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A history is given of the discovery between 1914 and 1935 of stars of intermediate luminosity between giants and dwarfs with spectral types between G0 to K3. The Mt Wilson spectroscopists identified about 90 such stars in their 1935 summary paper of spectroscopic absolute magnitudes for 4179 stars. Called "subgiants" by Str\"omberg, these 90 stars defined the group at the time. The position of the Mt Wilson subgiants in the HR diagram caused difficulties in comparisons of high weight trigonometric parallaxes being measured and with Russell's prevailing evolution proposal, and critics questioned the reality of the Mt Wilson subgiants. We compare, star-by-star, the Mt Wilson spectroscopic absolute magnitudes of the 90 stars defining their sample against those absolute magnitudes derived from Hipparcos (HIP) trigonometric parallaxes. We address concerns over biases in the Mt Wilson calibration sample and biases created by the adopted methodology for calibration. Historically, these concerns were sufficient to discredit the discovery of subgiants in the Mt Wilson sample. However, as shown here, the majority of the Mount Wilson stars identified as subgiants that also have reliable HIP trigonometric parallaxes do lie among the subgiant sequence in the HIP HR diagram. Moreover, no significant offset is seen between the M(V) brightnesses derived from the Mt Wilson spectroscopic parallaxes and the M(V) values derived from Hipparcos trigonometric parallaxes with a fractional error of 10%, which confirms in an impressive manner the efficacy of the original Mt Wilson assessments. The existence of subgiants proved that Russell's contraction proposal for stellar evolution from giants to the main sequence was incorrect. Instead, Gamow's 1944 unpublished conjecture that subgiants are post main-sequence stars just having left the main sequence was very nearly correct but was a decade before its time., Comment: 37 pages, 12 figures, 2 tables, 2 appendices; Accepted to PASP. Allan Sandage is posthumously maintained as the primary author as he was the originator and true leader of the work, albeit the later sections were completed after his death in 2010 (see discussion regarding the preparation of this manuscript in Section 7, pg 26 for more details)

The largest amplitude light curves for both RR Lyrae (RRL) variables and classical Cepheids with periods less than 10 days and greater than 20 days occur at the blue edge of the respective instability strips. It is shown that the equation for the decrease in amplitude with penetration into the strip from the blue edge, and hence the amplitude fine structure within the strip, is the same for RRL and the Cepheids despite their metallicity differences. However, the manifestation of this identity is different between the two classes of variables because the sampling of the RRL strip is restricted by the discrete strip positions of the horizontal branch, a restriction that is absent for the Cepheids in stellar aggregates with a variety of ages. To show the similarity of the strip amplitude fine structure for RRL and Cepheids we make a grid of lines of constant amplitude in the HR diagram of the strip using amplitude data for classical Cepheids in the Galaxy, LMC, and SMC. The model implicit in the grid, that also contains lines of constant period, is used to predict the correlations between period, amplitude, and color for the two Oosterhoff RRL groups in globular clusters. The good agreement of the predictions with the observations using the classical Cepheid amplitude fine structure also for the RRL shows one aspect of the unity of the pulsation processes between the two classes of variables., 24 pages, 3 tables, 5 figures, submitted to The Astrophysical Journal

The meaning of "linear expansion" is explained. Particularly accurate relative distances are compiled and homogenized a) for 246 SNe Ia and 35 clusters with v 3500 km/s - for a 495 km/s motion of the Local Supercluster towards the warm CMB pole at l=275, b=12; local peculiar motions are averaged out by large numbers. A test for linear expansion shows that the corrected velocities increase with distance as predicted by a standard model with q_0=-0.55 [corresponding to (Omega_M, Omega_Lambda)=(0.3,0.7)], but the same holds - due to the distance limitation of the present sample - for a range of models with q_0 between ~0.00 and -1.00. For these models H_0 does not vary systematically by more than +/-2.3% over the entire range. Local, distance-dependent variations are equally limited to 2.3% on average. In particular the proposed Hubble Bubble of Zehavi et al. and Jha et al. is rejected at the 4sigma level. - Velocity residuals in function of the angle from the CMB pole yield a satisfactory apex velocity of 448+/-73 km/s and a coherence radius of the Local Supercluster of ~3500 km/s (~56 Mpc), beyond which galaxies are seen on average at rest in co-moving coordinates with respect to the CMB. Since no obvious single accelerator of the Local Supercluster exists in the direction of the CMB dipole its motion must be due to the integral gravitational force of all surrounding structures. Most of the gravitational dipole comes probably from within 5000 km/s.

A graphical and an algebraic demonstration is made to show why the slope and zero point of the Cepheid period-luminosity (P-L) relation is rigidly coupled with the slope and zero point of the Cepheid instability strip in the HR diagram. The graphical demonstration uses an arbitrary (toy) ridge line in the instability strip, while the algebraic demonstration uses the pulsation equation into which the observed P-L relations for the Galaxy and the LMC are put to predict the temperature zero points and slopes of the instability strips. Agreement between the predicted and measured instability strip slopes argue that the observed P-L differences between the Galaxy and LMC are real. In another proof, the direct evidence for different P-L slopes in different galaxies is shown by comparing the Cepheid data in the Galaxy, the combined data in NGC 3351 and NGC 4321, in M31, LMC, SMC, IC 1613, NGC 3109, and in Sextans A+B. The P-L slopes for the Galaxy, NGC 3351, NGC 4321, and M31 are nearly identical and are the steepest in the sample. The P-L slopes decrease monotonically with metallicity in the order listed, showing that the P-L relation is not the same in different galaxies, complicating their use in calibrating the extragalactic distance scale., Comment: 15 pages, 1 table, 4 figures, submitted to The ApJ

This is the fifth and final summary paper of our 15 year program using the Hubble Space Telescope (HST) to determine the Hubble constant using Type Ia supernovae, calibrated with Cepheid variables in nearby galaxies that hosted them. Several developments not contemplated at the start of the program in 1990 have made it necessary to put the summary on H_0 on a broader basis than originally thought, making four preparatory papers necessary. The new Cepheid distances of the subset of 10 galaxies, which were hosts of normal SNeIa, give weighted mean luminosities in B, V, and I at maximum light of -19.49, -19.46, and -19.22, respectively. These calibrate the adopted SNeIa Hubble diagram from Paper III to give a global value of H_0 = 62.3 +/- 1.3 (random) +/- 5.0 (systematic). Local values of H_0 between 4.4 and 30 Mpc from Cepheids, SNeIa, 21cm-line widths, and the tip of the red-giant branch (TRGB) all agree within 5% of our global value. This agreement of H_0 on all scales from 4 - 200 Mpc finds its most obvious explanation in the smoothing effect of vacuum energy on the otherwise lumpy gravitational field due to the non-uniform distribution of the local galaxies. The physical methods of time delay of gravitational lenses and the Sunyaev-Zeldovich effect are consistent (but with large errors) with our global value. The present result is also not in contradiction with existing analyses of CMB data, because they either lead to wide error margins of H_0 or depend on the choice of unwarrented priors that couple the value of H_0 with a number of otherwise free parameters in the CMB acoustic waves. Our value of H_0 is 14% smaller than the value of H_0 found by Freedman et al. (2001) because our independent Cepheid distances to the six SNeIa-calibrating galaxies used in that analysis average 0.35mag larger than those used earlier.

The status of the absolute magnitude calibrations is reviewed for the long period Cepheids of population I and II, RR Lyrae stars, evolved “above horizontal branch” (AHB1) variables (periods 0.8 to 3 days), dwarf Cepheids of both populations (the Delta Scuti and SX Phoenicus variables), and the anomalous Cepheids (AC). Evidence shows that the period-color and period-luminosity (P-L) relations for population I Cepheids in the Galaxy and in the Large and Small Magellanic Clouds have different slopes and zero points. This greatly complicates use of Cepheids for the extragalactic distance scale. Strategies are discussed to patch the problem. A consensus exists for the long distance scale for RR Lyrae stars whose calibrations favor 〈MV(RR)〉 = 0.52 at [Fe/H] = −1.5. Exceptions exist for “second parameter” clusters where the variation of the morphology of the horizontal branch with metallicity is anomalous, the most blatant being NGC 6388 and NGC 6441. The status and calibrations of ABH1 and AC show that different evolutionary paths and masses explain the difference P-L relations for them. AC appear predominantly in the dwarf spheroidal galaxies, but are almost absent in Galactic globular clusters. AHB1 stars are absent in dwarf spheroidals but are present in globular clusters. The difference may be used to study the formation of the remote Galactic halo if it is partially made by tidal disruption of companion dwarf spheroidals.

▪ Abstract “You ask what is the use of classification, arrangement, systematization. I answer you; order and simplification are the first steps toward the mastery of a subject—the actual enemy is the unknown.” Settembrini to Hans Castorp in The Magic Mountain: Thomas MannDiscussion is made on the philosophy of classification, urging that the classification be made on the basis of morphology alone, not on the basis of supposed physics that some wish to be introduced to “explain” the classification. A history of the development of the present morphological galaxy classification system is given, starting with the purely descriptive systems of Herschel, Wolf, Shapley, and Vorontsov-Velyaminov that have no connective continuity between the classification descriptions. The development of the modern system that has an underlying continuity between the classification bins is reviewed, mainly featuring the 1926 system of Hubble that is the basis of the present extended Hubble system.

The correlation of particular Fourier components of the light curves of RR Lyrae variables with metallicity, discovered by Simon and later by Kovacs and his coworkers, is shown to have the same explanation as the period ratios (period shifts in log P) between RRab Lyrae variables that have the same colors, amplitudes, and light-curve shapes but different metallicities. A purpose of this paper is to demonstrate that the model which predicts the period-metallicity relations is the mediating parameters of colors, amplitudes, and light-curve shapes also explains the Simon/Kovacs et al. correlation between period, Phi_31, and metallicity. The proof is made by demonstrating that the combination of the first and third phase terms in a Fourier decomposition of RRab light curves, called Phi_31 by Simon and Lee, varies monotonically across the RR Lyrae instability strip in the same way that amplitude, color, and rise time vary with period within the strip. The premise of the model is that if horizontal branches at the RR Lyrae strip are stacked in luminosity according to the metallicity, then there necessarily must be a log period shift between RR Lyraes with different metallicities at the same Phi_31 values. However, there are exceptions to the model. (...), Comment: 17 pages, 8 figures, 1 table. Accepted for publication in The AJ

We review the history of the discovery of field subgiant stars and their importance in the age dating of the Galactic disk. We use the cataloged data from the Hipparcos satellite in this latter capacity. Based on Hipparcos parallaxes accurate to 10% or better, the absolute magnitude of the lower envelope of the nearly horizontal subgiant sequence for field stars in the H-R diagram for B-V colors between 0.85 and 1.05 is measured to be M_V = 4.03 +/- 0.06. The age of the field stars in the solar neighborhood is found to be 7.9 +/- 0.7 Gyr by fitting the theoretical isochrones for [Fe/H] = +0.37 to the lower envelope of the Hipparcos subgiants. The same grid of isochrones yields ages, in turn, of 4.0 +/- 0.2 Gyr, 6.2 +/- 0.5 Gyr, and 7.5 to 10 Gyr for the old Galactic clusters M67, NGC188, and NGC6791. The ages of both the Galactic disk in the solar neighborhood and of NGC6791 are, nevertheless, likely between 3 and 5 Gyr younger than the oldest halo globular clusters, which have ages of 13.5 Gyr. The most significant results are (1) the supermetallicity of the oldest local disk stars, and (2) the large age difference between the most metal-poor component of the halo and the thick and thin disk in the solar neighborhood. These facts are undoubtedly related and pose again the problem of the proper scenario for the timing of events in the formation of the halo and the Galactic disk in the solar neighborhood. [Abstract Abridged], 44 pages, 12 Figures; accepted for publication in PASP; high resolution versions of Figures 1, 2, 6 and 9 available at http://bubba.ucdavis.edu/~lubin/Sandage/

Cepheids have been observed in NGC 5236 (M83) using the Antu (Unit Telescope 1) 8.2 m telescope of the ESO Very Large Telescope with the Focal Reducer/Low Dispersion Spectrograph 1. Repeated imaging observations have been made between 2000 January and 2001 July. Images were obtained in 34 epochs in the V band and in six epochs in the I band. The photometry was made with the ROMAFOT reduction package and checked independently with DoPHOT and a modified version of HSTPHOT. Twelve Cepheid candidates have periods ranging between 12 and 55 days. The dereddened distance modulus is adopted to be (m - M)(0) = 28.25 +/- 0.15, which corresponds to a distance of 4.5 +/- 0.3 Mpc. The Cepheid distance of NGC 5253 has been rediscussed and strengthened by its SN 1972E. The mean distance of (m - M)(0) = 28.01 +/- 0.15 (based on SN 1972E) shows the galaxy to be a close neighbor of M83, suggesting that the two galaxies may have interacted in the past and thus possibly explaining the amorphous morphology of NGC 5253. The distance difference between M83 and NGC 5253 is only 0.5 +/- 0.4 Mpc. The projected distance is only similar to 0.15 Mpc. M83 is the principal member of the nearby M83 group containing also, besides NGC 5253, several dwarf members, for five of which tip of the red giant branch distances are available. The adopted group distance of (m - M)(0) = 28.28 +/- 0.10 (4.5 +/- 0.2 Mpc), together with its mean recession velocity of v(LG) = 249 +/- 42 km s(-1), shows again the extreme quietness of the local (1 - 10 Mpc) expansion field. M83. fits onto the local mean Hubble flow line of the velocity-distance relation (with H-0 similar to 60) with no significant deviation, supporting the earlier conclusion that the local velocity expansion field is remarkably cold on a scale of 10 Mpc, contrary to the predictions of the simplest cold dark matter model for large-scale structure. The role of a cosmological constant has been invoked as a possible solution in providing a nearly uniform force field everywhere in the presence of a lumpy galaxy distribution.

The Teerikorpi cluster incompleteness bias for galaxy clusters is demonstrated using a simplified model of an artificial cluster. The distance indicator for this demonstration is the combination of the Hubble morphological type (T) and the van den Bergh luminosity class (L) introduced in Paper V. The model shows that the luminosity function must be sampled to ~3.5 mag fainter than the brightest cluster galaxy if a distance modulus that is accurate to ~0.1 mag is to be achieved using the T-L method. The bias properties of the artificial model are demonstrated using actual data from the complete catalogs of the Virgo and the Ursa Major Cluster galaxies. The derived bias-free distance moduli derived from the data are (m - M)0 = 31.95 ± 0.15 mag for the Virgo complex and (m - M)0 = 31.61 ± 0.13 for the Ursa Major Cluster. These are larger than the values of (m - M)0 = 30.80 mag for Virgo and 30.95 mag for Ursa Major derived by Pierce & Tully in 1988 from the Tully-Fisher method. The Virgo modulus here is also larger than the (m - M) = 30.81 mag adopted by the "Key Project" consortium in their work for the Hubble constant, but it is consistent with 31.7 derived earlier by many methods. This modulus, combined with other data, led to H0 = 58 ± 6 km s-1 Mpc-1 in earlier papers and derived most securely from the Cepheid calibration of the mean absolute magnitude of Type Ia supernovae (e.g., Saha et al.; Parodi et al.).

Photometric data for 34 early-type galaxies in the three high-redshift clusters Cl 1324+3011 (z = 0.76), Cl 1604+4304 (z = 0.90), and Cl 1604+4321 (z = 0.92), observed with the Hubble Space Telescope (HST) and with the Keck 10-meter telescopes by Oke, Postman & Lubin, are analyzed to obtain the photometric parameters of mean surface brightness, magnitudes for the growth curves, and angular radii at various Petrosian eta radii. The angular radii at eta = 1.3 mag for the program galaxies are all larger than 0.24". All of the galaxies are well resolved at this angular size using HST whose point-spread function is 0.05", half width at half maximum. The data for each of the program galaxies are listed at eta = 1.0, 1.3, 1.5, 1.7, and 2.0 mag. They are corrected by color equations and K terms for the effects of redshift to the rest-frame Cape/Cousins I for Cl 1324+3011 and Cl 1604+4304 and R for Cl 1604+4321. The K corrections are calculated from synthetic spectral energy distributions derived from evolving stellar population models of Bruzual & Charlot which have been fitted to the observed broad-band (BVRI) AB magnitudes of each program galaxy. The listed photometric data are independent of all cosmological parameters. They are the source data for the Tolman surface brightness test made in Paper IV.

This paper is partly a review of the history of the making of the Mount Wilson Catalogue of Photographic Magnitudes in Selected Areas 1-139 (hereafter the MWC), begun in 1909 and completed in 1930, and it is partly the presentation of new photometric results concerning it. Photoelectric photometry of 435 stars in the 11 Selected Areas of SA 28, 29, 45, 55, 57, 71, 82, 94, 106, 107, and 118 of the MWC is given. The data are used to derive magnitude corrections to the MWC for these areas. Ten of the areas are in the Galactic meridional plane (Galactic longitudes of 0° and 180°). These are the same areas used by Becker in his Basel program of star counts for the study of Galactic structure.The first purpose of the paper is to extend the Basel star counts to fainter magnitudes. For this, 200 inch photographic plates were measured to the plate limits near B = 22, calibrated with the photoelectric photometry listed here. A second purpose is to derive certain properties of the catalog. The interests are (1) to determine the internal (random) measuring errors of the MWC as a function of magnitude after correcting for the systematic scale error in each area, (2) to test for a color equation between the corrected mpg(MWC) values and the Bpe system that must be present because of the difference in reflectivity between silvered and aluminized mirrors, and (3) to test for possible distance-to-center corrections of the scale-corrected MWC magnitudes.Photographic photometry is used to complete the count surveys in each of the program areas to the limit of the 200 inch plates. Color-magnitude diagrams are shown for each area, generally complete to V = 20, B–V = 2.0. The work is preparatory to an analysis for Galactic structure when the larger database is available in a program by Majewski using Kitt Peak 4 m plates, epoch circa 1975, that will be to provide both a deeper count survey in B and V and proper motions for the larger sample.

Type-speciÐc luminosity functions on the magnitude system of the Revised Shapley- M B(T) 0,i Ames Catalog (RSA) are derived for distance-limited samples of galaxies for all Hubble types and van den Bergh luminosity classes listed in the RSA. The distributions of 21 cm line widths are derived for the Sa to Sd spirals and the Sm/Im types in the same samples. The distance-limited subsamples have been separated from the complete Nux-limited listings in the RSA using properties of Spaenhauer diagrams. Each type-speciÐc luminosity function is bounded on the bright and faint ends. All galaxies in the sample that have an appreciable spiral pattern are brighter than There are no dwarf spirals M B(T) 0,i \( 15 (H 0 \ 50). in this sample. Galaxies on the exponentially rising faint end of "" general II luminosity functions in the recent literature called "" spirals II are not galaxies with spiral arms but rather are star-forming galaxies of Sm and Im types. The distinction is crucial in predictions of the morphological mix expected at faint apparent magnitudes and large redshifts. One of the purposes of this paper is to begin to provide the necessary morphological resolution to adjudicate the high-redshift suggestions for an appreciable morphological evolution with look-back time. The brightest and fastest rotating galaxies along the present-day Hubble sequence are large-bulge Sa types. The faintest and slowest rotators are Sd and Sm/Im galaxies. The luminosity function of E galaxies is appreciably fainter than for all spirals earlier than Sc IIEIII. S0 galaxies that have pronounced disk charac- teristics are fainter than those with "" intermediate II (I) and/or "" subtle II (S) S0 characteristics. Bias in the slope and zero point of the Tully-Fisher (TF) relation in Nux-limited samples compared with distance-limited subsamples is demonstrated using Sb and Sbc galaxies, similar to that shown for Sc galaxies in Paper VII. A Ðne structure in the TF correlation that varies with Hubble type and van den Bergh luminosity class is suggested for Sb and Sbc galaxies, also similar to that set out for Sc galaxies in Paper VII. The sense is that at Ðxed absolute magnitude the later luminosity classes (i.e., larger L numbers) for a Ðxed Hubble type have higher rotational velocities by D4% per luminosity L number. Said di†erently, the Sb, Sbc, and Sc galaxies with less developed spiral arms rotate faster at a given absolute magnitude. A larger sample is required to prove or disprove the trend seen in the present data.

Five episodes from the 1950s are reviewed that led to a fundamental change in prevalent hypotheses of how, when, and where the chemical elements were formed. The episodes are (1) the discovery that all stars do not have the same abundance ratios of heavy elements to hydrogen, and the inventions of methods to detect and measure the variations, culminating in the fundamental paper by Chamberlain and Aller; (2) Roman's discovery of the ultraviolet excess in 17 high-velocity F subdwarfs, and the subsequent discovery of the excess in globular cluster stars; (3) the development of the understanding of the physics of the H-R diagram and the evolution of stars, explaining the various sequences in that diagram; (4) Hoyle's idea of the recyclying of the products of nucleosynthesis from stellar interiors of evolving stars through the interstellar medium by stellar mass loss and supernovae explosions; and (5) the development of the theory of the various nuclear processes in stellar interiors by a small number of different buildup mechanisms (equilibrium burning, slow neutron capture using normally produced neutrons, proton capture, and fast neutron capture in supernova explosions) that can produce all the chemical elements.

Relative, reduced to absolute, magnitude distributions are obtained for Sb, Sbc, and Sc galaxies in the flux-limited Revised Shapley-Ames Catalog (RSA2) for each van den Bergh luminosity class (L), within each Hubble type (T). The method to isolate bias-free subsets of the total sample is via Spaenhauer diagrams, as in previous papers of this series. The distance-limited type and class-specific luminosity functions are normalized to numbers of galaxies per unit volume (105 Mpc3), rather than being left as relative functions, as in Paper V. The functions are calculated using kinematic absolute magnitudes, based on an arbitrary trial value of H0 = 50. Gaussian fits to the individual normalized functions are listed for each T and L subclass. As in Paper V, the data can be freed from the T and L dependencies by applying a correction of 0.23T + 0.5L to the individual absolute magnitudes. Here, T = 3 for Sb, 4 for Sbc, and 5 for Sc galaxies, and the L values range from 1 to 6 as the luminosity class changes from I to III-IV. The total luminosity function, obtained by combining the volume-normalized Sb, Sbc, and Sc individual luminosity functions, each corrected for the T and L dependencies, has an rms dispersion of 0.67 mag, similar to much of the Tully-Fisher parameter space. Absolute calibration of the trial kinematic absolute magnitudes is made using 27 galaxies with known T and L that also have Cepheid distances. This permits the systematic correction to the H0 = 50 kinematic absolute magnitudes of 0.22 ± 0.12 mag, giving The Cepheid distances are based on the Madore/Freedman Cepheid period-luminosity (PL) zero point that requires (m - M)0 = 18.50 for the LMC. Using the modern LMC modulus of (m - M)0 = 18.58 requires a 4% decrease in H0, giving a final value of H0 = 53 ± 7 (external) by this method. These values of H0, based here on the method of luminosity functions, are in good agreement with (1) H0 = 55 ± 5 by Theureau and coworkers from their bias-corrected Tully-Fisher method of "normalized distances" for field galaxies; (2) H0 = 56 ± 4 from the method through the Virgo Cluster, as corrected to the global kinematic frame (Tammann and coworkers); and (3) H0 = 58 ± 5 from Cepheid-calibrated Type Ia supernovae (Saha and coworkers). Our value here also disagrees with the final value from the NASA "Key Project" group value of H0 = 70 ± 7. Analysis of the total flux-limited sample of Sb, Sbc, and Sc galaxies in the RSA2 by the present method, but uncorrected for selection bias, would give an incorrect value of H0 = 71 using the same Cepheid calibration. The effect of the bias is pernicious at the 30% level; either it must be corrected by the methods in the papers of this series, or the data must be restricted to the distance-limited subset of any sample, as is done here.

Predictions are made of the effect of variations in the [Fe/H] metallicity on the zero point of the Cepheid period-luminosity relation in bolometric, B, V, and I magnitudes. Theoretical evolutionary tracks in the H-R diagram, computed by three independent groups at Geneva, Padua, and Basel, are combined with the positions of the blue and red edges of the instability strip in the relevant H-R diagrams to give the predicted P-L relations for [Fe/H] metallicities of 0.0, -0.4, -0.7, -1.3, and -1.7. The predictions are based on the pulsation equation, P(,L,Te,Z,Y), calculated at the points where the tracks of a given mass for each metallicity intersect the instability strip in the H-R diagrams. New model atmospheres and synthetic spectra are computed giving sets of grids of the bolometric corrections and B - V, V - R, R - I, and V - I colors for temperatures between 7500 and 5000 K, gravities between log g = 3.0 and log g = 0.75, and metallicities between [Fe/H] = 0.0 and [Fe/H] = -1.7. Interpolation in the grids at the relevant temperatures, gravities, and metallicities of the Cepheid instability strip give theoretical P-L relations on the Cape Cousins BVI photometric system at the blue and red edges of the strip. The metallicity dependence of the P-L relations, read at P = 10 days, are dM/d[Fe/H] = 0.00 mag dex-1 in M(bol), +0.03 mag dex-1 in B, -0.08 mag dex-1 in V, and -0.10 mag dex-1 in I in the sense that lower metallicities mean brighter magnitudes in B and fainter ones in V and I. Similar dependencies are found at P = 31.6 days. Confirmation that the zero points of the Cepheid P-L relations are not steeper functions of [Fe/H] than the theoretical values derived here is found by comparing the distance moduli of the LMC, the SMC, and IC 1613 based on the P-L relation for Galactic Cepheids (〈[Fe/H]〉 = 0) with the distance moduli determined for these galaxies using RR Lyrae variables with the steep absolute magnitude-metallicity calibration of MV(RR) = 0.30[Fe/H] + 0.94. Applying this bright calibration, based on the Oosterhoff-Arp-Preston (OAP) metallicity effect, to the RR Lyrae variables in the LMC, the SMC, and IC 1613 gives individual distance moduli that agree to within 0.10 mag with the Cepheid distance moduli for [Fe/H] =0 for each galaxy, confirming that no metallicity dependence of the Cepheid P-L relation can be detected at this level with the present observational data if the bright RR Lyrae MV ([Fe/H]) calibration is used. Using the stated calibrations with the Cepheid data from the literature gives the distance modulus of the LMC to be (m - M)0 = 18.57. The modulus for the SMC, corrected for the mild metallicity effect derived here, reconciles the deviant individual B, V, and I moduli to within ±0.01 mag, giving (m - M)0 = 18.94 for the SMC.

PROLOGUE▪ Abstract In 1999 we celebrate the 50th anniversary of the initial bringing into operation of the Palomar 200-inch Hale telescope. When this telescope was dedicated, it opened up a much larger and clearer window on the universe than any telescope that had gone before.Because the Hale telescope has played such an important role in twentieth century astrophysics, we decided to invite one or two of the astronomers most familiar with what has been achieved at Palomar to give a scientific commentary on the work that has been done there in the first fifty years.The first article of this kind which follows is by Allan Sandage, who has been an active member of the staff of what was originally the Mount Wilson and Palomar Observatories, and later the Carnegie Observatories for the whole of these fifty years.The article is devoted to the topics which covered the original goals for the Palomar telescope, namely observational cosmology and the study of galaxies, together with discoveries that were not anticipated, but were first made at Palomar and which played a leading role in the development of high energy astrophysics.The Palomar work first showed how optical astronomy would be the key to our understanding of observations made in other parts of the electromagnetic spectrum, particularly at radio wavelengths and at X-ray energies. —Geoffrey Burbidge, EditorAn account is given of the history of two observational programs set for the Palomar 200-inch telescope, one by Walter Baade and the other by Edwin Hubble near the start of the scheduled operation of the telescope 50 years ago. The review is partly an assessment of whether, and how well, these programs have been carried to completion, and partly an account of the response of Palomar to new discoveries and developments not foreseen in 1950. Stellar evolution, the discovery of variations in the metallicity of stars of different populations, the chemical evolution of the Galaxy, the Cepheid P-L relation, the redshift-distance relation of the expanding universe, and the extragalactic distance scale are discussed as they relate to the predictions for progress on the programs set out by Baade and Hubble. Not foreseen was the invention and development of radio astronomy and high energy astrophysics, leading to the discovery of radio galaxies, quasars, and the gradual realization of violent events, both in stars and in galaxies. The review is highly restricted to these subjects, covering only three areas among the totality of the work in observational astrophysics studied during the first 50 years at Palomar.

A distance-limited subset of the complete flux-limited sample of Sc galaxies in the Revised Shapley-Ames Catalog of Bright Galaxies is isolated by means of separate Spaenhauer diagrams for six individual van den Bergh luminosity class intervals from Sc I + I.2, .3 to Sc III–IV. The distribution functions of kinematic absolute B(220, 50) magnitudes and 21 cm line widths, W20, corrected to edge-on orientation, have been determined for the same six bins of luminosity class. The individual luminosity functions for each luminosity class are bounded on both the bright and faint ends, showing that the present sample includes no dwarf Sc spirals fainter than M(BT)(220, 50) = -18 belonging to luminosity classes I to III–IV, as defined by the regularity of the spiral pattern. Star-forming galaxies with spiral structures as regular as the ones found in these luminosity classes have absolute magnitudes brighter than MB(H = 50) = -18 and 21 cm line widths larger than W20/ sin i = 2vrot(max) = 165 km s-1. Furthermore, the 21 cm line-width distributions move toward smaller rotational velocities as the luminosity classes change from I to III, showing that rotation is a principal parameter determining the regularity of the spiral pattern. Whether it is the only parameter awaits a similar investigation for spirals of all luminosity classes along the complete Hubble sequence. In particular, it has not yet been proved that all Im and Sm galaxies, where, by definition, the spiral arms are either lacking or are semichaotic, have absolute magnitudes that are fainter than MB = -18 and whose 21 cm LWs are smaller than ~165 km s-1, presumably because of smaller mass than the high-luminosity, regular spirals. The Teerikorpi "cluster population incompleteness bias" is demonstrated again. Here, however, as in Papers II–IV of this series, we use field galaxies to show that the slope and zero point of the Tully-Fisher (T-F) relation are systematically incorrect for flux-limited samples, the error increasing with redshift. The data also support the possibility that the zero point of the T-F relation for Sc galaxies, even in the distance-limited sample, is a function of luminosity class, varying by 0.42 mag between Sc I + I.2, .3 and Sc III galaxies if the slope of the T-F relation for each class is taken to be that of the fundamental calibrating galaxies with Cepheid distances. If true, this is presumably due to differences in the mass distribution and, therefore, in the resulting rotational velocity field as a function of luminosity class even within a fixed Hubble type.

The distance of the Virgo cluster is derived in the B band from the 21 cm-line width-absolute magnitude relation. The latter is calibrated using 18 spirals with Cepheid distances mainly from HST. The calibration is applied to a complete sample of non-peculiar spirals with i>45 deg and lying within the optical (n=49) or X-ray (n=35) contour of the cluster, resulting in a mean cluster distance of (m-M)_0=31.58+/-0.24 mag (external error) or 20.7+/-2.4 Mpc. The mean distance of subcluster A is 0.46+/-0.18 mag smaller than that of subcluster B, but the individual distances of the members of the two substructures show considerable overlap. The distance modulus is corrected by -0.07 mag for the fact that cluster members have lower H I-surface fluxes and are redder in (B-I) at a given line width than the (field) calibrators. Different sources of the B magnitudes and line widths have little effect on the resulting distance. Different precepts for the internal-absorption correction change the result by no more than +/-0.17 mag. The individual distances of the cluster members do not show any dependence on recession velocity, inclination, Hubble type or line width. The dependence on apparent magnitude reflects the considerable depth effect of the cluster. The adopted distance is in good agreement with independent distance determinations of the cluster. Combining the cluster distance with the corrected cluster velocity of 1142+/-61 km/s gives H_0=55+/-7 km/s/Mpc (external error). If the Virgo cluster distance is inserted into the tight Hubble diagram of clusters out to 11000 km/s using relative distances to the Virgo cluster one obtains a global value of H_0=57+/-7 km/s/Mpc.

Comparisons show agreement at the 0.1-mag level between the calibration of the Cepheid period–luminosity (P–L) relation by Feast & Catchpole (FC) using the early release of Hipparcos data and four previous ground-based calibrations, three of which are either largely or totally independent of the distance to the Large Magellanic Cloud (LMC). Each of the comparisons has the sense that the FC calibration is brighter, but only at the level of ≲0.1 mag. In contrast, FC argue that their Hipparcos recalibration leads to a 0.2-mag revision in the distance to the LMC, and thereby to a 10 per cent decrease in the Hubble constant. We argue differently. The comparison of the Hipparcos recalibration with others should be made using only local Galactic Cepheids, not based on Cepheids in the LMC that require a set of precepts that are not germane to the direct Hipparcos recalibration. The comparison made here, using only Galactic Cepheids, gives a correction of ∼4 per cent or less to our value of H0 based on Type Ia supernovae, keeping all other factors and precepts the same. A second success of the Hipparcos mission is the calibration of the position of the main sequence in the Hertzsprung–Russell diagram as a function of metallicity using local subdwarfs. These data have been used by Reid and by Gratton et al. to obtain, similarly to FC, a brighter absolute magnitude of RR Lyrae stars by ∼0.3 mag from that often currently adopted. These new calibrations confirm the earlier brighter calibrations by Walker, by Sandage, and by Mazzitelli, D'Antona & Caloi, thereby reducing the ages of globular clusters by ∼30 per cent. This removes most of the cosmological time-scale problem if H0∼55 km s−1 Mpc−1. A similar conclusion, based on pulsation theory and MACHO data, has been reached by Alcock et al.

Repeated imaging observations have been made of NGC 3982 with the Hubble Space Telescope between 2000 March and May, over an interval of 53 days. Images were obtained on 12 epochs in the F555W band and on five epochs in the F814W band. The galaxy hosted the Type Ia supernova (SN Ia) SN 1998aq. A total of 26 Cepheid candidates were identified, with periods ranging from 10 to 45 days, using photometry with the DoPHOT program. The dereddened distance to NGC 3982 is estimated from these data using various criteria to maximize signal-to-noise ratio and reliability: the values lie between 31.71 and 31.82, with uncertainties in the mean of typically ±0.14 mag for each case. A parallel analysis using photometry with HSTphot discovered 13 variables, yielding a distance modulus of 31.85 ± 0.16. The final adopted modulus is (M-m)0 = 31.72 ± 0.14 (22 ± 1.5 Mpc). Photometry of SN 1998aq that is available in the literature is used in combination with the derived distance to NGC 3982 to obtain the peak absolute magnitude of this supernova. The lower limit (no extinction within the host galaxy) for MV is -19.47 ± 0.15 mag. Corrections for decline rate and intrinsic color to carry these to the reduced system of Parodi and collaborators have been performed. The derived luminosities at hand are fully consistent with the mean of the eight normal SNe Ia previously calibrated with Cepheids. Together they yield H0 ≈ 60 ± 2(internal) km s-1 Mpc-1 based on an assumed LMC distance modulus of 18.50. We point out that correcting some of the systematic errors and including uncertainty estimates due to them leads to H0 = 58.7 ± 6.3(internal) km s-1 Mpc-1.

Cepheid variables have been found in the SBcII galaxy NGC 4496A, parent to the Type Ia supernova 1960F. Of the 130 variables discovered with the Hubble Space Telescope (HST) over a 70 day observing internal from 1994 June to August, comprising 17 epochs in the F555W band and four epochs in the F814W band, 95 are bona fide Cepheids. The periods range from 7 days to greater than 70 days, with the mean magnitudes ranging from V = 24.4 to 26.8. The distance modulus of NGC 4496A, based on the Cepheids, is (m ? M)0 = 31.03 ? 0.14, where a formal reddening of E(V ? I) = 0.04 ? 0.06 derived from the colors of the Cepheids has been used to account for possible extinction. There is no measurable differential reddening over the field. The absolute magnitudes of SN 1960F at maximum are M(B)max = -19.43 ? 0.17 and M(V)max = ?19.52 ? 0.21. Combining these absolute magnitudes with the Hubble diagrams of Branch normal Type Ia supernovae (SNe Ia), determined earlier, gives Hubble constants, based on SN 1960F alone, of HO(B) = 56 ? 9 km s?1,? ? ?(1) and H0(V) = 55 ? 9 km s?1.? ? ?(2) Combining the calibration of SN 1960F here with six other extant calibrations set out in Paper VII gives interim mean absolute magnitude calibrations of M(B)max = ?19.45 ? 0.07 and M(V)max = ?19.47 ? 0.07, with no evidence for appreciable dependence on the light-curve decay rate. These mean interim calibrations require H0(B) = 57 ? 4 km s?1 and H0(V) = 58 ? 4 km s-1 Mpc?1.

An alternate calculation to that made by Whitmore et al. (WSLMB) is set out for the distance to M87 using their globular cluster luminosity function (GCLF) for M87 in the Virgo Cluster. They have concluded from these data that H0 = 78 ± 11 km s-1 Mpc-1. Our purpose is to show how a different set of precepts leads to a substantially smaller value of H0 that is in statistical agreement with other analyses that favor the long distance scale. Adopting the WSLMB observed turnover apparent magnitude for the GCLF of V = 23.79 ± 0.2 (external), together with AV = 0.00 mag for the foreground Galactic absorption, and MV0 = -7.62 ± 0.2 (external) as the calibration of the turnover luminosity gives (m - M)0 = 31.41 ± 0.28 for the distance modulus of M87. Using the cosmic velocity of the E galaxy Virgo core as v(cosmic) = 1179 ± 17 km s-1 gives H0 = 62 ± 9 km s-1 Mpc-1. The procedure of WSLMB and others in stepping a Virgo distance to the Coma Cluster and then using a Coma velocity that still contains a random component to determine H0 is argued. The cosmic velocity for Virgo, calculated by reading a Hubble diagram of relative distances of 17 "remote" clusters versus cosmic microwave background velocities at zero modulus difference to Virgo (Jerjen & Tammann), overcomes this error by circumventing the problem of accounting for any random and/or streaming motions of the Virgo Cluster and/or of the Coma Cluster about the ideal Hubble flow. This procedure cuts to the core of the distance scale problem, eliminating the major uncertainty concerning local random motions. Four sources of possible systematic errors in the Virgo Cluster modulus using the GCLF method, as applied to M87, are also set out, suggesting that the value of H0 = 62 is an upper limit.

The metal-poor, fundamental-mode (P0) and first-overtone (P1) Cepheids in the dwarf galaxies IC 1613, WLM, Pegasus, Sextans A, Sextans B, and Leo A are compared with the about equally metal-poor Cepheids of the Small Magellanic Cloud (SMC). The period-color (P-C) and period-luminosity (P-L) relations of the seven galaxies are indistinguishable, but differ distinctly from those in the Large Magellanic Cloud (LMC) and the solar neighborhood. Adopting (m-M)^{0}_{SMC}=18.93 from independent evidence, one can determine reliable distance moduli for the other dwarf galaxies of (m-M)^{0} = 24.34+/-0.03, 24.95+/-0.03, 24.87+/-0.06, 25.60+/-0.03 (mean for Sextans A & B), and 24.59+/-0.03, respectively., 14 pages, 10 figures, 5 tables, accepted for publication in Astronomy and Astrophysics. v2: restructured the whole paper and redrawn all figures

The photometric data for 460 classical, fundamental-mode Cepheids in the SMC with log P > 0.4 measured by Udalski et al. have been analyzed for their P-C and P-L relations, and for the variation of amplitude across the instability strip in a similar way that was done in Papers I and II of this series. The SMC Cepheids are bluer in (B-V) at a given period than for both the Galaxy and the LMC. Their P-C relation in (B-V) is best fit by two lines intersecting at P=10 d. Their break must necessarily exist also in the P-L relations in B and/or V, but remains hidden in the magnitude scatter. An additional pronounced break of the P-L relations in B, V, and I occurs at P=2.5 d. The observed slope of the lines of constant period in the HR diagram agrees with the theoretical expectation from the pulsation equation. The largest amplitude Cepheids for periods less than 13 days occur near the blue edge of the instability strip. The sense is reversed in the period interval from 13 to 20 days, as in the Galaxy and the LMC. The SMC P-L relation is significantly flatter than that for the Galaxy, NGC 3351, 4321, M31, all of which have nearly the same steep slope. The SMC P-L slope is intermediate between that of these steep slope cases and the very shallow slope of Cepheids in the lower metallicity galaxies of NGC 3109 and Sextans A/B, consistent with the premise that the Cepheid P-L relation varies from galaxy-to-galaxy as function of metallicity. Failure to take into account the slope differences in the P-L relation as a function of metallicity using Cepheids as distance indicators results in incorrect Cepheid distances. Part of the 15% difference between our long distance scale - now independently supported by TRGB distances - and that of the HST Key Project short scale is due to the effect of using an inappropriate P-L relation., 9 pages, 10 figures, accepted for publication in Astronomy & Astrophysics

Any calibration of the present value of the Hubble constant requires recession velocities and distances of galaxies. While the conversion of observed velocities into true recession velocities has only a small effect on the result, the derivation of unbiased distances which rest on a solid zero point and cover a useful range of about 4-30 Mpc is crucial. A list of 279 such galaxy distances within v4.5 Mpc. RR Lyr star-calibrated TRGB distances of 78 galaxies above this limit give H_0=63.0+/-1.6 at an effective distance of 6 Mpc. They compensate the effect of peculiar motions by their large number. Support for this result comes from 28 independently calibrated Cepheids that give H_0=63.4+/-1.7 at 15 Mpc. This agrees also with the large-scale value of H_0=61.2+/-0.5 from the distant, Cepheid-calibrated SNe Ia. A mean value of H_0=62.3+/-1.3 is adopted. Because the value depends on two independent zero points of the distance scale its systematic error is estimated to be 6%. Typical errors of H_0 come from the use of a universal, yet unjustified P-L relation of Cepheids, the neglect of selection bias in magnitude-limited samples, or they are inherent to the adopted models., 44 pages, 4 figures, 6 tables, accepted for publication in the Astronony and Astrophysics Review 159

The extragalactic distance scale relies heavily on Cepheids. However, it has become clear from observations and pulsation models that the slope and zero point of their P-L relations differ from galaxy to galaxy. This makes the determination of Cepheid distances complex and calls for an independent test of their differences. The test is provided by RR Lyrae star distances of 24 galaxies which calibrate the tip of the red-giant branch (TRGB; M_I = -4.05), which in turn confirms the adopted Cepheids distances on our 2006 distance scale in 18 cases to within 0.1 mag on average. Relative SN Ia and velocity distances deny a remaining significant metallicity effect of the adopted distances. The new support for these Cepheid distances increases the weight of our previous calibration of the SN Ia luminosity and of the 21cm line width - luminosity (TF) relation. The value of H_0 = 62.3 (+/-5) is confirmed on all scales., Comment: 55 pages, 9 figures, 9 tables, accepted for publication in the Astrophysical Journal

With this paper we continue the preparation for a forthcoming summary report of our experiment with the Hubble Space Telescope (HST) to determine the Hubble constant using type Ia supernovae as standard candles. Two problems are addressed. (1) We examine the need for, and determine the value of, the corrections to the apparent magnitudes of our program Cepheids in the eleven previous calibration papers due to sensitivity drifts and charge transfer effects of the HST WFPC2 camera over the life time of the experiment from 1992 to 2001. (2) The corrected apparent magnitudes are applied to all our previous photometric data from which revised distance moduli are calculated for the eight program galaxies that are parents to the calibrator Ia supernovae. Two different Cepheid P-L relations are used; one for the Galaxy and one for the LMC. These differ both in slope and zero-point at a fixed period. The procedures for determining the absorption and reddening corrections for each Cepheid are discussed. Corrections for the effects of metallicity differences between the program galaxies and the two adopted P-L relations are derived and applied. The distance moduli derived here for the eight supernovae program galaxies, and for 29 others, average 0.20 mag fainter (more distant) than those derived by Gibson et al. and Freedman et al. in their 2000 and 2001 summary papers for reasons discussed in this paper. The effect on the Hubble constant is the subject of our forthcoming summary paper., Comment: 73 pages, 16 figures, 8 tables, accepted for publication in the Astrophysical Journal

Photometric BVI and redshift data corrected for streaming motions are compiled for 111 "Branch normal", 4 1991T-like, 7 1991bg-like, and 2 unusual SNe Ia. Color excesses E(B-V)host of normal SNe Ia, due to the absorption of the host galaxy, are derived by three independent methods leading to the intrinsic colors at maximum of (B-V)00=-0.024, and (V-I)00=-0.265 if normalized to a common decline rate of Dm_15=1.1. The strong correlation between redshift absolute magnitudes (based on Ho=60), corrected only for the extrinsic Galactic absorption, and the derived E(B-V)host leads to well determined, yet abnormal absorption-to-reddening ratios of R_BVI=3.65, 2.65, and 1.35. Comparison with the canonical Galactic values of 4.1, 3.1, 1.8 forces the conclusion that the law of interstellar absorption in the path length to the SN in the host galaxy is different from the local Galactic law. Improved correlations of the fully corrected absolute magnitudes with host galaxy type, decline rate, and intrinsic color are derived. The four peculiar 1991T-type SNe are significantly overluminous as compared to Branch-normal SNe Ia. The overluminosity of the seven 1999aa-like SNe is less pronounced. The seven 1991bg-types in the sample constitute a separate class of SNeIa, averaging in B two magnitudes fainter than the normal Ia. New Hubble diagrams in BVI are derived out to ~30,000kms-1 using the fully corrected magnitudes and velocities, corrected for streaming motions. Nine solutions for the intercept magnitudes in these diagrams show extreme stability at the 0.04 level using various subsamples of the data. The same precepts for fully correcting SN magnitudes we shall use for the luminosity recalibration of SNe Ia in the forthcoming final review of our HST Cepheid-SN experiment for the Hubble constant., Comment: 49 pages, 15 figures, 8 tables, accepted for publication in the Astrophysical Journal

The purpose of the paper is to predict the temperature at the fundamental blue edge (FBE) of the instability strip for RR Lyrae (RRL) variables from the pulsation equation that relates temperature to period, luminosity, and mass. Modern data for the correlations between period, luminosity, and metallicity at the FBE for field and cluster RRL are used for the temperature calculation. The predicted temperatures are changed to B-V colors using an adopted color transformation. The predicted temperatures at the FBE become hotter as [Fe/H] changes from 0 to -1.5, and thereafter cooler as the metallicity decreases to -2.5 and beyond. The temperature range over this interval of metallicity is $\Delta$log $T_e$ = 0.04, or 640 K at 6900K. The predicted color variation is at the level of 0.03 mag in B-V. The predictions are compared with the observed RRL colors at the FBE for both the field and cluster variables, showing general agreement at the level of 0.02 mag in (B-V)$_o$, which, however, is the uncertainty of the reddening corrections. The focus of the problem is then reversed by fitting a better envelope to the observed FBE relation between color and metallicity for metallicities smaller than -1.8 which, when inserted in the pulsation equation, gives a non-linear calibration ...., Comment: 34 pages, 11 figures, 2 tables. To appear in March 2006 AJ

Photometric data for 593 Cepheids in the LMC, measured by Udalski et al. in the OGLE survey, augmented by 92 longer period Cepheids from other sources, are analyzed for the P-C and P-L relations, and for the variations of amplitude, light curve shape, and period across the instability strip at constant absolute magnitude. Both the P-C and P-L relations have different slopes for periods smaller and larger than 10 days. The break at 10 days is also seen in the period-amplitude relations, and the compound Fourier combinations of R_21 and Phi_21 introduced by Simon and Lee. The LMC Cepheids are bluer than Galactic Cepheids in the B,V,I color bands, part of which is due to differential Fraunhofer line blanketing and part to real differences in the temperature boundaries of the instability strip. The LMC strip is hotter by between 80K and 350K depending on the period. Hence, both the slopes and (necessarily) the zero points of the P-L relations in B,V,I must differ between LMC and the the Galaxy, and in fact they do. The LMC Cepheids are brighter by up to 0.5 mag at log P=0.4 (2 days) and fainter by 0.2 mag at log P=1.5 (32 days). These facts complicate the use of Cepheid as precision distance indicators until the reason is found for the non-universality of the P-L and P-C relations. The very large data base permits mapping of various Cepheid properties at different positions within the instability strip, both at constant period and at constant absolute magnitude over the range of 2 < P < 40 days and -2 > M_V > -5. (...), 50 pages, 20 figures, 5 tables, accepted for publication in Astronomy and Astrophysics. Minor changes in text and figures due to extended Table1

321 Galactic fundamental-mode Cepheids with good B,V,I photometry by Berdnikov et al. 2000 and with homogenized color excesses E(B-V) based on Fernie et al. 1995 are used to determine their P-C relation in the range 0.4, Comment: 29 pages, 19 figures, 7 tables. Accepted for publication in Astronomy and Astrophysics

We have detected a population of predominantly blue (B-V, 13 pages, 3 figures, submitted to ApJL, accepted for ApJ

We review a sample of the early literature in which the reality of the expansion is discussed, explain Hubble's reticence to accept the expansion as real, and contrast the Tolman surface brightness test with three other modern tests. We search for the Tolman surface brightness depression with redshift using the Hubble Space Telescope (HST) data from Paper III for 34 early-type galaxies from the three clusters Cl 1324+3011 (z=0.76), Cl 1604+4304 (z=0.90), and Cl 1604+4321 (z=0.92). Depressions of the surface brightness relative to the zero-redshift fiducial lines in the mean surface brightness, log linear radius diagrams of Paper I are found for all three clusters. Expressed as the exponent, n, in 2.5 log (1 + z)^n mag, the value of n for all three clusters is n = 2.59 +/- 0.17 in the R band and 3.37 +/- 0.13 in the I band for a q_o = 1/2 model. The sensitivity of the result to the assumed value of q_o is shown to be less than 23% between q_o = 0 and +1. For a true Tolman signal with n = 4, the luminosity evolution in the look-back time, expressed as the exponent in 2.5 log (1+z)^(4-n) mag, must then be between 1.72 to 1.19 in the R band and 0.94 to 0.45 in the I band. We show that this is precisely the range expected from the evolutionary models of Bruzual & Charlot. We conclude that the Tolman surface brightness test is consistent with the reality of the expansion. We have also used the high-redshift HST data to test the ``tired light'' speculation for a non-expansion model for the redshift. The HST data rule out the ``tired light'' model at a significance level of better than 10 sigma., 36 pages, 6 figures; accepted for publication in the Astronomical Journal

To complete the Tolman surface brightness test on the reality of the expansion of the Universe, we need to measure accurately the surface brightness profiles of the high-redshift galaxy sample. We, therefore, investigate the effects of various sizes of point-spread-functions composed of telescope diffraction, CCD pixel resolutions, and ground-based seeing on the measurements of mean surface brightness. We have done the calculations using two synthetic galaxies of effective radii of 0.70" and 0.25" with point-spread functions of 0.1, 0.3, and 0.9 arcseconds. We have also compared actual observations of three high-redshift galaxies in the cluster Cl 1324 + 3011 (z = 0.76) made both with the Keck telescopes in seeing of about 0.9" and with HST which has a PSF that is approximately ten times smaller. The conclusion is that HST data can be used as far into the galaxy image as a Petrosian metric radius of eta = 1.3 magnitudes, whereas the ground-based data will have systematic errors of up to 2.9 magnitudes in the mean surface brightness at eta values of less than 2.2 magnitudes. In the final section, we compare the differences in derived average surface brightness for nearly circular galaxy images compared with highly flattened images. The comparison is made by using the two reduction procedures of (1) integrating the profile curves using circular apertures, and (2) approximating an ``equivalent circular'' galaxy that is highly elongated by using an ``effective'' radius of sqrt{ab}, where a and b are the semi-major and semi-minor axis, respectively, of the best-fitting ellipse. The conclusion is that the two methods of reduction give nearly identical results and that either method can be used to analyze the low and high-redshift galaxy samples used in the Tolman test., Comment: 15 pages, 9 figures; accepted for publication in Astronomical Journal

A sample of 35 SNe Ia with good to excellent photometry in B and V, minimum internal absorption, and 1200 < v < \approx 30000 km/s is compiled from the literature. As far as their spectra are known they are all Branch-normal. For 29 of the SNe Ia also peak magnitudes in I are known. The SNe Ia have uniform colors at maximum, i.e. =-0.012 mag (sigma=0.051) and =-0.276 mag (sigma=0.078). In the Hubble diagram they define a Hubble line with a scatter of $\sigma_M$=0.21-0.16 mag, decreasing with wavelength. The scatter is further reduced if the SNe Ia are corrected for differences in decline rate Delta_m_15 or color (B-V). A combined correction reduces the scatter to sigma, Comment: 42 pages, including 9 figures; submitted to ApJ

Data obtained in the 1950-1955 Palomar campaign for the discovery of classical novae in M81 are set out in detail. Positions and apparent B magnitudes are listed for the 23 novae that were found. There is modest evidence that the spatial distribution of the novae does not track the B brightness distribution of either the total light or the light beyond an isophotal radius that is $70\arcsec$ from the center of M81. The nova distribution is more extended than the aforementioned light, with a significant fraction of the sample appearing in the outer disk/spiral arm region. We suggest that many (perhaps a majority) of the M81 novae that are observed at any given epoch (compared with say $10^{10}$ years ago) are daughters of Population I interacting binaries. The conclusion that the present day novae are drawn from two population groups, one from low mass white dwarf secondaries of close binaries identified with the bulge/thick disk population, and the other from massive white dwarf secondaries identified with the outer thin disk/spiral arm population, is discussed. We conclude that the M81 data are consistent with the two population division as argued previously from (1) the observational studies on other grounds by Della Valle et al. (1992, 1994), Della Valle & Livio (1998), and Shafter et al. (1996) of nearby galaxies, (2) the Hatano et al. (1997a,b) Monte Carlo simulations of novae in M31 and in the Galaxy, and (3) the Yungelson et al. (1997) population synthesis modeling of nova binaries. Two different methods of using M81 novae as distance indicators give a nova distance modulus for M81 as $(m-M)_0 = 27.75$, consistent with the Cepheid modulus that is the same value., 24 pages, 7 figures, accepted to PASP

Periods and light curves have been measured with the Hubble Space Telescope for 20 Cepheids in NGC 4639, parent galaxy to the Type Ia, prototypical supernova SN 1990N. The periods range from 17 to 69 days. The mean apparent magnitudes, averaged over the light curves, range from V = 25.6 to V = 27.3. Well-determined period-luminosity relations exist in V and I. Corrected for differential extinction, these give a true modulus for NGC 4639 of (m - M)0 = 32.00 ± 0.23. Combining the light curves for SN 1990N with this modulus gives MB(max) = -19.30 ± 0.23 and MV(max) = -19.39 ± 0.23. This, together with six previous calibrations of Type Ia supernovae, gives the mean calibrations of "Branch normal" supernovae to date as MB(max) = -19.47 ± 0.07 and MV(max) = -19.48 ± 0.07. The resulting Hubble constants, reading the Type Ia supernova Hubble diagrams at very large redshifts beyond any possible local velocity anomalies, give global values of the Hubble constant of H0(B) = 56 ± 4 (internal) km s-1 Mpc-1 and H0(V) = 58 ± 4 (internal) km s-1 Mpc-1.

Photometry of stars is described that defines a UBV(RI)MW photometric system, established between 1975 and 1980 using the Mount Wilson 60-inch and 100-inch reflectors. The MW natural system has been reduced to the UBV(RI)C Cape-Cousins system by linear equations for stars hotter than M0. Strong non-linear color and magnitude equations exit in R and I between the two systems for stars cooler than M0. The non-linearity is due to the change of the effective wavelengths of the red passbands caused by effect of the TiO b ands combines with the substantial difference between red response of the extended S20 cathodes used here and the GaAs cells used by Cousins (1976, 1980a,b), Bessell (1979, 1990), Landolt (1983, 1992), and others for the Cape system. We report (R-I)MW and (V-I)MW colors based on a linear extension of the MW natural system to the red for cool stars with (V-R)Cape greater than 0.8, (V-I)Cape greater than 1.8 (spectral types later than M0), as zero-pointed to the Cape system for bluer stars. Color equations are derived between the MW, the Cape, the Kron-Eggen, and Johnson photometric systems, and also the Hubble Space Telescope (V-I) colors as reduced to the (V-I)C Cape system by Holtzman et al. (1995). The Kron-Eggen and the Cape-Cousins R and I systems differ in their zero points of color and magnitudes, showing that the Kron-Eggen and the Cousins systems are not the same. The appellation of a "Kron-Cousins" photometric system used in much of the current literature is incorrect. Preparatory to determining photometric parallaxes of local higher proper motion M dwarfs in Paper IV, trigonometric HR diagrams are determined in V, (V-R)MW and (V-I)MW on the Mount Wilson system using 160 available parallax stars with parallaxes larger than 0.099 arcsec. A first appendix illustrates the difference in the effective wavelengths of the Cape-Cousins, Kron-Eggen, and Johnson systems for cool stars, based on the observed slope coefficients of the color equations that link them. A second appendix contains explicit color equations based on stars in common between Bessell's (1990) definition of the Cape system for the reddest stars and the Kron-Eggen and the MW photometric systems.