A decade of galactic center observations at the Crawford Hill 7 m antenna is summarized. The galactic center region contains several hundred high-mass, high-density molecular clouds with physical properties very different from clouds in the outer galactic disk. There is also a considerable amount of molecular gas not bound into clouds, but sheared by differential rotation into a molecular inter-cloud medium not seen elsewhere in the Galaxy. These observations can be explained by a combination of the tidal density limit and the virial theorem. The distribution of emission on the sky and in velocity suggests that most of the dense gas is confined to a 500 pc long ridge of emission which may be a dust lane along the central bar.

The distance from the Local Group to the ‘sphere’ of small galaxies that no longer expand with the Universe determines the time since the Big Bang, t x M1/2, where M is the mass of the Local Group. Adopting Feast's new distance scale, this distance is found to be 1.35 ± 0.1 Mpc. The velocity of approach and the distance to M31 give a different combination of t and M, thus both can be deduced. We find the time since the Big Bang and The importance of accurate distances for such results is stressed. If all distances are revised by a factor λ then both t and M change by that factor.

Many records of climatic and environmental changes based on various proxy data exhibit distinct cyclicities that have been attributed to extraterrestrial forcing such as changes in solar activity. To study the long-term changes of solar activity, different data sets of solar activity, both indirect data (the Schove series) and proxy data (cosmogenic isotopes) were analyzed. Both sets of solar activity clearly show centennial and millennial changes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Since we cannot put stars in a laboratory, astrophysicists had to wait till the invention of computers before becoming laboratory scientists. For half a century now, we have been conducting experiments in our virtual laboratories. However, we ourselves have remained behind the keyboard, with the screen of the monitor separating us from the world we are simulating. Recently, 3D on-line technology, developed first for games but now deployed in virtual worlds like Second Life, is beginning to make it possible for astrophysicists to enter their virtual labs themselves, in virtual form as avatars. This has several advantages, from new possibilities to explore the results of the simulations to a shared presence in a virtual lab with remote collaborators on different continents. I will report my experiences with the use of Qwaq Forums, a virtual world developed by a new company (see http://www.qwaq.com).

The changes in stellar polarization with time were first discovered in 1958 by GRIGORYAN (1958) for the red supergiant µ Cephei. In subsequent year BEHR (1959) gave a hint in a footnote to his catalogue that the emission-line B-type star α Cas seems to have variable polarization. However, several years had to pass before these discoveries were confirmed and the changes in polarization with time for the red giants and supergiants and for the emission-line B-type stars were firmly established, first by the observations made by SHAKHOVSKOJ (1963, 1964) and then by COYNE, GEHRELS (1967) and the writer (SERKOWSKI 1966, 1968). The changes in polarization with time were also found for the RV Tauri and T Tauri stars, R Coronae Borealis stars, novae, Wolf-Rayet stars, and white dwarfs. The rapid changes in polarization with time indicate that the polarization is not produced in the interstellar medium but in the vicinity of a star; such polarization is called intrinsic.

To bring out the basic problem of star formation, consider a non-rotating cosmical gas cloud which is free to contract and so to convert most of its gravitational energy into kinetic energy of mass motion. Fluid dynamical systems in general tend to dissipate their kinetic energy, and a diffuse gas cloud easily radiates excess heat. If the cloud did not break up into fragments, then the steady conversion of gravitational energy into radiation would lead ultimately into the formation of a compact massive body - perhaps a quasar - but not of a star cluster, which is maintained at a comparatively low mean density by random stellar kinetic energy. Thus the transition from a gravitationally-bound cloud of gas and dust into a bound star cluster - or a fortiori into an expanding O-B association - requires that gravitational energy released during collapse be conserved as the random macroscopic kinetic energy. It is very likely that star formation is often triggered by processes that are essentially dissipative, such as shocks following passage of the spiral wave, or cloud-cloud collisions; however, it is equally important to emphasise that we require at some stage a cut-off in kinetic energy dissipation. And indeed, once a cloud has been able to fragment into a group of self-gravitating blobs, each of small geometrical cross-section, the chance of inelastic collisions between blobs is sharply reduced.

Aromatic features at 3.3, 6.2, 7.7, 8.6, 11.3 μm are observed in proto-planetary nebulae (PPNe) as well as in PNe and H ii regions. Aliphatic features at 3.4 and 6.9 μm are also observed; however, these features are often stronger in PPNe than in PNe. These observations suggest an evolution in the features from simple molecules (C2H2) in AGB stars to aliphatics in PPNe to aromatics in PNe. In the same carbon-rich PPNe, a strong, broad, unidentified 21 μm emission feature has been found. We will present recent observations of the aromatic, aliphatic, and 21 μm emission features, along with C2H2 (13.7 μm) and a new feature at 15.8 μm, and discuss correlations among them and other properties of these PPNe.

In this brief review of recent work relating the DIBs to other gas-phase constituents of the ISM, we explore correlations between DIB equivalent widths and the column densities of various atomic and molecular species, drawn from a large database constructed for that purpose. The tightness and slopes of the correlations can provide information on how the DIBs might be related to those species (physically, chemically, spatially) and on various properties of the DIB carriers. Deviations from the mean relationships can reveal dependences of DIB strengths on other parameters, regional variations in DIB behavior, and individual sight lines where unusual environmental conditions affect the DIBs. Variations in DIB profiles (e.g., wings, substructure) and relative strengths may be related to differences in physical conditions inferred from atomic and/or molecular absorption lines.

Blue luminescence (BL) and extended red emission (ERE) are observed as diffuse, optical-wavelength emissions in interstellar space, resulting from photoluminescence by ultraviolet(UV)-illuminated interstellar grains. Faintness and the challenge of separating the BL and ERE from the frequently much brighter dust-scattered continuum present major observational hurdles, which have permitted only slow progress in testing the numerous models that have been advanced to explain these two phenomena. Both the ERE, peaking near 680 nm (FWHM ~ 60 - 120 nm) and the BL, asymmetrically peaking at ~ 378 nm (FWHM ~ 45 nm), were first discovered in the Red Rectangle nebula. Subsequently, ERE and BL have been observed in other reflection nebulae, and in the case of the ERE, in carbon-rich planetary nebulae, H II regions, high-latitude cirrus clouds, the galactic diffuse ISM, and in external galaxies. BL exhibits a close spatial and intensity correlation with emission in the aromatic emission feature at 3.3 micron, most likely arising from small, neutral polycyclic aromatic hydrocarbon (PAH) molecules. The spectral characteristics of the BL also agree with those of fluorescence by PAH molecules with 13 to 19 carbon atoms. The BL phenomenon is thus most readily understood as the optical fluorescence of small, UV-excited aromatic molecules. The ERE, by contrast, though co-existent with mid-IR PAH emissions, does not correlate with emissions from either neutral or ionized PAHs. Instead, the spatial ERE morphology appears to be strictly governed by the density of far-UV (E ≥ 10.5 eV) photons, which are required for the ERE excitation. The most restrictive observational constraint for the ERE process is its exceptionally high quantum efficiency. If the ERE results from photo-excitation of a nano-particle carrier by photons with E ≥ 10.5 eV in a single-step process, the quantum efficiency exceeds 100%. Such a process, in which one to three low-energy optical photons may be emitted following a single far-UV excitation, is possible in highly isolated small clusters, e.g. small, dehydrogenated carbon clusters with about 20 to 28 carbon atoms. A possible connection between the ERE carriers and the carriers of DIBs may exist in that both are ubiquitous throughout the diffuse interstellar medium and both have an abundance of low-lying electronic levels with E ≤ 2.3 eV above the ground state.

We carried out three-dimensional global MHD simulations of jet formation from an accretion disk threaded by large-scale magnetic fields. Numerical results show that bipolar jets with maximum speed υjet ~ υKepler are created. The surface layer of the disk accretes faster than the equatorial part because magnetic braking most effectively affects that layer. Accretion proceeds along spiral channels which correspond to the surface avalanche flow appearing in previous axisymmetric simulations. Spirally shaped low β (= Pgas/Pmag < 1) regions appear in the innermost part of accretion disks where toroidal magnetic fields become dominant.

The number of known diffuse radio sources in clusters of galaxies has grown in recent years, making it possible to derive statistical properties of these sources and of the hosting clusters. We show that diffuse sources are associated with X-ray luminous clusters which have undergone recent merger processes. The radio and X-ray structures are often similar, and correlations are found between radio and X-ray parameters. This is indication of a link between the diffuse relativistic and thermal plasma in clusters of galaxies.

We present our first results on a new sample containing all single G, K and M giants down to V = 4 mag in the Solar vicinity, suitable for spectropolarimetric (Stokes V) observations with Narval at TBL, France. For detection and measurement of the magnetic field (MF), the Least Squares Deconvolution (LSD) method was applied (Donati et al. 1997) that in the present case enables detection of large-scale MFs even weaker than the solar one (the typical precision of our longitudinal MF measurements is 0.1-0.2 G). The evolutionary status of the stars is determined on the basis of the evolutionary models with rotation (Lagarde et al. 2012; Charbonnel et al., in prep.) and fundamental parameters given by Massarotti et al. (1998). The stars appear to be in the mass range 1-4 M⊙, situated at different evolutionary stages after the Main Sequence (MS), up to the Asymptotic Giant Branch (AGB).

The sample contains 45 stars. Up to now, 29 stars are observed (that is about 64% of the sample), each observed at least twice. For 2 stars in the Hertzsprung gap, one is definitely Zeeman detected. Only 5 G and K giants, situated mainly at the base of the Red Giant Branch (RGB) and in the He-burning phase are detected. Surprisingly, a lot of stars ascending towards the RGB tip and in early AGB phase are detected (8 of 13 observed stars). For all Zeeman detected stars v sin i is redetermined and appears in the interval 2-3 km/s, but few giants with MF possess larger v sin i.

Current understanding of the stability of gas and stellar disks suggests very strongly that local stability to axisymmetric modes is not sufficient for global stability. A global instability to a bar mode will develop unless the rotational kinetic energy is sufficiently small compared with the random kinetic energy for the system as a whole. A disk as cool as the galactic disk near the Sun can survive only if most of the mass of the Galaxy is in a ‘hot’ component, such as a central bulge and/or an extended halo. We review the theoretical evidence for this conclusion coming from analytic results for simple gas and stellar disks, from numerical simulations of stellar disks, and from numerical calculations of the stability of gas disks. Some new results on the precise form of dynamic bar instabilities of gas disks with and without halos are reported.

Multi-wavelength studies of solar analogs (G0–5 V stars) with ages from ~50 Myr to 9 Gyr have been carried out as part of the “Sun in Time” program for nearly 20 yrs. From these studies it is inferred that the young (ZAMS) Sun was rotating more than 10× faster than today. As a consequence, young solar-type stars and the early Sun have vigorous magnetohydrodynamic (MHD) dynamos and correspondingly strong coronal X-ray and transition region/chromospheric FUV–UV emissions (up to several hundred times stronger than the present Sun). Also, rotational modulated, low amplitude light variations of young solar analogs indicate the presence of large starspot regions covering ~5–30% of their surfaces. To ensure continuity and homogeneity for this program, we use a restricted sample of G0–5 V stars with masses, radii, Teff, and internal structure (i.e. outer convective zones) closely matching those of the Sun. From these analogs we have determined reliable rotation-age-activity relations and X-ray–UV (XUV) spectral irradiances for the Sun (or any solar-type star) over time. These XUV irradiance measures serve as input data for investigating the photo-ionization and photo-chemical effects of the young, active Sun on the paleo-planetary atmospheres and environments of solar system planets. These measures are also important to study the effects of these high energy emissions on the numerous exoplanets hosted by solar-type stars of different ages. Recently we have extended the study to include lower mass, main-sequence (dwarf) dK and dM stars to determine relationships among their rotation spin-down rates and coronal and chromospheric emissions as a function of mass and age. From rotation-age-activity relations we can determine reliable ages for main-sequence G, K, M field stars and, subsequently, their hosted planets. Also inferred are the present and the past XUV irradiance and plasma flux exposures that these planets have endured and the suitability of the hosted planets to develop and sustain life.

The solar sector structure consists of a boundary in the north-south direction such that on one side of the boundary the large-scale weak photospheric magnetic field is predominantly directed out of the Sun, and on the other side of the boundary this field is directed into the Sun. The region westward of a solar sector boundary tends to be unusually quiet and the region eastward of a solar sector boundary tends to be unusually active. This tendency is discussed in terms of flares, coronal enhancements, plage structure and geomagnetic response.

Dynamical theories of the Earth’s rotation like SMART97 (Bretagnon et al., 1998) are to be considered in a DGRS (dynamically nonrotating geocentric reference system) (Brumberg et al., 1996). Such a theory gives the explicit expressions in terms of TCG (Geocentric Coordinate Time) of three Euler angles relating a DGRS to the ITRS (International Terrestrial Reference System). These angular quantities together with their TCG derivatives enable one to get all Earth’s rotation parameters. At the same time, the analysis of observations result in the values for slightly different angles and their TCG derivatives characterizing the relationship between the ITRS and a KGRS (kinematically nonrotating geocentric reference system). The differences between these two sets of six quantities represent kinematical relativistic corrections (due to geodesic precession, geodesic nutation and luni-planetary terms). The paper presents these differences computed by means of the VSOP87 series (Bretagnon and Francou, 1988). In particular, in analysing observations at the microarcsecond level these expressions will permit an experimental check of geodesic precession in a more direct manner than it is done nowadays (Bertotti et al., 1987).

The study of detached eclipsing binaries is one of the most powerful ways to investigate the properties of individual stars and stellar systems. We present preliminary masses, radii and effective temperatures for the eclipsing binary WW Aurigae, which is composed of two metallic-lined A-type stars. We also reanalyse the data on HD 23642, an A-type eclipsing binary member of the Pleiades open cluster with a metallic-lined component, and determine its distance to be $139 \pm 4$ pc. This is in agreement with the traditional Pleiades distance, but in disagreement with distance to the Pleiades, and to HD 23642 itself, derived from Hipparcos trigonometrical parallaxes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Observational data concerning the long-term history of cyclic solar activity as recorded in sunspot and isotopic data are discussed in the context of solar dynamo theory. In particular, a simple dynamo model based on differential rotation and the mirror asymmetry of convection with random fluctuations of dynamo governing parameters is shown to reproduce some basic features of the solar magnetic activity evolution.

According to semiempirical models, photoabsorption by fullerenes (single and multishell) could explain the shape, width and peak energy of the most prominent feature of the interstellar absorption, the UV bump at 2175 Å. Other weaker transitions are predicted in the optical and near-infrared providing a potential explanation for diffuse interstellar bands. In particular, we find that several fullerenes could contribute to the well known strong DIB at 4430 Å. Comparing cross sections and available data for this DIB and the UV bump we estimate a density of fullerenes in the diffuse interstellar medium of 0.1–0.2 ppm. These molecules could then be a major reservoir for interstellar carbon. We also study the rotation rates and electric dipole emission of hydrogenated icosahedral fullerenes. We investigate these molecules as potential carriers of the anomalous (dust-correlated) microwave emission recently detected by several cosmic microwave background experiments.

In this review, I discuss the use of galaxy-galaxy weak lensing measurements to study the masses of dark matter halos in which galaxies reside. After summarizing how weak gravitational lensing measurements can be interpreted in terms of halo mass, I review measurements that were used to derive the relationship between optical galaxy mass tracers, such as stellar mass or luminosity, and dark matter halo mass. Measurements of galaxy-galaxy lensing from the past decade have led to increasingly tight constraints on the connection between dark matter halo mass and optical mass tracers, including both the mean relationships between these quantities and the intrinsic scatter between them. I also review some of the factors that can complicate analysis, such as the choice of modeling procedure, and choices made when dividing up samples of lens galaxies.