Day 841

Thursday.

Nature 518
An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
Wu, et al

Cosmic redshifts of between 6 and 7 represent a time when the IGM was in transition from a neutral state to being completely ionized.  Report the discovery of an UL quasar at z=6.30 that has optical and NIR luminosity several times greater than previously known quasars at redshift beyond z=6.  Based on NIR spectral data, the authors estimate a mass of approximately twelve-billion Msun for the associated BH, consistent with the 13 billion Msun derived by assuming an Eddington-limited accretion rate, where the force of radiation acting outwards and the gravitational force acting inward are in balance.  As the most luminous quasar known to date at z=6, this object will be a useful resource for the study of galaxy formation around massive BHs at the end of the epoch of cosmic reionization.


1502.07024
Hiding in plain sight: an abundance of compact massive spheroids in the local universe
Graham, Dullo, Savorgnan

...This abundance of compact, massive spheroids in our own backyard - with a number density of 6.9e-6 Mpc^-3 (or 3.5e-5 Mpc^-3 per unit dec in stellar mass) - and with the same physical properties as the high-redshift galaxies, had been over-looked because they are encased in stellar disks which usually result in 'galaxy' sizes notably larger than 2 kpc.  Moreover, this number density is a lower limit because it has not come from a volume-limited sample.  The actual density may be closer to 1e-4 Mpc^-3, although further work is required to confirm this.  Conclude that not all massive 'spheroids' have undergone dramatic structural and size evolution since z~2pm0.6.  Given that the bulges of local early-type disk galaxies are known to consist of predominantly old stars which existed at z~2, it seems likely that some of the observed high-z spheroids did not increase in size by building 3d triaxial envelopes as commonly advocated, and that the growth of 2d disks has also been important over the past 9-11 billion years.