Search Publications
Evidence of a Significant Intermediate-Age Population in the M31 Halo from Main-Sequence Photometry
Ferguson, Henry C.; Brown, Thomas M.; Rich, R. Michael +5 more
We present a color-magnitude diagram (CMD) for a minor-axis field in the halo of the Andromeda galaxy (M31), 51' (11 kpc) from the nucleus. These observations, taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope, are the deepest optical images yet obtained, attaining 50% completeness at mV=30.7 mag. The CMD, c…
The Initial Helium Content of Galactic Globular Cluster Stars from the R-Parameter: Comparison with the Cosmic Microwave Background Constraint
Salaris, Maurizio; Cassisi, Santi; Irwin, Alan W.
Recent precise determinations of the primordial He abundance (Yp) from cosmic microwave background (CMB) analyses and cosmological nucleosynthesis computations provide Yp=0.248+/-0.001. On the other hand, recent works on the initial He abundance of Galactic globular cluster (GGC) stars, making use of the R-parameter as an He …
The Hubble Constant from the Gravitational Lens B1608+656
Treu, T.; Blandford, R. D.; Koopmans, L. V. E. +2 more
We present a refined gravitational lens model of the four-image lens system B1608+656 based on new and improved observational constraints: (1) the three independent time delays and flux ratios from Very Large Array observations, (2) the radio-image positions from Very Large Baseline Array observations, (3) the shape of the deconvolved Einstein rin…
Giant Lyα Nebulae Associated with High-Redshift Radio Galaxies
Dey, Arjun; Bland-Hawthorn, Joss; Stanford, S. A. +7 more
We report deep, Keck narrowband Lyα images of the luminous z>3 radio galaxies 4C 41.17, 4C 60.07, and B2 0902+34. The images show giant, 100-200 kpc scale, emission-line nebulae, centered on these galaxies, that exhibit a wealth of morphological structure, including extended low surface brightness emission in the outer regions, radially directe…
Solar Seismic Models and the Neutrino Predictions
Kosovichev, A. G.; Turck-Chièze, S.; Couvidat, S.
This paper focuses on the solar neutrino fluxes, the g-mode predictions, and the possible impact of the magnetic fields on the neutrino emission and transport. The Solar and Heliospheric Observatory (SOHO) spacecraft has allowed astrophysicists to achieve a major breakthrough in the knowledge of the solar core. Both GOLF and MDI instruments on SOH…
Lyα Emission in Starbursts: Implications for Galaxies at High Redshift
Mas-Hesse, J. M.; Kunth, D.; Leitherer, C. +3 more
We present the results of a high-resolution UV two-dimensional spectroscopic survey of star-forming galaxies observed with Hubble Space Telescope Space Telescope Imaging Spectrograph. Our main aim is to map the Lyα profiles to learn about the gas kinematics and its relation with the escape of Lyα photons and to detect extended Lyα emission due to …
The Evolution of a Mass-selected Sample of Early-Type Field Galaxies
Peng, C. Y.; Keeton, C. R.; Kochanek, C. S. +7 more
We investigate the evolution of mass-selected early-type field galaxies using a sample of 28 gravitational lenses spanning the redshift range 0<~z<~1. Based on the redshift-dependent intercept of the fundamental plane in the rest-frame B band, we measure an evolution rate of dlog(M/L)B/dz=-0.56+/-0.04 (all errors are 1 σ unless no…
Self-similar Models for the Mass Profiles of Early-Type Lens Galaxies
Keeton, C. R.; Kochanek, C. S.; Rusin, D.
We introduce a self-similar mass model for early-type galaxies and constrain it using the aperture mass-radius relations determined from the geometries of 22 gravitational lenses. The model consists of two components: a concentrated component, which traces the light distribution, and a more extended power-law component (ρ~r-n), which re…
Chandra X-Ray Observations of NGC 1316 (Fornax A)
Fabbiano, G.; Kim, Dong-Woo
We report the results of the Chandra ACIS subarcsecond resolution X-ray observation of the archetypal merger radio galaxy NGC 1316 (Fornax A). We confirm the presence of fine substructures in the hot interstellar medium (ISM). Some of these are likely to result from interaction with the radio jets, while others may be related to a complex intermin…
The Circumstellar Disk of the Butterfly Star in Taurus
Stapelfeldt, Karl R.; Padgett, Deborah L.; Wolf, Sebastian
We present a model of the circumstellar environment of the so-called Butterfly star in Taurus (IRAS 04302+2247). The appearance of this young stellar object is dominated by a large circumstellar disk seen edge-on and the light-scattering lobes above the disk. Our model is based on multiwavelength continuum observations: (1) millimeter maps and (2)…