All-Sky Map of Infrared Sources by AKIRA

This AKARI view of the sky shows infrared sources at 9 micrometers in blue, at 18 micrometers in green, and at 90 micrometers in red. The image is arranged with the Galactic Center in the middle, and the plane of the Galaxy running horizontally across the map. Emission from the photospheres of stars dominates the 9 micrometers catalog, where the galactic disc and nuclear bulge are clearly visible, whereas dust and star formation in the disc of our Galaxy become are more prominent at 90 micrometers. Away from the Galactic Plane, many extragalactic objects are detected, tracing galaxy evolution and star formation in the distant Universe.

Photo credit: JAXA

For more information, read ESA: AKARI Produces Two New Infrared All-Sky Catalogs.

Hubble Confirms Cosmic Acceleration with Weak Lensing

A new study led by European scientists presents the most comprehensive analysis of data from the most ambitious survey ever undertaken by the NASA/ESA Hubble Space Telescope. These researchers have, for the first time ever, used Hubble data to probe the effects of the natural gravitational "weak lenses" in space and characterize the expansion of the Universe.

A group of astronomers, led by Tim Schrabback of the Leiden Observatory, conducted an intensive study of over 446,000 galaxies within the COSMOS field, the result of the largest survey ever conducted with Hubble. In making the COSMOS survey, Hubble photographed 575 slightly overlapping views of the same part of the Universe using the Advanced Camera for Surveys (ACS) on board Hubble. It took nearly 1,000 hours of observations.

In addition to the Hubble data, researchers used redshift [1] data from ground-based telescopes to assign distances to 194,000 of the galaxies surveyed (out to a redshift of 5). "The sheer number of galaxies included in this type of analysis is unprecedented, but more important is the wealth of information we could obtain about the invisible structures in the Universe from this exceptional dataset," says co-author Patrick Simon from Edinburgh University.

In particular, the astronomers could "weigh" the large-scale matter distribution in space over large distances. To do this, they made use of the fact that this information is encoded in the distorted shapes of distant galaxies, a phenomenon referred to as weak gravitational lensing [2]. Using complex algorithms, the team led by Schrabback has improved the standard method and obtained galaxy shape measurements to an unprecedented precision. The results of the study will be published in an upcoming issue of Astronomy and Astrophysics.

The meticulousness and scale of this study enables an independent confirmation that the expansion of the Universe is accelerated by an additional, mysterious component named dark energy. A handful of other such independent confirmations exist. Scientists need to know how the formation of clumps of matter evolved in the history of the Universe to determine how the gravitational force, which holds matter together, and dark energy, which pulls it apart by accelerating the expansion of the Universe, have affected them. "Dark energy affects our measurements for two reasons. First, when it is present, galaxy clusters grow more slowly, and secondly, it changes the way the Universe expands, leading to more distant - and more efficiently lensed - galaxies. Our analysis is sensitive to both effects," says co-author Benjamin Joachimi from the University of Bonn. "Our study also provides an additional confirmation for Einstein's theory of general relativity, which predicts how the lensing signal depends on redshift," adds co-investigator Martin Kilbinger from the Institut d'Astrophysique de Paris and the Excellence Cluster Universe.

The large number of galaxies included in this study, along with information on their redshifts is leading to a clearer map of how, exactly, part of the Universe is laid out; it helps us see its galactic inhabitants and how they are distributed. "With more accurate information about the distances to the galaxies, we can measure the distribution of the matter between them and us more accurately," notes co-investigator Jan Hartlap from the University of Bonn. "Before, most of the studies were done in 2D, like taking a chest X-ray. Our study is more like a 3D reconstruction of the skeleton from a CT scan. On top of that, we are able to watch the skeleton of dark matter mature from the Universe's youth to the present," comments William High from Harvard University, another co-author.

The astronomers specifically chose the COSMOS survey because it is thought to be a representative sample of the Universe. With thorough studies such as the one led by Schrabback, astronomers will one day be able to apply their technique to wider areas of the sky, forming a clearer picture of what is truly out there.


Notes:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

[1] In astronomy, the redshift denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths due to the expansion of the Universe. The observed redshift of a remote galaxy provides an estimate of its distance. In this study the researchers used redshift information computed by the COSMOS team using data from the SUBARU, CFHT, UKIRT, Spitzer, GALEX, NOAO, VLT, and Keck telescopes.

[2] Weak gravitational lensing: The phenomenon of gravitational lensing is the warping of spacetime by the gravitational field of a concentration of matter, such as a galaxy cluster. When light rays from distant background galaxies pass this matter concentration, their path is bent and the galaxy images are distorted. In the case of weak lensing, these distortions are small, and must be measured statistically. This analysis provides a direct estimate for the strength of the gravitational field, and therefore the mass of the matter concentration. When determining precise shapes of galaxies, astronomers have to deal with three main factors: the intrinsic shape of the galaxy (which is unknown), the gravitational lensing effect they want to measure, and systematic effects caused by the telescope and camera, as well as the atmosphere, in case of ground-based observations.

Image credit: NASA, ESA, P. Simon (University of Bonn) and T. Schrabback (Leiden Observatory)

3D Map of Dark Matter in the Universe

This three-dimensional map offers a first look at the web-like large-scale distribution of dark matter, an invisible form of matter that accounts for most of the Universe's mass.

The map reveals a loose network of dark matter filaments, gradually collapsing under the relentless pull of gravity, and growing clumpier over time.

The three axes of the box correspond to sky position (in right ascension and declination), and distance from the Earth increasing from left to right (as measured by cosmological redshift). Note how the clumping of the dark matter becomes more pronounced, moving right to left across the volume map, from the early Universe to the more recent Universe.

Credit: NASA, ESA and R. Massey (California Institute of Technology)

NASA Mission "Movie" Posters

NASA, through its Space Flight Awareness division, is now making cute posters and images for its space shuttle missions and expeditions to the International Space Station (ISS). Many of the posters have a movie poster-quality to them, some more blatantly obvious than others. :) As you can see, the above image for the STS-124 mission, which flew to the ISS in May-June 2008, is patterned after the Harry Potter movie posters. My only complaint about the images available from the website is that the majority of downloads come in the form of PDF files; I prefer jpg images myself.

Check it out!

New Planck Images Reveal Large-Scale Structure in Milky Way

Planck's ability to measure the temperature of the coldest dust particles will provide an important indicator of the physical processes at play in the interstellar medium, and in regions of star formation.

The image above covers a portion of the sky about 55 degrees in total extent. It is a three-color combination constructed from Planck's two highest frequency channels (557 and 857 GHz, corresponding to wavelengths of 540 and 350 micrometers), and an image at the shorter wavelength of 100 micrometers obtained with the Infrared Astronomical Satellite (IRAS). This combination effectively traces the dust: reddish tones correspond to temperatures as cold as 12 degrees above absolute zero, and whitish tones to significantly warmer ones (of order a few tens of degrees) in regions where massive stars are currently forming. Overall, the image shows local dust structures within 500 light years of the Sun.

New images from ESA's Planck mission reveal details of the structure of the coldest regions in our Galaxy. Filamentary clouds predominate, connecting the largest to the smallest scales in the Milky Way. These images are a scientific by-product of a mission which will ultimately provide the sharpest picture ever of the early Universe.

ESA's Planck microwave observatory – the first European mission designed to study the Cosmic Microwave Background (CMB) - has begun the second of four sky surveys, which will ultimately provide the most detailed information yet about the size, mass, age, geometry, composition and fate of the Universe. Although the primary goal of Planck is to map the CMB, by surveying the entire sky with an unprecedented combination of frequency coverage, angular resolution, and sensitivity, Planck will also provide valuable data for a broad range of studies in astrophysics. This is clearly demonstrated by new Planck images, published on March 17, 2010, which trace cold dust in our Galaxy and reveal the large-scale structure of the interstellar medium filling the Milky Way.

The images are a scientific 'by-product' of the data analysis that is currently underway, which aims to produce the highest-sensitivity (a few parts per million), highest-angular resolution (5 arcminutes) maps of the CMB. Part of the analysis process involves peeling away the foreground emission arising from a number of 'contaminants' - namely: the cosmological dipole (a signal due to our motion relative to the microwave background), and the radiation from gas and dust in the Milky Way and in distant galaxies - to reveal the underlying map of the CMB. In the process, a series of scientifically valuable maps of this foreground emission is obtained. The maps will be constructed from images like these first Planck snapshots.

Pinpointing the location of stellar formation:
One of the key characteristics of Planck is its ability to measure the temperature of the coldest dust particles. Temperature is an important physical indicator as it reflects the balance of energies in the interstellar medium, and changes significantly from place to place, tracing the evolution of the star formation process.

Among the astrophysics-related investigations to be undertaken with Planck is a program which aims to locate the coldest dusty clumps in the Galaxy, areas where star formation is about to occur. The above image demonstrates how Planck traces this cold dust: reddish tones correspond to temperatures as cold as 12 degrees above absolute zero, and whitish tones to much warmer ones (of order a few tens of degrees) in regions where massive stars are currently forming. Planck excels at detecting these dusty clumps across the whole sky and contributes the crucial information required to measure accurately the temperature of dust at these large scales. By combining data from Planck with data from other satellites, such as Herschel or NASA's Spitzer Space Telescope (both of which probe the very small scales where star formation occurs), and IRAS (which has mapped the whole sky at shorter wavelengths) astronomers will be able to study the formation of stars across the entire Milky Way.

Filamentary structures permeate the cosmos:
The space between stars is not empty but rather is filled with clouds of dust and gas - intimately mixed together - known as the 'interstellar medium'.

Filamentary structures are apparent at large-scales (as shown in this Planck image, on the right) and small-scales (as seen on the left, a Herschel image of a region in Aquila) in the Milky Way.

The large clouds seen in this second Planck image (above, on the right), which covers a region of about 55 degrees across, show the filamentary structure of the interstellar medium in the solar neighborhood (within about 150 pc, or 500 light years from the Sun). The local filaments are connected to the Milky Way, the horizontal feature at the bottom of the image, where the emission is coming from much larger distances across the disc of our Galaxy.

The image on the left shows a typical 'stellar nursery' (about 3 degrees across) in the Aquila constellation, as recently imaged by the Herschel Space Observatory. The filamentary structures seen at the smallest scales by Herschel are strikingly similar in appearance to those seen at the largest scales by Planck.

The richness of structure that is observed, and the way in which small and large scales are interconnected, provide important clues to the physical mechanisms underpinning the formation of stars and of galaxies. This example illustrates the synergy between Herschel and Planck; together these missions are imaging both the large-scale and the small-scale structure of our Galaxy.

Editor's notes:
Planck maps the sky in nine frequencies using two state-of-the-art instruments, designed to produce high-sensitivity, multi-frequency measurements of the diffuse sky radiation: the High Frequency Instrument (HFI) includes the frequency bands 100 – 857 GHz, and the Low Frequency Instrument (LFI) includes the frequency bands 30-70 GHz.

The first Planck all-sky survey began in August 2009 and is 98% complete (as of mid-March 2010). Because of the way Planck surveys the sky, the last bit of the first scan will be completed by late-May 2010. Planck will gather data until the end of 2012, during which time it will complete four sky scans. A first batch of astronomy data, called the Early Release Compact Source Catalogue, is scheduled for release in January 2011. To arrive at the main cosmology results will require about two years of data processing and analysis. The first set of processed data will be made available to the worldwide scientific community towards the end of 2012.

Photo credits:
Top photo: ESA, HFI Consortium, IRAS
Bottom photo (left): ESA and the SPIRE & PACS consortia, P. André (CEA Saclay) for the Gould's Belt Key Programme Consortium
Bottom photo (right): ESA, HFI Consortium

ESA: Bully Galaxy Rules the Neighborhood

In general, galaxies can be thought of as "social" - hanging out in groups and frequently interacting. However, this recent NASA/ESA Hubble Space Telescope image highlights how some galaxies appear to be hungry loners. These cosmic oddities have set astronomers on the "case of the missing neighbor galaxies".

Located about 500 million light-years from Earth, ESO 306-17, is a large, bright elliptical galaxy in the southern sky of a type known as a fossil group. Astronomers use this term to emphasize the isolated nature of these galaxies. However, are they like fossils - the last remnants of a once active community - or is it more sinister than that? Did ESO 306-17 gobble up its next-door neighbors?

Gravity brings galaxies together and bigger ones swallow smaller ones. There is evidence that our own Milky Way galaxy has "snacked" on numerous smaller galaxies that strayed too close. ESO 306-17 and other fossil groups may be the most extreme examples of galaxy cannibalism, ravenous systems that don't stop until they've devoured all of their neighbors.

In this image, taken by the Advanced Camera for Surveys aboard Hubble in November 2008, it appears that ESO 306-17 is surrounded by other galaxies, but the bright galaxies at bottom left are thought to be in the foreground, not at the same distance in the sky. In reality, ESO 306-17 lies fairly abandoned in an enormous sea of dark matter and hot gas [1]. When zooming in closely on ESO 306-17, one can see faint clusters of stars through the bright shine of the galaxy's large halo. These are globular clusters - tightly bound groups of stars that can often fend off cannibalism from larger, "bully" galaxies. Studying these surrounding clusters will prove helpful to astronomers in their pursuit to put the pieces of ESO 306-17's history together.

Researchers are also using this image to search for nearby ultra-compact dwarf galaxies. Ultra-compact dwarfs are mini versions of dwarf galaxies that have been left with only their core due to interaction with larger, more powerful galaxies. Most ultra-compact dwarfs discovered to date are located near giant elliptical galaxies in large clusters of galaxies, so it will be interesting to see if researchers find similar objects in fossil groups.

Notes:
[1] Studies conducted by both ESA's XMM-Newton mission and NASA's Chandra X-ray Observatory have confirmed the existence of hot gas surrounding ESO 306-17.

For more information, see also A Giant Among Galaxies?

Photo Credit: NASA, ESA and Michael West (European Southern Observatory, Chile)