Contents
Images
Upload your image
DSS Images Other Images
Related articles
A Self-Absorption Census of Cold H I Clouds in the Canadian Galactic Plane Survey
We present a 21 cm line H I self-absorption (HISA) survey of cold atomicgas within Galactic longitudes l=75deg to 146° andlatitudes b=-3deg to +5°. We identify HISA as spatiallyand spectrally confined dark H I features and extract it from thesurrounding H I emission in the arcminute-resolution Canadian GalacticPlane Survey (CGPS). We compile a catalog of the most significantfeatures in our survey and compare our detections against those in theliterature. Within the parameters of our search, we find nearly allpreviously detected features and identify many new ones. The CGPS showsHISA in much greater detail than any prior survey and allows both newand previously discovered features to be placed into the larger contextof Galactic structure. In space and radial velocity, faint HISA isdetected virtually everywhere that the H I emission background issufficiently bright. This ambient HISA population may arise from smallturbulent fluctuations of temperature and velocity in the neutralinterstellar medium. By contrast, stronger HISA is organized intodiscrete complexes, many of which follow a longitude-velocitydistribution that suggests that they have been made visible by thevelocity reversal of the Perseus arm's spiral density wave. The cold H Irevealed in this way may have recently passed through the spiral shockand be on its way to forming molecules and, eventually, new stars. Thispaper is the second in a series examining HISA at high angularresolution. A companion paper (Paper III) describes our HISA search andextraction algorithms in detail.
| A wavelet add-on code for new-generation N-body simulations and data de-noising (JOFILUREN)
Wavelets are a new and powerful mathematical tool, whose most celebratedapplications are data compression and de-noising. In a previous paper,we have shown that wavelets can be used for removing noise efficientlyfrom cosmological, galaxy and plasma N-body simulations. The expectedtwo-orders-of-magnitude higher performance means, in terms of thewell-known Moore's law, an advance of more than one decade in thefuture. In this paper, we describe a wavelet add-on code designed forsuch an application. Our code can be included in common grid-basedN-body codes, is written in FORTRAN, is portable and is available onrequest from the first author. The code can also be applied for removingnoise from standard data, such as signals and images.
| Galaxy Luminosity Functions from Deep Spectroscopic Samples of Rich Clusters
Using a new spectroscopic sample and methods accounting forspectroscopic sampling fractions that vary in magnitude and surfacebrightness, we present R-band galaxy luminosity functions (GLFs) for sixnearby galaxy clusters with redshifts of 4000 kms-1
| A New Photometric Look at M51
A new technique is used to derive the extinction and age of populationsin the interacting galaxies NGC 5194 & NGC 5195 from high-S/Nmulti-colour photometric data. A new evolutionary scenario of theinteraction is proposed.
| Seeing Galaxies through Thick and Thin. IV. The Superposed Spiral Galaxies of NGC 3314
The superposed pair of spiral galaxies making up NGC 3314 offers aunique opportunity to trace the dust properties in a spiral galaxy. Weanalyze multicolor Hubble Space Telescope imaging, supported byground-based near-IR imaging and fiber-array spectroscopy, to measuredust extinction in the foreground Sc galaxy NGC 3314A, which is backlitby the Sb system NGC 3314B. The superposition allows us to measureextinctions over a wide range of galactocentric radii in the foregroundgalaxy from 0.4-4.5 kpc. In the outer half of the disk, the extinctionis strongly localized in discrete dust lanes, including some patcheswhose galactic setting is clear only because of associated Hαemission at the foreground velocity. These dust features show anextinction curve with a slope close to the Galactic mean (R=3.5+/-0.3)over a range in galactocentric radius from 1.6 to 3.8 kpc, with noradial trend. Using the I-K color of the background nucleus, we derivean extinction of AI=3.3 through the disk at a projecteddistance of 400 pc from the nucleus of NGC 3314A. The extinction in eventhe inner disk of NGC 3314A is quite patchy, since background Hαemission is detected from all parts of the system. Localanticorrelations between foreground and background line emissiondemonstrate that the dust is concentrated in star-forming regions, ashas been found for the blue light in several systems. The colors of thedust lanes in NGC 3314A that are projected only partially against thebackground disk indicate that the dust scale height in the foregrounddisk is substantially smaller than that of the stars. Thecolor-intensity behavior of the net light in these regions tracks thepredictions of a thin-layer model closely. Based on observations withthe NASA/ESA Hubble Space Telescope obtained at the Space TelescopeScience Institute, which is operated by the Association of Universitiesfor Research in Astronomy, Inc., under NASA contract NAS 5-26555.
| Possible Nova in NGC 3314
IAUC 7388 available at Central Bureau for Astronomical Telegrams.
| Seeing Galaxies through Thick and Thin. I. Optical Opacity Measures in Overlapping Galaxies
We describe the use of partially overlapping galaxies to provide directmeasurements of the effective absorption in galaxy disks, independent ofassumptions about internal disk structure. The nonoverlapping parts ofthe galaxies and symmetry considerations are used to reconstruct, viadifferential photometry, how much background galaxy light is lost inpassing through the foreground disks. Extensive catalog searches andfollow-up imaging yield ~15-25 nearby galaxy pairs suitable for varyingdegrees of our analysis; 11 of the best such examples are presentedhere. From these pairs, we find that interarm extinction is modest,declining from AB~1 mag at 0.3RB25 toessentially zero by RB25; the interarm dust has ascale length consistent with that of the disk starlight. In contrast,dust in spiral arms and resonance rings may be optically thick(AB>2) at virtually any radius. Some disks have flatterextinction curves than the Galaxy, with AB/AI~1.6this is probably the signature of clumpy dust distributions. Even thoughtypical spirals are not optically thick throughout their disks, wherethey are optically thick is correlated with where they are mostluminous: in spiral arms and inner disks. This correlation betweenabsorption and emission regions may account for their apparent surfacebrightness being only mildly dependent on inclination, erroneouslyindicating that spirals are generally optically thick. Taken as anensemble, the opacities of spiral galaxies may be just great enough tosignificantly affect QSO counts, though not enough to cause theirhigh-redshift cutoff. Based in part on archival observations with theNASA/ESA Hubble Space Telescope (HST) obtained at the Space TelescopeScience Institute, which is operated by the Association of Universitiesfor Research in Astronomy, Inc., under NASA contract NAS5-26555.
| UGC 3995: A Close Pair of Spiral Galaxies
UGC 3995 is a close pair of spiral galaxies whose eastern componenthosts a Seyfert 2 nucleus. The object was selected for observationbecause a bright filamentary structure that apparently connects thenuclei of the two galaxies made it a good candidate to investigate apossible connection between galaxy interactions and active galacticnuclei. We present a detailed analysis of this system using long-slitspectroscopy and narrowband (Hα+[N II] lambdalambda6548, 6583), aswell as broadband (B, R), imaging and an archival Wide Field PlanetaryCamera 2 image. The component galaxies reveal surprisingly small signsof interaction considering their spatial proximity and almost identicalrecession velocities, as the bright filament is probably an opticalillusion due to the superposition of the bar of the Seyfert galaxy andof the spiral arms of the companion. The broadband morphology, a B-Rcolor map, and a continuum-subtracted Hα+[N II] lambdalambda6548,6583 image demonstrate that the western component UGC 3995B is in frontof the Seyfert-hosting component UGC 3995A, partly obscuring its westernside. The small radial velocity difference leaves the relative motion ofthe two galaxies largely unconstrained. The observed lack of major tidaldeformations, along with some morphological peculiarities, suggests thatthe galaxies are proximate in space but may have recently approachedeach other on the plane of the sky. The geometry of the system and theradial velocity curve at P.A.~106 deg suggest that the encounter may beretrograde or, alternatively, prograde before perigalacticon. Thepartial overlap of the two galaxies allows us to estimate the opticalthickness of the disk of component B. We derive an extinction of ~0.18visual magnitudes in the interarm parts of the foreground galaxy disk,and >~1-1.5 visual magnitudes corresponding to the spiral arms.
| The Extinction Distribution in the Galaxy UGC 5041
We probe the dust extinction through the foreground disk of theoverlapping galaxy pair UGC 5041 by analyzing B-, I-, and H-band images.The inclined foreground disk of this infrared-selected pair is almostopaque in B at a projected distance of ~8 kpc. From the images, wedirectly estimate the area-weighted distribution of differential near-IRextinction: it is nearly Gaussian, with = 0.6 andsigma = 0.27. For a homogenous dust distribution and a Milky Wayextinction curve, this corresponds to a face-on distribution p(tau) witha mean of = 0.34 and sigma_V = 0.15. For a clumpy dustmodel, the optical depth estimate increases to = 0.41 andsigma_V = 0.19. Even though the galaxy pair is subject to differentselection biases and our analysis is subject to different systematics,the result is consistent with existing case studies, indicating that ~ 0.3 is generic for late-type spirals near theirhalf-light radii. We outline how to estimate from p(tau) by how muchbackground quasars are underrepresented, where projected within ~10 kpcof nearby spirals, such as damped Lyalpha absorbers or gravitationallenses; from our data we derive a factor of 2 deficit for flux-limited,optical surveys.
| Hα objective prism survey of Abell 1060
As part of a continuing study of the effect of cluster environment onthe star formation properties of galaxies, we have undertaken anHα objective prism survey of the nearby cluster, Abell 1060. Wedetect 33 galaxies in emission, 24 of which are cluster members. Wepresent new radial velocity measurements and Hα + [N Ii]equivalent widths and fluxes for a number of these galaxies. Wedistinguish between galaxies with diffuse and compact emission, thelatter having been associated in previous work with a disturbedmorphology of the galaxy and most likely resulting from tidally-inducedstar formation from galaxy-galaxy or cluster-galaxy interactions. Thefraction of cluster spirals in Abell 1060 detected with compact emissionagrees with the expected fraction for a cluster of its richness, asderived from results of a previous survey of 8 clusters. Some of thedetected cluster early-type spirals exhibit anomalously high globalHα equivalent widths, as compared to galaxies of similar type inthe field.
| On the morphology of peculiar ring galaxies
It is proposed that peculiar ring galaxies can be divided into fiveprincipal types according to the morphology of the ring and bulge, basedon the visual inspection of 489 selected objects. Those objects havebeen named ``peculiar'' following the ``Catalogue of Southern PeculiarGalaxies and Associations'' by \cite[Arp & Madore (1986]{am6}) Table2 with its notes is only available electronically via anonymous ftp130.79.128.5 or http://cdsweb.u-strasbg.fr.
| 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
| Measurement of mass distribution of galaxy clusters using the giant luminous arc statistics with Le Fevre et al.'s arc survey data.
We have constructed a scheme to predict the number of arcs that shouldbe observed in clusters, that fully takes into account both thedetection conditions in the arc survey and the evolution of the sourcegalaxies. The scheme has been applied to Le Fevre et al.'s arc surveydata in order to constrain the models of cluster mass distribution. Thecanonical model of the source galaxy evolution proposed by Yoshii(1993ApJ...403..552Y) is adopted. We have found that any sphericalcluster mass distribution models even with very small core radius,cannot reproduce a number of arcs as large as the number observed in LeFevre et al.'s arc survey. Recently, Bartelmann, Steinmetz & Weiss(1995A&A...297....1B; hereafter BSW) showed that their inhomogeneousmodel constructed numerically can produce a much larger number of giantluminous arcs than the non-singular isothermal sphere model with thesame core radius and the same velocity dispersion as those in theirmodel. However, we have found that their cluster mass distribution modelcannot reproduce a number of arcs as large as observed. We suggest thatone of the possible solutions to reproduce the observed arc number isthat the clusters have inhomogeneities similar to these in BSW's modelas a whole and that the core radius of the clusters may be much smallerthan that in BSW's model. A speculation on the evolution of the coolingflow and the hot gas in the cluster central region is made based on thissuggestion. A possible variation of the lens model with the non-thermalpressure is also briefly discussed in order to examine how it enhancesthe expected number of giant luminous arcs.
| Structure and kinematics of galaxy clusters. I. The redshift catalogue.
An extensive redshift survey has been conducted on a sample of 15 nearby(0.01<~z<~0.05) clusters of galaxies. A total number of 860redshifts were determined by fitting of emission-lines and/orcross-correlation techniques. Of this sample, 735 galaxies are within0.2-0.8Mpc (H_0_=50km/s/Mpc) of the center of clusters. Approximatemorphological types are available for most of the galaxies. A comparisonof the present redshifts with published data allows an extensive erroranalysis. The agreement is excellent with the most modern data, showinga zero point error of 5km/s and an overall consistency of themeasurements and their uncertainties. We estimate our redshifts to havemean random errors around 30km/s. A population analysis of the clusterswill be given in a forthcoming paper.
| A 20 CM VLA Survey of Abell clusters of galaxies. 4: The radio sample and cluster properties
This is the fourth in a series of papers describing an in depth study ofa large statistical sample of radio galaxies in Abell clusters. Thissample forms the basis of a detailed optical and radio study of the hostgalaxy properties, environments, and evolutionary models for radiogalaxies as a class of objects. In this paper, we examine the radiodetection statistics as a function of cluster morphological type, galaxyrichness, and spatial location within the cluster distribution. Theserelationships are also parameterized as a funtion of radio power. Thespatial distributions of the radio sources as a function of distancefrom the cluster center indicate that radio galaxies are preferentiallylocated at small radii from the center of the cluster potential. This isobserved as a factor of 2-3 excess over that predicted by a King-modelsurface-density distribution. The excess is higher in the upper radiopower bin. This result is easily explained, however, from the spatialdistribution of the brightest galaxies and the relationship betweenradio and optical luminosity. The sample is divided into richnessclasses 0, 1, and 2, according to Abell's criterion. and in two radiopower ranges. While simple counting shows that richer clusters have moreradio galaxies in both radio power bins, when the detections are scaledto the number of galaxies surveyed in each cluster, no significantcorrelations are found. This result implies that the number of radiogalaxies detected simply scales with the number of galaxies surveyed.The higher galaxy density (and presumably higher ICM gas density) inricher clusters does not appear to affect the rate of radio sourceformation. The clusters are divided into Rood-Sastry and Bautz-Morganmorphological types. While it would appear that the more regularclusters have higher radio detection rates, when the classes arenormalized to the number of galaxies, the radio detection rates arefound to be identical regardless of cluster morphology. In conclusion,it is the optical properties of the host galaxy which most influenceboth the radio detection rate and the radio source properties. Thecluster properties, galaxy density, and spatial location of the galaxydo not significantly affect the observed radio statistics.
| A measurement of the optical depth through a galaxy disk
The present approach to the controversy concerning the degree of dustobscuration of the disks of spiral galaxies notes that White and Keel's(1992) broadband color measurements of an overlapping galaxy pair wereunable to unambiguously separate the galaxies' respective contributions.Attention is accordingly given here to individual emission lines, whichare completely separated when the redshift difference between twogalaxies is sufficiently large. Significant optical depths are herenoted along three lines-of-sight through the foreground galaxy bycomparing H-alpha/H-beta ratios for the H II region in the backgroundgalaxy with those in isolated spiral galaxies, and then exploiting thewavelength dependence of extinction by dust.
| A 20 centimeter VLA survey of Abell clusters of galaxies. III - Images and optical identifications
Radio contour maps, models, and optical identifications for 250 radiogalaxies in Abell clusters of galaxies are presented. Consideration isgiven to the effect of environment on radio galaxies, the evolution ofradio galaxies in rich clusters, and the importance of beaming in acomplete sample of radio galaxies.
| Surface photometry of the Hydra I cluster of galaxies. I - Photometric data
Surface photometry was made for 137 galaxies on a UK Schmidt plate whosecenter is located at the center of the Hydra I (A1060 ) cluster ofgalaxies. For 133 of the 137 galaxies, such photometric parameters astotal magnitude, equivalent radius, concentration indices, and meansurface brightness were obtained. The total magnitudes were comparedwith those in the literature to check the accuracy of the present data.The estimated accuracy in the total magnitudes is about 0.1 mag at mostfor majority of the galaxies.
| H I imaging of NGC 3312 and NGC 3314a - A foreground group to the Hydra cluster?
A VLA neutral hydrogen image pointed toward the center of the Hydra I(Abell 1060) Galaxy Cluster, which is offset in velocity from thecluster mean is presented. The velocity range covers NGC 3312, NGC3314a, and a small ring galaxy. In contrast to an H I image of thespirals that are projected close to the center of Virgo, these threegalaxies are gas rich, have extended H I disks, and show signs of tidalinteractions. A comparison of the Einstein IPC data for Virgo and Hydrasuggests that the ICM density in Hydra is an order of magnitude higherthan at the location of the shrunken H I disks in Virgo. Althoughgalaxies with high relative velocities with respect to the cluster meanare expected to be close to the cluster center, the absence of anyeffects of the dense ICM on the H I distribution can most easily beunderstood if the three galaxies form a separate group, which is closeto the center of Hydra in projection only.
| Optical identifications of IRAS point sources - The Fornax, Hydra I and Coma clusters
Optical identifications are presented for 66 IRAS point sources in theregion of the Fornax cluster of galaxies, 106 IRAS point sources in theregion of the Hydra I cluster of galaxies (Abell 1060), and 59 IRASpoint sources in the region of the Coma cluster of galaxies (Abell1656). Eight other sources in Hydra I do not have optical counterpartsand are very probably due to IR cirrus. Twenty-three (35 percent) of theFornax sources are associated with stars and 43 (65 percent) withgalaxies; 48 (42 percent) of the Hydra I sources are associated withstars and 58 (51 percent) with galaxies; 18 (31 percent) of the Comasources are associated with stars and 41 (69 percent) with galaxies. Thestellar and infrared cirrus surface density is consistent with thegalactic latitude of each field.
| New observations and a photographic atlas of polar-ring galaxies
A photographic atlas of polar-ring galaxies and related objects ispresented. The atlas includes kinematically confirmed polar-ringgalaxies (category A), good condidates based on their morphologicalappearance (category B), possible candidates (category C), and possiblyrelated objects (category D). New photometric and kinematic observationsare reported for several galaxies in the catalog, including observationsthat show that UGC 7576 and UGC 9796 ( = II ZW 73) are S0 galaxies withpolar rings. Roughly 0.5 percent of all nearby S0 galaxies appear tohave polar rings. When corrected for various selection effects (e.g.,nonoptimal viewing orientation, possible dimming, or limited lifetime ofthe ring) the percentage increases to about 5 percent of S0 galaxieswhich have, or have had a polar ring.
| An expanding shell of galaxies in the center of the Hydra I cluster?
The velocities of galaxies in the right center of the Hydra I cluster ofgalaxies are not distributed at random, but exhibit a pattern that leadsto assume the existence of a shell of galaxies expanding away from thecenter of the cluster. This shell could be due to the absorption of agroup of galaxies by the cluster.
| The two superposed galaxies of NGC 3314
Spectroscopic data for the two superposed galaxies of NGC 3314 arepresented. The observations were carried out using the 4-meter telescopeof the Cerro Tololo Inter-American Observatory in the wavelength range6100-7000 A. Long-slit spectrograms show two sets of emission linesstemming from the superposed galaxies. The foreground galaxy, NGC 3314aappears to be a type SBbc or SBc spiral with an absolute magnitude of-20 mag and a radial velocity of 2835 + or - 15 km/s. The backgroundgalaxy, NGC 3314b, is probably an Sb type with an absolute magnitude of-20.5 mag and a radial velocity of 4641 + or - 6 km/s. It is suggestedon the basis of the observational data that at least NGC 3314a, andprobably also NGC 3314b, are members of the Hydra I cluster.
| Southern Galaxy Catalogue.
Not Available
| Optical studies of galaxies in clusters. I - Observations of hydrogen deficient galaxies
Optical observations are reported for eight galaxies in the Virgocluster and the galaxies NGC 3312 and NGC 3314 in the Hydra cluster.Within the sensitivity of the observations, it is shown that H Ideficient cluster galaxies and nondeficient galaxies have rotationcurves with characteristics similar to those of noncluster galaxies.There seems to be an indication of a correlation between the H Igalactic diameter and the extension of the region over which H II isdetected. An extended H-alpha feature detected in monochromatic imageryof the galaxy NGC 4438 is interpreted as due to the bow shock generatedby the motion of the galaxy in the intergalactic medium; the spacevelocity of the galaxy and the shock parameters are computed based onthis assumption and good agreement is found between the model and theobservations.
| NGC 3314 : ein Kuriosum.
Not Available
| Dust in backlit galaxies - Properties of the foreground systems in NGC 3314 and NGC 1275
New digital imaging of NGC 3314 and NGC 1275 is presented. NGC 3314consists of an Sc galaxy in front of an Sb; BVRI data are used toestimate the extinction through and between spiral arms and derive R =3.5 for the extinction curve, with large uncertainties due to structurein the foreground galaxy. Dust lanes are identified in NGC 1275, ofoptical depth similar to those in NGC 3314, and occurring in associationwith giant H II regions; these imply a type Sc or Scd for the foregroundobject. This object lies outside the low-velocity filament system and isprobably not interacting with the main body of NGC 1275.
| The Hydra I cluster of galaxies - A unique case of membership definition
New optical radial velocities for 71 galaxies in the Hydra I cluster arepresented. The recession velocity of the cluster is determined to 3425km/sec, yielding a distance of about 45.7 Mpc. The overall velocitydispersion is 676 km/sec. Results of galaxy counts could be fitted by atwo-component model. Many of the global cluster properties of Hydra Ilike, e.g., total galaxy content, velocity dispersion, X-ray flux, etc.,suggest a remarkable similarity with the Virgo cluster. No foregroundgalaxies and no background galaxies were noted in the observed area upto about 8000 km/sec, suggesting regions of empty space of the order of40-50 Mpc extent along the line of sight.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
