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A Survey of Merger Remnants. II. The Emerging Kinematic and Photometric Correlations
This paper is the second in a series exploring the properties of 51optically selected, single-nuclei merger remnants. Spectroscopic datahave been obtained for a subsample of 38 mergers and combined withpreviously obtained infrared photometry to test whether mergers exhibitthe same correlations as elliptical galaxies among parameters such asstellar luminosity and distribution, central stellar velocity dispersion(σ0), and metallicity. Paramount to the study is totest whether mergers lie on the fundamental plane. Measurements ofσ0 have been made using the Ca triplet absorption lineat 8500 Å for all 38 mergers in the subsample. Additionalmeasurements of σ0 were made for two of the mergers inthe subsample using the CO absorption line at 2.29 μm. The resultsindicate that mergers show a strong correlation among the parameters ofthe fundamental plane but fail to show a strong correlation betweenσ0 and metallicity (Mg2). In contrast toearlier studies, the σ0 values of the mergers areconsistent with objects that lie somewhere between intermediate-mass andluminous giant elliptical galaxies. However, the discrepancies withearlier studies appear to correlate with whether the Ca triplet or COabsorption lines are used to derive σ0, with the latteralmost always producing smaller values. Finally, the photometric andkinematic data are used to demonstrate for the first time that thecentral phase-space densities of mergers are equivalent to those inelliptical galaxies. This resolves a long-standing criticism of themerger hypothesis.Some of the data presented herein were obtained at the W. M. KeckObservatory, which is operated as a scientific partnership among theCalifornia Institute of Technology, the University of California, andthe National Aeronautics and Space Administration. The Observatory wasmade possible by the generous financial support of the W. M. KeckFoundation.
| A Deep K-Band Photometric Survey of Merger Remnants
We present K-band photometry for 51 candidate merger remnants to assessthe viability of whether spiral-spiral mergers can produce bona fideelliptical galaxies. Using both the de Vaucouleurs r1/4 andSérsic r1/n fitting laws, it is found that the stellarcomponent in a majority of the galaxies in the sample has undergoneviolent relaxation. However, the sample shows evidence for incompletephase mixing. The analysis also indicates the presence of ``excesslight'' in the surface brightness profiles of nearly one-third of themerger remnants. Circumstantial evidence suggests that this is due tothe effects of a starburst induced by the dissipative collapse of thegas. The integrated light of the galaxies also shows that mergers canmake L* elliptical galaxies, in contrast to earlier infrared studies.The isophotal shapes and related structural parameters are alsodiscussed, including the fact that 70% of the sample show evidence fordisky isophotes. The data and results presented are part of a largerphotometric and spectroscopic campaign to thoroughly investigate a largesample of mergers in the local universe.
| Compact groups in the UZC galaxy sample
Applying an automatic neighbour search algorithm to the 3D UZC galaxycatalogue (Falco et al. \cite{Falco}) we have identified 291 compactgroups (CGs) with radial velocity between 1000 and 10 000 kms-1. The sample is analysed to investigate whether Tripletsdisplay kinematical and morphological characteristics similar to higherorder CGs (Multiplets). It is found that Triplets constitute lowvelocity dispersion structures, have a gas-rich galaxy population andare typically retrieved in sparse environments. Conversely Multipletsshow higher velocity dispersion, include few gas-rich members and aregenerally embedded structures. Evidence hence emerges indicating thatTriplets and Multiplets, though sharing a common scale, correspond todifferent galaxy systems. Triplets are typically field structures whilstMultiplets are mainly subclumps (either temporarily projected orcollapsing) within larger structures. Simulations show that selectioneffects can only partially account for differences, but significantcontamination of Triplets by field galaxy interlopers could eventuallyinduce the observed dependences on multiplicity. Tables 1 and 2 are onlyavailable in electronic at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/35
| 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.
| Lopsided Galaxies, Weak Interactions, and Boosting the Star Formation Rate
To investigate the link between weak tidal interactions in disk galaxiesand the boosting of their recent star formation, we obtain images andspatially integrated spectra (3615 Å<=λ<=5315Å) for 40 late-type spiral galaxies (Sab-Sbc) with varying degreesof lopsidedness (a dynamical indicator of weak interactions). Wequantify lopsidedness as the amplitude of the m=1Fourier component of the azimuthal surface brightness distributionaveraged over a range of radii. The median spectrum of the most lopsidedgalaxies shows strong evidence for a more prominent young stellarpopulation (i.e., strong Balmer absorption, strong nebular emission, aweak 4000 Å break, and a blue continuum) when compared to themedian spectrum of the most symmetric galaxies. We compare the youngstellar content, quantified by EW(Hδabs) and thestrength of the 4000 Å break (D4000), with lopsidednessand find a 3-4 σ correlation between the two. We also find a 3.2σ correlation between EW(Hβemission) andlopsidedness. Using the evolutionary population synthesis code ofBruzual & Charlot we model the spectra as an ``underlyingpopulation'' and a superimposed ``boost population'' with the aim ofconstraining the fractional boost in the SFR averaged over the past 0.5Gyr (the characteristic lifetime of lopsidedness). From the differencein both EW(Hδabs) and the strength of the 4000 Åbreak (D4000) between the most and least symmetric thirds ofour sample, we infer that ~1×109 Msolar ofstars are formed over the duration of a lopsided event in addition tothe ``underlying'' star formation history (assuming a final galacticstellar mass of 1010 Msolar). This corresponds toa factor of 8 increase in the star formation rate over the past5×108 years. For the nuclear spectra, all of the abovecorrelations except D4000 versus areweaker than for the disk, indicating that in lopsided galaxies, the starformation boost is not dominated by the nucleus.
| Molecular Gas in Strongly Interacting Galaxies. I. CO (1-0) Observations
We present observations of the CO (1-0) line in 80 interacting galaxiesas part of a program to study the role of interactions and mergers intriggering starbursts. The sample, which only includes obviouslyinteracting pairs of galaxies, is the largest such sample observed inCO. The observations were carried out at the NRAO 12 m and IRAM 30 mtelescopes. CO emission was detected in 56 galaxies (of which 32 are newdetections), corresponding to a detection rate of 70%. Because mostgalaxies are slightly larger than the telescope beam, correction factorswere applied to include CO emission outside the beam. The correctionfactors were derived by fitting a Gaussian function or an exponential CObrightness distribution to galaxies with multiple pointings and byassuming an exponential model for galaxies with single pointing. Wecompared the global CO fluxes of 10 galaxies observed by us at bothtelescopes. We also compared the measured fluxes for another 10 galaxiesobserved by us with those by other authors using the NRAO 12 m and FCRAO14 m telescopes. These comparisons provide an estimate of the accuracyof our derived global fluxes, which is ~40%. Mapping observations of twoclose pairs of galaxies, UGC 594 (NGC 317) and UGC 11175 (NGC 6621), arealso presented. In subsequent papers we will report the statisticalanalyses of the molecular properties in our sample galaxies and makecomparisons between isolated spirals and interacting galaxies.
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://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.
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
| Effects of Interactions on the Radio Properties of Non-Seyfert Galaxies
On the basis of radio surveys published in the literature we havecompared the radio properties of samples of relatively isolated spiralgalaxies with LINER- and H II- region-like nuclei (hereafter called Land H galaxies) with corresponding samples of non-Seyfert interactinggalaxies, in order to explore the effects of interactions on their radioproperties. Basically, we have found enhanced total and central radioemission (per light unit) in interacting H galaxies (compared with theirrelatively isolated counterparts) and enhanced central radio emission(per light unit) in interacting L galaxies. Analogous enhancements inthe strength of the total and nuclear Hα emission lines areobserved in interacting galaxies. Furthermore, within a sample ofinteracting galaxies, there appears to be evidence of enhanced total andcentral radio emission (per light unit) in strongly interacting galaxieswhich are likely to have H II-region-like nuclei, compared withmoderately interacting objects of the same nuclear type. Interacting Hgalaxies contain more extended central radio sources than isolatedgalaxies, whereas no difference in this sense is observed in the case ofL galaxies. L galaxies which contain, on average, weaker total andcentral radio sources than the H galaxies have, on average, smallercentral radio sources (of greater radio surface brightness) than the Hgalaxies and follow a less-steep logarithmic radio power-radio sizerelation. As regards the Seyfert galaxies, which are known to becharacterized by powerful central radio emission, we have found thatthey contain, on average, central radio sources of intermediate size,which obey a power-size relation of intermediate steepness (with respectto the L and H galaxies). Thus our statistical study reveals basicstructural differences between the radio properties of the L, H andSeyfert galaxies, and between the effects of interactions on the radioproperties of the three classes of galaxies.
| Associations between quasi-stellar objects and galaxies
A table is presented here listing all close pairs of QSOs and galaxiesthat were found in a computer-aided search of catalogs of QSOs andbright galaxies and an extensive search of the literature. There is alarge excess of pairs with separations of 2 arcmin lor less, or about 60kpc, over the numbers expected if the configurations were accidental.The angular separation for 392 pairs adds to the evidence for physicalassociation, and it is shown that selection effects are not important. Ageneral rule is stated that QSOs tend to lie in the vicinity of normalgalaxies much more often than is expected by chance whether or not thegalaxies and the QSOs have the same redshifts. It is emphasized thatthis rule cannot be explained in terms of gravitational microlensing,and it is concluded that some part of the redshift of all classes ofactive nuclei is not associated with the expansion of the universe.
| H I profiles in IRAS galaxies
H-I line profiles have been obtained for a sample of 37 galaxies. Thirtyof these galaxies have IRAS fluxes representing a wide range of infraredluminosites and spectra. The galaxies also represent five levels ofoptical activity, nonactive, LINERs, H-II galaxies, Sy 2, and Sy 1. Theyalso have a wide range of tidal interaction activity with othergalaxies. The behavior of H-I is studied within a scenario that relatestidal events with star formation, dust formation, IR luminosity, andnuclear activity in galaxies. A strong correlation is found between H-Iand IR luminosity, which appears to be in the form of an excess of H-Iemission related to the interaction events. Detached weak extra H-Icomponents are common, and H-I absorption components are seen in severalobjects. H-I outflow is indicated in most cases. Relative velocities areof the order of a few hundred km/s. The most strongly disturbed galaxiesalso have peculiar H-I profiles. A fit to the Tully-Fisher relationindicates a mean extinction of about 1 mag for the group, and a generalspread in the relation with no systematic effects.
| IRAS observations of an optically selected sample of interacting galaxies
IRAS observations of a large, morphologically selected sample ofstrongly interacting disk-type galaxies have demonstrated thatgalaxy-galaxy collisions can lead to enhanced infrared emission, but notin all cases. Infrared luminosities of the interacting galaxies span alarge range, but are about a factor of 2 higher, on average, than thoseof isolated disk galaxies. The data suggest the existence of a cutoff inblue luminosity, below which no galaxies show markedly enhanced infraredemission. Only the most strongly interacting systems in the sample showextreme values of infrared excess, suggesting that deep,interpenetrating collisions are necessary to drive infrared emission toextreme levels. Comparisons with optical indicators of star formationshow that infrared excess and color temperatures correlate with thelevel of star-formation activity in the interacting galaxies. Allinteracting galaxies in our sample that exhibit an infrared excess andhave higher than normal color temperatures also have optical indicatorsof high levels of star formation. It is not necessary to invokeprocesses other than star formation to account for the enhanced infraredluminosity in this sample of interacting galaxies.
| A catalog of low-surface-brightness objects - Declination zone + 20 deg
Plates from the second Palomar Sky Survey are used to compile a list oflow-surface-brightness objects located along declination zone + 20 deg.Coordinates, descriptions, sizes, and ellipticities are presented usingthe same selection criteria of 1 arcmin limiting diameter as the UppsalaCatalog of Galaxies (Nilson 1973). Lists of previously known galaxieswith new low-surface-brightness features and interestinglow-surface-brightness objects with diameters between 0.5 and 1 arcminare also presented. As expected, the low-surface-brightness end of theluminosity function is dominated by late-type systems and dwarfs.Comparison with CCD surface photometry indicates an average limitingsurface brightness of 26.0 B mag/sq arcsec for this survey as comparedto 25.2 B mag/sq arcsec for the UGC. On the whole, too few newlow-surface-brightness galaxies have been found for the space density ofthese objects to be higher than that defined by conventional diskgalaxies.
| Global properties of interacting disk-type galaxies
Optical, far-IR, and radio observations of global properties arepresented for a sample of strongly interacting disk-type galaxies.Global star formation rates (SFRs) for the galaxies span a large rangeand are, on average, a factor of 2.5 higher than similarly determinedglobal SFRs for isolated spiral galaxies. New star formation occurspreferentially in or near the nuclear regions. H I 21 cm emission-lineprofiles indicate the presence of anomalous velocity material andchaotic patterns of gas motion in many interacting systems. Few systemsshow evidence for the presence of a well-organized rotating H I disksuch as are seen in isolated spiral galaxies. Neutral hydrogen gasmass-to-blue luminosity ratios are not atypical when compared withisolated spirals. The evidence indicates that local rather than globalproperties of these galaxies govern the star-formation process. Theobservations generally support the notion that enhanced SFRs are causedby increased cloud collision rates and dissipative flows of gas to thenucleus.
| The dependence of the Tully-Fisher relation on morphological type
A sample of 124 galaxies with Hubble types Sab-Sb and Scd-Sd is analyzedto investigate the dependence of the B band Tully-Fisher relation onmorphological type, together with the apparent Hubble rate variationwith velocities reported in a previous paper. From that sample, thefollowing conclusions are derived: (1) the offset of the zero-point ofthe Tully-Fisher relation in the B band for, respectively, the Sab-Sband the Scd-Sd galaxies varies from about 0.5 mag to about 1.6 mag asthe calibrating slope varies from 5 to 10; and (2) for a given 'class'(Sab-Sb or Scd-Sd) the dispersion of the Tully-Fisher relation increasesfrom about 0.5 mag to about 0.75 mag as the slope varies from 5 to 10.
| Star-formation rates in the nuclei of violently interacting galaxies
It has now been recognized that galaxy-galaxy interactions represent animportant evolutionary process in many extragalactic systems, takinginto account large-scale star-formation bursts, Seyfert activity, andQSO phenomena. The present paper provides results of aspectrophotometric survey of the nuclear regions of a large sample ofviolently interacting galaxies. Attention is given to sample selection,observational procedures and data reduction, data analysis, aspects ofspectral classification, ionization mechanisms, emission-line strengths,correlations with integral properties, comparisons with other studies,and a comparison with theoretical models.
| The Malmquist bias and the value of H0 from the Tully-Fisher relation
A large sample (n = 395) of spiral (Sab to Sd type) galaxies havingcorrected apparent magnitudes B-zero-sub-T and 21-cm line data (HI linewidths and radial velocities) is used to investigate in a new way theinfluence of the Malmquist bias on the determination of theextragalactic distance scale and the Hubble constant derived from theapplication of the B-band Tully-Fisher relation. This effect is clearlyidentified by using relative kinematic distances derived from aclassical local velocity field model and the concept of normalizedrelative kinematic distance. It results in an unbiased estimate of theHubble constant H0 which appears quite insensitive to the parameters(mean velocity of Virgo and infall velocity of the Local Group towardVirgo) adapted for the local velocity field model. A similar effect isfound from a sample of galaxies (n = 72) which are 'sosies' of 14primary galaxies. It is suggested that the presently derived H0represents the global value of the Hubble constant.
| Isolated galaxies
A new list of isolated galaxies has been compiled in order to determinewhether or not a true isolated sample can be selected. The sampleselection and the statistical characteristics of the sample arediscussed. In agreement with previous findings, it is concluded that anunclustered background seems to be observationally and operationallymeaningless, and that clustering dominates in all regions of space.
| Arecibo H I data for 136 spiral galaxies
The results of observations of the neutral hydrogen emission of 136spiral galaxies observed using the 21 cm spectral-line system of theArecibo Observatory are presented. Most of the 114 detected objects havebeen mapped along the major axis, and cumulative spectra andposition-velocity contour maps for each of them are presented. The dataare used to determine the overall H I content, systemic velocity, linewidths, and scale-length H I diameters. Data are also presented, indetailed tabular form, for each of the positions observed on thedetected objects.
| The nuclear activity of interacting galaxies
A search for active galactic nuclei among interacting galaxies isreported. A sample of 167 systems of interacting and asymmetric galaxieswas observed spectrophotometrically in the spectral range 4700-7100 A.The results are compared with a sample of isolated galaxies. It is foundthat (1) there are no Seyfert nuclei in elliptical or dwarf irregulargalaxies of the sample; (2) there is an excess of Seyfert nuclei amonginteracting spirals, but it is only at the 90 percent confidence level;(3) this excess becomes statistically significant (98 percent) when onlystrongly interacting spirals are included (four new Seyfert nuclei arepresented); (4) in the subgroup of galaxies with extreme tidaldistortions, no Seyfert nuclei were found.
| Seven poor clusters of galaxies
The measurement of 83 new redshifts from galaxies in the region of sevenof the poor clusters of galaxies identified by Morgan et al (1975) andAlbert et al (1977) has been followed by an estimation of cluster massesthrough the application of both the virial theorem and the projected masmethod. For each system, these two estimates are consistent. For the twoclusters with highest X-ray luminosities, the line-of-sight velocitydispersions are about 700 km/sec, while for the five other clusters, thedispersions are of the order of less than about 370 km/sec. The D or cDgalaxy in each poor cluster is at the kinematic center of each system.
| H I line studies of galaxies. III - Distance moduli of 822 disk galaxies
The distance scale established on the basis of a distance moduli catalog(for 822 galaxies) that was derived from 21-cm line widths via theB-band Tully-Fisher relation is compared with several independent scaleshaving a common zero point, that are based on the indicators forluminosity index, redshift, ring diameters, brightest superassociations,and effective diameters. These are in excellent systematic agreement,and confirm the linearity of the H I scale in the 24-35 modulusinterval, but indicate a small systematic zero point difference of about0.2 mag, which must be added to the H I moduli to place them on the same'short' distance scale defined by the others.
| A 21 centimeter line survey of a complete sample of interacting and isolated galaxies
The paper presents 21 cm line observations of a complete sample ofinteracting and isolated galaxies made with the National Radio AstronomyObservatory 91 and 43 m telescopes and the Arecibo 3035 m telescope. The21 cm line data are combined with a homogeneous set of optical data onangular diameters, axial ratios, magnitudes, and colors, and integralproperties are calculated for the galaxies in both samples. In thispaper, the sample selection procedures, the method of observation, thedata reduction, and the observational errors are described. Thedetection percentages are presented for both samples.
| Atlas of interacting galaxies, Part. II and the concept of fragmentation of galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...28....1V&db_key=AST
| 160 interacting galaxies of the M51 class
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