Day 741

Wednesday.

1409.1582
Minor vs major mergers: the stellar mass growth of massive galaxies from z=3 using number density selection techniques
Owensworth, Conselice, et al

Present a study on the stellar mass growth of the progenitors of local massive galaxies with a variety of number density selections with n<1e-4 Mpc^-3 (corresponding to M*=1e11.24 Msun at z=0.3) in 0.3<z<3.0.  Select the progenitors of massive galaxies using a constant number density selection, and one which is adjusted to account for major mergers.  Find that the progenitors of massive galaxies grow by a factor of four in total stellar mass over this redshift range.  On average the stellar mass added via the processes of SF, major and minor mergers account for 24pm8%, 17pm15%, and 34pm14%, respectively, of the total galaxy stellar mass at z=0.3.  Therefore 51pm20% of the total stellar mass in massive galaxies at z=0.3 is created externally to their z=3 progenitors.  Explore the implication of these results on the cold gas accretion rate and size evolution of the progenitors of most massive galaxies over the same z range.  Find an average gas accretion rate of ~66pm32 Msun/yr over 1.5<z<3.0.  Find that the size evolution of a galaxy sample selected this way is on average lower than the findings of other investigations.

1409.2488
MUSE observations of the lensing cluster SMACSJ2031.8-4036: new constraints on the mass distribution in the cluster core
Richard, et al

Lensing cluster observation with MUSE IFS as part of its commissioning on VLT.  MUSE ideally suited for identifying lensed galaxies in the cluster core, particularly in multiple-imaged systems.  Perform z analysis of all sources in the data cube, identifying a total of 12 systems ranging from z=1.46 to z=6.4, with all images of each system confirmed by spectra.  Allows accurate constraint on the cluster mass profile in this region.  Possible Lya emitter discovery with future MUSE observation due to strong magnification and the high sensitivity of this instrument.

1409.2492
The fundamental plane of massive quiescent galaxies out to z~2
van de Sande, Kriek, Franx, Beyanson, van Dokkum

Find preliminary evidence for the existence of the FP out to z~2, but the scatter increases from z~0 to ~2, even when taking into account the larger measurement uncertainties at higher z.  Find a strong evolution of the zero point from z~2 to 0.  At z>1 find that the spectroscopic sample is bluer.  Use the color offsets to estimate a M/L correction, which then the implied FP zero point evolution after correction is significantly smaller.  This is consistent with an apparent formation redshift of z_form=6.6+3.2-1.4 for the underling population, ignoring the effete of progenitor bias.  A more complete spectroscopic sample is required at z~2 to properly measure the M/L evolution from FP evolution.

1409.2506
On the role of GRBs on life extinction in the Universe
Piran, Jiminez

GRB can be a threat to life.  Using recent determinations of the rate, LF, and host properties of GRBs, estimate the probability that a life-trheatening GRB would take place.  Long GRBs are the most dangerous.  A very good chance that at least one lethal GRB took place during the past 5Gyr close enough to Earth as to significantly damage life.  50% chance that such GRB took place in the last 500 Myr causing one of the major mass extinction events.  Probability of lethal GRB is much larger in the inner MW (95% within a radius of 4kpc from the galactic center), making it inhospitable to life.  At more than 10 kpc from galactic center, probability drops below 50%.  Safest environment for life are the lowest density regions in the outskirts of large galaxies.  Life can exist in only ~10% of galaxies [how did they determine that?].  A cosmological constant is essential for such systems to exist.  Because both the higher GRB rate and galaxies being smaller, life as it exists on Earth could not take place at z>0.5.  Early life forms must have been much more resilient to radiation.

1409.2750
Coming of age in the dark sector: how dark matter haloes grow their gravitational potential wells
van den Bosch, Jiang, Hearin, Campbell, Watson, Padmanabhan

Present a detailed study of how DM haloes assemble their mass and grow their (central) potential well.  Characterize these via their mass accretion histories (MAHs) and potential well growth histories (PWGHs), which is extracted from the Bolshoi simulation and from SAM merger trees supplemented with a method to compute the maximum circular velocity, Vmax, of progenitor haloes.  The results of both methods are in excellent agreement, both in terms of the average and the scatter.  Show that MAH and PWGH are tightly correlated, and that growth of the central potential precedes the assembly of mass; the maximum circular velocity is already half the present day value by the time the halo has accreted only 2% of its final mass.  Finally, demonstrate that MAHs have universal form, which is used to develop a new and improved universal model that can be used to compute the average or median MAH and PWGH for halo of any mass in any LCDM cosmology, without having to run a numerical simulation or a set of halo merger trees.

1409.2838
How the cosmic web induces intrinsic alignments of galaxies
Codis, Dubois, Pichon, Devriendt, Slyz

Direct measurements of IA seem to agree on a contamination at a level of a few % of the shear correlation functions, although the amplitude of the effect depends on the population of galaxies considered.  Given this dependency, it is difficult to use DM-only sims as the sole resource to predict and control IA.  Report estimates on the level of IA in cosmo-hydro sim Horizon-AGN.  In particular, assuming that the spin of galaxies is a good proxy for their ellipticity, show how those spins are spatially correlated and how they couple to the tidal field in which they are embedded.  Also present theoretical calculations that illustrate and qualitatively explain the observed signals.