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|Massive Black Holes in Star Clusters. II. Realistic Cluster Models|
We have followed the evolution of multimass star clusters containingmassive central black holes through collisional N-body simulations doneon GRAPE6. Each cluster is composed of between 16,384 and 131,072 starstogether with a black hole with an initial mass ofMBH=1000Msolar. We follow the evolution of theclusters under the combined influence of two-body relaxation, stellarmass loss, and tidal disruption of stars by the massive central blackhole. We find that the (three-dimensional) mass density profile followsa power-law distribution ρ~r-α with slopeα=1.55 inside the sphere of influence of the central black hole.This leads to a constant-density profile of bright stars in projection,which makes it highly unlikely that core-collapse clusters containintermediate-mass black holes (IMBHs). Instead, globular clusterscontaining massive central black holes can be fitted with standard Kingprofiles. Because of energy generation in the cusp, star clusters withIMBHs expand. The cluster expansion is so strong that clusters thatstart very concentrated can end up among the least dense clusters. Theamount of mass segregation in the core is also smaller compared topostcollapse clusters without IMBHs. Most stellar mass black holes withmasses MBH>5Msolar are lost from the clusterswithin a few gigayears through mutual encounters in the cusp around theIMBH. Black holes in star clusters disrupt mainly main-sequence starsand giants and no neutron stars. The disruption rates are too small toform an IMBH out of a MBH~50Msolar progenitorblack hole even if all material from disrupted stars is accreted ontothe black hole, unless star clusters start with central densitiessignificantly higher than what is seen in present-day globular clusters.We also discuss the possible detection mechanisms for IMBHs. Oursimulations show that kinematical studies can reveal1000Msolar IMBHs in the closest clusters. IMBHs in globularclusters are weak X-ray sources, since the tidal disruption rate ofstars is low and the star closest to the IMBH is normally another blackhole, which prevents other stars from undergoing stable mass transfer.For globular clusters, dynamical evolution can push compact stars nearthe IMBH to distances small enough that they become detectable sourcesof gravitational radiation. If 10% of all globular clusters containIMBHs, extragalactic globular clusters could be one of the major sourcesof gravitational wave events for LISA.
|The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%|
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
|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.
|Large-Scale Structure at Low Galactic Latitude|
We have extended the CfA Redshift Survey to low galactic latitudes toinvestigate the relation between the Great Wall in the North GalacticCap and the Perseus-Pisces chain in the South Galactic Cap. We presentredshifts for 2020 galaxies in the Catalogue of Galaxies and of Clustersof Galaxies (Zwicky et al. 1961-68, CGCG) in the following regions: 4^h^<= α <= 8^h^, 17^h^ <= α <= 20^h^, 0^deg^ <=δ <= 45^deg^. In these regions, the redshift catalogue includes1664 galaxies with B(0) <= 15.5 (of which 820 are newly measured) andis 97% complete. We also include redshifts for an additional 356galaxies in these regions with B(O) > 15.5; of these, 148 werepreviously unmeasured. The CGCG samples the galaxy distribution down tob_II_ = 10^deg^. In this paper, we discuss the acquisition and reductionof the spectra, and we examine the qualitative features of the redshiftdistribution. The Great Wall and the Perseus-Pisces chain are not simplyconnected across the Zone of Avoidance. These structures, which at firstappear to be coherent on scales of ~100 h^-1^ Mpc or more, actually formthe boundaries of neighboring voids of considerably smaller scale,approximately 50h^-1^ Mpc. The structures delineated by ouroptically-selected sample are qualitatively similar to those detected bythe far-infrared-selected IRAS 1.2 Jansky Survey (Fisher et al. 1995).Although the IRAS survey probes more deeply into the Zone of Avoidance,our optically-selected survey provides better sampling of structures atb_II_ >= 10^deg^.
|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.
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