Home     Getting Started     To Survive in the Universe    
Inhabited Sky
    News@Sky     Astro Photo     The Collection     Forum     Blog New!     FAQ     Press     Login  

IC 4870



Upload your image

DSS Images   Other Images

Related articles

Star Formation in H I-selected Galaxies. II. H II Region Properties
A sample of 69 galaxies with radial velocities less than 2500 kms-1 was selected from the H I Parkes All Sky Survey (HIPASS)to deduce details about star formation in nearby disk galaxies selectedwith no bias to optical surface brightness selection effects. Broadband(B and R) and narrowband (Hα) images were obtained for all ofthese objects. More than half of the sample galaxies are late-type,dwarf disks (mostly Sc and Sm galaxies). We have measured the propertiesof the H II regions on Hα continuum-subtracted images, using theHIIphot package developed by Thilker et al. All but one of the galaxiescontained at least one detectable H II region. Examination of theproperties of the H II regions in each galaxy revealed that thebrightest regions in higher surface brightness galaxies tend to be moreluminous than those in lower surface brightness galaxies. A higherfraction (referred to as the diffuse fraction) of the Hα emissionfrom lower surface brightness galaxies comes from diffuse ionized gas. HII region luminosity functions (LFs) co-added according to surfacebrightness show that the shapes of the LFs for the lowest surfacebrightness galaxies are different from those for typical spiralgalaxies. This discrepancy could be caused by the lowest surfacebrightness galaxies having somewhat episodic star formation or by themforming a relatively larger fraction of their stars outside of dense,massive molecular clouds. In general, the results imply that theconditions under which star formation occurs in lower surface brightnessgalaxies are different than in more typical, higher surface brightnessspiral galaxies.

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.

Star Formation in H I-Selected Galaxies. I. Sample Characteristics
A sample of 69 galaxies with radial velocities of less than 2500 kms-1 was selected from the H I Parkes All-Sky Survey (HIPASS)and imaged in broadband B and R and narrowband Hα, to deducedetails about star formation in nearby disk galaxies while avoidingsurface brightness selection effects. The sample is dominated bylate-type, dwarf disks (mostly Sc and Sm galaxies) with exponential diskscale lengths of ~1-5 kpc. The HIPASS galaxies, on average, have lowerstar formation rates (SFRs), are bluer, and have lower surfacebrightness than an optically selected sample. H II regions were detectedin all but one of the galaxies. Many galaxies had as few as two to fiveH II regions. The galaxies' Hα equivalent widths, colors, and SFRsper unit of H I mass are best explained by young mean ages (~3-5 Gyr,according to Schmidt-law models) with star formation histories in whichthe SFRs were higher in the past. Comparison of the surface brightnesscoverage of the HIPASS galaxies with that of an optically selectedsample shows that such a sample may miss ~10% of the local galaxy numberdensity and could possibly miss as much as 3%-4% of the SFR density. Theamount lower surface brightness galaxies contribute to the totalluminosity density may be insignificant, but this conclusion is somewhatdependent on how the fluxes of these objects are determined.

The 1000 Brightest HIPASS Galaxies: H I Properties
We present the HIPASS Bright Galaxy Catalog (BGC), which contains the1000 H I brightest galaxies in the southern sky as obtained from the H IParkes All-Sky Survey (HIPASS). The selection of the brightest sourcesis based on their H I peak flux density (Speak>~116 mJy)as measured from the spatially integrated HIPASS spectrum. The derived HI masses range from ~107 to 4×1010Msolar. While the BGC (z<0.03) is complete inSpeak, only a subset of ~500 sources can be consideredcomplete in integrated H I flux density (FHI>~25 Jy kms-1). The HIPASS BGC contains a total of 158 new redshifts.These belong to 91 new sources for which no optical or infraredcounterparts have previously been cataloged, an additional 51 galaxiesfor which no redshifts were previously known, and 16 galaxies for whichthe cataloged optical velocities disagree. Of the 91 newly cataloged BGCsources, only four are definite H I clouds: while three are likelyMagellanic debris with velocities around 400 km s-1, one is atidal cloud associated with the NGC 2442 galaxy group. The remaining 87new BGC sources, the majority of which lie in the zone of avoidance,appear to be galaxies. We identified optical counterparts to all but oneof the 30 new galaxies at Galactic latitudes |b|>10deg.Therefore, the BGC yields no evidence for a population of``free-floating'' intergalactic H I clouds without associated opticalcounterparts. HIPASS provides a clear view of the local large-scalestructure. The dominant features in the sky distribution of the BGC arethe Supergalactic Plane and the Local Void. In addition, one can clearlysee the Centaurus Wall, which connects via the Hydra and Antlia Clustersto the Puppis Filament. Some previously hardly noticable galaxy groupsstand out quite distinctly in the H I sky distribution. Several newstructures, including some not behind the Milky Way, are seen for thefirst time.

A Catalog of H I-Selected Galaxies from the South Celestial Cap Region of Sky
The first deep catalog of the H I Parkes All Sky Survey (HIPASS) ispresented, covering the south celestial cap (SCC) region. The SCC areais ~2400 deg2 and covers δ<-62°. The average rmsnoise for the survey is 13 mJy beam-1. Five hundredthirty-six galaxies have been cataloged according to their neutralhydrogen content, including 114 galaxies that have no previous catalogedoptical counterpart. This is the largest sample of galaxies from a blindH I survey to date. Most galaxies in optically unobscured regions of skyhave a visible optical counterpart; however, there is a small populationof low-velocity H I clouds without visible optical counterparts whoseorigins and significance are unclear. The rms accuracy of the HIPASSpositions is found to be 1.9′. The H I mass range of galaxiesdetected is from ~106 to ~1011 Msolar.There are a large number of late-type spiral galaxies in the SCC sample(66%), compared with 30% for optically selected galaxies from the sameregion in the NASA Extragalactic Database. The average ratio of H I massto B luminosity of the sample increases according to optical type, from1.8 Msolar/Lsolar for early types to 3.2Msolar/Lsolar for late-type galaxies. The HI-detected galaxies tend to follow the large-scale structure traced bygalaxies found in optical surveys. From the number of galaxies detectedin this region of sky, we predict the full HIPASS catalog will contain~5000 galaxies, to a peak flux density limit of ~39 mJy (3 σ),although this may be a conservative estimate as two large voids arepresent in the region. The H I mass function for this catalog ispresented in a subsequent paper.

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.

Stellar populations in Seyfert 2 galaxies. I. Atlas of near-UV spectra
We have carried out a uniform spectroscopic survey of Seyfert 2 galaxiesto study the stellar populations of the host galaxies. New spectra havebeen obtained for 79 Southern galaxies classified as Seyfert 2 galaxies,7 normal galaxies, and 73 stars at a resolution of 2.2 Å over thewavelength region 3500-5300 Å. Cross-correlation between thestellar spectra is performed to group the individual observations into44 synthesis standard spectra. The standard groups include a solarabundance sequence of spectral types from O5 to M3 for dwarfs, giants,and supergiants. Metal-rich and metal-weak F-K giants and dwarfs arealso included. A comparison of the stellar data with previouslypublished spectra is performed both with the individual spectra and thestandard groups. For each galaxy, two distinct spatial regions areconsidered: the nucleus and the external bulge. Spectroscopic variationsfrom one galaxy to another and from the central to the external regionare briefly discussed. It is found that the central region of a Seyfert2 galaxy, after subtracting the bulge stellar population, always shows anear-UV spectrum similar to one of three representative categories: a)many strong emission lines and only two visible absorption lines (Ca IiK and G band) (Sey2e); b) few emission lines, many absorption lines, anda redder continuum than the previous category (Sey2a); c) an almost flatcontinuum and high-order Balmer lines seen in absorption (Sey2b). Theproportion of Seyfert 2 galaxies belonging to each class is found to be22%, 28%, and 50% respectively. We find no significative differencesbetween morphology distributions of Seyfert 2 galaxies with Balmer linesdetected in absorption and the rest of the sample. This quick lookthrough the atlas indicates that half of Seyfert 2 galaxies harbour ayoung stellar population (about or less than 100 Myr) in their centralregion, clearly unveiled by the high order Balmer series seen inabsorption. Based on observations collected at the European SouthernObservatory, Chile (ESO 65.P-0014(A)). Tables 1-3 and 8 and Fig. A.1(Appendix A) are only available in electronic form athttp://www.edpsciences.org

Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.

The emission line spectrum of active galactic nuclei and the unifying scheme
Recent papers dealing with the most controversial aspects of AGNs arereviewed. They suggest interesting conclusions: all Seyferts can bedescribed by a single parameter, the X-ray column density; radio loudAGNs may host a rapidly spinning black hole and radio quiet AGNs aslowly spinning black hole; high-ionization AGNs (Seyfert galaxies andQSOs) contain an optically thick, geometrically thin accretion disk,while low-ionization AGNs (Liners) contain an optically thin,geometrically thick accretion disk; a number of blazars have beenclassified as BLLs on the basis of insufficient data; most objects withweak broad emission lines are in fact HPQs; many objects have beencalled Liners although they are not AGNs but rather the result ofstellar activity; type 2 QSOs exist, but are quite inconspicuous ifradio quiet.

The QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.

New catalogue of Wolf-Rayet galaxies and high-excitation extra-galactic HII regions
We present a new compilation of Wolf-Rayet (WR) galaxies andextra-galactic Hii regions showing broad He ii lambda 4686 emissiondrawn from the literature. Relevant information on the presence of otherbroad emission lines ([N i] lambda 5199ii, C iv lambda 5808 and others)from WR stars of WN and WC subtypes, and other existing broad nebularlines is provided. In total we include 139 known WR galaxies. Amongthese, 57 objects show both broad He ii lambda 4686 and C iv lambda 5808features. In addition to the broad (stellar) He ii lambda 4686 emission,a nebular He ii component is well established (suspected) in 44 (54)objects. We find 19 extra-galatic Hii regions without WR detectionsshowing nebular He ii lambda 4686 emission. The present sample can beused for a variety of studies on massive stars, interactions of massivestars with the ISM, stellar populations, starburst galaxies etc. Thedata is accessible electronically and will be updated periodically. Thecatalogue is available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr ( or viahttp://cdsweb.u-strasbg.fr/Abstract.html

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.

A Comparison of the Intrinsic Shapes of Two Different Types of Dwarf Galaxies: Blue Compact Dwarfs and Dwarf Ellipticals
We measure the apparent shapes for a sample of 62 blue compact dwarfgalaxies (BCDs) and compare them with the apparent shapes for a sampleof 80 dwarf elliptical galaxies (dEs). The BCDs are flatter, on average,than the dEs, but the difference is only marginally significant. We thenuse both nonparametric and parametric techniques to determine possibledistributions of intrinsic shapes for the BCDs. The hypothesis that BCDsare oblate spheroids can be ruled out with a high confidence level(>99%), but the hypothesis that they are prolate spheroids cannot beexcluded. The apparent shapes of BCDs are totally consistent with thehypothesis that they are triaxial ellipsoids. If the intrinsic axisratios beta and gamma are distributed according to a Gaussian with meansbeta 0 and gamma 0 and standard deviation sigma , we find that thebest-fitting distribution for BCDs has ( beta 0, gamma 0, sigma ) =(0.66, 0.55, 0.16), while that for dEs has ( beta 0, gamma 0, sigma ) =(0.85, 0.64, 0.24). Our results are consistent with the hypothesis thatBCDs have a close evolutionary relation with dEs.

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.

Parsec-scale radio cores in spiral galaxies
We have used the Parkes-Tidbinbilla Interferometer to search for compact(<0.03 arcsec) radio continuum cores in 54 nearby spiral galaxies, 22of which have Seyfert nuclei. In contrast to the radio cores ofelliptical galaxies, the few parsec-scale cores seen in spirals usuallyhave steep radio spectra, with an apparent median spectral index of-1.0. At present, it is not clear whether this is because the radiocores of spiral galaxies are larger than those in ellipticals (and soare partly resolved by the interferometer), or whether the core spectraof ellipticals and spirals are intrinsically different.

Spectroscopic studies of emission line galaxies.
Not Available

A compilation of active and normal galaxies observed in both infrared and X-rays
Infrared and X-ray data from the IRAS and Einstein satellites have beencompiled for a total of 269 quasars, Seyferts, emission-line and normalgalaxies. It is found that galaxies with soft X-ray to infrared fluxratios greater than about 0.01 are almost certain to show broad-lineoptical emission. For the full IRAS/Einstein ensemble, a significantcorrelation between luminosities is found in the 60-micron and 0.5-4.5keV bands. A strong offset separates broad line from normal andnarrow-line galaxies. The jump toward higher X-ray emission inbroad-line galaxies is interpreted as evidence for the increasingimportance of a nonthermal nuclear source. The analysis of the empiricalrelationship between LX and L60 microns for normaland narrow optical emission-line galaxies makes it possible to convert60-micron IRAS luminosity functions into estimates of the 2-keV X-rayluminosity function of IR-emitting galaxies.

The supergalactic plane redshift survey
Redshift measurements, about 1000 of which are new, are presented for1314 galaxies in a survey toward the apex of the large-scale streamingflow for ellipticals. The velocity histogram shows that the excess ingalaxy number counts in this area is due to a substantial concentrationof galaxies with discrete peaks at V about 3000 km/s and V about 4500km/s. After correction for the sampling function, the centroid of thedensity distribution is found to be near V about 4500 km/s.Normalization to the more extensive SSRS survey, which was selected bythe same criteria, shows that the region studied contains a considerableoverdensity of galaxies from 2000 to 6000 km/s. This result is in goodagreement with the 'great attractor' model suggested by Lynden-Bell etal. (1988) which attributes the peculiar motions of elliptical galaxiesover a large region of space to an extensive mass overdensity whichincludes the Hydra-Centaurus and Pavo-Indus superclusters. The centroidof the density enhancement is also consistent with new data by Dresslerand Faber (1990) of peculiar motions of elliptical and spiral galaxies,both of which show a zero crossing of the Hubble line at approximately4500-5000 km/s.

A catalogue of Seyfert galaxies.
Not Available

A statistical study of properties of Seyfert and starburst galaxies
Spectral and morphological data for 282 Seyfert and emission-linegalaxies spanning radio to X-ray wavelengths are compiled. The datainclude a large number of optical emission-line measurements which havenot been reported previously. These data are intended to provide aconvenient summary of the relevant properties of these galaxies, as wellas a data base to search for correlations among the various parametersin order to obtain a better understanding of the active galaxyphenomenon. The paper presents the data and analyzes the distributionsof various properties of Seyfert 1 and Seyfert 2 galaxies and starburstgalaxies. It is found that Seyferts 2s have a higher 60 micron/forbiddenO III 5007 A flux ratio than Seyfert 1s. This result, combined with thefact that Seyfert 2s are more heavily reddened, indicate that they havea higher dust content. It is also found that starburst nuclei arecomparable to Seyfert 2s in far-infrared and 20 cm luminosities,although their optical spectra are markedly different.

Star formation in Seyfert galaxies
The far-IR properties of a sample of Seyfert galaxies are studied usingpreviously obtained UV-optical and mid-IR data. The results show thatactive nuclei do not seem to be responsible for the bulk of the far-IRemission form Seyfert galaxies at wavelengths longer than 30 microns.Seyfert galaxies have, on average, far-IR luminosities that are oneorder of magnitude greater than normal spiral galaxies. The far-IRluminosities of both Seyfert and starburst galaxies are of the sameorder of magnitude, and the far-IR spectral indices of Seyfert and ofstarburst galaxies are indistinguishable from each other. From theseresults, it is concluded that most of the far-IR emission from Seyfertgalaxies is due to starburst episodes occurring in the galacticenvelopes surrounding the active nuclei.

Warm IRAS sources. I. A. Catalogue of AGN candidates from the point source catalog
It was previously shown that a blue (warm) 60 to 25 micron infraredcolor provides a powerful parameter for discriminating between AGNs andnormal galaxies, and that the far-IR spectrum is therefore an efficienttool for finding new AGNs. A list of such AGN candidates based on warmIR sources from the IRAS Point Source Catalogue (PSC) is presented here.Identification data and finding charts are also given. In addition, thelist of warm IRAS sources is supplemented by a compendium of data fromthe IRAS PSC on detected sources identified with previously known AGNswhose infrared spectra do not bring them within this color selectioncriterion.

The narrow line region of active galaxies. I - Nuclear forbidden line profiles. II - Relations between forbidden line profile shape and other properties
A parameter scheme based on area measurements is developed whichcharacterizes the width, asymmetry and kurtosis of different parts ofeach of the high dispersion O III forbidden line profiles presented for42 Southern Hemisphere active and H II galaxies. A comparison withparameters defined by a cut at constant height indicates that the areaparameters are less sensitive to noise, more stable to the effects ofpoor resolution, and more sensitive to information contained in the baseand wings of the profile. The data thus obtained are combined with mostof the previously published O III forbidden line profile information toform a large sample of line width, asymmetry and kurtosis measurementsfor Seyfert galaxies. No correlations are found between forbidden O IIIline width and either the nuclear nonthermal luminosity, the relativestrength of the Broad Line Region, or the ionization and physical stateof the Narrow Line Region gas. Previous results suggesting that Seyfert2 galaxies on average possess broader O III forbidden line profiles thanSeyfert 1 galaxies are shown to be a consequence of selection effects.

Southern Galaxy Catalogue.
Not Available

Study of a complete sample of galaxies. I - UBV aperture photometry
UBV photometry was performed over the period September 1979-February1984 on 320 galaxies in the Revised Shapely-Ames catalog of galaxies(1981). The galaxies chosen had radial velocities under 3000 km/sec,declinations of no more than +20 deg and absolute magnitudes of at most-21.0. V, B-V and U-B data are provided for all the objects, along withdata for other galaxies which were either Seyfert galaxies or had astarburst nucleus.

The polarization of Seyfert galaxies
The optical linear polarization of 99 Seyfert galaxies has beenmeasured. Several highly polarized objects have been discovered and arediscussed elsewhere. However, most Seyferts have very littlepolarization (approximately equal to or less than 0.5%) and much of thismight be produced by foreground dust in the Galaxy; thus the occurrenceof substantial intrinsic polarization is quite rare. Some significantsimilarities and differences between Seyfert and QSO polarization arediscussed. A few measurements for narrow emission line galaxies are alsopresented.

On the width and profile of nuclear emission lines in galaxies
The widths and profiles of emission lines from the nuclei of Seyfertgalaxies and nuclear H II regions are investigated. Spectra wereobtained with a resolution of 100 km/sec for nine Seyfert 1, and eightSeyfert 2 galaxies and eight nuclear H II regions in the range 4600-5100A. From examination of the O III forbidden line at 5007 A of the nuclearregions, it is found that nuclear H II regions usually have narrowemission lines which can be fit, to a first approximation, by a gaussianprofile with FWHM not exceeding 150 km/sec. The forbidden lines of theSeyfert galaxy, on the other hand, are generally observed to haveasymmetric profiles, usually with broad red and blue wings and aprobable excess of blue wings. In most cases, a Seyfert nucleus can bedistinguished from an H II region on the basis of the N2 line profile.It is also observed that at a given resolution, the observed profiledepends on aperture parameters, due to the presence of distinct cloudsin the Seyfert 2 nucleus.

More Seyfert galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978MNRAS.184P..11W&db_key=AST

Submit a new article

Related links

  • - No Links Found -
Submit a new link

Member of following groups:

Observation and Astrometry data

Right ascension:19h37m37.60s
Aparent dimensions:1.66′ × 0.851′

Catalogs and designations:
Proper Names   (Edit)
ICIC 4870

→ Request more catalogs and designations from VizieR