Day 1041

Tuesday.


1601.06434
Subhalo accretion through filaments
Gonzalez, Padilla

Track sub halo orbits of galaxy and group sized haloes in cosmo sims.  Identify filamentary structures around haloes and use these to define a sample of sub haloes accreted from filaments as well as a control sample of sub haloes accreted from other directions.  Use these samples to study difference in satellite orbits produced by filamentary accretion.  The results depend on host halo mass.  Find that for low masses, sub halos accreted from filaments show ~10% shorter lifetimes compared to the control sample, they have more radial orbits, reach halo central regions earlier, and are more likely to merge with the host.  For higher mass haloes this lifetime difference dissipates and even reverses for cluster sized halos.  This behavior appears to be connected to the fact that more massive hosts are connected to stronger filaments with higher velocity coherence and density, with more radial sub halo orbits.  Because sub haloes tend to follow the coherent flow of the filament, it is possible that such thick filaments are enough to shield the sub halo from the effect of dynamical friction at least during their first infall.  Also identify sub halo pairs/clumps which merge with one another after accretion.  They survive as a clump for only a very short time, which is even shorter for higher sub halo masses.  There is a 50% and 90% chance they were accreted in the last 0.8 Gyr and 2.3 Gyr respectively.  This suggests that the Magellanic Clouds and other local group satellite associations, may have entered the MW viral radius very recently and probably are in their first infall -- or at least still in their first full orbit.  Filaments boost the accretion of satellite associations.


1601.06770
Dust grains from the heart of supernovae
Bocchio, et al

Dust grains are classically thought to form in the winds of AGB stars.  However, there is increasing evidence for dust formation in SNe.  In order to establish the relative importance of these two classes os stellar sources of dust, it is important to know what is the fraction of fretting formed dust in SN ejecta that is able to survive the passage of the reverse shock and be injected in the ISM.  With this aim, developed a new code, CRASH_Rev, that allows to follow the dynamics of dust grains in the shocked SN ejecta and to compute the time evolution of the mass, composition and size distribution of the grains.  Consider four well studied SNe ind the MW and LMC: SN 1987a, Cas A, the Crab Nebula, and N49.  For all the simulated models, find good agreement with observations.  Study suggests that SN 1987A is too young for the reverse shock to have affected the dust mass.  Conversely, in the other three SNe, the reverse shock has already destroyed between 10 and 40% of the initial dust mass.  However, the largest dust mass destruction is predicted to occur between 1e3 and 1e5 yr after the explosions.  Since the oldest SN in the sample has and estimated age of 4800 yr, current observations can only provide an upper limit to the mass of SN dust that will enrich the ISM, the so-called effective dust yields.  Find that only between 1 and 8% of the currently observed mass will survive.  This is in good agreement with the values adopted in chemical evolution models which consider the effect of the NS reverse shock.  Discuss the astrophysical implications of the realists for dust enrichment in local galaxies and at high redshift.