Search Publications
Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
Burrows, A.; Budaj, J.; Hubeny, I.
We present theoretical atmosphere, spectral, and light-curve models for extrasolar giant planets (EGPs) undergoing strong irradiation for which Spitzer planet/star contrast ratios or light curves have been published (circa 2007 June). These include HD 209458b, HD 189733b, TrES-1, HD 149026b, HD 179949b, and υ And b. By comparing models with data, …
Variations of the Mid-IR Aromatic Features inside and among Galaxies
Madden, Suzanne C.; Jones, Anthony P.; Galliano, Frédéric +2 more
We present the results of a systematic study of mid-IR spectra of Galactic regions, Magellanic H II regions, and galaxies of various types (dwarf, spiral, starburst), observed by the satellites ISO and Spitzer. We study the relative variations of the 6.2, 7.7, 8.6, and 11.3 µm features inside spatially resolved objects (such as M82, M51, 30 …
Evidence for Quasar Activity Triggered by Galaxy Mergers in HST Observations of Dust-reddened Quasars
Lacy, Mark; Becker, Robert H.; Urrutia, Tanya
We present Hubble Space Telescope ACS images of 13 dust-reddened type 1 quasars selected from the FIRST/2MASS Red Quasar Survey. These quasars have high intrinsic luminosities after correction for dust obscuration (-23.5 >= MB >= - 26.2 from K-magnitude). The images show strong evidence of recent or ongoing interaction in 11 of th…
Ultraviolet Survey of CO and H2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships
Abel, N. P.; Gredel, R.; Lambert, D. L. +4 more
We carried out a comprehensive far-UV survey of 12CO and H2 column densities along diffuse molecular Galactic sight lines. This sample includes new measurements of CO from HST spectra along 62 sight lines and new measurements of H2 from FUSE data along 58 sight lines. In addition, high-resolution optical data were …
Evidence of Cosmic Evolution of the Stellar Initial Mass Function
van Dokkum, Pieter G.
Theoretical arguments and indirect observational evidence suggest that the stellar IMF may evolve with time, such that it is more weighted toward high-mass stars at higher redshift. Here we test this idea by comparing the rate of luminosity evolution of massive early-type galaxies in clusters at 0.02 <= z<= 0.83 to the rate of their color ev…
The Low-z Intergalactic Medium. III. H I and Metal Absorbers at z < 0.4
Shull, J. Michael; Danforth, Charles W.
We conduct an ultraviolet (HST and FUSE) spectroscopic survey of H I (Lyman lines) and seven metal ions (O VI, N V, C IV, C III, Si IV, Si III, Fe III) in the low-redshift IGM at z < 0.4. We analyzed 650 Lyα absorbers over redshift path length Δ z = 5.27, detecting numerous absorbers: 83 O VI systems, 39 C III, 53 Si III, 24 C IV, 24 N V, and s…
Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity
Faucher-Giguère, Claude-André; Hernquist, Lars; Lidz, Adam +1 more
We investigate the implications of the intergalactic opacity for the evolution of the cosmic UV luminosity density and its sources. Our main constraint is our measurement of the Lyα forest opacity at redshifts 2 <= z <= 4.2 from 86 high-resolution quasar spectra. In addition, we impose the requirements that H I must be reionized by z = 6 and…
The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei
Maiolino, Roberto; Brandt, W. N.; Kaspi, Shai +2 more
We study the hard X-ray spectral properties of 10 highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z = 1.3-3.2, including new XMM-Newton observations of four of these sources. We find a significant correlation between the normalized accretion rate (L/LEdd) and the hard X-ray photon index (Γ) for 35 moderate- to high-lum…
Inverse Compton Origin of the Hard X-Ray and Soft Gamma-Ray Emission from the Galactic Ridge
Bouchet, L.; Porter, Troy A.; Strong, Andrew W. +2 more
A recent redetermination of the nonthermal component of the hard X-ray to soft γ-ray emission from the Galactic ridge, using the SPI instrument on the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), is shown to be well reproduced as inverse Compton emission from the interstellar medium. Both cosmic-ray primary electrons and secondary e…
A Highly Complete Spectroscopic Survey of the GOODS-N Field
Wang, W. -H.; Barger, A. J.; Cowie, L. L.
We present a table of redshifts for 2907 galaxies and stars in the 145 arcmin2 HST ACS GOODS-North, making this the most spectroscopically complete redshift sample obtained to date in a field of this size. We also include the redshifts, where available, in a table containing just under 7000 galaxies from the ACS area with Ks, AB