Contents
Images
Upload your image
DSS Images Other Images
Related articles
The Effects of Interactions on the Structure and Morphology of Elliptical/Lenticular Galaxies in Pairs
We present a structural and photometric analysis of 42elliptical/lenticular galaxies in E/S0 + S pairs observed in the BVRIcolor bands. The aim of the analysis is to empirically determine theeffects of interactions on the galaxies' morphology, structure, andstellar populations as seen from the CAS parameters (light concentrationC, asymmetry A, and clumpiness S). We further compare these values to acontrol sample of 67 mostly isolated noninteracting E/S0 galaxies. Wefind that the paired E/S0 galaxies occupy more scattered loci in CASspace than noninteracting E/S0s and that the structural effects ofinteractions on E/S0s are minor, in contrast to disk galaxies involvedin interactions. This suggests that observational methods forrecognizing interactions, such the CAS methodology of Conselice, wouldnot detect E/S0s involved in interactions (related to early phases ofthe so-called dry mergers), and that the majority of interactinggalaxies identified at high redshift must be gas-dominated systems.However, we find statistical differences in the asymmetry index whencomparing isolated and interacting E/S0s. On average, paired E/S0galaxies have A-values 2.96+/-0.72 times larger than those ofnoninteracting E/S0s. For the subset of presumably strongly interactingE/S0s, A and S can be several times larger than the typical values ofthe isolated E/S0s. We show that the asymmetries are consistent withseveral internal and external morphological distortions. We concludethat the subsample of interacting E/S0s should be dense, gas-poorgalaxies in systems spanning a wide range of interaction stages, withtypical merging timescales >~0.1-0.5 Gyr. We use the observedphenomenology of this subsample to predict the approximate loci of drypremergers in the CAS parameter space.
| 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.
| An IRAS High Resolution Image Restoration (HIRES) Atlas of All Interacting Galaxies in the IRAS Revised Bright Galaxy Sample
The importance of far-infrared observations for our understanding ofextreme activity in interacting and merging galaxies has beenillustrated by many studies. Even though two decades have passed sinceits launch, the most complete all-sky survey to date from which far-IRselected galaxy samples can be chosen is still that of the InfraredAstronomical Satellite (IRAS). However, the spatial resolution of theIRAS all-sky survey is insufficient to resolve the emission fromindividual galaxies in most interacting galaxy pairs, and hence previousstudies of their far-IR properties have had to concentrate either onglobal system properties or on the properties of very widely separatedand weakly interacting pairs. Using the HIRES image reconstructiontechnique, it is possible to achieve a spatial resolution ranging from30" to 1.5m (depending on wavelength and detector coverage), whichis a fourfold improvement over the normal resolution of IRAS. This issufficient to resolve the far-IR emission from the individual galaxiesin many interacting systems detected by IRAS, which is very importantfor meaningful comparisons with single, isolated galaxies. We presenthigh-resolution 12, 25, 60, and 100 μm images of 106 interactinggalaxy systems contained in the IRAS Revised Bright Galaxy Sample (RBGS,Sanders et al.), a complete sample of all galaxies having a 60 μmflux density greater than 5.24 Jy. These systems were selected to haveat least two distinguishable galaxies separated by less than threeaverage galactic diameters, and thus we have excluded very widelyseparated systems and very advanced mergers. Additionally, some systemshave been included that are more than three galactic diameters apart,yet have separations less than 4' and are thus likely to suffer fromconfusion in the RBGS. The new complete survey has the same propertiesas the prototype survey of Surace et al. We find no increased tendencyfor infrared-bright galaxies to be associated with other infrared-brightgalaxies among the widely separated pairs studied here. We find smallenhancements in far-IR activity in multiple galaxy systems relative toRBGS noninteracting galaxies with the same blue luminosity distribution.We also find no differences in infrared activity (as measured byinfrared color and luminosity) between late- and early-type spiralgalaxies.
| [O II] as a Star Formation Rate Indicator
We investigate the [O II] emission line as a star formation rate (SFR)indicator using integrated spectra of 97 galaxies from the Nearby FieldGalaxies Survey (NFGS). The sample includes all Hubble types andcontains SFRs ranging from 0.01 to 100 Msolaryr-1. We compare the Kennicutt [O II] and Hα SFRcalibrations and show that there are two significant effects thatproduce disagreement between SFR([O II]) and SFR(Hα): reddeningand metallicity. Differences in the ionization state of the interstellarmedium do not contribute significantly to the observed differencebetween SFR([O II]) and SFR(Hα) for the NFGS galaxies withmetallicities log(O/H)+12>~8.5. The Kennicutt [O II]-SFR relationassumes a typical reddening for nearby galaxies; in practice, thereddening differs significantly from sample to sample. We derive a newSFR([O II]) calibration that does not contain a reddening assumption.Our new SFR([O II]) calibration also provides an optional correction formetallicity. Our SFRs derived from [O II] agree with those derived fromHα to within 0.03-0.05 dex. We show that the reddening, E(B-V),increases with intrinsic (i.e., reddening-corrected) [O II] luminosityfor the NFGS sample. We apply our SFR([O II]) calibration withmetallicity correction to two samples: high-redshift 0.8
| The PDS versus Markarian starburst galaxies: comparing strong and weak IRAS emitter at 12 and 25 μm in the nearby Universe
The characteristics of the starburst galaxies from the Pico dos Diassurvey (PDS) are compared with those of the nearby ultraviolet (UV)bright Markarian starburst galaxies, having the same limit in redshift(vh < 7500 km s-1) and absolute B magnitude(MB < -18). An important difference is found: theMarkarian galaxies are generally undetected at 12 and 25 μm in IRAS.This is consistent with the UV excess shown by these galaxies andsuggests that the youngest star-forming regions dominating thesegalaxies are relatively free of dust.The far-infrared selection criteria for the PDS are shown to introduce astrong bias towards massive (luminous) and large size late-type spiralgalaxies. This is contrary to the Markarian galaxies, which are found tobe remarkably rich in smaller size early-type galaxies. These resultssuggest that only late-type spirals with a large and massive disc arestrong emitters at 12 and 25 μm in IRAS in the nearby Universe.The Markarian and PDS starburst galaxies are shown to share the sameenvironment. This rules out an explanation of the differences observedin terms of external parameters. These differences may be explained byassuming two different levels of evolution, the Markarian being lessevolved than the PDS galaxies. This interpretation is fully consistentwith the disc formation hypothesis proposed by Coziol et al. to explainthe special properties of the Markarian SBNG.
| The IRAS Revised Bright Galaxy Sample
IRAS flux densities, redshifts, and infrared luminosities are reportedfor all sources identified in the IRAS Revised Bright Galaxy Sample(RBGS), a complete flux-limited survey of all extragalactic objects withtotal 60 μm flux density greater than 5.24 Jy, covering the entiresky surveyed by IRAS at Galactic latitudes |b|>5°. The RBGS includes629 objects, with median and mean sample redshifts of 0.0082 and 0.0126,respectively, and a maximum redshift of 0.0876. The RBGS supersedes theprevious two-part IRAS Bright Galaxy Samples(BGS1+BGS2), which were compiled before the final(Pass 3) calibration of the IRAS Level 1 Archive in 1990 May. The RBGSalso makes use of more accurate and consistent automated methods tomeasure the flux of objects with extended emission. The RBGS contains 39objects that were not present in the BGS1+BGS2,and 28 objects from the BGS1+BGS2 have beendropped from RBGS because their revised 60 μm flux densities are notgreater than 5.24 Jy. Comparison of revised flux measurements forsources in both surveys shows that most flux differences are in therange ~5%-25%, although some faint sources at 12 and 25 μm differ byas much as a factor of 2. Basic properties of the RBGS sources aresummarized, including estimated total infrared luminosities, as well asupdates to cross identifications with sources from optical galaxycatalogs established using the NASA/IPAC Extragalactic Database. Inaddition, an atlas of images from the Digitized Sky Survey with overlaysof the IRAS position uncertainty ellipse and annotated scale bars isprovided for ease in visualizing the optical morphology in context withthe angular and metric size of each object. The revised bolometricinfrared luminosity function, φ(Lir), forinfrared-bright galaxies in the local universe remains best fit by adouble power law, φ(L)~Lα, withα=-0.6(+/-0.1) and α=-2.2(+/-0.1) below and above the``characteristic'' infrared luminosityL*ir~1010.5Lsolar,respectively. A companion paper provides IRAS High Resolution (HIRES)processing of over 100 RBGS sources where improved spatial resolutionoften provides better IRAS source positions or allows for deconvolutionof close galaxy pairs.
| 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.
| BVRI surface photometry of mixed morphology pairs of galaxies. I. The first data set
We present multicolor broad band (BVRI) photometry for a sample of 11mixed morphology (E/S0+S) binary galaxies drawn from the KarachentsevCatalogue of Isolated Pairs of Galaxies (KPG). The data is part of anobservational programme devoted to the systematic photometric study ofone of the most complete and homogeneous pair samples available in theliterature. We present B band, B-filtered images, B, V, R and I surfacebrightness and (B-V), (B-R) and (B-I) color profiles as well asgeometric (epsilon = 1 - b/a, PA and a4/a) profiles for eachcomponent pair. In addition, integrated corrected B, V, R and Imagnitudes and integrated (B-V), (B-R) and (B-I) colors are alsopresented. Internal and external data comparisons show consistencywithin the estimated errors. Most of this subsample have photometricparameters homogeneously derived for the first time. Geometric profilesfrom our surface photometry along with the broad-band imaging and colorinformation have been used to re-evaluate morphology in all pairs. Wefind an important number of true mixed pairs with 5/11 (E+S) pairs inthe present sample. The remaining objects include 3 disky pairs(composed of S0 and S members), 2 early-type pair comprising E and S0members and 1 spiral-irregular pair. The measurements will be used in aseries of forthcoming papers where we try to identify and isolate themain structural and photometric properties of disk and ellipticalgalaxies at different stages of interaction.Based on data obtained at the 0.84 m and 1.5 m telescopes of theObservatorio Astronómico Nacional, San Pedro Mártir, BajaCalifornia, México, operated by the Instituto deAstronomía, UNAM.Tables 1-3 and Figs. 5 to 15 are only available in electronic form athttp://www.edpsciences.org
| A Kinematic Study of M51-Type Galaxies
Not Available
| Physical Sources of Scatter in the Tully-Fisher Relation
We analyze residuals from the Tully-Fisher relation for theemission-line galaxies in the Nearby Field Galaxy Survey, a broadlyrepresentative survey designed to fairly sample the variety of galaxymorphologies and environments in the local universe for luminositiesfrom MB=-15 to -23. For a subsample consisting of the spiralgalaxies brighter than MiR=-18, we find strongcorrelations between Tully-Fisher residuals and both B-R color andEW(Hα). The extremes of the correlations are populated by Sagalaxies, which show consistently red colors, and spiral galaxies withmorphological peculiarities, which are often blue. If we apply anEW(Hα)-dependent or B-R color-dependent correction term to theTully-Fisher relation, the scatter in the relation no longer increasesfrom R to B to U but instead drops to a nearly constant level in allbands, close to the scatter we expect from measurement errors. We arguethat these results probably reflect correlated offsets in luminosity andcolor as a function of star formation history. Broadening the sample inmorphology and luminosity, we find that most nonspiral galaxies brighterthan MiR=-18 follow the same correlations betweenTully-Fisher residuals and B-R color and EW(Hα) as do spirals,albeit with greater scatter. However, the color and EW(Hα)correlations do not apply to galaxies fainter thanMiR=-18 or to emission-line S0 galaxies withanomalous gas kinematics. For the dwarf galaxy population, theparameters controlling Tully-Fisher residuals are instead related to thedegree of recent evolutionary disturbance: overluminous dwarfs havehigher rotation curve asymmetries, brighter U-band effective surfacebrightnesses, and shorter gas consumption timescales than theirunderluminous counterparts. As a result, sample selection stronglyaffects the measured faint-end slope of the Tully-Fisher relation, and asample limited to include only passively evolving, rotationallysupported galaxies displays a break toward steeper slope at lowluminosities.
| 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.
| 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.
| N-body model for M51 - I. Multiple encounter versus single passage?
A numerical survey of the encounter history of the interactinggrand-design system M51 (NGC 5194/5195) is performed with a 3D multiplespherical polar grid code, where both components of the pair aredescribed with self-gravitating star+gas discs embedded in rigidanalytical halo potentials. Two classes of models are investigated, (1)nearly parabolic single passages, and (2) bound encounters implyingseveral disc-plane crossings. Both types of models can approximate thegeneral morphology of the M51 system and simultaneously fit theprojected velocity difference and separation of the components. In bothcases the companion disc-plane crossing responsible for the main spiralstructure occurred nearly in the south, about 400-500Myr ago at adistance of 25-30kpc, but in opposite directions. In the bound encountermodel there is also a more recent crossing, at a distance of 20-25kpcabout 50-100Myr ago. Our models account for some important kinematicalobservations of the M51 system not explained by the previous models.Especially, we note that the multiple-encounter model with a recentpassage produces significant out-of-plane velocities, which manifest asan S-shaped structure of the major axis rotation curve, and which alsoexplain the high peculiar velocities in the north of the companion. Inthis model the resulting extended tail is tilted 40°-50° withrespect to the inner disc, leading to a velocity field that appears tosuggest counter-rotation of the tail with respect to the inner disc.Also some morphological features, like the direction of the tidalextensions from the companion, are better matched by a model with arecent encounter. Importantly, any pre-existing spiral arms are washedout by the tidally triggered spiral arms. The multiple-encounter modelassumes a high inclination Mdisc =2πΣ0Re2 [1 -(1+RdRe)exp(-RdRe)](i~85°) orbit, with a low current eccentricityz0σz2/2πGΣ(ɛ~0.2). The possible origin of this type of bound orbitalconfiguration is studied by simulations including the orbital decay viathe Chandrasekhar formula for dynamical friction, and also bysimulations including a self-consistently modelled live halo for theprimary. The gross features of the model, including the tilted far tail,are preserved even when allowing for the effects of several earlierpassages. The observed well-defined far tail seems to suggest that theprevious passages have been at least 30per cent more distant than thelatest two crossings. According to our limited orbital survey, such anorbital decay can be accounted for, provided that M51 has an extendeddark halo containing at least a few times the mass within the visibledisc region (total νh ∝√[r2/(r2 + Rc2)], r< Rh, MhaloMdisc~10).
| Spectrophotometry of Nearby Field Galaxies: The Data
We have obtained integrated and nuclear spectra as well as U, B, Rsurface photometry for a representative sample of 196 nearby galaxies.These galaxies span the entire Hubble sequence in morphological type, aswell as a wide range of luminosities (MB=-14 to -22). Here wepresent the spectrophotometry for these galaxies. The selection of thesample and the U, B, R surface photometry is described in a companionpaper. Our goals for the project include measuring the current starformation rates and metallicities of these galaxies, and elucidatingtheir star formation histories, as a function of luminosity andmorphology. We thereby extend the work of Kennicutt to lower luminositysystems. We anticipate that our study will be useful as a benchmark forstudies of galaxies at high redshift. We describe the observing, datareduction, and calibration techniques and demonstrate that ourspectrophotometry agrees well with that of Kennicutt. The spectra spanthe range 3550-7250 Å at a resolution (FWHM) of ~6 Å andhave an overall relative spectrophotometric accuracy of ~+/-6%. Wepresent a spectrophotometric atlas of integrated and nuclear rest-framespectra as well as tables of equivalent widths and synthetic colors. Theatlas and tables of measurements will be made available electronically.We study the correlations of galaxy properties determined from thespectra and images. Our findings include: (1) galaxies of a givenmorphological class display a wide range of continuum shapes andemission-line strengths if a broad range of luminosities are considered,(2) emission-line strengths tend to increase and continua tend to getbluer as the luminosity decreases, and (3) the scatter on the generalcorrelation between nuclear and integrated Hα emission-linestrengths is large.
| Surface Photometry of Nearby Field Galaxies: The Data
We have obtained integrated spectra and multifilter photometry for arepresentative sample of ~200 nearby galaxies. These galaxies span theentire Hubble sequence in morphological type, as well as a wide range ofluminosities (MB=-14 to -22) and colors (B-R=0.4-1.8). Herewe describe the sample selection criteria and the U, B, R surfacephotometry for these galaxies. The spectrophotometric results will bepresented in a companion paper. Our goals for the project includemeasuring the current star formation rates and metallicity of thesegalaxies, and elucidating their star formation histories, as a functionof luminosity and morphology. We thereby extend the work of Kennicutt tolower luminosity systems. We anticipate that our study will be useful asa benchmark for studies of galaxies at high redshift. We discuss theobserving, data reduction, and calibration techniques and show that ourphotometry agrees well with previous work in those cases in whichearlier data are available. We present an atlas of images, radialsurface brightness profiles, and color profiles as well as tables ofderived parameters. The atlas and tables of measurements will be madeavailable electronically. We study the correlations of galaxy propertiesdetermined from the galaxy images. Our findings include the following:(1) colors determined within the effective radius correlate better withmorphological type than with MB and (2) 50% of thelow-luminosity galaxies are bluest in their centers.
| The Arizona-New Mexico Spectroscopic Survey of Galaxies. I. Data for the Western End of the Perseus Supercluster
We present new optical spectroscopic data for 347 galaxies in the regionof the Perseus supercluster. The new data were obtained using theSteward Observatory 2.3 m telescope and cover the whole optical window.Included are redshifts (for 345 objects), absorption-line equivalentwidths, a continuum index measuring the 4000 Å break, andemission-line flux ratios. After 11 objects are rejected for being toofaint and redshifts for 26 objects are added from the literature, wearrive at a complete sample of 361 galaxies. The distribution ofredshifts for the whole sample is examined, and we show the relationshipof the continuum index to morphology.
| Galaxy collisions.
Theories of how galaxies, the fundamental constituents of large-scalestructure, form and evolve have undergone a dramatic paradigm shift inthe last few decades. Earlier views were of rapid, early collapse andformation of basic structures, followed by slow evolution of the stellarpopulations and steady buildup of the chemical elements. Currenttheories emphasize hierarchical buildup via recurrent collisions andmergers, separated by long periods of relaxation and secularrestructuring. Thus, collisions between galaxies are now seen as aprimary process in their evolution. This article begins with a briefhistory; we then tour parts of the vast array of collisional forms thathave been discovered to date. Many examples are provided to illustratehow detailed numerical models and multiwaveband observations haveallowed the general chronological sequence of collisional morphologiesto be deciphered, and how these forms are produced by the processes oftidal kinematics, hypersonic gas dynamics, collective dynamical frictionand violent relaxation. Galaxy collisions may trigger the formation of alarge fraction of all the stars ever formed, and play a key role infueling active galactic nuclei. Current understanding of the processesinvolved is reviewed. The last decade has seen exciting new discoveriesabout how collisions are orchestrated by their environment, howcollisional processes depend on environment, and how these environmentsdepend on redshift or cosmological time.
| 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.
| Very cold dust in galaxies
We present multi-filter far infrared photometry of active and inactivegalaxies obtained with ISOPHOT. We find that the far infrared andsubmillimeter spectrum of the active galaxies can be described by asingle modified black-body at a color temperature of 31.5 +/- 2.8 K. Theratio of infrared luminosity to gas mass, L_IR/M_gas, where the latterquantity has been obtained from 1.3 mm observations within the central11'' is about 90 L_sun/ M_sun. In contrast, the spectral energydistributions of inactive spirals require, apart from warm dust of 31.8+/- 2.8 K, an additional very cold component of at most 12.9+/- 1.7 K.Determining the gas mass from 1.3 mm dust continuum maps that cover theoptical extent of the inactive spirals we find L_IR/M_gas ~ 3 L_sun/M_sun , a factor ~ 30 lower than for the active galaxies. Based onobservations with ISO, an ESA project with instruments funded by ESAMember States (especially the PI countries: France, Germany, theNetherlands and the United Kingdom) with the participation of ISAS andNASA.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| Determination of orbital parameters of interacting galaxies using a genetic algorithm. Description of the method and application to artificial data
A method for determining the orbital parameters of interacting pairs ofgalaxies is presented and evaluated using artificial data. The methodconsists of a genetic algorithm which can search efficiently through thevery large space of possible orbits. It is found that orbital parametersclose to the actual orbital parameters of the pair can in general befound, even in the presence of fairly high levels of noise in the data.Both position and velocity data can be employed, but if no velocity dataare available, the orbital parameters can be determined using positiondata only. The inner regions of the galaxies, which are difficult tomodel, can be neglected, and the orbital parameters can be determinedusing the remaining information.
| 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.
| 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.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| Photometric study of polar-ring galaxies. III. Forming rings.
We present the results of detailed surface photometry of NGC 3808B andNGC 6286 - two spiral galaxies with possibly forming ring-likestructures rotating around major axes of the galaxies. The formation ofrings in NGC 3808B and NGC 6286 being accompanied by accretion of matteron galactic disk results in some interesting gasdynamical andstellar-dynamical effects in these galaxies. One can note, for instance,peculiar rotation curve of NGC 3808B gaseous disk; strong infrared andHα emission from the galaxies; bending and flaring stellar disksin both galaxies. Our observations clearly illustrate the possibilitythat polar-ring galaxies may be formed as a result of matter accretionfrom one galaxy to another.
| 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.
| Gas content of infrared luminous markarian galaxies
The atomic and molecular hydrogen gas properties of a complete sample ofMarkarian galaxies with flux density at 60 µm higher than 1.95 Jyare presented. We present the improved far-infrared luminosity functionof Markarian galaxies; and its comparison with other samples. We findthat 40% of the bright IRAS galaxies of far-infrared luminosity higherthan 1010.5 L are Markarian galaxies. There is an absence of correlationbetween HI content of Markarian galaxies and current star formationactivity, implying that star formation in these systems has complexstructure and it is not a simple function of the HI content. On thecontrary, the H2 content of Markarian galaxies is well correlated withstar formation activity. It is argued that tight correlation between HIand H2 contents is a consequence of transformation of atomic hydrogeninto molecular.
| At the 2.6 m telescope of Byurakan Perot-Fabry observations of gas emission in nebulae with cigale
During the summer of 1985, the CIGALE Perot-Fabry scanninginterferometer of Marseilles Observatory was installed at the primefocus of the 2.6 m telescope of Byurakan Observatory. The long run (twonew moons) was successful and gave matereial for numerous publications.
| Radio-far-infrared relation in Markarian galaxies
We have compared the radio continuum properties of Markarian galaxies atlambda lambda 6.3 and 2.8 cm with the integrated far-infraredluminosities over the 60 micrometer and 100 micrometer IRAS bands andover the 12 micrometer to 25 micrometer regime. We find that Markariangalaxies behave like normal star-forming galaxies. Comparing L60,100 with the radio emission, most objects lie in the region ofnormal star-forming galaxies. Only some Seyferts and most of theradio-quiet quasars show a higher radio-to-FIR ratio. ComparingL12, 25 with the radio luminosity, the correlation issurprisingly tight for all objects. In both cases the dispersion of thecorrelation seems to depend on the radio wavelength and is smaller atlambda 2.8 cm than at lambda 6.3 cm.
| 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.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
