Search Publications
Spitzer View on the Evolution of Star-forming Galaxies from z = 0 to z ~ 3
Papovich, Casey; Pérez-González, Pablo G.; Rieke, George H. +11 more
We use a 24 µm-selected sample containing more than 8000 sources to study the evolution of star-forming galaxies in the redshift range from z=0 to z~3. We obtain photometric redshifts for most of the sources in our survey using a method based on empirically built templates spanning from ultraviolet to mid-infrared wavelengths. The accuracy o…
The Effective Temperature Scale of FGK Stars. II. Teff:Color:[Fe/H] Calibrations
Meléndez, Jorge; Ramírez, Iván
We present up-to-date metallicity-dependent temperature versus color calibrations for main-sequence and giant stars based on temperatures derived with the infrared flux method (IRFM). Seventeen colors in the photometric systems UBV, uvby, Vilnius, Geneva, RI(Cousins), DDO, Hipparcos-Tycho, and Two Micron All Sky Survey (2MASS) have been calibrated…
Optimization of Starburst99 for Intermediate-Age and Old Stellar Populations
Leitherer, Claus; Vázquez, Gerardo A.
We have incorporated the latest release of the Padova models into the evolutionary synthesis code Starburst99. The Padova tracks were extended to include the full asymptotic giant branch (AGB) evolution until the final thermal pulse over the mass range 0.9-5 Msolar. With this addition, Starburst99 accounts for all stellar phases that co…
Toward an Understanding of the Rapid Decline of the Cosmic Star Formation Rate
Papovich, Casey; Pérez-González, Pablo G.; Bell, Eric F. +11 more
We present a first analysis of deep 24 µm observations with the Spitzer Space Telescope of a sample of nearly 1500 galaxies in a thin redshift slice, 0.65<=z<0.75. We combine the infrared data with redshifts, rest-frame luminosities, and colors from COMBO-17 and with morphologies from Hubble Space Telescope images collected by the Gala…
The Gemini Deep Deep Survey. VII. The Redshift Evolution of the Mass-Metallicity Relation
Juneau, S.; Glazebrook, K.; Abraham, R. G. +10 more
We have investigated the mass-metallicity (M-Z) relation using galaxies at 0.4<z<1.0 from the Gemini Deep Deep Survey (GDDS) and Canada-France Redshift Survey (CFRS). Deep K- and z'-band photometry allowed us to measure stellar masses for 69 galaxies. From a subsample of 56 galaxies, for which metallicity of the interstellar mediu…
Metallicities on the Double Main Sequence of ω Centauri Imply Large Helium Enhancement
Anderson, Jay; Bedin, Luigi R.; Recio-Blanco, Alejandra +9 more
Having shown in a recent paper that the main sequence of ω Centauri is split into two distinct branches, we now present spectroscopic results showing that the bluer sequence is less metal-poor. We have carefully combined VLT's GIRAFFE spectra of 17 stars on each side of the split into a single spectrum for each branch, with adequate signal-to-nois…
New Mass-Loss Measurements from Astrospheric Lyα Absorption
Linsky, J. L.; Redfield, S.; Zank, G. P. +2 more
Measurements of stellar mass-loss rates are used to assess how wind strength varies with coronal activity and age for solar-like stars. Mass loss generally increases with activity, but we find evidence that winds suddenly weaken at a certain activity threshold. Very active stars are often observed to have polar starspots, and we speculate that the…
Star Formation in NGC 5194 (M51a): The Panchromatic View from GALEX to Spitzer
Helou, G.; Roussel, H.; Leitherer, C. +32 more
Far-ultraviolet to far-infrared images of the nearby galaxy NGC 5194 (M51a), from a combination of space-based (Spitzer, GALEX, and Hubble Space Telescope) and ground-based data, are used to investigate local and global star formation and the impact of dust extinction. The Spitzer data provide unprecedented spatial detail in the infrared, down to …
Shock Geometry, Seed Populations, and the Origin of Variable Elemental Composition at High Energies in Large Gradual Solar Particle Events
Cohen, C. M. S.; Mewaldt, R. A.; Maclennan, C. G. +5 more
Above a few tens of MeV per nucleon, large, gradual solar energetic particle (SEP) events are highly variable in their spectral characteristics and elemental composition. The origin of this variability has been a matter of intense and ongoing debate. In this paper, we propose that this variability arises from the interplay of two factors-shock geo…
The Morphology-Density Relation in z ~ 1 Clusters
Ford, H. C.; Demarco, R.; Infante, L. +39 more
We measure the morphology-density relation (MDR) and morphology-radius relation (MRR) for galaxies in seven z~1 clusters that have been observed with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope. Simulations and independent comparisons of our visually derived morphologies indicate that ACS allows one to distinguish bet…