Search Publications
The Obscured Fraction of Active Galactic Nuclei in the XMM-COSMOS Survey: A Spectral Energy Distribution Perspective
Treister, E.; Salvato, M.; Vignali, C. +7 more
The fraction of active galactic nucleus (AGN) luminosity obscured by dust and re-emitted in the mid-IR is critical for understanding AGN evolution, unification, and parsec-scale AGN physics. For unobscured (Type 1) AGNs, where we have a direct view of the accretion disk, the dust covering factor can be measured by computing the ratio of re-process…
Magnetohydrodynamic Modeling of the Solar Eruption on 2010 April 8
van Ballegooijen, A. A.; DeLuca, E. E.; Kliem, B. +1 more
The structure of the coronal magnetic field prior to eruptive processes and the conditions for the onset of eruption are important issues that can be addressed through studying the magnetohydrodynamic (MHD) stability and evolution of nonlinear force-free field (NLFFF) models. This paper uses data-constrained NLFFF models of a solar active region (…
The Outburst Decay of the Low Magnetic Field Magnetar SGR 0418+5729
Tiengo, A.; Götz, D.; Stella, L. +20 more
We report on the long-term X-ray monitoring of the outburst decay of the low magnetic field magnetar SGR 0418+5729 using all the available X-ray data obtained with RXTE, Swift, Chandra, and XMM-Newton observations from the discovery of the source in 2009 June up to 2012 August. The timing analysis allowed us to obtain the first measurement of the …
The Atacama Cosmology Telescope: Dynamical Masses and Scaling Relations for a Sample of Massive Sunyaev-Zel'dovich Effect Selected Galaxy Clusters
Hilton, Matt; Hasselfield, Matthew; Sifón, Cristóbal +33 more
We present the first dynamical mass estimates and scaling relations for a sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample consists of 16 massive clusters detected with the Atacama Cosmology Telescope (ACT) over a 455 deg2 area of the southern sky. Deep multi-object spectroscopic observations were taken to …
Star Count Density Profiles and Structural Parameters of 26 Galactic Globular Clusters
Dalessandro, E.; Sanna, N.; Beccari, G. +6 more
We used an appropriate combination of high-resolution Hubble Space Telescope observations and wide-field, ground-based data to derive the radial stellar density profiles of 26 Galactic globular clusters from resolved star counts (which can be all freely downloaded on-line). With respect to surface brightness (SB) profiles (which can be biased by t…
The Space Motion of Leo I: Hubble Space Telescope Proper Motion and Implied Orbit
van der Marel, Roeland P.; Majewski, Steven R.; Besla, Gurtina +3 more
We present the first absolute proper motion measurement of Leo I, based on two epochs of Hubble Space Telescope ACS/WFC images separated by ~5 years in time. The average shift of Leo I stars with respect to ~100 background galaxies implies a proper motion of (µ W , µ N ) = (0.1140 ± 0.0295, -0.1256 ± 0.0293) mas y…
The Gemini NICI Planet-Finding Campaign: The Frequency of Giant Planets around Young B and A Stars
Nielsen, Eric L.; Lin, Douglas N. C.; Shkolnik, Evgenya L. +22 more
We have carried out high contrast imaging of 70 young, nearby B and A stars to search for brown dwarf and planetary companions as part of the Gemini NICI Planet-Finding Campaign. Our survey represents the largest, deepest survey for planets around high-mass stars (≈1.5-2.5 M ⊙) conducted to date and includes the planet hosts β Pic and F…
LoCuSS: The Steady Decline and Slow Quenching of Star Formation in Cluster Galaxies over the Last Four Billion Years
Finoguenov, A.; Smith, G. P.; Okabe, N. +8 more
We present an analysis of the levels and evolution of star formation activity in a representative sample of 30 massive galaxy clusters at 0.15 < z < 0.30 from the Local Cluster Substructure Survey, combining wide-field Spitzer/MIPS 24 µm data with extensive spectroscopy of cluster members. The specific SFRs of massive ( {M} \gtrsim 10^…
First Spectroscopic Evidence for High Ionization State and Low Oxygen Abundance in Lyα Emitters
Ono, Yoshiaki; Ouchi, Masami; Shimasaku, Kazuhiro +3 more
We present results from Keck/NIRSPEC and Magellan/MMIRS follow-up spectroscopy of Lyα emitters (LAEs) at z = 2.2 identified in our Subaru narrowband survey. We successfully detect Hα emission from seven LAEs, and perform a detailed analysis of six LAEs free from active galactic nucleus activity, two out of which, CDFS-3865 and COSMOS-30679, have […
Low Masses and High Redshifts: The Evolution of the Mass-Metallicity Relation
Martin, Crystal L.; Bunker, Andrew J.; Scarlata, Claudia +15 more
We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 108 <~ M/M ⊙ <~ 1010, obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 <~ z <~ 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope W…