Contenidos
Imágenes
Subir su imagen
DSS Images Other Images
Artículos relacionados
Radio Continuum and Far-infrared Emission from the Galaxies in the Eridanus Group
The Eridanus galaxies follow the well-known radio-FIR correlation. Themajority (70%) of these galaxies have their star formation rates belowthat of the Milky Way. The galaxies that have a significant excess ofradio emission are identified as low luminosity AGNs based on theirradio morphologies obtained from the GMRT observations. There are nopowerful AGNs (L20 cm>1023WHz-1) in the group. The twomost far-infrared and radio luminous galaxies in the group have opticaland HI morphologies suggestive of recent tidal interactions. TheEridanus group also has two far-infrared luminous but radio-deficientgalaxies. It is believed that these galaxies are observed within a fewMyr of the onset of an intense star formation episode after beingquiescent for at least a 100 Myr. The upper end of the radio luminositydistribution of the Eridanus galaxies (L20 cm1022WHz-1) isconsistent with that of the field galaxies, other groups, and late-typegalaxies in nearby clusters.
| The HI Content of the Eridanus Group of Galaxies
The HI content of galaxies in the Eridanus group is studied using theGMRT observations and the HIPASS data. A significant HI deficiency up toa factor of 2-3 is observed in galaxies in the high galaxy densityregions. The HI deficiency in galaxies is observed to be directlycorrelated to the local projected galaxy density, and inverselycorrelated to the lineof-sight radial velocity. Furthermore, galaxieswith larger optical diameters are predominantly in the lower galaxydensity regions. It is suggested that the HI deficiency in Eridanus isdue to tidal interactions. In some galaxies, evidences of tidalinteractions are seen. An important implication is that significantevolution of galaxies can take place in the group environment. In thehierarchical way of formation of clusters via mergers of groups, afraction of the observed HI deficiency in clusters could have originatedin groups. The co-existence of S0s and severely HI deficient galaxies inthe Eridanus group suggests that tidal interaction is likely to be aneffective mechanism for transforming spirals to S0s.
| GMRT HI Observations of the Eridanus Group of Galaxies I.
The GMRT HI 21cm-line observations of galaxies in the Eridanus group arepresented. The Eridanus group, at a distance of ~23 Mpc, is a loosegroup of ~200 galaxies. The group extends to more than 10 Mpc inprojection. The velocity dispersion of the galaxies in the group is ~240km s-1. The galaxies are clustered into different sub-groups. Theoverall population mix of the group is 30% (E + S0) and 70% (Sp + Irr).The observations of 57 Eridanus galaxies were carried out with the GMRTfor ~ 200 h. HI emission was detected from 31 galaxies. The channel rmsof ~1 mJy beam-1 was achieved for most of the image-cubes made with 4 hof data. The corresponding HI column density sensitivity (3σ) is~1 × 1020 cm-2 for a velocity-width of ~ 13.4 km s-1.The 3σ detection lss surface densities, HI disk parameters and HIrotation curves are presented. The velocity fields are analysedseparately for the approaching and the receding sides of the galaxies.These data will be used to study the HI and the radio continuumproperties, the Tully-Fisher relations, the dark matter halos, and thekinematical and HI lopsidedness in galaxies.
| A search for Low Surface Brightness galaxies in the near-infrared. I. Selection of the sample
A sample of about 3800 Low Surface Brightness (LSB) galaxies wasselected using the all-sky near-infrared (J, H and Ks-band)2MASS survey. The selected objects have a mean central surfacebrightness within a 5'' radius around their centre fainter than 18 magarcsec-2 in the Ks band, making them the lowestsurface brightness galaxies detected by 2MASS. A description is given ofthe relevant properties of the 2MASS survey and the LSB galaxy selectionprocedure, as well as of basic photometric properties of the selectedobjects. The latter properties are compared to those of other samples ofgalaxies, of both LSBs and ``classical'' high surface brightness (HSB)objects, which were selected in the optical. The 2MASS LSBs have aBT_c-KT colour which is on average 0.9 mag bluerthan that of HSBs from the NGC. The 2MASS sample does not appear tocontain a significant population of red objects.All tables and Figs. 2a-c are only available in electronic form athttp://www.edpsciences.org
| 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.
| Statistical study of M 51-type galaxies
We present a statistical analysis of a new sample of M 51-type galaxies.Using the MCG and VV catalogues, we selected 32 such binary systems. Wefound that a typical M 51-type pair consists of a bright L*spiral galaxy and a satellite with blue luminosity 1/30-1/3 of theprimary one. The main galaxies in such pairs are often barred and havetwo well-defined spiral arms. M 51-type systems show an enhanced starformation rate (from FIR luminosities). We found a weak dependence ofthe star formation rate of the system on relative luminosity of thecompanion. M 51-type galaxies are relatively frequent: about 1/12 of allpairs are of M 51-type.
| 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.
| 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.
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| 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 near-infrared imaging survey of interacting galaxies - The small angular-size ARP systems
Near-IR images of a large sample of interacting galaxies selected fromthe Atlas of Peculiar Galaxies by Arp (1966) have been obtained.Approximately 180 systems have been imaged in at least two, and usuallythree of the standard JHK bands. The survey and the observing and datareduction procedures, are described, and contour plots and aperturephotometry are presented. Future papers will analyze the imaging data bygroupings based on interaction type, stage, and progenitors. The goalsof the analysis are to explore the relationships between galaxyinteractions, activity, and morphology by studying the structure of thenear-IR luminosity distribution, where extinction effects are muchreduced relative to the optical and the major stellar mass component ofgalaxies dominates the observed light.
| Southern Sky Redshift Survey - The catalog
The catalog of radial velocities for galaxies which comprise thediameter-limited sample of the Southern Sky Redshift Survey ispresented. It consolidates the data of observations carried out at theLas Campanas Observatory, Observatorio Nacional, and South AfricanAstronomical Observatory. The criteria used for the sample selection aredescribed, as well as the observational procedures and the techniqueutilized to obtain the final radial velocities. The intercomparisonbetween radial velocity measurements from different telescopes indicatesthat the final data base is fairly homogeneous with a typical error ofabout 40 km/s. The sample is at present 90 percent complete, and themissing galaxies are predominantly objects with very low surfacebrightness for which it is very difficult to obtain optical redshifts.
| A catalog of southern groups of galaxies
A catalog of groups of galaxies identified in the southern Galactic capis presented. This catalog was constructed utilizing the group-findingalgorithm developed by Huchra and Geller (1982) to analyze galaxysamples with well-defined selection criteria and complete velocityinformation.
| Studies of nearby poor clusters - The Eridanus group
Results are reported from dynamical study of the Eridanus group ofgalaxies. This system is quite prominent in one of the large-scalefeatures found in the recently completed Southern Sky Redshift Survey(da Costa et al., 1988): the Eridanus-Fornax-Dorado filament. Theirregualr aspect of Eridanus suggests the existence of subclustering,which is confirmed by statistical tests. These subclusters are bound,suggesting that the system is still condensing from the Hubble flow andmay eventually form a cluster of about 10 to the 14th solar mass. Bycalculating the two-body orbital solution, it is found that the Eridanuscomplex and the Fornax cluster also form a bound system, although stillin the expansion phase.
| An extragalactic database. I - The Catalogue of Principal Galaxies
The Catalogue of Principal Galaxies is described, which lists equatorialcoordinates (for the equinoxes 1950 and 2000) and cross-identificationsfor 73,197 galaxies. The 40,932 coordinates have standard deviationssmaller than 10 arcsec. A total of 131,601 names from the 38 most commonsources are listed. In addition, mean data for each object are givenwhen available: 49,102 morphological descriptions, 52,954 apparent majorand minor axes, 67,116 apparent magnitudes, 20,046 radial velocities and24,361 position angles. This information was used for facilitatingproper identification. Finally, distribution options are explained.
| Southern Galaxy Catalogue.
Not Available
| The nuclear activity of interacting galaxies
A search for active galactic nuclei among interacting galaxies isreported. A sample of 167 systems of interacting and asymmetric galaxieswas observed spectrophotometrically in the spectral range 4700-7100 A.The results are compared with a sample of isolated galaxies. It is foundthat (1) there are no Seyfert nuclei in elliptical or dwarf irregulargalaxies of the sample; (2) there is an excess of Seyfert nuclei amonginteracting spirals, but it is only at the 90 percent confidence level;(3) this excess becomes statistically significant (98 percent) when onlystrongly interacting spirals are included (four new Seyfert nuclei arepresented); (4) in the subgroup of galaxies with extreme tidaldistortions, no Seyfert nuclei were found.
| Atlas of interacting galaxies, Part. II and the concept of fragmentation of galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...28....1V&db_key=AST
| A radio survey of interacting galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974MNRAS.167..251W&db_key=AST
| Atlas of Peculiar Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966ApJS...14....1A&db_key=AST
|
Enviar un nuevo artículo
Enlaces relacionados
- - No se han encontrado enlaces -
En viar un nuevo enlace
Miembro de los siguientes grupos:
|
Datos observacionales y astrométricos
Catálogos y designaciones:
|
