תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Circumnuclear Structure and Black Hole Fueling: Hubble Space Telescope NICMOS Imaging of 250 Active and Normal Galaxies
Why are the nuclei of some galaxies more active than others? If mostgalaxies harbor a central massive black hole, the main difference isprobably in how well it is fueled by its surroundings. We investigatethe hypothesis that such a difference can be seen in the detailedcircumnuclear morphologies of galaxies using several quantitativelydefined features, including bars, isophotal twists, boxy and diskyisophotes, and strong nonaxisymmetric features in unsharp-masked images.These diagnostics are applied to 250 high-resolution images of galaxycenters obtained in the near-infrared with NICMOS on the Hubble SpaceTelescope. To guard against the influence of possible biases andselection effects, we have carefully matched samples of Seyfert 1,Seyfert 2, LINER, starburst, and normal galaxies in their basicproperties, taking particular care to ensure that each was observed witha similar average scale (10-15 pc pixel-1). Severalmorphological differences among our five different spectroscopicclassifications emerge from the analysis. The H II/starburst galaxiesshow the strongest deviations from smooth elliptical isophotes, whilethe normal galaxies and LINERs have the least disturbed morphology. TheSeyfert 2s have significantly more twisted isophotes than any othercategory, and the early-type Seyfert 2s are significantly more disturbedthan the early-type Seyfert 1s. The morphological differences betweenSeyfert 1s and Seyfert 2s suggest that more is at work than simply theviewing angle of the central engine. They may correspond to differentevolutionary stages.
| Long slit spectroscopy of a sample of isolated spirals with and without an AGN
We present the kinematical data obtained for a sample of active(Seyfert) and non active isolated spiral galaxies, based on long slitspectra along several position angles in the Hα line region and,in some cases, in the Ca triplet region as well. Gas velocitydistributions are presented, together with a simple circular rotationmodel that allows us to determine the kinematical major axes. Stellarvelocity distributions are also shown. The main result is that activeand control galaxies seem to be equivalent in all kinematical aspects.For both subsamples, the departure from pure circular rotation in somegalaxies can be explained by the presence of a bar and/or of a spiralarm. They also present the same kind of peculiarities, in particular,S-shape structures are quite common near the nuclear regions. Theydefine very similar Tully-Fisher relations. Emission line ratios aregiven for all the detected HII regions; the analysis of the[NII]/Hα metallicity indicator shows that active and non-activegalaxies have indistinguishable disk metallicities. These results arguein favour of active and non-active isolated spiral galaxies havingessentially the same properties, in agreement with our previous resultsbased on the analysis of near infrared images. It appears now necessaryto confirm these results on a larger sample.Based on observations made with WHT operated on the island of La Palmaby ING in the Spanish Observatorio del Roque de Los Muchachos of theInstituto de Astrofísica de Canarias, the European SouthernObservatory (La Silla), Calar Alto Observatory (Almería, Spain)and Las Campanas Observatories (Chile).Table 3 and Figs. \ref{res_cen_u1395}, 5, 7, 9, 11, 13, 15, 17, 19, 21,23, 25, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50 and 52 are onlyavailable in electronic form at http://www.edpsciences.orgTable 5 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/475
| HYPERLEDA. II. The homogenized HI data
After a compilation of HI data from 611 references and new observationsmade in Nançay, we produce a catalog of homogenized HI data for16781 galaxies. The homogenization is made using the EPIDEMIC methodfrom which all data are progressively converted into the adoptedstandard. The result is a catalog giving: 1) the logarithm of twice themaximum rotation velocity, log 2V_Msin i, converted to thesystem of Mathewson et al. (\cite{Mathewson1996}). This quantity isgiven without correction for inclination; 2) the HI magnitude,m21, (area of the 21-cm line width expressed in magnitude)converted to the flux system of Theureau et al. (\cite{Theureau1998});3) the HI velocity, V_HI, expressed with the optical definition (i.e.,using wavelengths instead frequencies). The typical uncertainties are:0.04 for log 2V_Msin i, 0.25 mag for m21 and 9 kms-1 for V_HI.Full Tables \ref{epidemicw}, \ref{epidemicw2}, \ref{epidemicf},\ref{epidemicf2} and Fig. \ref{profiles} are available in electronicform at http://www.edpsciences.org. Full Tables \ref{references},\ref{cataf}, \ref{newdata} and \ref{notes} are available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/412/57
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| 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.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Near-infrared photometry of isolated spirals with and without an AGN --- II. Photometric properties of the host galaxies
We present here the analysis of morphological and photometric propertiesof a sample of isolated spirals with (18) and without (11) an activenucleus, based on near-infrared imaging in the J and K' bands (Paper I).The aim of that comparative analysis is to find the differentialproperties that could be directly connected with the phenomenon ofnuclear activity. We stress the importance of using isolated objects forthat purpose. Our study shows that both sets of galaxies are similar intheir global properties: they define the same Kormendy relation, theirdisk components share the same properties, the bulge and disk scalelengths are correlated in a similar way, bar strengths and lengths aresimilar for primary bars. Our results therefore indicate that hosts ofisolated Seyfert galaxies have bulge and disk properties comparable tothose of isolated non active spirals. Central colors (the innermost 200pc) of active galaxies are redder than the centers of non activespirals, most probably due to AGN light being re-emitted by the hot dustand/or due to circumnuclear star formation, through the contribution ofgiants/supergiants. Central to our analysis is the study of the possibleconnection between bars and similar non axisymmetric structures with thenuclear fuelling. We note that only one of the Seyfert galaxies in oursample, namely ESO 139-12, does not present a primary bar. But bars areequally present in active and control objects. The same applies tosecondary bars. Not all the active galaxies we have observed have them,and some control galaxies also present such central structures.Secondary central elongations (associated with secondary bars, lenses,rings or disks) may be somewhat different, but this result should beconfirmed with larger samples. We note that numerical models indicatethat such secondary bars are not strictly necessary to feed the centralengine when a primary bar is present. Our results show that down toscales of 100-300 pc, there are no evident differences between activeand non active spiral galaxies. Based on data obtained at: the EuropeanSouthern Observatory, La Silla, Chile, the Télescope BernardLyot, Calar Alto Observatory, Las Campanas Observatory. Also based onobservations made with the NASA/ESA Hubble Space Telescope, obtainedfrom the data archive at the Space --- II. Photometric properties of thehost galaxies
| The NICMOS Snapshot Survey of Nearby Galaxies
We present ``snapshot'' observations with the Near-Infrared Camera andMulti-Object Spectrometer (NICMOS) on board the Hubble Space Telescope(HST) of 94 nearby galaxies from the Revised Shapley Ames Catalog.Images with 0.2" resolution were obtained in two filters, a broadbandcontinuum filter (F160W, roughly equivalent to the H band) and anarrowband filter centered on the Paα line (F187N or F190N,depending on the galaxy redshift) with the 51^''x51^'' field of view ofthe NICMOS camera 3. A first-order continuum subtraction is performed,and the resulting line maps and integrated Paα line fluxes arepresented. A statistical analysis indicates that the average Paαsurface brightness in the central regions is highest in early-type(Sa-Sb) spirals.
| Near-infrared photometry of isolated spirals with and without an AGN. I. The data
We present infrared imaging data in the J and K' bands obtained for 18active spiral galaxies, together with 11 non active galaxies taken as acontrol sample. All of them were chosen to satisfy well definedisolation criteria so that the observed properties are not related togravitational interaction. For each object we give: the image in the K'band, the sharp-divided image (obtained by dividing the observed imageby a filtered one), the difference image (obtained by subtracting amodel to the observed one), the color J-K' image, the ellipticity andposition angle profiles, the surface brightness profiles in J and K',their fits by bulge+disk models and the color gradient. We have foundthat four (one) active (control) galaxies previously classified asnon-barred turn out to have bars when observed in the near-infrared. Oneof these four galaxies (UGC 1395) also harbours a secondary bar. For 15(9 active, 6 control) out of 24 (14 active, 10 control) of the opticallyclassified barred galaxies (SB or SX) we find that a secondary bar (or adisk, a lense or an elongated ring) is present. The work presented hereis part of a large program (DEGAS) aimed at finding out whether thereare differences between active and non active galaxies in the propertiesof their central regions that could be connected with the onset ofnuclear activity. Based on data obtained at: the European SouthernObservatory, La Silla, Chile, the Télescope Bernard Lyot, CalarAlto Observatory, Las Campanas Observatory. Also based on observationsmade with the NASA/ESA Hubble Space Telescope, obtained from the dataarchive at the Space Telescope Institute. Figures 1-35 are onlyavailable in electronic form at the http://www.edpsciences.org
| 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.
| Molecular Gas, Morphology, and Seyfert Galaxy Activity
We probe the cause of the elevated star formation in host galaxies ofSeyfert 2 nuclei compared with Seyfert 1 hosts and with field galaxies.12CO (1--0) observations of a large sample of Seyfert galaxies indicateno significant difference in the total amount of molecular gas as afunction of the Seyfert nuclear type, nor are Seyfert galaxiessignificantly different in this regard from a sample of field galaxiesonce selection effects are accounted for. Therefore, the total amount ofmolecular gas is not responsible for the enhanced star-forming activityin Seyfert 2 hosts. To probe how this gas is being converted moreefficiently into stars in Seyfert 2 hosts than in the other galaxies, weinvestigate the occurrence of bars, interactions, and distortedmorphologies among Seyfert galaxies. We find a significantly higher rateof asymmetric morphologies for Seyfert 2 galaxies with respect toSeyfert 1 galaxies and field galaxies. Relative to field galaxies, theeffect is at a greater than 99.9% confidence level. The presence ofasymmetric morphologies in individual Seyfert galaxies is correlatedwith their tendency to exhibit enhanced star-forming activity. Theseresults suggest that asymmetric morphologies are an important cause forthe link between Seyfert type and star-forming activity: bars anddistortions in Seyfert 2 hosts are likely both to enhance star-formingactivity and to funnel gas into the nuclear region, thus obscuring andpossibly contributing to the feeding of the active nucleus.
| More Satellites of Spiral Galaxies
We present a revised and expanded catalog of satellite galaxies of a setof isolated spiral galaxies similar in luminosity to the Milky Way. Thissample of 115 satellites, 69 of which were discovered in our multifiberredshift survey, is used to probe the results obtained from the originalsample further (Zaritsky et al.). The satellites are, by definition, atprojected separations <~500 kpc, have absolute recessional velocitydifferences with respect to the parent spiral of less than 500 km s-1,and are at least 2.2 mag fainter than their associated primary galaxy. Akey characteristic of this survey is the strict isolation of thesesystems, which simplifies any dynamical analysis. We find no evidencefor a decrease in the velocity dispersion of the satellite system as afunction of radius out to galactocentric radii of 400 kpc, whichsuggests that the halo extends well beyond 200 kpc. Furthermore, the newsample affirms our previous conclusions (Zaritsky et al.) that (1) thevelocity difference between a satellite and its primary is not stronglycorrelated with the rotation speed of the primary, (2) the system ofsatellites has a slight net rotation (34 +/- 14 km s-1) in the samesense as the primary's disk, and (3) that the halo mass of an ~L* spiralgalaxy is in excess of 2 x 1012 Mȯ.
| 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.
| Automated morphological classification of APM galaxies by supervised artificial neural networks
We train artificial neural networks to classify galaxies based solely onthe morphology of the galaxy images as they appear on blue surveyplates. The images are reduced, and morphological features such as bulgesize and the number of arms are extracted, all in a fully automatedmanner. The galaxy sample was first classified by six independentexperts. We use several definitions for the mean type of each galaxy,based on those classifications. We then train and test the network onthese features. We find that the rms error of the networkclassifications, as compared with the mean types of the expertclassifications, is 1.8 Revised Hubble types. This is comparable to theoverall rms dispersion between the experts. This result is robust andalmost completely independent of the network architecture used.
| 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.
| The Catalog of Southern Ringed Galaxies
The Catalog of Southern Ringed Galaxies (CSRG) is a comprehensivecompilation of diameters, axis ratios, relative bar position angles, andmorphologies of inner and outer rings, pseudorings, and lenses in 3692galaxies south of declination -17 deg. The purpose of the catalog is toevaluate the idea that these ring phenomena are related to orbitalresonances with a bar or oval in galaxy potentials. The catalog is basedon visual inspection of most of the 606 fields of the Science ResearchCouncil (SRC) IIIa-J southern sky survey, with the ESO-B, ESO-R, andPalomar Sky surveys used as auxiliaries when needed for overexposed coreregions. The catalog is most complete for SRC fields 1-303 (mostly southof declination -42 deg). In addition to ringed galaxies, a list of 859mostly nonringed galaxies intended for comparison with other catalogs isprovided. Other findings from the CSRG that are not based on statisticsare the identification of intrinsic bar/ring misalignment; bars whichunderfill inner rings; dimpling of R'1pseudorings; pointy, rectangular, or hexagonal inner or outer ringshapes; a peculiar polar-ring-related system; and other extreme examplesof spiral structure and ring morphology.
| The dependence of the cool matter content on galaxy morphology in galaxies of types E/S0, S0, and SA
Using the material assembled in earlier papers, we examine the manner inwhich the interstellar matter content varies along the Hubble sequencefrom S0 galaxies to Sa galaxies selected from the RSA2 compilation. Forthis we make use of a new and more detailed classification which isdescribed here as applied to these early disk/spiral galaxies. Theprominence of the disk in S0's and the visibility of features (H IIregions) in the Sa's serve as the basis for the subtypes. Three S0categories: subtle, intermediate, and pronounced, and four Sadescriptors: very early, early, intermediate, and late are assigned tothe galaxies. It is found that the total amount of hydrogen (H I + H2)is a function of subtype, being low in the S0's and rising smoothly fromthe early Sa's to the later Sa's. The average surface density ofhydrogen exceeds 3 solar masses/pc-squared only in the latest subtypesof the Sa's. We conclude that the prominence of the disk of a galaxyclosely follows the amount of cool gas which the disk contains.
| Interstellar matter in early-type galaxies. I - The catalog
A catalog is given of the currently available measurements ofinterstellar matter in the 467 early-type galaxies listed in the secondedition of the Revised Shapley-Ames Catalog of Bright Galaxies. Themorphological type range is E, SO, and Sa. The ISM tracers are emissionin the following bands: IRAS 100 micron, X-ray, radio, neutral hydrogen,and carbon monoxide. Nearly two-thirds of the Es and SOs have beendetected in one or more of these tracers. Additional observed quantitiesthat are tabulated include: magnitude, colors, radial velocity, centralvelocity dispersion, maximum of the rotation curve, angular size, 60micron flux, and supernovae. Qualitative statements as to the presenceof dust or emission lines, when available in the literature, are given.Quantities derivative from the observed values are also listed andinclude masses of H I, CO, X-ray gas, and dust as well as an estimate ofthe total mass and mass-to-luminosity ratio of the individual galaxies.
| 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.
| A millimeter-wave survey of CO emission in Seyfert galaxies
Emission in the 115 GHz 1-0 line of CO has been detected in 18 Seyfertgalaxies in a sample of 43. The CO properties of 29 Seyferts in theRevised Shapley Ames Catalog (RSA) are compared with the CO propertiesof normal galaxies of the same Hubble type. These RSA type 2 Seyfertshave an average ratio of CO-to-blue luminosity that is about twice aslarge as that of the normal galaxies, but the RSA type 1 Seyferts havenormal CO luminosities. The RSA type 2 Seyfert galaxies have anunusually large average ratio of CO luminosity-to-H I mass compared tonormal disk galaxies. The RSA type 2 Seyferts have an average far-IRluminosity that is about four times larger than a non-Seyfert comparisonsample, while the RSA type 1 Seyferts are not significantly moreluminous than the non-Seyferts. The result imply that the two classes ofSeyferts are intrinsically different from one another and that one classcannot evolve into another in less than a few million years.
| A southern redshift survey. I - Accurate redshifts for 500 galaxies observed at SAAO
Radial velocities are presented for about 500 galaxies observed with anintensified Reticon photon-counting detector attached to the 1.9 mtelescope at the Sutherland field station of SAAO. The velocities weredetermined by cross correlation with standard velocity templates, fromthe measured wavelengths of emission lines, or from both techniques,with spectra covering the wavelength range from 3700 to 5400 A. Thefinal velocities appear to have the same zero point as H I radiovelocities, and have standard deviations of the order of 35 km/s, thoughcross-correlation velocities on their own may have significantly largererrors.
| 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.
| Southern Galaxy Catalogue.
Not Available
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
קטלוגים וכינוים:
|
