Day 862

Thursday.


Nature
Planet heating prevents inward migration of planetary cores
Benitez, et al

Planetary systems are born in the disks of gas, dust and rocky fragments that surround newly formed stars.  Solid content assembles into ever-larger rocky fragments that eventually become planetary embryos.  These then continue their growth by accreting leftover material in the disk.  Concurrently, tidal effects in the disk cause a radial drift in the embryo orbits, a process known as migration.  Fast inward migration is predicted by theory for embryos smaller than 3 to 5 M_earth.  With only inward migration, these embryos can only rarely become giant planets located at Earth's distance from the Sun and beyond, in contrast with observations.  Here, report that asymmetries in the temperature rise associated with accreting infalling material produce a force (which gives rise to an effect called 'heating torque') that counteracts inward migration.  This provides a channel for the formation of giant planets and also explains the strong planet-metallicity correlation found between the incidence of giant planets and the heavy-element abundance of the host stars.


1504.00005
An increasing stellar baryon fraction in bright galaxies at high redshift
Finkelstein, et al

Recent observations have shown that the characteristic luminosity of the rest-frame UV luminosity function does not significantly evolve at 4<z<7 and is approximately M*_UV~-21.  Investigate the apparent non-evolution by examining a sample of 190 bright, M_UV<-21 galaxies at z=4 to 7, analyzing their stellar populations and host halo masses.  Including deep Spitzer/IRAC imaging to constrain the rest-frame optical light, find that M*_UV galaxies at z=4-7 have similar stellar masses of log (M/Msol)=9.8-9.9 and are thus relatively massive for these high z.  However, bright galaxies at z=4-7 are less massive and have younger inferred ages than similarly bright galaxies at z=2-3, even though the two populations have similar star formation rates and levels of dust attenuation.  Match the abundances of these bright z=4-7 galaxies to halo mass functions from the Boshoi LCDM simulation to estimate the halo masses.  Find that the typical halo masses in ~M*_UV galaxies decrease from log (M_h/Msun)=11.9 at z=4 to log (M_h/Msun)-11.4 at z=7.  Thus, although we are studying galaxies at a similar mass across multiple redshifts, these galaxies live in lower mass haloes at higher z.  The stellar baryon fraction in units of the cosmic mean Omega_b/Omega_m rises from 6% at z=4 to 16% at z=7; this evolution is significant at the 3.6 sigma level.  This rise does not agree with simple expectations of how galaxies grow, and implies that some effect, perhaps a diminishing efficiency of feedback, is allowing a higher fraction of available baryons to be converted into stars at high z.


1504.00034
Astroid systems: binaries, triples and pairs
Margot, et al

A unifying paradigm based on rotational fission and post-fission dynamics can explain the formation of small (<20 km) binaries, triples, and pairs.  Large (>20km) binaries with small satellites are most likely created during large collisions.


1504.00077
An observational detection of the bridge effect of void filaments
Shim, Lee, Hoyle

The bridge effect of void filaments is a phrase coined by Park&Lee(2009) to explain the correlations found in a numerical experiment between the luminosity of the void galaxies and the degree of the straightness of their host filaments.  Their numerical finding implies that straight void filament provides a narrow channel for the efficient transportation of gas and matter particles form the surroundings into the void galaxies.  To observationally confirm the presence of the bridge effect of void filaments, identify the filamentary structures from the Sloan void catalog and determine the specific size of each void filament as a measure of its straightness.  Using both classic and Bayesian statistics, indeed detect a strong tendency that the void galaxies located in the more straight filaments are on average more luminous, which is in agreement with the numerical prediction.  It is also shown that the strength of correlation increases with the spatial extent of the void filaments, which can be physically understood on the grounds that the more stretched filaments can connect the dense surroundings even to the galaxies located deep in the central parts of the voids.  This observational evidence may provide a key close to the puzzling issue of why the void galaxies have higher sSFR and bluer colors than their wall counterparts.


1504.00117
Catalogues of isolated galaxies, isolated paris, and isolated triplets in the local universe
Fernández et al

The catalogues are publicly available.  For isolated galaxies, isolated pairs, and isolated triplets, there is no difference in their degree of interaction with the large-scale structure, which may suggest that they have a common origin in their formation and evolution.  Find that most of them belong to the outer parts of filaments, walls, and clusters, and generally differ from the void population of galaxies.