Publication archive

Publication archive

Aims. Dust-obscured star-formation increases with increasing intensity and increasing redshift. We aim to reveal the cosmic starformation history obscured by dust using deep infrared observation with AKARI.
Methods. We constructed restframe 8 micron, 12 micron, and total infrared (TIR) luminosity functions (LFs) at 0.15 < z < 2.2 using 4128 infrared sources in the AKARI NEP-Deep field. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and 24 micron) by the AKARI satellite allowed us to estimate restframe 8 micron and 12 micron luminosities without using a large extrapolation based on an SED fit, which was the largest uncertainty in previous work.
Results. We find that all 8 micron (0.38 < z < 2.2), 12 micron (0.15 < z < 1.16), and TIR LFs (0.2 < z < 1.6) show continuous and strong evolution toward higher redshift. Our direct estimate of 8 micron LFs is useful since previous work often had to use a large extrapolation from the Spitzer 24 micron to 8 micron, where SED modeling is more difficult because of the PAH emissions. In terms of cosmic infrared luminosity density (OmegaIR), which was obtained by integrating analytic fits to the LFs, we find good agreement with previous work at z < 1.2. We find the OmegaIR evolves as proportinal to (1 + z)4.4±1.0. When we separate contributions to OmegaIR by LIRGs and ULIRGs, we found more IR luminous sources are increasingly more important at higher redshift. We find that the ULIRG (LIRG) contribution increases by a factor of 10 (1.8) from z=0.35 to z=1.4.
Published: 05 February 2010
This issue of Spatium summarizes a talk by Prof. Southwood, ESA's Director of Science and Robotic Exploration, on the European Space Agency's scientific programme: Cosmic Vision.
Published: 01 February 2010

A&A doi http://dx.doi.org/10.1051/0004-6361/200912983

The Planck mission was conceived in 1992, in the wake of the release of the results from the Cosmic Background Explorer (COBE) satellite (Boggess et al. 1992), notably the measurement by the FIRAS instrument of the shape of the spectrum of the Cosmic Microwave Background (CMB), and the detection by the DMR instrument of the spatial anisotropies of the temperature of the CMB. The latter result in particular led to an explosion in the number of ground-based and suborbital experiments dedicated to mapping of the anisotropies, and to proposals for space experiments both in Europe and the USA.

Published: 28 October 2010
Past spacecraft observations of Venus have found considerable spatial and temporal variations of water vapour abundance above the clouds. Previous searches for variability below the clouds at 30-45 km altitude found no large scale latitudinal gradients, but lacked the spatial resolution to detect smaller scale variations. Here we interpret results from the VIRTIS imaging spectrometer on Venus Express, remotely sounding at near-infrared "spectral window" wavelengths, as indicating that the water vapour abundance at 30-40 km altitude varies from 22 to 35 ppmv (±4 ppmv). Furthermore, this variability is correlated with cloud opacity, supporting the hypothesis that its genesis is linked to cloud convection. It is also possible to fit the observations without requiring spatial variation of water abundance, but this places a strong constraint on the spectral dependence of the refractive index data assumed for the lower cloud particles, for which there is as yet no supporting evidence.
Published: 26 January 2010
Aims. We explore spectral energy distributions (SEDs), star formation (SF), and dust extinction properties of galaxies in the Local Universe.
Methods. The AKARI All-Sky Survey provided the first bright point source catalog detected at 90 micron. Beginning with this catalog, we selected galaxies by matching the AKARI sources with those in the IRAS Point Source Catalog Redshift Survey. We measured the total GALEX FUV and NUV flux densities with a photometry software we specifically developed for this purpose. In a further step we matched this sample with the Sloan Digital Sky Survey (SDSS) and Two Micron All Sky Survey (2MASS) galaxies. With this procedure we obtained a basic sample which consists of 776 galaxies. After removing objects whose photometry was contaminated by foreground sources (mainly in the SDSS), we defined the "secure sample" which contains 607 galaxies.
Results. The sample galaxies have redshifts of <~ 0.15, and their 90-micron luminosities range from 106 to 1012 Lsun, with a peak at 1010 Lsun. The SEDs display a large variety, especially more than four orders of magnitude at the mid-far-infrared (M-FIR), but if we sort the sample with respect to 90 micron, the average SED shows a coherent trend: the more luminous an SED at 90 micron, the redder the global SED becomes. The Mr-NUV - r color-magnitude relation of our sample does not show bimodality, and the distribution is centered on the green valley.
- Remainder of abstract is truncated -
Published: 22 January 2010
The Euclid Mission Assessment Study is the industrial part of the Euclid assessment phase. This document summarizes the results of one such study performed between September 2008 and September 2009 by a team led by Thales Alenia Space (I) and including Thales Alenia Space (F), Kayser-Threde and Deimos Space.
Published: 30 October 2009
The Euclid Mission Assessment Study is the industrial part of the Euclid assessment phase. The study has been performed by Astrium from September 2008 to September 2009 and is intended for space segment definition and programmatic evaluation. The prime responsibility is with Astrium GmbH (Friedrichshafen, Germany) with support from Astrium SAS (Toulouse, France) and Astrium Ltd (Stevenage, UK).
Published: 01 October 2009
Since 2004, Saturn's moon Iapetus has been observed repeatedly with the Imaging Science Subsystem of the Cassini spacecraft. The images show numerous impact craters down to the resolution limit of ~10 meters per pixel. Small, bright craters within the dark hemisphere indicate a dark blanket thickness on the order of meters or less. Dark, equator-facing and bright, poleward-facing crater walls suggest temperature-driven water-ice sublimation as the process responsible for local albedo patterns. Imaging data also reveal a global color dichotomy, wherein both dark and bright materials on the leading side have a substantially redder color than the respective trailing-side materials. This global pattern indicates an exogenic origin for the redder leading-side parts and suggests that the global color dichotomy initiated the thermal formation of the global albedo dichotomy.
Published: 22 January 2010
The extreme albedo asymmetry of Saturn's moon Iapetus, which is about 10 times as bright on its trailing hemisphere as on its leading hemisphere, has been an enigma for three centuries. Deposition of exogenic dark material on the leading side has been proposed as a cause, but this alone cannot explain the global shape, sharpness, and complexity of the transition between Iapetus' bright and dark terrain. We demonstrate that all these characteristics, and the asymmetry's large amplitude, can be plausibly explained by runaway global thermal migration of water ice, triggered by the deposition of dark material on the leading hemisphere. This mechanism is unique to Iapetus among the saturnian satellites because its slow rotation produces unusually high daytime temperatures and water ice sublimation rates for a given albedo.
Published: 22 January 2010
Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray selected galaxy groups to investigate the scaling relation between X-ray luminosity (LX) and halo mass (M200) where M200 is derived via stacked weak gravitational lensing. This work draws upon a broad array of multiwavelength COSMOS observations including 1.64 degrees2 of contiguous imaging with the Advanced Camera for Surveys (ACS) to a limiting magnitude of IF814W = 26.5 and deep XMM-Newton/Chandra imaging to a limiting flux of 1.0 x 10-15 erg cm-2 s-1 in the 0.5-2 keV band. The combined depth of these two data-sets allows us to probe the lensing signals of X-ray detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law with a slope of alpha = 0.66 +/- 0.14. These results significantly extend the dynamic range for which the halo masses of X-ray selected structures have been measured with weak gravitational lensing. As a result, tight constraints are obtained for the slope of the M-LX relation. The combination of our group data with previously published cluster data demonstrates that the M-LX relation is well described by a single power law, alpha = 0.64 +/- 0.03, over two decades in mass. These results are inconsistent at the 3.7 sigma level with the self-similar prediction of alpha = 0.75. We examine the redshift dependence of the M - LX relation and find little evidence for evolution beyond the rate predicted by self-similarity from z ~0.25 to z ~0.8.
Published: 20 January 2010

Book published in the series "Astrophysics and Space Science Proceedings"; H. Laakso, M.G.G.T. Taylor, C.P. Escoubet (Eds.), 2010, XX, 489 p., Hardcover, ISBN: 978-90-481-3498-4, © Springer

Since the year 2000 the ESA Cluster mission has been investigating the small-scale structures and processes of the Earth's plasma environment, such as those involved in the interaction between the solar wind and the magnetospheric plasma, in global magnetotail dynamics, in cross-tail currents, and in the formation and dynamics of the neutral line and of plasmoids.

This book contains presentations made at the 15th Cluster workshop held in March 2008. It also presents several articles about the Cluster Active Archive and its datasets, a few overview papers on the Cluster mission, and articles reporting on scientific findings on the solar wind, the magnetosheath, the magnetopause and the magnetotail.

The contents of the book are grouped into seven main parts:

  • Part I - Products and Services of the Cluster Active Archive
  • Part II - Tools for the CAA Data Analysis
  • Part III - Measurement Techniques and Calibration Routines
  • Part IV - Magnetospheric Missions
  • Part V - Observations of Solar Wind and Magnetosheath
  • Part VI - Observations of Magnetopause and Cusp
  • Part VII - Observations of Magnetospheric Tail
Published: 15 January 2010
The European Space Agency's Rosetta mission encountered the main-belt asteroid (2867) Steins while on its way to rendezvous with comet 67P/Churyumov-Gerasimenko. Images taken with the OSIRIS (optical, spectroscopic, and infrared remote imaging system) cameras on board Rosetta show that Steins is an oblate body with an effective spherical diameter of 5.3 kilometers. Its surface does not show colour variations. The morphology of Steins is dominated by linear faults and a large 2.1-kilometer-diameter crater near its south pole. Crater counts reveal a distinct lack of small craters. Steins is not solid rock but a rubble pile and has a conical appearance that is probably the result of reshaping due to Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) spin-up. The OSIRIS images constitute direct evidence for the YORP effect on a main-belt asteroid.
Published: 08 January 2010
(Book in the series "Astronomers' Universe")

From prehistoric times, mankind has looked up at the night sky, and puzzled at the changing positions of the stars. How far away they are is a question that has confounded scientists for centuries. Over the last few hundred years, many scientific careers – and considerable resources – have been devoted to measuring their positions and motions with ever increasing accuracy. And in the last two decades of the 20th century, the European Space Agency developed and launched the Hipparcos satellite, around which this account revolves, to carry out these exacting measurements from space.

What has prompted these remarkable developments? Why have governments been persuaded to fund them? What are scientists learning from astronomy's equivalent of the Human Genome Project? This book traces the subject's history, explains why such enormous efforts are considered worthwhile, and interweaves these with a first-hand insight into the Hipparcos project, and how big science is conducted at an international level. The involvement of amateur astronomers, and the Hipparcos contributions to climate research, 'death stars' passing close to the Sun, and the search for extra-solar planets and even intelligent life itself, are some of the surprising facets of this unusual space mission.

Table of Contents
Prologue - Hipparcos Launch
1. Our Place in the Cosmos
2. Why Star Positions?
3. Early History
4. Developments 1850-1980
5. The Push to Space
6. From Concept to Launch
7. Disaster Unfolds
8. Mission Recovery
9. Science in the Making
10. The Finishing Touches
11. Our Galaxy
12. Inside the Stars
13. Our Solar System and Habitability
14. The Future
Epilogue
Notes
Stereo Views
Acknowledgments
Index

Published: 01 January 2010
NASA's Chandra X-ray Observatory and the ESA's X-ray Multi-Mirror Mission (XMM-Newton) made their first observations ten years ago. The complementary capabilities of these observatories allow us to make high-resolution images and precisely measure the energy of cosmic X-rays. Less than 50 years after the first detection of an extrasolar X-ray source, these observatories have achieved an increase in sensitivity comparable to going from naked-eye observations to the most powerful optical telescopes over the past 400 years. We highlight some of the many discoveries made by Chandra and XMM-Newton that have transformed twenty-first century astronomy.
Published: 24 December 2009
Stars in globular clusters are generally believed to have all formed at the same time, early in the Galaxy's history. 'Blue stragglers' are stars massive enough that they should have evolved into white dwarfs long ago. Two possible mechanisms have been proposed for their formation: mass transfer between binary companions and stellar mergers resulting from direct collisions between two stars. Recently the binary explanation was claimed to be dominant. Here we report that there are two distinct parallel sequences of blue stragglers in M 30. This globular cluster is thought to have undergone 'core collapse', during which both the collision rate and the mass transfer activity in binary systems would have been enhanced. We suggest that the two observed sequences are a consequence of cluster core collapse, with the bluer population arising from direct stellar collisions and the redder one arising from the evolution of close binaries that are probably still experiencing an active phase of mass transfer.
Published: 24 December 2009
The Herzberg II system of O2 has been a known feature of Venus' nightglow since the Venera 9 and 10 orbiters detected its c(0)-X(v") progression more than 3 decades ago. We search for its emission at 400 nm-700 nm in spectra obtained with the VIRTIS instrument on Venus Express. Despite the weakness of the signal, integration over a few hours of limb observations of the planet's upper atmosphere reveals the unambiguous pattern of the progression. The selected data sample mainly the northern latitudes within a few hours of local midnight. The emission is ubiquitous on the nightside of Venus and can be discerned at tangent altitudes from 80 km to 110 km. The average emission vertical profiles of the c(0)-X(v") progression and the O2 a(0)-X(0) band, the latter from simultaneous near-infrared spectra, are quite similar, with their respective peaks occurring within ±1 km of each other. We conclude that the net yield for production of the c(0) state is low, ~1%-2% of the oxygen recombination rate, and that O(3P) and CO2 are the two likely quenchers of the Herzberg II nightglow, although CO cannot be ruled out. We also derive a value of 2.45 × 10-16 cm3 s-1 for the rate constant at which CO2 collisionally quenches the c(0) state. Our VIRTIS spectra show hints of O2 A'(0)-a(v3) emission but no traces of the O (1S-1D) green line at 557.7 nm.
Published: 23 December 2009
This Newsletter is based on inputs from members of ISOC, and edited by Guillaume Bélanger with the help of Suzanne Philipsen.

Contents:

  • Foreword
  • AO-7 Results
  • AO-8 Timetable
  • Science Operations
  • 7th INTEGRAL Workshop
  • Science Highlights
  • Changes at ISOC
  • Contacting ISOC

Published: 22 December 2009
The Kuiper belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper belt objects. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars should be detectable. Observations at both optical and X-ray wavelengths claim to have detected such occultations, but their implied abundances are inconsistent with each other and far exceed theoretical expectations. Here we report an analysis of archival data that reveals an occultation by a body with an approximately 500-metre radius at a distance of 45 astronomical units. The probability of this event arising from random statistical fluctuations within our data set is about two per cent. Our survey yields a surface density of Kuiper belt objects with radii exceeding 250 metres of 2.1+4.8-1.7 x 107 deg-2, ruling out inferred surface densities from previous claimed detections by more than 5 sigma. The detection of only one event reveals a deficit of sub-kilometre-sized Kuiper belt objects compared to a population extrapolated from objects with radii exceeding 50 kilometres. This implies that sub-kilometre-sized objects are undergoing collisional erosion, just like debris disks observed around other stars.
Published: 17 December 2009
Whistler mode chorus has been shown to play a role in the process of local acceleration of electrons in the outer Van Allen radiation belt. Most of the quasi-linear and nonlinear theoretical studies assume that the waves propagate parallel to the terrestrial magnetic field. We show a case where this assumption is invalid. We use data from the Cluster spacecraft to characterize propagation and spectral properties of chorus. The recorded high-resolution waveforms show that chorus in the source region can be formed by a succession of discrete wave packets with decreasing frequency that sometimes change into shapeless hiss. These changes occur at the same time in the entire source region. Multicomponent measurements show that waves in both these regimes can be found at large angles to the terrestrial magnetic field. The hiss intervals contain waves propagating less than one tenth of a degree from the resonance cone. In the regime of discrete wave packets the peak of the wave energy density is found at a few degrees from the resonance cone in a broad interval of azimuth angles. The wave intensity increases with the distance from the magnetic field minimum along a given field line, indicating a gradual amplification of chorus in the source region.
Published: 15 December 2009
Reference: SRE-PA/2009/051

This technical review report for the Euclid candidate mission presents the outcome of ESA's internal review of this M-class candidate mission in the Cosmic Vision 2015-2025 plan. The review was concluded at the end of the mission assessment phase and carried out in frame of the down-selection to 3 or 4 M-class missions, which will proceed to the definition phase. The main goal of this internal review was to identify the mission's critical issues and associated risks at technical, programmatic and financial level.

Published: 14 December 2009
30-Sep-2020 09:28 UT

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