Search Publications
The Polytropic Behavior of Solar Wind Protons as Observed by the Ulysses Spacecraft during Solar Minimum
Livadiotis, George; Nicolaou, Georgios; McComas, David J.
We analyze proton bulk parameters derived from Ulysses observations and investigate the polytropic behavior of solar wind protons over a wide range of heliocentric distances and latitudes. The large-scale variations of the proton density and temperature over heliocentric distance indicate that plasma protons are governed by subadiabatic processes …
A Gaia Data Release 3 View on the Tip of the Red Giant Branch Luminosity
Casertano, Stefano; Li, Siyang; Riess, Adam G.
The tip of the red giant branch (TRGB) is a standard candle that can be used to help refine the determination of the Hubble constant. Gaia Data Release 3 (DR3) provides synthetic photometry constructed from low-resolution BP/RP spectra for Milky Way field stars that can be used to directly calibrate the luminosity of the TRGB in the Johnson-Cousin…
New Velocity Measurements of NGC 5128 Globular Clusters Out to 130 kpc: Outer Halo Kinematics, Substructure, and Dynamics
Forbes, Duncan A.; Caldwell, Nelson; Strader, Jay +11 more
We present new radial velocity measurements from the Magellan and the Anglo-Australian Telescopes for 175 previously known and 121 newly confirmed globular clusters (GCs) around NGC 5128, the nearest accessible massive early-type galaxy at D = 3.8 Mpc. Remarkably, 28 of these newly confirmed GCs are at projected radii $\gt 50^{\prime} $ (≳54 kpc),…
A Recipe for Unbiased Background Modeling in Deep Wide-field Astronomical Images
van Dokkum, Pieter; Abraham, Roberto; Pasha, Imad +9 more
Unbiased sky background modeling is crucial for the analysis of deep wide-field images, but it remains a major challenge in low surface brightness astronomy. Traditional image processing algorithms are often designed to produce artificially flat backgrounds, erasing astrophysically meaningful structures. In this paper, we present three ideas that …
Crossing the Rubicon of Reionization with z 5 QSOs
Grazian, Andrea; Boutsia, Konstantina; Fiore, Fabrizio +12 more
One of the key open questions in cosmology is the nature of sources that completed cosmological hydrogen reionization at z ~ 5.2. High-z primeval galaxies have been long considered the main drivers of reionization, with a minor role played by high-z active galactic nuclei (AGN). However, in order to confirm this scenario, it is fundamental to meas…
Lack of Correlations between Cold Molecular Gas and AGN Properties in Type 1 AGNs at z ≲ 0.5
Ho, Luis C.; Bauer, Franz E.; Treister, Ezequiel +3 more
We present new NOrthern Extended Millimeter Array (NOEMA) observations of the CO(2-1) emission in eight of the brightest Palomar-Green quasars at z ≲ 0.5 to investigate the role of active galactic nucleus (AGN) feedback in luminous quasars detected at low redshifts. We detect CO(2-1) emission in three objects, from which we derive CO luminosities,…
A Multiwavelength Light-curve Analysis of the Classical Nova YZ Ret: An Extension of the Universal Decline Law to the Nebular Phase
Kato, Mariko; Hachisu, Izumi
YZ Ret is the first X-ray flash detected classical nova, and is also observed in optical, X-ray, and gamma-ray. We propose a comprehensive model that explains the observational properties. The white dwarf mass is determined to be ~1.33 M ☉, which reproduces the multiwavelength light curves of YZ Ret, from optical, X-ray, to gamma-ray. W…
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K Dwarf
Vanderburg, Andrew; Bieryla, Allyson; Latham, David W. +31 more
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600 (V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of 6.80 ± 0.31 R ⊕
Metallicities of Classical Cepheids in the Inner Galactic Disk
Matsunaga, Noriyuki; D'Orazi, Valentina; McWilliam, Andrew +14 more
Metallicity gradients refer to the sloped radial profiles of the metallicities of gas and stars and are commonly seen in disk galaxies. A well-defined metallicity gradient of the Galactic disk is observed particularly well with classical Cepheids, which are good stellar tracers thanks to their period-luminosity relation, allowing precise distance …
A High-precision Survey of the D/H Ratio in the Nearby Interstellar Medium
Tripp, Todd M.; Jenkins, Edward B.; Chayer, Pierre +4 more
We present high signal-to-noise ratio measurements of the H I Lyα absorption line toward 16 Galactic targets that are at distances between approximately 190 and 2200 pc, all beyond the wall of the Local Bubble. We describe the models used to remove stellar emission and absorption features and the methods used to account for all known sources of er…