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|Ultraluminous X-Ray Sources in Nearby Galaxies from ROSAT High Resolution Imager Observations I. Data Analysis|
X-ray observations have revealed in other galaxies a class ofextranuclear X-ray point sources with X-ray luminosities of1039-1041 ergs s-1, exceeding theEddington luminosity for stellar mass X-ray binaries. Theseultraluminous X-ray sources (ULXs) may be powered by intermediate-massblack holes of a few thousand Msolar or stellar mass blackholes with special radiation processes. In this paper, we present asurvey of ULXs in 313 nearby galaxies withD25>1' within 40 Mpc with 467 ROSAT HighResolution Imager (HRI) archival observations. The HRI observations arereduced with uniform procedures, refined by simulations that help definethe point source detection algorithm employed in this survey. A sampleof 562 extragalactic X-ray point sources withLX=1038-1043 ergs s-1 isextracted from 173 survey galaxies, including 106 ULX candidates withinthe D25 isophotes of 63 galaxies and 110 ULX candidatesbetween 1D25 and 2D25 of 64 galaxies, from which aclean sample of 109 ULXs is constructed to minimize the contaminationfrom foreground or background objects. The strong connection betweenULXs and star formation is confirmed based on the striking preference ofULXs to occur in late-type galaxies, especially in star-forming regionssuch as spiral arms. ULXs are variable on timescales over days to yearsand exhibit a variety of long term variability patterns. Theidentifications of ULXs in the clean sample show some ULXs identified assupernovae (remnants), H II regions/nebulae, or young massive stars instar-forming regions, and a few other ULXs identified as old globularclusters. In a subsequent paper, the statistic properties of the surveywill be studied to calculate the occurrence frequencies and luminosityfunctions for ULXs in different types of galaxies to shed light on thenature of these enigmatic sources.
|Inner-truncated Disks in Galaxies|
We present an analysis of the disk brightness profiles of 218 spiral andlenticular galaxies. At least 28% of disk galaxies exhibit innertruncations in these profiles. There are no significant trends oftruncation incidence with Hubble type, but the incidence among barredsystems is 49%, more than 4 times that for nonbarred galaxies. However,not all barred systems have inner truncations, and not allinner-truncated systems are currently barred. Truncations represent areal dearth of disk stars in the inner regions and are not an artifactof our selection or fitting procedures nor the result of obscuration bydust. Disk surface brightness profiles in the outer regions are wellrepresented by simple exponentials for both truncated and nontruncateddisks. However, truncated and nontruncated systems have systematicallydifferent slopes and central surface brightness parameters for theirdisk brightness distributions. Truncation radii do not appear tocorrelate well with the sizes or brightnesses of the bulges. Thissuggests that the low angular momentum material apparently missing fromthe inner disk was not simply consumed in forming the bulge population.Disk parameters and the statistics of bar orientations in our sampleindicate that the missing stars of the inner disk have not simply beenredistributed azimuthally into bar structures. The sharpness of thebrightness truncations and their locations with respect to othergalactic structures suggest that resonances associated with diskkinematics, or tidal interactions with the mass of bulge stars, might beresponsible for this phenomenon.
|X-Ray Emission from a Sample of Young Supernovae|
When a massive star produces a powerful stellar wind prior to itssupernova event, theory predicts that the collision of the explodedstellar ejecta with the wind leads to a reverse shock, creating softX-ray emission. To understand the frequency at which luminous youngX-ray supernovae occur, we used ROSAT to observe a complete sample ofnearby supernovae (vhelio<1700 km s-1) thatoccurred in the period 1985.5 through 1994.3, which included eight TypeIa supernovae and 19 Type Ib and Type II events. Three supernovae aredetected in this time frame, SN 1987A (LMC), SN 1993J (NGC 3031), and apreviously unreported source, SN 1992ad, a Type II supernova in NGC4411b. No supernova had 0.5-2 keV luminosities exceeding2×1039 ergs s-1, so at the 95% confidencelevel, the probability of an individual supernova exceeding thisluminosity limit is less than 12%. Two of these supernovae hadluminosities brighter than 6×1038 ergs s-1and at the 95% confidence level, the probability of a supernova beingdetected above this luminosity is in the range 8.7%-51%. It is unlikelyfor young supernovae to be a large component of the IntermediateLuminosity X-Ray Object (IXO or ULX) class, where the luminosity exceeds2×1039 ergs s-1. The rate of successfuldetections appears to increase for sensitivities in the 1037ergs s-1 range, especially when obtained close to the time ofthe event.
|The Properties of Satellite Galaxies in External Systems. I. Morphology and Structural Parameters|
We present the first results of an ongoing project to study themorphological, kinematical, dynamical, and chemical properties ofsatellite galaxies of external giant spiral galaxies. The sample ofobjects has been selected from the catalog by Zaritsky et al. The paperanalyzes the morphology and structural parameters of a subsample of 60such objects. The satellites span a great variety of morphologies andsurface brightness profiles. About two-thirds of the sample are spiralsand irregulars, the remaining third being early-types. Some casesshowing interaction between pairs of satellites are presented andbriefly discussed.
|Bar Galaxies and Their Environments|
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
|Optical Spectroscopy of Type IB/C Supernovae|
We present 84 spectra of Type Ib/c and Type IIb supernovae (SNe),describing the individual SNe in detail. The relative depths of thehelium absorption lines in the spectra of the SNe Ib appear to provide ameasurement of the temporal evolution of the SN, with He I λ5876and He I λ7065 growing in strength relative to He I λ6678over time. Light curves for three of the SNe Ib provide a sequence forcorrelating the helium line strengths. We find that some SNe Ic showevidence for weak helium absorption, but most do not. Aside from thepresence or absence of the helium lines, there are other spectroscopicdifferences between SNe Ib and SNe Ic. On average, the O I λ7774line is stronger in SNe Ic than in SNe Ib. In addition, the SNe Ic havedistinctly broader emission lines at late times, indicating aconsistently larger explosion energy and/or lower envelope mass for SNeIc than for SNe Ib. While SNe Ib appear to be basically homogeneous, theSNe Ic are quite heterogeneous in their spectroscopic characteristics.Three SNe Ic that may have been associated with gamma-ray bursts arealso discussed; two of these have clearly peculiar spectra, while thethird seems fairly typical.
|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.
|The Centers of Early- to Intermediate-Type Spiral Galaxies: A Structural Analysis|
A recent Hubble Space Telescope (HST)/WFPC2 visual survey of early- andintermediate-type spiral galaxies has unveiled a great complexity in theinner regions of these systems, which include a high fraction ofphotometrically distinct compact sources sitting at the galactic centers(``nuclei''). The faint nuclei (M_V>~-12) are typically hosted byrather amorphous, quiescent, bulgelike structures with an exponential(rather than the classical R^1/4) light profile. These ``exponentialbulges'' are commonly found inside the intermediate-type disks,consistent with previous studies. Brighter nuclei (M_V<~-12) aretypically found instead in the centers of galaxies with circumnuclearrings/arms of star formation or dust and an active, i.e., H II- orAGN-type, central spectrum at ground-based resolution. On the structuralplane of half-light radius (R_e) versus mean surface brightness withinthe half-light radius (mu_e), faint and bright nuclei overlap with, andfill the region of parameter space between, the old Milky Way globularclusters and the young star clusters, respectively, with typical R_e ofabout a few up to ~20 pc. On the same plane, the exponential bulges havesignificantly fainter mu_e than R^1/4 bulges for any given radius andfollow a mu_e-R_e relation typical of disks, which strengthens thesuggestion that the exponential bulges grow inside the disks as a resultof the secular evolution of the latter. Under the likely assumption thatthe visual light from the faint nuclei embedded in the quiescentexponential bulges is of stellar origin and of a similar (>~1 Gyr)age for the central star clusters and their host bulges, the massesinferred for the former agree with those required to disrupt barscomparable in size to the latter. This offers support to scenarios inwhich the exponential bulges grow inside the disks owing to the orbitaldisruption of progenitor bars caused by the growth of a centralconcentration of mass and suggests that this specific mode of bulgeformation is (still) active in the present-day universe. On the otherhand, the presence of the massive clusters at the very center of thelow-density exponential bulges should prevent any other ``nuclear'' barfrom forming, thereby preventing further infall of dissipative fuel tothe nuclear regions. This may argue against the possibility of evolvingthe exponential bulges into denser, R^1/4 bulges by a simple looping forseveral cycles of the bar formation/disruption mechanism.
|Very Wide Galaxy Pairs of the Northern and Southern Sky|
We present highly accurate observations of the 21 cm line of hydrogen ingalaxies made at the Arecibo and Parkes Observatories. The galaxiesobserved have been identified, through rigorous selection criteriaapplied to the CfA and SSRS catalogs, as being members of pairs withprojected separations of up to 1.5 Mpc (H0 = 75 km s-1 Mpc-1). Theseobservations form the completion of the Chengalur-Nordgren galaxy pairsample with data previously published by Chengalur, Nordgren andcolleagues. The new selection criteria used in this paper are anextension to larger projected separations of the criteria usedpreviously. Forty-nine new galaxies are observed, while H I is detectedin 41 of them. With the addition of these galaxies, the completed samplehas highly accurate H I velocities for a total of 219 galaxies.
|Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles|
We present one of the largest homogeneous sets of spiral and lenticulargalaxy brightness profile decompositions completed to date. The 659galaxies in our sample have been fitted with a de Vaucouleurs law forthe bulge component and an inner-truncated exponential for the diskcomponent. Of the 659 galaxies in the sample, 620 were successfullyfitted with the chosen fitting functions. The fits are generally welldefined, with more than 90% having rms deviations from the observedprofile of less than 0.35 mag. We find no correlations of fittingquality, as measured by these rms residuals, with either morphologicaltype or inclination. Similarly, the estimated errors of the fittedcoefficients show no significant trends with type or inclination. Thesedecompositions form a useful basis for the study of the lightdistributions of spiral and lenticular galaxies. The object base issufficiently large that well-defined samples of galaxies can be selectedfrom it.
|Spiral Galaxies with WFPC2. II. The Nuclear Properties of 40 Objects|
We report the analysis of Hubble Space Telescope Wide Field PlanetaryCamera 2 F606W images of 40 spiral galaxies belonging to the sampleintroduced in Paper I, where 35 other targets were discussed. Wedescribe the optical morphological properties of the new 40 galaxies,derive the surface brightness profiles for 25 of them, and present theresults of photometric decompositions of these profiles into a ``bulge''(R^1/4 or exponential) and a disk component. The analysis of theenlarged sample of 75 galaxies puts on a statistically more solid groundthe main results presented in Paper I: (1) In ~30% of the galaxies, theinner, morphologically distinct structures have an irregular appearance.Some of these ``irregular bulges'' are likely to be currently formingstars. (2) Resolved, central compact sources are detected in about 50%of the galaxies. (3) The central compact sources in galaxies withnuclear star formation are brighter, for similar sizes, than those innon-star-forming galaxies. (4) The luminosity of the compact sourcescorrelates with the total galactic luminosity. Furthermore, the analysisof the enlarged sample of 75 objects shows the following: (a) Several ofthe nonclassical inner structures are well fitted by an exponentialprofile. These ``exponential bulges'' are typically fainter than R^1/4bulges, for a given total galaxy luminosity and (catalog) Hubble typelater than Sab. (b) Irregular/exponential bulges typically host centralcompact sources. (c) The central sources are present in all types ofdisk galaxies, starting with systems as early as S0a. About 60% of Sb toSc galaxies host a central compact source. Many of the galaxies thathost compact sources contain a barred structure. (d) Galaxies withapparent nuclear star formation, which also host the brightest compactsources, are preferentially the early- and intermediate-type (S0a-Sb)systems. (e) None of the features depend on environment: isolated andnonisolated galaxies show indistinguishable properties. Independent ofthe physical nature of the nonclassical inner structures, our mainconclusion is that a significant fraction of galaxies classified fromthe ground as relatively early-type spirals show a rich variety ofcentral properties and little or no morphological/photometric evidencefor a smooth, R^1/4 law bulge. Based on observations with the NASA/ESAHubble Space Telescope, obtained at the Space Telescope ScienceInstitute, which is operated by the Association of Universities forResearch in Astronomy, Inc., under NASA contract NAS 5-26555.
|Spiral Galaxies with WFPC2. III. Nuclear Cusp Slopes|
In this paper, the third of a series dedicated to the investigation ofthe nuclear properties of spiral galaxies, we (1) model the Wide FieldPlanetary Camera 2 F606W nuclear surface brightness profiles of 41spiral galaxies presented in Papers I and II with the analytic lawintroduced by Lauer et al. and (2) deconvolve these surface brightnessprofiles and their analytic fits, so as to estimate the nuclear stellardensities of bulges of spiral galaxies. We find that the nuclear stellarcusps (quantified by the average logarithmic slope of the surfacebrightness profiles within 0.1"-0.5") are significantly different forR^1/4 law and exponential bulges. The former have nuclear propertiessimilar to those of early-type galaxies, i.e., similar values of nuclearcusps for comparable luminosities, and increasingly steeper stellarcusps with decreasing luminosity. By contrast, exponential bulges have(underlying the light contribution from photometrically distinct,central compact sources) comparatively shallower stellar cusps, andlikely lower nuclear densities, than R^1/4 law bulges. Based onobservations with the NASA/ESA Hubble Space Telescope, obtained at theSpace Telescope Science Institute, which is operated by the Associationof Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
|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 18.104.22.168 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.
|Molecular Gas, Morphology, and Seyfert Galaxy Activity|
We probe the cause of the elevated star formation in host galaxies ofSeyfert 2 nuclei compared with Seyfert 1 hosts and with field galaxies.12CO (1--0) observations of a large sample of Seyfert galaxies indicateno significant difference in the total amount of molecular gas as afunction of the Seyfert nuclear type, nor are Seyfert galaxiessignificantly different in this regard from a sample of field galaxiesonce selection effects are accounted for. Therefore, the total amount ofmolecular gas is not responsible for the enhanced star-forming activityin Seyfert 2 hosts. To probe how this gas is being converted moreefficiently into stars in Seyfert 2 hosts than in the other galaxies, weinvestigate the occurrence of bars, interactions, and distortedmorphologies among Seyfert galaxies. We find a significantly higher rateof asymmetric morphologies for Seyfert 2 galaxies with respect toSeyfert 1 galaxies and field galaxies. Relative to field galaxies, theeffect is at a greater than 99.9% confidence level. The presence ofasymmetric morphologies in individual Seyfert galaxies is correlatedwith their tendency to exhibit enhanced star-forming activity. Theseresults suggest that asymmetric morphologies are an important cause forthe link between Seyfert type and star-forming activity: bars anddistortions in Seyfert 2 hosts are likely both to enhance star-formingactivity and to funnel gas into the nuclear region, thus obscuring andpossibly contributing to the feeding of the active nucleus.
|More Satellites of Spiral Galaxies|
We present a revised and expanded catalog of satellite galaxies of a setof isolated spiral galaxies similar in luminosity to the Milky Way. Thissample of 115 satellites, 69 of which were discovered in our multifiberredshift survey, is used to probe the results obtained from the originalsample further (Zaritsky et al.). The satellites are, by definition, atprojected separations <~500 kpc, have absolute recessional velocitydifferences with respect to the parent spiral of less than 500 km s-1,and are at least 2.2 mag fainter than their associated primary galaxy. Akey characteristic of this survey is the strict isolation of thesesystems, which simplifies any dynamical analysis. We find no evidencefor a decrease in the velocity dispersion of the satellite system as afunction of radius out to galactocentric radii of 400 kpc, whichsuggests that the halo extends well beyond 200 kpc. Furthermore, the newsample affirms our previous conclusions (Zaritsky et al.) that (1) thevelocity difference between a satellite and its primary is not stronglycorrelated with the rotation speed of the primary, (2) the system ofsatellites has a slight net rotation (34 +/- 14 km s-1) in the samesense as the primary's disk, and (3) that the halo mass of an ~L* spiralgalaxy is in excess of 2 x 1012 Mȯ.
|Scaleheights of 486 southern spiral galaxies and some statistical correlation|
Based on Peng's method (1988), we obtain scaleheights of 486 southernspiral galaxies, the images of which are taken from the Digitized SkySurvey at Xinglong Station of Beijing Astronomical Observatory. Thefitted spiral arms of 70 galaxies are compared with their images to gettheir optimum inclinations. The scaleheights of other 416 ones arelisted in Table A1 in Appendix. After compiling and analyzing the data,we find some statistical correlations. The most interesting results arethat a flatter galaxy is bluer and looks brighter, and galaxies becomeflatter along the Hubble sequence Sab -- Scd. Based on photographic dataof the National Geographic Society -- Palomar Observatory Sky Survey(NGS-POSS) obtained using the Oschin Telescope Palomar Mountain. TheNGS-POSS was funded by a grant from the National Geographic Society tothe California Institute of Technology. The plates were processed intothe present compressed digital form with their permission. The DigitizedSky Survey was produced at the Space Telescope Science Institute underUS Government grant NAG W-2166. Table A1 is available in electronic fromonly, via anonymous ftp 22.214.171.124 orhttp://cdsweb.u-strasbg.fr/Abstract.html
|Near-IR photometry of disk galaxies: Search for nuclear isophotal twist and double bars|
We present a near-IR, mainly $H$ band, photometry of 72 nearby (d <40 Mpc) disk galaxies. The main goal of the survey was to search forisophotal twist inside their nuclear regions. As the twist can be due insome cases to projection effects, rather than resulting from a dynamicalphenomenon, we deproject -- under the simplifying assumption of a 2Dgeometry -- all galaxies whose disk position angle and inclination areknown, the latter not exceeding 75 degrees. We show the ellipticity,position angle and surface brightness radial profiles, and discuss how aprojection of 2D and 3D bars can distort the isophotes, give an illusionof a non-existing double bar or mask a real one. We report 15 newdouble-barred galaxies and confirm 2 detected previously. We identify 14additional twists not known before and we also find nuclear triaxialstructures in three SA galaxies. The frequency of Seyferts amonggalaxies with nuclear bars or twists is high. Since these observationsare part of a larger survey, the interpretation of the results will begiven in a future paper, as soon as the number of objects grows enoughto permit meaningful statistics. As a secondary product, we publishstructural parameters (length and axis ratio) of large-scale bars inorder to extend still scarce data on bars in the near-IR.
|The statistics analysis of recent supernovae.|
|The APM Bright Galaxy Catalogue|
The APM Bright Galaxy Catalogue lists positions, magnitudes, shapes andmorphological types for 14681 galaxies brighter than b_J magnitude16.44, over a 4180 deg^2 area of the southern sky. Galaxy and stellarimages have been located from glass copy plates of the United KingdomSchmidt Telescope (UKST) IIIaJ sky survey using the automatedphotographic measuring (APM) facility in Cambridge, England. Themajority of stellar images are rejected by the regularity of their imagesurface brightness profiles. Remaining images are inspected by eye onfilm copies of the survey material and classed as stellar, multiplestellar, galaxy, merger or noise. Galaxies are further classified aselliptical, lenticular, spiral, irregular or uncertain. The 180 surveyfields are put on to a uniform photometric system by comparing themagnitudes of galaxies in the overlap regions between neighbouringplates. The magnitude zero-point, photometric uniformity andphotographic saturation are checked with CCD photometry. Finally, thecompleteness and reliability of the catalogue are assessed by usingvarious internal tests and by comparison with several independentlyconstructed galaxy catalogues.
|Supernovae and Massive Star Formation Regions|
We have extended the work of Van Dyk [AJ, 103, 1788 (1992)] on theassociation of supernovae with massive star formation regions, as tracedby giant H II regions, in late-type galaxies. In this paper, weconcentrate only on supernovae arising from massive progenitors, TypeIb/c and Type II, using ground-based CCD Hα images. We improveupon earlier studies by increasing the supernova sample, by includingonly spectroscopically classified supernovae, and by obtaining moreaccurate astrometry of the supernovae and their environments. We findthat the degree of association of both supernova types with H II regionsin their parent galaxies is not significantly different, implying thatboth types arise from essentially the same range of stellar masses. Fromconsideration of the statistics in this paper, including the Hαluminosities of the H II regions with which supernovae are associated,we can exclude the Wolf-Rayet star progenitor model for most Type Ib/csupernovae. Instead, the progenitors of Type Ib/c supernovae areprobably in relatively close binary systems, rather than single stars orstars in wide binaries (possible progenitor systems for Type Ilsupernovae); interaction with a companion star can severely deplete thehydrogen envelope prior to explosion.
|Photoelectric UBV Photometry of 179 Bright Galaxies|
This paper presents photoelectric UBV multiaperture photometry of 179bright galaxies that was used to compute total magnitudes and colorindices published in the Third Reference Catalog of Bright Galaxies(RC3). The observations were made at the McDonald Observatory from 1983December to 1986 September with an Amperex 56-DVP photometer attached tothe 0.76 and 0.91 m telescopes. The observations can also be used tocalibrate CCD images.
|Bias Properties of Extragalactic Distance Indicators. VI. Luminosity Functions of M31 and M101 Look-alikes Listed in the RSA2: H0 Therefrom|
Galaxies whose morphologies are similar to M 101 (Sc I) and M3 1 (Sb I-II) are listed in two tables. The selection is made by inspecting directimages of Shapley-Ames galaxies in the recent Carnegie Atlas ofGalaxies. Absolute magnitudes, calculated from redshifts, give meanvalues of
|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 Catalog of Southern Ringed Galaxies|
The Catalog of Southern Ringed Galaxies (CSRG) is a comprehensivecompilation of diameters, axis ratios, relative bar position angles, andmorphologies of inner and outer rings, pseudorings, and lenses in 3692galaxies south of declination -17 deg. The purpose of the catalog is toevaluate the idea that these ring phenomena are related to orbitalresonances with a bar or oval in galaxy potentials. The catalog is basedon visual inspection of most of the 606 fields of the Science ResearchCouncil (SRC) IIIa-J southern sky survey, with the ESO-B, ESO-R, andPalomar Sky surveys used as auxiliaries when needed for overexposed coreregions. The catalog is most complete for SRC fields 1-303 (mostly southof declination -42 deg). In addition to ringed galaxies, a list of 859mostly nonringed galaxies intended for comparison with other catalogs isprovided. Other findings from the CSRG that are not based on statisticsare the identification of intrinsic bar/ring misalignment; bars whichunderfill inner rings; dimpling of R'1pseudorings; pointy, rectangular, or hexagonal inner or outer ringshapes; a peculiar polar-ring-related system; and other extreme examplesof spiral structure and ring morphology.
|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.
|Distribution of supernovae relative to spiral arms and H II regions|
We have studied the association of supernovae in spiral galaxies withsites of recent stars formation -- sprial arms and H II regions. It isshown that supernovae (SNe) of Types Ia, Ib, and II exhibitconcentration to spiral arms and their distributions over the distanceto the nearest spiral arm do not differ significantly. This result isconfirmed by a Kolmogorov-Smirnov test comparison with the distancedistributions, expected if SNe are distributed randomly inside the modelgalaxy. SNe of types Ib and II show a strong concentration towards H IIregions, while distribution of SNe Ia can be explained by chancesuperposition. All studied distributions of SNe Ib and II show strikingsimilarity, which suggests that their progenitors are massive stars withsimilar ages and initial masses. The association of SNe Ia with spiralarms suggests that their progenitors in spiral galaxies are likely to beintermediate mass stars.
|A catalog of recent supernovae|
A listing is given of all supernovae discovered between 1 Jan 1989 and 1Apr 1993. The data show no evidence for a significant dependence of thediscovery probability of supernovae on parent galaxy inclination to theline of sight. If no inclination corrections need to be applied then thesupernova rates in spirals are only about half as large as previouslybelieved. The mean linear separation of supernovae of Type II (SNe II)from the center of their parent galaxy increases with increasingdistance (Shaw effect). The Shaw effect appears less evident, or absent,for (more luminous) supernovae of Type Ia. The data are consistent with,but do not prove, the hypothesis that (presumably reddended) SNe II aremore likely to be discovered in the red than in the blue. Due tointensive surveillance, most bright SNe Ia tend to be found beforemaximum, whereas the majority of faint SNe Ia are discovered aftermaximum light.
|On the law of star formation in disk galaxies|
The observational relationship between the stellar surface brightnessand the surface brightness in H-alpha in galactic disks is shown to bedetermined by the law of star formation in disk galaxies. Assuming therate of star formation to take a generalized Schmidt power-law formdependent on both the total local matter surface density,sigmag; d sigma*/dt = epsilonsigmaTn, we find that the observations constrain(n + m is greater than 1), and that the best fit is obtained for 1.5 isless than (n + m) is less than 2.5. Both a Schmidt Law of the form dsigma*/dt = epsilon sigmag, and a star-formationlaw of the form d sigma*/dt = epsilon Omegasigmag, where Omega is the angular velocity at the radialpoint considered, seem to be excluded by observations. The observedscatter in the stellar surface brightness versus H-alpha surfacebrigtness versus H-alpha surface relationship can be interpreted as ascatter in the ratio of galaxian age to star-formation efficiency;younger galaxies being more gas-rich, and currently more active informing stars. Finally, we discuss particular forms of the Schmidt Lawgiven by theory. We show that a model having n = 1/3 and m = 5/3, whichgives a particularly good fit to the observations, follows as aconsequence of stochastic self-regulating star formation moderated bycloud-cloud interactions in the disk potential, and by the energeticprocesses associated with the formation of massive stars. This modelsexplicitly includes the secular evolution of the vertical structure ofthe gaseous and stellar components of galactic disks, and the effectofthe galaxian potential.
|The relationship between past and present star formation in galactic disks from CCD surface photometry|
We present some results of a major new multiband imaging survey of 34nearby southern spiral galaxies. Images in V, I, H-alpha, and theadjacent red continuum have been obtained using a CCD and focal reduceron the 1.0 and 2.3 m telescopes at Siding Spring Observatory. Surfacephotometry using the GASP software package is used first to derive thedisk orientation parameters, then to provide deprojected radial surfacebrightness profiles for each galaxy in V and I, as well as thecontinuum-subtracted H-alpha, which traces the present-day rate ofmassive star formation. In the outer disk, the H-alpha profile can bereasonably well fitted by an exponential disk, but with a scale lengthmuch longer than the V scale length, which itself tends to be sligtlylonger than the I scale length. An almost universal relationship isobserved in the disk between the H-alpha surface brightness and theI-band surface brightness at a given radius, with any residual offsetfrom the mean trend being a weak function of the morphological type.Thus the rate of massive star formation per unit area in the disk isclosely related to the old stellar mass surface density at each radius,and to the mean H I surface density in the disk as a whole. This formsthe basis for a law of (or rather, a consistent on) massive starformation in the disks of spiral galaxies, one that has a surprisingdegree of independence from both galactic dynamics and molecular gascontent.
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Observation and Astrometry data
Catalogs and designations: