Search Publications
The Infrared Emission and Opening Angle of the Torus in Quasars
Ho, Luis C.; Zhuang, Ming-Yang; Shangguan, Jinyi
According to the unified model of active galactic nuclei (AGNs), a putative dusty torus plays an important role in determining an AGN’s external appearance. However, information on the physical properties of the torus is very scarce. We perform detailed decomposition of the infrared (1-500 µm) spectral energy distribution of 76 z < 0.5 Pa…
After the Fall: The Dust and Gas in E+A Post-starburst Galaxies
Draine, B. T.; Dale, D. A.; Crocker, A. F. +11 more
The traditional picture of post-starburst galaxies as dust- and gas-poor merger remnants, rapidly transitioning to quiescence, has been recently challenged. Unexpected detections of a significant interstellar medium (ISM) in many post-starburst galaxies raise important questions. Are they truly quiescent, and if so, what mechanisms inhibit further…
Reconnection Fluxes in Eruptive and Confined Flares and Implications for Superflares on the Sun
Veronig, Astrid M.; Hinterreiter, Jürgen; Pötzi, Werner +2 more
We study the energy release process of a set of 51 flares (32 confined, 19 eruptive) ranging from GOES class B3 to X17. We use Hα filtergrams from Kanzelhöhe Observatory together with Solar Dynamics Observatory HMI and Solar and Heliospheric Observatory MDI magnetograms to derive magnetic reconnection fluxes and rates. The flare reconnection flux …
An Analysis of ALMA Deep Fields and the Perceived Dearth of High-z Galaxies
Finkelstein, Steven L.; Casey, Caitlin M.; Zavala, Jorge A. +5 more
Deep, pencil-beam surveys from ALMA at 1.1-1.3 mm have uncovered an apparent absence of high-redshift dusty galaxies, with existing redshift distributions peaking around z ∼ 1.5-2.5. This has led to a perceived dearth of dusty systems at z ≳ 4 and the conclusion, according to some models, that the early universe was relatively dust-poor. In this p…
Two Episodes of Magnetic Reconnections during a Confined Circular-ribbon Flare
Hou, Yijun; Li, Ting; Yang, Shuhong +2 more
We analyze a unique event with an M1.8 confined circular-ribbon flare on 2016 February 13, with successive formations of two circular ribbons at the same location. The flare had two distinct phases of UV and extreme ultraviolet emissions with an interval of about 270 s, of which the second peak was energetically more important. The first episode w…
CME-driven Shock and Type II Solar Radio Burst Band Splitting
Temmer, Manuela; Kontar, Eduard P.; Chrysaphi, Nicolina +1 more
Coronal mass ejections (CMEs) are believed to be effective in producing shocks in the solar corona and interplanetary space. One of the important signatures of shocks and shock acceleration are Type II solar radio bursts that drift with the shock speed and produce bands of fundamental and higher harmonic plasma radio emission. An intriguing aspect…
IRIS and SDO Observations of Solar Jetlets Resulting from Network-edge Flux Cancelation
Tiwari, Sanjiv K.; De Pontieu, Bart; Panesar, Navdeep K. +3 more
Recent observations show that the buildup and triggering of minifilament eruptions that drive coronal jets result from magnetic flux cancelation at the neutral line between merging majority- and minority-polarity magnetic flux patches. We investigate the magnetic setting of 10 on-disk small-scale UV/EUV jets (jetlets, smaller than coronal X-ray je…
Statistical Analysis of Torus and Kink Instabilities in Solar Eruptions
Xu, Yan; Liu, Chang; Jing, Ju +4 more
A recent laboratory experiment of ideal magnetohydrodynamic instabilities revealed four distinct eruption regimes readily distinguished by the torus instability (TI) and helical kink instability (KI) parameters. To establish its observational counterpart, we collected 38 solar flares (stronger than GOES-class M5 in general) that took place within …
HelMod in the Works: From Direct Observations to the Local Interstellar Spectrum of Cosmic-Ray Electrons
Jóhannesson, G.; Moskalenko, I. V.; Porter, T. A. +11 more
The local interstellar spectrum (LIS) of cosmic-ray (CR) electrons for the energy range 1 MeV to 1 TeV is derived using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HELMOD, are combined to provide a single framework that…
MAGIICAT VI. The Mg II Intragroup Medium Is Kinematically Complex
Kacprzak, Glenn G.; Churchill, Christopher W.; Nielsen, Nikole M. +2 more
By comparing Mg II absorption in the circumgalactic medium (CGM) of group environments to isolated galaxies, we investigated the impact of environment on the CGM. An Mg II absorber is associated with a group if there are two or more galaxies at the absorption redshift within a projected distance of D = 200 kpc from a background quasar and a line-o…