Contenidos
Imágenes
Subir su imagen
DSS Images Other Images
Artículos relacionados
Principal component analysis of International Ultraviolet Explorer galaxy spectra
We analyse the UV spectral energy distribution of a sample of normalgalaxies listed in the International Ultraviolet Explorer (IUE) NewlyExtracted Spectra (INES) Guide No. 2 - Normal Galaxies using a principalcomponent analysis. The sample consists of the IUE short-wavelength (SW)spectra of the central regions of 118 galaxies, where the IUE apertureincluded more than 1 per cent of the galaxy size. The principalcomponents are associated with the main components observed in theultraviolet (UV) spectra of galaxies. The first component, accountingfor the largest source of diversity, may be associated with the UVcontinuum emission. The second component represents the UV contributionof an underlying evolved stellar population. The third component issensitive to the amount of activity in the central regions of galaxiesand measures the strength of star-formation events.In all the samples analysed here, the principal component representativeof star-forming activity accounts for a significant percentage of thevariance. The fractional contribution to the spectral energydistribution (SED) by the evolved stars and by the young population aresimilar.Projecting the SEDs on to their eigenspectra, we find that none of thecoefficients of the principal components can outline an internalcorrelation or can correlate with the optical morphological types. In asubsample of 43 galaxies, consisting of almost only compact and BCDgalaxies, the third principal component defines a sequence related tothe degree of starburst activity of the galaxy.
| Radio emission from AGN detected by the VLA FIRST survey
Using the most recent (April 2003) version of the VLA FIRST survey radiocatalog, we have searched for radio emission from >2800 AGN takenfrom the most recent (2001) version of the Veron-Cetty and Veron AGNcatalog. These AGN lie in the 9033 square degrees of sky alreadycovered by the VLA FIRST survey. Our work has resulted in positivedetection of radio emission from 775 AGN of which 214 are new detectionsat radio wavelengths.Tables 3 and 4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/35
| The FIRST Bright Quasar Survey. III. The South Galactic Cap
We present the results of an extension of the FIRST Bright Quasar Survey(FBQS) to the South Galactic cap, and to a fainter optical magnitudelimit. Radio source counterparts with SERC R magnitudes brighter than18.9 which meet the other FBQS criteria are included. We supplement thislist with a modest number of additional objects to test our completenessfor quasars with extended radio morphologies. The survey covers 589deg2 in two equatorial strips in the southern cap. We haveobtained spectra for 86% of the 522 candidates and find 321radio-selected quasars of which 264 are reported here for the firsttime. A comparison of this fainter sample with the FBQS sample shows thetwo to be generally similar. Fourteen new broad absorption line (BAL)quasars are included in this sample. When combined with the previouslyidentified BAL quasars in our earlier papers, we can discern a break inthe frequency of BAL quasars with radio loudness, namely that therelative number of high-ionization BAL quasars drops by a factor of 4for quasars with a radio-loudness parameter R*>100. Basedon observations obtained with the W. M. Keck Observatory, which isjointly operated by the California Institute of Technology and theUniversity of California, and the Multiple Mirror Telescope Observatory,which is jointly operated by the University of Arizona and theSmithsonian Institution.
| Star formation in distant starburst galaxies
This paper discusses the stellar population content of distant (5 000 kms^{-1} <== V_R<=16 000 km s^{-1}) galaxies with enhancedstar-formation activity. Distinction is made between isolated galaxiesand galaxies morphologically disturbed, with clear signs of interactionsuch as mergers. In these galaxies the International UltravioletExplorer (M_BoxIUE) large aperture samples most of the galaxy's body.Consequently, the resulting integrated spectra arise primarily from bluestellar populations of different ages together with significantcontributions from intermediate and old age components, subject tovarying reddening amounts. Instead of analysing individual, usually lowSignal-to-Noise ratio (S/N) spectra, our approach is to coadd thespectra of objects with similar spectral properties in the UV,considering as well their properties in the visible/near-infraredranges. Consequently, the resulting high (S/N) template spectra containthe average properties of a rather uniform class of objects, andinformation on spectral features can now be analysed with moreprecision. Three groups have been found for the interacting galaxies,corresponding to a red, blue and very blue continuum. Isolated galaxieshave been separated into two groups, one with a flat/red continuum andthe other with a blue continuum. For comparison, we also include in thepresent analysis two groups of nearby disturbed galaxies. Stellarpopulations are analysed by means of a synthesis algorithm based on starcluster spectral components of different ages which fit the observedspectra both in terms of continuum distribution and spectral features.Flux fractions of the different age groups found in the synthesis havebeen transformed into mass fractions, allowing inferences on the starformation histories. Young stellar populations (age <500 Myr) are themain flux contributors, except for the groups with a red spectrum notdue to extinction, arising from the intermediate (age ~1 - 2 Gyr) andold age populations. We also study the reddening values and theextinction law: a Small Magellanic Cloud-like extinction law isappropriate for all cases. As compared to nearby galaxies with enhancedstar-formation, the distant starburst galaxy spectral groups exhibitlarger contributions from the intermediate and old age populations. Thiseffect is mainly accounted for by the larger spatial area sampled by theM_BoxIUE slit in the distant galaxies, including not only the entirebulge but also evolved disk populations. The present results provide aquantitative measure of the star-forming activity in interactinggalaxies, compared to isolated galaxies. Based upon data collected withthe International Ultraviolet Explorer (IUE) Satellite, supported byNASA, SERC and ESA.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Soft X-Ray Properties of Seyfert Galaxies in the ROSAT All-Sky Survey
We present the results of ROSAT All-Sky Survey observations of Seyfertand IR luminous galaxies from the extended 12 micron galaxy sample andthe optically selected CfA sample. Detections are available for 80%(44/55) of the Seyfert 1's and 34% (23/67) of the Seyfert 2's in the 12micron sample, and for 76% (26/34) of the Seyfert 1's and 38% (6/16) ofthe Seyfert 2's in the CfA sample. Roughly half of the Seyfert galaxies(mostly Seyfert 1's) have been fitted to an absorbed power-law model,yielding an average photon index of {GAMMA} = 2.26 +/- 0.11 for 43Seyfert 1's and {GAMMA} = 2.45 +/- 0.18 for 10 Seyfert 2's, with bothtypes having a median value of 2.3. The soft X-ray luminosity correlateswith the 12 micron luminosity, with Seyfert 1's having relatively moresoft X-ray emission than Seyfert 2's of similar mid-IR luminosities by afactor of 1.6 +/- 0.3. Several physical interpretations of these resultsare discussed, including the standard unified model for Seyfertgalaxies. Infrared luminous non- Seyferts are shown to have similardistributions of soft X-ray luminosity and X-ray-to-IR slope as Seyfert2's, suggesting that some of them may harbor obscured active nuclei (ashas already been shown to be true for several objects) and/or that thesoft X-rays from some Seyferts 2's may be nonnuclear. A soft X-rayluminosity function (XLF) is calculated for the 12 micron sample, whichis described well by a single power law with a slope of - 1.75. Thenormalization of this XLF agrees well with that of a hard X-ray selectedsample. Several of our results, related to the XLF and the X- ray-to-IRrelation, are shown to be consistent with the hard X-ray observations ofthe 12 micron sample by Barcons et al.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| 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.
| Multiwavelength Energy Distributions and Bolometric Luminosities of the 12 Micron Galaxy Sample
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...453..616S&db_key=AST
| Gas content of infrared luminous markarian galaxies
The atomic and molecular hydrogen gas properties of a complete sample ofMarkarian galaxies with flux density at 60 µm higher than 1.95 Jyare presented. We present the improved far-infrared luminosity functionof Markarian galaxies; and its comparison with other samples. We findthat 40% of the bright IRAS galaxies of far-infrared luminosity higherthan 1010.5 L are Markarian galaxies. There is an absence of correlationbetween HI content of Markarian galaxies and current star formationactivity, implying that star formation in these systems has complexstructure and it is not a simple function of the HI content. On thecontrary, the H2 content of Markarian galaxies is well correlated withstar formation activity. It is argued that tight correlation between HIand H2 contents is a consequence of transformation of atomic hydrogeninto molecular.
| The extended 12 micron galaxy sample
We have selected an all-sky (absolute value of b greater than or equalto 25 deg) 12 micron flux-limited sample of 893 galaxies from the IRASFaint Source Catalog, Version 2 (FSC-2). We have obtained accurate totalfluxes in the IRAS wavebands by using the ADDSCAN procedure for allobjects with FSC-2 12 micron fluxes greater than 0.15 Jy and increasingflux densities from 12 to 60 microns, and defined the sample by imposinga survey limit of 0.22 Jy on the total 12 micron flux. Its completenessis verified, by means of the classical log N - log S andV/Vmax tests, down to 0.30 Jy, below which we have measuredthe incompleteness down to the survey limit, using the log N - log Splot, for our statistical analysis. We have obtained redshifts (mostlyfrom catalogs) for virtually all (98.4%) the galaxies in the sample.Using existing catalogs of active galaxies, we defined a subsample of118 objects consisting of 53 Seyfert 1s and quasars, 63 Seyfert 2s, andtwo blazars (approximately 13% of the full sample), which is the largestunbiased sample of Seyfert galaxies ever assembled. Since the 12 micronflux has been shown to be about one-fifth of the bolometric flux forSeyfert galaxies and quasars, the subsample of Seyferts (includingquasars and blazars) is complete not only to 0.30 Jy at 12 microns butalso with respect to a bolometric flux limit of approximately 2.0 x10-10 ergs/s/sq cm. The average value of V/Vmaxfor the full sample, corrected for incompleteness at low fluxes, is 0.51+/- 0.04, expected for a complete sample of uniformly distributedgalaxies, while the value for the Seyfert galaxy subsample is 0.46 +/-0.10. We have derived 12 microns and far-infrared luminosity functionsfor the AGNs, as well as for the entire sample. We extracted from oursample a complete subsample of 235 galaxies flux-limited (8.3 Jy) at 60microns. The 60 micron luminosity function computed for this subsampleis in satisfactory agreement with the ones derived from the brightgalaxy sample (BGS) and the deep high-galactic latitude sample, bothselected at 60 microns.
| Pairing properties of Markarian starburst Galaxies
The environmental parameters of 516 non-Seyfert Markarian galaxies werestudied in a redshift-bounded sample, supplemented by new spectra andredshift measures for possible companions, in order to evaluate theiroccurrence in galaxy pairs, defined through quantitative criteria. Itwas found that one-third of these galaxies occur in pairs (while only 6to 10 percent of optically-selected galaxies are known to be paired). Acomparison of various optical and IR properties of paired and nonpairedMarkarian galaxies showed no differences in the shape of the optical,far-IR, or H-alpha luminosity functions. It was found, however, that theMarkarian component is brighter than the other galaxy in each pair by0.66 magnitude in the mean at B.
| 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.
| KISO survey for ultraviolet-excess galaxies. IV
Presented here are the fourth list and identification charts of theultraviolet-excess galaxies which have been detected on the multicolorplates taken with the Kiso Schmidt telescope for 10 survey fields. Inthe sky area of some 300 square degrees 752 objects are cataloged downto the photographic magnitude of about 18.
| Photoelectric Observations of Interacting and Compact Galaxies
Not Available
| Spectral observations of Markaryan galaxies. IV
The results are given of spectral observations of 109 Markaryan galaxiesin lists X-XI. The radial velocities, absolute magnitudes, lineardimensions, and visual estimates of the relative intensities of theemission lines are given. Among these objects, five are identified asSeyfert galaxies: Markaryan 928, 957, 984, 1058, and 1066. The massesand mass-to-luminosity ratios are estimated for four pairs and groups ofgalaxies. A list is given of 25 Markaryan galaxies for which the authorshave not discovered emission lines.
| Accurate Optical Positions for Markarian Galaxies 798-1095
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981AJ.....86..811K&db_key=AST
|
Enviar un nuevo artículo
Enlaces relacionados
- - No se han encontrado enlaces -
En viar un nuevo enlace
Miembro de los siguientes grupos:
|
Datos observacionales y astrométricos
Catálogos y designaciones:
|
