bluuebunny/crossref_metadata_2025 huggingface dataset:
VLBI Imaging of Luminous Infrared Galaxies: Starbursts & AGN
Authors: E. Smith Harding , J. Lonsdale Carol , J. Lonsdale Colin , J. Diamond Philip
Published: July 2016

Luminous Infrared Galaxies (LIGs) are locally more numerous than normal galaxies, AGN, and QSOs above L ˜ 1011L⊙ and may be the evolutionary precursors of classical radio-quiet quasars. VLBI observations of a complete sample show that high-Tb radio cores are common, perhaps universal among LIGs. VLBI imaging shows that these radio cores may be produced by intense starbursts which generate luminous radio supernovae, as in the case of Arp 220 (Smith et al. 1998), or by a classical AGN core, as in the case of Mrk 231, which we interpret as a newly formed QSO emerging from a starburst. Compact OH 1667MHz maser emission appears to be common in LIGs and may be related to AGN activity. These results lend further support to the scenario suggested by Sanders et al (1988) in which mergers of gas-rich galaxies lead first to luminous starbursts which evolve into radio-quiet quasars.
Feeding the Central Engine in Giant Radio Galaxies
Authors: Mirabel I. F. , Laurent O.
Published: July 2016

Giant radio galaxies are thought to be massive ellipticals powered by accretion of interstellar matter onto a supermassive black hole. Interactions with gas rich galaxies may provide the interstellar matter to feed the active galactic nucleus (AGN). To power radio lobes that extend up to distances of hundreds of kiloparsecs, gas has to be funneled from kiloparsec size scales down to the AGN at rates of ˜1 M⊙ yr−1 during ≥108 years. Therefore, large and massive quasi-stable structures of gas and dust should exist in the deep interior of the giant elliptical hosts of double lobe radio galaxies. Recent mid-infrared observations with ISO revealed for the first time a bisymmetric spiral structure with the dimensions of a small galaxy at the centre of Centaurus A (Mirabel et al. 1999). The spiral was formed out of the tidal debris of accreted gas-rich object(s) and has a dust morphology that is remarkably similar to that found in barred spiral galaxies. The observations of the closest AGN to Earth suggest that the dusty hosts of giant radio galaxies like CenA, are “symbiotic” galaxies composed of a barred spiral inside an elliptical, where the bar serves to funnel gas toward the AGN.
The Variability of Optically Selected QSO Sample
Authors: Huang Keliang , Zhou Hongnan
Published: July 2016

Variability may be a common property of AGNs. It provides a powerful tool to study the physics of AGNs. For QSOs, variability is a suitable criterion for selecting candidates. Many variability studies on quasar samples have been made (e.g. Netzer and Sheffer 1983, User et al. 1983, Pica and Smith 1983, Wampler and Ponz 1985, Neugebauer et al. 1989, Huang et al 1990, Cristiani et al. 1990, Giallongo et al. 1991, Cimatti et al. 1994, Treverse et al. 1994, Hook et al. 1994, Cristiani et al. 1996, Axetxage et al. 1997). In some studies, a large percentage of quasars is found to have detectable variation. However, other studies find no variability evidence. Many studies also discuss the correlations of variability with luminosity or redshift. Some interesting results have been made. However, up to now, there are no positive conclusions. Further study on variability of quasar samples is obviously needed. In this paper, we report on a variability study of 32 members at the Medium Bright Quasar Sample (Mitchell et al. 1984). The study is actually a continuation of the previous study (Huang et al. 1990).
The Continuum Spectra of the Core and Hotspots of Cygnus-A in the Millimetre and Submillimetre
Authors: Leeuw L.L. , Robson E.I.
Published: July 2016

Submillimetre imaging (350 μm to 850 μm) and millimetre photometry (1.35 mm and 2 mm) observations, obtained with SCUBA (Holland et al. 1998), are used: (1) to investigate electron aging for synchrotron emission and (2) to determine the dust content in Cygnus-A.
The Variability of QSOs in the Optical Band
Authors: Trèvese D. , Bunone A. , Kron R.G.
Published: July 2016

Constraints on the emission mechanism of AGNs can be provided by the variability of their spectral energy distribution (SED). Recently Di Clemente et al. (1996) have shown that the positive correlation of QSO variability with redshift can be due to a hardening of the spectrum in bright phases, coupled with the increase of the rest-frame frequency of the (fixed) observing band, for increasing redshift. Direct evidences of slope changes in the SEDs of a limited number of individual AGNs have been provided by Cutri et al. (1985), Edelson et al. (1990), and Kinney et al. (1991). In the following we present some preliminary results of a direct measure of variations of the SED slope in the complete, magnitude limited, sample of QSOs of the Selected Area 57 (Koo, Kron & Cudworth 1986; Trèvese et al. 1989 (T89)). The data are derived from two sets of prime focus plates of the SA 57, in the U, BJ, F and N bands, obtained with the 4-m telescope at the Kitt Peak National Observatory at two epochs separated by one year. Photometric methods and signal-to-noise optimization are described in T89 and Trèvese et al. (1994). The quasar sample, of < z > ⋍ 1.4, consists of 33 objects from T89, plus the brightest 3 members of the the Bershady, Trèvese and Kron (1998) sample of extended objects selected on the basis of variability. In Figure 1a Δα is reported versus the changes Δlog fv in the BJ band and shows positive correlation, indicating a hardening of the spectrum in the bright phase. A special care is needed to avoid spurious Δα – Δlog fv correlations (see Massaro & Trèvese 1996). The correlation coefficient is r=0.46 with a probability P(>r)=0.995, after the exclusion of one deviant point, whose inclusion would produce a higher correlation. The slope of the linear regression of ΔαΔlogv is b=1.9. Assuming that the spectra are, dominated by the big blue bump (BBB) in the sampled spectral region, around λ ≍ 2000 Å, we can use the simple approximation of a single black-body spectrum. To check the hypothesis that both the slope and brightness changes are caused by a temperature variations only, we derive the black-body temperatures from the SED slope as deduced from a linear fit of the log fv v.s. logv relation, based on the U, BJ and F data. The average slope (excluding the two highest and lowest z objects) is 〈α〉=-0.4±0.6 and the average temperature is T ≍ 25000 K. For a black-body of fixed emitting surface and varying temperature T, the changes of the local SED slope and the relevant luminosity variations are related by (dα/dT)/(dlogBv/dT) ≡ f(x), where x ≡ hv/kT. The slope b of the linear regression of Δα v.s. log fv of Figure la is compared with the function f(x) values of the sample determined by the dispersion of α. We can conclude that dα/dlogBv and α are consistent for x ≍ 3. For an average sampling wavelength < λ > ≍ 2000 Å of the sample, this corresponds to an average temperature T ≍ 2.5 × 104 of a black-body of fluctuating temperature.
Energy Sources and Physical Processes in Active Galaxies
Authors: W. Weedman Daniel
Published: July 2016

The galaxy Markarian 231 is reviewed as a prototype that includes all physical processes associated with active galaxies. It contains both a starburst and an AGN which are highly obscured by dust. Its luminosity at various wavelengths is used to summarize how such a galaxy would appear at high redshift, as observed with missions such as HST, AXAF, and SIRTF. The conclusion is that Markarian 231 provides an excellent example for comparing low redshift and high redshift phenomena.
What Physics Drives the Unified Model?
Authors: A. Dopita Michael
Published: July 2016

The Unified Model holds that the aspect-dependent effects primarily determine the apperance of the active galactic nucleus that we observe. However, additional parameters will be needed to fully unify the different tribes of AGN. Three parameters; aspect, accretion rate into the nuclear regions, and the evolutionary status of the central black hole probably hold the key to “grand” unification schemes.
The Jets of Quasars 3C 345 and 1803+784
Authors: Matveenko L. I. , Witzel A. I.
Published: July 2016

We have studied the structures of AGN objects 3C345 and 1803+784. The objects have one sided jets with conic helix structure, determining step and diameter of the helix. The jets are surrounded by cocoon - thermal plasma, the transparency of which determines low frequency variability and absorption of the core emission.
An Asymmetric Relativistic Model for FRII Radio Sources
Authors: Arshakian T. G. , Longair M. S.
Published: July 2016

An asymmetric relativistic model for FRII radio sources is described which takes account of both relativistic effects and intrinsic/environmental asymmetries to explain the observed structural asymmetry of their radio lobes. A key feature of the model is jet-sidedness, which can now be determined for about 80% of the FRII sources in the 3CRR complete sample. It is shown that a simple asymmetric relativistic model can account for a wide range of observational data, and that the relativistic and intrinsic asymmetry effects are of comparable importance. The mean translational speed of the lobes is . The results are in agreement with an orientation-based unified scheme in which the critical angle separating the radio galaxies from the radio quasars is about 50°.
Can the Sonic Radius in ADAF Be Large?
Authors: Yuan F. , Huang K.L. , Lu Ju-fu
Published: July 2016

We obtain the global transonic solutions by solving numerically a set of equations describing advection dominated accretion flows around black holes. We find that the sonic points can locate themselves at almost any radius, independent of the viscosity parameter α and the polytropic index γ.
A UV Flare at the Center of the Elliptical Galaxy NGC 4552
Authors: M. Buson Lucio , Bertola Francesco , Burstein David , Cappellari Michele , Serego Alighieri Sperello di , Greggio Laura , Renzini Alvio
Published: July 2016

A self-consistent analysis of near-UV, HST/FOC images of the elliptical galaxy NGC 4552 is used to show that its central spike has brightened by a factor ˜ 4.5 between 1991 and 1993, and has decreased its luminosity by a factor ˜ 2.0 between 1993 and 1996. A strong UV continuum over the energy distribution of the underlying galaxy is concurrently revealed shortward of λ ˜ 3200 Å by our FOS spectra extending from the near-UV to red wavelengths. Nuclear emission-line profiles of both permitted and forbidden lines are best modelled with a combination of broad and narrow components, with FWHM of ˜ 3000 km s−1 and ˜ 700 km s−1, respectively. Current diagnostics based on the emission line intensity ratios definitely places the spike among AGNs, just at the border between Seyferts and LINERs. This evidence argues for the variable central spike being produced by a modest accretion event onto a central massive black hole (BH), with the accreted material having possibly being stripped from a star in a close fly-by with the BH. In this regard, one has to look at NGC 4552 as the faintest known AGN.
Emission-Line Galaxies in Shahbazian Compact Groups
Authors: Tiersch H. , Stoll D. , Neizvestny S. , Amirkhanian A.S. , Egikian A.G.
Published: July 2016

Based on the CCD photometric and spectroscopic observations taken with 1.23 m and 2.2 m telescopes at the German-Spanish Astronomical Center in Calar-Alto (Almeria, Spain) as well as with the 1.54 m telescope at the European Southern Observatory (La Silla, Chile) some emission-line galaxies (ELGs) surprisingly have been found in Shahbazian compact groups of galaxies (SHCGs) by our research group.
Rapid Profile Variations in the Broad Hα Line of the Seyfert Galaxy Markarian 6
Authors: Asatrian N. S. , Khachikian E. Ye. , Notni P.
Published: July 2016

We report on rapid variations of the Hα profile in Mark 6 over a period of about one hour and the implications for the velocity field of the BLR.
Multiwave Monitoring of the Nuclei of Seyfert Galaxies and Quasars at Several Telescopes of FSU and European Countries in the Frame of an INTAS Program
Authors: Bochkarev N.G. , Shapovalova A.I. , Burenkov A.N. , Vlasyuk V.V.
Published: July 2016

Several groups of astronomers in FSU (Former Soviet Union) and European countries have started, in 1998, a cooperative spectral and broad-band optical and UV-monitoring of the nuclei of selected Seyfert galaxies and quasars (10 objects). The monitoring is to be continued until Oct. 30, 2000. The spectral optical monitoring with CCD-cameras in the spectral range λλAA4000–8000ÅÅ is being carried out at two observatories: SAO RAS, Russia (6-m and 1-m telescopes) and at Kazakhstan (70-cm telescope). The resolution is about 3–10Å, the S/N ratio is ≍50–100. The broad-band optical monitoring with BVRI filters (with a 1% accuracy at the R-band) is being done at 5 observatories. NLR and ENLR in monitored galaxies will also be investigated.
Strong Radio Outbursts in Six Active Galactic Nuclei in 1997-1998
Authors: Kovalev Y.Y.
Published: July 2016

The beginnings of strong radio flares in six AGNs were detected and their evolution was studied using 1–22 GHz five epoch instantaneous spectral observations in 1997–1998. The phenomena started at the highest frequency and moved to the lower frequency in a regular fashion. Such behavior of the flares in AGNs can be explained by synchrotron emission from a compact relativistic jet implying different physical models which are discussed. For different types of AGNs the same behavior of flares is revealed, in favor of the same basic physical model for BL Lacs and quasars. A birth of new VLBI components in compact jets associated with these outbursts is predicted.
Seyfert Activity in Ring Galaxies Due to Galactic Interactions
Authors: K. Chatterjee Tapan
Published: July 2016

Observations indicate that ring galaxies are more active than spirals (e.g., Ghigo et al., 1983 Appleton and Struck-Marcell, 1987). However, Seyfert activity is noted in only a few ring galaxies, e.g. NGC 985 (de Vaucouleurs & de Vaucouleurs 1975), NGC 1144 = Arp 118 (Huchra et al. 1982), ring galaxy in Sextans-optical counterpart of the IRAS source 09595-0755 (Wakamatus & Nishida). This is indicative of the fact that this type of activity requires favorable circumstances. In this context a previous work on the stellar episode of ring formation, Chatterjee (1984), is extended, including gas and studying the evolution of the ring structure, due to rebounds of the compact elliptical about the plane of the disk.
Activity Phenomena Observed at Radio Frequencies in Sprial Galaxies
Authors: Malumian V.H.
Published: July 2016

It has been shown that the stage of activity of spiral galaxies depends on both the distance between them and their nearest neighbours and the structure of their central parts.
The Anisotropy in the Distribution of the Major Axes of Elongated Shakhbazian CGCG
Authors: Vardanian R.A.
Published: July 2016

In 1978 we have shown that Shakhbazian CGCG have an elongated form (Vardanian & Melik-Alaverdian 1978). Morever, they turned out to be of comet forms (1996), at the head of which basically are situated their bright members. This enables determination with high accuracy of the position angles θ of major axes of the elongated Shakhbazian CGCG. A closer examination of these angles shows that distribution of orientations of the major axes of groups is anisotropic and has two maximums (Vardanian 1996). (See Table, where θ is position angle, N is number of CGCG). These maximums are oriented in mutually perpendicular directions (θ = 45° and θ = 135°).
Future Directions in AGN Research
Authors: H. Krolik Julian
Published: July 2016

A review is given of the principal successes in AGN research (black holes as the central engines, radiation mechanisms, population studies) and the most important open questions (creation of AGN, dynamics of the accretion flow, acceleration and collimation of relativistic jets). Some recent work that gives hope for progress towards answering these questions is also discussed.
Influence of V. A. Ambartsumian on the Development of Astronomy
Authors: Boyarchuk Alexander
Published: July 2016

This is a great honour for me to present a report on the influence of the outstanding scientist academician V.A. Ambartsumian. I was well familiar with V.A. Ambartsumian, but unfortunately, I did not manage to work with him in scientific research. When, in 1948, I arrived in the Leningrad State University (LSU) V.A. Ambartsumian already had left LSU and worked in Armenia. My teacher in LSU, academician V.V. Sobolev, was the best student of V.A. Ambartsumian. Therefore, to some degree, I can consider myself as a scientific grandson of V.A. Ambartsumian. However, I very frequently met V.A. Ambartsumian at scientific conferences, discussed with him scientific problems and problems of organization of scientific research. Contacts with this outstanding, strong and talented person have rendered large influence on my formation as a scientist.
Particle Acceleration in Solar Flares and Coronal Mass Ejections
Authors: Lin R. P.
Published: July 2016

The Sun accelerates ions up to tens of GeV and electrons up to 100s of MeV in solar flares and coronal mass ejections. The energy in the accelerated tens-of-keV electrons and possibly ~1 MeV ions constitutes a significant fraction of the total energy released in a flare, implying that the particle acceleration and flare energy release mechanisms are intimately related. The total rate of energy release in transients from flares down to microflares/nanoflares may be significant for heating the active solar corona.

Shock waves driven by fast CMEs appear to accelerate the high-energy particles in large solar energetic particle events detected at 1 AU. Smaller SEP events are dominated by ~1 to tens-of-keV electrons, with low fluxes of up to a few MeV/nucleon ions, typically enriched in3He. The acceleration in gamma-ray flares appears to resemble that in these small electron-3He SEP events.
X-ray Emission as an Indicator of Cosmic ray Acceleration in Supernova Remnants
Authors: Petre R. , Allen G. E. , Hwang U. , Keohane J. W. , Gotthelf E. V.
Published: July 2016

X-ray observations over the past several years have led to the discovery of nonthermal X-ray emission arising in the shells of many young supernova remnants, including SN 1006, Cas A, and Tycho. This emission is thought to be synchrotron emission from electrons that have been shock accelerated to hundreds of TeV, and thus represents strong evidence that cosmic rays are accelerated in SNR shocks. The X-ray observations are corroborated by detection of TeV gamma rays from two of these remnants. A systematic investigation of young, shell-like remnants suggests that the nonthermal X-ray emission from shock-accelerated electrons is a common, if not ubiquitous, feature. We review the status of the X-ray observations and describe how they can be used to provide insight into the shock acceleration process.
Thermal Radiation from Isolated Neutron Stars
Authors: Pavlov G. G. , Zavlin V. E.
Published: July 2016

The analysis of thermal radiation emitted from the atmospheres of isolated neutron stars allows one to measure their surface temperatures, magnetic fields, masses, and radii, as well as the chemical composition of their atmospheres. Thus, multiwavelength observations of this radiation provide an important tool for studying the structure and evolution of neutron stars and for elucidating properties of the superdense matter in their interiors. We describe recent theoretical and observational results on thermal radiation from radio pulsars and radio-quiet neutron stars and discuss their astrophysical implications.
Properties of Nonthermal Emission in Plerions
Authors: Bandiera R.
Published: July 2016

The synchrotron emission observed in plerions depends on the characteristics of the magnetic fields and relativistic electrons in these supernova remnants. Therefore, an analysis of the spectral and spatial properties of this emission, combined with models for the evolution and structure of plerions, would allow one to investigate the evolution of the synchrotron nebula, the structure of the magnetic field, and the distribution of the relativistic electrons, as well as to put constraints on the history of the energy input from the associated neutron star.

The identification of a new class of plerionic remnants, with spectral properties different from the Crab Nebula, has been proposed. The spectra of these objects typically show a sharp spectral break at very low frequencies (below 50 GHz), with a steep spectrum right beyond the break. In order to model the properties of their emission, a nonstandard evolution of the pulsar output seems to be required.

X-ray observations of the synchrotron emission from the Crab Nebula are shown. They are compared with previous data, and their implications on the structure of the Crab are discussed. Recent millimetric data of this object are also presented. A spatially resolved analysis, based on radio, millimetric, and X-ray data, will be carried out also for other plerions.
A Three-dimensional Outer-magnetospheric Gap Model for Gamma-ray Pulsars: I. The Crab Pulsar
Authors: Cheng K. S. , Ruderman M. , Zhang L.
Published: July 2016

We use a three-dimensional pulsar magnetosphere model to study the geometry of outer-magnetospheric gaps. The vertical size of the “outer gap” is first determined by a self-consistent model in which the outer gap size is limited by pair production from collisions between (1) thermal photons produced from polar cap heating by backflow “outer gap” current, and (2) the curvature photons emitted by gap-accelerated charged particles. The transverse size of the outer gap is also determined by local pair production limits. In principle, there are two topologically disconnected outer gaps in the magnetosphere of a pulsar. Both incoming and outgoing particle flows are allowed. However, the emission morphologies produced by incoming particle flow is severely restricted by local pair production in the gap and the absorption of magnetic pair production near the star. Double-peaked light curves with strong bridges are most common. From the three-dimensional structure of the outer gap and its local properties, we calculate the emission morphologies and phase-resolved spectra of gamma-ray pulsars. Applications to the Crab pulsar illustrate the model.
Plasma Masers in Radio Pulsars
Authors: Lyutikov M. , Blandford R. , Machabeli G.
Published: July 2016

Relativistic plasma masers operating on the anomalous cyclotron-Cherenkov resonance (ω - k||v|| + ωB/γres = 0) and on the Cherenkovdrift resonance (ω - k||v|| - kxud = 0) are capable of explaining the main observational characteristics of pulsar radio emission. Both electromagnetic instabilities are due to the interaction of the fast particles of the primary beam and from the tail of the distribution with the normal modes of a strongly magnetized, one-dimensional electron-positron plasma. In a typical pulsar, both resonances occur in the outer parts of the magnetosphere at rres ≍ 109 cm.
Electron Trapping and Precipitation in Asymmetric Solar Flare Loops
Authors: Aschwanden M. J. , Fletcher L. , Sakao T. , Kosugi T. , Hudson H.
Published: July 2016

Acceleration, propagation, and energy loss of particles energized in solar flares cannot be studied separately because their radiative signatures observed in the form of hard X-ray bremsstrahlung or radio gyrosynchrotron emission represent a convolution of all these processes. We analyze hard X-ray emission from solar flares using a kinematic model that includes free-streaming electrons (having an energy-dependent time-of-flight delay) as well as temporarily trapped electrons (which are pitch-angle scattered by Coulomb collisional scattering) to determine various physical parameters (trapping times, flux asymmetry, loss-cone angles, magnetic mirror ratios) in flare loops with asymmetric magnetic fields.
Active Late-Type Stellar Coronae: Hints for Flare Heating?
Authors: Audard M. , Güdel M. , Drake J. J. , Kashyap V. , Guinan E. F.
Published: July 2016

The Extreme Ultraviolet Explorer data archive has been used to study flare energy distributions and infer the role of flares in coronal heating. We have constructed flare number distributions as a function of observed EUV and X-ray emitted thermal energy. We find cumulative flare distributions of the form N(> E) ∝ E−α+1 with α ≍ 1.5–2.6. We present results in the context of spectral type classification.
X-ray Emission from Supermassive Black Holes in Elliptical Galaxies and Low Radiative-efficiency Accretion
Authors: Matteo T. Di , Allen S. W.
Published: July 2016

We discuss the detection of hard, power-law emission components in the X-ray spectra of six nearby, giant elliptical galaxies observed with the ASCA satellite and its implication for low-radiative efficiency accretion models around the central, supermassive black holes.
Magnetic Helicity, Dynamo Action, Reconnection, and Particle Acceleration
Authors: Field G. B. , Blackman E. G.
Published: July 2016

Blackman & Field have shown that a working α-Ω dynamo requires finite but opposite flows of small- and large-scale magnetic helicity through a body's surface. The helicity is accompanied by magnetic energy available for dissipation. The observed solar coronal nonthermal power is consistent with the derived lower limit required. This link between dynamo field generation and nonthermal emission should generally apply to stars, spiral galaxies, and accretion disks.
Which Forces Accelerate Jets?
Authors: Kato S. X. , Kudoh T. , Shibata K.
Published: July 2016

We performed 2.5-dimensional, nonsteady MHD simulations of jets from geometrically thin accretion disks and investigated the acceleration forces of jets in detail.
Statistical Properties of Kerr BH Flywheel Model of QSOs/AGNs
Authors: Nitta S.
Published: July 2016

The aim of this work is to demonstrate the properties of the magnetospheric model around Kerr black holes, so-called the “flywheel” (rotation powered) model. The fly-wheel engine of the BH accretion disk system is applied to the statistics of QSOs/AGNs. Nitta, Takahashi, & Tomimatsu clarified the individual evolution of the Kerr black-hole fly-wheel engine, which is parameterized by black-hole mass, initial Kerr parameter, magnetic field near the horizon, and a dimensionless small parameter. We impose a statistical model for the initial mass function of an ensemble of black holes using the Press-Schechter formalism. With the help of additional assumptions, we can discuss the evolution of the luminosity function and the spatial number density (population) of QSOs/AGNs. The result explains well the decrease of very bright QSOs and decrease of population after z ~ 2.
The Isolated Neutron Star RX J185635-3754
Authors: Walter F. M. , An P. , Lattimer J. , Prakash M.
Published: July 2016

We use optical and X-ray data to investigate the atmosphere of the isolated neutron star RX J185635-3754. The space motion suggests an origin about 2 million years ago in the Upper Cen-Lup OB association.
Controlling Light Pollution in Chile: A Status Report
Authors: Smith Malcolm G.
Published: July 2016

A basic-level summary is provided of work since late 1993 to control light pollution in Chile. The purpose of this article is to stimulate such work inside Chile and to promote good lighting in developing countries in general. Chile is selected as the case study because of its critical importance to optical and radio astronomy, and the related economic and cultural benefits for Chile and the world. Examples are presented in some detail in order to illustrate adjustments that have been made to accommodate local scientific, cultural and economic realities and to show that it is necessary to anticipate the issues involved in controlling light pollution several decades before it would otherwise become a problem. It is hoped that international organizations such as the IAU, the IDA and the CIE can soon promote programmes in Chile that can serve as pilot programmes for other parts of the developing world.
Using DMSP Night-Time Imagery to Evaluate Lighting Practice in the American Southwest
Authors: Luginbuhl Christian B.
Published: July 2016

The U.S. Defense Meteorological Satellites provide an opportunity to measure the uplight produced by artificial lighting on the ground. In this study DMSP data are used to measure the integrated at-detector radiance of a number of communities in the American Southwest in an attempt to evaluate the effectiveness of outdoor lighting codes. Use of DMSP data in this manner is complicated by many factors, and some of these are briefly discussed.
Light Pollution and Energy Loss from Cairo
Authors: Osman A. I. I. , Isobe S. , Nawar S. , Morcos A. B.
Published: July 2016

Light pollution is a serious problem, not only to astronomy but also to the environment and the economy. The amount of light energy loss from Cairo has been calculated using data obtained at Kottamia Observatory in 1980 and 1995. The amount of energy loss is much greater in 1995. Comparison with a number of other world cities is given. These results show that much money is being wasted. Recommendations to overcome the problem, and the corresponding savings, are given.
Outdoor Lighting Ordinances: Tools to Preserve the Night Sky
Authors: Davis Donald R.
Published: July 2016

The dark night sky is rapidly being lost throughout the world due to wasted outdoor night lighting. Following warnings by astronomers and environmentalists, many communities are acting to preserve the night sky by enacting outdoor lighting codes. Here we briefly recount the history of codes and outline the essential elements of an effective code. Additional information, including a handbook on how to write a good outdoor lighting ordinance, is available from the International Dark-Sky Association web site, www.ida.org.
Plan of the Modification of Public Lighting in Frosinone in Accordance with the Rule for the Limitation of Light-Pollution and Power Consumption
Authors: Di Sora M.
Published: July 2016

The plan for modification of public lighting in Frosinone, in accordance with the rule for the limitation of light-pollution and power consumption, is summarized. The energy saving obtained is 40% per year, equivalent to over US$222,000.
Search for and Protection of Astronomical Sites in Developing Countries
Authors: Querci François R. , Querci Monique
Published: July 2016

The archives of meteorological satellites allow pre-selection of dry sites well adapted to astronomical observations (in the visible, infrared and millimetric ranges). The GSM (Grating Scale Monitor) technique then permits qualification of them as sites for future astronomical observatories. Such sites are found in new astronomical countries or in developing countries. At the same time, their protection from light pollution and/or radio interference has to be secured. In practice, once pre-selections are made, the governments of these countries ought to be alerted, for example by the IAU and/or the UN Office for Outer Space Affairs. The local site testing through GSM should be carried out in cooperation with scientists of these countries under the umbrella of the IAU. This could be an approach to help introduce astronomy and astrophysics into developing countries.
Radio Astronomy and the International Telecommunications Regulations
Authors: Robinson Brian
Published: July 2016

For forty years radio astronomers have had access to frequency bands allocated by the International Telecommunication Union (ITU) - initially a League of Nations body (from 1919) and then a United Nations body (since 1945). Hard work and skilful negotiation by a handful of radio astronomers since 1959 have ensured viable access to scarce spectral allocations. There have been many battles won, some key battles lost. The next treaty conference of the ITU is in the year 2000.
Radio Astronomy and the Radio Regulations
Authors: Cohen R. J.
Published: July 2016

This article gives a brief introduction to the status of radio astronomy within the International Telecommunication Union (ITU), the body which coordinates global telecommunications. Radio astronomy entered the ITU arena in 1959 as a relative latecomer. By its nature, radio astronomy does not fit into the ITU system very well: regulators are hoping to facilitate commercial development of the radio spectrum, whereas astronomers are hoping to retain quiet frequency bands through which to study the Universe at ever higher sensitivity. Nevertheless there are major long-term goals which radio astronomers can realistically hope to achieve via the ITU in the years ahead, including more favourable frequency allocations and better regulatory protection. The prospects for radio astronomy at the forthcoming World Radio Conference WRC-2000 are reviewed. It is vital that radio astronomers participate in force at this WRC.
Radio Astronomy and Recent Telecommunications Trends
Authors: Gergely Tomas E.
Published: July 2016

Radio astronomy was born in the 1930s and matured in the 1950s. The telecommunications environment of those decades was dominated by monopolies (often state monopolies) and a strong regulatory environment. Radio communications were analogue in nature and mostly confined to frequencies below a few hundred megahertz. The worldwide telecommunications environment began to change in the 1960s and has undergone a revolution during the last three decades. Impulse for this revolution, which has not yet ended, was provided by political, as well as by technological developments. The most influential among these were the end of the cold war and the emergence of giant, often multinational telecommunications companies or consortia, that provide services previously reserved to state monopolies. Technically, the new era can be characterized by a host of new types of satellite services, the use of digital communication techniques, the proliferation of low power devices that do not require individual licensing and by a steady move towards higher frequencies. I discuss the evolution of some of these trends and their implications for radio astronomy.
Preserving Radio Astronomy in Developing Nations
Authors: Swarup G. , Subramanya C. R.
Published: July 2016

Due to the very weak nature of signals from cosmic radio sources, the sensitivity of a radio telescope and receiver is about 40–60 dB higher than those of communications receivers. Hence, radio telescopes are generally located in relatively radio-quiet locations and operate in frequency bands that are protected against radio interference through frequency planning by national governments. Taking advantage of the much lower degree of radio interference in developing countries and the relatively labour-intensive nature of metre-wave radio telescopes, several such radio telescopes have been built and are planned in Argentina, Brazil, China, India, Mauritius and South Africa. Radio telescopes operating at cm-wavelengths are also planned in Egypt and Mexico.

A particularly severe problem arises for the radio astronomy service and other passive services below 2 GHz from the possibility of unacceptable emissions from satellites in unwanted bands (out-of-band and spurious emissions), due to the specific modulation schemes used in satellite transmitters. It is noted that this can be circumvented within the existing technologies if the satellite transmitters employ suitable bit-shaping or filtering techniques or use modulation schemes like Gaussian-filtered Minimum-Shift Keying (GMSK) which produce very little out-of-band emission. Although radio astronomy started in the western world at low frequencies, much low frequency radio astronomy is now planned or operational in developing countries. In order to protect the interests of these and other passive services within developing nations, it is important that suitable regulations be recommended to UNISPACE-III to provide appropriate protection.
The Light Pollution Programme in Greece
Authors: Metaxa M.
Published: July 2016

The problem of light pollution exists almost everywhere, and is still growing rapidly. The preservation of the astronomical environment requires effective education. In this paper we present our educational programme, based in Greece and also including other countries. For full information see our web pages: http://www.uoLgr/english/EPL/LP/lp.htm
Educating the Public about Light Pollution
Authors: Isobe Syuzo , Hamamura Shiomi , Elvidge Christopher D.
Published: July 2016

Using low-gain DMSP data, we obtained absolute values of light energy loss ejected to space from different cities. Showing these data to local people in each city encourages them to try to reduce light energy loss. This educational approach is very effective in reducing light pollution.
The Cultural Value of Radio Astronomy
Authors: Sullivan Woodruff T.
Published: July 2016

In order to compete successfully in the marketplace of the radio spectrum radio astronomers must appeal not to economic gain, but to the cultural value of their enterprise. In the real world this can be problematic, but it is not hopeless. This paper gives arguments why radio astronomy, no less than astronomy as a whole, has great cultural value whether considered from an environmental or an intellectual point of view.
Educating the Public About Interference to Radio Observatories
Authors: Finley David G.
Published: July 2016

Educating the public about interference to radio observatories is a different and more difficult task than educating the public about light pollution. Convincing and successful arguments against light pollution can be based on aesthetic, economic, cultural, safety and security considerations without relying solely on the need to preserve the environment for astronomy. In contrast, it is necessary to first convince members of the public of the value of radio astronomical research before making the case for interference protection. Once this is done, arguments about interference must be presented in ways understandable to a public that is, by and large, woefully uninformed about the technology involved. Successful approaches often borrow from the language of environmental protection and draw parallels to such issues as air and water pollution in justifying the expense of engineering measures to protect radio astronomy.
Postscript
Authors: Cohen R. J.
Published: July 2016

A summary is given of the results of WRC-2000 for radio astronomy and other developments since the end of Symposium 196 (up to April 2001).
Chemical Models of Collapsing Envelopes
Authors: Bergin Edwin A.
Published: July 2016

We discuss recent models of chemical evolution in the developing and collapsing protostellar envelopes associated with low-mass star formation. In particular, the effects of depletion of gas-phase molecules onto grain surfaces is considered. We show that during the middle to late evolutionary stages, prior to the formation of a protostar, various species selectively deplete from the gas phase. The principal pattern of selective depletions is the depletion of sulfur-bearing molecules relative to nitrogen-bearing species: NH3 and N2H+. This pattern is shown to be insensitive to the details of the dynamics and marginally sensitive to whether the grain mantle is dominated by polar or non-polar molecules. Based on these results we suggest that molecular ions are good tracers of collapsing envelopes. The effects of coupling chemistry and dynamics on the resulting physical evolution are also examined. Particular attention is paid to comparisons between models and observations.
Chemical Characteristics of Embedded Young Stellar Objects
Authors: Hogerheijde Michiel R.
Published: July 2016

Based on theoretical considerations, the chemistry around embedded young stellar objects is expected to be governed by the interplay between gas-phase reactions, condensation of molecules onto dust grains, grain surface reactions, and evaporation of altered ice mantles near the star and in the outflow. I discuss the chemical characteristics of embedded young stellar objects, with special emphasis on these processes.
Submillimetre Observations of UC HII Regions and Hot Molecular Cores
Authors: Macdonald G. H. , Thompson M. A.
Published: July 2016

Recent submillimetre observations of continuum radiation from warm dust and molecular line emission from hot gas in regions of high mass star formation are reviewed. Such regions are characterised by ultracompact HII regions around young OB stars and associated hot molecular cores which appear to harbour high mass protostars at an earlier stage of evolution.
Models of Gas-Grain Chemistry in Star-forming Regions
Authors: Herbst Eric
Published: July 2016

It is difficult if not impossible to explain the abundances of assorted interstellar molecules in both the gaseous and condensed phases without the use of grain chemistry. Unfortunately, the chemistry occurring on grains is not well understood because of a variety of uncertainties including the nature, size, and shape of dust particles, the binding energies of key species, the dominant mechanism of surface chemistry, and the correct mathematical treatment of surface processes. Still, intrepid astrochemists have used granular chemistry in chemical models of an assortment of sources including cold clouds, protostellar disks, and hot cores. Indeed, the dominant explanation of the saturated gas-phase molecules observed in hot cores involves grain chemistry during an earlier, low temperature phase. Although gas-grain models have elucidated major features of the chemistry, much more work remains to be accomplished before they can be used to help characterize the physical conditions in star-forming regions and their temporal variations.
Millimeter Observations of the Chemistry in Bipolar Outflows
Authors: Garay Guido
Published: July 2016

Millimeter wave observations of molecular lines provide a useful tool to study the chemistry of bipolar outflows. In this contribution we discuss recent observational results which have permitted to assess the chemical alterations of the ambient medium produced by the presence of bipolar collimated winds driven by young protostars. Discussed first are the results from molecular line surveys which have allowed to identify several species whose abundances in the outflow lobes are considerably enhanced with respect to that of the ambient medium. These enhancements are useful diagnostics of physical and chemical processes in the outflow lobes, such as sputtering of grain cores and/or desorption of grain mantles. Then we discuss the characteristics of the line profiles and of the spatial distribution of the emission in specific enhanced species, which provide information about the mechanisms responsible for the enhancements. In particular we give emphasis to the results derived from observations of two highly enhanced species, SiO and CH3OH, which are observed to trace different components of the outflows.
Crossed Molecular Beam Experiments of Radical-Neutral Reactions Relevant to the Formation of Hydrogen Deficient Molecules in Extraterrestrial Environments
Authors: Kaiser R. I. , Balucani N. , Asvany O. , Lee Y. T.
Published: July 2016

During the last 5 years, laboratory experiments relevant to the formation of carbon-bearing molecules in extraterrestrial environments have been performed employing the crossed molecular beam technique and a high intensity source of ground state atomic carbon, C(3Pj). These investigations unraveled for the first time detailed information on the chemical reaction dynamics, involved collision complexes and intermediates, and – most important – reaction products of neutral-neutral reactions. Here, we extend these studies even further, and report on very recent crossed beam experiments of cyano radical, CN(2Σ+), reactions with unsaturated hydrocarbons to form nitriles in extraterrestrial environments and Saturn's moon Titan. Further, preliminary results on reactions of small carbon clusters and with acetylene, ethylene, and methylacetylene to synthesize hydrogen-deficient carbon-bearing molecules are presented.
Laboratory and Astronomical Detection of New Carbon Chains and Rings
Authors: Mccarthy Michael C.
Published: July 2016

Discoveries of large new organic molecules in space help provide a foundation for understanding the role of the chemical bond and organic chemistry on a cosmic scale, and by extension, an opportunity to begin to address the interesting but far more complicated questions of chemical and biological origins and the issues that relate to them. Most of the organic molecules so far detected in the interstellar gas and circumstellar shells by radio telescopes are highly unsaturated carbon chains, a configuration of linear carbon which is unstable at high density, and therefore unfamiliar on Earth. For this reason laboratory detection until quite recently has lagged behind astronomical discovery of many new carbon molecules. The application of Fourier transform microwave spectroscopy to supersonic molecular beams has now largely overcome this obstacle, yielding in just over three years the laboratory detection of forty-four new carbon chains and eight new carbon ring-chains and rings, including two rhomboidal isomers of SiC3. The set consists of 14 polyynes, 20 carbon chain radicals, and 18 free carbenes. For four other triplet chains HC7H, HC9H, HC11H, and HC13H, which by symmetry are nonpolar, strong electronic spectra have been measured in the gas-phase by cavity ringdown absorption spectroscopy. Almost all of these molecules are good candidates for detection in space, and six in fact have now been detected in at least one astronomical source with large radio telescopes during the past two years. The laboratory astrophysics of the entire set is complete for the time being, in the sense that nearly all the rotational transitions of interest to radio astronomy can be calculated to a small fraction of 1 km sec–1 in equivalent radial velocity. With powerful new radio facilities planned or under construction it would be surprising if many more could not eventually be found. For each of the four new symmetric chains detected in the visible, the wavelength of the origin band has been measured to high accuracy, permitting deliberate searches for these molecules in diffuse and translucent molecular clouds.
Theoretical Simulations of Grain-Surface Processes
Authors: Takahashi Junko
Published: July 2016

Recent advances in theoretical simulations of grain-surface processes are reviewed. Classical molecular dynamics (MD) computer simulations were performed to investigate the whole process of H2 formation on icy mantles of interstellar dust grains within a single model. Amorphous water ice slabs were generated at 10 K and 70 K as a realistic model surface of dust grains, and then two incident H atoms were successively thrown onto the surface to reproduce the H2 formation process via H + H → H2 on the dust surface. The following fundamental processes were studied in detail; 1) the sticking of H atom onto the grain surface, 2) the diffusion of H atom on the surface, 3) the reaction of two H atoms on the surface, 4) the ejection of H2 from the surface. Then, the formation pumping mechanism of H2 and the chemical desorption mechanism of frozen CO molecules in the vicinity of H2 forming sites on dust grains were also studied.