Search Publications
The Implications of Local Fluctuations in the Galactic Midplane for Dynamical Analysis in the Gaia Era
Hogg, David W.; Laporte, Chervin F. P.; Ness, Melissa K. +6 more
Orbital properties of stars, computed from their six-dimensional phase-space measurements and an assumed Galactic potential, are used to understand the structure and evolution of the Galaxy. Stellar actions, computed from orbits, have the attractive quality of being invariant under certain assumptions and are therefore used as quantitative labels …
3.8 µm Imaging of 400-600 K Brown Dwarfs and Orbital Constraints for WISEP J045853.90+643452.6AB
Apai, D.; Rieke, Marcia; Marley, Mark S. +10 more
Half of the energy emitted by late-T- and Y-type brown dwarfs emerges at 3.5 ≤ λ µm ≤ 5.5. We present new L‧ (3.43 ≤ λ µm ≤ 4.11) photometry obtained at the Gemini North telescope for nine late-T and Y dwarfs, and synthesize L‧ from spectra for an additional two dwarfs. The targets include two binary systems that were imaged at a resol…
Carbon and Oxygen Isotopic Ratios. II. Semiregular Variable M Giants
Pilachowski, Catherine A.; Lambert, David L.; Hinkle, Kenneth H. +3 more
Carbon and oxygen isotopic ratios are reported for a sample of 51 SRb- and Lb-type variable asymptotic giant branch stars. Vibration-rotation first- and second-overtone CO lines in 1.5-2.5 µm spectra were measured to derive isotopic ratios for 12C/13C, 16O/17O, and 16O/18O. Co…
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…