Search Publications
MCR-TRGB: A Multiwavelength-covariant, Robust Tip of the Red Giant Branch Measurement Method
Dalcanton, J. J.; Boyer, M. L.; Williams, B. F. +2 more
We present a new method to measure colors and magnitudes of the tip of the red giant branch (TGRB) in multiple bandpasses simultaneously by fitting an n-dimensional Gaussian to photometry of candidate tip stars. We demonstrate that this method has several advantages over traditional edge detection, particularly in regimes where the TRGB magnitude …
Hyper Suprime-Cam Low Surface Brightness Galaxies. II. A Hubble Space Telescope Study of the Globular Cluster Systems of Ultradiffuse Galaxies in Groups
Greene, Jenny E.; Goulding, Andy D.; Beaton, Rachael L. +4 more
We increase the sample of ultradiffuse galaxies (UDGs) in lower-density environments with characterized globular cluster (GC) populations using new Hubble Space Telescope observations of nine UDGs in group environments. While the bulk of our UDGs have GC abundances consistent with normal dwarf galaxies, two of these UDGs have excess GC populations…
Imaging and Spectral Study on the Null Point of a Fan-spine Structure During a Solar Flare
Yang, Shuhong; Zhang, Jun; Zhong, Ze +3 more
Using the multi-instrument observations, we make the first simultaneous imaging and spectral study on the null point of a fan-spine magnetic topology during a solar flare. When magnetic reconnection occurs at the null point, the fan-spine configuration brightens in the (extreme-)ultraviolet channels. In the Hα images, the fan-spine structure is pa…
Revealing the Dark Threads of the Cosmic Web
Tripp, Todd M.; Prochaska, J. Xavier; Tejos, Nicolas +4 more
Modern cosmology predicts that matter in our universe today has assembled into a vast network of filamentary structures colloquially termed the "cosmic web." Because this matter is either electromagnetically invisible (I.e., dark) or too diffuse to image in emission, tests of this cosmic web paradigm are limited. Wide-field surveys do reveal web-l…
Binary Fraction Estimation of Main-sequence Stars in 12 Open Clusters: Based on the Homogeneous Data of LAMOST Survey and Gaia DR2
Wang, Jiaxin; Fu, Jianning; Niu, Hubiao
Based on the homogeneous low-resolution spectra data observed by Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the Gaia Data Release 2 (Gaia DR2) photometric data, we chose 12 open clusters (OCs) to study their fundamental parameters and binary fractions (BFs). For each OC, more than 20 cluster members were observed by LAM…
A Gravitational Redshift Measurement of the White Dwarf Mass-Radius Relation
Cheng, Sihao; Zakamska, Nadia L.; Chandra, Vedant +1 more
The mass-radius relation of white dwarfs is largely determined by the equation of state of degenerate electrons, which causes the stellar radius to decrease as mass increases. Here we observationally measure this relation using the gravitational redshift effect, a prediction of general relativity that depends on the ratio between stellar mass and …
ALMA Observations of Quasar Host Galaxies at z ≃ 4.8
Maiolino, Roberto; Trakhtenbrot, Benny; Netzer, Hagai +4 more
We present ALMA Band 7 data of the [C II] $\lambda 157.74\,\mu {\rm{m}}$ emission line and underlying far-IR (FIR) continuum for 12 luminous quasars at $z\simeq 4.8$ powered by fast-growing supermassive black holes (SMBHs). Our total sample consists of 18 quasars, 12 of which are presented here for the first time. The new sources consist of six He…
Disk Illumination and Jet Variability of the Herbig Ae Star HD 163296 Using Multi-epoch HST/STIS Optical, Near-IR, and Radio Imagery and Spectroscopy
Fukagawa, Misato; Sitko, Michael L.; Grady, Carol A. +3 more
We present two new epochs of Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph coronagraphic imaging, along with multi-epoch optical, near-IR, and radio monitoring, of the HD 163296 system. We find that ansae features identified in earlier-epoch HST imagery are a fourth ring that resides at a semimajor axis distance of 3"25 (330 au…
Properties of Solar Rossby Waves from Normal Mode Coupling and Characterizing Its Systematics
Mandal, Krishnendu; Hanasoge, Shravan
Rossby waves play an important role in mediating the angular momentum of rotating spherical fluids, creating weather on Earth and tuning exoplanet orbits in distant stellar systems. Their recent discovery in the solar convection zone provides an exciting opportunity to appreciate the detailed astrophysics of Rossby waves. Large-scale Rossby waves …
Using Data Imputation for Signal Separation in High-contrast Imaging
Debes, John H.; Duchêne, Gaspard; Perrin, Marshall D. +5 more
To characterize circumstellar systems in high-contrast imaging, the fundamental step is to construct a best point-spread function (PSF) template for the noncircumstellar signals (I.e., starlight and speckles) and separate it from the observation. With existing PSF construction methods, the circumstellar signals (e.g., planets, circumstellar disks)…