Contents
Images
Upload your image
DSS Images Other Images
Related articles
Supernova 2005am in NGC 2811
IAUC 8490 available at Central Bureau for Astronomical Telegrams.
| Ultraviolet, Optical, and X-Ray Observations of the Type Ia Supernova 2005am with Swift
We present ultraviolet and optical light curves in six broadband filtersand grism spectra obtained by Swift's Ultraviolet/Optical Telescope forthe Type Ia supernova SN 2005am. The data were collected beginning about4 days before the B-band maximum, with excellent coverage of the rapiddecline phase and later observations extending out to 69 days after thepeak. The optical and near-UV light curve match well those of SN 1992A.The other UV observations constitute the first set of light curvesshorter than 2500 Å and allow us to compare the light curveevolution in three UV bands. One interesting feature is that the decayin the intermediate UVM2 band is shallower than in the filters on eitherside and may result from the bump in the interstellar extinction curve.The UV behavior of this and other low-redshift supernovae can be used toconstrain theories of progenitor evolution or to interpret optical lightcurves of high-redshift supernovae. Using Swift's X-Ray Telescope, wealso report the upper limit to SN 2005am's X-ray luminosity to be6×1039 ergs s-1 in the 0.3-10 keV. Thisresult is derived from 58 ks of exposure time spread out over 7 weeksbeginning 4 days before the B-band maximum.
| 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.
| Long slit spectroscopy of a sample of isolated spirals with and without an AGN
We present the kinematical data obtained for a sample of active(Seyfert) and non active isolated spiral galaxies, based on long slitspectra along several position angles in the Hα line region and,in some cases, in the Ca triplet region as well. Gas velocitydistributions are presented, together with a simple circular rotationmodel that allows us to determine the kinematical major axes. Stellarvelocity distributions are also shown. The main result is that activeand control galaxies seem to be equivalent in all kinematical aspects.For both subsamples, the departure from pure circular rotation in somegalaxies can be explained by the presence of a bar and/or of a spiralarm. They also present the same kind of peculiarities, in particular,S-shape structures are quite common near the nuclear regions. Theydefine very similar Tully-Fisher relations. Emission line ratios aregiven for all the detected HII regions; the analysis of the[NII]/Hα metallicity indicator shows that active and non-activegalaxies have indistinguishable disk metallicities. These results arguein favour of active and non-active isolated spiral galaxies havingessentially the same properties, in agreement with our previous resultsbased on the analysis of near infrared images. It appears now necessaryto confirm these results on a larger sample.Based on observations made with WHT operated on the island of La Palmaby ING in the Spanish Observatorio del Roque de Los Muchachos of theInstituto de Astrofísica de Canarias, the European SouthernObservatory (La Silla), Calar Alto Observatory (Almería, Spain)and Las Campanas Observatories (Chile).Table 3 and Figs. \ref{res_cen_u1395}, 5, 7, 9, 11, 13, 15, 17, 19, 21,23, 25, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50 and 52 are onlyavailable in electronic form at http://www.edpsciences.orgTable 5 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/416/475
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| 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.
| Surface photometry of spiral galaxies in NIR: Structural parameters of disks and bulges
A sample of 40 bright spiral galaxies (BT < 12) with lowinclination and without bar was observed with JHK filters. For thispurpose the MAGIC NICMOS3 camera at the 2.2 m telescope of the CalarAlto observatory, Spain was used. With a newly developed 2-dimensionalalgorithm the distribution of the surface brightness was fittedsimultaneously by corresponding functions for the disk- andbulge-structure. While the disk was fitted with an exponential function,the bulge profile was fitted with a generalized de VaucouleursRbeta law, with the concentration parameter beta = 1/n as afurther fit variable. The correlation of the resulting structuralparameters of disks and bulges lead to some interesting relations: 1.The use of a variable exponent beta is necessary for a realisticdescription of the bulge structure; 2. Disks and bulges show similarcorrelations between effective radius, effective surface brightness andluminosity; 3. They populate a common strip in the fundamental plane; 4.From the correlations between beta and Hubble type some conclusionsabout the formation and evolution of spiral galaxies can be drawn.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Near-infrared photometry of isolated spirals with and without an AGN --- II. Photometric properties of the host galaxies
We present here the analysis of morphological and photometric propertiesof a sample of isolated spirals with (18) and without (11) an activenucleus, based on near-infrared imaging in the J and K' bands (Paper I).The aim of that comparative analysis is to find the differentialproperties that could be directly connected with the phenomenon ofnuclear activity. We stress the importance of using isolated objects forthat purpose. Our study shows that both sets of galaxies are similar intheir global properties: they define the same Kormendy relation, theirdisk components share the same properties, the bulge and disk scalelengths are correlated in a similar way, bar strengths and lengths aresimilar for primary bars. Our results therefore indicate that hosts ofisolated Seyfert galaxies have bulge and disk properties comparable tothose of isolated non active spirals. Central colors (the innermost 200pc) of active galaxies are redder than the centers of non activespirals, most probably due to AGN light being re-emitted by the hot dustand/or due to circumnuclear star formation, through the contribution ofgiants/supergiants. Central to our analysis is the study of the possibleconnection between bars and similar non axisymmetric structures with thenuclear fuelling. We note that only one of the Seyfert galaxies in oursample, namely ESO 139-12, does not present a primary bar. But bars areequally present in active and control objects. The same applies tosecondary bars. Not all the active galaxies we have observed have them,and some control galaxies also present such central structures.Secondary central elongations (associated with secondary bars, lenses,rings or disks) may be somewhat different, but this result should beconfirmed with larger samples. We note that numerical models indicatethat such secondary bars are not strictly necessary to feed the centralengine when a primary bar is present. Our results show that down toscales of 100-300 pc, there are no evident differences between activeand non active spiral galaxies. Based on data obtained at: the EuropeanSouthern Observatory, La Silla, Chile, the Télescope BernardLyot, Calar Alto Observatory, Las Campanas Observatory. Also based onobservations made with the NASA/ESA Hubble Space Telescope, obtainedfrom the data archive at the Space --- II. Photometric properties of thehost galaxies
| Near-infrared photometry of isolated spirals with and without an AGN. I. The data
We present infrared imaging data in the J and K' bands obtained for 18active spiral galaxies, together with 11 non active galaxies taken as acontrol sample. All of them were chosen to satisfy well definedisolation criteria so that the observed properties are not related togravitational interaction. For each object we give: the image in the K'band, the sharp-divided image (obtained by dividing the observed imageby a filtered one), the difference image (obtained by subtracting amodel to the observed one), the color J-K' image, the ellipticity andposition angle profiles, the surface brightness profiles in J and K',their fits by bulge+disk models and the color gradient. We have foundthat four (one) active (control) galaxies previously classified asnon-barred turn out to have bars when observed in the near-infrared. Oneof these four galaxies (UGC 1395) also harbours a secondary bar. For 15(9 active, 6 control) out of 24 (14 active, 10 control) of the opticallyclassified barred galaxies (SB or SX) we find that a secondary bar (or adisk, a lense or an elongated ring) is present. The work presented hereis part of a large program (DEGAS) aimed at finding out whether thereare differences between active and non active galaxies in the propertiesof their central regions that could be connected with the onset ofnuclear activity. Based on data obtained at: the European SouthernObservatory, La Silla, Chile, the Télescope Bernard Lyot, CalarAlto Observatory, Las Campanas Observatory. Also based on observationsmade with the NASA/ESA Hubble Space Telescope, obtained from the dataarchive at the Space Telescope Institute. Figures 1-35 are onlyavailable in electronic form at the http://www.edpsciences.org
| Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles
We present one of the largest homogeneous sets of spiral and lenticulargalaxy brightness profile decompositions completed to date. The 659galaxies in our sample have been fitted with a de Vaucouleurs law forthe bulge component and an inner-truncated exponential for the diskcomponent. Of the 659 galaxies in the sample, 620 were successfullyfitted with the chosen fitting functions. The fits are generally welldefined, with more than 90% having rms deviations from the observedprofile of less than 0.35 mag. We find no correlations of fittingquality, as measured by these rms residuals, with either morphologicaltype or inclination. Similarly, the estimated errors of the fittedcoefficients show no significant trends with type or inclination. Thesedecompositions form a useful basis for the study of the lightdistributions of spiral and lenticular galaxies. The object base issufficiently large that well-defined samples of galaxies can be selectedfrom it.
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| 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.
| Molecular Gas, Morphology, and Seyfert Galaxy Activity
We probe the cause of the elevated star formation in host galaxies ofSeyfert 2 nuclei compared with Seyfert 1 hosts and with field galaxies.12CO (1--0) observations of a large sample of Seyfert galaxies indicateno significant difference in the total amount of molecular gas as afunction of the Seyfert nuclear type, nor are Seyfert galaxiessignificantly different in this regard from a sample of field galaxiesonce selection effects are accounted for. Therefore, the total amount ofmolecular gas is not responsible for the enhanced star-forming activityin Seyfert 2 hosts. To probe how this gas is being converted moreefficiently into stars in Seyfert 2 hosts than in the other galaxies, weinvestigate the occurrence of bars, interactions, and distortedmorphologies among Seyfert galaxies. We find a significantly higher rateof asymmetric morphologies for Seyfert 2 galaxies with respect toSeyfert 1 galaxies and field galaxies. Relative to field galaxies, theeffect is at a greater than 99.9% confidence level. The presence ofasymmetric morphologies in individual Seyfert galaxies is correlatedwith their tendency to exhibit enhanced star-forming activity. Theseresults suggest that asymmetric morphologies are an important cause forthe link between Seyfert type and star-forming activity: bars anddistortions in Seyfert 2 hosts are likely both to enhance star-formingactivity and to funnel gas into the nuclear region, thus obscuring andpossibly contributing to the feeding of the active nucleus.
| Near-IR photometry of disk galaxies: Search for nuclear isophotal twist and double bars
We present a near-IR, mainly $H$ band, photometry of 72 nearby (d <40 Mpc) disk galaxies. The main goal of the survey was to search forisophotal twist inside their nuclear regions. As the twist can be due insome cases to projection effects, rather than resulting from a dynamicalphenomenon, we deproject -- under the simplifying assumption of a 2Dgeometry -- all galaxies whose disk position angle and inclination areknown, the latter not exceeding 75 degrees. We show the ellipticity,position angle and surface brightness radial profiles, and discuss how aprojection of 2D and 3D bars can distort the isophotes, give an illusionof a non-existing double bar or mask a real one. We report 15 newdouble-barred galaxies and confirm 2 detected previously. We identify 14additional twists not known before and we also find nuclear triaxialstructures in three SA galaxies. The frequency of Seyferts amonggalaxies with nuclear bars or twists is high. Since these observationsare part of a larger survey, the interpretation of the results will begiven in a future paper, as soon as the number of objects grows enoughto permit meaningful statistics. As a secondary product, we publishstructural parameters (length and axis ratio) of large-scale bars inorder to extend still scarce data on bars in the near-IR.
| 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.
| Galaxies, Human Eyes, and Artificial Neural Networks
The quantitative morphological classification of galaxies is importantfor understanding the origin of type frequency and correlations withenvironment. However, galaxy morphological classification is stillmainly done visually by dedicated individuals, in the spirit of Hubble'soriginal scheme and its modifications. The rapid increase in data ongalaxy images at low and high redshift calls for a re-examination of theclassification schemes and for automatic methods. Here are shown resultsfrom a systematic comparison of the dispersion among human expertsclassifying a uniformly selected sample of more than 800 digitizedgalaxy images. These galaxy images were then classified by six of theauthors independently. The human classifications are compared with eachother and with an automatic classification by an artificial neuralnetwork, which replicates the classification by a human expert to thesame degree of agreement as that between two human experts.
| Automated morphological classification of APM galaxies by supervised artificial neural networks
We train artificial neural networks to classify galaxies based solely onthe morphology of the galaxy images as they appear on blue surveyplates. The images are reduced, and morphological features such as bulgesize and the number of arms are extracted, all in a fully automatedmanner. The galaxy sample was first classified by six independentexperts. We use several definitions for the mean type of each galaxy,based on those classifications. We then train and test the network onthese features. We find that the rms error of the networkclassifications, as compared with the mean types of the expertclassifications, is 1.8 Revised Hubble types. This is comparable to theoverall rms dispersion between the experts. This result is robust andalmost completely independent of the network architecture used.
| A comparative study of morphological classifications of APM galaxies
We investigate the consistency of visual morphological classificationsof galaxies by comparing classifications for 831 galaxies from sixindependent observers. The galaxies were classified on laser print copyimages or on computer screen using scans made with the Automated PlateMeasuring (APM) machine. Classifications are compared using the RevisedHubble numerical type index T. We find that individual observers agreewith one another with rms combined dispersions of between 1.3 and 2.3type units, typically about 1.8 units. The dispersions tend to decreaseslightly with increasing angular diameter and, in some cases, withincreasing axial ratio (b/a). The agreement between independentobservers is reasonably good but the scatter is non-negligible. In spiteof the scatter, the Revised Hubble T system can be used to train anautomated galaxy classifier, e.g. an artificial neural network, tohandle the large number of galaxy images that are being compiled in theAPM and other surveys.
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| The dependence of the cool matter content on galaxy morphology in galaxies of types E/S0, S0, and SA
Using the material assembled in earlier papers, we examine the manner inwhich the interstellar matter content varies along the Hubble sequencefrom S0 galaxies to Sa galaxies selected from the RSA2 compilation. Forthis we make use of a new and more detailed classification which isdescribed here as applied to these early disk/spiral galaxies. Theprominence of the disk in S0's and the visibility of features (H IIregions) in the Sa's serve as the basis for the subtypes. Three S0categories: subtle, intermediate, and pronounced, and four Sadescriptors: very early, early, intermediate, and late are assigned tothe galaxies. It is found that the total amount of hydrogen (H I + H2)is a function of subtype, being low in the S0's and rising smoothly fromthe early Sa's to the later Sa's. The average surface density ofhydrogen exceeds 3 solar masses/pc-squared only in the latest subtypesof the Sa's. We conclude that the prominence of the disk of a galaxyclosely follows the amount of cool gas which the disk contains.
| Interstellar matter in early-type galaxies. I - The catalog
A catalog is given of the currently available measurements ofinterstellar matter in the 467 early-type galaxies listed in the secondedition of the Revised Shapley-Ames Catalog of Bright Galaxies. Themorphological type range is E, SO, and Sa. The ISM tracers are emissionin the following bands: IRAS 100 micron, X-ray, radio, neutral hydrogen,and carbon monoxide. Nearly two-thirds of the Es and SOs have beendetected in one or more of these tracers. Additional observed quantitiesthat are tabulated include: magnitude, colors, radial velocity, centralvelocity dispersion, maximum of the rotation curve, angular size, 60micron flux, and supernovae. Qualitative statements as to the presenceof dust or emission lines, when available in the literature, are given.Quantities derivative from the observed values are also listed andinclude masses of H I, CO, X-ray gas, and dust as well as an estimate ofthe total mass and mass-to-luminosity ratio of the individual galaxies.
| Revised supernova rates in Shapley-Ames galaxies
Observations of 855 Shapley Ames galaxies made from November 1, 1980 toOctober 31, 1988, together with improved supernova luminosities, havebeen used to derive the frequency of supernovae of different types, andthe results are presented in tables. From a uniform database of 24supernovae discovered, the following SN rates are found, expressed in SNper century per 10 to the 10th L(B)(solar): SN Ia, 0.3; SN Ib, 0.3; andSN II, 1.0. The present data confirm the relatively high frequency of SNII in late-type galaxies that has been found by many previousinvestigators.
| A millimeter-wave survey of CO emission in Seyfert galaxies
Emission in the 115 GHz 1-0 line of CO has been detected in 18 Seyfertgalaxies in a sample of 43. The CO properties of 29 Seyferts in theRevised Shapley Ames Catalog (RSA) are compared with the CO propertiesof normal galaxies of the same Hubble type. These RSA type 2 Seyfertshave an average ratio of CO-to-blue luminosity that is about twice aslarge as that of the normal galaxies, but the RSA type 1 Seyferts havenormal CO luminosities. The RSA type 2 Seyfert galaxies have anunusually large average ratio of CO luminosity-to-H I mass compared tonormal disk galaxies. The RSA type 2 Seyferts have an average far-IRluminosity that is about four times larger than a non-Seyfert comparisonsample, while the RSA type 1 Seyferts are not significantly moreluminous than the non-Seyferts. The result imply that the two classes ofSeyferts are intrinsically different from one another and that one classcannot evolve into another in less than a few million years.
| Population synthesis in galactic nuclei using a library of star clusters
A novel galactic-nucleus population-synthesis technique is described anddemonstrated. The procedure is applicable to normal nuclei of E/S0 andspiral galaxies and employs a data base of integrated star-clusterspectra, thus reducing the number of parameters in the analysis to two(age and metallicity), as proposed by Bica and Alloin (1986). Resultsare presented in extensive tables and spectra and discussed in detail.The populations in the E/S0s with normal metallicity/luminosityrelations are found to comprise mainly stars older than 10 Gyr, withsome as young as about 5 Gyr; younger groups are superimposed on older,solar-metallicity populations in the bluer spirals. In NGC 5236, forexample, 87 and 57 percent of the flux at 400 and 900 nm, respectively,is attributed to stars younger than about 300 Myr.
| Analysis of absorption-line spectra in a sample of 164 galactic nuclei
Spectral observations in the 3700-8000 A range of 154 normal galacticnuclei, two amorphous galaxies, and eight intrinsically faint activenuclei whose visible spectrum is dominated by the stellar component arediscussed. A typical red, strong-lined spectrum is found for each groupfrom E to Sb in the -23.2 to -19.0 luminosity range, as well as for thevery luminous Sbc and Sc galaxies, although a few atypical nucleiexhibit variable contents of bluer stellar components. No prototype canbe assigned to the Sbc and Sc galaxies in the -21.9 to -19.0 luminosityrange. Analysis of the equivalent widths shows that the CN 4216-4250 Afeature has the largest dynamical range as a function of metallicity. Itis suggested that young stars are responsible for the blue colors inNGC2865, 4382, and 5102, and that metal-poor stars do not contributesignificantly.
| Near-infrared spectral properties of star clusters and galactic nuclei
A powerful method for the correction of CCD fringes in the near-IR ispresented, together with 6300-9700 A CCD spectra of 30 star clusterscovering the 1 million to 16.5 billion age range and observations of 62galactic nuclei in galaxies of E to Sc morphological type. An analysisof the star cluster sample indicates that, in the near-IR spectralrange, metallicity is the dominant parameter. Attention is given to thesecond-order effects produced by age. Grid predictions as a function ofmetallicity and age are given for five metallic features and for thecontinuum distribution.
| Study of a complete sample of galaxies. II - Spectroscopy of the nuclei
Spectroscopic observations of a complete sample of 320 galaxies (fromthe Revised Shapley Ames Catalog of Sandage and Tammann, 1981) withdeclination less than or equal to +20 deg, galactocentric velocity lessthan 3000 km/s, and absolute magnitude brighter than M(B) = -21.0 arereported. The 400-700-nm spectra were obtained with resolution about 1nm using the Boller and Chivens spectrograph and image-dissector scannerat the Cassegrain focus of the 1.52-m telescope at ESO on 36 nightsduring 1980-1983. The data are presented in extensive tables and spectraand briefly characterized. The majority of the spectra are classified asH II regions ionized by hot stars or as Seyfert-like nebulosities.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
