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Predictions of Astrometric Jitter for Sun-like Stars. I. The Model and Its Application to the Sun as Seen from the Ecliptic
Solanki, Sami K.; Shapiro, Alexander I.; Krivova, Natalie A.
The advent of Gaia, capable of measuring stellar wobbles caused by orbiting planets, raised interest in the astrometric detection of exoplanets. Another source of such wobbles (often also called jitter) is stellar magnetic activity. A quantitative assessment of the stellar astrometric jitter is important for a more reliable astrometric detection a…
Cosmography using strong-lensing systems and cosmic chronometers
Motta, V.; Lizardo, Andrés; Amante, Mario H. +2 more
Using a new sub-sample of observed strong gravitational lens systems, for the first time, we present the equation for the angular diameter distance in the y-redshift scenario for cosmography and use it to test the cosmographic parameters. In addition, we also use the observational Hubble data from cosmic chronometers and a joint analysis of both d…
FUV Observations of the Inner Coma of 46P/Wirtanen
Parker, Joel Wm.; Harris, Walter M.; Bodewits, Dennis +6 more
Far-ultraviolet observations of comets yield information about the energetic processes that dissociate the sublimated gases from their primitive surfaces. Understanding which emission processes are dominant, their effects on the observed cometary spectrum, and how to properly invert the spectrum back to the composition of the presumably pristine s…
Strong Correlation between Fe II/Mg II Ratio and Eddington Ratio of Type 1 Active Galactic Nuclei
Kim, Minjin; Nagao, Tohru; Woo, Jong-Hak +2 more
The Fe II/Mg II line flux ratio has been used as an indicator of the Fe/Mg abundance ratio in the broad-line region (BLR) of active galactic nuclei (AGNs). On the basis of archival rest-frame UV spectra obtained via the Hubble Space Telescope and the Sloan Digital Sky Survey, we investigate the Fe II/Mg II ratios of type 1 AGNs at z < 2. Over w…
Polarization of the Corona Observed During the 2017 and 2019 Total Solar Eclipses
Hanaoka, Yoichiro; Sakai, Yoshiaki; Takahashi, Koichi
We carried out polarimetric observations of the white-light corona during the total solar eclipses that occurred on August 21, 2017, and July 2, 2019, and successfully obtained data at two different sites for both eclipses. After eliminating the sky background, we derived the brightness, polarization brightness, and degree of polarization of the K…
The HASHTAG Project: The First Submillimeter Images of the Andromeda Galaxy from the Ground
Ho, Luis C.; Lee, Chien-Hsiu; Clark, Christopher J. R. +46 more
Observing nearby galaxies with submillimeter telescopes on the ground has two major challenges. First, the brightness is significantly reduced at long submillimeter wavelengths compared to the brightness at the peak of the dust emission. Second, it is necessary to use a high-pass spatial filter to remove atmospheric noise on large angular scales, …
Subaru Hyper Suprime-Cam revisits the large-scale environmental dependence on galaxy morphology over 360 deg2 at z = 0.3-0.6
Shimakawa, Rhythm; Tanaka, Masayuki; Tanaka, Takumi S. +1 more
This study investigates the role of large-scale environments on the fraction of spiral galaxies at z = 0.3-0.6 sliced to three redshift bins of Δz = 0.1. Here, we sample 276220 massive galaxies in a limited stellar mass of 5 × 1010 solar mass (~M*) over 360 deg2, as obtained from the Second Public Data Release of the Hyper Su…
Multiwavelength constraints on the unidentified Galactic TeV sources HESS J1427-608, HESS J1458-608, and new VHE γ-ray source candidates
Lemoine-Goumard, M.; Vasileiadis, G.; Renaud, M. +1 more
Aims: Among the γ-ray sources discovered at high and very-high energies, a large fraction still lack a clear identification. In particular, the H.E.S.S. Galactic Plane Survey (HGPS) revealed 78 TeV sources among which 47 are not clearly associated with a known object. Multiwavelength data can help identify the origin of the very-high energy γ…
The Challenge to MOND from Ultra-faint Dwarf Galaxies
Loeb, Abraham; Safarzadeh, Mohammadtaher
Modified Newtonian dynamics (MOND) at low acceleration has been astonishingly powerful at explaining the rotation curve of galaxies and the relation between the baryonic content of the galaxies and their observed circular velocity, known as the baryonic TullyFisher relationship. It is known that MOND fails at explaining the observed velocity dispe…
The Transition from Diffuse Molecular Gas to Molecular Cloud Material in Taurus
Kim, Hwihyun; Federman, S. R.; Lambert, David L. +6 more
We study four lines of sight that probe the transition from diffuse molecular gas to molecular cloud material in Taurus. Measurements of atomic and molecular absorption are used to infer the distribution of species and the physical conditions toward stars behind the Taurus Molecular Cloud (TMC). New high-resolution spectra at visible and near-IR w…