Search Publications
The Radial Distributions of the Two Main-sequence Components in the Young Massive Star Cluster NGC 1856
Milone, Antonino P.; Deng, Licai; de Grijs, Richard +1 more
The recent discovery of double main sequences in the young, massive star cluster NGC 1856 has caught significant attention. The observations can be explained by invoking two stellar generations with different ages and metallicities or by a single generation of stars composed of two populations characterized by different rotation rates. We analyzed…
Hubble Space Telescope Imaging of the Ultra-compact High Velocity Cloud AGC 226067: A Stripped Remnant in the Virgo Cluster
Crnojević, D.; Sand, D. J.; Simon, J. D. +10 more
We analyze the optical counterpart to the ultra-compact high velocity cloud AGC 226067, utilizing imaging taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. The color-magnitude diagram of the main body of AGC 226067 reveals an exclusively young stellar population, with an age of ∼7-50 Myr, and is consistent with a meta…
The Asymmetric Bow Shock/Pulsar Wind Nebula of PSR J2124-3358
Slane, Patrick; Romani, Roger W.; Green, Andrew W.
We describe new measurements of the remarkable Hα/UV/X-ray bow shock and pulsar wind nebula (PWN) of the isolated millisecond pulsar (MSP) PSR J2124-3358. Chandra X-ray Observatory imaging shows a one-sided jet structure with a softer equatorial outflow. KOALA integral field unit spectroscopy shows that non-radiative emission dominates the bow sho…
Solar Tornadoes Triggered by Interaction between Filaments and EUV Jets
Zhang, Jun; Yan, Xiaoli; Xue, Jianchao +2 more
We investigate the formations and evolutions of two successive solar tornadoes in/near AR 12297 during 2015 March 19-20. Recurrent EUV jets close to two filaments were detected along a large-scale coronal loop prior to the appearances of the tornadoes. Under the disturbances from the activities, the filaments continually ascended and finally inter…
Impact of Radiogenic Heating on the Formation Conditions of Comet 67P/Churyumov-Gerasimenko
Wurz, P.; Altwegg, K.; Balsiger, H. +19 more
Because of the high fraction of refractory material present in comets, the heat produced by the radiogenic decay of elements such as aluminum and iron can be high enough to induce the loss of ultravolatile species such as nitrogen, argon, or carbon monoxide during their accretion phase in the protosolar nebula (PSN). Here, we investigate how heat …
Planetary Nebulae and H II Regions in the Starburst Irregular Galaxy NGC 4449 from LBT MODS Data
Tosi, M.; Cusano, F.; Mignoli, M. +7 more
We present deep 3500-10000 Å spectra of H II regions and planetary nebulae (PNe) in the starburst irregular galaxy NGC 4449, acquired with the Multi Object Double Spectrograph at the Large Binocular Telescope. Using the “direct” method, we derived the abundance of He, N, O, Ne, Ar, and S in six H II regions and in four PNe in NGC 4449. This is the…
Evolution of Alfvénic Fluctuations inside an Interplanetary Coronal Mass Ejection and Their Contribution to Local Plasma Heating: Joint Observations from 1.0 to 5.4 au
Li, Hui; Wang, Chi; Richardson, John D. +1 more
Tracking an interplanetary coronal mass ejection (ICME) by widely separated spacecraft could provide us with a good opportunity to study the evolution of embedded Alfvénic fluctuations (AFs) and their possible contribution to local plasma heating directly. In this study, an ICME observed by Wind at 1.0 au on 1998 March 4-6 is tracked to the locati…
The Shock Dynamics of Heterogeneous YSO Jets: 3D Simulations Meet Multi-epoch Observations
Hansen, E. C.; Hartigan, P.; Frank, A. +1 more
High-resolution observations of young stellar object (YSO) jets show them to be composed of many small-scale knots or clumps. In this paper, we report results of 3D numerical simulations designed to study how such clumps interact and create morphologies and kinematic patterns seen in emission line observations. Our simulations focus on clump scale…
Production of Sulfur Allotropes in Electron Irradiated Jupiter Trojans Ice Analogs
Ehlmann, Bethany L.; Brown, Michael E.; Choukroun, Mathieu +7 more
In this paper, we investigate sulfur chemistry in laboratory analogs of Jupiter Trojans and Kuiper Belt Objects (KBOs). Electron irradiation experiments of CH3OH-NH3-H2O and H2S-CH3OH-NH3-H2O ices were conducted to better understand the chemical differences between primor…
A New Approach to Convective Core Overshooting: Probabilistic Constraints from Color-Magnitude Diagrams of LMC Clusters
Williams, Benjamin F.; Johnson, L. Clifton; Dolphin, Andrew +7 more
We present a framework to simultaneously constrain the values and uncertainties of the strength of convective core overshooting, metallicity, extinction, distance, and age in stellar populations. We then apply the framework to archival Hubble Space Telescope observations of six stellar clusters in the Large Magellanic Cloud that have reported ages…