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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.
| 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.
| Fallacies in astronomy and medicine.
Not Available
| 3C 345: the historical light curve (1967-1990) from the digitized plates of the Asiago Observatory
As part of a large project to digitize the plate archives of the Italianand Vatican Astronomical Observatories, we have already performed thedigitization of all available plates of the field of the quasar 3C 345.The plates, approximately 100 in number, were taken with the threetelescopes of the Asiago Observatory (122 cm, 182 cm, 67/90 cm SchmidtTelescope) in the period from 1967 to 1990. We present here essentiallynew data, mostly in the B band, about the variability of 3C 345 and alsoof four other objects (three quasars - Q1, Q2 and Q3 - and the activegalaxy NGC 6212) in the same field, in that period. Beyond thewell-known 3C 345 itself, the other three quasars also show variability,with a range of 2.0 mag for Q1 and Q2, and 1 mag for Q3. The low-levelvariability detected for the nucleus of NGC 6212 is more doubtful, andshould be confirmed by linear detector data.
| Selection Effects in the Redshift Distribution of Gamma-Ray Bursts and Associated Quasi-stellar Objects and Active Galaxies
Redshift distributions of extragalactic objects have been suggested toexhibit periodicities. But based on which periodicities are claimed,peaks and troughs have been shown to be artifacts of observational andanalytical selection effects. The long debate over the matter has so farbeen concerned mostly with quasi-stellar objects (QSOs). However, theclaim for periodicities has now been extended to gamma-ray bursts(GRBs), another species of extragalactic objects with high redshifts.The redshift distribution of the 33 objects (23 GRBs and associated nineQSOs and one active galaxy) for which a periodicity is claimed(Burbidge), with one new GRB redshift added and one too many QSOredshift eliminated, is compared with distributions of three selectioneffect parameters. It is shown that the peaks and troughs in theredshift distribution of the 33 objects have appeared as a result ofobservational and analytical selection effects. This leads to theconclusion that there is no periodicity in the distribution.
| On the Observed Rapid Motions in Extragalactic Radio Sources
Using interferometric methods, radio astronomers have shown that veryrapid motions involving radio jets are detectable in a variety of activecenters: the nuclei of low-redshift radio galaxies, QSOs and BL Lacobjects, and active binary systems containing a black hole or a neutronstar in our own Galaxy. By comparing the positions of about 80extragalactic sources of this type with the position of the galaxies inthe de Vaucouleurs catalog and the updated QSO catalog ofVéron-Cetty and Véron, it is shown that about 50% of themlie within 1° of a low-redshift spiral galaxy, and about 15% lie soclose to galaxies (Δθ<=10') that theassociations are highly significant. Thus, the sources are probablyphysically associated with these galaxies. All the galaxies areclassified as spiral. In addition, many of the sources have other QSOslying very close to them. These results suggest that the motionsobserved in these radio sources, as well as in the nuclei of radiogalaxies and in Galactic microquasars, and perhaps in many more QSOs andother objects, are all similar and are mildly relativistic, and they donot require us to invoke large Lorentz factors. Some of the problemsassociated with this picture are discussed.
| 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
| NGC 6212, 3C 345, and Other Quasi-stellar Objects Associated with Them
It is pointed out that the Seyfert 1 galaxy NGC 6212 is surrounded by alarge number of quasi-stellar objects (QSOs), including the very activeand rapidly varying radio QSO 3C 345, which lies only 4.7′ awayfrom the center of the galaxy. There are two pairs of QSOs with the sameredshifts, including 3C 345, very close to the nucleus of NGC 6212, andthe very high density of the QSOs falls off rapidly with distance fromthat galaxy. If 3C 345 lies at the distance of NGC 6212, the propermotions in the radio jet in 3C 345, which have been studied in detail,correspond to only mildly relativistic speeds, of about 0.33c.
| 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.
| Spectral Energy Distributions of Flat-Spectrum Radio Quasars Observed with BeppoSAX
We report the BeppoSAX observations of six flat-spectrum radio quasars.Three of them have a clear detection up to 100 keV with the PDSinstrument. For four objects the X-ray spectrum is satisfactorily fittedby a power-law continuum with Galactic absorption. QSO 2251+158 showsthe presence of absorption higher than the Galactic value, while thespectrum of the source QSO 0208-512 shows a complex structure, withevidence of absorption at low energy. We construct the spectral energydistributions adding historical data to the broadband X-ray spectraobtained with BeppoSAX and reproduce them with a one-zonesynchrotron-inverse Compton model (including both synchrotronself-Compton and external Compton). The implications are brieflydiscussed.
| Mass Profile of the Infall Region of the Abell 2199 Supercluster
Using a redshift survey of 1323 galaxies (1092 new or remeasured) in aregion of 95 deg2 centered on the nearby galaxy cluster Abell2199, we analyze the supercluster containing A2199, A2197, and an X-raygroup. The caustic technique accurately reproduces the true massprofiles of simulated simple superclusters (i.e., superclusters forwhich the virial mass of one cluster is 2-10 times the virial mass ofall other clusters in the supercluster). We calculate the masses of thetwo main components of A2197 (A2197W and A2197E) by using archival X-rayobservations and demonstrate that the A2199 supercluster is simple (themass of A2199 is 5 and 12 times larger than A2197W and A2197E,respectively) and thus that the caustic technique should yield anaccurate mass profile. The masses of A2199, A2197W, and A2197E withinr500 (the radius within which the enclosed density is 500times the critical density) are 22.0, 3.8, and 1.7 times 1013h-1 Msolar, respectively. The mass profile isuncertain by ~30% within 3 h-1 Mpc and by a factor of 2within 8 h-1 Mpc and is one of only a few for a superclusteron such large scale. Independent X-ray mass estimates agree with ourresults at all radii where they overlap. The mass profile stronglydisagrees with an isothermal sphere profile but agrees with profilessuggested by simulations. We discuss the interplay of the superclusterdynamics and the dynamics of the bound subclusters. The agreementbetween the infall mass profile and other techniques shows that thecaustic technique is surprisingly robust for simple superclusters.
| 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.
| Soft X-ray properties of a spectroscopically selected sample of interacting and isolated Seyfert galaxies
We present a catalogue of ROSAT detected sources in the sample ofspectroscopically selected Seyfert 1 and Seyfert 2 galaxies of Rafanelliet al. (\cite{Rafanelli95}). The catalogue contains 102 Seyfert 1 and 36Seyfert 2 galaxies. The identification is based on X-ray contour mapsoverlaid on optical images taken from the Digitized Sky Survey. We havederived the basic spectral and timing properties of the X-ray detectedSeyfert galaxies. For Seyfert 1 galaxies a strong correlation betweenphoton index and X-ray luminosity is detected. We confirm the presenceof generally steeper X-ray continua in narrow-line Seyfert 1 galaxies(NLS1s) compared to broad-line Seyfert 1 galaxies. Seyfert 2 galaxiesshow photon indices similar to those of NLS1s. Whereas a tendency for anincreasing X-ray luminosity with increasing interaction strength isfound for Seyfert 1 galaxies, such a correlation is not found forSeyfert 2 galaxies. For Seyfert 1 galaxies we found also a strongcorrelation for increasing far-infrared luminosity with increasinginteraction strength. Both NLS1s and Seyfert 2 galaxies show the highestvalues of far-infrared luminosity compared to Seyfert 1 galaxies,suggesting that NLS1s and Seyfert 2 galaxies host strong (circumnuclear)star formation. For variable Seyfert galaxies we present the X-ray lightcurves obtained from the ROSAT All-Sky Survey and from ROSAT PSPC andHRI pointed observations. Besides the expected strong short- andlong-term X-ray variability in Seyfert 1 galaxies, we find indicationsfor X-ray flux variations in Seyfert 2 galaxies. All overlays can beretrieved via CDS anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)}or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/368/797
| 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.
| 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.
| Quasar Creation and Evolution into Galaxies
Building on evidence starting from 1966, X-ray observations have onceagain confirmed the association of quasars with low redshift galaxies.Enough examples of quasar-like objects ejected in opposite directionsfrom nearby, active galaxies have accumulated so that an empiricalevolutionary sequence can be outlined. The quasars start out with lowluminosity and high (z > 2) redshift. As they travel away from theirgalaxy of origin they grow in size and decay in redshift. The redshiftsdrop in steps and near the quantized values of z = 0.6, 0.3, and 0.06the quasars become particularly active, ejecting or breaking up intomany objects which evolve finally into groups and clusters of galaxies.The observations massively violate the assumptions of the Big Bang andrequire continuous, episodic creation in a non expanding universe ofindefinitely large size and age.
| Concentration of quasars around the active extragalactic object 3C 345.
It is shown that there is an over density of about a dozen fainter,generally higher redshift quasars around the bright,strongly variable 3C345. The associated quasars are generally aligned through 3C 345 with anaccuracy that is highly improbable to occur by chance. There is aSeyfert 1 galaxy (NGC 6212) within 4.7 arc min of 3C 345, as in manyother significant associations of quasars with low redshift galaxies.The excess of quasars around 3C 345 and the Seyfert (a factor of 15) issimilar to the excess of quasars around the jet Seyfert NGC1097 (afactor of 20) which was found in 1984. It is noted that at a redshift ofz=0.59, 3C 345 is like a number of other bright apparent magnitudequasars of medium redshift which fall significantly close to lowredshift, active galaxies and exhibit alignments of X-ray sources andX-ray BSO's and quasars.
| 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.
| Spectropolarimetry of high-polarization Seyfert 1 galaxies: Geometry and kinematics of the scattering regions
We present moderate-resolution (10 A) spectropolarimetry of nine Seyfert1 galaxies. Four of the objects are either essentially unpolarized (NGC6212 and NGC 7469) or polarized by interstellar dust in our own Galaxy(III Zw 2 and NGC 6814). The most striking result for the remainder isthat all of them show emission-line polarization and show evidence formultiple sources of polarization. Some objects appear to be polarized bydust reflection, others by electron scattering, and at least one byboth. These observations rule out simple, axisymmetric models of theSeyfert nuclei and their immediate environment. The high polarization ofMrk 231 results from light reflected by high-velocity dust clouds. Thenew absorption system reported by Boroson et al. (1991) is visible inour spectra, and we confirm the variability curve of this featurereported by Kollatschny et al. (1992). The spectral polarizationstructures of Mrk 376 and Mrk 704 are quite similar. In both Mrk 509 andNGC 5548 the H-alpha lines appear broader in polarized flux than intotal flux, with P rising above the continuum P in the far wings. Wehave proposed that Seyfert 1 galaxies and quasars are polarized byscattering preferentially in the plane of a relatively thin disk.However, the variety of effects seen in the polarization spectra of theSeyfert 1's studied show that these simple models are not sufficient toexplain the details observed.
| 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.
| 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.
| Associations between quasi-stellar objects and galaxies
A table is presented here listing all close pairs of QSOs and galaxiesthat were found in a computer-aided search of catalogs of QSOs andbright galaxies and an extensive search of the literature. There is alarge excess of pairs with separations of 2 arcmin lor less, or about 60kpc, over the numbers expected if the configurations were accidental.The angular separation for 392 pairs adds to the evidence for physicalassociation, and it is shown that selection effects are not important. Ageneral rule is stated that QSOs tend to lie in the vicinity of normalgalaxies much more often than is expected by chance whether or not thegalaxies and the QSOs have the same redshifts. It is emphasized thatthis rule cannot be explained in terms of gravitational microlensing,and it is concluded that some part of the redshift of all classes ofactive nuclei is not associated with the expansion of the universe.
| Kinematic evidence for a relativistic Keplerian disk - ARP 102B
Line profiles were calculated for a Keplerian disk with allowance madefor relativistic effects. Excellent agreement was found between theresulting double peaked asymmetric profiles and the H-alpha line of Arp102B; this yielded an accurate determination of several disk parameters.It is believed that the line profile of Arp 102B shows the mostconvincing direct kinematic evidence for rotation in any AGN.
| A catalogue of Seyfert galaxies.
Not Available
| Two elliptical galaxies with active nuclei - NGC 6212 and MKN 501
Spectrophotometric data for the elliptical galaxies NGC 6212 and Mkn501, as well as UBVRI photometry for Mkn 501, are presented. Bothgalaxies are known to harbor active nuclei. The Seyfert 1 nature of thenucleus of NGC 6212 is confirmed, and it is argued that the extendedemission in that galaxy could be due to recent star formation in it.Emission features have been detected at the center of Mkn 501,suggesting the presence of Seyfert-like activity in the nucleus. Bothgalaxies show early-type stellar absorption features, and some of theirmetallicity indicators are peculiar when compared with those ofelliptical galaxies in Formax. In particular, the strengths of themagnesium and iron features are very high. The photometric UBVRI datafor Mkn 501 show small amplitude variations which become more importantin the I band.
| NGC 6212 - an X-ray-selected active elliptical galaxy
Optical and X-ray data on the elliptical galaxy NGC 6212 are reported.The X-ray flux varies by a factor of four on a time scale of months. Theoptical spectrum shows broad Balmer emission lines and narrow forbiddenlines which are typical of low-luminosity X-ray selected Seyfertgalaxies. The continuum is predominantly stellar, with no evidence for anonthermal contribution. Narrow emission lines extend at least 11 kpcfrom the nucleus and are used to derive a rotation curve. The X-rayvariability and relatively weak radio emission of NGC 6212 are notunusual for Seyfert galaxies.
| NGC 6212.
Not Available
| NGC 6212.
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| NGC 6212.
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