Related papers: Verifying the Planetary Nebula Luminosity Function…
The methods of calibrating the luminosities of galactic Cepheids and determining Cepheid reddenings are considered in some detail. Together with work on NGC4258 this suggests that the calibration presented is valid to about 0.1mag (s.e.) at…
We have developed a Monte Carlo method to compute the luminosity function of galaxies, based on photometric redshifts, which takes into account the non-gaussianity of the probability functions, and the presence of degenerate solutions in…
We study morphology and luminosity segregation of galaxies in loose groups. We analyze the two catalogs of groups which have been identified in the Nearby Optical Galaxy (NOG) sample, by means of hierarchical and percolation…
We derive the relative distances to the Virgo, Fornax, and Coma clusters of galaxies by applying the Dn-sigma and the Fundamental Plane (FP) relations to the data of the homogeneous samples of early--type galaxies studied by Caon etal,…
Type Ia supernovae (SNe Ia), produced by the thermonuclear explosion of white dwarf (WD) stars, are used here to derive extragalactic distances and an estimate of the Hubble constant from their emission signatures at late phases ({\it…
We report on the discovery of Cepheids in the spiral galaxy NGC 2841, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. NGC 2841 was observed over 12 epochs using the F555W filter,…
Measuring the distances to Galactic planetary nebulae (PNe) has been an intractable problem for many decades. We have now established a robust optical statistical distance indicator, the H$\alpha$ surface brightness- radius or S-r relation,…
We compute the luminosity function of galaxies in groups. The data consists in two samples of groups of galaxies selected in distance and redshift space comprising a total number of 66 groups. The assignment of galaxies to the groups were…
We derive the basic properties of seven Galactic open clusters containing Cepheids and construct their period-luminosity (P-L) relations. For our cluster main-sequence fitting we extend previous Hyades-based empirical color-temperature…
We use the Expanding Photosphere Method to determine distances to 10 type II supernovae. The effects of asymmetries, extinction, and flux dilution are explored. Using empirical evidence and time-independent, spherical models which treat H…
Adopting a distance for RS Pup derived from a period-luminosity relation based on Cepheid parallaxes, it is shown that the phase-lag observations of the surrounding nebulosity by Kervella et al. are well fitted by a model of an equatorial…
We present an overview of and preliminary results from an ongoing comprehensive program that has a goal of determining the Hubble constant to a systematic accuracy of 2%. As part of this program, we are currently obtaining 3.6 micron data…
The distance of NGC1316, the brightest galaxy in Fornax, is an interesting test for the cosmological distance scale. First, because Fornax is the 2nd largest cluster of galaxies at <~25 Mpc after Virgo and, in contrast to Virgo, has a small…
The importance of the distance of the Virgo cluster in the ongoing debate on the value of the Hubble constant is reviewed. A new calibration of the Tully-Fisher 21-cm line width-absolute magnitude relation is made using Cepheid distances to…
A measurement of the distance to Virgo Cluster by a direct method along with a realistic error analysis is important for a reliable determination of the value of Hubble Constant. Cepheid variables in the face-on spiral M100 in the Virgo…
We measure the galaxy luminosity function (LF) for the Virgo Cluster between blue magnitudes M_B = -22 and M_B = -11 from wide-field CCD imaging data. The LF is only gradually rising for -22 < M_B < -16. Between M_B = -16 and M_B = -14 it…
We present a catalog of over 6.2 million stars with measured proper motions. All these stars are observed in the direction of the Magellanic Clouds within the brightness range 12 < I < 19 mag. Based on these proper motions about 440 000…
A complete sample of 18 X-ray selected clusters of galaxies belonging to the ROSAT North Ecliptic Pole (NEP) survey has been observed with the Very Large Array at 1.4 GHz. These are the most distant clusters in the X-ray survey with…
The DIRECT project aims to determine direct distances to two important galaxies in the cosmological distance ladder - M31 and M33 - using detached eclipsing binaries (DEBs) and Cepheids. We present the results of the first large-scale…
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope to determine the Hubble constant (H0) from optical and infrared observations of over 600 Cepheid variables in the host galaxies of 8 recent Type Ia supernovae (SNe Ia),…