Search Publications
Radio Jet Proper-motion Analysis of Nine Distant Quasars above Redshift 3.5
Frey, Sándor; Gabányi, Krisztina Éva; An, Tao +2 more
Up to now, jet kinematic studies of radio quasars have barely reached beyond the redshift range z > 3.5. This significantly limits our knowledge of high-redshift jets, which can provide key information for understanding the jet nature and the growth of black holes in the early universe. In this paper, we selected nine radio-loud quasars at z &g…
A Quarter Century of Guitar Nebula/Filament Evolution
Kargaltsev, Oleg; Klingler, Noel; Slane, Patrick +6 more
We have collected a new deep Chandra X-Ray Observatory exposure of PSR B2224+65 and the "Guitar Nebula," mapping the complex X-ray structure. This is accompanied by a new Hubble Space Telescope (HST) Hα image of the head of the Guitar. Comparing the HST and Chandra structures in four epochs over 25 yr, we constrain the evolution of the TeV particl…
The Dark Matter Halo of M54
Grillmair, Carl J.; Carlberg, Raymond G.
M54 is a prototype for a globular cluster embedded in a dark matter halo. Gaia Early Data Release 3 photometry and proper motions separate the old, metal-poor stars from the more metal-rich and younger dwarf galaxy stars. The metal-poor stars dominate the inner 50 pc, with a velocity dispersion profile that declines to a minimum around 30 pc then …
LARS XIII: High Angular Resolution 21 cm H I Observations of Lyα Emitting Galaxies
Cannon, John M.; Hayes, Matthew; Östlin, Göran +8 more
The Lyα emission line is one of the main observables of galaxies at high redshift, but its output depends strongly on the neutral gas distribution and kinematics around the star-forming regions where UV photons are produced. We present observations of Lyα and 21 cm H I emission at comparable scales with the goal to qualitatively investigate how th…
Optical-Radio Position Offsets Are Inversely Correlated with AGN Photometric Variability
Secrest, Nathan J.
Using photometric variability information from the new Gaia DR3 release, I show for the first time that photometric variability is inversely correlated with the prevalence of optical-radio position offsets in the active galactic nuclei (AGNs) that comprise the International Celestial Reference Frame (ICRF). While the overall prevalence of statisti…
Connecting Low- and High-redshift Weak Emission-line Quasars via Hubble Space Telescope Spectroscopy of Lyα Emission
Brandt, W. N.; Anderson, Scott F.; Fan, Xiaohui +10 more
We present ultraviolet spectroscopy covering the Lyα + N V complex of six candidate low-redshift (0.9 < z < 1.5) weak emission-line quasars (WLQs) based on observations with the Hubble Space Telescope. The original systematic searches for these puzzling Type 1 quasars with intrinsically weak broad emission lines revealed an N ≈ 100 WLQ popul…
SKYSURF-3: Testing Crowded Object Catalogs in the Hubble eXtreme Deep Field Mosaics to Study Sample Incompleteness from an Extragalactic Background Light Perspective
Pirzkal, Nor; Windhorst, Rogier A.; Koekemoer, Anton +6 more
Extragalactic background light (EBL) studies have revealed a significant discrepancy between direct measurements-via instruments measuring "bare" sky from which Zodiacal and Galactic light models are subtracted-and measurements of the integrated galaxy light (IGL). This discrepancy could lie in either method, whether it be an incomplete Zodiacal m…
A Star-sized Impact-produced Dust Clump in the Terrestrial Zone of the HD 166191 System
Rieke, G. H.; Kennedy, Grant M.; Su, Kate Y. L. +2 more
We report on five years of 3-5 µm photometry measurements obtained by warm Spitzer to track the dust debris emission in the terrestrial zone of HD 166191 in combination with simultaneous optical data. We show that the debris production in this young (~10 Myr) system increased significantly in early 2018 and reached a record high level (almos…
Radio Observations of Four Active Galactic Nuclei Hosting Intermediate-mass Black Hole Candidates: Studying the Outflow Activity and Evolution
Ho, Luis C.; Zhang, Shaohua; Yang, Jun +5 more
Observational searches for intermediate-mass black holes (IMBHs; 102-106 M ⊙) include relatively isolated dwarf galaxies. For those that host active galactic nuclei (AGNs), the IMBH nature may be discerned through the accretion-jet activity. We present radio observations of four AGN-hosting dwarf galaxies, which po…
Far-ultraviolet Flares on Accreting Protostars: Weak and Classical T Tauri Stellar Pair Analysis
Kowalski, Adam F.; France, Kevin; Hinton, P. C. +5 more
The far-ultraviolet (FUV) emission of classical T Tauri stars (CTTSs) is known to play an important role in protoplanetary disk dispersal and giant planet formation, yet the role played by protostellar flares in these processes is largely unknown. We use nearby star-forming regions as laboratories to probe the FUV flare characteristics of CTTSs an…