Search Publications
Detailed Decomposition of Galaxy Images. II. Beyond Axisymmetric Models
Ho, Luis C.; Rix, Hans-Walter; Peng, Chien Y. +1 more
We present a two-dimensional (2D) fitting algorithm (GALFIT, ver. 3) with new capabilities to study the structural components of galaxies and other astronomical objects in digital images. Our technique improves on previous 2D fitting algorithms by allowing for irregular, curved, logarithmic and power-law spirals, ring, and truncated shapes in othe…
Astrometry.net: Blind Astrometric Calibration of Arbitrary Astronomical Images
Hogg, David W.; Lang, Dustin; Blanton, Michael +2 more
We have built a reliable and robust system that takes as input an astronomical image, and returns as output the pointing, scale, and orientation of that image (the astrometric calibration or World Coordinate System information). The system requires no first guess, and works with the information in the image pixels alone; that is, the problem is a …
The Luminosity and Mass Functions of Low-mass Stars in the Galactic Disk. II. The Field
Hawley, Suzanne L.; Golimowski, David A.; Reid, I. Neill +4 more
We report on new measurements of the luminosity function (LF) and mass function (MF) of field low-mass dwarfs derived from Sloan Digital Sky Survey Data Release 6 photometry. The analysis incorporates ~15 million low-mass stars (0.1 {\cal M}_\odot {\cal M} < 0.8\,{\cal M}_\odot), spread over 8400 deg2. Stellar distances are estimated…
Discovery of Precursor Luminous Blue Variable Outbursts in Two Recent Optical Transients: The Fitfully Variable Missing Links UGC 2773-OT and SN 2009ip
Ghez, Andrea M.; Filippenko, Alexei V.; Smith, Nathan +11 more
We present progenitor-star detections, light curves, and optical spectra of supernova (SN) 2009ip and the 2009 optical transient in UGC 2773 (U2773-OT), which were not genuine SNe. Precursor variability in the decade before outburst indicates that both of the progenitor stars were luminous blue variables (LBVs). Their pre-outburst light curves res…
The Antennae Galaxies (NGC 4038/4039) Revisited: Advanced Camera for Surveys and NICMOS Observations of a Prototypical Merger
Leitherer, Claus; Whitmore, Bradley C.; Chandar, Rupali +7 more
The Advanced Camera for Surveys and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) have been used to obtain new Hubble Space Telescope images of NGC 4038/4039 ("The Antennae"). These new observations allow us to better differentiate compact star clusters from individual stars, based on both size and color. We use this ability to e…
Absorption-line Probes of the Prevalence and Properties of Outflows in Present-day Star-forming Galaxies
Weiner, Benjamin J.; Brinchmann, Jarle; Heckman, Timothy M. +4 more
We analyze star-forming galaxies drawn from SDSS DR7 to show how the interstellar medium (ISM) Na I λλ5890, 5896 (Na D) absorption lines depend on galaxy physical properties, and to look for evidence of galactic winds. We combine the spectra of galaxies with similar geometry/physical parameters to create composite spectra with signal-to-noise ~300…
The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters
Anderson, Jay; Dotter, Aaron; Sarajedini, Ata +3 more
We present new measurements of the centers for 65 Milky Way globular clusters. Centers were determined by fitting ellipses to the density distribution within the inner 2' of the cluster center, and averaging the centers of these ellipses. The symmetry of clusters was also analyzed by comparing cumulative radial distributions on opposite sides of t…
New Hubble Space Telescope WFC3/UVIS Observations Augment the Stellar-population Complexity of ω Centauri
Milone, A. P.; Marino, A. F.; Bedin, L. R. +3 more
We used archival multi-band Hubble Space Telescope observations obtained with the Wide Field Camera 3 in the UV-optical channel to present important new observational findings on the color-magnitude diagram (CMD) of the Galactic globular cluster ω Centauri. The UV WFC3 data have been coupled with available Wide Field Channel/Advanced Camera for Su…
The ACS Survey of Galactic Globular Clusters. VIII. Effects of Environment on Globular Cluster Global Mass Functions
Anderson, Jay; Dotter, Aaron; Sarajedini, Ata +12 more
We have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic Globular Clusters to construct global present-day mass functions for 17 globular clusters utilizing multi-mass King models to extrapolate from our observations to the global cluster behavior. The global present-day mass functions for these clusters are …
The Distance to NGC 1316 (Fornax A) from Observations of Four Type Ia Supernovae
Morrell, Nidia; Madore, Barry F.; Freedman, Wendy L. +15 more
The giant elliptical galaxy NGC 1316 (Fornax A) is a well-studied member of the Fornax Cluster and a prolific producer of Type Ia supernovae (SNe Ia), having hosted four observed events since 1980. Here, we present detailed optical- and near-infrared light curves of the spectroscopically normal SN 2006dd. These data are used, along with previously…