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The Milky Way has no in-situ halo other than the heated thick disc. Composition of the stellar halo and age-dating the last significant merger with Gaia DR2 and APOGEE
Katz, D.; Haywood, M.; Robichon, N. +5 more
Previous studies based on the analysis of Gaia DR2 data have revealed that accreted stars, possibly originating from a single progenitor satellite, are a significant component of the halo of our Galaxy, potentially constituting most of the halo stars at [Fe/H] < -1 within a few kpc from the Sun and beyond. In this paper, we couple astrometric d…
Cyclotron lines in highly magnetized neutron stars
Haberl, F.; Klochkov, D.; Santangelo, A. +10 more
Cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of…
MOSFIRE Spectroscopy of Quiescent Galaxies at 1.5 < z < 2.5. II. Star Formation Histories and Galaxy Quenching
Ellis, Richard S.; Belli, Sirio; Newman, Andrew B.
We investigate the stellar populations for a sample of 24 quiescent galaxies at 1.5 < z < 2.5 using deep rest-frame optical spectra obtained with Keck MOSFIRE. By fitting templates simultaneously to the spectroscopic and photometric data and exploring a variety of star formation histories, we obtain robust measurements of median stellar ages…
An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-ultraviolet Extinction and Its R-dependence
Gordon, Karl D.; Fitzpatrick, E. L.; Clayton, Geoffrey C. +2 more
We produce a set of 72 NIR-through-UV extinction curves by combining new Hubble Space Telescope/STIS optical spectrophotometry with existing International Ultraviolet Explorer spectrophotometry (yielding gapless coverage from 1150 to 10000 Å) and NIR photometry. These curves are used to determine a new, internally consistent NIR-through-UV Milky W…
Deep learning of multi-element abundances from high-resolution spectroscopic data
Bovy, Jo; Leung, Henry W.
Deep learning with artificial neural networks is increasingly gaining attention because of its potential for data-driven astronomy. However, this methodology usually does not provide uncertainties and does not deal with incompleteness and noise in the training data. In this work, we design a neural network for high-resolution spectroscopic analysi…
Detection of the Far-infrared [O III] and Dust Emission in a Galaxy at Redshift 8.312: Early Metal Enrichment in the Heart of the Reionization Era
Shibuya, Takatoshi; Inoue, Akio K.; Hashimoto, Takuya +19 more
We present the Atacama Large Millimeter/submillimeter Array detection of the [O III] 88 µm line and rest-frame 90 µm dust continuum emission in a Y-dropout Lyman break galaxy (LBG), MACS0416_Y1 lying behind the Frontier Field cluster MACS J0416.1-2403. This [O III] detection confirms the LBG with a spectroscopic redshift of z = 8.3118 …
Untangling the Galaxy. I. Local Structure and Star Formation History of the Milky Way
Kounkel, Marina; Covey, Kevin
Gaia DR2 provides unprecedented precision in measurements of the distance and kinematics of stars in the solar neighborhood. Through applying unsupervised machine learning on DR2's 5D data set (3D position + 2D velocity), we identify a number of clusters, associations, and comoving groups within 1 kpc and | b| < 30^\circ (many of which have not…
Observation of inverse Compton emission from a long γ-ray burst
Maraschi, L.; Troja, E.; Piro, L. +304 more
Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, kn…
Occurrence Rates of Planets Orbiting FGK Stars: Combining Kepler DR25, Gaia DR2, and Bayesian Inference
Ford, Eric B.; Ragozzine, Darin; Hsu, Danley C. +1 more
We characterize the occurrence rate of planets, ranging in size from 0.5 to 16 R ⊕, orbiting FGK stars with orbital periods from 0.5 to 500 days. Our analysis is based on results from the “DR25” catalog of planet candidates produced by NASA’s Kepler mission and stellar radii from Gaia “DR2.” We incorporate additional Kepler data product…
Compact Disks in a High-resolution ALMA Survey of Dust Structures in the Taurus Molecular Cloud
Pascucci, Ilaria; Edwards, Suzan; Banzatti, Andrea +24 more
We present a high-resolution (∼0.″12, ∼16 au, mean sensitivity of 50 µJy beam-1 at 225 GHz) snapshot survey of 32 protoplanetary disks around young stars with spectral type earlier than M3 in the Taurus star-forming region using the Atacama Large Millimeter Array. This sample includes most mid-infrared excess members that were not…