bluuebunny/crossref_metadata_2025 huggingface dataset:
Source-Noise in Radio Synthesis Images of Polarised Sources
Authors: Deshpande A.A.
Published: July 2016

We discuss the distribution of Source- and receiver-noise in radio synthesis images of polarised sources. Analytical expressions are presented for the rms noise at any location in the polarisation images. We compare these results with those for the images of unpolarised sources and discuss the usefulness of deconvolution of snap-shot images in reducing the source-noise from the off-source regions in the images.
Radio Arrays - mm to Meters
Authors: Perley R.A.
Published: July 2016

There are now approximately two dozen operating interferometers in astronomy, with more under construction or in planning. The wide distribution of interferometer arrays, and their acceptance as essential tools in astronomy are a result of the remarkable flexibility and imaging capabilities of modern arrays. Much of the success of these arrays is due to advances in data processing and imaging brought about by innovative and powerful algorithms.
The Big Optical Array
Authors: Simon R. S.
Published: July 2016

The Naval Research Laboratory and the US Naval Observatory are building a phase tracking optical interferometer for high resolution imaging and astrometry. This instrument will be a six element interferometer capable of true imaging using interferometric amplitudes and closure phases. This talk will describe the instrument, with an emphasis on those aspects of the array related to high resolution imaging. The status of the project will be presented. First light is planned for October 1993, with 6 element imaging beginning in 1994.
An Adaptive Steerable Imaging Array
Authors: Hege E.K. , Angel J.R.P. , Gleckler A.D. , Pflibsen K.P. , Ulich B.L.
Published: July 2016

We propose an optimized design for the redeployment of the Multiple Mirror Telescope (MMT) primary optics as a 25 m Adaptive Steerable Imaging Array (ASIA) providing direct focal plane image formation. The design incorporates concepts of active telescope alignment and adaptive optics proven in the existing MMT. Basing predictions on contemporary radio telescope mount technology, 45 m to 100 m optical baselines may be practical.
Super Resolution by Phase-Gradient Unravelling
Authors: Fraser D. , Hunt B. R.
Published: July 2016

In this work, we present another proof of the theoretical existence of super resolution, under certain conditions. The proof relies on an ideal model in which a prototypical discrete image is formed by summation of many discrete pulses placed anywhere on a regular grid. If the model is then band-limited in spatial frequency, the original, grid-resolution pulse image may be reconstructed from the band-limited information. The reconstruction uses “phase-gradient unravelling” — i.e., from a very limited number of terms of the discrete Fourier transform of an image, which defines a very limited spatial-frequency band, we extract or unravel the individual phase-gradients which, together, define the original image.
High Resolution Radio Source Maps at 73.8 MHz
Authors: Perley R. A. , Erickson W. C. , Kassim N. E. , Dwarakanath K.
Published: July 2016

In 1984 Perley and Erickson proposed a 73.8 MHz [4 meter wavelength] observing system at the VLA site (NRAO Scientific Memo #146). They proposed a stand-alone antenna system that would feed its signals into an existing spare channel of the VLA waveguide and utilize a separate correlator. Over the 35 km VLA baselines this system would produce images with 20 arcsec resolution, unprecedented at this frequency. The major technical problems are ionospheric refraction and interference. Some doubt existed as to whether or not it would be possible to cope with the large, rapidly-changing ionospheric phase fluctuations to be expected over 35 km baselines. Thus it was proposed, as a first step in the development, that 73.8 MHz feeds be installed in the present VLA dishes and that trial observations be made to prove that techniques such as self-calibration can be successful. Eight dishes now have 73.8 MHz instrumentation and a number of radio source images have been made with this initial system.
Preliminary Seeing Measurements for SUSI
Authors: Brummelaar T.A. Ten , Tango W.J. , Davis J. , Shobbrook R.R.
Published: July 2016

Some seeing statistics for the Narrabri site of SUSI are presented. These measurements are based on the motion of the wavefront tilt correcting mirrors used in the interferometer. The median seeing for the site to date is 1.3″.
Simulation Study of a Low-Light-Level Wavefront Sensor Driving a Low-Order, Near-IR Adaptive Optics System
Authors: Tyler David W. , Loos Gary C.
Published: July 2016

Two high-fidelity computer simulations are used to study low-order adaptive optics systems operating in the near-infrared. We study obtainable system performance using very dim reference sources at three IR wavelengths.
Optimal Linear Arrays for Wide Bandwidths
Authors: Marson R. G.
Published: July 2016

New technology has enabled modern aperture synthesis instruments to employ increasingly larger bandwidths. Large bandwidths can be exploited to enable a more complete coverage in the (u, v) plane and hence aid image reconstruction. This relies on the source having a structure that is invariant with observing frequency or a suitable image reconstruction algorithm to take frequency variations into account.
ATCA Radio Polarization Observations of NGC 1566 and NGC 1672
Authors: Beck R. , Ehle M. , Haynes R. F. , Harnett J. I.
Published: July 2016

NGC 1566 and NGC 1672 have successfully been observed in radio continuum at 6 cm (26″ HPBW) with the Australia Telescope Compact Array (ATCA) using a 375-m array. We have detected for the first time with this telescope linearly polarized radio emission from two southern hemisphere spiral galaxies, NGC 1566 and NGC 1672.
Speckle Observations of Solar Granulation
Authors: de Boer C.R. , Kneer F.
Published: July 2016

Image reconstruction by means of speckle interferometry was successfully used to restore the intensity distribution of solar features and to investigate the morphology and dynamics of small-scale structures in active regions of the Sun. The observations were obtained with the Vacuum Tower Telescope (D = 70 cm, f = 46 m) at Observatorio del Teide, Tenerife, on May 17 and 20, 1991, from a plage region close to a sunspot near disc centre. Sequences of bursts consisting of 100 exposures were recorded with a broad-band filter centred at 550 nm (FWHM ≈ 10 nm, diffraction limit 0.2 arcsec). The pickup unit was a video CCD – system with an exposure time of 4 ms and a frame rate of three pictures per second. A description of the observing procedure and of the data handling can be found in de Boer et al. (1992). To obtain the complex Fourier phases speckle masking (Lohmann et al. 1983) was used. The speckle transfer function of the atmosphere was calculated indirectly using Korff's equation (1973). The Fried parameter r0was estimated with the spectral ratio technique (von der Lühe 1984). This parameter was sometimes as large as 14 cm. With this the theoretical speckle transfer function could be determined for calculating the corrected Fourier amplitudes of the reconstruction. A new low pass filter, based on the reliability of each individual value in the Fourier plane, was applied to the amplitudes to suppress noise at high wavenumbers.
An HR Diagram for the LMC from the Medium Deep Survey
Authors: Forbes Duncan A. , Elson Rebecca A. W. , Griffiths R. E. , Ellis R. S. , Gilmore G. , Green R. F. , Huchra J. P. , Illingworth G. D. , Koo D. C. , Ratnatunga K. , Tyson A. , Windhorst R. A.
Published: July 2016

We summarise the first year of operation of the Medium Deep Survey - a key project of the HST. Two fields in the LMC are discussed and some preliminary scientific results presented. We also comment on image deconvolution for the extragalactic fields observed as part of the Medium Deep Survey.
Mk III Interferometer: Milliarcsecond “Visual” Orbits of Spectroscopic Binaries
Authors: Hummel C.A. , Armstrong J.T.
Published: July 2016

The spectroscopic binary observing program of the Mark III Optical Interferometer has produced four published orbits and 22 preliminary orbits. The mean (formal) precision is 0.3% for measurements of sin i and 0.7% for measurements of the semimajor axis a. We list the stars for which we have obtained orbits or preliminary orbits and describe our data and uncertainty analysis techniques.
Five Years of Stellar Position Measurements with the MKIII Optical Interferometer
Authors: Hummel C.A.
Published: July 2016

Using the north-south and east-south astrometric baselines of the MKIII optical interferometer on Mt. Wilson (each about 12 meters in length), we measured the positions of eleven EK5 stars with an accuracy of about 10 milliarcseconds (mas) in declination and 20 mas in right ascension.
Imaging with a Gravitational Lens
Authors: Webster R.L.
Published: July 2016

The basic ideas of gravitational microlensing are discussed. Particular attention is given to the use of a gravitational lens as a (non-standard) telescope, to probe the very small scale structure of extragalactic sources. The recovery of information from a gravitational lens telescope is discussed, as well as the unique contribution which can be made by imaging with a gravitational telescope.
A Search for Moving Groups in the Galactic Halo
Authors: Aguilar Luis A. , Hoogerwerf Ronnie
Published: July 2016

A new method to search for moving groups, specifically tailored for the HIPPARCOS database, is used to search for moving groups among the high velocity stars in this database. Although the sampled volume is small, the high quality of the astrometry makes this search interesting. No moving groups are detected, but limits in the velocity and number of members of possible non-detected groups are given.
The Magellanic Stream Revisited: - The Mass of the Galaxy in the Range of 100 kpc -
Authors: Murai T.
Published: July 2016

There is still a controversy on the mass of the Galaxy in the deep halo, some advocate a conservative view that the rotation velocity ultimately decays in accordance with the Keplerian law at the distance of 50 kpc, while others have come to consider that the rotation curve of the Milky Way, essentially stays flat or is still increasing at the distance of the Magellanic Clouds and the Magellanic Stream.
Compressive Effects on the Galactic Globular Clusters by Gravitational Disk-Shocking
Authors: Shimada Masaaki
Published: July 2016

What is our problem? Observed figures of the Galactic globular clusters are somewhat elliptic in many cases. For not a few clusters (e.g. 23 of 72), the observed ellipticities (Shawl & White 1987) are ≥ 0.1 within ~ 2rh. By a series of numerical experiments, we study whether or not tidal force from the Galactic disk can produce the observed ellipticities in such an inner region (Shimada 1996)
A Near Infrared Survey of the LMC
Authors: Wada Takehiko , Ueno Munetaka , Ebisuzaki Toshikazu , Ohno Yosuke
Published: July 2016

We surveyed the central 3° × 6° region of the Large Magellanic Cloud (LMC) with angular resolution of 10″.0 at the J(1.25μm), H(1.65μm) and K′(2.15μm) bands. The observations were performed from Oct to Nov, 1994 at the Siding Spring Observatory. We used a 25 cm/F3.5 Newtonian telescope equipped with a 512×512 PtSi-Camera (Ueno et al. 1992). The plate scale was 4.″6 × 6.″0/pixel and the total field of view was 40.′2 × 52.′3. The system was attached onto the Automated Patrol Telescope of the University of New South Wales. The limiting magnitudes of the survey were 13.6, 11.9, and 10.0 magnitude (3σ) at the J, H, and K′ bands, respectively. The positions and the J, H, and K′ magnitudes were derived for 1599 point sources whose S/N ratio were more than four at the K′-band. The dominant components of the sources are red super giants (RSG), luminous M-type giants and AGB stars in the LMC. The distributions of RSG, luminous giants and CO line flux are spatially different from each other. This supports the idea that the position of the active star forming region has changed during the past 108 years. The detected sources are cross-identified with the IRAS Point Source Catalog. Sixty-two of 680 IRAS sources in the region spatially coincide with the detected sources and the spectrum energy distributions from 1.25μm to 100μm were derived for these 62 sources. Half of them are well described by a black body spectrum, while the others show a flat or redder spectrum. These latter sources are supposed to be stars with dust envelopes.
Numerical Simulations of M51
Authors: Antonioletti M. , Nelson A.H.
Published: July 2016

No conference on the interaction of galaxies would be complete without a contribution on M51 (NGC5194) and its companion NGC5195. Much observational and theoretical work has been carried out to try to understand this interacting pair, and to elucidate the morphological features and weak AGN which are thought to be the result of the interaction.
Shells, Ripples and Tails
Authors: Carter D.
Published: July 2016

It has been known since the early simulations of Wright (1972), and Toomre & Toomre (1972), that interactions between galaxies can give rise to quite spectacular morphological features, including spiral structure in disk galaxies, and extensive tails. It appears that long tidal tails only arise from interactions involving disk galaxies (Toomre & Toomre 1972), and thus the presence of two opposed long tidal tails in a number of disturbed galaxies such as the Antennae (Whitmore & Schweizer 1995), NGC 3921 (Schweizer 1996), and NGC 7252 (Schweizer 1982), has led to the interpretation of these galaxies as disk-disk mergers in progress. These systems can be modeled rather successfully, as the work of Hibbard & Mihos (1995) has shown.
The Nature of the Dusty Ionized Gas in NGC 5846: (And Other Elliptical Galaxies ?)
Authors: Goudfrooij Paul , Trinchieri Ginevra
Published: July 2016

We present new optical imagery and ROSAT HRI X-ray imagery of the elliptical galaxy NGC 5846. A filamentary dust lane is detected in its central region, with a morphology strikingly similar to that observed for the optical nebulosity and the X-ray emission (cf. Fig. 1). A physical connection between the different phases of the interstellar medium therefore seems likely. The energy deposited from the hot gas into heating of the dust grains is consistent with the temperature distribution of the X-ray-emitting gas, which is found to be lowest in the dusty regions. The optical extinction of the dust is consistent with the Galactic extinction curve. We argue that the dust as well as the optical nebulosity are products of an interaction with a small, gas-rich galaxy, not remnants of a cooling flow. A full account of this work is currently in press in Astronomy and Astrophysics, and a preprint is available through http://www.stsci.edu/science/preprints/prep1191/prep1191.html.
The Origin of High Specific Frequency Globular Cluster Systems
Authors: Lee M.G. , Geisler D.
Published: July 2016

There are known to be several giant elliptical galaxies with high globular cluster specific frequencies, which possess about three or more times the normal number of globular clusters for their luminosity. The origin of high specific frequency globular cluster systems is not yet known.
Dramatic Changes in Molecular Cloud Properties Across the ARP 299 Merger
Authors: Aalto S. , Radford S.J.E. , Scoville N.Z. , Sargent A.I.
Published: July 2016

Arp 299 is an IR-luminous (LIR ≈ 8 × 1011L⊙) merger system of two galaxies, IC 694 and NGC 3690, at a distance of 40 Mpc. Its proximity and richness in molecular gas make it suitable for studying the effects of gravitational interactions and starburst activity on molecular cloud distributions, dynamics, and physical conditions. Previous low resolution observations (10 - 30″) indicated that the CO/13CO 1-0 intensity ratio is unusually high, > 20, suggesting an unusual population of molecular clouds (Aalto et al. 1991; Casoli et al. 1992).
The Stellar Initial Mass Function in Starburst Galaxies
Authors: Leitherer Claus
Published: July 2016

Starburst galaxies are currently forming massive stars at prodigious rates. I discuss the star-formation histories and the shape of the initial mass function, with particular emphasis on the high- and on the low-mass end. The classical Salpeter IMF is consistent with constraints from observations of the most massive stars, irrespective of environmental properties. The situation at the low-mass end is less clear: direct star counts in nearby giant H II regions show stars down to ~1 M⊙, whereas dynamical arguments in some starburst galaxies suggest a deficit of such stars.
Triggered Starbursts in Galaxy Mergers
Authors: Taniguchi Y. , Shioya Y. , Murayama T. , Wada K.
Published: July 2016

A unified formation mechanism of nuclear starbursts is presented; all the nuclear starbursts are triggered by binary supermassive black holes made in the final phase of galaxy mergers. Minor mergers cause both nuclear starbursts and hot-spot nuclei while major mergers cause (ultra) luminous infrared galaxies. We discuss the case of Arp 220 in detail.
Near Infrared Spectroscopy and the Search for CO Emission in 3 Extremely Luminous IRAS Sources
Authors: Evans Aaron S. , Sanders D.B. , Cutri Roc M. , Radford Simon J.E. , Solomon Phil M. , Downes Dennis , Kramer Carsten
Published: July 2016

Rest-frame 0.48–1.1 μm emission line strengths and molecular gas mass (H2) upper limits for three luminous infrared sources – the hyperluminous infrared galaxies (HyLIGs: Lir ≥ 1013L⊙ where Lir ~ L(8 – 1000μm) IRAS F09105+4108 (z = 0.4417), IRAS F15307+3252 (z = 0.926), and the optically-selected QSO PG 1634+706 (z = 1.338) - are presented. Diagnostic emission-line ratios ([O III] λ5007/Hβ, [S II] λ6724/Hα, [N II] λ6583/Hα, and [S III] λλ9069+9532/Hα) indicate a Seyfert 2-like spectrum for both infrared galaxies, consistent with previously published work. Upper limits on the molecular gas mass for all three sources are M(H2) < 1 - 3 × 1010h−2M⊙ (q0 = 0.5, H0 = 100h km s−1 Mpc−1), less than the H2 mass of the most gas-rich infrared galaxies in the local Universe. All three sources have Lir/L′CO ~ 1300 – 2000, the most extreme values for extragalactic sources measured to date. Given the relatively warm far-infrared colors for all three objects, much of their infrared luminosity may emanate from a relatively small quantity of hot dust near an AGN.
Seyfert Galaxies and Their Environment
Authors: Focardi P. , Kelm B. , Palumbo G.G.C.
Published: July 2016

The role played by environment on nuclear activity in galaxies is not clear and largely debated (see e.g. Barnes & Hernquist 1992, Kelm 1996). To overcome statistical uncertainties, environment properties of two large samples of Seyfert galaxies (Sy 1 and Sy 2 have been kept separated) have been computed and compared with equivalent size “normal galaxy” sample ones. Seyfert samples have been extracted from the Veron & Veron catalogue (Veron & Veron 1996), whilst “normal galaxies” have been randomly extracted from ZCAT (Huchra 1993). The samples are limited in cz ([1500–9500] km/sec) and contain 149 Sy 1, 173 Sy 2 and 160 “normal galaxies” (hundreds of random extractions from ZCAT). For each galaxy neighbors have been computed (from ZCAT) within two variables radii, R (isolation radius) and r (pair separation), which span [0.2 - 2] h100 Mpc. and [20–90]h100 kpc. respectively. Neighbors must lie also within 700 km/sec from the galaxy. In this way, for each value of R and r, environment of each galaxy has been “quantified”.
The Detection of a Large, Powerful FR I Radio Galaxy in a Spiral Host
Authors: Ledlow Michael J. , Owen Frazer N. , Keel William C.
Published: July 2016

We report the detection of a FR I-like radio galaxy with a total extent of more than 200 kpc in a disk-dominated host. Traditional wisdom maintains that these types of radio sources are only found in elliptical hosts. We confirm the optical classification of this galaxy from deep, multicolor optical/NIR imaging and the detection of a spiral arm, an optical rotation curve, and line-ratios in the disk consistent with HII regions and star formation. At 20cm, we find a 36kpc knotty, jet extending into the southern lobe. At 3.6cm we detect a kpc-scale jet with the same position angle. With the exception of the radio source, this galaxy appears to be a fairly ordinary, dusty, star-forming spiral, with some evidence for a weak, obscured, AGN.
CO Observations of High-z Objects
Authors: Ohta K. , Nakanishi K. , Akiyama M. , Takeuchi T.T. , Yamada T. , Shioya Y. , Kohno K. , Kawabe R. , Kuno N. , Nakai N.
Published: July 2016

We have made a CO(J=2-1) observations using the Nobeyama 45m telescope aimed at examining the physical properties of the molecular gas in this object. The upper limit obtained is 1.8 mK (3σ) at a velocity resolution of 100 km s−1, which leads to an upper limit on the molecular gas mass of 5.3 × 1011M⊙, if we assume a line width of 250 km s−1 obtained in the CO(J = 5 - 4) line (rest-frame) and the Galactic CO-to-H2 conversion factor of 4.5 (M⊙ K km s−1 pc2). The line ratio between the 2–1 line and the 5–4 line as well as those from the 7–6 and the 4–3 lines (Omont et al. 1996, Nature, 382, 428) imply that the mean gas density is as high as 103–5 cm−3, which is comparable to that in nearby star burst galaxies (e.g., Solomon et al. 1992, ApJ, 387, L55).
Galaxy Orientation in Some Abell Clusters
Authors: Godłowski W. , Baier F.
Published: July 2016

We analyze a sample of galaxies in a region of three rich Abell Clusters. The data are taken from the Edinburgh Catalogue of the cluster. First, we divide the whole cluster area into different parts according to the assumed subclusters. Now we can find the position angles of the cluster and subclusters. We find strong evidence that the position angles of galaxies within our clusters are aligned to a large extent. For the cluster A754, position angles of galaxies tend to be perpendicular to the direction of the position angle of the cluster. Consequently, the angular momentum of galaxies are preferentially perpendicular to the cluster plane. For the cluster A14, position angles of galaxies tend to be parallel to the direction of the position angle of the cluster. Consequently, the angular momentum of galaxies are preferentially parallel to the cluster plane. For the cluster A3667 we obtain a more complicated picture suggesting that the alignment of galaxies in this cluster may have a different shape. From the distribution of the positions angles of galaxies we also found evidence for possible subclustering inside the whole cluster. This result is confirmed by the investigation of the distribution of the vectors normal to the galactic planes. Moreover we confirm the existence of a “line of sight” effect, originally found by Godłowski &, Ostrowski (1996) for galaxies belonging to the clusters in the Tully Catalogue (1988), for the clusters in our basic catalog.
Efficient Star-Formation in the Tidal Arms of the Stephan's Quintet Group of Galaxies
Authors: Ohyama Y. , Nishiura S. , Murayama T. , Taniguchi Y.
Published: July 2016

NGC 7318B in Stephan's Quintet has two optical arms (toward N and S) emanating from the eastern part of the main body. Since these arms are similar morphologically to the tidal tails of merging galaxies such as NGC 4038/9, it is considered that NGC 7318B itself is a major merger with a retrograde orbit. In order to study the emission-line activity in the tidal arms of NGC 7318B, we took CCD narrow-band (Hα ON and OFF) images and then found a large-scale arc in Hα emission which traces closely the arms. This Hα arc resembles both the radio and the soft X-ray arcs morphologically (van der Hulst & Rots 1981; Pietsch et al. 1997), suggesting that a single physical mechanism is responsible for all of these kinds of emission. Our optical spectroscopic observations of the shell-like feature at the southern tip of the arc reveal both broad Hα emission and stronger-than-normal [NII] and [SII] emission lines, which are typical of supernova remnants (SNRs). The required number of SNRs is estimated to be as much as ~ 106.
Measuring Subclusters in Galaxy Clusters
Authors: Shao Z.Y.
Published: July 2016

We assume that there are Kc subclusters and Kf fields (foreground or background) in a cluster region. Then, the distribution of all galaxies in this region can be described as follow:

where, nc and nf are normalized numbers of subcluster members and field galaxies. φc, φf, are their normalized distributions in radial velocity space. Both of them can be assumed as Gaussian. μc and μf are normalized distributions in the projected surface of the celestial sphere. For field galaxies, it's uniform, and for subcluster members, usually we use the King's approximate formulae. Distribution parameters and their uncertainties can be found by using the standard maximum likelihood method. And membership probabilities of the ith galaxy belonging to the cth subcluster can be calculated as Pc(i) = φc(i)/φp(i).
Strong Gravitational Lensing on the Hubble Deep Field
Authors: Blandford R. D.
Published: July 2016

The Hubble Deep Field, henceforth HDF, (Williams et al 1996) is a unique data set for studies of faint galaxies. A small area was chosen well away from known local density enhancements and sources of obscuration. It was imaged for 30 complete orbits in each of four filters centered on wavelengths λ300, 450, 606, 814 nm. There are three, contiguous WFPC2 frames and a solid angle 15,500 arcsec2 is usable. This tiny region is teeming with galaxies. At least 2500 significant features can be identified down to R = 30, though it is not clear that these are all entire galaxies.
Measuring the Evolution of the Mass-to-Light Ratio from z = 0 to z = 0.6 from the Fundamental Plane
Authors: Franx Marijn , van Dokkum Pieter , Kelson Dan , Illingworth Garth , Fabricant Dan
Published: July 2016

Galaxy evolution is probably a complex process. Mergers, infall, and starbursts may change galaxy properties systematically with time. As a result, the interpretation of the luminosity function is ambiguous, and information on the mass evolution of galaxies is needed. Such information can be retrieved from the evolution of the Tully-Fisher relation, Faber-Jackson relation, or the Fundamental Plane with redshift.
Low-Ionization Balqsos: Warm Ultraluminous Galaxies at High Redshifts
Authors: Egami E.
Published: July 2016

A decade ago Sanders et al. (1988a, b) proposed a possible QSO formation scenario as a sequence of Galaxy Mergers → Ultraluminous IR Galaxies (ULIRGs) → Warm ULIRGs → QSOs. Since then, this proposal has become a paradigm against which all the subsequent observations will be compared. Fortunately for us, this paradigm makes two specific predictions: that is, 1) ULIRGs are powered by hidden AGNs, and 2) ULIRGs should be more abundant at z ~ 2, where the comoving density of optically-selected QSOs is sharply peaking up.
Galaxy Morphology, Initial Conditions and the Hubble Sequence
Authors: Williams P.R. , Nelson A.H.
Published: July 2016

We have carried out over 120 galaxy formation N-body simulations modeling gravity, gas dynamics and star formation using TREESPH on a parallel computer. Our aims were to investigate whether or not numerical galaxies formed from idealized cosmological perturbations can account for the Hubble sequence and the diversity of disk galaxies observed in the field.
Light Elements Abundances: New Insights on Stellar Mixing and Galactic Production
Authors: Primas F.
Published: July 2016

The remarkable finding that B follows Fe in almost direct proportion from the earliest times to the present, with little change of slope (if any) between halo and disk metallicities (cf Figure 1, open circles, Duncan et al. 1997), has stimulated the need for a revision of the classical cosmic-ray (CR) spallation scenario. A straightforward interpretation of Duncan et al. results is that the net rate of production of B (and Be too, since it shows a similar trend) does not depend on the CNO abundances in the ISM. It has been suggested that the CR spallation most important for light element production is not primarily protons and alpha particles colliding with CNO nuclei in the ISM (Reeves et al. 1970; Meneguzzi et al. 1971). Rather, it is C and O nuclei colliding with ambient protons and alpha particles, probably in regions of massive star formation (Cassé et al. 1995). This decouples light element production from the metallicity of the ISM and results in the approximately linear relationships observed, but some aspects are difficult to justify (see Prantzos, this volume).
Fluorine Production from AGB and WR Stars
Authors: Mowlavi Nami , Meynet Georges
Published: July 2016

The role of Wolf-Rayet and asymptotic giant branch stars in the production of the Solar System fluorine abundance is analyzed. It is shown that both these stars can be important sources of galactic fluorine. However, the uncertainties affecting the predictions, especially those from asymptotic giant branch stars, do not allow to give quantitative figures yet.
On the Progenitors of Type Ia Supernovae
Authors: Li X.-D. , van den Heuvel E. P. J.
Published: July 2016

Supersoft X-ray sources (hereafter SSS) are a class of luminous (bolometric luminosity ~ 1037 − 1038 erg s−1) objects with a characteristic radiation temperature of 30 to 60 eV (Hasinger 1994; Kahabka & Trümper 1996). The most popular model for SSS is that they are massive white dwarfs steadily burning nuclear fuel accreted from a more massive binary companion at a rate near or above the Eddington limit (van den Heuvel et al. 1992).
On the Origin of Metallicity in Lyman-Alpha Forest Systems
Authors: Chiba M. , Nath B. B.
Published: July 2016

Several recent observations indicate that even the low H I column density Lyα absorption lines may not be primordial, as they were previously thought to be. High-resolution observations using the Keck telescope (Cowie et al. 1995; Tytler et al 1995.; Songaila & Cowie 1996) have revealed that a large fraction of Lyα absorption lines with H I column density as low as NHI ~ 1014 cm−2 at redshift z ~ 3 are associated with metal lines (C IV). This fraction, hereafter denoted as fm, is estimated as 0.5-0.75. On the other hand, there is an indication that at low z a large fraction of Lyα absorption lines are directly associated with halos of visible galaxies. This fraction is hereafter denoted as fg. Lanzetta et al. (1995, hereafter LBTW) claimed fg ~ 0.6 at z ≲ 1 (see also Bowen, Pettini & Boyle 1997).
Stellar Yields and Chemical Evolution
Authors: Gibson Brad K.
Published: July 2016

Several speakers at this symposium have alluded to the zeroth-order agreement between the Type II supernovae (SNe) stellar yields, as predicted by the models of those most responsible for driving progress in the field - i.e. Arnett (1991,1996); Maeder (1992); Woosley & Weaver (1995); Langer & Henkel (1995); Thielemann et al. (1996), hereafter referred to as A91, A96, M92, WW95, LH95, and TNH96, respectively. It is important though for those entering (or indeed, already involved in!) the chemical evolution field to be cognizant of the fact that there are important first- and second-order differences between the yield compilations.
The Evolution of Old Stellar Populations in Our Galaxy
Authors: Majewski Steven R.
Published: July 2016

I would like to focus on one aspect regarding the evolution of Galactic stellar populations that is particularly relevant to discussions at this symposium: Where were the sites of early star formation in the Galaxy? The large scatter in abundance ratios for metal poor stars suggests multiple early settings of star formation in the Milky Way. In this and other ways, interpretation of detailed stellar chemical abundance analyses are converging with those of spatial-kinematical analyses of field stars, star clusters and satellite galaxies.
Chemical Evolution of the Magellanic Clouds
Authors: Barbuy B. , de Freitas Pacheco J. A. , Idiart T.
Published: July 2016

Chemical evolution studies of the Clouds based on detailed abundance analyses are essentially limited nowadays to young objects like HII regions (Dufour 1984; Garnett et al. 1995), planetary nebulae (e.g. de Freitas Pacheco et al. 1993), supernova remnants (Russell & Dopita 1990) and supergiant stars either of F-K type (Hill et al. 1995) or B ones (e.g. Rolleston et al. 1996 and references therein). One exception to this was presented by Dopita et al. (1997) where HST data permitted to date planetary nebulae nuclei and to present an age vs. metallicity model.
The Quest for X-Rays from Protostars
Authors: Montmerle Thierry
Published: July 2016

The field of low-mass star formation and early evolution has made rapid progress in recent years, thanks in particular to observations in the IR and mm ranges. The current evolutionary scheme calls for two main stages, themselves divided into two substages (e.g., André & Montmerle 1994): (i) protostars, comprizing the newly discovered so-called “Class 0 sources”, detected mostly or only in the mm range, which are young protostars with estimated ages ~ 104 yrs, and “Class I sources”, visible in the near- to mid-IR, which are evolved protostars with estimated ages ~ 105 yrs; (ii) T Tauri stars, which are visible in the IR but also in the optical, the younger being the “classical” T Tauri stars (called “Class II” in the IR), and the “weak-line” T Tauri stars (“Class III” in the IR), with a large age spread of ~ 106 – 107 yrs. According to current models (e.g., Shu et al. 1987), protostars consist of a forming star surrounded by an extended envelope (up to ~ 10,000 AU in radius); the star forms via an accretion disk inside a cavity ~ several 100 AU in radius. The disk probably plays an important role in generating molecular outflows, running through the envelope. Classical T Tauri stars are only surrounded by a disk, which disappears at the weak-line T Tauri stage.
AXAF in Context: A Revolution
Authors: Elvis Martin
Published: July 2016

AXAF has been a long time, 20 years, in coming. This has made AXAF so overfamiliar that it is hard to see how revolutionary it still is. Some even describe AXAF as the end of the line in X-ray technology; a never to be repeated venture to high resolution. This view is wrong. To see why we need to see where X-ray astrophysics is going.
Super-Eddington Sources in Galaxies
Authors: Fabbiano G.
Published: July 2016

Imaging X-ray observations have resolved X-ray sources in many nearby ‘normal’ galaxies. These sources are associated with different galaxian component, including: bulge and globular clusters(LMXB, e.g. in M31); the disk/arm component (LMXB, HMXB, SNR, SN, ISM shells); and low-luminosity AGN (see reviews in Fabbiano 1989; 1995; 1996). A number of these sources have X-ray luminosities in excess of the Eddington luminosity for 1 M⊙ accreting object (~ 1.3 × 1038ergs s−1), and have been called Super-Eddington sources. Nearly 100 Super-Eddington sources have been reported so far, based on Einstein and ROSAT images (see Fabbiano 1989; 1995; 1996; Makishima 1994). The number of these sources increases with the maximum distance of the galaxy sample considered (e.g. Read et al 97). This is in part due to confusion, but it is also true that considering the larger sample of galaxies one obtains in a larger volume of space the amount of these relatively rare sources would increase as well.
Millisecond Time Variations of X-Ray Binaries
Authors: Swank J. H.
Published: July 2016

Millisecond time-scales are natural for some neutron star and black hole processes, although possibly difficult to observe. The Rossi X-Ray Timing Explorer (RXTE) has found that for the neutron stars in low-mass X-ray binaries (LMXB) there are flux oscillations at high frequencies, with large amplitudes. Z sources and bursters tend to exhibit oscillations in the range 300-1200 Hz. Persistent emission may exhibit one or both of two features. In bursts from different bursters, a nearly coherent pulsation is seen, which may be the rotation period of the neutron star. For some the frequency equals the difference between the two higher frequencies, suggesting a beat frequency model, but in others it is twice the difference. The sources span two orders of magnitude in accretion rate, yet the properties are similar. The similar maximum frequencies suggests that it corresponds to the Kepler orbit frequency at the minimum stable orbit or the neutron star surface, either of which would determine the neutron star masses, radii and equation of state. Theories of accretion onto black holes predict a quasi-periodic oscillation (QPO) related to the inner accretion disk. The two microquasar black hole candidates (BHCs) have exhibited candidates for this or related frequencies.
Very High Energy Gamma Rays from Plerions: CANGAROO Results
Authors: Kifune T.
Published: July 2016

The current status of very high energy gamma ray astronomy (in ~ 1 TeV region) is described by using as example results of CANGAROO (Collaboration of Australia and Nippon for a GAmma Ray Observatory in the Outback). Gamma rays at TeV energies, emitted through inverse Compton effect of electrons or π0 decay from proton interaction, provide direct evidence on “hot” non-thermal processes of the Universe, as well as environmental features, such as the strength of magnetic field in the emission region, for the non-thermal processes.
Galactic Radio-Jet Sources: Multiwavelength Observations
Authors: Durouchoux PH. , Hannikainen D.
Published: July 2016

So far, seven X-ray sources have been identified to be radio-jet sources. We present a review of the observations of IE 1740-2942, GRS 1758-258, GRS 1915+105, GRO J1655-40, SS 433, Cir X-1, Cyg X-3.
Accretion Disks in Black Hole Candidates Observed with ASCA
Authors: Dotani T.
Published: July 2016

Structure of the accretion disk is compared between the soft and hard states of Cyg X-1 using the ASCA data. Large uncertainty of the disk parameters in hard state prevent us from drawing clear conclusion, but the data are consistent with a factor of 3 larger (optically thick) inner disk boundary in the hard state than in the soft state.
X-Ray Large Scale Structure and XMM
Authors: Pierre M.
Published: July 2016

The formation of Large Scale Structures (LSS) in the universe was first studied at optical wavelengths as the galaxy spatial distribution appeared to be far from homogeneous. Considerable effort has been invested in semi-analytical approaches and in numerical simulations (DM + hot gas) to explain the observed structures, given some set of initial conditions and using additional constraints provided by the COBE results. It is now clear however, that these two extreme data set are not sufficient to discriminate between the possible remaining cosmological scenarios. It is thus timely to investigate LSS at a much higher redshift than the present survey limits both in the optical and in other wavebands. In this context, the X-ray band will certainly become a hot field with the advent of the XMM observatory. The next section briefly summarizes what is known about LSS from optical wavelengths and simulations. Sect. 3 reviews the particular points that can be addressed in the X-ray band. Last section presents realistic prospects for mapping LSS with XMM.
Hot Electrons and Cold Photons: Galaxy Clusters and the Sunyaev-Zel'dovich Effect
Authors: Hughes J.P.
Published: July 2016

The hot gas in clusters of galaxies emits thermal bremsstrahlung emission that can be probed directly through measurements in the X-ray band. Another probe of this gas comes from its effect on the cosmic microwave background radiation (CMBR): the hot cluster electrons inverse Compton scatter the CMBR photons and thereby distort the background radiation from its blackbody spectral form. Although this, the Sunyaev-Zel'dovich (SZ) effect, is quite small, heroic efforts during the 1980's resulted in its detection in three moderately distant clusters of galaxies: A665, A2218, and CL 0016+16. It is well known that one of the purposes of conducting such measurements is to determine the Hubble constant. The technique has generated considerable interest because it is independent of all other rungs of the cosmic distance ladder and is effective over a wide range of redshifts: ~0.02 to ~1.
ASCA Sky Survey Observations and the Cosmic X-Ray Background in 2-10 KeV
Authors: Inoue H. , Takahashi T. , Ueda Y. , Yamashita A. , Ishisaki Y. , Ogasaka Y.
Published: July 2016

The X-ray background in the energy range above 2 keV is highly uniform except for an excess component along the Galactic plane. The excess along the plane is considered to be associated with our Galaxy, whereas the rest of the emission is believed to be of extragalactic origin. In this paper, the X-ray background at high Galactic latitude is discussed and is designated as the CXB (cosmic X-ray background) to distinguish it from the Galactic origin.
An Attempt to Classify Solar Microwave-Bursts by Source Localization Characteristics and Dynamics of Flare-Energy Release
Authors: Krüger A. , Kliem B. , Hildebrandt J. , Nefedev V.P. , Agalakov B.V. , Smolkov G.Ya.
Published: July 2016

An overview of spatially resolved observations of solar radio bursts obtained by the Siberian Solar Radio Telescope at 5.8 GHz during the last ten years reveals the occurrence of different classes of burst emission defined by their source localization characteristics. Four major classes of bursts according to the source position relative to sunspots, the source size and structure, and the source height, could be tentatively distinguished and compared with burst spectral characteristics as well as with soft X-ray emission oberved by YOHKOH. These findings are in favour of a magnetic origin of the underlying flare process.
Three-Dimensional Simulation Study of Plasmoid Injection into Magnetized Plasma
Authors: Suzuki Y. , Watanabe T.-H. , Kageyama A. , Sato T. , Hayashi T.
Published: July 2016

Resent observations suggest that, during solar flares, plasmoids are injected into the interplanetary medium (Stewart et al., 1982). It has also been pointed out that solar wind irregularities modeled as plasmoids are penetrated into the magnetosphere (Lemaire, 1977). These plasmoid injections are considered to be an important process because they transfer mass, momentum, and energy into such magnetized plasma regions. Our objective is to investigate the dynamics of a plasmoid, which is injected into a magnetized plasma region and to reveal mechanisms to transfer them. To achieve this, we carried out three-dimensional magnetohydrodynamic (MHD) simulations.
Coronal Variability and Flaring of the RS CVn Binaries σ2 CrB and HR1099
Authors: Brown A. , Osten R. A. , Drake S. A. , Jones K. L. , Stern R. A.
Published: July 2016

We present new X-ray, EUV, and radio observations of the coronal emission from the RS CVn binaries HR1099 (V711 Tau) and σ2 CrB. RS CVn systems possess coronae that display extreme activity levels and frequent flaring. Our observations provide multiwavelength records of coronal variability and flaring over more than two binary orbits for each system. While the EUV and X-ray spectra show the flare response of the thermal plasma, the radio data give the corresponding information for the nonthermal electron population. The HR1099 data contain one of the most energetic flare outbursts observed from HR1099 that lasts for over 3 days. Coronal flaring is common in these systems and, in fact, is the normal condition.
ASCA Observation of NGC1333 Star Forming Region
Authors: Itoh M. , Fukunaga H. , Koyama K. , Tsuboi Y. , Yamauchi S. , Kobayashi N. , Hayashi M. , Ueno S.
Published: July 2016

The region south of the reflection nebula NGC1333 in Perseus is an active star forming region including numerous Herbig-Haro objects and at least 5 protostar candidates with molecular outflows and far-infrared emission. It has been actively studied in various wave bands (e.g. Aspin et al 1994 and references therein). We observed this region with ASCA with the primary objective to detect X-rays from the protostars embedded deep in the molecular cloud.
X-Ray Valiabilities from Protostars in the RCrA Molecular Cloud
Authors: Hamaguchi Kenji , Murakami Hiroshi , Koyama Katsuji , Ueno Shiro
Published: July 2016

R CrA molecular cloud, at a distance of 130pc(Marraco, Rydgren 1981), is one of the active low-to-middle mass star forming regions. The core of this cloud, named Coronet, contains five protostar candidates. In 1994, we observed the Coronet Cluster using the X-ray satellite ASCA, and discovered hard X-rays from protostar candidates(Koyama et al. 1996).
New Detection of X-Ray Pulsar Nebulae by ASCA
Authors: Kawai N. , Tamura Keisuke , Shibata S.
Published: July 2016

X-ray images of rotation-powered pulsars were examined using ASCA Gas Imaging Spectrometer (GIS). The data sets are taken from those available in the ASCA public archive in the performance verification (PV) phase and the guest-observing (GO) phase 1. We detected diffuse X-ray sources in the vicinity of nine pulsars including five new detections. There are large variety in their morphology and spatial size. The high probability of finding such diffuse sources around pulsars suggests that they exist universally for all the active pulsars, and that they are powered by the pulsars. We propose that the pulsar-powered nebula is a good probe to measure the otherwise invisible energy flux dissipating from a pulsar into the surrounding space.
Evolution of Multiphase Hot Interstellar Medium in Elliptical Galaxies
Authors: Fujita Y. , Fukumoto J. , Okoshi K.
Published: July 2016

Theoretical arguments indicate that the ISM is inhomogeneous; Mathews estimated that the ~ 1M⊙ of metal ejected by each supernova event into the ISM is trapped locally within the hot bubbles. Since in elliptical galaxies, there is no overlapping of expanding supernova remnants after galactic wind period, it is expected that this inhomogeneity persists for a long time. The observations also suggests that the ISM of elliptical galaxies is inhomogeneous. Based on these arguments, we studied the evolution of the multiphase (inhomogeneous) ISM.
Solving the Mysteries in Hot ISM in Early-Type Galaxies
Authors: Matsushita K. , Ohashi T. , Makishima K.
Published: July 2016

We have analyzed ASCA data of about 30 early type galaxies, and studied their X-ray emitting ISM (InterStellar Medium) properties. Our study has been motivated by the apparently very low metallicity of the ISM, which cannot easily be reconciled with theoretical predictions. By carefully examining the abundance ratios and uncertainties in the Fe-L complex, we have concluded that the ISM abundances in X-ray luminous galaxies are in fact about 1 solar. Therefore, the severe discrepancy between the ISM and stellar abundance has been relaxed. The ISM metallicity of X-ray fainter galaxies are uncertain, but at least SNe Ia contribution to the ISM abundance is smaller than in the X-ray luminous ones.
ASCA X-Ray Observation of the Lobe Dominant Radio Galaxy NGC 612
Authors: Tashiro M. , Kaneda H. , Makishima K.
Published: July 2016

The radio galaxy NGC 612 (z = 0.0290; Spinrad et al. 1985) exhibits bright (~ 11 Jy at 843 MHz) double lobes at a large scale of about 500 kpc x 130 kpc with a very faint core (Jones & McAdam 1992). We performed ASCA observations (AO-4; PI = Kaneda) of NGC 612 on July 12-14, 1996, in search for inverse-Compton (IC) X-rays from the radio lobes.
ASCA Observations of the Abell 496 Cluster of Galaxies
Authors: Hatsukade I. , Ishizaka J. , Yamauchi M. , Takagishi K.
Published: July 2016

The metal in the intracluster medium (ICM) has been ejected or stripped from galaxies. Thus measurements of the metal distribution and the relative abundance of elements, in particular Si/Fe, are important to study the evolution of galaxies, as well as to study the chemical evolution of the ICM. We present the results from ASCA observations of Abell 496 cluster of galaxies. A496 is a nearby rich cluster with a central cD galaxy. At the redshift z=0.0327 of A496, 1 arcmin is 53kpc, where we assumed H0 = 50kms−1Mpc−1, q0 = 0.5. A496 is known as a cooling flow cluster. Edge and Stewart (1991) obtained the mass flow rate of and the cooling radius of 177 ± 52kpc.