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Sample records for galactic rotation curves

  1. Mass Distributions Implying Flat Galactic Rotation Curves

    ERIC Educational Resources Information Center

    Keeports, David

    2010-01-01

    The rotational speeds of stars in the disc of a spiral galaxy are virtually independent of the distances of the stars from the centre of the galaxy. In common parlance, the stellar speed versus distance plot known as a galactic rotation curve is by observation typically nearly flat. This observation provides strong evidence that most galactic…

  2. The galactic rotation curve from OH observations

    SciTech Connect

    Kolesnik, I.G.; Yurevich, L.V.

    1985-11-01

    This paper shows that the galactic rotation curve is determined up to galactocentric distances of 16 kpc from the relation between the parameters of the absorption lines for molecular OH clouds and the distance to them. Results are given separately for the two galactocentric guadrants which border each along the line from the center of the Galaxy to the Sun. The rotation curve so obtained repeats the kinematical laws established from observed parameters of the hydroxyl absorption lines in order to determine the distances to the molecular clouds in the Galaxy. The distance of the Sun from the center of the Galaxy is estimated.

  3. Study of galactic rotation curves in wormhole spacetime

    NASA Astrophysics Data System (ADS)

    Rahaman, Farook; Sen, Banashree; Chakraborty, Koushik; Shit, G. C.

    2016-03-01

    The spacetime of the galactic halo region is described by a wormhole like line element. We assume violation of Null Energy Condition (NEC) in the galactic halo. The Einstein Field equations are solved for two different conditions of pressure and density to obtain physical parameters like tangential velocity of test particles and parameters related to the wormhole geometry. The theoretical rotation curve of the test particles is plotted and compared the same with an observed rotation curve. We obtain a satisfactory fit between the observed curve and the curve obtained from the present theory for the radial distances in the range 9 Kpc to 100 Kpc.

  4. Testing MONDian dark matter with galactic rotation curves

    SciTech Connect

    Edmonds, Doug; Farrah, Duncan; Minic, Djordje; Takeuchi, Tatsu; Ho, Chiu Man; Ng, Y. Jack E-mail: farrah@vt.edu E-mail: takeuchi@vt.edu E-mail: yjng@physics.unc.edu

    2014-09-20

    MONDian dark matter (MDM) is a new form of dark matter quantum that naturally accounts for Milgrom's scaling, usually associated with modified Newtonian dynamics (MOND), and theoretically behaves like cold dark matter (CDM) at cluster and cosmic scales. In this paper, we provide the first observational test of MDM by fitting rotation curves to a sample of 30 local spiral galaxies (z ≈ 0.003). For comparison, we also fit the galactic rotation curves using MOND and CDM. We find that all three models fit the data well. The rotation curves predicted by MDM and MOND are virtually indistinguishable over the range of observed radii (∼1 to 30 kpc). The best-fit MDM and CDM density profiles are compared. We also compare with MDM the dark matter density profiles arising from MOND if Milgrom's formula is interpreted as Newtonian gravity with an extra source term instead of as a modification of inertia. We find that discrepancies between MDM and MOND will occur near the center of a typical spiral galaxy. In these regions, instead of continuing to rise sharply, the MDM mass density turns over and drops as we approach the center of the galaxy. Our results show that MDM, which restricts the nature of the dark matter quantum by accounting for Milgrom's scaling, accurately reproduces observed rotation curves.

  5. Impact of a global quadratic potential on galactic rotation curves.

    PubMed

    Mannheim, Philip D; O'Brien, James G

    2011-03-25

    We present a conformal gravity fit to the 20 largest of a sample of 110 spiral galaxies. We identify the presence of a universal quadratic potential V(κ)(r)=-κc²r²/2 with κ=9.54×10⁻⁵⁴ cm⁻² induced by cosmic inhomogeneities. When V(κ)(r) is taken in conjunction with both a universal linear potential V(γ₀)(r)=γ₀c²r/2 with γ₀=3.06×10⁻³⁰ cm⁻¹ generated by the homogeneous cosmic background and the contribution generated by the local luminous matter in galaxies, the theory then accounts for the rotation curve systematics observed in the entire 110 galaxies, without the need for any dark matter whatsoever. Our study suggests that using dark matter may be nothing more than an attempt to describe global effects in purely local galactic terms. With V(κ)(r) being negative, galaxies can only support bound orbits up to distances of order γ₀/κ=100kpc, with global physics imposing a limit on the size of galaxies. PMID:21517292

  6. Galactic Rotation Curves from Yang-Mills Gravity

    NASA Astrophysics Data System (ADS)

    Katz, Daniel

    2014-03-01

    Yang-Mills Gravity (YMG) is a gauge field theory based on the T4 group in flat spacetime. In its macroscopic limit, it modifies the trajectories of classical objects such that it serves as an alternative to General Relativity (GR). Since YMG is relatively new and unknown, a brief review of the general theory is given and a more comprehensive list of references is provided. In the present work, we find that the Schwarzchild-like solution to YMG supports a term like αr with constant α. This translates into an r-term in the effective gravitational potential of classical objects. We use this modified potential to predict the shape of the rotation curves of spiral galaxies, and then use data from SDSS to constrain α, which seems to be a free parameter in YMG. This work was supported the NSF's GK12 Vibes and Waves Fellowship.

  7. Tully-Fisher relation, galactic rotation curves and dissipative mirror dark matter

    SciTech Connect

    Foot, R.

    2014-12-01

    If dark matter is dissipative then the distribution of dark matter within galactic halos can be governed by dissipation, heating and hydrostatic equilibrium. Previous work has shown that a specific model, in the framework of mirror dark matter, can explain several empirical galactic scaling relations. It is shown here that this dynamical halo model implies a quasi-isothermal dark matter density, ρ(r) ≅ ρ{sub 0}r{sub 0}{sup 2}/(r{sup 2}+r{sub 0}{sup 2}), where the core radius, r{sub 0}, scales with disk scale length, r{sub D}, via r{sub 0}/kpc ≈ 1.4(r{sub D}/kpc). Additionally, the product ρ{sub 0}r{sub 0} is roughly constant, i.e. independent of galaxy size (the constant is set by the parameters of the model). The derived dark matter density profile implies that the galactic rotation velocity satisfies the Tully-Fisher relation, L{sub B}∝v{sup 3}{sub max}, where v{sub max} is the maximal rotational velocity. Examples of rotation curves resulting from this dynamics are given.

  8. A QUMOND galactic N-body code - I. Poisson solver and rotation curve fitting

    NASA Astrophysics Data System (ADS)

    Angus, G. W.; van der Heyden, K. J.; Famaey, B.; Gentile, G.; McGaugh, S. S.; de Blok, W. J. G.

    2012-04-01

    Here we present a new particle-mesh galactic N-body code that uses the full multigrid algorithm for solving the modified Poisson equation of the quasi-linear formulation of modified Newtonian dynamics (QUMOND). A novel approach for handling the boundary conditions using a refinement strategy is implemented and the accuracy of the code is compared with analytical solutions of Kuzmin discs. We then employ the code to compute the predicted rotation curves for a sample of five spiral galaxies from the THINGS sample. We generated static N-body realizations of the galaxies according to their stellar and gaseous surface densities and allowed their distances, mass-to-light ratios (M/L values) and both the stellar and gas scale-heights to vary in order to estimate the best-fitting parameters. We found that NGC 3621, NGC 3521 and DDO 154 are well fitted by MOND using expected values of the distance and M/L. NGC 2403 required a moderately larger M/L than expected and NGC 2903 required a substantially larger value. The surprising result was that the scale-height of the dominant baryonic component was well constrained by the rotation curves: the gas scale-height for DDO 154 and the stellar scale-height for the others. In fact, if the suggested stellar scale-height (one-fifth the stellar scale-length) was used in the case of NGC 3621 and NGC 3521 it would not be possible to produce a good fit to the inner rotation curve. For each of the four stellar dominated galaxies, we calculated the vertical velocity dispersions which we found to be, on the whole, quite typical compared with observed stellar vertical velocity dispersions of face-on spirals. We conclude that modelling the gas scale-heights of the gas-rich dwarf spiral galaxies will be vital in order to make precise conclusions about MOND.

  9. Dark matter or new physics?. [deviation of galactic rotation curves from their expected Keplerian fall-off

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes; Mannheim, Philip D.

    1991-01-01

    Several proposals for a new physics to explain the deviation of galactic rotation curves from their expected Keplerian falloff with distance are discussed. Emphasis is given to a locally scale-invariant theory of gravity posed by the authors. The observational consequences of this theory are pointed out.

  10. Diversity of Galactic Rotation Curves and Self-interacting Dark Matter

    NASA Astrophysics Data System (ADS)

    Pace, Andrew; Andrade, Kevin; Kaplinghat, Manoj; Tulin, Sean; Yu, Hai-bo

    2016-01-01

    We compile a large sample of rotation curves from the literature with maximum rotation velocity spanning the range of 20-300 km/s. We model each individual system including its stellar, gas and dark matter components. We use a prescription for self-interacting dark matter (SIDM) halos that has been tested against simulations to infer the cross section for elastic scattering between dark matter particles required to explain the large cores. We discuss how the diversity of observed rotation curves and the constancy of the inferred surface density of dark matter may arise in SIDM models.

  11. C II forbidden-line 158 micron mapping in Sagittarius A Rotation curve and mass distribution in the galactic center

    NASA Technical Reports Server (NTRS)

    Lugten, J. B.; Genzel, R.; Crawford, M. K.; Townes, C. H.

    1986-01-01

    Based on data obtained with the NASA Kuiper Airborne Observatory 91.4 cm telescope, the 158-micron fine structure line emission of C(+) is mapped near the galactic center. The strongest emission comes from a 10-pc FWHM diameter disk centered on Sgr A West whose dominant motion is rotation. Extended C(+) emission is also found from the +50 km/s galactic center molecular cloud, and a second cloud at v(LSR) of about -35 km/s. The rotation curve and mass distribution within 10 pc of the galactic center are derived, and the C(+) profiles show a drop-off of rotation velocity between 2 and 10 pc. A mass model is suggested with 2-4 million solar masses in a central point mass, and a M/L ratio of the central stellar cluster of 0.5 solar masses/solar luminosities, suggesting a large abundance of giants and relatively recent star formation in the center.

  12. Galactic rotation curves, the baryon-to-dark-halo-mass relation and space-time scale invariance

    NASA Astrophysics Data System (ADS)

    Wu, Xufen; Kroupa, Pavel

    2015-01-01

    Low-acceleration space-time scale invariant dynamics (SID) predicts two fundamental correlations known from observational galactic dynamics: the baryonic Tully-Fisher relation and a correlation between the observed mass discrepancy and acceleration (MDA) in the low-acceleration regime for disc galaxies. SID corresponds to the deep Modified Newtonian Dynamics limit. The MDA data emerging in cold/warm dark matter (C/WDM) cosmological simulations disagree significantly with the tight MDA correlation of the observed galaxies. Therefore, the most modern simulated disc galaxies, which are delicately selected to have a quiet merging history in a standard dark matter cosmological model, still do not represent the correct rotation curves. Also, the observed tight correlation contradicts the postulated stochastic formation of galaxies in low-mass dark matter haloes. Moreover, we find that SID predicts a baryonic to apparent virial halo (dark matter) mass relation which agrees well with the correlation deduced observationally assuming Newtonian dynamics to be valid, while the baryonic to halo mass relation predicted from CDM models does not. The distribution of the observed ratios of dark matter halo masses to baryonic masses may be empirical evidence for the external field effect, which is predicted in SID as a consequence of the forces acting between two galaxies depending on the position and mass of a third galaxy. Applying the external field effect, we predict the masses of galaxies in the proximity of the dwarf galaxies in the Miller et al. sample. Classical non-relativistic gravitational dynamics is thus best described as being Milgromian, rather than Newtonian.

  13. CO 7-6 submillimeter emission from the galactic center - warm molecular gas and the rotation curve in the central 10 parsecs

    SciTech Connect

    Harris, A.I.; Jaffe, D.T.; Silber, M.; Genzel, R.

    1985-07-01

    Bright CO J = 7-6 submillimeter line emission in the central 10 pc of the Galaxy has been mapped. This is the first detection of the 7-6 line from the Galactic center; it was made with a new submillimeter heterodyne spectrometer mounted on the 3.0-m NASA IRTF telescope at Mauna Kea, Hawaii. The 372-micrometer CO emission comes from a dense, clumpy disk (10,000 solar masses) of temperature about 300 K. The luminosity of all CO rotational lines emitted from this approximately 4-arcmin diameter region is about 20,000 solar luminosities. CO line emission is a major contribution to the cooling of the interstellar gas near Sgr A. The CO data show that the rotational velocities drop by a factor of 1.4 to 2 between 2 and 6 pc from the center. The rotation curve is consistent with a Keplerian fall off around a point mass and implies that most of the mass is in a more compact distribution than an isothermal stellar cluster. Broad line width emission toward the central 30 arcsec of the Galaxy indicates that there is a significant amount of molecular material in the inner, mostly ionized, cavity. 21 references.

  14. The Milky Way's rotation curve out to 100 kpc and its constraint on the Galactic mass distribution

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Liu, X.-W.; Yuan, H.-B.; Xiang, M.-S.; Zhang, H.-W.; Chen, B.-Q.; Ren, J.-J.; Wang, C.; Zhang, Y.; Hou, Y.-H.; Wang, Y.-F.; Cao, Z.-H.

    2016-08-01

    The rotation curve (RC) of the Milky Way out to ˜ 100 kpc has been constructed using ˜ 16,000 primary red clump giants (PRCGs) in the outer disk selected from the LSS-GAC and the SDSS-III/APOGEE survey, combined with ˜ 5700 halo K giants (HKGs) selected from the SDSS/SEGUE survey. To derive the RC, the PRCG sample of the warm disc population and the HKG sample of halo stellar population are respectively analyzed using a kinematical model allowing for the asymmetric drift corrections and re-analyzed using the spherical Jeans equation along with measurements of the anisotropic parameter β currently available. The typical uncertainties of RC derived from the PRCG and HKG samples are respectively 5-7 km s-1 and several tens km s-1. We determine a circular velocity at the solar position, Vc(R0) = 240 ± 6 km s-1 and an azimuthal peculiar speed of the Sun, V⊙ = 12.1 ± 7.6 km s-1, both in good agreement with the previous determinations. The newly constructed RC has a generally flat value of 240 km s-1 within a Galactocentric distance r of 25 kpc and then decreases steadily to 150 km s-1 at r ˜ 100 kpc. On top of this overall trend, the RC exhibits two prominent localized dips, one at r ˜ 11 kpc and another at r ˜ 19 kpc. From the newly constructed RC, combined with other constraints, we have built a parametrized mass model for the Galaxy, yielding a virial mass of the Milky Way's dark matter halo of 0.90^{+0.07}_{-0.08} × 10^{12} M⊙ and a local dark matter density, ρ _{odot , dm} = 0.32^{+0.02}_{-0.02} GeV cm-3.

  15. Shifts of the Al-26 line due to Galactic rotation

    NASA Technical Reports Server (NTRS)

    Skibo, Jeff; Ramaty, Reuven

    1991-01-01

    The shape of the Al-26 line is evaluated using a Galactic disk rotation curve and assuming various galactic distributions of radioactive aluminum. The line shape depends on galactic longitude, detector opening angle, and the assumed aluminum distribution. For a detector of 20 deg aperture and 2.5 keV resolution, the shift of the line peak can be as large as 0.4 keV. Such a shift could be detected with the proposed nuclear astrophysics explorer.

  16. Alternative Gravity Rotation Curves for the LITTLE THINGS Survey

    NASA Astrophysics Data System (ADS)

    Stulge, Modestas; Stefanski, Brian; Dentico, Jeremy; O'Brien, James; Gay, Joseph; Moss, Robert; Young, Bryan; Smith, Adam

    2016-03-01

    Galactic rotation curves have proven to be the testing ground for dark matter bounds in spiral galaxies of all morphologies. Dwarf Galaxies serve as an increasingly interesting testing ground of rotation curve dynamics due to their increased stellar formation and typically rising rotation curve. These galaxies usually are not dominated by typical stellar structure and mostly terminate at small radial distances. This, coupled with the fact that Cold Dark Matter theories such as NFW (ΛCDM) struggle with the universality of galactic rotation curves, allow for exclusive features of alternative gravitational models to be analyzed. Recently, the THINGS (The HI Nearby Galactic Survey) has been extended to include a sample of 25 dwarf galaxies now known as the LITTLE THINGS Survey. Here, we present a thorough application of alternative gravitational models to the LITTLE THINGS survey, specifically focusing on MOND and Conformal Gravity. An analysis and discussion of the results of the fitting procedure of the two alternative gravitational models are explored. We posit here that both the Conformal Gravity and MOND can provide an accurate description of the galactic dynamics without the need for copious dark matter.

  17. Combined Solar system and rotation curve constraints on MOND

    NASA Astrophysics Data System (ADS)

    Hees, Aurélien; Famaey, Benoit; Angus, Garry W.; Gentile, Gianfranco

    2016-01-01

    The Modified Newtonian Dynamics (MOND) paradigm generically predicts that the external gravitational field in which a system is embedded can produce effects on its internal dynamics. In this communication, we first show that this external field effect (EFE) can significantly improve some galactic rotation curves fits by decreasing the predicted velocities of the external part of the rotation curves. In modified gravity versions of MOND, this EFE also appears in the Solar system and leads to a very good way to constrain the transition function of the theory. A combined analysis of the galactic rotation curves and Solar system constraints (provided by the Cassini spacecraft) rules out several classes of popular MOND transition functions, but leaves others viable. Moreover, we show that Laser Interferometer Space Antenna Pathfinder will not be able to improve the current constraints on these still viable transition functions.

  18. EFFECT OF DARK MATTER HALO SUBSTRUCTURES ON GALAXY ROTATION CURVES

    SciTech Connect

    Roy, Nirupam

    2010-11-01

    In this paper, the effect of halo substructures on galaxy rotation curves is investigated using a simple model of dark matter clustering. A dark matter halo density profile is developed based only on the scale-free nature of clustering that leads to a statistically self-similar distribution of the substructures at the galactic scale. A semi-analytical method is used to derive rotation curves for such a clumpy dark matter density profile. It is found that the halo substructures significantly affect the galaxy velocity field. Based on the fractal geometry of the halo, this self-consistent model predicts a Navarro-Frenk-White-like rotation curve and a scale-free power spectrum of the rotation velocity fluctuations.

  19. The rotation curves of gas and stars

    NASA Astrophysics Data System (ADS)

    Westfall, Kyle; Bershady, Matthew A.; MaNGA Team

    2016-01-01

    In its first year alone, the SDSS-IV/MaNGA survey has provided kinematic data useful for determining the rotation curves of both the ionized-gas and stellar components for hundreds of disk galaxies. We use these data to study the well-known Tully-Fisher relation in the local Universe, as well as the difference between the ionized-gas and stellar rotation curves in a novel study of asymmetric drift. The physical scenario for the latter is that gas efficiently dissipates energy allowing it to settle toward the circular speed of the galactic potential, whereas the stellar ensemble orbits more slowly because stars are collisionless and retain any non-circular motions accrued over their dynamical history. In disk galaxies with line-of-sight velocity dispersions that are well-measured with MaNGA's moderate spectral resolution, we demonstrate the correlation between asymmetric drift and stellar velocity dispersion, as expected by the dynamical relation between the two via the stellar phase-space distribution function. This correlation is consistent with measurements obtained at higher spectral resolution by the DiskMass Survey, and it allows us to leverage asymmetric drift to provide stellar velocity dispersion estimates that probe well below the instrumental dispersion. These velocity dispersion measurements can then be used to estimate the dynamical mass surface density of the baryon-dominated disk (Bershady et al. 2010, 2011). Thus, by combining our circular-speed data --- which yield a well-defined Tully-Fisher relation that is consistent with literature studies --- and our measurements of asymmetric drift, we discuss the implications for the dark-matter mass fractions of our galaxy sample. Statistically, our results are consistent with previous claims (e.g., Martinsson et al. 2013) that dark matter is a significant, even dominant, mass component within the effective radius of disk galaxies.

  20. Smoothing Rotation Curves in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Berrier, Joel C.; Sellwood, Jerry

    2014-05-01

    We present evidence that spiral activity is responsible for the creation of featureless rotation curves. We examine a variety of simulations of disk galaxies beginning in equilibrium and allow them to evolve while adding particles in annuli to the hot disk using a variety of rules. Two unstable spiral modes develop when this new material forms a ridge-like feature in the surface density profile of the disk. The extra material is redistributed radially by the spiral activity, and the associated angular momentum changes remove more particles from the ridge than are added to it. This process eventually removes the density feature from the galaxy and creates a locally flat rotation curve. We argue that the lack of a feature when transitioning from disk to halo dominance in the rotation curves of disk galaxies, the so called ``disk-halo conspiracy'', could also be accounted for by this mechanism.

  1. Stellar Rotation Curves of Starbursting Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    van Zee, Liese; Skillman, Evan D.; Salzer, John J.

    2001-02-01

    A year ago, we successfully completed a pilot project to obtain stellar rotation curves of starbursting dwarf galaxies. These observations provided the first spatially resolved stellar rotation curves of gas-rich dwarf galaxies. We now propose to expand our sample (by a factor of 2) by observing 4 additional dwarf galaxies with the CTIO 4m. The fundamental question to be addressed is whether the gas and stars are kinematically coupled in these small galaxies. These observations will place the first kinematic constraints on evolutionary models for dwarf galaxies.

  2. Observational evidence of dust evolution in galactic extinction curves

    SciTech Connect

    Cecchi-Pestellini, Cesare; Casu, Silvia; Mulas, Giacomo; Zonca, Alberto E-mail: silvia@oa-cagliari.inaf.it E-mail: azonca@oa-cagliari.inaf.it

    2014-04-10

    Although structural and optical properties of hydrogenated amorphous carbons are known to respond to varying physical conditions, most conventional extinction models are basically curve fits with modest predictive power. We compare an evolutionary model of the physical properties of carbonaceous grain mantles with their determination by homogeneously fitting observationally derived Galactic extinction curves with the same physically well-defined dust model. We find that a large sample of observed Galactic extinction curves are compatible with the evolutionary scenario underlying such a model, requiring physical conditions fully consistent with standard density, temperature, radiation field intensity, and average age of diffuse interstellar clouds. Hence, through the study of interstellar extinction we may, in principle, understand the evolutionary history of the diffuse interstellar clouds.

  3. SMOOTHING ROTATION CURVES AND MASS PROFILES

    SciTech Connect

    Berrier, Joel C.; Sellwood, J. A.

    2015-02-01

    We show that spiral activity can erase pronounced features in disk galaxy rotation curves. We present simulations of growing disks, in which the added material has a physically motivated distribution, as well as other examples of physically less realistic accretion. In all cases, attempts to create unrealistic rotation curves were unsuccessful because spiral activity rapidly smoothed away features in the disk mass profile. The added material was redistributed radially by the spiral activity, which was itself provoked by the density feature. In the case of a ridge-like feature in the surface density profile, we show that two unstable spiral modes develop, and the associated angular momentum changes in horseshoe orbits remove particles from the ridge and spread them both inward and outward. This process rapidly erases the density feature from the disk. We also find that the lack of a feature when transitioning from disk to halo dominance in the rotation curves of disk galaxies, the so called ''disk-halo conspiracy'', could also be accounted for by this mechanism. We do not create perfectly exponential mass profiles in the disk, but suggest that this mechanism contributes to their creation.

  4. Smoothing Rotation Curves and Mass Profiles

    NASA Astrophysics Data System (ADS)

    Berrier, Joel C.; Sellwood, J. A.

    2015-02-01

    We show that spiral activity can erase pronounced features in disk galaxy rotation curves. We present simulations of growing disks, in which the added material has a physically motivated distribution, as well as other examples of physically less realistic accretion. In all cases, attempts to create unrealistic rotation curves were unsuccessful because spiral activity rapidly smoothed away features in the disk mass profile. The added material was redistributed radially by the spiral activity, which was itself provoked by the density feature. In the case of a ridge-like feature in the surface density profile, we show that two unstable spiral modes develop, and the associated angular momentum changes in horseshoe orbits remove particles from the ridge and spread them both inward and outward. This process rapidly erases the density feature from the disk. We also find that the lack of a feature when transitioning from disk to halo dominance in the rotation curves of disk galaxies, the so called "disk-halo conspiracy," could also be accounted for by this mechanism. We do not create perfectly exponential mass profiles in the disk, but suggest that this mechanism contributes to their creation.

  5. Invariant rotational curves in Sitnikov's Problem

    NASA Astrophysics Data System (ADS)

    Martinez Alfaro, J.; Chiralt, Cristina

    1993-04-01

    The Sitnikov's Problem is a restricted three-body problem of celestial mechanics depending on the eccentricity, e. The Hamiltonian, H(z, v, t, e), does not depend on t if e = 0 and we have an integrable system; if e is small the KAM Theory proves the existence of invariant rotational curves, IRC. For larger eccentricities, we show that there exist two complementary sequences of intervals of values of e that accumulate to the maximum admissible value of the eccentricity, 1, and such that, for one of the sequences IRC around a fixed point persist. Moreover, they shrink to the plane z = 0 as e tends to 1.

  6. Equation for the Origin of Spiral Galactic Formation and Rotation

    NASA Astrophysics Data System (ADS)

    Brekke, Stewart

    2012-03-01

    Already formed galactic arms existed in sets of two or more orbiting each other due to the Big Bang. As the orbits of the arms decayed due to gravitational attraction they attached in their fore sections tangentially accreting forming spiral galaxies which began to rotate due to the transformation of the orbital motion of the pre-galactic arms into the rotational motion of the newly formed spiral galaxy. If I1φ1, I2φ2, and Inφn are the angular momentums of the pre-galactic arms, and (Iφ)galaxy is the angular momentum of the newly formed spiral galaxy, the equation for the formation and origin of spiral galaxy rotation is I1φ1+ I2φ2+...+ Inφn= (Iφgalaxy).

  7. Dissipative dark matter explains rotation curves

    NASA Astrophysics Data System (ADS)

    Foot, R.

    2015-06-01

    Dissipative dark matter, where dark matter particles interact with a massless (or very light) boson, is studied. Such dark matter can arise in simple hidden sector gauge models, including those featuring an unbroken U (1 )' gauge symmetry, leading to a dark photon. Previous work has shown that such models can not only explain the large scale structure and cosmic microwave background, but potentially also dark matter phenomena on small scales, such as the inferred cored structure of dark matter halos. In this picture, dark matter halos of disk galaxies not only cool via dissipative interactions but are also heated via ordinary supernovae (facilitated by an assumed photon-dark photon kinetic mixing interaction). This interaction between the dark matter halo and ordinary baryons, a very special feature of these types of models, plays a critical role in governing the physical properties of the dark matter halo. Here, we further study the implications of this type of dissipative dark matter for disk galaxies. Building on earlier work, we develop a simple formalism which aims to describe the effects of dissipative dark matter in a fairly model independent way. This formalism is then applied to generic disk galaxies. We also consider specific examples, including NGC 1560 and a sample of dwarf galaxies from the LITTLE THINGS survey. We find that dissipative dark matter, as developed here, does a fairly good job accounting for the rotation curves of the galaxies considered. Not only does dissipative dark matter explain the linear rise of the rotational velocity of dwarf galaxies at small radii, but it can also explain the observed wiggles in rotation curves which are known to be correlated with corresponding features in the disk gas distribution.

  8. Conformal Gravity Rotation Curves in Tidal Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    O'Brien, James

    2013-04-01

    We extend the application of the conformal gravity theory to tidal dwarf galaxies (TDGs). These dwarf galaxies are formed in the tidal tails of collisions of disk galaxies, and are thought to be predominantly composed of material expelled from the galactic disk of a parent galaxy. With any dark matter present in the parent galaxies expected to predominantly be in spherical haloes, tidal galaxies should thus have a very low dark matter content, and thus should not themselves be expected to possess the substantial spherical dark matter haloes that are ordinarily required to accompany and stabilize disk galaxies in standard gravity. In consequence, in the standard dark matter picture TDG rotation curves should not be expected to display any substantial mass discrepancies. Tidal dwarf galaxies thus provide a quite unusual laboratory for exploring the missing mass problem. Rotation curve data have become available for three TDGs associated with the parent galaxy NGC 5291, and it has been shown that there are in fact mass discrepancies, and that a good accounting of the data can be provided by MOND. Here we show that conformal gravity can also provide a good accounting of the data.

  9. Widespread rotationally hot hydronium ion in the galactic interstellar medium

    SciTech Connect

    Lis, D. C.; Phillips, T. G.; Schilke, P.; Comito, C.; Higgins, R. E-mail: tgp@submm.caltech.edu E-mail: ccomito@ph1.uni-koeln.de; and others

    2014-04-20

    We present new Herschel observations of the (6,6) and (9,9) inversion transitions of the hydronium ion toward Sagittarius B2(N) and W31C. Sensitive observations toward Sagittarius B2(N) show that the high, ∼500 K, rotational temperatures characterizing the population of the highly excited metastable H{sub 3}O{sup +} rotational levels are present over a wide range of velocities corresponding to the Sagittarius B2 envelope, as well as the foreground gas clouds between the Sun and the source. Observations of the same lines toward W31C, a line of sight that does not intersect the Central Molecular Zone but instead traces quiescent gas in the Galactic disk, also imply a high rotational temperature of ∼380 K, well in excess of the kinetic temperature of the diffuse Galactic interstellar medium. While it is plausible that some fraction of the molecular gas may be heated to such high temperatures in the active environment of the Galactic center, characterized by high X-ray and cosmic-ray fluxes, shocks, and high degree of turbulence, this is unlikely in the largely quiescent environment of the Galactic disk clouds. We suggest instead that the highly excited states of the hydronium ion are populated mainly by exoergic chemical formation processes and the temperature describing the rotational level population does not represent the physical temperature of the medium. The same arguments may be applicable to other symmetric top rotors, such as ammonia. This offers a simple explanation of the long-standing puzzle of the presence of a pervasive, hot molecular gas component in the central region of the Milky Way. Moreover, our observations suggest that this is a universal process not limited to the active environments associated with galactic nuclei.

  10. Spiral galaxy HI models, rotation curves and kinematic classifications

    NASA Astrophysics Data System (ADS)

    Wiegert, Theresa B. V.

    Although galaxy interactions cause dramatic changes, galaxies also continue to form stars and evolve when they are isolated. The dark matter (DM) halo may influence this evolution since it generates the rotational behaviour of galactic disks which could affect local conditions in the gas. Therefore we study neutral hydrogen kinematics of non-interacting, nearby spiral galaxies, characterising their rotation curves (RC) which probe the DM halo; delineating kinematic classes of galaxies; and investigating relations between these classes and galaxy properties such as disk size and star formation rate (SFR). To generate the RCs, we use GalAPAGOS (by J. Fiege). My role was to test and help drive the development of this software, which employs a powerful genetic algorithm, constraining 23 parameters while using the full 3D data cube as input. The RC is here simply described by a tanh-based function which adequately traces the global RC behaviour. Extensive testing on artificial galaxies show that the kinematic properties of galaxies with inclination >40 degrees, including edge-on galaxies, are found reliably. Using a hierarchical clustering algorithm on parametrised RCs from 79 galaxies culled from literature generates a preliminary scheme consisting of five classes. These are based on three parameters: maximum rotational velocity, turnover radius and outer slope of the RC. To assess the relationship between DM content and the kinematic classes, we generate mass models for 10 galaxies from the THINGS and WHISP surveys, and J. Irwin's sample. In most cases mass models using GalAPAGOS RCs were similar to those using traditional "tilted-ring'' method RCs. The kinematic classes are mainly distinguished by their rotational velocity. We confirm correlations between increasing velocity and B-magnitude, optical disk size, and find earlier type galaxies among the strong rotators. SFR also increases with maximum rotational velocity. Given our limited subsample, we cannot discern a

  11. SIMULATED FARADAY ROTATION MEASURES TOWARD HIGH GALACTIC LATITUDES

    SciTech Connect

    Akahori, Takuya; Kim, Jongsoo; Ryu, Dongsu; Gaensler, B. M. E-mail: akahori@physics.usyd.edu.au E-mail: ryu@canopus.cnu.ac.kr

    2013-04-20

    We study the Faraday rotation measure (RM) due to the Galactic magnetic field (GMF) toward high Galactic latitudes. The RM arises from the global, regular component as well as from the turbulent, random component of the GMF. We model the former based on observations and the latter using the data of magnetohydrodynamic turbulence simulations. For a large number of different GMF models, we produce mock RM maps around the Galactic poles and calculate various statistical quantities with the RM maps. We find that the observed medians of RMs toward the north and south Galactic poles, {approx}0.0 {+-} 0.5 rad m{sup -2} and {approx} + 6.3 {+-} 0.5 rad m{sup -2}, are difficult to explain with any of our many alternate GMF models. The standard deviation of observed RMs, {approx}9 rad m{sup -2}, is clearly larger than that of simulated RMs. The second-order structure function of observed RMs is substantially larger than that of simulated RMs, especially at small angular scales. We discuss other possible contributions to RM toward high Galactic latitudes. Besides observational errors and the intrinsic RM of background radio sources against which RM is observed, we suggest that the RM due to the intergalactic magnetic field may account for a substantial fraction of the observed RM. Finally, we note that reproducing the observed medians may require additional components or/and structures of the GMF that are not present in our models.

  12. Running Newton constant, improved gravitational actions, and galaxy rotation curves

    NASA Astrophysics Data System (ADS)

    Reuter, M.; Weyer, H.

    2004-12-01

    A renormalization group (RG) improvement of the Einstein-Hilbert action is performed which promotes Newton’s constant and the cosmological constant to scalar functions on spacetime. They arise from solutions of an exact RG equation by means of a “cutoff identification” which associates RG scales to the points of spacetime. The resulting modified Einstein equations for spherically symmetric, static spacetimes are derived and analyzed in detail. The modifications of the Newtonian limit due to the RG evolution are obtained for the general case. As an application, the viability of a scenario is investigated where strong quantum effects in the infrared cause Newton’s constant to grow at large (astrophysical) distances. For two specific RG trajectories exact vacuum spacetimes modifying the Schwarzschild metric are obtained by means of a solution-generating Weyl transformation. Their possible relevance to the problem of the observed approximately flat galaxy rotation curves is discussed. It is found that a power law running of Newton’s constant with a small exponent of the order 10-6 would account for their non-Keplerian behavior without having to postulate the presence of any dark matter in the galactic halo.

  13. Pulsar rotation and dispersion measures and the galactic magnetic field.

    NASA Technical Reports Server (NTRS)

    Manchester, R. N.

    1972-01-01

    Use of observations of pulsar polarization and pulse time of arrival at frequencies between 250 and 500 MHz to determine rotation and dispersion measures for 19 and 21 pulsars, respectively. These measurements have been used to calculate mean line-of-sight components of the magnetic field in the path to the pulsars. These and other observations show that there is probably no contribution to the observed rotation measure from the pulsar itself. Low-latitude, low-dispersion pulsars are observed to have strong field components, and a strong dependence of rotation-measure sign on galactic longitude has been found. The observations are consistent with a relatively uniform field of about 3.5 microgauss directed toward about l = 90 deg in the local region, but appear to be inconsistent with the helical model for the local field.

  14. Rotational Velocities of B Stars in the Outer Galactic Disk

    NASA Astrophysics Data System (ADS)

    Garmany, Catharine D.; Glaspey, J. W.; Bensby, T.; Daflon, S.; Cunha, K.; Oey, M. S.; Wolff, S. C.

    2010-01-01

    Metallicity gradients in the Milky Way disk are important constraints to models of chemical evolution and galaxy formation. As part of a long term project to better constrain the galactic metallicity gradient (Daflon & Cunha) we have obtained spectra of early B stars in the outer disk with the Magellan 6.5m (Clay) and MIKE double echelle spectrograph. We present herein a preliminary analysis of the projected rotational velocities (v sin i), for 150 early B stars in the third galactic quadrant. The stars were selected from the Case-Hamburg Catalog of Luminous Stars (Reed, 2005). Distances have been computed from the reddening-free Q parameter and published Mv values. We use the spectral type information in the catalog to further refine distances of the non-main sequence B stars in our sample. We have followed the method described by Daflon et al (2007) to estimate v sin i for these stars from their He I lines. These stars are primarily field B stars, with galactocentric distances between 8 and 16 kpc, and most of them lie outside dense clusters and associations. Our analysis will address two questions: 1) Is there any evidence for a difference in mean rotation rate as a function of galactocentric distance and/or metallicity; and 2) Do these stars have on average low rotation rates, as seem to characterize stars in the field and in expanding associations near the Sun (Wolff, et al. 2007).

  15. 11. DOUBLE CURVED RACK. UPPER PORTION ROTATES; LOWER PORTION REMAINS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. DOUBLE CURVED RACK. UPPER PORTION ROTATES; LOWER PORTION REMAINS STATIONARY. DISCARDED ROLLER NEAR CENTER OF FRAME. - Chicago, Milwaukee & St. Paul Railway, Bridge No. Z-6, Spanning North Branch of Chicago River, South of Cortland Street, Chicago, Cook County, IL

  16. The Surface Density Profile of the Galactic Disk from the Terminal Velocity Curve

    NASA Astrophysics Data System (ADS)

    McGaugh, Stacy S.

    2016-01-01

    The mass distribution of the Galactic disk is constructed from the terminal velocity curve and the mass discrepancy-acceleration relation. Mass models numerically quantifying the detailed surface density profiles are tabulated. For R0 = 8 kpc, the models have stellar mass 5 < M* < 6 × 1010 {M}⊙ , scale length 2.0 ≤ Rd ≤ 2.9 kpc, LSR circular velocity 222 ≤ Θ0 ≤ 233 {km} {{{s}}}-1, and solar circle stellar surface density 34 ≤ Σd(R0) ≤ 61 {M}⊙ {{pc}}-2. The present interarm location of the solar neighborhood may have a somewhat lower stellar surface density than average for the solar circle. The Milky Way appears to be a normal spiral galaxy that obeys scaling relations like the Tully-Fisher relation, the size-mass relation, and the disk maximality-surface brightness relation. The stellar disk is maximal, and the spiral arms are massive. The bumps and wiggles in the terminal velocity curve correspond to known spiral features (e.g., the Centaurus arm is a ˜50% overdensity). The rotation curve switches between positive and negative over scales of hundreds of parsecs. The rms amplitude {< {| {dV}/{dR}| }2> }1/2≈ 14 {km} {{{s}}}-1 {{kpc}}-1, implying that commonly neglected terms in the Jeans equations may be nonnegligible. The spherically averaged local dark matter density is ρ0,DM ≈ 0.009 {M}⊙ {{pc}}-3 (0.34 {GeV} {{cm}}-3). Adiabatic compression of the dark matter halo may help reconcile the Milky Way with the c-V200 relation expected in ΛCDM while also helping to mitigate the too-big-to-fail problem, but it remains difficult to reconcile the inner bulge/bar-dominated region with a cuspy halo. We note that NGC 3521 is a near twin to the Milky Way, having a similar luminosity, scale length, and rotation curve.

  17. On curve veering and flutter of rotating blades

    NASA Technical Reports Server (NTRS)

    Afolabi, Dare; Mehmed, Oral

    1993-01-01

    The eigenvalues of rotating blades usually change with rotation speed according to the Stodola-Southwell criterion. Under certain circumstances, the loci of eigenvalues belonging to two distinct modes of vibration approach each other very closely, and it may appear as if the loci cross each other. However, our study indicates that the observable frequency loci of an undamped rotating blade do not cross, but must either repel each other (leading to 'curve veering'), or attract each other (leading to 'frequency coalescence'). Our results are reached by using standard arguments from algebraic geometry--the theory of algebraic curves and catastrophe theory. We conclude that it is important to resolve an apparent crossing of eigenvalue loci into either a frequency coalescence or a curve veering, because frequency coalescence is dangerous since it leads to flutter, whereas curve veering does not precipitate flutter and is, therefore, harmless with respect to elastic stability.

  18. The distribution of dark and luminous matter inferred from extended rotation curves

    NASA Astrophysics Data System (ADS)

    Bottema, Roelof; Pestaña, José Luis G.

    2015-04-01

    A better understanding of the formation of mass structures in the Universe can be obtained by determining the amount and distribution of dark and luminous matter in spiral galaxies. To investigate such matters a sample of 12 galaxies, most with accurate distances, has been composed of which the luminosities are distributed regularly over a range spanning two and a half orders of magnitude. Of the observed high quality and extended rotation curves of these galaxies decompositions have been made, for four different schemes, each with two free parameters. For a `maximum disc fit' the rotation curves can be well matched, yet a large range of mass-to-light (M/L) ratios for the individual galaxies is required. For the alternative gravitational theory of MOND (Modified Newtonian Dynamics) the rotation curves can be explained if the fundamental parameter associated with MOND is allowed as a free parameter. Fixing that parameter leads to a disagreement between the predicted and observed rotation curves for a few galaxies. When cosmologically motivated NFW dark matter haloes are assumed, the rotation curves for the least massive galaxies can, by no means, be reproduced; cores are definitively preferred over cusps. Finally, decompositions have been made for a pseudo-isothermal halo combined with a universal M/L ratio. For the latter, the light of each galactic disc and bulge has been corrected for extinction and has been scaled by the effect of stellar population. This scheme can successfully explain the observed rotations and leads to submaximum disc mass contributions. Properties of the resulting dark matter haloes are described and a ratio between dark and baryonic mass of ˜9 for the least, and of ˜5, for the most luminous galaxies has been determined, at the outermost measured rotation.

  19. An Analytic Mathematical Model to Explain the Spiral Structure and Rotation Curve of NGC 3198

    NASA Astrophysics Data System (ADS)

    Rout, Bruce; Rout, Cameron

    2016-06-01

    An analytical model of galactic morphology is presented. This model presents resolutions to two inter-related parameters of spiral galaxies: one being the flat velocity rotation profile and the other being the spiral morphology of such galaxies. This model is a mathematical transformation dictated by the general theory of relativity applied to rotating polar coordinate systems that conserve the metric. The model shows that the flat velocity rotation profile and spiral shape of certain galaxies are both products of the general theory. Validation of the model is presented by application to 878 rotation curves provided by Salucci, and by comparing the results of a derived distance modulus to those using Cepheid variables, water masers and Tully-Fisher calculations. The model suggests means of determining galactic linear density, mass and angular momentum. We also show that the morphology of NGC 3198 is congruent to the geodesic as observed within a rotating reference frame and that galaxies are gravitationally viscous and self bound.

  20. Fourth order gravity, scalar-tensor-vector gravity, and galaxy rotation curves

    NASA Astrophysics Data System (ADS)

    Mishra, Priti; Singh, Tejinder P.

    2013-11-01

    The lambda-CDM model is the best fit to cosmological data and to the observed galactic rotation curves. However, in the absence of a direct detection of dark matter one should explore theories such as modified Newtonian dynamics (MOND), and perhaps also modified gravity theories like fourth order gravity and scalar-tensor-vector gravity (STVG) as possible explanations for the non-Keplerian behavior of galaxy rotation curves. STVG has a modified law for gravitational acceleration which attempts to fit data by fixing two free parameters. We show that, remarkably, the biharmonic equation which we get in the weak field limit of the field equations in a fourth order gravity theory implies a modification of Newtonian acceleration which is precisely of the same repulsive Yukawa form as in the STVG theory, and the corrections could in principle be large enough to try and explain the observed rotation curves. We also explain how our model provides a first principles understanding of MOND. We also show that STVG and fourth order gravity predict an acceleration parameter a0 whose value is of the same order as in MOND.

  1. Galaxy rotation curves from a fourth order gravity

    NASA Astrophysics Data System (ADS)

    Mishra, P.; Singh, T. P.

    2014-03-01

    While the standard and most popular explanation for the flatness of galaxy rotation curves is dark matter, one cannot at this stage rule out an explanation based on a modified law of gravitation, which agrees with Newtonian gravitation on the scale of the Solar system, but differs from it on larger length scales. Examples include Modfied Newtonian Dynamics (MOND) and Scalar-Tensor-Vector Gravity (STVG). Here, we have reported on a fourth order modification of the Poisson equation, which yields the same Yukawa type modification of Newtonian gravity as STVG, and which can explain flat galaxy rotation curves for a large sample of galaxies, once specific values for two parameters have been chosen. We have speculated on two possible origins for this modified Poisson equation: First, a possible fourth order modification of general relativity, and second, quadrupole gravitational polarization induced on a galaxy because of the pull of neighbouring galaxies.

  2. Dissipative dark matter and the rotation curves of dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Foot, R.

    2016-07-01

    There is ample evidence from rotation curves that dark matter halos around disk galaxies have nontrivial dynamics. Of particular significance are: a) the cored dark matter profile of disk galaxies, b) correlations of the shape of rotation curves with baryonic properties, and c) Tully-Fisher relations. Dark matter halos around disk galaxies may have nontrivial dynamics if dark matter is strongly self interacting and dissipative. Multicomponent hidden sector dark matter featuring a massless `dark photon' (from an unbroken dark U(1) gauge interaction) which kinetically mixes with the ordinary photon provides a concrete example of such dark matter. The kinetic mixing interaction facilitates halo heating by enabling ordinary supernovae to be a source of these `dark photons'. Dark matter halos can expand and contract in response to the heating and cooling processes, but for a sufficiently isolated halo could have evolved to a steady state or `equilibrium' configuration where heating and cooling rates locally balance. This dynamics allows the dark matter density profile to be related to the distribution of ordinary supernovae in the disk of a given galaxy. In a previous paper a simple and predictive formula was derived encoding this relation. Here we improve on previous work by modelling the supernovae distribution via the measured UV and Hα fluxes, and compare the resulting dark matter halo profiles with the rotation curve data for each dwarf galaxy in the LITTLE THINGS sample. The dissipative dark matter concept is further developed and some conclusions drawn.

  3. Li abundances in F stars: planets, rotation, and Galactic evolution

    NASA Astrophysics Data System (ADS)

    Delgado Mena, E.; Bertrán de Lis, S.; Adibekyan, V. Zh.; Sousa, S. G.; Figueira, P.; Mortier, A.; González Hernández, J. I.; Tsantaki, M.; Israelian, G.; Santos, N. C.

    2015-04-01

    Aims: We aim, on the one hand, to study the possible differences of Li abundances between planet hosts and stars without detected planets at effective temperatures hotter than the Sun, and on the other hand, to explore the Li dip and the evolution of Li at high metallicities. Methods: We present lithium abundances for 353 main sequence stars with and without planets in the Teff range 5900-7200 K. We observed 265 stars of our sample with HARPS spectrograph during different planets search programs. We observed the remaining targets with a variety of high-resolution spectrographs. The abundances are derived by a standard local thermodynamic equilibrium analysis using spectral synthesis with the code MOOG and a grid of Kurucz ATLAS9 atmospheres. Results: We find that hot jupiter host stars within the Teff range 5900-6300 K show lower Li abundances, by 0.14 dex, than stars without detected planets. This offset has a significance at the level 7σ, pointing to a stronger effect of planet formation on Li abundances when the planets are more massive and migrate close to the star. However, we also find that the average vsini of (a fraction of) stars with hot jupiters is higher on average than for single stars in the same Teff region, suggesting that rotational-induced mixing (and not the presence of planets) might be the cause for a greater depletion of Li. We confirm that the mass-metallicity dependence of the Li dip is extended towards [Fe/H] ~ 0.4 dex (beginning at [Fe/H] ~-0.4 dex for our stars) and that probably reflects the mass-metallicity correlation of stars of the same Teff on the main sequence. We find that for the youngest stars (<1.5 Gyr) around the Li dip, the depletion of Li increases with vsini values, as proposed by rotationally-induced depletion models. This suggests that the Li dip consists of fast rotators at young ages whereas the most Li-depleted old stars show lower rotation rates (probably caused by the spin-down during their long lifes). We have also

  4. The unexpected diversity of dwarf galaxy rotation curves

    NASA Astrophysics Data System (ADS)

    Oman, Kyle A.; Navarro, Julio F.; Fattahi, Azadeh; Frenk, Carlos S.; Sawala, Till; White, Simon D. M.; Bower, Richard; Crain, Robert A.; Furlong, Michelle; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

    2015-10-01

    We examine the circular velocity profiles of galaxies in Λ cold dark matter (CDM) cosmological hydrodynamical simulations from the EAGLE and LOCAL GROUPS projects and compare them with a compilation of observed rotation curves of galaxies spanning a wide range in mass. The shape of the circular velocity profiles of simulated galaxies varies systematically as a function of galaxy mass, but shows remarkably little variation at fixed maximum circular velocity. This is especially true for low-mass dark-matter-dominated systems, reflecting the expected similarity of the underlying CDM haloes. This is at odds with observed dwarf galaxies, which show a large diversity of rotation curve shapes, even at fixed maximum rotation speed. Some dwarfs have rotation curves that agree well with simulations, others do not. The latter are systems where the inferred mass enclosed in the inner regions is much lower than expected for CDM haloes and include many galaxies where previous work claims the presence of a constant density `core'. The `cusp versus core' issue is thus better characterized as an `inner mass deficit' problem than as a density slope mismatch. For several galaxies, the magnitude of this inner mass deficit is well in excess of that reported in recent simulations where cores result from baryon-induced fluctuations in the gravitational potential. We conclude that one or more of the following statements must be true: (i) the dark matter is more complex than envisaged by any current model; (ii) current simulations fail to reproduce the diversity in the effects of baryons on the inner regions of dwarf galaxies; and/or (iii) the mass profiles of `inner mass deficit' galaxies inferred from kinematic data are incorrect.

  5. The Luminous Convolution Model for Galaxy Rotation Curves

    NASA Astrophysics Data System (ADS)

    Rubin, Shanon; Mucci, Maria; Sophia Cisneros Collaboration; Kennard Chng Collaboration; Meagan Crowley Collaboration

    2016-03-01

    The LCM takes as input only the observed luminous matter profile from galaxies, and allows us to confirm these observed data by considering frame-dependent effects from the luminous mass profile of the Milky Way. The LCM is useful when looking at galaxies that have similar total enclosed mass, but varying distributions. For example, variations in luminous matter profiles from a diffuse galaxy correlate to the LCM's five different Milky Way models equally well, but LCM fits for a centrally condensed galaxy distinguish between Milky Way models. In this presentation, we show how the rotation curve data of such galaxies can be used to constrain the Milky Way luminous mass modeling, by the physical characteristics of each galaxy used to interpret the fitting. Current Investigations will be presented showing how the convolved parameters of Keplerian predictions with rotation curve observations can be extracted with respect to the crossing location of the relative curvature versus the assumption of the luminous mass profiles from photometry. Since there currently exists no direct constraint to photometric estimates of the luminous mass in these systems, the LCM gives the first constraint based on the orthogonal measurement of Doppler shifted spectra from characteristic emitters.

  6. Conformal Gravity rotation curves with a conformal Higgs halo

    NASA Astrophysics Data System (ADS)

    Horne, Keith

    2016-06-01

    We discuss the effect of a conformally coupled Higgs field on conformal gravity (CG) predictions for the rotation curves of galaxies. The Mannheim-Kazanas (MK) metric is a valid vacuum solution of CG's fourth-order Poisson equation if and only if the Higgs field has a particular radial profile, S(r) = S0 a/(r + a), decreasing from S0 at r = 0 with radial scalelength a. Since particle rest masses scale with S(r)/S0, their world lines do not follow time-like geodesics of the MK metric gμν, as previously assumed, but rather those of the Higgs-frame MK metric tilde{g}_{μ ν }=Ω ^2 g_{μ ν }, with the conformal factor Ω(r) = S(r)/S0. We show that the required stretching of the MK metric exactly cancels the linear potential that has been invoked to fit galaxy rotation curves without dark matter. We also formulate, for spherical structures with a Higgs halo S(r), the CG equations that must be solved for viable astrophysical tests of CG using galaxy and cluster dynamics and lensing.

  7. Rapidly rotating lenses: repeating features in the light curves of short-period binary microlenses

    NASA Astrophysics Data System (ADS)

    Penny, Matthew T.; Kerins, Eamonn; Mao, Shude

    2011-11-01

    Microlensing is most sensitive to binary lenses with relatively large orbital separations, and as such, typical binary microlensing events show little or no orbital motion during the event. However, despite the strength of binary microlensing features falling off rapidly as the lens separation decreases, we show that it is possible to detect repeating features in the light curve of binary microlenses that complete several orbits during the microlensing event. We investigate the light-curve features of such rapidly rotating lens (RRL) events. We derive analytical limits on the range of parameters where these effects are detectable, and confirm these numerically. Using a population synthesis Galactic model, we estimate the RRL event rate for a ground-based and a space-based microlensing survey to be 0.32fb and 7.8fb events per year, respectively, assuming year-round monitoring, where fb is the binary fraction. We detail how RRL event parameters can be quickly estimated from their light curves, and suggest a method to model RRL events using timing measurements of light-curve features. Modelling RRL light curves will yield the lens orbital period and possibly measurements of all orbital elements, including the inclination and eccentricity. Measurement of the period from the light curve allows a mass-distance relation to be defined, which when combined with a measurement of microlens parallax or finite-source effects can yield a mass measurement to a twofold degeneracy. With sub-per cent accuracy photometry, it is possible to detect planetary companions, but the likelihood of this is very small.

  8. Rotating Type Ia SN progenitors: explosion and light curves

    SciTech Connect

    Dominguez, I.; Piersanti, L.; Gagliardi, S.; Straniero, O.; Tornambe, A.; Bravo, E.

    2005-10-21

    High redshift SNe Ia have been recently used to calibrate the cosmological distance scale and to infer the existence of the dark energy. The reliability of such a method depends on the effective knowledge of the absolute brightness of this class of supernovae. This would require a complete understanding of the physics of SNeIa.Starting from an accreting rotating white dwarf, the only progenitor that we found to be able to grow till the Chandrasekhar mass and undergo a thermonuclear explosion, we simulate the explosion, deriving the nucleosynthesis and the light curve. We explore the final outcome in the framework of a 1D delayed detonation model, where the characteristic density for which the transition from deflagration to detonation takes place is a free parameter.Although preliminary, our results imply that rotating white dwarfs produce a range of explosive conditions, characterized by different ignition densities and total masses. Maximum luminosities of successfully explosive models differ up to 0.11 mag. In a few cases, the formation of a small highly neutronised remnant is found.

  9. Kinematic Disturbances in Rotation Curves among 89 Virgo Galaxies

    NASA Astrophysics Data System (ADS)

    Rubin, V. C.; Waterman, A. H.; Kenney, J. D. P.

    1999-05-01

    For 89 (mostly) spirals in the Virgo cluster, we have obtained optical long-slit spectra of the ionized gas. We find: (1) 50% of the Virgo galaxies we observed have regular rotation patterns; 50% exhibit kinematic disturbances ranging from mild to major. Velocity complexities are consistent with those resulting from tidal encounters or accretion. Since kinematic disturbances will to fade within ~ 1Gyr, many Virgo galaxies have experienced several significant kinematic disturbances during their lifetimes. (2) There is no strong correlation of rotation curve complexity with Hubble type, galaxy luminosity, local galaxy density, or HI deficiency. (3) There is a remarkable difference in the distribution of galaxy systemic velocity for galaxies in the two classes. Galaxies with regular rotation patterns show a flat distribution with velocities ranging from V = -300 km/sec to V = +2500 km/sec; galaxies with disturbed kinematics have a Gaussian distribution which peaks at V = +1172+/-100 km/sec, near the cluster mean velocity. This distribution is virtually identical to the distribution of systemic velocities for elliptical galaxies in Virgo. However, disturbed spirals are less centrally concentrated than the ellipticals and those near the periphery are more likely to have the mean cluster velocity. We suggest that spirals with disturbed kinematics are preferentially on radial orbits, which bring them to the denser core, where tidal interactions are strong and/or more common. However, because they spend most of their time near apocenter, we observe them near the periphery of the cluster. Some may be falling into the core for the first time. For a non-virialized cluster like Virgo, galaxies may encounter either local (nearby galaxies) or global (cluster related) interactions. These interactions may alter the galaxy morphology, and may play a role in driving the Virgo cluster toward dynamical equilibrium.

  10. Rotation curve of the Milky Way out to ∼200 kpc

    SciTech Connect

    Bhattacharjee, Pijushpani; Chaudhury, Soumini; Kundu, Susmita E-mail: soumini.chaudhury@saha.ac.in

    2014-04-10

    The rotation curve (RC) of our Galaxy, the Milky Way, is constructed starting from its very inner regions (few hundred parsecs) out to a large galactocentric distance of ∼200 kpc using kinematical data on a variety of tracer objects moving in the gravitational potential of the Galaxy, without assuming any theoretical models of the visible and dark matter (DM) components of the Galaxy. We study the effect on the RC due to the uncertainties in the values of the Galactic constants (GCs) R {sub 0} and V {sub 0} (these being the Sun's distance from and circular rotation speed around the Galactic center, respectively) and the velocity anisotropy parameter β of the halo tracer objects used for deriving the RC at large galactocentric distances. The resulting RC in the disk region is found to depend significantly on the choice of the GCs, while the dominant uncertainty in the RC at large distances beyond the stellar disk comes from the uncertainty in the value of β. In general we find that the mean RC steadily declines at distances beyond ∼60 kpc, independently of the value of β. Also, at a given radius, the circular speed is lower for larger values of β (i.e., for more radially biased velocity anisotropy). Considering that the largest possible value of β is unity, which corresponds to stellar orbits being purely radial, our results for the case of β = 1 give a lower limit to the total mass of the Galaxy within ∼200 kpc, M(200 kpc) ≳ (6.8 ± 4.1) × 10{sup 11} M {sub ☉}, independently of any model of the DM halo of the Galaxy.

  11. Extraction of Rotational Velocities from Optical Rotation Curves of Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Catinella, B.; Haynes, M. P.; Giovanelli, R.

    2002-12-01

    Long-slit spectra of spiral galaxies are widely used to complement 21 cm HI observations, providing rotational velocity widths for the application of the Tully-Fisher (TF) relation. The accuracy of the velocity width measurement is of a key importance for a TF-based peculiar velocity (PV) survey, being the single dominant contribution to the TF error budget (besides the intrinsic scatter). We have used a large database of H-alpha optical rotation curves (ORCs), HI-line profiles, and I-band photometry designed for PV studies to investigate the errors and systematics associated with the velocity width measurement. A detailed comparison between different methods of measuring velocity widths from ORCs shows the importance of taking the ORC shape into account. In particular, estimating a line width from the ORC velocity histogram alone introduces systematic errors that correlate with the slope of the outer regions of the ORC. We have also studied the dependence of the extent of the H-alpha emission on the HI deficiency, a measure of the HI content. We find that HI-poor disks also appear to be H-alpha-truncated. Since rotation curves are typically rising in the outer regions of the disks, the optical histogram widths of HI-deficient galaxies are therefore systematically underestimated compared to the ones of HI-normal galaxies. A more reliable width estimate can be obtained by fitting a function to the ORC and measuring the velocity at a fixed metric distance from the center of the disk. Rotational widths measured in this way can account for systematic and environmental effects. This work has been supported by NSF grant AST99-00695.

  12. Changing Amplitudes: Detecting RR Lyrae Light Curve Shape Variations in the Galactic Disk and Inner Halo

    NASA Astrophysics Data System (ADS)

    De Lee, Nathan M.; Kinemuchi, K.; Pepper, J.; Rodriguez, J. E.

    2014-01-01

    In this poster we will discuss our ongoing program to use extant light curves from the Kilodegree Extremely Little Telescope (KELT) survey to find and characterize RR Lyrae (RRL) stars in the disk and inner halo of the Milky Way. RRL stars are of particular interest because they are standard candles and can be used to map out structure in the galaxy. The periods and shape of RRL light curves also contain information about their Oosterhoff type, which can probe galactic formation history, and metallicity respectively. Although there have been several large photometric surveys for RR Lyrae in the nearby galaxy (OGLE, NSVS, ASAS, and MACHO to name a few), they have each been limited in either sky coverage or number of epochs. The KELT survey represents a new generation of surveys that has many epochs over a large portion of the sky. KELT samples 60% of the sky in both northern and southern hemispheres, and has a long-time-baseline of 4-8 years with a very high cadence rate of less than 20 minutes. This translates into 4,000 to 9,000 epochs per light curve with completeness out to 3 kpc from the Sun. Recent results from both Kepler and ground based surveys results suggest that as many as 50% of RR Lyrae stars show long-term modulation of their light curve shapes (Blazhko effect). These stars combined with RRL stars that pulsate in more than one mode give a sample of objects that the KELT survey is uniquely suited to explore. This poster concentrates on a pilot project to examine RRL stars in a limited number of KELT fields. In particular, we focus on, detecting RR Lyrae, developing a light curve shape-metallicity relationship in the KELT band-pass, and some initial characterization of RRL with either amplitude-modulated or period-modulated light curves.

  13. Observational tests of nonlocal gravity: Galaxy rotation curves and clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Rahvar, S.; Mashhoon, B.

    2014-05-01

    A classical nonlocal generalization of Einstein's theory of gravitation has recently been developed via the introduction of a scalar causal "constitutive" kernel that must ultimately be determined from observational data. It turns out that the nonlocal aspect of gravity in this theory can simulate dark matter; indeed, in the Newtonian regime of nonlocal gravity, we recover the phenomenological Tohline-Kuhn approach to modified gravity. A simple generalization of the Kuhn kernel in the context of nonlocal general relativity leads to a two-parameter modified Newtonian force law that involves an additional repulsive Yukawa-type interaction. We determine the parameters of our nonlocal kernel by comparing the predictions of the theory with observational data regarding the rotation curves of spiral galaxies. The best-fitting stellar mass-to-light ratio turns out to be in agreement with astrophysical models; moreover, our results are consistent with the Tully-Fisher relation for spiral galaxies. Light deflection in nonlocal gravity is consistent with general relativity at solar-system scales, while beyond galactic scales, an enhanced deflection angle is predicted that is compatible with lensing by the effective "dark matter." Furthermore, we extend our results to the internal dynamics of rich clusters of galaxies and show that the dynamical mass of the cluster obtained from nonlocal gravity is consistent with the measured baryonic mass.

  14. On the dynamics of Armbruster Guckenheimer Kim galactic potential in a rotating reference frame

    NASA Astrophysics Data System (ADS)

    Elmandouh, A. A.

    2016-06-01

    In this article, we are interested in studying some dynamics aspects for the Armbruster Guckenheimer Kim galactic potential in a rotating reference frame. We introduce a non-integrability condition for this problem using Painlevé analysis. The equilibrium positions are given and their stability is studied. Furthermore, we prove the force resulting from the rotation of the reference frame can be used to stabilize the unstable maximum equilibrium positions. The periodic solutions near the equilibrium positions are constructed by applying Lyapunov method. The permitted region of motion is determined.

  15. Correlation Analysis of Optical and Radio Light Curves for a Large Sample of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Clements, S. D.; Smith, A. G.; Aller, H. D.; Aller, M. F.

    1995-08-01

    The Rosemary Hill Observatory has accumulated internally consistent light curves extending over as much as 26 years for a large sample of active galactic nuclei. Forty-six of these optical records have been compared with similar radio records from the University of Michigan Radio Astronomy Observatory and the Algonquin Radio Observatory. For 18 objects, pairs of records were sufficiently long and unconfused to allow reliable application of the Discrete Correlation Function analysis; this group included 8 BL Lacertids, 8 quasars, and 2 Seyfert galaxies. Nine of the 18 sources showed positive radio-optical correlations, with the radio events lagging the optical by intervals ranging from 0 to 14 months. Consistent with the relativistic beaming model of the BL Lacertids, the group displaying correlations was dominated by this type of object.

  16. Rotation vectors for homeomorphisms of non-positively curved manifolds

    NASA Astrophysics Data System (ADS)

    Lessa, Pablo

    2011-11-01

    Rotation vectors, as defined for homeomorphisms of the torus that are isotopic to the identity, are generalized to such homeomorphisms of any complete Riemannian manifold with non-positive sectional curvature. These generalized rotation vectors are shown to exist for almost every orbit of such a dynamical system with respect to any invariant measure with compact support. The concept is then extended to flows and, as an application, it is shown how non-null rotation vectors can be used to construct a measurable semi-conjugacy between a given flow and the geodesic flow of a manifold.

  17. Comment on 'Scalar-tensor gravity coupled to a global monopole and flat rotation curves'

    SciTech Connect

    Salucci, P.; Gentile, G.

    2006-06-15

    The recent paper by Lee and Lee [Phys. Rev. D 69, 127502 (2004)] may strongly leave the impression that astronomers have established that the rotation curves of spiral galaxies are flat. We show that the old paradigm of flat rotation curves lacks, today, any observational support and following it at face value leads to intrinsically flawed alternatives to the standard dark matter scenario. On the other hand, we claim that the rich systematics of spiral galaxy rotation curves, which reveals, in the standard Newtonian gravity framework, the phenomenon of dark matter, in alternative scenarios, works as a unique benchmark.

  18. Light-curve solutions for S Cancri and TT Hydrae with rapid rotation

    NASA Technical Reports Server (NTRS)

    Van Hamme, W.; Wilson, R. E.

    1993-01-01

    Physical model light- and velocity-curve solutions for S Cancri and TT Hydrae are obtained, and analyses with incorporation of asynchronous rotation are carried out. A photometric rotation rate for the primary star of TT Hya is determined, and excellent agreement with results from spectral line profiles is found. Both separate light- and velocity-curve solutions and simultaneous light-velocity solutions are listed. The photometric rotation for S Cnc from existing light curves is indeterminate, but is compatible with line profile measures. Evidence for third light from the light curves of S Cnc is found. An explanation for the apparent conflict between the rotational states and mass-transfer activities of the two binaries is suggested.

  19. ELECTROKINETIC PHENOMENA : VII. RELATIONSHIP BETWEEN ELECTRIC MOBILITY, CHARGE, TITRATION CURVE, AND OPTICAL ROTATION OF PROTEIN.

    PubMed

    Abramson, H A; Grossman, E B

    1932-05-20

    The specific rotation of egg albumin, gliadin, and gelatin (40 degrees C.) is discussed in connection with available data on (a) mobility, (b) titration curve, and (c) osmotic pressure. It seems likely that the change in specific rotation with pH of protein solutions is proportional to the change in net charge. PMID:19872669

  20. The Rotation and Galactic Kinematics of Mid M Dwarfs in the Solar Neighborhood

    NASA Astrophysics Data System (ADS)

    Newton, Elisabeth R.; Irwin, Jonathan; Charbonneau, David; Berta-Thompson, Zachory K.; Dittmann, Jason A.; West, Andrew A.

    2016-04-01

    Rotation is a directly observable stellar property, and it drives magnetic field generation and activity through a magnetic dynamo. Main-sequence stars with masses below approximately 0.35 {M}ȯ (mid-to-late M dwarfs) are fully convective, and are expected to have a different type of dynamo mechanism than solar-type stars. Measurements of their rotation rates provide insight into these mechanisms, but few rotation periods are available for these stars at field ages. Using photometry from the MEarth Project, we measure rotation periods for 387 nearby, mid-to-late M dwarfs in the northern hemisphere, finding periods from 0.1 to 140 days. The typical rotator has stable, sinusoidal photometric modulations at a semi-amplitude of 0.5%–1%. We find no period–amplitude relation for stars below 0.25 {M}ȯ and an anticorrelation between period and amplitude for higher-mass M dwarfs. We highlight the existence of older, slowly rotating stars without Hα emission that nevertheless have strong photometric variability. We use parallaxes, proper motions, radial velocities, photometry, and near-infrared metallicity estimates to further characterize the population of rotators. The Galactic kinematics of our sample is consistent with the local population of G and K dwarfs, and rotators have metallicities characteristic of the solar neighborhood. We use the W space velocities and established age–velocity relations to estimate that stars with P < 10 days have ages of on average <2 Gyr, and that those with P > 70 days have ages of about 5 Gyr. The period distribution is dependent on mass: as the mass decreases, the slowest rotators at a given mass have longer periods, and the fastest rotators have shorter periods. We find a lack of stars with intermediate rotation periods, and the gap between the fast and slow rotators is larger for lower masses. Our data are consistent with a scenario in which these stars maintain rapid rotation for several gigayears, then spin down quickly

  1. Reverberation mapping the dusty torus in Active Galactic Nuclei using Spitzer and optical light curves

    NASA Astrophysics Data System (ADS)

    Robinson, Andrew

    Dusty molecular tori play a central role in unification models for active galactic nuclei (AGN) and are also the dominant source of their mid-IR emission. Our limited knowledge of the size and structure of AGN tori and how these properties vary with luminosity hinders our ability to understand the observed spectral energy distribution and hence AGN demographics. Ultimately this inhibits our ability to understand the obscured AGN population and the cosmic evolution of super-massive black holes. Although the torus is, in general, inaccessible to direct imaging, its properties can be studied by analyzing the time response of the dust emission from the torus with respect to variations in the AGN continuum luminosity; a technique known as reverberation mapping. With this goal, we have completed a 2.5-year monitoring campaign on 12 broad-line AGN, using the Spitzer Space Telescope supported by ground-based optical observations, to measure the temporal response of thetorus 3.5 and 4.6μm mid-IR dust emission to variations in the AGN UV/optical continuum. The data obtained from the first 1.5 years in Spitzer Cycle 8 have been analysed. The aim of this project is to complete the time series analysis of the complete 2.5 year light curves, and to model these light curves in order extract structural and physical information contained in data, such as the size of the torus, its radial depth, opening angle, inclination and dust composition. This project will help to maximize the scientific returns on a significant investment of Spitzer Space Telescope time and supports the NASA strategic goal to "explore the origin and evolution of the galaxies, stars and planets that make up our universe".

  2. DARK MATTER, MAGNETIC FIELDS, AND THE ROTATION CURVE OF THE MILKY WAY

    SciTech Connect

    Ruiz-Granados, B.; Battaner, E.; Florido, E.; Calvo, J.; Rubino-Martin, J. A.

    2012-08-20

    The study of the disk rotation curve of our Galaxy at large distances provides an interesting scenario for us to test whether magnetic fields should be considered as a non-negligible dynamical ingredient. By assuming a bulge, an exponential disk for the stellar and gaseous distributions, and a dark halo and disk magnetic fields, we fit the rotation velocity of the Milky Way. In general, when the magnetic contribution is added to the dynamics, a better description of the rotation curve is obtained. Our main conclusion is that magnetic fields should be taken into account for the Milky Way dynamics. Azimuthal magnetic field strengths of B{sub {phi}} {approx} 2 {mu}G at distances of {approx}2 R{sub 0}(16 kpc) are able to explain the rise-up for the rotation curve in the outer disk.

  3. ROTATIONAL PROPERTIES OF JUPITER TROJANS. I. LIGHT CURVES OF 80 OBJECTS

    SciTech Connect

    Mottola, Stefano; Erikson, Anders; Gonano-Beurer, Maria; Carsenty, Uri; Hahn, Gerhard; Di Martino, Mario; Carbognani, Albino; Schober, Hans-Josef; Lahulla, Felix; Delbo, Marco; Lagerkvist, Claes-Ingvar

    2011-05-15

    We present the results of a Jupiter Trojans' light curve survey aimed at characterizing the rotational properties of Trojans in the approximate size range 60-150 km. The survey, which was designed to provide reliable and unbiased estimates of rotation periods and amplitudes, resulted in light curves for a total of 80 objects, 56 of which represent the first determinations published to date and nine of which supersede previously published erroneous values. Our results more than double the size of the existing database of rotational properties of Jovian Trojans in the selected size range. The analysis of the distributions of the rotation periods and light curve amplitudes is the subject of companion papers.

  4. Rotational Properties of Jupiter Trojans. I. Light Curves of 80 Objects

    NASA Astrophysics Data System (ADS)

    Mottola, Stefano; Di Martino, Mario; Erikson, Anders; Gonano-Beurer, Maria; Carbognani, Albino; Carsenty, Uri; Hahn, Gerhard; Schober, Hans-Josef; Lahulla, Felix; Delbò, Marco; Lagerkvist, Claes-Ingvar

    2011-05-01

    We present the results of a Jupiter Trojans' light curve survey aimed at characterizing the rotational properties of Trojans in the approximate size range 60-150 km. The survey, which was designed to provide reliable and unbiased estimates of rotation periods and amplitudes, resulted in light curves for a total of 80 objects, 56 of which represent the first determinations published to date and nine of which supersede previously published erroneous values. Our results more than double the size of the existing database of rotational properties of Jovian Trojans in the selected size range. The analysis of the distributions of the rotation periods and light curve amplitudes is the subject of companion papers.

  5. A SURVEY OF EXTRAGALACTIC FARADAY ROTATION AT HIGH GALACTIC LATITUDE: THE VERTICAL MAGNETIC FIELD OF THE MILKY WAY TOWARD THE GALACTIC POLES

    SciTech Connect

    Mao, S. A.; Gaensler, B. M.; Madsen, G. J.; Haverkorn, M.; Zweibel, E. G.; McClure-Griffiths, N. M.; Shukurov, A.; Kronberg, P. P.

    2010-05-10

    We present a study of the vertical magnetic field of the Milky Way toward the Galactic poles, determined from observations of Faraday rotation toward more than 1000 polarized extragalactic radio sources at Galactic latitudes |b| {>=} 77{sup 0}, using the Westerbork Radio Synthesis Telescope and the Australia Telescope Compact Array. We find median rotation measures (RMs) of 0.0 {+-} 0.5 rad m{sup -2} and +6.3 {+-} 0.7 rad m{sup -2} toward the north and south Galactic poles, respectively, demonstrating that there is no coherent vertical magnetic field in the Milky Way at the Sun's position. If this is a global property of the Milky Way's magnetism, then the lack of symmetry across the disk rules out pure dipole or quadrupole geometries for the Galactic magnetic field. The angular fluctuations in RM seen in our data show no preferred scale within the range {approx}0.{sup 0}1 to {approx}25{sup 0}. The observed standard deviation in RM of {approx}9 rad m{sup -2} then implies an upper limit of {approx}1 {mu}G on the strength of the random magnetic field in the warm ionized medium at high Galactic latitudes.

  6. Beryllium in the Galactic halo - Surface abundances from standard, diffusive, and rotational stellar evolution, and implications

    NASA Technical Reports Server (NTRS)

    Deliyannis, Constantine P.; Pinsonneault, Marc H.

    1990-01-01

    The recently observed upper limits to the beryllium abundances in population II stars are much lower than population I detections. This difference reflects an intrinsic difference in the initial abundances and is not caused by different degrees of depletion driven by stellar evolution processes from similar initial abundances. Evolutionary sequences of models from the early premain sequence to beyond the turnoff that correspond to halo dwarfs with Fe/H abundances of -1.3, -2.3, and -3.3 are constructed, and standard, diffusive, and rotational mechanisms are used to estimate a maximal possible beryllium depletion. Halo star models in the T(eff) range 6000 to 5000 K might be rotationally depleted by a factor of 1.5-2, and the total depletion should be no more than (conservatively) a factor of 3. Implications for cosmology, cosmic-ray theory, and Galactic chemical evolution are discussed.

  7. NEW CONSTRAINTS ON THE GALACTIC HALO MAGNETIC FIELD USING ROTATION MEASURES OF EXTRAGALACTIC SOURCES TOWARD THE OUTER GALAXY

    SciTech Connect

    Mao, S. A.; McClure-Griffiths, N. M.; Gaensler, B. M.; Brown, J. C.; Van Eck, C. L.; Stil, J. M.; Taylor, A. R.; Haverkorn, M.; Kronberg, P. P.; Shukurov, A.

    2012-08-10

    We present a study of the Milky Way disk and halo magnetic field, determined from observations of Faraday rotation measure (RM) toward 641 polarized extragalactic radio sources in the Galactic longitude range 100 Degree-Sign -117 Degree-Sign , within 30 Degree-Sign of the Galactic plane. For |b| < 15 Degree-Sign , we observe a symmetric RM distribution about the Galactic plane. This is consistent with a disk field in the Perseus arm of even parity across the Galactic mid-plane. In the range 15 Degree-Sign < |b| < 30 Degree-Sign , we find median RMs of -15 {+-} 4 rad m{sup -2} and -62 {+-} 5 rad m{sup -2} in the northern and southern Galactic hemispheres, respectively. If the RM distribution is a signature of the large-scale field parallel to the Galactic plane, then this suggests that the halo magnetic field toward the outer Galaxy does not reverse direction across the mid-plane. The variation of RM as a function of Galactic latitude in this longitude range is such that RMs become more negative at larger |b|. This is consistent with an azimuthal magnetic field of strength 2 {mu}G (7 {mu}G) at a height 0.8-2 kpc above (below) the Galactic plane between the local and the Perseus spiral arm. We propose that the Milky Way could possess spiral-like halo magnetic fields similar to those observed in M51.

  8. Invariant curves for exact symplectic twist maps of the cylinder with Bryuno rotation numbers

    NASA Astrophysics Data System (ADS)

    Gentile, Guido

    2015-07-01

    Since Moser's seminal work it is well known that the invariant curves of smooth nearly integrable twist maps of the cylinder with Diophantine rotation number are preserved under perturbation. In this paper we show that, in the analytic class, the result extends to Bryuno rotation numbers. First, we will show that the series expansion for the invariant curves in powers of the perturbation parameter can be formally defined, then we shall prove that the series converges absolutely in a neighbourhood of the origin. This will be achieved using multiscale analysis and renormalisation group techniques to express the coefficients of the series as sums of values which are represented graphically as tree diagrams and then exploit cancellations between terms contributing to the same perturbation order. As a byproduct we shall see that, when perturbing linear maps, the series expansion for an analytic invariant curve converges for all perturbations if and only if the corresponding rotation number satisfies the Bryuno condition.

  9. Determination of the Light Curve of the Artificial Satellite by its Rotation Path as Preparation to the Inverse Problem Solution

    NASA Astrophysics Data System (ADS)

    Pavlenko, Daniil

    Developing the algorithm of estimation of the rotational parameters of the artificial satellite by its light curve, we face the necessity to compute test light curves for various initially given types of rotation and specific features of lighting of the satellite. In the present study the algorithm of creation of such light curves with the simulation method and the obtained result are described.

  10. Flat rotation curve without dark matter: the generalized Newton's law of gravitation

    NASA Astrophysics Data System (ADS)

    Arbab, A. I.

    2015-02-01

    We have shown that flat rotation curve in the framework of the generalized Newton's law of gravitation need not require dark matter. The generalized Newton's force gives rise to logarithmic potential energy at large distances from the center of the galaxy. The effect of the gravitomagnetic force is to induce the constant velocity pattern observed in flat rotation curve at very large distances from the center of the galaxy. Dynamical matter arising from moving stars far away from the center of the galaxy is shown to provide a great part to the total mass of the galaxy.

  11. On the nature of local instabilities in rotating galactic coronae and cool cores of galaxy clusters

    SciTech Connect

    Nipoti, Carlo; Posti, Lorenzo

    2014-09-01

    A long-standing question is whether radiative cooling can lead to local condensation of cold gas in the hot atmospheres of galaxies and galaxy clusters. We address this problem by studying the nature of local instabilities in rotating, stratified, weakly magnetized, optically thin plasmas in the presence of radiative cooling and anisotropic thermal conduction. For both axisymmetric and nonaxisymmetric linear perturbations, we provide general equations which can be applied locally to specific systems to establish whether they are unstable and, in case of instability, to determine the kind of evolution (monotonically growing or overstable) and the growth rates of the unstable modes. We present results for models of rotating plasmas representative of Milky-Way-like galaxy coronae and cool-cores of galaxy clusters. We show that the unstable modes arise from a combination of thermal, magnetothermal, magnetorotational, and heat-flux-driven buoyancy instabilities. Local condensation of cold clouds tends to be hampered in cluster cool cores, while it is possible under certain conditions in rotating galactic coronae. If the magnetic field is sufficiently weak, then the magnetorotational instability is dominant even in these pressure-supported systems.

  12. On the Nature of Local Instabilities in Rotating Galactic Coronae and Cool Cores of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Nipoti, Carlo; Posti, Lorenzo

    2014-09-01

    A long-standing question is whether radiative cooling can lead to local condensation of cold gas in the hot atmospheres of galaxies and galaxy clusters. We address this problem by studying the nature of local instabilities in rotating, stratified, weakly magnetized, optically thin plasmas in the presence of radiative cooling and anisotropic thermal conduction. For both axisymmetric and nonaxisymmetric linear perturbations, we provide general equations which can be applied locally to specific systems to establish whether they are unstable and, in case of instability, to determine the kind of evolution (monotonically growing or overstable) and the growth rates of the unstable modes. We present results for models of rotating plasmas representative of Milky-Way-like galaxy coronae and cool-cores of galaxy clusters. We show that the unstable modes arise from a combination of thermal, magnetothermal, magnetorotational, and heat-flux-driven buoyancy instabilities. Local condensation of cold clouds tends to be hampered in cluster cool cores, while it is possible under certain conditions in rotating galactic coronae. If the magnetic field is sufficiently weak, then the magnetorotational instability is dominant even in these pressure-supported systems.

  13. A CONSTRAINT ON THE ORGANIZATION OF THE GALACTIC CENTER MAGNETIC FIELD USING FARADAY ROTATION

    SciTech Connect

    Law, C. J.; Brentjens, M. A.; Novak, G.

    2011-04-10

    We present new 6 and 20 cm Very Large Array (VLA) observations of polarized continuum emission of roughly 0.5 deg{sup 2} of the Galactic center (GC) region. The 6 cm observations detect diffuse linearly polarized emission throughout the region with a brightness of roughly 1 mJy per 15''x10'' beam. The Faraday rotation measure (RM) toward this polarized emission has structure on degree size scales and ranges from roughly +330 rad m{sup -2} east of the dynamical center (Sgr A) to-880 rad m{sup -2} west of the dynamical center. This RM structure is also seen toward several nonthermal radio filaments, which implies that they have a similar magnetic field orientation and constrains models for their origin. Modeling shows that the RM and its change with Galactic longitude are best explained by the high electron density and strong magnetic field of the GC region. Considering the emissivity of the GC plasma shows that while the absolute RM values are indirect measures of the GC magnetic field, the RM longitude structure directly traces the magnetic field in the central kiloparsec of the Galaxy. Combining this result with previous work reveals a larger RM structure covering the central {approx}2{sup 0} of the Galaxy. This RM structure is similar to that proposed by Novak and coworkers, but is shifted roughly 50 pc west of the dynamical center of the Galaxy. If this RM structure originates in the GC region, it shows that the GC magnetic field is organized on {approx}300 pc size scales. The pattern is consistent with a predominantly poloidal field geometry, pointing from south to north, that is perturbed by the motion of gas in the Galactic disk.

  14. A Constraint on the Organization of the Galactic Center Magnetic Field Using Faraday Rotation

    NASA Astrophysics Data System (ADS)

    Law, C. J.; Brentjens, M. A.; Novak, G.

    2011-04-01

    We present new 6 and 20 cm Very Large Array (VLA) observations of polarized continuum emission of roughly 0.5 deg2 of the Galactic center (GC) region. The 6 cm observations detect diffuse linearly polarized emission throughout the region with a brightness of roughly 1 mJy per 15''×10'' beam. The Faraday rotation measure (RM) toward this polarized emission has structure on degree size scales and ranges from roughly +330 rad m-2 east of the dynamical center (Sgr A) to-880 rad m-2 west of the dynamical center. This RM structure is also seen toward several nonthermal radio filaments, which implies that they have a similar magnetic field orientation and constrains models for their origin. Modeling shows that the RM and its change with Galactic longitude are best explained by the high electron density and strong magnetic field of the GC region. Considering the emissivity of the GC plasma shows that while the absolute RM values are indirect measures of the GC magnetic field, the RM longitude structure directly traces the magnetic field in the central kiloparsec of the Galaxy. Combining this result with previous work reveals a larger RM structure covering the central ~2° of the Galaxy. This RM structure is similar to that proposed by Novak and coworkers, but is shifted roughly 50 pc west of the dynamical center of the Galaxy. If this RM structure originates in the GC region, it shows that the GC magnetic field is organized on ~300 pc size scales. The pattern is consistent with a predominantly poloidal field geometry, pointing from south to north, that is perturbed by the motion of gas in the Galactic disk.

  15. SCIENTIFIC VERIFICATION OF FARADAY ROTATION MODULATORS: DETECTION OF DIFFUSE POLARIZED GALACTIC EMISSION

    SciTech Connect

    Moyerman, S.; Bierman, E.; Kaufman, J.; Keating, B. G.; Ade, P. A. R.; Aiken, R.; Hristov, V. V.; Jones, W. C.; Mason, P. V.; Barkats, D.; Bischoff, C.; Kovac, J. M.; Bock, J. J.; Dowell, C. D.; Chiang, H. C.; Duband, L.; Hivon, E. F.; Holzapfel, W. L.; Kuo, C. L.; Leitch, E. M.; and others

    2013-03-01

    The design and performance of a wide bandwidth linear polarization modulator based on the Faraday effect is described. Faraday Rotation Modulators (FRMs) are solid-state polarization switches that are capable of modulation up to 10 kHz. Six FRMs were utilized during the 2006 observing season in the Background Imaging of Cosmic Extragalactic Polarization (BICEP) experiment; three FRMs were used at each of BICEP's 100 and 150 GHz frequency bands. The technology was verified through high signal-to-noise detection of Galactic polarization using two of the six FRMs during four observing runs in 2006. The features exhibit strong agreement with BICEP's measurements of the Galaxy using non-FRM pixels and with the Galactic polarization models. This marks the first detection of high signal-to-noise mm-wave celestial polarization using fast, active optical modulation. The performance of the FRMs during periods when they were not modulated was also analyzed and compared to results from BICEP's 43 pixels without FRMs.

  16. Pressure Support in Galaxy Disks: Impact on Rotation Curves and Dark Matter Density Profiles

    NASA Astrophysics Data System (ADS)

    Dalcanton, Julianne J.; Stilp, Adrienne M.

    2010-09-01

    Rotation curves constrain a galaxy's underlying mass density profile, under the assumption that the observed rotation produces a centripetal force that exactly balances the inward force of gravity. However, most rotation curves are measured using emission lines from gas, which can experience additional forces due to pressure. In realistic galaxy disks, the gas pressure declines with radius, providing additional radial support to the disk. The measured tangential rotation speed will therefore tend to lag the true circular velocity of a test particle. The gas pressure is dominated by turbulence, and we evaluate its likely amplitude from recent estimates of the gas velocity dispersion and surface density. We show that where the amplitude of the rotation curve is comparable to the characteristic velocities of the interstellar turbulence, pressure support may lead to underestimates of the mass density of the underlying dark matter halo and the inner slope of its density profile. These effects may be significant for galaxies with rotation speeds lsim75 km s-1 but are unlikely to be significant in higher-mass galaxies. We find that pressure support can be sustained over long timescales, because any reduction in support due to the conversion of gas into stars is compensated for by an inward flow of gas. However, we point to many uncertainties in assessing the importance of pressure support in real or simulated galaxies. Thus, while pressure support may help to alleviate possible tensions between rotation curve observations and ΛCDM on kiloparsec scales, it should not be viewed as a definitive solution at this time.

  17. PRESSURE SUPPORT IN GALAXY DISKS: IMPACT ON ROTATION CURVES AND DARK MATTER DENSITY PROFILES

    SciTech Connect

    Dalcanton, Julianne J.; Stilp, Adrienne M. E-mail: adrienne@astro.washington.ed

    2010-09-20

    Rotation curves constrain a galaxy's underlying mass density profile, under the assumption that the observed rotation produces a centripetal force that exactly balances the inward force of gravity. However, most rotation curves are measured using emission lines from gas, which can experience additional forces due to pressure. In realistic galaxy disks, the gas pressure declines with radius, providing additional radial support to the disk. The measured tangential rotation speed will therefore tend to lag the true circular velocity of a test particle. The gas pressure is dominated by turbulence, and we evaluate its likely amplitude from recent estimates of the gas velocity dispersion and surface density. We show that where the amplitude of the rotation curve is comparable to the characteristic velocities of the interstellar turbulence, pressure support may lead to underestimates of the mass density of the underlying dark matter halo and the inner slope of its density profile. These effects may be significant for galaxies with rotation speeds {approx}<75 km s{sup -1} but are unlikely to be significant in higher-mass galaxies. We find that pressure support can be sustained over long timescales, because any reduction in support due to the conversion of gas into stars is compensated for by an inward flow of gas. However, we point to many uncertainties in assessing the importance of pressure support in real or simulated galaxies. Thus, while pressure support may help to alleviate possible tensions between rotation curve observations and {Lambda}CDM on kiloparsec scales, it should not be viewed as a definitive solution at this time.

  18. PROJECTED ROTATIONAL VELOCITIES AND STELLAR CHARACTERIZATION OF 350 B STARS IN THE NEARBY GALACTIC DISK

    SciTech Connect

    Braganca, G. A.; Daflon, S.; Cunha, K.; Bensby, T.; Oey, M. S.; Walth, G.

    2012-11-01

    Projected rotational velocities (v sin i) are presented for a sample of 350 early B-type main-sequence stars in the nearby Galactic disk. The stars are located within {approx}1.5 kpc from the Sun, and the great majority within 700 pc. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5 m telescope at the Las Campanas Observatory in Chile. Spectral types were estimated based on relative intensities of some key line absorption ratios and comparisons to synthetic spectra. Effective temperatures were estimated from the reddening-free Q index, and projected rotational velocities were then determined via interpolation on a published grid that correlates the synthetic FWHM of the He I lines at 4026, 4388 and 4471 A with v sin i. As the sample has been selected solely on the basis of spectral types, it contains a selection of B stars in the field, in clusters, and in OB associations. The v sin i distribution obtained for the entire sample is found to be essentially flat for v sin i values between 0 and 150 km s{sup -1}, with only a modest peak at low projected rotational velocities. Considering subsamples of stars, there appears to be a gradation in the v sin i distribution with the field stars presenting a larger fraction of the slow rotators and the cluster stars distribution showing an excess of stars with v sin i between 70 and 130 km s{sup -1}. Furthermore, for a subsample of potential runaway stars we find that the v sin i distribution resembles the distribution seen in denser environments, which could suggest that these runaway stars have been subject to dynamical ejection mechanisms.

  19. Photometric light curves for ten rapidly rotating stars in Alpha Persei, the Pleiades, and the field

    NASA Technical Reports Server (NTRS)

    Prosser, Charles F.; Schild, Rudolph E.; Stauffer, John R.; Jones, Burton F.

    1993-01-01

    We present the results from a photometric monitoring program of ten rapidly rotating stars observed during 1991 using the FLWO 48-in. telescope. Brightness variations for an additional six cluster stars observed with the Lick 40-in. telescope are also given. The periods and light curves for seven Alpha Persei members, two Pleiades members, and one naked T Tauri field star are reported.

  20. Hα kinematics of S4G spiral galaxies - III. Inner rotation curves

    NASA Astrophysics Data System (ADS)

    Erroz-Ferrer, Santiago; Knapen, Johan H.; Leaman, Ryan; Díaz-García, Simón; Salo, Heikki; Laurikainen, Eija; Querejeta, Miguel; Muñoz-Mateos, Juan Carlos; Athanassoula, E.; Bosma, Albert; Comerón, Sebastien; Elmegreen, Bruce G.; Martínez-Valpuesta, Inma

    2016-05-01

    We present a detailed study of the shape of the innermost part of the rotation curves of a sample of 29 nearby spiral galaxies, based on high angular and spectral resolution kinematic Hα Fabry-Perot observations. In particular, we quantify the steepness of the rotation curve by measuring its slope dRvc(0). We explore the relationship between the inner slope and several galaxy parameters, such as stellar mass, maximum rotational velocity, central surface brightness (μ0), bar strength and bulge-to-total ratio. Even with our limited dynamical range, we find a trend for low-mass galaxies to exhibit shallower rotation curve inner slopes than high-mass galaxies, whereas steep inner slopes are found exclusively in high-mass galaxies. This trend may arise from the relationship between the total stellar mass and the mass of the bulge, which are correlated among them. We find a correlation between the inner slope of the rotation curve and the morphological T-type, complementary to the scaling relation between dRvc(0) and μ0 previously reported in the literature. Although we find that the inner slope increases with the Fourier amplitude A2 and decreases with the bar torque Qb, this may arise from the presence of the bulge implicit in both A2 and Qb. As previously noted in the literature, the more compact the mass in the central parts of a galaxy (more concretely, the presence of a bulge), the steeper the inner slopes. We conclude that the baryonic matter dominates the dynamics in the central parts of our sample galaxies.

  1. Toward realistic dynamics of rotating orbital debris and implications for light curve

    NASA Astrophysics Data System (ADS)

    Ojakangas, G.; Hill, N.

    2011-09-01

    Optical observations of rotating space debris near GEO contain important information on size, shape, composition, and rotational states, but these aspects are difficult to extract due to data limitations and the high number of degrees of freedom in the modeling process. For tri-axial rigid debris objects created by satellite fragmentations, the most likely initial rotation states have large components of angular velocity directed along the intermediate axis of inertia, leading to large reorientations of the body on the timescale of the rotation period. This lends some support to the simplest possible interpretation of light curves -- that they represent sets of random orientations of the objects of study, although such rotation states do not typically sample orientation space uniformly even over a large number of rotations. Furthermore, effects of solar radiation can cause significant modification of rotation states within timescales of hours, for cm-sized objects of irregular shape. In order to examine the rotational dynamics under solar influence, a set of seven firstorder coupled equations of motion were assembled in state form: three are Euler equations describing the rates of change of the components of angular velocity in the body frame, and four describe the rates of change of the components of the unit quaternion. Quaternions are four-dimensional extensions of complex numbers that form a seamless, singularity-free representation of body orientation on S3. The Euler equations contain explicit terms describing torque from solar radiation. Numerical integrations reveal widely varying rotation states, such that in general, light curves for small objects of irregular shape can be expected to radically change character between different observation epochs. Because the axis of maximum rotational inertia tends to be roughly coincident with the normal to the largest projected cross-sectional area, internal friction or magnetic damping, if significant, may lead to

  2. VizieR Online Data Catalog: VI light curves of Galactic LPVs (Soszynski+, 2013)

    NASA Astrophysics Data System (ADS)

    Soszynski, I.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Wyrzykowski, L.; Ulaczyk, K.; Poleski, R.; Kozlowski, S.; Pietrukowicz, P.

    2013-08-01

    The fifteenth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) contains 232406 long-period variables (LPVs) detected in the OGLE-II and OGLE-III fields toward the Galactic bulge. The sample consists of 6528 Mira stars, 33235 semiregular variables and 192643 OGLE small amplitude red giants. The catalog data and data resources that are being published include observational parameters of stars, finding charts, and time-series I- and V-band photometry obtained between 1997 and 2009. (5 data files).

  3. Testing the recovery of stellar rotation signals from Kepler light curves using a blind hare-and-hounds exercise

    NASA Astrophysics Data System (ADS)

    Aigrain, S.; Llama, J.; Ceillier, T.; Chagas, M. L. das; Davenport, J. R. A.; García, R. A.; Hay, K. L.; Lanza, A. F.; McQuillan, A.; Mazeh, T.; de Medeiros, J. R.; Nielsen, M. B.; Reinhold, T.

    2015-07-01

    We present the results of a blind exercise to test the recoverability of stellar rotation and differential rotation in Kepler light curves. The simulated light curves lasted 1000 d and included activity cycles, Sun-like butterfly patterns, differential rotation and spot evolution. The range of rotation periods, activity levels and spot lifetime were chosen to be representative of the Kepler data of solar-like stars. Of the 1000 simulated light curves, 770 were injected into actual quiescent Kepler light curves to simulate Kepler noise. The test also included five 1000-d segments of the Sun's total irradiance variations at different points in the Sun's activity cycle. Five teams took part in the blind exercise, plus two teams who participated after the content of the light curves had been released. The methods used included Lomb-Scargle periodograms and variants thereof, autocorrelation function and wavelet-based analyses, plus spot modelling to search for differential rotation. The results show that the `overall' period is well recovered for stars exhibiting low and moderate activity levels. Most teams reported values within 10 per cent of the true value in 70 per cent of the cases. There was, however, little correlation between the reported and simulated values of the differential rotation shear, suggesting that differential rotation studies based on full-disc light curves alone need to be treated with caution, at least for solar-type stars. The simulated light curves and associated parameters are available online for the community to test their own methods.

  4. BONA FIDE, STRONG-VARIABLE GALACTIC LUMINOUS BLUE VARIABLE STARS ARE FAST ROTATORS: DETECTION OF A HIGH ROTATIONAL VELOCITY IN HR CARINAE

    SciTech Connect

    Groh, J. H.; Damineli, A.; Moises, A. P.; Teodoro, M.; Hillier, D. J.; Barba, R.; Fernandez-Lajus, E.; Gamen, R. C.; Solivella, G.

    2009-11-01

    We report optical observations of the luminous blue variable (LBV) HR Carinae which show that the star has reached a visual minimum phase in 2009. More importantly, we detected absorptions due to Si IV lambdalambda4088-4116. To match their observed line profiles from 2009 May, a high rotational velocity of v{sub rot} approx = 150 +- 20 km s{sup -1} is needed (assuming an inclination angle of 30 deg.), implying that HR Car rotates at approx =0.88 +- 0.2 of its critical velocity for breakup (v{sub crit}). Our results suggest that fast rotation is typical in all strong-variable, bona fide galactic LBVs, which present S-Dor-type variability. Strong-variable LBVs are located in a well-defined region of the HR diagram during visual minimum (the 'LBV minimum instability strip'). We suggest this region corresponds to where v{sub crit} is reached. To the left of this strip, a forbidden zone with v{sub rot}/v{sub crit}>1 is present, explaining why no LBVs are detected in this zone. Since dormant/ex LBVs like P Cygni and HD 168625 have low v{sub rot}, we propose that LBVs can be separated into two groups: fast-rotating, strong-variable stars showing S-Dor cycles (such as AG Car and HR Car) and slow-rotating stars with much less variability (such as P Cygni and HD 168625). We speculate that supernova (SN) progenitors which had S-Dor cycles before exploding (such as in SN 2001ig, SN 2003bg, and SN 2005gj) could have been fast rotators. We suggest that the potential difficulty of fast-rotating Galactic LBVs to lose angular momentum is additional evidence that such stars could explode during the LBV phase.

  5. Constraining the String Gauge Field by Galaxy Rotation Curves and Perihelion Precession of Planets

    NASA Astrophysics Data System (ADS)

    Cheung, Yeuk-Kwan E.; Xu, Feng

    2013-09-01

    We discuss a cosmological model in which the string gauge field coupled universally to matter gives rise to an extra centripetal force and will have observable signatures on cosmological and astronomical observations. Several tests are performed using data including galaxy rotation curves of 22 spiral galaxies of varied luminosities and sizes and perihelion precessions of planets in the solar system. The rotation curves of the same group of galaxies are independently fit using a dark matter model with the generalized Navarro-Frenk-White (NFW) profile and the string model. A remarkable fit of galaxy rotation curves is achieved using the one-parameter string model as compared to the three-parameter dark matter model with the NFW profile. The average χ2 value of the NFW fit is 9% better than that of the string model at a price of two more free parameters. Furthermore, from the string model, we can give a dynamical explanation for the phenomenological Tully-Fisher relation. We are able to derive a relation between field strength, galaxy size, and luminosity, which can be verified with data from the 22 galaxies. To further test the hypothesis of the universal existence of the string gauge field, we apply our string model to the solar system. Constraint on the magnitude of the string field in the solar system is deduced from the current ranges for any anomalous perihelion precession of planets allowed by the latest observations. The field distribution resembles a dipole field originating from the Sun. The string field strength deduced from the solar system observations is of a similar magnitude as the field strength needed to sustain the rotational speed of the Sun inside the Milky Way. This hypothesis can be tested further by future observations with higher precision.

  6. CONSTRAINING THE STRING GAUGE FIELD BY GALAXY ROTATION CURVES AND PERIHELION PRECESSION OF PLANETS

    SciTech Connect

    Cheung, Yeuk-Kwan E.; Xu Feng

    2013-09-01

    We discuss a cosmological model in which the string gauge field coupled universally to matter gives rise to an extra centripetal force and will have observable signatures on cosmological and astronomical observations. Several tests are performed using data including galaxy rotation curves of 22 spiral galaxies of varied luminosities and sizes and perihelion precessions of planets in the solar system. The rotation curves of the same group of galaxies are independently fit using a dark matter model with the generalized Navarro-Frenk-White (NFW) profile and the string model. A remarkable fit of galaxy rotation curves is achieved using the one-parameter string model as compared to the three-parameter dark matter model with the NFW profile. The average {chi}{sup 2} value of the NFW fit is 9% better than that of the string model at a price of two more free parameters. Furthermore, from the string model, we can give a dynamical explanation for the phenomenological Tully-Fisher relation. We are able to derive a relation between field strength, galaxy size, and luminosity, which can be verified with data from the 22 galaxies. To further test the hypothesis of the universal existence of the string gauge field, we apply our string model to the solar system. Constraint on the magnitude of the string field in the solar system is deduced from the current ranges for any anomalous perihelion precession of planets allowed by the latest observations. The field distribution resembles a dipole field originating from the Sun. The string field strength deduced from the solar system observations is of a similar magnitude as the field strength needed to sustain the rotational speed of the Sun inside the Milky Way. This hypothesis can be tested further by future observations with higher precision.

  7. Discriminating solar and antisolar differential rotation in high-precision light curves

    NASA Astrophysics Data System (ADS)

    Reinhold, Timo; Arlt, Rainer

    2015-04-01

    Context. Surface differential rotation (DR) is one major ingredient of the magnetic field generation process in the Sun and likely in other stars. The term solar-like differential rotation describes the observation that solar equatorial regions rotate faster than polar ones. The opposite effect of polar regions rotating faster than equatorial ones (termed as antisolar DR) has only been observed in a few stars, although there is evidence from theoretical dynamo models. Aims: We present a new method of detecting the sign of DR (i.e., solar-like or antisolar DR) by analyzing long-term high-precision light curves with the Lomb-Scargle periodogram. Methods: We compute the Lomb-Scargle periodogram and identify a set of significant periods Pk, which we associate with active regions located at different latitudes on the stellar surface. If detectable, the first harmonics (P_k') of these periods were identified to compute their peak-height-ratios rk:= h(P'k)/h(Pk) . Spots rotating at lower latitudes generate less sine-shaped light curves, which requires additional power in the harmonics, and results in larger ratios rk. Comparing different ratios rk and the associated periods Pk yields information about the spot latitudes, and reveals the sign of DR. Results: We tested our method on different sets of synthetic light curves all exhibiting solar-like DR. The number of cases where our method detects antisolar DR is the false-positive rate of our method. Depending on the set of light curves, the noise level, the required minimum peak separation, and the presence or absence of spot evolution, our method fails to detect the correct sign in at most 20%. We applied our method to 50 Kepler G stars and found 21-34 stars with solar-like DR and 5-10 stars with antisolar DR, depending on the minimum peak separation. Conclusions: The method is able to determine the sign of DR in a statistical way with a low false-positive rate. Applying our method to real data might suggest that - within

  8. Kinematic Disturbances in Optical Rotation Curves among 89 Virgo Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Rubin, Vera C.; Waterman, Andrew H.; Kenney, Jeffrey D. P.

    1999-07-01

    For 89 galaxies, mostly spirals, in the Virgo Cluster region, we have obtained optical long-slit major-axis spectra of the ionized gas. We find the following: (1) One-half of the Virgo galaxies we observed have regular rotation patterns, while the other half exhibit kinematic disturbances ranging from mild to major. Velocity complexities are generally consistent with those resulting from tidal encounters or accretion events. Since kinematic disturbances are expected to fade within ~10^9 yr, many Virgo galaxies have experienced several significant kinematic disturbances during their lifetimes. (2) There is no strong correlation of rotation curve complexity with Hubble type, with galaxy luminosity, with local galaxy density, or with H I deficiency. (3) A few Virgo galaxies have ionized gas of limited extent, with velocities exceptionally low for their luminosities. In these galaxies the gas must be not rotationally supported. (4) There is a remarkable difference in the distribution of galaxy systemic velocity for galaxies with regular rotation curves and galaxies with disturbed rotation curves. Galaxies with regular rotation patterns show a flat distribution with velocities ranging from V_0=-300 km s^-1 to V_0=+2500 km s^-1 galaxies with disturbed kinematics have a Gaussian distribution that peaks at V_0=+1172+/-100 km s^-1, close to the cluster mean velocity. This latter distribution is virtually identical to the distribution of systemic velocity for elliptical galaxies in Virgo. However, disturbed galaxies are less concentrated to the cluster core than are the ellipticals; those near the periphery have velocities closer to the mean cluster velocity. Thus, spirals with disturbed kinematics are preferentially on radial orbits, which bring them to the denser core, where tidal interactions are strong and/or more common. Because they spend much time near apocenter, we observe them near the cluster periphery. Some may be falling into the core for the first time. These

  9. VizieR Online Data Catalog: VI light curves of Galactic Bulge Cepheids (Soszynski+, 2011)

    NASA Astrophysics Data System (ADS)

    Soszynski, I.; Udalski, A.; Pietrukowicz, P.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Wyrzykowski, L.; Ulaczyk, K.; Poleski, R.; Kozlowski, S.

    2012-04-01

    The fourteenth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) contains Cepheid variables detected in the OGLE-II and OGLE-III fields toward the Galactic bulge. The catalog is divided into two main categories: 32 classical Cepheids (21 single-mode fundamental-mode F, four first-overtone 1O, two double-mode F/1O, three double-mode 1O/2O and two triple-mode 1O/2O/3O pulsators) and 335 type II Cepheids (156 BL Her, 128 W Vir and 51 RV Tau stars). Six of the type II Cepheids likely belong to the Sagittarius Dwarf Spheroidal Galaxy. The catalog data include the time-series photometry collected in the course of the OGLE survey, observational parameters of the stars, finding charts, and cross-identifications with the General Catalogue of Variable Stars. (3 data files).

  10. AN INVESTIGATION OF THE RELATIONSHIP BETWEEN SHAPE AND ROTATION TO EXPLAIN THE LIGHT CURVE OF NEREID

    SciTech Connect

    Hesselbrock, Andrew J.; Alexander, S. G.; Harp, Thomas W.; Abel, N. P.

    2013-06-15

    The observed photometric variability of Nereid over both short and long time scales has been known for some time and has remained a mystery. Schaefer et al. have documented some twenty years worth of observations that reveal that Nereid's light curve shows both short period intranight variations and long term active and inactive episodes. In this work, we report on a set of computational simulations of both the orbital and rotational motion of Nereid in an effort to understand Nereid's behavior. We model Nereid as an ellipsoid that is subject to torques from other bodies, and we calculate both its orbital and rotational motion. In addition, we only consider the case where Nereid is uniformly reflecting with no albedo variations on its surface. Thus, any brightness variations are caused solely by Nereid's changing orientation. We find for reasonable geometries, orientation, and spin rates that we can reproduce some of the features, but not all, of the observed light curve for Nereid. In particular, we show how active and inactive episodes can arise; however, our calculated light curve differs from observations in other aspects.

  11. TESTING MODIFIED NEWTONIAN DYNAMICS WITH ROTATION CURVES OF DWARF AND LOW SURFACE BRIGHTNESS GALAXIES

    SciTech Connect

    Swaters, R. A.; McGaugh, S. S.; Sanders, R. H.

    2010-07-20

    Dwarf and low surface brightness (LSB) galaxies are ideal objects to test modified Newtonian dynamics (MOND), because in most of these galaxies the accelerations fall below the threshold where MOND supposedly applies. We have selected from the literature a sample of 27 dwarf and LSB galaxies. MOND is successful in explaining the general shape of the observed rotation curves for roughly three quarters of the galaxies in the sample presented here. However, for the remaining quarter, MOND does not adequately explain the observed rotation curves. Considering the uncertainties in distances and inclinations for the galaxies in our sample, a small fraction of poor MOND predictions is expected and is not necessarily a problem for MOND. We have also made fits taking the MOND acceleration constant, a {sub 0}, as a free parameter in order to identify any systematic trends. We find that there appears to be a correlation between central surface brightness and the best-fit value of a{sub 0}, in the sense that lower surface brightness galaxies tend to have lower a{sub 0}. However, this correlation depends strongly on a small number of galaxies whose rotation curves might be uncertain due to either bars or warps. Without these galaxies, there is less evidence of a trend, but the average value we find for a{sub 0} {approx} 0.7 x 10{sup -8} cm s{sup -2} is somewhat lower than derived from previous studies. Such lower fitted values of a{sub 0} could occur if external gravitational fields are important.

  12. Unsteady laminar flow with convective heat transfer through a rotating curved square duct with small curvature

    NASA Astrophysics Data System (ADS)

    Mondal, Rabindra Nath; Roy, Titob; Shaha, Poly Rani; Yanase, Shinichiro

    2016-07-01

    Unsteady laminar flow with convective heat transfer through a curved square duct rotating at a constant angular velocity about the center of curvature is investigated numerically by using a spectral method, and covering a wide range of the Taylor number -300≤Tr≤1000 for the Dean number Dn = 1000. A temperature difference is applied across the vertical sidewalls for the Grashof number Gr = 100, where the outer wall is heated and the inner wall cooled, the top and bottom walls being adiabatic. Flow characteristics are investigated with the effects of rotational parameter, Tr, and the pressure-driven parameter, Dn, for the constant curvature 0.001. Time evolution calculations as well as their phase spaces show that the unsteady flow undergoes through various flow instabilities in the scenario `multi-periodic → chaotic → steady-state → periodic → multi-periodic → chaotic', if Tr is increased in the positive direction. For negative rotation, however, time evolution calculations show that the flow undergoes in the scenario `multi-periodic → periodic → steady-state', if Tr is increased in the negative direction. Typical contours of secondary flow patterns and temperature profiles are obtained at several values of Tr, and it is found that the unsteady flow consists of two- to six-vortex solutions if the duct rotation is involved. External heating is shown to generate a significant temperature gradient at the outer wall of the duct. This study also shows that there is a strong interaction between the heating-induced buoyancy force and the centrifugal-Coriolis instability in the curved channel that stimulates fluid mixing and consequently enhances heat transfer in the fluid.

  13. A Simple yet Accurate Method for Students to Determine Asteroid Rotation Periods from Fragmented Light Curve Data

    ERIC Educational Resources Information Center

    Beare, R. A.

    2008-01-01

    Professional astronomers use specialized software not normally available to students to determine the rotation periods of asteroids from fragmented light curve data. This paper describes a simple yet accurate method based on Microsoft Excel[R] that enables students to find periods in asteroid light curve and other discontinuous time series data of…

  14. Using Rotation Curves for Low Surface Brightness Galaxies to Evaluate LCDM

    NASA Astrophysics Data System (ADS)

    Tarantino, Elizabeth; Lelli, Federico; McGaugh, Stacy

    2016-01-01

    Λ Cold Dark Matter (ΛCDM) has been a successful paradigm for explaining large-scale structure in the universe. However, this model does not provide a satisfactory explanation for local, smaller scale features, such as the dynamics of dark matter dominated low surface brightness galaxies. Dubbed the core-cusp problem, the inner slope of these rotation curves is much lower than expected in pure ΛCDM simulations. High-resolution hydrodynamic simulations have attempted to alleviate this discrepancy by invoking baryonic feedback from supernovae driven gas outflows. These simulations can be tested by comparing to observed rotation curves directly. In applying this test, we take care to treat the simulations and the data in the same fashion, so that a direct comparison can be made. This publication was made possible through the support of the John Templeton Foundation. The opinions expressed in this are those of the author and do not necessary reflect the views of the John Templeton Foundation.

  15. Bona Fide, Strong-Variable Galactic Luminous Blue Variable Stars are Fast Rotators: Detection of a High Rotational Velocity in HR Carinae

    NASA Astrophysics Data System (ADS)

    Groh, J. H.; Damineli, A.; Hillier, D. J.; Barbá, R.; Fernández-Lajús, E.; Gamen, R. C.; Moisés, A. P.; Solivella, G.; Teodoro, M.

    2009-11-01

    We report optical observations of the luminous blue variable (LBV) HR Carinae which show that the star has reached a visual minimum phase in 2009. More importantly, we detected absorptions due to Si IV λλ4088-4116. To match their observed line profiles from 2009 May, a high rotational velocity of v rot sime 150 ± 20 km s-1 is needed (assuming an inclination angle of 30°), implying that HR Car rotates at sime0.88 ± 0.2 of its critical velocity for breakup (v crit). Our results suggest that fast rotation is typical in all strong-variable, bona fide galactic LBVs, which present S-Dor-type variability. Strong-variable LBVs are located in a well-defined region of the HR diagram during visual minimum (the "LBV minimum instability strip"). We suggest this region corresponds to where v crit is reached. To the left of this strip, a forbidden zone with v rot/v crit>1 is present, explaining why no LBVs are detected in this zone. Since dormant/ex LBVs like P Cygni and HD 168625 have low v rot, we propose that LBVs can be separated into two groups: fast-rotating, strong-variable stars showing S-Dor cycles (such as AG Car and HR Car) and slow-rotating stars with much less variability (such as P Cygni and HD 168625). We speculate that supernova (SN) progenitors which had S-Dor cycles before exploding (such as in SN 2001ig, SN 2003bg, and SN 2005gj) could have been fast rotators. We suggest that the potential difficulty of fast-rotating Galactic LBVs to lose angular momentum is additional evidence that such stars could explode during the LBV phase. Based on observations made with the 1.6 m telescope at the Observatório Pico dos Dias (OPD-LNA, Brazil), with the 2.15 m telescope of the Complejo Astronomico El Leoncito (CASLEO, Argentina), and with the 2.2 m ESO telescope at La Silla (Chile) under program 083.D-0589. CASLEO is operated under agreement between CONICET, SECYT, and the National Universities of La Plata, Córdoba and San Juan, Argentina.

  16. Declining rotation curves - The end of a conspiracy. [HI rotation velocity decrease of two galaxies as indication of large luminous to dark mass ratio

    SciTech Connect

    Casertano, S.; Van gorkom, J.H. Pittsburgh Univ., PA Columbia Univ., New York National Radio Astronomy Observatory, Socorro, NM )

    1991-04-01

    Two new H I rotation curves, observed at the Very Large Array as part of a search for galaxies with extended H I envelopes, are presented. The two curves are characterized by a large decrease in rotation velocity (more than 50 km/s, or about 25 percent of the maximum rotation velocity) between 1 and 3 optical radii. The velocity decrease is present on both sides of each galaxy and is not due to projection effects. The decrease in rotation velocity is interpreted as an indication of a large ratio of luminous to dark mass in the luminous regions of these systems. While confirming the idea that dark matter is ubiquitous, the discovery indicates that the match between the properties of luminous and dark matter required by the well-known 'conspiracy' is not perfect. 69 refs.

  17. Static spherically symmetric solutions in mimetic gravity: rotation curves and wormholes

    NASA Astrophysics Data System (ADS)

    Myrzakulov, Ratbay; Sebastiani, Lorenzo; Vagnozzi, Sunny; Zerbini, Sergio

    2016-06-01

    In this work, we analyse static spherically symmetric solutions in the framework of mimetic gravity, an extension of general relativity where the conformal degree of freedom of gravity is isolated in a covariant fashion. Here we extend previous works by considering, in addition, a potential for the mimetic field. An appropriate choice of such a potential allows for the reconstruction of a number of interesting cosmological and astrophysical scenarios. We explicitly show how to reconstruct such a potential for a general static spherically symmetric space-time. A number of applications and scenarios are then explored, among which are traversable wormholes. Finally, we analytically reconstruct potentials, which leads to solutions to the equations of motion featuring polynomial corrections to the Schwarzschild space-time. Accurate choices for such corrections could provide an explanation for the inferred flat rotation curves of spiral galaxies within the mimetic gravity framework, without the need for particle dark matter.

  18. Galaxy luminosity function and Tully-Fisher relation: reconciled through rotation-curve studies

    SciTech Connect

    Cattaneo, Andrea; Salucci, Paolo; Papastergis, Emmanouil E-mail: salucci@sissa.it

    2014-03-10

    The relation between galaxy luminosity L and halo virial velocity v {sub vir} required to fit the galaxy luminosity function differs from the observed Tully-Fisher relation between L and disk speed v {sub rot}. Because of this, the problem of reproducing the galaxy luminosity function and the Tully-Fisher relation simultaneously has plagued semianalytic models since their inception. Here we study the relation between v {sub rot} and v {sub vir} by fitting observational average rotation curves of disk galaxies binned in luminosity. We show that the v {sub rot}-v {sub vir} relation that we obtain in this way can fully account for this seeming inconsistency. Therefore, the reconciliation of the luminosity function with the Tully-Fisher relation rests on the complex dependence of v {sub rot} on v {sub vir}, which arises because the ratio of stellar mass to dark matter mass is a strong function of halo mass.

  19. A New Estimator of the Deceleration Parameter from Galaxy Rotation Curves

    NASA Astrophysics Data System (ADS)

    van Putten, Maurice H. P. M.

    2016-06-01

    The nature of dark energy can be probed by the derivative Q={{dq}(z)/{dz}| }0 at redshift z = 0 of the deceleration parameter q(z). It is probably static if Q\\lt 1 or dynamic if Q\\gt 2.5, supporting ΛCDM or {{Λ }}=(1-q){H}2, respectively, where H denotes the Hubble parameter. We derive q=1-{(4π {a}0/{cH})}2, enabling a determination of q(z) by measuring Milgrom’s parameter, {a}0(z), in galaxy rotation curves, equivalent to the coefficient A in the Tully–Fisher relation {V}c4={{AM}}b between a rotation velocity V c and a baryonic mass M b . We infer that dark matter should be extremely light, with clustering limited to the size of galaxy clusters. The associated transition radius to non-Newtonian gravity can conceivably be probed in a freefall Cavendish-type experiment in space.

  20. Declining rotation curves of galaxies as a test of gravitational theory

    NASA Astrophysics Data System (ADS)

    Haghi, Hosein; Bazkiaei, Amir E.; Zonoozi, Akram Hasani; Kroupa, Pavel

    2016-06-01

    Unlike Newtonian dynamics which is linear and obeys the strong equivalence principle, in any non-linear gravitation such as Milgromian dynamics (MOND), the strong version of the equivalence principle is violated and the gravitational dynamics of a system is influenced by the external gravitational field in which it is embedded. This so called external field effect (EFE) is one of the important implications of MOND and provides a special context to test Milgromian dynamics. Here, we study the rotation curves (RCs) of 18 spiral galaxies and find that their shapes constrain the EFE. We show that the EFE can successfully remedy the overestimation of rotation velocities in 80 per cent of the sample galaxies in Milgromian dynamics fits by decreasing the velocity in the outer part of the RCs. We compare the implied external field with the gravitational field for non-negligible nearby sources of each individual galaxy and find that in many cases it is compatible with the EFE within the uncertainties. We therefore argue that in the framework of Milgromian dynamics, one can constrain the gravitational field induced from the environment of galaxies using their RCs. We finally show that taking into account the EFE yields more realistic values for the stellar mass-to-light ratio in terms of stellar population synthesis than the ones implied without the EFE.

  1. LIGHT CURVE TEMPLATES AND GALACTIC DISTRIBUTION OF RR LYRAE STARS FROM SLOAN DIGITAL SKY SURVEY STRIPE 82

    SciTech Connect

    Sesar, Branimir; Ivezic, Zeljko; Grammer, Skyler H.; Morgan, Dylan P.; Becker, Andrew C.; Juric, Mario; De Lee, Nathan; Annis, James; Lampeitl, Hubert; Beers, Timothy C.; Fan Xiaohui; Jiang Linhua; Lupton, Robert H.; Gunn, James E.; Knapp, Gillian R.; Johnston, David E.; Jester, Sebastian

    2010-01-01

    We present an improved analysis of halo substructure traced by RR Lyrae stars in the Sloan Digital Sky Survey (SDSS) stripe 82 region. With the addition of SDSS-II data, a revised selection method based on new ugriz light curve templates results in a sample of 483 RR Lyrae stars that is essentially free of contamination. The main result from our first study persists: the spatial distribution of halo stars at galactocentric distances 5-100 kpc is highly inhomogeneous. At least 20% of halo stars within 30 kpc from the Galactic center can be statistically associated with substructure. We present strong direct evidence, based on both RR Lyrae stars and main-sequence stars, that the halo stellar number density profile significantly steepens beyond a Galactocentric distance of approx30 kpc, and a larger fraction of the stars are associated with substructure. By using a novel method that simultaneously combines data for RR Lyrae and main-sequence stars, and using photometric metallicity estimates for main-sequence stars derived from deep co-added u-band data, we measure the metallicity of the Sagittarius dSph tidal stream (trailing arm) toward R.A. approx2{sup h}-3{sup h} and decl. approx 0{sup 0} to be 0.3 dex higher ([Fe/H] = -1.2) than that of surrounding halo field stars. Together with a similar result for another major halo substructure, the Monoceros stream, these results support theoretical predictions that an early forming, smooth inner halo, is metal-poor compared to high surface brightness material that have been accreted onto a later-forming outer halo. The mean metallicity of stars in the outer halo that are not associated with detectable clumps may still be more metal-poor than the bulk of inner-halo stars, as has been argued from other data sets.

  2. Understanding A-type supergiants. II. Atmospheric parameters and rotational velocities of Galactic A-type supergiants

    NASA Astrophysics Data System (ADS)

    Verdugo, E.; Talavera, A.; Gómez de Castro, A. I.

    1999-06-01

    We present the second paper of a series whose aim is to perform a global study of Galactic A-supergiants. Very little work has been carried out to determine the stellar parameters of these stars. This is illustrated with a brief review of some previous works. In this paper we analyze the determination of absolute magnitudes, spectral types and atmospheric parameters using the most recent Kurucz LTE blanketed model atmospheres and we discuss the applicability of the calibrations, such as the Schmidt-Kaler's (\\cite{Sch-K}) calibration. Rotation is also an important parameter in A-supergiants but their rotational velocities are poorly known. We have calculated projected rotational velocities from the Fourier analysis of the observed Mg II (4481 Ä) line. Based on observations made with the INT and JKT telescopes operated on the island of La Palma by the RGO in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofisica de Canarias, with the 2.2m telescope at Calar Alto Observatory, Spain, with the Bernard Lyot 2m telescope at Pic Du Midi Observatory, France and observations collected at the European Southern Observatory at La Silla, Chile

  3. The inner structure of ΛCDM haloes - II. Halo mass profiles and low surface brightness galaxy rotation curves

    NASA Astrophysics Data System (ADS)

    Hayashi, E.; Navarro, J. F.; Power, C.; Jenkins, A.; Frenk, C. S.; White, S. D. M.; Springel, V.; Stadel, J.; Quinn, T. R.

    2004-12-01

    We use a set of high-resolution cosmological N-body simulations to investigate the inner mass profile of galaxy-sized cold dark matter (CDM) haloes. These simulations extend the numerical convergence study presented in Paper I of this series, and demonstrate that the mass profile of CDM galaxy haloes can be robustly estimated beyond a minimum converged radius of order rconv~ 1h-1 kpc in our highest-resolution runs. The density profiles of simulated haloes become progressively shallower from the virial radius inwards, and show no sign of approaching a well-defined power law near the centre. At rconv, the density profile is steeper than expected from the formula proposed by Navarro, Frenk & White, which has a ρ~r-1 cusp, but significantly shallower than the steeply divergent ρ~r-1.5 cusp proposed by Moore et al. We perform a direct comparison of the spherically averaged dark matter circular velocity profiles with Hα rotation curves of a sample of low surface brightness (LSB) galaxies. We find that most galaxies in the sample (about 70 per cent) have rotation curves that are consistent with the structure of CDM haloes. Of the remainder, 20 per cent have rotation curves which cannot be fit by any smooth fitting function with few free parameters, and 10 per cent are inconsistent with CDM haloes. However, the latter consist mostly of rotation curves that do not extend to large enough radii to accurately determine their shapes and maximum velocities. We conclude that the inner structure of CDM haloes is not manifestly inconsistent with the rotation curves of LSB galaxies.

  4. OPTICAL/NEAR-INFRARED SELECTION OF RED QUASI-STELLAR OBJECTS: EVIDENCE FOR STEEP EXTINCTION CURVES TOWARD GALACTIC CENTERS?

    SciTech Connect

    Fynbo, J. P. U.; Krogager, J.-K.; Vestergaard, M.; Geier, S.; Venemans, B.; Noterdaeme, P.; Moller, P.; Ledoux, C.

    2013-01-15

    We present the results of a search for red QSOs using a selection based on optical imaging from the Sloan Digital Sky Survey (SDSS) and near-infrared imaging from UKIDSS. Our main goal with the selection is to search for QSOs reddened by foreground dusty absorber galaxies. For a sample of 58 candidates (including 20 objects fulfilling our selection criteria that already have spectra in the SDSS), 46 (79%) are confirmed to be QSOs. The QSOs are predominantly dust-reddened except for a handful at redshifts z {approx}> 3.5. However, the dust is most likely located in the QSO host galaxies (and for two, the reddening is primarily caused by Galactic dust) rather than in the intervening absorbers. More than half of the QSOs show evidence of associated absorption (BAL absorption). Four (7%) of the candidates turned out to be late-type stars, and another four (7%) are compact galaxies. We could not identify the remaining four objects. In terms of their optical spectra, these QSOs are similar to the QSOs selected in the FIRST-2MASS Red Quasar Survey except they are on average fainter, more distant, and only two are detected in the FIRST survey. As per the usual procedure, we estimate the amount of extinction using the SDSS QSO template reddened by Small-Magellanic-Cloud-(SMC) like dust. It is possible to get a good match to the observed (rest-frame ultraviolet) spectra, but it is not possible to match the observed near-IR photometry from UKIDSS for nearly all the reddened QSOs. The most likely reasons are that the SDSS QSO template is too red at optical wavelengths due to contaminating host galaxy light and because the assumed SMC extinction curve is too shallow. Three of the compact galaxies display old stellar populations with ages of several Gyr and masses of about 10{sup 10} M{sub Sun} (based on spectral energy distribution modeling). The inferred stellar densities in these galaxies exceed 10{sup 10} M{sub Sun} kpc{sup -2}, which is among the highest measured for early

  5. A systematic study of the inner rotation curves of galaxies observed as part of the GASS and COLD GASS surveys

    NASA Astrophysics Data System (ADS)

    Kauffmann, Guinevere; Huang, Mei-Ling; Moran, Sean; Heckman, Timothy M.

    2015-07-01

    We present a systematic analysis of the rotation curves of 187 galaxies with stellar masses greater than 1010 M⊙, with atomic gas masses from the GALEX Arecibo Sloan Survey (GASS) and with follow-up long-slit spectroscopy from the MMT. Our analysis focuses on stellar rotation curves derived by fitting stellar template spectra to the galaxy spectra binned along the slit. In this way, we are able to obtain accurate rotation velocity measurements for a factor of 2 more galaxies than possible with the Hα line. Galaxies with high atomic gas mass fractions are the most dark-matter-dominated galaxies in our sample and have dark matter halo density profiles that are to first order well described by Navarro-Frenk-White profiles with an average concentration parameter of 10. The inner slopes of the rotation curves correlate more strongly with stellar population age than with galaxy mass or structural parameters. At fixed stellar mass, the rotation curves of more actively star-forming galaxies have steeper inner slopes than less actively star-forming galaxies. The ratio between the galaxy specific angular momentum and the total specific angular momentum of its dark matter halo, Rj, correlates strongly with galaxy mass, structure and gas content. Low-mass, disc-dominated galaxies with atomic gas mass fractions greater than 20 per cent have median values of Rj of around 1, but massive, bulge-dominated galaxies have Rj = 0.2-0.3. We argue that these trends can be understood in a picture where gas inflows triggered by disc instabilities lead to the formation of passive, bulge-dominated galaxies with low specific angular momentum.

  6. Violent gas dynamics in galactic cosmogony: spiral shocks and rotation of star complexes.

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.

    Star complexes are huge aggregates of stars and gas which are considered as the largest cells of star formation in spiral galaxies (Efremov 1988). Basic observational data on star complexes are presented with a special emphasis on their rotational properties. A possible model of the formation of star complexes and the origin of their spin momentum is discussed based on the physics of nonlinear supersonic gas dynamics effects in the interstellar medium.

  7. Imprints of fast-rotating massive stars in the Galactic Bulge.

    PubMed

    Chiappini, Cristina; Frischknecht, Urs; Meynet, Georges; Hirschi, Raphael; Barbuy, Beatriz; Pignatari, Marco; Decressin, Thibaut; Maeder, André

    2011-04-28

    The first stars that formed after the Big Bang were probably massive, and they provided the Universe with the first elements heavier than helium ('metals'), which were incorporated into low-mass stars that have survived to the present. Eight stars in the oldest globular cluster in the Galaxy, NGC 6522, were found to have surface abundances consistent with the gas from which they formed being enriched by massive stars (that is, with higher α-element/Fe and Eu/Fe ratios than those of the Sun). However, the same stars have anomalously high abundances of Ba and La with respect to Fe, which usually arises through nucleosynthesis in low-mass stars (via the slow-neutron-capture process, or s-process). Recent theory suggests that metal-poor fast-rotating massive stars are able to boost the s-process yields by up to four orders of magnitude, which might provide a solution to this contradiction. Here we report a reanalysis of the earlier spectra, which reveals that Y and Sr are also overabundant with respect to Fe, showing a large scatter similar to that observed in extremely metal-poor stars, whereas C abundances are not enhanced. This pattern is best explained as originating in metal-poor fast-rotating massive stars, which might point to a common property of the first stellar generations and even of the 'first stars'. PMID:21525928

  8. A numerical experiment on the equilibrium and stability of a rotating galactic bar

    NASA Technical Reports Server (NTRS)

    Miller, R. H.; Vandervoort, P. O.; Welty, D. E.; Smith, B. F.

    1982-01-01

    A self-consistent, three-dimensional numerical experiment is performed on an N-body system whose initial state is a realization of a certain theoretical model of a rotating triaxial galaxy. The model is a stellar-dynamical counterpart of a uniformly rotating polytrope of index equal to 0.5. The aim of the experiment is to study the equilibrium of the system and, in particular, to test its stability. The experimental system behaves in the mean like a realization of the theoretical model for at least seven crossing times. The principal departure of the system from equilibrium is an oscillation which is identified as a radial pulsation. There is no indication in its behavior that the system is unstable with respect to anu mode with an e-folding time shorter than or of the order of two crossing times. Certain changes that occur in the state of the system are interpreted, with the aid of the theoretical model, as secular changes which result from a slight failure of our numerical methods to conserve the mass, energy, and angular momentum of the system; these effects are small enough that they do not vitiate the experiment on a dynamical time scale.

  9. The variation of rotation curve shapes as a signature of the effects of baryons on dark matter density profiles

    NASA Astrophysics Data System (ADS)

    Brook, Chris B.

    2015-12-01

    Rotation curves of galaxies show a wide range of shapes, which can be paramaterized as scatter in Vrot(1 kpc)/Vmax , i.e. the ratio of the rotation velocity measured at 1 kpc and the maximum measured rotation velocity. We examine whether the observed scatter can be accounted for by combining scatters in disc scalelengths, the concentration-halo mass relation, and the M⋆-Mhalo relation. We use these scatters to create model galaxy populations; when housed within dark matter haloes that have universal, Navarro, Frenk & White density profiles, the model does not match the lowest observed values of Vrot(1 kpc)/Vmax and has too little scatter in Vrot(1 kpc)/Vmax compared to observations. By contrast, a model using a mass-dependent dark matter profile, where the inner slope is determined by the ratio of M⋆/Mhalo, produces galaxies with low values of Vrot(1 kpc)/Vmax and a much larger scatter, both in agreement with observation. We conclude that the large observed scatter in Vrot(1 kpc)/Vmax favours density profiles that are significantly affected by baryonic processes. Alternative dark matter core formation models such as self-interacting dark matter may also account for the observed variation in rotation curve shapes, but these observations may provide important constraints in terms of core sizes, and whether they vary with halo mass and/or merger history.

  10. Star formation in differentially rotating galactic disks: The physics of self-propagation.

    NASA Astrophysics Data System (ADS)

    Palous, J.; Tenorio-Tagle, G.; Franco, J.

    1994-09-01

    Large-scale propagating star formation in galaxies is studied as a self-regulatin process. The model connects the energy injection by star formation with the resultin interstellar structures in a differentially rotating disc. The star formation cycl includes the formation of new stars in groups, multisupernova remnants agglomerafin the gas into supershells, formation of clouds and repeated birth of stars. We investigat the evolution of a galaxy dominated by this cycle and conclude that the predicted radia distributions of H i and H2, the numbers of multisupernova remnants and massiv( cloud complexes, the surface filling factors of shells, the star formation rate (SFR) and the location of the molecular rings are in agreement with the properties of th( observed galaxies. Key words: stars: formation - supernova remnants - galaxies: ISM - galaxies: stella content - galaxies: structure.

  11. Dark matter from cosmic defects on galactic scales?

    SciTech Connect

    Guerreiro, N.; Carvalho, J. P. M. de; Avelino, P. P.; Martins, C. J. A. P.

    2008-09-15

    We discuss the possible dynamical role of extended cosmic defects on galactic scales, specifically focusing on the possibility that they may provide the dark matter suggested by the classical problem of galactic rotation curves. We emphasize that the more standard defects (such as Goto-Nambu strings) are unsuitable for this task but show that more general models (such as transonic wiggly strings) could in principle have a better chance. In any case, we show that observational data severely restricts any such scenarios.

  12. REDDENING AND EXTINCTION TOWARD THE GALACTIC BULGE FROM OGLE-III: THE INNER MILKY WAY'S R{sub V} {approx} 2.5 EXTINCTION CURVE

    SciTech Connect

    Nataf, David M.; Gould, Andrew; Johnson, Jennifer A.; Skowron, Jan; Fouque, Pascal; Gonzalez, Oscar A.; Udalski, Andrzej; Szymanski, Michal K.; Kubiak, Marcin; Pietrzynski, Grzegorz; Soszynski, Igor; Ulaczyk, Krzysztof; Wyrzykowski, Lukasz; Poleski, Radoslaw

    2013-06-01

    We combine VI photometry from OGLE-III with VISTA Variables in The Via Lactea survey and Two Micron All Sky Survey measurements of E(J - K{sub s} ) to resolve the longstanding problem of the non-standard optical extinction toward the Galactic bulge. We show that the extinction is well fit by the relation A{sub I} = 0.7465 Multiplication-Sign E(V - I) + 1.3700 Multiplication-Sign E(J - K{sub s} ), or, equivalently, A{sub I} = 1.217 Multiplication-Sign E(V - I)(1 + 1.126 Multiplication-Sign (E(J - K{sub s} )/E(V - I) - 0.3433)). The optical and near-IR reddening law toward the inner Galaxy approximately follows an R{sub V} Almost-Equal-To 2.5 extinction curve with a dispersion {sigma}{sub R{sub V}}{approx}0.2, consistent with extragalactic investigations of the hosts of Type Ia SNe. Differential reddening is shown to be significant on scales as small as our mean field size of 6'. The intrinsic luminosity parameters of the Galactic bulge red clump (RC) are derived to be (M{sub I,RC},{sigma}{sub I,RC,0}, (V-I){sub RC,0},{sigma}{sub (V-I){sub R{sub C}}}, (J-K{sub s}){sub RC,0}) = (-0.12, 0.09, 1.06, 0.121, 0.66). Our measurements of the RC brightness, brightness dispersion, and number counts allow us to estimate several Galactic bulge structural parameters. We estimate a distance to the Galactic center of 8.20 kpc. We measure an upper bound on the tilt {alpha} Almost-Equal-To 40 Degree-Sign between the bulge's major axis and the Sun-Galactic center line of sight, though our brightness peaks are consistent with predictions of an N-body model oriented at {alpha} Almost-Equal-To 25 Degree-Sign . The number of RC stars suggests a total stellar mass for the Galactic bulge of {approx}2.3 Multiplication-Sign 10{sup 10} M{sub Sun} if one assumes a canonical Salpeter initial mass function (IMF), or {approx}1.6 Multiplication-Sign 10{sup 10} M{sub Sun} if one assumes a bottom-light Zoccali IMF.

  13. Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry

    NASA Astrophysics Data System (ADS)

    Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; Surace, Jason; Cheng, Yu-Chi; Ip, Wing-Huen; Kinoshita, Daisuke; Helou, George; Prince, Thomas A.; Kulkarni, Shrinivas

    2015-09-01

    We fit 54,296 sparsely sampled asteroid light curves in the Palomar Transient Factory survey to a combined rotation plus phase-function model. Each light curve consists of 20 or more observations acquired in a single opposition. Using 805 asteroids in our sample that have reference periods in the literature, we find that the reliability of our fitted periods is a complicated function of the period, amplitude, apparent magnitude, and other light-curve attributes. Using the 805-asteroid ground-truth sample, we train an automated classifier to estimate (along with manual inspection) the validity of the remaining ∼53,000 fitted periods. By this method we find that 9033 of our light curves (of ∼8300 unique asteroids) have “reliable” periods. Subsequent consideration of asteroids with multiple light-curve fits indicates a 4% contamination in these “reliable” periods. For 3902 light curves with sufficient phase-angle coverage and either a reliable fit period or low amplitude, we examine the distribution of several phase-function parameters, none of which are bimodal though all correlate with the bond albedo and with visible-band colors. Comparing the theoretical maximal spin rate of a fluid body with our amplitude versus spin-rate distribution suggests that, if held together only by self-gravity, most asteroids are in general less dense than ∼2 g cm‑3, while C types have a lower limit of between 1 and 2 g cm‑3. These results are in agreement with previous density estimates. For 5–20 km diameters, S types rotate faster and have lower amplitudes than C types. If both populations share the same angular momentum, this may indicate the two types’ differing ability to deform under rotational stress. Lastly, we compare our absolute magnitudes (and apparent-magnitude residuals) to those of the Minor Planet Center’s nominal (G = 0.15, rotation-neglecting) model; our phase-function plus Fourier-series fitting reduces asteroid photometric rms scatter by a

  14. Rotation Measures of Extragalactic Sources behind the Southern Galactic Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky Way

    NASA Astrophysics Data System (ADS)

    Brown, J. C.; Haverkorn, M.; Gaensler, B. M.; Taylor, A. R.; Bizunok, N. S.; McClure-Griffiths, N. M.; Dickey, J. M.; Green, A. J.

    2007-07-01

    We present new Faraday rotation measures (RMs) for 148 extragalactic radio sources behind the southern Galactic plane (253deg<=l<=356deg, |b|<=1.5deg), and use these data in combination with published data to probe the large-scale structure of the Milky Way's magnetic field. We show that the magnitudes of these RMs oscillate with longitude in a manner that correlates with the locations of the Galactic spiral arms. The observed pattern in RMs requires the presence of at least one large-scale magnetic reversal in the fourth Galactic quadrant, located between the Sagittarius-Carina and Scutum-Crux spiral arms. To quantitatively compare our measurements to other recent studies, we consider all available extragalactic and pulsar RMs in the region we have surveyed, and jointly fit these data to simple models in which the large-scale field follows the spiral arms. In the best-fitting model, the magnetic field in the fourth Galactic quadrant is directed clockwise in the Sagittarius-Carina spiral arm (as viewed from the north Galactic pole), but is oriented counterclockwise in the Scutum-Crux arm. This contrasts with recent analyses of pulsar RMs alone, in which the fourth-quadrant field was presumed to be directed counterclockwise in the Sagittarius-Carina arm. Also in contrast to recent pulsar RM studies, our joint modeling of pulsar and extragalactic RMs demonstrates that large numbers of large-scale magnetic field reversals are not required to account for observations.

  15. Rotational kinematics of a curved fold: The Balzes anticline (Southern Pyrenees)

    NASA Astrophysics Data System (ADS)

    Rodríguez-Pintó, A.; Pueyo, E. L.; Calvín, P.; Sánchez, E.; Ramajo, J.; Casas, A. M.; Ramón, M. J.; Pocoví, A.; Barnolas, A.; Román, T.

    2016-05-01

    This study deals with how vertical-axis rotations are accommodated in thrust fronts. Studies on the rotational kinematics of fold and thrust belts are limited owing to the scarcity of the record of syntectonic rocks and other data required for 4D reconstruction approaches. We studied the Balzes anticline, a 17-km long, thrust-related, arc-shaped anticline with dense paleomagnetic sampling (75 sites) to unravel the origin of its curvature (about 50° of arc in map view). The availability of both synfolding and synrotational indicators enables us to decipher the complete kinematic history of the fold. Reliable paleomagnetic data (more than 500 specimens and about 1000 measurements) were obtained from Ypresian to Priabonian rocks, typically with six demagnetization steps. The ChRM is unblocked between 420 and 575 °C in most samples (85%), and at 675 °C in the others. The primary direction displays two polarities and passes the fold test. Vertical axis rotation values for the structure range from non-significant up to > 80° clockwise. A strike vs. rotation diagram clearly relates this variability to the fold curvature (VAR = - 46° + 0.5 ∗ TREND [R = 0.97]) and reveals the addition of primary and secondary curvatures. The original (primary) curvature is related to the emplacement of the thrust sheet underlying the Balzes anticline; it shows an obliquity of approximately 15° with respect to the expected Pyrenean trend. Progressive unconformity in the field (Santa Marina site) provides a record of a Middle-Late Lutetian major folding event. The detailed analysis of the synrotational sedimentary record together with accurate temporal calibration based on previous magnetostratigraphic data allows us to date the rotation stage as Lutetian-Bartonian and to estimate the rotation velocity of the Balzes anticline to have been about 5.2°/Ma, both in agreement with previously published observations for the South Pyrenean front.

  16. Thermal light curves of Earth-like planets: 1. Varying surface and rotation on planets in a terrestrial orbit

    NASA Astrophysics Data System (ADS)

    Gómez-Leal, I.; Codron, F.; Selsis, F.

    2016-05-01

    The integrated thermal emission of an exoplanet and its variations along the orbital motion can carry information about the climatic conditions and the rotation of the planet. In this study, we use the LMDZ 3D Global Climate Model (GCM) to simulate the climate of a synthetic Earth and three quasi-Earth configurations: a slowly rotating Earth, an ocean-covered Earth and its snowball counterpart. We also generate the time-dependent broadband thermal emission of the planet from these simulations. In a first step, we validate the model by comparing the synthetic Earth emission with the actual emission of our planet as constrained by observations. Then, we determine the main properties of the climate and emission of the three Earth-like planets and compare them to those of the Earth. We show that planets with an uneven distribution of continents exhibit a maximum of emission during the summer of the hemisphere with larger continental masses, and they may exhibit a maximum of emission at apastron. Large convective clouds might form over the continents of slow rotating planets, having an important effect over their climate and their emission. We also show that, in all the modeled cases, the equilibrium temperature, the Bond albedo and the rotation period can in theory be retrieved from the light curve by a distant observer. The values obtained at transiting geometries have a low deviation from the global values for cases with an axis tilt similar to that of the Earth, and we are able to distinguish between the four planets presented here by the data obtained from their light curves. However, this might not be the case under different conditions.

  17. Rotational Analysis of Phase Plane Curves: Complex and Pure Imaginary Eigenvalues

    ERIC Educational Resources Information Center

    Murray, Russell H.

    2005-01-01

    Although the phase plane can be plotted and analyzed using an appropriate software package, the author found it worthwhile to engage the students with the theorem and the two proofs. The theorem is a powerful tool that provides insight into the rotational behavior of the phase plane diagram in a simple way: just check the signs of c and [alpha].…

  18. Space telescope searches for black holes in galactic nuclei

    NASA Technical Reports Server (NTRS)

    Harms, Richard J.

    1989-01-01

    The Hubble Space Telescope (HST) will allow astronomers to obtain luminosity profiles, rotation curves, and velocity dispersions at angular scales that are an order of magnitude superior to those obtained previously. This enhanced spatial resolution will greatly improve the sensitivity for detecting centrally condensed matter in nearby galactic nuclei including, possibly, black holes.

  19. THE ROTATION PERIOD AND LIGHT-CURVE AMPLITUDE OF KUIPER BELT DWARF PLANET 136472 MAKEMAKE (2005 FY9)

    SciTech Connect

    Heinze, A. N.; DeLahunta, Daniel E-mail: ddelahun@mail.rochester.edu

    2009-08-15

    Kuiper Belt dwarf planet 136472 Makemake, formerly known as 2005 FY9, is currently the third-largest known object in the Kuiper Belt, after the dwarf planets Pluto and Eris. It is currently second only to Pluto in apparent brightness, due to Eris' much larger heliocentric distance. Makemake shows very little photometric variability, which has prevented confident determination of its rotation period until now. Using extremely precise time-series photometry, we find that the rotation period of Makemake is 7.7710 {+-} 0.0030 hr, where the uncertainty is a 90% confidence interval. An alias period is detected at 11.41 hr, but is determined with approximately 95% confidence not to be the true period. Makemake's 7.77 hr rotation period is in the typical range for Kuiper Belt objects, consistent with Makemake's apparent lack of a substantial satellite to alter its rotation through tides. The amplitude of Makemake's photometric light curve is 0.0286 {+-} 0.0016 mag in V. This amplitude is about 10 times less than Pluto's, which is surprising given the two objects' similar sizes and spectral characteristics. Makemake's photometric variability is instead similar to that of Eris, which is so small that no confident rotation period has yet been determined. It has been suggested that dwarf planets such as Makemake and Eris, both farther from the Sun and colder than Pluto, exhibit lower photometric variability because they are covered with a uniform layer of frost. Such a frost is probably the correct explanation for Eris. However, it may be inconsistent with the spectrum of Makemake, which resembles reddish Pluto more than neutrally colored Eris. Makemake may instead be a more Pluto-like object that we observe at present with a nearly pole-on viewing geometry-a possibility that can be tested with continuing observations over the coming decades.

  20. Could wormholes form in dark matter galactic halos?

    NASA Astrophysics Data System (ADS)

    Rahaman, Farook; Shit, G. C.; Sen, Banashree; Ray, Saibal

    2016-01-01

    We estimate expression for velocity as a function of the radial coordinate r by using polynomial interpolation based on the experimental data of rotational velocities at distant outer regions of galaxies. The interpolation technique has been used to estimate fifth degree polynomial followed by cubic spline interpolation. This rotational velocity is used to find the geometry of galactic halo regions within the framework of Einstein's general relativity. In this paper we have analyzed features of galactic halo regions based on two possible choices for the dark matter density profile, viz. Navarro, Frenk & White (NFW) type (Navarro et al. in Astrophys. J. 462:563, 1996) and Universal Rotation Curve (URC) (Castignani et al. in Nat. Sci. 4:265, 2012). It is argued that spacetime of the galactic halo possesses some of the characteristics needed to support traversable wormholes.

  1. MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. VIII. FARADAY ROTATION IN PARSEC-SCALE AGN JETS

    SciTech Connect

    Hovatta, Talvikki; Lister, Matthew L.; Aller, Margo F.; Aller, Hugh D.; Homan, Daniel C.; Kovalev, Yuri Y.

    2012-10-01

    We report observations of Faraday rotation measures for a sample of 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array observations were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. We detect parsec-scale Faraday rotation measures in 149 sources and find the quasars to have larger rotation measures on average than BL Lac objects. The median core rotation measures are significantly higher than in the jet components. This is especially true for quasars where we detect a significant negative correlation between the magnitude of the rotation measure and the de-projected distance from the core. We perform detailed simulations of the observational errors of total intensity, polarization, and Faraday rotation, and concentrate on the errors of transverse Faraday rotation measure gradients in unresolved jets. Our simulations show that the finite image restoring beam size has a significant effect on the observed rotation measure gradients, and spurious gradients can occur due to noise in the data if the jet is less than two beams wide in polarization. We detect significant transverse rotation measure gradients in four sources (0923+392, 1226+023, 2230+114, and 2251+158). In 1226+023 the rotation measure is for the first time seen to change sign from positive to negative over the transverse cuts, which supports the presence of a helical magnetic field in the jet. In this source we also detect variations in the jet rotation measure over a timescale of three months, which are difficult to explain with external Faraday screens and suggest internal Faraday rotation. By comparing fractional polarization changes in jet components between the four frequency bands to depolarization models, we find that an external purely random Faraday screen viewed through only a few lines of sight can explain most of our polarization observations, but in some sources, such as 1226+023 and 2251+158, internal

  2. Formation of Supermassive Black Holes in Galactic Bulges: A Rotating Collapse Model Consistent with the M(sub BH-sigma) Relation

    NASA Technical Reports Server (NTRS)

    Adams, Fred C.; Graff, David S.; Mbonye, Manasse; Richstone, Douglas O.

    2003-01-01

    Motivated by the observed correlation between black hole masses M(sub BH) and the velocity dispersion sigma of host galaxies, we develop a theoretical model of black hole formation in galactic bulges (this paper generalizes an earlier ApJ Letter). The model assumes an initial state specified by a uniform rotation rate OMEGA and a density distribution of the form rho = a(sup 2)(sub eff)per2piGR(sup 2)(so that a(sub eff)is an effective transport speed). The black hole mass is determined when the centrifugal radius of the collapse flow exceeds the capture radius of the central black hole (for Schwarzschild geometry). This model reproduces the observed correlation between the estimated black hole masses and the velocity dispersions of galactic bulges, i.e., M(sub BH) approximately equal to 10(sup 8) solar mass(sigma per 200 kilometers per second)(sup 4) where sigma = the square root of 2a(sub eff). To obtain this normalization, the rotation rate OMEGA approximately equal to 2 x 10(exp -15) rad per second. The model also defines a bulge mass scale M(sub B). If we identify the scale M(sub B) with the bulge mass, the model determines the ratio mu(sub B) of black hole mass to the host mass: mu(sub B) approximately equal to 0.0024(sigma per 200 kilometer per second), again in reasonable agreement with observed values. In this scenario, supermassive black holes form quickly (in approximately 10(exp 5) yr) and are born rapidly rotating (with a per M approximately 0.9). This paper also shown how these results depend on the assumed initial conditions; the most important quantity is the initial distribution of specific angular momentum in the precollapse state.

  3. Galactic Evolution

    NASA Astrophysics Data System (ADS)

    Brekke, Stewart

    2013-04-01

    All galaxies began as spiral galaxies. The early universe began with sets of two or more pre-galactic arms orbiting each other. As gravitational attraction between the arms took effect, the fore-sections of the arms tangentially collided forming spiral galaxies when they attached with the orbital motion of the arms being converted to the rotational motion of the newly formed spiral galaxies or (Iφ)arm1+ (Iφ)arm2+ ...+ (Iφ)armn= (Iφ)galaxy. If the centripetal force on the arms is more than the gravitational force on the arms, the spiral galaxy remains a spiral galaxy i.e. mv^2/r>=Gmarmmgalaxy/r^2. If the galaxy is slowly rotating, the spiral arms collapse into the body of the galaxy because the gravitational force is greater than the centripetal force on the arms and an elliptical galaxy is formed i.e. mv^2/r < Gmarmsmgalaxy/r^2.

  4. Effects of the dark energy and flat rotation curve on the gravitational time delay of particle with non-zero mass

    NASA Astrophysics Data System (ADS)

    Sarkar, Tamal; Ghosh, Shubhrangshu; Bhadra, Arunava

    2016-07-01

    The effects of several dark energy models on gravitational time delay of particles with non-zero mass are investigated and analytical expressions for the same are obtained at the first order accuracy. Also the expression for gravitational time delay under the influence of conformal gravity potential that well describes the flat rotation curve of spiral galaxies is derived. The findings suggest that (i) the conformal gravity description of dark matter reduces the net time delay in contrast to the effect of normal dark matter, and therefore in principle the models can be discriminated using gravitational time delay observations, and (ii) the effect of dark energy/flat rotation curve may be revealed from high-precision measurements of gravitational time delay of particles involving the megaparsec and beyond distance scale.

  5. Small-scale variations in the galactic magnetic field - The rotation measure structure function and birefringence in interstellar scintillations

    NASA Technical Reports Server (NTRS)

    Simonetti, J. H.; Cordes, J. M.; Spangler, S. R.

    1984-01-01

    The structure function of rotation measures of extragalactic sources and birefringence in interstellar scintillations are used to investigate variations in the interstellar magnetic field on length scales of about 0.01-100 pc and 10 to the 11th cm, respectively. Model structure functions are derived for the case of a power-law power spectrum of irregularities in the quantity (n(e)B), and an estimate for the structure function is computed for several regions of the sky using data on extragalactic sources. The results indicate an outer angular scale for rotation measure (RM) variations of not less than about 5 deg (a linear scale of about 9-90 pc at a distance of 0.1-1 kpc). There is also evidence for RM variations on angular scales as small as 1 arcmin, but it cannot be determined whether these are intrinsic to the source or caused by the interstellar medium. The effect of a random, Faraday-active medium on the diffraction of radio waves is derived, and an upper limit to the variations in n(e)B on a length scale of 10 to the 11th cm is obtained from available observations.

  6. Outer rotation curve of the Galaxy with VERA. II. Annual parallax and proper motion of the star-forming region IRAS 21379+5106

    NASA Astrophysics Data System (ADS)

    Nakanishi, Hiroyuki; Sakai, Nobuyuki; Kurayama, Tomoharu; Matsuo, Mitsuhiro; Imai, Hiroshi; Burns, Ross A.; Ozawa, Takeaki; Honma, Mareki; Shibata, Katsunori M.; Kawaguchi, Noriyuki

    2015-08-01

    We conducted astrometric very long baseline interferometry (VLBI) observations of water-vapor maser emission in the massive star-forming region IRAS 21379+5106 in order to measure the annual parallax and proper motion, using VLBI Exploration of Radio Astrometry (VERA). The annual parallax measured 0.262 ± 0.031 mas, corresponding to a distance of 3.82^{+0.51}_{-0.41}kpc. The proper motion was (μαcos δ, μδ) = (-2.74 ± 0.08, -2.87 ± 0.18) mas yr-1. By using this result, the Galactic rotational velocity was estimated to be Vθ = 218 ± 19 km s-1 at the galactocentric distance R = 9.22 ± 0.43 kpc, when we adopted the Galactic constants R0 = 8.05 ± 0.45 kpc and V0 = 238 ± 14 km s-1. With the newly determined distance, the bolometric luminosity of the central young stellar object was reestimated to be (2.15 ± 0.54) × 103 L⊙, which corresponds to the spectral type of B2-B3. The maser features were found to be distributed along a straight line extending from the southwest to the northeast. In addition, a vector map of the internal motions, constructed from the residual proper motions, implies that the maser features trace a bipolar flow, and that it cannot be explained by simple ballistic motions.

  7. Spectroastrometry of rotating gas disks for the detection of supermassive black holes in galactic nuclei. III. CRIRES observations of the Circinus galaxy

    NASA Astrophysics Data System (ADS)

    Gnerucci, A.; Marconi, A.; Capetti, A.; Axon, D. J.; Robinson, A.

    2013-01-01

    We present new CRIRES spectroscopic observations of the Brγ emission line in the nuclear region of the Circinus galaxy, obtained with the aim of measuring the black hole (BH) mass with the spectroastrometric technique. The Circinus galaxy is an ideal benchmark for the spectroastrometric technique given its proximity and secure BH measurement obtained with the observation of its nuclear H2O maser disk. The kinematical data have been analyzed both with the classical method based on the analysis of the rotation curves and with the new method developed by us that is based on spectroastrometry. The classical method indicates that the gas disk rotates in a gravitational potential resulting from an extended stellar mass distribution and a spatially unresolved dynamical mass of (1.7 ± 0.2) × 107 M⊙, concentrated within r < 7 pc, corresponding to the seeing-limited resolution of the observations. The new method is capable of probing the gas rotation at scales that are a factor ~3.5 smaller than those probed by the rotation curve analysis, highlighting the potential of spectroastrometry. The dynamical mass, which is spatially unresolved with the spectroastrometric method, is a factor ~2 smaller, 7.9+1.4-1.1 × 106M⊙, indicating that spectroastrometry has been able to spatially resolve the nuclear mass distribution down to 2 pc scales. This unresolved mass is still a factor ~4.5 larger than the BH mass measurement obtained with the H2O maser emission, indicating that even with spectroastrometry, it has not been possible to resolve the sphere of influence of the BH. Based on literature data, this spatially unresolved dynamical mass distribution is likely dominated by warm molecular gas and has been tentatively identified with the circum-nuclear torus that prevents a direct view of the central BH in Circinus. This mass distribution, with a size of ~2 pc, is similar in shape to that of the star cluster of the Milky Way, suggesting that a molecular torus, forming stars at

  8. Galactic Interactions and Dark Matter

    NASA Astrophysics Data System (ADS)

    Willig, T.; Storrs, A.

    2005-12-01

    In studying galactic interactions is it possible with present instrumentation to find evidence of dark matter within these interactions? The present theory is that dark matter and its gravitational force is what accounts for much of spiral galaxy rotation curves. If this is true, we should be able to find evidence of dark matter when two galaxies (one being a spiral galaxy) interact. Several pairs of interacting galaxies in various stages of interaction will be studied. In addition, several non interacting spiral galaxies will be studied for comparisons. We present analysis of a variety of archival imaging data from radio maps through x-ray images in an attempt to observe the effects of dark matter in galaxy interactions.

  9. Aberration in proper motions for Galactic stars

    NASA Astrophysics Data System (ADS)

    Liu, J.-C.; Xie, Y.; Zhu, Z.

    2014-12-01

    Accelerations of both the solar system barycenter (SSB) and stars in the MilkyWay cause a systematic observational effect on the stellar proper motions, which was first studied by J. Kovalevsky (2003). This paper intends to extend that work and aims to estimate the magnitude and significance of the aberration in proper motions of stars, especially in the region near the Galactic center (GC). We adopt two models for the Galactic rotation curve to evaluate the aberrational effect on the Galactic plane. We show that the effect of aberration in proper motions depends on the galactocentric distance of stars; it is dominated by the acceleration of stars in the central region of the Galaxy. Then we investigate the applicability of the theoretical expressions: if the orbital period of stars is only a fraction of the light time from the star to the SSB, the expression with approximation proposed by Kovalevsky is not appropriate. With a more suitable formulation, we found that the aberration has no effect on the determination of the stellar orbits on the celestial sphere. In the future this aberrational effect under consideration should be considered with high-accurate astrometry, particularly in constructing the Gaia celestial reference system realized by Galactic stars.

  10. Spiral Galactic Formation and Evolution

    NASA Astrophysics Data System (ADS)

    Brekke, Stewart

    2009-05-01

    Before the period of galactic formation the uiverse consisted of a vast number of pre-formed systems consisting of two or more pre-galactic arms, the arms orbiting each other. As the orbits of the arms decayed the sides of the fore-sections of the arms tangentially collided and joined and thereby forming multi-armed spiral galaxies which began to rotate.The rotation resulted from the conversion of the orbital motion of the individual arms when joined into faster rotational motion of the newly formed galaxy. The spiral arms were maintained by the centripital force of the rapidly rotational motion of the galaxy system. As the rotational motion of the galaxy slowed down the arms of the spiral galaxy collapsed towards the body of the galaxy due to lessening of centripetal force on the arms and elliptical galaxies were formed and with further lessening of galactic rotational motion galactic disks were formed. One can see in galaxies M51, M100, NGC2336 and NGC4939 the galactic arms came from external orbit, not disks or instabilities in support of this theory. Also in support of this theory of galactic evolution is that spiral galaxies rotate faster than ellipticals or disks.

  11. Numerical computation of gravitational field of infinitely thin axisymmetric disc with arbitrary surface mass density profile and its application to preliminary study of rotation curve of M33

    NASA Astrophysics Data System (ADS)

    Fukushima, Toshio

    2016-03-01

    We developed a numerical method to compute the gravitational field of an infinitely thin axisymmetric disc with an arbitrary surface mass density profile. We evaluate the gravitational potential by a split quadrature using the double exponential rule and obtain the acceleration vector by numerically differentiating the potential by Ridder's algorithm. The new method is of around 12 digit accuracy and sufficiently fast because requiring only one-dimensional integration. By using the new method, we show the rotation curves of some non-trivial discs: (i) truncated power-law discs, (ii) discs with a non-negligible centre hole, (iii) truncated Mestel discs with edge softening, (iv) double power-law discs, (v) exponentially damped power-law discs, and (vi) an exponential disc with a sinusoidal modulation of the density profile. Also, we present a couple of model fittings to the observed rotation curve of M33: (i) the standard deconvolution by assuming a spherical distribution of the dark matter and (ii) a direct fit of infinitely thin disc mass with a double power-law distribution of the surface mass density. Although the number of free parameters is a little larger, the latter model provides a significantly better fit. The FORTRAN 90 programs of the new method are electronically available.

  12. Ultrasound for the detection of full-thickness rotator cuff tears: the learning curve for an orthopaedic surgeon using a novel training method

    PubMed Central

    Ibrahim, Edward F; Petrou, Charalambos

    2014-01-01

    Background The present study aims to add to the body of evidence delineating the learning curve for a shoulder surgeon to become proficient in focussed ultrasound for the detection of full-thickness rotator cuff tears, as well as to describe a learning method for this skill. Methods Consecutive patients who were scheduled to undergo an arthroscopy for rotator cuff disease were scanned immediately before surgery by a senior shoulder surgeon with limited previous experience of shoulder ultrasound. The presence or absence of a full-thickness rotator cuff tear on scan was compared with intra-operative findings as the gold standard. Results Two hundred and ten shoulders were scanned over three equal learning periods. Comparing predictive values from the first to the third training period, sensitivity improved from 0.86 to 0.95, specificity from 0.92 to 0.98, negative predictive value from 0.94 to 0.98, and positive predictive value from 0.82 to 0.95. Conclusions The high predictive values obtained in the present study for surgeon-led detection of cuff tears using ultrasound are comparable with those quoted for musculoskeletal radiologists in the literature. The present study adds evidence that a shoulder surgeon can achieve accelerated learning of this skill and offers some potentially time-saving and patient-friendly alternatives to existing guidelines.

  13. Accurate ab initio potential energy curve of O2. II. Core-valence correlations, relativistic contributions, and vibration-rotation spectrum.

    PubMed

    Bytautas, Laimutis; Matsunaga, Nikita; Ruedenberg, Klaus

    2010-02-21

    In the first paper of this series, a very accurate ab initio potential energy curve of the (3)Sigma(g)(-) ground state of O(2) has been determined in the approximation that all valence shell electron correlations were calculated at the complete basis set limit. In the present study, the corrections arising from core electron correlations and relativity effects, viz., spin-orbit coupling and scalar relativity, are determined and added to the potential energy curve. From the 24 points calculated on this curve, an analytical expression in terms of even-tempered Gaussian functions is determined and, from it, the vibrational and rotational energy levels are calculated by means of the discrete variable representation. We find 42 vibrational levels. Experimental data (from the Schumann-Runge band system) only yield the lowest 36 levels due to significant reduction in the transition intensities of higher levels. For the 35 term values G(v), the mean absolute deviation between theoretical and experimental data is 12.8 cm(-1). The dissociation energy with respect to the lowest vibrational energy is calculated within 25 cm(-1) of the experimental value of 41,268.2+/-3 cm(-1). The theoretical crossing between the (3)Sigma(g)(-) state and the (1)Sigma(g)(+) state is found to occur at 2.22 A and the spin-orbit coupling in this region is analyzed. PMID:20170227

  14. Optimal control of a universal rotating magnetic vector for petal-shaped capsule robot in curve environment

    NASA Astrophysics Data System (ADS)

    Zhang, Yongshun; Bai, Jianwei; Chi, Minglu; Cheng, Cunxin; Wang, Dianlong

    2014-09-01

    Steering control of a capsule robot in curve environment by magnetic navigation is not yet solved completely. A petal-shaped capsule robot with less steering resistance based on multiple wedge effects is presented, and an optimization method with two processes for determining the orientation of a pre-applied universal magnetic spin vector is proposed. To realize quick and non-contact steering swimming, a fuzzy comprehensive evaluation method for optimizing the steering driving angle is presented based on two evaluation indexes including the average steering speed and the average steering trajectory deviation, achieving the initial optimal orientation of a universal magnetic spin vector. To further reduce robotic magnetic vibration, a main target method for optimizing its final orientation, which is used for fine adjustment, is employed under the constrains of the magnetic moments. Swimming experimental results in curve pipe verified the effectiveness of the optimization method, which can be effectively used to realize non-contact steering swimming of the petal-shaped robot and reduce its vibration.

  15. Large Picture of the Galactic Center Studied by H_3^+: High Ionization Rate, Prevailing Warm and Diffuse Gas, and Non-Rotating Expanding Molecular Ring

    NASA Astrophysics Data System (ADS)

    Oka, Takeshi; Geballe, Thomas R.; Indriolo, Nick

    2013-06-01

    Following our initial studies of the diffuse interstellar medium in the Central Molecular Zone (CMZ) of the Galactic center (GC) toward two remarkable sightlines--one 140 pc to the West of Sgr A* near Sgr E, and the other 85 pc to the East of Sgr A* near Sgr B --we are in the process of using newly identified bright stars with smooth continua suitable for H_3^+ spectroscopy to both fill the gap between these sightlines and expand coverage to wider regions of the CMZ. So far we have identified 43 qualified stars, of which 24 have been at least partially observed (i.e., in at least one spectral setting). The high ionization rate (on the order of ζ˜3×10^{-15} s^{-1}) and the existence of warm (T˜250 K) and diffuse (n≤100 cm^{-3}) gas previously reported in the GC have also been observed in some of the new sightlines, indicating these conditions fill a large portion of the CMZ. The velocity profiles observed in the diffuse clouds, some of which show absorption extending ˜ 140 km s^{-1}, allow us to draw a velocity-longitude diagram. The high-velocity fronts of such a diagram reveal the existence of an expanding molecular ring (EMR) with radius of ˜ 140 pc and velocity of ˜ 140 km s^{-1}. This ring is similar to those previously reported but is qualitatively different in that it is not rotating, suggesting an expulsion rather than the gravitational potential as causing the EMR. Possible relations between our observations and other high energy events will be discussed. T. R. Geballe and T. Oka, ApJ, 709, L70 (2010). T. Oka, T. R. Geballe, M. Goto, T. Usuda, and B. J. McCall ApJ, 632, 882 (2005). N. Kaifu, T. Kato, and T. Iguchi, Nature, 238, 105 (1972). N. Z. Scoville, ApJ, 175, L127 (1972). Y. Sofue, PASJ, 47, 551 (1995).

  16. Wormhole solutions for f(G) gravity in galactic halo region

    NASA Astrophysics Data System (ADS)

    Sharif, M.; Ismat Fatima, H.

    2016-04-01

    In this paper, we study static spherically symmetric wormhole solutions in galactic halo region. Two observational results, Navarro-Frenk-White energy density profile in standard cosmological model and the observed flat rotational curves, are used to discuss traversable wormholes supported by galactic halo in modified Gauss-Bonnet gravity. We explore these solutions either by considering a viable f(G) model to construct shape function or by specifying the shape function to deduce f(G) model. We explore energy conditions and find physically acceptable wormhole solutions threaded by normal matter for all values of r. Finally, we investigate stability of the resulting wormhole solutions.

  17. "Invisible" Galactic Halos.

    ERIC Educational Resources Information Center

    Lugt, Karel Vander

    1993-01-01

    Develops a simple core-halo model of a galaxy that exhibits the main features of observed rotation curves and quantitatively illustrates the need to postulate halos of dark matter. Uses only elementary mechanics. (Author/MVL)

  18. The α CrB binary system: A new radial velocity curve, apsidal motion, and the alignment of rotation and orbit axes

    NASA Astrophysics Data System (ADS)

    Schmitt, J. H. M. M.; Schröder, K.-P.; Rauw, G.; Hempelmann, A.; Mittag, M.; González-Pérez, J. N.; Czesla, S.; Wolter, U.; Jack, D.

    2016-02-01

    We present a new radial velocity curve for the two components of the eclipsing spectroscopic binary α CrB. This binary consists of two main-sequence stars of types A and G in a 17.3599-day orbit, according to the data from our robotic TIGRE facility that is located in Guanajuato, Mexico. We used a high-resolution solar spectrum to determine the radial velocities of the weak secondary component by cross-correlation and wavelength referencing with telluric lines for the strongly rotationally broadened primary lines (v sin(i) = 138 km s-1) to obtain radial velocities with an accuracy of a few hundred m/s. We combined our new RV data with older measurements, dating back to 1908 in the case of the primary, to search for evidence of apsidal motion. We find an apsidal motion period between 6600 and 10 600 yr. This value is consistent with the available data for both the primary and secondary and is also consistent with the assumption that the system has aligned orbit and rotation axes.

  19. The Skipping Rope Curve

    ERIC Educational Resources Information Center

    Nordmark, Arne; Essen, Hanno

    2007-01-01

    The equilibrium of a flexible inextensible string, or chain, in the centrifugal force field of a rotating reference frame is investigated. It is assumed that the end points are fixed on the rotation axis. The shape of the curve, the skipping rope curve or "troposkien", is given by the Jacobi elliptic function sn. (Contains 3 figures.)

  20. Pitch angle of galactic spiral arms

    SciTech Connect

    Michikoshi, Shugo; Kokubo, Eiichiro E-mail: kokubo@th.nao.ac.jp

    2014-06-01

    One of the key parameters that characterizes spiral arms in disk galaxies is a pitch angle that measures the inclination of a spiral arm to the direction of galactic rotation. The pitch angle differs from galaxy to galaxy, which suggests that the rotation law of galactic disks determines it. In order to investigate the relation between the pitch angle of spiral arms and the shear rate of galactic differential rotation, we perform local N-body simulations of pure stellar disks. We find that the pitch angle increases with the epicycle frequency and decreases with the shear rate and obtain the fitting formula. This dependence is explained by the swing amplification mechanism.

  1. A simple, efficient, and high-order accurate curved sliding-mesh interface approach to spectral difference method on coupled rotating and stationary domains

    NASA Astrophysics Data System (ADS)

    Zhang, Bin; Liang, Chunlei

    2015-08-01

    This paper presents a simple, efficient, and high-order accurate sliding-mesh interface approach to the spectral difference (SD) method. We demonstrate the approach by solving the two-dimensional compressible Navier-Stokes equations on quadrilateral grids. This approach is an extension of the straight mortar method originally designed for stationary domains [7,8]. Our sliding method creates curved dynamic mortars on sliding-mesh interfaces to couple rotating and stationary domains. On the nonconforming sliding-mesh interfaces, the related variables are first projected from cell faces to mortars to compute common fluxes, and then the common fluxes are projected back from the mortars to the cell faces to ensure conservation. To verify the spatial order of accuracy of the sliding-mesh spectral difference (SSD) method, both inviscid and viscous flow cases are tested. It is shown that the SSD method preserves the high-order accuracy of the SD method. Meanwhile, the SSD method is found to be very efficient in terms of computational cost. This novel sliding-mesh interface method is very suitable for parallel processing with domain decomposition. It can be applied to a wide range of problems, such as the hydrodynamics of marine propellers, the aerodynamics of rotorcraft, wind turbines, and oscillating wing power generators, etc.

  2. 3D rotating wall vessel and 2D cell culture of four veterinary virus pathogens: A comparison of virus yields, portions of infectious particles and virus growth curves.

    PubMed

    Malenovská, Hana

    2016-02-01

    Only very few comparative studies have been performed that evaluate general trends of virus growth under 3D in comparison with 2D cell culture conditions. The aim of this study was to investigate differences when four animal viruses are cultured in 2D and 3D. Suid herpesvirus 1 (SuHV-1), Vesicular stomatitis virus (VSIV), Bovine adenovirus (BAdV) and Bovine parainfluenza 3 virus (BPIV-3) were cultivated in 3D rotating wall vessels (RWVs) and conventional 2D cultures. The production of virus particles, the portion of infectious particles, and the infectious growth curves were compared. For all viruses, the production of virus particles (related to cell density), including the non-infectious ones, was lower in 3D than in 2D culture. The production of only infectious particles was significantly lower in BAdV and BPIV-3 in 3D cultures in relation to cell density. The two cultivation approaches resulted in significantly different virus particle-to-TCID50 ratios in three of the four viruses: lower in SuHV-1 and BPIV-3 and higher in BAdV in 3D culture. The infectious virus growth rates were not significantly different in all viruses. Although 3D RWV culture resulted in lower production of virus particles compared to 2D systems, the portion of infectious particles was higher for some viruses. PMID:26562056

  3. Alterations of the Danger Zone after Preparation of Curved Root Canals Using WaveOne with Reverse Rotation or Reciprocation Movements

    PubMed Central

    Shantiaee, Yazdan; Dianat, Omid; Paymanpour, Payam; Nahvi, Golnaz; Ketabi, Mohammad Ali; Kolahi Ahari, Golbarg

    2015-01-01

    Introduction: The aim of this study was to compare the changes that occur in the danger zone (DZ) after preparation of curved mesiobuccal (MB) canals of mandibular first molars with WaveOne instruments in two different movements [reciprocation (RCP) and counter-clockwise rotation (CCWR)] by means of cone-beam computed tomography (CBCT). Methods and Materials: MB canals of 30 mandibular molars were randomly divided into 2 groups (n=15); WaveOne/RCP and WaveOne/CCWR. Pre- and post-instrumentation CBCT images were assessed for changes in the dentin thickness in DZ (2 and 4 mm below the highest point of the root furcation) in both groups. Data was analyzed using the repeated measures ANOVA test. Results: There was no statistically significant difference between two experimental groups in terms of remaining dentin thickness at 2 and 4 mm levels below the highest point of the furcation (P>0.05). Conclusion: The efficacy of WaveOne instrument on changes of the dentin thickness in the DZ was not affected by different file movements. PMID:26213536

  4. Galactic dynamos

    NASA Astrophysics Data System (ADS)

    Moss, David

    There is a broad agreement between the predictions of galactic dynamo theory and observations; although there are still some unresolved difficulties, the theory appears to be robust. Now attention is turning from generic models to studies of particular features of the large-scale magnetic fields, and also to models for specific galaxies. The effects of noncircular flows, for example driven by the interaction of spiral arms and galactic bars with the dynamo, are of current interest.

  5. Axions and the galactic angular momentum distribution

    NASA Astrophysics Data System (ADS)

    Banik, N.; Sikivie, P.

    2013-12-01

    We analyze the behavior of axion dark matter before it falls into a galactic gravitational potential well. The axions thermalize sufficiently fast by gravitational self-interactions that almost all go to their lowest-energy state consistent with the total angular momentum acquired from tidal torquing. That state is a state of rigid rotation on the turnaround sphere. It predicts the occurrence and detailed properties of the caustic rings of dark matter for which observational evidence had been found earlier. We show that the vortices in the axion Bose-Einstein condensate (BEC) are attractive, unlike those in superfluid He4 and dilute gases. We expect that a large fraction of the vortices in the axion BEC join into a single big vortex along the rotation axis of the galaxy. The resulting enhancement of caustic rings explains the typical size of the rises in the Milky Way rotation curve attributed to caustic rings. We show that baryons and ordinary cold dark matter particles are entrained by the axion BEC and acquire the same velocity distribution. The resulting baryonic angular momentum distribution gives a good qualitative fit to the distributions observed in dwarf galaxies. We give estimates of the minimum fraction of dark matter that is composed of axions.

  6. Simulations of Galactic Dynamos

    NASA Astrophysics Data System (ADS)

    Brandenburg, Axel

    We review our current understanding of galactic dynamo theory, paying particular attention to numerical simulations both of the mean-field equations and the original three-dimensional equations relevant to describing the magnetic field evolution for a turbulent flow. We emphasize the theoretical difficulties in explaining non-axisymmetric magnetic fields in galaxies and discuss the observational basis for such results in terms of rotation measure analysis. Next, we discuss nonlinear theory, the role of magnetic helicity conservation and magnetic helicity fluxes. This leads to the possibility that galactic magnetic fields may be bi-helical, with opposite signs of helicity and large and small length scales. We discuss their observational signatures and close by discussing the possibilities of explaining the origin of primordial magnetic fields.

  7. Topics in galactic dynamics

    NASA Astrophysics Data System (ADS)

    Little, Frank Blane

    1989-01-01

    The distant satellites of the Milky Way Galaxy are used to probe the distribution of dark matter in the Galactic halo. A new method of statistical analysis based on Bayes' theorem was devised, which directly yields confidence intervals for the mass of the Galaxy once the eccentricity distribution of the satellites is specified. Assuming an isotropic velocity distribution for 10 objects at distances of 50 to 140 kiloparsecs, mass results suggest that the Galaxy's massive dark halo extends to approximately less than 50 kiloparsecs from the Galactic center. A model galaxy with an artificial bar is used to explore the effect of dynamical friction on a galactic bar. An analytic formula is provided which correctly predicts angular momentum changes for a bar in interaction with a non self-gravitating disk. N-body simulations further show that disk self-gravity tends to make a bar without inner Lindblad resonances spin down more rapidly, and tends to make a bar dominated by inner Lindblad resonances spin up less rapidly. The long-term dynamical evolution of galactic bars is investigated using fully self gravitating bar-unstable disk-halo models. The models develop rapidly rotating bars which then slow down through transfers of angular momentum both to the outer disk and to the halo. The models suggest that the distance between the end of a bar and its corotation circle is proportional to the bar's age, and an approximate formula is presented which expresses this relationship. It is also concluded that the average tangential velocity within a barlike object drops by a factor of about 2 over approximately 45 initial rotation periods.

  8. ATOMIC HYDROGEN IN A GALACTIC CENTER OUTFLOW

    SciTech Connect

    McClure-Griffiths, N. M.; Green, J. A.; Hill, A. S.; Lockman, F. J.; Dickey, J. M.; Gaensler, B. M.; Green, A. J.

    2013-06-10

    We describe a population of small, high-velocity, atomic hydrogen clouds, loops, and filaments found above and below the disk near the Galactic center. The objects have a mean radius of 15 pc, velocity widths of {approx}14 km s{sup -1}, and are observed at |z| heights up to 700 pc. The velocity distribution of the clouds shows no signature of Galactic rotation. We propose a scenario where the clouds are associated with an outflow from a central star-forming region at the Galactic center. We discuss the clouds as entrained material traveling at {approx}200 km s{sup -1} in a Galactic wind.

  9. The Galactic Dense Gas Distribution and Properties

    NASA Astrophysics Data System (ADS)

    Glenn, Jason

    2015-08-01

    As the nearest spiral galaxy, the Milky Way provides a foundation for understanding galactic astrophysics. However, our position within the Galactic plane makes it challenging to decipher the detailed disk structure. The Galactic distribution of dense gas is relatively poorly known; thus, it is difficult to assess models of galaxy evolution by comparison to the Milky Way. Furthermore, fundamental aspects of star formation remain unknown, such as why the stellar and star cluster initial mass functions appear to be ubiquitous.Sub/millimeter dust continuum surveys, coupled with molecular gas surveys, are revealing the 3D distribution and properties of dense, star-forming gas throughout the disk. Here we report on the use of BGPS and Hi-GAL. BGPS is a 1.1 mm survey of the 1st Galactic quadrant and some lines of sight in the 2nd quadrant, totalling 200 deg2. We developed a technique using the Galactic rotation curve to derive distance probability density functions (DPDFs) to molecular cloud structures identified with continuum surveys. DPDFs combine vLSR measures from dense gas tracers and 13CO with distance discriminators, such as 8 μm extinction, HI self absorption, and (l, b, vLSR) associations with objects of known distances. Typical uncertainties are σdist ≤ 1 kpc for 1,710 BGPS objects with well-constrained distances.From DPDFs we derived the dense gas distribution and the dense gas mass function. We find evidence for dense gas in and between putative spiral arms. A log-normal distribution describes the mass function, which ranges from cores to clouds, but is primarily comprised of clumps. High-mass power laws do not fit the entire data set well, although power-law behavior emerges for sources nearer than 6.5 kpc (α = 2.0±0.1) and for objects between 2 kpc and 10 kpc (α = 1.9±0.1). The power law indices are generally between those of GMC and the stellar IMF. We have begun to apply this approach to the Hi-GAL (70 - 500 μm). With coverage of the entire

  10. Galactic Winds

    NASA Astrophysics Data System (ADS)

    Veilleux, Sylvain

    Galactic winds have become arguably one of the hottest topics in extragalactic astronomy. This enthusiasm for galactic winds is due in part to the detection of winds in many, if not most, high-redshift galaxies. Galactic winds have also been invoked by theorists to (1) suppress the number of visible dwarf galaxies and avoid the "cooling catastrophe" at high redshift that results in the overproduction of massive luminous galaxies, (2) remove material with low specific angular momentum early on and help enlarge gas disks in CDM + baryons simulations, (3) reduce the dark mass concentrations in galaxies, (4) explain the mass-metallicity relation of galaxies from selective loss of metal-enriched gas from smaller galaxies, (5) enrich and "preheat" the ICM, (6) enrich the IGM without disturbing the Lyαforest significantly, and (7) inhibit cooling flows in galaxy clusters with active cD galaxies. The present paper highlights a few key aspects of galactic winds taken from a recent ARAA review by Veilleux, Cecil, &Bland-Hawthorn (2005; herafter VCBH). Readers interested in a more detailed discussion of this topic are encouraged to refer to the original ARAA article.

  11. Galactic oscillator symmetry

    NASA Technical Reports Server (NTRS)

    Rosensteel, George

    1995-01-01

    Riemann ellipsoids model rotating galaxies when the galactic velocity field is a linear function of the Cartesian coordinates of the galactic masses. In nuclear physics, the kinetic energy in the linear velocity field approximation is known as the collective kinetic energy. But, the linear approximation neglects intrinsic degrees of freedom associated with nonlinear velocity fields. To remove this limitation, the theory of symplectic dynamical symmetry is developed for classical systems. A classical phase space for a self-gravitating symplectic system is a co-adjoint orbit of the noncompact group SP(3,R). The degenerate co-adjoint orbit is the 12 dimensional homogeneous space Sp(3,R)/U(3), where the maximal compact subgroup U(3) is the symmetry group of the harmonic oscillator. The Hamiltonian equations of motion on each orbit form a Lax system X = (X,F), where X and F are elements of the symplectic Lie algebra. The elements of the matrix X are the generators of the symplectic Lie algebra, viz., the one-body collective quadratic functions of the positions and momenta of the galactic masses. The matrix F is composed from the self-gravitating potential energy, the angular velocity, and the hydostatic pressure. Solutions to the hamiltonian dynamical system on Sp(3,R)/U(3) are given by symplectic isospectral deformations. The Casimirs of Sp(3,R), equal to the traces of powers of X, are conserved quantities.

  12. Development of a Single Station 6C-Approach for Array Analysis and Microzonation: Using Vertical Rotation Rate to Estimate Love-Wave Disperion Curves and Direction Finding

    NASA Astrophysics Data System (ADS)

    Wassermann, J. M.; Wietek, A.; Hadziioannou, C.; Igel, H.

    2014-12-01

    Microzonation, i.e. the estimation of (shear) wave velocity profiles of the upper few 100m in dense 2D surface grids is one of the key methods to understand the variation in seismic hazard caused by ground shaking events. In this presentation we introduce a novel method for estimating the Love-wave phase velocity dispersion by using ambient noise recordings. We use the vertical component of rotational motions inherently present in ambient noise and the well established relation to simultaneous recordings of transverse acceleration. In this relation the frequency dependent phase velocity of a plane SH (or Love)-type wave acts as a proportionality factor between the anti-correlated amplitudes of both measures. In a first step we used synthetic data sets with increasing complexity to evaluate the proposed technique and the developed algorithm to extract the direction and amplitude of the incoming ambient noise wavefield measured at a single site. Since reliable weak rotational motion sensors are not yet readily available, we apply array derived rotation measurements in order to test our method. We next use the technique to analyze different real data sets of ambient noise measurements as well as seismic recordings at active volcanoes and compare these results with findings of the Spatial AutoCorrelation technique which was applied to the same data set. We demonstrate that the newly developed technique shows comparable results to more classical, strictly array based methods. Furthermore, we show that as soon as portable weak motion rotational motion sensors are available, a single 6C-station approach will be feasible, not only for microzonation but also for general array applications, with performance comparable to more classical techniques. An important advantage, especially in urban environments, is that with this approach, the number of seismic stations needed is drastically reduced.

  13. A Galactic ring of minimum stellar density near the solar orbit radius

    NASA Astrophysics Data System (ADS)

    Barros, D. A.; Lépine, J. R. D.; Junqueira, T. C.

    2013-11-01

    We analyse the secular effects of a long-lived Galactic spiral structure on the stellar orbits with mean radii close to the corotation resonance. By test-particle simulations and different spiral potential models with parameters constrained on observations, we verified the formation of a minimum with amplitude ˜30-40 per cent of the background disc stellar density at corotation. Such a minimum is formed by the secular angular momentum transfer between stars and the spiral density wave on both sides of corotation. We demonstrate that the secular loss (gain) of angular momentum and decrease (increase) of mean orbital radius of stars just inside (outside) corotation can counterbalance the opposite trend of exchange of angular momentum shown by stars orbiting the librational points L4/5 at the corotation circle. Such secular processes actually allow steady spiral waves to promote radial migration across corotation. We propose some pieces of observational evidence for the minimum stellar density in the Galactic disc, such as its direct relation to the minimum in the observed rotation curve of the Galaxy at the radius r ˜ 9 kpc (for R0 = 7.5 kpc), as well as its association with a minimum in the distribution of Galactic radii of a sample of open clusters older than 1 Gyr. The closeness of the solar orbit radius to the corotation resonance implies that the solar orbit lies inside a ring of minimum surface density (stellar + gas). This also implies a correction to larger values for the estimated total mass of the Galactic disc, and consequently, a greater contribution of the disc component to the inner rotation curve of the Galaxy.

  14. Galactic Diffuse Polarized Emission

    NASA Astrophysics Data System (ADS)

    Carretti, Ettore

    2011-12-01

    Diffuse polarized emission by synchrotron is a key tool to investigate magnetic fields in the Milky Way, particularly the ordered component of the large scale structure. Key observables are the synchrotron emission itself and the RM is by Faraday rotation. In this paper the main properties of the radio polarized diffuse emission and its use to investigate magnetic fields will be reviewed along with our current understanding of the galactic magnetic field and the data sets available. We will then focus on the future perspective discussing RM-synthesis - the new powerful instrument devised to unlock the information encoded in such an emission - and the surveys currently in progress like S-PASS and GMIMS.

  15. Gas as a Tracer of the Galactic Potential

    NASA Astrophysics Data System (ADS)

    Kalberla, Peter M. W.

    2004-02-01

    We consider a disk-like dark matter model for the Milky Way andcompare a few predictions with observations. The observed gaseousflaring for HI and molecular gas fits the model predictions indetail. The global HI distribution in the Milky Way needs to beexplained by a multiphase medium. The dark matter distribution in theGalactic halo is traced by a low density component of halogas. High-velocity clouds with distances up to ˜ 50 kpc may beexplained as condensations which originate from instabilities withinthe gaseous halo. Our model explains also ‘beards’ and ‘forbiddenvelocities’ as observed in the rotation curves of externalgalaxies. A disk-like dark matter model is self-consistent and inexcellent agreement with observations.

  16. A self-consistent field method for galactic dynamics

    NASA Technical Reports Server (NTRS)

    Hernquist, Lars; Ostriker, Jeremiah P.

    1992-01-01

    The present study describes an algorithm for evolving collisionless stellar systems in order to investigate the evolution of systems with density profiles like the R exp 1/4 law, using only a few terms in the expansions. A good fit is obtained for a truncated isothermal distribution, which renders the method appropriate for galaxies with flat rotation curves. Calculations employing N of about 10 exp 6-7 are straightforward on existing supercomputers, making possible simulations having significantly smoother fields than with direct methods such as tree-codes. Orbits are found in a given static or time-dependent gravitational field; the potential, phi(r, t) is revised from the resultant density, rho(r, t). Possible scientific uses of this technique are discussed, including tidal perturbations of dwarf galaxies, the adiabatic growth of central masses in spheroidal galaxies, instabilities in realistic galaxy models, and secular processes in galactic evolution.

  17. Frequency curves

    USGS Publications Warehouse

    Riggs, H.C.

    1968-01-01

    This manual describes graphical and mathematical procedures for preparing frequency curves from samples of hydrologic data. It also discusses the theory of frequency curves, compares advantages of graphical and mathematical fitting, suggests methods of describing graphically defined frequency curves analytically, and emphasizes the correct interpretations of a frequency curve.

  18. Kinematic Distances to Molecular Clouds Identified in the Galactic Ring Survey

    NASA Astrophysics Data System (ADS)

    Roman-Duval, Julia; Jackson, James M.; Heyer, Mark; Johnson, Alexis; Rathborne, Jill; Shah, Ronak; Simon, Robert

    2009-07-01

    Kinematic distances to 750 molecular clouds identified in the 13CO J = 1 → 0 Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey (GRS) are derived assuming the Clemens rotation curve of the Galaxy. The kinematic distance ambiguity is resolved by examining the presence of H I self-absorption toward the 13CO emission peak of each cloud using the Very Large Array Galactic Plane Survey. We also identify 21 cm continuum sources embedded in the GRS clouds in order to use absorption features in the H I 21 cm continuum to distinguish between near and far kinematic distances. The Galactic distribution of GRS clouds is consistent with a four-arm model of the Milky Way. The locations of the Scutum-Crux and Perseus arms traced by GRS clouds match star-count data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire star-count data. We conclude that molecular clouds must form in spiral arms and be short-lived (lifetimes < 107 yr) in order to explain the absence of massive, 13CO bright molecular clouds in the interarm space.

  19. INTEGRAL Galactic bulge monitoring program

    NASA Astrophysics Data System (ADS)

    Kuulkers, E.; Kouveliotou, C.; van der Horst, A. J.; Belloni, T.; Chenevez, J.; Ibarra, A.; Munoz-Darias, T.; Bazzano, A.; Cadolle Bel, M.; De Cesare, G.; Diaz Trigo, M.; Jourdain, E.; Lubinski, P.; Natalucci, L.; Ness, J. U.; Parmar, A.; Pollock, A. M. T.; Rodriguez, J.; Roques, J. P.; Sanchez-Fernandez; C.; Ubertini, P.; Winkler, C.

    2010-12-01

    The central region of our Galaxy, the Galactic bulge, is a rich host of variable high-energy X-ray and gamma-ray point sources. These sources include bright and relatively faint X-ray transients, X-ray bursters, persistent neutron star and black-hole candidate binaries, high-mass X-ray binaries, etc.. We have a program to monitor the Galactic bulge region regularly and frequently with the gamma-ray observatory INTEGRAL, whenever it is observable. As a service to the scientific community the high-energy light curves of sources present, as well as the images of the region are made available through the WWW at http://integral.esac.esa.int/BULGE/ as soon as possible after the observations have been performed. We show the ongoing results of this exciting program.

  20. Tool For Making Curved Holes

    NASA Technical Reports Server (NTRS)

    Allard, Robert; Calve, Andrew; Pastreck, Edwin; Padden, Edward

    1992-01-01

    Tool for use in electrical-discharge machining (EDM) guides EDM electrode in making curved holes. Guide rod fits in slot in arm, which moves through arc. Motion drives electrode into workpiece along desired curved path. Electrode burns into workpiece while arm rotates on spindle. Discharge cuts hole of same radius of curvature.

  1. The distances of the Galactic Novae

    NASA Astrophysics Data System (ADS)

    Ozdonmez, Aykut; Guver, Tolga; Cabrera-Lavers, Antonio; Ak, Tansel

    2016-07-01

    Using location of the RC stars on the CMDs obtained from the UKIDSS, VISTA and 2MASS photometry, we have derived the reddening-distance relations towards each Galactic nova for which at least one independent reddening measurement exists. We were able to determine the distances of 72 Galactic novae and set lower limits on the distances of 45 systems. The reddening curves of the systems are presented. These curves can be also used to estimate reddening or the distance of any source, whose location is close to the position of the nova in our sample. The distance measurement method in our study can be easily applicable to any source, especially for ones that concentrated along the Galactic plane.

  2. The Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Rich, R. M.

    2015-05-01

    Observations at Cerro Tololo Inter-American Observatory (CTIO) have had a critical formative impact on the study of the Galactic bulge, much of the work being inspired and supported by Victor Blanco and collaborators, which is presented in a historical overview. Recent observations at CTIO include the Blanco 4m/Hydra Bulge Radial Velocity Assay (BRAVA) that has mapped the Galactic bulge velocity field from -10rotation that is consistent with the population being dominated by a kinematic bar that appears to have originated from the secular evolution of a massive disk. Using the Hydra multi-object spectrograph at CTIO, it has been shown that the bulge is dominated by a population that is alpha enhanced relative to the thin and thick disk, and shows the signature of the r-process being important in enrichment. Both composition indicators are consistent with early, rapid formation of the bulge. Although proper motion selected and field-subtracted color-magnitude diagrams reaching the main sequence turnoff are consistent with the bulge being predominantly globular cluster-age, analysis of microlensed dwarf stars favors a substantial fraction of the bulge being younger than 5 Gyr. To help define the overall picture of the bulge better, the Blanco DECam Bulge Survey (BDBS) will produce a multicolor ugrizY map of the bulge from -10< l<+10 and -10

  3. Testing the Bose-Einstein Condensate dark matter model at galactic cluster scale

    NASA Astrophysics Data System (ADS)

    Harko, Tiberiu; Liang, Pengxiang; Liang, Shi-Dong; Mocanu, Gabriela

    2015-11-01

    The possibility that dark matter may be in the form of a Bose-Einstein Condensate (BEC) has been extensively explored at galactic scale. In particular, good fits for the galactic rotations curves have been obtained, and upper limits for the dark matter particle mass and scattering length have been estimated. In the present paper we extend the investigation of the properties of the BEC dark matter to the galactic cluster scale, involving dark matter dominated astrophysical systems formed of thousands of galaxies each. By considering that one of the major components of a galactic cluster, the intra-cluster hot gas, is described by King's β-model, and that both intra-cluster gas and dark matter are in hydrostatic equilibrium, bound by the same total mass profile, we derive the mass and density profiles of the BEC dark matter. In our analysis we consider several theoretical models, corresponding to isothermal hot gas and zero temperature BEC dark matter, non-isothermal gas and zero temperature dark matter, and isothermal gas and finite temperature BEC, respectively. The properties of the finite temperature BEC dark matter cluster are investigated in detail numerically. We compare our theoretical results with the observational data of 106 galactic clusters. Using a least-squares fitting, as well as the observational results for the dark matter self-interaction cross section, we obtain some upper bounds for the mass and scattering length of the dark matter particle. Our results suggest that the mass of the dark matter particle is of the order of μ eV, while the scattering length has values in the range of 10-7 fm.

  4. GALACTIC SPIRAL SHOCKS WITH THERMAL INSTABILITY IN VERTICALLY STRATIFIED GALACTIC DISKS

    SciTech Connect

    Kim, Chang-Goo; Kim, Woong-Tae; Ostriker, Eve C. E-mail: wkim@astro.snu.ac.k

    2010-09-10

    Galactic spiral shocks are dominant morphological features and believed to be responsible for substructure formation within spiral arms in disk galaxies. They can also contribute a substantial amount of kinetic energy to the interstellar gas by tapping the (differential) rotational motion. We use numerical hydrodynamic simulations to investigate dynamics and structure of spiral shocks with thermal instability (TI) in vertically stratified galactic disks, focusing on environmental conditions (of heating and the galactic potential) similar to the Solar neighborhood. We initially consider an isothermal disk in vertical hydrostatic equilibrium and let it evolve subject to interstellar cooling and heating as well as a stellar spiral potential. Due to TI, a disk with surface density {Sigma}{sub 0} {>=} 6.7 M{sub sun} pc{sup -2} rapidly turns to a thin dense slab near the midplane sandwiched between layers of rarefied gas. The imposed spiral potential leads to a vertically curved shock that exhibits strong flapping motions in the plane perpendicular to the arm. The overall flow structure at saturation is comprised of the arm, postshock expansion zone, and interarm regions that occupy typically 10%, 20%, and 70% of the arm-to-arm distance, in which the gas resides for 15%, 30%, and 55% of the arm-to-arm crossing time, respectively. The flows are characterized by transitions from rarefied to dense phases at the shock and from dense to rarefied phases in the postshock expansion zone, although gas with too-large postshock-density does not undergo this return phase transition, instead forming dense condensations. If self-gravity is omitted, the shock flapping drives random motions in the gas, but only up to {approx}2-3 km s{sup -1} in the in-plane direction and less than 2 km s{sup -1} in the vertical direction. Time-averaged shock profiles show that the spiral arms in stratified disks are broader and less dense compared to those in unstratified models, and that the vertical

  5. Galactic Spiral Shocks with Thermal Instability in Vertically Stratified Galactic Disks

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Goo; Kim, Woong-Tae; Ostriker, Eve C.

    2010-09-01

    Galactic spiral shocks are dominant morphological features and believed to be responsible for substructure formation within spiral arms in disk galaxies. They can also contribute a substantial amount of kinetic energy to the interstellar gas by tapping the (differential) rotational motion. We use numerical hydrodynamic simulations to investigate dynamics and structure of spiral shocks with thermal instability (TI) in vertically stratified galactic disks, focusing on environmental conditions (of heating and the galactic potential) similar to the Solar neighborhood. We initially consider an isothermal disk in vertical hydrostatic equilibrium and let it evolve subject to interstellar cooling and heating as well as a stellar spiral potential. Due to TI, a disk with surface density Σ0 >= 6.7 M sun pc-2 rapidly turns to a thin dense slab near the midplane sandwiched between layers of rarefied gas. The imposed spiral potential leads to a vertically curved shock that exhibits strong flapping motions in the plane perpendicular to the arm. The overall flow structure at saturation is comprised of the arm, postshock expansion zone, and interarm regions that occupy typically 10%, 20%, and 70% of the arm-to-arm distance, in which the gas resides for 15%, 30%, and 55% of the arm-to-arm crossing time, respectively. The flows are characterized by transitions from rarefied to dense phases at the shock and from dense to rarefied phases in the postshock expansion zone, although gas with too-large postshock-density does not undergo this return phase transition, instead forming dense condensations. If self-gravity is omitted, the shock flapping drives random motions in the gas, but only up to ~2-3 km s-1 in the in-plane direction and less than 2 km s-1 in the vertical direction. Time-averaged shock profiles show that the spiral arms in stratified disks are broader and less dense compared to those in unstratified models, and that the vertical density distribution is overall consistent

  6. Spinal curves and scoliosis.

    PubMed

    Anderson, Susan M

    2007-01-01

    Scoliosis, an abnormal side-to-side curve of the spine with associated vertebral rotation, affects as many as 4% of all adolescents. Several different categories of scoliosis exist, and treatment can range from observation and follow-up to bracing and surgical correction. This article discusses special imaging series for scoliosis and emphasizes the need for proper radiation protection techniques for patients with scoliosis, most of whom are girls in their early to mid-teens. PMID:17848532

  7. Modulating terrestrial impacts from Oort cloud comets by the adiabatically changing galactic tides

    NASA Technical Reports Server (NTRS)

    Matese, J. J.; Whitman, P. G.; Innanen, K. A.; Valtonen, M. J.

    1994-01-01

    Time modulation of the flux of new Jupiter-dominated Oort cloud comets is the subject of interest here. The major perturbation of these comets during the present epoch is due to the tidal field of the relatively smooth distribution of matter in the galactic disk. A secondary source of the near-parabolic comet flux are stars penetrating the inner Oort cloud and providing impulses that create brief comet showers. Substantial stellar-induced showers occur approximately every 100 m.y. Less frequent (but stronger) impulses due to giant molecular clouds can also perturb comets from the inner cloud. These occur on timescales of approximately equal to 500 m.y. In contrast to these infrequent stochastic shower phenomena is the continuously varying tidal-induced flux due to the galaxy. As the Sun orbits the galactic center it undergoes quasiharmonic motion about the galactic midplane, which is superimposed on the small eccentricity, near-Keplerian motion in the plane having epicycle period approximately equal to 150 m.y. In the process the galactic tidal field on the Sun/cloud system will vary causing a modulation of the observable Oort cloud flux. We have created a model of the galactic matter distribution as it affects the solar motion over a time interval ranging from 300 m.y. in the past to 100 m.y. into the future. As constraints on the disk's compact dark matter component we require consistency with the following: (1) the observed galactic rotation curve, (2) today's flux distribution of new comets, (3) the studies of K-giant distributions, and (4) the periodicity found in the terrestrial cratering record. The adiabatically varying galactic tidal torque is then determined and used to predict the time dependence of the flux. We find that a model in which approximately half the disk matter is compact is consistent with these constraints. Under such circumstances the peak-to-trough flux variation will be approx. equal to 5:1 with a full width of 9 m.y. This variability

  8. Models for galactic X-ray sources

    NASA Technical Reports Server (NTRS)

    Joss, P. C.

    1980-01-01

    Attention is given to those compact galactic X-ray sources whose X-ray luminosities are considerably in excess of the solar luminosity. It is pointed out that the key breakthrough in the development of an understanding of compact galactic X-ray sources was the discovery of X-ray pulsars with the UHURU satellite. There is now overwhelming evidence that these objects are neutron stars in close binary stellar systems. The X-ray pulsations are thought to be thermal emission from the magnetic polar caps of a neutron star that is accreting matter from a companion star and whose magnetic field is misaligned with its rotation axis. Among the compact galactic X-ray sources that are not X-ray pulsars, some still show direct evidence of binary membership, such as X-ray eclipses. There is evidence that the galactic-bulge sources are, in fact, close binary stellar systems. It is concluded, that the great majority of bright galactic X-ray sources, with only a tiny handful of exceptions (such as the Crab and Vela pulsars), are likely to be binaries.

  9. Discovery in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-11-01

    In our efforts to map our galaxys structure, one region has remained very difficult to probe: the galactic center. A new survey, however, uses infrared light to peer through the gas and dust in the galactic plane, searching for variable stars in the bulge of the galaxy. This study has discovered a population of very young stars in a thin disk in the galactic center, providing clues to the star formation history of the Milky Way over the last 100 million years.Obscured CenterThe center of the Milky Way is dominated by a region known as the galactic bulge. Efforts to better understand this region in particular, its star formation history have been hindered by the stars, gas, and dust of the galactic disk, which prevent us from viewing the galactic bulge at low latitudes in visible light.The positions of the 35 classical Cepheids discovered in VVV data, projected onto an image of the galactic plane. Click for a better look! The survey area is bounded by the blue lines, and the galactic bar is marked with a red curve. The bottom panel shows the position of the Cepheids overlaid on the VVV bulge extinction map. [Dkny et al. 2015]Infrared light, however, can be used to probe deeper through the dust than visible-light searches. A new survey called VISTA Variables in the Via Lactea (VVV) uses the VISTA telescope in Chile to search, in infrared, for variable stars in the inner part of the galaxy. The VVV survey area spans the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high.Led by Istvn Dkny, a researcher at the Millennium Institute of Astrophysics and the Pontifical Catholic University of Chile, a team has now used VVV data to specifically identify classical Cepheid variable stars in the bulge. Why? Cepheids are pulsating stars with a very useful relation between their periods and luminosities that allows them to be used as distance indicators. Moreover, classical Cepheids are indicators of young stellar populations which can

  10. Active galactic nuclei

    PubMed Central

    Fabian, Andrew C.

    1999-01-01

    Active galactic nuclei are the most powerful, long-lived objects in the Universe. Recent data confirm the theoretical idea that the power source is accretion into a massive black hole. The common occurrence of obscuration and outflows probably means that the contribution of active galactic nuclei to the power density of the Universe has been generally underestimated. PMID:10220363

  11. Bradford Curves.

    ERIC Educational Resources Information Center

    Rousseau, Ronald

    1994-01-01

    Discussion of informetric distributions shows that generalized Leimkuhler functions give proper fits to a large variety of Bradford curves, including those exhibiting a Groos droop or a rising tail. The Kolmogorov-Smirnov test is used to test goodness of fit, and least-square fits are compared with Egghe's method. (Contains 53 references.) (LRW)

  12. Estimating extragalactic Faraday rotation

    NASA Astrophysics Data System (ADS)

    Oppermann, N.; Junklewitz, H.; Greiner, M.; Enßlin, T. A.; Akahori, T.; Carretti, E.; Gaensler, B. M.; Goobar, A.; Harvey-Smith, L.; Johnston-Hollitt, M.; Pratley, L.; Schnitzeler, D. H. F. M.; Stil, J. M.; Vacca, V.

    2015-03-01

    Observations of Faraday rotation for extragalactic sources probe magnetic fields both inside and outside the Milky Way. Building on our earlier estimate of the Galactic contribution, we set out to estimate the extragalactic contributions. We discuss the problems involved; in particular, we point out that taking the difference between the observed values and the Galactic foreground reconstruction is not a good estimate for the extragalactic contributions. We point out a degeneracy between the contributions to the observed values due to extragalactic magnetic fields and observational noise and comment on the dangers of over-interpreting an estimate without taking into account its uncertainty information. To overcome these difficulties, we develop an extended reconstruction algorithm based on the assumption that the observational uncertainties are accurately described for a subset of the data, which can overcome the degeneracy with the extragalactic contributions. We present a probabilistic derivation of the algorithm and demonstrate its performance using a simulation, yielding a high quality reconstruction of the Galactic Faraday rotation foreground, a precise estimate of the typical extragalactic contribution, and a well-defined probabilistic description of the extragalactic contribution for each data point. We then apply this reconstruction technique to a catalog of Faraday rotation observations for extragalactic sources. The analysis is done for several different scenarios, for which we consider the error bars of different subsets of the data to accurately describe the observational uncertainties. By comparing the results, we argue that a split that singles out only data near the Galactic poles is the most robust approach. We find that the dispersion of extragalactic contributions to observed Faraday depths is most likely lower than 7 rad/m2, in agreement with earlier results, and that the extragalactic contribution to an individual data point is poorly

  13. BLACK HOLE AURORA POWERED BY A ROTATING BLACK HOLE

    SciTech Connect

    Takahashi, Masaaki; Takahashi, Rohta

    2010-05-15

    We present a model for high-energy emission sources generated by a standing magnetohydrodynamical (MHD) shock in a black hole magnetosphere. The black hole magnetosphere would be constructed around a black hole with an accretion disk, where a global magnetic field could be originated by currents in the accretion disk and its corona. Such a black hole magnetosphere may be considered as a model for the central engine of active galactic nuclei, some compact X-ray sources, and gamma-ray bursts. The energy sources of the emission from the magnetosphere are the gravitational and electromagnetic energies of magnetized accreting matters and the rotational energy of a rotating black hole. When the MHD shock generates in MHD accretion flows onto the black hole, the plasma's kinetic energy and the black hole's rotational energy can convert to radiative energy. In this Letter, we demonstrate the huge energy output at the shock front by showing negative energy postshock accreting MHD flows for a rapidly rotating black hole. This means that the extracted energy from the black hole can convert to the radiative energy at the MHD shock front. When an axisymmetric shock front is formed, we expect a ring-shaped region with very hot plasma near the black hole; this would look like an 'aurora'. The high-energy radiation generated from there would carry to us the information for the curved spacetime due to the strong gravity.

  14. Domain wall model in the galactic Bose-Einstein condensate halo

    SciTech Connect

    Souza, J.C.C. de; Pires, M.O.C. E-mail: marcelo.pires@ufabc.edu.br

    2013-05-01

    We assume that the galactic dark matter halo, considered composed of an axionlike particles Bose-Einstein condensate [1], can present topological defects, namely domain walls, arising as the dark soliton solution for the Gross-Pitaevskii equation in a self-graviting potential. We investigate the influence that such substructures would have in the gravitational interactions within a galaxy. We find that, for the simple domain wall model proposed, the effects are too small to be identified, either by means of a local measurement of the gradient of the gravitational field or by analysing galaxy rotation curves. In the first case, the gradient of the gravitational field in the vicinity of the domain wall would be 10{sup −31} (m/s{sup 2})/m. In the second case, the ratio of the tangential velocity correction of a star due to the presence of the domain wall to the velocity in the spherical symmetric case would be 10{sup −8}.

  15. Searching for IMBHs in Galactic globular clusters through radial velocities of individual stars

    NASA Astrophysics Data System (ADS)

    Lanzoni, Barbara

    2016-02-01

    I present an overview of our ongoing project aimed at building a new generation of velocity dispersion profiles ad rotation curves for a representative sample of Galactic globular clusters, from the the radial velocity of hundreds of individual stars distributed at different distances from the cluster center. The innermost portion of the profiles will be used to constrain the possible presence of intermediate-mass black holes. The adopted methodology consists of combining spectroscopic observations acquired with three different instruments at the ESO-VLT: the adaptive-optics assisted, integral field unit (IFU) spectrograph SINFONI for the innermost and highly crowded cluster cores, the multi-IFU spectrograph KMOS for the intermediate regions, and the multi-fiber instrument FLAMES/GIRAFFE-MEDUSA for the outskirts. The case of NGC 6388, representing the pilot project that motivated the entire program, is described in some details.

  16. Supernova Nucleosynthesis and Galactic Evolution

    NASA Astrophysics Data System (ADS)

    Thielemann, F.-K.; Argast, D.; Brachwitz, F.; Hix, W. R.; Höflich, P.; Liebendörfer, M.; Martinez-Pinedo, G.; Mezzacappa, A.; Nomoto, K.; Panov, I.

    The understanding of the abundance evolution in the interstellar medium, and especially the enrichment of heavy elements, as a function of space and time reflects the history of star formation and the lifetimes of the diverse contributing stellar objects. Therefore, the understanding of the endpoints of stellar evolution is essential. These are mainly planetary nebulae and type II/Ib/Ic supernovae as evolutionary endpoints of single stars, but also events in binary systems can contribute, like e.g. supernovae of type Ia, novae and possibly X-ray bursts and neutron star or neutron star - black hole mergers. Despite many efforts, a full and self-consistent understanding of supernovae (the main contributors to nucleosynthesis in galaxies) is not existing, yet. However, observed spectra, light curves, radioactivities/decay gamma-rays and galactic evolution witness the composition of their ejecta and constrain model uncertainties. We focus on (i) neutrino-induced explosions for type II supernovae and the innermost ejected layers, (ii) electron captures in type Ia supernovae and neutron-rich Fe-group nuclei and finally (iii) galactic chemical evolution and possible r-process sites.

  17. Fermi Galactic Center Zoom

    NASA Video Gallery

    This animation zooms into an image of the Milky Way, shown in visible light, and superimposes a gamma-ray map of the galactic center from NASA's Fermi. Raw data transitions to a view with all known...

  18. Galactic cosmic ray composition

    NASA Technical Reports Server (NTRS)

    Meyer, J. P.

    1986-01-01

    An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.

  19. Stellar Feedback: A Multiphase Interstellar Medium and Galactic Outflows

    NASA Astrophysics Data System (ADS)

    Ceverino, D.

    2009-12-01

    I am presenting new results in our ongoing effort of improving the theory of galaxy formation in a ΛCDM Universe. I pay a special attention to the role of supernova explosions and stellar winds in the galaxy assembly. These processes happen at very small scales, they affect the interstellar medium (ISM) at galactic scales and regulate the formation of a whole galaxy. Previous attempts of mimicking these effects in simulations of galaxy formation use very simplified assumptions. I develop a much more realistic prescription for modeling the feedback, which minimizes any ad hoc sub-grid physics. I start with developing high resolution models of the ISM and formulate the conditions required for its realistic functionality: formation of multi-phase medium with hot chimneys, super-bubbles, cold molecular phase, and very slow consumption of gas. Once these effects are resolved in cosmological simulations, galaxy formation proceeds more realistically. For example, I do not have the overcooling problem. The angular momentum problem (resulting in a too massive bulge) is also reduced substantially: the rotation curves are nearly flat. The galaxy formation also becomes more violent. At high redshift, I routinely find substantial gas outflows from star-forming galaxies. I describe several scaling relations between outflow properties and galaxy properties: maximum velocity, mass and kinetic energy versus stellar mass and SFR. The simulations reproduce this picture only if the resolution is very high: better than 70 pc.

  20. Planck 2013 results. XIII. Galactic CO emission

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Dempsey, J. T.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Fukui, Y.; Galeotta, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Handa, T.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hily-Blant, P.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jewell, J.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leonardi, R.; León-Tavares, J.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Moore, T. J. T.; Morgante, G.; Morino, J.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nakajima, T.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Okuda, T.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Thomas, H. S.; Toffolatti, L.; Tomasi, M.; Torii, K.; Tristram, M.; Tucci, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yamamoto, H.; Yoda, T.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-11-01

    Rotational transition lines of CO play a major role in molecular radio astronomy as a mass tracer and in particular in the study of star formation and Galactic structure. Although a wealth of data exists for the Galactic plane and some well-known molecular clouds, there is no available high sensitivity all-sky survey of CO emission to date. Such all-sky surveys can be constructed using the Planck HFI data because the three lowest CO rotational transition lines at 115, 230 and 345 GHz significantly contribute to the signal of the 100, 217 and 353 GHz HFI channels, respectively. Two different component separation methods are used to extract the CO maps from Planck HFI data. The maps obtained are then compared to one another and to existing external CO surveys. From these quality checks the best CO maps, in terms of signal to noise ratio and/or residual contamination by other emission, are selected. Three different sets of velocity-integrated CO emission maps are produced with different trade-offs between signal-to-noise, angular resolution, and reliability. Maps for the CO J = 1 → 0, J = 2 → 1, and J = 3 → 2 rotational transitions are presented and described in detail. They are shown to be fully compatible with previous surveys of parts of the Galactic plane as well as with undersampled surveys of the high latitude sky. The Planck HFI velocity-integrated CO maps for the J = 1 → 0, J = 2 → 1, and J = 3 →2 rotational transitions provide an unprecedented all-sky CO view of the Galaxy. These maps are also of great interest to monitor potential CO contamination of the Planck studies of the cosmological microwave background.

  1. Trajectories of ballistic impact ejecta on a rotating Earth

    NASA Technical Reports Server (NTRS)

    Alvarez, W.

    1994-01-01

    On an airless, slowly rotating planetary body like the Moon, ejecta particles from an impact follow simple ballistic trajectories. If gaseous interactions in the fireball are ignored, ejecta particles follow elliptical orbits with the center of the planetary body at one focus until they encounter the surface at the point of reimpact. The partial elliptical orbit of the ejecta particle lies in a plane in inertial (galactic) coordinates. Because of the slow rotation rate (for example, 360 degrees/28 days for the Moon), the intersection of the orbital plane and the surface remains nearly a great circle during the flight time of the ejecta. For this reason, lunar rays, representing concentrations of ejecta with the same azimuth but different velocities and/or ejecta angles, lie essentially along great circles. Ejecta from airless but more rapidly rotating bodies will follow more complicated, curving trajectories when plotted in the coordinate frame of the rotating planet or viewed as rays on the planetary surface. The curvature of trajectories of ejecta particles can be treated as a manifestation of the Coriolis effect, with the particles being accelerated by Coriolis pseudoforces. However, it is more straightforward to calculate the elliptical orbit in inertial space and then determine how far the planet rotates beneath the orbiting ejecta particle before reimpact. The Earth's eastward rotation affects ballistic ejecta in two ways: (1) the eastward velocity component increases the velocity of eastbound ejecta and reduces the velocity of westbound ejecta; and (2) the Earth turns underneath inflight ejecta, so that although the latitude of reimpact is not changed, the longitude is displaced westward, with the displacement increasing as a function of the time the ejecta remains aloft.

  2. Cosmic ray acceleration by spiral shocks in the galactic wind

    NASA Astrophysics Data System (ADS)

    Völk, H. J.; Zirakashvili, V. N.

    2004-04-01

    Cosmic ray acceleration by shocks related with Slipping Interaction Regions (SIRs) in the Galactic Wind is considered. SIRs are similar to Solar Wind Corotating Interaction Regions. The spiral structure of our Galaxy results in a strong nonuniformity of the Galactic Wind flow and in SIR formation at distances of 50 to 100 kpc. SIRs are not corotating with the gas and magnetic field because the angular velocity of the spiral pattern differs from that of the Galactic rotation. It is shown that the collective reacceleration of the cosmic ray particles with charge Ze in the resulting shock ensemble can explain the observable cosmic ray spectrum beyond the ``knee'' up to energies of the order of 1017 Z eV. For the reaccelerated particles the Galactic Wind termination shock acts as a reflecting boundary.

  3. Formation Models of the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Gerhard, O.

    2015-05-01

    The Galactic bulge is now considered to be the inner three-dimensional part of the Milky Way's bar. It has a peanut shape and is characterized by cylindrical rotation. In N-body simulations, box/peanut bulges arise from disks through bar and buckling instabilities. Models of this kind explain much of the structure and kinematics of the Galactic bulge and, in principle, also its vertical metallicity gradient. Cosmological disk galaxy formation models with high resolution and improved feedback models are now able to generate late-type disk galaxies with disk-like or barred bulges. These bulges often contain an early collapse stellar population and a population driven by later disk instabilities. Due to the inside-out disk formation, these bulges can be predominantly old, similar to the Milky Way bulge.

  4. THE STELLAR CONTENT OF OBSCURED GALACTIC GIANT H II REGIONS. VII. W3

    SciTech Connect

    Navarete, F.; Figueredo, E.; Damineli, A.; Moises, A. P.; Blum, R. D.; Conti, P. S.

    2011-09-15

    Spectrophotometric distances in the K band have been reported by different authors for a number of obscured Galactic H II regions. Almost 50% of them show large discrepancies compared to the classical method using radial velocities measured in the radio spectral region. In order to provide a crucial test of both methods, we selected a target that does not present particular difficulty for any method and which has been measured by as many techniques as possible. The W3 star-forming complex, located in the Perseus arm, offers a splendid opportunity for such a task. We used the Near-Infrared Integral Field Spectrograph on the Frederick C. Gillett Gemini North telescope to classify candidate 'naked photosphere' OB stars based on Two Micron All Sky Survey photometry. Two of the targets are revealed to be mid-O-type main-sequence stars leading to a distance of d = 2.20 kpc. This is in excellent agreement with the spectrophotometric distance derived in the optical band (d = 2.18 pc) and with a measurement of the W3 trigonometric parallax (d = 1.95 kpc). Such results confirm that the spectrophotometric distances in the K band are reliable. The radio-derived kinematic distance, on the contrary, gives a distance twice as large (d = 4.2 kpc). This indicates that this region of the Perseus arm does not follow the Galactic rotation curve, and this may also be the case for other H II regions for which discrepancies have been found.

  5. Review of the fermionic dark matter model applied to galactic structures

    SciTech Connect

    Krut, A.; Argüelles, C. R.; Rueda, J.; Ruffini, R.

    2015-12-17

    Baryonic components (e.g. bulge and disk) of galactic structures are assumed to be embedded in an isothermal dark matter halo of fermionic nature. Besides the Pauli principle only gravitational interaction is considered. Using the underlying Fermi-Dirac phase space distribution, typical of collisionless relaxation processes, it yields an one-parameter family of scaled solutions which reproduces the observed flat rotation curves in galaxies, and additionally predicts a degenerate core through their centers. In order to provide the right DM halo properties of galaxies a set of four parameters (particle mass, degeneracy parameter at the galactic center, central density and the velocity dispersion) is necessary. The more general density profile shows three regimes depending on radius: an almost uniform very dense quantum core followed by a steep fall, a plateau in the diluted regime and a Boltzmannian tail representing the halo. In contrast to purely Boltzmannian configurations the fermionic DM model containing a quantum core allows to determine the particle mass. We show that the quantum core can be well approximated by a polytrope of index n = 3/2, while the halo can be perfectly described by an isothermal sphere with a halo scale length radius equal to approximately 3/4 of the King-radius.

  6. Review of the fermionic dark matter model applied to galactic structures

    NASA Astrophysics Data System (ADS)

    Krut, A.; Argüelles, C. R.; Rueda, J.; Ruffini, R.

    2015-12-01

    Baryonic components (e.g. bulge and disk) of galactic structures are assumed to be embedded in an isothermal dark matter halo of fermionic nature. Besides the Pauli principle only gravitational interaction is considered. Using the underlying Fermi-Dirac phase space distribution, typical of collisionless relaxation processes, it yields an one-parameter family of scaled solutions which reproduces the observed flat rotation curves in galaxies, and additionally predicts a degenerate core through their centers. In order to provide the right DM halo properties of galaxies a set of four parameters (particle mass, degeneracy parameter at the galactic center, central density and the velocity dispersion) is necessary. The more general density profile shows three regimes depending on radius: an almost uniform very dense quantum core followed by a steep fall, a plateau in the diluted regime and a Boltzmannian tail representing the halo. In contrast to purely Boltzmannian configurations the fermionic DM model containing a quantum core allows to determine the particle mass. We show that the quantum core can be well approximated by a polytrope of index n = 3/2, while the halo can be perfectly described by an isothermal sphere with a halo scale length radius equal to approximately 3/4 of the King-radius.

  7. TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. VI. GALACTIC STRUCTURE, FUNDAMENTAL PARAMETERS, AND NONCIRCULAR MOTIONS

    SciTech Connect

    Reid, M. J.; Sato, M.; Menten, K. M.; Brunthaler, A.; Xu, Y.; Choi, Y. K.; Zheng, X. W.; Zhang, B.; Moscadelli, L.; Honma, M.; Hirota, T.; Hachisuka, K.; Moellenbrock, G. A.; Bartkiewicz, A.

    2009-07-20

    We are using the Very Long Baseline Array and the Japanese VLBI Exploration of Radio Astronomy project to measure trigonometric parallaxes and proper motions of masers found in high-mass star-forming regions across the Milky Way. Early results from 18 sources locate several spiral arms. The Perseus spiral arm has a pitch angle of 16 deg. {+-} 3 deg., which favors four rather than two spiral arms for the Galaxy. Combining positions, distances, proper motions, and radial velocities yields complete three-dimensional kinematic information. We find that star-forming regions on average are orbiting the Galaxy {approx}15 km s{sup -1} slower than expected for circular orbits. By fitting the measurements to a model of the Galaxy, we estimate the distance to the Galactic center R {sub 0} = 8.4 {+-} 0.6 kpc and a circular rotation speed {theta}{sub 0} = 254 {+-} 16 km s{sup -1}. The ratio {theta}{sub 0}/R {sub 0} can be determined to higher accuracy than either parameter individually, and we find it to be 30.3 {+-} 0.9 km s{sup -1} kpc{sup -1}, in good agreement with the angular rotation rate determined from the proper motion of Sgr A*. The data favor a rotation curve for the Galaxy that is nearly flat or slightly rising with Galactocentric distance. Kinematic distances are generally too large, sometimes by factors greater than 2; they can be brought into better agreement with the trigonometric parallaxes by increasing {theta}{sub 0}/R {sub 0} from the IAU recommended value of 25.9 km s{sup -1} kpc{sup -1} to a value near 30 km s{sup -1} kpc{sup -1}. We offer a 'revised' prescription for calculating kinematic distances and their uncertainties, as well as a new approach for defining Galactic coordinates. Finally, our estimates of {theta}{sub 0} and {theta}{sub 0}/R{sub 0}, when coupled with direct estimates of R {sub 0}, provide evidence that the rotation curve of the Milky Way is similar to that of the Andromeda galaxy, suggesting that the dark matter halos of these two

  8. Asteroseismology and Galactic Archaeology

    NASA Astrophysics Data System (ADS)

    Chiappini, C.

    2015-02-01

    Galactic Archeology is a coined term to describe the fact that the Milky Way's history is encoded both in the amounts of various chemical elements seen in the spectra of stellar atmospheres (abundances), and in stellar motions. One of the pillars of Galactic Archaeology is the use of stellar abundance ratios as an indirect age estimator, which although imprecise, has been proved useful in providing relative ages between the different galactic components. The lack of more precise age determination for large samples of field stars is one of the main reasons why different scenarios for the formation of our Galaxy can still be accommodated to current observational constraints, thus preventing a clear picture of the Milky Way's assembling history. Another difficulty is that most of the available information (especially on ages) has been confined to a region close to the Sun. These two main obstacles can now start to be overcome thanks to a) large spectroscopic and photometric surveys covering larger portions of the Milky Way, and b) the combination of the photometric and spectroscopic information with that coming from asteroseismology. The latter promises a breakthrough in the field of Galactic Archaeology, as it brings the opportunity to, for the first time, measure ages for large samples of distant field giant stars, which cover a large age-baseline. When combining this information with that soon available from Gaia, the field of Galactic Archaeology will be shaken and modelers will certainly have less flexibility in finding models that comply to these precious new observational constraints. The goal of these short lectures is to put Asteroseismology in the context of Galactic Archaeology.

  9. Numerical models of the galactic dynamo driven by supernovae and superbubbles

    NASA Astrophysics Data System (ADS)

    Ferrière, K.; Schmitt, D.

    2000-06-01

    We calculate the temporal evolution and spatial structure of the large-scale magnetic field in our Galaxy, in the framework of an axisymmetric SN-driven dynamo model. We consider various parameter regimes, allowing for anisotropies in the dynamo parameters, the existence of an effective vertical escape of the field (analogous to a Galactic wind carrying field lines away from the midplane), vertical variations in the Galactic rotation curve... In the linear regime, axisymmetric (m = 0) modes are always easier to excite than bisymmetric (m = 1) modes. Amongst the former, the even (S0) mode often has the larger growth rate, while the odd (A0) mode generally oscillates more readily. Under typical conditions, the S0 and A0 modes have very similar properties; both grow monotonically with time at an exponential rate =~ 0.45 Gyr-1, which suggests that the Galactic magnetic field has presently reached a state close to saturation. In the absence of vertical escape, the magnetic field oscillates and only its A0 component is amplified. Oscillatory behaviors are also found when the azimuthal alpha-parameter is enhanced by at least a factor of 3 or when the magnetic diffusivities are reduced by a factor > 1.7 with respect to their reference values; in both cases, the switch from monotonous to oscillatory behavior is accompanied by an increase in the growth rate. A height-dependence in the Galactic rotation velocity profoundly modifies the magnetic field morphology and is conducive to oscillatory decay. The nonlinear solutions obtained when the dynamo parameters are forced to decrease with increasing magnetic field strength are generally more spread out in space. For the growing modes, the field amplification saturates when its intensity in the peak region reaches ~ 20 \\ mu G, corresponding to a magnetic pressure of roughly four times the local gas pressure. The time to saturation, which depends on the seed field strength adopted, is typically of the order of a few 10 Gyr

  10. The rotation of comet nuclei

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1982-01-01

    Spin-vector research on cometary nuclei is reviewed with emphasis on the actual determination of rotation period and spin-axis orientation. The rotation periods of 47 comets are compared with those of 41 asteroids with diameters of not more than 40 km. It is shown that the median periods for the comets is 15.0 hr as compared with 6.8 hr for the asteroids and that the preliminary distribution curve for the logarithms of the comet periods is not Gaussian and is flatter than the corresponding curve for the asteroids. Slow accumulation at low relative velocities is suggested as the cause of the longer comet rotation periods.

  11. STELLAR TRANSITS IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Beky, Bence; Kocsis, Bence E-mail: bkocsis@cfa.harvard.edu

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 10{sup 6} solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or {approx}10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  12. Stellar Transits in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Béky, Bence; Kocsis, Bence

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 106 solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or ~10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  13. Curves and Their Properties.

    ERIC Educational Resources Information Center

    Yates, Robert C.

    This volume, a reprinting of a classic first published in 1952, presents detailed discussions of 26 curves or families of curves, and 17 analytic systems of curves. For each curve the author provides a historical note, a sketch or sketches, a description of the curve, a discussion of pertinent facts, and a bibliography. Depending upon the curve,…

  14. Global Rotation of Non-Rotating Origin

    NASA Astrophysics Data System (ADS)

    Fukushima, T.

    2001-11-01

    At its 24th General Assembly held at Manchester last year, the IAU has adopted the Celestial Ephemeris Origin (CEO) as a new longitude origin of the celestial coordinate system (Capitaine et al. 2000, IAU 2001). The CEO is the application of Guinot's non-rotating origin (NRO) to the Earth's equator (Guinot 1979, Capitaine et al. 1986, Capitaine 1990). By using the current IAU precession/nutation theory, we integrated the global orbit of CEO. It is a slightly curved zigzag pattern of the amplitude of around 23o moving secularly along the ecliptic. Among its kinematical features, we note that CEO has a large secular component of rotation with respect to the inertial reference frame. The current speed of this global rotation is as large as around -4.15 ''/yr. The negative sign shows that CEO rotates clockwise with respect to the inertial frame when viewed from the north celestial pole. Unfortunately this is a general property of NROs. On the other hand, such secular rotation does not exist for some geometrically-defined longitude origins like K, H, and Σ already discussed in Kovalevsky and McCarthy (1998). We think that the existence of a global secular rotaion means that the CEO, and NROs in general, is not appropriate to be specified as the x-axis of celestial coordinate systems.

  15. Magnetized galactic haloes and velocity lags

    NASA Astrophysics Data System (ADS)

    Henriksen, R. N.; Irwin, J. A.

    2016-06-01

    We present an analytic model of a magnetized galactic halo surrounding a Mestel gravitating disc. The magnetic field is taken to be in energy equipartition with the pressure dominant rotating halo gas (not with the cosmic rays), and the whole system is in a steady state. A more flexible `anisotropic equipartition' model is also explored. A definite pressure law is required to maintain the equilibrium, but the halo density is constant. The velocity/magnetic system is scale-free. The objective is to find the rotational velocity lag in such a halo. The magnetic field is not force-free so that angular momentum may be transported from the halo to the intergalactic medium. We find that the `X'-shaped structure observed for halo magnetic fields can be obtained together with a simple analytic formula for the rate of decline of the velocity with height z. The formula also predicts the change in lag with radius, r.

  16. Rotational moulding.

    PubMed

    Crawford, R J; Kearns, M P

    2003-10-01

    Rotational moulding promises designers attractive economics and a low-pressure process. The benefits of rotational moulding are compared here with other manufacturing methods such as injection and blow moulding. PMID:14603714

  17. Rotating Vesta

    NASA Video Gallery

    Astronomers combined 146 exposures taken by NASA's Hubble SpaceTelescope to make this 73-frame movie of the asteroid Vesta's rotation.Vesta completes a rotation every 5.34 hours.› Asteroid and...

  18. The Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Barbuy, B.

    2016-06-01

    The Galactic bulge is the least studied component of our Galaxy. Yet, its formation and evolution are key to understand the formation of the Galaxy itself. Studies on the Galactic bulge have increased significantly in the last years, but still there are many points of controversy. This volume contains several contributions from experts in different aspects of the bulge. Issues discussed include the following: the presence of an old spheroidal bulge, or identification of its old stellar population with the thick disk or halo; fraction of stars younger than 10 Gyr is estimated to be of < 5 to 22% depending on method and authors; multiple populations or only a metal-poor and a metal-rich ones; spheroidal or ellipsoidal distribution of RR Lyrae; formation of the bulge from early mergers or from secular evolution of the bar; different methods of mapping extinction; selection and identification of bulge globular clusters.

  19. Galactic-scale civilization

    NASA Technical Reports Server (NTRS)

    Kuiper, T. B. H.

    1980-01-01

    Evolutionary arguments are presented in favor of the existence of civilization on a galactic scale. Patterns of physical, chemical, biological, social and cultural evolution leading to increasing levels of complexity are pointed out and explained thermodynamically in terms of the maximization of free energy dissipation in the environment of the organized system. The possibility of the evolution of a global and then a galactic human civilization is considered, and probabilities that the galaxy is presently in its colonization state and that life could have evolved to its present state on earth are discussed. Fermi's paradox of the absence of extraterrestrials in light of the probability of their existence is noted, and a variety of possible explanations is indicated. Finally, it is argued that although mankind may be the first occurrence of intelligence in the galaxy, it is unjustified to presume that this is so.

  20. Radio polarimetry of Galactic Centre pulsars

    NASA Astrophysics Data System (ADS)

    Schnitzeler, D. H. F. M.; Eatough, R. P.; Ferrière, K.; Kramer, M.; Lee, K. J.; Noutsos, A.; Shannon, R. M.

    2016-07-01

    To study the strength and structure of the magnetic field in the Galactic Centre (GC), we measured Faraday rotation of the radio emission of pulsars which are seen towards the GC. Three of these pulsars have the largest rotation measures (RMs) observed in any Galactic object with the exception of Sgr A⋆. Their large dispersion measures, RMs and the large RM variation between these pulsars and other known objects in the GC implies that the pulsars lie in the GC and are not merely seen in projection towards the GC. The large RMs of these pulsars indicate large line-of-sight magnetic field components between ˜ 16 and 33 μG; combined with recent model predictions for the strength of the magnetic field in the GC this implies that the large-scale magnetic field has a very small inclination angle with respect to the plane of the sky (˜12°). Foreground objects like the Radio Arc or possibly an ablated, ionized halo around the molecular cloud G0.11-0.11 could contribute to the large RMs of two of the pulsars. If these pulsars lie behind the Radio Arc or G0.11-0.11 then this proves that low-scattering corridors with lengths ≳100 pc must exist in the GC. This also suggests that future, sensitive observations will be able to detect additional pulsars in the GC. Finally, we show that the GC component in our most accurate electron density model oversimplifies structure in the GC.

  1. Radio polarimetry of Galactic centre pulsars

    NASA Astrophysics Data System (ADS)

    Schnitzeler, D. H. F. M.; Eatough, R. P.; Ferrière, K.; Kramer, M.; Lee, K. J.; Noutsos, A.; Shannon, R. M.

    2016-04-01

    To study the strength and structure of the magnetic field in the Galactic centre (GC) we measured Faraday rotation of the radio emission of pulsars which are seen towards the GC. Three of these pulsars have the largest rotation measures (RMs) observed in any Galactic object with the exception of Sgr A⋆. Their large dispersion measures, RMs and the large RM variation between these pulsars and other known objects in the GC implies that the pulsars lie in the GC and are not merely seen in projection towards the GC. The large RMs of these pulsars indicate large line-of-sight magnetic field components between ˜ 16 - 33 μG; combined with recent model predictions for the strength of the magnetic field in the GC this implies that the large-scale magnetic field has a very small inclination angle with respect to the plane of the sky (˜ 12°). Foreground objects like the Radio Arc or possibly an ablated, ionized halo around the molecular cloud G0.11-0.11 could contribute to the large RMs of two of the pulsars. If these pulsars lie behind the Radio Arc or G0.11-0.11 then this proves that low-scattering corridors with lengths ≳ 100 pc must exist in the GC. This also suggests that future, sensitive observations will be able to detect additional pulsars in the GC. Finally, we show that the GC component in our most accurate electron density model oversimplifies structure in the GC.

  2. Theoretical Models of the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Shen, Juntai; Li, Zhao-Yu

    Near infrared images from the COBE satellite presented the first clear evidence that our Milky Way galaxy contains a boxy shaped bulge. Recent years have witnessed a gradual paradigm shift in the formation and evolution of the Galactic bulge. Bulges were commonly believed to form in the dynamical violence of galaxy mergers. However, it has become increasingly clear that the main body of the Milky Way bulge is not a classical bulge made by previous major mergers, instead it appears to be a bar seen somewhat end-on. The Milky Way bar can form naturally from a precursor disc and thicken vertically by the internal firehose/buckling instability, giving rise to the boxy appearance. This picture is supported by many lines of evidence, including the asymmetric parallelogram shape, the strong cylindrical rotation (i.e., nearly constant rotation regardless of the height above the disc plane), the existence of an intriguing X-shaped structure in the bulge, and perhaps the metallicity gradients. We review the major theoretical models and techniques to understand the Milky Way bulge. Despite the progresses in recent theoretical attempts, a complete bulge formation model that explains the full kinematics and metallicity distribution is still not fully understood. Upcoming large surveys are expected to shed new light on the formation history of the Galactic bulge.

  3. Galactic Diffuse Emissions

    SciTech Connect

    Digel, Seth W.; /SLAC

    2007-10-25

    Interactions of cosmic rays with interstellar nucleons and photons make the Milky Way a bright, diffuse source of high-energy {gamma}-rays. Observationally, the results from EGRET, COMPTEL, and OSSE have now been extended to higher energies by ground-based experiments, with detections of diffuse emission in the Galactic center reported by H.E.S.S. in the range above 100 GeV and of diffuse emission in Cygnus by MILAGRO in the TeV range. In the range above 100 keV, INTEGRAL SPI has found that diffuse emission remains after point sources are accounted for. I will summarize current knowledge of diffuse {gamma}-ray emission from the Milky Way and review some open issues related to the diffuse emission -- some old, like the distribution of cosmic-ray sources and the origin of the 'excess' of GeV emission observed by EGRET, and some recently recognized, like the amount and distribution of molecular hydrogen not traced by CO emission -- and anticipate some of the advances that will be possible with the Large Area Telescope on GLAST. We plan to develop an accurate physical model for the diffuse emission, which will be useful for detecting and accurately characterizing emission from Galactic point sources as well as any Galactic diffuse emission from exotic processes, and for studying the unresolved extragalactic emission.

  4. The age of the galactic disk

    NASA Technical Reports Server (NTRS)

    Sandage, Allan

    1988-01-01

    The galactic disk is a dissipative structure and must, therefore be younger than the halo if galaxy formation generally proceeds by collapse. Just how much younger the oldest stars in the galactic disk are than the oldest halo stars remains an open question. A fast collapse (on a time scale no longer than the rotation period of the extended protogalaxy) permits an age gap of the order of approximately 10 to the 9th power years. A slow collapse, governed by the cooling rate of the partially pressure supported falling gas that formed into what is now the thick stellar disk, permits a longer age gap, claimed by some to be as long as 6 Gyr. Early methods of age dating the oldest components of the disk contain implicit assumptions concerning the details of the age-metallicity relation for stars in the solar neighborhood. The discovery that this relation for open clusters outside the solar circle is different that in the solar neighborhood (Geisler 1987), complicates the earlier arguments. The oldest stars in the galactic disk are at least as old as NGC 188. The new data by Janes on NGC 6791, shown first at this conference, suggest a disk age of at least 12.5 Gyr, as do data near the main sequence termination point of metal rich, high proper motion stars of low orbital eccentricity. Hence, a case can still be made that the oldest part of the galactic thick disk is similar in age to the halo globular clusters, if their ages are the same as 47 Tuc.

  5. Standard Mastery Curves and Skew Curves.

    ERIC Educational Resources Information Center

    Warries, Egbert

    The objective of the study is to convince educational researchers of the necessity for "standard mastery curves" for the graphical representation of scores on summative tests for a group of students. Attention is drawn to the study of theoretical and empirical skew curves in education and biology. Use of standard mastery curves and study of skew…

  6. Galactic diffuse gamma rays from galactic plane

    NASA Astrophysics Data System (ADS)

    Tateyama, N.; Nishimura, J.

    2001-08-01

    The dominant part of the diffuse gamma rays from the Galactic plane, with energy greater than 1TeV, has been thought as due to the inverse Compton scattering of the interstellar photons with the high-energy cosmic electrons. In these energy regions, the diffuse gamma-ray observation gives us unique infor-mation on the energy spectrum of the high-energy electrons in the interstellar space, since we cannot observe those electrons directly. This provides us information on the cosmicray source, production mechanism and propagation in the Galaxy. We discuss the implication of our results by comparing with the work of Porter and Protheroe, and also compare with the data observed by the most recent extensive air showers. It is also pointed out that the patchy structure of gammaray distribution will appear at high-energy side, if we observe the distribution with a higher angular resolution of a few arc degrees. This patchy structure will become clear beyond 10TeV of IC gamma rays, where the number of contributing sources of parent decrease and the diffusion distance of the electrons become smaller.

  7. THE MILKY WAY'S CIRCULAR-VELOCITY CURVE BETWEEN 4 AND 14 kpc FROM APOGEE DATA

    SciTech Connect

    Bovy, Jo; Allende Prieto, Carlos; Meszaros, Szabolcs; Beers, Timothy C.; Bizyaev, Dmitry; Ebelke, Garrett L.; Malanushenko, Elena; Malanushenko, Viktor; Da Costa, Luiz N.; Girardi, Leo; Maia, Marcio A. G.; Cunha, Katia; Eisenstein, Daniel J.; Frinchaboy, Peter M.; Garcia Perez, Ana Elia; Hearty, Fred R.; Majewski, Steven R.; Nidever, David L.; Hogg, David W.; Holtzman, Jon; and others

    2012-11-10

    We measure the Milky Way's rotation curve over the Galactocentric range 4 kpc {approx}< R {approx}< 14 kpc from the first year of data from the Apache Point Observatory Galactic Evolution Experiment. We model the line-of-sight velocities of 3365 stars in 14 fields with b = 0 Degree-Sign between 30 Degree-Sign {<=} l {<=} 210 Degree-Sign out to distances of 10 kpc using an axisymmetric kinematical model that includes a correction for the asymmetric drift of the warm tracer population ({sigma} {sub R} Almost-Equal-To 35 km s{sup -1}). We determine the local value of the circular velocity to be V{sub c} (R {sub 0}) = 218 {+-} 6 km s{sup -1} and find that the rotation curve is approximately flat with a local derivative between -3.0 km s{sup -1} kpc{sup -1} and 0.4 km s{sup -1} kpc{sup -1}. We also measure the Sun's position and velocity in the Galactocentric rest frame, finding the distance to the Galactic center to be 8 kpc < R {sub 0} < 9 kpc, radial velocity V {sub R, Sun} = -10 {+-} 1 km s{sup -1}, and rotational velocity V {sub {phi}, Sun} = 242{sup +10} {sub -3} km s{sup -1}, in good agreement with local measurements of the Sun's radial velocity and with the observed proper motion of Sgr A*. We investigate various systematic uncertainties and find that these are limited to offsets at the percent level, {approx}2 km s{sup -1} in V{sub c} . Marginalizing over all the systematics that we consider, we find that V{sub c} (R {sub 0}) < 235 km s{sup -1} at >99 % confidence. We find an offset between the Sun's rotational velocity and the local circular velocity of 26 {+-} 3 km s{sup -1}, which is larger than the locally measured solar motion of 12 km s{sup -1}. This larger offset reconciles our value for V{sub c} with recent claims that V{sub c} {approx}> 240 km s{sup -1}. Combining our results with other data, we find that the Milky Way's dark-halo mass within the virial radius is {approx}8 Multiplication-Sign 10{sup 11} M {sub Sun }.

  8. Clouds Dominate the Galactic Halo

    NASA Astrophysics Data System (ADS)

    2003-01-01

    yet," he said. Earlier this year, data taken with the newly commissioned GBT demonstrated that rather than a diffuse mist or other ill-defined feature - as many astronomers had speculated - the halo was in fact made up of well-defined clouds. "The discovery of these clouds, each containing 50-to-100 solar masses of hydrogen and averaging about 100 light-years in diameter, challenged many of the prevailing theories about the structure and dynamics of the halo," said Lockman. The clouds were discovered about 25,000 light-years from Earth toward the center of our Galaxy. The latest findings show the clouds extend at least 5,000 light-years above and below the Galactic plane. Though the initial studies by Lockman revealed the presence of these clouds, the data were insufficient to conclusively show that they were present throughout the entire halo. These latest results provide valuable evidence that the earlier results were truly representative of the entire halo. "The richness and variety of this phenomenon continues to astound me," remarked Lockman. Lockman's new studies also confirm that these clouds travel along with the rest of the Galaxy, rotating about its center. These studies clearly rule out the possibility that so-called "high-velocity clouds" were responsible for what was detected initially. High-velocity clouds are vagabond clumps of intergalactic gas, possibly left over from the formation of the Milky Way and other nearby galaxies. "One thing that is for certain is that these are not high-velocity clouds, this is an entirely separate phenomenon," said Lockman. According to the researcher, the ubiquitous nature and dynamics of these newly discovered clouds support the theory that they are condensing out of the hot gas that is lifted into the halo through supernova explosions. When a massive star dies, it produces a burst of cosmic rays and an enormous expanding bubble of gas at a temperature of several million degrees Celsius. Over time, this hot gas will

  9. Properties of galactic dark matter: Constraints from astronomical observations

    SciTech Connect

    Burch, B.; Cowsik, R.

    2013-12-10

    The distributions of normal matter and of dark matter in the Galaxy are coupled to each other as they both move in the common gravitational potential. In order to fully exploit this interplay and to derive the various properties of dark matter relevant to their direct and indirect detection, we have comprehensively reviewed the astronomical observations of the spatial and velocity distributions of the components of normal matter. We then postulate that the phase-space distribution of dark matter follows a lowered-isothermal form and self-consistently solve Poisson's equation to construct several models for the spatial and velocity distributions of dark matter. In this paper, we compute the total gravitational potential of the normal and dark matter components and investigate their consistency with current observations of the rotation curve of the Galaxy and of the spatial and velocity distributions of blue horizontal-branch and blue straggler stars. Even with this demand of consistency, a large number of models with a range of parameters characterizing the dark matter distribution remain. We find that the best choice of parameters, within the range of allowed values for the surface density of the disk 55 M {sub ☉} pc{sup –2}, are the following: the dark matter density at the Galactic center ρ{sub DM,} {sub c} ≈ 100-250 GeV cm{sup –3}, the local dark matter density ρ{sub DM}(R {sub 0}) ≈ 0.56-0.72 GeV cm{sup –3}, and the rms speed of dark matter particles 〈v{sub DM}{sup 2}(R{sub 0})〉{sup 1/2}≈490−−550 km s{sup –1}. We also discuss possible astronomical observations that may further limit the range of the allowed models. The predictions of the allowed models for direct and indirect detection will be discussed separately in a companion paper.

  10. Explicit superconic curves.

    PubMed

    Cho, Sunggoo

    2016-09-01

    Conics and Cartesian ovals are extremely important curves in various fields of science. In addition, aspheric curves based on conics are useful in optical design. Superconic curves, recently suggested by Greynolds, are extensions of both conics and Cartesian ovals and have been applied to optical design. However, they are not extensions of aspheric curves based on conics. In this work, we investigate another type of superconic curves. These superconic curves are extensions of not only conics and Cartesian ovals but also aspheric curves based on conics. Moreover, these are represented in explicit form, while Greynolds's superconic curves are in implicit form. PMID:27607506

  11. TESTING TESTS ON ACTIVE GALACTIC NUCLEI MICROVARIABILITY

    SciTech Connect

    De Diego, Jose A.

    2010-03-15

    Literature on optical and infrared microvariability in active galactic nuclei (AGNs) reflects a diversity of statistical tests and strategies to detect tiny variations in the light curves of these sources. Comparison between the results obtained using different methodologies is difficult, and the pros and cons of each statistical method are often badly understood or even ignored. Even worse, improperly tested methodologies are becoming more and more common, and biased results may be misleading with regard to the origin of the AGN microvariability. This paper intends to point future research on AGN microvariability toward the use of powerful and well-tested statistical methodologies, providing a reference for choosing the best strategy to obtain unbiased results. Light curves monitoring has been simulated for quasars and for reference and comparison stars. Changes for the quasar light curves include both Gaussian fluctuations and linear variations. Simulated light curves have been analyzed using {chi}{sup 2} tests, F tests for variances, one-way analyses of variance and C-statistics. Statistical Type I and Type II errors, which indicate the robustness and the power of the tests, have been obtained in each case. One-way analyses of variance and {chi}{sup 2} prove to be powerful and robust estimators for microvariations, while the C-statistic is not a reliable methodology and its use should be avoided.

  12. The role of collective effects and secular mass migration on galactic transformation

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolei; Buta, Ronald J.

    2015-03-01

    During the lifetime of a galaxy, secular radial mass redistribution is expected to gradually build up a bulge and transform the Hubble type from late to early. The dominant dynamical process responsible for this transformation is a collective instability mediated by density-wave collisionless shocks (Zhang 1996, 1998, 1999). The ability of this new mechanism to secularly redistribute the STELLAR mass provides a general pathway for the formation and evolution of the majority of Hubble types, ranging from late type disk galaxiess to disky ellipticals. ATLAS3D results (Cappellari et al. 2013) showed that spirals and S0s and disky ellipticals form a continuous trend of evolution which also coincides with the aging of the stellar population of galactic disks. The importance of stellar accretion is also revealed in the results of the COSMOS team which showed that the evolution of the black-hole-mass/bulge-mass correlation since z = 1 was mainly due to the mass redistribution on pre-existing STELLAR disks which were already in place by z = 1 (Cisternas et al. 2011). The weaker correlation between the masses of late-type bulges and AGNs observed at any given epoch in our view is a result of the quicker initial onset of accretion events in AGN disks compared to that in galactic disks, since the dynamical timescale is shorter for smaller AGN accretion disks. The same secular dynamical process can produce and maintain the well-known scaling relations and universal rotation curves of observed galaxies during their Hubble-type transformation (Zhang 2008), as well as reproduce many other observed structural and kinematic properties of galaxies such as the size-line-width relation of the interstellar medium and the age-velocity dispersion relation of solar neighborhood stars in our own Galaxy. A by-product of this analysis is a powerful new method for locating the multiple corotation resonances in galaxies (Zhang & Buta 2007; Buta & Zhang 2009). The current work also highlights

  13. Galactic distribution of pulsars

    NASA Technical Reports Server (NTRS)

    Seiradakis, J. H.

    1977-01-01

    The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived, using a uniform sample of pulsars detected during a 408-MHz pulsar survey at Jodrell Bank. There are indications of a fine-scale structure in the spatial distributions and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in our galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy has been estimated and used to derive the pulsar birthrate.

  14. Galactic distribution of pulsars

    NASA Technical Reports Server (NTRS)

    Seiradakis, J. H.

    1976-01-01

    The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived using a uniform sample of pulsars detected during a 408 MHz pulsar survey at Jodrell Bank. There are indications of a fine scale structure in the spatial distribution and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in the galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy was estimated and used to derive the pulsar birthrate.

  15. Modeling Galactic Extinction with Dust and "Real" Polycyclic Aromatic Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Mulas, Giacomo; Zonca, Alberto; Casu, Silvia; Cecchi-Pestellini, Cesare

    2013-07-01

    We investigate the remarkable apparent variety of galactic extinction curves by modeling extinction profiles with core-mantle grains and a collection of single polycyclic aromatic hydrocarbons. Our aim is to translate a synthetic description of dust into physically well-grounded building blocks through the analysis of a statistically relevant sample of different extinction curves. All different flavors of observed extinction curves, ranging from the average galactic extinction curve to virtually "bumpless" profiles, can be described by the present model. We prove that a mixture of a relatively small number (54 species in 4 charge states each) of polycyclic aromatic hydrocarbons can reproduce the features of the extinction curve in the ultraviolet, dismissing an old objection to the contribution of polycyclic aromatic hydrocarbons to the interstellar extinction curve. Despite the large number of free parameters (at most the 54 × 4 column densities of each species in each ionization state included in the molecular ensemble plus the 9 parameters defining the physical properties of classical particles), we can strongly constrain some physically relevant properties such as the total number of C atoms in all species and the mean charge of the mixture. Such properties are found to be largely independent of the adopted dust model whose variation provides effects that are orthogonal to those brought about by the molecular component. Finally, the fitting procedure, together with some physical sense, suggests (but does not require) the presence of an additional component of chemically different very small carbonaceous grains.

  16. MODELING GALACTIC EXTINCTION WITH DUST AND 'REAL' POLYCYCLIC AROMATIC HYDROCARBONS

    SciTech Connect

    Mulas, Giacomo; Casu, Silvia; Cecchi-Pestellini, Cesare; Zonca, Alberto E-mail: silvia@oa-cagliari.inaf.it E-mail: azonca@oa-cagliari.inaf.it

    2013-07-01

    We investigate the remarkable apparent variety of galactic extinction curves by modeling extinction profiles with core-mantle grains and a collection of single polycyclic aromatic hydrocarbons. Our aim is to translate a synthetic description of dust into physically well-grounded building blocks through the analysis of a statistically relevant sample of different extinction curves. All different flavors of observed extinction curves, ranging from the average galactic extinction curve to virtually 'bumpless' profiles, can be described by the present model. We prove that a mixture of a relatively small number (54 species in 4 charge states each) of polycyclic aromatic hydrocarbons can reproduce the features of the extinction curve in the ultraviolet, dismissing an old objection to the contribution of polycyclic aromatic hydrocarbons to the interstellar extinction curve. Despite the large number of free parameters (at most the 54 Multiplication-Sign 4 column densities of each species in each ionization state included in the molecular ensemble plus the 9 parameters defining the physical properties of classical particles), we can strongly constrain some physically relevant properties such as the total number of C atoms in all species and the mean charge of the mixture. Such properties are found to be largely independent of the adopted dust model whose variation provides effects that are orthogonal to those brought about by the molecular component. Finally, the fitting procedure, together with some physical sense, suggests (but does not require) the presence of an additional component of chemically different very small carbonaceous grains.

  17. STRUCTURE IN THE ROTATION MEASURE SKY

    SciTech Connect

    Stil, J. M.; Taylor, A. R.; Sunstrum, C.

    2011-01-01

    An analysis of structure in rotation measure (RM) across the sky based on the RM catalog of Taylor et al. is presented. Several resolved RM structures are identified with structure in the local interstellar medium, including radio loops I, II, and III, the Gum nebula, and the Orion-Eridanus superbubble. Structure functions (SFs) of RM are presented for selected areas, and maps of SF amplitude and slope across the sky are compared with H{alpha} intensity and diffuse polarized intensity. RM variance on an angular scale of 1{sup 0} is correlated with length of the line of sight through the Galaxy, with a contribution from local structures. The slope of the SFs is less concentrated to the Galactic plane and less correlated with length of the line of sight through the Galaxy, suggesting a more local origin for RM structure on angular scales {approx}10{sup 0}. The RM variance is a factor of {approx}2 higher toward the South Galactic Pole than toward the North Galactic Pole, reflecting a more wide-spread asymmetry between the northern and southern Galactic hemispheres. Depolarization of diffuse Galactic synchrotron emission at latitudes <30{sup 0} can be explained largely by Faraday dispersion related to small-scale variance in RM, but the errors allow a significant contribution from differential Faraday rotation along the line of sight.

  18. Testing Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    2010-01-01

    Models of the Galactic Cosmic Ray Environment are used for designing and planning space missions. The exising models will be reviewed. Spectral representations from these models will be compared with measurements of galactic cosmic ray spectra made on balloon flights and satellite flights over a period of more than 50 years.

  19. Testing Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    2009-01-01

    Models of the Galactic Cosmic Ray Environment are used for designing and planning space missions. The existing models will be reviewed. Spectral representations from these models will be compared with measurements of galactic cosmic ray spectra made on balloon flights and satellite flights over a period of more than 50 years.

  20. Galactic cosmic rays and nucleosynthesis

    SciTech Connect

    Kiener, Juergen

    2010-03-01

    The nucleosynthesis of the light elements Li, Be and B by galactic cosmic rays is presented. Observations of cosmic rays and the nuclear reactions responsible for Li, Be and B nucleosynthesis are described, followed by some words on propagation. At the end, some open questions concerning galactic cosmic rays are discussed.

  1. Rotating Wavepackets

    ERIC Educational Resources Information Center

    Lekner, John

    2008-01-01

    Any free-particle wavepacket solution of Schrodinger's equation can be converted by differentiations to wavepackets rotating about the original direction of motion. The angular momentum component along the motion associated with this rotation is an integral multiple of [h-bar]. It is an "intrinsic" angular momentum: independent of origin and…

  2. Galactic Hearts of Glass

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Click on image for larger graph

    This artist's concept shows delicate greenish crystals sprinkled throughout the violent core of a pair of colliding galaxies. The white spots represent a thriving population of stars of all sizes and ages. NASA's Spitzer Space Telescope detected more than 20 bright and dusty galactic mergers like the one depicted here, all teeming with the tiny gem-like crystals.

    When galaxies collide, they trigger the birth of large numbers of massive stars. Astronomers believe these blazing hot stars act like furnaces to produce silicate crystals in the same way that glass is made from sand. The stars probably shed the crystals as they age, and as they blow apart in supernovae explosions.

    At the same time the crystals are being churned out, they are also being destroyed. Fast-moving particles from supernova blasts easily convert silicates crystals back to their amorphous, or shapeless, form.

    How is Spitzer seeing the crystals if they are rapidly disappearing? Astronomers say that, for a short period of time at the beginning of galactic mergers, massive stars might be producing silicate crystals faster than they are eliminating them. When our own galaxy merges with the Andromeda galaxy in a few billion years, a similar burst of massive stars and silicate crystals might occur.

    Crystal Storm in Distant Galaxy The graph (see inset above) of infrared data from NASA's Spitzer Space Telescope tells astronomers that a distant galaxy called IRAS 08752+3915 is experiencing a storm of tiny crystals made up of silicates. The crystals are similar to the glass-like grains of sand found on Earth's many beaches.

    The data were taken by Spitzer's infrared spectrograph, which splits light open to reveal its rainbow-like components. The resulting spectrum shown here reveals the signatures of both crystalline (green) and non-crystalline (brown) silicates.

    Spitzer detected the same

  3. The Galactic Nucleus

    NASA Astrophysics Data System (ADS)

    Melia, Fulvio

    Exciting new broadband observations of the galactic nucleus have placed the heart of the Milky Way under intense scrutiny in recent years. This has been due in part to the growing interest from theorists motivated to study the physics of black hole accretion, magnetized gas dynamics, and unusual star formation. The center of our Galaxy is now known to harbor the most compelling supermassive black hole candidate, weighing in at 3-4 million solar masses. Its nearby environment is comprised of a molecular dusty ring, clusters of evolved and young stars, diffuse hot gas, ionized gas streamers, and several supernova remnants. This chapter will focus on the physical makeup of this dynamic region and the feasibility of actually imaging the black hole's shadow in the coming decade with mm interferometry.

  4. The Galactic center wind

    NASA Technical Reports Server (NTRS)

    Chevalier, Roger A.

    1992-01-01

    The combined effect of winds from a cluster of stars in the central 0.8 pc of the Galaxy is modeled as uniform power and mass input over the central region. The flow becomes supersonic outside the central region, and the expected decrease in pressure is in approximate accord with observations. The pressure variations on a larger scale suggest that the Galactic center wind passes through a shock front at a radius of a few pc, leading to a shocked wind bubble on a scale of 100 pc. The tangential magnetic field can come to dominate the pressure in the shocked wind flow even if the energy density of the magnetic field in the initial wind is only 0.1 percent of the wind kinetic energy density. The magnetic region produced in this way may be related to some of the apparently magnetized structures observed in the central region of the Galaxy.

  5. Galactic antiprotons from photinos

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Rudaz, S.; Walsh, T. F.

    1985-01-01

    Stable photinos, the photino being the supersymmetry partner of the photon, can explain both the 'missing mass' in galactic halos and the cosmic-ray antiproton spectrum up to the highest energies observed so far. This requires a photino mass around 15 GeV; significantly higher masses are cosmologically disfavored. As a consequence, the observed cosmic-ray antiproton-to-proton ratio is predicted to decrease abruptly just above the measured energy range, at E = m(x). If observed, this striking effect would strongly support the hypothesis that photinos make up the missing matter in the galaxy and also lead to a measurement of the photino mass from cosmic-ray data.

  6. DISCOVERY OF CANDIDATE H{sub 2}O DISK MASERS IN ACTIVE GALACTIC NUCLEI AND ESTIMATIONS OF CENTRIPETAL ACCELERATIONS

    SciTech Connect

    Greenhill, Lincoln J.; Moran, James M.; Tilak, Avanti; Kondratko, Paul T.

    2009-12-10

    Based on spectroscopic signatures, about one-third of known H{sub 2}O maser sources in active galactic nuclei (AGNs) are believed to arise in highly inclined accretion disks around central engines. These 'disk maser candidates' are of interest primarily because angular structure and rotation curves can be resolved with interferometers, enabling dynamical study. We identify five new disk maser candidates in studies with the Green Bank Telescope, bringing the total number published to 30. We discovered two (NGC 1320, NGC 17) in a survey of 40 inclined active galaxies (v {sub sys} < 20, 000 km s{sup -1}). The remaining three disk maser candidates were identified in monitoring of known sources: NGC 449, NGC 2979, and NGC 3735. We also confirm a previously marginal case in UGC 4203. For the disk maser candidates reported here, inferred rotation speeds are 130-500 km s{sup -1}. Monitoring of three more rapidly rotating candidate disks (CG 211, NGC 6264, VV 340A) has enabled measurement of likely orbital centripetal acceleration, and estimation of central masses ((2-7) x10{sup 7} M {sub sun}) and mean disk radii (0.2-0.4 pc). Accelerations may ultimately permit estimation of distances when combined with interferometer data. This is notable because the three AGNs are relatively distant (10,000 km s{sup -1} galactic stellar disks, even without extensive interferometric mapping. We find no preference among published disk maser candidates to lie in high-inclination galaxies. This provides independent support for conclusions that in late-type galaxies, central engine accretion disks and galactic plane orientations are not

  7. Great Galactic Buddies

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Click on image for poster [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] 8.15 Billion Lightyears8.59 Billion Lightyears8.98 Billion Lightyears 9.09 Billion Lightyears

    Like great friends, galaxies stick together. Astronomers using NASA's Spitzer Space Telescope have spotted a handful of great galactic pals bonding back when the universe was a mere 4.6 billion years old. The universe is believed to be 13.7 billion years old.

    Collectively, these great galactic buddies are called galaxy clusters. A typical galaxy cluster can contain hundreds of galaxies and trillions of stars.

    In this false-color composite, some of the oldest galaxy clusters in the universe pose for Spitzer's infrared array camera. The individual galaxies that make up the distant clusters are shown as red dots in all four images.

    The green blobs are Milky Way stars along the line of sight, and the blue specks are faint galaxies at various distances along the line of sight. The green and blue data are from a visible-light, ground-based telescope.

    The cluster at 9.1 billion light-years away (lower right panel) is currently the most distant galaxy cluster ever detected.

    These images are three-color composites, in which blue represents visible light with a wavelength of 0.4 microns, and green indicates visible light of 0.8 microns. The visible data were captured by the ground-based Mosaic I camera at the Kitt Peak National Observatory in Tucson, Ariz. Red represents infrared light of 4.5 microns, captured by Spitzer's infrared array camera.

  8. Supergranulation rotation

    NASA Astrophysics Data System (ADS)

    Schou, Jesper; Beck, John G.

    2001-01-01

    Simple convection models estimate the depth of supergranulation at approximately 15,000 km which suggests that supergranules should rotate at the rate of the plasma in the outer 2% of the Sun by radius. Previous measurements (Snodgrass & Ulrich, 1990; Beck & Schou, 2000) found that supergranules rotate significantly faster than this, with a size-dependent rotation rate. We expand on previous work and show that the torsional oscillation signal seen in the supergranules tracks that obtained for normal modes. We also find that the amplitudes and lifetimes of the supergranulation are size dependent.

  9. Rice University observations of the galactic center

    NASA Technical Reports Server (NTRS)

    Meegan, C. A.

    1978-01-01

    The most sensitive of the four balloon fight observations of the galactic center made by Rice University was conducted in 1974 from Rio Cuarto, Argentina at a float altitude of 4 mbar. The count rate spectrum of the observed background and the energy spectrum of the galactic center region are discussed. The detector used consists of a 6 inch Nal(T 1ambda) central detector collimated to approximately 15 deg FWHM by a Nal(T lamdba) anticoincidence shield. The shield in at least two interaction mean free paths thick at all gamma ray energies. The instrumental resolution is approximately 11% FWHM at 662 keV. Pulses from the central detector are analyzed by two 256 channel PHA's covering the energy range approximately 20 keV to approximately 12 MeV. The detector is equatorially mounted and pointed by command from the ground. Observations are made by measuring source and background alternately for 10 minute periods. Background is measured by rotating the detector 180 deg about the azimuthal axis.

  10. Submillimeter Polarimetric Observations of the Galactic Center

    NASA Technical Reports Server (NTRS)

    Novak, G.; Dotson, J. L.; Dowell, C. D.; Hildebrand, R. H.; Renbarger, T.; Schleuning, D. A.

    2000-01-01

    We report the first detection of polarized submillimeter emission from the Sagittarius A region at the Galactic center. We observed three separate 2' x 2' fields: one centered on the circumnuclear disk, one centered on the peak of the molecular cloud M -0.02-0.07 (also called the "50 kilometer per second cloud"), and one centered on the peak of the molecular cloud M -0.13-0.08 (also called the "20 kilometer per second cloud"). Linear polarization at lambda = 350 micrometers was detected in each of the three regions, at a total of 106 distinct sky positions. In the circumnuclear disk, the projected magnetic field directions that we infer from our measurements are similar to those inferred from previous far-infrared (lambda = 100 micrometers) polarimetry. In the "curved ridge" region of M -0.02-0.07 that has been compressed by the expansion of Sgr A East, our results show clearly the effects of this compression on the magnetic field. In M -0.13-0.08, we observe what appears to be a stretched magnetic field, as expected for this tidally sheared cloud. It has been suggested that a "finger-like extension" or streamer" from M -0.13-0.08 is falling into the circumnuclear disk. We tentatively interpret a flaring of magnetic field lines that we see in M -0.13-0.08 as evidence that the entire cloud has a velocity component in the Galactic eastern direction, i.e., toward the circumnuclear disk. Further observations are needed to test this interpretation. We argue that polarimetry of dust emission provides a promising tool for obtaining new information on the complex dynamics of neutral gas in the Galactic center.

  11. Ultrahigh energy neutrinos from galactic neutron stars

    NASA Technical Reports Server (NTRS)

    Helfand, D. J.

    1979-01-01

    An attempt is made to estimate the production rate of ultrahigh energy (UHE) neutrinos from galactic neutron stars. The statistics of various stellar populations are reviewed as well as an evolutionary scheme linking several neutron star environments. An observational test for predicting stellar evolution is made using two mass ratio intervals of less than 0.3 and greater than or approximately equal to 0.3, which is supported by kinematical evidence. Attention is given to the problem of the target material that is required by UHE protons accelerated from the pulsar's surface to their rotational kinetic energy, and to the detectability of neutron stars in the UHE neutrinos by employing the deep underwater muon and neutrino detector (DUMAND) array.

  12. Tracing the Dynamics of the Galactic Disk with SIM PlanetQuest

    NASA Astrophysics Data System (ADS)

    Majewski, S. R.; Frinchaboy, P. M.; Patterson, R. J.

    2005-12-01

    Establishing the rotation curve of the Milky Way on an absolute scale is one of the fundamental contributions that SIM PlanetQuest can make to understanding the Galaxy and its mass distribution. As preparatory work for the ``Taking Measure of the Milky Way'' SIM Key Project, we have undertaken a systematic spectroscopic survey of open star clusters which can serve as tracers of Galactic disk dynamics. We report progress on our inital sample of over 100 clusters for which the Hydra multifiber spectrographs on the WIYN and Blanco telescopes have delivered ˜ 1 km s-1 radial velocities (RVs) of many dozens of stars per cluster. The RVs are used to derive cluster membership for individual stars in these crowded fields and to derive a bulk cluster RV. The clusters selected for study have a broad spatial distribution in order to be sensitive to the disk velocity field in all Galactic quadrants and across a Galactocentric radius range as much as 2.5 kpc from the solar circle. These clusters already have published ages, distances, and metallicity estimates, but these can be improved once chemical abundances on a uniform scale are measured from the homogenous spectra, and once SIM parallaxes are obtained for member stars. The new RVs combined with Tycho proper motions (for bright members in each cluster) allow an initial investigation of the local disk dynamics, but this will be substantially improved once SIM proper motions are obtained for these and even more distant open clusters. We acknowledge funding by NASA/JPL contract 1228235, NSF grant AST-0307851, and the F.H. Levinson Fund of the Peninsula Community Foundation. PMF is supported by a NASA-GSRP, a UVa Faculty Senate Dissertation-Year Fellowship, and the Virginia Space Grant Consortium.

  13. Solar rotation.

    NASA Astrophysics Data System (ADS)

    Dziembowski, W.

    Sunspot observations made by Johannes Hevelius in 1642 - 1644 are the first ones providing significant information about the solar differential rotation. In modern astronomy the determination of the rotation rate is done in a routine way by measuring positions of various structures on the solar surface as well as by studying the Doppler shifts of spectral lines. In recent years a progress in helioseismology enabled determination of the rotation rate in the layers inaccessible for direct observations. There are still uncertainties concerning, especially, the temporal variations of the rotation rate and its behaviour in the radiative interior. We are far from understanding the observations. Theoretical works have not yet resulted in a satisfactory model for the angular momentum transport in the convective zone.

  14. Rotational aerophones

    NASA Astrophysics Data System (ADS)

    Fletcher, N. H.; Tarnopolsky, A. Z.; Lai, J. C. S.

    2002-03-01

    Free rotational aerophones such as the bullroarer, which consists of a wooden slat whirled around on the end of a string, and which emits a loud pulsating roar, have been used in many ancient and traditional societies for ceremonial purposes. This article presents an experimental and theoretical investigation of this instrument. The aerodynamics of rotational behavior is elucidated, and relates slat rotation frequency to slat width and velocity through the air. Analysis shows that sound production is due to generation of an oscillating-rotating dipole across the slat, the role of the vortices shed by the slat being relatively minor. Apparent discrepancies between the behavior of a bullroarer slat and a slat mounted on an axle in a wind tunnel are shown to be due to viscous friction in the bearings of the wind-tunnel experiment.

  15. The WENSS & Dwingeloo surveys and the Galactic magnetic field

    NASA Astrophysics Data System (ADS)

    Schnitzeler, D. H. F. M.; Katgert, P.; Haverkorn, M.; de Bruyn, A. G.

    2007-01-01

    Aims:We investigate the structure of the Galactic magnetic field in the 2nd Galactic quadrant using radio continuum polarization data from the 325 MHz WENSS (WEsterbork Northern Sky Survey) survey in combination with earlier single-dish observations. Methods: We study gradients in polarization angle along Galactic longitude and latitude in the region 130° ⪉ l ⪉ 173° and -5° ⪉ b ⪉ 31°. These gradients were determined with a new method that we developed to efficiently and reliably fit linear gradients to periodic data like polarization angles. Since the WENSS data were obtained with a synthesis array they suffer from the "missing short spacing" problem. We have tried to repair this by adding an estimate of the large-scale emission based on the single-dish (Dwingeloo) data obtained by Brouw and Spoelstra. Combining all available data we derive a rotation measure map of the area, from which we estimate all 3 components of the magnetic field vector. Results: In the part of WENSS where large-scale structure in polarized intensity is relatively unimportant, we find that the magnetic field is predominantly perpendicular to the line-of-sight, and parallel to the Galactic plane. The magnetic field components along the line-of-sight and along Galactic latitude have comparable values, and the strength of these components is much smaller than the strength of the total magnetic field. Our observations also cover part of the so-called "fan" region, an area of strong polarized intensity, where large-scale structure is missing from our WENSS data. We tentatively show that Faraday rotation occurring in front of the Perseus arm is causing both the WENSS RM and the RM towards the fan region observed in previous single-dish surveys, and we suggest that the fan is formed by local emission that originates in front of the emission we see in WENSS.

  16. Observations of diffuse galactic gamma rays

    NASA Technical Reports Server (NTRS)

    Simpson, G. A.

    1979-01-01

    The observations of galactic diffuse gamma radiation are reviewed. The connections of the gamma ray observations with galactic structure and cosmic rays are discussed. The high latitude galactic component and the low latitude emission from the galactic plane are examined. The observations in other regions of the gamma ray spectrum are discussed.

  17. Mercury: infrared evidence for nonsynchronous rotation.

    PubMed

    Soter, S L

    1966-09-01

    An infrared observation of the dark side of Mercury made by Pettit and Nicholson in 1923 led them to suggest that the planet rotates nonsynchronously. Their early measurements, if taken at face value, would imply a brightness temperature of about 180 degrees K for the dark side. The asymmetry of the infrared phase curve is further interpreted as suggesting direct rotation. PMID:17737592

  18. Probabilistic stellar rotation periods with Gaussian processes

    NASA Astrophysics Data System (ADS)

    Angus, Ruth; Aigrain, Suzanne; Foreman-Mackey, Daniel

    2015-08-01

    Stellar rotation has many applications in the field of exoplanets. High-precision photometry from space-based missions like Kepler and K2 allows us to measure stellar rotation periods directly from light curves. Stellar variability produced by rotation is usually not sinusoidal or perfectly periodic, therefore sine-fitting periodograms are not well suited to rotation period measurement. Autocorrelation functions are often used to extract periodic information from light curves, however uncertainties on rotation periods measured by autocorrelation are difficult to define. A ‘by eye’ check, or a set of heuristic criteria are used to validate measurements and rotation periods are only reported for stars that pass this vetting process. A probabilistic rotation period measurement method, with a suitable generative model bypasses the need for a validation stage and can produce realistic uncertainties. The physics driving the production of variability in stellar light curves is still poorly understood and difficult to model. We therefore use an effective model for stellar variability: a Gaussian process with a quasi-periodic covariance function. By injecting fake signals into Kepler light curves we show that the GP model is well suited to quasi-periodic, non-sinusoidal signals, is capable of modelling noise and physical signals simultaneously and provides probabilistic rotation period measurements with realistic uncertainties.

  19. Hot Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Upgren, Arthur R.; Adelman, Carol J.

    2011-03-01

    in the halo; 32. Baade-Wesselink analyses of field vs. cluster RR lyrae variables; 33. The rotation of population II A stars; 34. Horizontal branch stars and possibly related objects; 35. A new group of post-AGB objects - the hot carbon-poor stars; 36. MK classifications of hot stars in the halo 37. Photometry of XX Virginis and V716 Ophiuchi and the period luminosity relations of type II cepheids; 38. Rotation and oxygen line strengths in blue horizontal branch stars; Part V. Miscellaneous: 39. UBV CCd photometry of the halo of M31; 40. Can stars still form in the galactic halo?; 41. The ultraviolet imaging telescope on the Astro -1 and Astro -2 missions; 42. Are analogues of hot subdwarf stars responsible for the UVX phenomenon in galaxy nucleli; 43. A survey for field BHB stars outside the solar circle; 44. Post-AGB A and F supergiants as standard candles; 45. The extended horizontal-branch: a challenge for stellar evolution theory; 46. Astronomical patterns in fractals: the work of A. G. Davis Philip on the Mandelbrot Set; Part VI. Summary: 47. Final remarks; Author index; Subject index.

  20. Hot Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Upgren, Arthur R.; Adelman, Carol J.

    1994-08-01

    in the halo; 32. Baade-Wesselink analyses of field vs. cluster RR lyrae variables; 33. The rotation of population II A stars; 34. Horizontal branch stars and possibly related objects; 35. A new group of post-AGB objects - the hot carbon-poor stars; 36. MK classifications of hot stars in the halo 37. Photometry of XX Virginis and V716 Ophiuchi and the period luminosity relations of type II cepheids; 38. Rotation and oxygen line strengths in blue horizontal branch stars; Part V. Miscellaneous: 39. UBV CCd photometry of the halo of M31; 40. Can stars still form in the galactic halo?; 41. The ultraviolet imaging telescope on the Astro -1 and Astro -2 missions; 42. Are analogues of hot subdwarf stars responsible for the UVX phenomenon in galaxy nucleli; 43. A survey for field BHB stars outside the solar circle; 44. Post-AGB A and F supergiants as standard candles; 45. The extended horizontal-branch: a challenge for stellar evolution theory; 46. Astronomical patterns in fractals: the work of A. G. Davis Philip on the Mandelbrot Set; Part VI. Summary: 47. Final remarks; Author index; Subject index.

  1. Phase Curves of Eccentric Exoplanets

    NASA Astrophysics Data System (ADS)

    Lewis, Nikole K.; de Wit, Julien; Laughlin, Gregory P.; Knutson, Heather

    2016-01-01

    Nearly 15% of the known exoplanet population have significantly eccentric orbits (e > 0.25). Systems with planets on highly eccentric orbits provide natural laboratories to test theories of orbital evolution, tidal forcing, and atmospheric response. The two best studied eccentric exoplanets are HAT-P-2b (e~0.5) and HD 80606 b (e~0.9). Both of these eccentric planets have full or partial orbit phase curve observations taken with the 3.6, 4.5, and 8.0 micron channels of the Spitzer IRAC instrument. These phase-curve observations of HAT-P-2b and HD 80606 b have given us important insights into atmospheric radiative timescales, planetary rotation rates and orbital evolution, and planet-star tidal interactions. Here I will overview the key results from the Spitzer observational campaigns for HAT-P-2b and HD 80606 b and look toward the future of phase curve observations of eccentric exoplanets in the era of JWST.

  2. Galactic planetary science.

    PubMed

    Tinetti, Giovanna

    2014-04-28

    Planetary science beyond the boundaries of our Solar System is today in its infancy. Until a couple of decades ago, the detailed investigation of the planetary properties was restricted to objects orbiting inside the Kuiper Belt. Today, we cannot ignore that the number of known planets has increased by two orders of magnitude nor that these planets resemble anything but the objects present in our own Solar System. Whether this fact is the result of a selection bias induced by the kind of techniques used to discover new planets--mainly radial velocity and transit--or simply the proof that the Solar System is a rarity in the Milky Way, we do not know yet. What is clear, though, is that the Solar System has failed to be the paradigm not only in our Galaxy but even 'just' in the solar neighbourhood. This finding, although unsettling, forces us to reconsider our knowledge of planets under a different light and perhaps question a few of the theoretical pillars on which we base our current 'understanding'. The next decade will be critical to advance in what we should perhaps call Galactic planetary science. In this paper, I review highlights and pitfalls of our current knowledge of this topic and elaborate on how this knowledge might arguably evolve in the next decade. More critically, I identify what should be the mandatory scientific and technical steps to be taken in this fascinating journey of remote exploration of planets in our Galaxy. PMID:24664916

  3. Galactic planetary science

    PubMed Central

    Tinetti, Giovanna

    2014-01-01

    Planetary science beyond the boundaries of our Solar System is today in its infancy. Until a couple of decades ago, the detailed investigation of the planetary properties was restricted to objects orbiting inside the Kuiper Belt. Today, we cannot ignore that the number of known planets has increased by two orders of magnitude nor that these planets resemble anything but the objects present in our own Solar System. Whether this fact is the result of a selection bias induced by the kind of techniques used to discover new planets—mainly radial velocity and transit—or simply the proof that the Solar System is a rarity in the Milky Way, we do not know yet. What is clear, though, is that the Solar System has failed to be the paradigm not only in our Galaxy but even ‘just’ in the solar neighbourhood. This finding, although unsettling, forces us to reconsider our knowledge of planets under a different light and perhaps question a few of the theoretical pillars on which we base our current ‘understanding’. The next decade will be critical to advance in what we should perhaps call Galactic planetary science. In this paper, I review highlights and pitfalls of our current knowledge of this topic and elaborate on how this knowledge might arguably evolve in the next decade. More critically, I identify what should be the mandatory scientific and technical steps to be taken in this fascinating journey of remote exploration of planets in our Galaxy. PMID:24664916

  4. Dynamics with a Nonstandard Inertia-Acceleration Relation: An Alternative to Dark Matter in Galactic Systems

    NASA Astrophysics Data System (ADS)

    Milgrom, M.

    1994-02-01

    We investigate particle dynamics that is governed by a nonstandard kinetic action of a special form. We are guided by a phenomenological scheme-the modified dynamics (MOND)-that imputes the mass discrepancy, observed in galactic systems, not to the presence of dark matter, but to a departure from Newtonian dynamics below a certain scale of accelerations, a0. The particle's equation of motion in a potential φ is derived from an action, S, of the form S ~ Sk[r(t), a0] - ∫ φ dt. The limit a0 --> 0 corresponds to Newtonian dynamics, and there the kinetic action Sk must take the standard form. In the opposite limit, a0 --> ∞ we require Sk --> 0-and more specifically, for circular orbits Sk ~ a-10-in order to attain the phenomenological success of MOND. Galilei-invariant such theories must be strongly nonlocal. This is a blessing, as such theories need not suffer from the illnesses that are endemic to higher-derivative theories. We comment on the possibility that such a modified law of motion is an effective theory resulting from the elimination of degrees of freedom pertaining to the universe at large (the near equality a0 ≍ cH0 being a trace of that connection). We derive a general virial relation for bounded trajectories. Exact solutions are obtained for circular orbits, which pertain to rotation curves of disk galaxies. We also explore, in passing, theories that depart from the conventional Newtonian dynamics for very low frequencies.

  5. Earth Rotation

    NASA Technical Reports Server (NTRS)

    Dickey, Jean O.

    1995-01-01

    The study of the Earth's rotation in space (encompassing Universal Time (UT1), length of day, polar motion, and the phenomena of precession and nutation) addresses the complex nature of Earth orientation changes, the mechanisms of excitation of these changes and their geophysical implications in a broad variety of areas. In the absence of internal sources of energy or interactions with astronomical objects, the Earth would move as a rigid body with its various parts (the crust, mantle, inner and outer cores, atmosphere and oceans) rotating together at a constant fixed rate. In reality, the world is considerably more complicated, as is schematically illustrated. The rotation rate of the Earth's crust is not constant, but exhibits complicated fluctuations in speed amounting to several parts in 10(exp 8) [corresponding to a variation of several milliseconds (ms) in the Length Of the Day (LOD) and about one part in 10(exp 6) in the orientation of the rotation axis relative to the solid Earth's axis of figure (polar motion). These changes occur over a broad spectrum of time scales, ranging from hours to centuries and longer, reflecting the fact that they are produced by a wide variety of geophysical and astronomical processes. Geodetic observations of Earth rotation changes thus provide insights into the geophysical processes illustrated, which are often difficult to obtain by other means. In addition, these measurements are required for engineering purposes. Theoretical studies of Earth rotation variations are based on the application of Euler's dynamical equations to the problem of finding the response of slightly deformable solid Earth to variety of surface and internal stresses.

  6. Instability of counter-rotating stellar disks

    NASA Astrophysics Data System (ADS)

    Hohlfeld, R. G.; Lovelace, R. V. E.

    2015-09-01

    We use an N-body simulation, constructed using GADGET-2, to investigate an accretion flow onto an astrophysical disk that is in the opposite sense to the disk's rotation. In order to separate dynamics intrinsic to the counter-rotating flow from the impact of the flow onto the disk, we consider an initial condition in which the counter-rotating flow is in an annular region immediately exterior the main portion of the astrophysical disk. Such counter-rotating flows are seen in systems such as NGC 4826 (known as the "Evil Eye Galaxy"). Interaction between the rotating and counter-rotating components is due to two-stream instability in the boundary region. A multi-armed spiral density wave is excited in the astrophysical disk and a density distribution with high azimuthal mode number is excited in the counter-rotating flow. Density fluctuations in the counter-rotating flow aggregate into larger clumps and some of the material in the counter-rotating flow is scattered to large radii. Accretion flow processes such as this are increasingly seen to be of importance in the evolution of multi-component galactic disks.

  7. The Galactic Magnetic Field and its lensing of Ultrahigh Energy and Galactic Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Farrar, Glennys

    2015-08-01

    It has long been recognized that magnetic fields play an important role in many astrophysical environments, but the magnetic field strength and structure has only been quantitatively determined for relatively few systems beyond our solar system.Our understanding of the Galactic magnetic field (GMF) has improved tremendously in recent years. The Jansson-Farrar (2012) (JF12) GMF model is the most realistic and comprehensive model available. It was constrained by fitting all-sky Faraday Rotation Measures of ~40k extragalactic sources, simultaneously with WMAP polarized (Q,U) and total synchrotron emission maps - together providing a total of more than 10,000 independent datapoints, each with measured astrophysical variance. In addition to disk and toroidal halo components, a previously overlooked coherent poloidal halo field proves to be necessary to account for the RM, Q and U data. Moreover a “striated” random component is needed in addition to a fully random component, in both disk and halo.The talk will give a concise review of the JF12 model and its derivation, with emphasis on which features of the GMF are well or poorly established. I will show that the data unambiguously demand a large scale coherent component to the halo field which is a diverging-spiral centered on the Galactic center, with field lines running from Southern to Northern hemispheres. The puzzles posed by the large scale coherent halo and disk magnetic fields, and their possible origins, will be discussed.Having a good model of the Galactic magnetic field is crucial for determining the sources of UHECRs, for modeling the transport of Galactic CRs (the halo field provides a heretofore-overlooked escape route for by diffusion along its field lines), and for calculating the background to dark matter and CMB-cosmology studies. I will present new results on the lensing effect of the GMF on UHECRs, which produces multiple images and dramatic magnification and demagnification that varies with

  8. Rotation Measurement

    NASA Technical Reports Server (NTRS)

    1979-01-01

    In aircraft turbine engine research, certain investigations require extremely precise measurement of the position of a rotating part, such as the rotor, a disc-like part of the engine's compressor which revolves around a shaft at extremely high speeds. For example, in studies of airflow velocity within a compressor, researchers need to know-for data correlation the instantaneous position of a given spot on the rotor each time a velocity measurement is made. Earlier methods of measuring rotor shaft angle required a physical connection to the shaft, which limited the velocity of the rotating object.

  9. Finding Distant Galactic HII Regions

    NASA Astrophysics Data System (ADS)

    Anderson, L. D.; Armentrout, W. P.; Johnstone, B. M.; Bania, T. M.; Balser, Dana S.; Wenger, Trey V.; Cunningham, V.

    2015-12-01

    The WISE Catalog of Galactic H ii Regions contains ˜2000 H ii region candidates lacking ionized gas spectroscopic observations. All candidates have the characteristic H ii region mid-infrared morphology of WISE 12 μ {{m}} emission surrounding 22 μ {{m}} emission, and additionally have detected radio continuum emission. We here report Green Bank Telescope hydrogen radio recombination line and radio continuum detections in the X-band (9 GHz; 3 cm) of 302 WISE H ii region candidates (out of 324 targets observed) in the zone 225^\\circ ≥slant {\\ell }≥slant -20^\\circ , | {\\text{}}b| ≤slant 6^\\circ . Here we extend the sky coverage of our H ii region Discovery Survey, which now contains nearly 800 H ii regions distributed across the entire northern sky. We provide LSR velocities for the 302 detections and kinematic distances for 131 of these. Of the 302 new detections, 5 have ({\\ell },{\\text{}}b,v) coordinates consistent with the Outer Scutum-Centaurus Arm (OSC), the most distant molecular spiral arm of the Milky Way. Due to the Galactic warp, these nebulae are found at Galactic latitudes >1° in the first Galactic quadrant, and therefore were missed in previous surveys of the Galactic plane. One additional region has a longitude and velocity consistent with the OSC but lies at a negative Galactic latitude (G039.183-01.422 -54.9 {km} {{{s}}}-1). With Heliocentric distances >22 kpc and Galactocentric distances >16 kpc, the OSC H ii regions are the most distant known in the Galaxy. We detect an additional three H ii regions near {\\ell }≃ 150^\\circ whose LSR velocities place them at Galactocentric radii >19 kpc. If their distances are correct, these nebulae may represent the limit to Galactic massive star formation.

  10. JASMINE: galactic structure surveyor

    NASA Astrophysics Data System (ADS)

    Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki; Yano, Taihei; Tsujimoto, Takuji; Suganuma, Masahiro; Niwa, Yoshito; Yamauchi, Masahiro; Kawakatsu, Yasuhiro; Matsuhara, Hideo; Noda, Atsushi; Tsuiki, Atsuo; Utashima, Masayoshi; Ogawa, Akira

    2006-06-01

    We introduce a Japanese plan of infrared(z-band:0.9μm) space astrometry(JASMINE-project). JASMINE is the satellite (Japan Astrometry Satellite Mission for INfrared Exploration) which will measure distances and apparent motions of stars around the center of the Milky Way with yet unprecedented precision. It will measure parallaxes, positions with the accuracy of 10 micro-arcsec and proper motions with the accuracy of ~ 4microarcsec/ year for stars brighter than z=14mag. JASMINE can observe about ten million stars belonging to the bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. Number of stars with σ/π < 0.1 in the direction of the Galactic central bulge is about 1000 times larger than those observed in optical bands, where π is a parallax and σ is an error of the parallax. With the completely new "map of the bulge in the Milky Way", it is expected that many new exciting scientific results will be obtained in various fields of astronomy. Presently, JASMINE is in a development phase, with a target launch date around 2015. We adopt the following instrument design of JASMINE in order to get the accurate positions of many stars. A 3-mirrors optical system(modified Korsch system)with a primary mirror of~ 0.85m is one of the candidate for the optical system. On the astro-focal plane, we put dozens of new type of CCDs for z-band to get a wide field of view. The accurate measurements of the astrometric parameters requires the instrument line-of-sight highly stability and the opto-mechanical highly stability of the payload in the JASMINE spacecraft. The consideration of overall system(bus) design is now going on in cooperation with Japan Aerospace Exploration Agency(JAXA).

  11. Galactic Habitable Orbits

    NASA Astrophysics Data System (ADS)

    Rahimi, A.; Mao, S.; Kawata, D.

    2014-03-01

    The fossil record shows that the Earth has experienced several mass extinctions over the past 500 million years1, and it has been suggested that there is a periodicity in extinction events on timescales of tens1 and/or hundreds of millions of years. Various hypotheses have been proposed to explain the cause of the mass extinctions, including the suggestion that the Earth's ozone layer may have been destroyed by intense radiation from a nearby supernovae2- 3, exposing the Earth's surface to damaging UV radiation. Recent observations of cores taken from the ocean floor revealed atoms of a very rare isotope of iron (60Fe) believed to have arrived on Earth around 2 million years ago as fallout from a nearby supernovae4. Astronomical evidence for that past supernovae was recently found in the debris of a young cluster of massive stars5, by tracing its past orbit, putting it at the right place at the right time to explain the mild extinction event. Here we report new high-resolution (both in space and time) N-body chemodynamical simulations (carried out with our novel code GCD+6) of the evolution of a model Milky Way Galaxy, tracing the orbit of èsun-like' stars over a 500 million year period, checking the proximity to supernovae throughout the history of the orbit and comparing the times when this occurs with past mass extinctions on Earth. We additionally explain the important effects of the spiral arm pattern, radial migration of stars and Galactic chemistry on habitability.

  12. The Bubbling Galactic Disk

    NASA Astrophysics Data System (ADS)

    Churchwell, E.; Povich, M. S.; Allen, D.; Taylor, M. G.; Meade, M. R.; Babler, B. L.; Indebetouw, R.; Watson, C.; Whitney, B. A.; Wolfire, M. G.; Bania, T. M.; Benjamin, R. A.; Clemens, D. P.; Cohen, M.; Cyganowski, C. J.; Jackson, J. M.; Kobulnicky, H. A.; Mathis, J. S.; Mercer, E. P.; Stolovy, S. R.; Uzpen, B.; Watson, D. F.; Wolff, M. J.

    2006-10-01

    A visual examination of the images from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) has revealed 322 partial and closed rings that we propose represent partially or fully enclosed three-dimensional bubbles. We argue that the bubbles are primarily formed by hot young stars in massive star formation regions. We have found an average of about 1.5 bubbles per square degree. About 25% of the bubbles coincide with known radio H II regions, and about 13% enclose known star clusters. It appears that B4-B9 stars (too cool to produce detectable radio H II regions) probably produce about three-quarters of the bubbles in our sample, and the remainder are produced by young O-B3 stars that produce detectable radio H II regions. Some of the bubbles may be the outer edges of H II regions where PAH spectral features are excited and may not be dynamically formed by stellar winds. Only three of the bubbles are identified as known SNRs. No bubbles coincide with known planetary nebulae or W-R stars in the GLIMPSE survey area. The bubbles are small. The distribution of angular diameters peaks between 1' and 3' with over 98% having angular diameters less than 10' and 88% less than 4'. Almost 90% have shell thicknesses between 0.2 and 0.4 of their outer radii. Bubble shell thickness increases approximately linearly with shell radius. The eccentricities are rather large, peaking between 0.6 and 0.7; about 65% have eccentricities between 0.55 and 0.85.

  13. A Disturbed Galactic Duo

    NASA Astrophysics Data System (ADS)

    2011-04-01

    The galaxies in this cosmic pairing, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166. Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger neighbours. This galactic grouping, found about 70 million light-years away in the constellation Sextans (The Sextant), was discovered by the English astronomer William Herschel in 1783. Modern astronomers have gauged the distance between NGC 3169 (left) and NGC 3166 (right) as a mere 50 000 light-years, a separation that is only about half the diameter of the Milky Way galaxy. In such tight quarters, gravity can start to play havoc with galactic structure. Spiral galaxies like NGC 3169 and NGC 3166 tend to have orderly swirls of stars and dust pinwheeling about their glowing centres. Close encounters with other massive objects can jumble this classic configuration, often serving as a disfiguring prelude to the merging of galaxies into one larger galaxy. So far, the interactions of NGC 3169 and NGC 3166 have just lent a bit of character. NGC 3169's arms, shining bright with big, young, blue stars, have been teased apart, and lots of luminous gas has been drawn out from its disc. In NGC 3166's case, the dust lanes that also usually outline spiral arms are in disarray. Unlike its bluer counterpart, NGC 3166 is not forming many new stars. NGC 3169 has another distinction: the faint yellow dot beaming through a veil of dark dust just to the left of and close to the galaxy's centre [1]. This flash is the leftover of a supernova detected in 2003 and known accordingly as SN 2003cg. A supernova of this

  14. A Disturbed Galactic Duo

    NASA Astrophysics Data System (ADS)

    2011-04-01

    The galaxies in this cosmic pairing, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166. Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger neighbours. This galactic grouping, found about 70 million light-years away in the constellation Sextans (The Sextant), was discovered by the English astronomer William Herschel in 1783. Modern astronomers have gauged the distance between NGC 3169 (left) and NGC 3166 (right) as a mere 50 000 light-years, a separation that is only about half the diameter of the Milky Way galaxy. In such tight quarters, gravity can start to play havoc with galactic structure. Spiral galaxies like NGC 3169 and NGC 3166 tend to have orderly swirls of stars and dust pinwheeling about their glowing centres. Close encounters with other massive objects can jumble this classic configuration, often serving as a disfiguring prelude to the merging of galaxies into one larger galaxy. So far, the interactions of NGC 3169 and NGC 3166 have just lent a bit of character. NGC 3169's arms, shining bright with big, young, blue stars, have been teased apart, and lots of luminous gas has been drawn out from its disc. In NGC 3166's case, the dust lanes that also usually outline spiral arms are in disarray. Unlike its bluer counterpart, NGC 3166 is not forming many new stars. NGC 3169 has another distinction: the faint yellow dot beaming through a veil of dark dust just to the left of and close to the galaxy's centre [1]. This flash is the leftover of a supernova detected in 2003 and known accordingly as SN 2003cg. A supernova of this

  15. Time Delay Evolution of Five Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Kovačević, A.; Popović, L. Č.; Shapovalova, A. I.; Ilić, D.; Burenkov, A. N.; Chavushyan, V. H.

    2015-12-01

    Here we investigate light curves of the continuum and emission lines of five type 1 active galactic nuclei (AGN) from our monitoring campaign, to test time-evolution of their time delays. Using both modeled and observed AGN light curves, we apply Gaussian kernel-based estimator to capture variation of local patterns of their time evolving delays. The largest variations of time delays of all objects occur in the period when continuum or emission lines luminosity is the highest. However, Gaussian kernel-based method shows instability in the case of NGC 5548, 3C 390.3, E1821 + 643 and NGC 4051 possibly due to numerical discrepancies between damped random walk (DRW) time scale of light curves and sliding time windows of the method. The temporal variations of time lags of Arp 102B can correspond to the real nature of the time lag evolution.

  16. Cosmological zoom simulations of z = 2 galaxies: The impact of galactic outflows

    SciTech Connect

    Anglés-Alcázar, Daniel; Davé, Romeel; Özel, Feryal; Oppenheimer, Benjamin D.

    2014-02-20

    We use high-resolution cosmological zoom simulations with ∼200 pc resolution at z = 2 and various prescriptions for galactic outflows in order to explore the impact of winds on the morphological, dynamical, and structural properties of eight individual galaxies with halo masses ∼10{sup 11}-2 × 10{sup 12} M {sub ☉} at z = 2. We present a detailed comparison to spatially and spectrally resolved Hα and other observations of z ≈ 2 galaxies. We find that simulations without winds produce massive, compact galaxies with low gas fractions, super-solar metallicities, high bulge fractions, and much of the star formation concentrated within the inner kiloparsec. Strong winds are required to maintain high gas fractions, redistribute star-forming gas over larger scales, and increase the velocity dispersion of simulated galaxies, more in agreement with the large, extended, turbulent disks typical of high-redshift star-forming galaxies. Winds also suppress early star formation to produce high-redshift cosmic star formation efficiencies in better agreement with observations. Sizes, rotation velocities, and velocity dispersions all scale with stellar mass in accord with observations. Our simulations produce a diversity of morphological characteristics—among our three most massive galaxies, we find a quiescent grand-design spiral, a very compact star-forming galaxy, and a clumpy disk undergoing a minor merger; the clumps are evident in Hα but not in the stars. Rotation curves are generally slowly rising, particularly when calculated using azimuthal velocities rather than enclosed mass. Our results are broadly resolution-converged. These results show that cosmological simulations including outflows can produce disk galaxies similar to those observed during the peak epoch of cosmic galaxy growth.

  17. RADIAL VELOCITIES OF GALACTIC O-TYPE STARS. I. SHORT-TERM CONSTANT VELOCITY STARS

    SciTech Connect

    Williams, S. J.; Gies, D. R.; Hillwig, T. C.; McSwain, M. V.; Huang, W. E-mail: gies@chara.gsu.edu E-mail: mcswain@lehigh.edu

    2011-11-15

    We present radial velocities for 18 Galactic O-type stars. These stars display small radial velocity scatter over timescales of one to two weeks. Some of them are long-period binaries while others are probably single stars. By fitting model spectra to our observed spectra we obtain estimates for effective temperature, log g, rotational velocity, and average radial velocity for each target.

  18. Making sense of the local Galactic escape speed estimates in direct dark matter searches

    NASA Astrophysics Data System (ADS)

    Lavalle, Julien; Magni, Stefano

    2015-01-01

    Direct detection (DD) of dark matter (DM) candidates in the ≲10 GeV mass range is very sensitive to the tail of their velocity distribution. The important quantity is the maximum weakly interacting massive particle speed in the observer's rest frame, i.e. in average the sum of the local Galactic escape speed vesc and of the circular velocity of the Sun vc. While the latter has been receiving continuous attention, the former is more difficult to constrain. The RAVE Collaboration has just released a new estimate of vesc [T. Piffl et al., Astron. Astrophys. 562, A91 (2014)] that supersedes the previous one [M. C. Smith, et al. Mon. Not. R. Astron. Soc. 379, 755 (2007)], which is of interest in the perspective of reducing the astrophysical uncertainties in DD. Nevertheless, these new estimates cannot be used blindly as they rely on assumptions in the dark halo modeling which induce tight correlations between the escape speed and other local astrophysical parameters. We make a self-consistent study of the implications of the RAVE results on DD assuming isotropic DM velocity distributions, both Maxwellian and ergodic. Taking as references the experimental sensitivities currently achieved by LUX, CRESST-II, and SuperCDMS, we show that (i) the exclusion curves associated with the best-fit points of P14 may be more constraining by up to ˜40 % with respect to standard limits, because the underlying astrophysical correlations induce a larger local DM density, and (ii) the corresponding relative uncertainties inferred in the low weakly interacting massive particle mass region may be moderate, down to 10-15% below 10 GeV. We finally discuss the level of consistency of these results with other independent astrophysical constraints. This analysis is complementary to others based on rotation curves.

  19. OH/IR stars near the Galactic Center: Pulsation periods, luminosities, and polarimetry

    NASA Technical Reports Server (NTRS)

    Jones, Terry Jay; Mcgregor, Peter J.; Gehrz, Robert D.; Lawrence, Geoffrey F.

    1994-01-01

    17 stars in the direction of the Galactic Center, 15 of which are OH/IR stars, have been monitored at infrared wavelengths over a period of nearly eight years. Pulsation periods, bolometric luminosities, and light curves for 14 OH/IR stars are presented. The Galactic Center OH/IR stars range in luminosity between M(sub Bol) = -4.5 to M(sub Bol) = -6, implying main sequence progenitors with masses less than 3 solar mass. When compared to optically visible long period variables in the Large Magellanic Cloud (LMC) with similar bolometric luminosities, the Galactic Center OH/IR stars have pulsation periods on average 30% longer. This shift to longer periods is consistent with the current picture of late asymptotic giant branch evolution, placing the OH/IR stars in a phase immediately following the optically visible Mira variable phase during which the star dramatically increases its mass loss rate, becoming invisible at optical wavelength. Infrared polarimetry of 11 of the stars is also presented. The polarization for all of the stars is consistent with purely interstellar polarization, with little evidence for a significant intrinsic component. When compared to OH/IR stars in the galactic plane, the Galactic Center OH/IR stars appear similar in photometric characteristics, except none of the Galactic Center OH/IR stars shows the extremely thick dust shells or very high intrinsic polarization found in the more extreme galactic plane OH/IR stars.

  20. CHARACTERIZING TRANSITION TEMPERATURE GAS IN THE GALACTIC CORONA

    SciTech Connect

    Wakker, Bart P.; Savage, Blair D.; Fox, Andrew J.; Benjamin, Robert A.; Shapiro, Paul R. E-mail: savage@astro.wisc.edu E-mail: benjamir@uww.edu

    2012-04-20

    We present a study of the properties of the transition temperature (T {approx} 10{sup 5} K) gas in the Milky Way corona, based on the measurements of O VI, N V, C IV, Si IV, and Fe III absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60 km s{sup -1}. On average the integrated column densities are log N(O VI) = 14.3, log N(N V) = 13.5, log N(C IV) = 14.2, log N(Si IV) = 13.6, and log N(Fe III) = 14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor {approx}2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions. We compare the column densities and ionic ratios to a series of theoretical predictions: collisional ionization equilibrium, shock ionization, conductive interfaces, turbulent mixing, thick disk supernovae, static non-equilibrium ionization (NIE) radiative cooling, and an NIE radiative cooling model in which the gas flows through the cooling zone. None of these models can fully reproduce the data, but it is clear that NIE radiative cooling is important in generating the transition temperature gas.

  1. Where Galactic Snakes Live

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This infrared image from NASA's Spitzer Space Telescope shows what astronomers are referring to as a 'snake' (upper left) and its surrounding stormy environment. The sinuous object is actually the core of a thick, sooty cloud large enough to swallow dozens of solar systems. In fact, astronomers say the 'snake's belly' may be harboring beastly stars in the process of forming.

    The galactic creepy crawler to the right of the snake is another thick cloud core, in which additional burgeoning massive stars might be lurking. The colorful regions below the two cloud cores are less dense cloud material, in which dust has been heated by starlight and glows with infrared light. Yellow and orange dots throughout the image are monstrous developing stars; the red star on the 'belly' of the snake is 20 to 50 times as massive as our sun. The blue dots are foreground stars.

    The red ball at the bottom left is a 'supernova remnant,' the remains of massive star that died in a fiery blast. Astronomers speculate that radiation and winds from the star before it died, in addition to a shock wave created when it exploded, might have played a role in creating the snake.

    Spitzer was able to spot the two black cloud cores using its heat-seeking infrared vision. The objects are hiding in the dusty plane of our Milky Way galaxy, invisible to optical telescopes. Because their heat, or infrared light, can sneak through the dust, they first showed up in infrared images from past missions. The cloud cores are so thick with dust that if you were to somehow transport yourself into the middle of them, you would see nothing but black, not even a star in the sky. Now, that's spooky!

    Spitzer's new view of the region provides the best look yet at the massive embryonic stars hiding inside the snake. Astronomers say these observations will ultimately help them better understand how massive stars form. By studying the clustering and range of masses of the stellar embryos, they hope

  2. CENTRAL ROTATIONS OF MILKY WAY GLOBULAR CLUSTERS

    SciTech Connect

    Fabricius, Maximilian H.; Rukdee, Surangkhana; Saglia, Roberto P.; Bender, Ralf; Hopp, Ulrich; Thomas, Jens; Williams, Michael J.; Noyola, Eva; Opitsch, Michael

    2014-06-01

    Most Milky Way globular clusters (GCs) exhibit measurable flattening, even if on a very low level. Both cluster rotation and tidal fields are thought to cause this flattening. Nevertheless, rotation has only been confirmed in a handful of GCs, based mostly on individual radial velocities at large radii. We are conducting a survey of the central kinematics of Galactic GCs using the new Integral Field Unit instrument VIRUS-W. We detect rotation in all 11 GCs that we have observed so far, rendering it likely that a large majority of the Milky Way GCs rotate. We use published catalogs of GCs to derive central ellipticities and position angles. We show that in all cases where the central ellipticity permits an accurate measurement of the position angle, those angles are in excellent agreement with the kinematic position angles that we derive from the VIRUS-W velocity fields. We find an unexpected tight correlation between central rotation and outer ellipticity, indicating that rotation drives flattening for the objects in our sample. We also find a tight correlation between central rotation and published values for the central velocity dispersion, most likely due to rotation impacting the old dispersion measurements.

  3. The Galactic Plane Infrared Polarization Survey (GPIPS)

    NASA Astrophysics Data System (ADS)

    Clemens, Dan P.; Pinnick, A. F.; Pavel, M. D.; Taylor, B. W.

    2012-06-01

    The scientific motivation, data collection strategy, data reduction, and analysis methods are presented for the Galactic Plane Infrared Polarization Survey (GPIPS). The chief goal for the Survey was to reveal the nature of the magnetic field threading the Galactic disk, in particular through regions of low to moderate extinction (1-20 mag of AV ) and star formation in the cool interstellar medium. The Survey region spans 76 deg2 of the northern Milky Way disk, from l = 18° to 56° and b =-1° to +1°. Linear polarimetric imaging observations began in 2006 in the near-infrared H band (1.6 μm) using the Mimir instrument on the 1.8 m Perkins telescope, located outside Flagstaff, AZ. Mimir used a cold, fixed wire grid and a rotateable cold, compound half-wave plate to obtain "step-and-integrate" polarimetry over its full 10 × 10 arcmin field of view. The GPIPS bright and faint polarimetric limits are approximately 7th and 15th mag, respectively, set by saturation and photon noise. Polarimetric uncertainties track with stellar magnitude, from about 0.1% to 25%, on average, from the brightest to faintest stars. Across the 3237 field GPIPS region, approximately 0.5 million stars are estimated to show detectable linear polarization (P/σ P > 3); most of these have mH < 12. This represents many orders of magnitude improvement in the number of polarization measurements across this region. GPIPS observations are more than 90% complete and should finish in 2012.

  4. Carbon Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Totten, E. J.; Irwin, M. J.

    1996-04-01

    A byproduct of the APM high redshift quasar survey (Irwin et al. 1991) was the discovery of ~ 20 distant (20-100kpc) cool AGB carbon stars (all N-type) at high Galactic latitude. In August we used the INT+IDS to survey the rest of the high latitude SGC sky visible from La Palma and found 10 more similar carbon stars. Before this work there were only a handful of published faint high latitude cool carbon stars known (eg. Margon et al., 1984, Mould et al., 1985) and there has been speculation as to their origin (eg. Sanduleak, 1980, van den Bergh & Lafontaine, 1984). Intermediate age carbon stars (3 -- 7 Gyrs) seem unlikely to have formed in the halo in isolation from other star forming regions so how did they get there ? One possiblity that we are investigating, is that they arise from either the disruption of tidally captured dSph galaxies or are a manifestion of the long sought after optical component of the Magellanic Stream. Lack of proper motion rules out the possibility of them being dwarf carbon stars (eg. Warren et al., 1992); indeed no N-type carbon stars have been found to be dwarf carbon stars. Our optical spectroscopy confirms their carbon star type (they are indistinguishable from cool AGB carbon stars in nearby dwarf galaxies) and hence probable large distances. We are extending our survey to the NGC region, obtaining radial velocities and good S:N fluxed spectra for all the carbon stars. This will enable us to investigate their kinematics, true spatial distribution and hence their origin. Even, in the event that these objects are somehow an integral part of the Galactic halo, then their velocities and large distances will enable direct studies of the velocity ellipsoid and rotation of the outer halo (eg. Green et al., 1994).

  5. On the alleged duality of the Galactic halo

    NASA Astrophysics Data System (ADS)

    Schönrich, Ralph; Asplund, Martin; Casagrande, Luca

    2011-08-01

    We examine the kinematics of the Galactic halo based on SDSS/SEGUE data by Carollo et al. We find that their claims of a counter-rotating halo are the result of substantial biases in distance estimates (of the order of 50 per cent): the claimed retrograde component, which makes up only a tiny fraction of the entire sample, prone to contaminations, is identified as the tail of distance overestimates. The strong overestimates also result in a lift in the vertical velocity component, which explains the large altitudes those objects were claimed to reach. Errors are worst for the lowest metallicity stars, which explains the metal-poor nature of the artificial component. We also argue that measurement errors were not properly accounted for and that the use of Gaussian fitting on intrinsically non-Gaussian Galactic components invokes the identification of components that are distorted or even artificial. Our evaluation of the data leads to a revision of the estimated velocity ellipsoids and does not yield any reliable evidence for a counter-rotating halo component. If a distinct counter-rotating halo component exists, then it must be far weaker than claimed by Carollo et al. Finally, we note that their revised analysis presented in Beers et al. does not alleviate our main concerns.

  6. Anodic Polarization Curves Revisited

    ERIC Educational Resources Information Center

    Liu, Yue; Drew, Michael G. B.; Liu, Ying; Liu, Lin

    2013-01-01

    An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into…

  7. Flow-duration curves

    USGS Publications Warehouse

    Searcy, James Kincheon

    1959-01-01

    The flow-duration curve is a cumulative frequency curve that shows the percent of time specified discharges were equaled or exceeded during a given period. It combines in one curve the flow characteristics of a stream throughout the range of discharge, without regard to the sequence of occurrence. If the period upon which the curve is based represents the long-term flow of a stream, the curve may be used to predict the distribution of future flows for water- power, water-supply, and pollution studies. This report shows that differences in geology affect the low-flow ends of flow-duration curves of streams in adjacent basins. Thus, duration curves are useful in appraising the geologic characteristics of drainage basins. A method for adjusting flow-duration curves of short periods to represent long-term conditions is presented. The adjustment is made by correlating the records of a short-term station with those of a long-term station.

  8. Observing the next galactic supernova

    SciTech Connect

    Adams, Scott M.; Kochanek, C. S.; Beacom, John F.; Stanek, K. Z.; Vagins, Mark R.

    2013-12-01

    No supernova (SN) in the Milky Way has been observed since the invention of the optical telescope, instruments for other wavelengths, neutrino detectors, or gravitational wave observatories. It would be a tragedy to miss the opportunity to fully characterize the next one. To aid preparations for its observations, we model the distance, extinction, and magnitude probability distributions of a successful Galactic core-collapse supernova (ccSN), its shock breakout radiation, and its massive star progenitor. We find, at very high probability (≅ 100%), that the next Galactic SN will easily be detectable in the near-IR and that near-IR photometry of the progenitor star very likely (≅ 92%) already exists in the Two Micron All Sky Survey. Most ccSNe (98%) will be easily observed in the optical, but a significant fraction (43%) will lack observations of the progenitor due to a combination of survey sensitivity and confusion. If neutrino detection experiments can quickly disseminate a likely position (∼3°), we show that a modestly priced IR camera system can probably detect the shock breakout radiation pulse even in daytime (64% for the cheapest design). Neutrino experiments should seriously consider adding such systems, both for their scientific return and as an added and internal layer of protection against false triggers. We find that shock breakouts from failed ccSNe of red supergiants may be more observable than those of successful SNe due to their lower radiation temperatures. We review the process by which neutrinos from a Galactic ccSN would be detected and announced. We provide new information on the EGADS system and its potential for providing instant neutrino alerts. We also discuss the distance, extinction, and magnitude probability distributions for the next Galactic Type Ia supernova (SN Ia). Based on our modeled observability, we find a Galactic ccSN rate of 3.2{sub −2.6}{sup +7.3} per century and a Galactic SN Ia rate of 1.4{sub −0.8}{sup +1.4} per

  9. QPOs from Random X-ray Bursts around Rotating Black Holes

    NASA Technical Reports Server (NTRS)

    Kukumura, Keigo; Kazanas, Demosthenes; Stephenson, Gordon

    2009-01-01

    We continue our earlier studies of quasi-periodic oscillations (QPOs) in the power spectra of accreting, rapidly-rotating black holes that originate from the geometric 'light echoes' of X-ray flares occurring within the black hole ergosphere. Our present work extends our previous treatment to three-dimensional photon emission and orbits to allow for arbitrary latitudes in the positions of the distant observers and the X-ray sources in place of the mainly equatorial positions and photon orbits of the earlier consideration. Following the trajectories of a large number of photons we calculate the response functions of a given geometry and use them to produce model light curves which we subsequently analyze to compute their power spectra and autocorrelation functions. In the case of an optically-thin environment, relevant to advection-dominated accretion flows, we consistently find QPOs at frequencies of order of approximately kHz for stellar-mass black hole candidates while order of approximately mHz for typical active galactic nuclei (approximately equal to 10(exp 7) solar mass) for a wide range of viewing angles (30 degrees to 80 degrees) from X-ray sources predominantly concentrated toward the equator within the ergosphere. As in out previous treatment, here too, the QPO signal is produced by the frame-dragging of the photons by the rapidly-rotating black hole, which results in photon 'bunches' separated by constant time-lags, the result of multiple photon orbits around the hole. Our model predicts for various source/observer configurations the robust presence of a new class of QPOs, which is inevitably generic to curved spacetime structure in rotating black hole systems.

  10. Galactic gamma-ray observations and galactic structure

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1975-01-01

    Recent observations of gamma-rays originating in the galactic disk together with radio observations, support an emerging picture of the overall structure of our galaxy with higher interstellar gas densities and star formation rates in a region which corresponds to that of the inner arms. The emerging picture is one where molecular clouds make up the dominant constituent of the interstellar gas in the inner galaxy and play a key role in accounting for the gamma-rays and phenomena associated with the production of young stars and other population 1 objects. In this picture, cosmic rays are associated with supernovae and are primarily of galactic origin. These newly observed phenomena can be understood as consequences of the density wave theories of spiral structure. Based on these new developments, the suggestion is made that a new galactic population class, Population O, be added to the standard Populations 1 and 2 in order to recognize important differences in dynamics and distribution between diffuse galactic H1 and interstellar molecular clouds.

  11. The Heliosphere and Galactic Cosmic Rays

    NASA Video Gallery

    The heliosphere deflects galactic cosmic rays from entering the system. Galactic cosmic rays are a very high energy form of particle radiation that are extremely difficult to shield against and are...

  12. V1117 Her: A Herbig Ae star at high Galactic latitude?

    NASA Astrophysics Data System (ADS)

    Kun, M.; Racz, M.; Szabados, L.

    2014-01-01

    We examine the long-term light curve, optical spectrum, spectral energy distribution, and Galactic location of V1117 Her in order to establish its nature. V1117 Her is most probably a young intermediate-mass star whose cyclic brightness dimmings are caused by changing circumstellar dust structures.

  13. Rotated balance in humans due to repetitive rotational movement

    NASA Astrophysics Data System (ADS)

    Zakynthinaki, M. S.; Madera Milla, J.; López Diaz De Durana, A.; Cordente Martínez, C. A.; Rodríguez Romo, G.; Sillero Quintana, M.; Sampedro Molinuevo, J.

    2010-03-01

    We show how asymmetries in the movement patterns during the process of regaining balance after perturbation from quiet stance can be modeled by a set of coupled vector fields for the derivative with respect to time of the angles between the resultant ground reaction forces and the vertical in the anteroposterior and mediolateral directions. In our model, which is an adaption of the model of Stirling and Zakynthinaki (2004), the critical curve, defining the set of maximum angles one can lean to and still correct to regain balance, can be rotated and skewed so as to model the effects of a repetitive training of a rotational movement pattern. For the purposes of our study a rotation and a skew matrix is applied to the critical curve of the model. We present here a linear stability analysis of the modified model, as well as a fit of the model to experimental data of two characteristic "asymmetric" elite athletes and to a "symmetric" elite athlete for comparison. The new adapted model has many uses not just in sport but also in rehabilitation, as many work place injuries are caused by excessive repetition of unaligned and rotational movement patterns.

  14. Veggie Light Curve Demo

    NASA Video Gallery

    In this activity, students will observe the surface of rotating potatoes to help them understand how astronomers can sometimes determine the shape of asteroids from variations in reflective brightn...

  15. PIPER and Polarized Galactic Foregrounds

    NASA Technical Reports Server (NTRS)

    Chuss, David

    2009-01-01

    In addition to probing inflationary cosmology, PIPER will measure the polarized dust emission from the Galaxy. PIPER will be capable of full (I,0,U,V) measurement over four frequency bands ' These measurements will provide insight into the physics of dust grains and a probe of the Galactic magnetic field on large and intermediate scales.

  16. Dust in the galactic environment

    NASA Astrophysics Data System (ADS)

    Whittet, D. C. B.

    An overview of dust in the galactic environment is given which covers general concepts, methods of investigation, important results and their significance, relevant literature, and suggestions for future research. The general topics addressed include: element abundances and depletions, interstellar extinction and scattering, interstellar polarization and grain alignment, spectral absorption features, continuum and line emission, and the origin and evolution of interstellar grains.

  17. Mechanics of Curved Folds

    NASA Astrophysics Data System (ADS)

    Dias, Marcelo A.; Santangelo, Christian D.

    2011-03-01

    Despite an almost two thousand year history, origami, the art of folding paper, remains a challenge both artistically and scientifically. Traditionally, origami is practiced by folding along straight creases. A whole new set of shapes can be explored, however, if, instead of straight creases, one folds along arbitrary curves. We present a mechanical model for curved fold origami in which the energy of a plastically-deformed crease is balanced by the bending energy of developable regions on either side of the crease. Though geometry requires that a sheet buckle when folded along a closed curve, its shape depends on the elasticity of the sheet. NSF DMR-0846582.

  18. The galactic cycle of extinction

    NASA Astrophysics Data System (ADS)

    Gillman, Michael; Erenler, Hilary

    2008-01-01

    Global extinction and geological events have previously been linked with galactic events such as spiral arm crossings and galactic plane oscillation. The expectation that these are repeating predictable events has led to studies of periodicity in a wide set of biological, geological and climatic phenomena. Using data on carbon isotope excursions, large igneous provinces and impact craters, we identify three time zones of high geological activity which relate to the timings of the passage of the Solar System through the spiral arms. These zones are shown to include a significantly large proportion of high extinction periods. The mass extinction events at the ends of the Ordovician, Permian and Cretaceous occur in the first zone, which contains the predicted midpoints of the spiral arms. The start of the Cambrian, end of the Devonian and end of the Triassic occur in the second zone. The pattern of extinction timing in relation to spiral arm structure is supported by the positions of the superchrons and the predicted speed of the spiral arms. The passage times through an arm are simple multiples of published results on impact and fossil record periodicity and galactic plane half-periods. The total estimated passage time through four arms is 703.8 Myr. The repetition of extinction events at the same points in different spiral arm crossings suggests a common underlying galactic cause of mass extinctions, mediated through galactic effects on geological, solar and extra-solar processes. The two largest impact craters (Sudbury and Vredefort), predicted to have occurred during the early part of the first zone, extend the possible pattern to more than 2000 million years ago.

  19. The Formation of Galactic Bulges

    NASA Astrophysics Data System (ADS)

    Carollo, C. Marcella; Ferguson, Henry C.; Wyse, Rosemary F. G.

    2000-03-01

    Part I. Introduction: What are galactic bulges?; Part II. The Epoch of Bulge Formation: Origin of bulges; Deep sub-mm surveys: High-z ULIRGs and the formation of spheroids; Ages and metallicities for stars in the galactic bulge; Integrated stellar populations of bulges: First results; HST-NICMOS observations of galactic bulges: Ages and dust; Inside-out bulge formation and the origin of the Hubble sequence; Part III. The Timescales of Bulge Formation: Constraints on the bulge formation timescale from stellar populations; Bulge building with mergers and winds; Role of winds, starbursts, and activity in bulge formation; Dynamical timescales of bulge formation; Part IV. Physical Processes in Bulge Formation: the role of bars for secular bulge formation; Bars and boxy/peanut-shaped bulges: an observational point of view; Boxy- and peanut-shaped bulges; A new class of bulges; The role of secondary bars in bulge formation; Radial transport of molecular gas to the nuclei of spiral galaxies; Dynamical evolution of bulge shapes; Two-component stellar systems: Phase-space constraints; Central NGC 2146 - a firehose-type bending instability?; Bulge formation: the role of the multi-phase ISM; Global evolution of a self-gravitating multi-phase ISM in the central kpc region of galaxies; Part V. Bulge Phenomenology: Bulge-disk decomposition of spiral galaxies in the near-infrared; The triaxial bulge of NGC 1371; The bulge-disk orthogonal decoupling in galaxies: NGC 4698 and NGC 4672; The kinematics and the origin of the ionized gas in NGC 4036; Optically thin thermal plasma in the galactic bulge; X-ray properties of bulges; The host galaxies of radio-loud AGN; The centers of radio-loud early-type galaxies with HST; Central UV spikes in two galactic spheroids; Conference summary: where do we stand?

  20. Curve Stitching in LOGO.

    ERIC Educational Resources Information Center

    Muscat, Jean-Paul

    1992-01-01

    Uses LOGO to enhance the applicability of curve stitching in the mathematics curriculum. Presents the formulas and computer programs for the construction of parabolas, concentric circles, and epicycloids. Diagrams of constructed figures are provided. (MDH)

  1. Highly curved microchannel plates

    NASA Technical Reports Server (NTRS)

    Siegmund, O. H. W.; Cully, S.; Warren, J.; Gaines, G. A.; Priedhorsky, W.; Bloch, J.

    1990-01-01

    Several spherically curved microchannel plate (MCP) stack configurations were studied as part of an ongoing astrophysical detector development program, and as part of the development of the ALEXIS satellite payload. MCP pairs with surface radii of curvature as small as 7 cm, and diameters up to 46 mm have been evaluated. The experiments show that the gain (greater than 1.5 x 10 exp 7) and background characteristics (about 0.5 events/sq cm per sec) of highly curved MCP stacks are in general equivalent to the performance achieved with flat MCP stacks of similar configuration. However, gain variations across the curved MCP's due to variations in the channel length to diameter ratio are observed. The overall pulse height distribution of a highly curved surface MCP stack (greater than 50 percent FWHM) is thus broader than its flat counterpart (less than 30 percent). Preconditioning of curved MCP stacks gives comparable results to flat MCP stacks, but it also decreases the overall gain variations. Flat fields of curved MCP stacks have the same general characteristics as flat MCP stacks.

  2. ROTATIONAL DOPPLER BEAMING IN ECLIPSING BINARIES

    SciTech Connect

    Groot, Paul J.

    2012-01-20

    In eclipsing binaries the stellar rotation of the two components will cause a rotational Doppler beaming during eclipse ingress and egress when only part of the eclipsed component is covered. For eclipsing binaries with fast spinning components this photometric analog of the well-known spectroscopic Rossiter-McLaughlin effect can exceed the strength of the orbital effect. Example light curves are shown for a detached double white dwarf binary, a massive O-star binary and a transiting exoplanet case, similar to WASP-33b. Inclusion of the rotational Doppler beaming in eclipsing systems is a prerequisite for deriving the correct stellar parameters from fitting high-quality photometric light curves and can be used to determine stellar obliquities as well as, e.g., an independent measure of the rotational velocity in those systems that may be expected to be fully synchronized.

  3. Using red clump stars to decompose the galactic magnetic field with distance

    SciTech Connect

    Pavel, Michael D.

    2014-09-01

    A new method for measuring the large-scale structure of the Galactic magnetic field is presented. The Galactic magnetic field has been probed through the Galactic disk with near-infrared starlight polarimetry; however, the distance to each background star is unknown. Using red clump stars as near-infrared standard candles, this work presents the first attempt to decompose the line-of-sight structure of the sky-projected Galactic magnetic field. Two example lines of sight are decomposed: toward a field with many red clump stars and toward a field with few red clump stars. A continuous estimate of magnetic field orientation over several kiloparsecs of distance is possible in the field with many red clump stars, while only discrete estimates are possible in the sparse example. Toward the outer Galaxy, there is a continuous field orientation with distance that shows evidence of perturbation by the Galactic warp. Toward the inner Galaxy, evidence for a large-scale change in the magnetic field geometry is consistent with models of magnetic field reversals, independently derived from Faraday rotation studies. A photo-polarimetric method for identifying candidate intrinsically polarized stars is also presented. The future application of this method to large regions of the sky will begin the process of mapping the Galactic magnetic field in a way never before possible.

  4. Using Red Clump Stars to Decompose the Galactic Magnetic Field with Distance

    NASA Astrophysics Data System (ADS)

    Pavel, Michael D.

    2014-09-01

    A new method for measuring the large-scale structure of the Galactic magnetic field is presented. The Galactic magnetic field has been probed through the Galactic disk with near-infrared starlight polarimetry; however, the distance to each background star is unknown. Using red clump stars as near-infrared standard candles, this work presents the first attempt to decompose the line-of-sight structure of the sky-projected Galactic magnetic field. Two example lines of sight are decomposed: toward a field with many red clump stars and toward a field with few red clump stars. A continuous estimate of magnetic field orientation over several kiloparsecs of distance is possible in the field with many red clump stars, while only discrete estimates are possible in the sparse example. Toward the outer Galaxy, there is a continuous field orientation with distance that shows evidence of perturbation by the Galactic warp. Toward the inner Galaxy, evidence for a large-scale change in the magnetic field geometry is consistent with models of magnetic field reversals, independently derived from Faraday rotation studies. A photo-polarimetric method for identifying candidate intrinsically polarized stars is also presented. The future application of this method to large regions of the sky will begin the process of mapping the Galactic magnetic field in a way never before possible.

  5. The Galactic Magnetic Field as Viewed from the VLA

    NASA Astrophysics Data System (ADS)

    van Eck, Cameron; Brown, Jo-Anne

    2009-05-01

    Interstellar magnetic fields play critical roles in many astrophysical processes. Yet despite their importance, our knowledge about magnetic fields in our Galaxy remains limited. For the field within the Milky Way much of what we do know comes from radio astronomy, through observations of polarization and Faraday rotation measures (RMs) of extragalactic sources and pulsars. A high angular density of RM measurements in several critical areas of the Galaxy is needed to clarify the Galactic magnetic field structure. Understanding the overall structure of the magnetic field will subsequently help us determine the origin and evolution of the field. In an effort to determine the overall structure of the field, Sun et al. (2008) produced 3 models of the Galactic magnetic field based on RM measurements available at the time. These models made distinct predictions for RMs in a region of the inner Galaxy at low Galactic latitude. Using observations made with the Very Large Array (VLA), we have determined RMs for sources in this critical region. In this talk we will present the results of our study and show how the RMs strongly support the ASS+RING model.

  6. Periodic variations in the vertical velocities of galactic masers

    NASA Astrophysics Data System (ADS)

    Bobylev, V. V.; Bajkova, A. T.; Shirokova, K. S.

    We compiled published data on Galactic masers with VLBI-measured trigonometric parallaxes and determined the residual tangential, Δ Vcirc, and radial, Δ VR, velocities for 120 masers. We used these data to re-determine the parameters of the Galactic spiral density wave using the method of spectral analysis. The tangential and radial perturbation amplitudes are fθ =6.5±2.4 km s-1 and fR=8.1±2.1 km s-1, respectively; the perturbation wavelengths are λ θ =3.2±0.5 kpc and λR=3.0±0.6 kpc for a four-armed spiral model, m=4. The phase of the Sun χ⊙ in the spiral density wave is -80o±14o and -192o±16o if inferred from the residual tangential and radial velocities, respectively. The most interesting result of this study is the detection of wavelike oscillations of vertical spatial velocities (W) versus distance R from the Galactic rotation axis. Spectral analysis allowed us to determine the perturbation wavelength and the amplitude of this wave, which we found to be equal to λW=3.4±0.7 kpc and fW=4.9±1.2 km s-1, respectively.

  7. Oxygen isotopic ratios toward molecular clouds in the Galactic disk

    NASA Astrophysics Data System (ADS)

    Li, Hai-Kun; Zhang, Jiang-Shui; Liu, Zhi-Wei; Lu, Deng-Rong; Wang, Min; Wang, Jin

    2016-03-01

    We present our observations of the J = 1 - 0 rotation transitions in molecular isotopes C18O and C17O toward a sample of molecular clouds with different galactocentric distances, using the Delingha 13.7m (DLH 13.7 m) telescope, administered by Purple Mountain Observatory, and its 9-beam SIS receiver. Complementary observations toward several sources with large galactocentric distance are obtained with the IRAM 30m and Mopra 22m telescopes. C18O/C17O abundance ratios reflecting the 18O/17O isotope ratios are obtained from integrated intensity ratios of C18O and C17O. We derived the ratio value for 13 sources covering a galactocentric distance range of 3kpc to 16kpc. In combination with our mapping results that provide a ratio value of 3.01±0.14 in the Galactic center region, it shows that the abundance ratio tends to increase with galactocentric distance, i.e., it supports a radial gradient along the Galactic disk for the abundance ratio. This is consistent with the inside-out formation scenario of our Galaxy. However, our results may suffer from small samples with large galactocentric distance. Combining our data with multi-transition lines of C18O and C17O will be helpful for constraining opacities and abundances and further confirming the Galactic radial gradient shown by the isotope ratio 18O/17O.

  8. Particle Acceleration in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Miller, James A.

    1997-01-01

    The high efficiency of energy generation inferred from radio observations of quasars and X-ray observations of Seyfert active galactic nuclei (AGNs) is apparently achieved only by the gravitational conversion of the rest mass energy of accreting matter onto supermassive black holes. Evidence for the acceleration of particles to high energies by a central engine is also inferred from observations of apparent superluminal motion in flat spectrum, core-dominated radio sources. This phenomenon is widely attributed to the ejection of relativistic bulk plasma from the nuclei of active galaxies, and accounts for the existence of large scale radio jets and lobes at large distances from the central regions of radio galaxies. Reports of radio jets and superluminal motion from galactic black hole candidate X-ray sources indicate that similar processes are operating in these sources. Observations of luminous, rapidly variable high-energy radiation from active galactic nuclei (AGNs) with the Compton Gamma Ray Observatory show directly that particles are accelerated to high energies in a compact environment. The mechanisms which transform the gravitational potential energy of the infalling matter into nonthermal particle energy in galactic black hole candidates and AGNs are not conclusively identified, although several have been proposed. These include direct acceleration by static electric fields (resulting from, for example, magnetic reconnection), shock acceleration, and energy extraction from the rotational energy of Kerr black holes. The dominant acceleration mechanism(s) operating in the black hole environment can only be determined, of course, by a comparison of model predictions with observations. The purpose of the work proposed for this grant was to investigate stochastic particle acceleration through resonant interactions with plasma waves that populate the magnetosphere surrounding an accreting black hole. Stochastic acceleration has been successfully applied to the

  9. Observational signatures of galactic winds powered by active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Nims, Jesse; Quataert, Eliot; Faucher-Giguère, Claude-André

    2015-03-01

    We predict the observational signatures of galaxy scale outflows powered by active galactic nuclei (AGN). Most of the emission is produced by the forward shock driven into the ambient interstellar medium (ISM) rather than by the reverse shock. AGN-powered galactic winds with energetics suggested by phenomenological feedback arguments should produce spatially extended ˜1-10 keV X-ray emission ˜ 1041-44 erg s- 1, significantly in excess of the spatially extended X-ray emission associated with normal star-forming galaxies. The presence of such emission is a direct test of whether AGN outflows significantly interact with the ISM of their host galaxy. We further show that even radio-quiet quasars should have a radio luminosity comparable to or in excess of the far-infrared-radio correlation of normal star-forming galaxies. This radio emission directly constrains the total kinetic energy flux in AGN-powered galactic winds. Radio emission from AGN wind shocks can also explain the recently highlighted correlations between radio luminosity and the kinematics of AGN narrow-line regions in radio-quiet quasars.

  10. Rotating Bioreactor

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues currently being cultured in rotating bioreactors by investigators.

  11. Galactic Fountains and Gas Accretion

    NASA Astrophysics Data System (ADS)

    Marinacci, F.; Binney, J.; Fraternali, F.; Nipoti, C.; Ciotti, L.; Londrillo, P.

    2010-06-01

    Star-forming disc galaxies such as the Milky Way need to accrete >~1 Msolar of gas each year to sustain their star formation. This gas accretion is likely to come from the cooling of the hot corona, however it is still not clear how this process can take place. We present simulations supporting the idea that this cooling and the subsequent accretion are caused by the passage of cold galactic-fountain clouds through the hot corona. The Kelvin-Helmholtz instability strips gas from these clouds and the stripped gas causes coronal gas to condense in the cloud's wake. For likely parameters of the Galactic corona and of typical fountain clouds we obtain a global accretion rate of the order of that required to feed the star formation.

  12. The Chandra Galactic Bulge Survey

    NASA Astrophysics Data System (ADS)

    Torres, Manuel

    2014-11-01

    The Chandra Galactic Bulge Survey (GBS) is a shallow survey with a flux limit of 1e-14 erg/cm2/s (0.5-10.0 keV) that covers a pair of 6 sq. deg. areas centred 1.5 deg. above and below the Galactic Center. The extinction and crowding in these regions are such that optical/infrared counterparts to the 1640 X-ray sources found with Chandra are accessible to detailed follow-up. The GBS is designed to set constraints on four important areas in astrophysics: stellar-mass black hole formation, the neutron star equation of state, the nature of the progenitors of type Ia supernovae and the common envelope evolution. Here I present the survey properties and goals, our multiwavelength methods to identify and clasify the counterparts to the X-ray sources and the first scientific results.

  13. Photometry Of Pluto At Low Galactic Latitudes

    NASA Astrophysics Data System (ADS)

    George, Erin; Buie, M.; Bagenal, F.

    2012-10-01

    Our research is part of an ongoing project to continue the long-term photometric monitoring of Pluto in hopes to constrain volatile migration on the surface. As Pluto passes near the center of the galaxy, the fields are too crowded with stars for normal aperture photometry. We approached this problem by using Optimal Image Subtraction (OIS). We took images, both containing and not containing Pluto, using the 0.8m robotic telescope at Lowell Observatory, the 1m robotic telescope at New Mexico State University, and the Faulkes 2m robotic telescope at Siding Spring, part of Las Cumbres Observatory. We are presently gathering data, but our main focus was the data from 2010. We began by taking images of the star fields at the galactic center without Pluto to build catalogs of standard stars. These catalogs were applied to the Pluto images in order to make interpolated images and to cross check our results. We extracted the photometry of Pluto from differenced images where the background stars were subtracted, and we then applied the transformation equation to solve for Pluto’s standard magnitude. We will present the details of our data processing methodology, as well as the 2010 Pluto B, V, and B-V light curves in comparison to those from previous years. This work was supported by NASA Planetary Astronomy Grant NNX09AB43G.

  14. ULTRAVIOLET EXTINCTION AT HIGH GALACTIC LATITUDES

    SciTech Connect

    Peek, J. E. G.; Schiminovich, David

    2013-07-01

    In order to study the properties and effects of high Galactic latitude dust, we present an analysis of 373,303 galaxies selected from the Galaxy Evolution Explorer All-Sky Survey and Wide-field Infrared Explorer All-Sky Data Release. By examining the variation in aggregate ultraviolet colors and number density of these galaxies, we measure the extinction curve at high latitude. We additionally consider a population of spectroscopically selected galaxies from the Sloan Digital Sky Survey to measure extinction in the optical. We find that dust at high latitude is neither quantitatively nor qualitatively consistent with standard reddening laws. Extinction in the FUV and NUV is {approx}10% and {approx}35% higher than expected, with significant variation across the sky. We find that no single R{sub V} parameter fits both the optical and ultraviolet extinction at high latitude, and that while both show detectable variation across the sky, these variations are not related. We propose that the overall trends we detect likely stem from an increase in very small silicate grains in the interstellar medium.

  15. The Chandra Galactic Bulge Survey

    NASA Astrophysics Data System (ADS)

    Britt, C. T.; Hynes, R. I.; Jonker, P. G.; Maccarone, T.; Torres, M. A. P.; Steeghs, D.; Nelemans, G.; Johnson, C.; Greiss, S.

    2015-05-01

    The Chandra Galactic Bulge Survey (GBS) is a multi-wavelength survey of two 6×1 degree strips above and below the Galactic plane, including deep r' and i' imaging and time domain photometry from CTIO and shallow, wide-field X-ray imaging with Chandra. Targeting fields above |b|=1 avoids most of the copious extinction along the Galactic plane while maintaining high source density. This results in targets that are accessible to follow up in optical and NIR wavelengths. The X-ray observations are shallow to maximize the number of quiescent Low Mass X-ray Binaries (LMXBs) relative to Cataclysmic Variables (CVs). The goals of the GBS are to conduct a census of Low Mass X-ray Binaries in the Milky Way in order to constrain models of binary evolution, the common envelope phase in particular, and to expand the number of known LMXBs for optical follow up. Mass measurements in particular will help constrain the black hole (BH) mass distribution and the equation of state for neutron stars (NS). Constraining the BH mass distribution will constrain models of their formation in supernovae. The current population of Galactic BHs suffers from selection effects, which the GBS avoids by finding new objects while still in quiescence. We expect to find qLMXBs, magnetic CVs, RS CVn stars, and smaller numbers of other types of sources. After removing duplicates, there are 1640 unique X-ray sources in the 12 square degree survey area, which closely matches the predicted number of 1648. We are currently matching X-ray sources to counterparts in other wavelengths using new photometric and spectroscopic observations as well as in archival data where it exists, and searching for variability and periodicity in the counterparts in photometric data. So far, we have spectroscopically identified 27 interacting binaries including promising candidates for quiescent black holes.

  16. Highly blueshifted H I gas toward the Galactic center

    NASA Technical Reports Server (NTRS)

    Yusef-Zadeh, Farhad; Lasenby, Anthony; Marshall, Jennifer

    1993-01-01

    Gusten and Downes (1981) discovered the presence of -190 km/s absorbing H I gas toward the Galactic center. Using the VLA in its most compact hybrid configuration, we were able to image the distribution of this high-negative-velocity H I spectral feature with a spatial and spectral resolution of about 25 arcsec and 6.2 km/s, respectively. The blueshifted H I gas is dominated by systematic radial motion as great as -210 km/s and is localized to within several arcmin of the dynamical center of the Galaxy. We show a striking column of diffuse H I gas extending for several arcmin in the direction along the rotation axis of the molecular disk encircling the Galactic center. The H I optical depth distribution indicates that a total of about 3000 solar masses of neutral material, with -211 to -160 km/sec velocity, appears to be associated with this feature. This unusual kinematic feature appears to coexist with two systems of rotationally supported ionized (Sgr A West) and molecular (circumnuclear disk) gas.

  17. Constraints on galactic wind models

    NASA Astrophysics Data System (ADS)

    Meiksin, Avery

    2016-09-01

    Observational implications are derived for two standard models of supernovae-driven galactic winds: a freely expanding steady-state wind and a wind sourced by a self-similarly expanding superbubble including thermal heat conduction. It is shown that, for the steady-state wind, matching the measured correlation between the soft X-ray luminosity and star formation rate of starburst galaxies is equivalent to producing a scaled wind mass-loading factor relative to the star formation rate of 0.5-3, in agreement with the amount inferred from metal absorption line measurements. The match requires the asymptotic wind velocity v∞ to scale with the star formation rate dot{M}_{ast } (in M⊙ yr-1) approximately as v_∞ ≃ (700-1000) {{km s^{-1}}} {dot{M}_{ast }}^{1/6}. The implied mass injection rate is close to the amount naturally provided by thermal evaporation from the wall of a superbubble in a galactic disc, suggesting that thermal evaporation may be a major source of mass loading. The predicted mass-loading factors from thermal evaporation within the galactic disc alone, however, are somewhat smaller, 0.2-2, so that a further contribution from cloud ablation or evaporation within the wind may be required. Both models may account for the 1.4 GHz luminosity of unresolved radio sources within starburst galaxies for plausible parameters describing the distribution of relativistic electrons. Further observational tests to distinguish the models are suggested.

  18. Rotating drops of axion dark matter

    NASA Astrophysics Data System (ADS)

    Davidson, Sacha; Schwetz, Thomas

    2016-06-01

    We consider how QCD axions produced by the misalignment mechanism could form galactic dark matter halos. We recall that stationary, gravitationally stable axion field configurations have the size of an asteroid with masses of order 10-13M⊙ (because gradient pressure is insufficient to support a larger object). We call such field configurations "drops." We explore whether rotating drops could be larger, and find that their mass could increase by a factor ˜10 . This mass is comparable to the mass of miniclusters generated from misalignment axions in the scenario where the axion is born after inflation. We speculate that misalignment axions today are in the form of drops, contributing to dark matter like a distribution of asteroids (and not as a coherent oscillating background field). We consider some observational signatures of the drops, which seem consistent with a galactic halo made of axion dark matter.

  19. IGMtransmission: Transmission curve computation

    NASA Astrophysics Data System (ADS)

    Harrison, Christopher M.; Meiksin, Avery; Stock, David

    2015-04-01

    IGMtransmission is a Java graphical user interface that implements Monte Carlo simulations to compute the corrections to colors of high-redshift galaxies due to intergalactic attenuation based on current models of the Intergalactic Medium. The effects of absorption due to neutral hydrogen are considered, with particular attention to the stochastic effects of Lyman Limit Systems. Attenuation curves are produced, as well as colors for a wide range of filter responses and model galaxy spectra. Photometric filters are included for the Hubble Space Telescope, the Keck telescope, the Mt. Palomar 200-inch, the SUBARU telescope and UKIRT; alternative filter response curves and spectra may be readily uploaded.

  20. Adiabatic growth of a black hole in a rotating stellar system

    NASA Technical Reports Server (NTRS)

    Lee, Man Hoi; Goodman, Jeremy

    1989-01-01

    The consequences of slowly adding a massive black hole to the center of a rotating stellar system are considered. Although both the rotation velocity V and the velocity dispersion sigma increase when the black hole is added, the rotation velocity increases faster. The effect goes in the right direction but is too gradual to explain the V/sigma profiles recently observed in several galactic nuclei.

  1. Rotation Periods of Nearby, Mid-to-late M Dwarfs from the MEarth Project

    NASA Astrophysics Data System (ADS)

    Newton, Elisabeth R.; Irwin, Jonathan; Charbonneau, David; Berta-Thomspon, Zachary K.; West, Andrew A.

    2016-01-01

    Field stars provide important constraints for the late stages of stars' angular momentum evolution. We measured rotation periods ranging from 0.1 to 150 days for approximately 450 mid-to-late M dwarfs using photometry from the MEarth transiting planet survey. We use parallaxes, proper motions, and radial velocities to calculate galactic kinematics for these solar neighborhood M dwarfs. The velocity dispersions increase towards longer rotation periods, indicating that there is a relationship between rotation and age for these stars.

  2. New Developments in Galactic Archaeology

    NASA Astrophysics Data System (ADS)

    Freeman, Kenneth C.; HERMES/GALAH Team

    2014-01-01

    The goal of Galactic Archaeology is to unravel observationally the events that occurred during the assembly of the Milky Way. For example, how did the star formation rate and the mass spectrum of the star-forming clusters change with time since the Galaxy began to form, how much did minor mergers and accretion of satellite galaxies contribute to the stellar content of the Galactic components, and how did the chemical properties of the Galaxy evolve? The data for Galactic Archaeology include the phase space coordinates of stars (position and velocity) and the chemical space coordinates (abundances of up to about 30 chemical elements). Although we know that the distribution of individual elements contains important information about the star formation history and chemical evolution of the Galaxy, the available data for large samples of stars has so far restricted the use of chemical space data mainly to the overall metallicity and the alpha-element enhancement. We are entering an era of large high-resolution spectroscopic surveys in which the abundances of many elements from all of the major nucleosynthesis processes will be measured. It will be possible to use chemical tagging techniques to identify the debris of individual dispersed star forming aggregates. In combination with astrometry from the Gaia mission, it will be possible to derive ages for this recovered star formation debris, and build up the star formation history of the regions of the Milky Way accessible to these large surveys. The Galactic thick disk is of particular interest. Because almost all disk galaxies appear to have an old thick disk, thick disks are an important but as yet poorly understood part of the formation process for disk galaxies. Some theories of thick disk formation associate the thick disk with the large star-bursting complexes seen in proto-disk galaxies at high redshift. If the Galactic thick disk was built in this way, from a relatively small number of large aggregates, it will

  3. Shepherding Tidal Debris with the Galactic Bar: The Ophiuchus Stream

    NASA Astrophysics Data System (ADS)

    Hattori, Kohei; Erkal, Denis; Sanders, Jason L.

    2016-04-01

    The dynamics of stellar streams in rotating barred potentials is explained for the first time. Naturally, neighbouring stream stars reach pericentre at slightly different times. In the presence of a rotating bar, these neighbouring stream stars experience different bar orientations during pericentric passage and hence each star receives a different torque from the bar. These differing torques reshape the angular momentum and energy distribution of stars in the stream, which in turn changes the growth rate of the stream. For a progenitor orbiting in the same sense as the bar's rotation and satisfying a resonance condition, the resultant stream can be substantially shorter or longer than expected, depending on whether the pericentric passages of the progenitor occur along the bar's minor or major axis respectively. We present a full discussion of this phenomenon focusing mainly on streams confined to the Galactic plane. In stark contrast with the evolution in static potentials, which give rise to streams that grow steadily in time, rotating barred potentials can produce dynamically old, short streams. This challenges the traditional viewpoint that the inner halo necessarily consists of well phase-mixed material whilst the tidally-disrupted structures in the outer halo are more spatially coherent. We argue that this mechanism may play an important role in explaining the mysteriously short Ophiuchus stream that was recently discovered near the bulge region of the Milky Way.

  4. Shepherding tidal debris with the Galactic bar: the Ophiuchus stream

    NASA Astrophysics Data System (ADS)

    Hattori, Kohei; Erkal, Denis; Sanders, Jason L.

    2016-07-01

    The dynamics of stellar streams in rotating barred potentials is explained for the first time. Naturally, neighbouring stream stars reach pericentre at slightly different times. In the presence of a rotating bar, these neighbouring stream stars experience different bar orientations during pericentric passage and hence each star receives a different torque from the bar. These differing torques reshape the angular momentum and energy distribution of stars in the stream, which in turn changes the growth rate of the stream. For a progenitor orbiting in the same sense as the bar's rotation and satisfying a resonance condition, the resultant stream can be substantially shorter or longer than expected, depending on whether the pericentric passages of the progenitor occur along the bar's minor or major axis, respectively. We present a full discussion of this phenomenon focusing mainly on streams confined to the Galactic plane. In stark contrast with the evolution in static potentials, which give rise to streams that grow steadily in time, rotating barred potentials can produce dynamically old, short streams. This challenges the traditional viewpoint that the inner halo necessarily consists of well phase-mixed material whilst the tidally disrupted structures in the outer halo are more spatially coherent. We argue that this mechanism may play an important role in explaining the mysteriously short Ophiuchus stream that was recently discovered near the bulge region of the Milky Way.

  5. Graphing Polar Curves

    ERIC Educational Resources Information Center

    Lawes, Jonathan F.

    2013-01-01

    Graphing polar curves typically involves a combination of three traditional techniques, all of which can be time-consuming and tedious. However, an alternative method--graphing the polar function on a rectangular plane--simplifies graphing, increases student understanding of the polar coordinate system, and reinforces graphing techniques learned…

  6. The Bacterial Growth Curve.

    ERIC Educational Resources Information Center

    Paulton, Richard J. L.

    1991-01-01

    A procedure that allows students to view an entire bacterial growth curve during a two- to three-hour student laboratory period is described. Observations of the lag phase, logarithmic phase, maximum stationary phase, and phase of decline are possible. A nonpathogenic, marine bacterium is used in the investigation. (KR)

  7. Textbook Factor Demand Curves.

    ERIC Educational Resources Information Center

    Davis, Joe C.

    1994-01-01

    Maintains that teachers and textbook graphics follow the same basic pattern in illustrating changes in demand curves when product prices increase. Asserts that the use of computer graphics will enable teachers to be more precise in their graphic presentation of price elasticity. (CFR)

  8. SAS-2 galactic gamma ray results, 1

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.; Lamb, R. C.; Oegelman, H.; Oezel, M. E.; Tuemer, T.

    1976-01-01

    Continuing analysis of the data from the SAS-2 high energy gamma-ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitude 310 and 45 deg, corresponding to a region within 7kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315 deg, 330 deg, 345 deg, 0 deg, and 35 deg. These peaks appear to be correlated with such galactic features and components as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic ray concentrations, and photon fields.

  9. The physics of galactic winds driven by active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Faucher-Giguère, Claude-André; Quataert, Eliot

    2012-09-01

    Active galactic nuclei (AGN) drive fast winds in the interstellar medium of their host galaxies. It is commonly assumed that the high ambient densities and intense radiation fields in galactic nuclei imply short cooling times, thus making the outflows momentum conserving. We show that cooling of high-velocity shocked winds in AGN is in fact inefficient in a wide range of circumstances, including conditions relevant to ultraluminous infrared galaxies (ULIRGs), resulting in energy-conserving outflows. We further show that fast energy-conserving outflows can tolerate a large amount of mixing with cooler gas before radiative losses become important. For winds with initial velocity vin ≳ 10 000 km s-1, as observed in ultraviolet and X-ray absorption, the shocked wind develops a two-temperature structure. While most of the thermal pressure support is provided by the protons, the cooling processes operate directly only on the electrons. This significantly slows down inverse Compton cooling, while free-free cooling is negligible. Slower winds with vin ˜ 1000 km s-1, such as may be driven by radiation pressure on dust, can also experience energy-conserving phases but under more restrictive conditions. During the energy-conserving phase, the momentum flux of an outflow is boosted by a factor ˜vin/2vs by work done by the hot post-shock gas, where vs is the velocity of the swept-up material. Energy-conserving outflows driven by fast AGN winds (vin ˜ 0.1c) may therefore explain the momentum fluxes Ṗ≫LAGN/c of galaxy-scale outflows recently measured in luminous quasars and ULIRGs. Shocked wind bubbles expanding normal to galactic discs may also explain the large-scale bipolar structures observed in some systems, including around the Galactic Centre, and can produce significant radio, X-ray and γ-ray emission. The analytic solutions presented here will inform implementations of AGN feedback in numerical simulations, which typically do not include all the important

  10. Detection of silicon in the Galactic center

    NASA Technical Reports Server (NTRS)

    Hertier, T.; Houck, J. R.; Graf, P.; Gull, G. E.

    1986-01-01

    The detection of the forbidden Si II 34.815 micron line in the Galactic center region is reported. It is demonstrated that, in the case of the Galactic center, the emission arises mainly from the photodissociation region and not the shocked molecular component seen via H2, CO, and OH lines. It is also shown that significant Si II emission is not expected from the ionized gas even though the Galactic center is a rather low excitation H II region.

  11. Galactic Building Blocks Seen Swarming Around Andromeda

    NASA Astrophysics Data System (ADS)

    2004-02-01

    University of Virginia. The Milky Way and Andromeda were formed many billions of years ago in a cosmic neighborhood brimming with galactic raw materials -- among which hydrogen, helium, and cold dark matter were primary constituents. By now, most of this raw material has probably been gobbled up by the two galaxies, but astronomers suspect that some primitive clouds are still floating free. Previous studies have revealed a number of clouds of neutral atomic hydrogen that are near the Milky Way but not part of its disk. These were initially referred to as high-velocity clouds (HVCs) when they were first discovered because they appeared to move at velocities difficult to reconcile with Galactic rotation. Scientists were uncertain if HVCs comprised building blocks of the Milky Way that had so far escaped capture, or if they traced gas accelerated to unexpected velocities by energetic processes (multiple supernovae) within the Milky Way. The discovery of similar clouds bound to the Andromeda Galaxy strengthens the case that at least some of these HVCs are indeed galactic building blocks. Astronomers are able to use radio telescopes to detect the characteristic 21-centimeter radiation emitted naturally by neutral atomic hydrogen. The great difficulty in analyzing these low-mass galactic building blocks has been that their natural radio emission is extremely faint. Even those nearest to us, clouds orbiting our Galaxy, are hard to study because of serious distance uncertainties. "We know the Milky Way HVCs are relatively nearby, but precisely how close is maddeningly tough to determine," said Thilker. Past attempts to find missing satellites around external galaxies at well-known distances have been unsuccessful because of the need for a very sensitive instrument capable of producing high-fidelity images, even in the vicinity of a bright source such as the Andromeda Galaxy. One might consider this task similar to visually distinguishing a candle placed adjacent to a spotlight. The

  12. Highly ionized gas in the Galactic halo

    NASA Technical Reports Server (NTRS)

    Shull, J. Michael; Slavin, Jonathan D.

    1994-01-01

    We reexamine the values of electron density n(sub e) and gas pressure P/k in the interstellar medium (ISM) of the Galactic halo, as inferred from C IV emission and absorption lines and using current C IV atomic data. In a homogeneous model with 4.7 less than or equal to log T less than or equal to 5.3, the data are consistent with 0.01 less than or equal to n(sub e) less than or equal to 0.02/cu cm and 2200 less than or equal to P/k less than or equal to 3700/cu cm K, a factor of 2-3 higher than advocated by Martin & Bowyer (1990) and comparable to the thermal pressure in the disk. If some of the C IV absorption arises from nonemitting, photoionized gas, then the inferred density and pressure will increase accordingly. The volume filling factor for homogeneous models ranges from 0.5% to 5%. Because of the constraints arising from filling factor and radiated power, most of the C IV must arise from gas near the peak of the cooling curve, at log t less than or equal to 5.6. We relate both emission-line and absorption-line observations to recent models in which turbulent mixing layers and isobarically cooling supernova remnants (SNRs) provide significant amounts of halo gas at approximately 10(exp 5.3) K and process 20-40 solar mass/yr with a power of approximately 10(exp 41) ergs/sec. Since the observed C IV and N V absorption scale heights have been reported to differ, at 4.9 kpc and 1.6 kpc, respectively, we examine inhomogeneous models with different exponential scale heights of T, P, and SN energy input. The ISM may change its character with distance above the Galactic plane, as superbubbles and mixing layers dominate over isolated SNRs as the source of the C IV. For appropiate scale heights, the midplane pressure is twice the homogeneous values quoted above. The O IV lambda 1034 diffuse emission line, which can be used as a temperature diagnostic of the hot gas, is predicted to be comparable in strength to that of C IV lambda 1549 (approximately 6000 photons

  13. Structure Formation inside Triaxial Dark Matter Halos: Galactic Disks, Bulges, and Bars

    NASA Astrophysics Data System (ADS)

    Heller, Clayton H.; Shlosman, Isaac; Athanassoula, E.

    2007-12-01

    We investigate formation and evolution of galactic disks immersed in assembling live DM halos. Models have been evolved from cosmological initial conditions and represent the collapse of an isolated density perturbation. The baryons include gas participating in star formation (SF) and stars with the energy feedback onto the ISM. We find that (1) the triaxial halo figure tumbling is insignificant and the angular momentum (J) is channeled into the internal circulation, while the baryonic collapse is stopped by the centrifugal barrier; (2) density response of the (disk) baryons is out of phase with DM, thus washing out the inner halo ellipticity; (3) the total J is neatly conserved, even in models accounting for stellar feedback; (4) the specific J for DM is nearly constant, while that for baryons is decreasing; (5) early stage of disk formation resembles the cat's cradle-a small amorphous disk fueled via radial string patterns-followed by growing oval disk whose shape varies with its orientation to the halo major axis; (6) the disk gas layer thins when the SF rate drops below ~5 Msolar yr-1 (7) about half of the baryons remain outside the disk SF region or in the halo as a hot gas; (8) rotation curves appear to be flat and account for the observed disk/halo contributions; (9) a range of bulge-dominated to bulgeless disks was obtained, depending on the stellar feedback parameter, ɛSF: smaller ɛSF leads to a larger and earlier bulge; lower density threshold for SF leads to a smaller, thicker disk; gas gravitational softening mimics a number of intrinsic processes within the ISM; (10) models are characterized by an extensive bar-forming activity; (11) nested bars form in response to the gas inflow along the primary bars, as shown by Heller, Shlosman, and Athanassoula.

  14. Anterior Overgrowth in Primary Curves, Compensatory Curves and Junctional Segments in Adolescent Idiopathic Scoliosis

    PubMed Central

    van Stralen, Marijn; Chu, Winnie C. W.; Lam, Tsz-Ping; Ng, Bobby K. W.; Vincken, Koen L.; Cheng, Jack C. Y.; Castelein, René M.

    2016-01-01

    Introduction Although much attention has been given to the global three-dimensional aspect of adolescent idiopathic scoliosis (AIS), the accurate three-dimensional morphology of the primary and compensatory curves, as well as the intervening junctional segments, in the scoliotic spine has not been described before. Methods A unique series of 77 AIS patients with high-resolution CT scans of the spine, acquired for surgical planning purposes, were included and compared to 22 healthy controls. Non-idiopathic curves were excluded. Endplate segmentation and local longitudinal axis in endplate plane enabled semi-automatic geometric analysis of the complete three-dimensional morphology of the spine, taking inter-vertebral rotation, intra-vertebral torsion and coronal and sagittal tilt into account. Intraclass correlation coefficients for interobserver reliability were 0.98–1.00. Coronal deviation, axial rotation and the exact length discrepancies in the reconstructed sagittal plane, as defined per vertebra and disc, were analyzed for each primary and compensatory curve as well as for the junctional segments in-between. Results The anterior-posterior difference of spinal length, based on “true” anterior and posterior points on endplates, was +3.8% for thoracic and +9.4% for (thoraco)lumbar curves, while the junctional segments were almost straight. This differed significantly from control group thoracic kyphosis (-4.1%; P<0.001) and lumbar lordosis (+7.8%; P<0.001). For all primary as well as compensatory curves, we observed linear correlations between the coronal Cobb angle, axial rotation and the anterior-posterior length difference (r≥0.729 for thoracic curves; r≥0.485 for (thoraco)lumbar curves). Conclusions Excess anterior length of the spine in AIS has been described as a generalized growth disturbance, causing relative anterior spinal overgrowth. This study is the first to demonstrate that this anterior overgrowth is not a generalized phenomenon. It is

  15. Rotator Cuff Tears

    MedlinePlus

    ... doctors because of a rotator cuff problem. A torn rotator cuff will weaken your shoulder. This means ... or more of the rotator cuff tendons is torn, the tendon no longer fully attaches to the ...

  16. Rotator Cuff Injuries

    MedlinePlus

    ... others can be very painful. Treatment for a torn rotator cuff depends on age, health, how severe ... is, and how long you've had the torn rotator cuff. Treatment for torn rotator cuff includes: ...

  17. Rotator cuff problems

    MedlinePlus

    ... days, such as in painting and carpentry Poor posture over many years Aging Rotator cuff tears TEARS ... also help prevent rotator cuff problems. Practice good posture to keep your rotator cuff tendons and muscles ...

  18. Factorization with genus 2 curves

    NASA Astrophysics Data System (ADS)

    Cosset, Romain

    2010-04-01

    The elliptic curve method (ECM) is one of the best factorization methods available. It is possible to use hyperelliptic curves instead of elliptic curves but it is in theory slower. We use special hyperelliptic curves and Kummer surfaces to reduce the complexity of the algorithm. Our implementation GMP-HECM is faster than GMP-ECM for factoring large numbers.

  19. Color variations of asteroids during rotation

    NASA Astrophysics Data System (ADS)

    Schober, H. J.; Schroll, A.

    Published rotational-color-variation data on 49 asteroids are compiled and listed in a table. Light-curve amplitudes, polarization measurements, and additional color indices are included whenever available. Ten objects are found to exhibit evidence of surface spots: 3 Juno, 4 Vesta, 6 Hebe, 25 Phocaea, 39 Laetitia, 42 Doris, 71 Niobe, 201 Penelope, 349 Dembowska, and 944 Hidalgo.

  20. THE GALACTIC CENTER: NOT AN ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    An, Deokkeun; Ramirez, Solange V.; Sellgren, Kris

    2013-06-01

    We present 10 {mu}m-35 {mu}m Spitzer spectra of the interstellar medium in the Central Molecular Zone (CMZ), the central 210 pc Multiplication-Sign 60 pc of the Galactic center (GC). We present maps of the CMZ in ionic and H{sub 2} emission, covering a more extensive area than earlier spectroscopic surveys in this region. The radial velocities and intensities of ionic lines and H{sub 2} suggest that most of the H{sub 2} 0-0 S(0) emission comes from gas along the line-of-sight, as found by previous work. We compare diagnostic line ratios measured in the Spitzer Infrared Nearby Galaxies Survey to our data. Previous work shows that forbidden line ratios can distinguish star-forming galaxies from low-ionization nuclear emission-line regions (LINERs) and active galactic nuclei (AGNs). Our GC line ratios agree with star-forming galaxies and not with LINERs or AGNs.

  1. Black holes in galactic centers

    SciTech Connect

    Rees, M.J. )

    1990-11-01

    For more than 25 years astronomers have known that some galaxies also have a bright, compact central nucleus whose emission does not come from normal stars. The most extreme instances of these so-called active galactic nuclei are quasars, objects no larger than the solar system whose total radiation exceeds that of 100 billion stars. Quasars seem to represent a particularly agitated stage in the development of some galaxies. Astronomers generally agree that gravity powers active galactic nuclei. The best candidate for the central engine of quasars is a black hole--a collapsed body whose gravity is so great that nothing, including light, can escape from it. The discovery of black holes in galactic centers, exciting in its own right, could affect current ideas about the evolution of the universe. Quasars appeared when the universe was less than one billion years old, indicting that some galaxies had already developed dense central regions. The early appearance of quasars rules out many cosmological models, which predict that the formation of galaxies should require billions of years, and even raises problems for the reigning cold dark matter model. Recent measurements of the cosmic background radiation intensify the puzzle. Most theorists think that galaxies formed from density variations in the newborn universe. Yet measurements of the background radiation indicate that any variations were so slight that it is difficult to understand how they could have produced the structures seen today. Apart from its cosmological significance, the detection of massive black holes also could elucidate predictions of Einstein's theory of general relativity.

  2. Searching for Faraday rotation in cosmic microwave background polarization

    NASA Astrophysics Data System (ADS)

    Ruiz-Granados, B.; Battaner, E.; Florido, E.

    2016-08-01

    We use the Wilkinson Microwave Anisotropy Probe (WMAP) 9th-year foreground reduced data at 33, 41 and 61 GHz to derive a Faraday rotation at map and at angular power spectrum levels taking into account their observational errors. A processing mask provided by WMAP is used to avoid contamination from the disc of our Galaxy and local spurs. We have found a Faraday rotation component at both, map and power spectrum levels. The lack of correlation of the Faraday rotation with Galactic Faraday rotation, synchrotron and dust polarization from our Galaxy or with cosmic microwave background anisotropies or lensing suggests that it could be originated at reionization (ℓ ≲ 12). Even if the detected Faraday rotation signal is weak, the present study could contribute to establish magnetic fields strengths of B0 ˜ 10-8 G at reionization.

  3. Galactic Sodium from AGB Stars

    NASA Astrophysics Data System (ADS)

    Izzard, R. G.; Gibson, B. K.; Stancliffe, R. J.

    2007-11-01

    Galactic chemical evolution (GCE) models which include sodium from type II supernovae (SNe) alone underestimate the abundance of sodium in the interstellar medium by a factor of 2 to 3 over about 3 ridex in metallicity and predict a flat behavior in the evolution of riNafe at super-solar metallicities. Conversely, recent observations of stars with rifeh ˜ +0.4 suggest that riNafe increases at high metallicity. We have combined stellar evolution models of asymptotic giant branch (AGB) and Wolf-Rayet (WR) stars with the latest SN yields in an attempt to resolve these problems dots and have created many more.

  4. Atlas of fatigue curves

    SciTech Connect

    Boyer, H.E.

    1986-01-01

    This Atlas was developed to serve engineers who are looking for fatigue data on a particular metal or alloy. Having these curves compiled in a single book will also facilitate the computerization of the involved data. It is pointed out that plans are under way to make the data in this book available in ASCII files for analysis by computer programs. S-N curves which typify effects of major variables are considered along with low-carbon steels, medium-carbon steels, alloy steels, HSLA steels, high-strength alloy steels, heat-resisting steels, stainless steels, maraging steels, cast irons, and heat-resisting alloys. Attention is also given to aluminum alloys, copper alloys, magnesium alloys, molybdenum, tin alloys, titanium and titanium alloys, zirconium, steel castings, closed-die forgings, powder metallurgy parts, composites, effects of surface treatments, and test results for component parts.

  5. Mouse Curve Biometrics

    SciTech Connect

    Schulz, Douglas A.

    2007-10-08

    A biometric system suitable for validating user identity using only mouse movements and no specialized equipment is presented. Mouse curves (mouse movements with little or no pause between them) are individually classied and used to develop classication histograms, which are representative of an individual's typical mouse use. These classication histograms can then be compared to validate identity. This classication approach is suitable for providing continuous identity validation during an entire user session.

  6. The Ultimate Spitzer Phase Curve Survey

    NASA Astrophysics Data System (ADS)

    Stevenson, Kevin; Bean, Jacob; Deming, Drake; Desert, Jean-Michel; Feng, Y. Katherina; Fortney, Jonathan; Kataria, Tiffany; Kempton, Eliza; Lewis, Nikole; Line, Michael; Morley, Caroline; Rauscher, Emily; Showman, Adam

    2016-08-01

    Exoplanet phase curves are sure to be one of the main enduring legacies of Spitzer. They provide a wealth of information about exoplanet atmospheres, including longitudinal constraints on atmospheric composition, thermal structure, and energy transport, that will continue to open new doors of scientific inquiry and propel future investigations for years to come. The measured heat redistribution efficiency (or ability to transport energy from a planet's highly-irradiated dayside to its eternally-dark nightside) shows considerable variation between exoplanets. Theoretical models predict a correlation between heat redistribution efficiency and planet temperature; however, the latest results are inconsistent with current predictions. Instead, a new potential trend is emerging, one that connects heat redistribution efficiency with planet rotation rate. We will test this hypothesis by performing Spitzer phase curve observations of seven exoplanets with physical properties that span the parameter space. We have identified high-contrast targets with short orbital periods around bright host stars to ensure the observations reveal robust phase curve results. Spitzer is uniquely suited for this program because we can achieve our primary goals using broadband photometry. Part of the phase curve legacy will be to combine our archived Spitzer data with transmission and dayside emission spectra from HST and JWST. Adding energy transport and cloud coverage constraints to the measured dayside abundances and thermal profiles will yield a fundamental understanding of these exoplanets' atmospheres that can be leveraged into new avenues of investigation.

  7. The Stephan Curve revisited.

    PubMed

    Bowen, William H

    2013-01-01

    The Stephan Curve has played a dominant role in caries research over the past several decades. What is so remarkable about the Stephan Curve is the plethora of interactions it illustrates and yet acid production remains the dominant focus. Using sophisticated technology, it is possible to measure pH changes in plaque; however, these observations may carry a false sense of accuracy. Recent observations have shown that there may be multiple pH values within the plaque matrix, thus emphasizing the importance of the milieu within which acid is formed. Although acid production is indeed the immediate proximate cause of tooth dissolution, the influence of alkali production within plaque has received relative scant attention. Excessive reliance on Stephan Curve leads to describing foods as "safe" if they do not lower the pH below the so-called "critical pH" at which point it is postulated enamel dissolves. Acid production is just one of many biological processes that occur within plaque when exposed to sugar. Exploration of methods to enhance alkali production could produce rich research dividends. PMID:23224410

  8. Lower extremity kinematics of athletics curve sprinting.

    PubMed

    Alt, Tobias; Heinrich, Kai; Funken, Johannes; Potthast, Wolfgang

    2015-01-01

    Curve running requires the generation of centripetal force altering the movement pattern in comparison to the straight path run. The question arises which kinematic modulations emerge while bend sprinting at high velocities. It has been suggested that during curve sprints the legs fulfil different functions. A three-dimensional motion analysis (16 high-speed cameras) was conducted to compare the segmental kinematics of the lower extremity during the stance phases of linear and curve sprints (radius: 36.5 m) of six sprinters of national competitive level. Peak joint angles substantially differed in the frontal and transversal plane whereas sagittal plane kinematics remained unchanged. During the prolonged left stance phase (left: 107.5 ms, right: 95.7 ms, straight: 104.4 ms) the maximum values of ankle eversion (left: 12.7°, right: 2.6°, straight: 6.6°), hip adduction (left: 13.8°, right: 5.5°, straight: 8.8°) and hip external rotation (left: 21.6°, right: 12.9°, straight: 16.7°) were significantly higher. The inside leg seemed to stabilise the movement in the frontal plane (eversion-adduction strategy) whereas the outside leg provided and controlled the motion in the horizontal plane (rotation strategy). These results extend the principal understanding of the effects of curve sprinting on lower extremity kinematics. This helps to increase the understanding of nonlinear human bipedal locomotion, which in turn might lead to improvements in athletic performance and injury prevention. PMID:25495196

  9. DOUBLE-PEAKED NARROW-LINE ACTIVE GALACTIC NUCLEI. II. THE CASE OF EQUAL PEAKS

    SciTech Connect

    Smith, K. L.; Shields, G. A.; Salviander, S.; Stevens, A. C.; Rosario, D. J. E-mail: shields@astro.as.utexas.edu E-mail: acs0196@mail.utexas.edu

    2012-06-10

    Active galactic nuclei (AGNs) with double-peaked narrow lines (DPAGNs) may be caused by kiloparsec-scale binary AGNs, bipolar outflows, or rotating gaseous disks. We examine the class of DPAGNs in which the two narrow-line components have closely similar intensity as being especially likely to involve disks or jets. Two spectroscopic indicators support this likelihood. For DPAGNs from Smith et al., the 'equal-peaked' objects (EPAGNs) have [Ne V]/[O III]ratios lower than for a control sample of non-double-peaked AGNs. This is unexpected for a pair of normal AGNs in a galactic merger, but may be consistent with [O III] emission from a rotating ring with relatively little gas at small radii. Also, [O III]/H{beta} ratios of the redshifted and blueshifted systems in the EPAGN are more similar to each other than in a control sample, suggestive of a single ionizing source and inconsistent with the binary interpretation.

  10. Smarandache curves according to Sabban frame of fixed pole curve belonging to the Bertrand curves pair

    NASA Astrophysics Data System (ADS)

    Şenyurt, Süleyman; Altun, Yasin; Cevahir, Ceyda

    2016-04-01

    In this paper, we investigate the Smarandache curves according to Sabban frame of fixed pole curve which drawn by the unit Darboux vector of the Bertrand partner curve. Some results have been obtained. These results were expressed as the depends Bertrand curve.

  11. Perception of spin and the interception of curved football trajectories.

    PubMed

    Casanova, Remy; Borg, Olivier; Bootsma, Reinoud J

    2015-01-01

    Using plain white and chequered footballs, we evaluated observers' sensitivity to rotation direction and the effects of ball texture on interceptive behaviour. Experiment 1 demonstrated that the maximal distance at which observers (n = 8) could perceive the direction of ball rotation decreased when rotation frequency increased from 5 to 11 Hz. Detection threshold distances were nevertheless always larger for the chequered (decreasing from 47 to 28 m) than for the white (decreasing from 15 to 11 m) ball. In Experiment 2, participants (n = 7) moved laterally along a goal line to intercept the two balls launched with or without ±4.3 Hz sidespin from a 30-m distance. The chequered ball gave rise to shorter movement initiation times when trajectories curved outward (±6 m arrival positions) or did not curve (±2 m arrival positions). Inward curving trajectories, arriving at the same ±2 m distances from the participants as the non-curving trajectories, evoked initial movements in the wrong direction for both ball types, but the amplitude and duration of these reversal movements were attenuated for the chequered ball. We conclude that the early detection of rotation permitted by the chequered ball allowed modulation of interception behaviour without changing its qualitative characteristics. PMID:25686376

  12. A NIR Atlas of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Rodríguez-Ardila, A.; Riffel, R.; Pastoriza, M. G.

    2006-06-01

    We present the most comprehensive atlas of near-infrared (NIR) mid-resolution (R=1000) spectra of active galactic nuclei (AGN) made to date in the interval 0.8-2.4 μm. The aim of this work is to provide a homogeneous database suitable to study the nuclear NIR properties of AGN in a region poorly studied spectroscopically but that keeps useful constraints to model the AGN physics. The sample is composed of 49 objects, 39 of them with z <0.05, distributed between 7 quasars, 25 Seyfert 1 (classical and narrow-line Seyfert 1) and 17 Seyfert 2 galaxies. A few LINERS and Starburst galaxies are also included for comparative purposes. The spectra are dominated by strong emission lines of H I, He I, He II, [S III] and conspicuous forbidden lines of low and high ionization species, including coronal lines. In addition, rotational/vibrational lines of H_2 are detected in most objects. Overall, the continuum of quasars and Seyfert 1s are rather similar, being essentially flat or slightly steep in the H and K bands. In J, the shape of the continuum is different from object to object, varying from that displaying a steep rise in flux towards shorter wavelengths, from 1.1 μm bluewards, to that remaining flat. In Seyfert 2s, the continuum smoothly decreases in flux with wavelength, from 1.2 μm redwards. Bluewards, the continuum flux steeply rises in some sources while in others it decreases towards shorter wavelengths, suggesting reddening. Independently of the AGN type, stellar absorption features of CO, Si I and Mg I are present in the H and K bands. They are found to be particularly strong in Seyfert 2s. Line identification and remarks on the most important characteristics observed in the sample are given.

  13. Kinetic temperatures in Galactic Center molecular clouds

    NASA Astrophysics Data System (ADS)

    Huettemeister, S.; Wilson, T. L.; Bania, T. M.; Martin-Pintado, J.

    1993-12-01

    Measurements of six metastable (J = K) inversion transitions of ammonia for 36 clouds in the galactic center region are presented. Most of the clouds are not related to Sgr A or Sgr B2. In order to minimize the effect of weather, either the (J,K) = (1,1), (2,2) and (4,4) or the (4,4) and (5,5) inversion lines of para-NH3 were measured simultaneously. A common calibration was obtained by forcing the integrated intensities of the (4,4) inversion line spectra from different periods to agree. The (3,3) and (6,6) lines of orthor-NH3 were also measured simultaneously. A determination of the rotational temperatures, Trot, obtained from these lines shows that there must be at least two kinetic temperature regimes in these clouds. In a few cases, small maps of the clouds were made; two of these show that the distribution of the (1,1) and (2,2) inversion lines are similar, but differ markedly from that of the (4,4) inversion line. An analysis of the data shows that the warmer temperature is approximately 200 K, the cooler is approximately 25 K. The warmer gas contains about approximately 25% of the total column density of NH3. The heating processes which give rise to the high kinetic temperatures in these clouds are not certain: These may include and enhanced flux of low energy cosmic rays, cloud-cloud collisions, or ion-slip (ambipolar diffusion).

  14. Introduction to Galactic Chemical Evolution

    NASA Astrophysics Data System (ADS)

    Matteucci, Francesca

    2016-04-01

    In this lecture I will introduce the concept of galactic chemical evolution, namely the study of how and where the chemical elements formed and how they were distributed in the stars and gas in galaxies. The main ingredients to build models of galactic chemical evolution will be described. They include: initial conditions, star formation history, stellar nucleosynthesis and gas flows in and out of galaxies. Then some simple analytical models and their solutions will be discussed together with the main criticisms associated to them. The yield per stellar generation will be defined and the hypothesis of instantaneous recycling approximation will be critically discussed. Detailed numerical models of chemical evolution of galaxies of different morphological type, able to follow the time evolution of the abundances of single elements, will be discussed and their predictions will be compared to observational data. The comparisons will include stellar abundances as well as interstellar medium ones, measured in galaxies. I will show how, from these comparisons, one can derive important constraints on stellar nucleosynthesis and galaxy formation mechanisms. Most of the concepts described in this lecture can be found in the monograph by Matteucci (2012).

  15. Chemical complexity in galactic nuclei

    NASA Astrophysics Data System (ADS)

    Martin-Pintado, Jesus

    2007-12-01

    In recent years our knowledge of the chemical complexity in the nuclei of galaxies has dramatically changed. Recent observations of the nucleus of the Milky Way, of the starburst galaxy NGC253 and of the ultraluminous infrared galaxy (ULIRG) Arp220 have shown large abundance of complex organic molecules believed to be formed on grains. The Galactic center appears to be the largest repository of complex organic molecule like aldehydes and alcohols in the galaxy. We also measure large abundance of methanol in starburst galaxies and in ULIRGs suggesting that complex organic molecules are also efficiently produced in the central region of galaxies with strong star formation activity. From the systematic observational studies of molecular abundance in regions dominated by different heating processes like shocks, UV radiation, X-rays and cosmic rays in the center of the Milky Way, we are opening the possibility of using chemistry as a diagnostic tool to study the highly obscured regions of galactic centers. The templates found in the nucleus of the Milky Way will be used to establish the main mechanisms driving the heating and the chemistry of the molecular clouds in galaxies with different type of activity. The role of grain chemistry in the chemical complexity observed in the center of galaxies will be also briefly discussed.

  16. The Chandra Galactic Bulge Survey

    NASA Astrophysics Data System (ADS)

    Hynes, Robert I.; Jonker, P. G.; Bassa, C. G.; Nelemans, G.; Steeghs, D.; Torres, M. A. P.; Maccarone, T. J.; Greiss, S.; Clem, J.; Dieball, A.; Mikles, V. J.; Britt, C. T.; Gossen, L.; Collazzi, A. C.; Wijnands, R.; In't Zand, J. J. M.; Mendez, M.; Rea, N.; Kuulkers, E.; Ratti, E. M.; van Haaften, L. M.; Heinke, C.; Ozel, F.; Groot, P. J.; Verbunt, F.

    2012-01-01

    The Chandra Galactic Bulge Survey (GBS) is a shallow but wide survey of two approximately 6x1 degree strips of the Galactic Bulge about a degree above and below the plane. The survey by design targets regions where extinction and crowding are manageable and optical counterparts are accessible to detailed follow-up. Our strategy is based on going deep enough to detect quiescent low-mass X-ray binaries (LMXBs), but no deeper in order to avoid an excess of cataclysmic variables (CVs), while covering a large area to maximize the numbers of recovered objects. The primary goals of the GBS are to test predictions of binary evolutionary models through number counts and period distributions of detected sources, and to greatly expand the sample of LMXBs suitable for detailed optical follow-up including mass determination. We have identified 1234 X-ray sources most with optical counterparts, and expect these to be divided evenly between quiescent LMXBs, magnetic CVs, and R CVn stars, with smaller numbers of other source types. We are actively pursuing multiwavelength follow-up including searches for optical, infrared, and ultraviolet counterparts, measurement of variability, and optical spectroscopy. I will summarize the goals of the project and highlight some of the results obtained so far. This work is supported by the National Science Foundation under Grant No. AST-0908789.

  17. Galactic evolution of 7Li

    NASA Astrophysics Data System (ADS)

    Matteucci, Francesca

    2010-04-01

    Lithium represents a key element in cosmology, as it is one of the few nuclei synthesized during the Big Bang. The primordial abundance of 7Li allows us to impose constraints on the primordial nucleosynthesis and on the baryon density of the universe. However, 7Li is not only produced during the Big Bang but also during galactic evolution: measures of stellar Li in our Galaxy suggest an almost constant Li abundance (the so-called Spite plateau) at low metallicities and a subsequent increase in the disk stars, leading to a Li abundance in Population I stars higher by a factor of ten than in Population II stars. This means that there must exist several possible stellar sources of 7Li: asymptotic giant branch stars, supernovae, novae, red giant stars. 7Li is also partly produced in spallation processes while 6Li is entirely produced by such processes. All of these sources have been included in galactic chemical evolution models and constraints have been derived on the primordial 7Li and its evolution, as well on stellar models. I will review these models and their results and what we have learned about 7Li evolution. Some still open problems, such as the disagreement between the primordial 7Li abundance as derived by WMAP and as measured in Population II stars, and the uncertainties about the main sources of stellar 7Li will be discussed.

  18. The Bolocam Galactic Plane Survey

    NASA Technical Reports Server (NTRS)

    Glenn, Jason; Aguirre, James; Bally, John; Battersby, Cara; Bradley, Eric Todd; Cyganowski, Claudia; Dowell, Darren; Drosback, Meredith; Dunham, Miranda K.; Evans, Neal J., II; Ginsburg, Adam; Harvey, Paul; Rosolowsky, Erik; Schlingman, Wayne; Shirley, Yancy L.; Stringfellow, Guy S.; Walawender, Josh; Williams, Jonathan

    2009-01-01

    The Bolocam Galactic Plane Survey (BGPS) is a 1.1 millimeter continuum survey of the northern Galactic Plane made with Bolocam and the Caltech Submillimeter Observatory. The coverage totals 170 square degrees, comprised of a contiguous range from -10.5 deg is less than or equal to 90.5 deg, 0.5 deg is less than or equal to b is less than or equal to 0.5 deg, with extended coverage in b in selected regions, and four targeted regions in the outer Galaxy, including: IC1396, toward the Perseus arm at l is approximately 111 deg, W3/4/5, and Gem OB1. Depths of the maps range from 30 to 60 mJy beam (sup 1). Approximately 8,400 sources were detected and the maps and source catalog have been made publicly available. Millimeter-wave thermal dust emission reveals dense regions within molecular clouds, thus the BGPS serves as a database for studies of the dense interstellar medium and star formation within the Milky Way.

  19. Special Features of Galactic Dynamics

    NASA Astrophysics Data System (ADS)

    Efthymiopoulos, Christos; Voglis, Nikos; Kalapotharakos, Constantinos

    This is an introductory article to some basic notions and currently open problems of galactic dynamics. The focus is on topics mostly relevant to the so-called `new methods' of celestial mechanics or Hamiltonian dynamics, as applied to the ellipsoidal components of galaxies, i.e., to the elliptical galaxies and to the dark halos and bulges of disk galaxies. Traditional topics such as Jeans theorem, the role of a `third integral' of motion, Nekhoroshev theory, violent relaxation, and the statistical mechanics of collisionless stellar systems are first discussed. The emphasis is on modern extrapolations of these old topics. Recent results from orbital and global dynamical studies of galaxies are then shortly reviewed. The role of various families of orbits in supporting self-consistency, as well as the role of chaos in galaxies, are stressed. A description is then given of the main numerical techniques of integration of the N-body problem in the framework of stellar dynamics and of the results obtained via N-Body experiments. A final topic is the secular evolution and self-organization of galactic systems.

  20. Star formation in Galactic flows

    NASA Astrophysics Data System (ADS)

    Smilgys, Romas; Bonnell, Ian A.

    2016-06-01

    We investigate the triggering of star formation in clouds that form in Galactic scale flows as the interstellar medium passes through spiral shocks. We use the Lagrangian nature of smoothed particle hydrodynamics simulations to trace how the star-forming gas is gathered into self-gravitating cores that collapse to form stars. Large-scale flows that arise due to Galactic dynamics create shocks of the order of 30 km s-1 that compress the gas and form dense clouds (n > several × 102 cm-3) in which self-gravity becomes relevant. These large-scale flows are necessary for creating the dense physical conditions for gravitational collapse and star formation. Local gravitational collapse requires densities in excess of n > 103 cm-3 which occur on size scales of ≈1 pc for low-mass star-forming regions (M < 100 M⊙), and up to sizes approaching 10 pc for higher mass regions (M > 103 M⊙). Star formation in the 250 pc region lasts throughout the 5 Myr time-scale of the simulation with a star formation rate of ≈10-1 M⊙ yr-1 kpc-2. In the absence of feedback, the efficiency of the star formation per free-fall time varies from our assumed 100 per cent at our sink accretion radius to values of <10-3 at low densities.

  1. How do the extinction curves in galaxies evolve?

    NASA Astrophysics Data System (ADS)

    Asano, R.; Takeuchi, T.; Hirashita, H.; Nozawa, T.

    We investigate the evolution of extinction curves in galaxies based on our evolution model of grain size distribution. In this model, we considered various processes: dust formation by SNe II and AGB stars, dust destruction by SN shocks in the interstellar medium (ISM), metal accretion onto the surface of grains, shattering and coagulation. We find that the extinction curve is flat in the earliest stage of galaxy evolution because the grain size distribution is dominated by large (a & 0.1 µ m, where a is the grain radius) grains produced by stars. As the galaxy is enriched with dust, shattering becomes effective to produce a large abundance of small grains (a . 0.01 µ m). Then, the total surface area of grains per grain mass becomes large, and grain growth becomes effective at small grain radii, forming a bump at a ˜ 10-3 -10-2 µ m on the grain size distribution. Consequently, the extinction curve at ultraviolet (UV) wavelengths becomes steep, and a bump at 1/λ ˜ 4.5 µ m-1 (λ : wavelength) on the extinction curve becomes prominent. The galactic age when the extinction curve has the bump is roughly estimated as t ˜ (τSF /Gyr)1/2 Gyr, where τSF is the star formation timescale. Once coagulation becomes effective, the extinction curves become flatter, but the UV extinction remains overproduced when compared with the Milky Way extinction curve. This discrepancy can be resolved by introducing a stronger contribution of coagulation. Thus, an interplay between shattering and coagulation could be important to reproduce the Milky Way extinction curve. We conclude that the extinction curves of galaxies change drastically through the galaxy lifetime because the main dust processes that contribute to the grain size distribution change.

  2. ROTATION AND MULTIPLE STELLAR POPULATION IN GLOBULAR CLUSTERS

    SciTech Connect

    Bekki, Kenji

    2010-11-20

    We investigate structure and kinematics of the second generation of stars (SG) formed from gaseous ejecta of the first generation of stars (FG) in forming globular clusters (GCs). We consider that SG can be formed from gaseous ejecta from asymptotic giant branch stars of FG with the initial total mass of 10{sup 6} M {sub sun}-10{sup 8} M {sub sun} to explain the present masses of the Galactic GCs. Our three-dimensional hydrodynamical simulations with star formation show that SG formed in the central regions of FG can have a significant amount of rotation (V/{sigma}{approx} 0.8-2.5). The rotational amplitude of SG can depend strongly on the initial kinematics of FG. We thus propose that some GCs composed of FG and SG had a significant amount of rotation when they were formed. We also suggest that although later long-term ({approx}10 Gyr) dynamical evolution of stars can smooth out the initial structural and kinematical differences between FG and SG to a large extent, initial flattened structures and rotational kinematics of SG can be imprinted on shapes and internal rotation of the present GCs. We discuss these results in terms of internal rotation observed in the Galactic GCs.

  3. Correlations between Kinematics and Metallicity in the Galactic Bulge: A Review

    NASA Astrophysics Data System (ADS)

    Babusiaux, Carine

    2016-06-01

    Recent large-scale surveys of galactic bulge stars allowed to build a detailed map of the bulge kinematics. The bulge exhibits cylindrical rotation consistent with a disky origin which evolved through bar-driven secular evolution. However, correlations between metallicity and kinematics complicate this picture. In particular a metal-poor component with distinct kinematic signatures has been detected. Its origin, density profile and link with the other Milky Way stellar populations are currently still poorly constrained.

  4. Galactic Variable Sky with EGRET and GLAST

    SciTech Connect

    Digel, S.W.; /SLAC

    2006-11-28

    The characteristics of the largely-unidentified Galactic sources of gamma rays that were detected by EGRET are reviewed. Proposed source populations that may have the correct spatial, spectral, luminosity, and variability properties to be the origins of the EGRET sources are also presented. Finally, the prospects for studying Galactic gamma-ray sources with the GLAST LAT are reviewed.

  5. A CATALOG OF GALACTIC INFRARED CARBON STARS

    SciTech Connect

    Chen, P. S.

    2012-02-15

    We collected almost all of the Galactic infrared carbon stars (IRCSs) from literature published up to the present to organize a catalog of 974 Galactic IRCSs in this paper. Some of their photometric properties in the near-, mid-, and far-infrared are discussed.

  6. Chemical and dynamical evolution of galactic discs

    NASA Technical Reports Server (NTRS)

    Clarke, Catherine J.

    1989-01-01

    The relative roles of star formation and viscously-induced radial flows in galactic disks are discussed. It is shown that the present-day distributions of stars, gas, and metals in galactic spirals need not reflect initial conditions but may instead indicate a cooperation between star forming and viscous processes over the disk lifetime.

  7. Formation of a Giant Galactic Gaseous Halo: Metal-Absorption Lines and High-Velocity Clouds

    NASA Astrophysics Data System (ADS)

    Li, Fan

    1992-04-01

    have been detected. Coordinates, apparent sizes, and colors were given for the first time (Kontizas et al. 1988). These clusters were found to have small masses and sizes (10^3 solar mass < M < 10^4 solar mass, 14 pc < r_t < 37 pc). (4) Small star clusters with similar dynamical parameters were also found situated at distances larger than 4.5 from the rotational center of the LMC. Their total dynamical masses are found to give a very good extrapolation to the LMC rotational curve. These lead us to the assumption of an extended disk in the LMC. Therefore the small intermediate-age (1.4 x 10^9 yr) clusters of the LMC occupy the extended disk of the LMC where the old stellar population is located. (5) The age of the stellar population for four star clusters was estimated from their HR diagrams and found to be 1.4 X 10^8-2 X 10^9 yr, confirming that the age range of the LMC small clusters is narrower than that of our own Galaxy since we did not find very young small clusters. (6)We have studied dynamically for the first time LMC clusters with masses smaller than 10^4 solar mass and found that the mass spectrum of the small LMC star clusters coincides partly with the mass spectrum of the galactic open clusters, but extends to larger values. (7) Finally we have compared the frequency distribution of the derived dynamical parameters of all studied clusters with those of the open clusters of our Galaxy. We found that faint and old globular LMC clusters form one disk system, which is similar to the open-cluster system of our Galaxy. The LMC clusters' disruptive mechanism must be weak and does not seem to affect the small- or intermediate-mass star clusters. Further progress in understanding the formation and early evolution of the LMC clusters requires a detailed study of the conditions prevailing in the inner regions of the molecular clouds from which they are probably formed. (SECTION: Dissertation Abstracts)

  8. Rotational properties of the Maria asteroid family

    SciTech Connect

    Kim, M.-J.; Byun, Y.-I.; Choi, Y.-J.; Moon, H.-K.; Hinse, T. C.; Park, J.-H.; Brosch, N.; Kaplan, M.; Kaynar, S.; Uysal, Ö.; Eker, Z.; Güzel, E.; Behrend, R.; Yoon, J.-N.; Mottola, S.; Hellmich, S.

    2014-03-01

    The Maria family is regarded as an old-type (∼3 ± 1 Gyr) asteroid family that has experienced substantial collisional and dynamical evolution in the main belt. It is located near the 3:1 Jupiter mean-motion resonance area that supplies near-Earth asteroids to the inner solar system. We carried out observations of Maria family asteroids during 134 nights from 2008 July to 2013 May and derived synodic rotational periods for 51 objects, including newly obtained periods of 34 asteroids. We found that there is a significant excess of fast and slow rotators in the observed rotation rate distribution. The one-sample Kolmogorov-Smirnov test confirms that the spin rate distribution is not consistent with a Maxwellian at a 92% confidence level. From correlations among rotational periods, amplitudes of light curves, and sizes, we conclude that the rotational properties of Maria family asteroids have been changed considerably by non-gravitational forces such as the YORP effect. Using a light-curve inversion method, we successfully determined the pole orientations for 13 Maria members and found an excess of prograde versus retrograde spins with a ratio (N{sub p} /N{sub r} ) of 3. This implies that the retrograde rotators could have been ejected by the 3:1 resonance into the inner solar system since the formation of the Maria family. We estimate that approximately 37-75 Maria family asteroids larger than 1 km have entered near-Earth space every 100 Myr.

  9. A Versatile Family of Galactic Wind Models

    NASA Astrophysics Data System (ADS)

    Bustard, Chad; Zweibel, Ellen G.; D'Onghia, Elena

    2016-03-01

    We present a versatile family of model galactic outflows including non-uniform mass and energy source distributions, a gravitational potential from an extended mass source, and radiative losses. The model easily produces steady-state wind solutions for a range of mass-loading factors, energy-loading factors, galaxy mass, and galaxy radius. We find that, with radiative losses included, highly mass-loaded winds must be driven at high central temperatures, whereas low mass-loaded winds can be driven at low temperatures just above the peak of the cooling curve, meaning radiative losses can drastically affect the wind solution even for low mass-loading factors. By including radiative losses, we are able to show that subsonic flows can be ignored as a possible mechanism for expelling mass and energy from a galaxy compared to the more efficient transonic solutions. Specifically, the transonic solutions with low mass loading and high energy loading are the most efficient. Our model also produces low-temperature, high-velocity winds that could explain the prevalence of low-temperature material in observed outflows. Finally, we show that our model, unlike the well-known Chevalier & Clegg model, can reproduce the observed linear relationship between wind X-ray luminosity and star formation rate (SFR) over a large range of SFR from 1-1000 M⊙ yr-1 assuming the wind mass-loading factor is higher for low-mass, and hence, low-SFR galaxies. We also constrain the allowed mass-loading factors that can fit the observed X-ray luminosity versus SFR trend, further suggesting an inverse relationship between mass loading and SFR as explored in advanced numerical simulations.

  10. An Axisymmetric, Hydrodynamical Model for the Torus Wind in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Dorodnitsyn, A.; Kallman, T.; Proga, D.

    2008-01-01

    We report on time-dependent axisymmetric simulations of an X-ray-excited flow from a parsec-scale, rotating, cold torus around an active galactic nucleus. Our simulations account for radiative heating and cooling and radiation pressure force. The simulations follow the development of a broad biconical outflow induced mainly by X-ray heating. We compute synthetic spectra predicted by our simulations. The wind characteristics and the spectra support the hypothesis that a rotationally supported torus can serve as the source of a wind which is responsible for the warm absorber gas observed in the X-ray spectra of many Seyfert galaxies.

  11. Anisotropy and corotation of galactic cosmic rays.

    PubMed

    Amenomori, M; Ayabe, S; Bi, X J; Chen, D; Cui, S W; Danzengluobu; Ding, L K; Ding, X H; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gao, X Y; Geng, Q X; Guo, H W; He, H H; He, M; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Huang, Q; Jia, H Y; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren; Le, G M; Li, A F; Li, J Y; Lou, Y-Q; Lu, H; Lu, S L; Meng, X R; Mizutani, K; Mu, J; Munakata, K; Nagai, A; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ouchi, T; Ozawa, S; Ren, J R; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Sasaki, T; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, B; Wang, H; Wang, X; Wang, Y G; Wu, H R; Xue, L; Yamamoto, Y; Yan, C T; Yang, X C; Yasue, S; Ye, Z H; Yu, G C; Yuan, A F; Yuda, T; Zhang, H M; Zhang, J L; Zhang, N J; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhaxisangzhu; Zhou, X X

    2006-10-20

    The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments. PMID:17053141

  12. Stellar Rotation Effects in Polarimetric Microlensing

    NASA Astrophysics Data System (ADS)

    Sajadian, Sedighe

    2016-07-01

    It is well known that the polarization signal in microlensing events of hot stars is larger than that of main-sequence stars. Most hot stars rotate rapidly around their stellar axes. The stellar rotation creates ellipticity and gravity-darkening effects that break the spherical symmetry of the source's shape and the circular symmetry of the source's surface brightness respectively. Hence, it causes a net polarization signal for the source star. This polarization signal should be considered in polarimetric microlensing of fast rotating stars. For moderately rotating stars, lensing can magnify or even characterize small polarization signals due to the stellar rotation through polarimetric observations. The gravity-darkening effect due to a rotating source star creates asymmetric perturbations in polarimetric and photometric microlensing curves whose maximum occurs when the lens trajectory crosses the projected position of the rotation pole on the sky plane. The stellar ellipticity creates a time shift (i) in the position of the second peak of the polarimetric curves in transit microlensing events and (ii) in the peak position of the polarimetric curves with respect to the photometric peak position in bypass microlensing events. By measuring this time shift via polarimetric observations of microlensing events, we can evaluate the ellipticity of the projected source surface on the sky plane. Given the characterizations of the FOcal Reducer and low dispersion Spectrograph (FORS2) polarimeter at the Very Large Telescope, the probability of observing this time shift is very small. The more accurate polarimeters of the next generation may well measure these time shifts and evaluate the ellipticity of microlensing source stars.

  13. Centrifugally driven MHD-winds in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Camenzind, M.

    1986-02-01

    When the prime mover in quasars is a supermassive magnetized and rapidly rotating object, the centrifugal instability can drive strong MHD-winds away from the equatorial region and extract angular momentum and rotational energy from the central object. The author shows that the necessary magnetic fields are produced, when this central object has been formed from the central part of a galactic disc. The position of the light cylinder for these objects requires a relativistic description for the corresponding MHD-winds. The author discusses the relevant equations for any stationary and axisymmetric spacetime and derives explicitly the position of the Alfvén point in the flow. He finds that centrifugally driven winds from supermassive objects carry a Poynting flux comparable with the kinetic energy flux. In addition, the magnetic field structure in the open wind zone requires the existence of a global current topology, which might explain the necessary magnetic collimation for escaping jet material. As a result, centrifugally driven winds from rapidly rotating supermassive objects carry the energy necessary to power the non-thermal emission of BLR AGNs and the material required to fuel the broad emission line clouds and the thermal jets.

  14. Abundances and rotational temperatures of the C2 interstellar molecule towards six reddened early-type stars

    NASA Astrophysics Data System (ADS)

    Kaźmierczak, M.; Schmidt, M. R.; Bondar, A.; Krełowski, J.

    2010-03-01

    Using high-resolution (~85000) and high signal-to-noise ratio (~200) optical spectra acquired with the European Southern Observatory Ultraviolet and Visual Echelle Spectrograph, we have determined the interstellar column densities of C2 for six Galactic lines of sight with E(B- V) ranging from 0.33 to 1.03. For our purposes, we identified and measured absorption lines belonging to the (1, 0), (2, 0) and (3, 0) Phillips bands A1Πu-X1Σ+g. We report on the identification of a few lines of the C2 (4, 0) Phillips system towards HD 147889. The curve-of-growth method is applied to the equivalent widths to determine the column densities of the individual rotational levels of C2. The excitation temperature is extracted from the rotational diagrams. The physical parameters of the intervening molecular clouds (e.g. gas kinetic temperatures and densities of collision partners) were estimated by comparison with the theoretical model of excitation of C2. E-mail: kazmierczak@astri.uni.torun.pl (MK); schmidt@ncac.torun.pl (MRS); arctur@inet.ua (AB); jacek@astri.uni.torun.pl (JK) Based on observations made with the European Southern Observatory telescope at the Paranal Observatory under programme IDs 266.D-5655(A), 67.C-0281(A), 71.C-0513(C) and 67.D-0439(A).

  15. Warps and Streams --- Pushing and lifting material out of the midplane from galactic and circumstellar disks

    NASA Astrophysics Data System (ADS)

    Quillen, Alice C.

    2016-05-01

    Sub-structures such as warps and streams in the vertical distribution of gas and dust can manifest as spiral shaped structures, twists in the velocity field, vertical streaming motions, X-shapes, and quasiperiodic dips in light curves. I will review and contrast physical mechanisms for lifting material out of the mid-plane in galactic and circumstellar disks including instabilities, resonant mechanisms and tidal excitations.

  16. The UKIDSS Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Lucas, P. W.; Hoare, M. G.; Longmore, A.; Schröder, A. C.; Davis, C. J.; Adamson, A.; Bandyopadhyay, R. M.; de Grijs, R.; Smith, M.; Gosling, A.; Mitchison, S.; Gáspár, A.; Coe, M.; Tamura, M.; Parker, Q.; Irwin, M.; Hambly, N.; Bryant, J.; Collins, R. S.; Cross, N.; Evans, D. W.; Gonzalez-Solares, E.; Hodgkin, S.; Lewis, J.; Read, M.; Riello, M.; Sutorius, E. T. W.; Lawrence, A.; Drew, J. E.; Dye, S.; Thompson, M. A.

    2008-11-01

    The UKIDSS Galactic Plane Survey (GPS) is one of the five near-infrared Public Legacy Surveys that are being undertaken by the UKIDSS consortium, using the Wide Field Camera on the United Kingdom Infrared Telescope. It is surveying 1868 deg2 of the northern and equatorial Galactic plane at Galactic latitudes -5° < b < 5° in the J, H and K filters and a ~200-deg2 area of the Taurus-Auriga-Perseus molecular cloud complex in these three filters and the 2.12 μm (1-0) H2 filter. It will provide data on ~2 × 109 sources. Here we describe the properties of the data set and provide a user's guide for its exploitation. We also present brief Demonstration Science results from DR2 and from the Science Verification programme. These results illustrate how GPS data will frequently be combined with data taken in other wavebands to produce scientific results. The Demonstration Science comprises six studies. (1) A GPS-Spitzer-GLIMPSE cross-match for the star formation region G28.983-0.603 to identify YSOs. This increases the number of YSOs identified by a factor of 10 compared to GLIMPSE alone. (2) A wide-field study of the M17 nebula, in which an extinction map of the field is presented and the effect of source confusion on luminosity functions in different subregions is noted. (3) H2 emission in the ρ Ophiuchi dark cloud. All the molecular jets are traced back to a single active clump containing only a few protostars, which suggests that the duration of strong jet activity and associated rapid accretion in low-mass protostars is brief. (4) X-ray sources in the nuclear bulge. The GPS data distinguishes local main-sequence counterparts with soft X-ray spectra from nuclear bulge giant counterparts with hard X-ray spectra. (5) External galaxies in the zone of avoidance. The galaxies are clearly distinguished from stars in fields at longitudes l > 90°. (6) IPHAS-GPS optical-infrared spectrophotometric typing. The (i' - J) versus (J - H) diagram is used to distinguish A-F type

  17. An alternative classical force of gravitation in order to explain the velocity curve of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Guiot, E.

    2015-03-01

    The purpose of this work is to investigate an alternative to modified Newtonian dynamics (MOND), in order to explain the rotation curve of galaxies without dark matter hypothesis, and with respect for classical physics. Our hypothesis is that the force of gravitation, in the case of large distances and under certain conditions, possesses a tangential component. We show that the force of gravitation we obtain is compatible with observational data, such as "flat" curve of rotation and the conic trajectories of the stars.

  18. New Horizons approach photometry of Pluto and Charon: light curves and Solar phase curves

    NASA Astrophysics Data System (ADS)

    Zangari, A. M.; Buie, M. W.; Buratti, B. J.; Verbiscer, A.; Howett, C.; Weaver, H. A., Jr.; Olkin, C.; Ennico Smith, K.; Young, L. A.; Stern, S. A.

    2015-12-01

    While the most captivating images of Pluto and Charon were shot by NASA's New Horizons probe on July 14, 2015, the spacecraft also imaged Pluto with its LOng Range Reconnaissance Imager ("LORRI") during its Annual Checkouts and Approach Phases, with campaigns in July 2013, July 2014, January 2015, March 2015, April 2015, May 2015 and June 2015. All but the first campaign provided full coverage of Pluto's 6.4 day rotation. Even though many of these images were taken when surface features on Pluto and Charon were unresolved, these data provide a unique opportunity to study Pluto over a timescale of several months. Earth-based data from an entire apparition must be combined to create a single light curve, as Pluto is never otherwise continuously available for observing due to daylight, weather and scheduling. From the spacecraft, Pluto's sub-observer latitude remained constant to within 0.05 degrees of 43.15 degrees, comparable to a week's worth of change as seen from Earth near opposition. During the July 2013 to June 2015 period, Pluto's solar phase curve increased from 11 degrees to 15 degrees, a small range, but large compared to Earth's 2 degree limit. The slope of the solar phase curve hints at properties such as surface roughness. Using PSF photometry that takes into account the ever-increasing sizes of Pluto and Charon as seen from New Horizons, as well as surface features discovered at closest approach, we present rotational light curves and solar phase curves of Pluto and Charon. We will connect these observations to previous measurements of the system from Earth.

  19. ON RINGS AND STREAMS IN THE GALACTIC ANTI-CENTER

    SciTech Connect

    Li Jing; Deng Licai; Xu Yan; Newberg, Heidi Jo; Carlin, Jeffrey L.; Newby, Matthew; Willett, Benjamin A.; Luo Zhiquan E-mail: heidi@rpi.edu

    2012-10-01

    We confirm that there are at least three separate low-latitude overdensities of blue F turnoff stars near the Milky Way anti-center: the Monoceros Ring, the Anti-Center Stream (ACS), and the Eastern Banded Structure (EBS). There might also be a small number of normal thick disk stars at the same location. The ACS is a tilted component that extends to higher Galactic latitude at lower Galactic longitude, 10 kpc from the Sun toward the anti-center. It has a sharp cutoff on the high-latitude side. Distance, velocity, and proper motion measurements are consistent with previous orbit fits. The mean metallicity is [Fe/H] =-0.96 {+-} 0.03, which is lower than the thick disk and Monoceros Ring. The Monoceros Ring is a higher density substructure that is present at 15 Degree-Sign < b < 22 Degree-Sign at all longitudes probed in this survey. The structure likely continues toward lower latitudes. The distances are consistent with a constant distance from the Galactic center of 17.6 kpc. The mean line-of-sight velocity of the structure is consistent with a thick disk rotation. However, the velocity dispersion of these stars is {approx}15 km s{sup -1} and the metallicity is [Fe/H] =-0.80 {+-} 0.01. Both of these quantities are lower than the canonical thick disk. We suggest that this ring structure is likely different from the thick disk, though its association with the disk cannot be definitively ruled out. The EBS is detected primarily photometrically, near (l, b) = (225 Degree-Sign , 30 Degree-Sign ), at a distance of 10.9 kpc from the Sun.

  20. The Galactic Bulge Radial Velocity/Abundance Assay

    NASA Astrophysics Data System (ADS)

    Rich, R. M.

    2012-08-01

    The Bulge Radial Velocity Assay (BRAVA) measured radial velocities for ˜ 9500 late-type giants in the Galactic bulge, predominantly from -10° < l < +10° and -2° < b < -10°. The project has discovered that the bulge exhibits cylindrical rotation characteristic of bars, and two studies of dynamics (Shen et al. 2010; Wang et al. 2012 MNRAS sub.) find that bar models- either N-body formed from an instability in a preexisting disk, or a self-consistent model- can account for the observed kinematics. Studies of the Plaut field at (l,b) = 0°, -8° show that alpha enhancement is found in bulge giants even 1 kpc from the nucleus. New infrared studies extending to within 0.25° = 35 pc of the Galactic Center find no iron or alpha gradient from Baade's Window (l,b) = 0.9°, -3.9° to our innermost field, in contrast to the marked gradient observed in the outer bulge. We consider the case of the remarkable globular cluster Terzan 5, which has a strongly bimodal iron and rm [α/Fe] within its members, and we consider evidence pro and con that the bulge was assembled from dissolved clusters. The Subaru telescope has the potential to contribute to study of the Galactic bulge, especially using the Hyper Superime-Cam and planned spectroscopic modes, as well as the high resolution spectrograph. The planned Jasmine satellite series may deliver a comprehensive survey of distances and proper motions of bulge stars, and insight into the origin and importance of the X-shaped bulge.

  1. Galactic cycles and their relationship to life on earth

    SciTech Connect

    Olson, A.P.

    1984-05-01

    This paper draws attention to episodic events in the geologic time scale of the evolution of life on earth, and discusses potentially cyclic behavior relative to galactic structure. The question is a simple one: Do galactic processes affect the solar system. It is known that the sun is moving at about 220 +- 15 km/sec at a distance of about 8.5 +- 0.5 kpc from the galactic center. This motion, if circular and unperturbed, implies an orbital period of 237 +- 21 My for the solar system around the galaxy. The Milky Way also evidences structure typically interpreted as spiral arms, in the distribution of gas clouds in its central plane. The relative motion of the spiral arms, known as the pattern speed, is about 2/3 that of the sun. Consequently the solar system gains upon and passes through all the structure in its orbital plane once in three rotations or approx.700 My. If this structure is persistent over times longer than 700 My, it is clear that the interaction (if any) can be called cyclic. Furthermore, if there is any sub-structure or inner pattern to the 700 My cycle, it may show up as higher harmonics. Age estimates for the Milky Way are 12-15 By, or approx.17 to 22 structure cycles of 0.70 By. It seems not unreasonable to expect some persistence of a pattern over a few structure cycles. It must be noted that the pattern speed is quite uncertain. Perhaps geophysical evidence can be used to improve on the nominally 700 My structure cycle which is assumed in this paper. 16 references, 8 figures.

  2. KS variables in rotating reference frame. Application to cometary dynamics

    NASA Astrophysics Data System (ADS)

    Langner, K.; Breiter, S.

    2015-06-01

    The problem of Keplerian motion in the uniformly rotating reference frame has been solved in terms of the Kustaanheimo-Stiefel (KS) variables using canonical formalism. No recourse to the Cartesian variables or orbital elements has been required. The form of solution is well suited for the application as a part of symplectic integrator. The results show that the motion is actually the composition of four independent harmonic oscillations and of the rotation in two specific coordinate planes and their conjugate momenta planes. As an example of application, we use the KS symplectic integrator to study the motion of comet C/1997 J2 (Meunier-Dupuoy) under the action of Galactic tides. The comet is found to follow an orbit in commensurability with the Sun motion around the Galactic centre, but the perturbations are not qualified as a resonance.

  3. Galactic Center Fly-in

    NASA Astrophysics Data System (ADS)

    Hanson, A.; Fu, C.-W.; Li, Y.; Frisch, P. C.

    2006-06-01

    Beginning with the familiar constellations of the night sky, we present a multispectral zoom into the core of the Milky Way Galaxy. After traveling over seven orders of magnitude in spatial scale, we discover the violent phenomena occurring within one light year of the Black Hole at the Galactic Core. This animated zoom includes data with wavelengths from radio to X-ray, and is based entirely on data or models that have been aligned at all spatial scales in order to provide a single continuous visual trip into the Center of the Milky Way Galaxy. The visualization challenge has been to align and choreograph data acquired over a wide range of wavelength and spatial scales, and obtain a new scientific as well as educational perspective of the dense core of our Galaxy.

  4. Star formation across galactic environments

    NASA Astrophysics Data System (ADS)

    Young, Jason

    I present here parallel investigations of star formation in typical and extreme galaxies. The typical galaxies are selected to be free of active galactic nuclei (AGN), while the extreme galaxies host quasars (the most luminous class of AGN). These two environments are each insightful in their own way; quasars are among the most violent objects in the universe, literally reshaping their host galaxies, while my sample of AGN-free star-forming galaxies ranges from systems larger than the Milky Way to small galaxies which are forming stars at unsustainably high rates. The current paradigm of galaxy formation and evolution suggests that extreme circumstances are key stepping stones in the assembly of galaxies like our Milky Way. To test this paradigm and fully explore its ramifications, this dual approach is needed. My sample of AGN-free galaxies is drawn from the KPNO International Spectroscopic Survey. This Halpha-selected, volume-limited survey was designed to detect star-forming galaxies without a bias toward continuum luminosity. This type of selection ensures that this sample is not biased toward galaxies that are large or nearby. My work studies the KISS galaxies in the mid- and far-infrared using photometry from the IRAC and MIPS instruments aboard the Spitzer Space Telescope. These infrared bands are particularly interesting for star formation studies because the ultraviolet light from young stars is reprocessed into thermal emission in the far-infrared (24mum MIPS) by dust and into vibrational transitions features in the mid-infrared (8.0mum IRAC) by polycyclic aromatic hydrocarbons (PAHs). The work I present here examines the efficiencies of PAH and thermal dust emission as tracers of star-formation rates over a wide range of galactic stellar masses. I find that the efficiency of PAH as a star-formation tracer varies with galactic stellar mass, while thermal dust has a highly variable efficiency that does not systematically depend on galactic stellar mass

  5. The galactic model of GRBs

    SciTech Connect

    Colgate, S.A.; Li, H.

    1997-09-01

    The galactic model of gamma ray bursts (GRBs) is based upon the observed production of soft gamma ray repeaters (SGRs) in the galaxy and the consequences of a reasonable model to explain them. In this view GRBs are the long term result of the burn-out conditions of the SGRs in this and in other galaxies. A delay of {approximately} 30 million years before GRBs are being actively produced can be understood as the time required for the ejected matter during the SGR phase to cool, condense, and form planetesimals that are eventually captured by the central neutron star. The amount of disk matter and the interaction between each GRB and the disk determine the rate of burst production and turn-off time of GRBs. The x-ray afterglow as well as optical emission is derived from x-ray fluorescence and ionization of previously ablated matter.

  6. Carbon and Oxygen Galactic Gradients

    NASA Astrophysics Data System (ADS)

    Carigi, L.; Peimbert, M.; Esteban, C.; García-Rojas, J.

    2006-06-01

    A chemical evolution model of the Galaxy has been computed to reproduce the O/H gradients from Galactic HII regions. This model solves the C enrichment problem because it fits the C/H and C/O gradients and the C and O histories of the solar vicinity. The model is based on C yields dependent on metallicity (Z) owing to stellar winds. The C yields of massive stars (MS) increase with Z and those of low and intermediate mass stars (LIMS) decrease with Z. An important result is that the fraction of carbon in the interstellar medium (ISM) due to MS and LIMS is strongly dependent on Z of the ISM, therefore, that fraction depends on time and on the Galactocentric distance. At present and in the solar vicinity about half of the C in the interstellar medium has been produced by MS and half by LIMS.

  7. Theory of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shields, G. A.

    1986-01-01

    The involvement of accretion disks around supermassive black holes in the theory of active galactic nuclei (AGN) is discussed. The physics of thin and thick accretion disks is discussed and the partition between thermal and nonthermal energy production in supermassive disks is seen as uncertain. The thermal limit cycle may operate in supermassive disks (Shields, 1985), with accumulation of gas in the disk for periods of 10 to the 4th to 10 to the 7th years, punctuated by briefer outbursts during which the mass is rapidly transferred to smaller radii. An extended X-ray source in AGN is consistent with observations (Tennant and Mushotsky, 1983), and a large wind mass loss rate exceeding the central accretion rate means that only a fraction of the mass entering the disk will reach the central object; the rest being lost to the wind. Controversy in the relationship between the broad lines and the disk is also discussed.

  8. Detecting galactic binaries with LISA

    NASA Astrophysics Data System (ADS)

    Cornish, Neil J.; Porter, Edward K.

    2005-09-01

    One of the main sources of gravitational waves for the LISA space-borne interferometer is galactic binary systems. The waveforms for these sources are represented by eight parameters of which four are intrinsic and four are extrinsic to the system. Geometrically, these signals exist in an 8D parameter space. By calculating the metric tensor on this space, we calculate the number of templates needed to search for such sources. We show in this study that below a particular monochromatic frequency of f0 ~ 1.6 × 10-3 Hz we can ignore one of the intrinsic parameters and search over a 7D space. Beyond this frequency, we have a change in dimensionality of the parameter space from 7 to 8 dimensions. This sudden change in dimensionality results in a change in the scaling of template number as a function of the monochromatic frequency from ~f1.250 to ~f5.880.

  9. Solar modulation of galactic antiprotons

    NASA Technical Reports Server (NTRS)

    Perko, J. S.

    1987-01-01

    Galactic antiproton data of current interest lie in an energy regime heavily influenced by solar modulation. Correcting for it needs to be done more carefully than it has been in the past. The well-known force-field analytic approximation of the spherically-symmetric, steady-state, cosmic-ray transport equation is applied in order to account for modulation down to at least 100 MeV. A sample solution which applies to the currently available antiproton data set (1979-80), and can be used to accurately modulate any possible interstellar antiproton spectrum, is given. The solution is easily adapted for comparison to future measurements. It also shows that boosting the low-energy (less than 600 MeV) side of the interstellar antiproton spectrum will not affect the low-energy spectrum at 1 AU, due to strong adiabatic deceleration during that time.

  10. The Characteristic Curves of Water

    NASA Astrophysics Data System (ADS)

    Neumaier, Arnold; Deiters, Ulrich K.

    2016-09-01

    In 1960, E. H. Brown defined a set of characteristic curves (also known as ideal curves) of pure fluids, along which some thermodynamic properties match those of an ideal gas. These curves are used for testing the extrapolation behaviour of equations of state. This work is revisited, and an elegant representation of the first-order characteristic curves as level curves of a master function is proposed. It is shown that Brown's postulate—that these curves are unique and dome-shaped in a double-logarithmic p, T representation—may fail for fluids exhibiting a density anomaly. A careful study of the Amagat curve (Joule inversion curve) generated from the IAPWS-95 reference equation of state for water reveals the existence of an additional branch.

  11. Microlensing by the galactic bar

    NASA Technical Reports Server (NTRS)

    Zhao, Hongsheng; Spergel, David N.; Rich, R. Michael

    1995-01-01

    We compute the optical depth and duration distribution of microlensing events towrd Baade's window in a model composed of a Galactic disk and a bar. The bar model is a self-consistent dynamical model built out of individual orbits that has been populated to be consistent with the COBE maps of the Galaxy and kinematic observations of the Galactic bulge. We find that most of the lenses are in the bulge with a line-of-sight distance 6.25 kpc (adopting R(sub 0) = 8 kpc). The microlensing optical depth of a 2 x 10(exp 10) solar mass bar plus a truncated disk is (2.2 +/- 0.45) x 10(exp -6), consistent with the large optical depth (3.2 +/- 1.2) x 10(exp -6) found by Udalski et al. (1994). This model optical depth is enhanced over the predictions of axisymmetric models by Kiraga & Paczynski (1994) by slightly more than a factor of 2, since the bar is elongated along the line of sight. The large Einstein radius and small transverse velocity dispersion also predict a longer event duration in the self-consistent bar model than in the Kiraga-Paczynski model. The event rate and duration distribution also depend on the lower mass cutoff of the lens mass function. With a 0.1 solar mass cutoff, five to seven events (depending on the contribution of disk lenses) with a logarithmic mean duration of 20 days are expected for the Optical Gravitational Lensing Experiment (OGLE) according to our model, while Udalski et al. (1994) observed nine events with durations from 8 to 62 days. On the other hand, if most of the lenses are brown dwarfs, our model predicts too many short-duration events. A Kolmogorov-Smirnov test finds only 7% probability for the model with 0.01 solar mass cutoff to be consistent with current data.

  12. PREFACE: Galactic Center Workshop 2006

    NASA Astrophysics Data System (ADS)

    Schödel, Rainer; Bower, Geoffrey C.; Muno, Michael P.; Nayakshin, Sergei; Ott, Thomas

    2006-12-01

    We are pleased to present the proceedings from the Galactic Center Workshop 2006—From the Center of the Milky Way to Nearby Low-Luminosity Galactic Nuclei. The conference took place in the Physikzentrum, Bad Honnef, Germany, on 18 to 22 April 2006. It is the third workshop of this kind, following the Galactic Center Workshops held 1998 in Tucson, Arizona, and 2002 in Kona, Hawaii. The center of the Milky Way is the only galactic nucleus of a fairly common spiral galaxy that can be observed in great detail. With a distance of roughly 8 kpc, the resolution that can currently be achieved is of the order 40 mpc/8000 AU in the X-ray domain, 2 mpc/400 AU in the near-infrared, and 0.01 mpc/1 AU with VLBI in the millimeter domain. This is two to three orders of magnitude better than for any comparable nearby galaxy, making thus the center of the Milky Way thetemplate object for the general physical interpretation of the phenomena that can be observed in galactic nuclei. We recommend the summary article News from the year 2006 Galactic Centre workshopby Mark Morris and Sergei Nayakshin—who also gave the summary talk of the conference—to the reader in order to obtain a first, concise overview of the results presented at the workshop and some of the currently most exciting—and debated—developments in recent GC research. While the workshops held in 1998 and 2002 were dedicated solely to the center of the Milky Way, the field of view was widened in Bad Honnef to include nearby low-luminosity nuclei. This new feature followed the realization that not only the GC serves as a template for understanding extragalactic nuclei, but that the latter can also provide the context and broader statistical base for understanding the center of our Milky Way. This concerns especially the accretion and emission processes related to the Sagittarius A*, the manifestation of the super massive black hole in the GC, but also the surprising observation of great numbers of massive, young

  13. The Galactic evolution of phosphorus

    NASA Astrophysics Data System (ADS)

    Caffau, E.; Bonifacio, P.; Faraggiana, R.; Steffen, M.

    2011-08-01

    Context. As a galaxy evolves, its chemical composition changes and the abundance ratios of different elements are powerful probes of the underlying evolutionary processes. Phosphorous is an element whose evolution has remained quite elusive until now, because it is difficult to detect in cool stars. The infrared weak P i lines of the multiplet 1, at 1050-1082 nm, are the most reliable indicators of the presence of phosphorus. The availability of CRIRES at VLT has permitted access to this wavelength range in stellar spectra. Aims: We attempt to measure the phosphorus abundance of twenty cool stars in the Galactic disk. Methods: The spectra are analysed with one-dimensional model-atmospheres computed in local thermodynamic equilibrium (LTE). The line formation computations are performed assuming LTE. Results: The ratio of phosphorus to iron behaves similarly to sulphur, increasing towards lower metallicity stars. Its ratio with respect to sulphur is roughly constant and slightly larger than solar, [P/S] = 0.10 ± 0.10. Conclusions: We succeed in taking an important step towards the understanding of the chemical evolution of phosphorus in the Galaxy. However, the observed rise in the P/Fe abundance ratio is steeper than predicted by Galactic chemical evolution model developed by Kobayashi and collaborators. Phosphorus appears to evolve differently from the light odd-Z elements sodium and aluminium. The constant value of [P/S] with metallicity implies that P production is insensitive to the neutron excess, thus processes other than neutron captures operate. We suggest that proton captures on 30Si and α captures on 27Al are possibilities to investigate. We see no clear distinction between our results for stars with planets and stars without any detected planet. Based on observations obtained with the CRIRES spectrograph at ESO-VLT Antu 8.2 m telescope at Paranal, Programme 386.D-0130, P.I. E. Caffau.

  14. PREFACE: Galactic Center Workshop 2006

    NASA Astrophysics Data System (ADS)

    Schödel, Rainer; Bower, Geoffrey C.; Muno, Michael P.; Nayakshin, Sergei; Ott, Thomas

    2006-12-01

    We are pleased to present the proceedings from the Galactic Center Workshop 2006—From the Center of the Milky Way to Nearby Low-Luminosity Galactic Nuclei. The conference took place in the Physikzentrum, Bad Honnef, Germany, on 18 to 22 April 2006. It is the third workshop of this kind, following the Galactic Center Workshops held 1998 in Tucson, Arizona, and 2002 in Kona, Hawaii. The center of the Milky Way is the only galactic nucleus of a fairly common spiral galaxy that can be observed in great detail. With a distance of roughly 8 kpc, the resolution that can currently be achieved is of the order 40 mpc/8000 AU in the X-ray domain, 2 mpc/400 AU in the near-infrared, and 0.01 mpc/1 AU with VLBI in the millimeter domain. This is two to three orders of magnitude better than for any comparable nearby galaxy, making thus the center of the Milky Way thetemplate object for the general physical interpretation of the phenomena that can be observed in galactic nuclei. We recommend the summary article News from the year 2006 Galactic Centre workshopby Mark Morris and Sergei Nayakshin—who also gave the summary talk of the conference—to the reader in order to obtain a first, concise overview of the results presented at the workshop and some of the currently most exciting—and debated—developments in recent GC research. While the workshops held in 1998 and 2002 were dedicated solely to the center of the Milky Way, the field of view was widened in Bad Honnef to include nearby low-luminosity nuclei. This new feature followed the realization that not only the GC serves as a template for understanding extragalactic nuclei, but that the latter can also provide the context and broader statistical base for understanding the center of our Milky Way. This concerns especially the accretion and emission processes related to the Sagittarius A*, the manifestation of the super massive black hole in the GC, but also the surprising observation of great numbers of massive, young

  15. Hercules and Wolf 630 stellar streams and galactic bar kinematics

    NASA Astrophysics Data System (ADS)

    Bobylev, V. V.; Bajkova, A. T.

    2016-04-01

    We have identified the four most significant features in the UV velocity distribution of solarneighborhood stars: H1, H2 in the Hercules stream and W1, W2 in the Wolf 630 stream. We have formulated the problemof determining several characteristics of the centralGalactic bar independently from each of the identified features by assuming that the Hercules and Wolf 630 streams are of a bar-induced dynamical nature. The problem has been solved by constructing 2: 1 resonant orbits in the rotating bar frame for each star in these streams. Analysis of the resonant orbits found has shown that the bar pattern speed is 45-55 km s-1 kpc-1, while the bar angle lies within the range 40°-60°. The results obtained are consistent with the view that the Hercules andWolf 630 streams could be formed by a long-term influence of the Galactic bar leading to a characteristic bimodal splitting of the UV velocity plane.

  16. Titration Curves: Fact and Fiction.

    ERIC Educational Resources Information Center

    Chamberlain, John

    1997-01-01

    Discusses ways in which datalogging equipment can enable titration curves to be measured accurately and how computing power can be used to predict the shape of curves. Highlights include sources of error, use of spreadsheets to generate titration curves, titration of a weak acid with a strong alkali, dibasic acids, weak acid and weak base, and…

  17. An eccentric binary millisecond pulsar in the galactic plane.

    PubMed

    Champion, David J; Ransom, Scott M; Lazarus, Patrick; Camilo, Fernando; Bassa, Cees; Kaspi, Victoria M; Nice, David J; Freire, Paulo C C; Stairs, Ingrid H; van Leeuwen, Joeri; Stappers, Ben W; Cordes, James M; Hessels, Jason W T; Lorimer, Duncan R; Arzoumanian, Zaven; Backer, Don C; Bhat, N D Ramesh; Chatterjee, Shami; Cognard, Ismaël; Deneva, Julia S; Faucher-Giguère, Claude-André; Gaensler, Bryan M; Han, Jinlin; Jenet, Fredrick A; Kasian, Laura; Kondratiev, Vlad I; Kramer, Michael; Lazio, Joseph; McLaughlin, Maura A; Venkataraman, Arun; Vlemmings, Wouter

    2008-06-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M(middle dot in circle)) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 M solar symbol, an unusually high value. PMID:18483399

  18. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

    NASA Technical Reports Server (NTRS)

    Champion, David J.; Ransom, Scott M.; Lazarus, Patrick; Camilo, Fernando; Bassa, Cess; Kaspi, Victoria M.; Nice, David J.; Freire, Paulo C. C.; Stairs, Ingrid H.; vanLeeuwen, Joeri; Stappers, Ben W.; Cordes, James M.; Hessels, Jason W. T.; Lorimer, Duncan R.; Arzoumanian, Zaven; Backer, Don C.; Bhat, N. D. Ramesh; Chatterjee, Shami; Cognard, Ismael; Deneva, Julia S.; Faucher-Giguere, Claude-Andre; Gaensler, Bryan M.; Han, JinLin; Jenet, Fredrick A.; Kasian, Laura

    2008-01-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M.) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 Solar Mass, an unusually high value.

  19. THE INFORMATION CONTENT IN ANALYTIC SPOT MODELS OF BROADBAND PRECISION LIGHT CURVES

    SciTech Connect

    Walkowicz, Lucianne M.; Basri, Gibor; Valenti, Jeff A.

    2013-04-01

    We present the results of numerical experiments to assess degeneracies in light curve models of starspots. Using synthetic light curves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler light curves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsin i or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the light curve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

  20. The Information Content in Analytic Spot Models of Broadband Precision Light Curves

    NASA Astrophysics Data System (ADS)

    Walkowicz, Lucianne M.; Basri, Gibor; Valenti, Jeff A.

    2013-04-01

    We present the results of numerical experiments to assess degeneracies in light curve models of starspots. Using synthetic light curves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler light curves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsin i or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the light curve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

  1. Rotational preference in gymnastics.

    PubMed

    Heinen, Thomas; Jeraj, Damian; Vinken, Pia M; Velentzas, Konstantinos

    2012-06-01

    In gymnastics, most skills incorporate rotations about one or more body axes. At present, the question remains open if factors such as lateral preference and/or vestibulo-spinal asymmetry are related to gymnast's rotational preference. Therefore, we sought to explore relationships in gymnast's rotation direction between different gymnastic skills. Furthermore, we sought to explore relationships between rotational preference, lateral preference, and vestibulo-spinal asymmetry. In the experiment n = 30 non-experts, n = 30 near-experts and n = 30 experts completed a rotational preference questionnaire, a lateral preference inventory, and the Unterberger-Fukuda Stepping Test. The results revealed, that near-experts and experts more often rotate rightward in the straight jump with a full turn when rotating leftward in the round-off and vice versa. The same relationship was found for experts when relating the rotation preference in the handstand with a full turn to the rotation preference in the straight jump with a full turn. Lateral preference was positively related to rotational preference in non-expert gymnasts, and vestibulo-spinal asymmetry was positively related to rotational preference in experts. We suggest, that gymnasts should explore their individual rotational preference by systematically practicing different skills with a different rotation direction, bearing in mind that a clearly developed structure in rotational preference between different skills may be appropriate to develop more complex skills in gymnastics. PMID:23486362

  2. Rotational Preference in Gymnastics

    PubMed Central

    Heinen, Thomas; Jeraj, Damian; Vinken, Pia M.; Velentzas, Konstantinos

    2012-01-01

    In gymnastics, most skills incorporate rotations about one or more body axes. At present, the question remains open if factors such as lateral preference and/or vestibulo-spinal asymmetry are related to gymnast’s rotational preference. Therefore, we sought to explore relationships in gymnast’s rotation direction between different gymnastic skills. Furthermore, we sought to explore relationships between rotational preference, lateral preference, and vestibulo-spinal asymmetry. In the experiment n = 30 non-experts, n = 30 near-experts and n = 30 experts completed a rotational preference questionnaire, a lateral preference inventory, and the Unterberger-Fukuda Stepping Test. The results revealed, that near-experts and experts more often rotate rightward in the straight jump with a full turn when rotating leftward in the round-off and vice versa. The same relationship was found for experts when relating the rotation preference in the handstand with a full turn to the rotation preference in the straight jump with a full turn. Lateral preference was positively related to rotational preference in non-expert gymnasts, and vestibulo-spinal asymmetry was positively related to rotational preference in experts. We suggest, that gymnasts should explore their individual rotational preference by systematically practicing different skills with a different rotation direction, bearing in mind that a clearly developed structure in rotational preference between different skills may be appropriate to develop more complex skills in gymnastics. PMID:23486362

  3. Predictors of curve flexibility in adolescent idiopathic scoliosis: a retrospective study of 100 patients.

    PubMed

    Ameri, Ebrahim; Behtash, Hamid; Mobini, Bahram; Daraie, Ariasb

    2015-01-01

    Curve flexibility in adolescent idiopathic scoliosis (AIS) was one of the major concerns of spinal surgeons since the evolution of surgical correction techniques. In this respect, many tried to identify which criteria denote more rigid curve. In the present study, we aimed toward determining important factors influencing AIS curve flexibility on supine bending films. We assessed radiographs of 100 patients with AIS for direction of curves, number of involved vertebrae, apical vertebral translation and rotation, magnitude of main thoracic curve and T5-T12 kyphosis. Statistical analysis performed via stepwise linear regression model with these variables plus age and sex against flexibility index. According to regression analysis, there was a clear relationship between flexibility indexes (FI) and magnitude of main thoracic curve at all (P<0.001). When we consider flexible curves (FI>50%) against rigid curves, apical vertebral rotation was a major determinant of curve flexibility also (P<0.001). Adolescent idiopathic scoliosis curves with larger Cobb's angle and apical vertebral rotation show less flexibility on supine bending films. PMID:25796026

  4. Spatial distribution of Galactic Wolf-Rayet stars and implications for the global population

    NASA Astrophysics Data System (ADS)

    Rosslowe, C. K.; Crowther, P. A.

    2015-03-01

    We construct revised near-infrared absolute magnitude calibrations for 126 Galactic Wolf-Rayet (WR) stars at known distances, based in part upon recent large-scale spectroscopic surveys. Application to 246 WR stars located in the field permits us to map their Galactic distribution. As anticipated, WR stars generally lie in the thin disc (˜40 pc half-width at half-maximum) between Galactocentric radii 3.5-10 kpc, in accordance with other star formation tracers. We highlight 12 WR stars located at vertical distances of ≥300 pc from the mid-plane. Analysis of the radial variation in WR subtypes exposes a ubiquitously higher NWC/NWN ratio than predicted by stellar evolutionary models accounting for stellar rotation. Models for non-rotating stars or accounting for close binary evolution are more consistent with observations. We consolidate information acquired about the known WR content of the Milky Way to build a simple model of the complete population. We derive observable quantities over a range of wavelengths, allowing us to estimate a total number of 1900 ± 250 Galactic WR stars, implying an average duration of ˜ 0.4 Myr for the WR phase at the current Milky Way star formation rate. Of relevance to future spectroscopic surveys, we use this model WR population to predict follow-up spectroscopy to KS ≃ 17.5 mag will be necessary to identify 95 per cent of Galactic WR stars. We anticipate that ESA's Gaia mission will make few additional WR star discoveries via low-resolution spectroscopy, though will significantly refine existing distance determinations. Appendix A provides a complete inventory of 322 Galactic WR stars discovered since the VIIth catalogue (313 including Annex), including a revised nomenclature scheme.

  5. OGLE Atlas of Classical Novae. I. Galactic Bulge Objects

    NASA Astrophysics Data System (ADS)

    Mróz, P.; Udalski, A.; Poleski, R.; Soszyński, I.; Szymański, M. K.; Pietrzyński, G.; Wyrzykowski, Ł.; Ulaczyk, K.; Kozłowski, S.; Pietrukowicz, P.; Skowron, J.

    2015-08-01

    Eruptions of classical novae are possible sources of lithium formation and gamma-ray emission. Nova remnants can also become Type Ia supernovae (SNe Ia). The contribution of novae to these phenomena depends on nova rates, which are not well established for the Galaxy. Here, we directly measure a Galactic bulge nova rate of 13.8 ± 2.6 {{yr}}-1. This measurement is much more accurate than any previous measurement of this kind thanks to many years’ monitoring of the bulge by the Optical Gravitational Lensing Experiment (OGLE) survey. Our sample consists of 39 novae eruptions, ∼1/3 of which are OGLE-based discoveries. This long-term monitoring allows us to not only measure the nova rate but also to study in detail the light curves of 39 eruptions and more than 80 post-nova candidates. We measured orbital periods for 9 post-novae and 9 novae, and in 14 cases we procured the first estimates. The OGLE survey is very sensitive to the frequently erupting recurrent novae. We did not find any object similar to M31 2008-12a, which erupts once a year. The lack of detection indicates that there is only a small number of them in the Galactic bulge.

  6. Difference Image Analysis of Galactic Microlensing. I. Data Analysis

    SciTech Connect

    Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.

    1999-08-20

    This is a preliminary report on the application of Difference Image Analysis (DIA) to Galactic bulge images. The aim of this analysis is to increase the sensitivity to the detection of gravitational microlensing. We discuss how the DIA technique simplifies the process of discovering microlensing events by detecting only objects that have variable flux. We illustrate how the DIA technique is not limited to detection of so-called ''pixel lensing'' events but can also be used to improve photometry for classical microlensing events by removing the effects of blending. We will present a method whereby DIA can be used to reveal the true unblended colors, positions, and light curves of microlensing events. We discuss the need for a technique to obtain the accurate microlensing timescales from blended sources and present a possible solution to this problem using the existing Hubble Space Telescope color-magnitude diagrams of the Galactic bulge and LMC. The use of such a solution with both classical and pixel microlensing searches is discussed. We show that one of the major causes of systematic noise in DIA is differential refraction. A technique for removing this systematic by effectively registering images to a common air mass is presented. Improvements to commonly used image differencing techniques are discussed. (c) 1999 The American Astronomical Society.

  7. Distant Galactic Halo Substructures Observed by the Palomar Transient Factory

    NASA Astrophysics Data System (ADS)

    Sesar, Branimir

    2013-01-01

    Characterization of Galactic halo substructures is important as their kinematic and chemical properties help constrain the properties of the Galactic dark matter halo, the formation history of the Milky Way, and the galaxy formation process in general. The best practical choice for finding distant halo substructures are pulsating RR Lyrae stars, due to their intrinsic brightness (M_V = 0.6 mag) and distinct light curves. I will present kinematic and chemical properties of two distant halo substructures that were traced using RR Lyrae stars observed by the Palomar Transient Factory. One of these substructures, located at 90 kpc from the Sun in the Cancer constellation, consists of two groups of RR Lyrae stars moving away from the Galaxy at ~80 and ~20 km/s, respectively. The second substructure is located at ~65 kpc from the Sun in the Hercules constellation. The kinematics of RR Lyrae stars tracing this substructure suggest a presence of 2 or 3 stellar streams extending in the similar direction on the sky. Due to their spatial extent, both of these substructures are clearly disrupted and would be very difficult to detect using tradiitonal techniques such as the color-magnitude diagram filtering.

  8. New form of road/railway transition curve

    SciTech Connect

    Lipicnik, M.

    1998-11-01

    Road and railway transition curves have again become the subject of important scientific research and serious traffic engineering analyses because of high driving speeds and demands for automatic drive (i.e., car pilots). This article shows, in an original way, how to define or reconstruct the track of a vehicle when passing the elements of a continuous curve (straight lines, circles) so the track (curve) suits all requirements to which transition curves must be adapted. The praxis whereby a known mathematical curve (e.g., a cubic parabola, lemniscate, or chlotoid) was assumed as a transition curve and its suitability was analyzed has been passed over. On the basis of assumed kinematics models of the motion of a vehicle along joint alignment elements with a changing radius of curvature, the writers have analyzed different transition curves resulting in safe, comfortable, and economic driving. The curve resulting from a parabolic velocity chart of front wheel rotation during such movement which found the most suitable has been named POLUSA; a geometrical analysis of POLUSA has been performed and a manual for practical use completed.

  9. How good a clock is rotation? The stellar rotation-mass-age relationship for old field stars

    SciTech Connect

    Epstein, Courtney R.; Pinsonneault, Marc H. E-mail: pinsono@astronomy.ohio-state.edu

    2014-01-10

    The rotation-mass-age relationship offers a promising avenue for measuring the ages of field stars, assuming the attendant uncertainties to this technique can be well characterized. We model stellar angular momentum evolution starting with a rotation distribution from open cluster M37. Our predicted rotation-mass-age relationship shows significant zero-point offsets compared to an alternative angular momentum loss law and published gyrochronology relations. Systematic errors at the 30% level are permitted by current data, highlighting the need for empirical guidance. We identify two fundamental sources of uncertainty that limit the precision of rotation-based ages and quantify their impact. Stars are born with a range of rotation rates, which leads to an age range at fixed rotation period. We find that the inherent ambiguity from the initial conditions is important for all young stars, and remains large for old stars below 0.6 M {sub ☉}. Latitudinal surface differential rotation also introduces a minimum uncertainty into rotation period measurements and, by extension, rotation-based ages. Both models and the data from binary star systems 61 Cyg and α Cen demonstrate that latitudinal differential rotation is the limiting factor for rotation-based age precision among old field stars, inducing uncertainties at the ∼2 Gyr level. We also examine the relationship between variability amplitude, rotation period, and age. Existing ground-based surveys can detect field populations with ages as old as 1-2 Gyr, while space missions can detect stars as old as the Galactic disk. In comparison with other techniques for measuring the ages of lower main sequence stars, including geometric parallax and asteroseismology, rotation-based ages have the potential to be the most precise chronometer for 0.6-1.0 M {sub ☉} stars.

  10. Photometric Monitoring of the Active Galactic Nucleus in NGC 7469

    NASA Astrophysics Data System (ADS)

    Roberts, Caroline A.; Bentz, M. C.; Stare Collaboration

    2014-01-01

    Reverberation mapping is a technique by which black hole masses in active galactic nuclei (AGN) are determined. The method determines an average radius for the broad line region by measuring the time delay between continuum and emission signatures in an object’s spectrum. Coupled with the broad line region cloud velocity values taken from Doppler emission line broadening and a correction for the angle at which the AGN is viewed, the black hole mass can be constrained. As part of a reverberation mapping campaign targeting NGC 7469, optical B and V photometry was obtained over the span of a 6-month period during the second half of 2011 using 14 different telescopes in the former bandwidth and 15 in the latter. Differential photometry was performed with IRAF and the light curves were compared with those obtained using the image subtraction program ISIS.

  11. DISCOVERY OF 5000 ACTIVE GALACTIC NUCLEI BEHIND THE MAGELLANIC CLOUDS

    SciTech Connect

    Kozlowski, Szymon; Kochanek, Christopher S. E-mail: ckochanek@astronomy.ohio-state.edu

    2009-08-10

    We show that using mid-IR color selection to find active galactic nuclei (AGNs) is as effective in dense stellar fields such as the Magellanic Clouds as it is in extragalactic fields with low stellar densities using comparisons between the Spitzer Deep Wide Field Survey data for the NOAO Deep Wide Field Survey Boeotes region and the SAGE Survey of the Large Magellanic Cloud. We use this to build high-purity catalogs of {approx}5000 AGN candidates behind the Magellanic Clouds. Once confirmed, these quasars will expand the available astrometric reference sources for the Clouds and the numbers of quasars with densely sampled, long-term (>decade) monitoring light curves by well over an order of magnitude and potentially identify sufficiently bright quasars for absorption line studies of the interstellar medium of the Clouds.

  12. Enhancements of Bayesian Blocks; Application to Large Light Curve Databases

    NASA Technical Reports Server (NTRS)

    Scargle, Jeff

    2015-01-01

    Bayesian Blocks are optimal piecewise linear representations (step function fits) of light-curves. The simple algorithm implementing this idea, using dynamic programming, has been extended to include more data modes and fitness metrics, multivariate analysis, and data on the circle (Studies in Astronomical Time Series Analysis. VI. Bayesian Block Representations, Scargle, Norris, Jackson and Chiang 2013, ApJ, 764, 167), as well as new results on background subtraction and refinement of the procedure for precise timing of transient events in sparse data. Example demonstrations will include exploratory analysis of the Kepler light curve archive in a search for "star-tickling" signals from extraterrestrial civilizations. (The Cepheid Galactic Internet, Learned, Kudritzki, Pakvasa1, and Zee, 2008, arXiv: 0809.0339; Walkowicz et al., in progress).

  13. Spitzer Digs Up Galactic Fossil

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1

    [figure removed for brevity, see original site] Figure 2

    This false-color image taken by NASA's Spitzer Space Telescope shows a globular cluster previously hidden in the dusty plane of our Milky Way galaxy. Globular clusters are compact bundles of old stars that date back to the birth of our galaxy, 13 or so billion years ago. Astronomers use these galactic 'fossils' as tools for studying the age and formation of the Milky Way.

    Most clusters orbit around the center of the galaxy well above its dust-enshrouded disc, or plane, while making brief, repeated passes through the plane that each last about a million years. Spitzer, with infrared eyes that can see into the dusty galactic plane, first spotted the newfound cluster during its current pass. A visible-light image (inset of Figure 1) shows only a dark patch of sky.

    The red streak behind the core of the cluster is a dust cloud, which may indicate the cluster's interaction with the Milky Way. Alternatively, this cloud may lie coincidentally along Spitzer's line of sight.

    Follow-up observations with the University of Wyoming Infrared Observatory helped set the distance of the new cluster at about 9,000 light-years from Earth - closer than most clusters - and set the mass at the equivalent of 300,000 Suns. The cluster's apparent size, as viewed from Earth, is comparable to a grain of rice held at arm's length. It is located in the constellation Aquila.

    Astronomers believe that this cluster may be one of the last in our galaxy to be uncovered.

    This image composite was taken on April 21, 2004, by Spitzer's infrared array camera. It is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

    Galactic Fossil Found Behind Curtain of Dust In Figure 2, the image mosaic shows the same patch of sky in various wavelengths of light. While the

  14. H II REGION DRIVEN GALACTIC BUBBLES AND THEIR RELATIONSHIP TO THE GALACTIC MAGNETIC FIELD

    SciTech Connect

    Pavel, Michael D.; Clemens, D. P. E-mail: clemens@bu.edu

    2012-12-01

    The relative alignments of mid-infrared traced Galactic bubbles are compared to the orientation of the mean Galactic magnetic field in the disk. The orientations of bubbles in the northern Galactic plane were measured and are consistent with random orientations-no preferential alignment with respect to the Galactic disk was found. A subsample of H II region driven Galactic bubbles was identified, and as a single population they show random orientations. When this subsample was further divided into subthermal and suprathermal H II regions, based on hydrogen radio recombination linewidths, the subthermal H II regions showed a marginal deviation from random orientations, but the suprathermal H II regions showed significant alignment with the Galactic plane. The mean orientation of the Galactic disk magnetic field was characterized using new near-infrared starlight polarimetry and the suprathermal H II regions were found to preferentially align with the disk magnetic field. If suprathermal linewidths are associated with younger H II regions, then the evolution of young H II regions is significantly affected by the Galactic magnetic field. As H II regions age, they cease to be strongly linked to the Galactic magnetic field, as surrounding density variations come to dominate their morphological evolution. From the new observations, the ratios of magnetic-to-ram pressures in the expanding ionization fronts were estimated for younger H II regions.

  15. Controlled sample orientation and rotation in an acoustic levitator

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Gaspar, Mark S. (Inventor); Trinh, Eugene H. (Inventor)

    1988-01-01

    A system is described for use with acoustic levitators, which can prevent rotation of a levitated object or control its orientation and/or rotation. The acoustic field is made nonsymmetrical about the axis of the levitator, to produce an orienting torque that resists sample rotation. In one system, a perturbating reflector is located on one side of the axis of the levitator, at a location near the levitated object. In another system, the main reflector surface towards which incoming acoustic waves are directed is nonsymmetrically curved about the axis of the levitator. The levitated object can be reoriented or rotated in a controlled manner by repositioning the reflector producing the nonsymmetry.

  16. Dark matter particles in the galactic halo

    SciTech Connect

    Bernabei, R. Belli, P.; Montecchia, F.; Nozzoli, F.; Cappella, F.; D'Angelo, A.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C. J.; He, H. L.; Kuang, H. H.; Ma, J. M.; Sheng, X. D.; Ye, Z. P.

    2009-12-15

    Arguments on the investigation of the DarkMatter particles in the galactic halo are addressed. Recent results obtained by exploiting the annual modulation signature are summarized and the perspectives are discussed.

  17. Dark matter particles in the galactic halo

    NASA Astrophysics Data System (ADS)

    Bernabei, R.; Belli, P.; Montecchia, F.; Nozzoli, F.; Cappella, F.; D'Angelo, A.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C. J.; He, H. L.; Kuang, H. H.; Ma, J. M.; Sheng, X. D.; Ye, Z. P.

    2009-12-01

    Arguments on the investigation of the DarkMatter particles in the galactic halo are addressed. Recent results obtained by exploiting the annual modulation signature are summarized and the perspectives are discussed.

  18. The source and distribution of Galactic positrons

    NASA Technical Reports Server (NTRS)

    Purcell, W. R.; Dixon, D. D.; Cheng, L.-X.; Leventhal, M.; Kinzer, R. L.; Kurfess, J. D.; Skibo, J. G.; Smith, D. M.; Tueller, J.

    1997-01-01

    The oriented scintillation spectrometer experiment (OSSE) observations of the Galactic plane and the Galactic center region were combined with observations acquired with other instruments in order to produce a map of the Galactic 511 keV annihilation radiation. Two mapping techniques were applied to the data: the maximum entropy method, and the basis pursuit inversion method. The resulting maps are qualitatively similar and show evidence for a central bulge and a weak galactic disk component. The weak disk is consistent with that expected from positrons produced by the decay of radioactive Al-26 in the interstellar medium. Both maps suggest an enhanced region of emission near l = -4 deg, b = 7 deg, with a flux of approximately 50 percent of that of the bulge. The existence of this emission appears significant, although the location is not well determined. The source of this enhanced emission is presently unknown.

  19. Evaluation of Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.; Heiblim, Samuel; Malott, Christopher

    2009-01-01

    Models of the galactic cosmic ray spectra have been tested by comparing their predictions to an evaluated database containing more than 380 measured cosmic ray spectra extending from 1960 to the present.

  20. The Heliosphere and the Galactic Environment

    NASA Video Gallery

    The boundaries surrounding our heliosphere can change both due to changes in our galactic environment and through changes in the solar wind emitted by the Sun. We see here an animation of the bound...

  1. A FUSE SURVEY OF THE ROTATION RATES OF VERY MASSIVE STARS IN THE SMALL AND LARGE MAGELLANIC CLOUDS

    SciTech Connect

    Penny, Laura R.; Gies, Douglas R. E-mail: gies@chara.gsu.edu

    2009-07-20

    We present projected rotational velocity values for 97 Galactic, 55 SMC, and 106 LMC O-B type stars from archival FUSE observations. The evolved and unevolved samples from each environment are compared through the Kolmogorov-Smirnov test to determine if the distribution of equatorial rotational velocities is metallicity dependent for these massive objects. Stellar interior models predict that massive stars with SMC metallicity will have significantly reduced angular momentum loss on the main sequence compared to their Galactic counterparts. Our results find some support for this prediction but also show that even at Galactic metallicity, evolved and unevolved massive stars have fairly similar fractions of stars with large Vsin i values. Macroturbulent broadening that is present in the spectral features of Galactic evolved massive stars is lower in the LMC and SMC samples. This suggests the processes that lead to macroturbulence are dependent upon metallicity.

  2. Birational maps that send biquadratic curves to biquadratic curves

    NASA Astrophysics Data System (ADS)

    Roberts, John A. G.; Jogia, Danesh

    2015-02-01

    Recently, many papers have begun to consider so-called non-Quispel-Roberts-Thompson (QRT) birational maps of the plane. Compared to the QRT family of maps which preserve each biquadratic curve in a fibration of the plane, non-QRT maps send a biquadratic curve to another biquadratic curve belonging to the same fibration or to a biquadratic curve from a different fibration of the plane. In this communication, we give the general form of a birational map derived from a difference equation that sends a biquadratic curve to another. The necessary and sufficient condition for such a map to exist is that the discriminants of the two biquadratic curves are the same (and hence so are the j-invariants). The result allows existing examples in the literature to be better understood and allows some statements to be made concerning their generality.

  3. Spatial Reasoning Training Through Light Curves Of Model Asteroids

    NASA Astrophysics Data System (ADS)

    Ziffer, Julie; Nakroshis, Paul A.; Rudnick, Benjamin T.; Brautigam, Maxwell J.; Nelson, Tyler W.

    2015-11-01

    Recent research has demonstrated that spatial reasoning skills, long known to be crucial to math and science success, are teachable. Even short stints of training can improve spatial reasoning skills among students who lack them (Sorby et al., 2006). Teaching spatial reasoning is particularly valuable to women and minorities who, through societal pressure, often doubt their spatial reasoning skill (Hill et al., 2010). We have designed a hands on asteroid rotation lab that provides practice in spatial reasoning tasks while building the student’s understanding of photometry. For our tool, we mount a model asteroid, with any shape of our choosing, on a slowly rotating motor shaft, whose speed is controlled by the experimenter. To mimic an asteroid light curve, we place the model asteroid in a dark box, shine a movable light source upon our asteroid, and record the light reflected onto a moveable camera. Students may then observe changes in the light curve that result from varying a) the speed of rotation, b) the model asteroid’s orientation with respect to the motor axis, c) the model asteroid’s shape or albedo, and d) the phase angle. After practicing with our tool, students are asked to pair new objects to their corresponding light curves. To correctly pair objects to their light curves, students must imagine how light scattering off of a three dimensional rotating object is imaged on a ccd sensor plane, and then reduced to a series of points on a light curve plot. Through the use of our model asteroid, the student develops confidence in spatial reasoning skills.

  4. Power Harvesting from Rotation?

    ERIC Educational Resources Information Center

    Chicone, Carmen; Feng, Z. C.

    2008-01-01

    We show the impossibility of harvesting power from rotational motions by devices attached to the rotating object. The presentation is suitable for students who have studied Lagrangian mechanics. (Contains 2 figures.)

  5. Relativistic Dark Matter at the Galactic Center

    SciTech Connect

    Amin, Mustafa A.; Wizansky, Tommer; /SLAC

    2007-11-16

    In a large region of the supersymmetry parameter space, the annihilation cross section for neutralino dark matter is strongly dependent on the relative velocity of the incoming particles. We explore the consequences of this velocity dependence in the context of indirect detection of dark matter from the galactic center. We find that the increase in the annihilation cross section at high velocities leads to a flattening of the halo density profile near the galactic center and an enhancement of the annihilation signal.

  6. WIMPs at the galactic center

    SciTech Connect

    Agrawal, Prateek; Batell, Brian; Fox, Patrick J.; Harnik, Roni

    2015-05-07

    Simple models of weakly interacting massive particles (WIMPs) predict dark matter annihilations into pairs of electroweak gauge bosons, Higgses or tops, which through their subsequent cascade decays produce a spectrum of gamma rays. Intriguingly, an excess in gamma rays coming from near the Galactic center has been consistently observed in Fermi data. A recent analysis by the Fermi collaboration confirms these earlier results. Taking into account the systematic uncertainties in the modelling of the gamma ray backgrounds, we show for the first time that this excess can be well fit by these final states. In particular, for annihilations to (WW, ZZ, hh, tt{sup -bar}), dark matter with mass between threshold and approximately (165, 190, 280, 310) GeV gives an acceptable fit. The fit range for bb{sup -bar} is also enlarged to 35 GeV≲m{sub χ}≲165 GeV. These are to be compared to previous fits that concluded only much lighter dark matter annihilating into b, τ, and light quark final states could describe the excess. We demonstrate that simple, well-motivated models of WIMP dark matter including a thermal-relic neutralino of the MSSM, Higgs portal models, as well as other simplified models can explain the excess.

  7. WIMPs at the galactic center

    DOE PAGESBeta

    Agrawal, Prateek; Batell, Brian; Fox, Patrick J.; Harnik, Roni

    2015-05-07

    Simple models of weakly interacting massive particles (WIMPs) predict dark matter annihilations into pairs of electroweak gauge bosons, Higgses or tops, which through their subsequent cascade decays produce a spectrum of gamma rays. Intriguingly, an excess in gamma rays coming from near the Galactic center has been consistently observed in Fermi data. A recent analysis by the Fermi collaboration confirms these earlier results. Taking into account the systematic uncertainties in the modelling of the gamma ray backgrounds, we show for the first time that this excess can be well fit by these final states. In particular, for annihilations to (WW,more » ZZ, hh, tt¯), dark matter with mass between threshold and approximately (165, 190, 280, 310) GeV gives an acceptable fit. The fit range for bb¯ is also enlarged to 35 GeV ≲ mχ ≲ 165 GeV. These are to be compared to previous fits that concluded only much lighter dark matter annihilating into b, τ, and light quark final states could describe the excess. We demonstrate that simple, well-motivated models of WIMP dark matter including a thermal-relic neutralino of the MSSM, Higgs portal models, as well as other simplified models can explain the excess.« less

  8. WIMPs at the galactic center

    SciTech Connect

    Agrawal, Prateek; Batell, Brian; Fox, Patrick J.; Harnik, Roni

    2015-05-07

    Simple models of weakly interacting massive particles (WIMPs) predict dark matter annihilations into pairs of electroweak gauge bosons, Higgses or tops, which through their subsequent cascade decays produce a spectrum of gamma rays. Intriguingly, an excess in gamma rays coming from near the Galactic center has been consistently observed in Fermi data. A recent analysis by the Fermi collaboration confirms these earlier results. Taking into account the systematic uncertainties in the modelling of the gamma ray backgrounds, we show for the first time that this excess can be well fit by these final states. In particular, for annihilations to (WW, ZZ, hh, tt¯), dark matter with mass between threshold and approximately (165, 190, 280, 310) GeV gives an acceptable fit. The fit range for bb¯ is also enlarged to 35 GeV ≲ mχ ≲ 165 GeV. These are to be compared to previous fits that concluded only much lighter dark matter annihilating into b, τ, and light quark final states could describe the excess. We demonstrate that simple, well-motivated models of WIMP dark matter including a thermal-relic neutralino of the MSSM, Higgs portal models, as well as other simplified models can explain the excess.

  9. A Galactic Binary Detection Pipeline

    NASA Technical Reports Server (NTRS)

    Littenberg, Tyson B.

    2011-01-01

    The Galaxy is suspected to contain hundreds of millions of binary white dwarf systems, a large fraction of which will have sufficiently small orbital period to emit gravitational radiation in band for space-based gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA). LISA's main science goal is the detection of cosmological events (supermassive black hole mergers, etc.) however the gravitational signal from the galaxy will be the dominant contribution to the data - including instrumental noise over approximately two decades in frequency. The catalogue of detectable binary systems will serve as an unparalleled means of studying the Galaxy. Furthermore, to maximize the scientific return from the mission, the data must be "cleansed" of the galactic foreground. We will present an algorithm that can accurately resolve and subtract 2:: 10000 of these sources from simulated data supplied by the Mock LISA Data Challenge Task Force. Using the time evolution of the gravitational wave frequency, we will reconstruct the position of the recovered binaries and show how LISA will sample the entire compact binary population in the Galaxy.

  10. Radioactivity in the galactic plane

    NASA Technical Reports Server (NTRS)

    Walraven, G. D.; Haymes, R. C.

    1976-01-01

    The paper reports the detection of a large concentration of interstellar radioactivity during balloon-altitude measurements of gamma-ray energy spectra in the band between 0.02 and 12.27 MeV from galactic and extragalactic sources. Enhanced counting rates were observed in three directions towards the plane of the Galaxy; a power-law energy spectrum is computed for one of these directions (designated B 10). A large statistical deviation from the power law in a 1.0-FWHM interval centered near 1.16 MeV is discussed, and the existence of a nuclear gamma-ray line at 1.15 MeV in B 10 is postulated. It is suggested that Ca-44, which emits gamma radiation at 1.156 MeV following the decay of radioactive Sc-44, is a likely candidate for this line, noting that Sc-44 arises from Ti-44 according to explosive models of supernova nucleosynthesis. The 1.16-MeV line flux inferred from the present data is shown to equal the predicted flux for a supernova at a distance of approximately 3 kpc and an age not exceeding about 100 years.

  11. Rotations with Rodrigues' Vector

    ERIC Educational Resources Information Center

    Pina, E.

    2011-01-01

    The rotational dynamics was studied from the point of view of Rodrigues' vector. This vector is defined here by its connection with other forms of parametrization of the rotation matrix. The rotation matrix was expressed in terms of this vector. The angular velocity was computed using the components of Rodrigues' vector as coordinates. It appears…

  12. Mechanism of rotational relaxation.

    NASA Technical Reports Server (NTRS)

    Polanyi, J. C.; Woodall, K. B.

    1972-01-01

    A model is presented which describes the characteristic pattern of relaxation of a nonthermal rotational distribution of hydrogen halide, peaked initially at high rotational quantum number J, to a thermal distribution without generating a peak at intermediate J. A method for correcting infrared chemiluminiscence data for modest rotational relaxation is also suggested.

  13. Curve walking in freely moving crayfish (Procambarus clarkii)

    PubMed

    Domenici; Jamon; Clarac

    1998-05-01

    The curve walking of freely moving crayfish trained to walk along a curved path during homing behaviour was investigated using a video-analysis system. The leg kinematics and leg phase relationships, as well as the relationship between stepping patterns and body axis rotation measured relative to external references, were studied.

    The anterior and posterior extreme positions of the power stroke (AEP and PEP, respectively) and step amplitudes were analysed. As in a previous study on crayfish curve walking on a treadmill, PEPs were more posterior in outer legs (the legs on the outside of the turn) than in the inner legs. As a result, outer legs showed larger step amplitudes than inner legs. Leg kinematics varied within each walking sequence. AEP leg angles (the angles between the body and leg axes at the AEP) tended to decrease over time for inner legs and increase for outer legs. This leg angle drift was present mainly in the anterior legs and it suggests that these legs did not completely compensate for the body rotation after each step. In addition, leg angle asymmetries in a direction opposite to that of leg angle drift were observed at the start of each curve-walking sequence, suggesting that the extensive training (3 weeks) may have allowed crayfish to anticipate the leg angle drift.

    The rotational component of curve walking showed a discontinuous pattern, with the animal's body axis turning towards the inside of the curve only periodically. Analysis of cross-correlation functions showed that the angular acceleration of the body axis in the direction of the turn occurred during the power strokes of inner legs 2 and 5 and outer leg 4. While the tripod formed by these three legs showed in-phase relationships, the legs of the corresponding contralateral tripod (outer legs 2 and 5 and inner leg 4) were not in phase. We hypothesize that inner legs 2 and 5 and outer leg 4 act synergically causing the inward body rotation observed in curve-walking crayfish and

  14. The link between ejected stars, hardening and eccentricity growth of super massive black holes in galactic nuclei

    SciTech Connect

    Wang, Long; Berczik, Peter; Spurzem, Rainer; Kouwenhoven, M. B. N.

    2014-01-10

    The hierarchical galaxy formation picture suggests that supermassive black holes (SMBHs) observed in galactic nuclei today have grown from coalescence of massive black hole binaries (MBHB) after galaxy merging. Once the components of an MBHB become gravitationally bound, strong three-body encounters between the MBHB and stars dominate its evolution in a 'dry' gas-free environment and change the MBHB's energy and angular momentum (semimajor axis, eccentricity, and orientation). Here we present high-accuracy direct N-body simulations of spherical and axisymmetric (rotating) galactic nuclei with order of 10{sup 6} stars and two MBHs that are initially unbound. We analyze the properties of the ejected stars due to slingshot effects from three-body encounters with the MBHB in detail. Previous studies have investigated the eccentricity and energy changes of MBHs using approximate models or Monte Carlo three-body scatterings. We find general agreement with the average results of previous semi-analytic models for spherical galactic nuclei, but our results show a large statistical variation. Our new results show many more phase space details of how the process works, and also show the influence of stellar system rotation on the process. We detect that the angle between the orbital plane of the MBHBs and that of the stellar system (when it rotates) influences the phase-space properties of the ejected stars. We also find that MBHBs tend to switch stars with counter-rotating orbits into corotating orbits during their interactions.

  15. A New High-Frequency Search for Galactic Center Millisecond Pulsars using DSS-43

    NASA Astrophysics Data System (ADS)

    Lemley, Cameron; Prince, Thomas Allen; Majid, Walid A.; Murchikova, Elena

    2016-01-01

    The primary 70-meter Deep Space Network antenna (DSS-43) in Canberra, Australia was equipped with a new high-frequency (18-28 GHz) receiver system in May 2015 for use in a search for Galactic Center (GC) millisecond pulsars. The primary motivation for this search is that a pulsar in the Galactic Center region (especially one that is gravitationally bound to the massive black hole at the GC) would provide unprecedented tests of gravity in the strong-field regime and would offer an entirely new tool for probing the characteristics of the Galactic Center region. Preparation for the GC pulsar search has involved the development of a single-pulse search pipeline that integrates tools from both Fortran and Python as well as the implementation of this pipeline on high performance CPUs. The original version of the search pipeline was developed using Vela Pulsar data from DSS-43, and a more refined version that relies upon chi-squared fitting techniques was ultimately developed using Crab Pulsar data. Future work will involve continued testing of the single-pulse search pipeline using data from the rotating radio transient (RRAT) J1819-1458, the characterization of RRAT pulses using high time resolution data from the new receiver system on DSS-43, and ultimately the analysis of high-frequency data using the existing pipeline to search for millisecond pulsars in the Galactic Center.

  16. Synthetic RR Lyrae velocity curves

    SciTech Connect

    Liu, Tianxing Boston Univ., MA )

    1991-02-01

    An amplitude correlation between the pulsation velocity curves and visual light curves of ab-type RR Lyrae stars is derived from a large number of RR Lyrae that have high-precision radial-velocity and photometric data. Based on the determined AVp, AV ralation, a synthetic radial-velocity curve for a typical ab-type RR Lyrae star is constructed. This would be of particular use in determining the systemic velocities of RR Lyrae. 17 refs.

  17. Observations of galactic magnetic fields

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    Magnetic fields are enchored in gas clouds. Field lines are tangled in spiral arms, but highly regular between the arms. The similarity of pitch angles between gaseous and magnetic arms suggests a coupling between the density wave and the magnetic wave. Observations of large-scale patterns in Faraday rotation favour a dynamo origin of the regular fields. Fields in barred galaxies do not reveal the strong shearing shocks observed in the cold gas, but swing smoothly from the upstream region into the bar. Magnetic fields are important for the dynamcis of gas clouds, for the formation of spiral structures, bars and halos, and for mass and angular momentum transport in central regions.

  18. SEAL FOR ROTATING SHAFT

    DOEpatents

    Coffman, R.T.

    1957-12-10

    A seal is described for a rotatable shaft that must highly effective when the shaft is not rotating but may be less effective while the shaft is rotating. Weights distributed about a sealing disk secured to the shaft press the sealing disk against a tubular section into which the shiilt extends, and whem the shaft rotates, the centrifugal forces on the weights relieve the pressurc of the sealing disk against the tubular section. This action has the very desirible result of minimizing the wear of the rotating disk due to contact with the tubular section, while affording maximum sealing action when it is needed.

  19. Hot, metastable hydronium ion in the Galactic centre: formation pumping in X-ray-irradiated gas?

    PubMed

    Lis, Dariusz C; Schilke, Peter; Bergin, Edwin A; Emprechtinger, Martin

    2012-11-13

    With a 3.5 m diameter telescope passively cooled to approximately 80 K, and a science payload comprising two direct detection cameras/medium resolution imaging spectrometers (PACS and SPIRE) and a very high spectral resolution heterodyne spectrometer (HIFI), the Herschel Space Observatory is providing extraordinary observational opportunities in the 55-670 μm spectral range. HIFI has opened for the first time to high-resolution spectroscopy the submillimetre band that includes the fundamental rotational transitions of interstellar hydrides, the basic building blocks of astrochemistry. We discuss a recent HIFI discovery of metastable rotational transitions of the hydronium ion (protonated water, H(3)O(+)), with rotational level energies up to 1200 K above the ground state, in absorption towards Sagittarius B2(N) in the Galactic centre. Hydronium is an important molecular ion in the oxygen chemical network. Earlier HIFI observations have indicated a general deficiency of H(3)O(+) in the diffuse gas in the Galactic disc. The presence of hot H(3)O(+) towards Sagittarius B2(N) thus appears to be related to the unique physical conditions in the central molecular zone, manifested, for example, by the widespread presence of abundant H(3)(+). One intriguing theory for the high rotational temperature characterizing the population of the H(3)O(+) metastable levels may be formation pumping in molecular gas irradiated by X-rays emitted by the Galactic centre black hole. Alternatively, the pervasive presence of enhanced turbulence in the central molecular zone may give rise to shocks in the lower-density medium that is exposed to energetic radiation. PMID:23028163

  20. Light Curve of Minor Planet 1026 Ingrid

    NASA Astrophysics Data System (ADS)

    Delos, S.; Ahrendts, G.; Barker, T.

    2012-06-01

    (Abstract only) We have imaged minor planet 1026 Ingrid over the time period of July 29, 2011, to late September 2011, using the Wheaton College 0.25m telescope at Grove Creek Observatory in Australia via internet access. This telescope is equipped with a Santa Barbara Instrument Group STL-1001E CCD Camera, used with a clear filter. Over 1,000 30-second images were obtained and imported into the MPO Canopus software package for light curve analysis. Our preliminary estimate of the rotation period of 1026 Ingrid is 5.390 ± 0.001 hours, which is consistent with the previous estimate of 5.3 ± 0.3 hours (Székely, P., et al. 2005, Planet. Space Sci., 53, 925).

  1. The baryonic Tully-Fisher relation and galactic outflows

    NASA Astrophysics Data System (ADS)

    Dutton, Aaron A.

    2012-08-01

    Most of the baryons in the Universe are not in the form of stars and cold gas in galaxies. Galactic outflows driven by supernovae/stellar winds are the leading mechanisms for explaining this fact. The scaling relation between galaxy mass and outer rotation velocity (also known as the baryonic Tully-Fisher relation, BTF) has recently been used as evidence against this viewpoint. We use a Λ cold dark matter (ΛCDM)-based semi-analytic disc galaxy formation model to investigate these claims. In our model, galaxies with less efficient star formation and higher gas fractions are more efficient at ejecting gas from galaxies. This somewhat counter intuitive result is due to the (observational) fact that galaxies with less efficient star formation and higher gas fractions tend to live in dark matter haloes with lower circular velocities, from which less energy is required to escape the potential well. In our model the intrinsic scatter in the BTF is ≃0.15 dex, and mostly reflects scatter in dark halo concentration. The scatter is largely independent of galaxy structure because of the large radius within which galaxy rotation velocities are measured. The observed scatter, equal to ≃0.24 dex, is dominated by measurement errors. The best estimate for the intrinsic scatter is that it is less than 0.15 dex, and thus our ΛCDM-based model (which does not include all possible sources of scatter) is only just consistent with this. Future observations of the BTF scatter could be made with a more stringent measurement of the intrinsic scatter, and thus provide a strong constraint to galaxy formation models. In our model, gas-rich galaxies, at fixed virial velocity (Vvir), with lower stellar masses have lower baryonic masses. This is consistent with the expectation that galaxies with lower stellar masses have had less energy available to drive an outflow. However, when the outer rotation velocity (Vflat) is used the correlation has the opposite sign, with a slope in agreement

  2. ARCADE 2 Observations of Galactic Radio Emission

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Mirel, P.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2010-01-01

    We use absolutely calibrated data from the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) flight in July 2006 to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index beta_synch = -2.5 +/- 0.1, with free-free emission contributing 0.10 +/- 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc|b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of CII emission. Both methods are consistent with a single power-law over the frequency range 22 MHz to 10 GHz, with total Galactic emission towards the north polar cap T_Gal = 0.498 +/- 0.028 K and spectral index beta = -2.55 +/- 0.03 at reference frequency 0.31 GHz. The well calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust, and is consistent with spinning dust contributing 0.4 +/- 0.1 of the Galactic plane emission at 23 GHz.

  3. Rotation statistics of Algol-type binaries and results on RY Geminorum, RW Monocerotis, and RW Tauri

    SciTech Connect

    Van Hamme, W.; Wilson, R.E. Florida Univ., Gainesville )

    1990-12-01

    Rotation rates and other parameters are estimated from light curves of three Algol-type binaries, and rotation statistics based on both spectral line broadening and light curves are collected for 36 Algol systems. The statistics suggest that a subset of Algols have primary stars which rotate at the centrifugal limit and that many Algols have sufficient continual mass transfer to maintain nonsynchronous rotation. A formal procedure for estimating the critical rotation rate (centrifugal limit) is described. It is found that RY Gem rotates about 14 times faster than synchronously, but not close to its centrifugal limit of about 24 times. For RW Mon, the rotation is about five times synchronous. For RW Tau it was not possible to estimate the rotation from the light curves, but consistency with a published result from line broadening is found. 97 refs.

  4. Imaging Starspots on LO Pegasi via Light-curve Inversion

    NASA Astrophysics Data System (ADS)

    Harmon, Robert O.; Deskins, R.; Vutisalchavakul, N.

    2007-12-01

    We present maps of the star LO Pegasi obtained via Light-curve Inversion, a computational technique which produces an image of a star's surface features based on variations in the star's observed brightness as dark starspots rotate into and out of view from Earth. LO Pegasi is a rapidly rotating (P=10.17 hr) K8V young solar analog. We inverted BVRI light curves obtained from CCD images acquired on July 7-9 and July 22-23, 2007 at Perkins Observatory in Delaware, OH. Using multiple filters significantly improves the latitude resolution of our maps. Our inversions revealed the presence of a large mid-latitude spot or spotted region on the map from July 7-9, which appears to have evolved into a more complex two-spot configuration by July 22-23. The authors wish to acknowledge the support of the NSF REU Program and the Ohio Wesleyan University Summer Science Research Program.

  5. Flux Calibration for LAMOST Spectroscopic Survey of the Galactic Anti-center

    NASA Astrophysics Data System (ADS)

    Xiang, M.-S.; Liu, X.-W.; Yuan, H.-B.; Zheng, Y.; Huo, Z.-Y.; Huang, Y.

    2014-01-01

    Unknown extinction of Galactic disk stars makes it difficult to select flux standards based on colors alone for the LAMOST Spectroscopic Survey of the Galactic Anti-center (LSS-GAC; Liu et al., this volume). To solve this problem, for each spectrograph of an LSS-GAC plate, 5 - 10 F-type stars are selected from spectroscopy-based stellar parameters (T eff, log g, [Fe/H]) and adopted as flux standards, and an iterative approach is adopted to calibrate spectra. From spectra processed with nominal response curves, stellar parameters are derived with the PKU stellar parameter pipeline, LSP3 (Liu et al., this volume). More realistic response curves are then derived by comparing the observed spectra with synthetic spectra (Munari et al. 2005). The later is reddened assuming a R=3.1 Fitzpatrick (1999) reddening law using E (B-V) obtained by comparing photometric and synthetic colors. New stellar parameters are derived from spectra reprocessed using the new response curves, iteratively. Comparison of LSS-GAC spectral colors with photometric ones yields differences on average 0.01+/-0.06 and -0.06+/-0.04 mag in g-r and r-i, respectively. The relatively large difference in r-i is caused by the fact that the current pipeline has opted to not to correct for the telluric absorption, most notably in the i-band. Comparison of multi-epoch LSS-GAC spectra indicates < 8% uncertainties in the spectral shape from 4000 to 9000 Å. The LSS-GAC seems to yields spectra of more realistic SEDs than the SDSS (DR7) at low Galactic latitudes (Fig. 1). The shape of LAMOST response curves may vary by up to 20% in a given night, and even larger for different nights, indicating that flux calibration plate by plate is essential.

  6. Very fast optical flaring from a possible new Galactic magnetar.

    PubMed

    Stefanescu, A; Kanbach, G; Słowikowska, A; Greiner, J; McBreen, S; Sala, G

    2008-09-25

    Highly luminous rapid flares are characteristic of processes around compact objects like white dwarfs, neutron stars and black holes. In the high-energy regime of X-rays and gamma-rays, outbursts with variabilities on timescales of seconds or less are routinely observed, for example in gamma-ray bursts or soft gamma-ray repeaters. At optical wavelengths, flaring activity on such timescales has not been observed, other than from the prompt phase of one exceptional gamma-ray burst. This is mostly due to the fact that outbursts with strong, fast flaring are usually discovered in the high-energy regime; most optical follow-up observations of such transients use instruments with integration times exceeding tens of seconds, which are therefore unable to resolve fast variability. Here we show the observation of extremely bright and rapid optical flaring in the Galactic transient SWIFT J195509.6+261406. Our optical light curves are phenomenologically similar to high-energy light curves of soft gamma-ray repeaters and anomalous X-ray pulsars, which are thought to be neutron stars with extremely high magnetic fields (magnetars). This suggests that similar processes are in operation, but with strong emission in the optical, unlike in the case of other known magnetars. PMID:18818651

  7. Variability of Optical Counterparts in the Chandra Galactic Bulge Survey

    NASA Astrophysics Data System (ADS)

    Britt, C. T.; Hynes, R. I.; Johnson, C. B.; Baldwin, A.; Jonker, P. G.; Nelemans, G.; Torres, M. A. P.; Maccarone, T.; Steeghs, D.; Greiss, S.; Heinke, C.; Bassa, C. G.; Collazzi, A.; Villar, A.; Gabb, M.; Gossen, L.

    2014-09-01

    We present optical light curves of variable stars consistent with the positions of X-ray sources identified with the Chandra X-ray Observatory for the Chandra Galactic Bulge Survey (GBS). Using data from the Mosaic-II instrument on the Blanco 4 m Telescope at CTIO, we gathered time-resolved photometric data on timescales from ~2 hr to 8 days over the 3/4 of the X-ray survey containing sources from the initial GBS catalog. Among the light curve morphologies we identify are flickering in interacting binaries, eclipsing sources, dwarf nova outbursts, ellipsoidal variations, long period variables, spotted stars, and flare stars. Eighty-seven percent of X-ray sources have at least one potential optical counterpart. Twenty-seven percent of these candidate counterparts are detectably variable; a much greater fraction than expected for randomly selected field stars, which suggests that most of these variables are real counterparts. We discuss individual sources of interest, provide variability information on candidate counterparts, and discuss the characteristics of the variable population.

  8. Variability in Active Galactic Nuclei from Propagating Turbulent Relativistic Jets

    NASA Astrophysics Data System (ADS)

    Pollack, Maxwell; Pauls, David; Wiita, Paul J.

    2016-03-01

    We use the Athena hydrodynamics code to model propagating two-dimensional relativistic jets as approximations to the growth of radio-loud active galactic nuclei for various input jet velocities and jet-to-ambient matter density ratios. Using results from these simulations we estimate the changing synchrotron emission by summing the fluxes from a vertical strip of zones behind the reconfinement shock, which is nearly stationary, and from which a substantial portion of the flux variability should arise. We explore a wide range of timescales by considering two light curves from each simulation; one uses a relativistic turbulence code with bulk velocities taken from our simulations as input, while the other uses the bulk velocity data to compute fluctuations caused by variations in the Doppler boosting due to changes in the direction and the speed of the flow through all zones in the strip. We then calculate power spectral densities (PSDs) from the light curves for both turbulent and bulk velocity origins for variability. The range of the power-law slopes of the PSDs for the turbulence induced variations is -1.8 to -2.3, while for the bulk velocity produced variations this range is -2.1 to -2.9 these are in agreement with most observations. When superimposed, these power spectra span a very large range in frequency (about five decades), with the turbulent fluctuations yielding most of the shorter timescale variations and the bulk flow changes dominating the longer periods.

  9. LINE DERIVED INFRARED EXTINCTION TOWARD THE GALACTIC CENTER

    SciTech Connect

    Fritz, T. K.; Gillessen, S.; Dodds-Eden, K.; Lutz, D.; Genzel, R.; Raab, W.; Ott, T.; Pfuhl, O.; Eisenhauer, F.; Yusef-Zadeh, F.

    2011-08-20

    We derive the extinction curve toward the Galactic center (GC) from 1 to 19 {mu}m. We use hydrogen emission lines of the minispiral observed by ISO-SWS and SINFONI. The extinction-free flux reference is the 2 cm continuum emission observed by the Very Large Array. Toward the inner 14'' x 20'', we find an extinction of A{sub 2.166{mu}m} = 2.62 {+-} 0.11, with a power-law slope of {alpha} = -2.11 {+-} 0.06 shortward of 2.8 {mu}m, consistent with the average near-infrared slope from the recent literature. At longer wavelengths, however, we find that the extinction is grayer than shortward of 2.8 {mu}m. We find that it is not possible to fit the observed extinction curve with a dust model consisting of pure carbonaceous and silicate grains only, and the addition of composite particles, including ices, is needed to explain the observations. Combining a distance-dependent extinction with our distance-independent extinction, we derive the distance to the GC to be R{sub 0} = 7.94 {+-} 0.65 kpc. Toward Sgr A* (r < 0.''5), we obtain A{sub H} = 4.21 {+-} 0.10, A{sub Ks} = 2.42 {+-} 0.10, and A{sub L'} = 1.09 {+-} 0.13.

  10. Testing General Relativity with Galactic-Centre Stars

    NASA Astrophysics Data System (ADS)

    Angélil, R.; Saha, P.

    2011-05-01

    The Galactic Centre S-stars orbiting the central supermassive black hole reach velocities of a few percent of the speed of light. The GR-induced perturbations to the redshift enter the dynamics via two distinct channels. The post-Newtonian regime perturbs the orbit from the Keplerian (Zucker et al., 2006, Kannan & Saha 2009), and the photons from the Minkowski (Angélil & Saha 2010). The inclusion of gravitational time dilation at O (v2) marks the first departure of the redshift from the line-of-sight velocities. The leading-order Schwarzschild terms curve space, and enter at O(v3). The classical Keplerian phenomenology dominates the total redshift. Spectral measurements of sufficient resolution will allow for the detection of these post-Newtonian effects. We estimate the spectral resolution required to detect each of these effects by fitting the redshift curve via the five Keplerian elements plus black hole mass to mock data. We play with an exaggerated S2 orbit - one with a semi-major axis a fraction of that of the real S2. This amplifies the relativistic effects, and allows clear visual distinctions between the relativistic terms. We argue that spectral data of S2 with a dispersion ˜ 10 km s-1 would allow for a clear detection of gravitational redshift, and ˜ 1 km s-1 would suffice for leading-order space curvature detection.

  11. VARIABILITY OF OPTICAL COUNTERPARTS IN THE CHANDRA GALACTIC BULGE SURVEY

    SciTech Connect

    Britt, C. T.; Hynes, R. I.; Johnson, C. B.; Baldwin, A.; Collazzi, A.; Gossen, L.; Jonker, P. G.; Torres, M. A. P.; Nelemans, G.; Maccarone, T.; Steeghs, D.; Greiss, S.; Heinke, C.; Bassa, C. G.; Villar, A.; Gabb, M.

    2014-09-01

    We present optical light curves of variable stars consistent with the positions of X-ray sources identified with the Chandra X-ray Observatory for the Chandra Galactic Bulge Survey (GBS). Using data from the Mosaic-II instrument on the Blanco 4 m Telescope at CTIO, we gathered time-resolved photometric data on timescales from ∼2 hr to 8 days over the 3/4 of the X-ray survey containing sources from the initial GBS catalog. Among the light curve morphologies we identify are flickering in interacting binaries, eclipsing sources, dwarf nova outbursts, ellipsoidal variations, long period variables, spotted stars, and flare stars. Eighty-seven percent of X-ray sources have at least one potential optical counterpart. Twenty-seven percent of these candidate counterparts are detectably variable; a much greater fraction than expected for randomly selected field stars, which suggests that most of these variables are real counterparts. We discuss individual sources of interest, provide variability information on candidate counterparts, and discuss the characteristics of the variable population.

  12. Digital-voltage curve generator

    NASA Technical Reports Server (NTRS)

    Perlman, M.

    1970-01-01

    Curve generator capable of producing precisely repeatable curve for any single-valued function of voltage versus time uses digital approach, implemented by means of clocked feedback shift register, large scale integrated circuit diode matrix comprising about 12,000 diodes, counter, and digital-to-analog converter.

  13. Dark matter massive fermions and Einasto profiles in galactic haloes

    NASA Astrophysics Data System (ADS)

    Siutsou, I.; Argüelles, C. R.; Ruffini, R.

    2015-07-01

    On the basis of a fermionic dark matter model we fit rotation curves of The HI Nearby Galaxy Survey (THINGS) sample and compare our 3-parametric model to other models widely used in the literature: 2-parametric Navarro-Frenk-White, pseudoisothermal sphere, Burkhert models, and 3-parametric Einasto model, suggested as the new "standard dark matter profile" model in the paper by Chemin et al., Astron. J. 142 (2011) 109. The results from the fitting procedure provides evidence for an underlying fermionic nature of the dark matter candidate, with rest mass above the keV regime.

  14. Inflow of halo gas from the direction of the Galactic north pole

    NASA Technical Reports Server (NTRS)

    De Boer, K. S.; Savage, B. D.

    1984-01-01

    A far-UV echelle spectrum has been obtained of the UV-bright star vZ1128 in the globular cluster M3. This cluster lies in a direction 11 deg off the Galactic north pole at a distance of about 10 kpc. Only the usually strong interstellar lines are recognizable in the faint spectrum, and they show absorption at velocities from near +40 km/s to -100 km/s. Since in the direction observed the line-of-sight component of the Milky Way rotation is negligible, the detected velocities demonstrate for this direction the motion of gas from the Milky Way halo toward the disk. Gas returning to the disk in a galactic fountainlike flow may explain the observations.

  15. The linear filaments of the radio arc near the Galactic center

    NASA Technical Reports Server (NTRS)

    Yusef-Zadeh, Farhad; Morris, Mark

    1987-01-01

    High-resolution radio continuum VLA images of a segment of the Galactic center arc centered at G0.16-0.15 at wavelengths of both 6 and 20 cm are presented. In this segment, the highest multiplicity of filaments, the largest degree of linear polarization, and a maximum rotation measure of -5500 rad/sq m between wavelengths 6.166 and 6.363 cm are found. The large 'helical segments' which surround the filamentary system are also shown and discussed. Based on a number of intriguing characteristics of the filamentary system, including the helical component and possible twisting of some of the filaments, a picture is considered in which the geometry of the magnetic structure is that of a cylindrically symmetric, force-free field anchored to the halo of the Galaxy. An analogy with solar flare filaments is used to discuss some aspects of the Galactic center filaments.

  16. Modeling populations of rotationally mixed massive stars

    NASA Astrophysics Data System (ADS)

    Brott, I.

    2011-02-01

    Stars: Rotation and Nitrogen Enrichment as the Key to Understanding Massive Star Evolution'', I.Hunter, I.Brott, D.J. Lennon, N. Langer, C. Trundle, A. de Koter, C.J. Evans and R.S.I. Ryans The Astrophysical Journal, 2008, 676, L29-L32 Ch. 4: ``The VLT-FLAMES Survey of Massive Stars: Constraints on Stellar Evolution from the Chemical Compositions of Rapidly Rotating Galactic and Magellanic Cloud B-type Stars '', I. Hunter, I. Brott, N. Langer, D.J. Lennon, P.L. Dufton, I.D. Howarth R.S.I. Ryan, C. Trundle, C. Evans, A. de Koter and S.J. Smartt Published in Astronomy & Astropysics, 2009, 496, 841- 853 Ch. 5: ``Rotating Massive Main-Sequence Stars II: Simulating a Population of LMC early B-type Stars as a Test of Rotational Mixing '', I. Brott, C. J. Evans, I. Hunter, A. de Koter, N. Langer, P. L. Dufton, M. Cantiello, C. Trundle, D. J. Lennon, S.E. de Mink, S.-C. Yoon, P. Anders submitted to Astronomy & Astrophysics Ch 6: ``The Nature of B Supergiants: Clues From a Steep Drop in Rotation Rates at 22 000 K - The possibility of Bi-stability braking'', Jorick S. Vink, I. Brott, G. Graefener, N. Langer, A. de Koter, D.J. Lennon Astronomy & Astrophysics, 2010, 512, L7

  17. Galaxy Rotation and Rapid Supermassive Binary Coalescence

    NASA Astrophysics Data System (ADS)

    Holley-Bockelmann, Kelly; Khan, Fazeel Mahmood

    2015-09-01

    Galaxy mergers usher the supermassive black hole (SMBH) in each galaxy to the center of the potential, where they form an SMBH binary. The binary orbit shrinks by ejecting stars via three-body scattering, but ample work has shown that in spherical galaxy models, the binary separation stalls after ejecting all the stars in its loss cone—this is the well-known final parsec problem. However, it has been shown that SMBH binaries in non-spherical galactic nuclei harden at a nearly constant rate until reaching the gravitational wave regime. Here we use a suite of direct N-body simulations to follow SMBH binary evolution in both corotating and counterrotating flattened galaxy models. For N > 500 K, we find that the evolution of the SMBH binary is convergent and is independent of the particle number. Rotation in general increases the hardening rate of SMBH binaries even more effectively than galaxy geometry alone. SMBH binary hardening rates are similar for co- and counterrotating galaxies. In the corotating case, the center of mass of the SMBH binary settles into an orbit that is in corotation resonance with the background rotating model, and the coalescence time is roughly a few 100 Myr faster than a non-rotating flattened model. We find that counterrotation drives SMBHs to coalesce on a nearly radial orbit promptly after forming a hard binary. We discuss the implications for gravitational wave astronomy, hypervelocity star production, and the effect on the structure of the host galaxy.

  18. The dynamical fate of binary star clusters in the Galactic tidal field

    NASA Astrophysics Data System (ADS)

    Priyatikanto, R.; Kouwenhoven, M. B. N.; Arifyanto, M. I.; Wulandari, H. R. T.; Siregar, S.

    2016-04-01

    Fragmentation and fission of giant molecular clouds occasionally results in a pair of gravitationally bound star clusters that orbit their mutual centre of mass for some time, under the influence of internal and external perturbations. We investigate the evolution of binary star clusters with different orbital configurations, with a particular focus on the Galactic tidal field. We carry out N-body simulations of evolving binary star clusters and compare our results with estimates from our semi-analytic model. The latter accounts for mass-loss due to stellar evolution and two-body relaxation, and for evolution due to external tides. Using the semi-analytic model, we predict the long-term evolution for a wide range of initial conditions. It accurately describes the global evolution of such systems, until the moment when a cluster merger is imminent. N-body simulations are used to test our semi-analytic model and also to study additional features of evolving binary clusters, such as the kinematics of stars, global cluster rotation, evaporation rates, and the cluster merger process. We find that the initial orientation of a binary star cluster with respect to the Galactic field, and also the initial orbital phase, is crucial for its fate. Depending on these properties, the binaries may experience orbital reversal, spiral-in, or vertical oscillation about the Galactic plane before they actually merge at t ≈ 100 Myr, and produce rotating star clusters with slightly higher evaporation rates. The merger process of a binary cluster induces an outburst that ejects ˜10 per cent of the stellar members into the Galactic field.

  19. Comparison of the Galactic coordinate frames realized by the PPMXL and UCAC4 catalogues

    NASA Astrophysics Data System (ADS)

    Vityazev, V. V.; Tsvetkov, A. S.

    2016-09-01

    We present a method of comparing the Galactic systems realized by two astrometric catalogues. The systematic differences between positions and proper motions are represented by vector spherical harmonics. To extract the signal from the noise, we use a statistical criterion adapted to using HEALPIX data pixelization to determine the significance of all the accessible harmonics. We also use a new analytical method that includes the magnitude equation in the vector spherical harmonics technique. The influence of the magnitude equation on the determination of the mutual orientation and rotation of the PPMXL and UCAC4 Galactic reference frames has been found in the range of J magnitudes from 10.25 to 15.75 mag. The angles of mutual orientation and the rates of mutual rotation of the Galactic frames under consideration depend on magnitude and can reach the level of 10 mas in orientation and 0.7 mas yr-1 for spin. We make a kinematic study of the low degree harmonics in the representation of the systematic differences between the Galactic proper motions. We have found that, averaged over the magnitude range, the biases of the Oort constants due to systematic differences of proper motions between the two catalogues, which are as large as <ΔA> = 1.60 ± 0.41 and <ΔB> = -1.91 ± 0.32 km s-1 kpc-1, are greater than the standard errors of their evaluation in the systems of these catalogues. The theoretical equations used in this paper are based on real vector harmonics. We present a set of formulae to convert them into the complex function formalism.

  20. K2 Extra-Galactic and Supernova Studies and C17

    NASA Astrophysics Data System (ADS)

    Tucker, Bradley E.; Garnavich, Peter M.; Rest, Armin; Shaya, Edward J.; Kasen, Daniel; Kepler Extra-Galactic Survey

    2016-06-01

    I will give an overview of the Kepler Extra-Galactic survey - a program using Kepler to search for supernovae, active galactic nuclei, and other transients in galaxies. To date we have found 17 supernova, and with 3 more years (through 2018) planned, including the forward-facing C17, we hope to discover 20 - 30 more SN. The 30-minute cadence of Kepler has reveales subtle features in the light-curves of these supernova not detectable with any other survey, including, shock break-out in a large number of SN, improving our understanding of supernova progenitors. We can also search in nearby galaxies for very fast and faint transients, filling in a previously unaccessible parameter space. Lastly, the precision data of any discovered type Ia supernova combined with ground based data can dramatically improve our use of type Ia for determining distances and measuring the properties of dark energy.

  1. GCN: a gaseous Galactic halo stream?

    NASA Astrophysics Data System (ADS)

    Jin, Shoko

    2010-10-01

    We show that a string of HI clouds that form part of the high-velocity cloud complex known as GCN is a probable gaseous stream extending over more than 50° in the Galactic halo. The radial velocity gradient along the stream is used to deduce transverse velocities as a function of distance, enabling a family of orbits to be computed. We find that a direction of motion towards the Galactic disc coupled with a mid-stream distance of ~20kpc provides a good match to the observed sky positions and radial velocities of the HI clouds comprising the stream. With an estimated mass of 105Msolar, its progenitor is likely to be a dwarf galaxy. However, no stellar counterpart has been found amongst the currently known Galactic dwarf spheroidal galaxies or stellar streams and the exact origin of the stream is therefore currently unknown.

  2. New Constraints on the Galactic Bar

    NASA Astrophysics Data System (ADS)

    Minchev, I.; Nordhaus, J.; Quillen, A. C.

    2007-07-01

    Previous work has related the Galactic bar to structure in the local stellar velocity distribution. Here we show that the bar also influences the spatial gradients of the velocity vector via the Oort constants. By numerical integration of test particles we simulate measurements of the Oort C-value in a gravitational potential including the Galactic bar. We account for the observed trend that C is increasingly negative for stars with higher velocity dispersion. By comparing measurements of C with our simulations we improve on previous models of the bar, estimating that the bar pattern speed is Ωb/Ω0=1.87+/-0.04, where Ω0 is the local circular frequency, and the bar angle lies within 20deg<=φ0<=45deg. We find that the Galactic bar affects measurements of the Oort constants A and B less than ~2 km s-1 kpc-1 for the hot stars.

  3. New Constraints on the Galactic Bar

    NASA Astrophysics Data System (ADS)

    Minchev, Ivan; Nordhaus, J.; Quillen, A. C.

    2007-07-01

    Previous work has related the Galactic Bar to structure in the local stellar velocity distribution. Here we show that the Bar also influences the spatial gradients of the velocity vector via the Oort constants. By numerical integration of test-particles we simulate measurements of the Oort C-value in a gravitational potential including the Galactic Bar. We account for the observed trend that C is increasingly negative for stars with higher velocity dispersion. By comparing measurements of C with our simulations we improve on previous models of the Bar, estimating that the Bar pattern speed is Omega_b/Omega_0=1.87\\pm0.04, where Omega_0 is the local circular frequency, and the Bar angle lies within 20Galactic Bar affects measurements of the Oort constants A and B less than 2 km/s/kpc for the hot stars.

  4. The Distances of the Galactic Novae

    NASA Astrophysics Data System (ADS)

    Özdönmez, Aykut; Güver, Tolga; Cabrera-Lavers, Antonio; Ak, Tansel

    2016-06-01

    Utilising the unique location of red clump giants on colour-magnitude diagrams obtained from various near-IR surveys, we derived specific reddening-distance relations towards 119 Galactic novae for which independent reddening measurements are available. Using the derived distance-extinction relation and the independent measurements of reddening we calculated the most likely distances for each system. We present the details of our distance measurement technique and the results of this analysis, which yielded the distances of 73 Galactic novae and allowed us to set lower limits on the distances of 46 systems. We also present the data of reddening-distance relations derived for each nova, which may be useful to analyze the different Galactic components present in the line of sight.

  5. The distances of the Galactic novae

    NASA Astrophysics Data System (ADS)

    Özdönmez, Aykut; Güver, Tolga; Cabrera-Lavers, Antonio; Ak, Tansel

    2016-09-01

    Utilizing the unique location of red clump giants on colour-magnitude diagrams obtained from various near-infrared surveys, we derived specific reddening-distance relations towards 119 Galactic novae for which independent reddening measurements are available. Using the derived distance-extinction relation and the independent measurements of reddening we calculated the most likely distances for each system. We present the details of our distance measurement technique and the results of this analysis, which yielded the distances of 73 Galactic novae and allowed us to set lower limits on the distances of 46 systems. We also present the reddening-distance relations derived for each nova, which may be useful to analyse the different Galactic components present in the line of sight.

  6. Gamma rays, cosmic rays, and galactic structure

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1977-01-01

    Observations of cosmic and gamma radiation by SAS-2 satellite are summarized and analyzed to determine processes responsible for producing observed galactic radiation. In addition to the production of gamma rays in discrete galactic objects such as pulsars, there are three main mechanisms by which high-energy (greater than 100 MeV) radiation is produced by high-energy interactions involving cosmic rays in interstellar space. These processes, which produce what may be called diffuse galactic gamma-rays, are: (1) the decay of pi mesons produced by interactions of cosmic ray nucleons with interstellar gas nuclei; (2) the bremsstrahlung radiation produced by cosmic ray electrons interacting in the Coulomb fields of nuclei of interstellar gas atoms; and (3) Compton interactions between cosmic ray electrons and low-energy photons in interstellar space.

  7. FIRE simulations: galactic outflows and their consequences

    NASA Astrophysics Data System (ADS)

    Keres, Dusan; FIRE team

    2016-06-01

    We study gaseous outflows and their consequences in high-resolution galaxy formation simulations with explicit stellar feedback from the Feedback in Realistic Environments project. Collective, galaxy scale, effect of stellar feedback results in episodic ejections of large amount of gas and heavy elements into the circum-galactic medium. Gas ejection episodes follow strong bursts of star formation. Properties of galactic star formation and ejection episodes depend on galaxy mass and redshift and, together with gas infall and recycling, shape the evolution of the circum-galactic medium and galaxies. As a consequence, our simulated galaxies have masses, star formation histories and heavy element content in good agreement with the observed population of galaxies.

  8. Nonthermal galactic emission below 10 MHz

    NASA Technical Reports Server (NTRS)

    Novaco, J. C.; Brown, L. W.

    1977-01-01

    The Radio Astronomy Explorer-2 (RAE-2) satellite has provided new measurements of the nonthermal galactic radio emission at frequencies below 10 MHz. Measurements of the emission spectra are presented for the center, anticenter, north polar, and south polar directions at 22 frequencies between 0.25 and 9.18 MHz. Survey maps of the spatial distribution of the observed low frequency galactic emission at 1.31, 2.20, 3.93, 4.70, 6.55, and 9.18 MHz are presented. The observations were obtained with the 229-meter traveling-wave V-antenna on this lunar orbiting spacecraft. The improved frequency coverage offers additional insights into structure of the local galactic neighborhood.

  9. Chemical abundances in the Galactic bulge

    NASA Astrophysics Data System (ADS)

    Zoccali, M.; Lecureur, A.; Hill, V.; Barbuy, B.; Renzini, A.; Minniti, D.; Gómez, A.; Ortolani, S.

    We spectroscopically characterize the Galactic Bulge to infer its star formation timescale, compared to the other Galactic components, through the chemical signature on its individual stars. O, Na, Mg, Al were obtained for 50 K giants in four fields towards the Galactic bulge from UVES spectra (R=45,000), while Fe was measured in more than 400 stars with a slightly low resolution (R=20,000) and the GIRAFFE spectrograph at VLT. Oxygen and Magnesium show a well defined trend with [Fe/H], with abundances larger than those measured in both thin and thick disk stars, supporting a scenario in which the bulge formed before and more rapidly than the disk. On the other hand the iron distribution peaks at solar metallicity and it is slightly narrower than that measured in previous works. Part of the present results have been published by \\citet{Zoccali06} and \\citet{Lecureur07}, and part will be discussed in forthcoming papers.

  10. SAS-2 gamma-ray results from the galactic plane and their implications for galactic structure and galactic cosmic-ray dynamics

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Kniffen, D. A.; Thompson, D. J.

    1977-01-01

    The final SAS-2 results related to high energy galactic gamma-ray emission show a strong correlation with galactic structural features seen at other wavelenghts, when the known gamma-ray sources are subtracted. Theoretical considerations and analysis of the gamma-ray data suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density is enhanced where the matter density is greatest on the scale of the galactic arms. This concept has been explored in a galactic model that assumes: (1) cosmic rays are galactic and not universal; (2)on the scale of the galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3)the cosmic ray scale height is significantly larger than the scale height to the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of over 2:1.

  11. Far-infrared and submillimeter survey of the galactic center and nearby galactic plane

    NASA Technical Reports Server (NTRS)

    Campbell, M. F.; Niles, D. W.; Kanskar, M.; Hoffmann, W. F.; Thronson, H. A.

    1985-01-01

    Maps are presented with 12-arcmin resolution of the Galactic Center and adjacent galactic plane, from l(Pc) = 359 deg to l(Pc) = 5 deg. The data were obtained with the Steward Observatory's cryogenically-cooled, balloon-borne telescope. The data are from channels filtered for a bandpass of 70 to 110 microns and for a longpass of wavelength greater than 80 microns. For the typical effective temperature of 25 K of a galactic H II region at this spatial resolution, the effective wavelengths of the channels are 93 microns and 145 microns. Continuous emission is mapped along the galactic plane in both wavelengths. There are two contrasts between the immediate vicinity of SgrA l(Pc) smaller than 1 deg, and the galactic plane in general. Firstly, for l(Pi) greater than 1 deg the galactic plane narrows dramatically at 93 microns, while retaining its width at 145 microns. Secondly, the individual sources at l(Pc) (which are associated with H II regions) have greater peak brightness in the 145-micron channel than the 93-micron channel, while SgrA has approximately equal peak brightness in each. The maps demonstrate the importance of submillimeter wavelengths to galactic surveys.

  12. The Gaia-ESO Survey: Kinematics of seven Galactic globular clusters

    NASA Astrophysics Data System (ADS)

    Lardo, C.; Pancino, E.; Bellazzini, M.; Bragaglia, A.; Donati, P.; Gilmore, G.; Randich, S.; Feltzing, S.; Jeffries, R. D.; Vallenari, A.; Alfaro, E. J.; Allende Prieto, C.; Flaccomio, E.; Koposov, S. E.; Recio-Blanco, A.; Bergemann, M.; Carraro, G.; Costado, M. T.; Damiani, F.; Hourihane, A.; Jofré, P.; de Laverny, P.; Marconi, G.; Masseron, T.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.

    2015-01-01

    The Gaia-ESO survey is a large public spectroscopic survey aimed at investigating the origin and formation history of our Galaxy by collecting spectroscopy of representative samples (about 105 Milky Way stars) of all Galactic stellar populations, in the field and in clusters. The survey uses globular clusters as intra- and inter-survey calibrators, deriving stellar atmospheric parameters and abundances of a significant number of stars in clusters, along with radial velocity determinations. We used precise radial velocities of a large number of stars in seven globular clusters (NGC 1851, NGC 2808, NGC 4372, NGC 4833, NGC 5927, NGC 6752, and NGC 7078) to validate pipeline results and to preliminarily investigate the cluster internal kinematics. Radial velocity measurements were extracted from FLAMES/GIRAFFE spectra processed by the survey pipeline as part of the second internal data release of data products to ESO. We complemented our sample with ESO archival data obtained with different instrument configurations. Reliable radial velocity measurements for 1513 bona fide cluster star members were obtained in total. We measured systemic rotation, estimated central velocity dispersions, and present velocity dispersion profiles of all the selected clusters, providing the first velocity dispersion curve and the first estimate of the central velocitydispersion for the cluster NGC 5927. Finally, we explore the possible link between cluster kinematics and other physical parameters. The analysis we present here demonstrates that Gaia-ESO survey data are sufficiently accurate to be used in studies of kinematics of stellar systems and stellar populations in the Milky Way. Full Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/573/A115Based on data products from observations made with ESO telescopes at the La Silla Paranal Observatory under programme 188.B-3002 (the

  13. The Optical-infrared Extinction Curve and Its Variation in the Milky Way

    NASA Astrophysics Data System (ADS)

    Schlafly, E. F.; Meisner, A. M.; Stutz, A. M.; Kainulainen, J.; Peek, J. E. G.; Tchernyshyov, K.; Rix, H.-W.; Finkbeiner, D. P.; Covey, K. R.; Green, G. M.; Bell, E. F.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Martin, N. F.; Metcalfe, N.; Wainscoat, R. J.; Waters, C.

    2016-04-01

    The dust extinction curve is a critical component of many observational programs and an important diagnostic of the physics of the interstellar medium. Here we present new measurements of the dust extinction curve and its variation toward tens of thousands of stars, a hundred-fold larger sample than in existing detailed studies. We use data from the APOGEE spectroscopic survey in combination with ten-band photometry from Pan-STARRS1, the Two Micron All-Sky Survey, and Wide-field Infrared Survey Explorer. We find that the extinction curve in the optical through infrared is well characterized by a one-parameter family of curves described by R(V). The extinction curve is more uniform than suggested in past works, with σ (R(V))=0.18, and with less than one percent of sight lines having R(V)\\gt 4. Our data and analysis have revealed two new aspects of Galactic extinction: first, we find significant, wide-area variations in R(V) throughout the Galactic plane. These variations are on scales much larger than individual molecular clouds, indicating that R(V) variations must trace much more than just grain growth in dense molecular environments. Indeed, we find no correlation between R(V) and dust column density up to E(B-V)≈ 2. Second, we discover a strong relationship between R(V) and the far-infrared dust emissivity.

  14. Kinematical and Chemical Vertical Structure of the Galactic Thick Disk. I. Thick Disk Kinematics

    NASA Astrophysics Data System (ADS)

    Moni Bidin, C.; Carraro, G.; Méndez, R. A.

    2012-03-01

    The variation of the kinematical properties of the Galactic thick disk with Galactic height Z is studied by means of 412 red giants observed in the direction of the south Galactic pole up to 4.5 kpc from the plane. We confirm the non-null mean radial motion toward the Galactic anticenter found by other authors, but we find that it changes sign at |Z| = 3 kpc, and the proposed inward motion of the local standard of rest alone cannot explain these observations. The rotational velocity decreases with |Z| by -30 km s-1 kpc-1, but the data are better represented by a power law with index 1.25, similar to that proposed from the analysis of Sloan Digital Sky Survey data. All the velocity dispersions increase with |Z|, but the vertical gradients are small. The dispersions grow proportionally, with no significant variation of the anisotropy. The ratio σU/σW = 2 suggests that the thick disk could have formed from a low-latitude merging event. The vertex deviation increases with Galactic height, reaching ~20° at |Z| = 3.5 kpc. The tilt angle also increases, and the orientation of the ellipsoid in the radial-vertical plane is constantly intermediate between the alignment with the cylindrical and the spherical coordinate systems. The tilt angle at |Z| = 2 kpc coincides with the expectations of MOdified Newtonian Dynamics, but an extension of the calculations to higher |Z| is required to perform a conclusive test. Finally, between 2.5 and 3.5 kpc we detect deviations from the linear trend of many kinematical quantities, suggesting that some kinematical substructure could be present. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile (proposal IDs 075.B-0459(A), 077.B-0348(A)). This paper includes data gathered with the 6.5 m Magellan and the duPont Telescopes, located at Las Campanas Observatory, Chile.

  15. Supernova feedback in a local vertically stratified medium: interstellar turbulence and galactic winds

    NASA Astrophysics Data System (ADS)

    Martizzi, Davide; Fielding, Drummond; Faucher-Giguère, Claude-André; Quataert, Eliot

    2016-07-01

    We use local Cartesian simulations with a vertical gravitational potential to study how supernova (SN) feedback in stratified galactic discs drives turbulence and launches galactic winds. Our analysis includes three disc models with gas surface densities ranging from Milky Way-like galaxies to gas-rich ultraluminous infrared galaxies (ULIRGs), and two different SN driving schemes (random and correlated with local gas density). In order to isolate the physics of SN feedback, we do not include additional feedback processes. We find that, in these local box calculations, SN feedback excites relatively low mass-weighted gas turbulent velocity dispersions ≈3-7 km s-1 and low wind mass loading factors η ≲ 1 in all the cases we study. The low turbulent velocities and wind mass loading factors predicted by our local box calculations are significantly below those suggested by observations of gas-rich and rapidly star-forming galaxies; they are also in tension with global simulations of disc galaxies regulated by stellar feedback. Using a combination of numerical tests and analytic arguments, we argue that local Cartesian boxes cannot predict the properties of galactic winds because they do not capture the correct global geometry and gravitational potential of galaxies. The wind mass loading factors are in fact not well defined in local simulations because they decline significantly with increasing box height. More physically realistic calculations (e.g. including a global galactic potential and disc rotation) will likely be needed to fully understand disc turbulence and galactic outflows, even for the idealized case of feedback by SNe alone.

  16. Variable Radio Sources in the Galactic Plane

    NASA Astrophysics Data System (ADS)

    Becker, Robert H.; Helfand, David J.; White, Richard L.; Proctor, Deanne D.

    2010-07-01

    Using three epochs of Very Large Array observations of the Galactic plane in the first quadrant taken ~15 years apart, we have conducted a search for a population of variable Galactic radio emitters in the flux density range 1-100 mJy at 6 cm. We find 39 variable sources in a total survey area of 23.2 deg2. Correcting for various selection effects and for the extragalactic variable population of active galactic nuclei, we conclude there are ~1.6 deg-2 Galactic sources which vary by more than 50% on a time scale of years (or shorter). We show that these sources are much more highly variable than extragalactic objects; more than 50% show variability by a factor >2 compared to <10% for extragalactic objects in the same flux density range. We also show that the fraction of variable sources increases toward the Galactic center (another indication that this is a Galactic population), and that the spectral indices of many of these sources are flat or inverted. A small number of the variables are coincident with mid-IR sources and two are coincident with X-ray emitters, but most have no known counterparts at other wavelengths. Intriguingly, one lies at the center of a supernova remnant, while another appears to be a very compact planetary nebula; several are likely to represent activity associated with star formation regions. We discuss the possible source classes which could contribute to the variable cohort and follow-up observations which could clarify the nature of these sources.

  17. The diffuse galactic far-ultraviolet sky

    SciTech Connect

    Hamden, Erika T.; Schiminovich, David; Seibert, Mark

    2013-12-20

    We present an all-sky map of the diffuse Galactic far ultraviolet (1344-1786 Å) background using Galaxy Evolution Explorer data, covering 65% of the sky with 11.79 arcmin{sup 2} pixels. We investigate the dependence of the background on Galactic coordinates, finding that a standard cosecant model of intensity is not a valid fit. Furthermore, we compare our map to Galactic all-sky maps of 100 μm emission, N {sub H} {sub I} column, and Hα intensity. We measure a consistent low level far-UV (FUV) intensity at zero points for other Galactic quantities, indicating a 300 photons cm{sup –2} s{sup –1} sr{sup –1} Å{sup –1} non-scattered isotropic component to the diffuse FUV. There is also a linear relationship between FUV and 100 μm emission below 100 μm values of 8 MJy sr{sup –1}. We find a similar linear relationship between FUV and N {sub H} {sub I} below 10{sup 21} cm{sup –2}. The relationship between FUV and Hα intensity has no such constant cutoff. For all Galactic quantities, the slope of the linear portion of the relationship decreases with Galactic latitude. A modified cosecant model, taking into account dust scattering asymmetry and albedo, is able to accurately fit the diffuse FUV at latitudes above 20°. The best fit model indicates an albedo, a, of 0.62 ± 0.04 and a scattering asymmetry function, g, of 0.78 ± 0.05. Deviations from the model fit may indicate regions of excess FUV emission from fluorescence or shock fronts, while low latitude regions with depressed FUV emission are likely the result of self-shielding dusty clouds.

  18. Chaotic Rotation of Nix and Hydra

    NASA Astrophysics Data System (ADS)

    Showalter, Mark R.

    2014-05-01

    Disk-integrated photometry of Hydra and Nix from HST during 2010-2012 show large variations, which can be attributed to a combination of the phase function and the rotational light curves of the moons. After dividing out a model phase curve, variations by more than a factor of two remain, indicating that both Nix and Hydra are distinctly irregular in shape. Unexpectedly, Nix and Hydra's variations show no correlation with orbital longitude, as one would expect for bodies in synchronous rotation. In fact, Fourier analysis of the measurements does not reveal any fixed rotation periods compatible with the data. Compounding the mystery, Nix increased in absolute brightness by about 30% between 2010 and 2012, whereas Hydra was stable.I have developed a numeric integrator that tracks the position, velocity, orientation and rotation state of a moon as it orbits the Pluto-Charon "binary planet". The moons are represented by triaxial ellipsoids with arbitrary axial ratios. Pluto and Charon follow circular orbits about their common barycenter. I have run simulations for periods of up to 1000 years and for a variety of axial ratios and starting conditions. If an object is started in synchronous rotation with its long axis pointed toward the system barycenter, then it remains synchronously locked for the duration of the integrations. However, other initial conditions commonly lead to chaotic rotation, with Lyupanov times as brief as 30 days. Moons will sometimes temporarily lock into a nearly fixed rotation state, but commonly break out again within ~ 500 days. Depending on the axial ratios, polar flips are also commonly observed; this polar wander provides a plausible explanation for the year-by-year change in the observed brightness of Nix.Chaotic rotation is rare in the solar system, having previously been noted only for Hyperion and possibly Nereid. However, both photometry and dynamical simulations support the notion that chaotic rotation is a natural state for

  19. The spatial rotator.

    PubMed

    Rasmusson, A; Hahn, U; Larsen, J O; Gundersen, H J G; Jensen, E B Vedel; Nyengaard, J R

    2013-05-01

    This paper presents a new local volume estimator, the spatial rotator, which is based on measurements on a virtual 3D probe, using computer assisted microscopy. The basic design of the probe builds upon the rotator principle which requires only a few manual intersection markings, thus making the spatial rotator fast to use. Since a 3D probe is involved, it is expected that the spatial rotator will be more efficient than the the nucleator and the planar rotator, which are based on measurements in a single plane. An extensive simulation study shows that the spatial rotator may be more efficient than the traditional local volume estimators. Furthermore, the spatial rotator can be seen as a further development of the Cavalieri estimator, which does not require randomization of sectioning or viewing direction. The tissue may thus be sectioned in any arbitrary direction, making it easy to identify the specific tissue region under study. In order to use the spatial rotator in practice, however, it is necessary to be able to identify intersection points between cell boundaries and test rays in a series of parallel focal planes, also at the peripheral parts of the cell boundaries. In cases where over- and underprojection phenomena are not negligible, they should therefore be corrected for if the spatial rotator is to be applied. If such a correction is not possible, it is needed to avoid these phenomena by using microscopy with increased resolution in the focal plane. PMID:23488880

  20. Numerical modeling of the interstellar medium in galactic disks

    NASA Technical Reports Server (NTRS)

    Rosen, A.; Bregman, J. N.; Norman, Michael L.

    1993-01-01

    We have been developing detailed hydrodynamic models of the global interstellar medium in the hope of understanding the mass and volume occupied by various phases, as well as their structure and kinematics. In our model, the gas is modeled by one fluid while representative Pop 1 stars are modeled by a second fluid. The two fluids are coupled in that the gas forms into stars at a rate given by a Schmidt law while stellar mass loss returns matter into the gas phase (on a time scale of 100 Myr). Also, the stars heat the gas through stellar winds and the gas cools through optically thin radiation. The time behavior of these two fluids is studied in two spatial dimensions with the Eulerian finite difference numerical hydrodynamic code Zen. The two spatial dimensions are along the plane of a disk (x, total length of 2 kpc) and perpendicular to the disk (z, total height of +/- 15 kpc) and a galactic gravitational field in the z direction, typical of that at the solar circle, is imposed upon the simulation; self-gravity and rotation are absent. For the boundary conditions, outflow is permitted at the top and bottom of the grid (z = +/- 15 kpc) while periodic boundary conditions are imposed upon left and right sides of the grid. As initial conditions, we assumed a gaseous distribution like that seen for the H1 by earlier researchers, although the results are insensitive to the initial conditions. We have run simulations in which the heating due to stars, parameterized as a stellar wind velocity, a, is varied from low (a = 150 km/s), to intermediate (a = 300 km/s), to high (a = 600 km/s). Since the intermediate case is roughly equivalent to the Galactic energy injection rate from supernovae, this summary will concentrate on results from this simulation.

  1. The Mysterious Galactic Center Radio Source N3

    NASA Astrophysics Data System (ADS)

    Ludovici, Dominic; Lang, Cornelia C.; Morris, Mark; Lucien Mutel, Robert; Mills, Elisabeth A. C.; Toomey, James E.; Ott, Juergen

    2016-06-01

    Here we report on new, multi-wavelength radio observations of the mysterious point source "N3" that appears to be located in the vicinity of the Galactic Center. VLA observations between 2 and 50 GHz reveal that N3 is a compact and bright non-thermal source (56 mJy at 10 GHz) which is superimposed upon the non-thermal radio filaments (NTFs) of the Radio Arc. Our highest frequency observations place a strict upper limit of 65x28 milli-arcseconds on the size of this source. We compare our observations to those of Yusef-Zadeh (1987) and Lang (1997) and conclude that N3 is variable over long time scales. Additionally, we present the detection of a compact molecular cloud located adjacent to N3 in projection. CH3CN, CH3OH, CS, HC3N, HNCO, SiO, SO, and NH3 are detected in the cloud and most transitions have FWHM line widths of ~20 km s-1. The rotational temperature determined from the metastable NH3 transitions ranges from 79 K to 183 K depending on the transitions used and the location in the cloud. We present evidence that this molecular cloud is interacting with N3. After exploring the relationship between the NTFs, molecular cloud, and N3, we conclude that N3 likely lies within the Galactic Center. While we are able to rule out many possible physical counterparts, including an active star, HII region, young supernova, AGN, and microquasar, further observations will be required to determine the true nature of this mysterious source.

  2. Unwrapping the X-ray spectra of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Reynolds, C. S.

    2016-05-01

    Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X-ray emitting corona and, sometimes, a relativistic jet. On larger scales, the outer accretion disk and molecular torus act as the reservoirs of gas for the continuing AGN activity. And on all scales from the black hole outwards, powerful winds are seen that probably affect the evolution of the host galaxy as well as regulate the feeding of the AGN itself. In this review article, we discuss how X-ray spectroscopy can be used to study each of these components. We highlight how recent measurements of the high-energy cutoff in the X-ray continuum by NuSTAR are pushing us to conclude that X-ray coronae are radiatively-compact and have electron temperatures regulated by electron-positron pair production. We show that the predominance of rapidly-rotating objects in current surveys of SMBH spin is entirely unsurprising once one accounts for the observational selection bias resulting from the spin-dependence of the radiative efficiency. We review recent progress in our understanding of fast (v˜ (0.1-0.3)c, highly-ionized (mainly visible in Fe XXV and Fe XXVI lines), high-column density winds that may dominate quasar-mode galactic feedback. Finally, we end with a brief look forward to the promise of Astro-H and future X-ray spectropolarimeters.

  3. Deciphering Thermal Phase Curves of Dry, Tidally Locked Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Koll, Daniel D. B.; Abbot, Dorian S.

    2015-03-01

    Next-generation space telescopes will allow us to characterize terrestrial exoplanets. To do so effectively it will be crucial to make use of all available data. We investigate which atmospheric properties can, and cannot, be inferred from the broadband thermal phase curve of a dry and tidally locked terrestrial planet. First, we use dimensional analysis to show that phase curves are controlled by six nondimensional parameters. Second, we use an idealized general circulation model to explore the relative sensitivity of phase curves to these parameters. We find that the feature of phase curves most sensitive to atmospheric parameters is the peak-to-trough amplitude. Moreover, except for hot and rapidly rotating planets, the phase amplitude is primarily sensitive to only two nondimensional parameters: (1) the ratio of dynamical to radiative timescales and (2) the longwave optical depth at the surface. As an application of this technique, we show how phase curve measurements can be combined with transit or emission spectroscopy to yield a new constraint for the surface pressure and atmospheric mass of terrestrial planets. We estimate that a single broadband phase curve, measured over half an orbit with the James Webb Space Telescope, could meaningfully constrain the atmospheric mass of a nearby super-Earth. Such constraints will be important for studying the atmospheric evolution of terrestrial exoplanets as well as characterizing the surface conditions on potentially habitable planets.

  4. Veggie Light Curve Teacher Prep

    NASA Video Gallery

    In this activity, students will observe the surface of rotating potatoes to help them understand how astronomers can sometimes determine the shape of asteroids from variations in reflective brightn...

  5. Automated generation of curved planar reformations from MR images of the spine

    NASA Astrophysics Data System (ADS)

    Vrtovec, Tomaz; Ourselin, Sébastien; Gomes, Lavier; Likar, Boštjan; Pernuš, Franjo

    2007-05-01

    A novel method for automated curved planar reformation (CPR) of magnetic resonance (MR) images of the spine is presented. The CPR images, generated by a transformation from image-based to spine-based coordinate system, follow the structural shape of the spine and allow the whole course of the curved anatomy to be viewed in individual cross-sections. The three-dimensional (3D) spine curve and the axial vertebral rotation, which determine the transformation, are described by polynomial functions. The 3D spine curve passes through the centres of vertebral bodies, while the axial vertebral rotation determines the rotation of vertebrae around the axis of the spinal column. The optimal polynomial parameters are obtained by a robust refinement of the initial estimates of the centres of vertebral bodies and axial vertebral rotation. The optimization framework is based on the automatic image analysis of MR spine images that exploits some basic anatomical properties of the spine. The method was evaluated on 21 MR images from 12 patients and the results provided a good description of spine anatomy, with mean errors of 2.5 mm and 1.7° for the position of the 3D spine curve and axial rotation of vertebrae, respectively. The generated CPR images are independent of the position of the patient in the scanner while comprising both anatomical and geometrical properties of the spine.

  6. Asteroseismology for Galactic archaeology: bridging two fields

    NASA Astrophysics Data System (ADS)

    Casagrande, Luca; Silva Aguirre, Victor; Stello, Dennis; Huber, Daniel; Serenelli, Aldo; Schlesinger, Katharine J.; Milone, Antonino; Asplund, Martin

    2015-08-01

    Asteroseismology has the capability of precisely determining stellar properties that would otherwise be inaccessible, such as radii, masses, and thus ages of field stars. When coupling this information with classical determinations of stellar parameters, such as metallicities, effective temperatures, and angular diameters, powerful new diagnostics for Galactic studies can be obtained. An overview of the ongoing Strömgren survey for Asteroseismology and Galactic Archaeology (SAGA) is presented, along with recent results using asteroseismology to investigate the age structure of the Milky Way disc.

  7. Poiseuille flow in curved spaces

    NASA Astrophysics Data System (ADS)

    Debus, J.-D.; Mendoza, M.; Succi, S.; Herrmann, H. J.

    2016-04-01

    We investigate Poiseuille channel flow through intrinsically curved media, equipped with localized metric perturbations. To this end, we study the flux of a fluid driven through the curved channel in dependence of the spatial deformation, characterized by the parameters of the metric perturbations (amplitude, range, and density). We find that the flux depends only on a specific combination of parameters, which we identify as the average metric perturbation, and derive a universal flux law for the Poiseuille flow. For the purpose of this study, we have improved and validated our recently developed lattice Boltzmann model in curved space by considerably reducing discrete lattice effects.

  8. Poiseuille flow in curved spaces.

    PubMed

    Debus, J-D; Mendoza, M; Succi, S; Herrmann, H J

    2016-04-01

    We investigate Poiseuille channel flow through intrinsically curved media, equipped with localized metric perturbations. To this end, we study the flux of a fluid driven through the curved channel in dependence of the spatial deformation, characterized by the parameters of the metric perturbations (amplitude, range, and density). We find that the flux depends only on a specific combination of parameters, which we identify as the average metric perturbation, and derive a universal flux law for the Poiseuille flow. For the purpose of this study, we have improved and validated our recently developed lattice Boltzmann model in curved space by considerably reducing discrete lattice effects. PMID:27176437

  9. Surface Imaging of HIP 106231 via Light Curve Inversion

    NASA Astrophysics Data System (ADS)

    Roettenbacher, Rachael; Harmon, Robert

    2006-10-01

    The star HIP 106231 (LO Pegasi) was observed with the intention of mapping its starspots. Starspots, similar to sunspots on the Sun, are dark areas on the surface of a star caused by intense magnetic fields. CCD images of HIP 106231 and the surrounding star field were obtained using an 8-inch Meade Schmidt-Cassegrain Telescope in conjunction with a Santa Barbara Instruments Group ST-8E CCD Camera and CFW8 filter wheel. Aperture photometry was used to create light curves (i.e. plots of brightness vs. time) for the B, V, R and I photometric filters. The light curves were analyzed via Light Curve Inversion, which is a technique that produces an image of the starspots based on the variations in the star's brightness they produce as they rotate into and out of view of Earth. We present a map which indicates the presence of a mid-latitude spot or projection from a polar spot.

  10. Vaporization of comet nuclei - Light curves and life times

    NASA Technical Reports Server (NTRS)

    Cowan, J. J.; Ahearn, M. F.

    1979-01-01

    The effects of vaporization from the nucleus of a comet are examined and it is shown that a latitude dependence of vaporization can explain the asymmetries in cometary light curves. An attempt is made to explain the observed variation in molecular production rates with heliocentric distance when employing CO2 and clathrate hydrate ice as cometary nuclei substances. The energy balance equation and the vapor pressure equations of water and CO2 are used in calculating the vaporization from a surface. Calculations were carried out from both dry-ice and water-ice nuclei, using a variety of different effective visual albedos, but primarily for a thermal infrared of 0 (emission). Attention is given to cometary lifetimes and light curves and it was determined that the asymmetry in light curves occurs (occasionally) as a 'seasonal' effect due to a variation in the angle between the comet's rotation axis and the sun-comet line.

  11. Estimation of the galactic spiral pattern speed from Cepheids

    NASA Astrophysics Data System (ADS)

    Bobylev, V. V.; Bajkova, A. T.

    2012-10-01

    To study the peculiarities of the Galactic spiral density wave, we have analyzed the space velocities of Galactic Cepheids with propermotions from the Hipparcos catalog and line-of-sight velocities from various sources. First, based on the entire sample of 185 stars and taking R 0 = 8 kpc, we have found the components of the peculiar solar velocity ( u ⊙, v ⊙) = (7.6, 11.6) ± (0.8, 1.1) km s-1, the angular velocity of Galactic rotation Ω0 = 27.5 ± 0.5 km s-1 kpc-1 and its derivatives Ω'0 = -4.12 ± 0.10 km s-1 kpc-2 and Ω″0 = 0.85 ± 0.07 km s-1 kpc-3, the amplitudes of the velocity perturbations in the spiral density wave f R = -6.8 ± 0.7 and f θ = 3.3 ± 0.5 km s-1, the pitch angle of a two-armed spiral pattern ( m = 2) i = -4.6° ± 0.1° (which corresponds to a wavelength λ = 2.0 ± 0.1 kpc), and the phase of the Sun in the spiral density wave χ⊙ = -193° ± 5°. The phase χ⊙ has been found to change noticeably with the mean age of the sample. Having analyzed these phase shifts, we have determined the mean value of the angular velocity difference Ω p - Ω, which depends significantly on the calibrations used to estimate the individual ages of Cepheids. When estimating the ages of Cepheids based on Efremov's calibration, we have found |Ω p - Ω0| = 10 ± 1stat ± 3syst km s-1 kpc-1. The ratio of the radial component of the gravitational force produced by the spiral arms to the total gravitational force of the Galaxy has been estimated to be f r0 = 0.04 ± 0.01.

  12. Filaments of neutral hydrogen toward the Galactic anticenter

    NASA Astrophysics Data System (ADS)

    Tamanaha, Christopher M.

    1994-10-01

    Wide-bandwidth H I 21 cm maps made with the Hat Creek 26 m (85 foot) telescope toward the Galactic anticenter reveal a wealth of filamentary structure at intermediate negative velocities. In order to study this filamentary structure, a median filtering technique is used to remove the smooth, large-scale background. Structures with widths less than about 5 deg are preserved. The filaments are untangled from one another by following those that have continuous velocity gradients. The selected filaments are oriented parallel to the Galactic plane and cover a range of lengths between 7 deg and 40 deg. Their appearance is similar to lines of constant longitude on the surface of a tilted sphere centered near l = 185 deg, b = 0 deg with a radius of about 25 deg. They are easily visible at intermediate velocities but become tangled in a web of filamentary structures at velocities greater than -17 km/s relative to the local standard of rest. I fit models of filaments on the surface of such a sphere to the data. The models are constrained to match the observations in both projected position and radial velocity. Velocity fields resulting from systemic motion, spherical expansion, differential rotation, and poloidal motion along the surface of the sphere from the poles toward the equator are considered. There is little, if any, evidence in the velocity fields for the filaments being on the surface of an expanding or contracting sphere. The spherical morphology may still be correct, but no robust signature of spherical expansion or poloidal motion resulting from a uniform magnetic field is observed. The overall negative radial velocities of the filaments (approximately -30 km/s) are explained as arising either from the noncircular orbits of gas in the Galaxy or from the impact of high-velocity clouds, observed toward the anticenter, with the disk in the outer Galaxy. The feasibility of these explanations depends upon the distance to the high-velocity clouds and intermediate

  13. Apsidal rotation in the eclipsing binary AG Persei

    NASA Technical Reports Server (NTRS)

    Koch, Robert H.; Woodward, Edith J.

    1987-01-01

    New three-filter light curves of AG Per are given. These yield times of minimum light in accord with the known rate of apsidal rotation but do not improve that rate. These light curves and all other published historical ones have been treated with the code EBOP and are shown to give largely consistent geometric and photometric parameters no matter which orientation of the orbit is displayed to the observer.

  14. Asymmetric supernova remnants generated by Galactic, massive runaway stars

    NASA Astrophysics Data System (ADS)

    Meyer, D. M.-A.; Langer, N.; Mackey, J.; Velázquez, P. F.; Gusdorf, A.

    2015-07-01

    After the death of a runaway massive star, its supernova shock wave interacts with the bow shocks produced by its defunct progenitor, and may lose energy, momentum and its spherical symmetry before expanding into the local interstellar medium (ISM). We investigate whether the initial mass and space velocity of these progenitors can be associated with asymmetric supernova remnants. We run hydrodynamical models of supernovae exploding in the pre-shaped medium of moving Galactic core-collapse progenitors. We find that bow shocks that accumulate more than about 1.5 M⊙ generate asymmetric remnants. The shock wave first collides with these bow shocks 160-750 yr after the supernova, and the collision lasts until 830-4900 yr. The shock wave is then located 1.35-5 pc from the centre of the explosion, and it expands freely into the ISM, whereas in the opposite direction it is channelled into the region of undisturbed wind material. This applies to an initially 20 M⊙ progenitor moving with velocity 20 km s-1 and to our initially 40 M⊙ progenitor. These remnants generate mixing of ISM gas, stellar wind and supernova ejecta that is particularly important upstream from the centre of the explosion. Their light curves are dominated by emission from optically thin cooling and by X-ray emission of the shocked ISM gas. We find that these remnants are likely to be observed in the [O III] λ 5007 spectral line emission or in the soft energy-band of X-rays. Finally, we discuss our results in the context of observed Galactic supernova remnants such as 3C 391 and the Cygnus Loop.

  15. GCIRS 7, a pulsating M1 supergiant at the Galactic centre . Physical properties and age

    NASA Astrophysics Data System (ADS)

    Paumard, T.; Pfuhl, O.; Martins, F.; Kervella, P.; Ott, T.; Pott, J.-U.; Le Bouquin, J. B.; Breitfelder, J.; Gillessen, S.; Perrin, G.; Burtscher, L.; Haubois, X.; Brandner, W.

    2014-08-01

    Context. The stellar population in the central parsec of the Galaxy is dominated in mass and number by an old (several Gyr) population, but young (6 ± 2 Myr), massive stars dominate the luminosity function. The most luminous of these stars is an M1 supergiant, GCIRS 7. Aims: We have studied GCIRS 7 in order to constrain the age of the recent star formation event in the Galactic centre and to characterise it as a visibility and phase reference for observations of the Galactic centre with the interferometric instrument GRAVITY, which will equip the Very Large Telescope Interferometer (VLTI) in the near future. Methods: We present the first H-band interferometric observations of GCIRS 7, obtained using the PIONIER visitor instrument on the VLTI using the four 8.2-m unit telescopes. In addition, we present unpublished K-band VLTI/AMBER data and build JHKL light curves based on archival data spanning almost 40 years, and measured the star's effective temperature using SINFONI integral field spectroscopy. Results: GCIRS 7 is marginally resolved in the H band with a uniform-disk diameter θUD(2013) = 1.076 ± 0.093 mas (RUD(2013) = 960 ± 92 R⊙ at 8.33 ± 0.35 kpc). We detect a significant circumstellar contribution in the K band. The star and its environment are variable in brightness and in size. The photospheric H-band variations are modelled well with two periods: P0 ≃ 470 ± 10 days (amplitude ≃0.64 mag) and long secondary period PLSP ≃ 2700 - 2850 days (amplitude ≃1.1 mag). As measured from 12CO equivalent width, ⟨Teff⟩ = 3600 ± 195 K. Conclusions: The size, periods, luminosity (⟨Mbol⟩ = -8.44 ± 0.22), and effective temperature are consistent with an M1 supergiant with an initial mass of 22.5 ± 2.5 M⊙ and an age of 6.5-10 Myr (depending on rotation). This age is in remarkable agreement with most estimates for the recent star formation event in the central parsec. Caution should be taken when using this star as a phase reference or visibility

  16. Gamma ray constraints on the Galactic supernova rate

    NASA Technical Reports Server (NTRS)

    Hartmann, D.; The, L.-S.; Clayton, Donald D.; Leising, M.; Mathews, G.; Woosley, S. E.

    1991-01-01

    We perform Monte Carlo simulations of the expected gamma ray signatures of Galactic supernovae of all types to estimate the significance of the lack of a gamma ray signal due to supernovae occurring during the last millenium. Using recent estimates of the nuclear yields, we determine mean Galactic supernova rates consistent with the historic supernova record and the gamma ray limits. Another objective of these calculations of Galactic supernova histories is their application to surveys of diffuse Galactic gamma ray line emission.

  17. Curved characteristics behind blast waves.

    NASA Technical Reports Server (NTRS)

    Laporte, O.; Chang, T. S.

    1972-01-01

    The behavior of nonisentropic flow behind a propagating blast wave is theoretically studied. Exact solutions, expressed in closed form in terms of elementary functions, are presented for three sets of curved characteristicseind a self-similar, strong blast wave.

  18. Parabolic curves in Lie groups

    SciTech Connect

    Pauley, Michael

    2010-05-15

    To interpolate a sequence of points in Euclidean space, parabolic splines can be used. These are curves which are piecewise quadratic. To interpolate between points in a (semi-)Riemannian manifold, we could look for curves such that the second covariant derivative of the velocity is zero. We call such curves Jupp and Kent quadratics or JK-quadratics because they are a special case of the cubic curves advocated by Jupp and Kent. When the manifold is a Lie group with bi-invariant metric, we can relate JK-quadratics to null Lie quadratics which arise from another interpolation problem. We solve JK-quadratics in the Lie groups SO(3) and SO(1,2) and in the sphere and hyperbolic plane, by relating them to the differential equation for a quantum harmonic oscillator00.

  19. On the rotation of elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Binney, J.

    1978-01-01

    The tensor virial theorem is applied to models of early-type galaxies. First the theorem is applied to rotating elliptical galaxies whose constant-density surfaces are similar ellipsoids. A relationship is obtained between the observed rotations and the forms of generally triaxial galaxies. By applying the results of Robert (1962) to the evaluation of the components of the Chandrasekhar tensor which occurs in this relationship, it is found that the form of a galaxy that lacks global velocity anisotropy uniquely determines the ratio of its rotational and random kinetic energies independently of the radial density profile of that galaxy. A distribution of three-dimensional prolate spheroids is derived which accounts for the observed distribution of ellipticities reported by Sandage, Freeman, and Stokes (1970). This is then used to derive curves giving the expected frequency of occurrence of galaxies of given rotational velocities for each of a number of different apparent elongations on the sky. It is found that if elliptical galaxies are prolate, there should be little correlation between apparent ellipticity and rotation velocity.

  20. Flow over riblet curved surfaces

    NASA Astrophysics Data System (ADS)

    Loureiro, J. B. R.; Silva Freire, A. P.

    2011-12-01

    The present work studies the mechanics of turbulent drag reduction over curved surfaces by riblets. The effects of surface modification on flow separation over steep and smooth curved surfaces are investigated. Four types of two-dimensional surfaces are studied based on the morphometric parameters that describe the body of a blue whale. Local measurements of mean velocity and turbulence profiles are obtained through laser Doppler anemometry (LDA) and particle image velocimetry (PIV).

  1. Smallest Black Hole in Galactic Nucleus Detected

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-08-01

    A team of astronomers have reported the detection of the smallest black hole (BH) ever observed in a galactic nucleus. The BH is hosted in the center of dwarf galaxy RGG 118, and it weighs in at 50,000 solar masses, according to observations made by Vivienne Baldassare of University of Michigan and her collaborators. Small Discoveries: Why is the discovery of a small nuclear BH important? Some open questions that this could help answer are: - Do the very smallest dwarf galaxies have BHs at their centers too? Though we believe that there's a giant BH at the center of every galaxy, we aren't sure how far down the size scale this holds true. - What is the formation mechanism for BHs at the center of galaxies? - What's the behavior of the M-sigma relation at the low-mass end? The M-sigma relation is an observed correlation between the mass of a galaxy's central BH and the velocity dispersion of the stars in the galaxy. This relation is incredibly useful for determining properties of distant BHs and their galaxies empirically, but little data is available to constrain the low-mass end of the relation. M-sigma relation, plotting systems with dynamically-measured black hole masses. RGG 118 is plotted as the pink star. The solid and dashed lines represent various determinations of scaling relations. Credit: Baldassare et al. 2015. Identifying a Black Hole: RGG 118 was identified as a candidate host for an accreting, nuclear BH from the catalog of dwarf galaxies observed in the Sloan Digital Sky Survey. Baldassare and her team followed up with high-resolution spectroscopy from the Clay telescope in Chile and Chandra x-ray observations. Using these observations, the team determined that RGG 118 plays host to a massive BH at its center based on three clues: 1) narrow emission line ratios, which is a signature of accretion onto a massive BH, 2) the presence of broad emission lines, indicating that gas is rotating around a central BH, and 3) the existence of an X-ray point

  2. Modeling rapidly rotating stars

    NASA Astrophysics Data System (ADS)

    Rieutord, M.

    2006-06-01

    We review the quest of modeling rapidly rotating stars during the past 40 years and detail the challenges to be taken up by models facing new data from interferometry, seismology, spectroscopy... We then present the progress of the ESTER project aimed at giving a physically self-consistent model for the structure and evolution of rapidly rotating stars.

  3. Rotatable shear plate interferometer

    DOEpatents

    Duffus, Richard C.

    1988-01-01

    A rotatable shear plate interferometer comprises a transparent shear plate mounted obliquely in a tubular supporting member at 45.degree. with respect to its horizontal center axis. This tubular supporting member is supported rotatably around its center axis and a collimated laser beam is made incident on the shear plate along this center axis such that defocus in different directions can be easily measured.

  4. CONTROL ROD ROTATING MECHANISM

    DOEpatents

    Baumgarten, A.; Karalis, A.J.

    1961-11-28

    A threaded rotatable shaft is provided which rotates in response to linear movement of a nut, the shaft being surrounded by a pair of bellows members connected to either side of the nut to effectively seal the reactor from leakage and also to store up energy to shut down the reactor in the event of a power failure. (AEC)

  5. THE OLD ROTATION, 2005

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Old Rotation (circa 1896) is the oldest, continuous cotton experiment in the world. Its 13 plots on 1 acre of land on the campus of Auburn University continue to document the long-term effects of crop rotations with and without winter legumes (crimson clover) as a source of nitrogen for cotton,...

  6. Dust Attenuation Curve in External Galaxies: Radiative Transfer Model in Turbulent Medium

    NASA Astrophysics Data System (ADS)

    Seon, Kwangil

    2015-08-01

    The dust attenuation curve of starlight in galactic environments is investigated through radiative transfer simulations in a spherical, turbulent interstellar medium (ISM), which is modeled using fractional Brownian motion structures appropriate for the isothermal turbulent ISM. The photon source is uniformed distributed within a varying radius in the medium. Extinction and scattering properties for the Milky Way (MW), Large Magellanic Cloud and Small Magellanic Cloud (SMC) are considered. Attenuation curves consistent in overall shape with the “Calzetti attenuation law” are found by adopting the extinction and scattering curves that are similar to the MW-type dust, but with no or a much weaker 2175Å UV bump. The resulting attenuation curves are well represented by a modified Calzetti curve with varying slope and UV bump strength. A strong correlation between the slope and UV bump strength, with steeper curve having stronger bump as revealed in star-forming galaxies, is also found. It is also illustrated that the attenuation curve strongly depends not only on extinction curve but also on scattering albedo.

  7. A Degeneracy in DRW Modelling of AGN Light Curves

    NASA Astrophysics Data System (ADS)

    Kozłowski, Szymon

    2016-04-01

    Individual light curves of active galactic nuclei (AGNs) are nowadays successfully modelled with the damped random walk (DRW) stochastic process, characterized by the power exponential covariance matrix of the signal, with the power β = 1. By Monte Carlo simulation means, we generate mock AGN light curves described by non-DRW stochastic processes (0.5 ≤ β ≤ 1.5 and β ≠ 1) and show they can be successfully and well-modelled as a single DRW process, obtaining comparable goodness of fits. A good DRW fit, in fact, may not mean that DRW is the true underlying process leading to variability and it cannot be used as a proof for it. When comparing the input (non-DRW) and measured (DRW) process parameters, the recovered time scale (amplitude) increases (decreases) with the increasing input β. In practice, this means that the recovered DRW parameters may lead to biased (or even non-existing) correlations of the variability and physical parameters of AGNs if the true AGN variability is caused by non-DRW stochastic processes. The proper way of identifying the processes leading to variability are model-independent structure functions and/or power spectral densities and then using such information on the covariance matrix of the signal in light curve modelling.

  8. A degeneracy in DRW modelling of AGN light curves

    NASA Astrophysics Data System (ADS)

    Kozłowski, Szymon

    2016-07-01

    Individual light curves of active galactic nuclei (AGNs) are nowadays successfully modelled with the damped random walk (DRW) stochastic process, characterized by the power exponential covariance matrix of the signal, with the power β = 1. By Monte Carlo simulation means, we generate mock AGN light curves described by non-DRW stochastic processes (0.5 ≤ β ≤ 1.5 and β ≠ 1) and show they can be successfully and well modelled as a single DRW process, obtaining comparable goodness of fits. A good DRW fit, in fact, may not mean that DRW is the true underlying process leading to variability and it cannot be used as a proof for it. When comparing the input (non-DRW) and measured (DRW) process parameters, the recovered time-scale (amplitude) increases (decreases) with the increasing input β. In practice, this means that the recovered DRW parameters may lead to biased (or even non-existing) correlations of the variability and physical parameters of AGNs if the true AGN variability is caused by non-DRW stochastic processes. The proper way of identifying the processes leading to variability are model-independent structure functions and/or power spectral densities and then using such information on the covariance matrix of the signal in light-curve modelling.

  9. Arthroscopic rotator cuff repair.

    PubMed

    Burkhart, Stephen S; Lo, Ian K Y

    2006-06-01

    Arthroscopic rotator cuff repair is being performed by an increasing number of orthopaedic surgeons. The principles, techniques, and instrumentation have evolved to the extent that all patterns and sizes of rotator cuff tear, including massive tears, can now be repaired arthroscopically. Achieving a biomechanically stable construct is critical to biologic healing. The ideal repair construct must optimize suture-to-bone fixation, suture-to-tendon fixation, abrasion resistance of suture, suture strength, knot security, loop security, and restoration of the anatomic rotator cuff footprint (the surface area of bone to which the cuff tendons attach). By achieving optimized repair constructs, experienced arthroscopic surgeons are reporting results equal to those of open rotator cuff repair. As surgeons' arthroscopic skill levels increase through attendance at surgical skills courses and greater experience gained in the operating room, there will be an increasing trend toward arthroscopic repair of most rotator cuff pathology. PMID:16757673

  10. Interferometry for rotating sources

    NASA Astrophysics Data System (ADS)

    Velle, S.; Mehrabi Pari, S.; Csernai, L. P.

    2016-06-01

    The two particle interferometry method to determine the size of the emitting source after a heavy ion collision is extended. Following the extension of the method to spherical expansion dynamics, here we extend the method to rotating systems. It is shown that rotation of a cylindrically symmetric system leads to modifications, which can be perceived as spatial asymmetry by the "azimuthal HBT" method. We study an exact rotating and expanding solution of the fluid dynamical model of heavy ion reactions. We consider a source that is azimuthally symmetric in space around the axis of rotation, and discuss the features of the resulting two particle correlation function. This shows the azimuthal asymmetry arising from the rotation. We show that this asymmetry leads to results similar to those given by spatially asymmetric sources.

  11. Rotation sensor switch

    DOEpatents

    Sevec, John B.

    1978-01-01

    A protective device to provide a warning if a piece of rotating machinery slows or stops comprises a pair of hinged weights disposed to rotate on a rotating shaft of the equipment. When the equipment is rotating, the weights remain in a plane essentially perpendicular to the shaft and constitute part of an electrical circuit that is open. When the shaft slows or stops, the weights are attracted to a pair of concentric electrically conducting disks disposed in a plane perpendicular to the shaft and parallel to the plane of the weights when rotating. A disk magnet attracts the weights to the electrically conducting plates and maintains the electrical contact at the plates to complete an electrical circuit that can then provide an alarm signal.

  12. THE EDGE OF THE YOUNG GALACTIC DISK

    SciTech Connect

    Carraro, Giovanni; Vazquez, Ruben A.; Perren, Gabriel; Moitinho, Andre

    2010-08-01

    In this work, we report and discuss the detection of two distant diffuse stellar groups in the third Galactic quadrant. They are composed of young stars, with spectral types ranging from late O to late B, and lie at galactocentric distances between 15 and 20 kpc. These groups are located in the area of two cataloged open clusters (VdB-Hagen 04 and Ruprecht 30), projected toward the Vela-Puppis constellations, and within the core of the Canis Major overdensity. Their reddening and distances have been estimated by analyzing their color-color and color-magnitude diagrams, derived from deep UBV photometry. The existence of young star aggregates at such extreme distances from the Galactic center challenges the commonly accepted scenario in which the Galactic disk has a sharp cutoff at about 14 kpc from the Galactic center and indicates that it extends to much greater distances (as also supported by the recent detection of CO molecular complexes well beyond this distance). While the groups we find in the area of Ruprecht 30 are compatible with the Orion and Norma-Cygnus spiral arms, respectively, the distant group we identify in the region of VdB-Hagen 04 lies in the external regions of the Norma-Cygnus arm, at a galactocentric distance ({approx}20 kpc) where no young stars have been detected so far in the optical.

  13. Argon and neon in Galactic nebulae

    NASA Technical Reports Server (NTRS)

    Simpson, Janet P.; Bregman, Jesse D.; Dinerstein, H. L.; Lester, Dan F.; Rank, David M.; Witteborn, F. C.; Wooden, D. H.

    1995-01-01

    KAO observations of the 6.98 micron line of (Ar II), and KAO and ground-based observations of the 8.99 micron line of (Ar III) and the 12.8 micron line of (Ne II) are presented for a number of Galactic H II regions and planetary nebulae.

  14. Terrestrial impact of the galactic historical SNe

    NASA Astrophysics Data System (ADS)

    Iyudin, A. F.

    2002-03-01

    Galactic supernovae (SNe) of the last millennium have left their signatures in many energy domains, with the optical being the best known due to the absence of astronomical instruments before the 17th century being more sophisticated than the human eye. Alongside with these records found in the scriptes of the ancient eastern and western astronomers, quite recently other signatures were recognised as valuable tracers of historical SNe, for example, different ionic and/or molecular depositions in the polar ice, radioactive isotopes depositions, and the /γ-ray emission from the radioactive 44Ti produced in the SN explosion. While the ice depositions are expected to be the result of the supernova flash in the UV and soft X-rays, the 60Fe radioactive isotope deposition into the deep-ocean ferromanganese crust is the result of direct isotope transfer by cosmic rays dust grains originating in the SN blast wave. These and other impacts of the galactic SNe are important from the point of view of their possible influence on the terrestrial environment. In this paper we consider known tracers of historical SNe and compare them to the proposed new tracer based on the atmospheric response to the galactic supernova emission in the UV and X-rays. In addition to using the 44Ti radioactive decay line photons for uncovering hidden galactic supernova remnants by imaging /γ-ray telescopes, all such tracers form an important complement to the historical SNe record.

  15. Einstein Observations of Galactic supernova remnants

    NASA Technical Reports Server (NTRS)

    Seward, Frederick D.

    1990-01-01

    This paper summarizes the observations of Galactic supernova remnants with the imaging detectors of the Einstein Observatory. X-ray surface brightness contours of 47 remnants are shown together with gray-scale pictures. Count rates for these remnants have been derived and are listed for the HRI, IPC, and MPC detectors.

  16. The Edge of the Young Galactic Disk

    NASA Astrophysics Data System (ADS)

    Carraro, Giovanni; Vázquez, Ruben A.; Costa, Edgardo; Perren, Gabriel; Moitinho, André

    2010-08-01

    In this work, we report and discuss the detection of two distant diffuse stellar groups in the third Galactic quadrant. They are composed of young stars, with spectral types ranging from late O to late B, and lie at galactocentric distances between 15 and 20 kpc. These groups are located in the area of two cataloged open clusters (VdB-Hagen 04 and Ruprecht 30), projected toward the Vela-Puppis constellations, and within the core of the Canis Major overdensity. Their reddening and distances have been estimated by analyzing their color-color and color-magnitude diagrams, derived from deep UBV photometry. The existence of young star aggregates at such extreme distances from the Galactic center challenges the commonly accepted scenario in which the Galactic disk has a sharp cutoff at about 14 kpc from the Galactic center and indicates that it extends to much greater distances (as also supported by the recent detection of CO molecular complexes well beyond this distance). While the groups we find in the area of Ruprecht 30 are compatible with the Orion and Norma-Cygnus spiral arms, respectively, the distant group we identify in the region of VdB-Hagen 04 lies in the external regions of the Norma-Cygnus arm, at a galactocentric distance (~20 kpc) where no young stars have been detected so far in the optical.

  17. Galactic Winds and Intragroup Medium Energetics

    NASA Technical Reports Server (NTRS)

    Dupke, Renato; Lloyd-Davies, Ed; Bregman, Joel

    2004-01-01

    The main objective of this proposal was to study the metallicity distribution of HCG 97 with the goals of determining the SN Type enrichment, the strength of galactic winds and how it impacts on the evolution of cluster's ICM within the framework of hierarchical formation scenarios.

  18. Young Massive Clusters in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Figer, D. F.

    2004-12-01

    The three young clusters in the Galactic Center represent the closest examples of massive starbursts and they define the upper mass limit of the Galactic cluster mass functions. In this review, I describe the characteristics and content of the Arches, Quintuplet, and Central clusters. They each are more massive than any other cluster in the Galaxy, and the Arches cluster, in particular, has a mass and age that make it ideal for studies of massive stellar evolution and dense stellar systems. A preliminary measurement indicates that the initial mass function in the Galactic center is top-heavy, suggesting an environmental effect that has otherwise been absent in similar observations for Galactic clusters. Given the relatively more evolved nature of the Quintuplet and Central clusters, these clusters contain stars in a wide range of evolutionary states, including Luminous Blue Variables and Wolf-Rayet stars. The Quintuplet cluster provides a particularly interesting view of the most massive stars that are known, the Pistol Star and FMM362. An analysis of the mass spectrum in the Arches cluster suggests an upper mass cutoff of ˜150-200 M⊙.

  19. Star formation around active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Keel, William C.

    1987-01-01

    Active galactic nuclei (Seyfert nuclei and their relatives) and intense star formation can both deliver substantial amounts of energy to the vicinity of a galactic nucleus. Many luminous nuclei have energetics dominated by one of these mechanisms, but detailed observations show that some have a mixture. Seeing both phenomena at once raises several interesting questions: (1) Is this a general property of some kinds of nuclei? How many AGNs have surround starbursts, and vice versa? (2) As in 1, how many undiscovered AGNs or starbursts are hidden by a more luminous instance of the other? (3) Does one cause the other, and by what means, or do both reflect common influences such as potential well shape or level of gas flow? (4) Can surrounding star formation tell us anything about the central active nuclei, such as lifetimes, kinetic energy output, or mechanical disturbance of the ISM? These are important points in the understanding of activity and star formation in galactic nuclei. Unfortunately, the observational ways of addressing them are as yet not well formulated. Some preliminary studies are reported, aimed at clarifying the issues involved in study of the relationships between stellar and nonstellar excitement in galactic nuclei.

  20. Modeling the evolution of galactic magnetic fields

    SciTech Connect

    Yar-Mukhamedov, D.

    2015-04-15

    An analytic model for evolution of galactic magnetic fields in hierarchical galaxy formation frameworks is introduced. Its major innovative components include explicit and detailed treatment of the physics of merger events, mass gains and losses, gravitational energy sources and delays associated with formation of large-scale magnetic fields. This paper describes the model, its implementation, and core results obtained by its means.