Search Publications
Spectroscopic Confirmation of the Dwarf Spheroidal Galaxy d0994+71 as a Member of the M81 Group of Galaxies
Simon, Joshua D.; Chiboucas, Kristin; Guhathakurta, Puragra +3 more
We use Keck/DEIMOS spectroscopy to measure the first velocity and metallicity of a dwarf spheroidal (dSph) galaxy beyond the Local Group using resolved stars. Our target, d0944+71, is a faint dSph found in the halo of the massive spiral galaxy M81 by Chiboucas et al. We coadd the spectra of 27 individual stars and measure a heliocentric radial vel…
Spectroscopic Diagnostics of Solar Magnetic Flux Ropes Using Iron Forbidden Line
Cheng, X.; Ding, M. D.
In this Letter, we present Interface Region Imaging Spectrograph Fe xxi 1354.08 Å forbidden line emission of two magnetic flux ropes (MFRs) that caused two fast coronal mass ejections with velocities of ≥1000 km s-1 and strong flares (X1.6 and M6.5) on 2014 September 10 and 2015 June 22, respectively. The extreme-ultraviolet images at t…
New Constraints on the Molecular Gas in the Prototypical HyLIRGs BRI1202-0725 and BRI1335-0417
Momjian, E.; Walter, F.; Riechers, D. A. +6 more
We present Karl G Jansky Very Large Array observations of CO(J=2\to 1) line emission and rest-frame 250 GHz continuum emission of the Hyper-Luminous IR Galaxies (HyLIRGs) BRI 1202-0725 (z = 4.69) and BRI 1335-0417 (z = 4.41), with an angular resolution as high as 0.″15. Our low-order CO observations delineate the cool molecular gas, the fuel for s…
Major-Merger Galaxy Pairs at Z = 0: Dust Properties and Companion Morphology
Domingue, Donovan L.; Cao, Chen; Xu, C. Kevin +4 more
We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by K s magnitude and redshift. The pairs represent the two populations of spiral-spiral (S+S) and mixed morphology spiral-elliptical (S+E). The Code Investigating GALaxy Emission software is used to fit dust models to the Two Micron All S…
The Optical Variability of SDSS Quasars from Multi-epoch Spectroscopy. III. A Sudden UV Cutoff in Quasar SDSS J2317+0005
Prochaska, J. Xavier; Ma, Jingzhe; Malkan, Matthew A. +6 more
We have collected near-infrared to X-ray data of 20 multi-epoch heavily reddened SDSS quasars to investigate the physical mechanism of reddening. Of these, J2317+0005 is found to be a UV cutoff quasar. Its continuum, which usually appears normal, decreases by a factor 3.5 at 3000 Å, compared to its more typical bright state during an interval of 2…
HST STIS Observations of the Mixing Layer in the Cat’s Eye Nebula
Toalá, Jesús A.; Guerrero, Martín A.; Chu, You-Hua +2 more
Planetary nebulae (PNe) are expected to have a ∼105 K interface layer between the ≥slant 106 K inner hot bubble and the ∼104 K optical nebular shell. The PN structure and evolution, and the X-ray emission, depend critically on the efficiency of the mixing of material at this interface layer. However, neither its lo…
Multiple Outflows in the Giant Eruption of a Massive Star
Humphreys, Roberta M.; Jones, Terry J.; Gordon, Michael S. +1 more
The supernova impostor PSN J09132750+7627410 in NGC 2748 reached a maximum luminosity of ≈-14 mag. It was quickly realized that it was not a true supernova, but another example of a nonterminal giant eruption. PSN J09132750+7627410 is distinguished by multiple P Cygni absorption minima in the Balmer emission lines that correspond to outflow veloci…
Investigating the Circumstellar Disk of the Be Shell Star 48 Librae
Okazaki, A. T.; Carciofi, A. C.; Bednarski, D. +6 more
A global disk oscillation implemented in the viscous decretion disk (VDD) model has been used to reproduce most of the observed properties of the well known Be star ζ Tau. 48 Librae shares several similarities with ζ Tau—they are both early-type Be stars, display shell characteristics in their spectra, and exhibit cyclic V/R variations—but has som…
Challenging Some Contemporary Views of Coronal Mass Ejections. I. The Case for Blast Waves
Pizzo, V. J.; Howard, T. A.
Since the closure of the “solar flare myth” debate in the mid-1990s, a specific narrative of the nature of coronal mass ejections (CMEs) has been widely accepted by the solar physics community. This narrative describes structured magnetic flux ropes at the CME core that drive the surrounding field plasma away from the Sun. This narrative replaced …
The [Ne III] Jet of DG Tau and its Ionization Scenarios
Herczeg, Gregory J.; Liu, Chun-Fan; Shang, Hsien +1 more
Forbidden neon emission from jets of low-mass young stars can be used to probe the underlying high-energy processes in these systems. We analyze spectra of the jet of DG Tau obtained with the Very Large Telescope/X-Shooter spectrograph in 2010. [Ne III] λ 3869 is clearly detected in the innermost 3″ microjet and the outer knot located at ∼ 6\build…