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Space Infrared Telescope for Cosmology and Astrophysics (SPICA), the cryogenic infrared space telescope recently pre-selected for a ‘Phase A’ concept study as one of the three remaining candidates for European Space Agency (ESA's) fifth medium class (M5) mission, is foreseen to include a far-infrared polarimetric imager [SPICA-POL, now called B-fields with BOlometers and Polarizers (B-BOP)], which would offer a unique opportunity to resolve major issues in our understanding of the nearby, cold magnetised Universe. This paper presents an overview of the main science drivers for B-BOP, including high dynamic range polarimetric imaging of the cold interstellar medium (ISM) in both our Milky Way and nearby galaxies. Thanks to a cooled telescope, B-BOP will deliver wide-field 100–350
m images of linearly polarised dust emission in Stokes Q and U with a resolution, signal-to-noise ratio, and both intensity and spatial dynamic ranges comparable to those achieved by Herschel images of the cold ISM in total intensity (Stokes I). The B-BOP 200
m images will also have a factor
30 higher resolution than Planck polarisation data. This will make B-BOP a unique tool for characterising the statistical properties of the magnetised ISM and probing the role of magnetic fields in the formation and evolution of the interstellar web of dusty molecular filaments giving birth to most stars in our Galaxy. B-BOP will also be a powerful instrument for studying the magnetism of nearby galaxies and testing Galactic dynamo models, constraining the physics of dust grain alignment, informing the problem of the interaction of cosmic rays with molecular clouds, tracing magnetic fields in the inner layers of protoplanetary disks, and monitoring accretion bursts in embedded protostars.
Euclid is a Europe-led cosmology space mission dedicated to a visible and near infrared survey of the entire extra-galactic sky. Its purpose is to deepen our knowledge of the dark content of our Universe. After an overview of the Euclid mission and science, this contribution describes how the community is getting organized to face the data analysis challenges, both in software development and in operational data processing matters. It ends with a more specific account of some of the main contributions of the Swiss Science Data Center (SDC-CH).
This review deals with the various aspects of interstellar dust in the Magellanic Clouds (MCs). Dust properties can be traced from interstellar absorption, with an emphasis on UV properties, and from infrared emission. Thanks to IRAS, most of the recent developments in this field have been found in the infrared. The low resolution of IRAS was, in fact, well suited for MC mapping and these observations offer a unique opportunity to study the dust properties in various conditions of the Interstellar Radiation Field (ISRF) and of chemical abundances. The proximity of the MCs allows a direct study of the link between the stellar population and the dust properties via the ISRF. On the other hand, the comparison of IRAS data in the MCs and in the Galaxy allows us to study the dust composition for metallicity varying by a factor of 10. From these data and the previous results on UV absorption, it emerges that if the gas-to-dust ratio changes with metallicity, there is also a variation in the relative abundances of the dust components. In this review, we will also discuss how our knowledge of the MCs will be used to prepare for observations of more distant galaxies, with the next generation of space observatories such as the Hubble Space Telescope and the Infrared Space Observatory.
We performed systematic infrared observations of the intermediate-age Magellanic Clouds clusters NGC 419, NGC 1783 and NGC 1978. Mid-infrared stars discovered in NGC 419 and NGC 1978 are very red and must be undergoing intense mass loss (comparable to superwinds). They are probably carbon stars but do not seem to show any FIR excesses. Three optically visible carbon stars as well as (at least) 2 near-infrared carbon stars observed with ISOPHOT show 60 μm excesses which may indicate mass loss in the past. It seems that the MIR stars are fainter than the AGB tip luminosity and that their Mbols are close to those of the transition luminosity from M type to C stars. Therefore, these MIR stars may not be in the final stage of the AGB phase. This may suggest that AGB stars lose mass heavily at some other time, possibly during the transition from M type to C stars.
NGC 595 is a giant Hɪɪ region located in the western part of the spiral galaxy M 33. It is the second in importance in this galaxy, after NGC 604. At 0.84 Mpc, HST is able to resolve its stellar content. Malumuth et al. (1996) obtained HST UV, U, B and V images of this region and derived an ionizing luminosity of 5 × 1050 phots-1 and an average reddening EB-V = 0.36±0.28 mag. The stars are mostly concentrated in the central part of the region, where little emission of gas is seen (the ionized gas lies more in a shell around the stars, figure 1a). Wilson & Scoville (1993) showed the molecular gas to be situated in the south-east part of the region, just outside of the bright knot of stars. Viallefond et al. (1986) found a reddening gradient in the north-east/south-west direction by observing the Hi gas, which was confirmed by Malumuth et al. (1996) with stellar photometry.
We obtained ISO images for NGC 595 in the 5.0 to 8.5 μm range. The emission in this spectral range is dominated by the so-called PAH bands. Current interpretation of these has them originating from stochastically heated molecules. Two of these bands are located in the range observed, at 6.2 μm and 7.7 μm. Stochastic heating implies that the in-band flux is directly proportional to the number of photons absorbed by the molecules. For typical HII regions, Cohen et al. (1989) found 0.58 for the I6.2/I7.7 in-band ratio. However many processes, ionization, dehydrogenation, can modify this ratio. Furthermore, an underlying continuum is present though its exact origin is unknown.
Theoretical and observational work show that jets from AGN can trigger star formation. However, in the Milky Way the first -and so far- only clear case of relativistic jets inducing star formation has been found in the surroundings of the microquasar GRS 1915+105. Here we summarize the multiwavelength observations of two compact star formation IRAS sources axisymmetrically located and aligned with the position angle of the sub-arcsec relativistic jets from the stellar black hole binary GRS 1915+105 (Mirabel & Rodríguez 1994). The observations of these two star forming regions at centimeter (Mirabel & Rodríguez 1998), millimeter and infrared (Chaty et al. 2001) wavelengths had suggested -despite the large uncertainties in the distances a decade ago- that the jets from GRS 1915+105 are triggering along the radio jet axis the formation of massive stars in a radio lobe of bow shock structure. Recently, Reid et al. (2014) found that the jet source and the IRAS sources are at the same distance, enhancing the evidence for the physical association between the jets from GRS 1915+105 and star formation in the IRAS sources. We conclude that as jets from AGN, jets from microquasars can trigger the formation of massive stars, but at distances of a few tens of parsecs. Although star formation induced by microquasar jets may not be statistically significant in the Milky Way, jets from stellar black holes may have been important to trigger star formation during the re-ionization epoch of the universe (Mirabel et al. 2011). Because of the relative proximity of GRS 1915+105 and the associated star forming regions, they may serve as a nearby laboratory to gain insight into the physics of jet-trigger star formation elsewhere in the universe.
Euclid is the next ESA mission devoted to cosmology. It aims at observing most of the extragalactic sky, studying both gravitational lensing and clustering over ~15,000 square degrees. The mission is expected to be launched in year 2020 and to last six years. The sheer amount of data of different kinds, the variety of (un)known systematic effects and the complexity of measures require efforts both in sophisticated simulations and techniques of data analysis. We review the mission main characteristics, some aspects of the the survey and highlight some of the areas of interest to this meeting.
Next year the second generation instrument SPHERE will begin science operations at the Very Large Telecope (ESO). This instrument will be dedicated to the search for exoplanets through the direct imaging techniques, with the new generation extreme adaptive optics. In this poster, we present the performances of one of the focal instruments, the Infra-Red Dual-beam Imaging and Spectroscopy (IRDIS). All the results have been obtained with tests in laboratory, simulating the observing conditions in Paranal. We tested several configurations using the sub-system Integral Field Spectrograph (IFS) in parallel and simulating long coronographic exposures on a star, calibrating instrumental ghosts, checking the performance of the adaptive optics system and reducing data with the consortium pipeline. The contrast one can reach with IRDIS is of the order of 10−6 at 0.5 arcsec separation from the central star.
The role of heterotrophic biofilm of water–sediment interface in detoxification processes was tested in abiotic and biotic conditions under laboratory conditions. Three toxicants, a herbicide (Diuron), a fungicide (Dimethomorph) and an insecticide (Chlorpyrifos-ethyl) have been tested in water percolating into columns reproducing hyporheic sediment. The detoxification processes were tested by comparing the water quality after 18 days of percolation with and without heterotrophic biofilm. Tested concentrations were 30 μg.L−1 of Diuron diluted in 0.1% dimethyl sulfoxide (DMSO), 2 μg.L−1 of Dimethomorph and 0.1 μg.L−1 of Chlorpyrifos-ethyl. To characterise the detoxification efficiency of the system, we performed genotoxicity bioassays in amphibian larvae and rotifers and measured the respiration and denitrification of sediments. Although the presence of biofilm increased the production of N-(3,4 dichlorophenyl)-N-(methyl)-urea, a metabolite of diuron, the toxicity did not decrease irrespective of the bioassay. In the presence of biofilm, Dimethomorph concentrations decreased compared with abiotic conditions, from 2 μg.L−1 to 0.4 μg.L−1 after 18 days of percolation. For both Dimethomorph and Chlorpyrifos-ethyl additions, assessment of detoxification level by the biofilm depended on the test used: detoxification effect was found with amphibian larvae bioassay and no detoxification was observed with the rotifer test. Heterotrophic biofilm exerts a major influence in the biochemical transformation of contaminants such as pesticides, suggesting that the interface between running water and sediment plays a role in self-purification of stream reaches.
Fifty years after the hyporheic zone was first defined (Orghidan, 1959), there are still gaps in the knowledge regarding the role of biodiversity in hyporheic processes. First, some methodological questions remained unanswered regarding the interactions between biodiversity and physical processes, both for the study of habitat characteristics and interactions at different scales. Furthermore, many questions remain to be addressed to help inform our understanding of invertebrate community dynamics, especially regarding the trophic niches of organisms, the functional groups present within sediment, and their temporal changes. Understanding microbial community dynamics would require investigations about their relationship with the physical characteristics of the sediment, their diversity, their relationship with metabolic pathways, their interactions with invertebrates, and their response to environmental stress. Another fundamental research question is that of the importance of the hyporheic zone in the global metabolism of the river, which must be explored in relation to organic matter recycling, the effects of disturbances, and the degradation of contaminants. Finally, the application of this knowledge requires the development of methods for the estimation of hydrological exchanges, especially for the management of sediment clogging, the optimization of self-purification, and the integration of climate change in environmental policies. The development of descriptors of hyporheic zone health and of new metrology is also crucial to include specific targets in water policies for the long-term management of the system and a clear evaluation of restoration strategies.
The Herschel Dwarf Galaxy Survey investigates the interplay of star formation activity and the the metal-poor gas and dust of local universe dwarf galaxies using FIR and submillimetre imaging spectroscopic and photometric observations in the 50 to 550 μm window of the Herschel Space Observatory. The dust spectral-energy distributions are well constrained with the new Herschel and MIR Spitzer data. A submillimetre excess is often found in low metallicity galaxies, which, if tracing very cold dust, would highlight large dust masses not easily reconciled in some cases, given the low metallicities and expected gas-to-dust mass ratios. The galaxies are also mapped in the FIR fine-structure lines (63 and 145 μm OI, 158 μm CII, 122 and 205 μm NII, 88 μm OIII) probing the low density ionised gas, the HII regions and photodissociation regions. While still early in the mission we can already see, along with earlier studies, that line ratios in the metal-poor ISM differ remarkably from those in the metal-rich starburst environments. In dwarf galaxies, L[CII]/L(CO) (≥104) is at least an order of magnitude greater than in the most metal-rich starburst galaxies. The 88 μm [OIII] line usually dominates the FIR line emission over galaxy-wide scales, not the 158 μm [CII] line which is the dominant FIR cooling line in metal-rich galaxies. All of the FIR lines together can contribute 1% to 2% of the LTIR. The Herschel Dwarf Galaxy survey will provide statistical information on the nature of the dust and gas in low metallicity galaxies and place constraints on chemical evolution models of galaxies.
We present a new method based on mid-IR (5 — 16 µm) emission
for classifying the origin of the mid-IR activity in galaxies. Our
method was devefoped using a set of 33 ISOCAM spectra of extragalactic
sources which exhibit diverse mid-IR spectral features. Detailed
analysis of our sample enables us to identify the general properties of
mid-IR emission from active galactic nuclei (AGNs), starbursts, and
quiescent star forming regions. The benefits of this mid-IR classification
for identifying obscured or faint AGNs and for estimating the star
formation intensity in star-forming regions are investigated.
The Herschel Dwarf Galaxy Survey investigates the metal enrichment of the dust and gas in galaxies through observations of the local universe dwarf galaxies via the new far-infrared (FIR) and submillimetre imaging spectroscopic and photometric observations from the recently launched Herschel Space Observatory. The dust spectral energy distributions can now be constrained out to submm wavelengths and often show a submm excess in the low metallicity galaxies, which, if tracing very cold dust, could highlight large dust masses, sometimes not easily reconciled with their low-metallicity and observed gas mass. Additionally, Herschel observations of the FIR fine-structure lines probe the low density ionised gas, the HII regions and photodissociation regions. L[CII]/LCO is remarkably high in dwarf galaxies – typically an order of magnitude larger than more metal-rich starburst galaxies, pointing to a potentially significant reservoir of H2 not traced by CO but shielded in the C+-emitting envelopes. Thus a more accurate estimate of the molecular gas mass in low metallicity galaxies will be via the (CO + [CII]) to H2 conversion factor. The 88 μm [OIII] line is the brightest of all FIR lines in low-metallicity galaxies, sometimes 1.5 to 2 time brighter than the 158 μm [CII] line which is usually the dominate FIR coolant in normal spiral and starburst galaxies. The 88 μm [OIII] line may become the workhorse diagnostic for the high-redshift low-metallicity galaxies which will be targets for future submm observatories, such as ALMA. Further observations from The Herschel Dwarf Galaxy survey will provide a more complete picture of the nature of the dust and gas in low metallicity galaxies and thus a more comprehensive view of the chemical evolution of galaxies.
We characterize PAH populations in 22 metal-poor blue compact dwarf galaxies (BCDs), 16
of which have an oxygen abundance 12+log(O/H) ≲ 8. This is the largest sample ever studied
at such low metallicities. The relative PAH intensities of the 6.2, 7.7, 8.6 and
11.3 μm features in these BCDs suggest a deficit of small PAH carriers,
or alternatively, an excess of large ones at these low abundances.
This is a copy of the slides presented at the meeting but not formally
written up for the volume.
Grain size reduction induced by severe plastic deformation (SPD) and the
resulting mechanical properties have been widely investigated for pure
metals but less is known and reported about multi-phase materials. To
study the grain size reduction mechanisms in multiphase structure
subjected to SPD, two copper based composites (Cu-10%Fe and Cu-43%Cr)
were severely deformed by torsion under high pressure. The grain size
achieved with these composite materials is much smaller than in pure
metals. It is for example in a range of 10 to 20 nm for the Cu-43%Cr
composite, e.g. one order of magnitude lower than in pure Cu processed by
SPD. Three dimensional atom probe data show also the formation of non
equilibrium supersaturated solid solutions. The mechanisms of the
deformation induced intermixing are discussed together with its influence
on the mechanical properties.
We have investigated the mid-infrared spontaneous and stimulated emission between confined subbands in the conduction band of GaAs/AlGaAs quantum wells. The carriers which give rise to the intersubband emission are excited in the upper subbands using an intersubband optical pumping in coupled asymmetric quantum wells. The quantum wells are designed using phonon engineering in order to obtain population inversion between the second and first excited subband. This is obtained by adjusting the subband energy spacing between E2 and E1 close to the optical phonon energy which in turn allows an efficient relaxation. We have first observed intersubband spontaneous emission between E3 and E2 at 14 μm using an intersubband pumping with a CO2 laser in resonance with the E1-E3 transition. In a second set of experiments, the quantum wells are embedded in an infrared waveguide. We have measured the stimulated intersubband gain using a picosecond two-color free electron laser. The first color bleaches the E1-E3 transition and provides the population inversion. The intersubband stimulated gain is measured versus the waveguide length and photon energy. Stimulated gains ≈ 80 cm−1 are reported thus demonstrating that laser emission under optical pumping appears feasible in optimized structures. Finally, we show that intersubband emission can also be observed in quantum wells using an interband optical pumping.
We have investigated the emission properties of InAs/GaAs self-assembled quantum dots in the mid-infrared. The emission relies on the intraband transitions in the valence band of the quantum dots. We first show that third-harmonic generation can be observed. The frequency tripling efficiency is enhanced by the resonances between the pump excitation and the quantum dot intraband transitions. A giant third-order nonlinear susceptibility is measured for one dot plane. The narrow spectral dependence of the nonlinear susceptibility is well explained by simulations which account for the three-dimensional confinement potential. We secondly show that the mid-infrared spontaneous emission between hole confined states can be observed under an interband optical pumping. The spontaneous emission involves transitions between either the ground and excited states or between excited states. These measurements demonstrate the potentiality of self-assembled quantum dots for mid-infrared emission.
LiFePO4-based powders prepared through various synthesis conditions are presented. Depending on whether the precursors contain carbon or not, LiFePO4-based composites obtained contain significant amounts of carbon as well. We did not succeed in doping LiFePO4 with Nb and produced, instead, crystalline β-NbOPO4 and/or an amorphous (Nb, Fe, C, O, P) matrix around LiFePO4 particles. The total electrical conductivity is of ∼10−9 S.cm−1 at 25°C with an activation energy of ca. 0.65 eV for pure LiFePO4 and LiFePO4/β-NbOPO4 composite. C-containing LiFePO4 samples, including those that had been tentatively doped with Nb, are much more conductive (up to 1.6.10−1 S.cm−1) with an activation energy ΔE ∼ 0.08 eV.