Day 969

Thursday.


1509.04822
Serendipitous discovery of an extended X-ray jet without a radio counterpart i a high-redshift quasar
Simionescu, et al

A recent Chandra observation of the nearby galaxy cluster Abell 585 has led to the discovery of an extended X-ray jet associated with the high-z background quasar B3 0727+409, a luminous radio source at z=2.5.  This is one of only few examples of high-z X-ray jets known to date.  It has a clear extension of about 10-12", corresponding to a projected length of 80-100 kpc, which a possible hot spot as far as 35" from the quasar.  The archival high resolution VLA maps surprisingly reveal no extended jet emission, except for one knot about 1.4" away from the quasar.  The high X-ray to radio luminosity ratio for this source appears consistent with the ~(1+z)^4 amplification expected from the inverse Compton radiative model.  This serendipitous discovery may signal the existence of an entire population of similar systems with bright X-ray and faint radio jets at high z, a selection bias which must be accounted for when drawing any conclusions about the z evolution of jet properties and indeed a out the cosmo evolution of SMBHs and AGN in general.


1509.02938
Probing dark matter substructure with pulsar timing: I. constraints on ultracompact minihalos
Clark, Lewis, Scott

Small-scale DM structure within the MW is expected to affect pulsar timing.  The change in gravitational potential induced by a DM halo passing near the LoS to a pulsar would produce a varying delay in the light travel time of photons for the pulsar.  Individual transits produce an effect that would either be too rare or too weak to be detected in 30-year pulsar observations.  However, a population of DM sub haloes would be expected to produce a detectable effect on the measured properties of pulsars if the subclass constitute a significant fraction of the total halo mass.  The effect is to increase the dispersion of measured period derivatives across the pulsar population.  By statistical analysis of the ATNF pulsar catalogue, place an upper limit on this dispersion of log sigma_P<=17.05. Use this to place strong upper limits on the number density of ultracompact mini halos within the MW.  These limits are completely independent of the particle nature of DM.