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|The Seyfert Population in the Local Universe|
The magnitude-limited catalog of the Southern Sky Redshift Survey(SSRS2) is used to characterize the properties of galaxies hostingactive galactic nuclei (AGNs). Using emission-line ratios, we identify atotal of 162 (3%) Seyfert galaxies out of the parent sample with 5399galaxies. The sample contains 121 Seyfert 2 galaxies and 41 Seyfert 1galaxies. The SSRS2 Seyfert galaxies are predominantly in spirals oftypes Sb and earlier or in galaxies with perturbed appearance as theresult of strong interactions or mergers. Seyfert galaxies in thissample are twice as common in barred hosts as the non-Seyfert galaxies.By assigning galaxies to groups using a percolation algorithm, we findthat the Seyfert galaxies in the SSRS2 are more likely to be found inbinary systems when compared with galaxies in the SSRS2 parent sample.However, there is no statistically significant difference between theSeyfert and SSRS2 parent sample when systems with more than two galaxiesare considered. The analysis of the present sample suggests that thereis a stronger correlation between the presence of the AGN phenomenonwith internal properties of galaxies (morphology, presence of bar,luminosity) than with environmental effects (local galaxy density, groupvelocity dispersion, nearest neighbor distance).Partly based on observations at European Southern Observatory (ESO),under the ESO-ON agreement to operate the 1.52 m telescope.
|Multicolor Optical Imaging of Infrared-Warm Seyfert Galaxies. V. Morphologies and Interactions: Challenging the Orientation Model|
This paper is the last in a series investigating the optical propertiesof a sample of mid-IR warm Seyfert galaxies and of a control sample ofmid-IR cold galaxies. In the present paper I parametrize themorphologies and interaction properties of the host galaxies and combinethese with the major conclusions in my previous papers. My resultsconfirm that nuclear activity is linked to galactic interactions. Isuggest an alternative view to the simple orientation-obscuration modelpostulated for Seyfert types 1 and 2 that takes into account the timeevolution of their environmental and morphological properties. Withinthis view, the distinction between warm Seyfert 1 and 2 galaxies is notone of simple orientation; the latter might instead represent an earlierevolutionary stage, with properties intermediate between the(starburst-dominated) cold galaxies and the (AGN-dominated) warm Seyfert1 galaxies.
|Multicolor Optical Imaging of Infrared-Warm Seyfert Galaxies. IV. Surface Photometry: Color Distributions|
This paper is the fourth in a series studying the optical properties ofa sample of mid-infrared warm Seyfert galaxies and of a control sampleof mid-infrared cold galaxies. The present paper is devoted to theanalysis of the color distributions characterizing the hosts. The warmSeyfert 1 and 2 galaxies show opposite color gradients and their colorprofiles are depicting age and dust effects within single-burst,solar-metallicity models. In particular, we find ample evidence for theoccurrence of strong star formation in the Seyfert 2 disks: their colorand emission line two-dimensional maps suggest dust extinctionassociated with ongoing star formation in spiral and tidal features;their color profiles show starbursts of 0.5-1 Gyr or younger, superposedon the older underlying galaxy population. Most of these properties areshared with the cold galaxies, while the warm Seyfert 1 galaxies showmostly older stellar populations and, in only a few cases, evidence forcircumnuclear star formation.
|Multicolor Optical Imaging of Infrared-Warm Seyfert Galaxies. III. Surface Photometry: Light Profile Decomposition|
This paper is the third in a series studying the optical properties of asample of mid-infrared warm Seyfert galaxies and a control sample ofmid-infrared cold galaxies. This paper is devoted to the analysis of theradial light distributions characterizing the galaxies outside theircentral 2 kpc. The light profiles are decomposed in inner and outercomponents using two generalized exponentials. Each component ischaracterized by a profile shape, a central surface brightness, and ascale length. We find that the warm Seyfert 1 galaxies tend to lie inearlier-type hosts with more centrally concentrated light profiles ascompared with the warm Seyfert 2 galaxies: the Seyfert 1 and 2 bulgeshave similar shapes, but the former are characterized by larger centralsurface brightness and smaller scale length. The cold galaxies aredisk-dominated systems with complex morphologies. All these differencesare confirmed at statistical significance levels better than 95%. Thethree parameters characterizing the bulge component correlate with eachother for all samples within a limited range of bulge luminosities. Thedisk structural parameters span similar ranges (with large scatter) forboth warm and cold samples. The parametrization of light profiles, asdescribed in this paper, shows that the warm Seyfert 1, Seyfert 2, andcold samples occupy different loci in parameter space, clearlysuggesting intrinsic differences between their host galaxy populations.This conclusion will be reinforced in two forthcoming papers, in whichwe will explore the color distributions and the interactioncharacteristics of our samples.
|Multicolor Optical Imaging of Infrared-warm Seyfert Galaxies. I. Introduction and Sample Selection|
The standard AGN unification models attempt to explain the diversity ofobserved AGN types by a few fundamental parameters, where orientationeffects play a paramount role. Whether other factors, such as theevolutionary stage and the host galaxy properties are equally importantparameters for the AGN diversity, is a key issue that we are addressingwith the present data. Our sample of IR-selected Seyfert galaxies isbased on the important discovery that their integrated IR spectrumcontains an AGN signature, the ``warm'' 25-60 μm color index. Thisbeing an almost isotropic property, our sample is much less affected byorientation/obscuration effects compared to most Seyfert samples. Ittherefore provides a test-bed for the orientation-dependent models ofSeyferts, involving dusty tori. We have obtained multicolor broadbandand narrowband imaging for a sample of mid-IR ``warm''(-1.5<=α(25,60)<=0) Seyferts and for a controlsample of mid-IR ``cold'' (α(25,60)<=-1.5) galaxies.The two samples span similar ranges of far-IR colors(~-3.0<=α(60,100)<=0.5). The warm sample contains21 Seyfert 1 and 33 Seyfert 2 galaxies with logLFIR=9.6-11.8and z=0.01-0.08, including some of the most extreme warm sources(L60>=1011 Lsolar). The cold samplecontains 16 IRAS sources selected to match the warm galaxies in redshiftand luminosity range, but show a variety of nuclear types (Seyfert 1,Seyfert 2, and starburst). In the present paper we describe in somedetail the sample selection and briefly discuss their IR properties. Wethen give an overview of the data collected and present broadband imagesfor all our objects. Finally, we summarize the main issues that will beaddressed with these data in a series of forthcoming papers: (i) theorientation versus evolutionary Seyfert unification schemes and (ii) theorigin of mid-IR excess in the warm Seyfert sample.
|Multicolor Optical Imaging of Infrared-warm Seyfert Galaxies. II. Optical and Infrared Properties and Their Correlations|
This paper is the second in a series, studying the optical properties ofa sample of mid-IR-warm Seyfert galaxies and a control sample ofmid-IR-cold galaxies. The present paper is devoted to aperturephotometry. We discuss nuclear (within the central 2 kpc) and diskoptical properties and their correlations with IR properties. Ourresults suggest intrinsic differences in the host properties of theSeyfert type 1 and 2 nuclei. We find a transition in the observedoptical and IR properties from the cold to the warm Seyfert 2 andSeyfert 1 samples, with a partial overlap between the first two. This isin the sense of (1) increasing nuclear optical luminosities and bluernuclear colors, (2) decreasing disk optical luminosities and sizes, and(3) increasing 25 μm luminosities, decreasing far-IR excess(LFIR/LB) and IR loudness(α(V,25), α(V,60)), and bluerα(25,60), and α(12,100) colors. Weinterpret these results as indicating larger dust content and disk starformation for Seyfert 2s, while the optical properties of Seyfert 1s aremostly dominated by their nuclei. The 25 μm emission of the warmsample is mainly due to the active galactic nucleus (AGN) thermalcomponent, although in Seyfert 2s it is probably further enhanced bydisk star formation. The far-IR (60-100 μm) luminosity traces mainlyemission at large scales (the host disks for both Seyfert types). In theIR-cold galaxies, the bulk of IR emission at all wavelengths appears tobe dominated by dust in their disks.
|Relationship between Infrared and Radio Emission of Seyfert Galaxies|
The relationships between the monochromatic luminosity of Seyfertgalaxies at frequencies of 0.408, 1.49, and 4.85 GHz and the integratedluminosity in the far infrared (IR) range are investigated. At all radiofrequencies they are linear and equally close. Some Seyfert galaxies, ofmorphological types S0/a, E, and S0, have a far higher radio luminositythan Seyfert spiral galaxies with the same IR luminosity. Most of themare found to have compact central radio components. Seyfert spiralgalaxies follow the same relationship between radio and IR emission asnon-Seyfert spiral galaxies. The relationships between radio and IRluminosity for the individual groups of galaxies of spectral types Sy1-Sy 1.5 and Sy 1.8-Sy 2 are also linear.
|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.
|The Southern Sky Redshift Survey|
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
|Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies|
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
|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.
|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.
|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.
|The Montreal Blue Galaxy survey. 2: Second list of UV-bright candidates|
We present and discuss the second list of the Montreal Blue Galaxysurvey. Following the inspection of 71 plates, we found 237 newcandidates with B less than 15.5. 73 percent of them are also detectedby Infrared Astronomy Satellite (IRAS). Spectrophotometry was carriedout, at medium resolution, for a subset of 40 objects leading to theidentification of three new AGNs and producing 13 new radial velocities.Spectral classification of our candidates confirms our previous findingthat the majority of our candidates are starburst nucleus galaxiessimilar to the objects studied by Balzano in 1983. Our survey is biasedagainst the high excitation starburst H II galaxies and the LINERgalaxies. Metallicities of our galaxies are found to be from log(O/H)=8.4 to 9.0, which suggests galaxies in advanced stages of chemicalevolution.
|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.
|Virial and jet-induced velocities in Seyfert galaxies. I - A compilation of narrow line region and host galaxy properties|
Data for a sample of 140 Seyfert galaxies have been compiled with theaim of studying the dependence of nuclear gas velocities on propertiesof the host galaxy and properties of the nuclear activity. Parameterswhich characterize these three basic qualities include (1) forbidden OIII 5007 emission line widths measured at various levels in the profile,(2) galaxy luminosity, morphology, inclination, disturbance, androtation amplitude, and (3) H-beta luminosity, forbidden III 5007luminosity, radio luminosity, radio morphology, and Seyfert type.Because compilations of this type draw on a wide range of data quality,each value has been assigned a simple yet well-defined quality rating(a, b, c, r = reject). These indicate the relative data reliability andmake it possible to monitor the influence of poor data on correlationanalyses. Simple descriptions of the parameter distributions are given.
|Warm IRAS sources. II - Optical spectroscopy of objects from the point source catalog|
Optical spectra are presented for a sample of 563 high latitude IRASsources exhibiting relatively warm 25-60 micron colors, with a view tothe efficient identification of Seyfert galaxies. Spectroscopic data areobtained on 358 extragalactic objects. The present census is consistentwith an obscuration scheme for producing both types of Seyfert objectfrom a single parent population, although the origin of excess cool IRradiation from many Seyferts remains unclear.
|Far infrared Seyfert galaxies and their confusing point sources.|
|Southern Sky Redshift Survey - The catalog|
The catalog of radial velocities for galaxies which comprise thediameter-limited sample of the Southern Sky Redshift Survey ispresented. It consolidates the data of observations carried out at theLas Campanas Observatory, Observatorio Nacional, and South AfricanAstronomical Observatory. The criteria used for the sample selection aredescribed, as well as the observational procedures and the techniqueutilized to obtain the final radial velocities. The intercomparisonbetween radial velocity measurements from different telescopes indicatesthat the final data base is fairly homogeneous with a typical error ofabout 40 km/s. The sample is at present 90 percent complete, and themissing galaxies are predominantly objects with very low surfacebrightness for which it is very difficult to obtain optical redshifts.
|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.
|UBVRI aperture photometry of southern Seyfert galaxies and related objects.|
|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.
|A catalogue of Seyfert galaxies.|
|Infrared sizes and colors of selected IRAS galaxies|
The authors have obtained 1.2-10 microns photometry on a sample ofgalaxies selected from the preliminary Infrared Astronomical Satellite(IRAS) circulars. The sizes of their emission regions have beendetermined at 10 microns by comparing the flux densities determined byIRAS with those measured from the ground using a 5.5 arcsec beam. It isfound that many infrared-selected galaxies have characteristic sizes oforder 0.5-2 kpc radius. Galaxies with high 25/60 micron flux densityratios tend to be smaller than those with a low ratio. Galaxies that arecompact and that have large 25/60 micron flux ratios tend also to havehigh 3.8/1.2 micron ratios, lending support to the idea that the 25/60micron color of a galaxy is a good indicator of the presence of anactive nucleus.
|IRAS galaxy redshifts|
Redshifts and brief spectral information are presented for 90 IRASgalaxies. A subsample selected from IRAS circulars 11 and 16 to havehigh 25 micron to 60 micron flux-density ratio includes many Seyfertgalaxies, two of which show broad lines.
|The link between IRAS spectra and near-infrared emission features in external galaxies|
The relationship in external galaxies between the presence of thenear-infrared (NIR) emission features attributed to polycyclic aromatichydrocarbon (PAH) molecules, and the far-infrared (FIR) properties asobserved by IRAS, is investigated. It is found that whenever the NIRfeatures are absent in a galaxy, the FIR spectrum displays anenhancement at shorter wavelengths relative to normal galaxies. Thisenhancement is always associated with a strong activity in the galacticnucleus. Some Seyfert galaxies do not exhibit such an infrared signatureand therefore they are probably energetically dominated bystar-formation processes. Finally, the importance of hard UV photons andof the hot medium in the narrow line region of active nuclei isemphasized in relation to the survival of the PAH molecules. In thisframe, the absence of PAHs in the galactic center could be taken asevidence for the presence of an active nucleus.
|Connection between Seyfert galaxies and clusters|
A Seyfert galaxy (SG) sample of 464 objects is compared with Zwicky andAbell clusters and southern clusters in an effort to determine which SGsare members of clusters. Sixty-seven SGs are identified in the Zwickyclusters, 15 in the Abell clusters, and 18 in the southern clusters.Lists of these objects are presented.
|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.
|Warmers - The missing link between Starburst and Seyfert galaxies|
Recent observational and theoretical work has shown that, as aconsequence of mass loss in the form of stellar winds in the last stagesof their evolution, massive stars can reach effective temperatures ofmore than 100,000 K, being observed as extreme WC or WO Wolf-Rayetstars. In this paper, the effect of these hot stars (which are calledWarmers) on the evolution of metal-rich giant H II regions is examined.It is shown that as a function of age, the emission-line spectrum of theHe II region evolves first into a type 2 Seyfert spectrum and then intoa Liner-type spectrum. It is suggested that many of the active nucleiclassified as type 2 Seyferts and Liners are not associated with anonthermal power source but rather with violent star formation activityat high metal abundance.
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