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Gas in early-type galaxies: cross-fuelling in late-type-early-type pairs?
We present 12CO (J= 1-0) and 12CO (J= 2-1)observations of eight early-type galaxies, forming part of a sample ofinteracting galaxies, each consisting of one late- and one early-typesystem. All of the early-type galaxies observed are undetected in CO tolow levels, allowing us to place tight constraints on their moleculargas content. Additionally, we present HI absorption data for one system.The implications for possible gas transfer from the late- to theearly-type galaxy during the interaction are discussed.
| GHASP: A 3-D Survey of Spiral and Irregular Galaxies at Hα
Not Available
| Galaxies with Rows
The 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 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.
| A 180 Kiloparsec Tidal Tail in the Luminous Infrared Merger ARP 299
We present VLA H I observations and University of Hawaii 88 inch (2.2 m)deep optical B- and R-band observations of the IR-luminous merger Arp299 (=NGC 3690+IC 694). These data reveal a gas-rich (M_HI=3.3x10^9M_solar) optically faint (mu_B>~27 mag arcsec^-2, mu_R>~26 magarcsec^-2) tidal tail with a length of over 180 kpc. The size of thistidal feature necessitates an old interaction age for the merger(>~750 Myr since first periapse), which is currently experiencing avery young starburst (<~20 Myr). The observations reveal a mostremarkable structure within the tidal tail: it appears to be composed oftwo parallel filaments separated by approximately 20 kpc. One of thefilaments is gas-rich with little if any starlight, while the other isgas-poor. We believe that this bifurcation results from a warped disk inone of the progenitors. The quantities and kinematics of the tidal H Isuggest that Arp 299 results from the collision of a retrograde Sab-Sbgalaxy (IC 694) and a prograde Sbc-Sc galaxy (NGC 3690) that occurred750 Myr ago and will merge into a single object in roughly 60 Myr. Wesuggest that the present IR-luminous phase in this system is due in partto the retrograde spin of IC 694. Finally, we discuss the apparent lackof tidal dwarf galaxies within the tail.
| 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.
| An Einstein X-Ray Survey of Optically Selected Galaxies. I. Data
We present the results of a complete Einstein imaging proportionalcounter X-ray survey of optically selected galaxies from theShapley-Ames Catalog, the Uppsala General Catalogue, and the EuropeanSouthern Observatory Catalog. Well-defined optical criteria are used toselect the galaxies, and X-ray fluxes are measured at the opticallydefined positions. The result is a comprehensive list of X-ray detectionand upper limit measurements for 1018 galaxies. Of these, 827 haveeither independent distance estimates or radial velocities. Associatedoptical, redshift, and distance data have been assembled for thesegalaxies, and their distances come from a combination of directlypredicted distances and those predicted from the Faber-Burstein GreatAttractor/Virgocentric infall model. The accuracy of the X-ray fluxeshas been checked in three different ways; all are consistent with thederived X-ray fluxes being of <=0.1 dex accuracy. In particular,there is agreement with previously published X-ray fluxes for galaxiesin common with a 1991 study by Roberts et al. and a 1992 study byFabbiano et al. The data presented here will be used in further studiesto characterize the X-ray output of galaxies of various morphologicaltypes and thus to enable the determination of the major sourcescontributing to the X-ray emission from galaxies.
| The Detection of Massive Molecular Complexes in the Ring Galaxy System ARP 143
We have imaged the kiloparsec-scale distribution of 12CO( J=1--0 )emission in the ring galaxy system Arp 143 (NGC 2444/2445) using theOVRO millimeter array. We find two giant molecular complexes in the ringcomponent (NGC 2445) and a bright central source. The ring complexesrepresent 20%--60% of the detected M _{{H}2} , depending onthe relative ICO- N_{{H}2} for the ring and nucleus. Theirindividual H2 masses and surface densities ( Sigma _{{H}2} )exceed typical spiral arm giant molecular clouds and associationsregardless of the conversion factor. Both are associated with a 6 kpcridge of peak Sigma H I and massive star formation activity. Halpha imaging shows a patchy ring of H II regions situated along theouter edge of the H I ring. The kinematics of the H I ring show clearsigns of expansion. A simple rotating-expanding ring model (V_{{exp}}=118+/-30 {km} {s}^{-1} ) fits the data reasonably well, whichimplies a ring age of 60+/-15 Myr. NGC 2445's ring is able to form verylarge molecular complexes promptly in a metal-poor ISM and triggermassive star formation. Nearly 80% of the detected 12CO(1--0) fluxoriginates in a resolved central source that is slightly offset from NGC2445's starburst nucleus. We find an ordered velocity field in thiscomponent. Assuming an inclined disk, we argue that it is dynamicallystable. The central Sigma _{{H}2} (9 x 10 Msolar pc-2)significantly exceeds Sigma _{{H}2} values commonly found innormal spirals but is much smaller than values derived in similar sizedregions of IR-luminous galaxies. The nuclear H2 may be the result of aprevious encounter with NGC 2444. 12CO(1--0) emission in ring galaxiesmay be dominated by the nucleus, which could bias the interpretation ofsingle-dish measurements.
| Collisional Ring Galaxies
We review the current state of knowledge of both the observational andtheoretical nature of collisional ring galaxies. Ring galaxies representa class of colliding galaxy in which nearly symmetrical density wavesare driven into a disk as a result of an almost bulls-eye collision withanother galaxy. Since the basic dynamics of the collision is now quitewell understood, the ring galaxies can be used as a form of cosmicperturbation "experiment" to explore various properties of galacticdisks. For example, as the density wave expands into the disk, ittriggers the birth of large numbers of massive stars. This provides uswith an opportunity to study the evolution of stars and star clusters inthe wake of the ring. We review the now extensive observations of ringgalaxies from the early photographic measurements to recent infrared,radio and optical studies. We also present a simple analytical treatmentof the ring-making collisions and compare them to recent N-body andgas-dynamical models. The importance of ring galaxies lies in theirrelative simplicity compared with other colliding systems and thepossibility that low-angular momentum collisions might have been morecommon in the past.
| Classification of colliding galaxies
Not Available
| Large-Scale Structure at Low Galactic Latitude
We have extended the CfA Redshift Survey to low galactic latitudes toinvestigate the relation between the Great Wall in the North GalacticCap and the Perseus-Pisces chain in the South Galactic Cap. We presentredshifts for 2020 galaxies in the Catalogue of Galaxies and of Clustersof Galaxies (Zwicky et al. 1961-68, CGCG) in the following regions: 4^h^<= α <= 8^h^, 17^h^ <= α <= 20^h^, 0^deg^ <=δ <= 45^deg^. In these regions, the redshift catalogue includes1664 galaxies with B(0) <= 15.5 (of which 820 are newly measured) andis 97% complete. We also include redshifts for an additional 356galaxies in these regions with B(O) > 15.5; of these, 148 werepreviously unmeasured. The CGCG samples the galaxy distribution down tob_II_ = 10^deg^. In this paper, we discuss the acquisition and reductionof the spectra, and we examine the qualitative features of the redshiftdistribution. The Great Wall and the Perseus-Pisces chain are not simplyconnected across the Zone of Avoidance. These structures, which at firstappear to be coherent on scales of ~100 h^-1^ Mpc or more, actually formthe boundaries of neighboring voids of considerably smaller scale,approximately 50h^-1^ Mpc. The structures delineated by ouroptically-selected sample are qualitatively similar to those detected bythe far-infrared-selected IRAS 1.2 Jansky Survey (Fisher et al. 1995).Although the IRAS survey probes more deeply into the Zone of Avoidance,our optically-selected survey provides better sampling of structures atb_II_ >= 10^deg^.
| The detection of molecular gas in the ring galaxy ARP 143
We have used the NRAO 12 m telescope to map the inner 10 kpc of NGC2445, the ring galaxy in Arp 143, in CO-12(J = 1-0). Emission is peakednear the ring galaxy nucleus, but we find evidence for an additionalasymmetric and extended CO component. This extended CO distribution isconsistent with an approximately 8 kpc diameter crescent-shaped ring ofmolecular gas, similar to the one seen in H I, accounting forapproximately half of the total CO flux. Assuming this distribution, wederive a total H2 mass for NGC 2445 of 0.4-2.4 x 1010 solarmass, depending on whether a Galactic or low-metallicity LargeMagellanic Cloud (LMC) conversion factor is used, and an H2/H I massratio between 0.9 and 5. The ring is experiencing low rates of massivestar formation despite very high gas column densities. We find that thegas surface density exceeds the critical threshold for star formationthroughout the ring, even without a possible contribution from asignificant molecular component. The absence of vigorous star formationis most simply understood in terms of its youth (approximately 30 Myr):massive stars have not had time to form in large numbers. Our resultssupport the interpretation that NGC 2445 is a nascent ring galaxy, seenprior to its ring starburst phase.
| A quasi-steady state cosmological model with creation of matter
A universe is envisioned in which there was a major creation episodewhen the mean universal density was about 10 to the -27 g/cu cm.Explicit equations are given for the creation of matter; in acosmological approximation, these equations lead to expressions for thetime-dependence of the cosmological scale factor S(t), but do notentail, as big bang cosmology does, that S(t) tend to zero at somefinite time t. The equations therefore possess a universality that isabsent from big bang cosmology. Creation occurs when certainconservation equations involving the gradient of a scalar field C(i) aresatisfied.
| IRAS CPC Observations of Galaxies - Part One - Catalog and Atlas
. - We present the results of far-infrared imaging observations of 258regions of 12' x9' each centered on a selected individual galaxy, aclose pair, or a compact group of galaxies mapped at 50 and 100 micronwavelength with the CPC instrument of the IRAS satellite. The CPCinstrument has a significantly better resolution than the IRAS Surveyinstrument at these wavelengths, i.e. a round beam with a FWHM of about80" at 50 microns and 95" at 100 microns, respectively, intended to bematched to the diffraction limit of the telescope at 100 microns. Themaps were made using a new algorithm to correct for gain variations,which gives better results than the one used previously for the imagesmade available on tape in 1985. Of 262 objects observed, 167 and 188were detected at 50 and 100 microns, respectively, about 85% of thegalaxies from the same sample listed as detected by the Surveyinstrument in the IRAS Point Source Catalog. For all 55 galaxiesresolved (i.e. with a FWHM major axis diameter exceeding 1.6 times thebeam FWHM and/or extended lower-level emission) by the CPC we alsopresent the averaged maps at 50 and 100 microns. These 55 objectsinclude 35 for which there are no published maps obtained with the IRASSurvey instrument. We rescaled the flux densities of the published CPCmaps using the more accurate IRAS Survey instrument data, since theabsolute flux density calibration of the CPC is only accurate to about+/-60%. We also present images of a triplet of galaxies associated witha single Survey point source, which were resolved into separate sourcesby the CPC.
| 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 Nuclear Near Infrared Properties of Spiral Galaxies
Using JHKL photometric measures available in the literature, we havecompared the near-infrared colour indices and central luminosities ofsamples of relatively isolated spiral galaxies with LINER and H IIregion-like nuclei (hereafter called L and H) with corresponding samplesof interacting galaxies, in order to explore the effects of interactionson their near-infrared properties. We have found that the L galaxies andthe isolated H galaxies have, in general, normal near-infrared colourswhich are fully explainable in terms of emission from late-type evolvedstars. On the other hand, the sample of interacting H galaxies displays,on average, somewhat peculiar near-infrared colours (specifically,normal J - H colours, but redward H - K and, especially, K - Lexcesses), which very probably indicate the presence of thermal emissionfrom hot dust, presumably related to intense star formation activityinduced by the interactions. Furthermore, for the same galaxy samplethere is some evidence that the emission at λ ~ 2.2 microns issomewhat more centrally concentrated than that at shorter wavelengths.Interestingly, the L galaxies appear to have greater centralnear-infrared luminosities than the H galaxies, for the samemorphological-type interval.
| A multiwavelength study of the peculiar interacting galaxies ARP 143 = VV 117 - Evidence for an emerging ring galaxy?
This study presents optical, near-IR, and H I observations of thepeculiar interacting galaxies Arp 143 = VV 117 = NGC 2445/4. The BVrJHKphotometry of the bright blue optical knots which form a crescent shapein the disk of NGC 2445 is compared with models of the evolution of astarburst population and is found to be consistent with an extremelyyoung stellar population (not more than 10 exp 7 yr old). This timescale is short compared with the propagation of a density wave,suggesting that the star formation has only recently been triggeredcoherently in the wave. The results are compared with the predictions ofcloud-fluid models for the formation of a ring galaxy. On the basis ofthe models, it is speculated that the overdensity will continue to riseas the wave propagates outward, and eventually the entire leading edgeof the wave will undergo a starburst giving NGC 2445 the appearance of aclassical ring galaxy.
| A ring galaxy in Canes Venatici and related ring galaxies
A spectroscopic observation was made of a ring-shaped object in CanesVenatici. A bright knot at the edge of the ring has a recession velocityof 10,960 + or - 30 km/s and so is confirmed as an extragalactic object.It shows no sign of nuclear activity but appears to be an H II region ofintermediate excitation class. The linear diameter of the ring is 14.2 +or - 0.8 kpc, a typical size for ring galaxies. Recession velocities ofseveral other ring galaxies are also given.
| 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.
| Properties of the redshift. I - Data and calibrations
Data at 21 cm are presented for 100 galaxies intended to be used forsystem comparisons between the NRAO 140 and 300 foot telescope and the100 m Effelsberg telescope. Data from the 300 foot telescope are alsogiven for galaxies selected for overlap comparisons with older studies.Flux calibrations and measurement uncertainties in flux, redshifts,profile width, and profile shape are discussed.
| Recent star formation in interacting galaxies. III - Evidence from mid-infrared photometry
Mid-IR (10 and 20 microns) observations of a sample of interactinggalaxies have been conducted to argue that interactions induce a burstof star formation in the nucleus of one member of the interacting pair.The observations are combined with existing mid-IR data and radio andoptical data. A simple starburst model is used to derive some of thequantitative features of interaction-induced starbursts. It is shownthat the starbursts are unusually efficient in using available gas, andthat the initial mass function is heavily biased toward massive stars.The supernova rate and radio luminosity implied by the model areconsistent with observations. It is concluded that if the observed rateof interactions is representative, interaction-induced starbursts arelikely to have occurred in the evolution of most galaxies.
| A giant intergalactic H I bubble near Arp143
The paper presents observations of the nearby ring galaxy Arp143(NGC2445/4) and describes the discovery of a giant H I shell 20 kpcacross, lying 100 kpc from Arp143. The shell, which shows evidence forline splitting near its center, lies in a long H I filament pointingtoward the Arp143 system. It is suggested that the shell is an expandingbubble of H I, and is direct evidence for a powerful galactic-scaleexplosion 10 to the 8th years ago which is associated with a strongburst of star formation. It is believed that both the ring galaxy andthe giant bubble have their origin in the passage of a gas-richcompanion through the inner disk of NGC2445, and its subsequentdisruption.
| The effects of interactions on spiral galaxies. III - A radio continuum survey of galactic nuclei at 1.49 GHz
The radio continuum emission from the central region of a sample ofinteracting spiral galaxies (92 galaxies of which 60 in a completesample) and of a control sample of more isolated spiral galaxies (94)was observed with the Very Large Array at 1.49 GHz. The angularresolution of the observations is about 1.3 arcsec, and the detectionlimits are about 0.6 and 1.5 mJy for point sources and extended sourceswith a half power size of 10 arcsec, respectively. This survey, incombination with published optical spectroscopy, provides the data for adetailed comparison of the central region in interacting and moreisolated spiral galaxies.
| Far-infrared and optical properties of starburst galaxies
The ability of a simple photometric model to explain the FIR and opticalproperties of both normal and starburst galaxies is studied. With theIMF proposed by Kennicutt (1983) and a larger absorption for stars moremassive than 20 solar masses, the FIR activity, IR excess, UBV colors,and H-alpha equivalent width of normal spirals are well reproduced. Thenthese photometric quantities are investigated. A burst of given strengthand internal of IRAS galaxies with L(IR)/L(b) up to 100 can be accountedfor rather easily in terms of burst activity, whereas extreme values(about 500) probably require a burst forming massive stars only. Finaly,the FIR absolute luminosity can be used to derive the presentstar-formation rate.
| Shells and rings around galaxies
It is pointed out that the outer parts of galaxies often exhibitdistinct surface brightness enhancements. The development of rings andshells around galaxies has been ascribed to mechanisms in which theinteraction of a galaxy with its neighbors plays a key role. Accordingto some concepts, the big events, such as those leading to the formationof ring galaxies, are interspersed with an entire set of smaller ones.In particular, small galaxies in a group are inclined to fall into theirbigger neighbors without affecting the latter very much. After theevent, the big galaxy is provided with certain features, taking intoaccount ellipticals with shells, and S0s with polar rings. A review isconducted of the properties of these types of galaxies, insofar as theiroutskirts have identifiable shells or rings. Attention is given to ringgalaxies, outer rings around spirals and S0s, polar ring galaxies, andshells around elliptical galaxies.
| The effects of interactions on spiral galaxies. I - Nuclear activity and star formation
When the present results of spectrophotometry for the nuclei of 161(mostly spiral) galaxies with bright companions and emission lineimaging of 63 galaxies were compared to a similarly observed sample ofisolated-spiral nuclei, both samples of interacting galaxies exhibitedsignificant excesses of nuclear emission. The rate of nuclear starformation is significantly above average even in systems withoutnoticeable tidal distortion in the outer disks, suggesting that thenear-nuclear gas is only marginally stable in isolated galaxies. Theresults obtained suggest that nuclear phenomena are triggered by atidally induced influx of gas from the disk into the nuclear regions,rather than gas transfer between the galaxies.
| Recent star formation in interacting galaxies. I - Evidence from JHKL photometry
A survey has been carried out using JHKL photometry to investigaterecent star formation in interacting galaxies. The objective was to lookfor a K-L excess produced by 'warm' dust heated by a putative burst ofstar formation. K-L excesses are found suggesting that interactionsinduce starbursts with an efficiency approaching 100 percent. Theappearance of these inferred starbursts in interacting systems ofdifferent morphological types is qualitatively consistent with dynamicalstudies of galaxy interactions. However, the common occurrence of suchstarbursts shows that interactions have implications for theastrophysics of galaxies well beyond purely morphological effects.
| Infrared observations of interacting/merging galaxies
The present sample of 20 galaxy systems, selected on the basis ofmorphological evidence for the tidal interaction or merger of twogalaxies and observed at 1-10 microns, is noted to include 11 systems,detected at 10 microns, which have on average a significantly higher IRluminosity than noninteracting galaxies. The enhanced IR radiation isdue to star formation bursts. On the basis of IR Astronomical Satelliteresults for a sample of galaxies, as much as 30 percent of all thefar-IR emission observed arises in bursts of star formation that aretriggered by interactions, and massive stars account for most of theluminosity in these bursts. It is suggested, in view of a massive starformation rate in the interacting and merging galaxies that is about 3times higher than in noninteracting systems, that much of this starformation occurred in either nuclear regions or merger remnants.
| 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.
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