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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…
Jupiter's main auroral oval observed with HST-STIS
Kim, J.; Clarke, J. T.; Cowley, S. W. H. +2 more
An extended series of FUV images obtained on 7 days during winter 2000-2001, with fixed pointing, yielded highly accurate tracking of emisson features as Jupiter rotated. They provided newly detailed measurements of the degree of corotation of auroral emissions and their variations with changing central meridian longitude. This 2-month data set pr…
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 …
Star formation rate in galaxies from UV, IR, and Hα estimators
Buat, V.; Inoue, A. K.; Hirashita, H.
Infrared (IR) luminosity of galaxies originating from dust thermal emission can be used as an indicator of the star formation rate (SFR). Inoue et al. (\cite{inoue00}, IHK) have derived a formula for the conversion from dust IR luminosity to SFR by using the following three quantities: the fraction of Lyman continuum luminosity absorbed by gas (f)…
Reprocessing the Hipparcos data of evolved stars. III. Revised Hipparcos period-luminosity relationship for galactic long-period variable stars
Jorissen, A.; Pourbaix, D.; Platais, I. +1 more
We analyze the K band luminosities of a sample of galactic long-period variables using parallaxes measured by the Hipparcos mission. The parallaxes are in most cases re-computed from the Hipparcos Intermediate Astrometric Data using improved astrometric fits and chromaticity corrections. The K band magnitudes are taken from the literature and from…
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…
Circumnuclear Dust in Nearby Active and Inactive Galaxies. I. Data
Pogge, Richard W.; Mulchaey, John S.; Martini, Paul +1 more
The detailed morphology of the interstellar medium (ISM) in the central kiloparsec of galaxies is controlled by pressure and gravitation. The combination of these forces shapes both circumnuclear star formation and the growth of the central, supermassive black hole. We present visible and near-infrared Hubble Space Telescope images and color maps …
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…