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Mixed-Morphology Pairs as a Breeding Ground for Active Nuclei
Mixed-morphology pairs offer a simplification of the interactionequation that involves a gas-rich fast rotator paired with a gas-poorslow rotator. In past low-resolution IRAS studies it was assumed thatthe bulk of the far-infrared (FIR) emission originated in the spiralcomponent. However, our Infrared Space Observatory studies revealed asurprising number of early-type components with significant IR emission,some of which turned out to show active nuclei. This motivated us tolook at the current statistics of active nuclei in mixed pairs using theradio-FIR continuum correlation as a diagnostic. We find a clear excessof early-type components with radio continuum emission and activenuclei. We suggest that they arise more often in mixed pairs viacross-fueling of gas from the spiral companion. This fuel is moreefficiently channeled into the nucleus of the slow-rotating receptor. Ina sample of 112 mixed-morphology pairs from the Karachentsev catalog, wefind that about 25%-30% of detected mixed pairs show a displacement fromthe radio-FIR relation defined by normal star-forming galaxies. Thelatter objects show excess radio continuum emission, while others extendthe relation to unusually high radio and FIR flux levels. Many of theoutliers or extreme emitters involve an early-type component with anactive nucleus. The paired E/S0 galaxies in the sample exhibit asignificant excess detection fraction and a marginal excess luminositydistribution compared to those of isolated unpaired E/S0 galaxies.
| BVRI surface photometry of mixed morphology pairs of galaxies. II. The second data set
In order to analyze the photometric signature of gravitationalinteractions in spiral and elliptical galaxies, we present results ofmulticolor broad band (BVRI) surface photometry for a second set of 10mixed pairs drawn from the Karachentsev Catalogue of Isolated Pairs ofGalaxies (KPG). We report total magnitudes and colors, as well assurface brightness, color and geometric (ɛ, PA anda4/a) profiles. Most of this subsample have photometricparameters homogeneously derived for the first time. Internal andexternal data comparisons show consistency within the estimated errors.We find 1 true (E+S) pair and 4 probable (E+S) pairs ((E/S0+S) cases) inthe present sample. The remaining objects include 3 lenticular-spiral(S0+S) systems, 1 spiral-spiral (S+S) pair and 1 probable spiral-spiralpair ((S0/Sa+S) case). Four lenticular galaxies show evidence ofunderlying (perhaps induced) structures like bars/arms. Among the spiralcomponents, an over-representation of early (Sa-Sb) types was found. Abrief discussion on the existence of a Holmberg Effect is alsopresented.Based on data obtained at the 0.84 m telescope of the ObservatorioAstronómico Nacional (OAN), San Pedro Mártir, BajaCalifornia, México, operated by the Instituto deAstronomía, UNAM.Tables 1-3 and Figs. 3-12 are only available in electronic form athttp://www.edpsciences.org
| Multiwavelength Insights into Mixed-Morphology Binary Galaxies. I. ISOCAM, ISOPHOT, and Hα Imaging
We present Hα and ISO mid- and far-IR observations for a sample ofmixed-morphology galaxy pairs that reveal both the stellar andnonstellar signatures of the interaction process. A mixed-morphologypair is perhaps the simplest form of galaxy-galaxy interaction becauseit is expected to involve only a single rapidly rotating gas-richcomponent paired with a gas-poor elliptical or lenticular galaxy. Aprimary assumption that we address is whether spirals are the only IRemitter in these mixed (E+S) pairs. Our observations reveal that many ofthe early-type galaxies exhibit weak (low equivalent width) emission, asoften observed in field elliptical galaxies. These are the classicalmixed-morphology pairs. However, some of the early-type components,especially the lenticular galaxies, show evidence for significant starformation, with Hα equivalent widths and 15 μm luminositiescomparable to or exceeding those of their often much larger spiralcompanions. Our sample contains five Seyfert 2 nuclei, of which threecan be described as companions on the end of a spiral arm. The Seyfertnucleus is often accompanied by a starburst region, while other suchcompanions currently show only the starburst component. These pairs areamong the best candidates for direct interaction fuelling of bothstarbursts and active galactic nuclei.Based on observations with the Infrared Space Observatory (ISO), an ESAproject with instruments funded by ESA Member States (especially the PIcountries: France, Germany, the Netherlands and the United Kingdom) withthe participation of ISAS and NASA.
| 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.
| Kinematical Observations of a Sample of Binary Galaxies
Not Available
| Corrections and additions to the third reference catalogue of bright galaxies
List of corrections and additions to the Third Reference Catalogue ofBright Galaxies (RC3) are given. The corrected version of the catalogue(RC3.9b), dated April 1994, is currently available through the nationaldata centers.
| Kinematic regulation of star formation in interacting galaxies
Kinematic data for a geometrically-selected set of spiral galaxies inpairs are presented, and analyzed for correlations between indicators ofstar formation and indices of orbital type and extent of kinematicdisturbance. Both nuclear and global star formation rate are connectedto kinematic disturbance with the kind and degree of disturbance moreimportant than either projected separation or relative directions ofgalaxy spin and companion orbit. Enhanced star formation is found forgalaxies with large areas of solid-body rotation and for galaxies withmore general kinds of disturbed velocity structure, with the highestlevels occurring in a set of galaxies distinguished by anomalously smalloverall velocity amplitude. The strongest correlation is between starformation rate (SFR) and amplitude of velocity disturbance, fromrotation curves, when the velocity disturbance is scaled by the galaxyrotation velocity. Triggered star formation is more sensitive to galaxydynamics than to strictly local phenomena such as cloud disruptionvelocities. Comparsion with various models for the enhanced SFR ininteracting systems shows that cloud-collision processes cannot accountfor the strong starbursts in retrograde systems, and models relying oninteractions between different phases of the interstellar mediumsimilarly require too many direct collisions between galaxy disks.Schemes involving gravitational instability of the disk driven initiallyby the external perturbation fare best; such instability can then drivethe rates of other processes such as cloud collisions, possibly in acascadelike series. Solid-body kinematics appear more important than thepresence of a stellar bar in this connection. Using a new set ofclassifications from uniform CCD images, there is a better correlationbetween disturbed kinematics and morphological disturbance of individualgalaxies than with pair interaction types in the Karachentsev catalog,though the relationship is not one-to-one. There is a substantialpopulation of pairs with disturbed kinematics but not disturbed forms.The kinds of disturbance found from direct and retrograde encountersmatch well the predictions of n-body calculations for each kind ofencounter.
| A list of some corrections to Zwicky's Catalogue of Galaxies and Clusters of Galaxies
Not Available
| Double galaxy investigations. I - Observations
Redshift information from 240 A/mm spectrograms is presented for 370double arcsec galaxy systems from the Karachentsev (1972) catalog,including all pairs in that catalog with separation less than 80 arcsec.An extensive error discussion utilizing internal and external (21 cm)comparisons provides calibration of systematic error and determines theuncertainty for a typical high weight optical redshift to be plus orminus 65 km/sec. Internal differential redshifts within single spectrausing common lines achieve accuracies of 18-30 km/sec, depending uponseparation, and are available for about 200 pairs. Extensive informationon emission and other properties is also provided.
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