Search Publications
Spatial Organization of Seven Extreme Solar Energetic Particle Events
Wang, Haimin; Vainio, Rami; Pohjolainen, Silja +4 more
Emission of relativistic protons and helium responsible for extreme solar particle events (ground level enhancements (GLEs)) is often structured. We investigate its organization depending on the eruption stage characterized by the heliocentric height of associated coronal mass ejections (CMEs). Seven GLEs are considered: events on 1997 November 6,…
NuSTAR Detection of a Hard X-Ray Source in the Supernova Remnant-molecular Cloud Interaction Site of IC 443
Hailey, Charles J.; Mori, Kaya; Zhang, Shuo +10 more
We report on a broadband study of a complex X-ray source (1SAX J0618.0+2227) associated with the interaction site of the supernova remnant (SNR) IC 443 and ambient molecular cloud (MC) using NuSTAR, XMM-Newton, and Chandra observations. Its X-ray spectrum is composed of both thermal and nonthermal components. The thermal component can be equally w…
The Distance to the Galaxy Coma P
Anand, Gagandeep S.; Shaya, Edward J.; Tully, R. Brent +4 more
If the extremely low surface-brightness galaxy Coma P lies at 5.5 ± 0.3 Mpc, as recently proposed, then it would have an extraordinarily deviant peculiar velocity of ∼900 km s-1 at a location where differential velocities between galaxies are low. We have accessed the images from the Hubble Space Telescope (HST) archives used to derive …
Understanding Fundamental Properties and Atmospheric Features of Subdwarfs via a Case Study of SDSS J125637.13-022452.4
Gonzales, Eileen C.; Faherty, Jacqueline K.; Gagné, Jonathan +2 more
We present the distance-calibrated spectral energy distribution (SED) of the sdL3.5 subdwarf SDSS J125637.13-022452.4 (J1256-0224) using its Gaia DR2 parallax. We report the bolometric luminosity and semi-empirical fundamental parameters, as well as updated UVW velocities. The SED of J1256-0224 is compared to field-age and low-gravity dwarfs of th…
Must Star-forming Galaxies Rapidly Get Denser before They Quench?
Morishita, T.; Abramson, L. E.
Using the deepest data yet obtained, we find no evidence preferring compaction-triggered quenching—where rapid increases in galaxy density truncate star formation—over a null hypothesis in which galaxies age at constant surface density ({{{Σ }}}e\equiv {M}* /2π {r}e2). Results from two fully empirical an…
Ionized Gas Motions and the Structure of Feedback near a Forming Globular Cluster in NGC 5253
Turner, Jean L.; Beck, Sara C.; Martin, Emily C. +2 more
We observed Brackett α 4.05 µm emission toward the supernebula in NGC 5253 with NIRSPEC on Keck II in adaptive optics mode, NIRSPAO, to probe feedback from its exciting embedded super star cluster (SSC). NIRSPEC's Slit-viewing Camera was simultaneously used to image the K-band continuum at ∼0.″1 resolution. We register the IR continuum with …
Exploring the Origins of Earth’s Nitrogen: Astronomical Observations of Nitrogen-bearing Organics in Protostellar Environments
Bergin, Edwin A.; Wampfler, S. F.; Jørgensen, Jes K. +1 more
It is not known whether the original carriers of Earth’s nitrogen were molecular ices or refractory dust. To investigate this question, we have used data and results of Herschel observations toward two protostellar sources: the high-mass hot core of Orion KL, and the low-mass protostar IRAS 16293-2422. Toward Orion KL, our analysis of the molecula…
Circumgalactic Gas at Its Extreme: Tidal Gas Streams around the Whale Galaxy NGC 4631 Explored with HST/COS
Wakker, B. P.; Gentile, G.; Winkel, B. +8 more
We present a detailed analysis of the absorption properties of one of the tidal gas streams around the “Whale” galaxy NGC 4631 in the direction of the quasar 2MASS J12421031+3214268. Our study is based on ultraviolet spectral data obtained with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST) and 21cm-data from the H…
Does Nearby Open Flux Affect the Eruptivity of Solar Active Regions?
DeRosa, Marc L.; Barnes, Graham
The most energetic solar flares are typically associated with the ejection of a cloud of coronal material into the heliosphere in the form of a coronal mass ejection (CME). However, large flares exist that are not accompanied by a CME. The existence of these noneruptive flares raises the question of whether such flares suffer from a lack of access…
The Envelope Kinematics and a Possible Disk around the Class 0 Protostar within BHR7
Bourke, Tyler L.; Dunham, Michael M.; Tobin, John J. +2 more
We present a characterization of the protostar embedded within the BHR7 dark cloud, based on both photometric measurements from the near-infrared to millimeter and interferometric continuum and molecular line observations at millimeter wavelengths. We find that this protostar is a Class 0 system, the youngest class of protostars, measuring its bol…