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|Companions to Isolated Elliptical Galaxies: Revisiting the Bothun-Sullivan Sample|
We investigate the number of physical companion galaxies for a sample ofrelatively isolated elliptical galaxies. The NASA/IPAC ExtragalacticDatabase (NED) has been used to reinvestigate the incidence of satellitegalaxies for a sample of 34 elliptical galaxies, first investigated byBothun & Sullivan using a visual inspection of Palomar Sky Surveyprints out to a projected search radius of 75 kpc. We have repeatedtheir original investigation using data cataloged in NED. Nine of theseelliptical galaxies appear to be members of galaxy clusters; theremaining sample of 25 galaxies reveals an average of +1.0+/-0.5apparent companions per galaxy within a projected search radius of 75kpc, in excess of two equal-area comparison regions displaced by 150-300kpc. This is significantly larger than the +0.12+/-0.42companions/galaxy found by Bothun & Sullivan for the identicalsample. Making use of published radial velocities, mostly availablesince the completion of the Bothun-Sullivan study, identifies thephysical companions and gives a somewhat lower estimate of +0.4companions per elliptical galaxy. This is still 3 times larger than theoriginal statistical study, but given the incomplete and heterogeneousnature of the survey redshifts in NED, it still yields a firm lowerlimit on the number (and identity) of physical companions. An expansionof the search radius out to 300 kpc, again restricted to sampling onlythose objects with known redshifts in NED, gives another lower limit of4.5 physical companions per galaxy. (Excluding five elliptical galaxiesin the Fornax Cluster, this average drops to 3.5 companions perelliptical.) These physical companions are individually identified andlisted, and the ensemble-averaged radial density distribution of theseassociated galaxies is presented. For the ensemble, the radial densitydistribution is found to have a falloff consistent withρ~R-0.5 out to approximately 150 kpc. For non-FornaxCluster companions the falloff continues out to the 300 kpc limit of thesurvey. The velocity dispersion of these companions is found to reach amaximum of 350 km s-1 at around 120 kpc, after which theyfall at a rate consistent with Keplerian falloff. This falloff may thenindicate the detection of a cut-off in the mass-density distribution inthe elliptical galaxies' dark matter halo at ~100 kpc.
|Bar Galaxies and Their Environments|
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
|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.
|Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles|
We present one of the largest homogeneous sets of spiral and lenticulargalaxy brightness profile decompositions completed to date. The 659galaxies in our sample have been fitted with a de Vaucouleurs law forthe bulge component and an inner-truncated exponential for the diskcomponent. Of the 659 galaxies in the sample, 620 were successfullyfitted with the chosen fitting functions. The fits are generally welldefined, with more than 90% having rms deviations from the observedprofile of less than 0.35 mag. We find no correlations of fittingquality, as measured by these rms residuals, with either morphologicaltype or inclination. Similarly, the estimated errors of the fittedcoefficients show no significant trends with type or inclination. Thesedecompositions form a useful basis for the study of the lightdistributions of spiral and lenticular galaxies. The object base issufficiently large that well-defined samples of galaxies can be selectedfrom it.
|The Southern Sky Redshift Survey|
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
|Influence of a partial incompleteness of the sample on the determination of the Hubble constant.|
This paper presents a study of the Malmquist bias effect in thedetermination of the Hubble constant from the method of "sosies"(look-alike) galaxies. It is shown that a bias appears when a partialincompleteness exists in the sample. A new method, based on the use ofthe completeness curve, is proposed to correct for such a bias. Afterthis correction, the Hubble constant drops of about 20% just because ofthe existence of the partial incompleteness. From the present resultsand on the acceptance of the distance modulus of primary calibrators,the value of the Hubble constant would be: H_0_=~60km/s/Mpc with aninternal statistical error of about 2km/s/Mpc.
|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.
|A comparative study of morphological classifications of APM galaxies|
We investigate the consistency of visual morphological classificationsof galaxies by comparing classifications for 831 galaxies from sixindependent observers. The galaxies were classified on laser print copyimages or on computer screen using scans made with the Automated PlateMeasuring (APM) machine. Classifications are compared using the RevisedHubble numerical type index T. We find that individual observers agreewith one another with rms combined dispersions of between 1.3 and 2.3type units, typically about 1.8 units. The dispersions tend to decreaseslightly with increasing angular diameter and, in some cases, withincreasing axial ratio (b/a). The agreement between independentobservers is reasonably good but the scatter is non-negligible. In spiteof the scatter, the Revised Hubble T system can be used to train anautomated galaxy classifier, e.g. an artificial neural network, tohandle the large number of galaxy images that are being compiled in theAPM and other surveys.
|A Preliminary Classification Scheme for the Central Regions of Late-Type Galaxies|
The large-scale prints in The Carnegie Atlas of Galaxies have been usedto formulate a classification scheme for the central regions oflate-type galaxies. Systems that exhibit small bright central bulges ordisks (type CB) are found to be of earlier Hubble type and of higherluminosity than galaxies that do not contain nuclei (type NN). Galaxiescontaining nuclear bars, or exhibiting central regions that are resolvedinto individual stars and knots, and galaxies with semistellar nuclei,are seen to have characteristics that are intermediate between those oftypes CB and NN. The presence or absence of a nucleus appears to be auseful criterion for distinguishing between spiral galaxies andmagellanic irregulars.
|Effect of Malmquist bias on correlation studies with IRAS data base|
The relationships between galaxy properties in the sample of Trinchieriet al. (1989) are reexamined with corrections for Malmquist bias. Thelinear correlations are tested and linear regressions are fit forlog-log plots of L(FIR), L(H-alpha), and L(B) as well as ratios of thesequantities. The linear correlations for Malmquist bias are correctedusing the method of Verter (1988), in which each galaxy observation isweighted by the inverse of its sampling volume. The linear regressionsare corrected for Malmquist bias by a new method invented here in whicheach galaxy observation is weighted by its sampling volume. The resultsof correlation and regressions among the sample are significantlychanged in the anticipated sense that the corrected correlationconfidences are lower and the corrected slopes of the linear regressionsare lower. The elimination of Malmquist bias eliminates the nonlinearrise in luminosity that has caused some authors to hypothesizeadditional components of FIR emission.
|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.
|A photon-counting imaging Fabry-Perot spectrometer for kinematic studies of extended astronomical objects|
A detailed description is presented of a photon-counting imagingFabry-Perot spectrometer constructed for seeing-limited high-resolutionvelocity field studies of extended astrophysical sources. The opticallayout, detector, and performance of the instrument are described.
|Revised supernova rates in Shapley-Ames galaxies|
Observations of 855 Shapley Ames galaxies made from November 1, 1980 toOctober 31, 1988, together with improved supernova luminosities, havebeen used to derive the frequency of supernovae of different types, andthe results are presented in tables. From a uniform database of 24supernovae discovered, the following SN rates are found, expressed in SNper century per 10 to the 10th L(B)(solar): SN Ia, 0.3; SN Ib, 0.3; andSN II, 1.0. The present data confirm the relatively high frequency of SNII in late-type galaxies that has been found by many previousinvestigators.
|Far-infrared emission and star formation in spiral galaxies|
The correlations between the emission in the far-IR, H-alpha, and bluein a sample of normal spiral galaxies are investigated. It is found thatthe luminosities in these three bands are all tightly correlated,although both the strength of the correlations and their functionaldependencies are a function of the galaxies' morphological types. Thebest-fit power laws to these correlations are different for thecomparison of different quantities and deviate significantly fromlinearity in some cases, implying the presence of additional emissionmechanisms not related to the general increase of luminosity withgalactic mass. Clear evidence is found of two independent effects in theincidence of warm far-IR emission in late-type spirals. One is aluminosity effect shown by the presence of excess far-IR relative toH-alpha or optical emission in the more luminous galaxies. The other isa dependence on widespread star-formation activity.
|Quantization of redshift differences in isolated galaxy pairs|
Improved 21 cm data on isolated galaxy pairs are presented whicheliminate questions of inhomogeneity in the data on such pairs andreduce observational error to below 5 km/s. Quantization is sharpened,and the 'zero' peak is shown to be displaced from zero to a locationnear 24 km/s. An exclusion principle is suggested whereby identicalredshifts are forbidden in limited volumes. The radio data and data fromSchweizer (1987) are combined with the best optical data on closeKarachentsev pairs to provide a cumulative sample of 84 of the bestdifferentials now available. New 21 cm observations are used to test forthe presence of small differentials in very wide pairs, and thedeficiency near zero is found to continue to very wide spacings. A lossof wide pairs by selection bias cannot produce the observed zerodeficiency. A new test using pairs selected from the Fisher-Tullycatalog is used to demonstrate quantization properties of thirdcomponents associated with possible pairs.
|The preponderance of bar and ring features in starburst galaxies and active galactic nuclei|
A detailed study of the spiral galaxy NGC 4321 showed that the nuclearstar formation mechanism in this galaxy is very likely related to theorbits perturbation at the Inner Linblad Resonances. In order to testthe hypothesis that the same physical mechanism accounts generally forsuch activity in spiral galaxies, a morphological analysis of a sampleof starburst nuclei and active galactic nuclei (STB, AGN) as well as acontrol sample of normal galaxies has been carried out. It is found thatthe morphological type expected for starbursters like NGC 4321 (SAB(rs)or stronger), occurs at a much higher frequency in the sample of STBsand AGNs than in the control sample. The effect is stronger for STBsthan for AGNs. This provides strong evidences that active formation ofstars in the nuclei of spiral galaxies is linked to the perturbation oforbits at the Inner Linblad Resonances. This interpretation leads to thesuggestion that an effective nuclear starburst phase is an inhibitionmechanism to a more powerful type of nuclear activity like in AGNs.
|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 two-component model for the 40-120-micron emission from normal disk galaxies|
By analogy with models available for the Galaxy, a model with a cold anda warm component is proposed to explain the 40-120-micron emission ofnormal late-type galaxies as observed with IRAS. The approach makes useof published H I, H-alpha, and FUV (200-nm) total fluxes. The coldcomponent dust is associated with the neutral ISM and heated by thegeneral interstellar radiation field. The temperature of this componentis constrained by the IRAS 100-micron flux density. Its emission isproportional to the H I flux and is found to correlate well with the FUVemission. The warm component dust is associated with ionized hydrogen inextended low-density H II regions and heated by hot ionizing stars. Itsemission is taken proportional to the H-alpha emission. The modelpredicts only 75 to 80 percent of the observed 40-120 fluxes. The mostplausible explanation for this discrepancy is an underestimation of thewarm component emission.
|The supernova rate in Shapley-Ames galaxies|
A visual search for SNs in 748 Shapley-Ames galaxies during the 5-yearperiod from November 1, 1980 to October 31, 1985 has yielded SN rates of0.3h-squared, 0.4h-squared, and 1.1h-squared for objects of types Ia,Ib, and II, respectively. These data are judged to imply that Tammann's(1974, 1982) SN rates are probably too high by a factor of about 3. Fora Galactic luminosity of 2 x 10 to the 10th solar L(B), the predicted SNrates in the Milky Way system are 0.6h-squared, 0.8h-squared, and2.2h-squared/century, respectively, for the three aforementioned types.
|On the origin of the 40-120 micron emission of galaxy disks A comparison with H-alpha fluxes|
The relationship between the integrated H-alpha flux and the far-IR fluxof spiral disks is investigated. This relationship is found to have asimilar dispersion to that between the far-IR and the blue flux,suggesting that the far-IR emission may be as closely linked to theinterstellar radiation field from the old disk population as to veryyoung OB associations. A large spread in the 60/100 micron colortemperature and the IR excess (IRE) is found, and there is evidence thatIRE decreases with increasing 60/100 micron color temperature. Thissupports the conclusion that nonionizing stars contribute to poweringthe far-IR emission. The far-IR spiral disk emission can be interpretedin terms of at least two thermal components with different temperatures.The low-IRE warm component comes from H II regions, while the high-IREcool one is interpreted as 'cirruslike' emission. For the median spiral,cirruslike emission contributes 50-70 percent of the total far-IR fluxof the disk.
|H I observations of galaxies in between the Local and the Hydra/Centaurus superclusters|
H I observations obtained with the 300-ft NRAO and 100-m Effelsbergradio telescopes in 1984-1985 are reported for 440 galaxies, ofmorphological types S0/a or later and diameter at least 2 arcmin in thecatalog of de Vaucouleurs et al., 1976, from the region between theLocal and Hya/Cen superclusters. The data are compiled in tables alongwith published data on 310 galaxies to form a data base for studies offilamentary structures in the intercluster region. More than 50 percentof the galaxies are detected in H I, and the redshift distribution isfound to be consistent with the existence of filaments.
|H I line studies of galaxies. IV - Distance moduli of 468 disk galaxies|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...43B&db_key=AST
|The rate of star formation in normal disk galaxies|
Quantitative estimates of the total star formation rate (SFR) in a largesample of field spiral and irregular galaxies have been obtained throughphotometry of the integrated H-alpha emission, and the photoionizationproperties of a stellar population have been modeled for a variety ofinitial mass function (IMF) choices. Excellent agreement with theobserved galaxy colors and H-alpha emission is obtained with modelsusing an IMF slope close to Salpeter's (1955) original value. Comparisonof the present SFRs with the remaining supply of interstellar gas yieldsconsumption time scales of only a few billion years in most cases, inagreement with the model estimates of Larson, Tinsley, and Caldwell(1980). It is possible that the present epoch is characterized by rapidchanges in the integrated properties and morphologies of disk galaxies.
|A survey of H-alpha emission in normal galaxies|
The combined results of photometric and spectrophotometric surveys ofH-alpha emission in 200 field and Virgo cluster galaxies are presented.In most spiral galaxies the emission is dominated by normal disk H IIregions, and consequently the integrated Balmer flux of a galaxy can beused as a quantitative index of its current OB star formation rate.Uncertainties due to instrumental effects, nuclear emission,forbidden-line N II emission, and extinction by dust, are evaluated. Theintegrated emission of a galaxy is strongly correlated with its Hubbletype and color, confirming the earlier conclusions of Cohen (1976).Emission among galaxies of a given type varies greatly, however, and inmost cases is due to a real dispersion in star formation activity. Thisactivity is only weakly correlated with galaxy luminosity or H Icontent, suggesting that some other parameter is more important.
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