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The Structural Properties of Isolated Galaxies, Spiral-Spiral Pairs, and Mergers: The Robustness of Galaxy Morphology during Secular Evolution
We present a structural analysis of nearby galaxies in spiral-spiralpairs in optical BVRI bands and compare them with the structures ofisolated spiral galaxies and galaxies in ongoing mergers. We use thesecomparisons to determine how galaxy structure changes during galaxyinteractions and mergers. We analyze light concentration (C), asymmetry(A), and clumpiness (S) parameters, and use the projections of CASparameter space to compare these samples. We find that the CASparameters of paired galaxies are correlated with the projectedseparations of the pair. For the widest and closest pairs, the CASparameters tend to be similar to those of isolated and ongoing majormergers (e.g., ultraluminous infrared galaxies), respectively. Ourresults imply that galaxy morphology is a robust property that onlychanges significantly during a strong interaction or major merger. Thetypical timescale for this change in our paired sample, based ondynamical friction arguments, is short, τ~0.1-0.5 Gyr. We findaverage enhancement factors for the spiral-pair asymmetries andclumpiness values of ~2.2 and 1.5. The S parameter, which is related tostar formation (SF) activity, has a moderate level of enhancement,suggesting that this activity in modern spirals depends more on internalprocesses than on external conditions. We further test the statisticalcriterion for picking up interacting galaxies in an automated way byusing the A-S projection plane. The diversity of our spiral-pair samplein the CAS space suggests that structural/SF/morphological properties ofinteracting galaxies change abruptly only when the interaction becomesvery strong and the criteria given previously by Conselice for findinggalaxies involved in major mergers are effective.
| Tidally Triggered Star Formation in Close Pairs of Galaxies. II. Constraints on Burst Strengths and Ages
Galaxy-galaxy interactions rearrange the baryons in galaxies and triggersubstantial star formation; the aggregate effects of these interactionson the evolutionary histories of galaxies in the universe are poorlyunderstood. We combine B- and R-band photometry and optical spectroscopyto estimate the strengths and timescales of bursts of triggered starformation in the centers of 190 galaxies in pairs and compact groups.Based on an analysis of the measured colors and EW(Hα), wecharacterize the preexisting and triggered populations separately. Thebest-fitting burst scenarios assume stronger reddening corrections forline emission than for the continuum and continuous star formationlasting for >~100 Myr. The most realistic scenarios require aninitial mass function that is deficient in the highest mass stars. Thecolor of the preexisting stellar population is the most significantsource of uncertainty. Triggered star formation contributessubstantially (probably >~50%) to the R-band flux in the centralregions of several galaxies; tidal tails do not necessarily accompanythis star formation. Many of the galaxies in our sample have bluercenters than outskirts, suggesting that pre- or nonmerger interactionsmay lead to evolution along the Hubble sequence. These objects wouldappear blue and compact at higher redshifts; the older, redder outskirtsof the disks would be difficult to detect. Our data indicate thatgalaxies with larger separations on the sky contain weaker, and probablyolder, bursts of star formation on average. However, confirmation ofthese trends requires further constraints on the colors of the olderstellar populations and on the reddening for individual galaxies.
| Dynamical Effects of Interactions and the Tully-Fisher Relation for Hickson Compact Groups
We investigate the properties of the B-band Tully-Fisher (T-F) relationfor 25 compact group galaxies, using Vmax derived fromtwo-dimensional velocity maps. Our main result is that the majority ofthe Hickson Compact Group galaxies lie on the T-F relation. However,about 20% of the galaxies, including the lowest-mass systems, havehigher B luminosities for a given mass, or alternatively, a mass that istoo low for their luminosities. We favor a scenario in which outliershave been brightened because of either enhanced star formation ormerging. Alternatively, the T-F outliers may have undergone truncationof their dark halo due to interactions. It is possible that in somecases both effects contribute. The fact that the B-band T-F relation issimilar for compact group and field galaxies tells us that thesegalaxies show common mass-to-size relations and that the halos ofcompact group galaxies have not been significantly stripped insideR25. We find that 75% of the compact group galaxies studied(22 out of 29) have highly peculiar velocity fields. Nevertheless, acareful choice of inclination, position angle, and center, obtained fromthe velocity field, and an average of the velocities over a large sectorof the galaxy enabled the determination of fairly well-behaved rotationcurves for the galaxies. However, two of the compact group galaxies HCG91a and HCG 96a, which are the most massive members in M51-like pairs,have very asymmetric rotation curves, with one arm rising and the otherone falling, indicating most probably a recent perturbation by the smallclose companions.
| Diffuse and Gravitationally Stable Molecular Gas in the Post-Starburst Galaxy NGC 5195
The Nobeyama Millimeter Array (NMA) has been used to make aperturesynthesis CO(1 - 0) observations of the post-starburst galaxy NGC 5195.CO(1 - 0) and HCN(1 - 0) observations of NGC 5195 using the Nobeyama 45m telescope are also presented. High-resolution (1".9 × 1".8 or 86pc × 81 pc or D = 9.3 Mpc) NMA maps show a strong concentration ofCO emission toward the central a few × 100 pc region of NGC 5195,despite the fact that the current massive star formation is suppressedthere. The face-on gas surface density, Σgas, withinthe r < 2'' or 90pc region reaches 3.7 × 103pc-2 if a Galactic NH2/ICOconversion factor is applied. The extent of the central CO peak is about5'', or 230pc, and is elongated along the E-W direction with two-armedspiral-like structures, which are typical for barred disk galaxies. TheHCN-to-CO integrated intensity rat io on the brightness temperaturescale, RHCN/CO, is about 0.02 within the central r < 400pc region. This RHCN/CO is smaller than those in starburstregions by a factor of 5 - 15. These molecular-gas properties wouldexplain why NGC 5195 is in a post-starburst phase; most of the densemolecular cores (i.e., the very sites of massive star formation) havebeen consumed away by a past starburst event, and therefore a burst ofmassive star formation can no longer last, although a large amount oflow density gas still exists. We find a steep rise of the rotationvelocity toward the center of NGC 5195. As a consequence, the criticalgas surface density for a local gravitational instability of the gasdisk becomes very high Σcrit 6.9 × 103Modot pc-2), suggesting that the molecular gas in the centralregion of NGC 5195 is gravitationally stable! ! , in contrast to that ofstarburst galaxies. We propose that dense molecular gas can not beformed from remaining diffuse molecular gas because the molecular gas inthe center of NGC 5195 is too stable to form dense cores viagravitational instabilities of diffuse molecular gas. The deduced veryhigh threshold density seems to be due to a high mass concentration inNGC 5195. The known trends on the occurrence and luminosity of nuclearstar formation in early-type galaxies can be understood naturally if thehigh threshold density is characteristic for early-type galaxies.
| A Kinematic Study of M51-Type Galaxies
Not Available
| 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.
| CO Observations of the Interacting Galaxy Pair NGC 5394/95
BIMA 12CO J=1-->0 observations are presented of the spiralgalaxies NGC 5394 and NGC 5395 that have undergone a recent, grazingencounter. In NGC 5394 approximately 80% of the CO emission detected byBIMA is concentrated in the central 800 pc (FWHM) starburst region, andthe rest is from a portion of the inner disk south and west of thecentral starburst. In an encounter simulation that reproduces some ofthe main features of this galaxy pair, a considerable amount of gas inNGC 5394 falls into the central region early in the collision. Theobserved total gas distribution in the disk of NGC 5394 is lopsided,with more H I, CO, and Hα emission coming from the western orsouthwestern side. The innermost western arm of NGC 5394 is seen in COand Hα emission, but the eastern inner-disk arm, which is verybright in the optical continuum, is not detected in CO or Hαemission. The NGC 5394 starburst region is similar in radio continuumluminosity and size to the M82 starburst and has a CO luminosity ~4times greater. A CO position-velocity diagram of the NGC 5394 nucleusreveals two separate velocity features very close to the center. Thismay indicate a nuclear ring or the ``twin peaks'' of an ILR or somedepletion of 12CO J=1-->0 at the nucleus. From acomparison of the radio continuum, Hα, 60 μm, and COluminosities, we estimate that the average extinction Av ofthe starburst nucleus is 3-4 mag, the star formation rate is ~6Msolar yr-1, and the conversion factorN(H2)/ICO in the starburst is a factor of 3-4below the standard value. Comparison of NGC 5394 with two other systemspreviously studied suggests that in prograde grazing encounters acentral starburst may not develop until near the end of the ocularphase. Very little of the CO emission from NGC 5395 found in previoussingle-dish observations is detected in the BIMA data; thus moleculargas in NGC 5395 does not appear to be strongly concentrated incompressed ridges.
| BVRI imaging of M51-type interacting galaxy pairs - III. Analysis of the photometric parameters
Photometric bulge and disc properties of a sample of 21 M51-type pairsobserved in BVRI bands are analysed, and the derived parameters obtainedby the R1/4-law and exponential bulge models are comparedwith the sample of normal galaxies reported by de Jong & van derKruit in 1994. Some characteristic properties of the intensity profilesare then interpreted by 3D N-body simulations, in which both componentsof the pair are described by an exponential star+gas disc embedded in alive bulge and halo. The disc central surface brightnessμ0 was found to be similar for the M51-type and for normalgalaxies, being 21.5+/-0.8Bmagarcsec-2, when the exponentialbulge model was used. The main galaxies had generally almost normalphotometric properties, whereas for the companions secular evolutionmust have played an important role. Even though the mean scalelengthsfor the M51-type galaxies were smaller than for the comparison galaxies,their bulges were larger: especially the companions had extremely largebulge sizes relative to their disc scalelengths having (B)=0.37+/-0.10 in comparison with0.15+/-0.09 for normal galaxies. Consequently, the bulge-to-discluminosity ratios for the companions were also generally larger thanknown for any of the Hubble types of normal galaxy. N-body simulationsindicated that the inner disc can be steepened during the interaction,and that this steepened disc can be erroneously interpreted as belongingto the bulge. Simultaneously material in the outer disc isredistributed, producing shallow outer profiles similar to thoseobserved for typical M51-type galaxies. These processes weredemonstrated by applying photometric bulge-to-disc decompositions forsome of the simulated intensity profiles. The decompositions also showedthat one must be cautious when applying the R1/4-law bulgemodel, especially for interacting galaxies. A nearly parabolicexperiment showed that the redistribution of matter in the disc duringthe close passage can be long-lived, suggesting that galaxy interactionseven with small companions may play an important role in secularevolution for galaxies in clusters.
| High-Resolution H I Mapping of NGC 4038/39 (``The Antennae'') and Its Tidal Dwarf Galaxy Candidates
We present new VLA C+D array H I observations and optical andnear-infrared imaging of the well-known interacting system NGC 4038/39,``The Antennae.'' At low spatial resolution (~40"), the radio data reacha limiting column density of ~1019 cm-2 (2.5σ), providing significantly deeper mapping of the tidal featuresthan afforded by earlier H I maps. At relatively high spatial resolution(~10"), the radio data reveal a wealth of gaseous substructure bothwithin the main bodies of the galaxies and along the tidal tails. Inagreement with previous H I studies, we find that the northern tail hasH I along its outer length but none along its base. We suggest that theH I at the base of this tail has been ionized by massive stars in thedisk of NGC 4038. The gas in the southern tail has a bifurcatedstructure, with one filament lying along the optical tail and anotherrunning parallel to it but with no optical counterpart. The twofilaments join just before the location of several star-forming regionsnear the end of the tail. The H I velocity field at the end of the tailis dominated by strong velocity gradients, which suggests that at thislocation the tail is bending away from us. We delineate and examine tworegions within the tail previously identified as possible sites of aso-called tidal dwarf galaxy condensing out of the expanding tidalmaterial. The tail velocity gradients mask any clear kinematic signatureof a self-gravitating condensation in this region. A dynamical analysissuggests that there is not enough mass in gas alone for either of theseregions to be self-gravitating. Conversely, if they are bound theyrequire a significant contribution to their dynamical mass from evolvedstars or dark matter. Even if there are no distinct dynamical tidalentities, it is clear that there is a unique concentration of gas,stars, and star-forming regions within the southern tail: the H Ichannel maps show clear evidence for a significant condensation near thetail star-forming regions, with the single-channel H I column densitieshigher than anywhere else in the system, including within the maindisks. Finally, the data reveal H I emission associated with the edge-on``superthin'' Scd galaxy ESO 572-G045, which lies just beyond thesouthern tidal tail of The Antennae, showing it to be a companionsystem.
| BVRI surface photometry of (S+S) binary galaxies I. The data
We present multicolour broad band (BVRI) photometry for a sample of 33spiral-spiral (S+S) binary galaxies drawn from the KarachentsevCatalogue of Isolated Pairs of Galaxies (KPG). The data is part of ajoint observational programme devoted to systematic photometric study ofone of the most complete and homogeneous pair samples available in theliterature. We present azimuthally averaged colour and surfacebrightness profiles, colour index (B-I) maps, B band and sharp/filteredB band images as well as integrated magnitudes, magnitudes at differentcircular apertures and integrated colours for each pair. Internal andexternal data comparisons show consistency within the estimated errors.Two thirds of the sample have total aperture parameters homogeneouslyderived for the first time. After reevaluating morphology for all thepairs, we find a change in Hubble type for 24 galaxies compared to theoriginal POSS classifications. More than half of our pairs showmorphological concordance which could explain, in part, the strongcorrelation in the (B-V) colour indices (Holmberg Effect) between paircomponents. We find a tendency for barred galaxies to show grand designmorphologies and flat colour profiles. The measurements will be used ina series of forthcoming papers where we try to identify and isolate themain structural and photometric properties of disk galaxies at differentstages of interaction. Table A.1 is only available in electronic form atthe CDS via anonymous ftp cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/379/54 and Tables 2-4 arealso available in electronic form at the CDS. Full Fig. 5 is onlyavailable in electronic form at the http://www.edpsciences.org Based ondata obtained at the 2.1 m telescope of the Observatorio Guillermo Haroat Cananea, Sonora, México, operated by the Instituto Nacional deAstrofísica, Optica y Electrónica.
| Statistical study of M 51-type galaxies
We present a statistical analysis of a new sample of M 51-type galaxies.Using the MCG and VV catalogues, we selected 32 such binary systems. Wefound that a typical M 51-type pair consists of a bright L*spiral galaxy and a satellite with blue luminosity 1/30-1/3 of theprimary one. The main galaxies in such pairs are often barred and havetwo well-defined spiral arms. M 51-type systems show an enhanced starformation rate (from FIR luminosities). We found a weak dependence ofthe star formation rate of the system on relative luminosity of thecompanion. M 51-type galaxies are relatively frequent: about 1/12 of allpairs are of M 51-type.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| BVRI imaging of M 51-type pairs. II. Bulge and disk parameters
We present decompositions of azimuthally averaged surface brightnessprofiles in optical B, V, R and I-bands for a sample of 40 M 51-typeinteracting galaxies. The profiles were modelled by an exponential diskand a spherical bulge described either by the R1/4 law or byan exponential function. Half of the galaxies were well fitted by bothbulge models, whereas for 35 % the exponential function was a betterchoice. Special care was taken on eliminating superpositions of thecompanion galaxies. The mean B-band central surface brightness mu_0 wasfound to be 21.5 mag arcsec-2, which is near to the valueoriginally found by Freeman (\cite{freeman70}), but the scatter wasfairly large. Galaxy interactions have strongly modified the disks inmany of the galaxies in the sample. For example, six of them hadextremely flat brightness profiles outside the exponential part of thedisk, and many showed significant isophotal twists. Tables 1 to 4 andFigs. 2 to 4 are only available in the electronic version athttp://www.edpsciences.org}
| The Interacting Galaxies NGC 5394/5395: A Post-Ocular Galaxy and Its Ring/Spiral Companion
H I, radio continuum, Fabry-Perot Hα, and ^12CO J=1-->0observations and broadband optical and near infrared images arepresented of the interacting spiral galaxies NGC 5395 and NGC 5394.Kinematically, there are three important, separate components to the H Igas associated with this galaxy pair: (1) the main disk of NGC 5395, (2)a long, northern tidal arm of NGC 5395 distinct in velocity from itsmain disk, and (3) the disk of NGC 5394. The H I northern tidal arm ofNGC 5395 has a line of-sight velocity as much as 75-100 km s^-1 greaterthan the main disk of NGC 5395 at the same projected location and thusis not in the same plane as the disk. The velocity field of the disk ofNGC 5395 is asymmetric and distorted by large-scale and small-scalenoncircular motions. In NGC 5395, the encounter appears to be excitingm=1 and m=0 modes in what had been a two-armed spiral. The dominantspiral arm of NGC 5395 forms a large ring or pseudo-ring of Hα,radio continuum, and H I emission, somewhat off center with respect tothe nucleus. The H I trough in the center of NGC 5395 is not filled inby molecular gas. The Hα velocity contours exhibit an organizedpattern of kinks in crossing the ring and also show streaming motions ina large stellar caustic feature. The eastern side of the ring isbrighter in radio continuum and Hα the western side is brighter inH I and contains massive (10^8 M_solar) H I clouds not associated withthe most luminous H II regions. The smaller galaxy NGC 5394 is in animmediate post-ocular phase, with a central starburst, an intrinsicallyoval disk, two long, fairly symmetric, open tidal arms with higharm-interarm contrast, and very bright inner spiral arms, disjoint fromthe outer tidal arms. Most of the gas in NGC 5394 is in molecular formand concentrated within 3.8 kpc of the center, so is suitable forfueling the starburst. Despite the presence of H I gas, two of the threeoptically bright inner spiral arms of NGC 5394 show no evidence ofongoing star formation. A galaxy encounter simulation reproduces some ofthe main features of this system with a collision that is prograderelative to NGC 5394 and retrograde at a high tilt angle relative to NGC5395. The model finds that the inner spiral structure of NGC 5394developed from an eye-shaped (``ocular'') structure at slightly earliertimes. NGC 5394 and the two ocular galaxies IC 2163 and NGC 2535,studied earlier, form an evolutionary sequence of structures resultingfrom prograde encounters and thus confirm the generic models of suchcollisions. The agreement between the model for NGC 5394/95 and thering/spiral structures seen in NGC 5395 extends our understanding ofcollisional ring galaxies.
| A 180 Kiloparsec Tidal Tail in the Luminous Infrared Merger ARP 299
We present VLA H I observations and University of Hawaii 88 inch (2.2 m)deep optical B- and R-band observations of the IR-luminous merger Arp299 (=NGC 3690+IC 694). These data reveal a gas-rich (M_HI=3.3x10^9M_solar) optically faint (mu_B>~27 mag arcsec^-2, mu_R>~26 magarcsec^-2) tidal tail with a length of over 180 kpc. The size of thistidal feature necessitates an old interaction age for the merger(>~750 Myr since first periapse), which is currently experiencing avery young starburst (<~20 Myr). The observations reveal a mostremarkable structure within the tidal tail: it appears to be composed oftwo parallel filaments separated by approximately 20 kpc. One of thefilaments is gas-rich with little if any starlight, while the other isgas-poor. We believe that this bifurcation results from a warped disk inone of the progenitors. The quantities and kinematics of the tidal H Isuggest that Arp 299 results from the collision of a retrograde Sab-Sbgalaxy (IC 694) and a prograde Sbc-Sc galaxy (NGC 3690) that occurred750 Myr ago and will merge into a single object in roughly 60 Myr. Wesuggest that the present IR-luminous phase in this system is due in partto the retrograde spin of IC 694. Finally, we discuss the apparent lackof tidal dwarf galaxies within the tail.
| Study of the Interacting System NGC 6845
We present optical spectroscopy, B, V, R, and I CCD photometry, and VLAneutral hydrogen observations of the interacting quartet NGC 6845, alsoknow as Klemola 30. NGC 6845 A, the dominant component, sports a broadand bright tidal bridge and a faint tidal tail, which bifurcates. Thetidal bridge has a B-I color bluer than that of the inner disk of NGC6845 A. Five strong condensations, identified as H II regions brighterthan the brightest one known in our Galaxy, are found along the tidalbridge, with the two most luminous located at the bridge tip. Two giantH II regions, comparable to 30 Dor, are located where the tidal bridgeand the tidal tail join the disk of NGC 6845 A. Since the age of the HII regions is 3-8 Myr, star formation continued to occur along the tidalbridge and in the tidal arm well after they began to be torn apart(>=100 Myr). Satoh model fitting to the optical rotation curve of theA component reveals a kinematical mass of (4.4+/-1.2)x10^11 M_solar,inside the central 12 kpc (H_0=75 km s^-1 Mpc^-1). The H I emissionconsist of two components, a more massive one that belongs to NGC 6845 Aand a second one associated with NGC 6845 B. We do not detect gasassociated with galaxies C and D. The total amount of H I is 1.4x10^10M_solar, 5 time higher than the H I content of the Milky Way. The H Ikinematics indicates an amount of dark matter associated with the Acomponent 2 times higher than the mass inside its central 12 kpc. Thegroup kinematics indicates M/L~43(+/-2)(M/L)_solar orM/L~66(+/-2)(M/L)_solar, according to two different prescriptions forthe internal absorption correction. In spite of this large difference,both values furnish a similar group mass (~1x10^13 M_solar). Althoughpreliminary results on N-body simulations indicate that either B or Cmight well create a tidal feature like the bridge of the A component,the collision with B appears to be more favorable.
| BVRI imaging of M51-type interacting galaxy pairs. I. Data reductions
Deep broad-band BVRI photometry of a sample of 22 closely interactingisolated galaxy pairs is presented. The sample consists of pairs with alarge variety of orbital geometries, but most of them are M51-typepairs: a small companion in the vicinity of a prominent two-armedspiral. This subsample will be later modelled in detail with N-bodysimulations. Nine of the thirteen M51-type pairs show enhanced starformation in the central regions of the companions, detected in B-V orR-I color maps, and only one pair in the nucleus of the main galaxy.This is expected if there is mass transfer from the main galaxy to thecompanion. Some pairs with larger separation, and with more massivecompanions show global instabilities manifesting as strong colorgradients at least in one of the members.
| A catalogue of dwarf galaxy candidates around interacting galaxies
We present results from the imaging of a sample of 12 interactinggalaxies for which we have cataloged all potential dwarf systems in thevicinity of these strongly interacting galaxies. After careful cleaningof the images and applying a restrictive S/N criterion we haveidentified, measured and cataloged all possible extended objects in eachfield. On the frames, covering 11.4 x 10.5 arcmins, typically 100-200non-stellar faint, extended objects were found. The vast majority(>98%) of these objects had not been previously identified. Thenumber of expected objects in the magnitude range R= 18 - 19.5 exceedsthe expected count of background galaxies. This supports the possibilitythat a density enhancement of extended objects around some interactinggalaxies results from the addition of a locally formed dwarf galaxypopulation. Tables 4 to 15 only available in electronic form at CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| The Ocular Galaxy NGC 2535 and its Small Starburst Companion NGC 2536
Not Available
| Observations of the Ocular Galaxy NGC 2535 and its Starburst Companion NGC 2536
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2323K&db_key=AST
| Gravitational Instabilities in Tidally-Agitated Gas Produce 10(8) M_ȯ Clouds in an Encounter Between NGC 2535 and NGC 2536
We made VLA HI observations of the young, interacting galaxy pair NGC2535/36 in C and D Arrays (resolution = 12'' = 2.9 kpc). NGC 2535 has an"ocular" structure similar to that in IC 2163, which we studiedpreviously. In NGC 2535, the intrinsic HI velocity dispersion is high,30 km s(-1) over much of the disk, as compared to less than 10 km s(-1)in undisturbed spirals. The tidal arms of NGC 2535 contain fiveunusually massive clouds, with HI masses exceeding 10(8) M_ȯ andradii = 2 -- 3 kpc. These masses are comparable to the masses of HI-richdwarf galaxies. Most of these clouds do not have prominent counterpartsin the older stellar population. The HI column densities and velocitydispersions in these clouds imply a Jeans mass close to the observed HIcloud mass; the high gas turbulence apparently leads to the large cloudmass as a result of gravitational instabilities in the gas. Elmegreen etal. (1993, ApJ, 412, 90; 1995, ApJ, in press) found similar widespreadhigh gas turbulence and very massive HI clouds without strong stellarcounterparts in the young interacting pair IC 2163/NGC 2207. Thissuggests that enhanced turbulence and unusually massive gas cloudsproduced by gravitational instabilities in the gaseous disk may be ageneral feature of interacting spiral galaxies during the early phasesof post-encounter evolution. The massive HI clouds in NGC 2535, IC 2163,and NGC 2207 give observational support to the gravitational instabilitymodel in Elmegreen et al. (1993, ApJ, 412, 90) and are not predicted bythe Barnes and Hernquist (1992, Nature, 360, 715) model for theformation of tidal dwarf galaxies.
| The spatial distribution of supernovae in paired and interacting galaxies
In order to investigate the location of supernovae (SNe) in paired andinteracting galaxies, the 54 supernovae discovered up to May 1993 in 14Isolated Pairs of Galaxies and the 32 Interacting Systems were taken asa sample and studied. The whole sample of SNe, as well as a subsampleformed of type II, and Ib SNe, whose progenitors are young massivestars, do not appear in any one particluar direction with respect to thecompanion. On paired and interacting galaxies, the radial distributionof type Ib and II SNe peaks more toward the galaxy centers than it doesin isolated galaxies, indicating an enhanced Star Formation Rate (SFR)around the nuclei and in the inner disks. The distribution of SNIaappear similar in both samples, confirming that their progenitors arenot the same as those of SNII and IB. The SN rates are related to galaxyluminosity and, as expected, the discovery of SNe is twice more frequentin the brighter galaxy of the pair than in fainter ones. We did not findany relation between the locations of SNe in parent galaxies, the totalStar Formation activity and the kinematics of paired and interactinggalaxies.
| Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxies
Multivariate data have been collected as part of an effort to develop anew classification system for spiral galaxies, one which is notnecessarily based on subjective morphological properties. A sample of492 moderately bright northern Sa and Sc spirals was chosen for futurestatistical analysis. New observations were made at 20 and 21 cm; thelatter data are described in detail here. Infrared Astronomy Satellite(IRAS) fluxes were obtained from archival data. Finally, new estimatesof arm pattern radomness and of local environmental harshness werecompiled for most sample objects.
| A Simulation Atlas of Tidal Features in Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...417..502H&db_key=AST
| Effects of Interactions on the Nuclear Near Infrared Properties of Spiral Galaxies
Using JHKL photometric measures available in the literature, we havecompared the near-infrared colour indices and central luminosities ofsamples of relatively isolated spiral galaxies with LINER and H IIregion-like nuclei (hereafter called L and H) with corresponding samplesof interacting galaxies, in order to explore the effects of interactionson their near-infrared properties. We have found that the L galaxies andthe isolated H galaxies have, in general, normal near-infrared colourswhich are fully explainable in terms of emission from late-type evolvedstars. On the other hand, the sample of interacting H galaxies displays,on average, somewhat peculiar near-infrared colours (specifically,normal J - H colours, but redward H - K and, especially, K - Lexcesses), which very probably indicate the presence of thermal emissionfrom hot dust, presumably related to intense star formation activityinduced by the interactions. Furthermore, for the same galaxy samplethere is some evidence that the emission at λ ~ 2.2 microns issomewhat more centrally concentrated than that at shorter wavelengths.Interestingly, the L galaxies appear to have greater centralnear-infrared luminosities than the H galaxies, for the samemorphological-type interval.
| Models and observations of starbursts. II - Starbursts in interacting galaxies
Evolutionary models are applied here to starburst galaxies in a sampleof 30 interacting or merged systems in order to determine the durationof the starbursts. The time delay between bursts in both components ofinteracting pairs of disk galaxies is investigated and it is found thatstarbursts in the minor galaxies of these pairs started earlier thanthose in the major galaxies. While strong starbursts are found to beactive for only about 2 x 10 exp 7 yrs, the time delay between thebursts in both components of the interacting pairs can be significantlylarger. Delays of up to 2 x 10 exp 8 yrs are found in the sample. Modelfits show that the mass-to-luminosity ratios of strong centralstarbursts indicate a deficiency of low-mass stars in the starburstinitial mass function. The required low-mass-star deficiency is smallerthan previously believed.
| When galaxies go wrong.
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| Properties and simulations of interacting spiral galaxies with transient 'ocular' shapes
Computer simulations of interacting galaxies show a transient oval-apexstructure resembling an eye, which sometimes leads to the formation of apermanent central bar. A dimensionless tidal strength parametereffectively distinguishes between the different possible outcomes.Several examples of ocular structure in real galaxies have been found.The rotation curves of ocular galaxies are predicted to have largevelocity irregularities that correspond to distinctive spiral arm anddouble-parallel arm features. The amplitude of the velocity features maybe useful in determining the strength of the tidal interactions.
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