Search Publications
Probing Supergranular Flow in the Solar Interior
Woodard, M. F.
Helioseismic correlation data computed from SOHO MDI high-resolution Doppler images were inverted for solar subsurface supergranular flow, using an improved forward model. The statistical error of the inversion is set by the stochastic nature of solar wave excitation, which limits the detection of supergranular flow with these data to the first 4 …
A Comprehensive Study of the Initiation and Early Evolution of a Coronal Mass Ejection from Ultraviolet and White-Light Data
Romoli, M.; Bemporad, A.; Poletto, G. +1 more
In this work we analyze simultaneous UV and white-light (WL) observations of a slow CME that occurred on 2000 January 31. Unlike most CMEs studied in the UV so far, this event was not associated with a flare or filament eruption. Based on vector magnetograph data and magnetic field models, we find that field disruption in an active region (AR) was…
Confirming the Detection of an Intergalactic X-Ray Absorber toward PKS 2155-304
Canizares, Claude R.; Yao, Yangsen; Fang, Taotao
We present new observations of PKS 2155-304 with the Chandra Low Energy Transmission Grating (LETG), using the Advanced CCD Imaging Spectrometer (ACIS). We confirm the detection of an absorption line plausibly identified as O VIII Lyα from a warm-hot intergalactic medium associated with a small group of galaxies along the line of sight, as origina…
The Color-Magnitude Distribution of Field Galaxies to z~3: The Evolution and Modeling of the Blue Sequence
van Dokkum, Pieter G.; Franx, Marijn; Labbé, Ivo +7 more
Using deep NIR VLT ISAAC and optical HST WFPC2 imaging in the HDF-S and MS 1054-03, we study the rest-frame UV-to-optical colors and magnitudes of galaxies to z~3. Unlike the present day, there is no evidence for a red sequence at z~3, but there does appear to be a well-defined CMR for blue galaxies at all redshifts, with more luminous galaxies ha…
Measuring Flexion
Goldberg, David M.; Leonard, Adrienne
We describe practical approaches to measuring flexion in observed galaxies. In particular, we look at the issues involved in using the shapelets and HOLICs techniques as means of extracting second-order lensing information. We also develop an extension of HOLICs to estimate flexion in the presence of noise and with a nearly isotropic PSF. We test …
Observations of Dark Lanes in Umbral Fine Structure from the Hinode Solar Optical Telescope: Evidence for Magnetoconvection
Bharti, Lokesh; Joshi, Chandan; Jaaffrey, S. N. A.
An analysis of high-resolution G-band images of active region NOAA 10930 is presented. The observations were recorded with the Broadband Filter Imager (BFI) attached to the Solar Optical Telescope (SOT) on board the Hinode mission. We observed dark lanes in umbral dots up to six folds in larger ones. Formation of umbral dots from dark core penumbr…
Radiative Transfer Effects on Doppler Measurements as Sources of Surface Effects in Sunspot Seismology
Scherrer, P. H.; Wachter, R.; Sankarasubramanian, K. +1 more
We show that the use of Doppler shifts of Zeeman-sensitive spectral lines to observe waves in sunspots is subject to measurement-specific phase shifts arising from (1) the altered height range of spectral line formation and the propagating character of p-mode waves in penumbrae and (2) Zeeman broadening and splitting. We also show that these phase…
Modeling Spitzer Observations of VV Ser. I. The Circumstellar Disk of a UX Orionis Star
van Dishoeck, Ewine F.; Dullemond, Cornelis P.; Pontoppidan, Klaus M. +5 more
We present mid-infrared Spitzer IRS spectra of the UX Orionis star VV Ser, combined with interferometric and spectroscopic data from the literature covering UV to submillimeter wavelengths. The full set of data are modeled by an axisymmetric Monte Carlo radiative transfer code to test the prediction of Dullemond et al. that disks around UX Orionis…
The Survey of Nearby Nuclei with the Space Telescope Imaging Spectrograph: Emission-Line Nuclei at Hubble Space Telescope Resolution
Filippenko, Alexei V.; Ho, Luis C.; Shields, Joseph C. +6 more
We present results from a program of optical spectroscopy for 23 nearby galaxies with emission-line nuclei. This investigation takes advantage of the spatial resolution of the Hubble Space Telescope to study the structure and energetics of the central ~10-20 pc, and the resulting data have value for quantifying central black hole masses, star form…
An Alternative Interpretation of the Relationship between the Inferred Open Solar Flux and the Interplanetary Magnetic Field
Riley, Pete
Photospheric observations at the Wilcox Solar Observatory (WSO) represent an uninterrupted data set of 32 years and are therefore unique for modeling variations in the magnetic structure of the corona and inner heliosphere over three solar cycles. For many years, modelers have applied a latitudinal correction factor to these data, believing that i…