Search Publications
The Connection between Bar Strength and Circumnuclear Dust Structure
Martini, Paul; Peeples, Molly S.
We present a comparison of bar strength Qb and circumnuclear dust morphology for 75 galaxies in order to investigate how bars affect the centers of galaxies. We trace the circumnuclear dust morphology and amount of dust structure with structure maps generated from visible-wavelength HST data, finding that tightly wound nuclear dust spir…
The Structure and Star Formation History of Early-Type Galaxies in the Ultra Deep Field/GRAPES Survey
Daddi, E.; Panagia, N.; Koekemoer, A. M. +9 more
We present a two-pronged approach to the formation of early-type galaxies, using a sample of 18 galaxies at 0.5<~z<~1 from the HST ACS Ultra Deep Field and GRAPES surveys: (1) We combine slitless low-resolution spectroscopy from the GRAPES data set with simple models of galaxy formation to explore their star formation histories. (2) We also …
The Pulsar Wind Nebula of the Geminga Pulsar
Pavlov, G. G.; Zavlin, V. E.; Sanwal, D.
The superb spatial resolution of Chandra has allowed us to detect a 20" long tail behind the Geminga pulsar, with a hard spectrum (photon index Γ=1.0+/-0.2) and a luminosity of (1.3+/-0.2)×1029 ergs s-1 in the 0.5-8 keV band, for an assumed distance of 200 pc. The tail could be either a pulsar jet, confined by a toroidal magn…
Spectroscopic Redshifts for Seven Lens Galaxies
Maoz, Dan; Rix, Hans-Walter; Kochanek, Christopher S. +2 more
The use of gravitationally lensed quasars for cosmological applications and as probes of galaxy structure and evolution requires knowledge about the lens redshift, which is unknown for a large fraction of lenses. We report Very Large Telescope observations of 11 lensed quasars, designed to measure the redshifts of their lens galaxies. We successfu…
Kinematics of Interstellar Gas in Nearby UV-selected Galaxies Measured with HST STIS Spectroscopy
Leitherer, C.; Oey, M. S.; Heckman, T. M. +3 more
We measure Doppler shifts of interstellar absorption lines in HST STIS spectra of individual star clusters in nearby UV-selected galaxies. Values for systemic velocities, which are needed to quantify outflow speeds, are taken from the literature and verified with stellar lines. We detect outflowing gas in 8 of 17 galaxies via low-ionization lines …
Warm Water Vapor around Sagittarius B2
Cernicharo, José; Goicoechea, Javier R.; Pardo, Juan R. +1 more
Several condensations heated externally by nearby hot stars are present in the Sgr B2 region for which H2O far-IR lines are expected to probe only an external low-density and high temperature section. Millimeter-wave lines can penetrate deeper into them (higher densities and lower Tk). We have conducted a study combining H
Luminous Compact Blue Galaxies up to z~1 in the Hubble Space Telescope Ultra Deep Field. I. Small Galaxies or Blue Centers of Massive Disks?
Koo, D. C.; Melbourne, J.; Willmer, C. N. A. +4 more
We analyze 26 luminous compact blue galaxies (LCBGs) in the Hubble Space Telescope ACS Ultra Deep Field (UDF) at z~0.2-1.3, to determine whether these truly are small galaxies or, rather, bright central starbursts within existing or forming large disk galaxies. Surface brightness profiles from UDF images reach fainter than rest-frame 26.5 B mag ar…
Sources of the Solar Wind at Ulysses during 1990-2006
Sheeley, N. R., Jr.; Wang, Y. -M.
The Ulysses spacecraft is now well into its third polar orbit around the Sun. Using stackplot displays, we summarize the wind speeds and interplanetary sector polarities recorded by Ulysses since its launch in 1990 and relate the observed patterns to the global evolution of open magnetic regions (coronal holes) over the solar cycle. We verify that…
Halo Structures of Gravitational Lens Galaxies
Kochanek, Christopher S.; Falco, Emilio E.; Yoo, Jaiyul +1 more
We explore the halo structure of four gravitational lenses with well-observed, thin Einstein rings. We find that the gravitational potentials are well described by ellipsoidal density distributions in the sense that the best-fit nonellipsoidal models have parameters consistent with their ellipsoidal counterparts. We find upper limits on the standa…
High Spatial Resolution T-ReCS Mid-Infrared Imaging of Luminous Infrared Galaxies
Colina, Luis; Rieke, George H.; Alonso-Herrero, Almudena +4 more
We present diffraction-limited (FWHM~0.3") Gemini/T-ReCS mid-infrared (MIR; N-band or narrowband at 8.7 µm) imaging of four luminous infrared galaxies (LIRGs) drawn from a representative local sample. The MIR emission in the central few kiloparsecs is strikingly similar to that traced by Paα and generally consists of bright nuclear emission …