1512.08800
Gravitational potential wells and the cosmic bulk flow
Kumar, Wang, Feldman, Watkins
The bulk flow is a volume average of the peculiar velocities and a useful probe of the mass distribution on large scales. The gravitational instability model view the bulk flow as a potential flow that obeys a Maxwellian Distribution. Use two N-body sims, the Las Damas Carmen and the Horizon Run, to calculate the bulk flows of various sized volumes in the simulation boxes. Once the bulk flow velocities ad a function of scale is found, investigate the mass and gravitational potential distribution around the volume. Find that matter densities can be asymmetrical and difficult to detect in real surveys, however, the gravitation potential and its gradient may provide better tolls to investigate the underlying matter distribution. This study shows that bulk flows are indeed potential flows and thus provides information on the flow sources. Also show that bulk flow magnitudes follow a Maxwellian distribution on scales >10 Mpc/h.
1512.09093
SN Refsdal: classification as a luminous and blue SN 1987A-like Type II supernova
Kelly, et al
HST and VLT NIR spectra and images of SN Refsdal, discovered as an Einstein cross in Fall 2014, show that the HST light curve of SN Refsdal matches the distinctive, slowly rising light curves of SN 1987A-like SNe, and find strong evidence for a broad H-alpha P-Cygni profile in the HST grism spectrum at z=1.49 of the spiral host galaxy. SNe IIn, powered by circumstellar interaction, could provide a good match to the light curve of SN Refsdal, but the spectrum of a SN IIn would not show broad and strong H-alpha absorption. From the grism spectrum, measure an H-alpha expansion velocity consistent with those of SN 1987A-like SNe at a similar phase. The luminosity, evolution, and Gaussian profile of the H-alpha emission of the WFC3 and X-shooter spectra, separated by ~2.5 months in the rest frame, provides additional evidence that supports the SN 1987A-like classification. In comparison with other examples of SN 1987A-like SNe, SN Refsdal has a blue B-V color and a high luminosity for the assumed range of potential magnifications. If SN Refsdal can be modeled as scaled version of SN 1987A, estimate it would have an eject mass of 20±5 Msun. The evolution of the light curve at late times will provide additional evidence about the potential existence of any substantial circumstellar material (CSM). Using MOSFILRE and X-shoter spectra, estimate a sub solar host-galaxy metallicity (8.3±0.1 dex and <8.4 dex, respectively) near the explosion site.
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