We present a compilation of Cepheid distance moduli and data for four secondary distance indicators that employ stars in the old stellar populations: the planetary nebula luminosity function (PNLF), the globular cluster luminosity function (GCLF), the tip of the red giant branch (TRGB), and the surface brightness fluctuation (SBF) method. The database includes all data published as of 1999 July 15. The main strength of this compilation resides in the fact that all data are on a consistent and homogeneous system: all Cepheid distances are derived using the same calibration of the period-luminosity relation, the treatment of errors is consistent for all indicators, and measurements that are not considered reliable are excluded. As such, the database is ideal for comparing any of the distance indicators considered, or for deriving a Cepheid calibration to any secondary distance indicator, such as the Tully-Fisher relation, the Type Ia supernovae, or the fundamental plane for elliptical galaxies. This task has already been undertaken by Ferrarese et at, Sakai et al., Kelson et al., and Gibson et al. Specifically the database includes (1) Cepheid distances, extinctions, and metallicities; (2) reddened apparent lambda 5007 Angstrom magnitudes of the PNLF cutoff; (3) reddened apparent magnitudes and colors of the turnover of the GCLF (in both the V and B bands); (4) reddened apparent magnitudes of the TRGB (in the I band) and V-I colors at 0.5 mag fainter than the TRGB; and (5) reddened apparent surface brightness fluctuation magnitudes measured in Kron-Cousin I, K', and K-short, and using the F814W filter with the Hubble Space Telescope (HST) WFPC2. In addition, for every galaxy in the database we give reddening estimates from IRAS/DIRBE as well as H I maps, J2000 coordinates, Hubble and T-type morphological classification, apparent total magnitude in B, and systemic velocity.

The evolution of galaxies is likely to be complex, involving mergers, starbursts, and other dramatic changes in morphology and luminosity. The measurement of the evolution of the mass function of galaxies is therefore essential. This can be accomplished by measuring the evolution of the mass-to-light ratios of galaxies as a function of redshift. The Fundamental Plane relation is uniquely suited to measure the evolution of the mass-to-light ratio of early-type galaxies. We show that the evolution depends sensitively on cosmology and star-formation history. We present results on the evolution of the mass-to-light ratio from the Fundamental Plane out to z = 0.83. The early-type galaxies in clusters follow a well-defined relation out the highest redshift. The mass-to-light evolution is very slow, and implies a high mean stellar age in an open universe.

We present a study of 81 I-band selected, spectroscopically confirmed members of the X-ray cluster MS 1054-03 at z = 0.83. Redshifts and spectral types were determined from Keck spectroscopy. Morphologies and accurate colors were determined from a large mosaic of HST WFPC2 images in R-F606W and I-F814W, corresponding to U and B in the rest frame. Early-type galaxies constitute only 44% of this galaxy population. This fraction is much lower than in comparable rich clusters at low redshift. Thirty-nine percent are spiral galaxies, and 17% are mergers. The early-type galaxies follow a tight and well-defined color-magnitude relation, with the exception of a few outliers. The observed scatter is 0.029 +/- 0.005 mag in rest frame U-B. Most of the mergers lie close to the CM relation defined by the early-type galaxies. They are bluer by only 0.07 +/- 0.02 mag, and the scatter in their colors is 0.07 +/- 0.04 mag. Spiral galaxies in MS 1054-03 exhibit a large range in their colors. The bluest spiral galaxies are similar to 0.7 mag bluer than the early-type galaxies, but the majority is within +/-0.2 mag of the early-type galaxy sequence. The red colors of the mergers and the majority of the spiral galaxies are reflected in the fairly low Butcher-Oemler blue fraction of MS 1054-03: f(B) = 0.22 +/- 0.05, similar to intermediate redshift clusters and much lower than previously reported values for clusters at z similar to 0.8. The slope and scatter of the CM relation of early-type galaxies are roughly constant with redshift, confirming previous studies that were based on ground-based color measurements and very limited membership information. However, the scatter in the combined sample of early-type galaxies and mergers (i.e., the sample of future early-type galaxies) is twice as high as the scatter of the early-type galaxies alone. This is a direct demonstration of the "progenitor bias": high-redshift early-type galaxies seem to form a homogeneous, old population because the progenitors of the youngest present-day early-type galaxies are not included in the sample.

We present new results from a systematic study of absorption-line strengths of galaxies in clusters approaching redshifts of unity. In this Letter, we specifically compare the strengths of the high-order Balmer absorption features of H gamma and H delta in E/SO galaxies in the four clusters Abell 2256 (z = 0.06), Cl 1358+62 (z = 0.33), MS 2053 -04 (z = 0.58), and MS 1054-03 (z = 0.83). By comparing the correlation of the Balmer line strengths with the velocity dispersions for E/SO galaxies in the four clusters, we find moderate evolution in the zero point of the (H delta (A)+ H gamma (A))-sigma relation with redshift. The trend is consistent with the passive evolution of old stellar populations. Under the assumption that the samples can be compared directly, we use single-burst stellar population synthesis models to constrain the last major occurrences of star formation in the observed E/SO galaxies to be z(f) > 2.5 (95% confidence). We have compared the evolution of the Balmer absorption with the evolution of the B-band fundamental plane and find that simple stellar population models agree very well with the data. While the best agreement occurs with a low value for Omega (m), the data provide strong confirmation of the time evolution in recent stellar population models.

We study the fundamental plane (FP) of field early-type galaxies at intermediate redshift, using Hubble Space Telescope Wide Field Planetary Camera 2 observations and deep Keck spectroscopy. Structural parameters and internal velocity dispersions are measured for 18 galaxies at 0.15 < z < 0.55. Rest-frame M/L-B ratios are determined from the FP and compared to those of cluster early-type galaxies at the same redshifts. The systematic offset between MIL ratios of field and cluster early-type galaxies at intermediate redshift is small and not significant: [ln M/L-B](field) - [ln M/L-B](clus) = -0.18 +/- 0.11. The M/L-B ratio of field early-type galaxies evolves as Delta ln M/L-B = (-1.35 +/- 0.35)z, very similar to cluster early-type galaxies. After correcting for luminosity evolution, the FP of field early-type galaxies has a scatter sigma = 0.09 +/- 0.02 in log r(e), similar to that in local clusters. The scatter appears to be driven by low-mass S0 galaxies; for the elliptical galaxies alone we find a = 0.03(-0.03)(+0.04). There is a hint that the FP has a different slope than in clusters, but more data are needed to confirm this. The similarity of the MIL ratios of cluster and field early-type galaxies provides a constraint on the relative ages of their stars. At (z) = 0.43, held early-type galaxies are younger than cluster early-type galaxies by only 21% +/- 13%, and we infer that the stars in field early-type galaxies probably formed at z greater than or equal to 1.5. Recent semianalytical models for galaxy formation in a Lambda CDM universe predict a systematic difference between held and cluster galaxies of Delta ln M/L-B similar to -0.6, much larger than the observed difference. This result is consistent with the hypothesis that field early-type galaxies formed earlier than predicted by these models.

We present here the final results of the Hubble Space Telescope (HST) Key Project to measure the Hubble constant. We summarize our method, the results, and the uncertainties, tabulate our revised distances, and give the implications of these results for cosmology. Our results are based on a Cepheid calibration of several secondary distance methods applied over the range of about 60-400 Mpc. The analysis presented here benefits from a number of recent improvements and refinements, including (1) a larger LMC Cepheid sample to define the fiducial period-luminosity (PL) relations, (2) a more recent HST Wide Field and Planetary Camera 2 (WFPC2) photometric calibration, (3) a correction for Cepheid metallicity, and (4) a correction for incompleteness bias in the observed Cepheid PL samples. We adopt a distance modulus to the LMC (relative to which the more distant galaxies are measured) of mu (o)(LMC) = 18.50 +/- 0.10 mag, or 50 kpc. New, revised distances are given for the 18 spiral galaxies for which Cepheids have been discovered as part of the Key Project, as well as for 13 additional galaxies with published Cepheid data. The new calibration results in a Cepheid distance to NGC 4258 in better agreement with the maser distance to this galaxy. Based on these revised Cepheid distances, we find values (in km s(-1) Mpc(-1)) of H-o = 71 +/- 2 (random) +/- 6 (systematic) (Type Ia supernovae), H-o = 71 +/- 3 +/- 7 (Tully-Fisher relation), H-o = 70 +/- 5 +/- 6 (surface brightness fluctuations), H-o = 72 +/- 9 +/- 7 (Type II supernovae), and H-o = 82 +/- 6 +/- 9 (fundamental plane). We combine these results for the different methods with three different weighting schemes, and find good agreement and consistency with H-o = 72 +/- 8 km s(-1) Mpc(-1). Finally, we compare these results with other, global methods for measuring H-o.

We have obtained deep, long-slit spectroscopy along the major axis of NGC 6166, the cD galaxy in the cluster A2199, in order to measure the kinematics of intracluster stars at large radii. The velocity dispersion initially decreases from the central value of 300 to 200 km s(-1) within a few kiloparsecs and then steadily rises to 660 km s(-1) at a radius of 60 kpc (H-0 = 75 km s(-1) Mpc(-1), Omega(m) = 0.3, Omega(Lambda) = 0.7), nearly reaching the velocity dispersion of the cluster (sigma(A2199) = 775 +/- 50 km s(-1)). These data suggest that the stars in the halo of the cD galaxy trace the potential of the cluster and that the kinematics of these intracluster stars can be used to constrain the mass pro le of the cluster. In addition, we find evidence for systematic rotation (V/sigma approximate to 0.3) in the intracluster stars beyond 20 kpc. Such rotation is not seen in the kinematics of the cluster members. The surface brightness and velocity dispersion profiles can be fitted using a single-component mass model only by making unphysical assumptions about the level of anisotropy for both the stars in the cD galaxy and the kinematics of the galaxies in the cluster. Two-component mass models for the cD galaxy and its halo are subsequently explored using the kinematics of known cluster members as an additional constraint on the total enclosed mass beyond the extent of the stellar kinematics. Under the assumption of isotropy, the observed major-axis kinematics can be reproduced only if the halo, parameterized by a generalized Navarro-Frenk-White (NFW) profile, has a soft core, i.e., alpha < 1 ( a generalized NFW halo with alpha = 1 is excluded because of low implied stellar mass-to-light ratios). This result is inconsistent with the predictions of current N-body simulations for dark matter halos. To test the consistency of our halo profiles with those derived from strong lensing measurements in intermediate-redshift clusters, we calculate the critical radii for tangential arcs, assuming that our best-fit mass models for A2199 were placed at cosmological redshifts between 0.2 <= z <= 0.5. The calculated critical radii for our best-fit two-component isotropic models range from 5" to 40", depending on the assumed source redshift, consistent with the radii for gravitational arcs observed in intermediate-redshift clusters. We also present the results of Monte Carlo simulations testing the general reliability of velocity dispersion measurements in the regime of low signal-to-noise ratio and large intrinsic Doppler broadening.

In two-dimensional spectrographs, the optical distortions in the spatial and dispersion directions produce variations in the subpixel sampling of the background spectrum. Using knowledge of the camera distortions and the curvature of the spectral features, one can recover information regarding the background spectrum on wavelength scales much smaller than a pixel. As a result, one can propagate this better sampled background spectrum through inverses of the distortion and rectification transformations and accurately model the background spectrum in two-dimensional spectra for which the distortions have not been removed (i.e., the data have not been rebinned/rectified). The procedure, as outlined in this paper, is extremely insensitive to cosmic rays, hot pixels, etc. Because of this insensitivity to discrepant pixels, sky modeling and subtraction need not be performed as one of the later steps in a reduction pipeline. Sky subtraction can now be performed as one of the earliest tasks, perhaps just after dividing by a flat field. Because subtraction of the background can be performed without having to "clean" cosmic rays, such bad pixel values can be trivially identified after removal of the two-dimensional sky background.

Combining Hubble Space Telescope WFPC2 mosaics with extensive ground-based spectroscopy, we study the nature of E+A galaxies in three intermediate-redshift clusters (z = 0.33, 0.58, and 0.83). From a sample of similar to500 confirmed cluster members, we isolate 46 E+A candidates to determine the E+A fraction and study their physical properties. Spectral types are assigned using Balmer (Hdelta, Hgamma, Hbeta) and [O II] lambda3727 equivalent widths. For all members, we have galaxy colors, luminosities, Hubble types, and quantitative structural parameters. We also include measured internal velocity dispersions for 120 cluster members and estimate velocity dispersions for the rest of the cluster sample using the fundamental plane. We find that E+A galaxies comprise a nonnegligible component (similar to7%-13%) of the cluster population at these redshifts, and their diverse nature indicates a heterogeneous parent population. While cluster E+A's are predominantly disk-dominated systems, they span the range in Hubble type and bulge-to-total fraction to include even early-type members. Cluster E+A's also cover a wide range in luminosity [L-B similar to (0.2-2.5)L-B*], internal velocity dispersion (sigma similar to30-220 km s(-1)), and half-light radius [r(1/2) similar to (0.4-4.3)h(-1) kpc]. From their velocity dispersions and half-light radii, we infer that the descendants of E+A's in our highest redshift cluster are massive early-type galaxies. In contrast to the wide range of luminosity and internal velocity dispersion spanned by E+A's at higher redshift, only low-mass E+A's are found in nearby clusters, e. g., Coma. The observed decrease in the characteristic E+A mass is similar to the decrease in the luminosity of rapidly star-forming field galaxies since z similar to 1, i.e., galaxy "downsizing." In addition, we argue that our statistics imply that greater than or similar to30% of the E-S0 members have undergone an E+A phase; the true fraction could be 100% if the effects of E+A downsizing, an increasing E+A fraction with redshift, and the conversion of spiral galaxies into early type galaxies are also considered. Thus, the E+A phase may indeed be an important stage in the transformation of star-forming galaxies into early-type members.

We select E+A candidates from a spectroscopic data set of similar to800 field galaxies and measure the E+A fraction at 0.3 < z < 1 to be 2.7% +/- 1.1%, a value lower than that in galaxy clusters at comparable redshifts (11% +/- 3%). HST WFPC2 imaging for five of our six E+A's shows that they have a heterogeneous parent population: these E+A's span a range in half-light radius (0.8 h(-1) kpc < r(1/2) < 8 h(-1) kpc) and estimated internal velocity dispersion (50 km s(-1) less than or similar to sigma(est) less than or similar to 220 km s(-1)), and they include luminous systems (-21.6 less than or equal to M-Bz - 5 log h less than or equal to - 19.2). Despite their diversity in some aspects, the E+A's share several common characteristics that indicate that the E+A phase is an important link in the evolution of star-forming galaxies into passive systems: the E+A's are uniformly redder than the blue, star-forming galaxies that make up the majority of the field, they are more likely to be bulge-dominated than the average field galaxy, and they tend to be morphologically irregular. We find that E+A's make up similar to9% of the absorption-line systems in this redshift range and estimate that greater than or similar to25% of passive galaxies in the local field had an E+A phase at z less than or similar to 1.