bluuebunny/crossref_metadata_2025 huggingface dataset:
Periodical Errors of Hipparcos Star Abscissae
Authors: Makarov V. V.
Published: June 2019

An origin of both accidental and systematic errors of Hipparcos star abscissae is studied in the frames of the great circle reduction algorithm, adopted in the Hipparcos mission. Systematic variations of the basic angle within one turn of the Hipparcos satellite may be caused by periodical irregularities of the thermal flow from the sun radiation inside the satellite optical unit, enclosed in a hexagonal envelope. This would lead to periodical errors in the star abscissae at certain periods. It is shown, that an oscillation of the basic angle with a period of 60 degrees is the most dangerous one, as it is amplifyed 4.5 times. Lindegren et al. (1992) found, that the sixth harmonic in the star abscissae residuals clearly dominated with an amplitude of 0.96 milli-arcsec. If this is caused by basic angle disturbances, it follows that the amplitude of such variation may be up to 0.21 milli-arcsec. It is pointed out, that the thermal basic angle disturbances are not the only reason to expect periodical errors in star abscissae. Random abscissa errors too are inevitably of strong periodical sort, the periods of the largest harmonics being 60, 30, 18.9 (2π/19), 14.4 (2π/25) and 11.6 (2π/31) degrees for a basic angle of 58 degrees. They arise from the spatial spectrum transformation of the white noise in the primary observational data due to so-called ‘non-rigidity’ of star abscissae. The non-rigidity term acts as a factor to the photon noise errors of observations for stars of certain magnitude. A radical way to diminish both accidental and systematic periodical errors in a future Hipparcos-like astrometric satellite would be to use two different basic angles (Makarov, 1992). The basic angles of 58 and 74 degrees were considered, as they were found to be an optimal combination. In that case an improvement of precision by a factor of 2.8 can be achieved with the same Hipparcos parameters, some part of which should be explained by doubling number of observations, that is 2. It may be concluded, that using two telescopes with different basic angles for space astrometry allows to increase significantly precision for a great deal of stars under the same conditions.
Researches on the Accuracy of the DCMT Circle Reading System
Authors: Zi Zhu
Published: June 2019

The declinations of stars are determined by the circle micrometers on the meridian circle. The determined accuracy of declinations depends on the systematic accuracy of the micrometers. The DCMT (Danish Chinese Meridian Telescope) adopts photoelectric scanning micrometers as the circle reading system. It contains 6 micrometers forming 3 pairs to measure the circle posistion simultaneously. The repeatability of the circle reading and systematic errors of micrometers are discussed in this paper.
Astrometric Observations after 1988.0
Authors: Li Zheng-Xin
Published: June 2019

Shanghai Observatory has been the institute where astrometric observations are collected and treated after 1988.0, some tables are given here with which one may understand its recent situation.
The VLBI Complex “Quasar”: Current State and Perspective
Authors: Finkelstein A. M. , Gubanov V. S. , Yatskiv Ya. S.
Published: June 2019

The Institute of Applied Astronomy of the Russian Academy of Sciences (IAA RAS) is constructing the VLBI complex “QUASAR” consisting of six antennas across the former USSR. The complex will be a dedicated instrument for space geodesy and radioastrometry. Three aspects of the “QUASAR” project will be discussed. First, the description of the project and its concept will be presented. Secondly, the current state and problems of constructing the network will be outlined. Finally, some information on the international cooperation will be given.
Prediction of the Length of Day from Atmospheric Angular Momentum with LSTAR Model
Authors: Zheng Dawei
Published: June 2019

Adopting the time series of atmospheric angular momentum (AAM) from the National Meteorological Center of USA, the study of the prediction of the length of day (LOD) has been made by the Leap-Step Threshold AutoRegressive (LSTAR) model. The LSTAR model presented by the author is a sort of models for nonlinear time series analysis such as

where Dj is the j-th leap-step domain of the data series Zn, and (j) if the sample number N=L×M, then Zj+(L×K) εDj and K=0,1,…,M−1. En denotes the white noise of data in the j-th leap-step domain. TSM denotes a class of models in time series analysis and the nonlinear threshold autoregressive model is used here.
Deficiencies in the Nutation Model from VLBI Observations
Authors: Xia Y. F. , Gao J.
Published: June 2019

A VLBI series of celestial pole offsets has been used for deriving the corrections to the main terms of the IAU 1980 nutation series using the least squares solution and amplitude spectra method. The results are compared with current geophysical models. The discrepancies between observations and theory are largely due to deficiencies in the nutation models. A retrograde periodic variation (at a period of 420.0 days) has been revealed. The free mode will give us futher information on the core-mantle boundary.
The Contribution of the IERS to Astrophysics and Geodynamics
Authors: Feissel M. , Yatskiv Yaroslav
Published: June 2019

The International Earth Rotation Service (IERS) maintains a celestial reference frame and a terrestrial reference frame based on observations in Very Long Baseline radio Interferometry, Lunar and Satellite Laser Ranging, and Global Positioning System, as well as a time series of the Earth Orientation Parameters in a system that is consistent at the level of 0.001″.
Caractéres spectrophotomètriques de l'age
Authors: Chalonge D.
Published: June 2019

Sur les trois paramètres utilisés dans la classification tridimensionnelle deux sont indépendants de l'absorption interstellaire : ce sont D et λ1 qui mesurent la grandeur et la position dans le spectre de la discontinuité de Balmer. Si l'on classe les étoiles de la population I en se bornant à l'emploi de ces deux paramètres, on obtient directement et sans qu'aucune correction soit nécessaire un graphique analogue au diagramme HR : les points représent ant les étoiles de divers amas connus permettent de « graduer en âge » le diagramme composite ainsi établi directement et l'on peut en déduire des informations sur l'âge des étoiles individuelles n'appartenant pas aux amas précédents.

On a de même commencé à construire le diagramme relatif aux étoiles de la population II voisines du soleil.
The Cold Interstellar Medium in Elliptical Galaxies – Observations of HI and Radio Continuum Emission
Authors: Knapp G. R.
Published: June 2019

About 10% of nearby elliptical galaxies contain HI, with typical values of M(HI) ~ 5 × 108 M⊙ and M(HI)/LB ~ 0.03 M⊙/L⊙. The HI content is unrelated to the stellar content, (unlike the situation in spiral galaxies) suggesting that the HI in early-type galaxies has an external origin and is not produced by mass loss. This conclusion is strengthened by the distribution and kinematics of the HI structures, which lie outside the main optical body of the galaxies, have much larger specific angular momentum than do the stars, and are often highly inclined to the kinematic and distribution axes of the optical bodies.

The HI and stellar kinematics show that the rotation curves of E and SO galaxies are approximately flat from small (a few hundred pc) to large (10-20 kpc) radii, as is the case for spirals. Likewise, large mass-to-light ratios are found for some systems. Comparison with mass models derived from X-ray emission suggests that these may in some cases overestimate the mass.

The presence of HI is shown to enhance the likelihood that an E/SO galaxy has a nuclear radio continuum source, in agreement with models which suggest that the central engine is fuelled by cold gas. Current data suggest that the gas-to-dust ratio for the cold interstellar medium in ellipticals has a value similar to that found in the solar neighborhood.
Deprojection of Galaxies: How Much Can Be Learned?
Authors: Rybicki George B.
Published: June 2019

A general discussion, based on the ht “Fourier Slice Theorem,” is given for the problem of deprojecting the observed light distribution of galaxies to obtain their intrinsic three dimensional light distribution or “shape.” Several results are obtained: 1) A model-independent deprojection of an axially symmetric galaxy is shown to be possible only if the symmetry axis lies in the plane of the sky. 2) A simple criterion is given to test whether two different galaxies can have the same intrinsic shape, based solely on their observed projections. 3) It is shown that a homogeneous class of galaxies can be deprojected using a sufficiently large number of projections of random perspective.
Metal-Enhanced Galactic Winds
Authors: Patricia Vader J.
Published: June 2019

Constraints on supernova-driven galactic winds from elliptical galaxies at the epoch of star formation are investigated. The occurrence of mass loss is found to depend critically on the supernova rate in the case of dwarf galaxies, while the depth of the potential well is the most important constraint for giant ellipticals. The smallest dwarf ellipticals must have evolved from significantly more massive progenitors in order to have sustained a wind that carried away most of their metal production.
Dynamical Friction and Orbit Circularization
Authors: Casertano Stefano , Sterl Phinney E. , Villumsen Jens V.
Published: June 2019

We study the change in shape of the orbit of a satellite sinking (because of dynamical friction) towards the center of a larger galaxy. the galaxy is assumed spherically symmetric with distribution function either isotropic or predominantly radial. the satellite is a softened point mass.
Analytic Axisymmetric Dynamical Models with Three Integrals of Motion
Authors: Dejonghe Herwig , de Zeeuw Tim
Published: June 2019

We consider a family of inhomogeneous axisymmetric mass models with a simple gravitational potential originally introduced by Kuzmin (1956):

where R2 = x2 + y2, a and c are parameters, G is the gravitational constant, and M is the total mass of the corresponding density distribution.
Triaxial Scale-Free Models of Highly Flattened Elliptical Galaxies with Massive Halos
Authors: Levison Harold F. , Richstone Douglas O.
Published: June 2019

Two surveys of dynamical models of highly flattened, triaxial elliptical galaxies with isothermal potentials have been constructed. These models were constructed in order to better understand the range of possible observable dynamical properties of triaxial galaxies. All models have been constructed so that they appear as E6 galaxies when seen from their intermediate axes. However, one set of models is nearly oblate; the other is nearly prolate. the models are constructed with massive halos such that M/L ∝ r. Triaxial models of either shape can be constructed with their projected axes of rotation at any position angle with respect to the major axes of the galaxies. the most surprising result is that in most models, the position angle of maximum observed rotation is not perpendicular to the position angle of zero rotation.
Statistical Mechanics and Equilibrium Sequences of Ellipticals
Authors: Stiavelli M. , Bertin G.
Published: June 2019

Elliptical galaxies are expected to have undergone incomplete violent relaxation. Here incomplete relaxation is regarded as a process producing a metastable, long-lived state which is dynamically stabilized by the approximate conservation of one global quantity in addition to the total energy and number of particles.
Galactic Centers – Ours and Other Galaxies'
Authors: Rieke G. H.
Published: June 2019

Viewed from outside the Local Group, the Galactic Center would be a paragon of ordinariness, both with regard to its stellar population and its nonstellar emission in the radio, infrared, and X-ray.

Nonetheless, at a very modest level it shows evidence for many of the processes that we believe dominate the properties of exotic galactic nuclei.
Proper Motions of H2O Masers in W49(N) and the Distance to the Galactic Center
Authors: Gwinn C. R. , Moran J. M. , Reid M. J. , Schneps M. H. , Genzel R. , Downes D.
Published: June 2019

A distance of R0 = 7.6 ± 1.6 kpc for the galactic center is given by comparison of expansion parallax of a cluster of H2O masers in W49(N) with the kinematic distance of that source. Data from additional epochs, now being calibrated, should further improve the accuracy of our determination of R0.
The Nature of The Carbon Stars in The Galactic Bulge
Authors: Azzopardi M. , Lequeux J. , Rebeirot E. , Rich M.
Published: June 2019

JHK photometry of 33 carbon stars we found in the direction of the galactic bulge shows that they most likely belong to the bulge population and that they are intrinsically faint, metal rich objects. The conventional mixing mechanism is excluded in their case and thus their formation is still a mystery.
Detection of the 20 ↠ 3-1 Transition of 13CH3OH
Authors: Kuiper T. B. H. , Gardner F. F. , Whiteoak J. B. , Peters W. L. , Reynolds J. E.
Published: June 2019

The 20 → 3−1 E-type transition of 13CH3OH at 14.78 GHz has been detected towards four continuum sources: Sgr B2, two positions in Sgr A (the peaks of the ' + 20 km/s' and the '40 km/s' clouds), and W33. The NASA Deep Space Network 70-m antenna near Canberra, Australia, which has a 66 arcsec beam at this frequency, was used. A comparison of the 13C and 12C profiles for Sgr B2 indicates a rest frequency of 14,782.27 ± .03 MHz, 0.12 MHz above the laboratory value of Haque et al. (1974). For the Galactic Centre sources, the 12C/13C abundance ratios derived using the simplest assumptions lie in the range 30–40, higher than the 20–25 range derived from H2CO observations. For W33 the apparent value of ∼ 50 is lower than the value of ∼100 derived by Henkel et al. (1983) from H2CO. There may be no discrepancy, however, as W33 contains two velocity components — the higher velocity one at 36 km/s is more prominent in CH3OH and the lower 33 km/s more prominent in H2CO.
Bright Near-Infrared Sources Within 1° of the Galactic Center
Authors: Nagata Tetsuya , Sato Shuji , Hyland A. R. , Tokunaga Alan T.
Published: June 2019

A near-infrared survey has been conducted of 0.55 square degrees around the Galactic center with the 1 m telescope of Siding Spring Observatory, Australia. From the detected sources, 39 objects which are bright (K<7.6) and red (H-K>1.4) and 11 objects slightly fainter (K~8) have been selected. Subsequently, their 1–20 μm photometry and 2–3.5 μm spectra at a resolution of λ/Δλ∼150 have been obtained with the IRTF atop Mauna Kea, Hawaii.
HI Absorption Measurements over the Galactic Centre Radio Arc and Arches Regions
Authors: Lasenby J. , Lasenby A. N. , Yusef-Zadeh F.
Published: June 2019

An HI absorption study of the central ~ 100 pc of the galactic centre was performed using the compact array of the VLA2. The results of these observations lead us to believe that the body of gas at 40–50 km s−1, known as the ‘40 km s−1molecular cloud’, is placedbehindthe Arc. In addition, the distribution of gas around +20km s−1across the Arc and its correlation with 3cm polarized emission suggests that it may be this 20km s−1gas which is associated with the Arc and is depolarizing much of its synchrotron radiation. The kinematic structure of the negative velocity HI gas across the arched filaments implies an association between the neutral atomic gas and the ionized and molecular material.
The Kinematics of the Ionized Filaments in Sgr A West
Authors: Serabyn E.
Published: June 2019

The ionized gas within a few parsecs of the center of our galaxy is contained primarily in a number of thin elongated filaments (Ekers, this volume). Infrared and radio line observations have succeeded in determining the gas velocities along the majority of these filaments. A comparison of the line emission velocities with general kinematic models indicates that the motion of the filaments between 0.3 and 2 pc from the center is consistent with predominantly orbital motion.
High Quality VLA Imaging of Sgr A West at 6 Cm
Authors: Killeen N.E.B. , Lo K. Y.
Published: June 2019

VLA data of the Galactic center at 6 cm from the A, B, and C configurations have been combined to produce a high quality image at 0.76″ × 0.41″ resolution with a dynamic range of ≈ 5000. The new combined array image enables a clear definition of the diffuse and filamentary structures in Sgr A West. The bulk of the image processing was carried out with the National Center for Supercomputing Applications' Cray XMP-48 at Urbana-Champaign.
Flare activity levels for fully convective red dwarfs
Authors: Pettersen B.R.
Published: June 2019

Current stellar models predict fully convective structures for masses less than about 0.3 Mo. We have monitored low luminosity dMe and dM stars for flare activity with the 2.1 m telescope at McDonald Observatory. The dMe stars produced 2-5 detectable U-filter flares per hour while none were seen in the dM stars. Typically, 15-30% of the U-filter flux received from the dMe stars is due to flares. The flare activity level of dMe stars (on an absolute scale) decreases as one approaches the lower end of the main sequence. Non-linear frequency distributions of flare energy are seen in some binary flare stars, suggesting that both stars contribute to the ensemble of flares observed from the binary. Upper limits for the dM stars suggest activity levels about one thousand times smaller than in the dMe stars.
A prediction of the flare activity of stellar aggregates
Authors: Mnatsakanian M.A. , Mirzoyan A.L.
Published: June 2019

The problem of the statistical prediction of flare activity of a group of flare stars in stellar aggregates is considered.
Pinch-model of flares and its observational consequences
Authors: Hayrapetyan V.S. , Nikoghossian A.G.
Published: June 2019

The paper presents the basic ideas of pinch-model for UV Cet star flares. The observational consequences and predictions are discussed.
Closing remarks
Authors: Lada Charles J.
Published: June 2019

A number of years ago, the nobel-prize winning Chilean poet Pablo Neruda paid a visit to the Byurakan and wrote these comments in his Memoirs (1978:Penguin Books, New York, pg. 243.): “I shall never forget my visit to the astronomical observatory of Byurakan, where I saw the writing of stars for the first time. The trembling light of the stars was picked up; very fine mechanisms were taking down the palpitation of the stars in space, like an electrocardiogram of the sky. In those graphics I observed that each star has its own distinct way of writing, tremulous and fascinating, but unintelligible to the eyes of an earthbound poet” Unintelligible to the eyes of a poet, but as we have seen from this symposium, to the eyes of the astronomer, the phenomenon of flare stars is becoming more and more comprehensible. Before I came here to Byurakan I must confess that I (like Neruda) knew very little about the flare star phenomenon. As a result of this symposium I have learned much about these objects and now have a keen appreciation for their importance for studies of early stellar evolution. In this regard, I find it a particular priviledge and extremely appropriate to have a meeting on the subject of flare stars here at the Byurakan Observatory, where so much seminal work on this topic has been done. I have been impressed by the dedicated efforts of the astronomers at the Byurakan Observatory in flare star research. Their efforts represent an important contribution to galactic astronomy.
Extrasolar Planets and Prospects for Terrestrial Planets
Authors: Marcy Geoffrey W. , Butler R. Paul , Vogt Steven S. , Fischer Debra A.
Published: June 2019

Examination of ∼2000 sun–like stars has revealed 97 planets (as of 2002 Nov), all residing within our Milky Way Galaxy and within ∼200 light years of our Solar System. They have masses between 0.1 and 10 times that of Jupiter, and orbital sizes of 0.05–5 AU. Thus planets occupy the entire detectable domain of mass and orbits. News & summaries about extrasolar planets are provided at: http://exoplanets.org. These planets were all discovered by the wobble of the host stars, induced gravitationally by the planets, causing a periodicity in the measured Doppler effect of the starlight. Earth–mass planets remain undetectable, but space–based missions such as Kepler, COROT and SIM may provide detections of terrestrial planets within the next decade.

The number of planets increases with decreasing planet mass, indicating that nature makes more small planets than jupiter–mass planets. Extrapolation, though speculative, bodes well for an even larger number of earth–mass planets. These observations and the theory of planet formation suggests that single sun–like stars commonly harbor earth–sized rocky planets, as yet undetectable. The number of planets increases with increasing orbital distance from the host star, and most known planets reside in non–circular orbits. Many known planets reside in the habitable zone (albeit being gas giants) and most newly discovered planets orbit beyond 1 AU from their star. A population of Jupiter–like planets may reside at 5–10 AU from stars, not easily detectable at present. The sunlike star 55 Cancri harbors a planet of 4–10 Jupiter masses orbiting at 5.5 AU in a low eccentricity orbit, the first analog of our Jupiter, albeit with two large planets orbiting inward.

To date, 10 multiple–planet systems have been discovered, with four revealing gravitational interactions between the planets in the form of resonances. GJ 876 has two planets with periods of 1 and 2 months. Other planetary systems are “hierarchical”, consisting of widely separated orbits. These two system architectures probably result from gravitational interactions among the planets and between the planets and the proto-planetary disk out of which they formed.
Searching for Extrasolar Planets Using Transits
Authors: Hidas M. G. , Webb J. K. , Ashley M. C. B. , Lineweaver C. H. , Anderson J. , Irwin M.
Published: June 2019

The presence of an extrasolar planet can be revealed when it passes in front of its host star, reducing the star's apparent brightness by ∼ 1%. We are monitoring a large sample (of order 104) of stars using our own 0.5 m telescope at Siding Spring Observatory, Australia, in search of such transiting planets.
HST/FGS High-Speed Photometric Observations of Transits of HD 209458b
Authors: Welsh William F. , Schultz A. B. , Kinzel W. , Kochte M. , Jordan I. , Hamilton F. , Bruhweiler F. , Hart H. , Hamilton D.P. , Henry G. , Miskey C. , Rodrigue M. , Bennum D. , Rassuchine J. , Storrs A. , Vogt S. , Orosz J. A. , Wittenmyer R.
Published: June 2019

We present preliminary analysis of new HST observations of the transiting extrasolar planet HD 209458b. Photometric observations were obtained with the Fine Guidance Sensor (FGS) on the Hubble Space Telescope (HST), providing milli-mag precision and high time resolution (40 Hz). The FGS photometry allows us to derive precise stellar/orbital parameters (ephemeris, inclination, limb darkening) and planetary radius, and also allows a search for the presence of planetary rings and satellites. We discuss preliminary results and two approaches to modelling the observations.
Searches for Pulsar Planetary Systems
Authors: Lazio T. Joseph W. , Fischer J. , Cordes James M.
Published: June 2019

The first extrasolar planetary system was discovered around the pulsar PSR B1257+12, and the planets therein remain the lowest mass exoplanets known (with one whose mass is of order a lunar mass). Pulsar planetary systems will remain the only extrasolar planetary systems within which terrestrial-mass planets can be detected for the near future, and multiple pulsar planetary systems would provide strong circumstantial evidence that terrestrial-mass planets are ubiquitous, and possibly information about the formation of terrestrial-mass planets. We summarize two searches for planetary or proto-planetary systems around pulsars. The first is a series of infrared observations of millisecond pulsars in which the objective is to detect (proto-planetary) disks. The second uses a genetic algorithm—a function optimization method based on evolutionary processes in the natural world—to search for the signatures of planetary perturbations in pulse timing data.
Life among the Craters
Authors: Schmitt Harrison H.
Published: June 2019

The Moon forms one end-member in the planetary mass series Earth-Venus-Mars-Mercury-Asteroids-Moon (Weissman 1999). Having a detailed understanding of the nature and evolution of the two end-members of this series, rather than of just the Earth, has increased the value of other data and inferences by orders of magnitude. As a consequence of obtaining an understanding of the evolution of a second planet, we now can look at other terrestrial planets with far greater insight than ever would have been possible otherwise (Fig. 1).
Three Years of SETI@home: A Status Report
Authors: Korpela Eric J. , Cobb Jeff , Fulton Steve , Lebofsky Matt , Heien Eric , Person Eric , Demorest Paul , Bankay Robert , Anderson David , Werthimer Dan
Published: June 2019

The SETI@home project has recently completed its third year of active data analysis. Over 4 million volunteers have joined the search, providing a combined total of over 1 million CPU-years of processing power. SETI@home performs a sensitive search for extraterrestrial signals in a 2.5 MHz band centered on 1420 MHz. SETI@home searches a wide parameter space including 14 octaves of signal bandwidth and 15 octaves of pulse period with Doppler drift corrections from −50 Hz/s to +50 Hz/s. We will briefly describe the SETI@home project and the algorithms used in the SETI@home client. We will describe the post-processing methods we use to reject RFI and select candidate signals from the nearly 4 billion “hits” returned by SETI@home clients.
Origin and Evolution of the UCLA AstroBiology Society
Authors: Methot Laurel , Finley Jason
Published: June 2019

Co-sponsored by the NASA Astrobiology Institute (NAI) at UCLA, and the Center for the Study of Evolution and the Origin of Life (CSEOL), the UCLA AstroBiology Society (ABS) was founded in 1999 to become the first student-run organization devoted to astrobiology. An interdisciplinary group, ABS unifies undergraduates, graduate students, and faculty of all fields through events and discussions centered around the diversity of themes that compose astrobiology science. ABS provides particular benefit to NAI's Education and Public Outreach efforts as a means of increasing awareness of and appreciation for astrobiology, particularly in the college community. A greater goal of the organization involves networking to seed AstroBiology Societies on other college campuses nation-wide. Additionally, ABS is currently doing research for NAI's Astrobiology Pathfinder program, which will help students at all stages to become Astrobiologists.
Maps of the Cosmos: The Cosmic Microwave Background
Authors: A. Page Lyman
Published: June 2019

Since the IAU XXIV meeting in 2000, the CMB anisotropy has matured from being one of a number of cosmological probes to forming the bedrock foundation for what is now the standard model of cosmology. The large advances over the past three years have come from making better and better maps of the cosmos. We review the state of measurements of the anisotropy and outline some of what we have learned since 2000. The recent advancements may be placed roughly into three categories: 1) What we learn from the CMB with minimal input from other cosmic measurements such as the Hubble constant; 2) What we learn from the CMB in combination with other probes of large scale structure; and 3) What we learn by using the CMB as a back light. Future directions are also discussed. It is clear: we have much more to learn from the CMB anisotropy.
Imaging the Cosmic Microwave Background with the Arcminute Cosmology Bolometer Array Receiver
Authors: Peterson J. B. , Romer A. K. , Gomez P. L. , Ade P. A. R. , Bock J. J. , Bond J. R. , Contaldi C. R. , Pogosyan D. , Cantalupo C. , Daub M. D. , Holzapfel W. L. , Lueker M. , Newcomb M. , Woolsey D. , Kuo C. L. , Lange A. E. , Runyan M. C. , Ruhl J. , Goldstein J. H. , Torbet E.
Published: June 2019

The Arcminute Cosmology Bolometer Array Receiver (Acbar) is a multifrequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. Acbar was installed on the 2.1 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. The power spectrum of the CMB at 150 GHz over the range ℓ = 150 — 3000 measured by Acbar is presented along with estimates for the values of the cosmological parameters within the context of ΛCDM models. The inclusion of ΩΛ greatly improves the fit to the power spectrum. Three-frequency images of the SZ decrement/increment are also presented for the galaxy cluster 1E0657–67.
Mapping the Dark Energy Equation of State
Authors: Linder Eric V.
Published: June 2019

The acceleration of the expansion of the universe has deep implications for structure formation, the composition of the universe, and its fate. Roughly 70% of the energy density is in a dark energy, whose nature remains unknown. Mapping the expansion history through supernovae, mapping the geometry of the universe and formation of structure through redshift surveys, and mapping the distance to recombination through the cosmic microwave background provide complementary, precise probes of the equation of state of the dark energy. Together these next generation maps of the cosmos can reveal not only the value today, but the redshift variation, of the equation of state, providing a critical clue to the underlying physics.
Cosmology from the 2dF QSO Redshift Survey
Authors: Croom Scott , Boyle Brian , Shanks Tom , Outram Phil , Myers Adam , Smith Robert , Miller Lance , Lopes Ana , Loaring Nicola , Hoyle Fiona
Published: June 2019

The 2dF QSO Redshift Survey (2QZ) is now complete and available to the astronomical community (see www.2dfquasar.org). In this paper we review some of the principle science results to come from the survey, in particular concentrating on tests for cosmological parameters. Measurements of large-scale structure using the correlation function and power spectrum, together with determinations of the geometric distortion of clustering in redshift-space have been used. These produce a consistent picture which is well matched to the now standard cosmological model with Ωm ≃ 0.3 and ΩΛ ≃ 0.7. In particular, geometric distortions provide evidence for non-zero ΩΛ independent of type Ia supernovae, the CMB, or the assumed type of dark matter (e.g. CDM). However, gravitational lensing results in the form of potential arcminute separation lensed pairs and a stronger than expected anti-correlation between QSOs and foreground galaxies in groups and clusters may prove to be inconsistent with the current standard model. These issues certainly require further investigation.
Mapping the Dark Matter Using Weak Lensing
Authors: Hoekstra Henk
Published: June 2019

Weak gravitational lensing of distant galaxies by foreground structures has proven to be a powerful tool to study the mass distribution in the universe. The advent of panoramic cameras on 4-m class telescopes has led to a first generation of surveys that already compete with large redshift surveys in terms of the accuracy with which cosmological parameters can be determined. The next surveys, which already have started taking data, will provide another major step forward. At the current level, systematics appear under control, and it is expected that weak lensing will develop into a key tool in the era of precision cosmology, provided we improve our knowledge of the non-linear matter power spectrum and the source redshift distribution. In this review we will briefly describe the principles of weak lensing and discuss the results of recent cosmic shear surveys. We show how the combination of weak lensing and cosmic microwave background measurements can provide tight constraints on cosmological parameters. We also demonstrate the usefulness of weak lensing in studies of the relation between the galaxy distribution and the underlying dark matter distribution (“galaxy biasing”), which can provide important constraints on models of galaxy formation. Finally, we discuss new and upcoming large cosmic shear surveys.
Subaru Suprime-Cam Weak Lensing Survey Over 33 deg2 — Suprime33
Authors: Miyazaki Satoshi , Hamana Takashi , Refregier Alexandre , Ellis Richard
Published: June 2019

We have demonstrated that newly developed Suprime-Cam on the 8-m Subaru telescope is capable of blind searches of mass concentration via weak lensing. We then propose to extend the survey up to 33 square degrees where archival X-ray data is available (Suprime33 Survey). The survey status and the performance of Suprime-Cam in the weak lensing survey are shown.
“Cosmic Windows” Sky Surveys
Authors: Condon J. J. , Cotton W. D. , Yin Q. F. , Heckman T. M. , Lonsdale C. J. , Smith H. E. , Martin C. D. , Schiminovich D. , Oliver S. J. , Röttgering H. J. A.
Published: June 2019

Far-infrared (FIR), ultraviolet (UV), and soft X-ray observations are easily degraded by dust and gas between the source and the telescope. They must be made from space, where they are still affected by the interstellar medium (ISM) of our Galaxy. Fortunately the ISM is quite patchy, with several “cosmic windows” covering ∼ 100 deg2 of sky having exceptionally low interstellar extinction and cirrus emission. Since the universe is nearly isotropic, these windows contain representative samples of cosmologically distant sources and will be the targets of deep multiwavelength studies including SWIRE, GALEX/DIS, and XMM-LSS. Overlapping optical and radio surveys provide essential source identifications, redshifts, morphologies, and continuum spectra. The prototype VLA survey (see http://www.cv.nrao.edu/sirtf_fls/) covers the 5 deg2 SIRTF First-Look Survey (FLS) and is being used to identify the expected FIR sources in advance. Most will be star-forming galaxies obeying the very tight far-infrared/radio correlation and thus continuum radio sources stronger than S ≈ 100 μJy at 1.4 GHz. Proposed VLA surveys covering the remaining “cosmic windows” will be useful for studying the evolution of obscured AGNs, clusters, and other uncommon objects.
Early Results from the VIMOS VLT Deep Survey
Authors: Le Fèvre O. , Adami C. , Ilbert O. , Le Brun V. , Marinoni C. , Mazure A. , Meneux B. , Paltani S. , Tresse L. , Vettolani G. , Bondi M. , Cappi A. , Ciliegi P. , Marano B. , McCracken H. J. , Pozzetti L. , Zanichelli A. , MaCcagni D. , Bottini D. , Foucaud S. , Franzetti P. , Garilli B. , Scodeggio M. , Picat J. P. , Contini T. , Gavignaud I. , Mathez G. , Pellò R. , Arnaboldi M. , Busarello G. , Merluzzi P. , Radovich M. , Mellier Y. , Charlot S. , Guzzo L. , Iovino A. , Pollo A. , Rizzo D. , Scaramella R. , Bardelli S. , Bolzonelle M. , Zamorani G. , Zucca E.
Published: June 2019

The VIMOS VLT Deep Survey (VVDS) is underway to study the evolution of galaxies, large scale structures and AGNs, from the measurement of more than 100 000 spectra of faint objects. We present here the results from the first epoch observations of more than 20000 spectra. The main challenge of the program, the redshift measurements, is described, in particular entering the “redshift desert” in the range 1.5 < z < 3 for which only very weak features are detected in the observed wavelength range. The redshift distribution of a magnitude limited sample brighter than IAB = 24 is presented for the first time, showing a peak at a low redshift z ∼ 0.7, and a tail extending all the way above z = 4. The evolution of the luminosity function out to z = 1.5 is presented, with the LF of blue star forming galaxies carrying most of the evolution, with L* changing by more than two magnitudes for this sub-sample.
Characteristics of the diffuse interstellar medium
Authors: Cox D. P.
Published: June 2019

There have been several recent changes in perspective on the diffuse interstellar environment, including recognition of a thick disk of warm gas, cosmic rays, and magnetic field. In addition, evidence for a pervasive hot phase driven by supernova disruption has weakened to the point that a quasihomogeneous warm intercloud gas may occupy most of the interstellar volume at midplane, with individual bubbles created by supernovae and OB associations occupying perhaps 10 and 20 per cent respectively. The bubble population is sufficient to explain the high stage ions (0 VI, N V, C IV, perhaps Si IV) found in the disk, though possibly not those found at higher z. The estimated midplane pressure has increased, leaving the thermal pressure inside clouds almost negligible. The reduced porosity of the medium, its greater thickness, and its larger pressure all act to suppress fountain activity, either arising from the disk generally, or from the blowout of superbubbles. Finally, there appears to be a peculiar coincidence between the cloud heating mechanism and the activity determining the interstellar pressure.
The atomic hydrogen/molecular cloud association: an unavoidable relationship
Authors: Joncas G.
Published: June 2019

The presence of HI in the interstellar medium is ubiquitous. HI is the principal actor in the majority of the physical processes at work in our Galaxy. Restricting ourselves to the topics of this symposium, atomic hydrogen is involved with the formation of molecular clouds and is one of the byproducts of their destruction by young stars. HI has different roles during a molecular cloud's life. I will discuss here a case of coexisting HI and H2 at large scale and the origin of HI in star forming regions. For completeness' sake, it should be mentionned that there are at least three other aspects of HI involvement: HI envelopes around molecular clouds, the impact of SNRs (see work on IC 443), and the role of HI in quiescent dark clouds (see van der Werf's work).
The investigation of the hierarchical structure of the interstellar magnetic fields
Authors: Lazarian A.L.
Published: June 2019

A new method of investigation of the hierarchical structure of the interstellar magnetic fields is discussed. Synchrotron intensity fluctuations are used. Statistical characteristics of the irregular magnetic field are available. The method was successfully tested.
Loss of magnetic flux and angular momentum from molecular clouds
Authors: Nakano Takenori
Published: June 2019

The magnetic field and the angular momentum are major obstacles against cloud contraction. I will review recent results on magnetic flux loss rate and angular momentum loss rate and will investigate a gross feature of cloud contraction.
Magnetic fields and the dynamics of molecular clouds
Authors: Puget J. L.
Published: June 2019

Magnetic fields are believed to play an important role in the star formation process. Correlations in the velocity field in molecular filaments are indicative of dynamical interactions between clouds and parts within a cloud. The magnetic field is a likely candidate as the vector of such interactions. Perturbations of the field at large scales can feed the velocity dispersion within condensations at small scale. This mechanism is discussed in the framework of two simple analytical approximations describing transverse waves fed into plane parallel slabs.
Variations in the abundance of small particles
Authors: Boulanger F.
Published: June 2019

IRAS images of nearby molecular clouds show that the mid-IR emission from small particles in the size range 102 to 105 atoms is distributed very differently from the 100 μm emission from large dust grains. Variations in color ratios by as much as one order of magnitude are seen on all angular scales. We summarize observational properties of the color variations and argue that neither their large amplitude nor their morphology can be explained by changes of the excitation by the UV radiation field only. The color variations reflect considerable inhomogeneities in the abundance of small particles. We suggest that the abundance variations are related to the cycling of interstellar matter between the gas phase and dust grains. This interpretation entails that clouds with distinct IR colors differ in their density and velocity structure and that cycling of matter between gas phase and dust grains is more ubiquitous and rapid that generally thought.
Dense core structure and fragmentation in the Rho Ophiuchi molecular cloud
Authors: Wootten Alwyn
Published: June 2019

About a dozen distinct dense cores have been identified in the Rho Ophiuchi molecular cloud. The properties of these cores are summarized and compared to the properties of cores in the Taurus molecular cloud, a less efficient region of star formation, and in DR21(OH), a more massive region of star formation. The data are consistent with a picture in which more massive clouds have a higher surface density of cores, which in turn are more massive. The adjacent cores in L1689N have been studied with very high resolution; one has formed stars and one never has. The structure of these cores shows a tendency for duplicity of structures from the largest scales (1 pc) to the smallest (50 AU).
UV penetrated clumpy molecular cloud cores
Authors: Stutzki Jürgen , Genzel Reinhard , Graf Urs , Harris Andrew I. , Sternberg Amiel , Güsten Rolf
Published: June 2019

Recent observations of sub-mm and far-IR atomic fine structure and molecular rotational lines give evidence that due to the clumpiness of the molecular cloud cores the UV radiation from newly formed stars affects a very large fraction of the cloud material. Direct observations of the clumpy structure in M17 SW allow to derive several parameters of the clump distribution, in particular the clump mass spectrum and the volume filling factor. Implications of these results in regard to star formation are shortly discussed.
Aperture synthesis observations of Orion-KL in CS lines and 3mm continuum
Authors: Murata Y. , Kawabe R. , Ishiguro M. , Hasegawa T. , Hayashi M.
Published: June 2019

We have made aperture synthesis maps toward the Orion-KL nebula in CS(1-0), CS(2-1) and 3mm continuum with the Nobeyama Millimeter Array (NMA). The CS(1-0) maps were obtained across the central 2′ region of the Orion-KL nebula. Our maps show the rotating disk around the KL nebula with the diameter of 0.3 pc and the mass of 25 M⊙. The disk clearly shows the Keplerian rotation, which indicates that the mass of the KL nebula is 100 — 150 M⊙. The shell structure around the molecular outflow is also found in CS(1-0) map. This structure also appears in CS(2-1) map.

From 3mm continuum map, we have found at least six continuum sources. One of them is f-f emission from the ultra-compact HII region around BN. Other sources are the dust clumps whose masses are estimated to be 1 — 4 M⊙. The distribution of the dust clumps shows clear anti-correlation with the 20 μm emissions. This indicates that the 20 μm emissions are obscured by these dust clumps.
A 45 AU radius source around L1551-IRS 5: a possible accretion disk
Authors: Keene J. , Masson C. R.
Published: June 2019

Our interferometric and single-dish observations of the continuum emission from L1551-IRS 5 show that, at millimeter wavelengths, there are two distinct components to the source, an envelope with a radius ≥ 2000 AU, and a compact core with a radius ≤ 64 AU. The compact core has a large optical depth, indicating a high column density (∼ 1000 g cm—2). By modeling the temperature in the region of the compact core, we show that its size must lie in the range 45 ± 20 AU. The compact core is most plausibly identified with an accretion, or preplanetary, disk around the star, although the present observations do not have sufficient angular resolution to rule out other structures.
High-Velocity molecular bullets in bipolar outflows: L1448 and HH7-11
Authors: Bachiller R. , Cernicharo J. , Martin-Pintado J. , Tafalla M. , Lazareff B.
Published: June 2019

On the main axis of two bipolar outflows (L1448 and HH7-11), we have discovered molecular clumps (“bullets”) moving at extremely high-velocities. The observations were made in CO lines (mainly J = 2 — 1) with the IRAM 30-m telescope at Pico Veleta, near Granada (Spain). We present in Figure 1 some profiles observed toward the axis of the two outflows. In addition to the ambient line and to the extremely high-velocity wings, we observe several very well defined peaks at high velocities. Our maps show that these features are well delimited in the space, indicating that they arise in small high-velocity clumps or “bullets”.
First Detection of 661 GHz 13CO J=6 →5: Large Amounts of Warm Molecular Gas
Authors: Graf U.U. , Genzel R. , Harris A.I. , Hills R.E. , Russell A.P.G. , Stutzki J.
Published: June 2019

Submillimeter and far-infrared observations of carbon monoxide (Jaffe, Harris, and Genzel 1987; Genzel, Poglitsch, and Stacey 1988; Schmid-Burgk et al. 1989; Boreiko, Betz, and Zmuidzinas 1989) have indicated the presence of warm, dense molecular gas near regions of recent star forming activity. Estimates based on the comparison of mid-J (submm) and high-J (far-IR) 12CO lines in M17 and S106 (Harris et al. 1987a) gave a lower limit of ≈1018 cm−2 (τ(12CO 7 →6) ≈ 1) to the CO column density of quiescent (Δv ≤ 10 km/s) gas at temperatures of at least 100 K and H2 densities of 104 to 106 cm−3. The mid-J 12CO lines are likely to be optically thick in most sources. In order to obtain a better estimate of the column densities, it is thus of great interest to observe isotopic mid-J CO lines, which are likely to be optically thin.
CO multitransition observations of L 1228: A molecular outflow destructing its parent cloud?
Authors: Haikala L.K. , Weikard H.
Published: June 2019

CO, J=3 →2, J=2 →1 and J = 1 →0 observations of the extended molecular outflow in the high latitude cloud L 1228 are presented. The 12CO, J=3 →2 and J=2 →1 observations reveal a well collimated and extended outflow. The 12CO, J = 1 →0 observations show that the red shifted part of the outflow has blown a large cavity into the parent cloud and has thus dispersed a significant part of the surrounding cloud.
Ammonia clumps in the Orion and Cepheus clouds
Authors: Harju J. , Walmsley C.M. , Wouterloot J.G.A.
Published: June 2019

We present statistics of clump properties in the Orion and Cepheus cloud complexes based on ammonia mapping observations. Surroundings of about 50 IRAS sources earlier found to have associated molecular line emission (Wouterloot, Walmsley and Henkel, 1988) were mapped in NH3(1,1) and (2,2) with the Effelsberg 100-m telescope. Our main interest has been in determining the clump sizes and masses on the basis of the ammonia column density distribution, which together with the observed velocity dispersion lead to a rough estimate of the dynamical state. We also have studied the star-clump separations which should give us estimates of the source ages. Special attention has been paid to comparison of our Orion data with the Benson and Myers (1989, hereafter BM89) results in Taurus because the linear resolutions in the two studies are similar.