WIKISKY.ORG
 Home Getting Started To Survive in the Universe News@Sky Astro Photo The Collection Forum Blog New! FAQ Press Login

# NGC 3930

Contents

### Images

DSS Images   Other Images

### Related articles

 The Hα galaxy survey. I. The galaxy sample, Hα narrow-band observations and star formation parameters for 334 galaxiesWe discuss the selection and observations of a large sample of nearbygalaxies, which we are using to quantify the star formation activity inthe local Universe. The sample consists of 334 galaxies across allHubble types from S0/a to Im and with recession velocities of between 0and 3000 km s-1. The basic data for each galaxy are narrowband H\alpha +[NII] and R-band imaging, from which we derive starformation rates, H\alpha +[NII] equivalent widths and surfacebrightnesses, and R-band total magnitudes. A strong correlation is foundbetween total star formation rate and Hubble type, with the strongeststar formation in isolated galaxies occurring in Sc and Sbc types. Moresurprisingly, no significant trend is found between H\alpha +[NII]equivalent width and galaxy R-band luminosity. More detailed analyses ofthe data set presented here will be described in subsequent papers.Based on observations made with the Jacobus Kapteyn Telescope operatedon the island of La Palma by the Isaac Newton Group in the SpanishObservatorio del Roque de los Muchachos of the Instituto deAstrofísica de Canarias.The full version of Table \ref{tab3} is available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/414/23 Reduced image datafor this survey can be downloaded fromhttp://www.astro.livjm.ac.uk/HaGS/ The UZC-SSRS2 Group CatalogWe 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. Galaxies with RowsThe results of a search for galaxies with straight structural elements,usually spiral-arm rows (“rows” in the terminology ofVorontsov-Vel'yaminov), are reported. The list of galaxies that possess(or probably possess) such rows includes about 200 objects, of whichabout 70% are brighter than 14m. On the whole, galaxies with rows makeup 6 8% of all spiral galaxies with well-developed spiral patterns. Mostgalaxies with rows are gas-rich Sbc-Scd spirals. The fraction ofinteracting galaxies among them is appreciably higher than amonggalaxies without rows. Earlier conclusions that, as a rule, the lengthsof rows are similar to their galactocentric distances and that theangles between adjacent rows are concentrated near 120° areconfirmed. It is concluded that the rows must be transient hydrodynamicstructures that develop in normal galaxies. Nearby Optical Galaxies: Selection of the Sample and Identification of GroupsIn 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. Arcsecond Positions of UGC GalaxiesWe 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. Groups of galaxies. III. Some empirical characteristics.Not Available Asymmetry in high-precision global H I profiles of isolated spiral galaxiesNew high-SNR 21 cm H I line profiles have been obtained for 104 galaxieswith the Green Bank 43 m telescope. The primary sample is composed ofisolated spirals with no known optical companions within a 1 radius anda median ratio of optical diameter to beamwidth of 0.17. An effort wasmade to ensure linearity of baseline fitting and precise flux densitycalibration to better than 5 percent. Two quantitative measures ofasymmetry are applied to assess the occurrence of lopsidedness in theglobal H I profiles. In agreement with previous estimates, half thegalaxies show significant H I profile asymmetries. The lopsidednesscannot be explained by pointing offsets but, rather, must result fromnoncircular motions, confusion with unidentified companions within thetelescope beam, or true distortions in the H I distribution. 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 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. The CfA Redshift Survey: Data for the NGP +36 ZoneWe have assembled redshifts for a complete sample of 719 galaxies withm_zw_ <= 15.5 in the declination range 32.5^deg^ <= δ <=38.5^deg^ and right ascension range 8^h^ <= α <= 17^h^. Wehave determined morphological types for all galaxies in the magnitudelimited sample by direct inspection of the POSS-O plates. 576 of theredshifts are measurements from Mount Hopkins, and 405 are newredshifts. We also include new redshifts for 77 fainter galaxies in thesame strip. The orientation of spin vectors of galaxies in the Ursa Major filamentSpin vectors of 60 galaxies in the 'Ursa Major filament' are obtainedfrom CCD images and spectroscopic determinations of the directions ofrotation. These data are used to remove the fourfold degeneracyintroduced by the projected images of galaxies, making possible thecomplete reconstruction of the galaxy spin vectors. Several possibleorganizations of spin vectors are investigated by means of statisticalanalyses of the three-dimensional spin vector maps. The results indicatethat there exists no significant alignment of galaxy spin vectors withrespect to the supergalactic plane, the supergalactic axis, or thecylindrical axis of the filament itself. No tendency for linearalignment of spin vectors toward any specific direction was detected. Wealso obtain a statistically negative result for azimuthal, radial, andcircular-helical orientation of spin vectors. Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxiesMultivariate 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. Groups of galaxies within 80 Mpc. II - The catalogue of groups and group membersThis paper gives a catalog of the groups and associations obtained bymeans of a revised hierarchical algorithm applied to a sample of 4143galaxies with diameters larger than 100 arcsec and redshifts smallerthan 6000 km/s. The 264 groups of galaxies obtained in this way (andwhich contain at least three sample galaxies) are listed, with the looseassociations surrounding them and the individual members of eachaggregate as well; moreover, the location of every entity among 13regions corresponding roughly to superclusters is specified. Finally,1729 galaxies belong to the groups, and 466 to the associations, i.e.,the total fraction of galaxies within the various aggregates amounts to53 percent. Star formation in spiral galaxies. I - H-alpha observationsThis paper presents large-aperture photometric measurements of H-alpha +forbidden N II emission line strengths in 110 spiral galaxies. Thesegalaxies represent three different samples of objects: (1) low surfacebrightness spiral galaxies; (2) galaxies of extreme arm classifications(flocculent versus grand design); and (3) galaxies with measured (B -H)colors which have been used to study the color-absolute magnituderelation for spiral galaxies. Details of the observations are given, anda comparison is made with previous work. Future papers will use thisdata to study the star-formation rates in the various samples. Groups of galaxies in the Center for Astrophysics redshift surveyBy applying the Huchra and Geller (1982) objective group identificationalgorithm to the Center for Astrophysics' redshift survey, a catalog of128 groups with three or more members is extracted, and 92 of these areused as a statistical sample. A comparison of the distribution of groupcenters with the distribution of all galaxies in the survey indicatesqualitatively that groups trace the large-scale structure of the region.The physical properties of groups may be related to the details oflarge-scale structure, and it is concluded that differences among groupcatalogs may be due to the properties of large-scale structures andtheir location relative to the survey limits. The peculiar velocity of the Local Group. II - H I observations of SC galaxiesH I observations of a sample of 163 Sc galaxies have been obtained usingthe Mk IA and Mk II Jodrell Bank radio telescopes. In the presentanalysis, the overall rms error in redshift determination is 5 km/s andthe rms error in velocity width determination is 10 km/s. The resultssuggest that Sc galaxies have high internal obscuration and may beoptically thicker in blue light than earlier-type spirals. An orthogonalthree-dimensional classification system based on three uncorrelatedparameters related to linear diameter, quiescent star-formation rate,and embedded starburst-type activity is shown to account for the globalproperties of Sc galaxies with an accuracy close to the limit ofmeasurement error. Cosmology from a galaxy group catalog. I - BinariesA new, completely objective group-finding algorithm is described andapplied to the CfA redshift catalog. The binary galaxies are isolatedfor analysis. The assumptions underlying the analysis are (1) that lighttraces mass, (2) that our binary galaxy subsets are representative lighttracers, and (3) that the binary orbits are circular. The primary resultof the work is that the resulting bias-free binary catalogs are afunction of the assumed cosmological model. For virtually any inputvalue of Omega(0) in the range 0.01-5.00, there is a reasonablyconsistent interpretation of the CfA survey such that the specifiedvalue of Omega(0) can be derived from the binary sample obtained underthat interpretation. A secondary result is that the higher the inputvalue of Omega(0), the broader the intrinsic distribution in M/L, andhence the less valid the assumption that light traces mass. Arm classifications for spiral galaxiesThe spiral arm classes of 762 galaxies are tabulated; 636 galaxies withlow inclinations and radii larger than 1 arcmin were classified on thebasis of their blue images on the Palomar Observatory Sky Survey (POSS),76 SA galaxies in the group catalog of Geller and Huchra were alsoclassified from the POSS, and 253 galaxies in high-resolution atlaseswere classified from their atlas photographs. This spiral armclassification system was previously shown to correlate with thepresence of density waves, and galaxies with such waves were shown tooccur primarily in the densest galactic groups. The present sampleindicates, in addition, that grand design galaxies (i.e., those whichtend to contain prominent density wave modes) are physically larger thanflocculent galaxies (which do not contain such prominent modes) by afactor of about 1.5. A larger group sample confirms the previous resultthat grand design galaxies are preferentially in dense groups. KISO survey for ultraviolet-excess galaxies. VI.Not Available The extragalactic distance scale derived from 'sosie' galaxies. I - Distances of 167 galaxies which are sosies of 14 nearby galaxiesThe method of 'sosie' galaxies is applied to a large sample of galaxiesextracted from the BGP catalog of H I line data and the Second ReferenceCatalog of Bright Galaxies. The sosies of 14 calibrating galaxies(primary calibrators and galaxies in the nearest groups) are defined asthose having the same parameters, either (1) morphological type T, axisratio R, and maximum rotation velocity VM or (2) T, R, andluminosity index lambdac. Distance moduli directly derivedfrom apparent magnitudes and/or diameters are provided on the distancescale whose zero point is defined by the adopted distance moduli of thecalibrators. The external mean error (0.4 mag) is competitive with thebest currently available. Morphology of spiral galaxies. I - General propertiesRed Palomar Sky Survey plates are scanned to characterize a completesample of 605 spiral galaxies north of declination -33 deg havinginclination angle less than 56 deg and blue diameter 2-15 arcmin. Theselection of the data and the reduction and parameter-extractionprocedures are explained, and the data and the results of statisticalanalysis are presented in tables and graphs. Findings reported include alow frequency of occurrence for small inclination angles (suggestingdistortion of outer structures), similar distributions of central diskbrightness for types Sa-Sc but not for types Sd-Sm (where mean valuesare smaller), fewer late-type galaxies with large exponential-disk scalelengths, no galaxies with both high central brightness and large scalelength (indicating a limit on angular momentum in galaxy formation), anda correlation between mean surface brightness and absolute magnitude forlater-type galaxies but not for types Sa-Scd. H I line studies of galaxies. IV - Distance moduli of 468 disk galaxiesAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...43B&db_key=AST H I line studies of galaxies. III - Distance moduli of 822 disk galaxiesThe 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 catalogue of HI diameters for 238 galaxiesA large catalog of effective H I diameters for 238 galaxies has beencompiled from new measurements made with the Nancay radiotelescope (40percent of the catalog), and previously published diameters homogenizedto the same definition. A good covering both in morphological types andin luminosity within each type is thus achieved. A survey of galaxy redshifts. IV - The dataThe complete list of the best available radial velocities for the 2401galaxies in the merged Zwicky-Nilson catalog brighter than 14.5mz and with b (II) above +40 deg or below -30 deg ispresented. Almost 60 percent of the redshifts are from the CfA surveyand are accurate to typically 35 km/s. Flocculent and grand design spiral structure in field, binary and group galaxiesA 12-division morphological system emphasizing arm continuity, lengthand symmetry has been developed for the classification of all spiralgalaxies according to the regularity of their spiral arm structure. Armclassifications were tabulated for 305 barred and nonbarred spiralgalaxies; of these, 79 are isolated, 52 are binary and 174 are ingroups. Among the isolated SA galaxies, 68 + or - 10% have irregular andfragmented, or 'flocculent', spiral structures. Only 32 + or - 10% havesymmetric spiral arms in the classic grand design pattern. Flocculentspirals are the most common structures of galaxies without companions orbars. Since flocculent galaxies may have bars and companions, and granddesign galaxies may have neither bars nor companions, such perturbationsare neither perfectly effective nor always necessary in the driving ofgrand design patterns. The H I content of isolated galaxiesH I data are presented for 33 galaxies from Huchra and Thuan's list(1977) among which eleven are isolated. Analysis of the data shows that(1) the H I content of isolated galaxies is about 60% higher than thatof group galaxies; (2) at least 6 out of the 9 isolated galaxiesexamined appear to be associated with groups of galaxies of the sameredshift, at distances of about 4 Mpc on an average; and (3) the excessof H I in isolated galaxies is related to their large distances to thecenters of the groups.
Submit a new article