Search Publications
Reversal of Fortune: Increased Star Formation Efficiencies in the Early Histories of Dwarf Galaxies?
Conroy, Charlie; Weisz, Daniel R.; Madau, Piero
On dwarf galaxy scales, the different shapes of the galaxy stellar mass function and the dark halo mass function require a star-formation efficiency (SFE) in these systems that is currently more than 1 dex lower than that of Milky Way-size halos. Here, we argue that this trend may actually be reversed at high redshift. Specifically, by combining t…
Exploring the X-Ray and γ-Ray Properties of the Redback Millisecond Pulsar PSR J1723-2837
Cheng, K. S.; Takata, J.; Kong, A. K. H. +5 more
We have investigated the X-ray and γ-ray properties of the redback millisecond pulsar PSR J1723-2837 with XMM-Newton, Chandra, and Fermi. We have discovered the X-ray orbital modulation of this binary system with a minimum that coincides with the phases of radio eclipse. The X-ray emission is clearly non-thermal in nature, which can be described w…
The Active Galactic Nucleus Population in X-Ray-selected Galaxy Groups at 0.5 < z < 1.1
Mulchaey, John S.; Bauer, Franz E.; Finoguenov, Alexis +6 more
We use Chandra data to study the incidence and properties of active galactic nuclei (AGNs) in 16 intermediate redshift (0.5 < z < 1.1) X-ray-selected galaxy groups in the Chandra Deep Field-South. We measure an AGN fraction of f(LX,H \gt 1042;MR < {-20}) = 8.0-2.3+3.0% at \bar{z} ∼ 0.…
HST/COS Detection of Deuterated Molecular Hydrogen in a Damped Lyα System at z = 0.18
Sembach, Kenneth R.; Tumlinson, Jason; Thom, Christopher +2 more
We report on the detection of deuterated molecular hydrogen, HD, at z = 0.18. HD and H2 are detected in HST/COS data of a low-metallicity (Z ~ 0.07 Z ⊙) damped Lyα (DLA) system at z = 0.18562 toward QSO B0120-28, with log N(H I) = 20.50 ± 0.10. Four absorption components are clearly resolved in H2, while two compon…
The Herschel Cold Debris Disks: Confusion with the Extragalactic Background at 160 µm
Rieke, George H.; Gáspár, András
The Herschel "DUst around NEarby Stars" (DUNES) survey has found a number of debris disk candidates that are apparently very cold, with temperatures near 22 K. It has proven difficult to fit their spectral energy distributions with conventional models for debris disks. Given this issue, we carefully examine the alternative explanation that the det…
The Formation and Launch of a Coronal Mass Ejection Flux Rope: A Narrative Based on Observations
DeForest, C. E.; Howard, T. A.
We present a data-driven narrative of the launch and early evolution of the magnetic structure that gave rise to the coronal mass ejection (CME) on 2008 December 12. The structure formed on December 7 and launched early on December 12. We interpret this structure as a flux rope based on prelaunch morphology, postlaunch magnetic measurements, and t…
Spinning Like a Blue Straggler: The Population of Fast Rotating Blue Straggler Stars in ω Centauri
Dalessandro, E.; Monaco, L.; Mucciarelli, A. +3 more
By using high-resolution spectra acquired with FLAMES-GIRAFFE at the ESO/VLT, we measured the radial and rotational velocities for 110 blue straggler stars (BSSs) in ω Centauri, the globular cluster-like stellar system harboring the largest known BSS population. According to their radial velocities, 109 BSSs are members of the system. The rotation…
Probing Asymmetric Structures in the Outskirts of Galaxies
Zheng, Xian Zhong; Wen, Zhang Zheng; An, Fang Xia
Upcoming large imaging surveys will allow detailed studies of the structure and morphology of galaxies aimed at addressing how galaxies form and evolve. Computational approaches are needed to characterize their morphologies over large samples. We introduce an automatic method to quantify the outer structure of galaxies. The key to our approach is …
A 33 Yr Constancy of the X-Ray Coronae of AR Lac and Eclipse Diagnosis of Scale Height
Drake, Jeremy J.; Huenemoerder, David P.; Ratzlaff, Peter +3 more
Extensive X-ray and EUV photometric observations of the eclipsing RS CVn system AR Lac were obtained over the years 1997-2013 with the Chandra X-Ray Observatory Extreme-Ultraviolet Explorer (EUVE). During primary eclipse, High Resolution Camera count rates decrease by ~40%. A similar minimum is seen during one primary eclipse observed by EUVE but …
Accretion-Inhibited Star Formation in the Warm Molecular Disk of the Green-valley Elliptical Galaxy NGC 3226?
Duc, P. -A.; Armus, L.; Appleton, P. N. +7 more
We present archival Spitzer photometry and spectroscopy and Herschel photometry of the peculiar "Green Valley" elliptical galaxy NGC 3226. The galaxy, which contains a low-luminosity active galactic nucleus (AGN), forms a pair with NGC 3227 and is shown to lie in a complex web of stellar and H I filaments. Imaging at 8 and 16 µm reveals a cu…