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Geometrical Effect of Supercritical Accretion Flows: Observational Implications of Galactic Black-Hole Candidates and Ultraluminous X-Ray Sources
We consider the dependence of the viewing angle in supercriticalaccretion flows and discuss the observational implications of galacticblack-hole candidates and ultraluminous X-ray sources. Model spectra ofsupercritical accretion flows strongly depend on the inclination angle.For example, the maximum temperature of the supercritical disk (theaccretion rate and the black-hole mass are dot{M} = 1000LE/c2 and M = 10 Modot, respectively)is kTin 2.0 keV for a low-inclination angle, i lesssim40°, while kTin 0.6 keV for a high-inclinationangle, i gtrsim 60°. This spectral softening originates fromself-occultation of the disk, i.e., the outer disk blocks emission fromthe disk inner region, even if we take into account the effect ofgeneral relativity (light bending, Doppler boosting). This is because,when the mass accretion rate exceeds the critical rate, then the shapeof the disk is geometrically thick due to enhanced radiation pressure.We also find that the spectral properties of low-i and lowaccretion-rate disks are very similar to those of high-i and highaccretion-rate disks. That is, if an object has a high i and a highaccretion rate, such a system suffers from self-occultation and thespectrum will be extremely soft. Therefore, we cannot distinguish thesedisks by only the difference in their spectrum shapes. Conversely, if weuse the self-occultation properties, we could constrain the inclinationangle of the system. We suggest that some observed high-temperatureultraluminous X-ray sources have low-inclination angles, i.e., nearface-on geometry, i lesssim 40°, and the Galactic black-holecandidate XTE J1550 ‑ 564 possesses relatively high-inclinationangles, i gtrsim 60°.
| 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.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| The CfA Redshift Survey: Data for the NGP +36 Zone
We have assembled redshifts for a complete sample of 719 galaxies withm_zw_ <= 15.5 in the declination range 32.5^deg^ <= δ <=38.5^deg^ and right ascension range 8^h^ <= α <= 17^h^. Wehave determined morphological types for all galaxies in the magnitudelimited sample by direct inspection of the POSS-O plates. 576 of theredshifts are measurements from Mount Hopkins, and 405 are newredshifts. We also include new redshifts for 77 fainter galaxies in thesame strip.
| HI observations of galaxies in nearby Zwicky clusters
The results of a long term project of H I observations of galaxieswithin the boundaries of nearby Zwicky clusters are presented. Thedetection rate is rather low (233 out of 618, i.e., 38 percent) ascompared to other surveys carried out recently. Most of the radialvelocities of the detected galaxies are new determinations. The largespread in radial velocities for many of these clusters is a strongindication for the presence of several foreground and/or backgroundgalaxies.
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