Home     Getting Started     To Survive in the Universe    
Inhabited Sky
    News@Sky     Astro Photo     The Collection     Forum     Blog New!     FAQ     Press     Login  

NGC 684



Upload your image

DSS Images   Other Images

Related articles

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.

Study of MCLeish's Interacting Object
We discuss the morphology, kinematics, and physical conditions of theemitting gas of the interacting system IRAS 20048-6621. We present aswell numerical simulations of this interacting system, discovered byDavid McLeish in 1946. The main galaxy (McL A) is an edge-on spiralgalaxy with highly distorted NW side. On this side is also located McLB, the perturber galaxy. We determined a distance of 151 Mpc (h=0.75)and a diameter of 70 kpc for McL A. It presents a bright nucleus withbroad red emission lines (~500 km s-1). McL A has far-IRcolor indexes closely comparable to NGC 3628, one the few nearby edge-ongalaxies which is a bright infrared emitter. Nevertheless, McL A is moreluminous (in these bands) than any of the edge-on galaxies in the sampleof bright infrared galaxies of Young et al. (1988). The two sides of McLA rotation curve are remarkably different. The N-body model that bestreproduces McL A kinematical and morphological data (Kuijken &Dubinski 1995) gives a total mass 7x1011 Msolarfor McL A. Numerical simulations with the TREESPH code closely reproducethe morphology and radial velocity observations. The best scenario forthis system is that of a prograde encounter between McL A and B, withMcL B's orbit 35 deg tilted with respect to the spiral disk of McL A anda perigalactic distance of 17.6 kpc. The derived mass ratio is McL B/McLA~1/26. In the last 5x108 yr the perturber has crossed themain galaxy disk twice, in between it crossed the perigalacticon.According to our simulations, the emitting gas present in McL B has notbeen stripped out from the McL A disk, so that leads us to conclude thatMcL B is an irregular or small spiral galaxy.

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 ( or viahttp://cdsweb.u-strasbg.fr/Abstract.html

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.

Near-infrared observations of galaxies in Pisces-Perseus. I. vec H-band surface photometry of 174 spiral
We present near-infrared, H-band (1.65 $() μm), surface photometry of174 spiral galaxies in the area of the Pisces-Perseus supercluster. Theimages, acquired with the ARNICA camera mounted on various telescopes,are used to derive radial profiles of surface brightness, ellipticities,and position angles, together with global parameters such as H-bandmagnitudes and diameters Radial profiles in tabular form and images FITSfiles are also available upon request from gmorio@arcetri.astro.it.}.The mean relation between H-band isophotal diameter D_{21.5} and theB-band D25 implies a B-H color of the outer disk bluer than3.5; moreover, D_{21.5}/D25 depends on (global) color andabsolute luminosity. The correlations among the various photometricparameters suggest a ratio between isophotal radius D_{21.5}/2 and diskscale length of ~ m3.5 and a mean disk central brightness ~ meq 17.5H-mag arcsec^{-2}. We confirm the trend of the concentration indexC31$ with absolute luminosity and, to a lesser degree, withmorphological type. We also assess the influence of non-axisymmetricstructures on the radial profiles and on the derived parameters. Basedon observations at the TIRGO, NOT, and VATT telescopes. TIRGO(Gornergrat, CH) is operated by CAISMI-CNR, Arcetri, Firenze. NOT (LaPalma, Canary Islands) is operated by NOTSA, the Nordic ObservatoryScientific Association. VATT (Mt. Graham, Az) is operated by VORG, theVatican Observatory Research Group Table 3 and Fig. 4 are only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr( or via http://cdsweb.u-strasbg.fr/Abstract.html.

Groups of galaxies. III. Some empirical characteristics.
Not Available

Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp orhttp://cdsweb.u-strasbg.fr/Abstract.html

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.

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.

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 flattening distribution of dwarf elliptical galaxies in the Virgo Cluster
We have obtained R-band surface photometry of 70 dwarf ellipticalgalaxies in the Virgo Cluster. We find, in contrast to the results ofearlier studies, that the dwarfs have a markedly flatter distribution ofellipticities than either 'normal' elliptical galaxies or brightestcluster ellipticals. The ensemble of nucleated dwarfs is rounder thanthe non-nucleated galaxies. Neither the nucleated nor the nonnucleateddwarfs, however, have distributions as round as giant ellipticals.

A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.

General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.

Axial ratios of edge-on spirals
A diameter-limited sample of 888 normal Sa-Sc galaxies was compiled fromthe Uppsala General Catalog. New micrometer measures of the axial ratiosR of the disk components of 262 edge-on spirals in this sample were madeon copies of blue Palomar Sky Survey plates and calibrated againstphotometric standards. The distribution of isophotal axial ratios forthe whole sample was analyzed to give information on the true axialratios R0 of spiral disks. The mean value of logR0 is 0.95 +/- 0.03 and the dispersion about this mean is0.12 +/- 0.04. A similar mean value (0.90) was obtained from avolume-limited sub-sample of 348 spirals. The dispersion in logR0 is partly due to a dependence of R0 onmorphological type, and the mean value of log R0 for eachtype was estimated. Inclinations of 342 edge-on (R is greater than about3) spirals were determined from their isophotal axial ratios and types.No significant dependence of R0 on luminosity at each typewas found.

The far-infrared properties of the CfA galaxy sample. I - The catalog
IRAS flux densities are presented for all galaxies in the Center forAstrophysics magnitude-limited sample (mB not greater than 14.5)detected in the IRAS Faint Source Survey (FSS), a total of 1544galaxies. The detection rate in the FSS is slightly larger than in thePSC for the long-wavelength 60- and 100-micron bands, but improves by afactor of about 3 or more for the short wavelength 12- and 25-micronbands. This optically selected sample consists of galaxies which are, onaverage, much less IR-active than galaxies in IR-selected samples. Itpossesses accurate and complete redshift, morphological, and magnitudeinformation, along with observations at other wavelengths.

Frequency of Warped Spiral Galaxies at Visible Wavelengths
A list of optical warped spiral galaxies with basic position andgeometrical parameters is presented. From this list an attempt todetermine the frequency of warped discs has been made. All northern NGChigh inclined spirals were examined in the Palomar Observatory SkySurvey. Warps were observed in about half of these galaxies, whichindicate that nearly all spiral galaxies are warped.

The Southern Supercluster
The Southern Supercluster is described using data compiled from fivecatalogs, reduced to a homogeneous system following RC2. In terms ofmass, luminosity, and mass-to-light ratio, the Southern Superclustercompares well with the Coma and Hercules superclusters, but is lessmassive than the Local Supercluster. It is shown that, even though theSouthern Supercluster is the nearest supercluster to the LocalSupercluster, it is well separated from the Local Supercluster. However,there is evidence of a tenuous stream of galaxies connecting theSouthern Supercluster with the Perseus Supercluster.

Observations of galaxies in groups at 102 MHz
Observations of 325 galaxies in groups were carried out at a frequencyof 102 MHz via the scintillation method. Radio emission was found in 42of these components. Eleven of these have a meridional component.

Isolated Triplets of Galaxies - a Complete Summary of Radial Velocities and Reduced Data
Not Available

Cosmology from a galaxy group catalog. I - Binaries
A new, completely objective group-finding algorithm is described andapplied to the CfA redshift catalog. The binary galaxies are isolatedfor analysis. The assumptions underlying the analysis are (1) that lighttraces mass, (2) that our binary galaxy subsets are representative lighttracers, and (3) that the binary orbits are circular. The primary resultof the work is that the resulting bias-free binary catalogs are afunction of the assumed cosmological model. For virtually any inputvalue of Omega(0) in the range 0.01-5.00, there is a reasonablyconsistent interpretation of the CfA survey such that the specifiedvalue of Omega(0) can be derived from the binary sample obtained underthat interpretation. A secondary result is that the higher the inputvalue of Omega(0), the broader the intrinsic distribution in M/L, andhence the less valid the assumption that light traces mass.

The peculiar velocity of the Local Group. I - H I observations of SB and SBC galaxies
H I observations of a sample of 128 Sb and Sbc galaxies ranging inlinear diameter from 9-128 kpc, and in total mass from 6.3 x 10 to the9th solar masses to 1.3 x 10 to the 12th solar masses, are presented.Measurements of H I self-absorption are not found to vary withinclination, though a dependence of observed diameters and luminositieson inclination is noted. Total surface mass density and color index areshown to be highly correlated, implying that star-formation in thesegalaxies is governed by disk density rather than total mass or gasrichness. From 12-arcmin resolution local Galactic H I observations, newcorrection factors for diameters and luminosities are derived to allowfor the effects of galactic obscuration.

Box-shaped galaxies - A complete list
A survey of box-shaped galaxies complete to B(tau) = 13.2 in the wholesky is presented, consisting of 74 objects, 60 of which are newidentifications. The observed frequency of lenticulars exhibiting thisphenomenon is shown to be consistent with the hypothesis of their beingedge-on barred galaxies. A sequence noted in the morphology of thebox-shaped bulges is thought to be related to the global dynamicalstructure of these galaxies.

A 21 CM survey of the Pisces-Perseus supercluster. II - The declination zone +21.5 to +27.5 degrees
Neutral-hydrogen 21-cm line spectra and derived parameters are presentedfor a sample of spiral galaxies in the region bounded by an R.A. greaterthan 22 h and less then 0.04 h, and a declination greater than +21 deg30 min and less than +27 deg 30 min, covering the Zwicky fields 470 to488, as the second installment of a survey of the region of thePisces-Perseus supercluster. New H I line observations made with theArecibo 305 m telescope detected 275 galaxies of 318 studied. Atabulation of derived galaxian properties is given. The redshiftdistribution shows gross departures from that expected for a sample withsimilar magnitude characteristics but homogeneously located in space.These new data will be incorporated into the overall survey of thethree-dimensional structure in the Pisces-Perseus region.

A search for environmental effects on the optical properties of galaxies in groups
Environmental density-related modifications of basic optical properties(luminosities, sizes, axial ratios, and colors) of galaxies belonging toGeller and Huchra's (1983) groups have been investigated. Remarkably, itis found that the broad maxima of the distributions of luminosities anddiameters of spirals and the whole corresponding distributions oflenticulars tend to move to lower values as one goes to groups of highcompactness, whereas the luminosity-diameter relationship of spiralstends to become flatter. No color and axial ratio differences betweengalaxies of high- and low-compactness groups have been detected.

A catalogue of HI diameters for 238 galaxies
A large catalog of effective H I diameters for 238 galaxies has beencompiled from new measurements made with the Nancay radiotelescope (40percent of the catalog), and previously published diameters homogenizedto the same definition. A good covering both in morphological types andin luminosity within each type is thus achieved.

Study of the open cluster IC 1805
Photoelectric magnitudes and colours in the UBV system have beendetermined for 169 stars in IC 1805. The reddening is variable acrossthe cluster. The distance modulus to the cluster is estimated at 11.7 m.Star-formation activities are still in progress in the cluster region.

A survey of galaxy redshifts. IV - The data
The complete list of the best available radial velocities for the 2401galaxies in the merged Zwicky-Nilson catalog brighter than 14.5mz and with b (II) above +40 deg or below -30 deg ispresented. Almost 60 percent of the redshifts are from the CfA surveyand are accurate to typically 35 km/s.

Groups of galaxies. III - The CfA survey
A statistically homogeneous group catalog (CfA) is based on the CfAredshift survey (Huchra et al.) is presented. Groups in the catalog areall density enhancements in redshift space of a factor greater than 20.Group members are identified according to the procedure described in aprevious study (Huchra and Geller) of a shallower whole-sky sample. Allgroups contain at least three members. Of the 176 groups in the CfAcatalog, 102 have been identified in one or more previous studies.Because the utilized algorithm searches for volume rather than surfacedensity enhancements, the groups in a given region generally change onlythrough the addition of fainter members when the magnitude limit of thegalaxy catalog increases. In the region of overlap, agreement betweenthe shallow catalog and the CfA catalog is excellent.

Radio observations of galaxies of the Byurakan classification at 102 MHz
Interplanetary-scintillation observations at 102 MHz have been made of131 galaxies of the Biurakan classification (1975). It is found thatgalaxies with more pronounced nuclei have higher activity in the radiorange and that scintillating components (with angular dimensions about0.1 arcsec) are more frequently found in them. The scintillatingcomponents have steep spectra.

Submit a new article

Related links

  • - No Links Found -
Submit a new link

Member of following groups:

Observation and Astrometry data

Right ascension:01h50m14.00s
Aparent dimensions:3.162′ × 0.676′

Catalogs and designations:
Proper Names   (Edit)
NGC 2000.0NGC 684
ICIC 165

→ Request more catalogs and designations from VizieR