214 citations · 1.5k across the 40 of their papers we have counts for
27 papers · 1 filter
Black Hole Spins of Radio Sources
Ruth A. Daly
A new approach to constraining or determining the spin of a massive black hole is proposed. A key parameter in the analysis is the dimensionless ratio, r, of the energy released to…
Physical Properties of Very Powerful FRII Radio Galaxies
Christopher P. O'Dea, Ruth A. Daly, Preeti Kharb +2
We estimate ages and physical properties of powerful radio galaxies. An analysis of new multi-wavelength VLA observations of eleven very powerful classical double (FRIIb) radio gal…
The Acceleration History of the Universe and the Properties of the Dark Energy
Ruth A. Daly, S. G. Djorgovski
The model-independent method of using type Ia supernovae proposed and developed by Daly and Djorgovski (2003, 2004) has been applied to the Riess et al. (2007) supernovae sample. A…
Improved Constraints on the Acceleration History of the Universe and the Properties of the Dark Energy
Ruth A. Daly, S. G. Djorgovski, Kenneth A. Freeman +4
We extend and apply a model-independent analysis method developed earlier by Daly & Djorgovski to new samples of supernova standard candles, radio galaxy and cluster standard ruler…
Cosmological Studies with Radio Galaxies and Supernovae
Ruth A. Daly, Matthew P. Mory, C. P. O'Dea +4
Physical sizes of extended radio galaxies can be employed as a cosmological "standard ruler", using a previously developed method. Eleven new radio galaxies are added to our previo…
The Properties and Gaseous Environments of Powerful Classical Double Radio Galaxies
Ruth Daly, C. O'Dea, P. Kharb +3
The properties of a sample of 31 very powerful classical double radio galaxies with redshifts between zero and 1.8 are studied. The source velocities, beam powers, ambient gas dens…
A Radio Study of 13 Powerful FRII Radio Galaxies
P. Kharb, C. O'Dea, S. Baum +4
We have observed a sample of 13 large, powerful Fanaroff-Riley type II radio galaxies with the Very Large Array in multiple configurations and at multiple frequencies. We have comb…
A Nearly Model-Independent Characterization of Dark Energy Properties as a Function of Redshift
Ruth A. Daly, S. G. Djorgovski
Understanding the acceleration of the universe and its cause is one of the key problems in physics and cosmology today, and is best studied using a variety of mutually complementar…
Constraints on the Physical Parameters of the Dark Energy Using a Model-Independent Approach
Ruth A. Daly, S. G. Djorgovski
Understanding the physical nature of the dark energy which appears to drive the accelerated expansion of the unvierse is one of the key problems in physics and cosmology today. Thi…
Comparison of Radio Observations and Numerical Simulations of the Radio Lobes of Cygnus A
J. C. Carvalho, R. A. Daly, M. P. Mory +1
We present a comparison of radio observations of the archetypal powerful radio galaxy Cygnus A and 2-D numerical hydrodynamical simulations. We characterize some global trends in t…
Direct Constraints on the Properties and Evolution of Dark Energy
Ruth A. Daly, S. G. Djorgovski
We describe a method to derive the expansion and acceleration rates directly from the data, without the need for the specification of a theory of gravity, and without adopting an a…
Direct Determinations of the Redshift Behavior of the Pressure, Energy Density, and Equation of State of the Dark Energy and the Acceleration of the Universe
Ruth A. Daly, S. G. Djorgovski
One of the goals of current cosmological studies is the determination of the expansion and acceleration rates of the universe as functions of redshift, and the determination of the…
Direct Determination of the Kinematics of the Universe and Properties of the Dark Energy as Functions of Redshift
Ruth A. Daly, S. G. Djorgovski
Understanding of the nature of dark energy, which appears to drive the expansion of the universe, is one of the central problems of physical cosmology today. In an earlier paper [D…
A Model-Independent Determination of the Expansion and Acceleration Rates of the Universe as a Function of Redshift and Constraints on Dark Energy
Ruth A. Daly, S. G. Djorgovski
Determination of the expansion and acceleration history of the universe is one of the fundamental goals of cosmology. Detailed measurements of these rates as a function of redshift…
Radio Galaxies and the Acceleration of the Universe Beyond a Redshift of One
Ruth A. Daly
Radio galaxies provide a means to determine the coordinate distance,the luminosity distance, the dimensionless luminosity distance, or the angular size distance to sources with red…
Constraints on the Cluster Environments and Hot Spot Magnetic Field Strengths of the Radio Sources 3C254 and 3C280
Megan Donahue, Ruth A. Daly, Donald J. Horner
We present new Chandra Observatory observations with archival HST and radio observations of 3C254, a radio quasara at z=0.734, and 3C280, a radio galaxy at z=0.996. We report the d…
Quintessence, Cosmology, and Fanaroff-Riley Type IIB Radio Galaxies
Ruth A. Daly, E. J. Guerra
Fanaroff-Riley type IIb (FR IIb) radio galaxies provide a modified standard yardstick that allows constraints to be placed on global cosmological parameters. A sample of 20 FR IIb…
Radio Galaxy Redshift-Angular Size Data Constraints on Dark Energy
Silviu Podariu, Ruth A. Daly, Matthew P. Mory +1
We use FRIIb radio galaxy redshift-angular size data to constrain cosmological parameters in a dark energy scalar field model. The derived constraints are consistent with but weake…
High-Redshift Radio Galaxies as a Cosmological Tool: Exploration of a Key Assumption and Comparison with Supernova Results
Ruth A. Daly, Matthew P. Mory, Erick J. Guerra
There are many different approaches to using observations to constrain or determine the global cosmological parameters that describe our universe. Methods that rely upon a determin…
Cosmological Parameters and Quintessence From Radio Galaxies
Ruth A. Daly, Erick J. Guerra
FRIIb radio galaxies provide a tool to determine the coordinate distance to sources out to redshifts of two. The coordinate distance depends on the present values of global cosmolo…
Determinations of Key Physical Parameters Related to Classical Double Radio Sources
Lin Wan, Ruth A. Daly, E. J. Guerra
Multi-frequency radio observations of the radio bridge of a powerful classical double radio source can be used to determine: the beam power of the jets emanating from the AGN; the…
Global Cosmological Parameters Determined Using Classical Double Radio Galaxies
E. J. Guerra, Ruth A. Daly, Lin Wan
A sample of 20 powerful extended radio galaxies with redshifts between zero and two were used to determine constraints on global cosmological parameters. Data for six radio sources…
Empirical Determinations of Key Physical Parameters Related to Classical Double Radio Sources
Lin Wan, Ruth A. Daly, Erick J. Guerra
Multi-frequency radio observations of the radio bridge of powerful classical double radio sources can be used to determine: the beam power of the jets emanating from the AGN; the t…
Updated Estimates of Global Cosmological Parameters Determined Using Classical Double Radio Galaxies
Erick J. Guerra, Ruth A. Daly, Lin Wan
A sample of 20 powerful extended radio galaxies with redshifts between zero and two were used to determine constraints on global cosmological parameters. Data for six radio sources…