Cluster Ellipticals Research Articles

Effect of inclusion orientation upon acoustic emission-microstructural relationships in ferritic steels

A comparison of the acoustic emission, mechanical properties and fracture behaviour of three model low-alloy steels containing manganese sulphide inclusions of varying orientation has been made as a function of tempering conditions. The majority of the inclusions existed in elliptical clusters whose major axis was aligned with the rolling direction and whose plane lay on the rolling plane. Both the yield region acoustic emission activity and ductility in the through-thickness (short transverse) sample orientation were reduced compared with the longitudinal, and to a lesser extent, transverse orientation samples. These effects are shown to be a consequence of inter-inclusion cluster shear localization in material of high yield stress and low work-hardening capacity. Because of the wide range of yield strengths and work-hardening capacities used in this study, the results extend our insight of the interactions between inclusion distribution, stress state and work-hardening capacity during ductile fracture of this class of materials.

The nuclear regions of NGC 3311 and NGC 7768 imaged with the Hubble Space Telescope Planetary Camera

We present high-resolution, V band images of the central regions of the brightest cluster ellipticals NGC 3311 and NGC 7768 taken with the Planetary Camera of the Hubble Space Telescope. The nuclei of both galaxies are found to be obscured by dust, though the morphology of the dust is quite different in the two cases. The dust cloud which obscures the central 3 arcsec of NGC 3311 is complex and irregular, while the central region of NGC 7768 contains a disk of material similar in appearance and scale to that recently observed in HST images of NGC 4261. The bright, relatively blue source detected in ground-based studies of NGC 3311 is marginally resolved and is likely to be a site of ongoing star formation. We examine the distribution of globular clusters in the central regions of NGC 3311. The gradient in the surface density profile of the cluster system is significantly shallower than that found by previous investigators at larger radii. We find a core radius for the cluster distribution of 12 plus or minus 3 kpc, which is even larger than the core radius of the globular cluster system surrounding M87. It is also an order of magnitude larger than the upper limit on the core radius of NGC 3311's stellar light and suggests that the central field-star population and the globular cluster system are dynamically distinct. We briefly discuss possible sources for the cold/warm interstellar material in early-type galaxies. While the issue has not been resolved, models which involve galactic wind failure appear to be mo st naturally consistent with the observations.

Production and Circulation of Iron in Elliptical Galaxies and Clusters of Galaxies

view Abstract Citations (252) References (85) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Production and Circulation of Iron in Elliptical Galaxies and Clusters of Galaxies Renzini, Alvio ; Ciotti, Luca ; D'Ercole, Annibale ; Pellegrini, Silvia Abstract We introduce the concept of cluster iron mass-to-light ratio (IMLR) and estimate its value for both the intracluster medium and the stars, finding the amount of iron to be nearly the same in the two cluster components. We discuss under which conditions the past supernova activity can account for the observed IMLR and provide evidence that either the past average rate of Type Ia supernovae was at least a factor of ∼10 higher than the present rate in ellipticals, or massive stars in clusters formed with a very flat initial mass function (IMF). A solution in which ∼¼ of the observed iron in clusters of galaxies was contributed by Type II supernovae, and ∼¾ by Type Ia supernovae, presents several advantages, as it would allow to preserve the current scenario for the establishment of element abundance ratios in the Galactic halo, bulge, and disk and would leave open the possibility of a universal IMF. We consider the iron abundance in the gas flow of individual elliptical galaxies, emphasize a macroscopic discrepancy that has recently emerged between the predicted iron abundance in the flow and that derived from X-ray observations, and discuss possible solutions of the discrepancy. We argue that the iron in the intracluster medium (ICM) of rich clusters was ejected from individual galaxies by internal forces generated by supernovae or active galactic nuclei (AGNs), rather than stripped by external forces such as ram pressure. We go further in considering the supernova heating and the presupernova light production which are implied by the observed IMLR and discuss their implications for elliptical galaxy formation. We suggest a possible test for the proposed scenarios, based on the predicted difference in elemental ratios between the ICM and cluster elliptical galaxies, with alpha-elements to iron ratio being below solar in the ICM and above solar in the stellar component of galaxies. Publication: The Astrophysical Journal Pub Date: December 1993 DOI: 10.1086/173458 Bibcode: 1993ApJ...419...52R Keywords: GALAXIES: ABUNDANCES; GALAXIES: CLUSTERING; GALAXIES: ELLIPTICAL AND LENTICULAR; CD; GALAXIES: EVOLUTION; GALAXIES: INTERGALACTIC MEDIUM; STARS: SUPERNOVAE: GENERAL full text sources ADS | data products SIMBAD (9)

Metal abundances for a large sample of globular clusters in M87

We present deep integrated Washington CCD photometry of the extremely populous globular cluster system of NGC 4486 (M87) in Virgo. The metallicities of 407 of the best candidates with T_1_ < 22 have been estimated from the (C - T_1_) color. These values are internally precise to ~0.15 dex and accurate to ~0.25 dex. The mean metallicity of the globular clusters is [Fe/H] = -0.86 dex, with a formal standard error of the mean of 0.03 dex but a more realistic uncertainty of about 0.2 dex. This value is higher than that of the corresponding means of the globular clusters in the Galaxy and M 31, but similar to those of the globular clusters in NGC 1399 and NGC 5128, as expected from the relative parent galaxy luminosities. ApproximatelY 10% of the clusters exceed solar abundance, similar to the case for the globular clusters in NGC 1399 and NGC 5128. As found by Couture et al. [ApJS, 73,671(1990)], there is a large metallicity dispersion at any radius, with a σ ~ 0.65 dex. However, in contrast to their result and that of previous small-field CCD studies, the globular clusters display a marked gradient in both mean (M- T_1_) and (C - T_1_) color with galactocentric distance. The mean metallicity decreases by some 0.6 dex over the radial extent of the cluster sample. This result is consistent with the early photographic study by Strom et al. [ApJ, 245,416 (1981)]. The metallicity distribution function is remarkably similar to that of NGC 1399 found by Ostrov et al. [AJ, 105,1762(1993)] using the same technique. The two central cluster ellipticals show significant peaks at very similar metallicities, indicating similar formation and enrichment histories. We also find that this structure in the metallicity distribution function persists to radii where the halo light is dominated by the cD envelope.

The shapes of brightest cluster galaxies

view Abstract Citations (24) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Shapes of Brightest Cluster Galaxies Ryden, Barbara S. ; Lauer, Tod R. ; Postman, Marc Abstract The distribution of axis ratios presently computed for a sample of brightest cluster galaxies (BCGs) is found to not vary greatly from a similar distribution for a sample of ordinary ellipticals. A significant difference is noted, however, between the distribution of axis ratios for a sample of BCGs and for a sample of second-brightest cluster ellipticals. It is also noted, in partial support for a hypothesized competition of BCGs for cluster galaxies that would otherwise merge with the second-brightest cluster ellipticals, that the shape of a merger remnant can reflect the relative masses of the progenitor as well as the angular momentum of the merging system. Publication: The Astrophysical Journal Pub Date: June 1993 DOI: 10.1086/172769 Bibcode: 1993ApJ...410..515R Keywords: Elliptical Galaxies; Galactic Clusters; Galactic Structure; Brightness Distribution; Distribution Functions; Shapes; Astrophysics; GALAXIES: CLUSTERING; GALAXIES: ELLIPTICAL AND LENTICULAR; CD; GALAXIES: INTERACTIONS; GALAXIES: PHOTOMETRY full text sources ADS |

X-ray substructure in A1656 and A2256

We report the confirmation of X-ray substructure in two rich clusters of galaxies, A1656 (Coma) and A2256. Using data from the Einstein Observatory imaging proportional counter, we present a technique of fitting the cluster profile and searching for contributions to the X-ray emission from small regions within the cluster. Using this method we find substructure in both A1656 and A2256 while simultaneously fitting the cluster profile. We obtain the ellipticity and position angle of both clusters as a function of radius and find that both have ellipticity and position angles which vary with radius. We interpret the existence of substructure along with the variable ellipticity and position angle as evidence for a recent merger in both of these clusters.

Expert system development using ellipsoid-based clustering

Most classification systems classify given data into one of a number of predefined groups, which have an associated response or action. These groups form a knowledge base, whose acquisition is crucial for successful data classification. This paper describes the design and implementation of an expert system, whose knowledge base is made up of elliptical clusters. The clusters are acquired using a clustering technique specifically designed and developed for mineral processing applications. The use of clustering techniques provides significant advantages over rule-based and neural network expert systems for many applications. The expert system is demonstrated using the classification of colour density tracer samples used in spiral separator experiments.

Dynamics of the intermediate-age elliptical LMC cluster NGC 1978

view Abstract Citations (37) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Dyanamics of the Intermediate-Age Elliptical LMC Cluster NGC 1978 Fischer, Philippe ; Welch, Douglas L. ; Mateo, Mario Abstract BY CCD images of the elliptical LMC cluster NGC 1978 out to a projected radius R ~ 100 pc were obtained using the 1.0 m telescope at Las Campanas. In addition, radial velocities with a precision of 1.5 km s^-1^ were measured for 35 member giants using the echelle spectrographs and 2D-Frutti detectors on the Las Campanas 2.5 m and the Cerro Tololo 4.0 m telescopes. After star subtraction and median filtering the ellipticity of the surface brightness distribution was determined to be ɛ = 0.30+/-0.03 and the major axis position angle to be PA = 152^deg^+/- 7^deg^. The stellar radial velocities indicate that NGC 1978 has a systemic velocity of v^bar^ = 293.3+/-1.0 km s^-1^. NGC 1978 appears to be several times older than its central relaxation time but considerably younger than its half-mass relaxation time. Single- and multimass anisotropic King-Michie models and single-mass rotating and nonrotating oblate spheriod models were fitted to both the surface luminosity profiles and the radial velocity data. The total cluster luminosity is L_B_= 3.1-3.7+/-0.2X10^5 L_B sun_ and L_v_ = 3.0-3.5+/-0.2X10^5^ L_V sun_ (for an assumed LMC distance of 50 kpc), where the range results from different model extrapolations of the brightness profile. The multimass models, while very effective at constraining the central mass-to-light ratios (hereafter referred to as M/Ls) at about (M/L)_0_ = 0.13+/-0.06 M_sun_/L_sun_, yielded global M/Ls which ranged over a factor of 5; M/L = 0.3 - 1.5 M_sun_/L_sun_ for a sample of mass function slopes. The best agreement between population and dynamical M/Ls is seen for the cases x = 0.0 for the B band [(M/L)_0_ = 0.14+/-0.06 M_sun_/L_B sun_ and M/L = 0.35+/- 0.15 M_sun_/L_B sun_] and x = 0.5 for the V[(M/L)_0_ = 0.13+/- 0.06 M_sun_/L_V sun_ and M/L = 0.40+/-0.15 M_sun_/L_V sun_]. The single- mass models tended to give better agreement with the luminosity profiles but produced M/Ls (i.e., M/L = 0.20+/-0.08 M_sun_/L_V sun_) that were difficult to reconcile with simple population studies without invoking a rather high low-mass cutoff (i.e. 0.8 M_sun_). We found no significant differences between the M/Ls derived with oblate spheroid models and those derived with spherical models. While the nonrotating (anisotropic) models were in better agreement with the kinematic data, it was impossible to completely rule out the rotating models. As well, there is no morphological evidence for a merger. Publication: The Astronomical Journal Pub Date: September 1992 DOI: 10.1086/116299 arXiv: arXiv:astro-ph/9206004 Bibcode: 1992AJ....104.1086F Keywords: Charge Coupled Devices; Globular Clusters; Magellanic Clouds; Stellar Systems; Astronomical Models; Celestial Mechanics; Oblate Spheroids; Radial Velocity; Astrophysics; MAGELLANIC CLOUDS; OPEN CLUSTERS AND ASSOCIATIONS: INDIVIDUAL: NGC 1978; Astrophysics E-Print: 36 pages (plus 8 figures available through anonymous FTP, see below) full text sources arXiv | ADS | data products SIMBAD (38) NED (2)

The environmental dependence of the Mg2 correlations for elliptical galaxies

We present Mg2 measurements for 51 Coma cluster ellipticals. Unlike previous studies, our sample includes many ellipticals that lie well outside the cluster core. These data have been used to investigate how the σ–Mg2 and D–Mg2 relationships of Coma ellipticals vary with distance from the cluster centre. We find a small environmental effect in the sense that ellipticals lying in the cluster halo, compared with those in the inner regions, have: (i) a larger intrinsic scatter about the Mg2 relations, and (ii) their Mg2 relations significantly offset to a lower Mg2 for a given σ or D. For a 1° sample division we find that the halo sample, as compared to an inner sample, has an average σ–Mg2 relation that is offset by |$0.017 \pm 0.005$| mag and an average D-Mg2 relation that is offset by |$0.025 \pm 0.008$| mag. Previously we have reported that for the same sample of ellipticals the D–σ relation does not vary significantly with distance from the cluster centre. For the 1° division the measured offset in the D–σ relation is |$0.039 \pm 0.024$| dex, in the sense that the halo ellipticals possess, on average, slightly larger D diameters at a fixed σ. We show that the D–σ, σ-Mg2 and D-Mg2 offsets are all consistent with the hypothesis that halo ellipticals have, on average, younger stellar populations.

Systematic differences between the field and cluster elliptical galaxies

Multivariate statistical techniques and fundamental plane fits are used here to study possible systematic differences between field ellipticals (FEs) and cluster ellipticals (CEs). The FEs show more intrinsic scatter in their properties, especially when stellar population variables are included. Pairwise correlations for the two samples are different; the correlations are systematically better for the cluster sample, meaning that ellipticals in the two samples populate their fundamental planes in different ways. Bivariate correlations are different for the two samples, implying that they have different fundamental planes. This is especially true for the correlations which include the population variables Mg2 and (B-V), which are sensitive both to the enrichment history and the storm formation history.

THE INTERSTELLAR MEDIUM OF ELLIPTICAL GALAXIES

ABSTRACT Initial investigation showed elliptical galaxies to be deficient in gas compared to their spiral cousins. However, in the past decade more sensitive observations have revealed a varied interstellar medium in many ellipticals--from a hot gaseous corona of 107 K plasma to disks of cold neutral and molecular gas. In this thesis, both the cold and hot gaseous components are investigated and compared. The presence of gas in elliptical galaxies may give important clues to their recent history; the balance of the various phases may indicate the relevant energy input mechanisms; the gas kinematics trace the gravitational potential of these systems. First, observations of 12CO(2-1) emission from far-infrared-bright (FIR-bright) elliptical galaxies, of which 40% are detected, are described. Typical molecular masses are similar to that of the atomic gas, about 107-109 solar mass. The ellipticals display a power-law distribution of the ratio of molecular gas mass to blue luminosity. MH2/LB, increasing slowly toward the lower values of the gas-to-luminosity ratio, implying that most elliptical galaxies may contain small quantities of cold gas. They display the same relationships between molecular gas mass (MH2) and FIR luminosity (LFIR) and between MH2 and the H I mass (MHI) as do spiral galaxies, so that the global interstellar medium properties of early-type systems appear to be similar to those of the late-type galaxies, although for gas masses over an order of magnitude smaller. Second, the X-ray and FIR data for elliptical galaxies are compared, and it is shown that ellipticals obey a relationship between the X-ray luminosity (LX), LB, and LFIR such that LX approaches L2.3B L-0.3FIR. The scatter in this relationship is significantly lower than that in the well-known LX-LB correlation. Furthermore, the ratio of cold-to-hot gas mass shows a bimodal distribution with field ellipticals containing more cold than hot gas (with the ratio of cold-to-hot gas masses Mcold/Mhot > 1 for ellipticals in groups with fewer members) and cluster ellipticals having cold gas masses only a few percent of their hot gas mass (with Mcold/Mhot 0.03 for ellipticals in groups with more than ten members). Finally, VLA H I 21 cm observations of the atomic gas disk in the nearby elliptical galaxy NGC 4278, and other members of the group, are presented. NGC 4278 shows a very extended cold gas disk in well-ordered rotation, ideal for mapping the potential of this system. Models of the gas kinematics using spherical, oblate, and triaxial mass distributions are employed to constrain the mass-to-light ratio out to over ten half-light radii. The triaxial mass models for NGC 4278 are able to reproduce the twisting of the central gas velocity contours and the global properties of the stellar light distribution very well. All models show a mass-to-light ratio which increases rapidly with radius in the outer parts, with a global value of M/L 30-100 solar mass/luminosity mass.

New D - results for Coma cluster ellipticals

We present velocity dispersions (σ) and photometric diameters (D) for 51 ellipticals in the Coma cluster. Unlike previous studies, our sample includes many ellipticals that lie well outside the cluster core. These data have been used to estimate th environmental dependence of the D-σ relation. The zero-point of the D−σ relation is found to vary by only 6±9 per cent from Coma's core to a projected distance of ∼4 h −1 Mpc. This is in the sense that the outer ellipticals possess, on average, slightly larger D diameters at a fixed σ.

Systematic effects in lens inversions - Aleph(1) exact models for 0957 + 561

Due to the careful study of its VLBI structures, the gravitational lens 0957 + 561 is the most accurately characterized of the lens candidates. Nonetheless, the observational data supplies only five firm constraints, compared to a minimum of nine free parameters in simple models for the lens using an elliptical galaxy and an elliptical cluster both with fixed radial structure. This paper examines the systematic variations between models for the lens potential that satisfy the constraints exactly. This is done using both the 4 degrees of freedom left when the radial structure of the galaxy is fixed, as well as variations due to changes in the radial structure. The systematic variations between the models allow for a range of time delays from approximately 0.1h^-1^ to 1.0h^-1^ yr for a fixed Einstein-de Sitter cosmology if the galaxy and the cluster satisfy the velocity dispersion constraints of 240 <~σ_g_<~ 320 km s^-1^, and 500<~σ_c_<~ 1500 km s^-1^, and the center of the cluster lies within 30" of the galaxy. Given the formal value for the velocity dispersion (303 +/- 50 km s^-1^) and the measured time delay (1.3 +/- 0.1 yr), I find that h <~ 0.6 +/- 0.2 considering only the observational errors in the velocity dispersion. However, there are large uncertainties in the relationship between the observed velocity dispersion and the mass distribution. For example, the presence of a dark matter halo which raises the velocity dispersion which characterizes the mass by a factor of (3/2)^1/2^ relative to the observed velocity dispersion, formally increases the value of the Hubble constant to h <~ 0.9 +/- 0.3, although the + 0.3 error bar is probably an exaggeration. Even with a known velocity dispersion, uncertainties in other parameters of the system, such as the principal axis of the mass distribution in the galaxy, can also introduce large uncertainties into the time delay. Because the images in 0957 + 561 only weakly constrain the mass distribution of the lens, the 0957 + 561 system can be used to measure the Hubble constant only to the accuracy with which observational parameters such as central velocity dispersion, ellipticities, and orientations can be translated into information on the mass distribution in the system. This systematic problem is the ultimate limitation on the measurement, and the statement that the 0957 + 561 system can measure H_0_ to a given level of accuracy is equivalent to the claim that the mass distribution in the lens galaxy or cluster is understood to the same level of accuracy.

Upper limit on interstellar gas in Coma cluster ellipticals

view Abstract Citations (4) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Upper Limit on Interstellar Gas in Coma Cluster Ellipticals Canizares, Claude R. ; Blizzard, Paula Abstract Using data from the Imaging Proportional Counter on the Einstein Observatory, we search for X-ray emission from 45 early-type galaxies in Coma. Some galaxies lying within 13' of the cluster center give statistically significant signals which, however, we determine to be spurious. Data for a clean subsample of 27 observations of galaxies greater than 13' from the cluster center yield only upper limits, which are generally larger than those of field ellipticals with similar optical luminosities. The mean galaxy X-ray and blue luminosities for the subsample are <L_x_> <2.2 x 10^40^ erg s^-1^ and <LB>=4.4 X 10^10^L_sun_, respectively. This X-ray limit lies well within the range observed for field galaxies and near the value estimated for a galaxy devoid of a hot interstellar medium. We can exclude the hypothesis that Coma Cluster galaxies show excess emission, such as has been attributed to galaxies in A 1367, and we conclude that environmental effects in rich clusters do not enhance the X-ray emission from individual elliptical galaxies. Conclusive evidence that the emission is strongly suppressed, e.g., by stripping of the interstellar gas, must await more sensitive studies. Publication: The Astrophysical Journal Pub Date: November 1991 DOI: 10.1086/170695 Bibcode: 1991ApJ...382...79C Keywords: Elliptical Galaxies; Galactic Clusters; Interstellar Gas; X Ray Spectra; Active Galactic Nuclei; Emission Spectra; Heao 2; High Temperature Gases; Luminosity; Astrophysics; GALAXIES: CLUSTERING; GALAXIES: INTERSTELLAR MATTER; GALAXIES: X-RAYS full text sources ADS | data products SIMBAD (22) NED (21)

Time variation of ellipticity of globular clusters in the Large Magellanic Cloud

Dynamical evolution of globular clusters in the Large Magellanic Cloud (LMC) is investigated by means of N-body simulations; particular attention is paid to time evolution in the ellipticitical figure of globular clusters. The simulations were started with a binary globular cluster. It merged into a single cluster with ellipticity of about 0.3. The simulations were continued until the cluster became rounder due to the effects of two body relaxation and of tidal field of LMC. It is found that the outward angular momentum transport due to the gravothermal contraction makes the inner region rounder; the ellipticity at about the initial half-mass radius (rh) decreases with the e-folding time of 20 relaxation times. On the other hand, the outer region becomes rounder due to the stripping of stars by the tidal field; the ellipticity at about 3rh decreases with the e-folding time of 80 crossing times therein, though the time scale depends on the direction of the tidal field relative to the spin of the cluster. These two effects are comparable at about the half-mass radius. Taking account of such theoretical results we reanalyzed observed data for the ellipticity at about the half-mass radius of LMC clusters. We estimated the relaxation time and crossing time for each of the observed clusters, from which we calculated the effective time of getting round of the cluster. We plotted the observed ellipticity of the clusters against their non-dimensional age — i.e., the age normalized by the effective time. We found that observed ellipticity distribution is consistent with our picture.

Optical coronal emission lines from cooling flows in elliptical galaxies and galaxy clusters

Luminosities, surface brightnesses, and line profiles of the coronal lines predicted by standard models for cooling flows in clusters of galaxies and in individual early-type galaxies are presented. The coronal line luminosities of cooling flows depend primarily on the total rate at which gas is cooling. In homogeneous cooling flow models (HMs) in which all of the gas flows into the central regions, the coronal lines are very centrally concentrated, coming mainly from a limb-brightened shell lying just within the sonic radius of the inflow. For HMs, the central surface brightnesses of the stronger coronal lines from nearby clusters with large cooling rates are expected to be about 6 x 10 to the -17th ergs/sq cm/s/sq arcsec. For inhomogeneous models (IMs) in which gas cools out of the flow at large radii, the surface brightness profiles of the coronal lines are more extended, and the central surface brightness is much lower. The integrated line profiles of the HMs are very wide and flat and the central line profiles are double-peaked. The IMs have nearly Gaussian line profiles.

The luminosity distribution of globular clusters in three giant Virgo ellipticals

The present CCD photometry in B for globular clusters around three of Virgo's 'normal' ellipticals (NGCs 4365, 4472, and 4649) defines the luminosity distribution of the clusters and indicates that the globular clusters in giant ellipticals follow similar luminosity distributions. A fitting of the composite Virgo globular cluster luminosity function to the Galaxy's cluster distribution yields a Virgo distance modulus estimate of 31.5 + or {minus} 0.25. Evidence, in the form of a flattening of the radial density distribution, is noted in each galaxy for a core radius in the cluster system. 81 refs.

CCD observations of Abell clusters. V - Isophotometry of 175 brightest elliptical galaxies in Abell clusters

Profiles of major- and minor-axis surface brightness, ellipticity, position angle, and isophote centroid are presently derived from isophotometry for a sample of 175 brightest cluster ellipticals (BCEs). The BCEs' average ellipticity is a sharply rising function of metric radius; less than a fourth of the sample exhibits significant ellipticity decrease with increasing radius. While at radii of less than 16 kpc the BCEs are rounder than the average elliptical, they become too flattened at radii greater than 30 kpc to represent a randomly-oriented oblate-spheroid population. These results indicate that BCE outer regions are dynamically strongly coupled to their either prolate or stringy clusters. 136 refs.

The fundamental plane of cluster ellipticals

It is shown that, for the Coma cluster ellipticals of normal surface brightness, there is a highly significant correlation between the residual from the D n -σ relation and effective surface brightness μ. The higher surface brightness ellipticals give systematically larger D n -σ distances. New, independent V-band photometry, when combined with the published velocity dispersion data, also show the same, highly significant correlation. This correlation arises because, for the Coma ellipticals, D n does not give a precise edge-on view of the fundamental plane. The Coma ellipticals with μ < 22.0 define a fundamental plane with no intrinsic scatter, indicating a remarkable degree of homogeneity

Color distributions in early type galaxies. III - Radial gradients in spectral features

Long-slit spectra covering the wavelength range 5000-9500 A have been obtained for three Virgo cluster ellipticals. Measurements of features in the spectra are presented, and their implications are discussed with particular reference to (1) anomalous r-i gradients; (2) ionized gas in the nucleus of NGC 4472; (3) nuclear emission line spectrum of M87; and (4) radial absorption line gradients in NGC 4472 with emphasis on the Na I 8190 A feature. 25 refs.