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A Fundamental Relation between Compact Stellar Nuclei, Supermassive Black Holes, and Their Host Galaxies
Imaging surveys with the Hubble Space Telescope (HST) have shown that~50%-80% of low- and intermediate-luminosity galaxies contain a compactstellar nucleus at their center, regardless of host galaxy morphologicaltype. We combine HST imaging for early-type galaxies from the ACS VirgoCluster Survey with ground-based long-slit spectra from KPNO to showthat the masses of compact stellar nuclei in Virgo Cluster galaxies obeya tight correlation with the masses of the host galaxies. The samecorrelation is obeyed by the supermassive black holes (SBHs) found inpredominantly massive galaxies. The compact stellar nuclei in the LocalGroup galaxies M33 and NGC 205 are also found to fall along this samescaling relation. These results indicate that a generic by-product ofgalaxy formation is the creation of a central massive object(CMO)-either an SBH or a compact stellar nucleus-that contains a meanfraction, ~0.2%, of the total galactic mass. In galaxies with massesgreater than Mgal ~ a few × 1010Msolar, SBHs appear to be the dominant mode of CMOformation.Based on observations with the NASA/ESA Hubble Space Telescope obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy (AURA), Inc.,under NASA contract NAS 5-26555.
| Supermassive Black Holes in Galactic Nuclei: Past, Present and Future Research
This review discusses the current status of supermassive black holeresearch, as seen from a purely observational standpoint. Since theearly ‘90s, rapid technological advances, most notably the launchof the Hubble Space Telescope, the commissioning of the VLBA andimprovements in near-infrared speckle imaging techniques, have not onlygiven us incontrovertible proof of the existence of supermassive blackholes, but have unveiled fundamental connections between the mass of thecentral singularity and the global properties of the host galaxy. It isthanks to these observations that we are now, for the first time, in aposition to understand the origin, evolution and cosmic relevance ofthese fascinating objects.
| The X-ray emission properties and the dichotomy in the central stellar cusp shapes of early-type galaxies
The Hubble Space Telescope has revealed a dichotomy in the centralsurface brightness profiles of early-type galaxies, which havesubsequently been grouped into two families: core, boxy, anisotropicsystems; and cuspy (`power-law'), discy, rotating ones. Here weinvestigate whether a dichotomy is also present in the X-ray propertiesof the two families. We consider both their total soft emission(LSX,tot), which is a measure of the galactic hot gascontent, and their nuclear hard emission (LHX,nuc), mostlycoming from Chandra observations, which is a measure of the nuclearactivity. At any optical luminosity, the highest LSX,totvalues are reached by core galaxies; this is explained by their beingthe central dominant galaxies of groups, subclusters or clusters, inmany of the logLSX,tot (ergs-1) >~ 41.5 cases.The highest LHX,nuc values, similar to those of classicalactive galactic nuclei (AGNs), in this sample are hosted only by core orintermediate galaxies; at low luminosity AGN levels, LHX,nucis independent of the central stellar profile shape. The presence ofoptical nuclei (also found by HST) is unrelated to the level ofLHX,nuc, even though the highest LHX,nuc are allassociated with optical nuclei. The implications of these findings forgalaxy evolution and accretion modalities at the present epoch arediscussed.
| Origin of Radio Emission from Nearby Low-Luminosity Active Galactic Nuclei
We use the observational data in radio, optical, and X-ray wave bandsfor a sample of active galactic nuclei (AGNs) with measured black holemasses to explore the origin of radio emission from nearbylow-luminosity active galactic nuclei (LLAGNs). The maximal luminosityof an advection-dominated accretion flow (ADAF) can be calculated for agiven black hole mass, as there is a critical accretion rate above whichthe ADAF is no longer present. We find that the radio luminosities arehigher than the maximal luminosities expected from the ADAF model formost sources in this sample. This implies that the radio emission ispredominantly from the jets in these sources. The radio emission from asmall fraction of the sources (15/60; referred to as radio-weak sources)in this sample can be explained by the ADAF model. However, comparingthe observed multiband emission data with the spectra calculated for theADAF or adiabatic inflow-outflow solution (ADIOS) cases, we find thatneither ADAF nor ADIOS models can reproduce the observed multibandemission simultaneously, with reasonable magnetic field strengths, forthese radio-weak sources. A variety of other possibilities arediscussed, and we suggest that the radio emission is probably dominatedby jet emission even in these radio-weak LLAGNs.
| On the Black Hole Mass-Bulge Mass Relation
We have reexamined the relation between the mass of the central blackholes in nearby galaxies, Mbh, and the stellar mass of thesurrounding spheroid or bulge, Mbulge. For a total of 30galaxies bulge masses were derived through Jeans equation modeling oradopted from dynamical models in the literature. In stellarmass-to-light ratios, the spheroids and bulges span a range of a factorof 8. The bulge masses were related to well-determined black hole massestaken from the literature. With these improved values forMbh, compared to Magorrian et al., and our redetermination ofMbulge, we find that the Mbh-Mbulgerelation becomes very tight. We findMbh~M1.12+/-0.06bulge with an observedscatter of <~0.30 dex, a fraction of which can be attributed tomeasurement errors. The scatter in this relation is therefore comparableto the scatter in the relations of Mbh with σ and thestellar concentration. These results confirm and refine the work ofMarconi & Hunt. For Mbulge~5×1010Msolar the median black hole mass is 0.14%+/-0.04% of thebulge mass.
| Difficulties with Recovering the Masses of Supermassive Black Holes from Stellar Kinematical Data
We investigate the ability of three-integral, axisymmetric, orbit-basedmodeling algorithms to recover the parameters defining the gravitationalpotential (mass-to-light ratio Υ and black hole massM•) in spheroidal stellar systems using stellarkinematical data. We show that the potential estimation problem isgenerically underdetermined when applied to long-slit kinematical dataof the kind used for most black hole mass determinations to date. Arange of parameters (Υ, M•) can provide equallygood fits to the data, making it impossible to assign best-fit values.The indeterminacy arises from the large variety of orbital solutionsthat are consistent with a given mass model. We demonstrate theindeterminacy using a variety of data sets derived from realisticmodels, as well as published observations of the galaxy M32. Theindeterminacy becomes apparent only when a sufficiently large number ofdistinct orbits are supplied to the modeling algorithm; if too feworbits are used, spurious minima appear in theχ2(Υ,M•) contours, and these minimado not necessarily coincide with the parameters defining thegravitational potential. We show that the range of degeneracy inM• depends on the degree to which the data resolve theradius of influence rh of the black hole. ForFWHM/2rh>~0.5, where FWHM refers to the instrumentalresolution, we find that only very weak constraints can be placed onM•. In the case of M32, our reanalysis demonstrates thatwhen a large orbit library is used, data published prior to 2000(FWHM/2rh~0.25) are equally consistent with black hole massesin the range1.5×106Msolar
| HST observations of nuclear stellar disks
We present observations of four nearby early-type galaxies withpreviously known nuclear stellar disks using two instruments on-boardthe Hubble Space Telescope. We observed NGC 4128, NGC 4612, and NGC 5308with the Wide Field Planetary Camera 2, and the same three galaxies,plus NGC 4570, with the Space Telescope Imaging Spectrograph. We havedetected a red nucleus in NGC 4128, a blue nucleus in NGC 4621, and ablue disk in NGC 5308. Additionally, we have discovered a blue disk-likefeature with position angle 15° from the major axis in NGC4621. In NGC 5308 there is evidence for a blue region along the minoraxis. We discovered a blue transient on the images of NGC 4128 atposition 0.14 arcsec west and 0.32 arcsec north from the nucleus. Theextracted kinematic profiles belong to two groups: fast (NGC 4570 andNGC 5308) and kinematically disturbed rotators (NGC 4128 and NGC 4621).We report the discovery of a kinematically decoupled core in NGC 4128.Galaxies have mostly old (10-14 Gyr) stellar populations with largespread in metallicities (sub- to super-solar). We discuss the possibleformation scenarios, including bar-driven secular evolution and theinfluence of mergers, which can explain the observed color and kinematicfeatures.Appendix A is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/ cgi-bin/ qcat?J/A+A/428/877Appendix B, Tables \ref{t:wfpc2}, \ref{t:filters},\ref{t:stis_obs}-\ref{t:lsi} and Figs. \ref{f:isophote},\ref{f:ngc5308_slit}-\ref{f:chi2}, \ref{f:ngc4128}-\ref{f:ngc5308} areonly available in electronic form at http://www.edpsciences.org
| Axisymmetric dynamical models for SAURON and OASIS observations of NGC3377
We present a unique set of nested stellar kinematical maps of NGC3377obtained with the integral-field spectrographs OASIS and SAURON . Wethen construct general axisymmetric dynamical models for this galaxy,based on the Schwarzschild numerical orbit superposition techniqueapplied to these complementary measurements. We show how these twodatasets constrain the mass of the central massive object and theoverall mass-to-light ratio of the galaxy by probing the inner and outerregions respectively. The simultaneous use of both datasets leads us toconfirm the presence of a massive black hole with a mass of M= 7-5+4 107 Msun (99.7%confidence level), with a best-fit stellar mass-to-light ratio ML[I] =2.1 ± 0.2 (for an assumed edge-on inclination).
| The Realm of the Supermassive Black Holes
Not Available
| Kinematics of 10 Early-Type Galaxies from Hubble Space Telescope and Ground-based Spectroscopy
We present stellar kinematics for a sample of 10 early-type galaxiesobserved using the Space Telescope Imaging Spectrograph (STIS) aboardthe Hubble Space Telescope and the Modular Spectrograph on the MDMObservatory 2.4 m telescope. These observations are a part of an ongoingprogram to understand the coevolution of supermassive black holes andtheir host galaxies. Our spectral ranges include either the calciumtriplet absorption lines at 8498, 8542, and 8662 Å or the Mg babsorption at 5175 Å. The lines are used to derive line-of-sightvelocity distributions (LOSVDs) of the stars using a maximum penalizedlikelihood method. We use Gauss-Hermite polynomials to parameterize theLOSVDs and find predominantly negative h4 values (boxy distributions) inthe central regions of our galaxies. One galaxy, NGC 4697, hassignificantly positive central h4 (high tail weight). The majority ofgalaxies have a central velocity dispersion excess in the STISkinematics over ground-based velocity dispersions. The galaxies with thestrongest rotational support, as quantified withvmax/σSTIS, have the smallest dispersionexcess at STIS resolution. The best-fitting, general, axisymmetricdynamical models (described in a companion paper) require black holes inall cases, with masses ranging from 106.5 to 109.3Msolar. We replot these updated masses on theMBH-σ relation and show that the fit to only these 10galaxies has a slope consistent with the fits to larger samples. Thegreatest outlier is NGC 2778, a dwarf elliptical with relatively poorlyconstrained black hole mass. The two best candidates for pseudobulges,NGC 3384 and NGC 7457, do not deviate significantly from the establishedrelation between MBH and σ. Neither do the threegalaxies that show the most evidence of a recent merger, NGC 3608, NGC4473, and NGC 4697.Based in part on observations made with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc., under NASA contract NAS 5-26555. These observations are associatedwith proposal GO-7388.
| The Relation between Black Hole Mass, Bulge Mass, and Near-Infrared Luminosity
We present new accurate near-infrared (NIR) spheroid (bulge) structuralparameters obtained by a two-dimensional image analysis of all galaxieswith a direct black hole (BH) mass determination. As expected, NIR bulgeluminosities Lbul and BH masses are tightly correlated, andif we consider only those galaxies with a secure BH mass measurement andan accurate Lbul (27 objects), the spread ofMBH-Lbul is similar toMBH-σe, where σe is theeffective stellar velocity dispersion. We find an intrinsic rms scatterof ~=0.3 dex in logMBH. By combining the bulge effectiveradii Re measured in our analysis with σe,we find a tight linear correlation (rms~=0.25 dex) betweenMBH and the virial bulge mass(~Reσ2e), with~0.002. A partial correlationanalysis shows that MBH depends on both σeand Re and that both variables are necessary to drive thecorrelations between MBH and other bulge properties.
| Axisymmetric Dynamical Models of the Central Regions of Galaxies
We present axisymmetric, orbit superposition models for 12 galaxiesusing data taken with the Hubble Space Telescope (HST) and ground-basedobservatories. In each galaxy, we detect a central black hole (BH) andmeasure its mass to accuracies ranging from 10% to 70%. We demonstratethat in most cases the BH detection requires both the HST andground-based data. Using the ground-based data alone does provide anunbiased measure of the BH mass (provided that they are fitted withfully general models), but at a greatly reduced significance. The mostsignificant correlation with host galaxy properties is the relationbetween the BH mass and the velocity dispersion of the host galaxy; wefind no other equally strong correlation and no second parameter thatimproves the quality of the mass-dispersion relation. We are also ableto measure the stellar orbital properties from these general models. Themost massive galaxies are strongly biased to tangential orbits near theBH, consistent with binary BH models, while lower mass galaxies have arange of anisotropies, consistent with an adiabatic growth of the BH.
| Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
| 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
| Evidence for black holes
As an important test for General Relativity, the existence of a blackhole is always the focus of physicists and astronomers. Particularly inthese years, since a large number of advanced observational facilitiesare put into use and the techniques improved, the search for theevidence for black holes have made great progress, becoming one ofastronomical researching hotspots. In this paper, evidence for stellarblack holes and super-massive black holes in galactic nuclei isreviewed, and the great advances in black hole astrophysics are alsointroduced. Finally, we discuss some great developing projects and theprimary results of pursuing primordial black holes. The suggestions forobservations and the respect of astronomical evidence for black holesare put forward.
| The `Photometric Plane' of elliptical galaxies
The Sérsic (r1/n) index n of an elliptical galaxy (orbulge) has recently been shown to correlate strongly (r= 0.8) with thecentral velocity dispersion of a galaxy. This index could thereforeprove extremely useful and cost-effective (in terms of both telescopetime and data reduction) for many fields of extragalactic research. Itis a purely photometric quantity which apparently not only traces themass of a bulge but has additionally been shown to reflect the degree ofbulge concentration. This paper explores the affect of replacing thecentral velocity dispersion term in the Fundamental Plane with theSérsic index n. Using a sample of early-type galaxies from theVirgo and Fornax clusters, various (B-band) `Photometric Planes' wereconstructed and found to have a scatter of 0.14-0.17 dex in logre, or a distance error of 38-48 per cent per galaxy (thehigher values arising from the inclusion of the S0 galaxies). Thecorresponding Fundamental Plane yielded a 33-37 per cent error indistance for the same galaxy samples (i.e. ~15-30 per cent lessscatter). The gains in using a hyperplane (i.e. adding the Sérsicindex to the Fundamental Plane as a fourth parameter) were small, givinga 27-33 per cent error in distance, depending on the galaxy sample used.The Photometric Plane has been used here to estimate the Virgo-Fornaxdistance modulus; giving a value of 0.62 +/- 0.30 mag[cf. 0.51 +/- 0.21,Hubble Space Telescope (HST) Key Project on the Extragalactic DistanceScale]. The prospects for using the Photometric Plane at higherredshifts appears promising. Using published data on the intermediateredshift cluster Cl 1358 + 62 (z= 0.33) gave a Photometric Planedistance error of 35-41 per cent per galaxy.
| Efficient multi-Gaussian expansion of galaxies
We describe a simple, efficient, robust and fully automatic algorithmfor the determination of a multi-Gaussian expansion (MGE) fit to galaxyimages, to be used as a parametrization for the galaxy stellar surfacebrightness. In most cases the least-squares solution found by thismethod essentially corresponds to the minimax, constant relative error,MGE approximation of the galaxy surface brightness, with the chosennumber of Gaussians. The algorithm is well suited to be used withmultiple-resolution images (e.g. Hubble Space Telescope (HST) andground-based images). It works orders of magnitude faster and is moreaccurate than currently available methods. An alternative, morecomputing-intensive, fully linear algorithm that is guaranteed toconverge to the smallest χ2 solution is also discussed.Examples of MGE fits are presented for objects with HST or ground-basedphotometry, including galaxies with significant isophote twist.
| The Slope of the Black Hole Mass versus Velocity Dispersion Correlation
Observations of nearby galaxies reveal a strong correlation between themass of the central dark object MBH and the velocitydispersion σ of the host galaxy, of the formlog(MBH/Msolar)=α+βlog(σ/σ0) however, published estimates of the slope βspan a wide range (3.75-5.3). Merritt & Ferrarese have argued thatlow slopes (<~4) arise because of neglect of random measurementerrors in the dispersions and an incorrect choice for the dispersion ofthe Milky Way Galaxy. We show that these explanations and several othersaccount for at most a small part of the slope range. Instead, the rangeof slopes arises mostly because of systematic differences in thevelocity dispersions used by different groups for the same galaxies. Theorigin of these differences remains unclear, but we suggest that onesignificant component of the difference results from Ferrarese &Merritt's extrapolation of central velocity dispersions tore/8 (re is the effective radius) using anempirical formula. Another component may arise from dispersion-dependentsystematic errors in the measurements. A new determination of the slopeusing 31 galaxies yields β=4.02+/-0.32, α=8.13+/-0.06 forσ0=200 km s-1. The MBH-σrelation has an intrinsic dispersion in logMBH that is nolarger than 0.25-0.3 dex and may be smaller if observational errors havebeen underestimated. In an appendix, we present a simple kinematic modelfor the velocity-dispersion profile of the Galactic bulge.
| Nuclear Stellar Disks in Spiral Galaxies
We report evidence for nuclear stellar disks in three early-typespirals, namely, NGC 1425, NGC 3898, and NGC 4698, revealed by WideField Planetary Camera 2 F606W images out of a sample of 38 spiralgalaxies, selected from the Hubble Space Telescope data archive.Adopting the photometric method introduced by Scorza & Bender, wederived their central surface brightness and scale length by assumingthem to be infinitesimally thin exponential disks. No nuclear disk wasfound in barred galaxies or galaxies of Hubble type later than Sb. Theexternal origin of the disk in NGC 4698 is strongly suggested by itsorthogonal geometrical decoupling with respect to the host galaxy. Basedon observations with the NASA/ESA Hubble Space Telescope, obtained fromthe data archive at the Space Telescope Science Institute, which isoperated by the Association of the Universities for Research inAstronomy, Inc., under NASA contract NAS 5-26555.
| On the Relationship between Radio Emission and Black Hole Mass in Galactic Nuclei
We use a comprehensive database of black hole masses (MBH)and nuclear luminosities to investigate the relationship between radioemission and MBH. Our sample covers a wide range of nuclearactivity, from nearby inactive nuclei to classical Seyfert 1 nuclei andluminous quasars. Contrary to some previous studies, we find that theradio continuum power, either integrated for the entire galaxy orisolated for the core, correlates poorly with MBH. The degreeof nuclear radio loudness, parameterized by the radio-to-opticalluminosity ratio R, also shows no clear dependence on MBH.Radio-loud nuclei exist in galaxies with a wide range of MBH,from ~106 to a few times 109 Msolar,and in a variety of hosts, from disk-dominated spiral to giantelliptical galaxies. We demonstrate that R is strongly inverselycorrelated with L/LE, the ratio of nuclear luminosity to theEddington luminosity, and hence with the mass accretion rate. Most orall of the weakly active nuclei in nearby galaxies are radio-loud,highly sub-Eddington systems that are plausibly experiencingadvection-dominated accretion.
| 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.
| Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Hα surface photometry of galaxies in the Virgo cluster. II. Observations with the OHP and Calar Alto 1.2 m telescopes
We present Hα line imaging observations of 122 galaxies obtainedwith the 1.20 m telescopes of the Observatoire de Haute Provence (OHP)and of Calar Alto. The observed galaxies are mostly Virgo clustermembers (95), along with 10 objects in the Coma/A1367 supercluster, 6 inthe clusters A2197 and A2199, and 11 nearby galaxies taken as fillers.Hα +[NII] fluxes and equivalent widths, as well as images of allthe detected targets, are presented. Based on observations taken at theObservatoire de Haute Provence (OHP) (France), operated by the FrenchCNRS, and Calar Alto Observatory (Spain), operated by theMax-Planck-Institut für Astronomie (Heidelberg) jointly with theSpanish National Commission for Astronomy. Figure 1 is only available inelectronic form at http://www.edpsciences.org
| Nuclear Activity in Nearby Galaxies
I discuss some recent observational results in the research of nearbyactive galactic nuclei (AGN). These results cover three main topics: (i)evidences for the current paradigm for AGN's, which includes a nuclearsupermassive blackhole (SMBH) fed via an accretion disk; (ii) evidencethat this paradigm may also apply to LINER's, the lowest luminous AGN'sand to normal galaxies; (iii) evidences of how the fueling of the SMBHoccurs and its relation to recent and intermediate age (106to 108 yrs old) episodes of star formation.
| Supermassive Black Holes in Galactic Nuclei
Dynamical searches find central dark objects, candidate supermassiveblack holes (BHs), in 22 galaxies. Their demographics lead to thefollowing conclusions: (1) BH mass is consistent with predictions basedon quasar energetics. (2) BH mass correlates with the luminosity of the``bulge'' but not the disk component of the host galaxy. (3) BH masscorrelates with the luminosity of the high-density central component indisk galaxies independent of whether this is a real bulge (amini-elliptical) or a ``pseudobulge'' (believed to form via inwardtransport of disk material). (4) BH results increasingly support thehypothesis that the major event that forms a giant elliptical and themain AGN phase of the BH are the same event. Issues that need furtherwork include: (i) BH masses from reverberation mapping are a factor of ~5 smaller than those from detailed dynamical studies. Contributingfactors are identified that suggest that this discrepancy may not befundamental. (ii) Do any bulges or ellipticals lack BHs? Are there BHsin pure disk galaxies? (iii) We need to know whether some of the massdetected in dynamical studies is in dark clusters of objects and not inBHs.
| Total Magnitudes of Virgo Galaxies. I. Construction of a Self-Consistent Reference Dataset Spanning 8th to 18th Magnitude
The main objectives of this series of papers are: (1) to demonstrate theexistence of serious mutual disagreements between established total (andother integrated) magnitude scales for Virgo galaxies; (2) to attempt toquantify both the systematic and random errors present within thesemagnitude scales; (3) to investigate the origins of any large erroruncovered; and thereby (4) to encourage the general adoption of rigoroustotal-magnitude measurement procedures by the astronomical community.The ramifications of the findings presented in this series of paperswill be discussed in detail at a later date. In this paper, the first inthe series, a self-consistent dataset of trustworthy total-magnitudemeasurements is compiled for a sample of Virgo galaxies spanning a rangeof 10 000 in apparent brightness, based on only the most reliablemeasurements and photometry currently available. This reference dataset,which includes luminosity profile shape information, will be used insubsequent papers as one of the bases for assessing existing magnitudescales for Virgo galaxies. As most published magnitudes are based onB-band observations, this series of papers will also focus primarily onB-band measurements.
| SAURON: integral-field spectroscopy of galaxies
We present the first results from a new and unique integral-fieldspectrograph, SAURON, for the 4.2-m William Herschel Telescope on LaPalma. Based upon the TIGER concept, SAURON uses a lens array to obtaintwo-dimensional spectroscopy with complete spatial coverage over a fieldof 33''×41'' in low-resolution mode (0.94'' lenslets) and of9''×11'' in high-resolution mode (0.26'' lenslets). The spectracover 4800 Å to 5400 Å with a resolution of 3 Å(σ=75 km s-1). SAURON achieved first light duringcommissioning on the WHT on 1 February 1999. The instrument performedwell and we are commencing a systematic survey of the velocitydispersions, velocity fields, and line-strength distributions in nearbyellipticals and spiral bulges. The wide field of SAURON will be crucialfor unravelling complicated velocity structures. In combination withavailable long-slit spectroscopy of the outer regions of the galaxies,HST spectra of the nuclei, and HST imaging, we will constrain theintrinsic shapes, mass-to-light ratios, and stellar populations inspheroids. In this presentation we will give a status report andpreliminary results from our first science run in February 1999.
| 2D modelling of the light distribution of early-type galaxies in a volume-limited sample - II. Results for real galaxies
In this paper we analyse the results of the two-dimensional (2D) fit ofthe light distribution of 73 early-type galaxies belonging to the Virgoand Fornax clusters, a sample volume- and magnitude-limited down toMB=-17.3, and highly homogeneous. In our previous paper(Paper I) we have presented the adopted 2D models of thesurface-brightness distribution - namely the r1/n and(r1/n+exp) models - we have discussed the main sources oferror affecting the structural parameters, and we have tested theability of the chosen minimization algorithm (MINUIT) in determining thefitting parameters using a sample of artificial galaxies. We show that,with the exception of 11 low-luminosity E galaxies, the best fit of thereal galaxy sample is always achieved with the two-component(r1/n+exp) model. The improvement in the χ2due to the addition of the exponential component is found to bestatistically significant. The best fit is obtained with the exponent nof the generalized r1/n Sersic law different from theclassical de Vaucouleurs value of 4. Nearly 42 per cent of the samplehave n<2, suggesting the presence of exponential `bulges' also inearly-type galaxies. 20 luminous E galaxies are fitted by thetwo-component model, with a small central exponential structure (`disc')and an outer big spheroid with n>4. We believe that this is probablydue to their resolved core. The resulting scalelengths Rh andRe of each component peak approximately at ~1 and ~2kpc,respectively, although with different variances in their distributions.The ratio Re/Rh peaks at ~0.5, a value typical fornormal lenticular galaxies. The first component, represented by ther1/n law, is probably made of two distinct families,`ordinary' and `bright', on the basis of their distribution in theμe-log(Re) plane, a result already suggested byCapaccioli, Caon and D'Onofrio. The bulges of spirals and S0 galaxiesbelong to the `ordinary' family, while the large spheroids of luminous Egalaxies form the `bright' family. The second component, represented bythe exponential law, also shows a wide distribution in theμ0c-log(Rh) plane. Small discs (orcores) have short scalelengths and high central surface brightness,while normal lenticulars and spiral galaxies generally have scalelengthshigher than 0.5kpc and central surface brightness brighter than20magarcsec-2 (in the B band). The scalelengths Reand Rh of the `bulge' and `disc' components are probablycorrelated, indicating that a self-regulating mechanism of galaxyformation may be at work. Alternatively, two regions of theRe-Rh plane are avoided by galaxies due todynamical instability effects. The bulge-to-disc (B/D) ratio seems tovary uniformly along the Hubble sequence, going from late-type spiralsto E galaxies. At the end of the sequence the ratio between the largespheroidal component and the small inner core can reach B/D~100.
| Evidence for a massive dark object in NGC 4350
In this work we build a detailed dynamic model for an S0 galaxy possiblyhosting a central massive dark object (MDO). We show that thephotometric profiles and the kinematics along the major and minor axes,including the h3 and h4 profiles, imply thepresence of a central MDO of massMMDO~1.5-9.7×108Msolar, i.e.0.3-2.8per cent of the mass derived for the stellar spheroidalcomponent. Models without MDO are unable to reproduce the kinematicproperties of the inner stars and of the rapidly rotating nuclear gas.The stellar population consists of an exponential disc (27per cent ofthe light) and a diffuse spheroidal component (73per cent of the light)that cannot be represented by a simple de Vaucouleurs profile at anyradius. The ML ratios we found for the stellar components (3.3 and 6.6respectively) are typical of those of disc and elliptical galaxies.
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