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The host galaxy/AGN connection in nearby early-type galaxies. Sample selection and hosts brightness profiles
This is the first of a series of three papers exploring the connectionbetween the multiwavelength properties of AGNs in nearby early-typegalaxies and the characteristics of their hosts. We selected twosamples, both with high resolution 5 GHz VLA observations available andproviding measurements down to 1 mJy level, reaching radio-luminositiesas low as 1019 W Hz-1. We focus on the 116radio-detected galaxies as to boost the fraction of AGN with respect toa purely optically selected sample. Here we present the analysis of theoptical brightness profiles based on archival HST images, available for65 objects. We separate early-type galaxies on the basis of the slope oftheir nuclear brightness profiles, into core and power-law galaxiesfollowing the Nuker's scheme, rather than on the traditionalmorphological classification (i.e. into E and S0 galaxies). Our sampleof AGN candidates is indistinguishable, when their brightness profilesare concerned, from galaxies of similar optical luminosity but hostingweaker (or no) radio-sources. We confirm previous findings thatrelatively bright radio-sources (Lr > 1021.5 WHz-1) are uniquely associated to core galaxies. However,below this threshold in radio-luminosity core and power-law galaxiescoexist and they do not show any apparent difference in theirradio-properties. Not surprisingly, since our sample is deliberatelybiased to favour the inclusion of active galaxies, we found a higherfraction of optically nucleated galaxies. Addressing the multiwavelengthproperties of these nuclei will be the aim of the two forthcomingpapers.
| Molecular gas in compact galaxies
New observations of eleven compact galaxies in the 12CO J =2{-}1 and J = 3{-}2 transitions are presented. From these observationsand literature data accurate line ratios in matched beams have beenconstructed, allowing the modelling of physical parameters. Matching asingle gas component to observed line ratios tends to produce physicallyunrealistic results, and is often not possible at all. Much betterresults are obtained by modelling two distinct gas components. In mostobserved galaxies, the molecular gas is warm (Tk = 50{-}150K) and at least partially dense (n(H2) ≥ 3000cm-3). Most of the gas-phase carbon in these galaxies is inatomic form; only a small fraction ( 5%) is in carbon monoxide.Beam-averaged CO column densities are low (of the order of1016 cm-2). However, molecular hydrogen columndensities are high (of the order of 1022 cm-2)confirming large CO-to- H2 conversion factors (typically X =1021{-}1022 cm-2/ {K kms-1}) found for low-metallicity environments by othermethods. From CO spectroscopy, three different types of molecularenvironment may be distinguished in compact galaxies. Type I (highrotational and isotopic ratios) corresponds to hot and dense molecularclouds dominated by star-forming regions. Type II has lower ratios,similar to the mean found for infrared-luminous galaxies in general, andcorresponds to environments engaged in, but not dominated by,star-forming activity. Type III, characterized by low 12CO(2-1)/(1-0) ratios, corresponds to mostly inactive environments ofrelatively low density.
| 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.
| H I and CO in Blue Compact Dwarf Galaxies: Haro 2 and Haro 4
We present Very Large Array H I imaging of two blue compact dwarfgalaxies, Haro 2 and Haro 4, and of the spiral galaxy Haro 26, which isprojected some 22' southwest of Haro 4. We also show a map of theCO(1-0) distribution of Haro 2 obtained with the Owens Valley RadioObservatory Millimeter Array, as well as derive an upper limit forCO(2-1) emission from Haro 4 obtained with the Caltech SubmillimeterObservatory. The H I data of Haro 2 reveal that the kinematical majoraxis lies perpendicular to the photometric major axis, indicating thatthe atomic hydrogen rotates about the major axis of the galaxy. Thisconfirms earlier indications based on CCD photometry that Haro 2 is adust-lane dE rather than a dIrr. We propose that the present neutral andmolecular ISM configuration is due to recent gas accretion or a merger.The H I distribution and dynamics of Haro 4 and the neighboring spiralHaro 26 suggest that they are currently undergoing a tidal interaction,reinforcing the notion that interactions play an important role intriggering the star formation witnessed in blue compact galaxies.
| Radio emission from AGN detected by the VLA FIRST survey
Using the most recent (April 2003) version of the VLA FIRST survey radiocatalog, we have searched for radio emission from >2800 AGN takenfrom the most recent (2001) version of the Veron-Cetty and Veron AGNcatalog. These AGN lie in the 9033 square degrees of sky alreadycovered by the VLA FIRST survey. Our work has resulted in positivedetection of radio emission from 775 AGN of which 214 are new detectionsat radio wavelengths.Tables 3 and 4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/35
| The Millennium Galaxy Catalogue: 16 <=BMGC < 24 galaxy counts and the calibration of the local galaxy luminosity function
The Millennium Galaxy Catalogue (MGC) is a 37.5 deg2,medium-deep, B-band imaging survey along the celestial equator, takenwith the Wide Field Camera on the Isaac Newton Telescope. The surveyregion is contained within the regions of both the Two Degree FieldGalaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey EarlyData Release (SDSS-EDR). The survey has a uniform isophotal detectionlimit of 26 mag arcsec-2 and it provides a robust,well-defined catalogue of stars and galaxies in the range 16<=BMGC < 24 mag.Here we describe the survey strategy, the photometric and astrometriccalibration, source detection and analysis, and present the galaxynumber counts that connect the bright and faint galaxy populationswithin a single survey. We argue that these counts represent the stateof the art and use them to constrain the normalizations (φ*) of anumber of recent estimates of the local galaxy luminosity function. Wefind that the 2dFGRS, SDSS Commissioning Data (CD), ESO Slice Project,Century Survey, Durham/UKST, Mt Stromlo/APM, SSRS2 and NOG luminosityfunctions require a revision of their published φ* values by factorsof 1.05 +/- 0.05, 0.76 +/- 0.10, 1.02 +/- 0.22, 1.02 +/- 0.16, 1.16 +/-0.28, 1.75 +/- 0.37, 1.40 +/- 0.26 and 1.01 +/- 0.39, respectively.After renormalizing the galaxy luminosity functions we find a mean localbJ luminosity density of .1
| Palomar/Las Campanas Imaging Atlas of Blue Compact Dwarf Galaxies. I. Images and Integrated Photometry
We present B, R, and Hα images for a total of 114 nearby galaxies(vhelio<4000 km s-1) that, with exception ofnine objects, are classified as blue compact dwarfs (BCDs). BRintegrated magnitudes, Hα fluxes and Hα equivalent widthsfor all the objects in the sample are presented. A new set ofquantitative, observational criteria for a galaxy to be classified as aBCD is proposed. These criteria include a limit on the K-band luminosity(i.e., stellar mass; MK>-21 mag), peak surface brightness(μB,peak<22 mag arcsec-2), and color at thepeak surface brightness(μB,peak-μR,peak<~1). Hα emissionis detected in all but three sample galaxies. Typical color, absolutemagnitude, and Hα luminosity are (B-R)=0.7+/-0.3 mag,MB=-16.1+/-1.4 mag, and log (LHα)=40.0+/-0.6(ergs s-1). Galaxies morphologically classified as nE and iEBCDs within our sample show lower Hα equivalent widths and reddercolors, on average, than the iI- and i0-type BCDs. For most of thegalaxies the presence of an evolved stellar population is required toexplain their observed properties; only the most metal-poor BCDs (e.g.,I Zw 18, Tol 65) are still compatible with a pure, young burst. Theflux-calibrated and WCS-compliant images in this Atlas are individuallyavailable through the NASA/IPAC Extragalactic Database (NED) imageserver and collectively through a dedicated Web page.
| Neutral Hydrogen Mapping of Virgo Cluster Blue Compact Dwarf Galaxies
A new installment of neutral hydrogen mappings of blue compact dwarf(BCD) galaxies, as defined by optical morphology, in and near the VirgoCluster is presented. The primary motivation was to search for outlyingclouds of H I as potential interactive triggers of enhanced starformation, and therefore the mapped galaxies were selected for large H Imass, large optical diameter, and large velocity profile width.Approximately half the sample proved to have one or more small, lowcolumn density, star-free companion clouds, either detached or appearingas an appendage in our maps, at a resolution on the order of 4 kpc.Comparison is made with a sample of similarly mapped field BCD galaxiesdrawn from the literature; however, the Virgo Cluster sample of mappedBCDs is still too small for conclusive comparisons to be made. We found,on the one hand, little or no evidence for ram-pressure stripping nor,on the other, for extremely extended low column density H I envelopes.The H I rotation curves in most cases rise approximately linearly andslowly, as far out as we can trace the gas.
| 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
| The 2dF Galaxy Redshift Survey: the population of nearby radio galaxies at the 1-mJy level
We use redshift determinations and spectral analysis of galaxies in the2dF Galaxy Redshift Survey to study the properties of local radiosources with S>=1mJy. 557 objects (hereafter called the spectroscopicsample) drawn from the FIRST survey, corresponding to 2.3 per cent ofthe total radio sample, are found in the 2dFGRS catalogue within thearea9h48m<~RA(2000)<~14h32m and -2.77°<~Dec.(2000)<~2.25°, down to a magnitudelimit bJ=19.45. The excellent quality of 2dF spectra allowsus to divide these sources into classes, according to their opticalspectra. Absorption-line systems make up 63 per cent of thespectroscopic sample. These may or may not show emission lines due toAGN activity, and correspond to `classical' radio galaxies belongingmainly to the FRI class. They are characterized by relatively highradio-to-optical ratios, red colours, and high radio luminosities(1021<~P1.4GHz/WHz-1sr-1<~1024). Actively star-forming galaxies contributeabout 32 per cent of the sample. These objects are mainly found at lowredshifts (z<~0.1) and show low radio-to-optical ratios, blue coloursand low radio luminosities. We also found 18 Seyfert 2 galaxies (3 percent) and four Seyfert 1s (1 per cent). Analysis of the local radioluminosity function (LF) shows that radio galaxies are well described bymodels that assume pure luminosity evolution, at least down to radiopowersP1.4GHz<~1020.5WHz-1sr-1.Late-type galaxies, whose relative contribution to the radio LF is foundto be lower than was predicted by previous works, present an LF which iscomparable with the IRAS galaxy LF. This class of sources thereforeplausibly constitutes the radio counterpart of the dusty spirals andstarbursts that dominate the counts at 60μm.
| An H I Survey of Actively Star-forming Dwarf Galaxies
We present the results of H I 21 cm observations of 139 activelystar-forming dwarf galaxies obtained with the 305 m radio telescope atArecibo Observatory. Our sample consists of all objects cataloged inobjective-prism surveys for UV-excess or emission-line galaxiespublished prior to the start of the survey that have luminosities belowMB=-17.0 and that are located within the declination limitsof the Arecibo telescope. Galaxies from the Markarian, Michigan, Case,Wasilewski, Haro, and Zwicky lists are included. The sample spans a widerange of both H I gas content and star formation levels. A total of 122objects (88%) were detected; 82 galaxies have been observed for thefirst time in H I. The median velocity width for our sample is 88 kms-1, and the median H I gas mass is 3.0×108Msolar. In general, the sample galaxies are gas-rich, with anaverage MHI/LB=1.3 after correcting for theluminosity enhancement due to the starburst. The progenitors of many ofthe star-forming dwarfs have higher MHI/LB thantypically seen in samples of nearby ``normal'' galaxies, emphasizingtheir distinct nature.
| Dynamical condition of neutral hydrogen envelopes of dwarf galaxies and their possible morphological evolution
We investigate the star-formation history of gas-rich dwarf galaxies,taking account of the dynamical evolution of their neutral hydrogen (HI)envelope. Gas-rich dwarfs are classified into blue compact dwarfs (BCDs)and dwarf irregulars (dIrrs). In this paper, their HI envelope isclearly shown not to be blown away by their stellar feedback. This isconcluded since the observed star-formation rate (SFR) of gas-richdwarfs is generally smaller than a critical SFR, psicrit, atwhich stellar feedback accelerates the HI envelope to the escapevelocity. From this standpoint and the chemical property of sample BCDs,we suggest two possibilities; (1) the HI gas in the envelope of BCDs isconsumed to fuel their star-formation; and (2) BCDs have a similarstar-formation history. We also discuss morphological evolution amongdwarf galaxies. As long as gas-rich dwarfs are isolated, it is difficultfor them to evolve into dwarf ellipticals (dEs). When the HI envelope ingas-rich dwarfs is consumed in subsequent star-formation, amorphological exchange between BCDs and dIrrs is still expected,consistent with previous studies. If the SFR of gas-rich dwarfs was muchhigher than psicrit in the past, interestingly, anevolutionary scenario from dEs to gas-rich dwarfs is possible.
| Dust-to-gas ratio and star formation history of blue compact dwarf galaxies
This paper investigates the origin of the observed large variety indust-to-gas ratio, D, among blue compact dwarf galaxies (BCDs). Byapplying our chemical evolution model, we find that the dust destructioncan largely suppress the dust-to-gas ratio when the metallicity of a BCDreaches 12+log (O/H) ~ 8, i.e., a typical metallicity level of BCDs. Wealso show that dust-to-gas ratio is largely varied owing to the changeof dust destruction efficiency that has two effects: (i) a significantcontribution of Type Ia supernovae to total supernova rate; (ii)variation of gas mass contained in a star-forming region. While massloss from BCDs was previously thought to be the major cause for thevariance of D, we suggest that the other two effects are also important.We finally discuss the intermittent star formation history, whichnaturally explains the large dispersion of dust-to-gas ratio among BCDs.
| A synthesis of data from fundamental plane and surface brightness fluctuation surveys
We perform a series of comparisons between distance-independentphotometric and spectroscopic properties used in the surface brightnessfluctuation (SBF) and fundamental plane (FP) methods of early-typegalaxy distance estimation. The data are taken from two recent surveys:the SBF Survey of Galaxy Distances and the Streaming Motions of AbellClusters (SMAC) FP survey. We derive a relation between(V-I)0 colour and Mg2 index using nearly 200galaxies and discuss implications for Galactic extinction estimates andearly-type galaxy stellar populations. We find that the reddenings fromSchlegel et al. for galaxies with E(B-V)>~0.2mag appear to beoverestimated by 5-10 per cent, but we do not find significant evidencefor large-scale dipole errors in the extinction map. In comparison withstellar population models having solar elemental abundance ratios, thegalaxies in our sample are generally too blue at a given Mg2;we ascribe this to the well-known enhancement of the α-elements inluminous early-type galaxies. We confirm a tight relation betweenstellar velocity dispersion σ and the SBF `fluctuation count'parameter N, which is a luminosity-weighted measure of the total numberof stars in a galaxy. The correlation between N and σ is eventighter than that between Mg2 and σ. Finally, we deriveFP photometric parameters for 280 galaxies from the SBF survey data set.Comparisons with external sources allow us to estimate the errors onthese parameters and derive the correction necessary to bring them on tothe SMAC system. The data are used in a forthcoming paper, whichcompares the distances derived from the FP and SBF methods.
| The Multitude of Unresolved Continuum Sources at 1.6 Microns in Hubble Space Telescope Images of Seyfert Galaxies
We examine 112 Seyfert galaxies observed by the Hubble Space Telescopeat 1.6 μm. We find that ~50% of the Seyfert 2.0 galaxies which arepart of the Revised Shapely-Ames (RSA) Catalog or the CfA redshiftsample contain unresolved continuum sources at 1.6 μm. All but acouple of the Seyfert 1.0-1.9 galaxies display unresolved continuumsources. The unresolved sources have fluxes of order 1 mJy,near-infrared luminosities of order 1041 ergs s-1,and absolute magnitudes MH~-16. Comparison non-Seyfertgalaxies from the RSA Catalog display significantly fewer (~20%),somewhat lower luminosity nuclear sources, which could be due to compactstar clusters. We find that the luminosities of the unresolved Seyfert1.0-1.9 sources at 1.6 μm are correlated with [O III] λ5007and hard X-ray luminosities, implying that these sources are nonstellar.Assuming a spectral energy distribution similar to that of a Seyfert 2galaxy, we estimate that a few percent of local spiral galaxies containblack holes emitting as Seyferts at a moderate fraction,~10-1-10-4, of their Eddington luminosities. Wefind no strong correlation between 1.6 μm fluxes and hard X-ray or [OIII] λ5007 fluxes for the pure Seyfert 2.0 galaxies. Thesegalaxies also tend to have lower 1.6 μm luminosities compared to theSeyfert 1.0-1.9 galaxies of similar [O III] luminosity. Either largeextinctions (AV~20-40) are present toward theircontinuum-emitting regions or some fraction of the unresolved sources at1.6 μm are compact star clusters. With increasing Seyfert type thefraction of unresolved sources detected at 1.6 μm and the ratio of1.6 μm to [O III] fluxes tend to decrease. These trends areconsistent with the unification model for Seyfert 1 and 2 galaxies.
| The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
We report data for I-band surface brightness fluctuation (SBF)magnitudes, (V-I) colors, and distance moduli for 300 galaxies. Thesurvey contains E, S0, and early-type spiral galaxies in the proportionsof 49:42:9 and is essentially complete for E galaxies to Hubblevelocities of 2000 km s-1, with a substantial sampling of Egalaxies out to 4000 km s-1. The median error in distancemodulus is 0.22 mag. We also present two new results from the survey.(1) We compare the mean peculiar flow velocity (bulk flow) implied byour distances with predictions of typical cold dark matter transferfunctions as a function of scale, and we find very good agreement withcold, dark matter cosmologies if the transfer function scale parameterΓ and the power spectrum normalization σ8 arerelated by σ8Γ-0.5~2+/-0.5. Deriveddirectly from velocities, this result is independent of the distributionof galaxies or models for biasing. This modest bulk flow contradictsreports of large-scale, large-amplitude flows in the ~200 Mpc diametervolume surrounding our survey volume. (2) We present adistance-independent measure of absolute galaxy luminosity, N and showhow it correlates with galaxy properties such as color and velocitydispersion, demonstrating its utility for measuring galaxy distancesthrough large and unknown extinction. Observations in part from theMichigan-Dartmouth-MIT (MDM) Observatory.
| The Morphologies of Dwarf Markarian Galaxies
The morphologies of the 96 dwarf (M(B) -17m) galaxies in the Markariancatalog are determined from the digitized Schmidt plates obtained forthe construction of the Hubble Space Telescope Guide Star Catalog. Thefraction of double nucleus galaxies within the dwarf Markarian galaxiesis determined to be twice that found for all galaxies in the Markariancatalog. In addition to the 12 previously known cases, four definite andtwo probable galaxies with double nuclei are identified. The fraction ofdwarf Markarian galaxies with bright star forming regions is found to betwice that of Virgo cluster dwarf galaxies. No Elliptical galaxies arefound in the sample. Galaxies with blue compact dwarf and S0morphologies are more often found to contain unresolved regions of UVexcess emission. Dwarf Markarian galaxies with different morphologicalstructures and spectral classes are found to have similar FIRproperties.
| On faint companions in the close environment of star-forming dwarf galaxies. Possible external star formation triggers?
We have searched for companion galaxies in the close environment of 98star-forming dwarf galaxies (SFDGs) from field and low densityenvironments, using the NASA Extragalactic Database. Most of thecompanions are dwarf galaxies which due to observational selectioneffects were previously disregarded in environmental studies of SFDGs. Asubsample at low redshift, cz < 2000 km s-1, was chosen topartially eliminate the observational bias against distant dwarfcompanions. We find companion candidates for approximately 30% of theobjects within a projected linear separation s_p <100 kpc and aredshift difference Delta cz < 500 km s-1. The limitedcompleteness of the available data sets, together with thenon-negligible frequency of H I clouds in the vicinity of SFDGsindicated by recent radio surveys, suggest that a considerably largerfraction of these galaxies may be accompanied by low-mass systems. Thiscasts doubt on the hypothesis that the majority of them can beconsidered truly isolated. The velocity differences between companioncandidates and sample SFDGs amount typically to la 250 kms-1, and show a rising distribution towards lower Delta cz.This is similarly found for dwarf satellites of spiral galaxies,suggesting a physical association between the companion candidates andthe sample SFDGs. SFDGs with a close companion do not show significantdifferences in their Hβ equivalent widths and B-V colours ascompared to isolated ones. However, the available data do not allow usto rule out that interactions with close dwarf companions can influencethe star formation activity in SFDGs.
| Molecular gas in blue compact dwarf galaxies
Blue compact dwarf galaxies (BCDGs) are currently undergoing strongbursts of star formation. Nevertheless, only a few of them have beenclearly detected in CO, which is thought to trace the `fuel' of starformation, H2. In this paper we present a deep search for COJ=1->0 and J=2->1 emission lines in a sample of eight BCDGs andtwo companions. Only two of them (Haro 2 and UM 465) are detected. Forthe other galaxies we have obtained more stringent upper limits on theCO luminosity than in previously published values. We could not confirmthe previously reported `detection' of CO for the galaxies UM 456 and UM462. We analyse a possible relation between metallicity, CO luminosityand absolute blue magnitude of the galaxies. We use previouslydetermined relations between X≡N(H2)/ICO andthe metallicity to derive molecular cloud masses or upper limits forthem. With these `global' XCO values we find that, for thegalaxies that we detect in CO, the molecular gas mass is similar to theHi mass, whereas for the non-detections, the upper limits on themolecular gas masses are significantly lower than on the Hi mass. Usingan LVG (large velocity gradient) model we show that XCOdepends not only on metallicity but also on other physical parameters,such as volume density and kinetic temperature, which raises thequestion about the validity of `global' XCO factors.
| H I observations of emission-line galaxies
We present single-dish Lovell telescope H i observations of a sample of67 emission-line and UV-excess galaxies, of which 52 are taken from theUniversity of Michigan (UM) catalogue. In addition, H i observations of24 gas-rich irregular galaxies are presented. We find that emission-linegalaxies are H i-rich with a median H i mass to blue luminosity ratioMHI/LB of ~ 0.45 Msun/Lsun.Within the UM galaxy sample the MHI/LB ratio tendsto increase with decreasing luminosity. Finally, it is found that themost H i-rich UM galaxies are the most metal deficient, implying thatthese objects are less evolved.
| Spectral classification of emission-line galaxies
The main goal of this work is to further investigate the classificationof emission-line galaxies from the ``Spectrophotometric Catalogue of HII galaxies'' by Terlevich et al. (1991) in a homogeneous and objectiveway, using the three line-ratio diagrams, called diagnostic diagrams, ofVeilleux & Osterbrock (1987). On the basis of the resultingcatalogue, we critically discuss the classification methods in theoptical range. In particular we compare our classification scheme to theone done by Rola et al. (1997) which is efficient for the classificationof redshifted galaxies. We also propose a new diagnostic diagraminvolving the known intensity ratio R23=([O II],l 3727+[OIII] l 4959+{[O III] l 5007)/Hb which appears to be a very goodcriterion allowing to discriminate the Seyfert 2 from H ii galaxies. Therevised catalogue including 314 narrow-emission-line galaxies contains HII galaxies, Seyfert 2 galaxies, Low Ionization Nuclear Emission-LineRegions (hereafter LINERs) galaxies and some particular types ofgalaxies with the most intriguing ones, called ``ambiguous'', due to theambiguity of their location in the diagnostic diagrams. These galaxiesappear as H II galaxies and as active galactic nuclei (hereafter AGNs)in different diagrams of Veilleux & Osterbrock and constitutecertainly a sample of particularly interesting candidates for a thoroughstudy of connections between starbursts and AGNs. Available inelectronic form only via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Arcsecond Positions of UGC Galaxies
We 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.
| Study of New Sample of Candidate Blue Compact Dwarf Galaxies. HI Observations of 73 Objects at Nancay Radio Telescope
Not Available
| Photometric studies of some starburst galaxies
We present the results of a detailed morphological analysis of tenstarburst galaxies selected from the Markarian catalog of uv-excessobjects. CCD surface photometry of these galaxies was carried out basedon observations made in B, V (Johnson) and R, I (Kron-Cousins) bandpasses. We present the radial variations of surface brightness,ellipticity, position angle and the colour indices for each galaxyobtained using ellipse fitting isophotal analysis. The residual imagesconstructed for extracting the fine structure are also presented. Avariety of morphological types are found to host the starburstphenomenon. The star formation activity is not confined to the nuclearregion alone, but it also occurs at various locations in the galaxy andis seen as clumpy regions. The colour index and the residual images areused for deriving information about the sites of enhanced star formationactivity and the triggers of the starburst. The luminosity profiles showan exponential behaviour in the outer region. The disk scale lengths andthe half-light radii are derived. The contribution of the burstcomponent has been estimated and the colours of the burst component arepresented. Strong isophotal twisting is detected in all the S0 and Egalaxies: Mrk 1002, Mrk 1308 and Mrk 14, in the sample. This isaccompanied by boxiness in some cases, suggesting that a merger isresponsible for the starburst activity in these galaxies. In case ofisolated spirals, a bar or a central oval distortion appear to be thelikely trigger for the starburst.
| Multi-spectral study of a new sample of Blue Compact Dwarf Galaxies. II. B and R surface photometry of 22 southern objects
We present the results of surface photometry on a new sample of BlueCompact Dwarf galaxies (BCDGs), in continuation to a previous paper(Doublier et al. 1997, hereafter Paper I). The 22 galaxies (plus twocompanions) discussed in the present paper have been selected in theSouthern Hemisphere, from several lists. An atlas containing isophotalmaps, surface brightnesses and B-R color profiles of the sample isgiven, together with the tables containing the photometric parameters.The results are consistent with those obtained in Paper I for objectsselected from the Byurakan Surveys in the Northern hemisphere.Similarly, we find about one fourth of the BCDGs showing a dominantr(1/4) brightness distribution component, one fourth of the BCDG showinga dominant exponential surface brightness profile, and about half ofthem show composite brightness distributions. Integrated properties,colors, mean surface brightnesses and luminosity-radius relations areinvestigated and discussed for the objects presented in this paper andPaper I. We found that r(1/4) BCDGs tend to show a different behaviourcompared to the exponential BCDGs, with respect to colors, compactnessand luminosity-radius relations. We also include a brief study of thesurroundings of the galaxies, where we find several candidatecompanions. Based on observations collected at the 1.54 m DanishTelscope at the European Southern observatory (La Silla, Chile).
| A Complete Redshift Survey to the Zwicky Catalog Limit in a 2^h X 15 deg Region around 3C 273
We compile 1113 redshifts (648 new measurements, 465 from theliterature) for Zwicky catalog galaxies in the region (-3.5d <= delta<= 8.5d, 11h5 <= alpha <= 13h5). We include redshifts for 114component objects in 78 Zwicky catalog multiplets. The redshift surveyin this region is 99.5% complete to the Zwicky catalog limit, m_Zw =15.7. It is 99.9% complete to m_Zw = 15.5, the CfA Redshift Survey(CfA2) magnitude limit. The survey region is adjacent to the northernportion of CfA2, overlaps the northernmost slice of the Las CampanasRedshift Survey, includes the southern extent of the Virgo Cluster, andis roughly centered on the QSO 3C 273. As in other portions of theZwicky catalog, bright and faint galaxies trace the same large-scalestructure.
| A Hubble Space Telescope Imaging Survey of Nearby Active Galactic Nuclei
We have obtained WFPC2 images of 256 of the nearest (z <= 0.035)Seyfert 1, Seyfert 2, and starburst galaxies. Our 500 s broadband(F606W) exposures reveal much fine-scale structure in the centers ofthese galaxies, including dust lanes and patches, bars, rings, wisps,and filaments, and tidal features such as warps and tails. Most of thisfine structure cannot be detected in ground-based images. We haveassigned qualitative classifications for these morphological featuresand a Hubble type for the inner region of each galaxy, and we have alsomeasured quantitative information such as 0."18 and 0."92 aperturemagnitudes, position angles, and ellipticities, where possible. There islittle direct evidence for unusually high rates of interaction in theSeyfert galaxies. Slightly less than 10% of all the galaxies show tidalfeatures or multiple nuclei. The incidence of inner starburst rings isabout 10% in both classes of Seyfert galaxies. In contrast, galaxieswith H II region emission-line spectra appear substantially moreirregular and clumpy because of their much higher rates of current starformation per unit of galactic mass. The presence of an unresolvedcentral continuum source in our Hubble Space Telescope images is avirtually perfect indicator of a Seyfert 1 nucleus as seen byground-based spectroscopy. Fifty-two percent of these Seyfert 1 pointsources are saturated in our images; we use their wings to estimatemagnitudes ranging from 15.8 to 18.5. The converse is not universallytrue, however, as over one-third of Seyferts with direct spectroscopicevidence for broad Balmer wings show no nuclear point source. These 34resolved Seyfert 1's have fainter nonstellar nuclei, which appear to bemore extinguished by dust absorption. Like the Seyfert 2's, they havecentral surface brightnesses consistent with those expected for thebulges of normal galaxies. The rates for the occurrences of bars inSeyfert 1's and 2's and non-Seyferts are the same. We found onesignificant morphological difference between the host galaxies ofSeyfert 1 and Seyfert 2 nuclei. The Seyfert 2 galaxies are significantlymore likely to show nuclear dust absorption, especially in lanes andpatches that are irregular or reach close to the nucleus. A few simpletests show that the difference cannot be explained by different averageredshifts or selection techniques. It is confirmed by our galaxymorphology classifications, which show that Seyfert 1 nuclei reside inearlier type galaxies than Seyfert 2 nuclei. If, as we believe, this isan intrinsic difference in host galaxy properties, it undermines one ofthe postulates of the strong unification hypothesis for Seyfertgalaxies, that they merely appear different because of the orientationof their central engine. The excess galactic dust we see in Seyfert 2'smay cause substantial absorption that obscures their hypothesized broademission line regions and central nonstellar continua. This galacticdust could produce much of the absorption in Seyfert 2 nuclei that hadinstead been attributed to a thick dusty accretion torus forming theouter part of the central engine.
| CO Emission in Low-Luminosity, H I-rich Galaxies
We present ^12CO 1 --> 0 observations of 11 low-luminosity (M_B >-18), H I-rich dwarf galaxies. Only the three most metal-rich galaxies,with 12 + log (O/H) ~ 8.2, are detected. Very deep CO spectra of sixextremely metal-poor systems [12 + log (O/H) <= 7.5] yield only lowupper limits on the CO surface brightness, I_CO < 0.1 K km s^-1.Three of these six have never before been observed in a CO line, whilethe others now have much more stringent upper limits. For the very lowmetallicity galaxy Leo A, we do not confirm a previously reporteddetection in CO, and the limits are consistent with another recentnondetection. We combine these new observations with data from theliterature to form a sample of dwarf galaxies that all have COobservations and measured oxygen abundances. No known galaxies with 12 +log (O/H) < 7.9 (Z < 0.1 Z_ȯ) have been detected in CO. Mostof the star-forming galaxies with higher [12 + log (O/H) > 8.1]metallicities are detected at similar or higher I_CO surfacebrightnesses. The data are consistent with a strong dependence of theI_CO/M_H_2=X_CO conversion factor on ambient metallicity. The strikinglylow upper limits on some metal-poor galaxies lead us to predict that theconversion factor is nonlinear, increasing sharply below ~1/10 of thesolar metallicity [12 + log (O/H) <= 7.9].
| Catalogue of HI maps of galaxies. II. Analysis of the data
We use some of the maps of the catalogue presented in Paper I to providesome evidence for global conditions that must be fulfilled by thegalaxies to have extended hydrogen. For this purpose, we tried to findpossible connections between the HI gas extension and other propertiesof the galaxies (morphological type, surface brightness, gas density,etc.). With isophotal hydrogen diameters of a large sample, we couldobserve that optically smaller galaxies seem to have greater relative HIextensions. By means of the relation with the apparent HI surfacedensity, we found an expression that should provide a rough estimate ofthe gas extension. With respect to the dependence on morphological type,we could not find any significant correlation either for the real HIsurface density or the relative gas extension. Nevertheless, whereas forspiral and irregular galaxies the real HI surface density exhibits abroad range of values, the values are rather lower for elliptical and S0galaxies. Table 1 is also available in electronic form at the CDS viaanonymous ftp 130.79.128.5 or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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
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