Interstellar Medium

Our laboratory research program is about the formation of molecules on dust grains analogues in conditions mimicking interstellar medium environments. Using surface science techniques, in the last ten years we have investigated the formation of molecular hydrogen and other molecules on different types of dust grain analogues. We analyzed the results to extract quantitative information on the processes of molecule formation on and ejection from dust grain analogues. The usefulness of these data lies in the fact that these results have been employed by theoreticians in models of the chemical evolution of ISM environments.

An anomalous radio continuum component at cm-wavelengths has been observed in various sources, including dark clouds. This continuum component represents a new property of the ISM. In this work we focus on one particular dark cloud, the bright reflection nebula M 78. The main goal of this work is to invetigate cm-wave continuum emission in a prominent molecular cloud, nearby and with complementary observational data. We acquired Cosmic Background Imager (CBI) visibility data of M 78 at 31 GHz with an angular resolution of $\sim 5.8\arcmin$ and CBI2 data at an angular resolution of $\sim 4.2\arcmin$. A morphological analysis was undertaken to search for possible correlations with templates that trace different emission mechanisms. Using data from WMAP and the Rhodes/HartRAO 2326 MHz survey we constructed the spectral energy distribution (SED) of M 78 in a $45\arcmin$ circular aperture. We used results from the literature to constrain the physical conditions and the stellar content. The 5 GHz -- 31 GHz spectral index in flux density ($\alpha = 1.89\pm 0.15$) is significantly different from optically thin free-free values. We also find closer morphological agreement with IR dust tracers than with free-free sources. Dust-correlated cm-wave emission that is not due to free-free is significant at small scales ($\sim 8\arcmin$). However, a free-free background dominates at cm-wavelengths on large scales ($\sim 1$ deg). We correct for this uniform background by differencing against a set of reference fields. The differenced SED of M 78 shows excess emission at 10-70 GHz over free-free and a modified blackbody, at $3.4\sigma$. The excess is matched by the spinning dust model from Draine and Lazarian (1998).

New models of thermally pulsing asymptotic giant branch (TP-AGB) stars of low mass and solar chemical composition are presented, namely, Z \ 0.02, and Y \ 0.28. The inÑuence of 1 ¹ M/M _ ¹ 3, various parameters (such as the initial core mass, the envelope mass, the mass-loss rate, the opacity, and the mixing length) on the properties of the models is discussed in detail. Our main Ðndings are the following :

Zodiacal Light: an Old Problem and New Hypotheses
A.V.Byalko
Landau Institute for Theoretical Physics, RAS (Moscow, Russia)
Zodiacal light is a white luminous cone that is easily observed in the west a few hours after the sunset or in the east until dawn. The spectrum of the zodiacal light gives an evidence of its origin from the reflected radiation of the Sun, although it is not known exactly where the scattering objects are located. Analysis of the dynamics of fragments of the Moon formation shows the possibility of capturing a part of the fragments by stable Lagrange points. In this paper, by solving the three-body problem, it is shown that these stability regions are much wider and the bodies captured at the Lagrange points drift along horseshoe-shaped trajectories. The estimated brightness of the sunlight reflected by them is compared with observations. Additionally, a number of related hypotheses have been expressed.
Keywords: zodiacal light, Lagrange points, three-body problem, cosmic dust

Институт теоретической физики имени Л.Д.Ландау РАН (Москва, Россия)
Зодиакальный свет-это белый светящийся конус, легко наблюдаемый на западе через несколько часов после захода солнца или на востоке до рассвета. По спектру зодиакального света ясно, что это отраженное излучение Солнца, хотя точно неизвестно, где именно расположены рассеивающие объекты. В процессе анализа динамики осколков образования Луны была указана возможность захвата части осколков устойчивы ми точками Лагранжа. В данной работе решениями задачи трех тел показано, что эти области устойчивости оказались существенно шире, а те ла, захваченные около точек Лагранжа, далее дрейфуют по подковообразным замкнутым траекториям. Рассчитанная яркость отражаемого ими солнечного света сравнивается с наблюдениями. Дополнительно высказан ряд сопряженных гипотез.
Ключевые слова: зодиакальный свет, точки Лагранжа, задача трех тел, статистика космической пыли.

According to the internal-external shocks model for γ-ray bursts (GRBs), the GRB is produced by internal shocks within a relativistic flow while the afterglow is produced by external shocks with the ISM. We explore the early afterglow emission. For short GRBs the peak of the afterglow will be delayed, typically, by few dozens of seconds after the burst. For long GRBs the early afterglow emission will overlap the GRB signal. We calculate the expected spectrum and the light curves of the early afterglow in the optical, X-ray and γ-ray bands. These characteristics provide a way to discriminate between late internal shocks emission (part of the GRB) and the early afterglow signal. If such a delayed emission, with the characteristics of the early afterglow, will be detected it can be used both to prove the internal shock scenario as producing the GRB, as well as to measure the initial Lorentz factor of the relativistic flow. The reverse shock, at its peak, contains energy which is comparable to that of the GRB itself, but has a much lower temperature than that of the forward shock so it radiates at considerably lower frequencies. The reverse shock dominates the early optical emission, and an optical flash brighter than 15th magnitude, is expected together with the forward shock peak at x-rays or γ-rays. If this optical flash is not observed, strong limitations can be put on the baryonic contents of the relativistic shell deriving the GRBs, leading to a magnetically dominated energy density.

A mission to interstellar space has been under discussion for over 25 years. Many fundamental scientific questions about the nature of the surrounding galactic medium and its interaction with the solar system can only be answered by in situ measurements that such a mission would provide. The technical difficulties and budgetary and programmatic realities have prevented implementation of previous studies based on the use of a near-Sun perihelion propulsive maneuver, solar sails, and large fission-reactor-powered nuclear electric propulsion systems. We present an alternative approach -the Innovative Interstellar Explorer -based on Radioisotope Electric Propulsion. A high-energy, current-technology launch of the small spacecraft is followed by long-term, lowthrust, continuous acceleration enabled by a kilowatt-class ion thruster powered by Pu-238 Stirling radioisotope generators. We describe the science, payload, and mission and spacecraft design. We also discuss the role such a mission plays in assessing heliospheric "space climate," knowledge of which is vital for human exploration to Mars and beyond.

We are presently on the verge of expanding our technology in the outer solar system environment. Voyager 1 has landed its first step outside the hemisphere. Data transfer at large distances of astronomical units and light years is a challenging matter of research and a key issue of the interstellar communication. If robotic instruments are sent aboard interstellar spaceflights, managing them from earth with a definite time lag is a puzzle of its own kind. However artificial intelligence can come out to as a great tool in the future for missions beyond and far from the solar system. For such interstellar medium missions, we need to develop appropriate technology to recover the data from Earth from very large astronomical distances. Assuming that such high velocity unmanned robotic spacecrafts are a nearby possibility, we look into this problem in detail and try to explore the related fields which can help in upgrading the present level of interplanetary space communication. Data transfer has to be efficient with a minimum amount of data loss in travelling long distance in the space particularly the interstellar medium. Properties of interstellar medium can be studied closely in such missions that will carry advanced space based sensors, detectors and scientific instruments for taking measurements during the mission. Such a data can be analyzed by onboard computers and also be sent to earth with minimum possible attenuation due to the effect of large distances in the interstellar medium. Advanced data encryption methods and holographic techniques can be studied in details to shortlist the advanced onboard data-sending instruments technology. This paper discusses these in detail and the inception of appropriate protocols for dealing with these issues

A review is presented of the scientific benefits of rapid (v 0.1 c) interstellar spaceflight. Significant benefits are identified in the fields of interstellar medium studies, stellar astrophysics, planetary science and astrobiology. In the latter three areas the benefits would be considerably enhanced if the interstellar vehicle is able to decelerate from its interstellar cruise velocity to rest relative to the target system. Although this will greatly complicate the mission architecture, and extend the overall travel time, the scientific benefits are such that this option should be considered seriously in future studies.

I review those properties of the interstellar medium within 15 light-years of the Sun which will be relevant for the planning of future rapid (v ≥ 0.1c) interstellar space missions to the nearest stars. As the detailed properties of the local interstellar medium (LISM) may only become apparent after interstellar probes have been able to make in situ measurements, the first such probes will have to be designed conservatively with respect to what can be learned about the LISM from the immediate environment of the Solar System. It follows that studies of interstellar vehicles should assume the lowest plausible density when considering braking devices which rely on transferring momentum from the vehicle to the surrounding medium, but the highest plausible densities when considering possible damage caused by impact of the vehicle with interstellar material. Some suggestions for working values of these parameters are provided. This paper is a submission of the Project Icarus Study Group.

Advances and applications of microwave spectroscopy are recommended, and the instrument structure and principle are also illuminated. Its applications in the analyses of molecular structure, conformation, weakly bound complexes, analytical chemistry, and interstellar media are reviewed. Future trends of microwave spectroscopy are discussed.

Planetary systems are angular momentum reservoirs generated during star formation. Solutions to three of the most important problems in contemporary astrophysics are needed to understand the entire process of planetary system formation: The physics of the ISM. Stars form from dense molecular clouds that contain ∼ 30% of the total interstellar medium (ISM) mass. The structure, properties and lifetimes of molecular clouds are determined by the overall dynamics and evolution of a very complex system – the ISM. Understanding the physics of the ISM is of prime importance not only for Galactic but also for extragalactic and cosmological studies. Most of the ISM volume (∼ 65%) is filled with diffuse gas at temperatures between 3000 and 300 000 K, representing about 50% of the ISM mass. The physics of accretion and outflow. Powerful outflows are known to regulate angular momentum transport during star formation, the so-called accretion–outflow engine. Elementary physical considerations show that, to be efficient, the acceleration region for the outflows must be located close to the star (within 1 AU) where the gravitational field is strong. According to recent numerical simulations, this is also the region where terrestrial planets could form after 1 Myr. One should keep in mind that today the only evidence for life in the Universe comes from a planet located in this inner disk region (at 1 AU) from its parent star. The temperature of the accretion–outflow engine is between 3000 and 10 7 K. After 1 Myr, during the classical T Tauri stage, extinction is small and the engine becomes naked and can be observed at ultraviolet wavelengths. The physics of planet formation. Observations of volatiles released by dust, planetesimals and comets provide an extremely powerful tool for determining the relative abundances of the vaporizing species and for studying the photochemical and physical processes acting in the inner parts of young planetary systems. This region is illuminated by the strong UV radiation field produced by the star and the accretion–outflow engine. Absorption spectroscopy provides the most sensitive tool for determining the properties of the circumstellar gas as well as the characteristics of the atmospheres of the inner planets transiting the stellar disk. UV radiation also pumps the electronic transitions of the most abundant molecules (H 2, CO, etc.) that are observed in the UV. Here we argue that access to the UV spectral range is essential for making progress in this field, since the resonance lines of the most abundant atoms and ions at temperatures between 3000 and 300 000 K, together with the electronic transitions of the most abundant molecules (H 2, CO, OH, CS, S 2, CO 2+, C 2, O 2, O3, etc.) are at UV wavelengths. A powerful UV-optical instrument would provide an efficient mean for measuring the abundance of ozone in the atmosphere of the thousands of transiting planets expected to be detected by the next space missions (GAIA, Corot, Kepler, etc.). Thus, a follow-up UV mission would be optimal for identifying Earth-like candidates.

Astrophysical fluids, including interstellar and interplanetary medium, are magnetized and turbulent. Their appearance, evolution, and overall properties are determined by the magnetic turbulence that stirs it. We argue that examining magnetic turbulence at a fundamental level is vital to understanding many processes. A point that frequently escapes the attention of researchers is that magnetic turbulence cannot be confidently understood only using "brute force" numerical approaches. In this review we illustrate this point on a number of examples, including intermittent heating of plasma by turbulence, interactions of turbulence with cosmic rays and effects of turbulence on the rate of magnetic reconnection. We show that the properties of magnetic turbulence may vary considerably in various environments, e.g. imbalanced turbulence in solar wind differs from balanced turbulence and both of these differ from turbulence in partially ionized gas. Appealing for the necessity of more observational data on magnetic fields, we discuss a possibility of studying interplanetary turbulence using alignment of Sodium atoms in the tail of comets.

"The ether-drift experiments of Dayton Miller (c.1906-1929) using a highly sensitive Michelson lightbeam interferometer, demonstrated systematic positive effects. Subsequent work by Michelson-Pease-Pearson (1929), Galaev (2001-2002) and others have experimentally confirmed Miller's result, which suggests: 1) the cosmological ether is substantive with a slight mass, and may be blocked or reflected by dense material surroundings, 2) Earth-entrainment occurs, and the best detections are made at high-altitude locations. 3) Miller's
computed axis of Earth's net motion of ether-drift is in close agreement with findings from diverse disciplines, including from biology and physics, regarding ether-like phenomena with similar sidereal-day and seasonalsidereal fluctuations. Neither an intangible static, or even a tangible entrainable but stagnant ether appear reconcilable with such results. A dynamic ether acting as cosmic "prime mover" is the alternative solution, but requires the ether to have both slight mass and specific motions in space. A solution is found in the bioenergetic
research of Wilhelm Reich (1934-1957) who demonstrated an energy continuum with distinct biological and meteorological
properties, existing in high vacuum, interactive with matter, reflected by metals, and with selfattracting  (ie., gravitational) spiral-form streaming motions. Giorgio Piccardi (c.1950-1970) and his followers also demonstrated a metal-reflectable solar-modulated energy affecting the physical chemistry of water, chemical reactions and radioactive decay rates, correlated to Earth's spiral-form motion through cosmic space. More recent research on the annual variation in "dark matter wind" also shows very similar velocity shifts associated
with Earth's spiral-form motion around the moving Sun, suggesting "dark matter" is a misunderstood substitute
for a dynamic and substantive cosmological ether."

We present a model for nonlinear decay of the weak wave in three-dimensional incompressible magnetohydrodynamic (MHD) turbulence. We show that the decay rate is different for parallel and perpendicular waves. We provide a general formula for arbitrarily directed waves and discuss particular limiting cases known in the literature. We test our predictions with direct numerical simulations of wave decay in three-dimensional MHD turbulence, and discuss the influence of turbulent damping on the development of linear instabilities in the interstellar medium and on other important astrophysical processes.

The multivariate technique of principal component analysis (PCA) is a powerful statistical tool with which to describe spectral line imaging observations of the molecular interstellar medium. In particular, as formulated by Heyer & Schloerb (1997), PCA can retrieve statistical information about the velocity fields within the interstellar gas. However, the nature of the transformation of the intrinsic velocity field onto an observable velocity axis is extremely complex if the velocity field is macroturbulent. In this work, PCA is used to show that interstellar velocity fields are characterized by stochastic fluctuations on all measurable scales (i.e., are macroturbulent) and to obtain a quantitative measure of the turbulent velocity dispersion as a function of scale. To relate the measurable statistical information to intrinsic velocity field statistics, an ensemble of artificial density and velocity fields are translated onto the observational domain, utilizing non-LTE radiative transfer calculations. The intrinsic statistical properties of these fields are well-defined and accurately known, which allows the retrieved information to be calibrated to the intrinsic information. Additional results dealing with the instrumental noise and telescope beam-smearing effects on the PCA method are derived and demonstrated. An application of the reformulated method is carried out on an ensemble of outer Galaxy molecular spectral line imaging observations to obtain the first calibrated measurements of interstellar cloud velocity fields.

We propose the concept of a "Galactic Habitable Zone" (GHZ). Analogous to the Circumstellar Habitable Zone (CHZ), the GHZ is that region in the Milky Way where an Earth-like planet can retain liquid water on its surface and provide a long-term habitat for animal-like aerobic life. In this paper we examine the dependence of the GHZ on Galactic chemical evolution. The single most important factor is likely the dependence of terrestrial planet mass on the metallicity of its birth cloud. We estimate, very approximately, that a metallicity at least half that of the Sun is required to build a habitable terrestrial planet. The mass of a terrestrial planet has important consequences for interior heat loss, volatile inventory, and loss of atmosphere. A key issue is the production of planets that sustain plate tectonics, a critical recycling process that provides feedback to stabilize atmospheric temperatures on planets with oceans and atmospheres. Due to the more recent decline from the early intense star formation activity in the Milky Way, the concentration in the interstellar medium of the geophysically important radioisotopes 40 K, 235,238 U, and 232 Th has been declining relative to Fe, an abundant element in the Earth. Also likely important are the relative abundances of Si and Mg to Fe, which affects the mass of the core relative to the mantle in a terrestrial planet. All these elements and isotopes vary with time and location in the Milky Way; thus, planetary systems forming in other locations and times in the Milky Way with the same metallicity as the Sun will not necessarily form habitable Earth-like planets. As a result of the radial Galactic metallicity gradient, the outer limit of the GHZ is set primarily by the minimum required metallicity to build large terrestrial planets. Regions of the Milky Way least likely to contain Earth-mass planets are the halo (including globular clusters), the thick disk, and the outer thin disk. The bulge should contain Earth-mass planets, but stars in it have a mix of elements different from the Sun's. The existence of a luminosity-metallicity correlation among galaxies of all types means that many galaxies are too metal-poor to contain Earth-mass planets. Based on the observed luminosity function of nearby galaxies in the visual passband, we estimate that (1) the Milky Way is among the 1.3% most luminous (and hence most metal-rich) galaxies and (2) about 23% of stars in a typical ensemble of galaxies are more metal-rich than the average star in the Milky Way. The GHZ zone concept can be easily extrapolated to the universe as a whole, especially with regard to the changing star formation rate and its effect on metallicity and abundances of the long-lived radioisotopes.

The first gamma-ray line originating from outside the solar system that was ever detected is the 511 keV emission from positron annihilation in the Galaxy. Despite 30 years of intense theoretical and observational investigation, the main sources of positrons have not been identified up to now. Observations in the 1990's with OSSE/CGRO showed that the emission is strongly concentrated towards the Galactic bulge. In the 2000's, the SPI instrument aboard ESA's INTEGRAL gamma-ray observatory allowed scientists to measure that emission across the entire Galaxy, revealing that the bulge/disk luminosity ratio is larger than observed in any other wavelength. This mapping prompted a number of novel explanations, including rather "exotic ones (e.g. dark matter annihilation). However, conventional astrophysical sources, like type Ia supernovae, microquasars or X-ray binaries, are still plausible candidates for a large fraction of the observed total 511 keV emission of the bulge. A closer study of the subject reveals new layers of complexity, since positrons may propagate far away from their production sites, making it difficult to infer the underlying source distribution from the observed map of 511 keV emission. However, contrary to the rather well understood propagation of high energy (>GeV) particles of Galactic cosmic rays, understanding the propagation of low energy (~MeV) positrons in the turbulent, magnetized interstellar medium, still remains a formidable challenge. We review the spectral and imaging properties of the observed 511 keV emission and we critically discuss candidate positron sources and models of positron propagation in the Galaxy.

Stellar nucleosynthesis of heavy elements such as carbon allowed the formation of organic molecules in space, which appear to be widespread in our Galaxy. The physical and chemical conditions-including density, temperature, ultraviolet (UV) radiation and energetic particles-determine reaction pathways and the complexity of organic molecules in different space environments. Dense interstellar clouds are the birth sites of stars of all masses and their planetary systems. During the protostellar collapse, interstellar organic molecules in gaseous and solid phases are integrated into protostellar disks from which planets and smaller solar 0034-4885/02/101427+61$90.00

Low mass stars, like our Sun, are born from the collapse of a molecular cloud. The matter falls in the center of the cloud, creating a protoplanetary disk surrounding a protostar. Planets and other solar system bodies will be formed in the disk.The chemical composition of the interstellar matter and its evolution during the formation of the disk are important to better understand the formation process of these objects.I studied the chemical and physical evolution of this matter, from the cloud to the disk, using the chemical gas-grain code Nautilus.A sensitivity study to some parameters of the code (such as elemental abundances and parameters of grain surface chemistry) has been done. More particularly, the updates of rate coefficients and branching ratios of the reactions of our chemical network showed their importance, such as on the abundances of some chemical species, and on the code sensitivity to others parameters.Several physical models of collapsing dense core have also been considered. The more complex and solid approach has been to interface our chemical code with the radiation-magneto-hydrodynamic model of stellar formation RAMSES, in order to model in three dimensions the physical and chemical evolution of a young disk formation. Our study showed that the disk keeps imprints of the past history of the matter, and so its chemical composition is sensitive to the initial conditions.

(Abridged) We have discovered a strong DLA coincident in redshift with the faint QSO Q2343-BX415 (R = 20.2, z_em = 2.57393). Follow-up observations at intermediate spectral resolution reveal that the metal lines associated with this 'proximate' DLA consist of two sets of absorption components. One set is moving towards the quasar with velocities of ~ 150-600 km/s; this gas is highly ionized and does not fully cover the continuum source, suggesting that it is physically close to the active nucleus. The other, which accounts for most of the neutral gas, is blueshifted relative to the QSO, with the strongest component at ~ -160 km/s. We consider the possibility that the PDLA arises in the outflowing interstellar medium of the host galaxy of Q2343-BX415, an interpretation supported by strong C IV and N V absorption at nearby velocities, and by the intense radiation field longward of the Lyman limit implied by the high C II*/H I ratio. If Q2343-BX415 is the main source of these UV photons, then the PDLA is located at either ~ 8 or ~ 37 kpc from the active nucleus. Alternatively, the absorber may be a foreground star-forming galaxy unrelated to the quasar and coincidentally at the same redshift, but our deep imaging and follow-up spectroscopy of the field of Q2343-BX415 has not yet produced a likely candidate. We measure the abundances of 14 elements in the PDLA, finding an overall metallicity of ~ 1/5 solar and a normal pattern of relative element abundances for this metallicity. Thus, in this PDLA there is no evidence for the super-solar metallicities that have been claimed for some proximate, high ionization, systems.

Superbubbles surrounding OB associations provide ideal laboratories to study the stellar energy feedback problem because the stellar energy input can be estimated from the observed stellar content of the OB associations and the interstellar thermal and kinetic energies of superbubbles are well-defined and easy to observe. We have used DEM L 192, also known as N 51D, to carry out a detailed case study of the energy budget in a superbubble, and we find that the expected amount of stellar mechanical energy injected into the ISM, (18+-5)x10^51 ergs, exceeds the amount of thermal and kinetic energies stored in the superbubble, (6+-2)x10^51 ergs. Clearly, a significant fraction of the stellar mechanical energy must have been converted to other forms of energy. The X-ray spectrum of the diffuse emission from DEM L 192 requires a power-law component to explain the featureless emission at 1.0-3.0 keV. The origin of this power-law component is unclear, but it may be responsible for the discrepancy between the stellar energy input and the observed interstellar energy in DEM L 192.

We estimate the cosmic production rate of helium relative to metals (DeltaY/DeltaZ) using K dwarf stars in the Hipparcos catalog with accurate spectroscopic metallicities. The best fitting value is DeltaY/DeltaZ = 2.1 +/- 0.4 at the 68% confidence level. Our derived value agrees with determinations from H II regions and with theoretical predictions from stellar yields with standard assumptions for

Context. Significant quantities of magnetized plasma are transported from the Sun to the interstellar medium via Interplanetary Coronal Mass Ejections (ICMEs). Magnetic Clouds (MCs) are a particular subset of ICMEs, forming large scale magnetic flux ropes. Their evolution in the solar wind is complex and mainly determined by their own magnetic forces and the interaction with the surrounding solar wind. Aims. In this work we analyze the evolution of a particular MC (observed on March 1998) using in situ observations made by two spacecraft approximately aligned with the Sun, the first one at 1 AU from the Sun and the second one at 5.4 AU. We study the MC expansion, its consequent decrease of magnetic field intensity and mass density, and the possible evolution of the so-called global ideal-MHD invariants. Methods. We describe the magnetic configuration of the MC at both spacecraft using different models and compute relevant global quantities (magnetic fluxes, helicity and energy) at both helio-distances. We also track back this structure to the Sun, in order to find out its solar source. Results. We find that the flux rope is significantly distorted at 5.4 AU. However, we are able to analyze the data before the flux rope center is over-passed and compare it with observations at 1 AU. From the observed decay of magnetic field and mass density, we quantify how anisotropic is the expansion, and the consequent deformation of the flux rope in favor of a cross section with an aspect ratio at 5.4 AU of ≈ 1.6 (larger in the direction perpendicular to the radial direction from the Sun). We quantify the ideal-MHD invariants and magnetic energy at both locations, and find that invariants are almost conserved, while the magnetic energy decays as expected with the expansion rate found.

The interaction of the solar wind with the local interstellar medium is characterized by the self-consistent coupling of solar wind plasma, both upstream and downstream of the heliospheric termination shock, the interstellar plasma, and the neutral atom component of interstellar and solar wind origin. The complex coupling results in the creation of new plasma components (pickup ions), turbulence, and anomalous cosmic rays, and new populations of neutral atoms and their coupling can lead to energetic neutral atoms that can be detected at 1 AU. In this review, we discuss the interaction and coupling of global sized structures (the heliospheric boundary regions) and kinetic physics (the distributions that are responsible for the creation of energetic neutral atoms) based on models that have been developed by the University of Alabama in Huntsville group.

The first gamma-ray line originating from outside the solar system that was ever detected is the 511 keV emission from positron annihilation in the Galaxy. Despite 30 years of intense theoretical and observational investigation, the main sources of positrons have not been identified up to now. Observations in the 1990's with OSSE/CGRO showed that the emission is strongly concentrated towards the Galactic bulge. In the 2000's, the SPI instrument aboard ESA's INTEGRAL gamma-ray observatory allowed scientists to measure that emission across the entire Galaxy, revealing that the bulge/disk luminosity ratio is larger than observed in any other wavelength. This mapping prompted a number of novel explanations, including rather "exotic ones (e.g. dark matter annihilation). However, conventional astrophysical sources, like type Ia supernovae, microquasars or X-ray binaries, are still plausible candidates for a large fraction of the observed total 511 keV emission of the bulge. A closer study of the subject reveals new layers of complexity, since positrons may propagate far away from their production sites, making it difficult to infer the underlying source distribution from the observed map of 511 keV emission. However, contrary to the rather well understood propagation of high energy (>GeV) particles of Galactic cosmic rays, understanding the propagation of low energy (~MeV) positrons in the turbulent, magnetized interstellar medium, still remains a formidable challenge. We review the spectral and imaging properties of the observed 511 keV emission and we critically discuss candidate positron sources and models of positron propagation in the Galaxy.

We present here the results from an extensive scintillation study of twenty pulsars in the dispersion measure (DM) range 3 – 35 pc cm−3 carried out using the Ooty Radio Telescope, to investigate the distribution of ionized material in the local interstellar medium (LISM). Our analysis reveals several anomalies in the scattering strength, which suggest that the distribution of scattering material in the solar neighborhood is not uniform. Our model suggests the presence of a low density bubble surrounded by a shell of much higher density fluctuations. We are able to put some constraints on geometrical and scattering properties of such a structure, and find it to be morphologically similar to the local bubble known from other studies.

The AMIGA project (Analysis of the interstellar Medium of Isolated GAlaxies) is an international collaboration led from the Instituto de Astrof\'isica de Andaluc\'ia (CSIC). The group's experience in radio astronomy databases turned, as a natural evolution, into an active participation in the development of data archives and radio astronomy software. The contributions of the group to the VO have been mostly oriented towards the deployment of large VO compliant databases and the development of access interfaces (IRAM 30m Pico Veleta, DSS-63 70m in Robledo de Chavela). We also have been working in the development of an API for VO tools that will ease access to VO registries and communication between different VO software. A collaboration with the Kapteyn Astronomical Institute has started recently in order to perform a complete renovation of the only existing high-level software (GIPSY) for the analysis of datacubes, allowing its fully integration in the VO.

We revisit the question of the ionization of the diffuse medium in late-type galaxies, by studying NGC 891, the prototype of edge-on spiral galaxies. The most important challenge for the models considered so far was the observed increase of [O III]/Hβ, [O II]/Hβ and [N II]/Hα with increasing distance to the galactic plane. We propose a scenario based on the expected population of massive OB stars and hot low-mass evolved stars (HOLMES) in this galaxy to explain this observational fact. In the framework of this scenario we construct a finely meshed grid of photoionization models. For each value of the galactic altitude z we look for the models which simultaneously fit the observed values of the [O III]/Hβ, [O II]/Hβ and [N II]/Hα ratios. For each value of z we find a range of solutions which depends on the value of the oxygen abundance. The models which fit the observations indicate a systematic decrease of the electron density with increasing z. They become dominated by the HOLMES with increasing z only when restricting to solar oxygen abundance models, which argues that the metallicity above the galactic plane should be close to solar. They also indicate that N/O increases with increasing z.

The SPEAR micro-satellite payload consists of dual imaging spectrographs optimized for detection of the faint, diffuse FUV (900-1750 Å) radiation emitted from interstellar gas. The instrument provides spectral resolution, R~750, and long slit imaging of <10 over a large (8) field of view. We enhance the sensitivity by using shutters and filters for removal of background noise. Each spectrograph channel uses identically figured optics: a parabolic-cylinder entrance mirror and a constant-ruled ellipsoidal grating. Two microchannel plate photon-counting detectors share a single delayline encoding system. A payload electronics system conditions data and controls the instrument. We will describe the design and predicted performance of the SPEAR instrument system and its elements.

The Herschel Reference Survey is a guaranteed time Herschel key project and will be a benchmark study of dust in the nearby universe. The survey will complement a number of other Herschel key projects including large cosmological surveys that trace dust in the distant universe. We will use Herschel to produce images of a statistically-complete sample of 323 galaxies at 250, 350 and 500 µm. The sample is volume-limited, containing sources with distances between 15 and 25 Mpc and flux limits in the K-band to minimize the selection effects associated with dust and with young high-mass stars and to introduce a selection in stellar mass. The sample spans the whole range of morphological types (ellipticals to late-type spirals) and environments (from the field to the centre of the Virgo Cluster) and as such will be useful for other purposes than our own. We plan to use the survey to investigate (i) the dust content of galaxies as a function of Hubble type, stellar mass and environment, (ii) the connection between the dust content and composition and the other phases of the interstellar medium and (iii) the origin and evolution of dust in galaxies. In this paper, we describe the goals of the survey, the details of the sample and some of the auxiliary observing programs that we have started to collect complementary data. We also use the available multi-frequency data to carry out an analysis of the statistical properties of the sample.

The Herschel Reference Survey is a guaranteed time Herschel key project and will be a benchmark study of dust in the nearby universe. The survey will complement a number of other Herschel key projects including large cosmological surveys that trace dust in the distant universe. We will use Herschel to produce images of a statistically-complete sample of 323 galaxies at 250, 350 and 500 µm. The sample is volume-limited, containing sources with distances between 15 and 25 Mpc and flux limits in the K-band to minimize the selection effects associated with dust and with young high-mass stars and to introduce a selection in stellar mass. The sample spans the whole range of morphological types (ellipticals to late-type spirals) and environments (from the field to the centre of the Virgo Cluster) and as such will be useful for other purposes than our own. We plan to use the survey to investigate (i) the dust content of galaxies as a function of Hubble type, stellar mass and environment, (ii) the connection between the dust content and composition and the other phases of the interstellar medium and (iii) the origin and evolution of dust in galaxies. In this paper, we describe the goals of the survey, the details of the sample and some of the auxiliary observing programs that we have started to collect complementary data. We also use the available multi-frequency data to carry out an analysis of the statistical properties of the sample.

Organic compounds are synthesized in the interstellar medium and can be delivered to plan- etary surfaces such as the early Earth, where they mix with endogenous species. Some of these compounds are amphiphilic, having polar and nonpolar groups on the same molecule. Am- phiphilic compounds spontaneously self-assemble into more complex structures such as bi- molecular layers, which in turn form closed membranous vesicles. The first forms of cellular life required self-assembled membranes that were likely to have been produced from am- phiphilic compounds on the prebiotic Earth. Laboratory simulations show that such vesicles readily encapsulate functional macromolecules, including nucleic acids and polymerases. The goal of future investigations will be to fabricate artificial cells as models of the origin of life.

The main objective of a paper is to discuss the most important Concepts for any Cosmological model: Space, Time, and Gravitation; Cosmological principle (homogeneous and isotropic universe); Universality of physical laws; Law of the conservation of angular momentum; Expansion of universe; Content of the World; Formation of galaxies and large-scale structures; Speed of light in vacuum; Origin of cosmic microwave background radiation. The performed analysis shows that Big Bang Model (BBM) fails to account for these Concepts and should be obsolete. Hypersphere World-Universe Model (WUM) is, in fact, a Paradigm Shift in Cosmology [1]. WUM and BBM are principally different Models: 1) Instead of the Initial Singularity with the infinite energy density and the extremely rapid expansion of the space (Inflation) in BBM; in WUM, there was a Fluctuation (4D Nucleus of the World with an extrapolated radius equals to a basic unit of size) in the Eternal Universe with a finite extrapolated energy density (four orders of magnitude less than the nuclear density) and a finite expansion of the Nucleus in Its fourth spatial dimension with speed that is the gravitodynamic constant; 2) Instead of a practically Infinite Homogeneous and Isotropic Universe around the Initial Singularity in BBM; in WUM, the 3D Finite Boundless World (the Hypersphere of the 4D Nucleus) presents a Patchwork Quilt of different Luminous Superclusters (≳10^3), which emerged in different places of the World at different Cosmological times. The Medium of the World is Homogeneous and Isotropic. The distribution of Macroobjects in the World is spatially Inhomogeneous and Anisotropic and temporally Non-simultaneous. The Absolute Age of the entire World (determined by the parameters of the Medium) is 14.22 Gyr. The Medium of the World, Dark Matter, and Angular Momentum are the main Three Pillars of WUM.

available online at Abstract-We report combined micro-infrared, micro-Raman, and field emission scanning electron microscope (FESEM) analyses of particles collected by the Stardust spacecraft during its flyby of comet 81P/Wild 2 on 2 January 2004 and successfully returned back to Earth on 15 January 2006. We present mid-infrared (IR) spectra of six of these particles. The CH 2 /CH 3 ratios inferred from the infrared data are greater than those seen in organics in the diffuse interstellar medium, possibly indicating the presence of longer or less branched aliphatic chains. The micro-Raman data offer insights into the state of the order of the carbonaceous component present in the particles. Raman parameters for most of the particles span a similar range to that observed in interplanetary dust particles (IDPs) and the most primitive meteorites. Both the IR and Raman data imply the presence of a very labile carbonaceous component. Hydrated silicates may be present in two particles of Track 35, one of which may also contain carbonates, but further investigations with other techniques need to be performed to confirm these findings. In some cases, the analyses are difficult to interpret because of the presence of compressed aerogel mixed with the grains.

An introductory exposition of Chandrasekhar&#39;s gravitational dynamical friction, appropriate for an undergraduate class in mec hanics, is presented. This friction results when a massive particle moving through a ``sea&#39;&#39; of much lighter star particles experiences a retarding force du to an exchange of energy and momentum. General features of dynamical friction are presented, both in an elementary and in a