Search Publications
Elemental Abundance Distributions in the (R, V ϕ ) Plane with LAMOST DR5 and Gaia DR2
Zhao, Gang; Chen, Yuqin; Zhao, Jingkun +4 more
Since Gaia DR2 was released, many velocity structures in the disk have been revealed, such as large-scale ridge-like patterns in phase space. Both kinematic information and stellar elemental abundances are needed to reveal their evolution history. We have used labels from the APOGEE survey to predict elemental abundances for a huge amount of low-r…
A Cepheid-based Distance to the Seyfert Galaxy NGC 6814
Peterson, Bradley M.; Ferrarese, Laura; Onken, Christopher A. +2 more
We present a Cepheid-based distance to the nearby Seyfert galaxy NGC 6814 from Hubble Space Telescope observations. We obtained F555W and F814W imaging over the course of 12 visits with logarithmic time spacing in 2013 August-October. We detected and made photometric measurements for 16,469 unique sources across all images in both filters, from wh…
COS Observations of the Cosmic Web: A Search for the Cooler Components of a Hot, X-Ray Identified Filament
Zahedy, Fakhri S.; Chen, Hsiao-Wen; Mulchaey, John S. +3 more
In the local universe, a large fraction of the baryon content is believed to exist as diffuse gas in filaments. While this gas is directly observable in X-ray emission around clusters of galaxies, it is primarily studied through its UV absorption. Recently, X-ray observations of large-scale filaments connecting to the cosmic web around the nearby …
Electron Acceleration in Middle-age Shell-type γ-Ray Supernova Remnants
Zhang, Xiao; Liu, Siming
Over the past decade, γ-ray observations of supernova remnants (SNRs) and accurate cosmic-ray (CR) spectral measurements have significantly advanced our understanding of particle acceleration in SNRs. In combination with multiwavelength observations of a large sample of SNRs, it has been proposed that the highest energy particles are mostly accele…
Asymmetric Mean Metallicity Distribution of the Milky Way’s Disk
An, Deokkeun
I present the mean metallicity distribution of stars in the Milky Way based on photometry from the Sloan Digital Sky Survey. I utilize an empirically calibrated set of stellar isochrones developed in previous work to estimate the metallicities of individual stars to a precision of 0.2 dex for reasonably bright stars across the survey area. I also …
Formation of Transition Alumina Dust around Asymptotic Giant Branch Stars: Condensation Experiments using Induction Thermal Plasma Systems
Tsuchiyama, Akira; Takigawa, Aki; Kim, Tae-Hee +5 more
Mid-infrared spectroscopic observations of oxygen-rich asymptotic giant branch (AGB) stars show the common presence of dust species that have a broad feature at ∼11-12 µm. Chemically synthesized amorphous alumina (Al2O3) is widely accepted as the source of this emission, although it is not obvious that amorphous alumina…
The Mass Dependence of Structure, Star Formation Rate, and Mass Assembly Mode at 0.5 < z < 2.5
Fang, Guanwen; Kong, Xu; Gu, Yizhou +5 more
To investigate the mass dependence of structural transformation and star formation quenching, we construct three galaxy samples using massive (M * > 1010 M ⊙) red, green, and blue galaxy populations at 0.5 < z < 2.5 in five 3D-HST/CANDELS fields. The structural parameters, including effective radius (r
Evolution of the Extended X-Ray Emission from the PSR B1259-63/LS 2883 Binary in the 2014-2017 Binary Cycle
Kargaltsev, Oleg; Hare, Jeremy; Pavlov, George +1 more
We have performed a series of Chandra X-ray Observatory observations of the gamma-ray binary LS 2883, which is composed of a young pulsar (PSR B1259-63) orbiting a massive Be star with a period of 1236.7 days. The system was observed in five epochs, spanning a range from 352 to 1175 days after the periastron passage on 2014 May 4. The observations…
Does High-density or Mass Help Star Clusters Produce X-Ray Binaries in Star-forming Galaxies?
Chandar, R.; Johns Mulia, P.; Rangelov, B.
It is now widely accepted that many X-ray binaries (XRBs) form in compact star clusters. Therefore, it follows that there may be a link between the properties of star clusters and the production of XRBs. We study the masses and densities of compact clusters with different ages found in the merging Antennae galaxies and in the dwarf starburst NGC 4…
Atmospheres and UV Environments of Earth-like Planets throughout Post-main-sequence Evolution
Kaltenegger, Lisa; Kozakis, Thea
During the post-main-sequence (post-MS) phase of stellar evolution, the orbital distance of the habitable zone (HZ), which allows for liquid surface water on terrestrial planets, moves out past the system’s original frost line, providing an opportunity for outer planetary system surface habitability. We use a 1D coupled climate/photochemistry code…