Search Publications
A Gaia-Enceladus Analog in the EAGLE Simulation: Insights into the Early Evolution of the Milky Way
Helmi, Amina; Tissera, Patricia B.; Bignone, Lucas A.
We identify a simulated Milky Way analog in the EAGLE suite of cosmological hydrodynamical simulations. This galaxy not only shares similar global properties as the Milky Way, but was specifically selected because its merger history resembles that currently known for the Milky Way. In particular we find that this Milky Way analog has experienced i…
Evidence for the Third Stellar Population in the Milky Way’s Disk
Beers, Timothy C.; Lee, Young Sun; Carollo, Daniela +6 more
The Milky Way is a unique laboratory in which stellar properties can be measured and analyzed in detail. In particular, stars in the older populations encode information on the mechanisms that led to the formation of our Galaxy. In this article, we analyze the kinematics, spatial distribution, and chemistry of a large number of stars in the solar …
The Near-ultraviolet Continuum Radiation in the Impulsive Phase of HF/GF-type dMe Flares. I. Data
Kowalski, Adam F.; Hawley, Suzanne L.; Valenti, Jeff A. +8 more
We present near-UV (NUV) flare spectra from the Hubble Space Telescope (HST)/Cosmic Origins Spectrograph during two moderate-amplitude U-band flares on the dM4e star GJ 1243. These spectra are some of the first accurately flux-calibrated, NUV flare spectra obtained over the impulsive phase in M dwarf flares. We observed these flares with a fleet o…
Discovery of a Close-separation Binary Quasar at the Heart of a z ∼ 0.2 Merging Galaxy and Its Implications for Low-frequency Gravitational Waves
Strauss, Michael A.; Mingarelli, Chiara M. F.; Greene, Jenny E. +3 more
Supermassive black hole (SMBH) binaries with masses of ∼108-109 M ⊙ are expected to dominate the contribution to the as-yet undetected gravitational wave background (GWB) signal at the nanohertz frequencies accessible to pulsar timing arrays. We currently lack firm empirical constraints on the amplitude of the GWB …
Fine-scale Explosive Energy Release at Sites of Prospective Magnetic Flux Cancellation in the Core of the Solar Active Region Observed by Hi-C 2.1, IRIS, and SDO
Tiwari, Sanjiv K.; Golub, Leon; Winebarger, Amy R. +14 more
The second Hi-C flight (Hi-C 2.1) provided unprecedentedly high spatial and temporal resolution (∼250 km, 4.4 s) coronal EUV images of Fe IX/X emission at 172 Å of AR 12712 on 2018 May 29, during 18:56:21-19:01:56 UT. Three morphologically different types (I: dot-like; II: loop-like; III: surge/jet-like) of fine-scale sudden-brightening events (ti…
Using Surface Brightness Fluctuations to Study Nearby Satellite Galaxy Systems: Calibration and Methodology
Greene, Jenny E.; Beaton, Rachael L.; Carlsten, Scott G. +1 more
We explore the use of ground-based surface brightness fluctuation (SBF) measurements to constrain distances to nearby dwarf galaxies. Using archival CFHT Megacam imaging data for a sample of 28 nearby dwarfs, we demonstrate that reliable SBF measurements and distances accurate to 15% are possible even for very low surface brightness (µ …
The Proper-motion Field along the Magellanic Bridge: A New Probe of the LMC-SMC Interaction
van der Marel, Roeland P.; Anderson, J.; Besla, Gurtina +6 more
We present the first detailed kinematic analysis of the proper motions (PMs) of stars in the Magellanic Bridge, from both the Gaia Data Release 2 catalog and from Hubble Space Telescope (HST) Advanced Camera for Surveys data. For the Gaia data, we identify and select two populations of stars in the Bridge region, young main-sequence (MS) and red g…
Fast Outflows Identified in Early Star-forming Galaxies at z = 5-6
Ouchi, Masami; Blaizot, Jérémy; Bouché, Nicolas +3 more
We present velocities of galactic outflows in seven star-forming galaxies at z = 5-6 with stellar masses of M * ∼ 1010.1 {M}⊙ . Although it is challenging to observationally determine the outflow velocities, we overcome this by using ALMA [C II] 158 µm emission lines for systemic velocities and deep Keck spec…
The Largest M Dwarf Flares from ASAS-SN
Drout, Maria R.; Kochanek, C. S.; Madore, Barry F. +13 more
The All-sky Automated Survey for Supernovae (ASAS-SN) is the only project in existence to scan the entire sky in optical light approximately every day, reaching a depth of g ∼ 18 mag. Over the course of its first 4 yr of transient alerts (2013-2016), ASAS-SN observed 53 events classified as likely M dwarf flares. We present follow-up photometry an…
On the Gas Content, Star Formation Efficiency, and Environmental Quenching of Massive Galaxies in Protoclusters at z ≈ 2.0-2.5
Treister, E.; Toft, S.; Scoville, N. +10 more
We present ALMA Band 6 (ν = 233 GHz, λ = 1.3 mm) continuum observations toward 68 “normal” star-forming galaxies within two Coma-like progenitor structures at z = 2.10 and 2.47, from which ISM masses are derived, providing the largest census of molecular gas mass in overdense environments at these redshifts. Our sample comprises galaxies with a st…