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 $\mu$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 $\mu$m images will also have a factor $\sim $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.

We present a statistical analysis of the relative orientation between the plane-of-sky magnetic field and the filaments associated with the Galactic Cold Clumps. We separated polarization parameters components of the filaments and their background using thin optical medium assumption, the filaments were detected using the Rolling Hough Transform algorithm and we separated the clump and the filament contributions in our maps. We found that in high column density environments the magnetic fields inside the filaments and in the background are less likely to be aligned with each other. This suggests a decoupling between the inner and background magnetic fields at some stage of filaments’ evolution. A preferential alignment between the filaments and their inferred magnetic fields is observed in the whole selection if the clumps’ contribution is subtracted. Interestingly, a bimodal distribution of relative orientation is observed between the filamentary structures of the clumps and the filaments’ magnetic field. Similar results are seen in a subsample of nearby filaments. The relative orientation clearly shows a transition from parallel to no preferential and perpendicular alignment depending on the volume densities of both clumps and filaments. Our results confirm a strong interplay between the magnetic field and filamentary structures during their formation and evolutionary process.


Future cosmology space missions will concentrate on measuring the polarization of the Cosmic Microwave Background (CMB), which potentially carries invaluable information about the earliest phases of the evolution of our universe. Such ambitious projects will ultimately be limited by the sensitivity of the instrument and by the accuracy at which polarized foreground emission from our own Galaxy can be subtracted out. We present the PILOT balloon project which will aim at characterizing one of these foreground sources, the polarization of the dust continuum emission in the diffuse interstellar medium. The PILOT experiment will also constitute a test-bed for using multiplexed bolometer arrays for polarization measurements.


The "Herschel Space Observatory" (formerly known as the "Far InfraRed and Submillimetre Telescope" - FIRST) is the fourth cornerstone mission in the European Space Agency (ESA) science programme. It will perform imaging photometry and spectroscopy in the far infrared and submillimetre part of the spectrum, covering approximately the 57-670 μm range. The key science objectives emphasize current questions connected to the formation of galaxies and stars, however, having unique capabilities in several ways, Herschel will be a facility available to the entire astronomical community. Because Herschel to some extent will be its own pathfinder, the issue of instrument calibration and data processing timescales has special importance. Herschel will carry a 3.5 metre diameter passively cooled telescope. The science payload complement - two cameras/medium resolution spectrometers (PACS and SPIRE) and a very high resolution heterodyne spectrometer (HIFI) - will be housed in a superfluid helium cryostat. Herschel will be placed in a transfer trajectory towards its operational orbit around the Earth-Sun L2 point by an Ariane 5 (shared with the ESA cosmic background mapping mission Planck) in early 2007. Once operational Herschel will offer a minimum of 3 years of routine observations; roughly 2/3 of the available observing time is open to the general astronomical community through a competitive proposal procedure.

We have studied the effects of the laboratory-measured, temperature-dependent dust emissivity indices on the FIR/sub-mm emission properties of amorphous silicate and amorphous carbonaceous dust. When the experimentally-determined temperature dependence of the dust emissivity index is taken into account we find temperatures that can differ by as much as 1.5 K and emissivity indices that can differ by ~15%, with respect to the values obtained using published refractive index data as is to calculate these quantities. In addition, we find that the observed diffuse ISM dust temperature of ~17.5 K and emissivity index of 2 can seemingly be produced with a mixture of amorphous carbon and silicate grains only if temperature-dependent dust emissivity indices are adopted. We find that dust masses determined using the temperature-dependent dust emissivity indices are not significantly different from those derived using standard dust properties.

PRONAOS was born as a project in the mid eighties. The Far Infrared Space Telescope (now Herschel), a Cornerstone of the horizon 2000 plan of ESA, was the clear future of submillimetre astronomy, after several balloon experiments and the tremendous success of the IRAS satellite in the neighbour field of infrared astronomy. Guy Serra and other French scientists proposed to build a learning process in this new field around the PRONAOS project, a technical and scientific precursor to future submm space missions. This project was fully supported by CNES and by CNRS (IAS and CESR at the first place). PRONAOS (Projet National d'AstronOmie Submillimétrique) was based on the use of a two meter telescope aboard a stratospheric balloon-borne gondola. The size and the complexity of the instrument made PRONAOS a very unusual balloon-borne payload. Along the 15 years of the project, and three flights, a lot of learning processes took place. The main goals of this enterprise were reached. New and sometimes surprising scientific results came out from the observations. Teams learned critical scientific and technical lessons from this pioneering experiment. Some contributions to Herschel benefit directly from this experience, and the project Planck, a satellite of ESA, was born inside the PRONAOS team. This project was also a major professional and human experience for young (and also mature) scientists.

We have developed a dust emission model in order to reproduce the evolution of the far-infrared (FIR) to sub-millimetre (sub-mm) dust emission properties which is observed in the transition between the diffuse and the dense interstellar medium (ISM). We propose that the coagulation of grains into fluffy aggregates could be the process responsible for the observed dust evolution from the diffuse to the dense ISM in the Galaxy. In dense clouds, dust coagulation can explain the increase in grain size, the decrease in the grain temperature in excess of that predicted by extinction, the sub-mm emissivity excess and the decrease in the small grain abundance.

Compact Antenna Test-Ranges (CATR) represent a high standard of state-of-the-art test facilities with a fast and real time measurement capability up to the sub-millimeter range. Future scientific observation instruments of ESA such as the Planck and Herschel telescopes are working within this frequency ranges and require a high measurement accuracy for large antenna apertures. This present paper shows the first modelling of a large CATR at millimetre frequency. The software used in this paper is GRASP8 (from TICRA), and specially the recent Multi-Reflector Geometrical Theory of Diffraction upgrade (MR-GTD thereafter).

The balloon borne experiment PRONAOS has measured the sub-millimetre emission from the diffuse interstellar medium to a quiescent filament in the Taurus molecular cloud. We model the output emission of this filament using a radiative transfer code and an independent tracer of the total column density (near infrared extinction). We show that inside the filament the transiently heated particles responsible of the 60 μm emission are removed and the dust sub-millimetre emissivity is increased by a significant factor, 3.4+0.3-0.7 (for typically nH > 3 ± 1 × 103 cm-3, AV > 2.1 ± 0.5). This induces a deficit in the IRAS I60 μm/I100 μm flux ratio in comparison with the diffuse interstellar medium and a decrease of the grain equilibrium temperature in excess to that predicted by extinction.

This paper reports the first results obtained on the photodissociation of the isolated PAH cations 12C24H+12, 13C12C23H+12 and 12C24H+10, using the astrochemistry experimental set-up PIRENEA. The dissociation patterns of these ions involve the loss of pairs of hydrogen atoms. A first interpretation indicates that the -H2 dissociation path is favoured compared to the -H path in our experimental conditions. These results might have important implications on the formation of H2 in the interstellar medium.

Infrared Astronomy Group of the Tata Institute of Fundamental Research (TIFR) has an ongoing programme of high resolution mapping of star forming regions in two trans-IRAS far infrared bands using a 1 metre balloon-borne telescope. The telescope has been flown many times from TIFR Balloon Facility, Hyderabad, India. The photometer consists of two bolometer arrays cooled to 0.3 K by a closed cycle liquid 3He refrigerator. The effective wavelengths of the two bands are ~140 and 200 μm and the angular resolution of the MEM deconvolved maps is ~1'.2. These bands are suitable for the study of cold sources (temperature ≤30 K). Using this system many Galactic star forming regions have been mapped. Using simultaneous maps in the two bands, maps of dust temperature and optical depth have also been obtained. Our maps are combined with other available data and radiation transfer calculations have been made. In this paper we will describe the telescope and give a sample of the results obtained for some of the star forming regions in the Galaxy.

We are modeling the spectra of dwarf galaxies from infrared to submillimeter wavelengths to understand the nature of the various dust components in low-metallicity environments, which may be comparable to the ISM of galaxies in their early evolutionary state. The overall nature of the dust in these environments appears to differ from those of higher metallicity starbursting systems. Here, we present a study of one of our sample of dwarf galaxies, NGC 1569, which is a nearby, well-studied starbursting dwarf. Using ISOCAM, IRAS, ISOPHOT and SCUBA data with the Désert et al. (1990) [1] model, we find consistency with little contribution from PAHs and Very Small Grains and a relative abundance of bigger colder grains, which dominate the FIR and submillimeter wavelengths. We are compelled to use 4 dust components, adding a very cold dust component, to reproduce the submillimetre excess of our observations.

We review the submillimetric PRONAOS observations in the direction of the IC 1318a nebular located at the edge of an ionized region in the Cygnus X complex. The extended emission measured in the PRONAOS four broad photometric bands extending from 200 up to 1100 μm enables a full characterization of the interstellar dust big grains component radiating at thermal equilibrium, leading to a temperature and column density mapping.

Strip scanning measurements with crossing position angles have been carried out at 120 μm and 180 μm with the ISOPHOT instrument aboard ISO to observe extended FIR emission from six Abell clusters. The raw I120 μm/I180 μm surface brightness ratio including zodiacal light shows a bump towards Abell 1656 (Coma), dips towards Abell 262 and Abell 2670, and is without an unambiguous feature towards Abell 400, Abell 496, and Abell 4038. The subtraction of the zodiacal light leaves the bump towards Abell 1656 still present, while the dips towards Abell 262 and Abell 2670 are no longer discernible. This behavior can be reconciled in Abell 1656 with a localized excess of emitting material outside the Galaxy with properties different from the galactic foreground cirrus, and in Abell 262 and Abell 2670 with galactic cirrus structures localized on the line-of-sight to these clusters. At 120 μm the excess towards Abell 1656 (Coma) is ≈ 0.2 MJy/sr, with an integrated excess flux within the central region of 10'-15' diameter of ≈ 2.8 Jy. It is interpreted as being due to thermal emission from intracluster dust distributed in the hot X-ray emitting intracluster medium. Only a rough estimate of the associated dust mass of MD ≈ 107 M⊙ can be derived, since the dust temperature is poorly constrained. The visual extinction associated with this dust mass is negligible (AV << 0.1 mag) and much smaller than claimed from optical observations. No evidence for intracluster dust is found in the other five clusters observed. The rather low inferred dust mass in Abell 1656 together with the absence of a signature for intracluster dust in the other clusters observed indicates that intracluster dust is likely not responsible for the excess X-ray absorption seen in cooling flow clusters. These observations thereby represent a further unsuccessful attempt in detecting the presumed final stage of the cooling flow material, in accord with quite a number of previous studies. Finally, the observed dimming of the high - redshift supernovae is unlikely be attributable to extinction caused by dust in the intracluster or even a presumed intercluster medium.

The balloon-borne submillimeter instrument PRONAOS has observed one square degree areas towards the Orion and M 17 molecular clouds. The 2'-3.5' resolution maps obtained in four wide wavelength bands between 200 μm and 600 μm, exhibit the dust distribution in these regions. We analyze the temperature and spectral index of the dust, and we show the anticorrelation between these two parameters. We derive estimations of the ISM column densities and masses in these regions.

The Stratospheric Observatory For Infrared Astronomy (SOFIA) is a 2.5 m telescope which will fly in a Boeing 747SP, commencing operation in late summer 2004. SOFIA is a joint American/German project and for most of this decade it will be the largest far-infrared telescope. SOFIA will have a suite of instruments available to the astronomical community, including the High-resolution Airborne Wide-band Camera (HAWC) - its facility far-infrared camera.

The maximum luminosity of protostars forming in molecular clouds is investigated as a function of the parent cloud mass on the basis of a rich cloud sample searched for in the literature. In total, we gathered 499 molecular clouds among the published data, out of which 243 clouds are found to be associated with candidates for protostars selected from the IRAS point source catalog. A diagram of the maximum stellar luminosity in each cloud and the parent cloud mass shows that the young stars in the clouds associated with regions are apparently more luminous than those in clouds away from HII regions over the entire cloud mass range investigated (1 < MCL/M⊙ < 106). In addition, we found that there are well-defined upper and lower limits in the maximum stellar luminosity distribution with the lower limit having a steeper dependence on the cloud mass (LMAX ∝ MCL1.5) than the upper one (LMAX ∝ MCL0.8). All these features could be naturally accounted for if we assume that the luminosity function of protostars is controlled by the cloud mass and the external pressure imposed on the cloud surface. We introduce a simple model for the stellar luminosity function as a function of these quantities.

We present initial results of a deep mid-infrared survey conducted in the high galactic latitude field SSA13 with ISO. We have surveyed through the broad band filter LW2 (5-8.5 μm) of the mid-infrared camera ISOCAM to probe the near-infrared light at high redshift. The 80% completeness limit for point sources in the central 6 arcmin2 reaches 10 μJy at 6.7 μm. 65 sources are detected down to 6 μJy in 16 arcmin2. The integral galaxy number counts are 1.4 × 104 deg-2 at 10 μJy with the slope of -1.5. The integrated 6.7 μm light down to 6 μJy is estimated as 0.43 nWm-2sr-1. Our counts are consistent with the results in the HDF and the model prediction based on the K band local luminosity function. It suggests that the majority of the detected sources are E/S0 galaxies at z>1.

Faint submillimeter sources detected with JCMT/SCUBA have faced an identification problem due to their broad beam profiles. Here we propose a new method to identify these sources at the mid-infrared utilizing a finer point spread function. ISOCAM has provided us a very deep 6.7 μm image of the Hawaii Deep Field SSA13. For all three 850 μm sources in this field, we have found their 6.7 μm counterparts. All of them have been identified with interacting galaxy pairs at the optical. Two of the pairs are very faint and red (I>24, I - K > 4), one of the two has the hard X-ray detection with Chandra. Assuming an Arp 220 SED, we have found a typical redshift of z ~ 2. This requires that the sources should be a few times more luminous than Arp 220. It appears that extremely high star formation rates are occurring in galaxies at high redshift with massive stellar contents already in place.

We provide insight into the origin of the far-IR to mm emission from the Galaxy by presenting a decomposition of the emission where we separate the contributions from dust in the atomic gas and dust associated with quiescent molecular gas, as a function of Galacto-centric distance. We find that the sub-mm dust emissivity per hydrogen change by a factor 3 between the diffuse ISM and molecular clouds, first observed on localized clouds in the Solar Neighborhood, applies on large scale to the Molecular Ring. The decomposition leaves an emission excess in the sub-mm with a very cold effective temperature, concentrated in the plane but with a brightness independent of Galactic longitude. This emission might be associated with interstellar matter in the outer Galaxy not traced by H I nor CO emission.