Search Publications
Detailed Structural Decomposition of Galaxy Images
Ho, Luis C.; Rix, Hans-Walter; Peng, Chien Y. +1 more
We present a two-dimensional fitting algorithm (GALFIT) designed to extract structural components from galaxy images, with emphasis on closely modeling light profiles of spatially well-resolved, nearby galaxies observed with the Hubble Space Telescope. Our algorithm improves on previous techniques in two areas: by being able to simultaneously fit …
Analytic Light Curves for Planetary Transit Searches
Agol, Eric; Mandel, Kaisey
We present exact analytic formulae for the eclipse of a star described by quadratic or nonlinear limb darkening. In the limit that the planet radius is less than a tenth of the stellar radius, we show that the exact light curve can be well approximated by assuming the region of the star blocked by the planet has constant surface brightness. We app…
Detection of an Extrasolar Planet Atmosphere
Gilliland, Ronald L.; Charbonneau, David; Brown, Timothy M. +1 more
We report high-precision spectrophotometric observations of four planetary transits of HD 209458, in the region of the sodium resonance doublet at 589.3 nm. We find that the photometric dimming during transit in a bandpass centered on the sodium feature is deeper by (2.32+/-0.57)×10-4 relative to simultaneous observations of the transit…
The Observed Offset Distribution of Gamma-Ray Bursts from Their Host Galaxies: A Robust Clue to the Nature of the Progenitors
Bloom, J. S.; Djorgovski, S. G.; Kulkarni, S. R.
We present a comprehensive study to measure the locations of gamma-ray bursts (GRBs) relative to their host galaxies. In total, we find the offsets of 20 long-duration GRBs from their apparent host galaxy centers by utilizing ground-based images from Palomar and Keck and space-based images from the Hubble Space Telescope (HST). We discuss in detai…
The Rest-Frame Extreme-Ultraviolet Spectral Properties of Quasi-stellar Objects
Kriss, Gerard A.; Zheng, Wei; Davidsen, Arthur F. +1 more
We use a sample of 332 Hubble Space Telescope spectra of 184 quasi-stellar objects (QSOs) with z>0.33 to study the typical ultraviolet spectral properties of QSOs, with emphasis on the ionizing continuum. Our sample is nearly twice as large as that from previous work by W. Zheng and colleagues and provides much better spectral coverage in the e…
Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
Kirkpatrick, J. Davy; Burgasser, Adam J.; Gizis, John E. +15 more
Trigonometric parallax determinations are presented for 28 late-type dwarfs and brown dwarfs, including eight M dwarfs with spectral types between M7 and M9.5, 17 L dwarfs with spectral types between L0 and L8, and three T dwarfs. Broadband photometry at CCD wavelengths (VRIz*) and/or near-IR wavelengths (JHK) is presented for these objects and fo…
The rich 6 to 9 vec mu m spectrum of interstellar PAHs
Hony, S.; Tielens, A. G. G. M.; Allamandola, L. J. +4 more
IR spectroscopy provides a valuable tool for the characterisation and identification of interstellar molecular species. Here, we present 6-9 µm spectra of a sample of reflection nebulae, HII regions, YSOs, evolved stars and galaxies that show strong unidentified infrared bands, obtained with the SWS spectrograph on board ISO. The IR emission…
The SAURON project - II. Sample and early results
Emsellem, Eric; Miller, Bryan W.; Carollo, C. M. +9 more
Early results are reported from the SAURON survey of the kinematics and stellar populations of a representative sample of nearby E, S0 and Sa galaxies. The survey is aimed at determining the intrinsic shape of the galaxies, their orbital structure, the mass-to-light ratio as a function of radius, the age and metallicity of the stellar populations,…
Numerical methods of star formation history measurement and applications to seven dwarf spheroidals
Dolphin, A. E.
A comprehensive study of the measurement of star formation histories from colour-magnitude diagrams (CMDs) is presented, with an emphasis on a variety of subtle issues involved in the generation of model CMDs and maximum likelihood solution. Among these are the need for a complete sampling of the synthetic CMD, the use of proper statistics for dea…
Efficient multi-Gaussian expansion of galaxies
Cappellari, Michele
We describe a simple, efficient, robust and fully automatic algorithm for the determination of a multi-Gaussian expansion (MGE) fit to galaxy images, to be used as a parametrization for the galaxy stellar surface brightness. In most cases the least-squares solution found by this method essentially corresponds to the minimax, constant relative erro…