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The Relationship of Hard X-Ray and Optical Line Emission in Low-Redshift Active Galactic Nuclei
In this paper we assess the relationship of the population of activegalactic nuclei (AGNs) selected by hard X-rays to the traditionalpopulation of AGNs with strong optical emission lines. First, we studythe emission-line properties of a new hard-X-ray-selected sample of 47local AGNs (classified optically as Type 1 and 2 AGNs). We find that thehard X-ray (3-20 keV) and [O III] λ5007 optical emission-lineluminosities are well-correlated over a range of about 4 orders ofmagnitude in luminosity (mean luminosity ratio 2.15 dex with a standarddeviation of σ=0.51 dex). Second, we study the hard X-rayproperties of a sample of 55 local AGNs selected from the literature onthe basis of the flux in the [O III] line. The correlation between thehard X-ray (2-10 keV) and [O III] luminosity for the Type 1 AGNs isconsistent with what is seen in the hard-X-ray-selected sample. However,the Type 2 AGNs have a much larger range in the luminosity ratio, andmany are very weak in hard X-rays (as expected for heavily absorbedAGNs). We then compare the hard X-ray (3-20 keV) and [O III] luminosityfunctions of AGNs in the local universe. These have similar faint-endslopes, with a luminosity ratio of 1.60 dex (0.55 dex smaller than themean value for individual hard-X-ray-selected AGNs). We conclude that atlow redshift, selection by narrow optical emission lines will recovermost AGNs selected by hard X-rays (with the exception of BL Lacobjects). However, selection by hard X-rays misses a significantfraction of the local AGN population with strong emission lines.
| Kinematics of the local universe . XII. 21-cm line measurements of 586 galaxies with the new Nançay receiver
This paper presents 586 new 21-cm neutral hydrogen line measurementscarried out with the FORT receiver of the meridian transit Nançayradiotelescope in the period July 2000-March 2003. This observationalprogramme is part of a larger project aiming at collecting an exhaustiveand magnitude-complete HI extragalactic catalogue for Tully-Fisherapplications. It is associated with the building of the MIGALEspectroscopic archive and database.Tables 2, 3 and HI-profiles and corresponding comments are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/373, or directly atour web site http://klun.obs-nancay.fr
| High-energy sources before INTEGRAL. INTEGRAL reference catalog
We describe the INTEGRAL reference catalog which classifies previouslyknown bright X-ray and gamma-ray sources before the launch of INTEGRAL.These sources are, or have been at least once, brighter than ~ 1 mCrababove 3 keV, and are expected to be detected by INTEGRAL. This catalogis being used in the INTEGRAL Quick Look Analysis to discover newsources or significantly variable sources. We compiled several publishedX-ray and gamma-ray catalogs, and surveyed recent publications for newsources. Consequently, there are 1122 sources in our INTEGRAL referencecatalog. In addition to the source positions, we show an approximatespectral model and expected flux for each source, based on which wederive expected INTEGRAL counting rates. Assuming the default instrumentperformances and at least ~ 105 s exposure time for anypart of the sky, we expect that INTEGRAL will detect at least ~ 700sources below 10 keV and ~ 400 sources above 20 keV over the missionlife.The Catalog is available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/411/L59
| JHK' Imaging Photometry of Seyfert 1 Active Galactic Nuclei and Quasars. I. Multiaperture Photometry
Near-infrared JHK' imaging photometry was obtained of 331 AGNsconsisting mainly of Seyfert 1 active galactic nuclei (AGNs) and quasars(QSOs). This sample was selected to cover a range of radio emissionstrength, redshift from z=0 to 1, and absolute B magnitude fromMB=-29 mag to -18 mag. Among low-z AGNs with z<0.3,Seyfert 1-1.5 AGNs are distributed over a region from a location typicalof ``galaxies'' to a location typical of ``QSOs'' in the two-color J-Hto H-K' diagram, but Seyfert 1.8-2 AGNs are distributed around thelocation of ``galaxies.'' Moreover, bright AGNs with respect to absoluteB magnitude are distributed near the location of ``QSOs,'' while faintAGNs are near the location of ``galaxies.'' The distribution of suchlow-z AGNs in this diagram was found to have little dependence on their6 cm radio flux. The near-infrared colors of the AGNs observed with anaperture of 7 pixels (7.49") are more QSO-like than those observed withlarger apertures up to 15 pixels (16.1"). This aperture effect may beexplained by contamination from the light of host galaxies within largerapertures. This effect is more prominent for less luminous AGNs.
| ``Hidden'' Seyfert 2 Galaxies and the X-Ray Background
Obscured active galactic nuclei, which are classified optically as type2 (narrow line) Seyfert galaxies in the local universe, are by far themost promising candidates for the origin of the hard (2-10 keV) X-raybackground radiation. However, optical follow-up observations of faintX-ray sources in deep Chandra images have revealed surprising numbers ofapparently normal galaxies at modest redshift. Such objects represent~40%-60% of the sources classified in deep Chandra surveys, raising thepossibility that the X-ray galaxy population has evolved with cosmictime. Alternatively, most of the faint X-ray galaxies in question are sodistant that their angular diameters are comparable to the slit widthsused in ground-based spectroscopic observations; thus, their nuclearspectral features may be overwhelmed (``hidden'') by host galaxy light.To test this hypothesis, we have obtained integrated spectra of a sampleof nearby, well-studied Seyfert 2 galaxies. The data, which accuratelysimulate observations of distant Chandra sources, demonstrateconvincingly that the defining spectral signatures of Seyfert 2s can behidden by light from their host galaxies. In fact, 60% of the observedobjects would not be classified as Seyfert 2s on the basis of theirintegrated spectra, similar to the fraction of faint X-ray sourcesidentified with ``normal'' galaxies. Thus, the numbers of narrow-lineactive galaxies in deep Chandra surveys (and perhaps all ground-basedspectroscopic surveys of distant galaxies) are likely to have beenunderestimated.
| Seyfert 2 Galaxies with Spectropolarimetric Observations
We present a compilation of radio, infrared, optical, and hard X-ray(2-10 keV) data for a sample of 90 Seyfert 2 galaxies (Sy2s) withspectropolarimetric observations (41 Sy2s with detection of polarizedbroad lines [PBLs] and 49 without PBLs). Compared to Sy2s without PBLs,Sy2s with PBLs tend to be earlier type spirals and show warmermidinfrared color and significant excess of emissions (including thehard X-ray [2-10 keV], [O III] λ5007, infrared [25 μm], andradio). Our analyses indicate that the majority of Sy2s without PBLs arethose sources having less powerful active galactic nucleus (AGN)activities, most likely caused by a low accretion rate. It implies thatthe detectability of the polarized broad emission lines in Sy2s maydepend on their central AGN activities in most cases. Based on theavailable data, we find no compelling evidence for the presence of twotypes of Sy2s; one of which has been proposed to be intrinsicallydifferent from Sy2s claimed in the unification model.
| Empirical Diagnostics of the Starburst-AGN Connection
We examine a representative sample of 35 Seyfert 2 nuclei. Previous workhas shown that nearly half (15) of these nuclei show the direct (butdifficult to detect) spectroscopic signature at optical/near-UVwavelengths of the hot massive stars that power circumnuclearstarbursts. In the present paper we examine a variety of more easilymeasured quantities for this sample, such as the equivalent widths ofstrong absorption features, continuum colors, emission line equivalentwidths, emission line ratios and profiles, far-IR luminosities, andnear-UV surface brightness. We compare the composite starburst+Seyfert 2nuclei to ``pure'' Seyfert 2 nuclei, Starburst galaxies, and normalgalactic nuclei. Our goals are to verify whether the easily measuredproperties of the composite nuclei are consistent with the expectedimpact of a starburst and to investigate alternative less demandingmethods to infer the presence of starbursts in Seyfert 2 nuclei,applicable to larger or more distant samples. We show that starbursts doindeed leave clear and easily quantifiable imprints on the near-UV tooptical continuum and emission line properties of Seyfert 2's. Compositestarburst+Seyfert 2 systems can be recognized by: (1) a strong``featureless continuum'' (FC), which dilutes the Ca II K line from oldstars in the host's bulge to an equivalent width WK<10Å (2) emission lines whose equivalent widths are intermediatebetween starburst galaxies and ``pure'' Seyfert 2's (3) relatively lowexcitation line ratios, which indicate that part of the gas ionizationin these Seyfert 2's (typically ~50% of Hβ) is due tophotoionization by OB stars; (4) large far-IR luminosities(>~1010 Lsolar) (5) high near-UV surfacebrightness (~103 Lsolar pc-2). Thesecharacteristics are all consistent with the expected impact ofcircumnuclear starbursts on the observed properties of Seyfert 2's.Furthermore, they offer alternative empirical diagnostics of thepresence of circumnuclear starbursts from a few easily measuredquantities.
| A Composite Seyfert 2 X-Ray Spectrum: Implications for the Origin of the Cosmic X-Ray Background
We present a composite 1-10 keV Seyfert 2 X-ray spectrum derived fromASCA observations of a distance-limited sample of nearby galaxies. All29 observed objects were detected. Above ~3 keV, the composite spectrumis inverted, confirming that Seyfert 2 galaxies as a class have thespectral properties necessary to explain the flat shape of the cosmicX-ray background spectrum. Integrating the composite spectrum overredshift, we find that the total emission from Seyfert 2 galaxies,combined with the expected contribution from unabsorbed type 1 objects,provides an excellent match to the spectrum and intensity of the hardX-ray background. The principal uncertainty in this procedure is thecosmic evolution of the Seyfert 2 X-ray luminosity function. Separatecomposite spectra for objects in our sample with and without polarizedbroad optical emission lines are also presented.
| Radio-loud and Radio-quiet Active Galactic Nuclei
We have generated a sample of 409 active galactic nuclei (AGNs) forwhich both the radio luminosity at 5 GHz and the line luminosity in [OIII] lambda5007 have been measured. The radio luminosity spans a rangeof 10 orders of magnitude, and the [O III] line luminosity spans a rangeof 8 orders of magnitude-both considerably larger than the ranges inprevious studies. We show that these two quantities are correlated in asimilar way for both radio-loud and radio-quiet AGNs. We demonstratethat the observed correlation can be explained in terms of a model inwhich jets are accelerated and collimated by a vertical magnetic field.
| Radio continuum morphology of southern Seyfert galaxies
We present radio observations for 29 southern Seyfert galaxies selectedfrom a volume limited sample with cz<3600 km s(-1) , and declinationdelta <0{(deg} ) r. Objects with declination -30{(deg} }r
| 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.
| A Survey for H 2O Megamasers in Active Galactic Nuclei. II. A Comparison of Detected and Undetected Galaxies
A survey for H2O megamaser emission from 354 active galaxies hasresulted in the detection of 10 new sources, making 16 known altogether.The galaxies surveyed include a distance-limited sample (coveringSeyferts and LINERs with recession velocities less than 7000 km s-1) anda magnitude-limited sample (covering Seyferts and LINERs with mB <=14.5). In order to determine whether the H2O-detected galaxies are"typical" active galactic nuclei (AGNs) or have special properties thatfacilitate the production of powerful masers, we have accumulated adatabase of physical, morphological, and spectroscopic properties of theobserved galaxies. The most significant finding is that H2O megamasersare detected only in Seyfert 2 and LINER galaxies, not Seyfert 1's. Thislack of detection in Seyfert 1's indicates either that they do not havemolecular gas in their nuclei with physical conditions appropriate toproduce 1.3 cm H2O masers or that the masers are beamed away from Earth,presumably in the plane of the putative molecular torus that hides theSeyfert 1 nucleus in Seyfert 2's. LINERs are detected at a similar rateto Seyfert 2's, which constitutes a strong argument that at least somenuclear LINERs are AGNs rather than starbursts, since starbursts havenot been detected as H2O megamasers. We preferentially detect H2Oemission from the nearer galaxies and from those that are apparentlybrighter at mid- and far-infrared and centimeter radio wavelengths.There is also a possible trend for the H2O-detected galaxies to be moreintrinsically luminous in nuclear 6 cm radio emission than theundetected ones, though these data are incomplete. We find evidence thatSeyfert 2's with very high (NH > 1024 cm-2) X-ray--absorbing columnsof gas are more often detected as H2O maser emitters than Seyfert 2'swith lower columns. It may be that the probability of detecting H2Omaser emission in Seyfert galaxies increases with increasing column ofcool gas to the nucleus, from Seyfert 1's through narrow-line X-raygalaxies to Seyfert 2's.
| Optical and Far-Infrared Emission of IRAS Seyfert Galaxies
This paper presents an analysis of moderately large samples of type 1and 2 Seyfert galaxies through optical observations and far-infraredIRAS data, also taking into account theoretical color indices derivedfrom dust emission models. The galaxies in the samples cover a ratherlarge interval in far-infrared luminosity, i.e., 7.6 <= log(LIR/Lȯ) <= 12.6. We show that both types of Seyferts haveapproximately the same distribution of number of objects with a givenLIR. Galaxies with similar far-infrared color indices alpha (100, 60)are grouped together, and the corresponding average color indices areinterpreted in terms of a simple model in which the observed colorsresult from the combination of dust directly heated by the activegalactic nucleus with a component from the host galaxy represented bythe emission of cool dust. On the basis of the average IRAS colors ofthe derived groups, we show that type 1 and 2 Seyfert galaxies areundistinguishable from each other. From the luminosity ratios LIR/LHalpha and LIR/L[O III], we show that basically the same model can beapplied to both types of Seyfert, only allowing for the variation ofmodel conditions: type 2 Seyferts would be like type 1 Seyferts but withthe Seyfert nucleus and broad line region more effectively "hidden" bydust.
| VRI CCD surface photometry of Seyfert 1, Seyfert 2 and intermediate Seyfert-type galaxies
VRI CCD surface photometry of 27 both isolated and interacting Seyfertgalaxies (8 Seyfert 1, 14 Seyfert 2 and 5 intermediate types) is used toexamine possible differences in their broad-band properties. All Seyferttypes occupy host galaxies representing almost the same Hubbleclassification. Seyfert 1 galaxies have bluer nuclei than Seyfert 2s,while intermediate types have intermediate properties or propertiescloser to Seyfert 1s. Disc colours and structural parameters, however,are the same. More than 50 per cent of the Seyfert galaxies (42 per centof the Seyfert 1 and 60 per cent of the Seyfert 2) are barred galaxieswhich may be higher than that found in `normal' galaxy samples.
| A Multiwavelength Catalog of Seyfert 2 Galaxies Observed in the 2--10 keV Energy Band
This paper is a catalog of Seyfert 2 galaxies observed in the 2-10 keVband (339 flux entries). In total, it contains data on 150 objects; for76 objects, a positive detection is reported, while for the remainingsources, 2 σ upper limits to the X-ray emission are given. Most ofthe data have been collected from the literature over a period startingfrom 1974 up to the middle of 1995. Accurate searches of literature anddatabases were performed for all objects, and frequently spectral fitswere reevaluated in order to make the data in the catalog uniform andcomplete. Some unpublished data are also included. For six objects,EXOSAT/ME date have been extracted from the satellite database andanalyzed; the 13 fluxes obtained have been added to the present catalog.The compilation of hard X-ray data has been complemented with data inthe soft (0.1-3 keV) X-ray band, as well as in ultraviolet (1450 A),optical (5500 A), infrared (3.5, 12, 25, 60, 100 micron), and radio (6cm) bands. Fluxes of the [O II] λ5007 and Hβ emission linesas well as the Balmer decrement Hα/Hβ, and axial ratio a/bare also given. The present database is meant to be a useful tool forthe study of the Seyfert 2 phenomenon in its various aspects.
| A Survey for H 2O Megamasers in Active Galactic Nuclei. I. Observations
We report an extensive search for 22 GHz H_2_O maser emission fromnearby active galaxies. Our sample includes all Seyfert and LINERgalaxies listed in the Huchra catalog or the Veron-Cetty & Veroncatalog with recessional velocities less than 7000 km s^-1^, and allSeyfert galaxies and LINERs in Huchra's catalog with m_b_ <= 14. Inaddition to these distance- and magnitude-limited samples, we have alsoobserved a number of active galaxies, including radio galaxies, athigher redshift; In all, some 354 galaxies have been surveyed. Ten newH_2_O megamaser sources have been detected, resulting in 16 galaxiesthat are currently known to contain H_2_O masers with isotropicluminosities greater than 20 L_sun_. Of the observed active galaxieswith cz < 7000 km s^-1^, 5.4% have detectable H_2_O megamaseremission. This fraction increases to 11% for those sources with cz <2000 km s^-1^. The newly discovered megamaser sources were monitored onsubsequent observing runs. The strength of the maser features varies forthese sources, as they do for Galactic masers. Three of the galaxieshave sufficient data to test for velocity changes of narrow masercomponents comparable in magnitude to those of the well-studied systemicfeatures in NGC 4258. The maser line in one of these galaxies-NGC2639-is found to have a systematic redward velocity drift of 6.6 +/- 0.4km s^-1^ yr^-1^. No systematic velocity drifts are found for the othertwo sources. We also report large apparent velocity changes in theunusual broad H_2_O emission feature in NGC 1052.
| Survey Observations of Emission-Line Stars in the Orion Region V. The Outer Regions
We carried out survey observations for Hα emission stars in six Kisoareas A-0831 (5(deg}×5({deg)) , centered at alpha = 5() h 20() m, delta = +5(deg) ), A-0832 (alpha = 5() h 40() m, delta = +5(deg) ),A-0833 (alpha = 6() h 00() m, delta = +5(deg) ), A-0902 (alpha = 5() h00() m, delta = +0(deg) ), A-0905 (alpha = 6() h 40() m, delta = +0(deg)), and A-0974 (alpha = 5() h 00() m, delta = -5(deg) ) in a series ofextensive surveys in the Orion region. The observations were made usingthe Kiso Schmidt telescope. The numbers of detected Hα emissionstars were 4, 3, 6, 3, 12, and 20 for areas A-0831, A-0832, A-0833,A-0902, A-0905, and A-0974, respectively. Since four of the starsoverlapped each other, the total number is 44. Out of them, 31 are newfindings. Five new nonstellar objects with Hα emission were alsodetected. The celestial coordinates and V magnitudes of the detectedstars were measured, along with an eye estimation of the Hα emissionstrengths. The brightness distribution, which peaks at V = 15 suggeststhat the detected Hα -emission stars are probable candidates of TTauri-type stars.
| On the excess of physical companions among Seyfert galaxies
The results of a search for close companions in two magnitude limitedsamples (mB less than or equal to 15.5) of 99 Seyfert 1 and98 Seyfert 2 galaxies are presented. It is found that there is an excessof physical companions in both samples of galaxies, compared with twocontrol samples of normal field spiral galaxies. The calculated lowerlimit percentages of physical companions are (12 +/- 3)% and (12 +/- 4)%for Seyfert 1 and Seyfert 2, respectively, while the upper limits on thepercentage of galaxies with physical companions are in the range (0%-5%)in both control samples. The excess is confirmed by analysis of theredshifts for all pairs found in the complete, magnitude limited (B(O)less than or equal to 14.5) CfA sample of Seyfert galaxies.
| MEPSICRON spectrophotometry of Seyfert galaxies. 1: Spectral atlas
A spectrophotometric study of 51 Seyfert galaxies is presented. Thegalaxies were observed with a long-slit spectrograph coupled to thephoton-counting bidimensional detector MEPSICRON. The paper includes thecalibrated spectra of the inner nuclear region of the galaxies, obtainedwith spectral resolution of 12 A and a signal-to-noise ratio greaterthan 50 on strong emission lines. A detailed spectral lineidentification was carried out and is presented with the correspondingderived line fluxes and equivalent widths.
| Blue spectropolarimetry of Seyfert 2 galaxies. 1: Analysis and basic results
Spectropolarimetry in the 3200-6200 A range was obtained on 50 Seyert 2galaxies. After careful subtraction of a template galaxy, the fractionsof the total flux due to starlight Fg and to the featurelesscontinuum Fc were estimated. All of the Seyfert 2 galaxieshave a nonstellar component to their spectrum. Polarization is notcorrelted with Fc which argues against the hypothesis thatall Seyfert 2s have highly polarized featureless continua which areunseen because of dilution by starlight. The nine Seyfert 2s withspectropolarimetrically identified hidden broad-line regions (BLRs) havethe mean value of Fg = 0.30 considerably less than theaverage of 0.70 found for the larger sample. This suggests that thespectropolarimetric method of identifying hidden BLRs in Seyfert 2s ismost sensitive to objects in which the polarization is less contaminatedby a large fraction of starlight. The spectopolarimetric data indicatesa few additional objects, Mrk 266SW and Mrk 573, which may containhidden BLRs, but they require further study at H-alpha.
| The morphological catalogue of galaxies equatorial survey
We present 865 redshifts of galaxies located in the equatorial stripdelta between -17.5 deg and -2.5 deg in the right ascension rangebetween 20 h and 5 h. Redshifts have been obtained for the completesample of all 833 galaxies in the Morphological Catalog of Galaxies withmagnitudes brighter than m = 14.5 (corresponding approximately tom(Zwicky) = 15.0). This sample also includes three galaxies from othersources with more reliable magnitudes, satisfying this limit, and 29fainter galaxies, usually companions of the galaxies in the magnitudelimited sample. Our maps of a very large volume of nearby spacedemonstrate a variety of coherent large scale structures which includelarge voids, 20-50/h Mpc in diameter and large walls at least 70/h Mpcacross.
| 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.
| 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.
| Stationary solutions of a variant of the photogravitational two-body problem and their possible connection with the shape of some galaxies
Not Available
| An optical catalog of extragalactic emission-line objects similar to quasi-stellar objects
A catalog of 935 galaxies which have optical properties similar to thoseof QSOs is given. A subsidiary table of cross-identifications enablesthe reader to relate the name of a given object to its coordinate name.Most of the objects appear to be nonstellar. The majority, more than700, have redshifts z = 0.2 or less, and have mostly been classified asSeyfert galaxies, N systems, or radio galaxies. The Hubble diagram forall of the objects with z = 0.2 or less is shown. The redshiftdistribution peaks at z = 0.025, but there are about 200 powerful radiogalaxies in the extended tail of the distribution which have z greaterthan 0.2. There is a separate and distinct peak in the redshiftdistribution at z = 0.06.
| An Optical and Near Infrared Polarization Survey of Seyfert and Broadline Radio Galaxies - Part Two - the Wavelength Dependence of Polarization
We discuss the wavelength dependence (0.44-2.2 micron) of polarizationof the sample of 71 Seyfert and three broad-line radio galaxiespresented in Paper I. For four galaxies, 3A 0557-353, Fairall 51, IC4329A and NGC 3753, we also present spectropolarimetry covering thewavelength range of 0.4-0.6 microns. Most objects in our sample showdecreasing polarization with increasing wavelength, as might be expectedfor polarization produced by dichroic absorption or by scattering (whenhost galaxy dilution is taken into account). Thirteen objects havewavelength-dependent polarization which resembled that produced by thetransmission of light through aligned dust grains. Two objects (NGC 1065and Mkn 704) show a clear increase in polarized flux density towards theblue, as expected for scattering off small dust grains. However, in manyobjects a similar increase may not be seen, due to reddening. Only eightobjects show any significant wavelength dependence of polarizationposition angle. Seven objects (3C 234, MCG-5-23-16, Tol 0109-353,I11058-1131, NGC 5506, NGC 6300 and I19550-1818) show increasingpolarized flux density with increasing wavelength, which could beproduced by the scattering of radiation off electrons, or the presenceof a non-thermal component. Only four of these objects, all type 2Seyferts (NGC 1685, MCG-5-23-16, NGC 5506 and I19580-1818), show anincrease in degree of polarization to the red. The spectropolarimetricdata show that, for the two Seyfert 1 galaxies 3A 0557-383 and Fairall51, the forbidden lines are less polarized than the continuum andpermitted lines.
| An optical and near-infrared polarization survey of Seyfert and broad-line radio galaxies. I - Statistical properties. II - The wavelength dependence of polarization
The present broad-band and near-IR flux density and polarizationmeasurements of a sample of 71 Seyfert galaxies and three broad-lineradio galaxies confirms earlier indications that the polarization ofSeyferts is generally low in the V-band and at longer wavelengths. Atendency is noted for the polarization to be parallel to the galaxyoptical or dust-lane axis; previous indications that the polarization ofSeyfert 2s tends to be perpendicular to the radio axis are confirmed. Inthe second part of this work, the 0.44-2.2 micron wavelength dependenceof polarization for this sample of 71 Seyfert and three broad-line radiogalaxies is discussed. Most objects in the sample exhibit decreasingpolarization with increasing wavelength, as may be expected inpolarization induced by either dichroic absorption or scattering.
| Optical positions of Seyfert galaxies. III
Positions of B1950.0 with an accuracy of about 0.15 arcsec are given forthe nuclei of 72 galaxies (mostly Seyferts) observed with the 26-inchand 13-inch refractors at Herstmonceux. A comparison is made with radiopositions of those galaxies observed with the Very Large Array whichappear unresolved at radio wavelengths. Some evidence is found for asystematic difference of about +0.12 arcsec in Right Ascension (RA)between the optical and radio positions.
| X-ray and infrared selected active galactic nuclei. I - The missing edge-on galaxies
Morphological classification and axial ratio measurements for a sampleof 288 Seyfert Galaxies (SGs) are presented. Seyferts are predominantlyspirals, and a deficiency of edge-on objects is found of both classesSeyfert 1 and 2 in comparison with a sample of 1600 normal spirals. Thedata suggest that obscuration extends beyond line region, and that thedistribution of dust is flattened and coplanar with the disk of theparent galaxy. A way to find the missing edge-on SGs on the basis oftheir infrared and X-ray emission is proposed. A sample of 144 IRASgalaxies lying inside or close to unidentified hard X-ray HEAO-1 sourcesis selected. Most of the target galaxies are in fact seen edge-on, andit is estimated that at least about 34 of them are obscured activegalactic nuclei (AGN) associated with the X-ray sources.
| Radio structures of Seyfert galaxies. VII - Extension of a distance-limited sample
The VLA has been used at 6 and 20 cm to observe 27 Seyfert galaxies withrecessional velocities less than 4600 km/s that had not been mappedpreviously. The sample shows weak trends for Seyfert 2 galaxies to havemore luminous and larger radio sources than Seyfert 1 galaxies. A 20 cmradio luminosity function is constructed for each Seyfert type and shownto be fairly flat for powers betwen 10 to the 20th and 10 to the 23rdW/Hz. About 10 percent of the galaxies in the present sample may haveflat-spectrum components contributing a substantial amount of theirtotal flux density at centimeter wavelengths.
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