Astronomy

Ion Pre-acceleration in Fully Self-consistent Particle-in-cell Simulations of Supercritical Perpendicular Reforming Shocks in Multiple Ion Species Plasmas
Supernova remnant and heliopause termination shock plasmas may contain significant populations of minority heavy ions, with relative number densities n α / n i up to 50%. Preliminary kinetic simulations of collisionless shocks in these environments showed that the reformation cycle and acceleration mechanisms at quasi-perpendicular shocks can depend on the value of n α / n i . Shock reformati...


New Detections of Arsenic, Selenium, and Other Heavy Elements in Two Metal-poor Stars
We use the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope to obtain new high-quality spectra covering the 1900 ≤λ ≤ 2360 Å wavelength range for two metal-poor stars, HD 108317 and HD 128279. We derive abundances of Cu II , Zn II , As I , Se I , Mo II , and Cd II , which have not been detected previously in either star. Abundances derived for Ge I , Te I , Os II...
The Census of Complex Organic Molecules in the Solar-type Protostar IRAS16293-2422
Complex organic molecules (COMs) are considered to be crucial molecules, since they are connected with organic chemistry, at the basis of terrestrial life. More pragmatically, they are molecules which in principle are difficult to synthesize in harsh interstellar environments and, therefore, are a crucial test for astrochemical models. Current models assume that several COMs are synthesized on ...


The Identification of Filaments on Far-infrared and Submillimiter Images: Morphology, Physical Conditions and Relation with Star Formation of Filamentary Structure
Of molecular clouds reveal a complex structure, with gas and dust often arranged in filamentary, rather than spherical geometries. The association of pre- and proto-stellar cores with the filaments suggests a direct link with the process of star formation. Any study of the properties of such filaments requires representative samples from different environments for an unbiased detection method. ...
Electron-Ion Equilibrium and Shock Precursors in the Northeast Limb of the Cygnus Loop
We present an observational study using high-resolution echelle spectroscopy of collisionless shocks in the Cygnus Loop supernova remnant. Measured Hα line profiles constrain pre-shock heating processes, shock speeds, and electron-ion equilibration ( T e / T i ). The shocks produce faint Hα emission line profiles, which are characterized by narrow and broad components. The narrow component is...


Fifty M31 Black Hole Candidates Identified by Chandra and XMM-Newton
Over approximately the last five years, we have identified ~35 black hole candidates (BHCs) in M31 from their X-ray spectra. Our BHCs exhibited 0.3-10 keV spectra consistent with the X-ray binary (XB) hard state at luminosities that are above the upper limit for neutron star (NS) XBs. When our BHC spectra were modeled with a disk blackbody + blackbody model for comparison with bright NS XBs, w...
The Origin of the X-Ray Emission from the High-velocity Cloud MS30.7–81.4–118
A soft X-ray enhancement has recently been reported toward the high-velocity cloud MS30.7–81.4–118 (MS30.7), a constituent of the Magellanic Stream. In order to investigate the origin of this enhancement, we have analyzed two overlapping XMM-Newton observations of this cloud. We find that the X-ray enhancement is ~6' or ~100 pc across, and is concentrated to the north and west of the dense...

Searching for Diffuse Light in the M96 Galaxy Group
We present deep, wide-field imaging of the M96 galaxy group (also known as the Leo I Group). Down to surface brightness limits of μ B = 30.1 and μ V = 29.5, we find no diffuse, large-scale optical counterpart to the "Leo Ring," an extended H I ring surrounding the central elliptical M105 (NGC 3379). However, we do find a number of extremely low surface brightness (μ B ##IMG## [http://ej.iop...
Three-dimensional MHD Simulation of the Caltech Plasma Jet Experiment: First Results
Magnetic fields are believed to play an essential role in astrophysical jets with observations suggesting the presence of helical magnetic fields. Here, we present three-dimensional (3D) ideal MHD simulations of the Caltech plasma jet experiment using a magnetic tower scenario as the baseline model. Magnetic fields consist of an initially localized dipole-like poloidal component and a toroidal ...

Quasi-Periodic Pulsations with Varying Period in Multi-Wavelength Observations of an X-class Flare
This work presents an interesting phenomenon of the period variation in quasi-periodic pulsations (QPPs) observed during the impulsive phase of a coronal mass ejection-related X1.1 class flare on 2012 July 6. The period of QPPs was changed from 21 s at soft X-rays (SXR) to 22-23 s at microwaves, to ~24 s at extreme ultraviolet emissions (EUV), and to 27-32 s at metric-decimetric waves. The ...
Robotic Laser Adaptive Optics Imaging of 715 Kepler Exoplanet Candidates Using Robo-AO
The Robo-AO Kepler Planetary Candidate Survey is observing every Kepler planet candidate host star with laser adaptive optics imaging to search for blended nearby stars, which may be physically associated companions and/or responsible for transit false positives. In this paper, we present the results from the 2012 observing season, searching for stars close to 715 Kepler planet candidate hosts....

The Black Hole Mass of NGC 4151. II. Stellar Dynamical Measurement from Near-infrared Integral Field Spectroscopy
We present a revised measurement of the mass of the central black hole ( M BH ) in the Seyfert 1 galaxy NGC 415The new stellar dynamical mass measurement is derived by applying an axisymmetric orbit-superposition code to near-infrared integral field data obtained using adaptive optics with the Gemini Near-infrared Integral Field Spectrograph (NIFS). When our models attempt to fit both the NIFS...
Star Formation and Black Hole Growth at z 4.8
We report Herschel /SPIRE, Spitzer and Wide-field Infrared Survey Explorer observations of 44 z ##IMG## [http://ej.iop.org/icons/Entities/sime.gif] {sime} 4.8 optically selected active galactic nuclei (AGNs). This flux-limited sample contains the highest mass black holes (BHs) at this redshift. Ten of the objects were detected by Herschel and five show emission that is not clearly associated wi...
Dense Cores in Galaxies Out to z = 2.5 in SDSS, UltraVISTA, and the Five 3D-HST/CANDELS Fields
The dense interiors of massive galaxies are among the most intriguing environments in the universe. In this paper,we ask when these dense cores were formed and determine how galaxies gradually assembled around them. We select galaxies that have a stellar mass >3 × 10 10 M ☉ inside r = 1 kpc out to z = 2.5, using the 3D-HST survey and data at low redshift. Remarkably, the number density of g...
Reconstructed moisture evolution of the deserts in northern China since the Last Glacial Maximum and its implications for the East Asian Summer Monsoon
The East Asian Summer Monsoon (EASM) affects rainfall variability and consequently terrestrial ecosystems in the densely populated Asian region. Understanding the nature of EASM evolution is vital for interpreting the paleoclimatic conditions of the region and for predicting future climate changes. However, the relative importance of factors such as high northern latitude ice volume, low northe...