Search Publications
Modeling the Gravitational Potential of a Cosmological Dark Matter Halo with Stellar Streams
Helmi, Amina; Sanderson, Robyn E.; Hartke, Johanna
Stellar streams result from the tidal disruption of satellites and star clusters as they orbit a host galaxy, and can be very sensitive probes of the gravitational potential of the host system. We select and study narrow stellar streams formed in a Milky-Way-like dark matter halo of the Aquarius suite of cosmological simulations, to determine if t…
A Multi-wavelength Study of the Turbulent Central Engine of the Low-mass AGN Hosted by NGC 404
Davis, Timothy A.; Nguyen, Dieu D.; Nyland, Kristina +9 more
The nearby dwarf galaxy NGC 404 harbors a low-luminosity active galactic nucleus powered by the lowest-mass (<150,000 M ⊙) central massive black hole (MBH), with a dynamical mass constraint, currently known, thus providing a rare low-redshift analog to the MBH “seeds” that formed in the early universe. Here, we present new imaging of…
Type 2 AGN Host Galaxies in the Chandra-COSMOS Legacy Survey: No Evidence of AGN-driven Quenching
Schawinski, Kevin; Elvis, Martin; Lusso, Elisabeta +16 more
We investigate the star formation properties of a large sample of ∼2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z∼ 3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in th…
First Scattered-light Images of the Gas-rich Debris Disk around 49 Ceti
Debes, John H.; Roberge, Aki; Schneider, Glenn +31 more
We present the first scattered-light images of the debris disk around 49 Ceti, a ∼40 Myr A1 main-sequence star at 59 pc, famous for hosting two massive dust belts as well as large quantities of atomic and molecular gas. The outer disk is revealed in reprocessed archival Hubble Space Telescope NICMOS-F110W images, as well as new coronagraphic H-ban…
Global Solar Magnetic Field Organization in the Outer Corona: Influence on the Solar Wind Speed and Mass Flux Over the Cycle
Réville, Victor; Brun, Allan Sacha
The dynamics of the solar wind depends intrinsically on the structure of the global solar magnetic field, which undergoes fundamental changes over the 11-year solar cycle. For instance, the wind terminal velocity is thought to be anti-correlated with the expansion factor, a measure of how the magnetic field varies with height in the solar corona, …
Modulation of Galactic Cosmic Rays in the Inner Heliosphere, Comparing with PAMELA Measurements
Qin, G.; Shen, Z. -N.
We develop a numerical model to study the time-dependent modulation of galactic cosmic rays in the inner heliosphere. In the model, a time-delayed modified Parker heliospheric magnetic field (HMF) and a new diffusion coefficient model, NLGCE-F, from Qin & Zhang, are adopted. In addition, the latitudinal dependence of magnetic turbulence magnit…
The Properties of the Galactic Hot Gaseous Halo from X-Ray Emission
Li, Yunyang; Bregman, Joel
The extended hot X-ray emitting gaseous halo of the Milky Way has an optical depth ∼1 for the dominant emission lines of O vii and O viii, which are used to infer the halo properties. To improve on halo gas properties, we treat optical depth effects with a Monte Carlo radiative transfer model, which leads to slightly steeper density profiles (β ≈ …
Surge-like Oscillations above Sunspot Light Bridges Driven by Magnetoacoustic Shocks
He, Jiansen; Tian, Hui; Zhang, Jingwen +1 more
High-resolution observations of the solar chromosphere and transition region often reveal surge-like oscillatory activities above sunspot light bridges (LBs). These oscillations are often interpreted as intermittent plasma jets produced by quasi-periodic magnetic reconnection. We have analyzed the oscillations above an LB in a sunspot using data t…
The Bright and Dark Sides of High-redshift Starburst Galaxies from Herschel and Subaru Observations
Daddi, E.; Rodighiero, G.; Sanders, D. B. +15 more
We present rest-frame optical spectra from the FMOS-COSMOS survey of 12 z ∼ 1.6 Herschel starburst galaxies, with star formation rate (SFR) elevated by ×8, on average, above the star-forming main sequence (MS). Comparing the Hα to IR luminosity ratio and the Balmer decrement, we find that the optically thin regions of the sources contain on averag…
Observations of the Formation, Development, and Structure of a Current Sheet in an Eruptive Solar Flare
Seaton, Daniel B.; Bartz, Allison E.; Darnel, Jonathan M.
We present Atmospheric Imaging Assembly observations of a structure we interpret as a current sheet associated with an X4.9 flare and coronal mass ejection that occurred on 2014 February 25 in NOAA Active Region 11990. We characterize the properties of the current sheet, finding that the sheet remains on the order of a few thousand kilometers thic…