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A superfamily with halo of extremely high energy named Fianit was recorded in X-ray emulsion chamber (XEC) at the Pamirs (atmospheric depth 600 g/sq.cm.). Detailed description of the superfamily and results of its analysis are presented.
Among 91 mini-clusters from 30 high energy Chiron-type families in Chacaltaya emulsion chambers, there were observed several extremely large multiplicity clusters in the highest energy range, far beyond the average of ordinary type clusters. Some details of microscopic observation of those giant mini-clusters in nuclear emulsion plates and some phenomenological regularity found in common among them are described. Such giant mini-clusters are possible candidates for the origin of narrow symmetric single halo phenomena in X-ray films which are frequently observed in super-families of visible energy greater than 1,000 TeV.
A significant fraction of known galaxies contain an active galactic nucleus (AGN) at their cores, the site of violent activity and non-stellar radiation seen across the entire electromagnetic spectrum. This activity is thought to be due to the accretion of gas onto a massive black hole. A fraction of AGNs also eject collimated beams of energetic material, usually seen by virtue of its synchrotron emission in the radio band. Efforts to study these jets from AGNs in the X-ray band with the Einstein Observatory has led to several detections, most notably the jets in the nearby radio galaxies Centaurus A and Virgo A = M87. In their study of M87, Schreier, Gorenstein and Feigelson (1982) noted that, in addition to the synchrotron jet 10"-20" from the nucleus, X-rays appear to be generated in the diffuse radio halo 2'-5' from the nucleus. This finding may be particularly important as it may constitute the first known case of X-ray inverse Compton emission from AGN ejecta, allowing for the first time direct determination of the magnetic field strengths.
The purpose of this study is to investigate in more detail the associated X-ray and radio emission in the Virgo A halo discovered by SGF. Improved Einstein HRI data and new radio maps obtained with the Very Large Array are described and the relation between the X-ray and radio structures is carefully examined. Several possible explanations are presented for the X-ray emission. The inverse compton model is found to be viable only if the magnetic field is variable and substantially weaker than the equipartition value. The principal alternative is excess thermal X-rays due to compression of the intracluster medium by the radio lobe. In either case, the association of such prominent radio and X-ray structures is unique among known radio galaxies.
Studies of the effects of cometary dust halos and dust mantles on outgassing from the nucleus are reviewed. The chemical differentiation of the outer layers of a comet during perihelion passage is discussed. It is shown how this differentiation may explain a number of observations pertaining to the relative production rates of various cometary molecules.
Forty-five high-latitude, OB stars have been observed in the Ly alpha and 21 cm lines of HI in an effort to map out the vertical distribution and extent of the local HI halo. The 25 stars for which a reliable HI column density can be obtained from Ly alpha lie between 60 and 3100 pc from the plane. The principal result is that the total column density of HI at an absolute value of z greater than 1 kpc is, on the average, 5 + or - 3 x 10 to the 19th power/sq cm, or 15 percent of the total sub HI. At relatively low z the data toward some stars suggest a low effective scale height and fairly high average foreground density, while toward others the effective scale height is large and the average density is low. This can be understood as the result of irregularities in the interstellar medium. A model with half of the HI mass in clouds having radii of a few pc and a Gaussian vertical distribution with sigma sub 2 = 135 pc, and half of the mass in an exponential component with a scale height of 500 pc, gives a satisfactory fit to the data. The technique of comparing Ly alpha and 21 cm column densities is also used to discuss the problem of estimating the distance to several possibly subluminous stars.
Large-area, HgCdTe MW photovoltaic detectors have been developed for the NASA-HALOE instrument scheduled for operation on the Upper Atmospheric Research Satellite. The photodiodes will be TE-cooled and were designed to operate in the 5.1-5.4 micron band at 185 K to measure nitric oxide concentrations in the atmosphere. The active area required 15 micron thick devices and a full backside common contact. Reflections from the backside contact doubled the effective thickness of the detectors. Optical interference from reflections was eliminated with a dual layer front surface A/R coating. Bakeout reliability was optimized by having Au metallization for both n and p interconnects. Detailed performance data and a model for the optical stack are presented.
The subject of cosmic ray antiproton production is reexamined by considering other choices for the nature of the Majorana fermion chi other than the photino considered in a previous article. The calculations are extended to include cosmic-ray positrons and cosmic gamma rays as annihilation products. Taking chi to be a generic higgsino or simply a heavy Majorana neutrino with standard couplings to the Z-zero boson allows the previous interpretation of the cosmic antiproton data to be maintained. In this case also, the annihilation cross section can be calculated independently of unknown particle physics parameters. Whereas the relic density of photinos with the choice of parameters in the previous paper turned out to be only a few percent of the closure density, the corresponding value for Omega in the generic higgsino or Majorana case is about 0.2, in excellent agreement with the value associated with galaxies and one which is sufficient to give the halo mass.
The well-known starburst in M82 at 10.8, 19.2, and 30 microns has been mapped. Scans along the galactic plane which are derived from these data reveal marked color variations with position. These color variations are correlated with the UV energy density in a manner explicable in terms of a heated mixture of dust grains extending to very small sizes. Many of the small grains may have been destroyed in the most intense regions of the starburst, but they have survived in a halo where the UV energy density is too low to destroy them but still high enough to significantly heat them. Implications of the results for interpreting IR continuum emission from starburst galaxies are considered.
Researchers have detected the Warm Ionized Medium (WIM) phase in the galaxy NGC 891. They found that the radial distribution of the WIM follows the molecular or young star distribution - an expected dependence. The amount of the WIM in this galaxy exceeds that in our Galaxy. The major surprize is the large thickness of the WIM phase - about 9 kpc instead 3 kpc as in our Galaxy. Clearly, this is the most significant result of the observations. The presence of low ionization gas at high z as well as at large galactocentric radii (where young stars are rare) is an important clue to the origin of the halo and observations such as the one reported here provide important data on this crucial question. In particular, the ionization of gas at high absolute z implies that either the UV photons manage to escape from the disk of the galaxy or that the extragalactic UV background plays an important role. The bulk of the WIM in spiral galaxies is a result of star-formation activity and thus these results can be understood by invoking a high star formation rate in NGC 891. Only the concerted action of supernovae can get the gas to the large z-heights as is observed in this galaxy. Support for this view comes from our detection of many worms i.e., bits and pieces of supershells in the form of kilo-parsec long vertical filaments. Researchers also saw a 600-pc size supershell located nearly one kpc above the plane of the galaxy.
Binary galaxies, as binary stars, are important to measure masses, as suggested by Page (1952). Because three orbit parameters are measurable for galaxies at one instant of time, severe uncertainties remain in the orbit and mass determinations. These uncertainties can partly be overcome by statistical studies of selected samples and/or n-body simulations. Close double galaxies (and isolated galaxies) could also be useful to estimate dynamical masses if we can find test particles around them. Interacting elliptical pairs or dumb-bell galaxies are found with a large range, between 0-1200 km s(exp -1), of relative radial velocities. Standard 2-body orbit calculations, highly uncertain due to projection factors, suggest for the largest velocity differences very large galaxy masses, if the systems are bound and stationary. However, recent n-body simulations model these binaries as galaxies captured from hyperbolic orbits, requiring masses of order a few times 10(exp 11) solar maximum (Borne et al. 1988), but producing systems that are short lived. A different picture appears when we study observationally the dynamical mass of interacting double ellipticals using faint satellite galaxies. These satellites contribute little luminosity and, presumably, little mass to the system. The authors present results of two such groups, basically forming systems of test particles, around the dumb-bells NGC 4782/3 and IC 5049. They also briefly discuss the satellite group around the central dumb-bell in the cluster Sersic 40/6. Apparently, they detect large quantities of dark matter in the vicinity of these dumb-bell galaxies, because the system masses of approx. 4.5 times 10(exp 13) solar mass and 8 times 10(exp 13) solar mass for NGC 4782/3 and IC 5049, respectively, are quite high. Likewise, the mass of the Sersic 40/6 inner core is 7 times 10(exp 13) solar mass. The possibility that a common massive dark matter halo increases the merging times of these types of galaxies is suggested. Here, the authors assume H sub o = 100 km s (exp -1) Mpc(exp -1).
Possible causes for the large dispersion in the X-ray luminosities (Lx) of early-type galaxies are discussed. It is shown that early-type galaxies with relatively low values of Lx for a given optical luminosity L(B) have about 50 percent more neighbors than galaxies with relatively high Lx, suggesting that low-Lx galaxies tend to be in denser environments. It is concluded that the large dispersion in X-ray luminosity, for a given L(B) might be caused either by ram-pressure stripping of the gaseous halos or by mergers.
A grid of extremely metal-poor stellar evolutionary tracks (Z = 0.00001) is constructed to compare the predicted lithium abundance depletion to observations of the lithium abundance in correspondingly metal-poor stars (Fe/H = -3.3), and, combined with an earlier work to investigate trends of lithium isochrones with metal abundance. Lithium abundances in the most extreme halo stars hint at the possibility of small downward slope toward lower T(eff) in the flat Li-T(eff) relation (the Spite lithium plateau) observed in slightly less extreme stars; the models also predict this. In the cool star region of the Li-T(eff) plane, higher metallicity lithium isochromes are cooler at fixed lithium abundance, consistent with the observations. Current data thus agree well with the lithium trends from standard model.
Observational data are presented relating to the boundary regions between dense, molecular clouds and the more diffuse atomic gas. The data set consists of H I 21 cm and CO (J = 1-0) strip maps in 14 molecular clouds which traverse 62 known CO cloud boundaries. The angular lengths of the strips range from 0.5 deg to several degrees of arc, which is generally adequate to eliminate confusion with background (and foreground) H I. Most of the crossed boundaries (49 of 62) show clear evidence for the presence of H I emission maxima, or halos, lying outside the molecular clouds' gas. There is also general evidence for limb brightening in the CO emission.
Results of initial spectroscopy using the Goddard High-Resolution Spectrograph and the Hubble Space Telescope on the bright low-redshift quasar 3C 273 are presented. Absorption lines produced by gas in the disk and halo of the Galaxy from numerous neutral and weakly ionized atoms and also from highly ionized atoms are detected. The detection of N v provides additional strong support for the existence of gas with T about 200,000 K at large distances away from the disk of the Galaxy. Ten absorption lines with EW greater than 50 mA, and four possible lines with EW between 25 and 50 mA, are also found in the region between 1235 and 1406 A. These cannot be identified with any lines in the galactic interstellar medium and must therefore all be Ly-alpha systems at very low redshifts. This number of lines is 5-10 times larger than expected from a simple extrapolation of the high-redshift evolution derived from ground-based observations and is consistent with no evolution in cloud properties since z = 2.
The possibility of detecting halo cold dark matter through the annihilation process chi chi(bar)-gamma gamma is studied. This process produces monoenergetic gamma rays, and may be a clear signature of particle dark matter. If there is a closure density of dark matter, it is shown that it will be very difficult to observe this annihilation line from a Space Station-borne experiment. On the contrary, a large lunar-based gamma-ray telescope could detect hundreds of events per year.
Models of metal-poor stars with rotation were computed and their lithium depletion was compared with observations of halo stars. The models that have turn-off ages compatible with the observations have a nearly flat Li-T(eff) relationship in the region of the Spite lithium 'plateau'. Depending on the initial angular momentum, the models have a depletion factor ranging between a factor of 5 and a factor of 10 at fixed T(eff), implying a maximum initial lithium abundance of 3.1. Both the dispersion and the overall depletion factor are much smaller for metal-poor models than for solar metallicity ones. The factors that determine lithium depletion in rotational models are discussed and the different depletion patterns in solar metallicity and metal-poor models are traced to differences in their structure and evolution. The dependence of the lithium depletion on age, mass, initial angular momentum, and metallicity is also discussed. The dispersion predicted from these models is not inconsistent with the observations.
Statistical properties of the distribution of gamma-ray bursts are calculated for a large range of different luminosity functions assumed for the sources. Surprisingly, the observable parameters are almost the same as in the 'standard-candle' scenario. In particular, no way is found to reconcile the observed distribution of gamma-ray bursts with any Galactic disk model. A Galactic halo distribution must have a core radius greater than 18 kpc to have no measurable dipole anisotropy. A cosmological distribution of the bursters is a more reasonable alternative.