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Abstract
Two virial formulas, which take into account the observed flattening,
are established for oblate ellipticals obeying the r to the 1/4th power
law and used to derive the mean mass to light ratios in their central
part. One of them, which requires the knowledge of only one kinematical
parameter, the central (stellar) velocity dispersion, is applied to 197
ellipticals. The other one, which uses in addition the maximum stellar
rotation velocity, is shown to be less sensitive to the unknown true
flattenings and to possible velocity anisotropies. It is applied to 30
ellipticals. Both methods give a mean blue mass to luminosity ratio of
about 13, without any clear correlation with the absolute luminosity of
the galaxy.
... It is evidently of interest to study more dwarfs in detail. In order to determine both the intrinsic shape and the internal dynamical structure of a number of dwarfs with confidence it is necessary to have not only accurate two-dimensional surface photometry but also two-dimensional velocity information ( Bacon 1985;Fillmore 1986;Statler 1987;Franx 1988). The low surface brightness of the dwarfs makes the required absorption-line spectroscopy a formidable task. ...
Kinematic observations along the major and minor axis of the E5 dwarf
elliptical galaxy NGC 205 are presented. A velocity dispersion of 60
km/s was measured over the central 1 arcmin with no signifiant rotation.
The upper limit on rotation about either axis is 25 km/s, and implies an
anisotropic velocity distribution. Mass/LB = 7 in solar units was
deduced.
High resolution images of the gravitational lens candidate B1422+231 in Gunn r and g have been obtained using the HRCam at Canada-France-Hawaii Telescope (CFHT). These images have full width at half maximum (FWHM) of 0.36 sec, to 0.46 sec, sufficient to resolve all four components of the lens, which have a smallest separation of 0.5 sec. The four components are achromatic and have positions which are identical to those of the radio image taken by Patnaik et al. (1992), further confirming the gravitational lens interpretation. Component A in the optical image is approximately 0.30 mag fainter than the brightest component, whereas the radio image shows them to be of equal brightness, suggesting that the source is variable. After subtraction of the components, a faint (r approximately 21.8 mag) galaxy is detected, which is most likely responsible for the lensing. The photometric properties and mass-to-light ratio of this galaxy suggest that it is probably an early-type galaxy at a redshift between 0.4 and 0.8.
The first generation of stars at high redshift should have produced
bright optical lines of common elements. These lines would appear now in
near-infrared bands. We estimate the line fluxes and large-area surface
brightnesses of the prominent lines Ly-alpha, H-alpha, H-beta, (O III)
lambda 5007, and (O II) lambda 3727 from the first galaxies under a
variety of assumptions about the epochs of star formation and cosmology.
The results show that these galaxies are within the reach of the present
generation of infrared instrumentation for a wide range of star
formation histories. We discuss the efficacy for searching for
emission-line objects in the near-infrared as a means of finding
primeval galaxies and discuss the possible searching strategies with
respect to the expected intrinsic scatter of the properties of the
forming galaxies.
A detailed test of the quality of a simple family of anisotropic
self-consistent global models for quasi-spherical galaxies is made by
considering a set of bright ellipticals with available photometric and
kinematical data. The photometric fit, under the assumption of constant
mass-to-light ratio, not only proves to be very good, but also better
than fits based upon the isotropic King models or the R1/4
law. In addition, the fit to the kinematical data is used to determine
total masses and mass-to-light ratios. Seeing convolution effects are
also briefly discussed and illustrated.
A numerical code is developed to follow the dynamical evolution of
groups of galaxies, starting from virial equilibrium. The code assigns a
single particle to each galaxy and to a diffuse intergalactic
background, both with appropriately softened potentials, and explicitly
incorporates many of the physical processes occuring in groups, such as
collisional stripping, tidal stripping from the background mean field,
dynamical friction on the background, mergers, and orbital braking.
Groups of eight galaxies with surface densities similar to Hickson's
compact groups are unstable against rapid galaxy merging. No dense
groups of eight galaxies still appear compact (in Hickson's sense) after
1/2tHubble. These "instability" times are insensitive to the
uncertainties of the physics used in the code, but are increased with
larger group membership, and larger group mass-luminosity ratios.
Kinematic observations along the major and minor axis of the E2 dwarf elliptical galaxy NGC 185 are presented. The velocity dispersion is constant at 28 +/- 8 km/s between 3 and 40 arcsec, but may increase to about twice that value in the center. An upper limit of 10 km/s is found for the rotation along either axis, so that the velocity distribution is anisotropic. The derived solar mass/LB is about 3 in solar units. Analysis of the kinematic and photometric data now available shows that giant ellipticals and dwarfs fall on a continuous sequence in the (L, sigma) plane.
The observed correlation between galaxy bulge luminosities and central
velocity dispersions is examined, with emphasis on the use of accurate
bulge-to-disk ratios. Bulges are chosen whose stellar populations
resemble those in elliptical galaxies, and the possible differences
between bulges in barred and unbarred galaxies are explored together
with the effects on the adopted distances of a Virgocentric flow field.
Study results extend the conclusions of recent studies which note that
some bulges have lower central dispersions than ellipticals of similar
luminosity. It is inferred that the central dynamics and stellar content
of bulges and ellipticals are similar, although the global dynamics
differ in that rotation is more important in bulges than in bright
ellipticals.
Rotation curves and velocity dispersion profiles are obtained for 11
faint elliptical galaxies, together with central velocity dispersions
for an additional six faint ellipticals. It is noted that faint
ellipticals rotate more rapidly than bright ellipticals, and almost as
rapidly as predicted by models with oblate figures and isotropic
distributions of residual velocities. No significant difference is found
between disk galaxy bulge rotational properties and ellipticals with
similar absolute magnitudes, when ellipticity differences are taken into
account. Attention is given to the relation between central velocity
dispersion and luminosity, and indication is found that it may be
steeper at low luminosities. It may be possible to satisfy the empirical
correlation between rotation and luminosity, if the ellipticals formed
in a clustering hierarchy, although the slow rotation of bright
ellipticals is difficult to reconcile with their high densities
Morphological, photometric, and kinematic data are employed to examine
the structure and evolution of barred and unbarred galaxies. Data is
currently being acquired with CCDs coupled to automatic image processing
equipment. Approaches to developing a physical taxonomy of galaxies are
discussed, with a focus on the Hubble-de Vaucouleurs model and its
limitations. Physical delineations in the Hubble sequence are explored,
noting the fundamental parameter, the total mass. Extensions of the
classifications to obtain additional distinctions based on halos, lens,
and bar features are explored. Attention is also given to the surface
photometry of galaxies, searches for massive halos, and features of
elliptical and cD galaxies. Gas and stellar velocity fields in galaxies
are discussed, as are bar characteristics and secular evolutionary
processes.
A technique is developed for estimating the rotation curves of oblate-spheroidal elliptical galaxies under a variety of assumptions
regarding their velocity dispersion structure. This technique is then used to derive rotation curves of Hubble-type constant
ellipticity pseudo-galaxies and of three galaxies for which King has obtained density and ellipticity profiles. The rotation
curves derived in this way peak at two to ten core radii, their behaviour beyond the peak depending on the ellipticity profile
of the galaxy in question. The ratio of peak rotation to central velocity dispersion depends more sensitively on the ellipticity
near two to three core radii than on the peak ellipticity interior to the rotation curve crest. NGC 4406 has less than 20
per cent and NGC4621 less than 50 per cent of the rotational kinetic energy required by models in which they are flattened
by rotation. Unless observations of the central regions are dominated by the effects of seeing, the central velocity–anisotropy
structures of these systems must be rather complex and highly radius-dependent. Even if no allowance is made for the effects
of seeing, one fmds that the central velocity dispersions should be less than those near one core radius.
Generalized techniques for determining density enhancements in redshift
space are presented, and one of these techniques is used to examine the
effects of varying selection criteria on the dynamical parameters
defined for groups of galaxies. There is a broad range of selection
parameters which yields well defined and well behaved groups. A whole
sky catalog of nearby groups with outer number density enhancement
exceeding 20 is presented; the median M/L for these groups is
approximately 170, corresponding to a cosmological density Omega = 0.1.
A two-dimensional projection of several contours near the Virgo cluster
is examined, and the clustering is found to exhibit both concentric and
hierarchical structure.
Velocity dispersions for 25 E and S0 galaxies are presented which were
measured by employing conventional and Fourier techniques to reduce
spectral data obtained in scans of the nuclear regions with an
image-dissector scanner. The estimates are based primarily on certain
sensitive blends near the Mg b triplet and also on the width of the Na D
line. Nuclear values of the mass-to-light ratio (M/L(B)) are calculated
using measured values of core radii and central surface brightnesses for
several of the sampled galaxies, and it is found that the mean value of
M/L(B) for giant ellipticals with an absolute bolometric magnitude of
less than -20 is 7(H/50) in solar units. This value agrees well with the
values for early-type spirals, implies that there is no large
discontinuity in M/L between early-type spirals and ellipticals, and
constitutes evidence against a stellar population strongly enriched in
M-dwarfs. Both velocity dispersion and M/L(B) are found to be correlated
with absolute magnitude for normal ellipticals, and the observed
increase in M/L(B) is shown to be consistent with an increase in metal
abundance with luminosity. It is concluded that ellipticals are close to
being a one-parameter family with total mass as the most important
independent variable.
Measurements of velocity dispersions for 32 galaxies, most of them
elliptical, are presented. These are compared with several other recent
efforts. The Faber-Jackson (1976) correlation between velocity
dispersion and absolute magnitude is discussed. Mass-to-light ratios for
17 of the galaxies are determined. The effects of anisotropic velocity
dispersion tensors on the computed mass-to-light ratios are analyzed,
and the dependence of mass-to-light ratios on absolute magnitude is
considered.
The Faber-Jackson relation between absolute magnitude
MT0 and central velocity dispersion
σupsilon is reexamined for a sample of 157 normal,
noninteracting galaxies, 82 ellipticals (T = -5, -4), and 75
lenticulars (T = - 3, - 2, -1). The values of
σupsilon are weighted means from various sources
reduced to a uniform system (Table 1).
Absolute magnitudes are calculated from corrected apparent magnitudes
BT0 and distance moduli μ0 which
are weighted means of a variety of independent determinations (from
optical tertiary indicators and from revised versions of the
Tully-Fisher relation) for spirals associated with ellipticals or
lenticulars in our sample; group distance moduli derived from
redshifts were also used in some cases. The slope and zero point of
the one-parameter F-J relation, MT0 (log
σupsilon), were derived by Jefferys's generalized
least-squares technique for differentsamples (E vs. L,
lower vs. higher redshifts, Virgo cluster).
The best-fit slope (8-9) is generally less than the canonical value
(10) and varies slightly with wavelength from ∼8.5 in the U, B,
and V bands to ∼10 in the infrared (Appendix A). The zero point is
not significantly different for the E and L classes in the red and
infrared, but lenticulars are ∼0.2-0.3 mag brighter in the U and B
bands. Alternative expressions in the B and V bands are approximately
-MT0(B)
=A+9(logσupsilon-2.3),
with A = 19.4 (E) or 19.6 (L), and, more precisely,
-MT0(V) =
20.35+8.5(logσupsilon-2.3)
for both classes. These expressions give absolute magnitudes with mean
errors of∼ 0.5 mag (E) and ∼0.6-0.7 mag (L). The effects of
second-order parameters including color index, surface brightness, and
apparent axis ratio are investigated. Small but significant effects of
the first two are indicated. Generalized expressions of the F-J
relation including such terms are given. Weighted mean distance moduli
in the range 29 ≤ μw0
(σupsilon) ≤ 35 calculated by one-, two-, and
three-parameter expressions are given for the 157 galaxies in our
sample. The mean errors of these distance moduli from all sources are
of the order ∼0.5 mag (E) and ∼0.6 mag (L), depending on the
precision of the input parameters. Comparison of the distance moduli
derived from σupsilon for E, L galaxies and from
other indicators for spirals in the same groups indicates no
appreciable systematic scale difference in the range 29 <
μ0 lt; 35 and, possibly, 24 < μ0 <
35.
The method of dispersion calculation employed in the reported
investigation uses cross-correlation against a filtered template. It is
a linear process that does not require nonlinear least-square parameter
estimation. A description is given of tests which were performed to
check the accuracy of the conducted measurements. Dispersion estimates
are presented for 373 elliptical and S0 galaxies. Mass-to-luminosity
ratios are computed, and the obtained global values are compared to core
values of M/L derived by Schechter (1980). Plots are presented of M/L
versus luminosity, dispersion, and equivalent width. The observed M/L
ratio shows no correlation with luminosity, although the luminosity
varies by a factor of 100. This is evidence that the stellar population
within elliptical galaxies is relatively insensitive to the size of the
galaxy. The question of correlations between various observable
parameters of elliptical galaxies is investigated, and the relationship
is exploited between absolute luminosity and velocity dispersion to
measure the infall velocity of the Local Group toward the Virgo
supercluster.
Long slit SIT spectra for 12 elliptical galaxies, obtained with the Hale
5 m reflector, have been measured using a Fourier quotient technique to
yield rotation curves, velocity dispersion profiles, and line strength
profiles down to a fraction of the night sky. We confirm Illingworth's
conclusion that ellipticals exhibit far less rotation along their major
axes than is predicted by isotropic oblate models. They also fall short
of Binney's predictions for isotropic prolate models. Not one of nine
galaxies shows rotation along its minor axis greater than 15% of its
central dispersion. NGC 596, a galaxy in which the position angle of the
major axis changes dramatically, rotates fairly rapidly in its nearly
spherical core. Galaxies of the same ellipticity exhibit substantially
different amounts of rotation. Making use of the mean relation between
absolute magnitude and central velocity dispersion, we find remarkably
small scatter in the core mass-to-light ratios of the ellipticals
studied by King and no dependence of this ratio on absolute magnitude.
The velocity-distance relations in different directions are derived from a sample of 322 spirals whose distance moduli ..mu../sub 0//sup w/ where obtained in Paper VI from tertiary distance indicators. The range of distance moduli is 26.5<..mu../sub 0//sup w/<33.2 (2<..delta..<42 Mpc) and of corrected velocities 90<V/sub 0/<5760 km s/sup -1/.Solutions of the form y- =a/sub 1/(x- ) and x- =a/sub 2//sup -1/(y- ), where y=5 log V/sub 0/, x=..mu../sub 0//sup w/, are presented for 11 sky areas (seven in supergalactic equatorial belt, four in the polar caps). Neither the mean slope nor the mean Hubble ratio is constant but varies with supergalactic longitude L and latitude B. Both tend to be lower than average in the supergalactic center sector (L<180/sup 0/) and higher in the anticenter sector (L>180/sup 0/), with intermediate values in the poar caps ( vertical-bar B vertical-bar>30/sup 0/). In particular varies from a minimum approx. =70 near Lapprox. =75/sup 0/ to a maximum approx. =110 near Lapprox. =330/sup 0/, and significant systematic departures from a linear isotropic expansion are in evidence. In particular the anisotropy of the velocity field in the supergalactic equatorial belt is illustrated for seven distance intervals (7<..delta..<29 Mpc). If the equatorial belt sector dominated by the Local Supercluster (0<L<180/sup 0/) is excluded, a close approximation of the asymptotic (low-density) Hubble expansion rate is obtained, =100 +- 10 km s/sup -1/ Mpc/sup -1/, where the mean error includes the Zero-point error of the tertiary indicators. This value is in good agreement with a number of recent, independent estimates corrected for zero point.Possible sources of systematic errors and selection effects are investigated by dividing the data according to distance modulus, apparent magnitude, luminosity index, and corrected velocity. Minimum bias intervals are identified.
A new series of three-dimensional mass models for axisymmetric galaxies
is proposed. In a similar fashion to "thickening up" of Toomre's (1963)
disk models (Miyamoto and Nagai 1975; Nagai and Miyamoto 1976), we
"flatten" the higher order Plummer models, which are generated by
differentiating successively the Plummer (1911) model with respect to
its scale parameter. The models can reproduce quite well the mass
distribution of spirals as well as ellipticals.
Using one of the present pairs of potential and density functions, we
construct a self-consistent model of the elliptical galaxy NGC 4697. The
model is compatible with all the available kinematic and photometric
observations. The present analyses of this galaxy lead to the value of
about 7 for the mass-to-luminosity ratio, which is the smallest among
the values obtained previously for elliptical galaxies. The present
analyses show also that the residual velocity distribution of stars in
NGC 4697 is likely to be far from isotropic. It is inferred therefrom
that even in ellipticals the usual relaxation mechanism has not worked
effectively.