目录
图像
上传图像
DSS Images Other Images
相关文章
Structure and kinematics of edge-on galaxy discs - V. The dynamics of stellar discs
In earlier papers in this series we determined the intrinsic stellardisc kinematics of 15 intermediate- to late-type edge-on spiral galaxiesusing a dynamical modelling technique. The sample covers a substantialrange in maximum rotation velocity and deprojected face-on surfacebrightness, and contains seven spirals with either a boxy orpeanut-shaped bulge. Here we discuss the structural, kinematical anddynamical properties. From the photometry we find that intrinsicallymore flattened discs tend to have a lower face-on central surfacebrightness and a larger dynamical mass-to-light ratio. This observationsuggests that, at a constant maximum rotational velocity, lower surfacebrightness discs have smaller vertical stellar velocity dispersions.Although the individual uncertainties are large, we find from thedynamical modelling that at least 12 discs are submaximal. The averagedisc contributes 53 +/- 4 per cent to the observed rotation at 2.2 discscalelengths (hR), with a 1σ scatter of 15 per cent.This percentage becomes somewhat lower when effects of finite discflattening and gravity by the dark halo and the gas are taken intoaccount. Since boxy and peanut-shaped bulges are probably associatedwith bars, the result suggests that at 2.2hR the submaximalnature of discs is independent of barredness. The possibility remainsthat very high surface brightness discs are maximal, as these discs areunderrepresented in our sample. We confirm that the radial stellar discvelocity dispersion is related to the galaxy maximum rotationalvelocity. The scatter in this σ versus vmax relationappears to correlate with the disc flattening, face-on central surfacebrightness and dynamical mass-to-light ratio. Low surface brightnessdiscs tend to be more flattened and have smaller stellar velocitydispersions. The findings are consistent with the observed correlationbetween disc flattening and dynamical mass-to-light ratio and cangenerally be reproduced by the simple collapse theory for disc galaxyformation. Finally, the disc mass Tully-Fisher relation is offset fromthe maximum-disc scaled stellar mass Tully-Fisher relation of the UrsaMajor cluster. This offset, -0.3 dex in mass, is naturally explained ifthe discs of the Ursa Major cluster spirals are submaximal.
| Structure and kinematics of edge-on galaxy discs - IV. The kinematics of the stellar discs
The stellar disc kinematics in a sample of 15 intermediate- to late-typeedge-on spiral galaxies are studied using a dynamical modellingtechnique. The sample covers a substantial range in maximum rotationvelocity and deprojected face-on surface brightness and contains sevenspirals with either a boxy- or peanut-shaped bulge. Dynamical models ofthe stellar discs are constructed using the disc structure from I-bandsurface photometry and rotation curves observed in the gas. Thedifferences in the line-of-sight stellar kinematics between the modelsand absorption-line spectroscopy are minimized using a least-squaresapproach. The modelling constrains the disc surface density and stellarradial velocity dispersion at a fiducial radius through the freeparameter (σz/σR)-1, whereσz/σR is the ratio of vertical andradial velocity dispersion and M/L is the disc mass-to-light ratio. For13 spirals a transparent model provides a good match to the meanline-of-sight stellar velocity dispersion. Models that include arealistic radiative transfer prescription confirm that the effect ofdust on the observable stellar kinematics is small at the observed slitpositions. We discuss possible sources of systematic error and concludethat most of these are likely to be small. The exception is the neglectof the dark halo gravity, which has probably caused an overestimate ofthe surface density in the case of low surface brightness discs.
| Structure and kinematics of edge-on galaxy discs - III. The rotation curves in the gas
A technique is introduced for deriving the gaseous rotation curves ofedge-on spiral galaxies. The entire major axis position-velocity (XV)diagram is modelled with a set of rings in a least-squares sense,allowing for the effects of beam-smearing and line-of-sight projection.The feasibility of the technique is demonstrated by applying it to goodquality HI XV diagrams of eight edge-on spirals. For seven additionalspirals the XV diagrams are of insufficient quality, and the HIrotational velocities derived earlier using the envelope-tracing methodare retained. The HI results are augmented with the optical emissionline (HII) kinematics to arrive at estimates of the full rotationcurves. A detailed comparison of the HI and HII kinematics shows thatthe discs in our sample are sufficiently transparent at the heightsabove the plane where we have taken our optical spectra to derive thestellar kinematics. In several of these spirals the HII is mainlyconfined to the spiral arms and does not extend out to the edge of theHI layer, which may have caused the HII velocity profiles to besignificantly narrower than those of HI.
| Structure and kinematics of edge-on galaxy discs - II. Observations of the neutral hydrogen
We present Australia Telescope Compact Array and Westerbork SynthesisRadio Telescope HI observations of 15 edge-on spiral galaxies ofintermediate to late morphological type. The global properties and thedistribution and kinematics of the HI gas are analysed and discussed. Wedetermine the rotation curves using the envelope-tracing method. For 10spiral galaxies with a stellar disc truncation we find an average ratioof the HI radius to the truncation radius of the stellar disc of 1.1 +/-0.2 (1σ).
| Structure and kinematics of edge-on galaxy discs - I. Observations of the stellar kinematics
We present deep optical long-slit spectra of 17 edge-on spiral galaxiesof intermediate to late morphological type, mostly parallel to theirmajor axes and in a few cases parallel to the minor axes. Theline-of-sight stellar kinematics are obtained from the stellarabsorption lines using the improved cross-correlation technique. Ingeneral, the stellar kinematics are regular and can be traced well intothe disc-dominated region. The mean stellar velocity curves are far fromsolid-body, indicating that the effect of dust extinction is not large.The line-of-sight stellar disc velocity dispersion correlates with thegalaxy maximum rotational velocity, but detailed modelling is necessaryto establish whether this represents a physical relation. In fourspirals with a boxy- or peanut-shaped bulge we are able to detectasymmetric velocity distributions, having a common signature withprojected radius in the mean line-of-sight velocity and theh3 and h4 curves. In two cases this kinematicasymmetry probably represents the `figure-of-eight' pattern synonymouswith a barred potential. We emphasize, however, that the signatures seenin the h3 and h4 curves may also be due to thedisc seen in projection.
| Extraplanar Emission-Line Gas in Edge-On Spiral Galaxies. I. Deep Emission-Line Imaging
The extraplanar diffuse ionized gas (eDIG) in 17 nearby, edge-on diskgalaxies is studied using deep Taurus Tunable Filter Hα and [N II]λ6583 images and conventional interference filter Hα+[N II]λλ6548, 6583 images that reach flux levels generally below~1×10-17 ergs s-1 cm-2arcsec-2. [N II] λ6583/Hα excitation maps areavailable for 10 of these objects. All but one galaxy in the sampleexhibit eDIG. The contribution of the eDIG to the total Hαluminosity is relatively constant, on the order of 12%+/-4%. TheHα scale height of the eDIG derived from a two-exponential fit tothe vertical emission profile ranges from 0.4 to 17.9 kpc, with anaverage of 4.3 kpc. This average value is noticeably larger than theeDIG scale height measured in our Galaxy and other galaxies. Thisdifference in scale height is probably due in part to the lower fluxlimits of our observations. The ionized mass of the extraplanarcomponent inferred by assuming a constant filling factor of 0.2 and aconstant path length through the disk of 5 kpc ranges from1.4×107 to 2.4×108 Msolar,with an average value of 1.2×108 Msolar.Under these same assumptions, the recombination rate required to keepthe eDIG ionized ranges from 0.44×106 to13×106 s-1 cm-2 of the disk, orabout 10%-325% of the Galactic value. A quantitative analysis of thetopology of the eDIG confirms that several galaxies in the sample have ahighly structured eDIG morphology. The distribution of the eDIG emissionis often correlated with the locations of the H II regions in the disk,supporting the hypothesis that the predominant source of ionization ofthe eDIG is photoionization from OB stars located in the H II regions. Astrong correlation is found between the IR (or far-IR) luminosities perunit disk area (basically a measure of the star formation rate per unitdisk area) and the extraplanar ionized mass, further providing supportfor a strong connection between the disk and eDIG components in thesegalaxies. The excitation maps confirm that the [N II]/Hα ratiosare systematically higher in the eDIG than in the disk. Althoughphotoionization by disk OB stars is generally able to explain theseelevated [N II]/Hα ratios, a secondary source of ionizationappears to be needed when one also takes into account other line ratios;more detail is given in a companion paper (our Paper II).
| A Survey for H2O Megamasers. III. Monitoring Water Vapor Masers in Active Galaxies
We present single-dish monitoring of the spectra of 13 extragalacticwater megamasers taken over a period of 9 years and a single epoch ofsensitive spectra for seven others. The primary motivation is a searchfor drifting line velocities analogous to those of the systemic featuresin NGC 4258, which are known to result from centripetal acceleration ofgas in an edge-on, subparsec molecular disk. We detect a velocity driftanalogous to that in NGC 4258 in only one source, NGC 2639. Another, themaser source in NGC 1052, exhibits erratic changes in its broad maserprofile over time. Narrow maser features in all of the other diskgalaxies discussed here either remain essentially constant in velocityover the monitoring period or are sufficiently weak or variable inintensity that individual features cannot be traced reliably from oneepoch to the next. In the context of a circumnuclear, molecular diskmodel, our results suggest that either (a) the maser lines seen aresystemic features subject to a much smaller acceleration than present inNGC 4258, presumably because the gas is farther from the nuclear blackhole, or (b) we are detecting ``satellite'' lines for which theacceleration is in the plane of the sky.Our data include the first K-band science observations taken with thenew 100 m Green Bank Telescope (GBT). The GBT data were taken duringtesting and commissioning of several new components and so are subjectto some limitations; nevertheless, they are in most cases the mostsensitive H2O spectra ever taken for each source and cover800 MHz (~=10,800 km s-1) of bandwidth. Many new maserfeatures are detected in these observations. Our data also include atentative and a clear detection of the megamaser in NGC 6240 at epochs ayear and a few months, respectively, prior to the detections reported byHagiwara et al. and Nakai et al.We also report a search for water vapor masers toward the nuclei of 58highly inclined (i>80deg), nearby galaxies. These sourceswere selected to investigate the tendency that H2O megamasersfavor inclined galaxies. None were detected, confirming that megamasersare associated exclusively with active galactic nuclei.
| X-ray emission from haloes of simulated disc galaxies
Bolometric and 0.2-2 keV X-ray luminosities of the hot gas haloes ofsimulated disc galaxies have been calculated at redshift z= 0. TheTREESPH simulations are fully cosmological and the sample of 44 discgalaxies span a range in characteristic circular speeds ofVc= 130-325 km s-1. The galaxies have beenobtained in simulations with a considerable range of physicalparameters, varying the baryonic fraction, the gas metallicity, themeta-galactic ultraviolet field, the cosmology, the dark matter type,and also the numerical resolution. The models are found to be inagreement with the (few) relevant X-ray observations available atpresent. The amount of hot gas in the haloes is also consistent withconstraints from pulsar dispersion measures in the Milky Way.Forthcoming XMM and Chandra observations should enable much morestringent tests and provide constraints on the physical parameters. Wefind that simple cooling flow models overpredict X-ray luminosities byup to two orders of magnitude for high (but still realistic) coolingefficiencies relative to the models presented here. Our results displaya clear trend that increasing cooling efficiency leads to decreasingX-ray luminosities at z= 0. The reason is found to be that increasedcooling efficiency leads to a decreased fraction of hot gas relative tototal baryonic mass inside of the virial radius at present. At gas metalabundances of one-third the solar value this hot gas fraction becomes aslow as just a few per cent. We also find that most of the X-ray emissioncomes from the inner parts (r<~ 20 kpc) of the hot galactic haloes.Finally, we find for realistic choices of the physical parameters thatdisc galaxy haloes possibly were one order of magnitude brighter in softX-ray emission at z~ 1 than at present.
| The WARPS Survey. VI. Galaxy Cluster and Source Identifications from Phase I
We present in catalog form the optical identifications for objects fromthe first phase of the Wide Angle ROSAT Pointed Survey (WARPS). WARPS isa serendipitous survey of relatively deep, pointed ROSAT observationsfor clusters of galaxies. The X-ray source detection algorithm used byWARPS is Voronoi Tessellation and Percolation (VTP), a technique whichis equally sensitive to point sources and extended sources of lowsurface brightness. WARPS-I is based on the central regions of 86 ROSATPSPC fields, covering an area of 16.2 square degrees. We describe herethe X-ray source screening and optical identification process forWARPS-I, which yielded 34 clusters at 0.06
| 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.
| Photometric parameters of edge-on galaxies from 2MASS observations
To analyze the vertical structure of edge-on galaxies, we have usedimages of a large uniform sample of flat galaxies that have been takenduring the 2MASS all-sky survey. The photometric parameters, such as theradial scale length, the vertical scale height, and the deprojectedcentral surface brightness of galactic disks have been obtained. We finda strong correlation between the central surface brightness and theratio of the vertical scale height to the vertical scale length: thethinner the galaxy, the lower the central surface brightness of itsdisk. The vertical scale height does not increase systematically withthe distance from the galaxy center in the frames of this sample.
| Modelling the Dust Content of Spiral Galaxies
We compare optical and near-infrared surface photometry of seven edge-onspiral galaxies with corresponding surface photometry calculated from arealistic model of spiral galaxies which takes into account bothabsorption and scattering by the interstellar dust. For the stars andthe dust in the disc we use exponential distributions in bothdirections, radially and perpendicular to the plane of the disc, whilethe de Vaucouleurs (R^1/4) profile is used for the description of thebulge. The effect of the spiral structure in the galactic discs is alsoexamined and it is found that the simple exponential disc model is ableto describe quite accurately the real galaxy. From this analysis we wereable to obtain some general conclusions, the most significant of whichare: 1) The face-on central optical depth is less than unity in alloptical bands, indicating that typical spiral galaxies like those wehave modelled would be completely transparent if they were to be seenface on. 2) The dust scale height is about half that of the stars, whichmeans that dust is more concentrated near the plane of the disc. 3) Thedust scale length is about 1.4 times larger than that of the stars anddust is more radially extended than the stars. 4) The gas-to-dust massratio calculated, with the dust mass derived from the model, is close tothe value derived for our Galaxy. 5) The derived extinction law matchesthe Galactic extinction law quite well, indicating a universal dustbehaviour.
| HI observations of loose galaxy groups. I. Data and global properties
At Nançay, 21-cm H I line observations were made of 15spiral-dominated loose groups of galaxies, divided into two samples: an``interacting'' sample containing at least one pair of interactinggalaxies, and a ``control'' sample having no optical evidence ofinteractions or morphological disturbances among the group members. Theinteracting sample consists of 62 galaxies representing 9 differentgroups, and the control sample contains 40 galaxies representing 6groups. Of the 91 galaxy and galaxy pairs observed, 74 were detected,while upper limits were placed on the remaining 17 objects. Thesehomogeneous H I data, which will be used in future analyses, providecomparative information on the H I content of groups and serve as aprobe of the vicinity of the target spirals for H I clouds or very lowsurface brightness gas-rich galaxies.
| Properties of tidally-triggered vertical disk perturbations
We present a detailed analysis of the properties of warps andtidally-triggered perturbations perpendicular to the plane of 47interacting/merging edge-on spiral galaxies. The derived parameters arecompared with those obtained for a sample of 61 non-interacting edge-onspirals. The entire optical (R-band) sample used for this study waspresented in two previous papers. We find that the scale height of disksin the interacting/merging sample is characterized by perturbations onboth large ( =~ disk cut-off radius) and short ( =~ z0)scales, with amplitudes of the order of 280 pc and 130 pc on average,respectively. The size of these large (short) -scale instabilitiescorresponds to 14% (6%) of the mean disk scale height. This is a factorof 2 (1.5) larger than the value found for non-interacting galaxies. Ahallmark of nearly all tidally distorted disks is a scale height thatincreases systematically with radial distance. The frequent occurrenceand the significantly larger size of these gradients indicate that diskasymmetries on large scales are a common and persistent phenomenon,while local disturbances and bending instabilities decline on shortertimescales. Nearly all (93%) of the interacting/merging and 45% of thenon-interacting galaxies studied are noticeably warped. Warps ofinteracting/merging galaxies are ~ 2.5 times larger on average thanthose observed in the non-interacting sample, with sizes of the order of340 pc and 140 pc, respectively. This indicates that tidal distortionsdo considerably contribute to the formation and size of warps. However,they cannot entirely explain the frequent occurrence of warped disks.Based on observations obtained at the European Southern Observatory(ESO, La Silla, Chile), Calar Alto Observatory operated by the MPIA(DSAZ, Spain), Lowell Observatory (Flagstaff,AZ, USA), and Hoher ListObservatory (Germany).
| Diffuse X-ray emission from late-type galaxy haloes
Current theories of galaxy formation predict that spiral galaxies areembedded in a reservoir of hot gas. This gas is able to cool on to thegalaxy, replenishing cold gas that is consumed by star formation.Estimates of the X-ray luminosity emitted in the cooling region suggesta bolometric luminosity of the order of10×1041ergs-1 in massive systems. We haveused ROSAT PSPC data to search for extended X-ray emission from thehaloes of three nearby, massive, late-type galaxies: NGC 2841, 4594 and5529. We infer 95per cent upper limits on the bolometric X-rayluminosities of the haloes of NGC 2841, 4594 and 5529 of 0.4, 1.2 and3.8×1041ergs-1 respectively. Thus, the trueluminosity lies well below the straightforward theoretical prediction.We discuss this discrepancy and suggest a number of ways in which thetheoretical model might be brought into agreement with the observationalresults. A possible solution is that the gravitational potentials of thedark matter haloes of these galaxies are weaker than assumed in thecurrent model. Alternatively, the present-day accretion may besubstantially less than is required on average to build the disc overthe Hubble time. Our results are, however, based on only three galaxies,none of which is ideal for this kind of study. A larger data set isrequired to explore this important problem further.
| A list of peculiar velocities of RFGC galaxies
A list of radial velocities, HI line widths and peculiar velocities of1327 galaxies from the RFGC catalogue has been compiled using actualobservations and literature data. The list can be used for studying bulkmotions of galaxies, construction of the field of peculiar velocitiesand other tasks.
| 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
| The influence of interactions and minor mergers on the structure of galactic disks I. Observations and disk models
This paper is the first part in our series on the influence of tidalinteractions and minor mergers on the radial and vertical disk structureof spiral galaxies. We report on the sample selection, our observations,and data reduction. Surface photometry of the optical and near infrareddata of a sample of 110 highly-inclined/edge-on disk galaxies arepresented. This sample consists of two subsamples of 61 non-interactinggalaxies (control sample) and of 49 interacting galaxies/minor mergingcandidates. Additionally, 41 of these galaxies were observed in the nearinfrared. We show that the distribution of morphological types of bothsubsamples is almost indistinguishable, covering the range between 0<= T <= 9. An improved, 3-dimensional disk modelling- and fittingprocedure is described in order to analyze and to compare the diskstructure of our sample galaxies by using characteristic parameters. Wefind that the vertical brightness profiles of galactic disks respondvery sensitive even to small deviations from the perfect edge-onorientation. Hence, projection effects of slightly inclined disks maycause substantial changes in the value of the disk scale height and musttherefore be considered in the subsequent study. Based on observationsobtained at the European Southern Observatory (ESO, La Silla, Chile),Calar Alto Observatory operated by the MPIA (DSAZ, Spain), LowellObservatory (Flagstaff/AZ, USA), and Hoher List Observatory (Germany).
| The influence of interactions and minor mergers on the structure of galactic disks. II. Results and interpretations
We present the second part of a detailed statistical study focussed onthe effects of tidal interactions and minor mergers on the radial andvertical disk structure of spiral galaxies. In the first part wereported on the sample selection, observations, and applied disk models.In this paper the results are presented, based on disk parametersderived from a sample of 110 highly-inclined/edge-on galaxies. Thissample consists of two subsamples of 49 interacting/merging and 61non-interacting galaxies. Additionally, 41 of these galaxies wereobserved in the NIR. We find significant changes of the disk structurein vertical direction, resulting in ~ 1.5 times larger scale heights andthus vertical velocity dispersions. The radial disk structure,characterized by the cut-off radius and the scale length, shows nostatistically significant changes. Thus, the ratio of radial to verticalscale parameters, h/z0, is ~ 1.7 times smaller for the sampleof interacting/merging galaxies. The total lack of typical flat diskratios h/z0 > 7 in the latter sample implies that verticaldisk heating is most efficient for (extremely) thin disks. Statisticallynearly all galactic disks in the sample (93%) possess non-isothermalvertical luminosity profiles like the sech (60%) and exp (33%)distribution, independent of the sample and passband investigated. Thisindicates that, in spite of tidal perturbations and disk thickening, theinitial vertical distribution of disk stars is not destroyed byinteractions or minor mergers. Based on observations obtained at theEuropean Southern Observatory (ESO, La Silla, Chile), Calar AltoObservatory operated by the MPIA (DSAZ, Spain), Lowell Observatory(Flagstaff/AZ, USA), and Hoher List Observatory (Germany).
| The QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
| The Revised Flat Galaxy Catalogue.
We present a new improved and completed version of the Flat GalaxyCatalogue (FGC) named the Revised Flat Galaxy Catalogue (RFGC)containing 4236 thin edge-on spiral galaxies and covering the whole sky.The Catalogue is intended to study large-scale cosmic streamings as wellas other problems of observational cosmology. The dipole moment ofdistribution of the RFGC galaxies (l = 273 degr; b =+19 degr) lieswithin statistical errors (+/-10 degr) in the direction of the LocalGroup motion towards the Microwave Background Radiation (MBR).
| 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.
| Are spiral galaxies optically thin or thick?
The opacity of spiral galaxies is examined by modelling the dust andstellar content of individual galaxies. The three dimensional model thatwe use assumes exponential distributions for the dust and the stars inthe disk, while the R(1/4) law is used to describe the bulge. In thismodel, both absorption and scattering by the dust are taken intoaccount. The model is applied to five late-type spiral galaxies (NGC4013, IC 2531, UGC 1082, NGC 5529 and NGC 5907) using their optical (andnear infrared for IC 2531) surface photometry. For these galaxies wehave determined the scalelengths and scaleheights of the stars and thedust in the disk, the bulge characteristics, the inclination angle andthe face-on optical depth. Computation of the dust masses, as well asthe extinction as a function of the wavelength, are also reported.Having analyzed a total of seven galaxies thus far, the five galaxiesmentioned above plus UGC 2048 and NGC 891 presented in (Xilouris et al.1997, 1998), we are able to draw some general conclusions, the mostsignificant of which are: 1) The face-on central optical depth is lessthan one in all optical bands, indicating that typical spiral galaxieslike the ones that we have modelled would be completely transparent ifthey were to be seen face-on. 2) The dust scaleheight is about half thatof the stars, which means that the dust is more concentrated near theplane of the disk. 3) The dust scalelength is about 1.4 times largerthan that of the stars and the dust is more radially extended than thestars. 4) The dust mass is found to be about an order of a magnitudemore than previously measured using the IRAS fluxes, indicating theexistence of a cold dust component. The gas-to-dust mass ratiocalculated is close to the value derived for our Galaxy. 5) The derivedextinction law matches quite well the Galactic extinction law,indicating a universal dust behaviour.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| 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.
| A catalogue of spatially resolved kinematics of galaxies: Bibliography
We present a catalogue of galaxies for which spatially resolved data ontheir internal kinematics have been published; there is no a priorirestriction regarding their morphological type. The catalogue lists thereferences to the articles where the data are published, as well as acoded description of these data: observed emission or absorption lines,velocity or velocity dispersion, radial profile or 2D field, positionangle. Tables 1, 2, and 3 are proposed in electronic form only, and areavailable from the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (to130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| Short 21-cm WSRT observations of spiral and irregular galaxies. HI properties.
We present the analysis of neutral hydrogen properties of 108 galaxies,based on short 21-cm observations with the Westerbork Synthesis RadioTelescope (WSRT). The results of two HI surveys are analysed toinvestigate the existence of relations between optical and HIproperties, like diameters, hydrogen masses and average surfacedensities. For all galaxies in our sample we find that the HI diameter,defined at a surface density level of 1Msun_/pc^2^, is largerthan the optical diameter, defined at the 25^th^mag/arcsec^2^ isophotallevel. The Hi-to-optical-diameter ratio does not depend on morphologicaltype or luminosity. The strongest, physically meaningful, correlationfor the sample of 108 galaxies is the one between logM_HI_ and logD_HI_,with a slope of 2. This implies that the HI surface density averagedover the whole HI disc is constant from galaxy to galaxy, independent ofluminosity or type. The radial HI surface density profiles are studiedusing the technique of principal component analysis. We find that about81% of the variation in the density profiles of galaxies can beexplained by two dimensions. The most dominant component can be relatedto "scale" and the second principal component accounts for the variancein the behaviour of the radial profile in the central parts of galaxies(i.e. "peak or depression") . The third component accounts for 7% of thevariation and is most likely responsible for bumps and wiggles in theobserved density profiles.
| On the question of radio emission of spiral galaxies in groups of galaxies
It has been shown that the radio emission properties of spiral galaxies,if the other conditions are the same, are determined rather by thepresence of the close neighbours than by space density of galaxiesaround them. The rate of occurence of radio sources and their radioluminosities among the spiral members of groups of galaxies depend onthe projected seperation between them and their nearest neighbour. Theshorter this seperation the higher the probability of radio emission.
| 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.
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
