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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…
Discovery of Interacting Molecular Gas toward the TeV Gamma-Ray Peak of the SNR G 347.3--0.5
Takahashi, Tadayuki; Uchiyama, Yasunobu; Fukui, Yasuo +10 more
Supernova remnants ( = SNR) are suggested to be sites of cosmic-ray acceleration. In particular, it has been an issue of keen interest whether cosmic ray protons are being accelerated in a SNR which emits TeV γ-rays. A crucial observational test for this is to find dense molecular gas towards the SNR, because such molecular gas can best verify the…
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…
Multiple magnetic clouds: Several examples during March-April 2001
Wang, S.; Wang, Y. M.; Ye, P. Z.
Multiple magnetic cloud (Multi-MC), which is formed by the overtaking of successive coronal mass ejections (CMEs), is a kind of complex structure in interplanetary space. Multi-MC is worthy of notice due to its special properties and potential geoeffectiveness. Using the data from the ACE spacecraft, we identify the three cases of Multi-MC in the …
Hubble Space Telescope Imaging of Brightest Cluster Galaxies
O'Dea, Christopher P.; van der Marel, Roeland P.; Lauer, Tod R. +3 more
We used the Hubble Space Telescope Wide Field Planetary Camera 2 to obtain I-band images of the centers of 81 brightest cluster galaxies (BCGs), drawn from a volume-limited sample of nearby BCGs. The images show a rich variety of morphological features, including multiple or double nuclei, dust, stellar disks, point-source nuclei, and central surf…
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…