Search Publications
The True Durations of Starbursts: Hubble Space Telescope Observations of Three Nearby Dwarf Starburst Galaxies
McQuinn, Kristen B. W.; Cannon, John M.; Skillman, Evan D. +4 more
The duration of a starburst is a fundamental parameter affecting the evolution of galaxies yet, to date, observational constraints on the durations of starbursts are not well established. Here we study the recent star formation histories of three nearby dwarf galaxies to rigorously quantify the duration of their starburst events using a uniform an…
Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition
Dupuy, Trent J.; Ireland, Michael J.; Liu, Michael C.
We present Keck laser guide star adaptive optics imaging and aperture masking observations of the M8+L7 binary LHS 2397aAB. Together with archival Hubble Space Telescope, Gemini-North, and Very Large Telescope data, our observations span 11.8 years of the binary's 14.2 year orbital period. We determine a total dynamical mass of 0.146+0.015
On the Structure and Evolution of Complexity in Sigmoids: A Flux Emergence Model
Golub, L.; Hood, A. W.; Savcheva, A. +2 more
Sigmoids are structures with a forward or inverse S-shape, generally observed in the solar corona in soft X-ray emission. It is believed that the appearance of a sigmoid in an active region is an important factor in eruptive activity. The association of sigmoids with dynamic phenomena such as flares and coronal mass ejections (CMEs) make the study…
The Color-Magnitude Relation for Metal-Poor Globular Clusters in M87: Confirmation from Deep HST/ACS Imaging
Meurer, Gerhardt R.; Jordán, Andrés; Mieske, Steffen +6 more
Metal-poor globular clusters (GCs) are our local link to the earliest epochs of star formation and galaxy building. Studies of extragalactic GC systems using deep, high-quality imaging have revealed a small but significant slope to the color-magnitude relation for metal-poor GCs in a number of galaxies. We present a study of the M87 GC system usin…
Infrared Spectrograph Spectroscopy and Multi-Wavelength Study of Luminous Star-Forming Galaxies at z ≃ 1.9
Smail, I.; Daddi, E.; Le Floc'h, E. +24 more
We analyze a sample of galaxies chosen to have F 24 µm > 0.5 mJy and satisfy a certain IRAC color criterion. Infrared Spectrograph (IRS) spectra yield redshifts, spectral types, and polycyclic aromatic hydrocarbons (PAH) luminosities, to which we add broadband photometry from optical through IRAC wavelengths, MIPS from 24-160 &…
z ~ 7-10 Galaxies Behind Lensing Clusters: Contrast with Field Search Results
Broadhurst, Tom; Franx, Marijn; Illingworth, Garth D. +6 more
We conduct a search for z gsim 7 dropout galaxies behind 11 massive lensing clusters using 21 arcmin2 of deep Hubble Space Telescope NICMOS, ACS, and WFPC2 image data. In total, over this entire area, we find only one robust z ~ 7 z-dropout candidate (previously reported around Abell 1689). Four less robust z-dropout and J-dropout candi…
The Physics of Crystallization From Globular Cluster White Dwarf Stars in NGC 6397
Kepler, S. O.; Montgomery, M. H.; Winget, D. E. +4 more
We explore the physics of crystallization in the deep interiors of white dwarf (WD) stars using the color-magnitude diagram and luminosity function constructed from proper-motion cleaned Hubble Space Telescope photometry of the globular cluster NGC 6397. We demonstrate that the data are consistent with the theory of crystallization of the ions in …
Comparing GC and Field LMXBs in Elliptical Galaxies with Deep Chandra and Hubble Data
Zezas, A.; Gallagher, J. S.; King, A. R. +15 more
We present a statistical study of the low-mass X-ray binary (LMXB) populations of three nearby, old elliptical galaxies: NGC 3379, NGC 4278, and NGC 4697. With a cumulative ~1 Ms Chandra ACIS observing time, we detect 90-170 LMXBs within the D25 ellipse of each galaxy. Cross-correlating Chandra X-ray sources and HST optical sources, we …
The Optical Structure of the Starburst Galaxy M82. I. Dynamics of the Disk and Inner-Wind
Bastian, N.; Smith, L. J.; Gallagher, J. S., III +3 more
We present Gemini-North GMOS-IFU observations of the central starburst clumps and inner wind of M82, together with WIYN DensePak IFU observations of the inner 2 × 0.9 kpc of the disk. These cover the emission lines of Hα, [N II], [S II], and [S III] at a spectral resolution of 45-80 km s-1. The high signal-to-noise of the data is suffic…
A Photoionized Nebula Surrounding and Variable Optical Continuum Emission from the Ultraluminous X-Ray Source in NGC 5408
Kaaret, Philip; Corbel, Stéphane
We obtained optical spectra of the counterpart of the ultraluminous X-ray source NGC 5408 X-1 using the FORS spectrograph on the Very Large Telescope. The spectra show strong high-excitation emission lines, He II λ4686 and [Ne V] λ3426, indicative of X-ray photoionization. Using the measured X-ray spectrum as input to a photoionization model, we c…