Search Publications
Passively Evolving Early-Type Galaxies at 1.4 <~ z <~ 2.5 in the Hubble Ultra Deep Field
Cimatti, A.; Daddi, E.; Panagia, N. +13 more
We report on a complete sample of seven luminous early-type galaxies in the Hubble Ultra Deep Field (UDF) with spectroscopic redshifts between 1.39 and 2.47, and to KAB<23. Using the BzK selection criterion, we have preselected a set of objects over the UDF, which fulfill the photometric conditions for being passively evolving galaxi…
The Relationship between Luminosity and Broad-Line Region Size in Active Galactic Nuclei
Kaspi, Shai; Peterson, Bradley M.; Maoz, Dan +3 more
We reinvestigate the relationship between the characteristic broad-line region size (RBLR) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of RBLR for a large number of active galactic nuclei (AGNs) from Peterson et al. Using their determina…
Evolution of the Solar Activity over Time and Effects on Planetary Atmospheres. I. High-Energy Irradiances (1-1700 Å)
Güdel, Manuel; Guinan, Edward F.; Audard, Marc +1 more
We report on the results of the Sun in Time multiwavelength program (X-rays to UV) of solar analogs with ages covering ~0.1-7 Gyr. The chief science goals are to study the solar magnetic dynamo and to determine the radiative and magnetic properties of the Sun during its evolution across the main sequence. The present paper focuses on the latter go…
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…
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 …