The Atacama Large Millimeter/submillimeter Array (ALMA) has been producing a growing number of impressive and scientifically compelling results as the most powerful mm/submm interferometer in the world. Held in central Tokyo, the aim of this four day conference is to highlight the most recent science results from ALMA obtained during the first three years of science operations, and to motivate future collaboration among researchers around the world. Continua a leggere Revolution in Astronomy with ALMA
This meeting will be held in Cefalù (Sicily) and will consist of two main topics, The Distant Universe and The Local Universe.
Quella di Abell 2744 è la prima di una serie di spettacolari immagini che saranno realizzate dal programma Hubble’s Frontier Fields attraverso il fenomeno della lente gravitazionale causata dagli ammassi di galassie allo scopo di esplorare le regioni più remote dell’Universo (post). Noto anche come Pandora’s Cluster, si ritiene che Abell 2744 abbia avuto un passato violento dato che la sua formazione è emersa in seguito ad un processo di ammassamento di più ammassi di galassie.
Astronomers previously observed Abell 2744 with the NASA/ESA Hubble Space Telescope back in 2011, exploring the cluster’s history. They found that at least four galaxy clusters had crashed into one another to form Abell 2744, causing some weird and wonderful effects. This mix of cosmic phenomena, some of which had never been seen before, led to the nickname of Pandora’s Cluster (heic1111). A mix of hazy elliptical galaxies and colourful spirals can be seen clumping together in the centre of this image. The effects of the cluster’s gravity can be seen in the blue arcs and distorted shapes that are scattered across the frame, including galaxies that seem to be bleeding into the surrounding space. The arcs are actually the distorted images of galaxies far in the distance. Abell 2744 is the first of six targets for an observing programme known as Frontier Fields.
This three-year, 840-orbit programme will yield our deepest views of the Universe to date, using the power of Hubble to explore more distant regions of space than could otherwise be seen, by observing gravitational lensing effects around six different galaxy clusters.
Gravitational lensing is a phenomenon caused by an object’s influence on the space-time around it. Massive objects like galaxy clusters warp and distort this space-time. This causes light from more distant objects hidden behind this makeshift lens to be deflected and bent, leading to a bizarre array of optical effects, for example, it caused a cosmic space invader to appear around cluster Abell 68 (heic1304) by creating mirror images of one galaxy, as well as smearing galaxies out into arcs, and creating multiple images of individual objects. As well as creating these weird shapes, lensing also magnifies the images so that astronomers can see more detail. This means that distant objects that otherwise would be too distant and faint to be seen become visible, something that Frontier Fields aims to exploit over the coming years. Some results from this programme are already starting to emerge, with Abell 2744 as the first target. In a new paper submitted to The Astrophysical Journal on 29 November 2013 (available on the ArXiv Preprint Server), a group of astronomers detected a large number of distant, gravitationally lensed galaxy candidates, all viewed through Abell 2744, with the galaxy cluster acting as a lens. They also found that five of these candidates are part of distant systems that appear to have been imaged multiple times due to the cluster’s gravitational lensing effects. These deep surveys using massive galaxy clusters like Abell 2744 show that looking through cosmic lenses can be an effective and useful way to study the distant Universe. For more information on gravitational lensing see Hubblecast 70: Peering around cosmic corners.
La NASA utilizzerà i telescopi spaziali Hubble, Spitzer e Chandra in un ‘tour-de-force’ per esplorare le regioni più remote dell’Universo. Grazie alla tecnica della lente gravitazionale, gli astronomi saranno in grado di studiare le galassie più distanti la cui luce è almeno 100 volte più debole di quella che riescono a catturare oggi con i grandi osservatori.
This ambitious collaborative program is called The Frontier Fields. Astronomers will spend the next three years peering at six massive clusters of galaxies. Researchers are interested not only as to what’s inside the clusters, but also what’s behind them. The gravitational fields of the clusters brighten and magnify distant background galaxies that are so faint they would otherwise be unobservable. The clusters themselves are among the most massive assemblages of matter known.
Astronomers anticipate that these observations will reveal populations of never-before-seen galaxies that existed when the Universe was only a few hundred million years old.
The Hubble and Spitzer data will be combined to measure the galaxies’ distances and masses more accurately than either observatory could measure alone, demonstrating the synergy of these Great Observatories for such studies. The Chandra X-ray Observatory will also peer deep into the fields, imaging them at X-ray wavelengths to help determine the masses and lensing power of the clusters, as well as identify background galaxies with massive black holes. “The idea is to use nature’s natural telescopes in combination with the Great Observatories to look much deeper than before and find the most distant and faint galaxies we can possibly see“, said principal investigator Jennifer Lotz of the Space Telescope Science Institute (STScI) in Baltimore, Md. “We want to understand when and how the first stars and galaxies formed in the universe, and each Great Observatory gives us a different piece of the puzzle. Hubble tells you which galaxies to look at and how many stars are being born in those systems. Spitzer tells you how old the galaxy is and how many stars have formed“, said Peter Capak, the Spitzer principal investigator of the Frontier Fields program. The high-resolution Hubble data from the Frontier Fields program will also be used to trace the distribution of dark matter within the foreground clusters. Accounting for the bulk of the Universe’s mass, dark matter is the underlying, invisible scaffolding attached to galaxies. “The apparent positions of those lensed galaxies then tell you what’s happening with the cluster itself, where the dark matter is in that cluster“, Lotz said. “We’ll use that information to make a better model of the cluster to better understand its lensing power“. The Hubble and Spitzer observations will be much more challenging for researchers than previous deep fields that have been studied by this powerful pair of observatories with great success. “With a deep image, you’ve got a direct image, what you see is what you get. But when we use a gravitational lens, background galaxies appear distorted and brighter“, Lotz said. “In order to understand the true properties of a background galaxy, you have to understand how it is distorted and how it is magnified. This depends on the distribution of dark matter in the gravitational lens, the foreground cluster“. What’s more, the galaxies seen in previous ultra-deep fields are just the most massive at those epochs. “They are the tip of the iceberg. If you want to see the galaxies that will turn into ones like our Milky Way, you have to go much fainter“, Lotz said. Without using the big natural telescopes in space, astronomers would have to wait for the James Webb Space Telescope. In fact, the Frontier Fields offer a sneak peek of what the Webb telescope will routinely see anywhere it points in space, when it is launched in 2018. The Hubble Frontier Fields initiative grew out of high-level discussions at STScI concerning what important, forward-looking science Hubble should be doing in upcoming years. Despite several deep field surveys, astronomers realized that a lot was still to be learned about the distant Universe. And, such knowledge would help in planning the observing strategy for the Webb telescope. To get a better assessment of whether doing more deep field observations was scientifically interesting or urgent, STScI chartered a “Hubble Deep Field Initiative” working group, which included U.S. and European astronomers who were expert users of the Great Observatories. The astronomers also considered synergies with other observatories, such as Spitzer, Chandra, and the new Atacama Large Millimeter Array. STScI Director Matt Mountain allocated his director’s discretionary time to the program. The first object to be looked at this month is called Pandora’s Cluster (Abell 2744), which has been previously observed by all three Great Observatories but not to the depth of the new observations. The giant galaxy cluster appears to be the result of a simultaneous pile-up of at least four separate, smaller galaxy clusters that took place over a span of 350 million years.