Search Publications
Star Formation in NGC 5194 (M51a). II. The Spatially Resolved Star Formation Law
Gordon, Karl D.; Bot, Caroline; Calzetti, Daniela +20 more
We have studied the relationship between the star formation rate (SFR), surface density, and gas surface density in the spiral galaxy M51a (NGC 5194), using multiwavelength data obtained as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS). We introduce a new SFR index based on a linear combination of Hα emission-line and 24 µm con…
Radio Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications
Stawarz, Łukasz; Sikora, Marek; Lasota, Jean-Pierre
We investigate how the total radio luminosity of AGN-powered radio sources depends on their accretion luminosity and the central black hole mass. Our studies cover about 7 orders of magnitude in accretion luminosity (expressed in Eddington units, i.e., as Eddington ratios) and the full range of AGN black hole masses. We find that AGNs form two dis…
The Sloan Lens ACS Survey. IV. The Mass Density Profile of Early-Type Galaxies out to 100 Effective Radii
Treu, Tommaso; Gavazzi, Raphaël; Koopmans, Léon V. E. +5 more
We present a weak-lensing analysis of 22 early-type (strong) lens galaxies, based on deep HST images obtained as part of the Sloan Lens ACS Survey. Using advanced techniques to control systematic uncertainties, we show that weak-lensing signal is detected out to ~300 h-1 kpc (at the mean lens redshift z=0.2). We analyze blank control fi…
The Masses of Nuclear Black Holes in Luminous Elliptical Galaxies and Implications for the Space Density of the Most Massive Black Holes
Filippenko, Alexei V.; Ho, Luis C.; Gebhardt, Karl +11 more
Black hole (BH) masses predicted from the M•-σ relationship conflict with predictions from the M•-L relationship for high-luminosity galaxies, such as brightest cluster galaxies (BCGs). The M•-L relationship predicts that some BCGs may harbor BHs with M• approaching 1010 Msolar, whi…
The Hubble Diagram to Redshift >6 from 69 Gamma-Ray Bursts
Schaefer, Bradley E.
One of the few ways to measure the properties of dark energy is to extend the Hubble diagram (HD) to higher redshifts with gamma-ray bursts (GRBs). GRBs have at least five properties (their spectral lag, variability, spectral peak photon energy, time of the jet break, and the minimum rise time) that have correlations to the luminosity of varying q…
The X-Ray Properties of the Most Luminous Quasars from the Sloan Digital Sky Survey
Brandt, W. N.; Garmire, G. P.; Chartas, G. +4 more
Utilizing 21 new Chandra observations as well as archival Chandra, ROSAT, and XMM-Newton data, we study the X-ray properties of a representative sample of 59 of the most optically luminous quasars in the universe (Mi~-29.3 to -30.2) spanning a redshift range of z~1.5-4.5. Our full sample consists of 32 quasars from the Sloan Digital Sky…
What Do We Learn from IRAC Observations of Galaxies at 2 < z < 3.5?
van Dokkum, Pieter G.; Franx, Marijn; Labbé, Ivo +9 more
We analyze very deep HST, VLT, and Spitzer photometry of galaxies at 2<z<3.5 in the Hubble Deep Field-South. The sample is selected from the deepest public K-band imaging currently available. We show that the rest-frame U-V versus V-J color-color diagram is a powerful diagnostic of the stellar populations of distant galaxies. Galaxies with r…
Tip of the Red Giant Branch Distances. II. Zero-Point Calibration
Dolphin, Andrew E.; Shaya, Edward J.; Tully, R. Brent +4 more
The luminosity of the tip of the red giant branch (TRGB) provides an excellent measure of galaxy distances and is easily determined in the resolved images of nearby galaxies observed with Hubble Space Telescope. There is now a large amount of archival data that are relevant to the TRGB methodology and offer comparisons with other distance estimato…
Resolved Galaxies in the Hubble Ultra Deep Field: Star Formation in Disks at High Redshift
Ravindranath, Swara; Elmegreen, Bruce G.; Elmegreen, Debra Meloy +1 more
The photometric redshift distributions, spectral types, Sérsic indices, and sizes of all resolved galaxies in the Hubble Space Telescope Ultra Deep Field (UDF) are studied in order to understand the environment and nature of star formation in the early universe. Clumpy disk galaxies that are bright at short wavelengths (rest-frame λ<5000 Å) dom…
The Infrared Luminosity Function of Galaxies at Redshifts z = 1 and z ~ 2 in the GOODS Fields
Le Floc'h, E.; Dole, H.; Helou, G. +6 more
We present the rest-frame 8 µm LF at redshifts z=1 and ~2, computed from Spitzer 24 µm-selected galaxies in the GOODS fields over an area of 291 arcmin2. Using classification criteria based on X-ray data and IRAC colors, we identify the AGNs in our sample. The rest-frame 8 µm LFs for star-forming galaxies at redshifts …