (Université Lyon, France); E. Jullo (Laboratoire d’Astrophysique de Marseille, France); H. Ebeling (University of Hawaii, USA); H. Atek (Ecole Polytechnique Fédérale de Lausanne, Switzerland); J.-P. Kneib (Ecole Polytechnique Fédérale de Lausanne, Switzerland and Laboratoire d’Astrophysique de Marseille, France); K. Knowles (University of KwaZulu-Natal, South Africa); P. Natarajan (Yale University, USA); D. Eckert (University of Geneva, Switzerland); E. Egami (University of Arizona, USA); R. Massey (Durham University, UK); and M. Rexroth (Ecole Polytechnique Fédérale de Lausanne, Switzerland)

    See the full article, with notes, here.

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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    • viswamjyoti 7:13 am on August 30, 2014 Permalink | Reply

      Sub;MCS J0416.1–2403
      Data is useful but in-adequate perception of Galaxy Cluster formations -ignore the cosmic function of the Universe.

      Like

  • richardmitnick 5:09 am on May 24, 2014 Permalink | Reply
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    From Frontier Fields: “Einstein’s Crazy Idea” 

    Frontier Fields
    Frontier Fields

    May 23, 2014
    Dr. Frank Summers

    General relativity is just plain weird.

    The basic idea of gravity we are taught in school comes from Isaac Newton’sPrincipia” in 1687. Gravity is a force exerted by objects with mass. The greater the mass, the greater the gravitational force. The larger the distance between objects, the lesser the force ( it decreases with the square of the distance). The gravity of the Sun pulls on Earth and holds it, along with the other planets, asteroids, comets, etc., in orbit.

    Not so, according to Albert Einstein in 1916. He came up with a completely new, and quite radical, alternative explanation.

    Einstein’s crazy idea is that the presence of mass warps the fabric of space around it. Then, that warped space controls the motion of other masses nearby. Newton’s idea of a gravitational force is thus replaced with four-dimensional space-time geometry. Planets orbiting around stars, and stars traveling through galaxies — these are space-time distortions moving within other space-time distortions. As one famous description puts it: mass tells space how to warp, while warped space tells mass how to move. Yeah, weird.

    On the face of it, Isaac and Albert are just describing the same phenomenon from two different points of view: the former sees a force, while the latter sees geometric distortions. And, since the algebraic equations of the gravitational force are so, so, so, so, so very much simpler than the tensor calculus of general relativity, why go to all the relativistic trouble?

    The answer is that there are certain situations, generally involving very large masses, where Newton’s gravity is demonstrably wrong. The most famous of these is the precession of the perihelion of Mercury.

    The orbit of Mercury is not fixed in space. Each time Mercury orbits the Sun, its orbit rotates by a minuscule amount. The position when Mercury is closest to the Sun, called perihelion, is used to measure this orbit rotation, called precession. While Newton’s gravity predicts a precession of the perihelion of Mercury, the measured value is significantly higher. This mismatch between prediction and observation is resolved by Einstein’s general relativity in that the warping of space at such a close distance to the Sun produces a slightly stronger precession than gravitational force.

    eclipse
    One of the original plates from the 1919 solar eclipse used to measure the effects of general relativity.

    The other famous demonstration of general relativity is the bending of light as it passes a massive object. Light rays also have their paths changed by passing through warped space. A total solar eclipse on May 29, 1919, served to test this effect. During the eclipse, astronomers could see stars whose light had passed close to the Sun. Their apparent position on the sky would be shifted from their normal position due to passage through the warped space around the Sun. By observing the precise positions of such stars both before and during the eclipse, astronomers measured the effects of general relativity. (See the image accompanying this post.)

    Those 1919 observations did much to confirm that this crazy idea of general relativity reflected the reality of the universe. We now have many tests of general relativity. Most are subtle and require significant explanation. However, there is one that is visually striking, and which is critical to the scientific underpinnings of the Frontier Fields project. I’ll address that in my next blog post.

    See the full article here.

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

    NASA Hubble Telescope
    Hubble
    NASA James Webb Telescope
    Webb

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  • richardmitnick 8:37 am on May 14, 2014 Permalink | Reply
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    From Frontier Fields: “Frontier Fields Q&A: Redshift and Looking Back in Time” 

    Frontier Fields
    Frontier Fields

    May 13, 2014
    Tracy Vogel

    Q: What do you mean when you say you’re “seeing some of the earliest galaxies in the universe?” How does looking into deep space allow you to look back in time?

    The simple answer is that light travels and the universe is huge. Light travels very fast – 186,000 miles (300,000 km) per second, but it still has to move across the vast distances of space. Remember that for us to see anything – from the flash of a camera to the glow of a really distant galaxy, we have to wait for its light to strike our eyes.

    That camera flash shows in our vision instantaneously because it doesn’t have far to go. But distances in the cosmos are so vast that it takes light a long time to reach us. The light from our closest companion, the Moon, takes about 1.3 seconds to cross the 239,000 miles (390,000 km) between us. So when you look up at the sky, you don’t see the Moon as it currently is. You see it as it appeared 1.3 seconds ago.
    This is so 1.3 seconds ago. Credit: Luc Viatour, Wikimedia Commons

    moon
    This is so 1.3 seconds ago.
    Credit: Luc Viatour, Wikimedia Commons

    The greater the distances, the greater the time difference. Light from the Sun needs about 500 seconds, or about eight minutes, to reach us from 93,200 miles (150 million km) away. Light from Neptune needs about four hours to cross the solar system.

    We refer to these distances by the time it takes light to cross them. So Neptune is four light-hours away, and the Sun is 500 light-seconds away. Light from the next nearest star, however, needs four years to reach us across space. We say that star is four light-years away. The light we see from that star in today’s sky is also four years old. For galaxies, we’re talking millions to billions of light years. So we see the farthest galaxies as they appeared in the early universe, because the light that left them way back then is finally reaching us just now.

    Q: What does it mean when you talk about a galaxy’s redshift?

    When we’re discussing the Frontier Fields project, we’re talking about something more precisely called “cosmological redshift.” The space light is traveling through is expanding. That means that the light wave gets stretched as it travels, like a spring being pulled into a different shape. This stretching shifts light into longer wavelengths.

    redshft
    Since red light has a longer wavelength than blue light, the light is said to be “red-shifted.” Credit: NASA

    The farthest galaxies in the universe would have originally emitted visible and ultraviolet light, but since that light has been stretched as it travels, those galaxies appear to us instead in the form of infrared light. Cosmological redshift refers to that change and the measure of that change.

    Q: Why do we hear the Frontier Fields galaxies described in terms of redshift and light-years? Which is right?

    They tell us different things. Light-years are a measurement of distance defined by the time it takes light to travel in a year. But distance is notoriously difficult to measure in astronomy.

    Cosmological redshift is a direct measurement of the expansion of space. Astronomers describe galaxies in terms of their redshift because unlike distance, it’s a clear and definite value that’s relatively easy to measure without many errors.

    Astronomers have different models of how the universe works, and they can plug the redshift into those models to get the distance to a galaxy – but the distance will differ depending on which model of the universe they use. The variations in those models include things like the shape of the universe, the rate at which it’s expanding, the amount of normal matter it contains, etc.

    Astronomy is about figuring out how the universe works and narrowing down all those models to the best one, and we still have a long way to go. Projects like Frontier Fields will help us rule out those models that don’t fit the incoming data.

    Q: Everywhere we look with the Frontier Fields project, galaxies appear to be moving away from us. Does this mean we’re in the center of the universe?

    No. It’s evidence that space is expanding. The easiest way to visualize this is to imagine a balloon. If you cover the balloon with dots, and then inflate it, no matter which dot you pick to represent your position, all the other dots will appear to be moving away from it as the balloon expands. Imagine this happening in three dimensions instead of on a flat surface, and you can understand why it looks like other galaxies are rushing away.

    Q: So space is expanding and the light from the earliest galaxies has traveled over 13 billion years to reach us. If space is expanding, are those galaxies even farther away now?

    Yes. For nearby galaxies, the expansion doesn’t make much of a difference. But for galaxies extremely far away, the distance is significant. That’s because the farther away an object is, the more space there is between us and the object. That in turn means there’s more space to undergo expansion, so the objects appear to be moving away from us much faster. Light from the earliest galaxies may have traveled 13 billion years to reach us, but those galaxies could be around 45 billion light-years distant by now.

    Q: Does this mean the galaxies are moving faster than the speed of light?

    No. No object can travel through space faster than the speed of light. But the expansion of space itself is not so constrained – in fact, theories of the beginning of the universe visualize the initial expansion of the Big Bang happening with unthinkable speed. But because the speed of light is only so fast, there are galaxies in the distance whose light we cannot yet see. We call this the edge of the visible universe.

    Q: What’s out there, past the edge?

    drag
    Space dragons! Ok, probably not. Credit: Uranometria

    DRAGONS! SPACE DRAGONS! GIANT, COSMIC FIRE-BREATHING SPACE DRA– Ok, fine, probably not. Credit: Uranometria, Wikimedia Commons

    We expect more of the same, though this is still an open question that astronomers are researching and theorizing about. We’ve found we tend to see the same distribution of galaxies no matter which direction we look in the universe. If we were somehow transported to a galaxy on what, for Earth, is the edge of the visible universe, the border of the visible universe would move, but the universe would neither change nor look very different to us.

    See the full article here.

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

    NASA Hubble Telescope
    Hubble
    NASA James Webb Telescope
    Webb

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  • richardmitnick 5:32 am on May 3, 2014 Permalink | Reply
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    From Frontier Fields: “What’s Really in a Frontier Fields Image?” 

    Frontier Fields
    Frontier Fields

    April 28, 2014
    Tracy Vogel

    What are we actually seeing when we look at one of the Frontier Fields images? The gravitational lensing that produces the strange, almost artistic-looking effects in the images — the streaks and blobs of light among glowing galaxies – is visually striking, but little of it falls into typical expectations of what we see when we look into the universe.

    abell 2744
    Archival image of the Abell 2744 cluster taken with Hubble’s visible light ACS instrument.
    Credit: NASA, ESA, and R. Dupke (Eureka Scientific, Inc.), et al.

    Let’s break it down by examining this image of galaxy cluster Abell 2744, also known as Pandora’s Cluster. Four separate galaxy clusters containing several hundred galaxies are colliding in this image, providing the vast amount of mass — both normal and, most importantly, dark matter — needed to create a gravitational lens. The galaxies’ mass warps space and brightens, distorts and magnifies the light of nearly 3,000 galaxies located much farther away, behind the cluster.

    For simplicity’s sake we’ve highlighted a representative sample of objects in the image. The highlighting therefore doesn’t capture every single object — just a handful of good examples.

    Stars

    In this image, the white circles enclose stars in our own Milky Way galaxy. The stars have a distinctive cross-shape created by light reflecting off the struts in the telescope. We call these diffraction spikes. These spikes only occur with bright, point-like objects, such as relatively nearby stars.

    box

    Foreground Galaxies

    The green circles here capture galaxies that reside in the space between us and the Abell 2744 galaxy cluster. These galaxies are not affected by the gravitational lens – only galaxies behind the cluster are distorted and magnified. If you look at them, you see that their shapes are generally sharp, distinctive and recognizable. There aren’t many of these galaxies – the Frontier Fields project deliberately sought out galaxy clusters that didn’t have a lot of other objects in the way of Hubble’s view.

    box2

    Cluster Galaxies

    The yellow circles enclose the galaxies of the Abell 2744 galaxy cluster. These galaxies vary a lot in size, from dwarf galaxies a thousandth of the mass of our Milky Way to monster-sized central galaxies up to 100 times more massive than the Milky Way. Since the clusters are colliding, these galaxies are interacting with one another – each galaxy’s gravity is affecting the other galaxies, though the galaxies that are closest to one another affect each other more strongly. Some galaxies contain greater concentrations of mass than others, and thus have stronger gravitational effects – and make for stronger gravitational lenses.

    box3

    As we go on, you’ll see that some of the lensed galaxies in this image appear less or more warped than others. This is because the distribution of the cluster’s mass is uneven, and thus the bending of space-time is uneven. Think of it as looking at objects at the bottom of a lake – the surface of the water is uneven, so some of the objects are more distorted than others.

    As a side note, astronomers can actually study the distortion created by gravitational lensing to get an idea of how mass – both visible matter and the invisible dark matter — is distributed within the Abell 2744 galaxy cluster.

    Strongly Lensed Galaxies

    Now you’re seeing galaxies that are behind Abell 2744, and affected by the cluster’s gravitational lens. The light of these blue-circled galaxies is shining through the cluster, and is clearly distorted in many cases. In fact, many of these galaxies look like lines, streaks and arcs. They’re often concentrated along the same lines, and many of them have similar color schemes – blue with red patches.

    box3

    Some of these objects are actually the exact same galaxy, because the gravitational lens breaks the image up, as though we were looking through a very strangely shaped piece of glass. This brings us to …

    Weakly Lensed Galaxies

    These magenta-circled objects are galaxies that are still behind the gravitational lens, but are not strongly distorted. You see distinctive galaxy shapes, like spirals. Their light is still being magnified and brightened, but they fall in an area where the bumpy pane of glass in our earlier metaphor is smooth. They are not as magnified as the strongly lensed galaxies.

    box5

    Distant Galaxies

    The tiny red specks circled here don’t look like much, but they’re actually some of the most intriguing objects in the image. These are the farthest and faintest of the galaxies being magnified by the gravitational lens. Their light could be reaching us from so far away that we see them as they appeared in the early universe – as far back as just millions of years after the Big Bang. (In a universe that’s 13.7 billion years old, that’s extremely far indeed.) One of these objects, Abell2744_Y1, is a candidate for being the most distant galaxy discovered in this image.

    bopx

    See the full article here.

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

    NASA Hubble Telescope
    Hubble
    NASA James Webb Telescope
    Webb

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  • richardmitnick 5:15 pm on April 24, 2014 Permalink | Reply
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    From Frontier Fields: “What is Dark Matter?” 

    Frontier Fields

    Frontier Fields

    One of the most novel aspects of the Frontier Fields project is the innovative way in which the Hubble Space Telescope is being made more powerful — without adding a single piece of equipment or changing a single hardware component.

    NASA Hubble Telescope

    While Hubble itself isn’t altered physically in any way to allow us to peer farther than we ever have into the universe, these observations wouldn’t be possible without one crucial component: dark matter.

    Frontier Fields is turbocharging Hubble by looking at the distant universe through gravitational lenses that boost the signal from the feeble light of remote galaxies, essentially making Hubble a more powerful telescope.

    For the amateur astronomers out there, these gravity lenses are like adding a Barlow lens to the eyepiece of Hubble.

    What creates these gravitational lenses?

    Matter, and lots of it. Thanks to the theory of general relativity, we know that space-time is warped by stars, planets, galaxies, black holes — anything with mass. The light bends as it travels through this warped space-time.

    This is exactly what ordinary lenses in a telescope do with light: they bend it. Hence the term “gravitational lens.”

    In order to make a decent gravitational lens that will show you the most distant galaxies in the universe, you need lots of matter. Among the largest collections of matter in the universe are of galaxies. Hundreds of billions of stars all grouped together can bend a lot of space-time (and they do). What could be better?

    A lot of galaxies all grouped together, otherwise known as galaxy clusters.

    We’ve written before about the galaxy clusters that the Frontier Fields team will observe throughout the course of the survey. They were chosen because they made good gravitational lenses.

    But while the galaxies in these clusters do have lots of stars in them — hundreds of billions in each one – stars actually are not the major factor contributing to the bending of space-time around the clusters.

    The largest contributor to the creation of those gravitational lenses is something we can’t see, smell, taste, hear, touch or interact with in any way: dark matter.

    This stuff is all over the universe — in fact, there is five times more of it in the universe than there is ordinary matter. Everything we can see in the cosmos — stars, planets, comets, all life on Earth, anything that’s made up of atoms — constitutes roughly 5% of the total matter and energy in the universe. Dark matter makes up about 24%.
    matter
    Composition of matter in the universe. Credit: NASA

    It’s usually at this point the astute person starts asking, “If dark matter won’t interact with us in any way, how do we know it’s there?”

    The answer is simple enough. We know dark matter exists because we can see its effects on those things we can see. We were first tipped off to dark matter in the 1950′s by the motions of galaxies. We noticed that if we added all the mass of all the stars inside of galaxies, something wasn’t right. The galaxies didn’t rotate the way they should. Their motions suggested that something else had to be there mixed in all the stars we could see.

    What’s more, the galaxies that were gathered together into clusters were short on mass. If just the mass we could observe was all there was, the clusters would fly apart. There wasn’t enough observed mass to make them stay together.

    This stuff, whatever it was, was making galaxies rotate as if they had more matter than we could see and was also holding galaxy clusters together. In astronomy, we are used to investigating celestial objects by the light they emit, reflect, or block. We called this strange new discovery dark matter because it does not interact with light — though clearly it has a gravitational field we can detect.

    We’re starting to get pretty good at estimating where the dark matter is in galaxy clusters. We can even make maps of it. Here is a map of dark matter around the Abell 1689 cluster, home to thousands of galaxies and trillions of stars.
    abell 1689
    Dark matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster contains about 1,000 galaxies and trillions of stars. Hubble cannot see the dark matter directly. Astronomers inferred its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster. Credit: NASA, ESA, and Z. Levay (STScI)

    Astronomers have gone so far as to map where most of the dark matter is in the universe. Here’s a graphic showing the distribution of dark matter in the universe.
    map
    This three-dimensional map offers a first look at the web-like large-scale distribution of dark matter. The map reveals a loose network of dark matter filaments, gradually collapsing under the relentless pull of gravity, and growing clumpier over time. Credit: NASA, ESA, and R. Massey (California Institute of Technology)

    Most astronomers believe that dark matter is concentrated in and around small clusters of galaxies.

    For the purposes of the Frontier Fields Survey, dark matter plays a crucial role. Without it, these galaxy clusters would have less mass, and space-time would bend less significantly, creating a weaker lens. By using these powerful natural lenses, the Frontier Fields project will enable Hubble to see galaxies about 10 times deeper than the Ultra Deep Field, the current record holder for the deepest image ever taken.

    And that corresponds to 40 billion times fainter than what the human eye can see.

    Now the next question you may be asking is, “What’s this dark matter stuff made of?” Astronomers are actively researching that question, but that’s a post for another day — so stay tuned!

    See the full article here.

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

    NASA Hubble Telescope
    Hubble
    NASA James Webb Telescope
    Webb

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  • richardmitnick 4:02 am on April 12, 2014 Permalink | Reply
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    From Frontier Fields: “Hubble Observations: From the Ground to Your Computer” 

    Frontier Fields

    April 11, 2014
    Ann Jenkins

    This post is the second in a two-part series.

    In my last post, Hubble Observations: From the Sky to the Ground*, I wrote about the route Hubble images take as they are digitally transferred from space to the ground.

    This is the story of what happens after that data makes the 30-mile trip over land-lines from NASA’s Goddard Space Flight Center in Greenbelt, Md., to the Space Telescope Science Institute in Baltimore, Md., and ultimately to your computer as iconic Hubble pictures.

    Hubble generates approximately 855 gigabytes of new science data each month. That’s the equivalent of an 8,550-yard-long shelf of books. Astronomers, in turn, typically download six terabytes of data monthly from this growing archive. That would be the equivalent of the printed paper from 300,000 trees. By the beginning of April 2014, Hubble data had been used to publish more than 12,000 peer-reviewed scientific papers.

    The raw Frontier Fields data are available to the public immediately from a repository called the Barbara A. Mikulski Archive for Space Telescopes, or MAST. However, these data are not the beautiful, color Hubble images we have come to know and love. Raw images from the telescope are black and white, and include distortions introduced by the instruments, as well other unwanted artifacts from Earthshine, occasional Earth-orbiting satellite trails, bad pixels, and random hits by small, charged particles called cosmic rays.

    ray
    Cosmic ray signatures are removed by combining two exposures in a way that removes everything not in both images. Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, the HFF Team, and Ann Feild (STScI).

    It takes a team of about a dozen instrument analysts to “clean” these images by removing the distortions and artifacts. The refined images are posted once a week on MAST. These are the combination of multiple exposures taken in seven different filters, which allow light at specific wavelengths to enter the instruments.

    Hubble’s instruments have many filters. The Frontier Fields observations use four in infrared from the Wide Field Camera 3 (WFC3), and three in visible light from the Advanced Camera for Surveys (ACS). The final, deep, combined color image for each Frontier Field will have a total of 560 exposures, divided evenly between the main cluster and its parallel field.

    NASA Hubble WFC3
    WFC3

    NASA Hubble ACS
    ACS

    To produce a color picture, exposures from the seven filters are assigned the three primary colors of blue, green, and red based on their wavelengths. Images from the shortest, bluest wavelengths are assigned to blue, while images from the longest, reddest wavelengths are assigned to red, and intermediate wavelengths are assigned to green. These primary color images are then composited to produce the full-color picture so familiar to Hubble followers.

    filters
    The top row shows the combined exposures through each of the seven filters as single images. To produce the color pictures, exposures from several selected filters from Hubble’s WFC3 and ACS were combined into one of three primary colors based on their wavelengths. The primary color images were then composited to produce the full-color image. Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, the HFF Team, and Ann Feild (STScI).

    *My post

    See the full article here.

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

    NASA Hubble Telescope
    Hubble
    NASA James Webb Telescope
    Webb

    ScienceSprings is powered by MAINGEAR computers

     
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