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מאמרים קשורים
Scale Heights of Non-Edge-on Spiral Galaxies
We present a method of calculating the scale height of non-edge-onspiral galaxies, together with a formula for errors. The method is basedon solving Poisson's equation for a logarithmic disturbance of matterdensity in spiral galaxies. We show that the spiral arms can not extendto inside the ``forbidden radius'' r0, due to the effect ofthe finite thickness of the disk. The method is tested by re-calculatingthe scale heights of 71 northern spiral galaxies previously calculatedby Ma, Peng & Gu. Our results differ from theirs by less than 9%. Wealso present the scale heights of a further 23 non-edge-on spiralgalaxies.
| Vertical Scale Parameter Estimates for 48 Non-edge-on Spiral Galaxies
In the first paper of this series, we directly studied the mathematicalforms, symmetry of spiral structure, and the projection of galacticdiscs on the images, and measured the pitch angles of the spiral armsand inclination angles of the galactic discs for 60 spiral galaxies. Inthis second paper, we estimate the vertical scale parameters of 48non-edge-on spiral galaxies based on the method proposed by Peng et al.and on the results given in Paper I. As we know, for edge-on discgalaxies we can obtain the vertical scale parameter from the photometry,once a mathematical form is specified for the vertical lightdistribution. For non-edge-on galaxies, some other methods have to beused. The statistical result was that the vertical scale parameter iscomparable for edge-on and non-edge-on galaxies, although it is obtainedfrom two very different methods.
| A Method of Obtaining the Pitch Angle of Spiral Arms and the Inclination of Galactic Discs
We investigate the mathematical form, the symmetry of spiral structureand the projected images of galactic discs. The measured pitch angles ofspiral arms and inclination angles of galactic discs for 60 spiralgalaxies are presented. The global spiral structure is emphasized in thestudy. It is found that, except for small-scale distortions, the spiralarms of those galaxies that were classified as AC 12 in the armclassification system of Elmegreen & Elmegreen, can be representedby the logarithmic spiral form.
| Galaxies with Rows
The results of a search for galaxies with straight structural elements,usually spiral-arm rows (“rows” in the terminology ofVorontsov-Vel'yaminov), are reported. The list of galaxies that possess(or probably possess) such rows includes about 200 objects, of whichabout 70% are brighter than 14m. On the whole, galaxies with rows makeup 6 8% of all spiral galaxies with well-developed spiral patterns. Mostgalaxies with rows are gas-rich Sbc-Scd spirals. The fraction ofinteracting galaxies among them is appreciably higher than amonggalaxies without rows. Earlier conclusions that, as a rule, the lengthsof rows are similar to their galactocentric distances and that theangles between adjacent rows are concentrated near 120° areconfirmed. It is concluded that the rows must be transient hydrodynamicstructures that develop in normal galaxies.
| Lopsided Galaxies, Weak Interactions, and Boosting the Star Formation Rate
To investigate the link between weak tidal interactions in disk galaxiesand the boosting of their recent star formation, we obtain images andspatially integrated spectra (3615 Å<=λ<=5315Å) for 40 late-type spiral galaxies (Sab-Sbc) with varying degreesof lopsidedness (a dynamical indicator of weak interactions). Wequantify lopsidedness as the amplitude of the m=1Fourier component of the azimuthal surface brightness distributionaveraged over a range of radii. The median spectrum of the most lopsidedgalaxies shows strong evidence for a more prominent young stellarpopulation (i.e., strong Balmer absorption, strong nebular emission, aweak 4000 Å break, and a blue continuum) when compared to themedian spectrum of the most symmetric galaxies. We compare the youngstellar content, quantified by EW(Hδabs) and thestrength of the 4000 Å break (D4000), with lopsidednessand find a 3-4 σ correlation between the two. We also find a 3.2σ correlation between EW(Hβemission) andlopsidedness. Using the evolutionary population synthesis code ofBruzual & Charlot we model the spectra as an ``underlyingpopulation'' and a superimposed ``boost population'' with the aim ofconstraining the fractional boost in the SFR averaged over the past 0.5Gyr (the characteristic lifetime of lopsidedness). From the differencein both EW(Hδabs) and the strength of the 4000 Åbreak (D4000) between the most and least symmetric thirds ofour sample, we infer that ~1×109 Msolar ofstars are formed over the duration of a lopsided event in addition tothe ``underlying'' star formation history (assuming a final galacticstellar mass of 1010 Msolar). This corresponds toa factor of 8 increase in the star formation rate over the past5×108 years. For the nuclear spectra, all of the abovecorrelations except D4000 versus areweaker than for the disk, indicating that in lopsided galaxies, the starformation boost is not dominated by the nucleus.
| 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.
| Extensive Spiral Structure and Corotation Resonance
Spiral density wave theories demand that grand-design spiral structurebe bounded, at most, between the inner and outer Lindblad resonances ofthe spiral pattern. The corotation resonance lies between the outer andthe inner Lindblad resonances. The locations of the resonances are atradii whose ratios to each other are rather independent of the shape ofthe rotation curve. The measured ratio of outer to inner extent ofspiral structure for a given spiral galaxy can be compared to thestandard ratio of corotation to inner Lindblad resonance radius. In thecase that the measured ratio far exceeds the standard ratio, it islikely that the corotation resonance is within the bright optical disk.Studying such galaxies can teach us how the action of resonances sculptsthe appearance of spiral disks. This paper reports observations of 140disk galaxies, leading to resonance ratio tests for 109 qualified spiralgalaxies. It lists candidates that have a good chance of having thecorotation resonance radius within the bright optical disk.
| The thicknesses and inclinations of 71 northern spiral galaxies
This paper presents the thicknesses and inclinations (i.e., the anglebetween the galactic plane and the tangent plane) of 71 northern spiralgalaxies. The method for measuring the thickness has been proposed byPeng. It is based on the solution of Poisson's equation for alogarithmic disturbance of density. The inclination is determined byassuming that the pattern of spiral structure is a logarithmic spiral.We find that the thickness is correlated with color and with theH_α+[NII] equivalent width.
| 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.
| 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.
| The CfA Redshift Survey: Data for the NGP +36 Zone
We have assembled redshifts for a complete sample of 719 galaxies withm_zw_ <= 15.5 in the declination range 32.5^deg^ <= δ <=38.5^deg^ and right ascension range 8^h^ <= α <= 17^h^. Wehave determined morphological types for all galaxies in the magnitudelimited sample by direct inspection of the POSS-O plates. 576 of theredshifts are measurements from Mount Hopkins, and 405 are newredshifts. We also include new redshifts for 77 fainter galaxies in thesame strip.
| 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.
| Groups of galaxies in the Center for Astrophysics redshift survey
By applying the Huchra and Geller (1982) objective group identificationalgorithm to the Center for Astrophysics' redshift survey, a catalog of128 groups with three or more members is extracted, and 92 of these areused as a statistical sample. A comparison of the distribution of groupcenters with the distribution of all galaxies in the survey indicatesqualitatively that groups trace the large-scale structure of the region.The physical properties of groups may be related to the details oflarge-scale structure, and it is concluded that differences among groupcatalogs may be due to the properties of large-scale structures andtheir location relative to the survey limits.
| H I survey of face-on galaxies - The frequency of distortions in H I disks
The full results of an H I survey of face-on galaxies are presented andit is shown that narrow H I profiles are rare in normal spiral galaxies.This is due in part to the wider-than-expected range of the integraldispersion and in part to the frequent occurrence of large-scaledistortions in the H I disk. These factors reduce the number of galaxieswith half-power widths less than 30 km/s to about 24 percent of thosethat would occur if galaxies generally had quiescent, coplanar H Idisks. Two useful subsets may be drawn from this study of 212 face-ongalaxies with axial ratios greater than 0.87. Fifty-two spirals of allmorphological types have half-power widths smaller than 100 km/s and maybe used for studies that benefit from a small velocity spread and anenhanced beam-filling factor. About 40 galaxies have velocity widthsmuch larger than expected and are of interest in studies of dynamicallypeculiar systems.
| Arm classifications for spiral galaxies
The spiral arm classes of 762 galaxies are tabulated; 636 galaxies withlow inclinations and radii larger than 1 arcmin were classified on thebasis of their blue images on the Palomar Observatory Sky Survey (POSS),76 SA galaxies in the group catalog of Geller and Huchra were alsoclassified from the POSS, and 253 galaxies in high-resolution atlaseswere classified from their atlas photographs. This spiral armclassification system was previously shown to correlate with thepresence of density waves, and galaxies with such waves were shown tooccur primarily in the densest galactic groups. The present sampleindicates, in addition, that grand design galaxies (i.e., those whichtend to contain prominent density wave modes) are physically larger thanflocculent galaxies (which do not contain such prominent modes) by afactor of about 1.5. A larger group sample confirms the previous resultthat grand design galaxies are preferentially in dense groups.
| Morphology of spiral galaxies. I - General properties
Red Palomar Sky Survey plates are scanned to characterize a completesample of 605 spiral galaxies north of declination -33 deg havinginclination angle less than 56 deg and blue diameter 2-15 arcmin. Theselection of the data and the reduction and parameter-extractionprocedures are explained, and the data and the results of statisticalanalysis are presented in tables and graphs. Findings reported include alow frequency of occurrence for small inclination angles (suggestingdistortion of outer structures), similar distributions of central diskbrightness for types Sa-Sc but not for types Sd-Sm (where mean valuesare smaller), fewer late-type galaxies with large exponential-disk scalelengths, no galaxies with both high central brightness and large scalelength (indicating a limit on angular momentum in galaxy formation), anda correlation between mean surface brightness and absolute magnitude forlater-type galaxies but not for types Sa-Scd.
| Very large spiral galaxies
As a first step in the systematic study of large spirals, which may beuseful in cosmological tests and studies of galaxy evolution, a catalogof the 107 largest known spiral galaxies is presented. Catalog galaxieshave isophotal diameters greater than 90 kpc, assuming an H(zero) valueof 50 km/sec per Mpc. UBVR photoelectric photometry is presented for 20of these galaxies, and absolute magnitudes are derived for all galaxiesin the catalog by transforming Zwicky magnitudes to the B(T) system.
| 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.
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