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Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks
Long-slit stellar kinematic observations were obtained along the majoraxis of 30 edge-on spiral galaxies, 24 with a boxy or peanut-shaped(B/PS) bulge and six with other bulge types for comparison. Such B/PSbulges are identified in at least 45% of highly inclined systems, and agrowing body of theoretical and observational work suggests that theyare the edge-on projection of thickened bars. Profiles of the meanstellar velocity V, the velocity dispersion σ, as well as theasymmetric (h3) and symmetric (h4) deviations froma pure Gaussian are presented for all objects. Comparing these profileswith stellar kinematic bar diagnostics developed from N-bodysimulations, we find bar signatures in 24 of our sample galaxies (80%).Galaxies with a B/PS bulge typically show a double-humped rotation curvewith an intermediate dip or plateau. They also frequently show a ratherflat central velocity dispersion profile accompanied by a secondary peakor plateau, and numerous galaxies have a local central σ minimum(>~40%). The h3 profiles display up to three slopereversals. Most importantly, h3 is normally correlated with Vover the presumed bar length, contrary to expectations from axisymmetricdisks. These characteristic bar signatures strengthen the case for aclose relationship between B/PS bulges and bars and leave little roomfor other explanations of the bulges' shape. We also find thath3 is anticorrelated with V in the very center of mostgalaxies (>~60%), indicating that these objects additionally harborcold and dense decoupled (quasi-) axisymmetric central stellar disks,which may be related to the central light peaks. These central diskscoincide with previously identified star-forming ionized-gas disks(nuclear spirals) in gas-rich systems, and we argue that they formed outof gas accumulated by the bar at its center through inflow. As suggestedby N-body models, the asymmetry of the velocity profile (h3)appears to be a reliable tracer of asymmetries in disks, allowing us todiscriminate between axisymmetric and barred disks seen in projection.B/PS bulges (and thus a large fraction of all bulges) appear to be madeup mostly of disk material, which has acquired a large vertical extentthrough bar-driven vertical instabilities. Their formation is thusprobably dominated by secular evolution processes rather than merging.
| Box- and peanut-shaped bulges. III. A new class of bulges: Thick Boxy Bulges
Inspecting all 1224 edge-on disk galaxies larger than 2\arcmin in theRC3 on Digitized Sky Survey (DSS) images (Lütticke et al.\cite{lue2000a}) we have found several galaxies with extraordinarybulges meeting two criteria: they are box shaped and large in respect tothe diameters of their galaxies. These bulges are often disturbed, showfrequently prominent irregularities and asymmetries, and some possesspossible merger remnants or merging satellites. For these bulges we haveintroduced the term ``Thick Boxy Bulges'' (TBBs). About 2% of all diskgalaxies (S0-Sd), respectively 4% of all galaxies with box- andpeanut-shaped (b/p) bulges, belong to this class of galaxies. Usingmulticolour CCD and NIR data we have enlarged and followed up our sampleof nearly 20 galaxies with a TBB. The disturbed morphology of a largefraction of these galaxies shows that many of the TBB galaxies are notdynamically settled. For the TBBs the extent of the box shape seems tobe too large to result from a normal bar potential. Therefore weconclude that two classes of b/p bulges exist with different origins.While most (96%) b/p bulges can be explained by bars alone(Lütticke et al. \cite{lue2000b}), the extended boxy structures ofTBBs result most likely from accreted material by infalling satellitecompanions (soft merging).
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Nature of Boxy/Peanut-Shaped Bulges in Spiral Galaxies
We present a systematic observational study of the relationship betweenbars and boxy/peanut-shaped (B/PS) bulges. We first review and discussproposed mechanisms for their formation, focusing on accretion andbar-buckling scenarios. Using new methods relying on the kinematics ofedge-on disks, we then look for bars in a large sample of edge-on spiralgalaxies with a B/PS bulge and in a smaller control sample of edge-onspirals with more spheroidal bulges. We present position-velocitydiagrams of the ionized gas obtained from optical long-slitspectroscopy. We show that almost all B/PS bulges are due to a thick barviewed edge-on, while only a few extreme cases may be due to theaccretion of external material. This strongly supports the bar-bucklingmechanism for the formation of B/PS bulges. None of the galaxies in thecontrol sample show evidence for a bar, which suggests conversely thatbars are generally B/PS.We consider the effects of dust in the disk ofthe galaxies but conclude that it does not significantly affect ourresults. Unusual emission-line ratios correlating with kinematicalstructures are observed in many objects, and we argue that this isconsistent with the presence of strong bars in the disk of the galaxies.As expected from N-body simulations, the boxy-peanut transition appearsto be related to the viewing angle, but more work is required to derivethe precise orientation of the bars in the bulges. The reliableidentification of bars in edge-on spiral galaxies opens up for the firsttime the possibility of studying observationally the vertical structureof bars.
| The kinematics of the bulge and the disc of NGC 7331
Results are presented of spectroscopic emission and absorption lineobservations along the major axis of the Sb galaxy NGC 7331. Thekinematics of the ionized gas and stellar component are derived, beingregular and symmetric with respect to the centre of the galaxy. Contraryto what may be expected, for R la 40'' the emission line gas appears torotate slower than the stars. A likely explanation for this phenomenonis an inclined and warped gas layer in those inner regions. In the bulgedominated region the absorption line profiles are asymmetric in thesense that they have a shallow extension towards the systemic velocity.No counterrotating stellar component is observed, which is contrary toprevious claims. As demonstrated, these claims might be based on a wronginterpretation of the employed analysis method. Outside the bulgedominated region the stellar radial velocities are in agreement with theneutral hydrogen dynamics and the stellar velocity dispersion decreasestowards larger radii. A detailed bulge/disc light decomposition has beenmade. This has been used to construct a kinematical model of NGC 7331from which model absorption line profiles were calculated. Theseprofiles have been compared with the observations and model parametershave been adjusted to obtain a good match. It appeared necessary tocombine a rapidly rotating disc having a radially decreasing velocitydispersion with a slowly rotating constant dispersion bulge. Then,simultaneously, the observed stellar radial velocities, the velocitydispersions and the observed asymmetry of the line profile could beexplained satisfactorily. An even better fit to the data can be achievedwhen the disc is relatively thinner and colder inside the bulge region.For the disc the stellar velocity dispersions and photometry result in amass-to-light ratio of 1.6 +/- 0.7 Msun/Lsun(I) .This value agrees with previous determinations for other discs usingobserved velocity dispersions. A rotation curve analysis allows thecalculation of the mass-to-light ratio of the bulge which amounts to 6.8in the I-band; considerably larger than the disc value. It appears thatthe mass distribution of NGC 7331 is completely dominated by thecombination of bulge and dark halo at all radii. Comparing welldetermined mass-to-light ratios of a number of bulges with disc values(M/L)_bulge is, on average, three times as large as (M/L)_disc in theI-band. For the B-band this ratio goes up to 7.2, a fact which shouldhave cosmological consequences.
| Dynamical Properties of Tidally Induced Galactic Bars
We simulated a series of fully three-dimensional N-body models of tidalencounters between a disk galaxy and a perturbing galaxy to investigatethe dynamical properties of tidally induced galactic bars, especially inconnection with the resonance structure, which we have little knowledgeabout. We also calculated another set of N-body models on isolatedgalaxies with bar-unstable disks to make a comparison between galacticbars of different origins. To reveal the resonances in a highlynonaxisymmetric potential for which the ordinary method of derivingresonances using the Omega +/- kappa /2 curves gives unreliable results,we employed the analysis based on the families of periodic orbits in abarred potential. It is found from our simulations that the tidallyinduced bars sometimes rotate quite slowly and have inner Lindbladresonances (ILR) near the bar ends, whereas the spontaneously formedbars have no ILR and end near corotation because of their fast rotation.Since the difference in resonance structures affects the kinematics ofthe interstellar gas, these peculiar bars terminated by ILRs may give usa new way of creating the vast morphological and kinematical varietyobserved in the real barred galaxies, which may not be explained solelyby the spontaneous bars. Slow rotation of the tidal bar is caused by twomajor factors. First, the small mass fraction of the disk in which atidal bar is created leads to a small pattern speed. Second, the angularmomentum transfer from the inner disk to the perturber at the time whenthe perturber passes the pericenter serves to reduce the pattern speed.The former effect is observed most clearly in the light disk models inwhich only 10% of the total mass of the galaxy is ascribed to the diskcomponent. On the other hand, massive disk models in which the disk isstabilized by large random motions in disk stars are quite sensitive tothe second process. This complicated behavior of tidal bars can beunderstood naturally by recognizing two regimes of tidal bar formation.When the tidal perturbation is relatively weak, it works only as atrigger of bar formation, and the bar properties are determined largelyby the internal structure of the target galaxy. On the other hand, asufficiently strong tidal perturbation washes out the intrinsic propertyof the target galaxy and imposes on the bar a common characteristicdetermined by the parameters of the tidal encounter.
| 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.
| Metallicity Indices for Multi-Population Models.II.Bulges of Galaxies
We report metallicity indices in the Lick system (Hβ, Fe52, Fe53,NaD, Mg_2_) for a sample of 45 spiral bulges in the southern hemisphere.The velocity dispersion σ was also derived for each object. Spiralbulges and elliptical galaxies show a continuity in diagrams like theplane Mg_2_- or σ-Mg_2_. Using calibrations derived fromchemical evolutionary models, we estimated metallicities and abundanceratios for those bulges. The sample mean metallicity is [Fe/H]= -0.19+/- 0.27(rmsd), and the mean abundance ratios are [Mg/Fe] = 0.46 +/-0.11 (rmsd) and [Na/Fe] = 0.45 +/- 0.19(rmsd). These abundances suggestthat spiral bulges (like E's) were chemically enriched by type IIsupernovae, and that the main star formation era occurred in a timescale of the order of 1-2 Gyr.
| 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.
| Southern Sky Redshift Survey - The catalog
The catalog of radial velocities for galaxies which comprise thediameter-limited sample of the Southern Sky Redshift Survey ispresented. It consolidates the data of observations carried out at theLas Campanas Observatory, Observatorio Nacional, and South AfricanAstronomical Observatory. The criteria used for the sample selection aredescribed, as well as the observational procedures and the techniqueutilized to obtain the final radial velocities. The intercomparisonbetween radial velocity measurements from different telescopes indicatesthat the final data base is fairly homogeneous with a typical error ofabout 40 km/s. The sample is at present 90 percent complete, and themissing galaxies are predominantly objects with very low surfacebrightness for which it is very difficult to obtain optical redshifts.
| The plane W(Na I) X W(Mg I) - Effects of interstellar Na I in a sample of southern galaxies
Galaxy spectra from a subsample of the Southern Sky Redshift Survey databank were used to study the equivalent width plane for the lines Na Ilambda 5893 A vs Mg I lambda 5175 A. An estimate of how important thecontribution of the interstellar gas for the sodium line is compared tothat of the stellar population. The sample is made up of galaxies withmorphological types from E to Sc and are distributed up to radialvelocities of 25,000 km/s, most of them smaller than 15,000 km/s. Mostearly type galaxies with dust lanes, particularly nearly edge-on So's,present an enhancement of the Na I line. Inclined spiral galaxies tendto present enhanced Na I with respect to face-on spirals. This tendency,previously found in a smaller sample of galaxies limited to V equal toor less than 6000 km/s, is now confirmed for more distant ones. In thelarge velocity sample it shows the global bulge rather than the verynucleus; the persistence of the effect suggests that the scale height ofthe gas layer in the central disk can reach a considerable fraction ofthe bulge radius.
| The multicomponent structure of stellar spheroids.
Not Available
| Near-infrared surface photometry of three early-type, edge-on spiral galaxies - NGC 4594, NGC 7123, and NGC 7814
Near-infrared surface photometry of three early-type, edge-on spiralgalaxies is presented. Two of these galaxies, NGC 7814 and NGC 7123, arealmost exactly edge-on and have dust lanes which at optical wave-lengthshide much of the disk light. At K (2.2 microns), the disk is seen asemission in each of these galaxies. The bulge light distribution in eachof these galaxies is well-fitted by the de Vaucouleurs R exp 1/4 law.Bulge/disk decompositions have been performed for each galaxy, and diskparameters determined. The disks of NGC 7814 and NGC 7123 are asubstantially more important component of these galaxies than might beexpected from examining optical photographs or optical surfacephotometry, and the scale height of the dust in the disk is suggested tobe very similar to the stellar scale height in order to so effectivelyeliminate the stellar disk emission at optical wavelengths. The disk ofNGC 4594 contains a stellar ring; the dust in NGC 4594 also has aringlike structure.
| Low-luminosity radio sources in early-type galaxies
A sensitive radio continuum survey of 114 nearby E and S0 galaxies hasbeen made to search for weak sources. The radio detection rate is 42percent, with a flux limit of 0.8 mJy at 5 GHz. By deriving the radioluminosity function for a complete sample, it is shown that most brightearly-type galaxies have low-luminosity nonthermal radio sources.Galaxies of similar optical luminosity vary widely in radio luminosity,but a characteristic radio power rises roughly as the optical luminositysquared. S0 galaxies have weaker radio sources on average thanelliptical galaxies, but this can be explained by the low luminosity ofmost S0 bulges relative to ellipticals. No correlation is found betweenradio power and axial ratio for galaxies with radio luminosities below10 to the 23rd W/Hz.
| On the relationship between radio emission and optical properties in early-type galaxies
To study the origin of radio activity in early-type galaxies, thepossible dependence of their radio emission on basic optical parameters,such as the absolute magnitude, the central velocity dispersion sigma,and the mean surface brightness mu is explored. A sample of 743 E and SOgalaxies is used which is based on three independent radio surveys ofoptically selected galaxies with virtually complete information onmagnitudes, morphological types, redshift distances, diameters, andradio fluxes. For both E and SO galaxies, only the absolute magnitudeappears to be directly related to the radio activity, while sigma and mudo not. Also, a significant dependence of the apparent flattening onradio power is confirmed for E galaxies. Some relevant implications ofthese results are discussed.
| 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.
| Ionized gas in elliptical and S0 galaxies. I - A survey for H-alpha and forbidden N II emission
A spectroscopic survey of a large sample of southern E and S0 galaxiesin order to detect ionized gas in the nuclei is reported. The strongestline in the 6000-7000 A range was nearly always forbidden N II 6584 A,followed by H-alpha and forbidden S II 6716, 6731 A. Identical detectionrates of about 50 percent were obtained for the forbidden N II line inboth E and S0 galaxies. The mass of ionized gas in early-type galaxieswas very small, with values typically in the range 1000-10,000 solarmasses. The relative emission-line strengths in virtually every casewere indistinguishable from those of LINER nuclei. The observed valuesof the forbidden N II 6584 A/H-alpha ratios fell mostly between one andthree and seem correlated with galaxy absolute magnitude. The existenceof such a correlation may be indicative of metallicity differences.
| How common are 'dust-lanes' in early-type galaxies?
Despite much recent interest in the properties of elliptical galaxieswith dust lanes, no attempt has yet been made to determine the incidenceof such galaxies among the elliptical population as a whole. Using acomplete sample of early-type galaxies, and accounting as far aspossible for selection effects, the true fraction of galaxies with dustis estimated to be about 40 percent for nearby ellipticals and somewhathigher than this for S0s. On the basis of their observed axial ratiosand absolute magnitudes, diskless galaxies with dust constitute a classof true elliptical galaxies quite distinct from S0(2/3) dust-lanegalaxies. Dust absorption in elliptical galaxies may mimic isophotaltwisting in some cases (e.g., IC3370). This can be distinguished fromtrue twisting by two-color surface photometry. Shells are found aroundabout 25 percent of elliptical galaxies in the sample studied, but thereis no strong correlation between the presence of shells and dust. Thisis intriguing since both features are often taken as signs of pastinteractions with the environment.
| Southern Galaxy Catalogue.
Not Available
| Redshifts for 228 southern galaxies
In this paper, new redshifts are presented for 228 galaxies locatedsouth of declination -30 deg. The observations were made with aphoton-counting Reticon detector on the Observatorio Nacional (ON)60-in. telescope. The detector is identical to the one used at MountHopkins for the CfA Redshift Survey, and the redshifts were derivedusing the same data-analysis system. A preliminary comparison withpublished 21-cm redshifts indicates that the velocities have azero-point offset of about -4 km/s, with a typical uncertainty of 40km/s. The observations reported here are the initial results of theON-CfA Redshift Survey currently being undertaken in the southernhemisphere.
| Radio and optical observations of a complete sample of E and SO galaxies. III. A radio continuum survey at 2.7 and 5.0 GHz.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984AJ.....89...53S&db_key=AST
| Radio and optical observations of a complete sample of E and SO galaxies. II. UBV aperture photometry.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984AJ.....89...34S&db_key=AST
| Radio and optical observations of a complete sample of E and S0 galaxies. I - Radial velocities. II - UBV aperture photometry. III - A radio continuum survey at 2.7 and 5.0 GHz
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984AJ.....89...23S&db_key=AST
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