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An Hα survey of cluster galaxies - V. Cluster-field comparison for early-type galaxies
We have extended our Hα objective prism survey of eightlow-redshift clusters (viz. Abell 262, 347, 400, 426, 569, 779, 1367 and1656) to include a complete sample of early-type galaxies within 1.5Abell radii of the cluster centres. Of the 379 galaxies surveyed, 3 percent of E, E-S0 galaxies, 6 per cent of S0 galaxies, and 9 per cent ofS0/a galaxies were detected in emission. From a comparison of clusterand supercluster field galaxies, we conclude that the frequency ofemission-line galaxies (ELGs; Wλ>= 20 Å) issimilar for field and cluster early-type galaxies. A similar result haspreviously been obtained for galaxies of types Sa and later. Together,these results confirm the inference of Biviano et al. that the relativefrequency of ELGs in clusters and the field can be entirely accountedfor by the different mix of morphological types between the differingenvironments, and that, for galaxies of a given morphological type, thefraction of ELGs is independent of environment. Detected emission isclassified as `compact' or `diffuse', identified as circumnuclearstarburst or active galactic nucleus (AGN) emission and disc emission,respectively. By comparing spectroscopic data for cluster early-typeELGs with data for field galaxies from the Palomar spectroscopic surveyof nearby galactic nuclei, we demonstrate that there is modest evidencefor an enhancement of compact HII emission relative to AGN emission inthe early-type cluster ELGs as compared to the field. For the clusterearly-type galaxies, compact HII emission correlates strongly with adisturbed morphology. This suggests that, as for later-type clustergalaxies, this enhanced compact HII emission can readily be explained asan enhancement of circumnuclear starburst emission due to gravitationaltidal interactions, most likely caused by subcluster merging and otheron-going processes of cluster virialization.
| Catalog of Double Nucleus Disk Galaxies
We have compiled a catalog of disk galaxies that have a double nucleus,through systematic examination of existing catalogs and publications.The Catalog of Double Nucleus Disk Galaxies includes 107 objects,together with their basic data. The aim of the catalog is to provide amore systematic and homogeneous basis for the study of the relevance ofgalaxy interactions and minor mergers in the formation of these doublenuclei. We have also investigated possible correlations betweengeometric and photometric parameters of the double nuclei and their hostgalaxies. The preliminary results indicate the presence of severalsignificant correlations that should be considered in any theoreticalscenario describing minor mergers and disk galaxy evolution.
| Starbursts in barred spiral galaxies. VI. HI observations and the K-band Tully-Fisher relation
This paper reports a study of the effect of a bar on the neutralhydrogen (HI) content of starburst and Seyfert galaxies. We also makecomparisons with a sample of ``normal'' galaxies and investigate howwell starburst and Seyfert galaxies follow the fundamental scalingTully-Fisher (TF) relation defined for normal galaxies. 111 Markarian(Mrk) IRAS galaxies were observed with the Nançay radiotelescope,and HI data were obtained for 80 galaxies, of which 64 are newdetections. We determined the (20 and 50%) linewidths, the maximumvelocity of rotation and total HI flux for each galaxy. Thesemeasurements are complemented by data from the literature to form asample of Mrk IRAS (74% starburst, 23% Seyfert and 3% unknown) galaxiescontaining 105 unbarred and 113 barred ones. Barred galaxies have lowertotal and bias-corrected HI masses than unbarred galaxies, and this istrue for both Mrk IRAS and normal galaxies. This robust result suggeststhat bars funnel the HI gas toward the center of the galaxy where itbecomes molecular before forming new stars. The Mrk IRAS galaxies havehigher bias-corrected HI masses than normal galaxies. They also showsignificant departures from the TF relation, both in the B and K bands.The most deviant points from the TF relation tend to have a strongfar-infrared luminosity and a low oxygen abundance. These resultssuggest that a fraction of our Mrk IRAS galaxies are still in theprocess of formation, and that their neutral HI gas, partly of externalorigin, has not yet reached a stationary state.Based on observations obtained at the large radiotelescope ofObservatoire de Nançay, operated by Observatoire de Paris.Tables 5 and 6 are only (and Table 4 also) available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/515
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Seyfert Galaxies with Circumnuclear/Nuclear Starbursts
In this paper, we present our preliminary results on Seyfert galaxieswith circumnuclear/nuclear starburst (SB) activity. We have searched therecent available literature and found 76 active galaxies with clearevidence of nuclear SB activity, among which 16 are Seyfert 1s, 51Seyfert 2s, and 9 LINERs. After studying the 51 Seyfert 2s, we find thatthose Seyfert 2s with hidden Seyfert 1 nuclei, have similarInfrared-Radio properties as Seyfert 1 galaxies, and are different from``real'' Seyfert 2s without a hidden Seyfert 1 nucleus. The later aresimilar to starburst galaxies.
| The Narrow-Line Region of Seyfert Galaxies: Narrow-Line Seyfert 1 Galaxies versus Broad-Line Seyfert 1 Galaxies
It is known that the spectral energy distribution (SED) of the nuclearradiation of narrow-line Seyfert 1 galaxies (NLS1's) has differentshapes with respect to that of ordinary broad-line Seyfert 1 galaxies(BLS1's) particularly in X-ray wavelengths. This may cause somedifferences in the ionization degree and the temperature of gas innarrow-line regions (NLRs) between NLS1's and BLS1's This paper aims toexamine whether or not there are such differences in the physicalconditions of NLR gas between them. For this purpose, we have compiledthe emission-line ratios of 36 NLS1's and 83 BLS1's from the literature.Comparing these two samples, we have found that the line ratios of [O I]λ6300/[O III] λ5007 and [O III] λ4363/[O III]λ5007, which represent the ionization degree and the gastemperature respectively, are statistically indistinguishable betweenNLS1's and BLS1's. Based on new photoionization model calculations, weshow that these results are not inconsistent with the difference of theSED between them. The influence of the difference of SEDs on the highlyionized emission lines is also briefly discussed.
| Surface Density of Bright, Active Extragalactic Objects
A new sample of local, active extragalactic objects has been compiled: acombined sample that is the sum of two samples, of Sy1 galaxies and ofquasars from Markarian's survey and quasars from the Bright QuasarSurvey. A log N(B)-B relation is constructed for the new sample ofactive galaxies, limited to the apparent stellar magnitude B = 15 m .5.It can be represented by a straight line with a slope = 0.60 ±0.06. It is a good extension, without a noticeable jog, of the analogousrelationship for the HamburgESO survey, which has a slope = 0.59± 0.04. The combined surface density of bright active galaxiesand quasars down to B = 15 m .5 is 0.01 per square degree.
| Starburst or Seyfert? Adding a Radio and Far-Infrared Perspective to the Investigation of Activity in Composite Galaxies
It was once common to regard Seyfert and starburst galaxies ascompletely different types of object, but there is growing recognitionthat these classifications refer to the extremes of a continuousspectrum of galaxy types. In a previous study we investigated a sampleof galaxies with ambiguous optical emission-line ratios and concludedfrom near-infrared spectroscopic observations that the sample consistedof composite galaxies, containing both a starburst and an activegalactic nucleus (AGN). We now extend our study using radio synthesisand long-baseline interferometer observations made with the AustraliaTelescope, together with far-infrared IRAS observations, to discuss therelative contribution of starburst and AGN components to the overallluminosity of the composite galaxies. We find that only a small fractionof the radio emission (<10%) can be attributed to an AGN and that themajority of the far-infrared emission (>90%) is probably due to thestarburst component. We also show that an AGN contribution to theoptical emission of as little as 10% is sufficient to account for theambiguous line-ratio diagnostics.
| The second Kiso Survey for ultraviolet-excess galaxies. II.
Not Available
| Binary globular clusters
The dynamics of a close binary system of globular clusters isconsidered. It is shown that the star transfer process from one of thecomponents to the other should lead to the decrease of the dimension ofthe first cluster with simultaneous increase of the dimension of thesecond one. The rates of variations of clusters' sizes due to the mutualtidal interaction between the components, as well as of the orbitalrotation of the binary system on the evolution of clusters' sizes, areestimated. The results may be attributed to the double nuclei observedin certain galaxies and to globular clusters in LMC.
| An Hα survey of eight Abell clusters: the dependence of tidally induced star formation on cluster density
We have undertaken a survey of Hα emission in a substantiallycomplete sample of CGCG galaxies of types Sa and later within 1.5 Abellradii of the centres of eight low-redshift Abell clusters (Abell 262,347, 400, 426, 569, 779, 1367 and 1656). Some 320 galaxies weresurveyed, of which 116 were detected in emission (39 per cent ofspirals, 75 per cent of peculiars). Here we present previouslyunpublished data for 243 galaxies in seven clusters. Detected emissionis classified as `compact' or `diffuse'. From an analysis of the fullsurvey sample, we confirm our previous identification of compact anddiffuse emission with circumnuclear starburst and disc emissionrespectively. The circumnuclear emission is associated either with thepresence of a bar, or with a disturbed galaxy morphology indicative ofongoing tidal interactions (whether galaxy-galaxy, galaxy-group, orgalaxy-cluster). The frequency of such tidally induced (circumnuclear)starburst emission in spirals increases from regions of lower to higherlocal galaxy surface density, and from clusters with lower to highercentral galaxy space density. The percentages of spirals classed asdisturbed and of galaxies classified as peculiar show a similar trend.These results suggest that tidal interactions for spirals are morefrequent in regions of higher local density and for clusters with highercentral galaxy density. The prevalence of such tidal interactions inclusters is expected from recent theoretical modelling of clusters witha non-static potential undergoing collapse and infall. Furthermore, inaccord with this picture, we suggest that peculiar galaxies arepredominantly ongoing mergers. We conclude that tidal interactions arelikely to be the main mechanism for the transformation of spirals to S0sin clusters. This mechanism operates more efficiently in higher densityenvironments, as is required by the morphological type-local surfacedensity (T-Σ) relation for galaxies in clusters. For regions ofcomparable local density, the frequency of tidally induced starburstemission is greater in clusters with higher central galaxy density. Thisimplies that, for a given local density, morphological transformation ofdisc galaxies proceeds more rapidly in clusters of higher central galaxydensity. This effect is considered to be the result of subclustermerging, and could account for the previously considered anomalousabsence of a significant T-Σ relation for irregular clusters atintermediate redshift.
| Numerous Old Starburst Galaxies in the Local Universe
Old starburst galaxies are deficient in O stars and hence do not exhibitstrong line emission in the optical regime. However, there remain many Bstars, which are expected to heat dust grains and generate strongcontinuum emission in the far-infrared. The IRAS data for astatistically complete sample of nearby galaxies reveal for the firsttime that such objects are as numerous as 30%-40% of the local galaxypopulation.
| Relationship between Infrared and Radio Emission of Seyfert Galaxies
The relationships between the monochromatic luminosity of Seyfertgalaxies at frequencies of 0.408, 1.49, and 4.85 GHz and the integratedluminosity in the far infrared (IR) range are investigated. At all radiofrequencies they are linear and equally close. Some Seyfert galaxies, ofmorphological types S0/a, E, and S0, have a far higher radio luminositythan Seyfert spiral galaxies with the same IR luminosity. Most of themare found to have compact central radio components. Seyfert spiralgalaxies follow the same relationship between radio and IR emission asnon-Seyfert spiral galaxies. The relationships between radio and IRluminosity for the individual groups of galaxies of spectral types Sy1-Sy 1.5 and Sy 1.8-Sy 2 are also linear.
| Radio-loud and Radio-quiet Active Galactic Nuclei
We have generated a sample of 409 active galactic nuclei (AGNs) forwhich both the radio luminosity at 5 GHz and the line luminosity in [OIII] lambda5007 have been measured. The radio luminosity spans a rangeof 10 orders of magnitude, and the [O III] line luminosity spans a rangeof 8 orders of magnitude-both considerably larger than the ranges inprevious studies. We show that these two quantities are correlated in asimilar way for both radio-loud and radio-quiet AGNs. We demonstratethat the observed correlation can be explained in terms of a model inwhich jets are accelerated and collimated by a vertical magnetic field.
| A Dual-Transition Survey of CO in the Coma Cluster of Galaxies
We present CO (1-0) and (2-1) observations of 33 galaxies in theComa/Abell 1367 supercluster made with the IRAM 30 m telescope. Inaddition, we observed four of the galaxies with the 15 m JCMT, at CO(2-1). The indicative molecular gas mass correlates strongly with thedust mass, and a stronger relationship is seen between the far-infraredand CO surface brightnesses than between the simple luminosities.Comparison of CO (2-1) spectra from IRAM and JCMT allows an estimate ofthe size of the CO emission region, which varies between 10% and 100% ofthe size of the optical disk, contrary to earlier estimates that the COis contained within the optical half-light radius. There is a slightsuggestion that starburst galaxies have a lower ratio of brightnesstemperatures, T_b(2-1)/T_b(1-0), than other galaxies.
| AGNs with composite spectra. II. Additional data
In a previous paper \cite[(Véron et al. 1997)]{ver97} wepresented medium resolution (3.4 Angstroms FWHM) spectroscopicobservations of 15 ``transition objects'', selected for having anambiguous location in the \cite[Veilleux & Osterbrock (1987)]{vei87}diagnostic diagrams, and showed that most of them were in fact``composite'', this being due to the simultaneous presence on the slitof both a Seyfert or Liner nucleus and a H Ii region. Here, we reportnew spectroscopic observations of 53 emission-line galaxies with a``transition'' spectrum, bringing up to 61 the total number of observedobjects in an unbiased sample of 88 ``transition objects''. Almost allof the observed galaxies have a ``composite" nature, confirming thefinding that true ``transition'' spectra may not exist at all. Byeliminating ``composite objects'' from the diagnostic diagrams, a clearseparation between the different classes of nuclear emission-lineregions (Seyfert 2s, Liners and H Ii regions) becomes apparent; byrestricting the volume occupied by the different line-emitting regionsin the 3-dimensional diagnostic diagrams, we are also restricting therange of possible physical parameters in these regions. There seems tobe no continuity between Seyfert 2s and Liners, the two classesoccupying distinct volumes in the 3-dimensional space defined by lambda6300/Hα ii, lambda 6583/Hα , and lambda 6300/Hα .Based on observations collected at the Observatoire de Haute-Provence(CNRS), France, and Hubble Space Telescope (HST) data obtained from theSpace Telescope European Coordinating Facility (ST-ECF) archive. Tables5 and 6 are also available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Supernova Rate in Starburst Galaxies
We conducted an optical CCD search for supernovae in a sample of 142bright [m(B) <= 16 mag], nearby (z<=0.03) starburst galaxies overthe period 1988 December to 1991 June, to a limiting R-band magnitude of18. Five supernovae were found, in all cases outside the host galaxy'snucleus. We determine supernova rates (in supernova units or SNU) in theextranuclear regions to be 0.7 h^2 SNU for Type Ia, 0.7 h^2 SNU for TypeIb/c, and ~0.6 h^2 SNU for Type II, with large uncertainties but upperlimits of 2.2 h^2, 2.5 h^2, and 1.7 h^2 SNU, respectively. These ratesare similar to those measured in ``normal'' galaxies. We found noevidence for a supernova-induced brightening in any galactic nucleusand, with a few reasonable assumptions, can place upper limits of 9 h^2,12 h^2, and 7 h^2 SNU on the rates of unobscured supernovae Types Ia,Ib/c, and II, respectively, inside the nuclei.
| Tidally induced star formation in Abell 1367
Our principal aim is to compare global star formation rates betweencluster galaxies and field galaxies in order to clarify environmentalinfluence on star formation. We use an objective prism technique tosurvey over 200 Zwicky catalogue (CGCG) galaxies within ~2 deg.5 ofAbell 1367 for Hα emission. After a brief discussion of the surveycharacteristics, we consider first the dependence of Hα detection onHubble type, galaxy disturbance and the presence of a bar. As expected,we rarely detect early-type galaxies and consequently restrict furtherdiscussion to spirals (type S0/a and later), of which we detect ~35percent in Hα. We find that an extremely valuable distinction to makeis between galaxies with diffuse Hα and galaxies with compactHα. There is a very significant tendency for galaxies with compactHα emission to be disturbed, and there may be a weak tendency forthem to be barred. Neither of these tendencies is found for galaxieswith diffuse Hα emission. We infer that compact emission resultsfrom tidally induced star formation, while diffuse emission results frommore normal disc star formation. After considering field contamination,we adopt as a `predominantly cluster' sample the spiral populationinside 0.5 r_A; a `predominantly field' sample outside 0.5 r_A; and a`pure field' sample outside 1.5 r_A. We consistently find a much largerfraction of spirals detected with compact Hα in the cluster samplecompared to the field samples (e.g. 38 versus 0per cent detected incluster and `pure field' samples, chi^2 significance 3.6sigma). Thisincreased fraction detected in the cluster is found for early-, mid- andlate-type spirals separately. No such cluster/field differences arefound for galaxies with diffuse Hα emission. We conclude that tidalperturbations are more common in the cluster than in the field, leadingto a higher incidence of compact tidally triggered star formation. Bycombining information on galaxy disturbance, galaxy companions, and thelocation of galaxies within the cluster, we have tried to identify theorigin of the tidal perturbations. We find strong evidence thatnear-neighbour interaction plays a significant role in triggering starformation. However, we also find candidate objects near the cluster corewhich may be perturbed by the overall cluster tidal field, and candidateobjects which may be influenced by a higher speed `harassment'interaction between galaxies.
| Environments of Redshift Survey Compact Groups of Galaxies
Redshift survey compact groups (RSCGs) are tight knots of N >= 3galaxies selected from the CfA2+SSRS2 redshift survey. The selection isbased on physical extent and association in redshift space alone. Wemeasured 300 new redshifts of fainter galaxies within 1 h^-1 Mpc of 14RSCGs to explore the relationship between RSCGs and their environments.Thirteen of 14 RSCGs are embedded in overdense regions of redshiftspace. The systems range from a loose group of five members to an Abellcluster. The remaining group, RSCG 64, appears isolated. RSCGs areisolated and distinct from their surroundings to varying degrees, as arethe Hickson compact groups. Among the 13 embedded RSCGs, three aredistinct from their general environments (RSCG 9, RSCG 11, and RSCG 85).
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| A catalogue of spatially resolved kinematics of galaxies: Bibliography
We present a catalogue of galaxies for which spatially resolved data ontheir internal kinematics have been published; there is no a priorirestriction regarding their morphological type. The catalogue lists thereferences to the articles where the data are published, as well as acoded description of these data: observed emission or absorption lines,velocity or velocity dispersion, radial profile or 2D field, positionangle. Tables 1, 2, and 3 are proposed in electronic form only, and areavailable from the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (to130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| Rotation Curves and Velocity Measures for Spiral Galaxies in Pairs
Rotation curves have been obtained for 76 spiral galaxies in pairs,including a geometrically selected subset from the Karachentsev catalogand a set of Seyfert galaxies with close companions. Derived parametersof the rotation curves and the galaxies light distributions are alsopresented. The rotation curves are classified broadly by shape, withspecial emphasis on kinematic disturbances and regions of solid-bodybehavior that may lead to bar development. Broadband images of thegalaxies allow assessments of their degree of symmetry or disturbance.These velocity slices afford an empirical basis for evaluating theaccuracy of radial velocity measures for spiral galaxies in pairs, andthe dynamically important radial velocity differences. Specifically, thedisagreement among several plausible ways of estimating the centralvelocity from these rotation data is used to estimate how closely any ofthese might approximate the nuclear or center-of-mass values. From sevenindicators of central velocity, the internal scatter is σ_vv_ = 34km s^-1^. Of these, the velocity weighted by Hα intensity alongthe slit shows a systematic offset of about 20 km s^-1^ with respect tothe others for the Karachentsev pairs, in the sense that this measure isredshifted with respect to the other indicators. This is in the sense(but not of the total magnitude) required to account for statisticalasymmetries in pair velocity differences. Individual scatter between thevelocity indicators taken pairwise ranges from σ = 20 to 52 km s^-1^. These results imply that emission-line data such as these cannotspecify the center of mass or nuclear redshift at a level more accuratethan this, even for arbitrarily precise velocity measurements, becauseit is not clear how the observed quantities relate to the desiredmeasurement in a physical sense. No useful predictor of which galaxieshave large or small scatter among velocity measures was found, exceptthat the scatter is small for the class of "nonrotating" galaxies withsmall overall velocity amplitudes. Projected separation, separationnormalized to disk scale length, and morphological disturbance do notcorrelate with the velocity scatter.
| Galactic H i Column Densities toward Quasars and Active Galactic Nuclei
We have determined accurate values of the Galactic neutral hydrogencolumn density, N_H_, toward 220 quasars and active galactic nuclei from21 cm H I measurements made on the 140 Foot Telescope (42.7 m). Accuratevalues of N_H_ have now been obtained for the whole PG bright quasarsample and most quasars that have been observed by ROSAT and the HubbleSpace Telescope through mid-1993. The spectra were corrected for stray21 cm radiation yielding values of NH with a typical uncertainty of 1 x1O^19^ cm^-2^ for high Galactic latitude directions. The H I columndensities will be useful for correcting for interstellar opacity at UVand soft X-ray wavelengths, and for estimating the reddening andextinction toward these objects.
| Seyfert Galaxies With Companions: Orbital and Kinematic Clues to AGN Triggering
This paper presents imaging and optical spectroscopy of paired Seyfertgalaxies and their companions. The aim is to seek common properties ofSeyfert galaxies in interacting systems, which might provide evidence ofAGN triggering in a way independent of the usual two-sample statisticswhich have proven ambiguous on this issue. Three kinds of comparisonhave been made-the kinds of interactions involving Seyfert galaxies, therelative luminosities of the Seyferts and their companions, and thelevel of kinematic disturbance as measured from rotation curves. (1)Dynamics and tidal features have been used to determine (or at leastlimit) the sense of orbital motion (direct/retrograde/polar with respectto the Seyfert galaxy's disk) for many of these pairs. There is noobviously preferred kind of interaction-direct, polar, and retrogradeencounters are all well represented, despite the gross differences indynamical response of a disk to these various kinds of encounter. To theextent that triggering of Seyfert nuclei occurs due to tidal encounters,the existence of a perturbation seems more important than its exactduration or detailed effects on the disk. However, the ratio of mergingto paired Seyferts is higher than for disk galaxies in general,consistent with more effective triggering of AGN in this specific phase;the implied time scale for enhanced occurrence during mergers is thesame as the timescape for merger remnants to appear as such, a fewdisk-edge crossing times (typically several times 10^8^ yr). (2) Seyfertnuclei occur preferentially in the brighter members of galaxy pairs, bya median of 0.93 mag after making the maximal correction forcontaminating nonstellar light in the nuclei. Only about 1/3 of thiseffect can be accounted for by the known tendency of Seyfert nuclei tooccur in more luminous galaxies. Enhancement of AGN by interactions isevidently more effective for more luminous galaxies (though this willalso be the case if both star formation and AGN occurrence are enhancedin the same galaxies). (3) The rotation curves of the paired Seyfertsshow systematically small regions of rising or solid-body rotationcompared to the disk radius, as a group comparable to Sa but verydifferent from Sb or Sc galaxies (even for Seyfert galaxies with Hubbletype later than Sa). There is weak evidence that this difference is alsopresent with respect to more isolated Seyfert galaxies. Despite theobvious utility of a dynamically disturbed disk for transport of angularmomentum and "feeding the monster," Seyfert galaxies in pairs actuallyhave smaller kinematic disturbances (measured by the maximum departurefrom a symmetric rotation curve, normalized to the full rotationamplitude) than found in a complete sample of non-Seyfert spirals inpairs.
| A ^12^CO(1-0) survey of spiral galaxies in the region of the Coma supercluster.
We present observations of the ^12^CO(J=1-0) line at 2.6mm of 65galaxies located in the Coma supercluster region: 33 actually belong tothe Coma supercluster while 32 are either foreground or backgroundobjects. These data have been obtained using the NRAO 12m telescope atKitt Peak (United States), and for four galaxies, using the IRAM 30mtelescope at Pico Veleta (Spain). Out of these 65 galaxies, 54 had neverbeen observed in the CO(1-0) line; 49 have been detected by us, of which37 are new detections. We give molecular gas masses deduced from the COline integrated intensities, and upper limits for the 16 undetectedobjects, computed with a Galactic conversion factorN(H_2_)=2.3x10^20^I(CO) and H_0_=75km/s/Mpc.
| Parsec-scale radio cores in spiral galaxies
We have used the Parkes-Tidbinbilla Interferometer to search for compact(<0.03 arcsec) radio continuum cores in 54 nearby spiral galaxies, 22of which have Seyfert nuclei. In contrast to the radio cores ofelliptical galaxies, the few parsec-scale cores seen in spirals usuallyhave steep radio spectra, with an apparent median spectral index of-1.0. At present, it is not clear whether this is because the radiocores of spiral galaxies are larger than those in ellipticals (and soare partly resolved by the interferometer), or whether the core spectraof ellipticals and spirals are intrinsically different.
| A multifrequency radio continuum and IRAS faint source survey of markarian galaxies
Results are presented from a multifrequency radio continumm survey ofMarkarian galaxies (MRKs) and are supplemented by IRAS infrared datafrom the Faint Source Survey. Radio data are presented for 899 MRKsobserved at nu = 4.755 GHz with the National Radio Astronomy Observatory(NRAO)-Green Bank 300 foot (91 m) telescope, including nearly 88% ofthose objects in Markarian lists VI-XIV. In addition, 1.415 GHzmeasurements of 258 MRKs, over 30% of the MRKs accessible from theNational Aeronomy and Ionosphere Center (NAIC)-Arecibo, are reported.Radio continuum observations of smaller numbers of MRKs were made at10.63 GHz and at 23.1 GHz and are also presented. Infrared data from theIRAS Faint Source Survey (Ver. 2) are presented for 944 MRKs, withreasonably secure identifications extracted from the NASA/IPACExtragalactic Database. MRKs exhibit the same canonical infraredcharacteristics as those reported for various other galaxy samples, thatis well-known enhancement of the 25 micrometer/60 micrometer color ratioamong Seyfert MRKs, and a clear tendency for MRKs with warmer 60micrometer/100 micrometer colors to also possess cooler 12 micrometer/25micrometer colors. In addition, non-Seyfert are found to obey thewell-documented infrared/radio luminosity correlation, with the tightestcorrelation seen for starburst MRKs.
| MEPSICRON spectrophotometry of Seyfert galaxies. 1: Spectral atlas
A spectrophotometric study of 51 Seyfert galaxies is presented. Thegalaxies were observed with a long-slit spectrograph coupled to thephoton-counting bidimensional detector MEPSICRON. The paper includes thecalibrated spectra of the inner nuclear region of the galaxies, obtainedwith spectral resolution of 12 A and a signal-to-noise ratio greaterthan 50 on strong emission lines. A detailed spectral lineidentification was carried out and is presented with the correspondingderived line fluxes and equivalent widths.
| 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.
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