DustPedia is a project funded by the

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...

for exploitation of space science and exploration data. It is a collaboration of six European institutes with a primary goal of exploiting existing data in the ''Herschel'' Space Observatory and ''Planck'' Telescope databases. This data will be combined with other available data from both ground-based and space-based telescopes to make the most extensive and intensive study of

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

in the nearby Universe.

Context

Many observations of galaxies over large look back times correspond very well with

cosmological Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', and in 1731 taken up in Latin by German philosopher ...

models of galaxy and larger scale structure formation. This has led to the wide spread belief that the current

cosmological model Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of f ...

is broadly correct. Although there is good agreement over large spatial scales there are some challenging disagreements between theory and observation when one looks over smaller scales and particularly at the properties of nearby galaxies. The distributions of galaxy

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...

and size, their locations within larger scale structures in the Universe and their star formation histories as a function of galactic mass are all examples of disparity with the currently favoured model. In a recent ''

Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...

'' article Peebles and Nusser stress the importance of nearby galaxies if one is to understand the detailed processes of galaxy evolution and hence develop a complete model of how galaxies change with time. They specifically say that "….nearby galaxies offer rich and still far from completely explored clues to a better picture of how galaxies form." The reason of course is that nearby galaxies can be studied in far greater detail than those that lie at the edge of the Cosmos and importantly that in general cosmological surveys cover such small areas of sky that they in fact do not sample the local population at all. Observations of

cosmic dust Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...

address many aspects of the current galaxy evolutionary model i.e.

star formation Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space

rate, growth of the metal abundance, loss of metals in galactic winds, physical processes in the

interstellar medium In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...

etc. and so offer the potential for a much better understanding.

Objectives

The DustPedia project aims at addressing five specific but quite broad science issues that have a direct bearing on current evolutionary models of galaxies: * Measure the complete UV-mm

spectral energy distribution A spectral energy distribution (SED) is a plot of energy versus frequency or wavelength of light (not to be confused with a 'spectrum' of flux density vs frequency or wavelength). It is used in many branches of astronomy to characterize astron ...

(SEDs) for a large number (> 1000) of galaxies, and for different environments within individual galaxies. * Interpret the galaxy SEDs using radiative transfer and full SED models, to derive stellar, gas and dust properties, star formation rates and histories as a function of morphological type. * Determine how the dust NIR-mm/radio SED evolves throughout the Universe and how this is related to the underlying dust properties * Develop a dust evolution model that is consistent with the SEDs of galaxies of different morphological types and determine the primary sources and sinks for cosmic dust. * Derive dust mass functions to the lowest-possible luminosities and masses and to compare these with cosmological surveys and the cosmic far infrared background.

Sample selection

To achieve the objectives set out above a representative sample of galaxies for study was defined. The Herschel data alone does not provide a large completely sampled region of sky, but it is possible to use the WISE data to define a near infrared selected sample. As many galaxy properties correlate first with stellar mass, the near infrared, where for most galaxies the bulk of the stellar radiation emerges, provides the best available choice for galaxy selection. There are 3045 galaxies with a WISE 3.4μm detection (SN > 3) within 3000 km s⁻¹ (≈40 Mpc) of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

and with a size of D₂₅>1 arc min (≈12 kpc at 40 Mpc) – the W sample. Currently within the Herschel archive there are 613 observations of galaxies from this W sample. The intersection of these two samples will be referred to as the WH sample. A similar selection will be carried out for galaxies detected by

Planck Max Karl Ernst Ludwig Planck (, ; 23 April 1858 – 4 October 1947) was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial contributions to theoretical p ...

once the final data becomes available in late 2013 and the intersection of this sample with the WH sample is the WHP sample. The WH sample consists of 80 early type galaxies (T< 0) and 533 late types, 70 of which may be described as star forming irregulars/dwarfs. Also, within the WH sample, 94 galaxies have D₂₅> 5 arc min and so are resolved in the Herschel bands and lend themselves to full radiative transfer and infrared/mm SED modelling.

References

External links

*{{official, http://dustpedia.astro.noa.gr - the science database Computational astronomy Educational policies and initiatives of the European Union Information technology organizations based in Europe