Search Publications
X-Ray Emission from the Hot Interstellar Medium and Southwest Radio Lobe of the Nearby Radio Galaxy Centaurus A
Churazov, E.; Hardcastle, M. J.; Worrall, D. M. +5 more
We present results from two Chandra/ACIS-I observations and one XMM-Newton observation of X-ray emission from the interstellar medium (ISM) and the inner radio lobes of the nearby radio galaxy Centaurus A. The ISM has an average radial surface brightness profile that is well described by a β-model profile with index β=0.40+/-0.04 and a temperature…
On the Central Structure of M15
Baumgardt, Holger; Makino, Junichiro; Hut, Piet +2 more
We present a detailed comparison between the latest observational data on the kinematical structure of the core of M15, obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph and Wide Field Planetary Camera 2 instruments, and the results of dynamical simulations carried out using the special purpose GRAPE-6 computer. The obs…
Changes in Solar Dynamics from 1995 to 2002
Basu, Sarbani; Antia, H. M.
Data obtained by the GONG and MDI instruments over the last 7 years are used to study how solar dynamics-both rotation and other large scale flows-has changed with time. In addition to the well-known phenomenon of bands of faster and slower rotation moving toward the equator and pole, we find that the zonal flow pattern rises upward with time. Lik…
Infrared Emission of Normal Galaxies from 2.5 to 12 Micron: Infrared Space Observatory Spectra, Near-Infrared Continuum, and Mid-Infrared Emission Features
Beichman, Charles A.; Dale, Daniel A.; Dinerstein, Harriet L. +6 more
We present ISOPHOT spectra of the regions 2.5-4.9 µm and 5.8-11.6 µm for a sample of 45 disk galaxies from the US Infrared Space Observatory Key Project on Normal Galaxies. The galaxies were selected to span the range in global properties of normal, star-forming disk galaxies in the local universe. The spectra can be decomposed into th…
Coronal Mass Ejections and Solar Polarity Reversal
Howard, R. A.; Gopalswamy, N.; Yashiro, S. +1 more
We report on a close relationship between the solar polarity reversal and the cessation of high-latitude coronal mass ejections (CMEs). This result holds good for individual poles of the Sun for cycles 21 and 23, for which CME data are available. The high-latitude CMEs provide a natural explanation for the disappearance of the polar crown filament…
The Fundamental Plane at z=1.27: First Calibration of the Mass Scale of Red Galaxies at Redshifts z>1
van Dokkum, Pieter G.; Stanford, S. A.
We present results on the fundamental plane of early-type galaxies in the cluster RDCS J0848+4453 at z=1.27. Internal velocity dispersions of three K-selected early-type galaxies are determined from deep Keck spectra, using absorption lines in the rest-frame wavelength range 3400-4000 Å. Structural parameters are determined from Hubble Space Teles…
High-Resolution Measurements of the Dark Matter Halo of NGC 2976: Evidence for a Shallow Density Profile
Bolatto, Alberto D.; Simon, Joshua D.; Blitz, Leo +1 more
We have obtained two-dimensional velocity fields of the dwarf spiral galaxy NGC 2976 in Hα and CO. The high spatial (~75 pc) and spectral (13 and 2 km s-1, respectively) resolution of these observations, along with our multicolor optical and near-infrared imaging, allows us to measure the shape of the density profile of the dark matter …
Identifying Lenses with Small-Scale Structure. I. Cusp Lenses
Keeton, Charles R.; Gaudi, B. Scott; Petters, A. O.
The inability of standard models to explain the flux ratios in many four-image gravitational lens systems has been presented as evidence for significant small-scale structure in lens galaxies. That claim has generally relied on detailed lens modeling, so it is both model dependent and somewhat difficult to interpret. We present a more robust and g…
The Magnetic Helicity Budget of Solar Active Regions and Coronal Mass Ejections
Zhang, H.; Zhang, J.; Nindos, A.
We compute the magnetic helicity injected by transient photospheric horizontal flows in six solar active regions associated with halo coronal mass ejections (CMEs) that produced major geomagnetic storms and magnetic clouds (MCs) at 1 AU. The velocities are computed using the local correlation tracking (LCT) method. Our computations cover time inte…
The Effects of UV Continuum and Lyα Radiation on the Chemical Equilibrium of T Tauri Disks
Herczeg, Gregory J.; Calvet, Nuria; Bergin, Edwin +1 more
We show in this Letter that the spectral details of the far-ultraviolet (FUV) radiation fields have a large impact on the chemistry of protoplanetary disks surrounding T Tauri stars. We show that the strength of a realistic stellar FUV field is significantly lower than typically assumed in chemical calculations and that the radiation field is domi…