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HI content in galaxies in loose groups
Gas deficiency in cluster spirals is well known and ram-pressurestripping is considered the main gas removal mechanism. In some compactgroups too gas deficiency is reported. However, gas deficiency in loosegroups is not yet well established. Lower dispersion of the membervelocities and the lower density of the intragroup medium in small loosegroups favour tidal stripping as the main gas removal process in them.Recent releases of data from the HI Parkes All-Sky Survey (HIPASS) andcatalogues of nearby loose groups with associated diffuse X-ray emissionhave allowed us to test this notion. In this paper, we address thefollowing questions: (i) do galaxies in groups with diffuse X-rayemission statistically have lower gas content compared to the ones ingroups without diffuse X-ray emission? (ii) does HI deficiency vary withthe X-ray luminosity, LX, of the loose group in a systematicway? We find that (i) galaxies in groups with diffuse X-ray emission, onaverage, are HI deficient, and have lost more gas compared to those ingroups without X-ray emission; the latter are found not to havesignificant HI deficiency; (ii) no systematic dependence of the HIdeficiency with LX is found. Ram-pressure-assisted tidalstripping and evaporation by thermal conduction are the two possiblemechanisms to account for this excess gas loss.
| The evolution of actively star-forming galaxies in the mid-infrared
In this paper we analyze the evolution of actively star-forming galaxiesin the mid-infrared (MIR). This spectral region, characterized bycontinuum emission by hot dust and by the presence of strong emissionfeatures generally ascribed to polycyclic aromatic hydrocarbon (PAH)molecules, is the most strongly affected by the heating processesassociated with star formation and/or active galactic nuclei (AGNs).Following the detailed observational characterization of galaxies in theMIR by the Infrared Space Observatory (ISO), we have updated themodelling of this spectral region in our spectrophotometric modelGRASIL. In the diffuse component we have updated the treatment of PAHsaccording to the model by Li & Draine. As for the dense phase of theinterstellar medium associated with the star-forming regions, themolecular clouds, we strongly decrease the abundance of PAHs as comparedto that in the cirrus, based on the observational evidence of the lackor weakness of PAH bands close to the newly formed stars, possibly dueto the destruction of the molecules in strong ultraviolet fields. Therobustness of the model is checked by fitting near-infrared to radiobroad-band spectra and the corresponding detailed MIR spectra of a largesample of galaxies, at once. With this model, we have analyzed thelarger sample of actively star-forming galaxies by Dale et al. We showthat the observed trends of galaxies in the ISO-IRAS-radio colour-colourplots can be interpreted in terms of the different evolutionary phasesof star formation activity, and the consequent different dominance inthe spectral energy distribution of the diffuse or dense phase of theISM. We find that the observed colours indicate a surprising homogeneityof the starburst phenomenon, allowing only a limited variation of themost important physical parameters, such as the optical depth of themolecular clouds, the time-scale of the escape of young stars from theirfor mation sites, and the gas consumption time-scale. In this paper wedo not attempt to reproduce the far-infrared coolest region in thecolour-colour plots, as we concentrate on models meant to reproduceactive star-forming galaxies, but we discuss possible requirements of amore complex modelling for the coldest objects.
| The Distribution of Bar and Spiral Arm Strengths in Disk Galaxies
The distribution of bar strengths in disk galaxies is a fundamentalproperty of the galaxy population that has only begun to be explored. Wehave applied the bar-spiral separation method of Buta and coworkers toderive the distribution of maximum relative gravitational bar torques,Qb, for 147 spiral galaxies in the statistically well-definedOhio State University Bright Galaxy Survey (OSUBGS) sample. Our goal isto examine the properties of bars as independently as possible of theirassociated spirals. We find that the distribution of bar strengthdeclines smoothly with increasing Qb, with more than 40% ofthe sample having Qb<=0.1. In the context of recurrent barformation, this suggests that strongly barred states are relativelyshort-lived compared to weakly barred or nonbarred states. We do notfind compelling evidence for a bimodal distribution of bar strengths.Instead, the distribution is fairly smooth in the range0.0<=Qb<0.8. Our analysis also provides a first look atspiral strengths Qs in the OSUBGS sample, based on the sametorque indicator. We are able to verify a possible weak correlationbetween Qs and Qb, in the sense that galaxies withthe strongest bars tend to also have strong spirals.
| Bar-induced perturbation strengths of the galaxies in the Ohio State University Bright Galaxy Survey - I
Bar-induced perturbation strengths are calculated for a well-definedmagnitude-limited sample of 180 spiral galaxies, based on the Ohio StateUniversity Bright Galaxy Survey. We use a gravitational torque method,the ratio of the maximal tangential force to the mean axisymmetricradial force, as a quantitative measure of the bar strength. Thegravitational potential is inferred from an H-band light distribution byassuming that the M/L ratio is constant throughout the disc. Galaxiesare deprojected using orientation parameters based on B-band images. Inorder to eliminate artificial stretching of the bulge, two-dimensionalbar-bulge-disc decomposition has been used to derive a reliable bulgemodel. This bulge model is subtracted from an image, the disc isdeprojected assuming it is thin, and then the bulge is added back byassuming that its mass distribution is spherically symmetric. We findthat removing the artificial bulge stretch is important especially forgalaxies having bars inside large bulges. We also find that the massesof the bulges can be significantly overestimated if bars are not takeninto account in the decomposition.Bars are identified using Fourier methods by requiring that the phasesof the main modes (m= 2, m= 4) are maintained nearly constant in the barregion. With such methods, bars are found in 65 per cent of the galaxiesin our sample, most of them being classified as SB-type systems in thenear-infrared by Eskridge and co-workers. We also suggest that as muchas ~70 per cent of the galaxies classified as SAB-types in thenear-infrared might actually be non-barred systems, many of them havingcentral ovals. It is also possible that a small fraction of the SAB-typegalaxies have weak non-classical bars with spiral-like morphologies.
| Classification of Spectra from the Infrared Space Observatory PHT-S Database
We have classified over 1500 infrared spectra obtained with the PHT-Sspectrometer aboard the Infrared Space Observatory according to thesystem developed for the Short Wavelength Spectrometer (SWS) spectra byKraemer et al. The majority of these spectra contribute to subclassesthat are either underrepresented in the SWS spectral database or containsources that are too faint, such as M dwarfs, to have been observed byeither the SWS or the Infrared Astronomical Satellite Low ResolutionSpectrometer. There is strong overall agreement about the chemistry ofobjects observed with both instruments. Discrepancies can usually betraced to the different wavelength ranges and sensitivities of theinstruments. Finally, a large subset of the observations (~=250 spectra)exhibit a featureless, red continuum that is consistent with emissionfrom zodiacal dust and suggest directions for further analysis of thisserendipitous measurement of the zodiacal background.Based on observations with the Infrared Space Observatory (ISO), aEuropean Space Agency (ESA) project with instruments funded by ESAMember States (especially the Principle Investigator countries: France,Germany, Netherlands, and United Kingdom) and with the participation ofthe Institute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA).
| Deprojecting spiral galaxies using Fourier analysis. Application to the Ohio sample
We use two new methods developed recently (Barberàet al.\cite{bar03}, A&A, 415, 849), as well as information obtained fromthe literature, to calculate the orientation parameters of the spiralgalaxies in the Ohio State University Bright Galaxy Survey. We comparethe results of these methods with data from the literature, and find ingeneral good agreement. We provide a homogeneous set of mean orientationparameters which can be used to approximately deproject the disks of thegalaxies and facilitate a number of statistical studies of galaxyproperties.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/421/595
| Infrared Emission of Normal Galaxies from 2.5 to 12 Micron: Infrared Space Observatory Spectra, Near-Infrared Continuum, and Mid-Infrared Emission Features
We present ISOPHOT spectra of the regions 2.5-4.9 μm and 5.8-11.6μm for a sample of 45 disk galaxies from the US Infrared SpaceObservatory Key Project on Normal Galaxies. The galaxies were selectedto span the range in global properties of normal, star-forming diskgalaxies in the local universe. The spectra can be decomposed into threespectral components: (1) continuum emission from stellar photospheres,which dominates the near-infrared (NIR; 2.5-4.9 μm) spectral region;(2) a weak NIR excess continuum, which has a color temperature of~103 K, carries a luminosity of a few percent of the totalfar-infrared (FIR) dust luminosity LFIR and most likelyarises from the interstellar medium (ISM); and (3) the well-known broademission features at 6.2, 7.7, 8.6, and 11.3 μm, which are generallyattributed to aromatic carbon particles. These aromatic features inemission (AFEs) dominate the mid-infrared (MIR; 5.8-11.6 μm) part ofthe spectrum and resemble the so-called type A spectra observed in manynonstellar sources and the diffuse ISM in our own Galaxy. The fewnotable exceptions include NGC 4418, where a dust continuum replaces theAFEs in MIR, and NGC 1569, where the AFEs are weak and the strongestemission feature is [S IV] 10.51 μm. The relative strengths of theAFEs vary by 15%-25% among the galaxies. However, little correlation isseen between these variations and either IRAS 60 μm/100 μm fluxdensity ratio R(60/100) or the FIR/blue luminosity ratioLFIR/LB, two widely used indicators of the currentstar formation activity, suggesting that the observed variations are nota consequence of the radiation field differences among the galaxies. Wedemonstrate that the NIR excess continuum and AFE emission arecorrelated, suggesting that they are produced by similar mechanisms andsimilar (or the same) material. On the other hand, as the current starformation activity increases, the overall strengths of the AFEs and theNIR excess continuum drop significantly with respect to that of the FIRemission from large dust grains. In particular, the summed luminosity ofthe AFEs falls from ~0.2 LFIR for the most ``IR-quiescent''galaxies to ~0.1 LFIR for the most ``IR-active'' galaxies.This is likely a consequence of the preferential destruction in intenseradiation fields of the small carriers responsible for the NIR/AFEemission.Based on observations with ISO, an ESA project with instruments fundedby ESA member states (especially the PI countries, France, Germany, theNetherlands, and the United Kingdom) and with the participation of ISASand NASA.
| Near-Infrared and Optical Morphology of Spiral Galaxies
We announce the initial release of data from the Ohio State University(OSU) Bright Spiral Galaxy Survey, a BVRJHK imaging survey of awell-defined sample of 205 bright, nearby spiral galaxies. We presentH-band morphological classification on the Hubble sequence for the OSUSurvey sample. We compare the H-band classification to B-bandclassification from our own images and from standard galaxy catalogs.Our B-band classifications match well with those of the standardcatalogs. On average, galaxies with optical classifications from Sathrough Scd appear about one T type earlier in the H band than in the Bband, but with large scatter. This result does not support recent claimsmade in the literature that the optical and near-IR morphologies ofspiral galaxies are uncorrelated. We present detailed descriptions ofthe H-band morphologies of our entire sample, as well as B- and H-bandimages for a set of 17 galaxies chosen as type examples and BRHcolor-composite images of six galaxies chosen to demonstrate the rangein morphological variation as a function of wavelength. Based partiallyon observations obtained at the Cerro Tololo Inter-American Observatory,operated by the Association of Universities for Research in Astronomy(AURA), Inc., under cooperative agreement with the National ScienceFoundation.
| Arm Structure in Anemic Spiral Galaxies
Anemic galaxies have less prominent star formation than normal galaxiesof the same Hubble type. Previous studies showed they are deficient intotal atomic hydrogen but not in molecular hydrogen. Here we compare thecombined surface densities of H I and H2 at mid-disk radiiwith the Kennicutt threshold for star formation. The anemic galaxies arebelow the threshold, which explains their lack of prominent starformation, but they are not much different than other early-typegalaxies, which also tend to be below threshold. The spiral waveamplitudes of anemic and normal galaxies were also compared, usingimages in B and J passbands from the OSU Bright Spiral Galaxy Survey.Anemic galaxies have normal spiral wave properties too, with the sameamplitudes and radial dependencies as other galaxies of the same armclass. Because of the lack of gas, spiral waves in early-type galaxiesand anemics do not have a continuous supply of stars with low velocitydispersions to maintain a marginally stable disk. As a result, they areeither short lived, evolving toward lenticulars and S0 types in only afew rotations at mid-disk, or they are driven by the asymmetriesassociated with gas removal in the cluster environment.
| Far-Infrared Spectroscopy of Normal Galaxies: Physical Conditions in the Interstellar Medium
The most important cooling lines of the neutral interstellar medium(ISM) lie in the far-infrared (FIR). We present measurements by theInfrared Space Observatory Long Wavelength Spectrometer of seven linesfrom neutral and ionized ISM of 60 normal, star-forming galaxies. Thegalaxy sample spans a range in properties such as morphology, FIR colors(indicating dust temperature), and FIR/blue ratios (indicating starformation activity and optical depth). In two-thirds of the galaxies inthis sample, the [C II] line flux is proportional to FIR dust continuum.The other one-third show a smooth decline inL[CII]/LFIR with increasing Fν(60μm)/Fν(100 μm) and LFIR/LB,spanning a range of a factor of more than 50. Two galaxies at the warmand active extreme of the range haveL[CII]/LFIR<2×10-4 (3 σupper limit). This is due to increased positive grain charge in thewarmer and more active galaxies, which leads to less efficient heatingby photoelectrons from dust grains. The ratio of the two principalphotodissociation region (PDR) cooling linesL[OI]/L[CII] shows a tight correlation withFν(60 μm)/Fν(100 μm), indicating thatboth gas and dust temperatures increase together. We derive atheoretical scaling between [N II] (122 μm) and [C II] from ionizedgas and use it to separate [C II] emission from neutral PDRs and ionizedgas. Comparison of PDR models of Kaufman et al. with observed ratios of(1) L[OI]/L[CII] and(L[CII]+L[OI])/LFIR and (2)L[OI]/LFIR and Fν(60μm)/Fν(100 μm) yields far-UV flux G0 andgas density n. The G0 and n values estimated from the twomethods agree to better than a factor of 2 and 1.5, respectively, inmore than half the sources. The derived G0 and n correlatewith each other, and G0 increases with n asG0~nα, where α~1.4 . We interpret thiscorrelation as arising from Strömgren sphere scalings if much ofthe line and continuum luminosity arises near star-forming regions. Thehigh values of PDR surface temperature (270-900 K) and pressure(6×104-1.5×107 K cm-3)derived also support the view that a significant part of grain and gasheating in the galaxies occurs very close to star-forming regions. Thedifferences in G0 and n from galaxy to galaxy may be due todifferences in the physical properties of the star-forming clouds.Galaxies with higher G0 and n have larger and/or denserstar-forming clouds.
| Homogenization of the Stellar Population along Late-Type Spiral Galaxies
We present a study of the broadband UBV color profiles for 257 Sbcbarred and nonbarred galaxies, using photoelectric aperture photometrydata from the literature. Using robust statistical methods, we haveestimated the color gradients of the galaxies, as well as the total andbulge mean colors. A comparative photometric study using CCD images wasdone. In our sample, the color gradients are negative (reddish inward)in approximately 59% of the objects, are almost null in 27%, and arepositive in 14%, considering only the face-on galaxies, which representapproximately 51% of the sample. The results do not change, essentially,when we include the edge-on galaxies. As a consequence of this study wehave also found that barred galaxies are overrepresented among theobjects having null or positive gradients, indicating that bars act as amechanism of homogenization of the stellar population. This effect ismore evident in the U-B color index, although it can also be detected inthe B-V color. A correlation between the total and bulge colors wasfound that is a consequence of an underlying correlation between thecolors of bulges and disks found by other authors. Moreover, the meantotal color is the same irrespective of the gradient regime, whilebulges are bluer in galaxies with null or positive gradients, whichindicates an increase of the star formation rate in the central regionsof these objects. We have also made a quantitative evaluation of theamount of extinction in the center of these galaxies. This was doneusing the Wide Field Planetary Camera 2 (WFPC2) and the Near InfraredCamera and Multi-Object Spectrometer (NICMOS) Hubble Space Telescope(HST) archival data, as well as CCD B, V, and I images. We show thatalthough the extinction in the V-band can reach values up to 2 mag inthe central region, it is unlikely that dust plays a fundamental role inglobal color gradients. We found no correlation between color and O/Habundance gradients. This result could suggest that the color gradientsare more sensitive to the age rather than to the metallicity of thestellar population. However, the absence of this correlation may becaused by dust extinction. We discuss this result by considering apicture in which bars are a relatively fast, recurrent phenomenon. Theseresults are not compatible with a pure classical monolithic scenario forbulge and disk formation. On the contrary, they favor a scenario inwhich both these components are evolving in a correlated process inwhich stellar bars play a crucial role. Based partly on observationsmade at the Pico dos Dias Observatory (PDO/LNA-CNPq), Brazil.
| The impact of bars on the mid-infrared dust emission of spiral galaxies: global and circumnuclear properties
We study the mid-infrared properties of a sample of 69 nearby spiralgalaxies, selected to avoid Seyfert activity contributing a significantfraction of the central energetics, or strong tidal interaction, and tohave normal infrared luminosities. These observations were obtained withISOCAM, which provides an angular resolution of the order of 10arcsec(half-power diameter of the point spread function) and low-resolutionspectro-imaging information. Between 5 and 18 mu m, we mainly observetwo dust phases, aromatic infrared bands and very small grains, both outof thermal equilibrium. On this sample, we show that the globalF15/F_7 colors of galaxies are very uniform, the onlyincrease being found in early-type strongly barred galaxies, consistentwith previous IRAS studies. The F15/F_7 excesses areunambiguously due to galactic central regions where bar-inducedstarbursts occur. However, the existence of strongly barred early-typegalaxies with normal circumnuclear colors indicates that therelationship between a distortion of the gravitational potential and acentral starburst is not straightforward. As the physical processes atwork in central regions are in principle identical in barred andunbarred galaxies, and since this is where the mid-infrared activity ismainly located, we investigate the mid-infrared circumnuclear propertiesof all the galaxies in our sample. We show how surface brightnesses andcolors are related to both the available molecular gas content and themean age of stellar populations contributing to dust heating. Therefore,the star formation history in galactic central regions can beconstrained by their position in a color-surface brightness mid-infrareddiagram. Based on observations with ISO, an ESA project with instrumentsfunded by ESA Member States (especially the PI countries: France,Germany, the Netherlands and the UK) and with the participation of ISASand NASA.
| 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.
| ISO Mid-Infrared Observations of Normal Star-Forming Galaxies: The Key Project Sample
We present mid-infrared maps and preliminary analysis for 61 galaxiesobserved with the ISOCAM instrument aboard the Infrared SpaceObservatory. Many of the general features of galaxies observed atoptical wavelengths-spiral arms, disks, rings, and bright knots ofemission-are also seen in the mid-infrared, except the prominent opticalbulges are absent at 6.75 and 15 μm. In addition, the maps are quitesimilar at 6.75 and 15 μm, except for a few cases where a centralstarburst leads to lower Iν(6.75μm)/Iν(15 μm) ratios in the inner region. We alsopresent infrared flux densities and mid-infrared sizes for thesegalaxies. The mid-infrared color Iν(6.75μm)/Iν(15 μm) shows a distinct trend with thefar-infrared color Iν(60 μm)/Iν(100μm). The quiescent galaxies in our sample [Iν(60μm)/Iν(100 μm)<~0.6] show Iν(6.75μm)/Iν(15 μm) near unity, whereas this ratio dropssignificantly for galaxies with higher global heating intensity levels.Azimuthally averaged surface brightness profiles indicate the extent towhich the mid-infrared flux is centrally concentrated, and provideinformation on the radial dependence of mid-infrared colors. Thegalaxies are mostly well resolved in these maps: almost half of themhave <10% of their flux in the central resolution element. Acomparison of optical and mid-infrared isophotal profiles indicates thatthe flux at 4400 Å near the optical outskirts of the galaxies isapproximately 8 (7) times that at 6.75 μm (15 μm), comparable toobservations of the diffuse quiescent regions of the Milky Way. Thispaper is based on observations with the Infrared Space Observatory(ISO). ISO is an ESA project with instruments funded by ESA memberstates (especially the PI countries: France, Germany, The Netherlands,and the United Kingdom) and with the participation of ISAS and NASA.
| The Frequency of Barred Spiral Galaxies in the Near-Infrared
We have determined the fraction of barred galaxies in the H-band for astatistically well-defined sample of 186 spirals drawn from the OhioState University Bright Spiral Galaxy Survey. We find 56% of our sampleto be strongly barred in the H band while another 16% is weakly barred.Only 27% of our sample is unbarred in the near-infrared. The RC3 and theCarnegie Atlas of Galaxies both classify only about 30% of our sample asstrongly barred. Thus strong bars are nearly twice as prevalent in thenear-infrared as in the optical. The frequency of genuine opticallyhidden bars is significant but lower than many claims in the literature:40% of the galaxies in our sample that are classified as unbarred in theRC3 show evidence for a bar in the H band while the Carnegie Atlas liststhis fraction as 66%. Our data reveal no significant trend in barfraction as a function of morphology in either the optical or H band.Optical surveys of high-redshift galaxies may be strongly biased againstfinding bars, as bars are increasingly difficult to detect at bluer restwavelengths. Based partially on observations obtained at the CerroTololo Inter-American Observatory, operated by the Association ofUniversities for Research in Astronomy, Inc., under cooperativeagreement with the National Science Foundation.
| 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.
| Imaging and spectroscopy of ten southern galaxies selected from a catalogue of peculiar galaxies
We present BVRI broad band photometry and long slit spectroscopy for asample of ten southern galaxies selected from the Aguero Catalogue ofPeculiar Galaxies. The analysis of the images shows that only fourgalaxies of the sample are truly peculiar galaxies and four are normalspirals. The remaining two galaxies, a normal spiral and a SO, form aninteracting pair. Despite the rather complicated structure of thepeculiar galaxies we did not find evidence of mergers in our analysis ofimages and rotation curves. Almost all galaxies in our sample show starforming regions with very blue colors, (B-V) ranging from 0.2 to 0.6.The SO galaxy shows a very interesting structure in the V-I color mapsuggesting that star formation events have occurred in concentric annulicentered in the nucleus. In our photometric analysis we did not findcharacteristics that could distinguish between normal and peculiargalaxies. We obtained the ``pure-emission'' line spectra for sixgalaxies of the sample by subtracting appropriate templates. Thesetemplates correspond to ellipticals selected from our library ofspectra. This subtraction technique provides a powerful tool tocalculate line flux ratios uncontaminated by the underlying stellarpopulation. Our spectroscopic analysis confirms that the spiral galaxyof the interacting system AM 2054-433 has a LINER-type nucleus. In thenormal galaxy ESO 316-29 we find evidence of a LINER nucleus and wereport a new Seyfert 2 galaxy, AM 2054-433 N. For this SO galaxy theline flux ratios measured from the pure-emission spectrum are indicativeof a Seyfert 2 rather than a LINER nucleus as it was previously reportedby other authors. Three of the four peculiar galaxies in our sample havemuch higher star-formation rate than normal galaxies, as measured byHα + [NII] line emission. The observed EW(Hα + [NII]) valuesfor these peculiar galaxies are around 60 Angstroms, compared to 22Angstroms for normal galaxies. Whole-aperture spectra for these peculiargalaxies show very similar EW(Hα + [NII]) values to those observedin their nuclear region suggesting that a global starburst has occurred.Although our sample is small the results presented suggest that peculiarmorphology and global starburst events are closely related.
| Multiwavelength Energy Distributions and Bolometric Luminosities of the 12 Micron Galaxy Sample
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...453..616S&db_key=AST
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| Disc galaxies with multiple triaxial structures. I. BVRI and Hα surface photometry.
We present a BVRI survey of 36 galaxies selected as candidates forhaving a misaligned secondary bar or a triaxial bulge inside the primarybar. Fifteen galaxies have also been observed in Hα. A positivedetection of more than one triaxial structure has been found in 22galaxies shared out as follows: 13 double-barred galaxies, 3triple-barred galaxies, 3 double-barred galaxies with an additionalstructure with twisted isophotes, and 3 galaxies with a bar and astructure with twisted isophotes. Triaxial deformation(s) have beenfound in 6 galaxies classified as unbarred in RC3. The number of Seyfertnuclei amongst double-barred systems is high (6 over 13).
| The extended 12 micron galaxy sample
We have selected an all-sky (absolute value of b greater than or equalto 25 deg) 12 micron flux-limited sample of 893 galaxies from the IRASFaint Source Catalog, Version 2 (FSC-2). We have obtained accurate totalfluxes in the IRAS wavebands by using the ADDSCAN procedure for allobjects with FSC-2 12 micron fluxes greater than 0.15 Jy and increasingflux densities from 12 to 60 microns, and defined the sample by imposinga survey limit of 0.22 Jy on the total 12 micron flux. Its completenessis verified, by means of the classical log N - log S andV/Vmax tests, down to 0.30 Jy, below which we have measuredthe incompleteness down to the survey limit, using the log N - log Splot, for our statistical analysis. We have obtained redshifts (mostlyfrom catalogs) for virtually all (98.4%) the galaxies in the sample.Using existing catalogs of active galaxies, we defined a subsample of118 objects consisting of 53 Seyfert 1s and quasars, 63 Seyfert 2s, andtwo blazars (approximately 13% of the full sample), which is the largestunbiased sample of Seyfert galaxies ever assembled. Since the 12 micronflux has been shown to be about one-fifth of the bolometric flux forSeyfert galaxies and quasars, the subsample of Seyferts (includingquasars and blazars) is complete not only to 0.30 Jy at 12 microns butalso with respect to a bolometric flux limit of approximately 2.0 x10-10 ergs/s/sq cm. The average value of V/Vmaxfor the full sample, corrected for incompleteness at low fluxes, is 0.51+/- 0.04, expected for a complete sample of uniformly distributedgalaxies, while the value for the Seyfert galaxy subsample is 0.46 +/-0.10. We have derived 12 microns and far-infrared luminosity functionsfor the AGNs, as well as for the entire sample. We extracted from oursample a complete subsample of 235 galaxies flux-limited (8.3 Jy) at 60microns. The 60 micron luminosity function computed for this subsampleis in satisfactory agreement with the ones derived from the brightgalaxy sample (BGS) and the deep high-galactic latitude sample, bothselected at 60 microns.
| Dynamics of the Pavo-Indus and Grus clouds of galaxies
A study of groups of galaxies in the above regions was carried out byselecting a sample extending one magnitude deeper than previous work inthe area, complete down to 15 mag. We report new redshift determinationsfor 58 galaxies in the region and 13 other miscellaneous galaxies, basedon La Silla observations. Using a total of 266 galaxies with measuredredshifts in the Pavo-Indus and Grus clouds, we perform a new analysisof groupings following a well-tested algorithm. A total of 18 groups issingled out, most of them known from previous work, even though a fewadditional members are added. For all the groups, we have calculateddynamical parameters and M/L ratios. All groups are found to be boundaggregates, but only one group can be virialized. For the six mostpopulated examples, having at least five members, we also calculateseveral mass estimators and discuss the wide range of observed M/Lratios, which extends from nine to nearly 500 M(solar)/L(solar). Weintroduce two parameters to measure the presence of either a dominantgalaxy or internal subcondensations, respectively, and test whether anycorrelation with the M/L ratios can be detected. No clear correlationsare found.
| Analysis of the distribution of H II regions in external galaxies. II - Analysis of the spiral structure
This paper is the second of a series where we study the distribution ofH II regions in spiral galaxies. We use a Fourier decomposition toobtain the main spiral components of 44 galaxies, extracted from thesample of Garcia Gomez & Athanassoula (1991) as those having somestructure in their H II region distribution. We recompose the densitydistribution using more than one component from each Fourier spectrum,thus obtaining more accurate results than in previous studies. We alsostudy the dependences of the pitch angles of these components on otherphysical parameters of the galaxies, like the Hubble type and the armclass. For the galaxies where information on the flux of the H IIregions is available, we use the Fourier decomposition to separate the HII regions in the arms from those in the interarm zones. The H IIregions in the arms are, on the average, brighter by a factor of theorder of 1.25 than those in the interarm. The brightest H II regions arepreferentially located in the arms.
| 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.
| Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members
This paper gives a catalog of the groups and associations obtained bymeans of a revised hierarchical algorithm applied to a sample of 4143galaxies with diameters larger than 100 arcsec and redshifts smallerthan 6000 km/s. The 264 groups of galaxies obtained in this way (andwhich contain at least three sample galaxies) are listed, with the looseassociations surrounding them and the individual members of eachaggregate as well; moreover, the location of every entity among 13regions corresponding roughly to superclusters is specified. Finally,1729 galaxies belong to the groups, and 466 to the associations, i.e.,the total fraction of galaxies within the various aggregates amounts to53 percent.
| 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.
| Analysis of the distribution of HII regions in external galaxies. I - Position and inclination angles
A sample of galaxies has been compiled, with published catalogues of HII regions forming the basis for subsequent studies of the H II regiondistribution in spiral galaxies. The problem of the deprojection of agalaxy image as seen on the sky is addressed. Two methods to do this,based on the H II region distributions themselves have been devised andapplied to the sample. The results are compared with the ones obtainedusing several other methods. The new methods are capable of obtaininggood values for the position and inclination angles of the galaxies.
| Models for infrared emission from IRAS galaxies
The far-infrared spectra of galaxies detected in four wavelength bandsby IRAS have been modeled in terms of a cool disk component, a warmerstarburst component, and a Seyfert component peaking at 25 microns.Although the models are found to fit the observed spectra of non-Seyfertand several Seyfert galaxies, a more complex geometry for the dustdistribution is indicated for NGC 1068 and many other Seyfert galaxies.In some cases, the dust in the narrow-line region has a nonsphericallysymmetric geometry.
| 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.
| Revised supernova rates in Shapley-Ames galaxies
Observations of 855 Shapley Ames galaxies made from November 1, 1980 toOctober 31, 1988, together with improved supernova luminosities, havebeen used to derive the frequency of supernovae of different types, andthe results are presented in tables. From a uniform database of 24supernovae discovered, the following SN rates are found, expressed in SNper century per 10 to the 10th L(B)(solar): SN Ia, 0.3; SN Ib, 0.3; andSN II, 1.0. The present data confirm the relatively high frequency of SNII in late-type galaxies that has been found by many previousinvestigators.
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