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The impact of the visibility of the [OIII]λ4363 line on the general properties of HII galaxies in the Local Universe
We present a statistical study of a very large sample of HII galaxiestaken from the literature. We focus on the differences in severalproperties between galaxies that show the auroral line[OIII]λ4363 and those that do not present this feature in theirspectra. It turns out that objects without this auroral line are moreluminous, are more metal-rich and present a lower ionization degree. Theunderlying population is found to be much more important for objectswithout the [OIII]λ4363 line, and the effective temperature ofthe ionizing star clusters of galaxies not showing the auroral line isprobably lower. We also study the subsample of HII galaxies whoseproperties most closely resemble the properties of theintermediate-redshift population of luminous compact blue galaxies(LCBGs). The objects from this subsample are more similar to the objectsnot showing the [OIII]λ4363 line. It might therefore be expectedthat the intermediate-redshift population of LCBGs is powered by verymassive, yet somewhat aged, star clusters. The oxygen abundance of LCBGswould be greater than the average oxygen abundance of local HIIgalaxies.
| The Structure of the Underlying Stellar Host in Blue Compact Dwarf Galaxies
Nowadays it is well established that BCDs are mostly old systems, as thevast majority of them have an extended low-surface brightness (LSB)stellar host underlying their central starburst component. This hostgenerally extends several kpc from the star-forming (SF) regions, showsregular elliptical isophotes, and displays red colors indicative of anevolved stellar population Papaderos96a,Cairos01a,Cairos01b,Cairos03.
| Unveiling the Nature of the Low Surface Brightness Stellar Host in Blue Compact Dwarf Galaxies
In order to characterize the low surface brightness component in bluecompact dwarf galaxies, we determine their structural parameters foreight objects by fitting a Sérsic law to their B, V, and R lightprofiles. We restrict the fit to the outer regions, excluding thestarburst emission with the help of color and Hα maps. We discussthe problems and the uncertainties involved in fitting the Sérsicmodel, in particular the limited surface brightness interval and thesky-subtraction errors. We show that by carefully selecting the fittedradial range and by performing consistency checks on the fits in thedifferent bands we can derive reliable structural parameters. Allgalaxies but one show very good agreement on the Sérsicparameters in the three bands. Six of these galaxies have Sérsicindexes n very close to 1, while the other two have n~2.5.We compare the distribution of the BCDs with that of dI, dE, and LSBgalaxies in the diagrams built upon the Sérsic parameters. Whileprevious works claimed that BCDs are segregated from the other dwarfs insuch diagrams, here we find that six BCDs occupy the same region as theother dwarf types, while two galaxies have larger n, smallerRe, and brighter μ0. These results indicatethat evolutionary connections between BCDs and the other dwarf classescannot be ruled out.
| Palomar/Las Campanas Imaging Atlas of Blue Compact Dwarf Galaxies. II. Surface Photometry and the Properties of the Underlying Stellar Population
We present the results from an analysis of surface photometry of B, R,and Hα images of a total of 114 nearby galaxies(vhelio<4000 km s-1) drawn from the Palomar/LasCampanas Imaging Atlas of blue compact dwarf (BCD) galaxies. Surfacebrightness and color profiles for the complete sample have beenobtained. We determine the exponential and Sérsic profiles thatbest fit the surface brightness distribution of the underlying stellarpopulation detected in these galaxies. We also compute the (B-R) colorand total absolute magnitude of the underlying stellar population andcompared them to the integrated properties of the galaxies in thesample. Our analysis shows that the (B-R) color of the underlyingpopulation is systematically redder than the integrated color, except inthose galaxies where the integrated colors are strongly contaminated byline and nebular-continuum emission. We also find that galaxies withrelatively red underlying stellar populations [typically (B-R)>=1mag] show structural properties compatible with those of dwarfelliptical galaxies (i.e., a smooth light distribution, fainterextrapolated central surface brightness, and larger scale lengths thanBCD galaxies with blue underlying stellar populations). At least ~15% ofthe galaxies in the sample are compatible with being dwarf elliptical(dE) galaxies experiencing a burst of star formation. For the remainingBCD galaxies in the sample we do not find any correlation between therecent star formation activity and their structural differences withrespect to other types of dwarf galaxies.
| The Molecular Interstellar Medium of Dwarf Galaxies on Kiloparsec Scales: A New Survey for CO in Northern, IRAS-detected Dwarf Galaxies
We present a new survey for CO in dwarf galaxies using the ARO Kitt Peak12 m telescope. This survey consists of observations of the centralregions of 121 northern dwarfs with IRAS detections and no known COemission. We detect CO in 28 of these galaxies and marginally detectanother 16, increasing by about 50% the number of such galaxies known tohave significant CO emission. The galaxies we detect are comparable instellar and dynamical mass to the Large Magellanic Cloud, althoughsomewhat brighter in CO and fainter in the far-IR. Within dwarfs, wefind that the CO luminosity LCO is most strongly correlatedwith the K-band and the far-infrared luminosities. There are also strongcorrelations with the radio continuum (RC) and B-band luminosities andlinear diameter. Conversely, we find that far-IR dust temperature is apoor predictor of CO emission within the dwarfs alone, although a goodpredictor of normalized CO content among a larger sample of galaxies. Wesuggest that LCO and LK correlate well because thestellar component of a galaxy dominates the midplane gravitational fieldand thus sets the pressure and density of the atomic gas, which controlthe formation of H2 from H I. We compare our sample with moremassive galaxies and find that dwarfs and large galaxies obey the samerelationship between CO and the 1.4 GHz RC surface brightness. Thisrelationship is well described by a Schmidt law withΣRC~Σ1.3CO. Therefore,dwarf galaxies and large spirals exhibit the same relationship betweenmolecular gas and star formation rate (SFR). We find that this result isrobust to moderate changes in the RC-to-SFR and CO-to-H2conversion factors. Our data appear to be inconsistent with large (orderof magnitude) variations in the CO-to-H2 conversion factor inthe star-forming molecular gas.
| Optimization of Starburst99 for Intermediate-Age and Old Stellar Populations
We have incorporated the latest release of the Padova models into theevolutionary synthesis code Starburst99. The Padova tracks were extendedto include the full asymptotic giant branch (AGB) evolution until thefinal thermal pulse over the mass range 0.9-5 Msolar. Withthis addition, Starburst99 accounts for all stellar phases thatcontribute to the integrated light of a stellar population witharbitrary age from the extreme-ultraviolet to the near-infrared. AGBstars are important for ages between 0.1 and 2 Gyr, with theircontribution increasing at longer wavelengths. We investigatesimilarities and differences between the model predictions by the Genevaand the Padova tracks. The differences are particularly pronounced atages >1 Gyr, when incompleteness sets in for the Geneva models. Wealso perform detailed comparisons with the predictions of other majorsynthesis codes and find excellent agreement. Our synthesized opticalcolors are compared to observations of old, intermediate-age, and youngpopulations. Excellent agreement is found for the old globular clustersystem of NGC 5128 and for old and intermediate-age clusters in NGC4038/4039. In contrast, the models fail for red supergiant-dominatedpopulations with subsolar abundances. This failure can be traced back toincorrect red supergiant parameters in the stellar evolutionary tracks.Our models and the synthesis code are publicly available as version 5.0of Starburst99 at http://www.stsci.edu/science/starburst99.
| New insights to the photometric structure of Blue Compact Dwarf Galaxies from deep near-infrared studies. II. The sample of northern BCDs
This paper is part of a series of publications which present asystematic study of Blue Compact Dwarf (BCD) Galaxies in the nearinfrared (NIR). Compared to the visible light, NIR data allow a betterseparation of the starburst emission from the light distribution of theold stellar low-surface brightness (LSB) host galaxy. We analyze deepNIR broad band images of a sample of 11 BCDs, observed with the CalarAlto 3.6 m telescope. This work enlarges the samples presented inpreceding papers of this study (Noeske et al. \cite{Noeske2003},A&A, 410, 481; Cairós et al. \cite{c03a}, ApJ, 593, 312) byBCDs of the most common morphological type, displaying a regularelliptical LSB host galaxy. The data presented here allow the detectionand quantitative study of the extended stellar LSB host galaxy in allsample BCDs. The NIR surface brightness profiles (SBPs) of the LSB hostgalaxies agree at large galactocentric radii with those from opticalstudies, showing also an exponential intensity decrease and compatiblescale lengths. Similar to Noeske et al. (\cite{Noeske2003}), we findcentrally flattening exponential (type V) SBPs of the host galaxy forseveral BCDs. Such SBPs remain mostly undetected in optical bands, dueto the comparatively stronger starburst emission at these wavelengths.We apply a modified exponential distribution to decompose andquantitatively analyze SBPs of LSB hosts with a type V intensitydistribution. We present the results of the surface photometry and thedecomposition of SBPs, and discuss individual objects with respect tomorphological details of their star-forming regions.Table 2 is also available in electronic form 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/429/115Figures 2 to 11 are only available in electronic form athttp://www.edpsciences.orgGerman-Spanish Astronomical Center, Calar Alto, operated by theMax-Planck-Institute for Astronomy, Heidelberg, jointly with the SpanishNational Commission for Astronomy.
| Catalog of Double Nucleus Disk Galaxies
We have compiled a catalog of disk galaxies that have a double nucleus,through systematic examination of existing catalogs and publications.The Catalog of Double Nucleus Disk Galaxies includes 107 objects,together with their basic data. The aim of the catalog is to provide amore systematic and homogeneous basis for the study of the relevance ofgalaxy interactions and minor mergers in the formation of these doublenuclei. We have also investigated possible correlations betweengeometric and photometric parameters of the double nuclei and their hostgalaxies. The preliminary results indicate the presence of severalsignificant correlations that should be considered in any theoreticalscenario describing minor mergers and disk galaxy evolution.
| Infrared Observations of Galaxies in the Local Universe. II. 391 Calibrated Images with Photometric and Structural Measurements
This paper presents empirical results from a deep imaging survey ofgalaxies in the local universe at the J and Ks wavelengths.Three hundred ninety-one images have been obtained and calibrated usingthe same camera and filter set with the Steward Observatory 1.6 m KuiperTelescope on Mount Bigelow and the 2.3 m Bok Telescope on Kitt Peak. Thelimiting magnitude is typically 22 mag arcsec-1 at J and 21mag arcsec-1 at Ks. The central surfacebrightness, apparent magnitudes, sizes, scale lengths, and inclinationsare tabulated from measurements made using these data. The purpose ofthis paper is to provide basic near-infrared data on a variety of galaxytypes.
| 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.
| Deep Near-Infrared Mapping of Young and Old Stars in Blue Compact Dwarf Galaxies
We analyze J, H, and Ks near-infrared data for nine bluecompact dwarf (BCD) galaxies, selected from a larger sample that we havealready studied in the optical. We present contour maps, surfacebrightness and color profiles, and color maps of the sample galaxies.The morphology of the BCDs in the near-infrared (NIR) has been found tobe basically the same as in the optical. The inner regions of thesesystems are dominated by the starburst component. At low surfacebrightness levels the emission is due to the underlying host galaxy; thelatter is characterized by red, radially constant colors and isophoteswell fitted by ellipses. We derive accurate optical-NIR host galaxycolors for eight of the sample galaxies; these colors are typical of anevolved stellar population. Interestingly, optical-NIR color maps revealthe presence of a complex, large-scale absorption pattern in three ofthe sample galaxies. We study the applicability of the Sérsic lawto describe the surface brightness profiles of the underlying hostgalaxy and find that, because of the limited surface brightness intervalover which the fit can be made, the derived Sérsic parameters arevery sensitive to the selected radial interval and to errors in the skysubtraction. Fitting an exponential model gives generally more stableresults and can provide a useful tool to quantify the structuralproperties of the host galaxy and compare them with those of other dwarfclasses, as well as with those of star-forming dwarfs at higherredshifts.
| New insights to the photometric structure of Blue Compact Dwarf galaxies from deep Near-Infrared studies. I. Observations, surface photometry and decomposition of surface brightness profiles
We have analyzed deep Near Infrared (NIR) broad band images for a sampleof Blue Compact Dwarf Galaxies (BCDs), observed with the ESO NTT andCalar Alto 3.6 m telescopes. The data presented here allows for thedetection and quantitative study of the extended stellar low-surfacebrightness (LSB) host galaxy in all sample BCDs. NIR surface brightnessprofiles (SBPs) of the LSB host galaxies agree at large galactocentricradii with those from optical studies, showing also an exponentialintensity decrease and compatible scale lengths. At small tointermediate radii (within 1-3 exponential scale lengths), however, theNIR data reveals for more than one half of our sample BCDs evidence fora significant flattening of the exponential profile of the LSBcomponent. Such profiles (type V SBPs, Binggeli & Cameron\cite{binggeli91}) have rarely been detected in the LSB component ofBCDs at optical wavelengths, where the relative flux contribution of thestarburst, being stronger than in the NIR, can readily hide a possiblecentral intensity depression in the underlying LSB host. The structuralproperties, frequency and physical origin of type V LSB profiles in BCDsand dwarf galaxies in general have not yet been subject to systematicstudies. Nevertheless, the occurrence of such profiles in an appreciablefraction of BCDs would impose important new observational constraints tothe radial mass distribution of the stellar LSB component, as well as tothe photometric fading of these systems after the termination ofstar-forming activities. We test the suitability of two empiricalfitting functions, a modified exponential distribution (Papaderos et al.\cite{papaderos96a}) and the Sérsic law, for the systematizationof the structural properties of BCD host galaxies which show a type Vintensity distribution. Either function has been found to satisfactorilyfit a type V distribution. However, it is argued that the practicalapplicability of Sérsic fits to the LSB emission of BCDs islimited by the extreme sensitivity of the achieved solutions to, e.g.,small uncertainties in the sky subtraction and SBP derivation. We findthat most of the sample BCDs show in their stellar LSB host galaxyoptical-NIR colors indicative of an evolved stellar population withsubsolar metallicity. Unsharp-masked NIR maps reveal numerousmorphological details and indicate in some cases, in combination withoptical data, appreciable non-uniform dust absorption on a spatial scaleas large as ~ 1 kpc.European Southern Observatory, program ID 65.N-0318(A).German-Spanish Astronomical Center, Calar Alto, operated by theMax-Planck-Institute for Astronomy, Heidelberg, jointly with the SpanishNational Commission for Astronomy.
| Spectrophotometric Observations of Blue Compact Dwarf Galaxies: Markarian 370
We present results from a detailed spectrophotometric analysis of theblue compact dwarf galaxy (BCD) Mrk 370, based on deep UBVRI broadbandand Hα narrowband observations, and on long-slit andtwo-dimensional spectroscopy of its brightest knots. The spectroscopicdata are used to derive the internal extinction and to computemetallicities, electronic density, and temperature in the knots. Bysubtracting the contribution of the underlying older stellar population,modeled by an exponential function, removing the contribution fromemission lines, and correcting for extinction, we can measure the truecolors of the young star-forming knots. We show that the colors obtainedthis way differ significantly from those derived without the abovecorrections and lead to different estimates of the ages and star-forminghistory of the knots. Using predictions of evolutionary synthesismodels, we estimate the ages of both the starburst regions and theunderlying stellar component. We found that we can reproduce the colorsof all the knots with an instantaneous burst of star formation and theSalpeter initial mass function (IMF) with an upper mass limit of 100Msolar. The resulting ages range between 3 and 6 Myr. Thecolors of the low surface brightness component are consistent with ageslarger than 5 Gyr. The kinematic results suggest ordered motion aroundthe major axis of the galaxy.
| 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.
| The blue compact dwarf galaxy I Zw 18: A comparative study of its low-surface-brightness component
Using HST and ground-based optical and NIR imaging data we investigatewhether the blue compact dwarf (BCD) galaxy I Zw 18 possesses anextended low-surface-brightness (LSB) old stellar population underlyingits star-forming regions, as is the case in the majority of BCDs. Thisquestion is central to the long-standing debate on the evolutionarystate of I Zw 18. We show that the exponential intensity decreaseobserved in the filamentary LSB envelope of the BCD out to ga 18 arcsec(ga 1.3 kpc assuming a distance of 15 Mpc) is not due to an evolvedstellar disc underlying its star-forming regions, but rather, due toextended ionized gas emission. Ionized gas accounts for more than 80% ofthe line-of-sight emission at a galactocentric distance of ~ 0.65 kpc (~ 3 effective radii), and for ga 30% to 50% of the R light of the mainbody of I Zw 18. Broad-band images reveal, after subtraction of nebularline emission, a relatively smooth stellar host extending slightlybeyond the star-forming regions. This unresolved stellar component,though very compact, is not exceptional for intrinsically faint dwarfswith respect to its structural properties. However, being blue over aradius range of ~ 5 exponential scale lengths and showing little colourcontrast to the star-forming regions, it differs strikingly from the redLSB host of standard BCDs. This fact, together with the comparably bluecolours of the faint C component, ~ 1.6 kpc away from the main body of IZw 18, suggests that the formation of I Zw 18 as a whole has occurredwithin the last 0.5 Gyr, making it a young BCD candidate. Furthermore,we show that the ionized envelope of I Zw 18 is not exceptional amongstar-forming dwarf galaxies, neither by its exponential intensityfall-off nor by its scale length. However, contrary to evolved BCDs, thestellar LSB component of I Zw 18 is much more compact than the ionizedgas envelope. In the absence of an appreciable underlying stellarpopulation, extended ionized gas emission dominates in the outer partsof I Zw 18, mimicking an exponential stellar disc on optical surfacebrightness profiles. Based on observations with the NASA/ESA HubbleSpace Telescope, obtained at the Space Telescope Science Institute,which is operated by AURA, Inc., under NASA contract No. NAS 5-26555.Obtained at the German-Spanish Astronomical Center, Calar Alto, operatedby the Max-Planck-Institute for Astronomy, Heidelberg, jointly with theSpanish National Commission for Astronomy. Obtained at the Kitt PeakNational Observatory, operated by the Association of Universities forResearch in Astronomy, Inc., under cooperative agreement with theNational Science Foundation.
| Rotation curves and metallicity gradients from HII regions in spiral galaxies
In this paper we study long slit spectra in the region of Hαemission line of a sample of 111 spiral galaxies with recognizable andwell defined spiral morphology and with a well determined environmentalstatus, ranging from isolation to non-disruptive interaction withsatellites or companions. The form and properties of the rotation curvesare considered as a function of the isolation degree, morphological typeand luminosity. The line ratios are used to estimate the metallicity ofall the detected HII regions, thus producing a composite metallicityprofile for different types of spirals. We have found that isolatedgalaxies tend to be of later types and lower luminosity than theinteracting galaxies. The outer parts of the rotation curves of isolatedgalaxies tend to be flatter than in interacting galaxies, but they showsimilar relations between global parameters. The scatter of theTully-Fisher relation defined by isolated galaxies is significantlylower than that of interacting galaxies. The [NII]/Hα ratios, usedas a metallicity indicator, show a clear trend between Z andmorphological type, t, with earlier spirals showing higher ratios; thistrend is tighter when instead of t the gradient of the inner rotationcurve, G, is used; no trend is found with the change in interactionstatus. The Z-gradient of the disks depends on the type, being almostflat for early spirals, and increasing for later types. The[NII]/Hα ratios measured for disk HII regions of interactinggalaxies are higher than for normal/isolated objects, even if all thegalaxy families present similar distributions of Hα EquivalentWidth. Tables 3 and 4 and Figs. 6, 7 and 21 are only available inelectronic form at http://www.edpsciences.org. Table 5 is only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/389 Based on dataobtained Asiago/Ekar Observatory. Also based on observations made withINT operated on the island of La Palma by ING in the SpanishObservatorio del Roque de Los Muchachos of the Instituto deAstrofísica de Canarias.
| Two-Dimensional Spectroscopy of BCDs: MRK 370
Not Available
| Spectrophotometric Observations of Blue Compact Dwarf Galaxies: Mkn 370, Mkn 600 and Mkn 36
Not Available
| Multiband Analysis of a Sample of Blue Compact Dwarf Galaxies. II. Spatially Resolved and Integrated Photometry
This is the second in a series of papers devoted to the study of asample of 28 blue compact dwarf galaxies (BCDs). In the first paper, wepresented the broadband observations in B, V, R, and I. Deep contourmaps, surface-brightness profiles, and color profiles were used toanalyze and discuss their morphology and structure. Here, we present newU-band and Hα observations. We compute isophotal and asymptoticmagnitudes of the sample galaxies and total Hα fluxes. Comparisonwith previous works is done to assess the quality of the data availablefor BCDs. Finally, we produce an atlas of detailed color and Hαmaps, the first systematic atlas of this kind published so far. The highquality of the data allows us to identify the different star-formingknots in the maps and to discriminate between them and the regions wherestar formation activity has already ceased. We supplement the atlas witha morphological description of each galaxy and group the galaxies infour classes according to the distribution of their star-formingregions.
| Multiband Analysis of a Sample of Blue Compact Dwarf Galaxies. I. Surface Brightness Distribution, Morphology, and Structural Parameters
Broadband observations in B, V, R, and I have been performed for asample of 28 galaxies cataloged as blue compact dwarf galaxies (BCDs).Our deep imaging, reaching surface brightness levels of a few percent ofthe sky brightness, has allowed the detection of underlying emission orlow surface brightness features for a substantial fraction of thesample. In this paper we present the first results of the program: deepcontour maps in the B band, surface brightness profiles, and colorprofiles for all the galaxies. The information derived for this sampleof galaxies has allowed us to analyze the morphology and the structuralcomponents of BCDs. Over 70% of the galaxies show complex profiles thatpreclude fitting by a single standard law, with extra structure at highto intermediate intensity levels. In 21 galaxies of the sample, anunderlying low surface brightness component has been detected.
| Multiband Analysis of a Sample of Blue Compact Dwarf Galaxies
We present preliminary results of the surface photometry of a sample ofblue compact dwarf galaxies (BCDGs). A total of 28 galaxies have beenobserved in the BVRI bands. From these data the contour maps and surfacebrightness distributions in each band have been built. Contour maps andsurface profiles of the 22 galaxies already analysed are presented,together with preliminary conclusions regarding their morphology andstructural components.
| 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.
| INTEGRAL: A Simple and Friendly Integral Field Unit Available at the WHT
Integral-field spectroscopy (IFS) has merited much attention in recentyears due to its advantages with respect to classical sequential 2-Dspectroscopic techniques (e.g., long-slit scans, Fabry-Perot) whenstudying relatively small extended objects. IFS is able tosimultaneously obtain a spectrum for each spatial sample of atwo-dimensional field.
| Galaxy Structural Parameters: Star Formation Rate and Evolution with Redshift
Not Available
| 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.
| Galaxy Structural Parameters: Star Formation Rate and Evolution with Redshift
The evolution of the structure of galaxies as a function of redshift isinvestigated using two parameters: the metric radius of the galaxy(R_eta) and the power at high spatial frequencies in the disk of thegalaxy (chi). A direct comparison is made between nearby (z~0) anddistant (0.2<~z<~1) galaxies by following a fixed range in restframe wavelengths. The data of the nearby galaxies comprise 136broadband images at ~4500 Å observed with the 0.9 m telescope atKitt Peak National Observatory (23 galaxies) and selected from thecatalog of digital images of Frei et al. (113 galaxies). Thehigh-redshift sample comprises 94 galaxies selected from the Hubble DeepField (HDF) observations with the Hubble Space Telescope using the WideField Planetary Camera 2 in four broad bands that range between ~3000and ~9000 Å (Williams et al.). The radius is measured from theintensity profile of the galaxy using the formulation of Petrosian, andit is argued to be a metric radius that should not depend very stronglyon the angular resolution and limiting surface brightness level of theimaging data. It is found that the metric radii of nearby and distantgalaxies are comparable to each other. The median value of the radius ofthe local sample is ~5+/-1 kpc, and the median radius ofthe HDF sample is ~6+/-2 kpc for q_0=0.5, H_0=65 km s^-1Mpc^-1 however, for q_0=0.1, ~7 kpc and for q_0=1,~5 kpc. In the HDF, galaxies with redshifts larger thanz>0.6 have flatter R_eta distributions than galaxies with redshiftssmaller than z<=0.6. However, the median R_eta values of high- andlow-redshift galaxies are consistent with each other. This result isconsistent with the simulations of galaxy images at redshifts z=0.35,z=0.5, and z=0.9, which show that the metric sizes can be recoveredwithin +/-2 kpc. The flocculency or power at high spatial frequencies isquantified using a simple method that is based on surface photometry inone band and that depends on the size of the star-forming regions and onthe intensity profile of the galaxy. In nearby galaxies, the flocculencyis found to trace the star formation rate as chi is correlated withoptical colors (B-V) and the strength of the hydrogen recombinationlines (Hα). In the HDF, galaxies at redshifts smaller than z~1 andwith fluxes brighter than B=25 have values of chi similar to what ismeasured in nearby galaxies and to what is expected from simulations ofdistant galaxy images. Among the HDF galaxies, I find that at most 4%can be identified as dwarf galaxies with rates of star formation similarto NGC 4449 and NGC 1569. Most HDF galaxies are giants with starformation rates similar to those in nearby giant galaxies. In summary,in this study I have introduced a method to measure the metric sizes andflocculency of the two-dimensional light distribution of galaxies. As aresult, I find that the high spatial frequency power is related to thestar formation rate. Further, I find that the sizes and power at highspatial frequencies of HDF galaxies remain largely unchanged between thepresent epoch and redshifts lower than z~1.
| Infrared Observations of Galaxies in the Local Universe. I. The Survey and Some Representative Results
This paper introduces a continuing survey of galaxies in the localuniverse. Consistent deep images are being acquired for a representativesample of 321 galaxies in the Uppsala General Catalogue down to 21.7 magarcsec-2 at Ks (2.16 mu m) and 22.4 mag arcsec-2 at J (1.25 mu m) usinga NICMOS camera with a 3.'8 x 3.'8 field of view attached to the 61 inch(1.5 m) telescope on Mount Bigelow. We provide some examples of theresults being obtained by employing 64 deep images of a subset of 44galaxies. Bulge-to-disk ratios are tabulated for 30 galaxies. Thebrightness of the central region of 44 galaxies declines approximately 5mag from Hubble type S0 to Sm. An exponential vertical scale height atKs is found to be 500 pc for the disk of UGC 5173. Arm amplitudes offour nearly face-on spiral galaxies are found to range between 11% and88% compared to the interarm region. There is some evidence that the armamplitude is larger at Ks than it is at J. Color gradients are measuredfor 15 galaxies with only one showing a significant nonzero result. Ameasurement of galactic symmetry applied to 64 deep images reveals anaverage asymmetry of 7.6% ( sigma = 4.6%) for these galaxies.
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| Relationship of Markarian galaxies with their surroundings.
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