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A Sample of IRAS Infrared-selected Seyfert 1.5 Galaxies: Infrared Color α(60, 25)-dominated Eigenvector 1
The well-documented E1 relationships are first extended to infraredcolor α(60, 25) and flux ratio [O III]/Hβn bycomparing emission-line properties to continuum properties in infraredwavelengths. Both direct correlations and a principal component analysisare used in a sample of 50 IRAS IR-selected Seyfert 1.5 galaxies. Inaddition, to confirm the correlations of E1 in Boroson & Green, oureigenvector 1 turns out to be dominated by the mid-infrared colorα(60, 25) and most strongly affected by RFe, [OIII]/Hβn, and EW(Hβb). Our analysisindicates that the objects with large E1 tend to coexist with relativelyyoung nuclear stellar populations, which implies that E1 is related tothe nuclear star formation history. The IR-dominated eigenvector 1 cantherefore be inferred to be interpreted as the ``age'' of an AGN. Inconfirmation of the work of Xu and coworkers, it is clear that theextreme Seyfert galaxies with both large RFe and large [OIII]/Hβn are rare in our universe.
| The 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.
| Numerous Old Starburst Galaxies in the Local Universe
Old starburst galaxies are deficient in O stars and hence do not exhibitstrong line emission in the optical regime. However, there remain many Bstars, which are expected to heat dust grains and generate strongcontinuum emission in the far-infrared. The IRAS data for astatistically complete sample of nearby galaxies reveal for the firsttime that such objects are as numerous as 30%-40% of the local galaxypopulation.
| The Asiago-ESO/RASS QSO Survey. I. The Catalog and the Local QSO Luminosity Function
This paper presents the first results of a survey for bright quasars(V<14.5 and R<15.4) covering the northern hemisphere at Galacticlatitudes |b|>30°. The photometric database is derived from theGuide Star and USNO catalogs. Quasars are identified on the basis oftheir X-ray emission measured in the ROSAT All-Sky Survey. The surfacedensity of quasars brighter than 15.5 mag turns out to be(10+/-2)×10-3 deg-2, about 3 times higherthan that estimated by the PG survey. The quasar optical luminosityfunction (LF) at 0.04
| The ROSAT/IRAS Galaxy Sample Revisited
Galaxies in the ROSAT/IRAS sample were selected by their soft X-ray(0.1-2.4 keV) and far-infrared (lambda = 60 μm) emission. Therelatively large uncertainties in the original ROSAT and IRAS positionscaused some contamination by close pairs and forced the exclusion ofmost ``high-flux'' (S > 10 Jy at lambda = 100 μm) IRAS sourcesfrom the original sample. We used new 1.4 GHz VLA images of all objectsnorth of delta = -45 deg along with improved X-ray and far-infraredpositions to eliminate incorrect identifications, many of which appearedto be starburst galaxies with high X-ray luminosities, log [X(ergs^-1)]> 43. We also used VLA images to search for new X-ray identificationsamong the ``high-flux'' sources with delta > -45 deg. Only two werefound, indicating that luminous starburst galaxies have relatively lowsoft X-ray luminosities, in part due to absorption by a denseinterstellar medium. No starburst galaxies in our revised sample haveX-ray luminosities approaching log [X(ergs^-1)] = 43. We conclude thatmost galaxies in the revised ROSAT/IRAS sample contain X-ray-emittingactive galactic nuclei (AGNs) residing in star-forming disks that emitmost of the lambda = 60 μm radiation. Normal and starburst galaxiesprobably do not account for a significant fraction of the soft X-raybackground.
| ROSAT All-Sky Survey observations of IRAS galaxies. I. Soft X-ray and far-infrared properties
The 120 000 X-ray sources detected in the RASS II processing of theROSAT All-Sky Survey are correlated with the 14 315 IRAS galaxiesselected from the IRAS Point Source Catalogue: 372 IRAS galaxies showX-ray emission within a distance of 100 arcsec from the infraredposition. By inspecting the structure of the X-ray emission in overlayson optical images we quantify the likelihood that the X-rays originatefrom the IRAS galaxy. For 197 objects the soft X-ray emission is verylikely associated with the IRAS galaxy. Their soft X-ray properties aredetermined and compared with their far-infrared emission. X-ray contourplots overlaid on Palomar Digitized Sky Survey images are given for eachof the 372 potential identifications. All images and tables displayedhere are also available in electronic form.
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| Classification of IRAS-selected X-Ray Galaxies in the ROSAT All-Sky Survey
To explore the possibility that star-forming galaxies or obscuredSeyfert galaxies, both of which are known to be luminous infraredsources, contribute significantly to the cosmic X-ray background, wehave carried out an extensive program to obtain accurate spectroscopicclassifications of the BoIler et al. (1992) catalog of IRAS sourcesdetected in the ROSAT All-Sky Survey. This has involved careful opticalspectroscopy, a review of the literature, and efforts to reveal thecontaminants in the sample. Classifications have been determined for 210of the 241 X-ray sources in the catalog; 105 are presented here for thefirst time. A large number of IR/X-ray source chance coincidences arefound in this sample; of the 40-50 expected, we have identified 18firmly and have established strong cases for 29 others. Most chancecoincidences involve bright stars or Seyfert galaxies close (inprojection) to IR- bright H II galaxies. Although this work wasmotivated initially by the report that a new class of X-ray-luminous,normal spiral galaxies was to be found in this sample, we find noevidence for such a class. Most of the extragalactic X-ray sources areactive galactic nuclei (AGNs), consistent with the results of previousstudies of X-ray-selected objects. However, many of these AGNs exhibitweak or heavily reddened Seyfert features in their optical spectra. Inaddition, two rare types of AGNs are found in this sample withsurprising frequency: I Zw 1 objects (also called narrow-line Seyfert 1galaxies) and starburst/Seyfert composite galaxies, a new class ofluminous X-ray sources. We have shown that the Boller et al. object202103 - 223434 (= IRAS 20181-2244), reported to be the best example ofa narrow-line quasar, is actually a member of the I Zw 1 class. Theenigmatic starburst/Seyfert composite galaxies have optical spectradominated by the features of H II galaxies but X-ray luminositiestypical for Seyfert galaxies. Close examination of their optical spectrareveals subtle Seyfert signatures: [O III] lines broader than all otherlines in the spectrum and, in some cases, a weak, broad Hαcomponent. Obscuration of the active nucleus is likely to explain theX-ray and optical properties of these objects. We describe a scenario inwhich such optically innocuous, obscured AGNs could comprise animportant new component of the X-ray background.
| Seyfert Galaxies. IV. Nuclear Profiles of Markarian Seyfert Galaxies from Hubble Space Telescope Images
We have examined the nuclear profiles of the Seyfert and non-SeyfertMarkarian galaxies in our near-infrared Hubble Space Telescope WF/PC-1snapshot survey. We find that nuclei of types 1-1.5 Seyfert galaxies aredominated by strong point sources, while those of Seyfert 2 and non-Seyfert Markarian galaxies tend to be resolved, less distinguished, andsimilar in shape to normal galaxy luminosity profiles. Two possibleinterpretations of this result for type 2 Seyfert galaxies are thattheir nuclear continuum sources are undetected in our bandpass,contributing less than 10% of the nuclear light (within 0.5 radius) inall cases or that their nuclear components are resolved and blend insmoothly with the brightness profile of the host galaxy's bulge. Sincespectroscopic studies support typical nuclear continuum fractionsdistinctly greater than 10%, the latter conclusion is clearlypreferable. If the continua observed in Seyfert 2 galaxies originate asnuclear light that is redirected into the line of sight by scattering,as predicted by unified models of active galactic nuclei, then thescattering regions must be extended. Simple simulations suggest thatthese regions must cover several tens of parsecs or more, in agreementwith estimates of the sizes of the scattering "mirrors" in other Seyfert2 galaxies. However, the similarity of the profiles of non-SeyfertMarkarian and type 2 Seyfert nuclei suggests that circumnuclear starformation may also be an important component in the nuclear profiles ofthe latter.
| A multifrequency radio continuum and IRAS faint source survey of markarian galaxies
Results are presented from a multifrequency radio continumm survey ofMarkarian galaxies (MRKs) and are supplemented by IRAS infrared datafrom the Faint Source Survey. Radio data are presented for 899 MRKsobserved at nu = 4.755 GHz with the National Radio Astronomy Observatory(NRAO)-Green Bank 300 foot (91 m) telescope, including nearly 88% ofthose objects in Markarian lists VI-XIV. In addition, 1.415 GHzmeasurements of 258 MRKs, over 30% of the MRKs accessible from theNational Aeronomy and Ionosphere Center (NAIC)-Arecibo, are reported.Radio continuum observations of smaller numbers of MRKs were made at10.63 GHz and at 23.1 GHz and are also presented. Infrared data from theIRAS Faint Source Survey (Ver. 2) are presented for 944 MRKs, withreasonably secure identifications extracted from the NASA/IPACExtragalactic Database. MRKs exhibit the same canonical infraredcharacteristics as those reported for various other galaxy samples, thatis well-known enhancement of the 25 micrometer/60 micrometer color ratioamong Seyfert MRKs, and a clear tendency for MRKs with warmer 60micrometer/100 micrometer colors to also possess cooler 12 micrometer/25micrometer colors. In addition, non-Seyfert are found to obey thewell-documented infrared/radio luminosity correlation, with the tightestcorrelation seen for starburst MRKs.
| ROSAT All Sky Survey observations of IRAS galaxies
Cross-correlations are established between 14,708 selected IRAS sourcesand the ROSAT All Sky Survey X-ray sources. The resulting catalog of 244IRAS galaxies positionally coincident with ROSAT X-ray sources ispresented. For 222 of them, optical counterparts could be identified bya comparison with the NASA/IPAC Extragalactic Database. An unexpectedresult was the discovery of several spiral galaxies with luminosities upto 10 exp 43 erg/s, well above those found with the Einstein satellite.
| A dynamical analysis of twelve clusters of galaxies
Four-hundred-twenty-eight new redshift measurements for galaxies in thevicinity of 12 Abell clusters are presented. The data are supplementedby previously published data with 3 deg of each cluster center. Thecluster selection, the variety of telescopes and instrumentation used toobtain the galaxy redshifts, and the available X-ray observations arediscussed. Each cluster is exmained in some detail, with the emphasisplaced on the nature of the observed velocity distributions. Robust andresistant estimators of the velocity location and scale are applied inorder to quantify these distributions. The offset in velocity space ofthe dominant galaxy in each cluster or subcluster is considered withrespect to the central location in the velocity space of the cluster asa whole, and the physical implications of significant offsets found inseveral clusters are discussed. Dynamical estimates of the masses ofclusters and/or subclusters are obtained; for clearly bimodal systems,two-body models are employed to specify their likely dynamical state.
| Seyfert galaxies. II - Environments and IRAS colors
The environments of Seyfert galaxies are compared to the environments ofnon-Seyfert Markarian galaxies using galaxy counts obtained from thePalomar Observaory Sky Survey prints. While previous work by Dahari,confirmed here, indicates that Seyfert galaxies are more likely to haveclose companion galaxies than field galaxies, the Seyfert galaxiesexamined here have essentially the same environments as the comparisonsample of non-Seyfert Markarian galaxies. The IRAS colors of the Seyfertand non-Seyfert Markarian galaxies are used to distinguish betweenSeyfert activity and bursts of star formation. The results suggest thatclose companion galaxies enhance star formation rather than directlyenhancing Seyfert-like activity.
| Far-infrared luminosities of Markarian starburst galaxies. II - Individual galaxies
IRAS observations of galaxies in the Balzano sample of opticallyselected starburst nuclei and of a comparison of Virgo spiral galaxiesare used to derive far-infrared luminosities. Distances and blue andH-alpha luminosities of the starburst galaxies are also tabulated.
| A catalog of Markarian galaxies
A catalog of Markarian galaxies is presented which tabulates redshifts,spectral and morphological classifications, magnitudes, infrared andradio flux densities, and over 600 references to available datapublished before January 1, 1986. Redshifts are now available for 1228objects with strong ultraviolet continua, and follow-up spectroscopicand photometric observations of Markarian galaxies have providedclassifications of 115 Seyfert 1, 43 Seyfert 2, and 137 starburst and HII-type galaxies. After a description of the Markarian survey and thecurrent catalog, a summary of the general results obtained from the datais presented. A preliminary study of the infrared properties ofMarkarian galaxies as measured by IRAS reveals a number of interestingresults, including the existence of a sample of elliptical andlenticular galaxies with appreciable infrared emission.
| Four double galaxies with ultraviolet-excess components
A morphological and spectroscopic analysis indicates that the galaxiesMarkarian 316 and 552 are bound in stable pairs having a smallmass/luminosity ratio. Although both Mkn 530 (NGC 7603) and Mkn 958differ greatly from their companions in radial velocity, Mkn 958 mightbe physically associated with its companion.
| Star-burst galactic nuclei
Markarian (1967) has conducted a survey of galaxies having strongultraviolet continua. In connection with this survey, a new group ofgalaxies was discovered which could provide additional insight into thenature and evolution of active galactic nuclei. The optical morphologyof the discovered galaxies is similar to that shown by Seyfert galaxies,with dominant feature often being a bright, starlike nucleus. However,these nuclei do not usually display the broad emission-line spectra socharacteristic of the Seyferts. Their narrow emission features and otherobservable properties can be explained by the presence of a hot, youngstar population. For this reason, these objects have become known asstar-burst nuclei. The nuclear star-burst phenomenon might supplymaterial for gravitational accretion, and, therefore, for thedevelopment of active galaxies. Balzano and Weedman (1981) have studiedthese nuclei as a distinct group. The present investigation representsthe first comprehensive survey.
| Emission-line widths in galactic nuclei
Line width measures for the forbidden O III emission lines have beenobtained for 116 galactic nuclei with instrumental resolution of 165km/sec. Galaxies observed include 53 Seyfert 1 galaxies, 16 Seyfert 2galaxies, and 47 star-burst galaxies for which the nuclear emissionlines are attributed to ionization by hot, short-lived stars. The medianFWHM for the forbidden O III lines is 375 km/sec for Seyfert 1, 510km/sec for Seyfert 2, and 160 km/sec for star-burst nuclei. It issuggested that an empirical criterion for dividing Seyfert galaxies fromother emission line galaxies is a FWHM greater than 250 km/sec for theforbidden O III lines. From dynamical arguments, the star-burst nucleiare determined to have the star formation activity restricted to anuclear disk with radius less than a few hundred parsecs.
| The near-infrared properties of galactic nuclei
Infrared J, H, and K observations are given for the nuclei of 107galaxies, including 44 nuclei with blue colors or strong emission linesbut not classified as Seyferts, 33 nuclei classified morphologically asbeing bright and compact, and 30 Seyfert galaxies. Comparison of (U - B)and (J - K) colors shows that most galaxies with (J - K) greater than1.1 are Seyferts regardless of the (U - B). Such near-infrared excessesare attributed primarily to nonthermal continua rather than dustreradiation, because galaxy nuclei with bright ultraviolet continua notclassified spectroscopically as Seyferts do not show infrared colorsdifferent from those expected for composite starlight. Virtually allnuclei with emission lines less than 250 km/s in width have thenear-infrared colors of starlight, which quantifies suspicions that bothbroad emission lines and near-infrared color excesses are consequencesof nonthermal processes.
| Radio emission from some Markarian galaxies at 430 MHz
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..649T&db_key=AST
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