bluuebunny/crossref_metadata_2025 huggingface dataset:
Solar System Size Proto-Stellar Sources Embedded in the ρ Oph Dark Cloud
Authors: Zinnecker H. , Chelli A. , Perrier C.
Published: June 2019

High spatial resolution infrared observations (mostly at L, some at K) of several young stars in the ρ Oph dark cloud were obtained with the specklegraph at the ESO 3.6m telescope in Chile in July 1985. Sources included EL29, EL21, EL14 and EL9 (Elias 1978, Table 2), and were all measured in two orthogonal directions, W-E (PA=90°) and N-S (PA=180°). Here we shall present visibility functions for EL29 and EL21 and indicate the spatial structure and dimension of these objects. We refer to Elias (1978, p.468/69) for earlier studies of EL29 and EL21.
CO Observations of B361 and its Environment
Authors: Hirano N. , Hasegawa T. , Kameya O. , Takakubo K. , Seki M.
Published: June 2019

Extensive mapping of the CO and 13CO (J = 1-0) emission of the Bok globule, B361, is reported. The observations were made with the 4-m millimeter-wave telescope of Nagoya University. The mapped area extends over 60'x40′ which includes some filamentary dark clouds: L967, L964, L961, and L960, located to the west of B361.
Massive Star Formation in W49
Authors: Dreher J. , Vogel S. , Terebey S. , Welch W. J.
Published: June 2019

W49 is the most luminous H II region complex in the galaxy. VLA maps in the continuum reveal a complex of more than two dozen compact HII regions, including a ring-like distribution of a dozen such regions within a volume of 1 pc. In addition to the VLA maps, we have obtained high resolution maps in this field with the Hat Creek Millimeter Interferometer in the following molecular lines: HCO+(1-0), H13CO+(1-0), SiO(v = 0, J = 2-1), SiO(v = 1, J = 2-1), H13CN(1-0), HC15N(1-0), SO2 [8(3,5)-9(2,8)], SO2[8(1,7)-8(0,8)], SO[2(2)-1(1)], and CH3CH2CN[10(1,10)-9(1,9)], all near 3 mm wavelengh. These maps will be discussed. The HCO+distribution corresponds to the larger scale structures observed in the continuum maps. In contrast the SO and SiO sources are quite compact. Using the detailed molecular line results obtained in the ORION/KL region as a guide, we are able to identify these latter sources as regions in which the star formation is at an earlier stage, regions where there are outflows.
The Submillimetre Wavelength Spectrum of Orion A
Authors: White Glenn J. , Monteiro Tania , Rainey Ruth , Richardson Kevin , Griffin Matthew , Avery L.
Published: June 2019

We report on the first submillimetre wavelength spectral scan of the Orion A molecular cloud in the frequency range 342-463 GHz (0.88-0.65 mm) using the Queen Mary College Submillimetre Heterodyne Receiver at UKIRT. Twenty-eight molecular transitions were detected, the majority of these for the first time. The lines include transitions of CO, CS, HCN, HCO+, H2CO, H2CS, SO, SO2, CCH, SiO and CH3OH. Upper limits are reported for a number of lines including CO+ and the ground state transition of NH2. A number of the lines are surprisingly intense, and we will present maps of the relative distributions of HCO+, HCN, H2CO and CCH, which show striking differences in their spatial structures. We will present details of the excitation of a number of the lines based on the results from this survey.
The Sgr B2 Region Seen at 43 GHZ
Authors: Hirabayashi Hisashi , Akabane Kenji , Morimoto Masaki , Sofue Yosiaki , Inoue Makato , Handa Toshihiro
Published: June 2019

The Sgr B2 region was mapped at 43 GHz (λ = 6.9 mm) with the 45m radio telescope of Nobeyama Radio Observatory. The observing parameters were: a) half power beamwidth 38″, b) pointing accuracy better than 10″, c) central frequency 43.0 GHz, d) bandwidth 500 MHz, and e) system noise temperature 400 K; and the observational aspects were: a) mapping with one polarization, b) liquid-nitrogen cooled load switching and c) reduction by NOD-2 programme. The obtained map is shown in Figure 1. Sgr B2 is resolved into several components which correspond to those by Martin and Downes (1972) and Downes et al. (1978). But the component at RA = 17h44m11.8s Dec. = −28°23′55″ at 1950 is not seen in Martin and Downes (1972) nor in the 5 GHz map of Downes et al. (1978), although the feature is seen in the 10.7 GHz map of Downes et al. (1978). The components derived from the map in Figure 1 by a morphological estimate are listed in Table 1. The total flux density of the region is 146J±30 Jy. The intensity calibration was made by observing NGC 7027.
Sub-Millimeter Spectral Line Observations in Very Dense Regions
Authors: Evans Neal J. , Mundy Lee G. , Davis John H. , Bout Paul Vanden
Published: June 2019

In a search for very high density (n ≳ 107 cm−3) regions, the Millimeter Wave Observatory 5-m telescope was used to observe several submillimeter lines. The regions studied were Orion A, M17, S140, and NGC2024. The lines were CS(J=7-6), H2CO(JK-1K1=515→414), and HCN(J=4-3). These data are combined with data at millimeter wavelengths to derive the volume density and the results are compared to those deduced from millimeter lines alone (Snell et al. 1984). In NGC2024, higher densities (≳ 107 cm−3) are clearly indicated by the sub-mm lines than were derived by Snell et al. In M17, derived densities are also higher, but uncertainties overlap the Snell et al. solutions. The range of densities derived from CS and HCN are consistent. The sub-millimeter lines of these species appear to be good probes of the highest densities present in regions of active star formation.
A Study of Continuum Emission at 3.5 mm from Selected H II Regions
Authors: Gordon M. A. , Jewell P. R. , Kaftan-Kassim M.A. , Salter C. J.
Published: June 2019

As the first part of a program to investigate the thermal emission of dust at millimeter wavelengths, we present maps of the continuum emission from radio-bright HII regions. These maps have been made with a filled aperture telescope, the NRAO 12-m telescope at Kitt Peak, with a HPBW of 70 arc seconds at 3.5 mm. We used a switched dual-beam technique and a restoration algorithm developed by Emerson et al. (1979 Astron. Ap. 76, 92). We compare these maps with maps made at centimeter wavelengths.
MON R2: A Blister Type H II Region
Authors: Massi M. , Felli M. , Catarzi M. , Simon M.
Published: June 2019

The compact H II region MONR2 has been studied with the VLA at 6 and 1.3 cm (Massi, Felli, and Simon 1985). With a resolution of 1″ the source is now well resolved. The H II region has a circular shape 27″ in diameter and a non uniform surface brightness distribution. The peak of the emission is concentrated in a small sharp strip along the SE edge.
Disks and Toroids Around Young Stars
Authors: Rodríguez L.F.
Published: June 2019

We review the observational evidence for interstellar and circumstellar size gaseous structures that appear to be collimating the bipolar outflows observed in regions of star formation. In particular, there is growing evidence for circumstellar disk-like objects that may be related to a protoplanetary cloud like the one that once surrounded the Sun. There are similarities between these disks around young stars and that found around the main sequence star β Pictoris. Both flattened structures around L1551 IRS5 and β Pictoris appear to have an inner “hole” with radius of a few tens of AU. On the other hand, there is observational support for focusing and collimation processes acting on the same source from tens of AU (circumstellar dimensions) to tenths of pc (interstellar dimensions).
High Velocity Co Wings in NGC 2071 and GL 490 Observed with the 45-m Telescope
Authors: Fukui Y. , Iwata T. , Takano T.
Published: June 2019

We have used the 45-m telescope for mapping two CO broad wing sources NGC 2071 and GL490 with a 15″ beam in the J = 1-0 line. We obtained 250 CO and 130 13CO spectra for NGC 2071 and 150 CO spectra for GL490. The observations were made with the highest angular resolution for the CO line and, as well, cover the whole extent of the outflows. The results reveal significant details of the angular distribution of the CO wings.
High Resolution Studies of Star-Forming Molecular Clouds
Authors: Sargent A. I. , Scoville N. Z. , Masson C. R. , Lo K. Y. , Phillips T. G.
Published: June 2019

Observations of star formation sites in a number of molecular clouds, including NGC 7538, NGC 2071, Cepheus A and K3-50A, have been made using the Owens Valley millimeter wave interferometer. The measurements of 12CO, 13CO, CS and continuum emission are at resolutions of order 7″. Continuum emission at 2.7 mm is detected from all the cloud cores and, in general, the 12CO interferometer maps reveal the presence of high velocity, bipolar outflows within 10″ of these continuum sources. Thus, the origins of the outflows are readily identifiable; the flows themselves appear to remain collimated on scales of less than 1017 cm. The orientations of the flows are similar to those seen at lower resolution, except in Cepheus A, where the interferometer is capable of distinguishing between two outflows which are confused in single telescope maps.
Masers in Star Forming Regions
Authors: Cohen R. J.
Published: June 2019

OH and H2O masers in star forming regions are important because they are readily detectable indicators of star formation and because they provide unique information on the kinematics and physical conditions in high density regions (106 – 1010 cm−3) surrounding young stars, regions which cannot be studied by other means at present. The Jodrell Bank MERLIN interferometer has been used to map a sample of OH and H2O masers associated with bipolar molecular outflows. The maps of Cepheus A show that the masers are closely associated with the densest compact H II regions at the centre of the flow. The masers appear to be located at the inner edges of the circumstellar disk thought to play a role in collimating the outflow. It is suggested that the H2O masers trace the interaction between the stellar wind and the dense molecular gas, and the OH masers trace shocks propagating into the molecular gas. Rapid and sometimes correlated variations in the maser emission suggest that radiative pumping is likely in this source (Rowland and Cohen, Mon. Not. R. Astr. Soc. in press). Study of the other sources is still in progress.
S106-IRS4: A Star Loosing Mass in the Centre of a Bipolar Nebula
Authors: Felli M. , Simon M.
Published: June 2019

S106-IRS4 is the brightest near IR source associated with the S106 bipolar nebula. It is located exactly at the centre of the bipolar structure, inside the narrow gap of emission between the two radio lobes. It is also a weak radio source. An analysis of the near IR photometric measurements and of the radio fluxes suggests the presence of an ionized envelope produced by mass loss of the early type star which is responsible for the ionization of the nebula (Felli et al. 1984).
Hydrodynamical Simulation of Bipolar Flows
Authors: Clausset F. , Combes F.
Published: June 2019

High velocity bipolar gas flows are observed very frequently towards regions of star formation, and it has been conjectured that almost every star of mass larger than 1 M⊙ could undergo a phase of mass ejection during its formation (see e.g. Lada 1985). To explain the collimation of gas flows at interstellar scale, models have been proposed based on a stellar wind or violent isotropic ejection of matter by the protostar, that is pressure collimated by the molecular cloud in which it is embedded (Canto 1980, Königl 1982). In some cases, a molecular disk is observed perpendicular to the direction of the flow, but it is not quite sufficient to collimate it, see for example the high resolution CS observations of Takano et al. (1984) and Kawabe et al. (1984). Also, collimation occurs at a distance smaller than 3x1013m, according to the optical emission line observations of Mundt and Fried (1983).
Sweeping-Magnetic-Twist Mechanism and Molecular Bipolar Flows
Authors: SHIBATA Kazunari , UCHIDA Yutaka
Published: June 2019

Uchida and Shibata have proposed the “sweeping-magnetic-twist” mechanism for the formation of astrophysical jets in relation to the accretion disks (disks around protostars, around black hole in the center of active galactic nuclei, and so on) in which a jet is accelerated by thejxBforce in the relaxing magnetic twist created in the winding-up of the poloidal magnetic field by the rotation of the contracting disk (Uchida and Shibata 1985a, b; Shibata and Uchida 1986a, b; Uchidaet al.1985). In this mechanism, a jet is collimated also by thejxBforce due to the large scale poloidal magnetic field whose footpoints are squeezed in the contracting disk. The main mechanism involved is different from that of centrifugal wind models (Blandford and Payne 1982, Pudritz and Norman 1983) and worked out indepentently, but the centrifugal effect itself is automatically built-in.
Elongated Structures Near Young Stars: Jets or Projection Effects?
Authors: Cantó J. , Sarmiento A. , Rodríguez L.F.
Published: June 2019

Recent observations in radio, infrared and visible wavelengths have revealed the presence of small, elongated gaseous structures that appear to emanate from young stars. These structures are frequently interpreted as jets, perhaps similar in nature to those observed in extragalactic objects. We argue that these apparent “jets” could simply be light emitted by, or reflected from the walls of the cavities expected to be formed when the winds of these young stars drive their surrounding gaseous medium away. When viewed from certain positions the radiation from the walls of these cavities appears to the observer as elongated structures. A simple model is presented to illustrate this projection effect.
High Resolution CO Observations of the Bipolar Nebula CRL2688
Authors: Kawabe R. , Kasuga T. , Ishiguro M. , Morita K-I. , Ukita N. , Kobayashi H. , Okumura S. , Fomalont E. B. , Kaifu N.
Published: June 2019

CRL2688 is suggested to be one of the proto-planetary nebulae which are probably at a stage in which the central star is evolving from the red giant phase with rapid mass loss (Zuckerman 1978). The bipolar shape in both the optical and H2emission indicates that a dense toroid of dust and gas obscures the star and surrounds the optical emission. The toroid is probably responsible for channelling the mass loss to the polar directions (Neyet al.1975, Morris 1981, Beckwithet al.1984). We present the results of mapping observations of CO (J = 1-0) emission from the expanding molecular envelope (Zuckermanet al.1976, Loet al.1976, Knappet al.1982, Thronsonet al.1983) of the bipolar reflection nebula CRL2688 using the Nobeyama 45-m telescope with a 1.5″ resolution at a 7″.5 observing spacing.
Star Formation in Molecular Cloud Cores
Authors: Shu Frank H. , Lizano Susana , Adams Fred C.
Published: June 2019

The problem of gravitational collapse and star formation is entirely different when the ratio of the mass of a molecular cloud Mcl to its magnetic flux Φ is high than when it is low. Magnetically-diluted overall collapse of a large dense core and the formation of an OB association or a bound cluster are the likely outcomes in the former case; quasi-static contraction of many small cores and their ultimate collapse to form a T association, in the latter. In our picture, the birth of a T association in a dark cloud like Taurus proceeds by ambipolar diffusion on a time-scale of ∼ 107 years. As magnetic and turbulent support is gradually lost from a small condensing core, it approaches a state resembling a slowly rotating singular isothermal sphere which, when it passes the brink of instability, collapses from “inside-out,” building up a central protostar and nebular disk. The emergent spectral energy distributions of theoretical models in this stage of protostellar evolution resemble closely those of recently found sources with steep spectra in the infrared. The protostellar phase is ended by the reversal of the infall by an intense stellar wind, whose ultimate source of energy derived from the differential rotation of the star. We argue that the initial breakout is likely to occur along the rotational poles, leading to collimated jets and bipolar outflows. The stellar jet eventually widens to sweep out gas in nearly all 4π steradian, revealing at the center a T Tauri star and a remnant nebular disk. We give rough scaling relations which must apply if an analogous process is to succeed for producing high mass stars.
Star Formation Driven by Thermal-Chemical Instability in a Pre-Galactic Gas Cloud
Authors: Sabano Yutaka , Tosa Makoto
Published: June 2019

The hydrogen molecule would work as an efficient coolant in a pre-galactic medium which is free from heavy elements. It is shown by linear perturbation analysis that molecular reactions lead to a thermal instability of condensation mode (Sabano and Yoshii 1977, Yoshii and Sabano 1979, Silk 1983). In the present paper we study the nonlinear growth of perturbations by a one-dimensional simulation of gas dynamics, which includes molecular reactions as well as an energy equation. We numerically follow the time-evolution of a spherically symmetric perturbation, which is superposed on initially uniform medium under free-fall contraction, by a Lagrangian hydrodynamical programme with an artificial viscosity (Richtmyer and Morton 1967).
Formation of Giant Molecular Clouds by Coagulation of Small Molecular Clouds in a Spiral Gravitational Potential
Authors: Tomisaka Kohji
Published: June 2019

The formation process of giant molecular clouds (GMCs) is investigated from the standpoint of the coagulation theory of molecular clouds. Small clouds collide with each other and grow to become massive ones. Ultimately they form GMCs with a finite lifetime. The occurrence of star formation in a GMC destroys it and consequently small clouds are formed again. We study the time evolution of the clouds which move through a spiral gravitational potential by an N-body simulation. Then the ensemble of clouds responds to the spiral potential and forms a spiral structure similar to that produced by hydrodynamical galactic shock. It is shown that GMCs are formed in the spiral arm region by collisions between clouds. The distribution of GMCs indicates their short lifetime, of the order of a few times 107 years.
A 200 pc Ring of Molecular Gas and an Outburst in the Galaxy M82
Authors: Nakai N. , Hayashi M. , Hasegawa T. , Sofue Y. , Handa T. , Sasaki M.
Published: June 2019

The CO (J=1-0) emission in M82 has been mapped with the Nobeyama 45-m telescope. The CO intensity distribution in the central region is resolved into two peaks. An axisymmetric model reveals a ring structure of molecular gas at a distance of 80-400 pc (centered near 200 pc) from the nucleus. This “200-pc ring” corresponds to just the region of a star formation burst. The molecular gas in M82 is also expanding out of the galactic plane with a velocity of 100-500 km s−1. The expansion energy of (0.1-1.4) x 1056 erg can be explained by the energy supply of supernovae in the central region.
Radio Continuum Observations of the Barred Galaxy NGC 4314
Authors: García-Barreto J.A. , Pişmiş P.
Published: June 2019

VLA observations have been made of the continuum emission at 20-cm from the barred spiral galaxy NGC 4314 with an angular resolution of 3.5 arcseconds that corresponds to a linear scale of approximately 156 pc at a distance to the galaxy. This resolution was sufficient to resolve the central region into several compact sources. The radiation is linearly polarized which may indicate a non-thermal origin. No emission was detected from the extended bar to a level of 130 Jy.
Large Scale Dissociation of Molecular Gas and Star Formation in M83
Authors: Allen R. J. , Atherton P. D. , Tilanus R.P.J.
Published: June 2019

Observations of the distribution of the CO-molecule in several prominent late-type galaxies indicate that the central HI depressions may very well be filled in with molecular gas. One such galaxy is M83 (NGC 5236) and, although the angular resolution of the CO-observations is insufficient to discern details on the scale of a spiral arm, it is known that CO is concentrated in the central regions within a radius of 1′. Furthermore, at a resolution of 50″, the CO profile at the position of the nucleus is as bright in M83 as it is for example in NGC 6946, IC 346 and M51.
CCD Echellogram of the Starburst Galaxy Tol 1924-416
Authors: Iye Masanori
Published: June 2019

The starburst galaxy Tol 1924-416 was observed on May 18, 1985 using an echelle spectrograph coupled with a cooled CCD camera (CASPEC) mounted at the Cassegrain focus of the ESO 3.6-m telescope. The echellogram covers the 4320-5260 A spectral range with 0.33 A/pixel and a spatial extent of 12 arcsec at 1.5 arcsec seeing. The estimated spectral resolution is 25 kms−1 and the velocity calibration error is as small as 3 km s−1.
FIR and Blue Luminosities and Gas Mass in Spiral Galaxies
Authors: Rengarajan T. N. , Verma R. P.
Published: June 2019

We present results on correlations between gas mass in spiral galaxies and their FIR and blue luminosities. We have used the published 12CO emission data of the University of Massachusetts and the FIR data from IRAS Galaxy Catalogue. In order to derive the H2 mass from 12CO data, we have used a relation of the form, N(H2) = A TA dV cm−2 with A = 2x1020 K−1 km s−1 cm−2. The total gas mass Mg was obtained using an additional factor of 1.36 to take care of the fraction of mass in He. Those galaxies that were classified as peculiar, interacting or included in Arp's catalogue were termed peculiar and the rest normal.
The Chemical Evolution of the Galactic Halo and Disk
Authors: Ferrini Federico , Palla Francesco , Shore Steven N.
Published: June 2019

The history of star formation in our galaxy is written in the metal abundance distributions of the stellar populations. Any star formation model is constrained by two facts. First, there was a period in the early stages of galactic evolution during which the metallicity of the gas out of which stars were being formed was significantly lower than the present epoch. Second, there is a paucity of extremely metal deficient stars in the disk of the galaxy.
The Discovery of the Chemical Composition - Kinematics Connection in the 1950's
Authors: Roman Nancy Grace
Published: June 2019

This paper reviews the recognition that kinematic characteristics of stars are related to their spectroscopic appearance on low and intermediate dispersion spectra. These differences result from the differences in the abundances of metals as determined from high dispersion spectra. Presumably, these abundance differences reflect differences in age. The high-velocity carbon stars share the molecular peculiarities of the high-velocity oxygen giants but, because of the greater strength of the bands of carbon-containing molecules, exhibit them to a greater degree.
Dark Matter in Spiral Galaxies
Authors: Van Der Kruit P.C.
Published: June 2019

In this review I will concentrate on three questions concerning the issue of dark matter in spiral galaxies. In the first place (and for the most part) I will discuss the analysis of rotation curves and the question whether the “maximum–disk hypothesis” is valid. Then I will discuss independent measurements of the disk mass distribution from the thickness of stellar and HI disks. Then follows a review of estimates of the flattening of the dark halos and a short discussion on the possible nature of the dark matter.
Measuring the Evolution of the M/L Ratio from the Fundamental Plane
Authors: Franx Marijn
Published: June 2019

The Fundamental plane provides a sensitive tool to measure the change in the M/L ratio of early type galaxies with redshift. The evolution of the M/L ratio is a function of the star formation history. It depends on the IMF, the formation redshift, and cosmology. Some model examples are shown, and a first result on the cluster Abell 665 at z=0.18 is given. The measurements confirm the cosmological surface brightness dimming, and imply an evolution of the (red) L/M ratio ∝ (1 + z)1,8±0,7. More data are needed to extend this result to higher redshifts, and to test the underlying assumptions.
The Morphological Evolution of Field Galaxies
Authors: Ellis Richard S.
Published: June 2019

I review two observational programs which, together, promise to unravel the detailed astrophysical evolution of normal field galaxies over the last 5-7 Gyr. Systematic ground-based spectroscopy of faint galaxies have revealed an increasing faint end slope for the luminosity function with redshift. The trend is strongest for galaxies undergoing intense star-formation. Deep images taken with the repaired HST can be used to count galaxies as a function of morphological type. Regular “Hubble sequence” galaxies follow the no-evolution prediction, but irregular/peculiar sources have a steeper count slope and provide the excess population. Although the overlap between the spectral and HST samples is currently small, plans to merge similar datasets should reveal the physical explanation for the demise of star formation in faint blue galaxies since z ≃0.5-l.
Flare Stars Database II
Authors: Tsvetkova K. P. , Tsvetkov M. K. , Stavrev K. Y.
Published: June 2019

Formation of the flare stars database (FSDB) continues (Tsvetkov et al. 1993). Since the beginning of systematic monitoring up to the present 1608 flare stars have been discovered with more than 3107 flare events observed for more than 9313 hours. (Repeated flares for stars from the solar neighbourhood, as well as the time used for their monitoring, are not yet considered).
Galactic Distribution of Symbiotic Stars
Authors: Tanco G. A. Medina , Steiner J. E.
Published: June 2019

Statistical distances to the known galactic symbiotic stars are derived from the calibration of the absolute K magnitude of galactic bulge symbiotic giants versus spectral type. The resulting space distributions of S, D and yellow symbiotic stars are studied.
An Estimate of the Dark-Matter Content in the Galaxy
Authors: Ninković Slobodan
Published: June 2019

The total mass of the Milky-Way dark corona and its contribution to the total mass of the Galaxy, is estimated by combining the limits imposed by the Local Group as probably bound and the constraints on the local escape velocity. The results: total mass of the Milky Way about 1.6 TM⊙ (dark corona over 1.5 TM⊙; T = 1012), local escape velocity about 600 kms−1.
Dark Matter Inside and Around Binary Galaxies: Formation of Interacting Galaxies
Authors: Anosova J. , Anandarao B.G.
Published: June 2019

We study here the dynamics of an extended shell of relatively low-mass (almost zero-mass) particles around massive binary systems by computer simulations in the framework of approximately restricted three-body problem. We examine a set of several initial conditions concerning the masses M1 and M2 of the binary components surrounded by N test particles in uniform random distribution on a spherical envelope of radius R expanding with a velocity V. We apply this model to binary galaxy systems with a halo of baryonic dark matter, e.g., massive black holes. It is shown that, initially, the shell expands isotropically with decreasing velocity and then, falls back into the system forming zones of compressed matter. At some moment of time there could be a collapse of these particles on to the heavier component of the binary. Further in time, a number of particles escape from the system. We consider a number of different models with different initial parameters. For models with smaller R and V, about one-half of the particles escape from the system; while for larger values the shell disrupts as a whole. The escaping particles form a collimated flow in the plane of the orbit of the binary. The position of the flow and the directions of motions depend on the position of the heavier component of the binary at the moment of the closest approach of the particles and on the ratio M1/M2.
Local and Global Optical, Far-Infrared (FIR) and X-ray Properties of the FIR Quiescent Sc Galaxy NGC 247
Authors: Mackie Glen , Fabbiano G. , Kim D.-W. , Ikebe Y.
Published: June 2019

We present an Optical, FIR and X-ray study of the low LFIR Sc galaxy, NGC 247. Global correlations (ie. B or X vs. Radio or FIR) in late-type spirals suggest that some luminosities do not scale linearly. We describe first results of a program to study emission in late-type spirals on local (kpc) scales to investigate this non-linear behaviour. Our data includes B, I, Hα+[Nii] CCD, IRAS 60, 100μm (Rice 1993), and ROSAT PSPC, (0.1-2.4keV) images. Since abstract submission we have added H I (Carignan and Puche 1990) and 1.49 GHz continuum (Condon 1987). The Hα+[Nii] is generally coextensive with the IRAS emission and H I. The brightest Hα+[Nii] region (log LHα~38.6 ergs s−1) in a region of low FIR flux, may possess a locally warm 60/100μm ratio suggesting a similarity with more luminous galaxies that have warm 60/100μm ratios globally. 1.49 GHz sources are not cospatial with bright X-ray sources, nor with Hα+[Nii]. Three extended 1.49 GHz sources are cospatial with very faint, soft X-ray emission, suggesting a SNR origin. We cannot rule out a direct 1.49 GHz/X-ray or 1.49 GHz/ H ii origin due to relativistic e− propagation. ROSAT PSPC results suggest 4 4σ (0.1-2.4 keV) X-ray sources are intrinsic. Their LX range of 1036–37 ergs s−1 is consistent with X-ray binaries, whilst the total LX = 3.0×1037 ergs s−1 is underluminous by ~3, compared to previous regression fits. A faint soft, LX ~ 1×1036 ergs s−1 nuclear X-ray feature may be a SNR outflow, and similar to plumes/outflows seen in starbursts, but 104 less luminous.
Chemodynamic and Photometric Evolution of Elliptical Galaxies
Authors: Loxen J. , Fritze-V. Alvensleben U. , Fricke K.J. , Hensler G.
Published: June 2019

In many hydrodynamical models of elliptical galaxies the absence of information about the detailed evolution of stars and the spectro-photometric output by hot gas and stars leads to a missing link between the data we obtain in observations (photons) and the internal behavior (dynamics) of a galaxy.
HST Far–UV Imaging of M 31, M 32 and NGC 205
Authors: Bertola F. , Chiosi C. , Bressan A. , Buson L.M. , Burstein D. , Alighieri S. Di Serego
Published: June 2019

Direct measures of luminosity functions, UV fluxes and colors of the hot stars that produce the UV turn–up in the SED of ellipticals and spiral bulges is the scientific goal of the HST observations presented here (see Bertola et al. 1995 for details). We concentrated our analysis on the hot stellar content of the M31 bulge. HST/FOC f/48 images were analyzed as observed (before the repair mission) through the F150W broad-band UV filter. We find that both individual stars and unresolved objects contribute to about 50% of the UV (1200-2450 Å) flux. Making use of the isochrones calculated by Bertelli et al. (1994) and Chiosi et al. (1994) together with the models of population synthesis presented by Bressan et al. (1994), we constructed theoretical CMDs to be compared with the CMD obtained by combining our F150W observations with the F175W observations of King et al. (1992). We conclude that the stars we resolved in M31 are classical P-AGB stars belonging to an old standard metallicity population. However, the P-EAGB and AGB-manqué stages as well as H-HB stars could be the source of the diffuse UV emission.
Populations in the z=0.23 Rich Cluster Abell 2390
Authors: Hutchings J.B. , Abraham R. , Smecker-Hane T. , Morris S. , Davidge T. , Rigler M. , Carlberg R. , Yee H. , Ellingson E.
Published: June 2019

We have spectra, colours and morphologies from the CFHT for 240 cluster members and 80 field galaxies over a 7 × 46 arcmin field. The cluster galaxies show strong radial gradients in colour, morphology, and spectrum. The central group has only red early-type galaxies of high central concentration, which must have formed at least 5 Gy ago. The population becomes bluer and shows an increasing fraction of disk morphology and recent star-formation with clustocentric radius, and eventually blends into the field. However, the fraction of blue galaxies is significantly lower than in Butcher-Oemler clusters, and there are only two starburst galaxies (one of which is the cluster cD). Fitting of line measures with stellar population models indicates that star-formation has been truncated in the 15-20% of the cluster galaxies that have strong Hδ absorption, and that these galaxies are not all blue. There is evidence that cluster galaxies are dusty compared with the field. The morphology gradient can be fit with models of disk fading. However, there is a small fraction of interacting and merging galaxies, which must play a part in the population evolution. The cluster is accreting from the field in a non-violent way, including some distinct subgroups. This is different from what is seen at both higher and lower redshift, and if generally true, suggests a high Omega universe.

These results are being published in detail elsewhere.
The radiostar α Scorpii
Authors: Clauzet L.B.F. , Debarbat S. , Chollet F.
Published: June 2019

In order to provide a direct connection between the radio reference frame and the fundamental optical system, based on fundamental stars, a radiostar observing programme has been started. Most of the astrolabe stations in the world are participating following the proposal of one of us (Débarbat, 1980), after Commission 24 of the IAU created a Working Group “On the Identification of Optical/Radio Astrometric Sources”.
The VLBI celestial reference frame of the NASA Crustal Dynamics Project
Authors: Ma C.
Published: June 2019

A celestial reference frame can be defined by precise positions of extragalactic radio sources using Mark III VLBI data available to the NASA Crustal Dynamics Project for geodynamic research. Seven years of such data have been analyzed to generate a catalogue of 101 sources with formal statistical errors between 0.01 and 0.77 ms in right ascension and between 0.2 and 9.3 mas in declination. In order to achieve such precision it is necessary to adjust the standard IAU nutation model. The rotations and scatter of the positions from year to year are generally less than 1 mas. A comparison of this catalogue with a completely independent catalogue derived from Mark II data shows a weighted average position difference, after a rotation, of 1.9 mas.
Toward a unified terrestrial coordinate system
Authors: Ryan James W. , Himwich W. E.
Published: June 2019

In order to obtain coordinate transformations between our CDP-VLBI terrestrial coordinate frame and the corresponding frames used by the Goddard Space Flight Center SLR group, the University of Texas Center for Space Research SLR group, and Deep Space Network, we obtained geocentric, Cartesian coordinates and formal errors of five locations in our system and those of the two SLR groups, and of three locations in our system and that of the Deep Space Network. After transformation we found that both SLR coordinate sets agree at the 20 to 30 mm level with our values. The Deep Space Network values, with higher formal errors than the other sets, agree at the half meter level.
Earth rotation from lunar laser ranging
Authors: Newhall X. X. , Williams J. G. , Dickey J. O.
Published: June 2019

Results from Lunar Laser Ranging data analysis are presented: (a) the values and statistics of UT1 determined by three stations are given; (b) the lunar tidal accelerationnis found to be −24.9 ± 1.0 arc sec/century2; (c) the tidal-effect coefficientk/Cfor UT1 is shown to be in strong agreement with the theoretical value; and (d) corrections to the IAU values of precession and nutation are estimated.
Earth orientation from Doppler tracking of the Navy navigation satellite system
Authors: Wooden William H.
Published: June 2019

For more than a dozen years, Doppler tracking of the Navy Navigation Satellite System (NNSS) has demonstrated the ability to give solutions for polar motion as a byproduct of precise ephemerides generation. The polar motion estimation process at the Defense Mapping Agency is reviewed and comparisons of the Doppler results with the polar motion series of the newer observational techniques and the Bureau International de l'Heure (BIH) Circular-D are made. This paper extends the analyses and comparisons done during the MERIT Main Campaign for one additional Chandler period.
Predicting Earth orientation
Authors: McCarthy Dennis D.
Published: June 2019

Predictions of Earth orientation parameters are affected by the accuracy of the input data, the quality of the statistical models, and the delay between the last observed data and the date of the first prediction. The accuracy of the prediction of polar motion is adequate to meet most user needs, but the prediction of UT1-UTC is more difficult. Extended forecasts of polar motion and the rotational time can also be made with useful accuracies.
Forecasting short-term changes in the Earth's rotation
Authors: Hide Raymond
Published: June 2019

Summary of Poster

It has long been appreciated that atmospheric motions must contribute to the excitation of fluctuations in the Earth's rotation (Munk and MacDonald 1960, Lambeck 1980, Rochester 1984) but the exploitation of modern meteorological data, collected largely to meet the demands of daily global weather forecasting, in the routine evaluation of angular momentum exchange between the atmosphere and the solid Earth was not initiated until comparatively recently (Hide et al. 1980). This procedure constitutes a necessary step towards the accurate separation of these features of the observed non-tidal changes in the length of day and polar motion and that are of meteorological origin from those that must be attributed to other geophysical processes, such as angular momentum transfer between the solid Earth and other fluid regions of the Earth (liquid metallic core, oceans, etc.), and to changes in the inertia tensor of the solid Earth associated with earthquakes, melting of ice, etc.
Is Chandler frequency constant?
Authors: Vondrák Jan
Published: June 2019

The observed polar motion in the period 1860–1985 is analyzed in order to decide whether Chandler frequency was constant. It is shown that while the phase of annual wobble was very stable throughout the interval in question, Chandler wobble phase was subject to sometimes very rapid changes. The most pronounced negative phase changes were always accompanied by extremely low amplitudes, and a significant correlation was found between Chandler wobble phase and its integrated amplitude. The most probable explanation is that the frequency of Chandler wobble is variable and amplitude-dependent, which might be caused by non-equilibrium response of the ocean.
Computation of water storage contributions to polar motion
Authors: Wilson Clark R. , Kuehne John , Zhian Li
Published: June 2019

We have undertaken a computation of water storage fluctuations and their contribution to polar motion excitation for the period 1900–1982. The calculation is based mainly upon monthly mean observations of precipitation at individual stations around the globe. Seasonal average variations are computed for over 500 individual drainage basins, permitting a comparison with observed annual polar motion.
A new research for the secular polar motion in this century
Authors: Ming Zhao , Danan Dong
Published: June 2019

A new research for the secular drift of the Earth's pole was made based on nine long sequences of latitude observations and led to the following conclusions.

1.

During this century, the Earth's pole has been moving with a mean rate of about 0″.0016/yr along the meridian about 70° (W). This drift rate is much less than the 0″.0035/yr derived from the ILS sequence.

2.

Relative to the North American continent, the Ukiah station located on the west coast of the U.S. shows a local drift of about 6 cm/yr northward, which coincides well with that determined by new techniques.

3.

Referring to the Europe-Asia plate, the whole North American continent shows a drift northward with a rate of about 8 cm/yr. The Mediterranian shows a similar drift of about 6 cm/yr. Perhaps these drifts are the consequences of plate motion and/or deflection of local vertical. It is useful for ascertaining the sources of the drifts to intercompare longer sequences observed with different techniques, including classical and new ones.

4.

Three of five ILS stations, Ukiah, Gaithersburg, and Carloforte, show significant local drifts. Therefore, the Conventional International Origin (CIO), which is defined by the 1903.0 mean latitudes of five ILS stations, is far from fixed on the Earth's surface. It is necessary to re-define an origin of the pole of the Conventional Terrestrial System (CTS).

5.

The quasi-30-year libration showed by the ILS data is not the real pattern of the Earth's polar motion, but results from both the irregular polar motion over some period and the local motion of Ukiah.
How Does One Detect An Accretion Disk?
Authors: Kaitchuck Ronald H.
Published: June 2019

The history of the first detection of an accretion disk in a interacting binary system is presented. The nature of transient and permanent disks in Algol-type binaries is discussed as are the problems associated with the interpretation of emission line profiles from the disks in cataclysmic variable stars. The new technique of eclipse mapping from continuum photometry is reviewed. Some results of Doppler tomography of emission lines are presented.
A Model for R Aqr from HST
Authors: Burgarella Denis , Vogel Manfred , Paresce Francesco
Published: June 2019

High spatial resolution observations R Aqr have been carried out with the HST/FOC. R Aqr is the nearest symbiotic star, i.e. an interacting system consisting of a cool giant star and a hot ionizing source embedded in a larger and complex nebula. We suggest, here, that the binary system is composed of a Mira and a hot stellar source with a radiation temperature of T* ≈ 40 000 K, a luminosity of L ≈ 10L⊙ and a radius R ≲ 0.1 R⊙. Mass transfer between the two components of the system occurs via capture of the Mira wind. Of the plausible mechanisms that may produce the R Aqr jet, an accretion/ejection scenario or the collision of winds seem to be unlikely, but spectral observations of the core are needed to conclude. Another possible origin is based on a spherically symmetric stellar wind that sweeps out a cavity in an ambient medium. This bubble elongates in the directions of least resistance, and matter eventually flows out through two symmetric nozzles. Comparison with models shows that the emission in the NE and SW outer features of the jets is due to a radiative shock but the pre-shock gas must be partially photoionized by the central hot stellar source.
Observations of Two Binary Systems with 04f Type Components
Authors: Niemela V. S. , Cerruti M. A. , Morrell N. I. , Luna H. G.
Published: June 2019

We present linear polarization observations of two binary systems with early Of type components, namely Sk-67°105 in the Large Magellanic Cloud, and LSS 3074 in our Galaxy. Both binaries show phase-locked polarization variations, from which we determined orbital inclinations for the systems.
Reversing the Supernova Order in Massive Binaries
Authors: Pols Onno R.
Published: June 2019

Using simultaneous evolutionary calculations of both components of a massive binary, it is shown that the initial secondary component can explode before the primary, if Roche lobe overflow occurs on the main sequence. Also, it is found that initially wide binaries are more likely to come into contact than close ones.
Overview of Infrared Solar Physics
Authors: Jefferies John T.
Published: June 2019

A brief overview of the field of infrared solar physics is given with particular reference to the topics to be considered during the Symposium.
A Solar Plage Model
Authors: Kučera A. , Baranovsky E. A.
Published: June 2019

An investigation of a solar plage based on observations of UV, visible, and IR spectral lines is presented. Using model calculations, we have established distributions of the main physical parameters (temperature, density, turbulent velocity) in both plage and quiet-Sun atmospheres. Details of the models are presented and the role of magnetic pressure is discussed.
Potential IR Observations of the Solar Corona
Authors: Kumar C. Krishna , Davila Joseph
Published: June 2019

We examine the potential for observations of the solar corona using forbidden lines in the near infrared.
The Sun in Submillimeter Radiation
Authors: Lindsey Charles
Published: June 2019

Continuum observations in the far IR have given us a broad spectrum of new and powerful diagnostic utilities for the solar atmosphere. The infrared continuum is formed in LTE with thermal free electrons by free-free interactions. This gives us a flexible and accurate atmospheric thermometer that has made infrared measurements fundamental to modeling of the quiet solar medium for more than two decades. The submillimeter and millimeter continua are particularly useful with respect to thermal diagnostics of the low chromospheric temperature minimum, where non-radiative heating of the solar medium becomes clearly manifest. Modern submillimeter telescopes and instrumentation on Mauna Kea, in Hawaii, are now revolutionizing solar observations in the submillimeter spectrum, giving us the first observations of detail on the scale of the chromospheric supergranular network, sunspots and prominences. These observations are showing us a remarkable and unexpected view of thermal structure that emerges as one probes to successively higher levels above the chromospheric temperature minimum.
Infrared Images of the Sun During the July 11, 1991 Solar Eclipse
Authors: Tollestrup E. V. , Fazio G. G. , Woolaway J. , Blackwell J. , Brecher K.
Published: June 2019

Infrared images (1.65 μm) of the eclipsed Sim were taken atop Mauna Kea, Hawaii, during the July 11, 1991 total eclipse with an Amber Engineering 128 × 128 InSb array camera. The camera, mounted on a portable solar tracker, had a 3.8-cm, f/2 objective that produced a 4.9° field of view. The primary objective of the experiment was to search for dust or rocky rings around the Sun, previously detected at about 4 R⊙. High thin clouds, atmospheric dust and aerosols from the June 1991 explosion of Mount Pinatubo in the Philippines, and the overall brightness of the solar corona resulted in a very high infrared background. Despite this, high signal-to-noise radial infrared intensity profiles were obtained of the solar corona from the Moon's limb out to about 10 R⊙. Preliminary analysis shows some evidence for an enhanced surface brightness between 3 to 4 R⊙ along the east-west direction, but much fainter than seen in previous solar eclipses. The transition region between the K-corona and the F-corona clearly shows at 2.5 R⊙, and the surface brightness of the F-corona as a function of radius (from about 2 to 10 R⊙) can be fit by a simple power law.
Measurements of Horizontal Flows in 1.6 μm Granulation
Authors: Darvann Tron A.
Published: June 2019

We report on a first analysis of the horizontal motions in a 45 minute (32 × 22 arcsec2 field of view) granulation time series (movie presented at the present IAU Symposium) obtained at 1.6 μm with the Vacuum Tower Telescope (VTT) of the National Solar Observatory at Sacramento Peak (NSO/SP). High signal/noise flow maps are obtained by use of the local cross correlation technique (November 1986) which incorporates efficient attenuation of seeing and 5-min oscillations. The flow pattern, showing a (≈ 30 arcsec diameter) supergranule with (≈ 8-15 arcsec) mesogranules superposed, is long lived compared to the 45 min of observations. The computed flows (velocity, divergence, vorticity) resemble the ones obtained at visible wavelengths (e.g., by Brandt et al. 1991, November 1989, November and Simon 1988, Simon et al. 1988). The high quality of the the flow maps (due to a large number of selected images (1500), and (supposedly) smaller 5-min oscillations and better seeing conditions at 1.6 μm) allows us to study time evolution (resolution ≈ 15 min) of the details of the flow (spatial resolution ≈ 3 arcsec). An interesting new finding is the short lifetime (< 45 min) of vorticity as opposed to the long lived (≫ 45 min) divergence of the flow. Our study demonstrates the possibility of using the 1.6 μm window to the opacity minimum region to study the horizontal flows at these deep layers of the photosphere.