Search Publications
H 0 Tension and the Phantom Regime: A Case Study in Terms of an Infrared f(T) Gravity
El-Zant, Amr; El Hanafy, Waleed; Elgammal, Sherif
We propose an f(T) teleparallel gravity theory including a torsional infrared (IR) correction. We show that the governing Friedmann’s equations of a spatially flat universe include a phantom-like effective dark energy term sourced by the torsion IR correction. As has been suggested, this phantom phase does indeed act to reconcile the tension betwe…
Constraining the Magnetic Field in the TeV Halo of Geminga with X-Ray Observations
Liu, Ruo-Yu; Ge, Chong; Wang, Xiang-Yu +1 more
Recently, the High Altitude Water Cherenkov (HAWC) collaboration reported the discovery of a TeV halo around the Geminga pulsar. The TeV emission is believed to originate from the inverse Compton scattering of pulsar-injected electrons/positrons off cosmic microwave background photons. During this time, these electrons should inevitably radiate X-…
Chemical and Kinematic Properties of the Galactic Disk from the LAMOST and Gaia Sample Stars
Shi, Jianrong; Chen, Yuqin; Ma, Jun +5 more
We determined the chemical and kinematic properties of the Galactic thin and thick disk using a sample of 307,246 A/F/G/K-type giant stars from the LAMOST spectroscopic survey and Gaia DR2 survey. Our study found that the thick disk globally exhibits no metallicity radial gradient, but the inner disk (R ≤ 8 kpc) and the outer disk (R > 8 kpc) h…
Testing the Evolutionary Link between Type 1 and Type 2 Quasars with Measurements of the Interstellar Medium
Ho, Luis C.; Shangguan, Jinyi
In a popular scenario for the coevolution of massive black holes and galaxies, major mergers of gas-rich galaxies fuel vigorous star formation and obscured (type 2) quasar activity until energy feedback from the active galactic nucleus (AGN) clears away the gas and dust to reveal an unobscured (type 1) quasar. Under this scenario, the precursor ty…
Multi-epoch Direct Imaging and Time-variable Scattered Light Morphology of the HD 163296 Protoplanetary Disk
Henning, Thomas; Nakagawa, Takao; Terada, Hiroshi +58 more
We present H-band polarized scattered light imagery and JHK high-contrast spectroscopy of the protoplanetary disk around HD 163296 observed with the High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) and Subaru Coronagraphic Extreme Adaptive Optics (SCExAO)/Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) instrument…
X-Ray Observations of a z ∼ 6.2 Quasar/Galaxy Merger
Fan, Xiaohui; Mulchaey, John S.; Walter, Fabian +7 more
Quasars at early redshifts (z > 6) with companion galaxies offer unique insights into the growth and evolution of the first supermassive black holes. Here, we report on a 150 ks Chandra observation of PSO J308.0416-21.2339, a z = 6.23 quasar with a merging companion galaxy identified in [C II] and rest-frame UV emission. With {72.3}-8.6
Exomoons in the Habitable Zones of M Dwarfs
Piro, Anthony L.; Barnes, Rory; Martínez-Rodríguez, Héctor +2 more
M dwarfs host most of the exoplanets in the local Milky Way. Some of these planets, ranging from sub-Earths to super-Jupiters, orbit in their stars’ habitable zones (HZs), although many likely possess surface environments that preclude habitability. Moreover, exomoons around these planets could harbor life for long timescales and thus may also be …
A Method to Search for Black Hole Candidates with Giant Companions by LAMOST
Liu, Jifeng; Bai, Yu; Gu, Wei-Min +10 more
We propose a method to search for stellar-mass black hole (BH) candidates with giant companions from spectroscopic observations. Based on the stellar spectra of Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) Data Release 6, we obtain a sample of seven giants in binaries with large radial velocity variation ΔV R >…
Investigating the Transition Region Explosive Events and Their Relationship to Network Jets
Chen, Yajie; Tian, Hui; Peter, Hardi +2 more
Recent imaging observations with the Interface Region Imaging Spectrograph (IRIS) have revealed prevalent intermittent jets with apparent speeds of 80-250 km s-1 from the network lanes in the solar transition region (TR). Additionally, spectroscopic observations of the TR lines have revealed the frequent presence of highly non-Gaussian …
The Impact of the Environment on the Early Stages of Radio Source Evolution
Ostorero, Luisa; Guainazzi, Matteo; Stawarz, Łukasz +4 more
Compact symmetric objects (CSOs) show radio features such as jets, lobes, and hot spots that are contained within the central 1 kpc region of their host galaxy. Thus, they are thought to be among the progenitors of large-scale radio galaxies. A debate regarding whether the CSOs are compact primarily because they are young or because they are surro…