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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.
| 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
| 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.
| 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.
| CO, HI and cold dust in a sample of IRAS galaxies.
Using the IRAM 30m, SEST 15m, and Nancay radiotelescopes, we havegathered the 1mm continuum emission, the intensities of the J=1-0 lineof the CO molecule and of the atomic hydrogen line at 21cm for twosamples of IRAS galaxies. The southern sample was selected from the IRASCatalogue and is complete at the limiting flux of 2Jy at 60μm; of the10 northern objects 7 belong to the Smith et al. complete sample (1987)and 3 are isolated objects. Using these data, we have estimated theatomic hydrogen masses from the 21cm emission, the molecular gas massesfrom the CO(1-0)line brightness, and the dust and gas masses from the mmcontinuum emission using two "extreme" dust models. The main conclusionsof this work for far-infrared selected galaxies can be summarized in thefollowing points: (1) the median value of M_H_2__/M_HI_ is 0.5, meaningthat the atomic phase dominates in these galaxies. The fraction of gasin molecular form increases with increasing FIR luminosity but does notshow any obvious trend with other galaxy properties, in particular withthe FIR surface brightness. (2) the H_2_ surface density derived fromCO(1-0)emission is better correlated with the cold dust surface densitythan the HI surface density, but the correlation of HI with dust is notnegligible (we found a correlation coefficient of 0.5, while thecorrelation coefficient with σ_H_2__ is 0.70). Thus, globally inthese galaxies, the cold dust emission is likely associated with boththe molecular and atomic phases. Indeed, the dust surface density isalso correlated with the total gas surface density. (3) the FIR surfacebrightness increases as the third power of the S(60μm) /S(100μm)ratio. It shows a tight correlation with both the H_2_ and dust surfacedensities and a weaker one with the HI surface density. This suggeststhat a large part of the far-infrared emission of these galaxiesoriginates in the molecular medium. (4) the gas-to-dust ratio, (M_H_2__+M_HI_)/M_d_ ranges between 100 and 1000 and its average value is 230,close to the Galactic value. There is indeed a clear trend: this ratiodecreases as the FIR surface density increases. This result can beexplained in the framework of an enhancement of metallicity in galaxydiscs having a higher star formation rate.
| The Montreal Blue Galaxy survey. 2: Second list of UV-bright candidates
We present and discuss the second list of the Montreal Blue Galaxysurvey. Following the inspection of 71 plates, we found 237 newcandidates with B less than 15.5. 73 percent of them are also detectedby Infrared Astronomy Satellite (IRAS). Spectrophotometry was carriedout, at medium resolution, for a subset of 40 objects leading to theidentification of three new AGNs and producing 13 new radial velocities.Spectral classification of our candidates confirms our previous findingthat the majority of our candidates are starburst nucleus galaxiessimilar to the objects studied by Balzano in 1983. Our survey is biasedagainst the high excitation starburst H II galaxies and the LINERgalaxies. Metallicities of our galaxies are found to be from log(O/H)=8.4 to 9.0, which suggests galaxies in advanced stages of chemicalevolution.
| New HI Observations for Possible Group Member Galaxies
We present new HI-observations made at the Nancay radiotelescope for 120spiral galaxies. These galaxies have been selected because of theirpossible membership to groups of the LGG catalog. For each object wegive the heliocentric HI-velocity, HI-linewidths at 20% and 50% of themaximum intensity and the HI-flux.
| Southern Galaxy Catalogue.
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