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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.
| NGC 7679: an anomalous, composite Seyfert 1 galaxy whose X-ray luminous AGN vanishes at optical wavelengths
Morphological disturbances and gas kinematics of the SB0 galaxy NGC 7679= Arp 216 are investigated to understand the history of this highlycomposite object, where AGN and starburst signatures dominate in theX-ray and optical/IR regime, respectively. Perturbations of the ionizedgas velocity field appear quite mild within 15'' (~5 kpc) of the center,so it can be straightforwardly modeled as a circularly rotating disk.Outside that radius, significant disturbances are seen. In particular,the eastern distorted arm as well as the huge neutral hydrogen bridgeconnecting NGC 7679 to the nearby Seyfert spiral NGC 7682 unambiguouslyrepresent the vestige of a close encounter of the two objects ~500 Myrago. The relationship of such a past event with the much more recent,centrally located starburst (not older than 20 Myr) cannot be easilyestablished. Together, the classification of NGC 7679 is less extremethan that proposed in the past, being simply a (disturbed) galaxy wherestarburst and AGN activity coexist with a starburst dominating thebolometric luminosity.
| 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.
| Mid-infrared luminosity as an indicator of the total infrared luminosity of galaxies
The infrared (IR) emission plays a crucial role in understanding thestar formation in galaxies hidden by dust. We first examined fourestimators of the IR luminosity of galaxies, LFIR [CITE],LTIR [CITE], revised version of LTIR [CITE] (wedenote LTIR2), and LIR [CITE] by using theobserved SEDs of well-known galaxies. We found that LIRprovides excellent estimates of the total IR luminosity for a variety ofgalaxy SEDs. The performance of LTIR2 was also found to bevery good. Using LIR, we then statistically analyzed the IRASPSCz galaxy sample [CITE] and found useful formulae relating the MIRmonochromatic luminosities [ L(12 μm) and L(25 μm)] andLIR. For this purpose we constructed a subsample of 1420galaxies with all four IRAS band (12, 25, 60, and 100 μm) fluxdensities. We found linear relations between LIR and MIRluminosities, L(12 μm) and L(25 μm). The prediction error with a95% confidence level is a factor of 4-5. Hence, these formulae areuseful for the estimation of the total IR luminosity only from 12 μmor 25 μm observations. We further tried to make an“interpolation” formula for galaxies at 0
| 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.
| Classification of Spectra from the Infrared Space Observatory PHT-S Database
We have classified over 1500 infrared spectra obtained with the PHT-Sspectrometer aboard the Infrared Space Observatory according to thesystem developed for the Short Wavelength Spectrometer (SWS) spectra byKraemer et al. The majority of these spectra contribute to subclassesthat are either underrepresented in the SWS spectral database or containsources that are too faint, such as M dwarfs, to have been observed byeither the SWS or the Infrared Astronomical Satellite Low ResolutionSpectrometer. There is strong overall agreement about the chemistry ofobjects observed with both instruments. Discrepancies can usually betraced to the different wavelength ranges and sensitivities of theinstruments. Finally, a large subset of the observations (~=250 spectra)exhibit a featureless, red continuum that is consistent with emissionfrom zodiacal dust and suggest directions for further analysis of thisserendipitous measurement of the zodiacal background.Based on observations with the Infrared Space Observatory (ISO), aEuropean Space Agency (ESA) project with instruments funded by ESAMember States (especially the Principle Investigator countries: France,Germany, Netherlands, and United Kingdom) and with the participation ofthe Institute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA).
| A Uniform Database of 2.2-16.5 μm Spectra from the ISOCAM CVF Spectrometer
We present all ISOCAM circular variable filter (CVF) spectra that covermore than one-third of the 2.2-16.5 μm spectral range of theinstrument. The 364 spectra have been classified according to theclassification system of Kraemer et al., as modified by Hodge et al. toaccount for the shorter wavelength range. Prior to classification, thespectra were processed and recalibrated to create a uniform database.Aperture photometry was performed at each wavelength centered on thebrightest position in each image field and the various spectral segmentsmerged into a single spectrum. The aperture was the same for all scalesizes of the images. Since this procedure differs fundamentally fromthat used in the initial ISOCAM calibration, a recalibration of thespectral response of the instrument was required for the aperturephotometry. The recalibrated spectra and the software used to createthem are available to the community on-line via the ISO Data Archive.Several new groups were added to the KSPW system to describe spectrawith no counterparts in either the SWS or PHT-S databases: CA, E/SA,UE/SA, and SSA. The zodiacal dust cloud provides the most commonbackground continuum to the spectral features, visible in almost 40% ofthe processed sources. The most characteristic and ubiquitous spectralfeatures observed in the CVF spectral atlas are those of theunidentified infrared bands (UIR), which are typically attributed toultraviolet-excited fluorescence of large molecules containing aromatichydrocarbons. The UIR features commonly occur superimposed on thezodiacal background (18%) but can also appear in conjunction with otherspectral features, such as fine-structure emission lines or silicateabsorption. In at least 13 of the galaxies observed, the pattern of UIRemission features has been noticeably shifted to longer wavelengths.Based on observations with the Infrared Space Observatory, a EuropeanSpace Agency (ESA) project with instruments funded by ESA Member States(especially the Principal Investigator countries: France, Germany, theNetherlands, and the United Kingdom) and with the participation of theInstitute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA).
| Star Formation History and Extinction in the Central Kiloparsec of M82-like Starbursts
We report on the star formation histories and extinction in the centralkiloparsec region of a sample of starburst galaxies that have similarfar-infrared (FIR), 10 μm, and K-band luminosities as those of thearchetype starburst M82. Our study is based on new optical spectra andpreviously published K-band photometric data, both sampling the samearea around the nucleus. Model starburst spectra were synthesized as acombination of stellar populations of distinct ages formed over theHubble time and were fitted to the observed optical spectra and K-bandflux. The model is able to reproduce simultaneously the equivalentwidths of emission and absorption lines, the continuum fluxes between3500 and 7000 Å, and the K-band and FIR flux. A good fit requiresa minimum of three populations: (1) a young population of age <=8Myr, with its corresponding nebular emission, (2) an intermediate-agepopulation (age <500 Myr), and (3) an old population that forms partof the underlying disk or/and bulge population. The birthrate parameter,which is defined as the ratio of the current star formation rate to theaverage past rate, is found to be in the range 1-12. The contribution ofthe old population to the K-band luminosity depends on the birthrateparameter and remains above 60% in the majority of the sample galaxies.Even in the blue band, the intermediate-age and old populationscontribute more than 40% of the total flux in all the cases. Arelatively high contribution from the old stars to the K-band nuclearflux is also apparent from the strength of the 4000 Å break andthe Ca II K line. The extinction of the old population is found to bearound half that of the young population. The contribution to thecontinuum from the relatively old stars has the effect of diluting theemission equivalent widths below the values expected for young bursts.The mean dilution factors are found to be 5 and 3 for the Hα andHβ lines, respectively.
| 2-10 keV luminosity of high-mass binaries as a gauge of ongoing star-formation rate
Based on recent work on spectral decomposition of the emission ofstar-forming galaxies, we assess whether the integrated 2-10 keVemission from high-mass X-ray binaries (HMXBs),L2-10HMXB, can be used as a reliable estimator ofongoing star formation rate (SFR). Using a sample of 46 local (z 0.1) star-forming galaxies, and spectral modeling of ASCA, BeppoSAX, andXMM-Newton data, we demonstrate the existence of a linear SFR -L2-10^ HMXB relation which holds over 5 decades in X-rayluminosity and SFR. The total 2-10 keV luminosity is not a precise SFRindicator because at low SFR (i.e., in normal andmoderately-starbursting galaxies) it is substantially affected by theemission of low-mass X-ray binaries, which do not trace the current SFRdue to their long evolution lifetimes, while at very high SFR (i.e., forvery luminous FIR-selected galaxies) it is frequently affected by thepresence of strongly obscured AGNs. The availability of purelySB-powered galaxies - whose 2-10 keV emission is mainly due to HMXBs -allows us to properly calibrate the SFR -L2-10HMXB relation. The SFR -L2-10HMXB relation holds also for distant (z 1) galaxies in the Hubble Deep Field North sample, for which we lackspectral information, but whose SFR can be estimated from deep radiodata. If confirmed by more detailed observations, it may be possible touse the deduced relation to identify distant galaxies that are X-rayoverluminous for their (independently estimated) SFR, and are thereforelikely to hide strongly absorbed AGNs.Appendix A is only available in electronic form athttp://www.edpsciences.org
| The relation between AGN hard X-ray emission and mid-infrared continuum from ISO spectra: Scatter and unification aspects
We use mid-infrared spectral decomposition to separate the 6 μmmid-infrared AGN continuum from the host emission in the ISO lowresolution spectra of 71 active galaxies and compare the results toobserved and intrinsic 2-10 keV hard X-ray fluxes from the literature.We find a correlation between mid-infrared luminosity and absorptioncorrected hard X-ray luminosity, but the scatter is about an order ofmagnitude, significantly larger than previously found with smallerstatistics. Main contributors to this scatter are likely variations inthe geometry of absorbing dust, and AGN variability in combination withnon-simultaneous observations. There is no significant differencebetween type 1 and type 2 objects in the average ratio of mid-infraredand hard X-ray emission, a result which is not consistent with the mostsimple version of a unified scheme in which an optically andgeometrically thick torus dominates the mid-infrared AGN continuum. Mostprobably, significant non-torus contributions to the AGN mid-IRcontinuum are masking the expected difference between the two types ofAGN.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/465Based on observations with ISO, an ESA project with instruments fundedby ESA member states (especially the PI countries: France, Germany, TheNetherlands, and the UK) with the participation of ISAS and NASA.
| The XMM-Newton HBS28 sample: Studying the obscuration in hard X-ray selected AGNs
This paper presents the analysis of a statistically complete sample of28 serendipitous X-ray sources selected in 82 pointed XMM-Newton fieldsdown to a count-rate of 0.002 counts s-1 (4.5-7.5 keV energyband). This is the first sample selected in this energy range to havecomplete spectroscopic identifications and redshift determinations forall the objects. Apart from one Galactic source (an interacting binary),all the objects are AGNs. Their optical and X-ray properties (derivedfrom the spectral analysis of the XMM-EPIC data) are compared together.The good correlation between the optical spectral type and the X-rayabsorption properties supports the AGN unified model. Only one objectthat does not fit the relation between optical and X-ray absorption isfound, namely a Seyfert 1.9 with no evidence of obscuration in the X-rayband (NH<1.3×1020 cm-2). Intotal, 7 sources out of 27 are heavily obscured in the X-ray(NH>1022 cm-2), corresponding to asurface density of 0.7 deg-2 at the flux limit the sample(4-7×10-14 erg s-1 cm-2 in the4.5-7.5 keV energy band). Among these obscured objects, two sources showa large (intrinsic) luminosity (L2-10 keV >1044erg s-1) and are thus classified as type 2 QSO. Finally, wehave compared the fraction of X-ray absorbed AGNs (26%) with thatpredicted by the current XRB synthesis models at the flux limit of thesurvey. We find that the models significantly (90% confidencelevel) over predict the fraction of absorbed AGNs thus confirming alsoin this hard energy band (4.5-7.5 keV) similar results recently obtainedin the 2-10 keV band.Based on observations collected at the European Southern Observatory, LaSilla, Chile and on observations obtained with XMM-Newton, an ESAscience mission with instruments and contributions directly funded byESA Member States and the USA (NASA).Appendix A and B are only available in electronic form athttp://www.edpsciences.org
| Starbursts in barred spiral galaxies. VI. HI observations and the K-band Tully-Fisher relation
This paper reports a study of the effect of a bar on the neutralhydrogen (HI) content of starburst and Seyfert galaxies. We also makecomparisons with a sample of ``normal'' galaxies and investigate howwell starburst and Seyfert galaxies follow the fundamental scalingTully-Fisher (TF) relation defined for normal galaxies. 111 Markarian(Mrk) IRAS galaxies were observed with the Nançay radiotelescope,and HI data were obtained for 80 galaxies, of which 64 are newdetections. We determined the (20 and 50%) linewidths, the maximumvelocity of rotation and total HI flux for each galaxy. Thesemeasurements are complemented by data from the literature to form asample of Mrk IRAS (74% starburst, 23% Seyfert and 3% unknown) galaxiescontaining 105 unbarred and 113 barred ones. Barred galaxies have lowertotal and bias-corrected HI masses than unbarred galaxies, and this istrue for both Mrk IRAS and normal galaxies. This robust result suggeststhat bars funnel the HI gas toward the center of the galaxy where itbecomes molecular before forming new stars. The Mrk IRAS galaxies havehigher bias-corrected HI masses than normal galaxies. They also showsignificant departures from the TF relation, both in the B and K bands.The most deviant points from the TF relation tend to have a strongfar-infrared luminosity and a low oxygen abundance. These resultssuggest that a fraction of our Mrk IRAS galaxies are still in theprocess of formation, and that their neutral HI gas, partly of externalorigin, has not yet reached a stationary state.Based on observations obtained at the large radiotelescope ofObservatoire de Nançay, operated by Observatoire de Paris.Tables 5 and 6 are only (and Table 4 also) available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/515
| Near-infrared observations of galaxies in Pisces-Perseus. V. On the origin of bulges
We investigate the scaling relations of bulge and disk structuralparameters for a sample of 108 disk galaxies. Structural parameters ofindividual galaxies are obtained from two-dimensional bulge/diskdecomposition of their H-band surface brightness distributions. Bulgesare modelled with a generalized exponential (Sérsic) withvariable integer shape index n. We find that bulge effectivescalelengths reB and luminosity MBincrease with increasing n, but disk properties are independent of bulgeshape. As Hubble type T increases, bulges become less luminous and theirmean effective surface brightness <μeB>gets fainter; disk <μeD> shows a similar,but much weaker, trend. When bulge parameters(<μeB>, reB,MB) are compared with disk ones(<μeD>, reD,MD), they are tightly correlated for n=1 bulges. Thecorrelations gradually worsen with increasing n such that n=4 bulgesappear virtually independent of their disks. The Kormendy relation,<μeB> vs. reB, isshown to depend on bulge shape n; the two parameters are tightlycorrelated in n=4 bulges (r=0.8), and increasingly less so as ndecreases; disk <μeD> andreD are well correlated (r=0.7). Bulge-to-disksize ratios reB/reD areindependent of Hubble type, but smaller for exponential bulges; the meanreB/reD for n=1 bulges is 4times smaller than that for n=4, with a spread which is 9 times smaller.Strongly barred SB galaxies with exponential bulges are more luminousthan their unbarred counterparts. Exponential bulges appear to beclosely related to their underlying disks, while bulges with higher nvalues are less so; n=4 bulges and their disks apparently have norelation. We interpret our results as being most consistent with asecular evolutionary scenario, in which dissipative processes in thedisk are responsible for building up the bulges in most spirals.Based on observations at the TIRGO, NOT, and VATT telescopes. TIRGO(Gornergrat, CH) is operated by IRA-CNR, Arcetri, Firenze. NOT (LaPalma, Canary Islands) is operated by NOTSA, the Nordic ObservatoryScientific Association. VATT (Mt. Graham, AZ) is operated by VORG, theVatican Observatory Research Group.Full Table 1 is 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/414/905.
| Asteroid database
The development and significance of asteroid database are reviewed inthis paper. Some of online database of asteroid are presented andcompared briefly, including asteroid orbital elements database, asteroidphotometric database, asteroid infrared database, near earth asteroiddatabase and asteroid database. Ephemeris service based on asteroiddatabase is mentioned. The trend of development of asteroid database hasalso been discussed.
| Nuclear Starburst Activity in the Seyfert 2 Galaxy NGC 2273
We present spectrophotometric results of the Seyfert 2 galaxy NGC 2273.The presence of high-order Balmer absorption lines (H8, H9, H10) andweak equivalent widths of CaII K λ3933, CN λ4200, G-bandλ4300 and MgIb λ5173 clearly indicate recent star-formingactivity in the nuclear region. Using a simple stellar populationsynthesis model, we find that for the best fit, the contributions of apower-law featureless continuum, an intermediate-age (108 yr) and an old (>109 yr) stellar populationto the total light at the reference normalization wavelength are 10.0%,33.4% and 56.6%, respectively. The existence of recent starburstactivity is also consistent with its high far-infrared luminosity (logLFIR/ Lȯ = 9.9), its infrared color indexes [α(25,60) = -1.81 and α(60, 100)= -0.79, typical values for Seyfertgalaxies with circumnuclear starburst], and its q-value (2.23, ratio ofinfrared to radio flux, very similar to that of normal spirals andstarburst galaxies). Byrd et al. have suggested that NGC 2273 might haveinteracted with NGC 2273B in less than 109 yr ago, so thestarburst activity in this galaxy could have been triggered by tidalinteraction, as indicated in recent numerical simulations.
| 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.
| The IRAS Revised Bright Galaxy Sample
IRAS flux densities, redshifts, and infrared luminosities are reportedfor all sources identified in the IRAS Revised Bright Galaxy Sample(RBGS), a complete flux-limited survey of all extragalactic objects withtotal 60 μm flux density greater than 5.24 Jy, covering the entiresky surveyed by IRAS at Galactic latitudes |b|>5°. The RBGS includes629 objects, with median and mean sample redshifts of 0.0082 and 0.0126,respectively, and a maximum redshift of 0.0876. The RBGS supersedes theprevious two-part IRAS Bright Galaxy Samples(BGS1+BGS2), which were compiled before the final(Pass 3) calibration of the IRAS Level 1 Archive in 1990 May. The RBGSalso makes use of more accurate and consistent automated methods tomeasure the flux of objects with extended emission. The RBGS contains 39objects that were not present in the BGS1+BGS2,and 28 objects from the BGS1+BGS2 have beendropped from RBGS because their revised 60 μm flux densities are notgreater than 5.24 Jy. Comparison of revised flux measurements forsources in both surveys shows that most flux differences are in therange ~5%-25%, although some faint sources at 12 and 25 μm differ byas much as a factor of 2. Basic properties of the RBGS sources aresummarized, including estimated total infrared luminosities, as well asupdates to cross identifications with sources from optical galaxycatalogs established using the NASA/IPAC Extragalactic Database. Inaddition, an atlas of images from the Digitized Sky Survey with overlaysof the IRAS position uncertainty ellipse and annotated scale bars isprovided for ease in visualizing the optical morphology in context withthe angular and metric size of each object. The revised bolometricinfrared luminosity function, φ(Lir), forinfrared-bright galaxies in the local universe remains best fit by adouble power law, φ(L)~Lα, withα=-0.6(+/-0.1) and α=-2.2(+/-0.1) below and above the``characteristic'' infrared luminosityL*ir~1010.5Lsolar,respectively. A companion paper provides IRAS High Resolution (HIRES)processing of over 100 RBGS sources where improved spatial resolutionoften provides better IRAS source positions or allows for deconvolutionof close galaxy pairs.
| Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
| The Hamburg/RASS Catalogue of optical identifications. Northern high-galactic latitude ROSAT Bright Source Catalogue X-ray sources
We present the Hamburg/RASS Catalogue (HRC) of optical identificationsof X-ray sources at high-galactic latitude. The HRC includes all X-raysources from the ROSAT Bright Source Catalogue (RASS-BSC) with galacticlatitude |b| >=30degr and declination delta >=0degr . In thispart of the sky covering ~ 10 000 deg2 the RASS-BSC contains5341 X-ray sources. For the optical identification we used blue Schmidtprism and direct plates taken for the northern hemisphere Hamburg QuasarSurvey (HQS) which are now available in digitized form. The limitingmagnitudes are 18.5 and 20, respectively. For 82% of the selectedRASS-BSC an identification could be given. For the rest either nocounterpart was visible in the error circle or a plausibleidentification was not possible. With ~ 42% AGN represent the largestgroup of X-ray emitters, ~ 31% have a stellar counterpart, whereasgalaxies and cluster of galaxies comprise only ~ 4% and ~ 5%,respectively. In ~ 3% of the RASS-BSC sources no object was visible onour blue direct plates within 40\arcsec around the X-ray sourceposition. The catalogue is used as a source for the selection of(nearly) complete samples of the various classes of X-ray emitters.
| The intrinsic emission of Seyfert galaxies observed with BeppoSAX/PDS. I. Comparison of the average spectra of the three classes of Seyfert galaxies
We present a study of the hard X-ray spectrum (>15 keV) of differentclasses of Seyfert galaxies observed with BeppoSAX/PDS. Using hard X-raydata, we avoid absorption effects modifying the Seyfert emission andhave direct access to the central engine of these sources. The aim ofthis study is first to characterize the general properties of the hardX-ray spectrum of Seyfert 1, 1.5 and 2 galaxies and secondly to comparetheir intrinsic emission to test unified models according to which allthe classes have the same nucleus.\ We compute the average spectrum of14 Sy 1, 9 Sy 1.5 and 22 Sy 2 galaxies observed by the PDS (15-136 keV).The average spectrum of Sy 1 differs from that of Sy 2, the firstrequiring the presence of a high energy cutoff which is absent in thesecond. We also show that the reflection component is possibly moreimportant in the Sy 2 emission. The nature of Sy 1.5 galaxies isambiguous as they have a negligible reflection component (like Sy 1) anddo not require a cutoff (like Sy 2).
| The cold gas properties of Markarian galaxies
A sample of 61 Markarian galaxies detected in the CO line was compiled.Using available HI, element H2, optical and radio continuumdata, the analysis of the gas kinematics and the star formationproperties for this sample of galaxies was performed. The mainconclusion can be summarized as follows: (1) The HI and CO line widthsare well correlated. Interaction between galaxies has no influence onthe CO line broadening. A rapidly rotating nuclear disk in the galaxymight lead to the CO line broadening with less influence on the HI line.(2) The atomic and molecular gas surface densities are well correlatedwith the blue, FIR and radio continuum surface brightness; however, thecorrelation for molecular component is stronger.\ (3) In general, thegalaxies with UV-excess (Markarian galaxies) do not differ in their starformation properties from the non-UV galaxies.
| A New Empirical Method for Estimating the Far-Infrared Flux of Galaxies
We propose a new empirical method to estimate the total far-infraredflux of galaxies from the spectral energy distribution (SED) atwavelengths of λ <= 100 μm. It is difficult to derive thetotal far-infrared luminosity from only the IRAS data, though it is oneof the most important properties of galaxies. Observations by InfraredTelescope in Space (IRTS) indicate that the SED of the diffuse emissionfrom the Galactic plane in this wavelength region can be derived fromthe 60 μm to 100 μm color. This empirical SED relation wasimproved in order to obtain a better fit to the Galactic plane data forIν(60 μm) / Iν(100 μm) > 0.6, andapplied to 96 IRAS galaxies for which ISOPHOT and KAO data are availableat λ > 100 μm. As a result, the empirical relation welldescribes the far-infrared (FIR) SED for a majority of galaxies.Additionally, the total FIR flux for λ >= 40 μm was derivedfrom the flux densities at 60 and 100 μm by using this model. For the96 IRAS galaxies, the uncertainty in the total far-infrared flux of thepresent method is 26%. The present method is more accurate than theprevious one widely used to derive the total infrared flux from the IRAS60 and 100 μm data.
| Chandra Observations of Markarian 273: Unveiling the Central Active Galactic Nucleus and the Extended Hot Gas Halo
We report X-ray observations of the field containing the ultraluminousIRAS galaxy Mrk 273. The data were obtained using the Advanced CCDImaging Spectrometer S3 instrument on board Chandra. The high-resolutionX-ray image for the first time reveals a compact hard X-ray nucleus inMrk 273. Its position is coincident with the northern nucleus identifiedin the optical, infrared, and radio and in molecular CO maps. Its X-rayenergy distribution is well described by a heavily obscured activegalactic nucleus (AGN) spectrum with an absorbed power law plus a narrowFe Kα emission line at 6.4 keV. The neutral hydrogen columndensity is about 4×1023 cm-2, implying anabsorption-corrected X-ray luminosity (0.1-10 keV) for the nucleus ofLX~6.5×1043 ergs s-1 forH0=50 km s-1 Mpc-1. The X-rayproperties therefore firmly establish the northern nucleus of Mrk 273 asa Seyfert 2 AGN. There are also bright soft X-ray clumps and diffusesoft X-ray emissions surrounding the central hard X-ray nucleus withinthe 10" of the nuclear region. Its spectrum can be fitted by a MEKALthermal model with a temperature of about 0.8 keV and high metallicity(Z~1.5 Zsolar) plus emission lines from α elements andions. We find that a soft X-ray clump, about 4" (projected separation ofabout 4 kpc) southwest of the northern hard X-ray nucleus, is coincidentwith a nebula with strong [O III] λ5007 emissions. Furtheroutside the central region, the Chandra observations reveal a veryextended hot halo in Mrk 273. The X-ray halo encompasses the entireoptical tidal tail and plume, with a projected diameter of about108×68 kpc. The total soft X-ray luminosity (0.1-2.4 keV) of thehot halo is LX~1.9×1041 ergs s-1,in the range of the soft X-ray luminosity of bright elliptical galaxies.The temperature of the hot gas is about 0.62 keV with a low metallicity(Z~0.1 Zsolar). We discuss the nature of the AGN in Mrk 273and the implications of our results on the origin of X-ray halos inelliptical galaxies. We also discuss the properties of Mrk 273x, abackground AGN at redshift z=0.46 in the Mrk 273 field. The AGN has anX-ray luminosity of LX~2.43×1044 ergss-1 in the 0.5-10 keV band. Its X-ray properties resemblethose of Seyfert 1 galaxies, while its optical properties are similar toSeyfert 2 galaxies. Such mixed classifications in the optical and X-raymay be a challenge for the unification scheme of AGNs.
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| 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.
| Unabsorbed Seyfert 2 galaxies
We present a sample of 17 type 2 Seyfert galaxies which have an X-raycolumn density lower than 1022 cm-2. The Comptonthin nature of these sources is strongly suggested by isotropicindicators. We estimate the fraction of these sources to be in the rangeof 10%-30% of the population of type 2 Seyfert galaxies. Furthermore,this fraction appears to increase progressively at lower luminosities.The simple formulation of the Unified Model for Seyfert galaxies is notapplicable in such sources since the pc-scale molecular torus is notlikely to be responsible for the low column density observed; insteadthe absorption observed is likely to originate at larger scales.According to this hypothesis, in these objects the broad line regionsare covered by some dusty obscuring material. In particular, this couldoccur in objects with dust lanes, patches or HII regions. However, wecannot rule out that in the lowest luminosity sources the BLR is weak,absent or has faded away. This last scenario is consistent with thepredictions of some recent theoretical models for low luminosity AGNs.
| The BeppoSAX view of bright Compton-thin Seyfert 2 galaxies
We present the analysis of 31 observations (17 of which are publishedhere for the first time) of 20 bright Compton thin Seyfert 2 s, in the0.1-200 keV band, performed with the BeppoSAX satellite. The sampleconsists of all Seyfert 2 s in the BeppoSAX public archive, with a 2-10keV flux higher than 5*E-12 erg cm-2s-1. The good statistics available and the broad energy bandpermit a detailed study of the main continuum components of thesesources, i.e. the primary power-law, the reflected component, the softemission and the high-energy cut-off. The main results of our analysisare: (1) the 3-200 keV intrinsic power-law has a mean photon index Gamma= 1.79 +/- 0.01, with a dispersion of sigma =0.23. (2) The high-energyexponential cut-off at E ~ 100-300 keV is not an ubiquitous property ofSeyfert galaxies: in ~ 30% of the objects the continuum power-law doesnot drop up to energies of 300 keV or more. (3) A reflected component ispresent in almost all the sources (17 out of 21). The small variationsof this component with respect to the intrinsic continuum, in objectswith multiple observations, suggests that the reflector is not theaccretion disk, but must be located much farther from the nucleus. (4)The range of ratios between the reflected and intrinsic componentssuggests that the circumnuclear medium is not homogeneous, and asignificant fraction of the solid angle is covered by a gas thicker thanthat along the line of sight. (5) The iron Kalpha line is present is allbut one the sources. The equivalent width is in the typical range ofSeyfert 1 s (EW=100-300 eV) in sources with low absorption(NH < 3x 1023 cm-2), and increasesin more absorbed objects, as expected according to unified models. (6)The energy resolution of BeppoSAX is in general too low to measure theiron line width. However, in 6 cases we measured a significant linebroadening.
| The SCUBA Local Universe Galaxy Survey - II. 450-μm data: evidence for cold dust in bright IRAS galaxies
This is the second in a series of papers presenting results from theSCUBA Local Universe Galaxy Survey. In our first paper we provided850-μm flux densities for 104 galaxies selected from the IRAS BrightGalaxy Sample and we found that the 60-, 100-μm (IRAS) and 850-μm(SCUBA) fluxes could be adequately fitted by emission from dust at asingle temperature. In this paper we present 450-μm data for thegalaxies. With the new data, the spectral energy distributions of thegalaxies can no longer be fitted with an isothermal dust model - twotemperature components are now required. Using our 450-μm data andfluxes from the literature, we find that the 450/850-μm flux ratiofor the galaxies is remarkably constant, and this holds from objects inwhich the star formation rate is similar to our own Galaxy, toultraluminous infrared galaxies (ULIRGs) such as Arp 220. The onlypossible explanation for this is if the dust emissivity index for all ofthe galaxies is ~2 and the cold dust component has a similar temperaturein all galaxies [formmu3](Tc~20-21K). The 60-μmluminosities of the galaxies were found to depend on both the dust massand the relative amount of energy in the warm component, with a tendencyfor the temperature effects to dominate at the highest L60.The dust masses estimated using the new temperatures are higher by afactor of ~2 than those determined previously using a singletemperature. This brings the gas-to-dust ratios of the IRAS galaxiesinto agreement with those of the Milky Way and other spiral galaxieswhich have been intensively studied in the submm.
| Stellar populations in Seyfert 2 galaxies. I. Atlas of near-UV spectra
We have carried out a uniform spectroscopic survey of Seyfert 2 galaxiesto study the stellar populations of the host galaxies. New spectra havebeen obtained for 79 Southern galaxies classified as Seyfert 2 galaxies,7 normal galaxies, and 73 stars at a resolution of 2.2 Å over thewavelength region 3500-5300 Å. Cross-correlation between thestellar spectra is performed to group the individual observations into44 synthesis standard spectra. The standard groups include a solarabundance sequence of spectral types from O5 to M3 for dwarfs, giants,and supergiants. Metal-rich and metal-weak F-K giants and dwarfs arealso included. A comparison of the stellar data with previouslypublished spectra is performed both with the individual spectra and thestandard groups. For each galaxy, two distinct spatial regions areconsidered: the nucleus and the external bulge. Spectroscopic variationsfrom one galaxy to another and from the central to the external regionare briefly discussed. It is found that the central region of a Seyfert2 galaxy, after subtracting the bulge stellar population, always shows anear-UV spectrum similar to one of three representative categories: a)many strong emission lines and only two visible absorption lines (Ca IiK and G band) (Sey2e); b) few emission lines, many absorption lines, anda redder continuum than the previous category (Sey2a); c) an almost flatcontinuum and high-order Balmer lines seen in absorption (Sey2b). Theproportion of Seyfert 2 galaxies belonging to each class is found to be22%, 28%, and 50% respectively. We find no significative differencesbetween morphology distributions of Seyfert 2 galaxies with Balmer linesdetected in absorption and the rest of the sample. This quick lookthrough the atlas indicates that half of Seyfert 2 galaxies harbour ayoung stellar population (about or less than 100 Myr) in their centralregion, clearly unveiled by the high order Balmer series seen inabsorption. Based on observations collected at the European SouthernObservatory, Chile (ESO 65.P-0014(A)). Tables 1-3 and 8 and Fig. A.1(Appendix A) are only available in electronic form athttp://www.edpsciences.org
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