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Discovery of a strong Baldwin effect in mid-infrared AGN lines
We present the discovery of a Baldwin effect in 8 nearby Seyfertgalaxies for the three most prominent mid-infrared forbidden emissionlines observable from the ground that are commonly found in AGN, [ARIII](λ8.99 μm), [S IV](λ10.51 μm), and [NeII](λ12.81 μm). The observations were carried out using theVLT/VISIR imager and spectrograph at the ESO/Paranal observatory. Thebulk of the observed line emission originates in the innermost regionwithin a diameter of 0.4 arcsec, which corresponds to spatial scales ofless than 100 pc within the targeted galaxies. The correlation index isapproximately -0.6 and does not vary significantly for all linesstudied. To date, this is the strongest anticorrelation that has beenmeasured between line equivalent width and continuum luminosity. In thecase of Circinus, we show that, despite using mid-infrared lines,obscuration by either the host galaxy or the circumnuclear dust torusmight affect the measurement. Given the small observed spatial scalesfrom which most of the line emission emanates, it is unclear how wellthese observations agree with the favored “disappearing NLR”scenario for the narrow-line Baldwin effect.Based on ESO observing programmes 078.B-0303, 080.B-0240, and the DDTprogram 280.B-5068.
| XMM-Newton Observations of the Red Type 1.8 Quasar 2M1049+5837: Reflection from Cold and Warm (Ionized) Matter
Chandra observations of the type 1.8, low-redshift (z=0.115), red(J-KS~2) quasar 2MASSJ 104943+583750 (2M1049+5837) indicatedan unusually hard X-ray spectrum (HR~0.6), suggesting obscuration ofNH~4×1022 cm-2 and a flatΓ~0.4 power-law slope. A higher signal-to-noise ratio XMM-Newtonobservation reported here reveals a more complex spectrum, beingextremely hard above ~2 keV, Γ~-0.6, with a well-defined softexcess similar to the bright, nearby Seyfert 2 galaxy Mrk 3. Suchextremely hard quasar spectra cannot be a dominant contributor to thecosmic X-ray background (CXRB; Γ~1.4). Modeling of 2M1049+5837shows the observed 2-10 keV spectrum to be the sum of a stronglyabsorbed ``normal'' Γ~1.8 underlying quasar X-ray continuum, and acold reflection component (R~2). The strong attenuation of the intrinsicX-ray continuum by a sub-Compton-thick line-of-sight column,NH~3.4×1023 cm-2, reveals a softX-ray emission component whose spectrum indicates reprocessing/emissionfrom, possibly extended, photoionized gas. The luminosity of the softX-ray component is similar to Seyfert 2 galaxies, an order of magnitudeless than comparable type 1 AGNs, suggesting partial obscuration ofcore-bright emission. The optical emission is complex, with distinct redand blue scattered light components believed to originate in twoextended regions visible in HST imaging data. The unusual combination ofproperties: optical and X-ray obscuration of the nuclear emission,partially obscured broad but unobscured narrow emission lines, andpartially obscured soft X-ray excess, implies an intermediate viewingangle, over or through the edge of an obscuring disk+wind or torus.2M1049+5837 again demonstrates both the ambiguity of low signal-to-noiseX-ray spectra/hardness ratios and the potential of 2MASS-selected redsources for exploring the complex obscuration and geometry of thenuclear regions in AGNs.
| Mapping of molecular gas inflow towards the Seyfert nucleus of NGC4051 using Gemini NIFS
We present 2D stellar and gaseous kinematics of the inner ~130×180pc2 of the Narrow-Line Seyfert 1 galaxy NGC4051 at a samplingof 4.5pc, from near-infrared K-band spectroscopic observations obtainedwith the Gemini's Near-infrared Integral Field Spectrograph (NIFS)operating with the ALTAIR adaptive optics module. We have used the COabsorption band heads around 2.3μm to obtain the stellar kinematicswhich show the turnover of the rotation curve at only ~55pc from thenucleus, revealing a highly concentrated gravitational potential. Thestellar velocity dispersion of the bulge is ~60kms-1 -implying on a nuclear black hole mass of~106Msolar - within which patches of lowervelocity dispersion suggest the presence of regions of more recent starformation. From measurements of the emission-line profiles we haveconstructed 2D maps for the flux distributions, line ratios, radialvelocities and gas velocity dispersions for the H2, HII and[CaVIII] emitting gas. Each emission-line samples a distinct kinematics.The Brγ emission-line shows no rotation as well as no blueshiftsor redshifts in excess of 30kms-1, and is thus not restrictedto the galaxy plane. The [CaVIII] coronal region is compact butresolved, extending over the inner 75pc. It shows the highest blueshifts- of up to -250kms-1, and the highest velocity dispersions,interpreted as due to outflows from the active nucleus, supporting anorigin close to the nucleus. Subtraction of the stellar velocity fieldfrom the gaseous velocity field has allowed us to isolate non-circularmotions observed in the H2 emitting gas. The most conspicuouskinematic structures are two nuclear spiral arms - one observed inblueshift in the far side of the galaxy (to the north-east), and theother observed in redshift in the near side of the galaxy (to thesouth-west). We interpret these structures as inflows towards thenucleus, a result similar to those of previous studies in which we havefound streaming motions along nuclear spirals in ionized gas usingoptical Integral Filed Unit (IFU) observations. We have calculated themass inflow rate along the nuclear spiral arms, obtaining , a value ~100times smaller than the accretion rate necessary to power the activenucleus. This can be understood as due to the fact that we are onlyseeing the hot `skin' (the H2 emitting gas) of the total massinflow rate, which is probably dominated by cold molecular gas. From theH2 emission-line ratios we conclude that X-ray heating canaccount for the observed emission, but theH2λ2.1218μm/Br γ line ratio suggests somecontribution from shocks in localized regions close to the compact radiojet.
| "Hidden" Seyfert 2 Galaxies in the Chandra Deep Field North
We have compared the X-ray-to-optical flux ratios(FX/Fopt) of absorbed active galactic nuclei(AGNs) in the Chandra Deep Field North (CDF-N) with those of nearby,optically classified Seyfert 2 galaxies. The comparison provides anopportunity to explore the extent to which the local population ofabsorbed AGNs can account for the properties of the distant,spectroscopically ambiguous sources that produce the hard X-raybackground. Our nearby sample consists of 38 objects that well representthe local Seyfert 2 luminosity function. Integrated UBVRI photometry andbroadband X-ray observations are presented. Using these data, we havesimulated the FX/Fopt ratios that local Seyfert 2swould exhibit if they were observed in the redshift range 0.2 <= z<= 1.3 as part of the CDF-N. In the simulations we account for theeffects of redshift on flux measurements in fixed observed-frame bandsand the way the luminosity function of a given population is sampled ina flux-limited survey like the CDF-N. Overall, we find excellentagreement between our simulations and the observed distribution ofFX/Fopt ratios for absorbed AGNs in the CDF-N. Ouranalysis has thus failed to reveal any physical differences between thelocal population of Seyfert 2s and CDF-N sources with similar X-rayproperties. These results support the hypothesis that the nuclearemission lines of many distant hard X-ray galaxies are hidden inground-based spectra due to a combination of observational effects:signal-to-noise ratio, wavelength coverage, and dilution by host-galaxylight.
| New techniques for integral field spectroscopy - II. Performance of the GNIRS IFU
We present results on the performance of the integral field spectroscopy(IFS) capability of the Gemini Near-Infrared Spectrograph installed onthe Gemini-North telescope. This makes use of the innovative AdvancedImage Slicer optical concept described in Paper 1 and uses newdevelopments in diamond-machining to produce its complex micro-optics.The system delivers near-optimal performance for IFS in a small packagethat can be adapted to work with a wide range of spectrographs.In this paper, we present results of extensive tests carried out on thetelescope to verify the measurements of throughput, image quality andscattered light obtained in the laboratory and characterize theinstrument's geometry and spectroscopic performance. This shows that theperformance model, when fed with results of the component surfacemetrology, provides a good match to the throughput of the integral fieldunit measured on the telescope between 1 and 2.5 μm (65 and 90 percent, respectively). At longer wavelengths, the throughput exceeds 90per cent and the way that the design handles diffraction means that itsperformance can actually exceed that of the spectrograph alone with aslit of equivalent width.We also present examples of data obtained during commissioning andsystem verification and compare this with data obtained in other ways,to verify the system performance in recovering astrophysical data.Finally, we review the performance and its relevance to futureterrestrial and space observatories, in particular for large-scalemultiple-IFS applications. We make the case that our design is of greatrelevance to instrumentation for Extremely Large Telescopes. We showthat the throughput can be improved further by techniques to improve thequality of the optical surfaces.
| Formation of ionization-cone structures in active galactic nuclei: I. Stationary model and linear stability analysis
We discuss causes of the formation of the observed kinematics andmorphology of cones of ionized matter in the neighborhood of the nucleiof Seyfert galaxies. The results of linear stability analysis of anoptically thin conic jet where radiation cooling and gravity play animportant part are reported. The allowance for radiation cooling isshown to result in strong damping of all acoustic modes and to haveinsignificant effect on unstable surface Kelvin-Helmholtz modes. In thecase of waveguide-resonance internal gravity modes radiative coolingsuppresses completely the instability of waves propagating away from theejection source and, vice versa, reduces substantially the growth timescale of unstable sourceward propagating modes. The results obtained canbe used to study ionization cones in Seyfert galaxies with radio jets.In particular, our analysis shows that surface Kelvin-Helmholtz modesand volume harmonics are capable of producing regular features observedin optical emission-line images of such galaxies.
| Investigating the Nuclear Obscuration in Two Types of Seyfert 2 Galaxies
We build a large sample of Seyfert 2 galaxies (Sy2s) with both opticalspectropolarimetric and X-ray data available, in which 29 of the Sy2shave a detection of polarized broad emission lines (PBLs) and 25 do not.We find that for luminous Sy2s with L[OIII>1041ergs s-1, sources with PBLs have smaller X-ray absorptioncolumn densities in comparison to those without PBLs (at a 92.3%confidence level): most of the Sy2s withNH<1023.8 cm-2 show PBLs (86%; 12out of 14), while the fraction is much smaller for sources with heavierobscuration (54%; 15 out of 28). The confidence level of the differencein absorption bounces up to 99.1% when using the thickness (``T'') ratio(F2-10keV/F[OIII) as an indicator. We rule outobservation or selection bias as the origin for the difference. Ourresults, for the first time with high statistical confidence, show that,in additional to the activity of the nuclei, the nuclear obscurationalso plays an important role in the visibility of PBLs in Sy2s. Theseresults can be interpreted in the framework of the unified model. We canreach these results in the unified model if (1) the absorption columndensity is higher at large inclinations and (2) the scattering region isobscured at large inclinations.
| The Eddington Ratios in Seyfert 2 Galaxies with and without Hidden Broad-Line Regions
Using a large sample of 90 Seyfert 2 galaxies (Sy2s) withspectropolarimetric observations, we test the suggestion that thepresence of hidden broad-line regions (HBLRs) in Sy2s depends upon theEddington ratio. The stellar velocity dispersion andextinction-corrected [O III] luminosity are used to derive the masses ofcentral supermassive black holes and the Eddington ratio. We find that(1) below an Eddington ratio threshold of 10-1.37, all of theobjects but one are non-HBLR Sy2s, while at higher Eddington ratiosthere is no obvious distinction in the Eddington ratio and black holemass distributions between Sy2s with and without HBLRs; (2) almost nolow-luminosity Sy2s (e.g., L[OIII]<1041 ergss-1) show HBLRs, regardless of the column density of neutralhydrogen; (3) for high luminosities, the possibility of detecting HBLRSy2s is almost the same as that for non-HBLR Sy2s; and (4) whenconsidering only Compton-thin Sy2s with higher [O III] luminosity(>1041 ergs s-1), the detectability of HBLRs isvery high, ~85%. These results suggest that AGN luminosity plays a majorrole in the failure to detect HBLRs in low-luminosity Sy2s, while forhigh-luminosity Sy2s the detectability of HBLRs depends not only uponthe AGN activity, but also upon the torus obscuration.
| A Relation between the Mid-Infrared [Ne V] 14.3 μm and [Ne III] 15.6 μm Lines in Active Galactic Nuclei
We present a strong correlation between the [Ne V] 14.3 μm and [NeIII] 15.6 μm emission lines arising from the narrow-line regions(NLRs) of active galactic nuclei (AGNs), spanning 4 orders of magnitudein luminosity. The data are compiled primarily from Spitzer SpaceTelescope observations of nearby Seyfert galaxies (median z=0.01) and 3Cradio sources (median z=0.52). This correlation is consistent withearlier studies in the optical/UV bands showing that line ratios arisingin the NLRs are remarkably constant across AGNs. We also show that thecorrelation allows only a very narrow range in ionization parameter forsimple photoionization models. The observed correlation will place tightconstraints on alternative models, which predict constant line ratiosover a broader range in ionization parameter.
| BeppoSAX observations in the 2-100 keV band of the nearby Seyfert galaxies: an atlas of spectra
An atlas of high energy (E≥2 keV) spectra of nearby (z≤0.1)Seyfert galaxies observed with BeppoSAX is presented. The data have beenanalyzed in an homogeneous way. The final sample contains BeppoSAXMECS+PDS (LECS data were not used here) pointings of 113 objects. Nouseful X-ray data were present for eight targets. The catalog of X-rayspectra contains data for 43 type-I Seyfert (including Seyfert 1.0, 1.2,and 1.5) and for 62 type-II objects (including Seyfert 1.8, 1.9, and2.0). A total of 163 X-ray spectra (84 for type-I and 79 for type-IIobjects) were analyzed, since some sources were observed several times.81 sources were detected at high energy (above 10 keV) by the PDS: 39are Seyfert I and 42 are Seyfert II. The broadband X-ray spectracovering the ~2-100 keV band are 130 in total. In a forthcoming paper,the statistical analysis of these data will be presented.
| Outflows of Very Ionized Gas in the Centers of Seyfert Galaxies: Kinematics and Physical Conditions
Mid-resolution spectra are used to deduce the size and kinematics of thecoronal region in a sample of Seyfert galaxies by means of observationsof the [Fe XI], [Fe X], [Fe VII], [Si VI], and [Si VII] lines. Thesecoronal lines (CLs) extend from the unresolved nucleus up to a few tensto a few hundreds of parsecs. The region of the highest ionized ionsstudied, [Fe XI] and [Fe X], is the least spatially extended andconcentrates at the center; intermediate-ionization lines extend fromthe nucleus up to a few tens to a few hundred parsecs; lower [OIII]-like ions are known to extend to the kpc range. All togetherindicate a stratification in the ionized gas, usually interpreted interms of nuclear photoionization as the driving ionization mechanism.However, CL profiles show various peculiarities: they are broader by afactor of 2 than lower ionization lines, the broadening being in termsof asymmetric blue wings, and their centroid position at the nucleus isblueshifted by a few hundred km s-1. Moreover, in NGC 1386and NGC 1068, a double-peaked [Fe VII] line is detected in the nuclearand extended coronal region, this being the first report of this type ofprofile in CLs in active galactic nuclei. If interpreted as outflowsignatures, the total broadening of the lines at zero-intensity levelsimplies gas velocities up to 2000 km s-1. Although thestratification of ions across the coronal region means thatphotoionization is the main power mechanism, the high velocities deducedfrom the profiles, the relatively large spatial extension of theemission, and the results from photoionization models indicate that anadditional mechanism is at work. We suggest that shocks generated by theoutflow could provide the additional required power for line formation.Based on observations made with ESO Telescopes at the ParanalObservatory under program 68.B-0627.
| The Hot Gas Content of Low-Luminosity Early-Type Galaxies and the Implications Regarding Supernova Heating and Active Galactic Nucleus Feedback
We have analyzed Chandra observations of 18 low-luminosity early-typegalaxies with LB<~3×1010LsolarB. Thermal emission from hot gas with temperaturesbetween 0.2 and 0.8 keV comprises 5%-70% of the total 0.5-2.0 keVemission from these galaxies. We find that the total X-ray luminosityfrom LMXBs (resolved plus the power-law component of the unresolvedemission) scales roughly linearly with the K-band luminosity of thegalaxies with a normalization comparable to that found in more luminousearly-type galaxies. All of the galaxies in our sample are gas-poor,with gas masses much less than that expected from the accumulation ofstellar mass loss over the lifetime of the galaxies. The average ratioof gas mass to stellar mass in our sample isMgas/M*=0.001, compared to more luminousearly-type galaxies that typically haveMgas/M*=0.01. The time required to accumulate theobserved gas mass from stellar mass loss in these galaxies is typically3×108 yr. Since the cooling time of the gas is longerthan the replenishment time, the gas cannot be condensing out of the hotphase and forming stars, implying that the gas is most likely beingexpelled from these galaxies in a wind. The one exception to this is NGC4552, which is the most optically luminous galaxy in our sample and hasthe highest gas content. Using recent estimates of the Type Ia supernovarate and AGN heating rate in early-type galaxies, we find that, onaverage, heating by Type Ia supernovae should exceed AGN heating ingalaxies with LB<~3×1010LsolarB. We also find that heating by Type Ia supernovae isenergetically sufficient to drive winds in these galaxies, even if thepresent Type Ia supernova rate is overestimated by a factor of 2 or thepresent stellar mass-loss rate is underestimated by a factor of 2.
| The Unified Model of Active Galactic Nuclei. I. Non-Hidden Broad-Line Region Seyfert 2 and Narrow-Line Seyfert 1 Galaxies
The unified model of Seyfert galaxies suggests that there are hiddenbroad-line regions (HBLRs) in Seyfert 2 galaxies (S2s). However, thereis increasing evidence for the appearance of a subclass of S2s lackingHBLRs (non-HBLR S2s). An interesting issue arises as to the relations ofnon-HBLR S2s with other types of Seyfert galaxies and whether or notthey can be included in the unified model. We assemble two subsamplesconsisting of 42 non-HBLR S2s and 44 narrow-line Seyfert 1 galaxies(NLS1s) with redshift z<=0.05 from published literatures to explorethis issue. We compare black hole masses in the galactic centers,accretion rates, and infrared color ratio(f60μm/f25μm) as a potential indicator ofthe dusty torus orientation, [O III] λ5007, radio, andfar-infrared luminosities. We find that non-HBLR S2s and NLS1s have (1)similar distributions of black hole masses [(0.1-3)×107Msolar] and Eddington ratios(LBol/LEdd~1) (2) significantly differentdistributions of f60μm/f25μm ratios; and (3)similar distributions of bulge magnitudes and luminosities of [O III],radio, and far-infrared emission. The similarities and differences canbe understood naturally if they are intrinsically the same, but non-HBLRS2s are viewed at larger angles of the observer's sight than NLS1s. Wethus suggest that non-HBLR S2s only have ``narrower'' broad-line regionsand that they are the counterparts of NLS1s viewed at high inclinationangles. The absence of the polarized emission line in non-HBLR S2s iscaused by the less massive black holes and high accretion rate similarto NLS1s. The implications of the unification scheme of non-HBLR S2s andNLS1s are discussed.
| Gemini near-infrared integral field spectroscopy of the narrow-line region of ESO428-G14: kinematics, excitation and the role of the radio jet
We present two-dimensional (2D) gas kinematics and excitation of theinner 300pc of the Seyfert galaxy ESO428-G14 at a sampling of14pc2, from near-infrared spectroscopic observations at R ~6000 obtained with the Integral Field Unit (IFU) of the GeminiNear-Infrared Spectrograph. From measurements of fluxes and profiles ofthe emission lines [FeII]λ1.257μm, Paβ,H2λ 2.121μm and Brγ, we construct 2D maps ofline intensities and ratios, radial velocities and velocity dispersions.Emission line `tomography' is provided by velocity slices obtainedacross the line profiles, a unique capability of IFUs, which allows themapping of not only the peak velocities but including also the wings. Wecompare these maps with a previously published high spatial resolutionradio map and find a tight relation between the radio structure and theemission-line flux distributions and kinematics, revealing that theradio jet plays a fundamental role not only in shaping the narrow-lineregion but also in the imprint of its kinematics. Blueshifts of up to400kms-1 and velocity dispersions of up to150kms-1 are observed in association with the radio jet at aposition angle (PA)=129°, which is also the PA of the photometricmajor axis of the galaxy. We conclude that the radio jet is launched ata small angle relative to the galactic plane, with the north-westernside slightly oriented towards us. This angle is small enough for theradio jet to shock and compress the gas in the plane of the galaxy, andfor the nuclear continuum to ionize and heat it. The distinct kinematicsand flux distributions observed for the different emission lines suggestdifferent origins for their emission. The [FeII] shows the largestblueshifts and velocity dispersions and its flux distribution isconcentrated along the jet, while the H2 shows the lowestvelocity dispersions and has additional flux contribution from regionsbeyond the jet. Both X-rays emitted by the active galactic nucleus andshocks produced by the radio jet can excite the H2 and [FeII]emission lines. We use the 2D velocity dispersion maps to estimate upperlimits to the contribution of the radio jet to the excitation of [FeII]and H2 which may reach 90 per cent for [FeII] and 80 per centfor H2 in the jet region. The [FeII]/Paβ emission-lineratios and the association of the [FeII] flux distribution andkinematics with the radio structure support a stronger contribution ofthe radio jet to the [FeII] excitation than that of H2. Inthe regions beyond the jet, the observations favour X-ray excitation.
| A 0.8-2.4 μm spectral atlas of active galactic nuclei
Aims.We present a near-infrared spectral atlas of 47 active galacticnuclei (AGN) of all degrees of activity in the wavelength interval of0.8-2.4 μm, including the fluxes of the observed emission lines. Weanalyze the spectroscopic properties of the continuum and emission linespectra of the sources. Methods: . In order to exclude apertureand seeing effects we used near-infrared spectroscopy in the shortcross-dispersed mode (SXD, 0.8-2.4 μm), taking the JHK-bands spectrasimultaneously. Results: .We present the most extensive NIRspectral atlas of AGN to date. This atlas offers a suitable database forstudying the continuum and line emission properties of these objects ina region full of interesting features. The shape of the continuum ofQSOs and Sy 1's are similar, being essentially flat in the H and Kbands, while a strong variation is found in the J band. In Seyfert 2galaxies, the continuum in the Fλ × λ space smoothlydecreases in flux from 1.2 μm redwards in almost all sources. In J,it smoothly rises bluewards in some sources, while in others a smalldecrease in flux is observed. The spectra are dominated by strongemission features of H I, He I, He II, [S III] and by conspicuousforbidden lines of low and high ionization species. Molecular lines ofH{2} are common features of most objects. The absence of O I and Fe IIlines in Seyfert 2 galaxies and the smaller FWHM of these lines relativeto that of H I in the Seyfert 1 give observational support to the factthat they are formed in the outermost portion of the broad-line region.The[P II] and coronal lines are detected for all degrees of activity.The [Fe II] 12 570 Å/16 436 Å line ratio becomes a reliablereddening indicator for the narrow-line region of Seyfert galaxies.
| Penetrating the Deep Cover of Compton-thick Active Galactic Nuclei
We analyze observations obtained with the Chandra X-Ray Observatory ofbright Compton-thick active galactic nuclei (AGNs), those with columndensities in excess of 1.5×1024 cm-2 alongthe lines of sight. We therefore view the powerful central engines onlyindirectly, even at X-ray energies. Using high spatial resolution andconsidering only galaxies that do not contain circumnuclear starbursts,we reveal the variety of emission AGNs alone may produce. Approximately1% of the continuum's intrinsic flux is detected in reflection in eachcase. The only hard X-ray feature is the prominent Fe Kαfluorescence line, with equivalent width greater than 1 keV in allsources. The Fe line luminosity provides the best X-ray indicator of theunseen intrinsic AGN luminosity. In detail, the morphologies of theextended soft X-ray emission and optical line emission are similar, andline emission dominates the soft X-ray spectra. Thus, we attribute thesoft X-ray emission to material that the central engines photoionize.Because the resulting spectra are complex and do not reveal the AGNsdirectly, crude analysis techniques, such as hardness ratios, wouldmisclassify these galaxies as hosts of intrinsically weak, unabsorbedAGNs and would fail to identify the luminous, absorbed nuclei that arepresent. We demonstrate that a three-band X-ray diagnostic can correctlyclassify Compton-thick AGNs, even when significant soft X-ray lineemission is present. The active nuclei produce most of the galaxies'total observed emission over a broad spectral range, and much of theirlight emerges at far-infrared wavelengths. Stellar contamination of theinfrared emission can be severe, however, making long-wavelength dataalone unreliable indicators of the buried AGN luminosity.
| A catalogue of quasars and active nuclei: 12th edition
Aims.This catalogue is aimed at presenting a compilation of all knownAGN in a compact and convenient form and we hope that it will be usefulto all workers in this field.Methods.Like the eleventh edition, itincludes position and redshift as well as photometry (U, B, V) and 6 cmflux densities when available. We now give 20 cm rather than 11 cm fluxdensities.Results.The present version contains 85 221 quasars,1122 BL Lac objects and 21 737 active galaxies (including 9628 Seyfert1s), almost doubling the number listed in the 11th edition. We also givea list of all known lensed and double quasars.
| The radio structure of radio-quiet quasars
Aims.We investigate the radio emitting structures of radio-quiet activegalactic nuclei with an emphasis on radio-quiet quasars to study theirconnection to Seyfert galaxies. Methods: .We present and analysehigh-sensitivity VLA radio continuum images of 14 radio-quiet quasarsand six Seyfert galaxies. Results: .Many of the low redshiftradio-quiet quasars show radio structures that can be interpreted asjet-like outflows. However, the detection rate of extended radiostructures on arcsecond scales among our sample decreases withincreasing redshift and luminosity, most likely due to a lack ofresolution. The morphologies of the detected radio emission indicatestrong interactions of the jets with the surrounding medium. We alsocompare the radio data of seven quasars with corresponding HST images ofthe [O III] emitting narrow-line region (NLR). We find that the scenarioof interaction between the radio jet and the NLR gas is confirmed in twosources by structures in the NLR gas distribution as previously knownfor Seyfert galaxies. The extended radio structures of radio-quietquasars at sub-arcsecond resolution are by no means different from thatof Seyferts. Among the luminosities studied here, the morphologicalfeatures found are similar in both types of objects while the overallsize of the radio structures increases with luminosity. This supportsthe picture where radio-quiet quasars are the scaled-up versions ofSeyfert galaxies. In addition to known luminosity relations we find acorrelation of the NLR size and the radio size shared by quasars andSeyferts.
| The K-band properties of Seyfert 2 galaxies
Aims. It is well known that the [O iii]λ5007 emission line andhard X-ray (2-10 keV) luminosities are good indicators of AGN activitiesand that the near and mid-infrared emission of AGN originates fromre-radiation of dusty clouds heated by the UV/optical radiation from theaccretion disk. In this paper we present a study of the near-infraredK-band (2.2 μm) properties for a sample of 65 Seyfert 2 galaxies. Methods: .By using the AGN/Bulge/Disk decomposition technique, weanalyzed the 2MASS K_S-band images for Seyfert 2 galaxies in order toderive the K_S-band magnitudes for the central engine, bulge, and diskcomponents. Results: .We find that the K_S-band magnitudes of thecentral AGN component in Seyfert 2 galaxies are tightly correlated withthe [O iii]λ5007 and the hard X-ray luminosities, which suggeststhat the AGN K-band emission is also an excellent indicator of thenuclear activities at least for Seyfert 2 galaxies. We also confirm thegood relation between the central black hole masses and bulge's K-bandmagnitudes for Seyfert 2s.
| GNIRS Integral Field Spectroscopy of the Seyfert galaxy ESO 428-G 14
We present GNIRS IFU spatially resolved spectra of the central region ofthe Seyfert 2 galaxy ESO 428-G 14 in the J and K bands of the near-IR.Intensity, line-ratio, kinematic and velocity dispersion maps wereconstructed for the [Fe II]λ1.257μm,Paβλ1.282μm, H_2λ2.122μm andBrγλ2.166μm emission lines. All emission lines areextended along the PA ˜ 129^o, presenting a double structure toboth sides of the nucleus aligned with the radio jet. The H_2 emissionmap, besides presenting a double structure at the highest intensitylevels, present also, at lower levels a more uniform distribution,suggesting a disk origin for its emission. Along the radio jet the ratioH_2/Brγ is approximately constant, with value 0.8+/-0.11indicating that the main excitation mechanism is due thermal processes,which include shocks and X-ray excitation. The ratio [Fe II]/Paβ is0.9+/-0.25 for the nucleus which is a typical value for AGNs, butsmaller than the more extreme ratios presented by some AGNs, whereshocks are the main excitation mechanism for [Fe II] emission. Arotation pattern is present in the four kinematic maps although it canbe observed that in all cases there are other important kinematiccomponents, as there are large deviations from simple rotation. The H_2velocity field is the most similar to the classical spider diagram andits velocity dispersion values are lower than those of [Fe II] and H Ilines, indicating that the neutral and ionized gas are more perturbedthan the molecular gas in agreement with the idea that the H_2 isemitted by the galactic disk.
| Extragalactic H_2O masers and X-ray absorbing column densities
Having conducted a search for the λ 1.3 cm (22 GHz) water vaporline towards galaxies with nuclear activity, large nuclear columndensities or high infrared luminosities, we present H2O spectra for NGC2273, UGC 5101, and NGC 3393 with isotropic luminosities of 7, 1500, and400 Lȯ. The H2O maser in UGC 5101 is by far the mostluminous yet found in an ultraluminous infrared galaxy. NGC 3393 revealsthe classic spectrum of a "disk maser", represented by three distinctgroups of Doppler components. As in all other known cases except NGC4258, the rotation velocity of the putative masing disk is well below1000 km s-1. Based on the literature and archive data, X-rayabsorbing column densities are compiled for the 64 galaxies withreported maser sources beyond the Magellanic Clouds. For NGC 2782 andNGC 5728, we present Chandra archive data that indicate the presence ofan active galactic nucleus in both galaxies. Modeling the hard nuclearX-ray emission, NGC 2782 is best fit by a high energy reflectionspectrum with NH 1024 cm-2. ForNGC 5728, partial absorption with a power law spectrum indicatesNH 8 × 1023 cm-2. Thecorrelation between absorbing column and H2O emission is analyzed. Thereis a striking difference between kilo- and megamasers with megamasersbeing associated with higher column densities. All kilomasers (L_H_2O< 10 Lȯ) except NGC 2273 and NGC 5194 areCompton-thin, i.e. their absorbing columns are <1024cm-2. Among the H{2}O megamasers, 50% arise fromCompton-thick and 85% from heavily obscured (>1023cm-2) active galactic nuclei. These values are not larger butconsistent with those from samples of Seyfert 2 galaxies not selected onthe basis of maser emission. The similarity in column densities can beexplained by small deviations in position between maser spots andnuclear X-ray source and a high degree of clumpiness in thecircumnuclear interstellar medium.
| Emission-line properties of Seyfert 2 nuclei
This is the third paper of a series devoted to the study of the globalproperties of Joguet's sample of 79 nearby galaxies observable from thesouthern hemisphere, of which 65 are Seyfert 2 galaxies. We use thepopulation synthesis models of Paper II to derive `pure' emission-linespectra for the Seyfert 2 galaxies in the sample, and thus explore thestatistical properties of the nuclear nebular components and theirrelation to the stellar populations. We find that the emission-lineclouds suffer substantially more extinction than the starlight, and weconfirm the correlations between stellar and nebular velocitydispersions and between emission-line luminosity and velocitydispersions, although with substantial scatter. Nuclear luminositiescorrelate with stellar velocity dispersions, but Seyferts withconspicuous star-forming activity deviate systematically towards higherluminosities. Removing the contribution of young stars to the opticalcontinuum produces a tighter and steeper relation,L~σ4*, consistent with the Faber-Jacksonlaw.Emission-line ratios indicative of the gas excitation such as[OIII]/Hβ and [OIII]/[OII] are statistically smaller for Seyfertswith significant star formation, implying that ionization by massivestars is responsible for a substantial and sometimes even a dominantfraction of the Hβ and [OII] fluxes. We use our models to constrainthe maximum fraction of the ionizing power that can be generated by ahidden active galactic nucleus (AGN). We correlate this fraction withclassical indicators of AGN photoionization (i.e. X-ray luminosity andnebular excitation), but find no significant correlations. Thus, whilethere is a strong contribution of starbursts to the excitation of thenuclear nebular emission in low-luminosity Seyferts, the contribution ofthe hidden AGN remains elusive even in hard X-rays.
| Molecular hydrogen and [FeII] in active galactic nuclei - II. Results for Seyfert 2 galaxies
Near-infrared spectroscopy is used to study the kinematics andexcitation mechanisms of H2 and [FeII] lines in a sampledominated by Seyfert 2 galaxies. The spectra simultaneously cover theJHK bands, allowing us to compare line fluxes emitted in the interval0.8-2.4 μm and avoiding aperture and seeing effects. TheH2 lines are systematically narrower than the narrow-lineregion lines, suggesting that, very likely, the H2 does notoriginate from the same parcel of gas that forms the narrow-line region.Emission-line ratios between H2 lines favour thermalexcitation mechanisms for the molecular gas in active galactic nuclei.It was found that non-thermal excitation contributes, at most, 30 percent of the observed H2. Thermal excitation is also confirmedby the rather similar vibrational and rotational temperatures in theobjects (~2000 K). The mass of hot H2 ranges from102 to 103Msolar, with nearly half ofobjects showing values of <500 Msolar. It shows that thefraction of molecular mass present in the nuclear region and emitting inthe near-infrared is a very small fraction of the warm molecular masspresent in the centre. A diagnostic diagram composed of the line ratiosH2/Brγ and [FeII]/Paβ proves to be a useful toolin the near-infrared for separating emission-line objects by theirdegree of nuclear activity. We found that active galactic nuclei arecharacterized by H2 2.121 μm/Brγ and [FeII] 1.257μm/Paβ flux ratios between 0.6 and 2. Starburst/HII galaxiesdisplay line ratios <0.6 while low-ionization nuclear emission-lineregions are characterized by values larger than 2 in either ratio.
| Morphology of the coronal-line region in active galactic nuclei*
We present new images of the coronal-line region, as traced by [SiVII]2.48 μm, in some of the nearest Seyfert 2 galaxies. In each of thesegalaxies, the coronal-line emission comprises a bright, compact centralsource and extended emission showing broad alignment along a particulardirection, usually coinciding with that defined by the radio emission orthe extended narrow-line region. The full extent of the coronal-lineemission ranges from a few tens of parsecs to ~150 pc radius from thenucleus and is a factor of ~10 smaller than that seen in the extended,lower ionization gas. With a spatial resolution of 10 pc or better, thecoronal region shows diffuse and filamentary structure in all cases, andit is difficult to see whether it breaks down into discrete blobs suchas those seen in lower ionization lines or radio images of comparableresolution. The extent of the coronal-line emission is larger than wouldbe predicted by photoionization models, which argues for additional insitu gas excitation, the most plausible energy source being shockexcitation.Observations done under ESO/VLT programmes 70.B-0409 and74.B-0404.E-mail: prieto@mpia.de
| Galactic Winds
Galactic winds are the primary mechanism by which energy and metals arerecycled in galaxies and are deposited into the intergalactic medium.New observations are revealing the ubiquity of this process,particularly at high redshift. We describe the physics behind thesewinds, discuss the observational evidence for them in nearbystar-forming and active galaxies and in the high-redshift universe, andconsider the implications of energetic winds for the formation andevolution of galaxies and the intergalactic medium. To inspire futureresearch, we conclude with a set of observational and theoreticalchallenges.
| Water-Vapor Maser Survey for Active Galactic Nuclei: A Megamaser in NGC 6926
We made a survey of water-vapor maser emission for 93 AGNs with theNobeyama 45-m and Mopra 22-m telescopes from 1999 to 2002. A megamaserwas detected in a Seyfert 2 galaxy, NGC 6926, at a distance of 80Mpc, in2002 June. [Greenhill et al. (2003a) have also reported a detection ofthe megamaser at the close date.] The peak flux density was 110mJy, andthe total isotropic luminosity was 340 Lȯ. The masershows triply peaked spectrum, suggesting an edge-on disk. A narrow-linefeature of the maser components at VLSR = 6001 kms-1 was strongly variable with a time scale of a few tens ofdays, and the variation should be of intrinsic origin. We also showed apossibility of variability of water-vapor maser emission of a megamaserpreviously detected in a Seyfert/ultraluminous FIR galaxy, NGC 6240.
| On the transmission-dominated to reprocessing-dominated spectral state transitions in Seyfert 2 galaxies
We present Chandra and XMM-Newton observations of a small sample (11objects) of optically selected Seyfert 2 galaxies, for which ASCA andBeppoSAX had suggested Compton-thick obscuration of the active galacticnucleus (AGN). The main goal of this study is to estimate the rate oftransitions between `transmission-dominated' and`reprocessing-dominated' states. We discover one new transition in NGC4939, with a possible additional candidate in NGC 5643. This indicates atypical occurrence rate of at least ~0.02yr-1. Thesetransitions could be due to large changes of the obscuring gas columndensity, or to a transient dimming of the AGN activity, the latterscenario being supported by detailed analysis of the best-studiedevents. Independently of the ultimate mechanism, comparison of theobserved spectral dynamics with Monte Carlo simulations demonstratesthat the obscuring gas is largely inhomogeneous, with multiple absorbingcomponents possibly spread through the whole range of distances from thenucleus between a fraction of parsecs up to several hundred parsecs. Asa by-product of this study, we report the first measurement ever of thecolumn density covering the AGN in NGC 3393 (NH~= 4.4 ×1024cm-2), and the discovery of soft X-rayextended emission, apparently aligned along the host galaxy main axis inNGC 5005. The latter object most likely hosts an historicallymisclassified low-luminosity Compton-thin AGN.
| The star formation history of Seyfert 2 nuclei
We present a study of the stellar populations in the central ~200 pc ofa large and homogeneous sample comprising 79 nearby galaxies, most ofwhich are Seyfert 2s. The star formation history of these nuclei isreconstructed by means of state-of-the-art population synthesismodelling of their spectra in the 3500-5200 Åinterval. Aquasar-like featureless continuum (FC) is added to the models to accountfor possible scattered light from a hidden active galactic nucleus(AGN).We find the following. (1) The star formation history of Seyfert 2nuclei is remarkably heterogeneous: young starbursts, intermediate-ageand old stellar populations all appear in significant and widely varyingproportions. (2) A significant fraction of the nuclei show a strong FCcomponent, but this FC is not always an indication of a hidden AGN: itcan also betray the presence of a young, dusty starburst. (3) We detectweak broad Hβ emission in several Seyfert 2s after cleaning theobserved spectrum by subtracting the synthesis model. These are mostlikely the weak scattered lines from the hidden broad-line regionenvisaged in the unified model, given that in most of these casesindependent spectropolarimetry data find a hidden Seyfert 1. (4) The FCstrengths obtained by the spectral decomposition are substantiallylarger for the Seyfert 2s which present evidence of broad lines,implying that the scattered non-stellar continuum is also detected. (5)There is no correlation between the star formation in the nucleus andeither the central or overall morphology of the parent galaxies.
| Spatial distribution of galaxies in the Puppis region
We determine the spatial distribution of the galaxies located behind thepart of the zone of avoidance of the Milky Way defined by 220°
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
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