Search Publications
The Substructures in the Local Stellar Halo from Gaia and LAMOST
Donlon, Thomas; Du, Cuihua; Li, Hefan +2 more
Based on the second Gaia data release and spectroscopy from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope Data, we identified 20,089 halo stars kinematically and chemically. The halo streams in the solar neighborhood could be detected in the space of energy and angular momentum. We reshuffle the velocities of these stars to determi…
High- and Low-α Disk Stars Separate Dynamically at All Ages
Ness, Melissa K.; Gandhi, Suroor S.
There is a dichotomy in the Milky Way in the [α/Fe]-[Fe/H] plane, in which stars fall into high-α and low-α sequences. The high-α sequence comprises mostly old stars, and the low-α sequence comprises primarily young stars. The origin of this dichotomy is uncertain. To better understand how the high- and low-α stars are affiliated, we examine if th…
Probing Structure in Cold Gas at z ≲ 1 with Gravitationally Lensed Quasar Sight Lines
Ellison, Sara L.; Kulkarni, Varsha P.; Lopez, Sebastian +3 more
Absorption spectroscopy of gravitationally lensed quasars (GLQs) enables study of spatial variations in the interstellar and/or circumgalactic medium of foreground galaxies. We report observations of four GLQs, each with two images separated by 0.″8-3.″0, that show strong absorbers at redshifts 0.4 < z abs < 1.3 in their spectra, …
The Stellar-to-halo Mass Ratios of Passive and Star-forming Galaxies at z ∼ 2-3 from the SMUVS Survey
Caputi, Karina I.; Le Fèvre, Olivier; Fazio, Giovanni G. +6 more
In this work, we use measurements of galaxy stellar mass and two-point angular correlation functions to constrain the stellar-to-halo mass ratios (SHMRs) of passive and star-forming galaxies at z ∼ 2-3, as identified in the Spitzer Matching Survey of the UltraVISTA ultra-deep Stripes. We adopt a sophisticated halo modeling approach to statisticall…
Rotating Solar Models with Low Metal Abundances as Good as Those with High Metal Abundances
Yang, Wuming
Standard solar models (SSMs) constructed in accord with low metal abundances disagree with seismically inferred results. We constructed rotating solar models with low metal abundances that included enhanced settling and convection overshoot. In one of our rotating models, AGSSr2a, the convection overshoot allowed us to recover the radius of the ba…
Properties of the Umbral Filament Observed in Active Region NOAA 12529
Murabito, Mariarita; Guglielmino, Salvo L.; Romano, Paolo +2 more
Recent observations of the solar photosphere revealed the presence of elongated filamentary bright structures inside sunspot umbrae, called umbral filaments (UFs). These features differ in morphology, magnetic configuration, and evolution from light bridges (LBs) that are usually observed to intrude in sunspots. To characterize a UF observed in th…
Fluorine Abundances in the Galactic Disk
Cunha, Katia; Smith, Verne V.; Hayes, Christian R. +5 more
The chemical evolution of fluorine is investigated in a sample of Milky Way red giant stars that span a significant range in metallicity from [Fe/H] ∼ -1.3 to 0.0 dex. Fluorine abundances are derived from vibration-rotation lines of HF in high-resolution infrared spectra near 2.335 µm. The red giants are members of the thin and thick disk/ha…
Unusual Isotopic Abundances in a Fully Convective Stellar Binary
Mills, E. A. C.; Crossfield, I. J. M.; Lothringer, J. D. +6 more
Low-mass M dwarfs represent the most common outcome of star formation, but their complex emergent spectra hinder detailed studies of their composition and initial formation. The measurement of isotopic ratios is a key tool that has been used to unlock the formation of our solar system, the Sun, and the nuclear processes within more massive stars. …
The Duration of Star Formation in Galactic Giant Molecular Clouds. I. The Great Nebula in Carina
Povich, Matthew S.; Nuñez, Evan Haze; Robitaille, Thomas P. +1 more
We present a novel infrared spectral energy distribution (SED) modeling methodology that uses likelihood-based weighting of the model fitting results to construct probabilistic Hertzsprung-Russell diagrams (pHRD) for X-ray-identified, intermediate-mass (2-8 M ⊙), pre-main-sequence young stellar populations. This methodology is designed …
High-fidelity Imaging of the Inner AU Mic Debris Disk: Evidence of Differential Wind Sculpting?
Stark, Christopher C.; Kowalski, Adam F.; Davenport, James R. A. +17 more
We present new high-fidelity optical coronagraphic imagery of the inner ∼50 au of AU Mic’s edge-on debris disk using the BAR5 occulter of the Hubble Space Telescope Imaging Spectrograph (HST/STIS) obtained on 2018 July 26-27. This new imagery reveals that “feature A,” residing at a projected stellocentric separation of 14.2 au on the southeast sid…