Related papers: The Distance to the Coma Cluster from Surface Brig…
We present Globular Cluster Luminosity Functions for four ellipticals and one S0-Galaxy in the Fornax cluster of galaxies, derived from CCD photometry in V and I. The averaged turnover magnitudes are $V_{TO} = 23.80 \pm 0.06$ and $I_{TO}…
Using single channel infrared photometry from the literature, a provisional K-band diameter--velocity dispersion relation for elliptical galaxies in the Coma and Virgo clusters is derived. The Coma cluster relation has \~1.5 times lower…
We review the use of Type Ia supernovae for cosmological distance determinations. Low-redshift SNe Ia (z < 0.1) demonstrate that (a) the Hubble expansion is linear, (b) H_0 = 65 +/- 2 (statistical) km/s/Mpc, (c) the bulk motion of the Local…
Aiming at providing a firm mean distance estimate to the Small Magellanic Cloud (SMC), and thus to place it within the internally consistent Local Group distance framework we recently established, we compiled the current-largest database of…
In the era of precision cosmology, it is essential to empirically determine the Hubble constant with an accuracy of one per cent or better. At present, the uncertainty on this constant is dominated by the uncertainty in the calibration of…
We present new measurements of the diffuse radio halo emission from the Coma cluster of galaxies at 2.675 GHz and 4.85 GHz using the Effelsberg 100--m telescope. After correction for the contribution from point sources we derive the…
The origin of dark energy driving the accelerated expansion of the universe is still mysterious. We explore the possibility that dark energy fluctuates, resulting in spatial correlations. Due to these fluctuations, the Hubble rate itself…
We present observations of 10 type Ia supernovae (SNe Ia) between 0.16 < z < 0.62. With previous data from our High-Z Supernova Search Team, this expanded set of 16 high-redshift supernovae and 34 nearby supernovae are used to place…
We investigate the extent to which correlated distortions of the luminosity distance-redshift relation due to large-scale bulk flows limit the precision with which cosmological parameters can be measured. In particular, peculiar velocities…
Spatially-resolved gas pressure maps of the Coma galaxy cluster are obtained from a mosaic of XMM-Newton observations in the scale range between a resolution of 20 kpc and an extent of 2.8 Mpc. A Fourier analysis of the data reveals the…
The status of the determination of the Hubble constant is reviewed, setting out the evidence for the long distance scale with H_0=55+/-5. In parallel, various precepts said to favor the short distance scale with H_0>70 are discussed. The…
We present the study of a large sample of early-type dwarf galaxies in the Coma cluster observed with DEIMOS on the Keck II to determine their internal velocity dispersion. We focus on a subsample of 41 member dwarf elliptical galaxies for…
We present an improved determination of the Hubble constant (H0) from Hubble Space Telescope (HST) observations of 70 long-period Cepheids in the Large Magellanic Cloud. These were obtained with the same WFC3 photometric system used to…
The [O III] 5007 planetary nebula luminosity function (PNLF) occupies an important place on the extragalactic distance ladder. Since it is the only method that is applicable to all the large galaxies of the Local Supercluster, it is…
I use the largest available sample of Type II plateau supernovae to examine the previously reported luminosity-velocity relation. This study confirms such relation which permits one to standardize the luminosities of these objects from a…
We present HST photometry of 17 Cepheids in open clusters and their mean parallaxes from Gaia EDR3. These parallaxes are more precise than those from individual Cepheids (G<8 mag) previously used to measure the Hubble constant because they…
In this work, we obtain Hubble constant ($H_0$) estimates by using two galaxy cluster gas mass fraction measurement samples, Type Ia supernovae luminosity distances, and the validity of the cosmic distance duality relation. Notably, the…
Although cosmologists have been trying to determine the value of the Hubble constant for nearly 65 years, they have only succeeded in limiting the range of possibilities: most of the current observational determinations place the Hubble…
In this paper we study the stellar populations of 356 bright, $M_{r}$ $\leq$ -19, Coma cluster members located in a 2 degree field centred on the cluster core using SDSS DR7 spectroscopy. For the quiescent galaxies we find strong…
We consider the published distance moduli to the Fornax and Coma galaxy clusters, with emphasis on the period since 1990. We have carefully homogenized our catalogs of distance moduli onto the distance scale established in the previous…