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|High-Energy Emission from Millisecond Pulsars|
The X-ray and γ-ray spectrum of rotation-powered millisecondpulsars is investigated in a model for acceleration and pair cascades onopen field lines above the polar caps. Although these pulsars have lowsurface magnetic fields, their short periods allow them to have largemagnetospheric potential drops, but the majority do not producesufficient pairs to completely screen the accelerating electric field.In these sources, the primary and secondary electrons continue toaccelerate to high altitude, and their Lorentz factors are limited bycurvature and synchrotron radiation reaction. The accelerating particlesmaintain high Lorentz factors and undergo cyclotron resonant absorptionof radio emission that produces and maintains a large pitch angle,resulting in a strong synchrotron component. The resulting spectraconsist of several distinct components: curvature radiation from primaryelectrons dominating from 1 to 100 GeV, synchrotron radiation fromprimary and secondary electrons dominating up to about 100 MeV, and muchweaker inverse Compton radiation from primary electrons at 0.1-1 TeV. Wefind that the relative size of these components depends on pulsarperiod, period derivative, and neutron star mass and radius, with thelevel of the synchrotron component also depending sensitively on theradio emission properties. This model is successful in describing theobserved X-ray and γ-ray spectrum of PSR J0218+4232 as synchrotronradiation, peaking around 100 MeV and extending up to a turnover aroundseveral GeV. The predicted curvature radiation components from a numberof millisecond pulsars, as well as the collective emission from themillisecond pulsars in globular clusters, should be detectable withAGILE and GLAST. We also discuss a hidden population of X-ray-quiet andradio-quiet millisecond pulsars that have evolved below the pair deathline, some of which may be detectable by telescopes sensitive above 1GeV.
|Nearby Optical Galaxies: Selection of the Sample and Identification of Groups|
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
|The Southern Sky Redshift Survey|
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
|Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies|
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
|The Montreal Blue Galaxy Survey.III.Third List of UV-Bright Candidates|
We present and discuss the latest addition of the Montreal Blue Galaxy(MBG) survey. Inspection of 59 Curtis Schmidt plates resulted in theidentification of 135 new UV-bright galaxies with B < 15.5. Thisbrings the total number of MBGs to 469. New results of the V/V_m testshow that our survey is complete to B = 14.7. From our most recentspectroscopic follow-up, we confirm the discovery of one new Seyfert 1galaxy and possibly one new Seyfert 2 galaxy. We confirm also the biasof the MBG survey towards the low-excitation and metal rich StarburstNucleus Galaxies (SBNGs). The spectral characteristics of the MBGs aresimilar to those of the infrared luminous IRAS galaxies. As a commoncharacteristic, they show a mean ratio Log([NII]/Hα ) in excess of0.2 dex as compared to normal disk HII regions. In general, the MBGshave lower far-infrared luminosities (LIR < 10(11)Lsun) and are nearer (z < 0.05) than the luminous IRASgalaxies. The distribution of the morphologies of the MBGs indicates ahigh number of early-type spirals (Sb and earlier). Nearly half of thesegalaxies also possess a bar. In our sample, the fraction of galaxieswith bars depends on the morphology and increases towards the late-typespirals. However, if we consider only isolated galaxies, the late-typespirals show a clear tendency to be barred. Signs of a recentinteraction with neighbor galaxies are obvious only in 24% of ourcandidates. Although this number is only a lower limit, it isnevertheless sufficiently low to suggest that in a majority of massivegalaxies the burst of star formation do not depends solely on dynamicalprocesses.
|An image database. II. Catalogue between δ=-30deg and δ=70deg.|
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
|Candidates for a southern extension of the Karachentsev catalogue of isolated pairs of galaxies.|
|The relationship between the radio and far-infrared emission in IRAS galaxies - VLA observations of a large well-defined sample at 1420 MHz|
An examination of VLA observations at 1420 MHz of a well-defined sampleof 156 IRAS galaxies reveals a strong correlation between the radio andfar-infrared emission from IRAS galaxies. The flux density ratio isfound to have a constant value of -4.82. The results suggest that thenonthermal radio emission is closely related to the current level ofstar formation, and that the star formation region in most IRAS galaxiesis confined to the central few kpc of the galaxy.
|The Identification of IRAS Point Sources - Part One - a 304-DEGREE Field Centred on the South Galactic Pole|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986MNRAS.223..279W&db_key=AST
|Southern Galaxy Catalogue.|
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