Related papers: The Distance to the Coma Cluster from Surface Brig…
The theoretical evaluations of the Red Giant Branch Tip (TRGB) luminosity presented in Salaris & Cassisi (1997) are extended to higher metallicities, and compared with analogous independent results recently published. The comparison between…
The relationship between galaxy luminosities and rotation rates is studied with total luminosities in the K' band. Extinction problems are essentially eliminated at this band centered at 2.1 micron. A template luminosity-linewidth relation…
We establish a cosmological-model-independent method to determine the Hubble constant $H_0$ from the localized fast radio bursts (FRBs) and the Hubble parameter measurements from cosmic chronometers and obtain a first such determination…
We have obtained wide field images of the Coma cluster in the B, V, R and I bands with the CFH12K camera at CFHT. In order to search for large scale diffuse emission, we have applied to these images an iterative multi scale wavelet analysis…
A large luminosity--linewidth template sample is now available, improved absorption corrections have been derived, and there are a statistically significant number of galaxies with well determined distances to supply the zero point. A…
We performed a fluctuation analysis of the Hubble Extremely Deep Field (XDF) at four optical wavelength bands and found large fluctuations that are significantly brighter than those expected for ordinary galaxies. Good cross-correlations…
New distances, larger than previous ones, have been obtained for M 31 and M 81 based on the geometrical zero-point of the Cepheid Period-luminosity relation provided by the HIPPARCOS satellite. By combining them with independent…
Infrared J and H surface photometry are carried out for nearby 12 galaxies whose distances have been accurately measured via HST Cepheid observations. Using the total, isophotal, and surface-photometric aperture magnitudes we calibrate the…
Determining the distance to the open cluster M29 (NGC 6913) has proven difficult, with distances determined by various authors differing by a factor of two or more. To solve this problem, we have initiated a new photometric investigation of…
The local expansion rate of the Universe is parametrized by the Hubble constant, $H_0$, the ratio between recession velocity and distance. Different techniques lead to inconsistent estimates of $H_0$. Observations of Type Ia supernovae…
We present Hubble Space Telescope imaging of two ultra diffuse galaxies (UDGs) with measured stellar velocity dispersions in the Coma cluster. The galaxies, Dragonfly 44 and DFX1, have effective radii of 4.7 kpc and 3.5 kpc and velocity…
We summarize here the first results of a new spectroscopic survey of galaxies in the Coma cluster with -20.5 < M_B < -14. Differences between the last epoch of star formation (SF) activity in S0 and elliptical galaxies are discussed.…
Since the launch of the Hubble Space Telescope nine years ago, Cepheid distances to 25 galaxies have been determined for the purpose of calibrating secondary distance indicators. A variety of these can now be calibrated, and the…
We demonstrate a novel technique for calibrating the energy scale of the XMM EPIC-pn detector, which allows us to measure bulk flows in the intracluster medium (ICM) of the Perseus and Coma clusters. The procedure uses the instrumental…
The surface brightness fluctuation (SBF) method is a powerful tool to derive distances to galaxies for which single stars cannot be resolved. Up to now, the method has been calibrated mainly at red colours due to the intrinsic faintness of…
We present an empirical method which uses visual band light curve shapes (LCS) to estimate the luminosity of type Ia supernovae (SN Ia). This method is first applied to a ``training set'' of 8 SN Ia light curves with independent distance…
We have investigated the possibility of inferring peculiar velocities for clusters of galaxies from the Doppler shift of scattered cosmic microwave background (CMB) photons. We find that if the core radius of the gas distribution or the…
We report on a first application of the infrared surface brightness technique on a Cepheid in the Large Magellanic Cloud, the variable HV 12198 in the young globular cluster NGC 1866. From this one star, we determine a distance modulus of…
I review the current state of determinations of the Hubble constant, which gives the length scale of the Universe by relating the expansion velocity of objects to their distance. There are two broad categories of measurements. The first…
NGC 4258 is a critical galaxy for establishing the extragalactic distance scale and estimating the Hubble constant (Ho). Water masers in the nucleus of the galaxy orbit about its supermassive black hole, and very long baseline…