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Local and Large-Scale Environment of Seyfert Galaxies
We present a three-dimensional study of the local (<=100h-1 kpc) and the large-scale (<=1 h-1 Mpc)environment of the two main types of Seyfert AGN galaxies. For thispurpose we use 48 Seyfert 1 galaxies (with redshifts in the range0.007<=z<=0.036) and 56 Seyfert 2 galaxies (with0.004<=z<=0.020), located at high galactic latitudes, as well astwo control samples of nonactive galaxies having the same morphological,redshift, and diameter size distributions as the corresponding Seyfertsamples. Using the Center for Astrophysics (CfA2) and Southern SkyRedshift Survey (SSRS) galaxy catalogs (mB~15.5) and our ownspectroscopic observations (mB~18.5), we find that within aprojected distance of 100 h-1 kpc and a radial velocityseparation of δv<~600 km s-1 around each of ourAGNs, the fraction of Seyfert 2 galaxies with a close neighbor issignificantly higher than that of their control (especially within 75h-1 kpc) and Seyfert 1 galaxy samples, confirming a previoustwo-dimensional analysis of Dultzin-Hacyan et al. We also find that thelarge-scale environment around the two types of Seyfert galaxies doesnot vary with respect to their control sample galaxies. However, theSeyfert 2 and control galaxy samples do differ significantly whencompared to the corresponding Seyfert 1 samples. Since the maindifference between these samples is their morphological typedistribution, we argue that the large-scale environmental differencecannot be attributed to differences in nuclear activity but rather totheir different type of host galaxies.
| A Sample of IRAS Infrared-selected Seyfert 1.5 Galaxies: Infrared Color α(60, 25)-dominated Eigenvector 1
The well-documented E1 relationships are first extended to infraredcolor α(60, 25) and flux ratio [O III]/Hβn bycomparing emission-line properties to continuum properties in infraredwavelengths. Both direct correlations and a principal component analysisare used in a sample of 50 IRAS IR-selected Seyfert 1.5 galaxies. Inaddition, to confirm the correlations of E1 in Boroson & Green, oureigenvector 1 turns out to be dominated by the mid-infrared colorα(60, 25) and most strongly affected by RFe, [OIII]/Hβn, and EW(Hβb). Our analysisindicates that the objects with large E1 tend to coexist with relativelyyoung nuclear stellar populations, which implies that E1 is related tothe nuclear star formation history. The IR-dominated eigenvector 1 cantherefore be inferred to be interpreted as the ``age'' of an AGN. Inconfirmation of the work of Xu and coworkers, it is clear that theextreme Seyfert galaxies with both large RFe and large [OIII]/Hβn are rare in our universe.
| The Host Galaxies of Narrow-Line Seyfert 1 Galaxies: Nuclear Dust Morphology and Starburst Rings
We present a study of the nuclear morphology of a sample of narrow- andbroad-line Seyfert 1 galaxies (NLS1s and BLS1s, respectively) based onbroadband images in the Hubble Space Telescope archives. In our previousstudy we found that large-scale stellar bars at >1 kpc from thenucleus are more common in NLS1s than BLS1s. In this paper we find thatNLS1s preferentially have grand-design dust spirals within ~1 kpc oftheir centers. We also find that NLS1s have a higher fraction of nuclearstar-forming rings than BLS1s. We find that many of the morphologicaldifferences are due to the presence or absence of a large-scale stellarbar within the spiral host galaxy. In general, barred Seyfert 1 galaxiestend to have grand-design dust spirals at their centers, confirming theresults of other researchers. The high fraction of grand-design nucleardust spirals and stellar nuclear rings observed in NLS1s' host galaxiessuggests a means for efficient fueling of their nuclei to support theirhigh Eddington ratios.
| Interstellar polarization and the position-angle orientations of type 1 Seyfert galaxies
We comment on recent spectropolarimetric studies that compare theobserved polarization position angles (PAs) of type 1 Seyfert galaxiesnear Hα with the observed orientations of their radio-source axeson the sky. For a Seyfert galaxy in which scattering occurs mainly in anequatorial scattering region, the polarization PA is expected to beparallel to the radio axis, while for a case in which light scatterspredominantly in the polar regions, the Hα polarization PA shouldbe perpendicular to the radio axis. In practice, these correlations aredifficult to establish because a Galactic interstellar polarizationcontribution can introduce a significant uncertainty into thepolarization PA determination, even when the magnitude of interstellarpolarization is small. We show how such uncertainties may affect theanalysis of PA alignments, and present spectropolarimetric observationsof a probe star along the line of sight to the type 1 Seyfert galaxy Mrk871 that allow us to assess the intrinsic Hα polarization and PAof Mrk 871. These results suggest that spectropolarimetric observationsof such probe stars should form an integral part of future polarizationstudies of Seyfert galaxies.
| Starbursts in barred spiral galaxies. VI. HI observations and the K-band Tully-Fisher relation
This paper reports a study of the effect of a bar on the neutralhydrogen (HI) content of starburst and Seyfert galaxies. We also makecomparisons with a sample of ``normal'' galaxies and investigate howwell starburst and Seyfert galaxies follow the fundamental scalingTully-Fisher (TF) relation defined for normal galaxies. 111 Markarian(Mrk) IRAS galaxies were observed with the Nançay radiotelescope,and HI data were obtained for 80 galaxies, of which 64 are newdetections. We determined the (20 and 50%) linewidths, the maximumvelocity of rotation and total HI flux for each galaxy. Thesemeasurements are complemented by data from the literature to form asample of Mrk IRAS (74% starburst, 23% Seyfert and 3% unknown) galaxiescontaining 105 unbarred and 113 barred ones. Barred galaxies have lowertotal and bias-corrected HI masses than unbarred galaxies, and this istrue for both Mrk IRAS and normal galaxies. This robust result suggeststhat bars funnel the HI gas toward the center of the galaxy where itbecomes molecular before forming new stars. The Mrk IRAS galaxies havehigher bias-corrected HI masses than normal galaxies. They also showsignificant departures from the TF relation, both in the B and K bands.The most deviant points from the TF relation tend to have a strongfar-infrared luminosity and a low oxygen abundance. These resultssuggest that a fraction of our Mrk IRAS galaxies are still in theprocess of formation, and that their neutral HI gas, partly of externalorigin, has not yet reached a stationary state.Based on observations obtained at the large radiotelescope ofObservatoire de Nançay, operated by Observatoire de Paris.Tables 5 and 6 are only (and Table 4 also) available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/515
| Radio emission from AGN detected by the VLA FIRST survey
Using the most recent (April 2003) version of the VLA FIRST survey radiocatalog, we have searched for radio emission from >2800 AGN takenfrom the most recent (2001) version of the Veron-Cetty and Veron AGNcatalog. These AGN lie in the 9033 square degrees of sky alreadycovered by the VLA FIRST survey. Our work has resulted in positivedetection of radio emission from 775 AGN of which 214 are new detectionsat radio wavelengths.Tables 3 and 4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/35
| An Optical Spectroscopic Atlas of Low-Redshift Active Galactic Nuclei
We present a spectral atlas of the Hβ region for 215 type 1 AGNs(luminous Seyfert 1/radio galaxy nuclei and low-z quasars) up to z~0.8.Line profiles and measures were derived from the database ofintermediate resolution spectra (R>~1000) with average continuumlevel S/N ratio ~30. Parameters including rest frame equivalent widthand FWHM are provided for the Fe IIopt blend at λ4570,Hβ, He II λ4686, and the [O III] λλ4959, 5007emission lines. We extract clean broad component Hβ profiles andprovide wavelength measurements at 0, 1/4, 1/2, 3/4, and 0.9 peakintensity levels in order to permit a quantitative definition of theHβ broad component for statistical studies. We also discuss sourcesof uncertainty, selection effects, and biases in our sample. The dataare especially important for tests of the eigenvector 1 parameter spaceoccupation and correlation. We show that the I Zw 1 template FeIIopt spectrum reproduces well the observed FeIIopt emission for a wide range of line width and strength. Adetailed analysis of the data within the eigenvector 1 context isdeferred to a companion paper.Based in part on data collected at ESO La Silla.
| The Host Galaxies of Narrow-Line Seyfert 1 Galaxies: Evidence for Bar-Driven Fueling
We present a study of the host galaxy morphologies of narrow- andbroad-line Seyfert 1 galaxies (NLS1's and BLS1's) based on broadbandoptical images from the Hubble Space Telescope archives. We find thatlarge-scale stellar bars, starting at ~1 kpc from the nucleus, are muchmore common in NLS1's than BLS1's. Furthermore, the fraction of NLS1spirals that have bars increases with decreasing full width athalf-maximum of the broad component of Hβ. These results suggest alink between the large-scale bars, which can support high fueling ratesto the inner kiloparsecs, and the high mass accretion rates associatedwith the supermassive black holes in NLS1's.
| Iron Is Not Depleted in High-Ionization Nuclear Emission-Line Regions of Active Galactic Nuclei
To examine whether or not high-ionization nuclear emission-line regions(HINERs) in narrow-line regions of active galactic nuclei are dusty, wefocus on two high-ionization forbidden emission lines, [Fe VII]λ6087 and [Ne V] λ3426. We perform photoionization modelcalculations to investigate possible dependences of the flux ratio of[Fe VII] λ6087/[Ne V] λ3426 on various gas properties, inorder to investigate how useful this flux ratio is to explore the dustabundances in HINERs. Based on our photoionization model calculations,we show that the observed range of the flux ratio of [Fe VII]λ6087/[Ne V] λ3426 is consistent with the dust-freemodels, while it cannot easily be explained by the dusty models. Thissuggests that iron is not depleted in HINERs, which implies that theHINERs are not dusty. This result is consistent with the idea that theHINERs are located closer than the dust-sublimation radius (i.e., theinner radius of dusty tori) and thus can be hidden by dusty tori whenseen from a edge-on view toward the tori, which is also suggested by theAGN-type dependence of the visibility of high-ionization emission lines.
| A spectropolarimetric atlas of Seyfert 1 galaxies
We present optical spectropolarimetry of the nuclei of 36 Seyfert 1galaxies, obtained with the William Herschel and the Anglo-AustralianTelescopes from 1996 to 1999. In 20 of these, the optical emission fromthe active nucleus is intrinsically polarized. We have measured asignificant level of polarization in a further seven objects but thesemay be heavily contaminated by Galactic interstellar polarization. Theintrinsically polarized Seyfert 1 galaxies exhibit a variety ofcharacteristics, with the average polarization ranging from <0.5 to 5per cent and with many showing variations in both the degree andposition angle of polarization across the broad Hα emission line.We identify a small group of Seyfert 1 galaxies that exhibitpolarization properties similar to those of Seyfert 2 galaxies in whichpolarized broad lines have been discovered. These objects representdirect observational evidence that a Seyfert 2-like far-field polarscattering region is also present in Seyfert 1 galaxies. Several otherobjects have features that can be explained in terms of equatorialscattering of line emission from a rotating disc. We propose that muchof the diversity in the polarization properties of Seyfert galaxies canbe understood in terms of a model involving both equatorial and polarscattering, the relative importance of the two geometries as sources ofpolarized light being determined principally by the inclination of thesystem axis to the line of sight.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Surface Density of Bright, Active Extragalactic Objects
A new sample of local, active extragalactic objects has been compiled: acombined sample that is the sum of two samples, of Sy1 galaxies and ofquasars from Markarian's survey and quasars from the Bright QuasarSurvey. A log N(B)-B relation is constructed for the new sample ofactive galaxies, limited to the apparent stellar magnitude B = 15 m .5.It can be represented by a straight line with a slope = 0.60 ±0.06. It is a good extension, without a noticeable jog, of the analogousrelationship for the HamburgESO survey, which has a slope = 0.59± 0.04. The combined surface density of bright active galaxiesand quasars down to B = 15 m .5 is 0.01 per square degree.
| High-Ionization Nuclear Emission-Line Region of Seyfert Galaxies
Recently, Murayama & Taniguchi proposed that a significant part ofthe high-ionization nuclear emission-line region (HINER) in Seyfertnuclei arises from the inner wall of dusty tori because type 1 Seyfertnuclei (S1s) show excess HINER emission with respect to type 2 Seyfertnuclei (S2s). This means that the radiation from the HINER isanisotropic, and thus statistical properties of the HINER emission canbe used to investigate the viewing angle toward dusty tori for varioustypes of Seyfert nuclei. In order to investigate viewing angles towardnarrow-line Seyfert 1 galaxies (NLS1s) and intermediate types of Seyfertgalaxies (i.e., type 1.5, 1.8, and 1.9 Seyfert galaxies, hereafter S1.5,S1.8, and S1.9, respectively), we apply this HINER test to them. We alsoapply the same test for S2s with and without the hidden broad-lineregion. The sample of Seyfert nuclei analyzed here consists of 124Seyfert nuclei compiled from the literature. Our main results andsuggestions are as follows: (1) The NLS1s are viewed more face-on towarddusty tori than the S2s. However, the HINER properties of the NLS1s areindistinguishable from those of the S1s. (2) The S1.5s appear to composeheterogeneous populations; e.g., (a) some of them may be seen from anintermediate viewing angle between S1s and S2s, (b) some S1.5s arebasically S1s but a significant part of the broad-line region (BLR)emission is accidentally obscured by dense, clumpy gas clouds, or (c)some S1.5s are basically S2s, but a part of the BLR emission can be seenfrom some optically thin regions of the dusty torus. (3) The S1.8s, theS1.9s, and the objects showing either a broad Paβ line or polarizedbroad Balmer lines are seen from a large inclination angle, and theemission from the BLRs of such objects reaches us through optically thinparts of dusty tori. These three results support strongly the currentunified model of Seyfert nuclei. Finally, (4) the line ratios of [Fe X]λ6374 to the low-ionization emission lines are rather moreisotropic than those of [Fe VII] λ6087. Therefore, it issuggested that the [Fe X] λ6374 emission is not useful forinvestigating the viewing angle toward the dusty torus in Seyfertnuclei. The most plausible reason seems to be that the [Fe X]λ6374 emission is spatially extended, and thus its strength tendsto show less viewing-angle dependence.
| Starbursts in barred spiral galaxies. V. Morphological analysis of bars
We have measured the bar lengths and widths of 125 barred galaxiesobserved with CCDs. The dependence of bar strength (identified with baraxis ratio) on morphological type, nuclear activity, central and mid-barsurface brightness is investigated. The properties of the bars are bestexplained if the sample is divided into early- (< SBbc) and late-typegalaxies, and into active (starburst, Seyfert or LINER) and normalgalaxies. We find that galaxies with very long bars are mostly activeand that normal late-type galaxies have a distinct behavior from thethree other groups of galaxies. We confirm earlier findings that activelate-type galaxies tend to have both stronger and longer bars thannormal ones. An important result of this paper is that early-typegalaxies do not share this behavior: they all tend to have strong bars,whether they are active or not. We also find correlations between barstrength and relative surface brightness in the middle and at the edgeof the bar, which are not followed by normal late-type galaxies. Theseresults are interpreted in the light of recent numerical simulations andparadigms about galaxy evolution. They suggest that normal late-typegalaxies represent the first stage of galaxy evolution, and that bars inearly- and late-type galaxies do not have the same properties becausethey have a different origin. Based on observations obtained at the 2meter telescope of Observatoire du Pic du Midi, operated by INSU (CNRS)
| 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.
| The Difference between the Narrow-Line Regions of Seyfert 1 and Seyfert 2 Galaxies
This paper presents a comparative study of emission-line ratios of thenarrow-line regions (NLRs) of Seyfert 1 and Seyfert 2 galaxies. Itincludes a literature compilation of the emission-line fluxes [O II]lambda3727, [Ne III] lambda3869, [O III] lambda5007, and [Ne V]lambda3426 as well as 60 μm continuum flux, for a sample of 52Seyfert 1 and 68 Seyfert 2 galaxies. The distribution of theemission-line ratios [O II]/[Ne III] and [O II]/[Ne V] shows thatSeyfert 1 and Seyfert 2 galaxies are statistically different: Seyfert 1galaxies have smaller values than Seyfert 2 galaxies, indicating ahigher excitation spectrum. These and other emission-line ratios arecompared with sequences of models that combine different proportions ofmatter and ionization-bounded clouds and also with sequences of modelsthat vary only the ionization parameter. This comparison shows that theformer models better reproduce the overall distribution of emission-lineratios, indicating that Seyfert 1 galaxies have a smaller number ofionization-bounded clouds than Seyfert 2 galaxies. This difference,together with other results available in the literature, are interpretedfrom the point of view of four different scenarios. The most likelyscenario assumes that Seyfert 1 galaxies have smaller NLRs than Seyfert2 galaxies, possibly due to a preferential alignment of the torus axisclose to the host galaxy plane axis in Seyfert 1 galaxies.
| Starbursts in barred spiral galaxies. III. Definition of a homogeneous sample of starburst nucleus galaxies
This paper presents optical long-slit spectroscopic observations of 105barred Markarian IRAS galaxies. These observations are used to determinethe spectral type (starburst or Seyfert) of emission-line regions in thenucleus and along the bar of the galaxies, in order to define ahomogeneous sample of Starburst Nucleus Galaxies (SBNGs). Our selectioncriteria (ultraviolet excess, far infrared emission and barredmorphology) have been very efficient for selecting star-forminggalaxies, since our sample of 221 emission-line regions includes 82%nuclear or extranuclear starbursts. The contamination by Seyferts is low(9%). The remaining galaxies (9%) are objects with ambiguousclassification (Hii or LINER). The dust content and Hα luminosityincrease towards the nuclei of the galaxies. No significant variation ofthe electron density is found between nuclear and bar Hii regions.However, the mean Hα luminosity and electron density in the barare higher than in typical disk Hii regions. We investigate differentmechanisms for explaining the excess of nitrogen emission observed inour starburst nuclei. There is no evidence for the presence of a weakhidden active galactic nucleus in our starburst galaxies. The cause ofthis excess is probably a selective enrichment of nitrogen in the nucleiof the galaxies, following a succession of short and intense bursts ofstar formation. Our sample of SBNGs, located at a mean redshift of ~0.015, has moderate Hα ( ~ 10(41) erg s(-1) ) and far infrared ( ~10(10) Lsun) luminosities. The types are distributed equallyamong early- and late-type giant spirals with a slight preference forSbc/Sc types because of their barred morphology. The majority (62%) ofSBNGs are isolated with no sign of gravitational interaction. In termsof distance, luminosity and level of interaction, SBNGs are intermediatebetween Hii galaxies and luminous infrared galaxies. Based onobservations obtained at the 1.93 meter telescope of Observatoire deHaute-Provence operated by INSU (CNRS). Tables 1, 3, 4, 5 and 6 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/Abstract.html
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| 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.
| The nature of the FHIL winds from AGN.
In order to investigate the properties of the forbidden high-ionizationlines (FHILs) in the spectra of AGN we observed 15 Seyfert galaxies andtwo emission line radio galaxies with a spectral resolution of about2000 in the spectral range 3200-11000Å. All observed spectracontained significant [Ne V] and [Fe VII] lines. The spectra of theSeyfert nuclei (but not the radio galaxies) showed also [Fe X], [Fe XI],and in some cases [Fe XIV] emission. Our data confirm that the FHILs areon average broader and blueshifted relative to the lines of lowerionization stages. The amount of the blueshift was found to becorrelated with the line widths. Large blueshifts were observed only forlines with high FWHM. An analysis of the line ratios indicates for theFHIL producing plasma an average electron temperature of about 7x10^4^K.Comparing our results with ROSAT data we found a correlation between theX-ray spectral index and the strength of the FHILs. Strong FHIL emissionwas found to occur predominantly in objects with a soft X-ray excess. Wepropose that the FHIL emission and the X-ray absorption edges in AGN("warm absorbers") are related and that both phenomena result from aradiation driven warm wind originating in the central region of the AGN.
| Seyfert Galaxies. IV. Nuclear Profiles of Markarian Seyfert Galaxies from Hubble Space Telescope Images
We have examined the nuclear profiles of the Seyfert and non-SeyfertMarkarian galaxies in our near-infrared Hubble Space Telescope WF/PC-1snapshot survey. We find that nuclei of types 1-1.5 Seyfert galaxies aredominated by strong point sources, while those of Seyfert 2 and non-Seyfert Markarian galaxies tend to be resolved, less distinguished, andsimilar in shape to normal galaxy luminosity profiles. Two possibleinterpretations of this result for type 2 Seyfert galaxies are thattheir nuclear continuum sources are undetected in our bandpass,contributing less than 10% of the nuclear light (within 0.5 radius) inall cases or that their nuclear components are resolved and blend insmoothly with the brightness profile of the host galaxy's bulge. Sincespectroscopic studies support typical nuclear continuum fractionsdistinctly greater than 10%, the latter conclusion is clearlypreferable. If the continua observed in Seyfert 2 galaxies originate asnuclear light that is redirected into the line of sight by scattering,as predicted by unified models of active galactic nuclei, then thescattering regions must be extended. Simple simulations suggest thatthese regions must cover several tens of parsecs or more, in agreementwith estimates of the sizes of the scattering "mirrors" in other Seyfert2 galaxies. However, the similarity of the profiles of non-SeyfertMarkarian and type 2 Seyfert nuclei suggests that circumnuclear starformation may also be an important component in the nuclear profiles ofthe latter.
| The Properties of X-Ray--selected Active Galactic Nuclei. IV. The Local Optical Luminosity Function of Broad-Line Active Galactic Nuclei
We have selected a local (z <= 0.3) subsample of 226 broad lineactive galactic nuclei (BLAGNs) from the Einstein Observatory ExtendedMedium Sensitivity Survey. This sample represents the largest unbiasedand complete sample of local BLAGNs ever assembled and has allowed us toderive their space density in regions of the m_B_ - z plane where, withthe usual optical selection criteria, it is very difficult to obtaincomplete samples of BLAGNs. Using total integrated magnitudes (i.e.,nucleus + host galaxy), we have computed the local optical luminosityfunction of this X-ray selected sample and compared it with thosederived from local optical samples. Thanks to the large number ofobjects at our disposal we can set more stringent constraints on thespace density of BLAGNs than has previously been possible. Theluminosity function derived from our sample is in good agreement withthe composite luminosity function which can be derived from opticallyselected samples only by using different selection criteria in differentranges of absolute magnitude. In particular, at low luminosity (M_B_>= - 22) we confirm the flattening of the local optical luminosityfunction originally suggested by Meurs & Wilson (1984) while in themagnitude range from M_B_ ~ -23 to -25 we find a very good agreementwith the optical spatial density derived using data from the BrightQuasars Survey. By convolving our luminosity function with thedistribution of the ratio of nuclear to total flux of a sample of ~40Seyfert 1 and 1.5 galaxies from the literature, we have also derived anestimate for the nuclear luminosity function of BLAGNs: This nuclearluminosity function is in rather good agreement with the nuclearluminosity functions previously derived, using a much smaller number ofobjects, from optical samples of low-luminosity BLAGNs. A reasonablygood agreement is also found between our luminosity function and theextrapolation to low redshift (z = 0.15, the average redshift of oursample) of the quasar luminosity function derived from more than 1000optically selected quasars. The integration of our nuclear luminosityfunction over the M_B_ - z plane shows that good agreement is obtainedwith the observed number counts of low luminosity (M_B_ >= - 23)BLAGNs at faint magnitudes, if the M_B_ >= -23 population evolvessimilarly to the QSO population.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| A multifrequency radio continuum and IRAS faint source survey of markarian galaxies
Results are presented from a multifrequency radio continumm survey ofMarkarian galaxies (MRKs) and are supplemented by IRAS infrared datafrom the Faint Source Survey. Radio data are presented for 899 MRKsobserved at nu = 4.755 GHz with the National Radio Astronomy Observatory(NRAO)-Green Bank 300 foot (91 m) telescope, including nearly 88% ofthose objects in Markarian lists VI-XIV. In addition, 1.415 GHzmeasurements of 258 MRKs, over 30% of the MRKs accessible from theNational Aeronomy and Ionosphere Center (NAIC)-Arecibo, are reported.Radio continuum observations of smaller numbers of MRKs were made at10.63 GHz and at 23.1 GHz and are also presented. Infrared data from theIRAS Faint Source Survey (Ver. 2) are presented for 944 MRKs, withreasonably secure identifications extracted from the NASA/IPACExtragalactic Database. MRKs exhibit the same canonical infraredcharacteristics as those reported for various other galaxy samples, thatis well-known enhancement of the 25 micrometer/60 micrometer color ratioamong Seyfert MRKs, and a clear tendency for MRKs with warmer 60micrometer/100 micrometer colors to also possess cooler 12 micrometer/25micrometer colors. In addition, non-Seyfert are found to obey thewell-documented infrared/radio luminosity correlation, with the tightestcorrelation seen for starburst MRKs.
| 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.
| Multiwavelength tests of the dusty torus model for Seyfert galaxies
We present a compilation of emission properties for a sample of 116Seyfert galaxies based on both previously unpublished data andmeasurements available in the literature. These measurements includefluxes in the emission lines (O III) lambda(5007) and H-beta, as well asthe infrared (25-60 microns), ultraviolet (1450 A), soft (0.2-4 keV),and hard (2-10 keV) X-ray continua. These are used to try to distinguishbetween isotropic and anisotropic emission properties of Seyfertgalaxies. The distribution functions of (O III) lambda 5007 infrared,and hard X-ray continuum are similar for Seyfert 1's and Seyfert 2's,consistent with these properties being isotropic. The ultraviolet andsoft X-ray continua of Seyfert 2's are underluminous relative to thetype 1's suggesting photons at these energies escape from the centralsource anisotropically. There is a correlation between the ultravioletcontinuum and emission-line fluxes in Seyfert 1's consistent with theidea that the central engine is responsible for powering the lineemission. No such correlation is found for the Seyfert 2's. Instead, thescatter in the plot of ultraviolet continuum versus line emissionsuggests the true nuclear continuum luminosity is not seen at Earth inthese objects. These properties are consistent with those expected inthe dusty torus model.
| Compact radio cores in Seyfert galaxies
We have observed a sample of 157 Seyfert galaxies with a 275 km baselineradio interferometer to search for compact, high brightness temperatureradio emission from the active nucleus. We obtain the surprising resultthat compact radio cores are much more common in Seyfert 2 than inSeyfert 1 galaxies, which at first seems to be inconsistent withorientation unification schemes. We propose a model, involving opticaldepth effects in the narrow-line region, which can reconcile our resultwith the standard unified scheme.
| Galaxy structures in the Hercules region
216 redshifts have been obtained in a region of 981 sq deg south of theHercules supercluster. 172 of these redshifts are of galaxies withmpg less than or equal to 15.1, 110 of which had no previousvelocity measurement. 44 new redshifts are of galaxies fainter thanmpg = 15.1. With these new data we have been able to define asample in a vast region (approximately 1700 sq deg) around Herculeslimited to mpg less than or equal to 15.1 with a velocitycompleteness of 81.5%. 189 galaxies have been morphologically classifiedso that all galaxies in the sample with known velocity now also haveknown morphology. The magnitude limited sample, including 556 galaxies,is then used to identify and describe galaxy structures in the region.We find that the overdense volume is small, that its overall appearanceis that of a coral branch floating in a sea of nothing and that earlyand late type galaxies defined different structures.
| Environments of Seyfert galaxies. I. Construction of the sample and selection effects.
In order to build a satisfactory picture of Seyferts in relation tonormal galaxies we have started a series of papers first establishingsome of their basic environmental properties, especially the differencein the number of close companions between Seyfert 1 and Seyfert 2galaxies. Here we report sample selections and discuss selection effectsinvolved for the samples of 104 Seyferts and 138 control galaxies. Theresults of the statistical analyses are presented by Laurikainen &Salo (1994, Paper II). The neighbouring galaxies are counted on thePalomar Sky Survey Plates to the limiting magnitude =~19m_pg_ within thecircles of 1.5Mpc in diameter (H_0_=100km/s/Mpc), large measuringcircles enabling good elimination of the background galaxies. Subsamplesare selected in order to test the methods by Dahari (1984) and byFuentes-Williams & Stocke (1988). Elimination of background galaxiesand problems related to comparison galaxy sample selection arediscussed. The most important problem in our control galaxy sampleselection is that the redshifts for most of the control galaxies areunknown. The size of this uncertainty is estimated by determining theredshifts by two ways: (1) by assuming that the selected comparisongalaxy has the same redshift as the nearby Seyfert and (2) byMonte-Carlo simulations for Holmberg (1975) galaxy size distribution inspace, taking into account the Malmquist bias. The mean redshifts of thecomparison sample are estimated with these methods to be 0.028 and0.029, respectively, compared with 0.026 for the Seyfert sample.Distribution of Seyferts in Zwicky's clusters is also addressed, andcompared with previous studies. Taking into account optical projections,about 3/4 of the Seyferts are found to be field galaxies. Galaxies inclusters lie preferentially at the cluster borders.
| Warm IRAS sources from the point source catalog. IV. Extended optical line emission.
We present a list of objects observed to have extended line emission inour spectroscopic survey of infrared-warm AGN. Slit spectroscopic datawere obtained for 225 galaxies identified with objects in our compendiumof warm sources from the IRAS Point Source Catalog. Of these, 44 havespatially-resolved emission-line regions along the (arbitrarily placed)slit direction. Measured (projected) linear sizes of the ionized gasregions extend to >10kpc. In the case of the IRAS Seyfert galaxiesthe spatially extended line emission appears to have a lower ionizationstate than the nuclear emission. This contrasts with the warm IRASstarbust galaxies for which there is no significant difference betweenthe ionization states of the nuclear and extended emission. For thestarburst galaxies, there is a relation between the extent of starformation as seen at Hα and the far-IR colors, with more compactbursts having "warmer" colors.
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