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|Accurate Positions for MCG Galaxies|
We have measured accurate celestial coordinates for 4741 extragalacticobjects, primarily drawn from a list of MCG galaxies with no recentlypublished accurate positions. The standard deviations in the newpositions depend slightly on the measurement method but are on the orderof 1.0" to 1.2". Standard deviations in the original MCG positions areconfirmed to be at the 1.5′-2.0′ level. These new positionswere integrated into NED in 1997 December.
|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.
|Environments of Seyfert galaxies. I. Construction of the sample and selection effects.|
In order to build a satisfactory picture of Seyferts in relation tonormal galaxies we have started a series of papers first establishingsome of their basic environmental properties, especially the differencein the number of close companions between Seyfert 1 and Seyfert 2galaxies. Here we report sample selections and discuss selection effectsinvolved for the samples of 104 Seyferts and 138 control galaxies. Theresults of the statistical analyses are presented by Laurikainen &Salo (1994, Paper II). The neighbouring galaxies are counted on thePalomar Sky Survey Plates to the limiting magnitude =~19m_pg_ within thecircles of 1.5Mpc in diameter (H_0_=100km/s/Mpc), large measuringcircles enabling good elimination of the background galaxies. Subsamplesare selected in order to test the methods by Dahari (1984) and byFuentes-Williams & Stocke (1988). Elimination of background galaxiesand problems related to comparison galaxy sample selection arediscussed. The most important problem in our control galaxy sampleselection is that the redshifts for most of the control galaxies areunknown. The size of this uncertainty is estimated by determining theredshifts by two ways: (1) by assuming that the selected comparisongalaxy has the same redshift as the nearby Seyfert and (2) byMonte-Carlo simulations for Holmberg (1975) galaxy size distribution inspace, taking into account the Malmquist bias. The mean redshifts of thecomparison sample are estimated with these methods to be 0.028 and0.029, respectively, compared with 0.026 for the Seyfert sample.Distribution of Seyferts in Zwicky's clusters is also addressed, andcompared with previous studies. Taking into account optical projections,about 3/4 of the Seyferts are found to be field galaxies. Galaxies inclusters lie preferentially at the cluster borders.
|CO observations of Arp's interacting galaxies|
We performed a (C-12)O (J= 1-0) line survey involving fifty fourinteracting galaxies from the Arp's Catalogue of Peculiar Galaxies, andcompared our results with various other data. The far infraredluminosities, as normalized by the CO luminosities, are much greater forinteracting galaxies than for normal galaxies. From correlations withthe interaction class we found that the molecular gas concentration inthe central few kpc is not necessarily enhanced by interaction. However,the efficiency of star formation from the molecular gas increasessignificantly with the interaction class, which results in an apparentincrease in the star-formation rate with the interaction class.
|On the relationship between radio emission and optical properties in early-type galaxies|
To study the origin of radio activity in early-type galaxies, thepossible dependence of their radio emission on basic optical parameters,such as the absolute magnitude, the central velocity dispersion sigma,and the mean surface brightness mu is explored. A sample of 743 E and SOgalaxies is used which is based on three independent radio surveys ofoptically selected galaxies with virtually complete information onmagnitudes, morphological types, redshift distances, diameters, andradio fluxes. For both E and SO galaxies, only the absolute magnitudeappears to be directly related to the radio activity, while sigma and mudo not. Also, a significant dependence of the apparent flattening onradio power is confirmed for E galaxies. Some relevant implications ofthese results are discussed.
|The effects of interactions on spiral galaxies. III - A radio continuum survey of galactic nuclei at 1.49 GHz|
The radio continuum emission from the central region of a sample ofinteracting spiral galaxies (92 galaxies of which 60 in a completesample) and of a control sample of more isolated spiral galaxies (94)was observed with the Very Large Array at 1.49 GHz. The angularresolution of the observations is about 1.3 arcsec, and the detectionlimits are about 0.6 and 1.5 mJy for point sources and extended sourceswith a half power size of 10 arcsec, respectively. This survey, incombination with published optical spectroscopy, provides the data for adetailed comparison of the central region in interacting and moreisolated spiral galaxies.
|A 5-GHz survey of bright Southern elliptical and S0 galaxies|
The Parkes 64-m telescope has been used in a 5.0-GHz survey of 181Southern E and S0 galaxies from the Reference catalogue of brightgalaxies. Of the 39 detections above the nominal limit of 12 mJy, 15 arenew, several have radio spectra indicating membership in the activeclass, and two have shown intensity variations at centimeterwavelengths. The results of this survey combined with results fromearlier surveys of lower sensitivity suggest that only about 40 per centof the E/S0 galaxies in the Reference catalogue have a flux density at 5GHz exceeding 1 mJy.
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