Search Publications
How to find magnetic nulls and reconstruct field topology with MMS data?
André, M.; Vaivads, A.; Cao, J. B. +6 more
In this study, we apply a new method—the first-order Taylor expansion (FOTE)—to find magnetic nulls and reconstruct magnetic field topology, in order to use it with the data from the forthcoming MMS mission. We compare this method with the previously used Poincare index (PI), and find that they are generally consistent, except that the PI method c…
Cometary Isotopic Measurements
Jehin, Emmanuël; Engrand, Cécile; Sheridan, Simon +12 more
Isotopic ratios in comets provide keys for the understanding of the origin of cometary material, and the physical and chemical conditions in the early Solar Nebula. We review here measurements acquired on the D/H, 14N/15N, 16O/18O, 12C/13C, and 32S/34S ratios i…
Reconciling Planck results with low redshift astronomical measurements
Berezhiani, Zurab; Dolgov, A. D.; Tkachev, I. I.
We show that emerging tension between the direct astronomical measurements at low redshifts and cosmological parameters deduced from the Planck measurements of the cosmic microwave background anisotropies can be alleviated if the dark matter consists of two fractions, the stable part being dominant with a smaller unstable fraction. The latter cons…
Evolution of column density distributions within Orion A⋆
Stutz, A. M.; Kainulainen, J.
We compare the structure of star-forming molecular clouds in different regions of Orion A to determine how the column density probability distribution function (N-PDF) varies with environmental conditions such as the fraction of young protostars. A correlation between the N-PDF slope and Class 0 protostar fraction has been previously observed in a…
Deep radio imaging of 47 Tuc identifies the peculiar X-ray source X9 as a new black hole candidate
Maccarone, T. J.; Knigge, C.; van den Berg, M. +8 more
We report the detection of steady radio emission from the known X-ray source X9 in the globular cluster 47 Tuc. With a double-peaked C IV emission line in its ultraviolet spectrum providing a clear signature of accretion, this source had been previously classified as a cataclysmic variable. In deep ATCA (Australia Telescope Compact Array) imaging …
The Rate of Core Collapse Supernovae to Redshift 2.5 from the CANDELS and CLASH Supernova Surveys
Ravindranath, Swara; Mobasher, Bahram; Riess, Adam G. +6 more
The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and Cluster Lensing And Supernova survey with Hubble multi-cycle treasury programs with the Hubble Space Telescope (HST) have provided new opportunities to probe the rate of core-collapse supernovae (CCSNe) at high redshift, now extending to z≈ 2.5. Here we use a sample of approxim…
A Very Deep Chandra Observation of the Galaxy Group NGC 5813: AGN Shocks, Feedback, and Outburst History
Simionescu, A.; Giacintucci, S.; David, L. +11 more
We present results from a very deep (650 ks) Chandra X-ray observation of the galaxy group NGC 5813, the deepest Chandra observation of a galaxy group to date. This system uniquely shows three pairs of collinear cavities, with each pair associated with an unambiguous active galactic nucleus (AGN) outburst shock front. The implied mean kinetic powe…
Gravitational slopes, geomorphology, and material strengths of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations
Jorda, L.; Lara, L. M.; Bertaux, J. -L. +49 more
Aims: We study the link between gravitational slopes and the surface morphology on the nucleus of comet 67P/Churyumov-Gerasimenko and provide constraints on the mechanical properties of the cometary material (tensile, shear, and compressive strengths).
Methods: We computed the gravitational slopes for five regions on the nucleus that are…
The Panchromatic Hubble Andromeda Treasury. XI. The Spatially Resolved Recent Star Formation History of M31
Bell, Eric F.; Monachesi, Antonela; Dolphin, Andrew E. +15 more
We measure the recent star formation history (SFH) across M31 using optical images taken with the Hubble Space Telescope as part of the Panchromatic Hubble Andromeda Treasury (PHAT). We fit the color-magnitude diagrams in ∼9000 regions that are ∼100 pc × 100 pc in projected size, covering a 0.5 square degree area (∼380 kpc2, deprojected…
Neutral Hydrogen Structures Trace Dust Polarization Angle: Implications for Cosmic Microwave Background Foregrounds
Peek, J. E. G.; Hill, J. Colin; Clark, S. E. +2 more
Using high-resolution data from the Galactic Arecibo L-Band Feed Array HI (GALFA-Hi) survey, we show that linear structure in Galactic neutral hydrogen (Hi) correlates with the magnetic field orientation implied by Planck 353 GHz polarized dust emission. The structure of the neutral interstellar medium is more tightly coupled to the magnetic field…