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|Optical spectroscopy for a sample of southern binary galaxies|
Aims.This work is part of a joint observational program aiming to getphotometric and spectroscopic information on southern pairs of galaxies.We present optical long-slit spectroscopic data on 80 probablecomponents of pairs, 61 of them collected with a spectral resolution of3.4 Å, and 19 with 12 Å. Nevertheless, our analysis takesinto account 53 components of pairs with better spectral resolution, as8 of these target galaxies actually belong to optical pairs. For thesample with better resolution, the covered wavelength range is 5724≤ λ ≤ 7036 Å. The spectroscopic and photometricinformation is gathered for an analysis relating galaxy morphologies totheir spectra. Methods: .We use Hα +[NII] and Hα equivalent widths as star formationtracers for the central region of our sample galaxies, and we classifythe spectra according to the emission lines' relative strength bylooking at their behavior. Results: . Some of our sample galaxiesexhibit high central star formation, most of them belonging to closepairs. However, not all galaxies' components of close pairs show thisbehavior. This may be a clue that besides interaction, other agents canstimulate central emission in binary galaxies. We suggest an enhancementin the number of galaxies with peculiar spectra (probably Seyferts) inour binary sample, when compared to isolated galaxies. Our dataindicates that the morphological types of interacting galaxies arerelated to their spectral characteristics, as almost all early-typegalaxies of our sample do not exhibit central optical emission. We notethat the star formation activity is most likely to take place in bothpairs' components, with a slightly higher mean strength for the lessbright component of the pair. It is interesting to point out that mostspirals exhibiting a strong HII emission line spectra present either abar or a peculiarity, but on a general basis we do not find anenhancement of star formation in our interaction sample.
|Photometric study of a sample of southern binary galaxies|
Aims.This work exhibits the basic optical photometric data for a sampleof 50 probable southern binary galaxies. Our sample covers a broad rangeof pair separations, stages of interaction, and morphologies. From theinitial list of selected pairs, using spectroscopic data from theliterature and our own data, we conclude that 84% of these systems aretrue binary galaxies. Methods: .We present residual and asymmetricmaps, R major semi-axis profiles of surface brightness, ellipticity,position-angle, harmonic Fourier coefficients of third and fourth order(b3 and b_4) for 50 probable pairs, and B-R color maps for 47of these pairs. For most galaxies, we present the profiles in twodifferent ways, aiming to verify the influence of random errors onthem. Results: . We note that random errors in position-angleprofiles are at least 2°, but a more significant result must takeinto account a variation larger than 11° for this distribution.Barred galaxies usually show a typical behavior in ellipticity andposition-angle profiles: these profiles display variations when changingfrom a bar to a disk region. In some cases, the variations also occuralong the bar. Some galaxies show distribution profiles that are commonfor their morphological type, and the interaction signature is onlyevidenced by their residual maps. Bars are usually redder and rings arebluer, when compared with the galaxy outskirts. Conclusions: .Ourdata indicates that there is a connection between interaction strengthand morphological distortions in binary galaxies. If we consider theprojected separation of a pair as an indication of interaction strength,distortions such as displaced centers, anomalous shapes of spiral arms,and twistings of external regions are easily detected in some closepairs, although not all components of close pairs show this behavior.Our data suggests that besides interaction, other parameters, likeorbital geometry and internal properties of galaxies, can stimulatebinary galaxies' peculiarities.
|The gas content of peculiar galaxies: Strongly interacting systems|
A study of the gas content in 1038 interacting galaxies, essentiallyselected from Arp, Arp & Madore, Vorontsov-Velyaminov catalogues andsome of the published literature, is presented here. The data on theinterstellar medium have been extracted from a number of sources in theliterature and compared with a sample of 1916 normal galaxies. The meanvalues for each of the different ISM tracers (FIR, 21 cm, CO lines,X-ray) have been estimated by means of survival analysis techniques, inorder to take into account the presence of upper limits. From the datait appears that interacting galaxies have a higher gas content thannormal ones. Galaxies classified as ellipticals have both a dust and gascontent one order of magnitude higher than normal. Spirals have in mostpart a normal dust and HI content but an higher molecular gas mass. TheX-ray luminosity also appears higher than that of normal galaxies ofsame morphological type, both including or excluding AGNs. We consideredthe alternative possibilities that the molecular gas excess may derivefrom the existence of tidal torques which produce gas infall from thesurrounding regions or from a different metallicity which affects the Xconversion factor between the observed CO line luminosity and the H_2calculated mass. According to our tests, it appears that interactinggalaxies possess a higher molecular mass than normal galaxies but with asimilar star formation efficiency.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/941
|Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data|
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
|The Durham/UKST Galaxy Redshift Survey - V. The catalogue|
We present the radial velocities and blue, optical magnitudes for all ofthe galaxies within the Durham/UKST Galaxy Redshift Survey. Thiscatalogue consists of ~2500 galaxy redshifts to a limiting apparentmagnitude of B_J⋍17 mag, covering a ~1500-deg^2 area around theSouth Galactic Pole. The galaxies in this survey were selected from theEdinburgh/Durham Southern Galaxy Catalogue and were sampled, in order ofapparent magnitude, at a rate of one galaxy in every three. Thespectroscopy was performed at the 1.2-m UK Schmidt Telescope inAustralia using the FLAIR multi-object spectrograph. We show that ourradial velocity measurements made with this instrument have an empiricalaccuracy of +/-150 km s^-1. The observational techniques and datareduction procedures used in the construction of this survey are alsodiscussed. This survey demonstrates that the UKST can be used to make athree-dimensional map of the large-scale galaxy distribution, via aredshift survey to b_J⋍17 mag, over a wide area of the sky.
|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.
|Candidates for a southern extension of the Karachentsev catalogue of isolated pairs of galaxies.|
|Simulated aperture-photometry on CCD-frames for 67 southern galaxies in B and R|
As part of a large project to calibrate all the Schmidt plates of theESO Quick blue and the red survey, CCD-photometry in B and R has beenobtained for galaxies on 67 different survey fields. On these framessynthetic-aperture photometry is applied in order to present the data ina way which makes the comparison with photographic photometry easy.
|Southern Galaxy Catalogue.|
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