Day 648

Tuesday.

1405.0292
Helioseismology and astroseismology: looking for gravitational waves in acoustic oscillations
Lopes, Silk

Current helioseismology observations allow the determination of the frequencies and the surface velocity amplitudes of solar acoustic modes with exceptionally high precision.  In some cases, the frequency accuracy is better than one part in a million.  Show that there is a distinct possibility that the quadrupole acoustic modes of low order could be excited by GWs if the GWs have a strain amplitude in the range 1d-17 h_-17 with h_-17 ~ 1-3 -1, as predicted by several types of GW sources including the coalescence of BHs and ultra compact binaries.  If the damping rate at low order is 1e-3 eta_N s^-1, with eta_N~1, as inferred from the theory of stellar pulsations, then GW radiation will lead to rms surface velocity amplitudes of quadrupole modes of order 1e-3 h_-17 eta_N^-1 ~ 1e-3 cm/s, on the verge of what is currently detectable via helioseismology.  The frequency and sensitivity range probed by helioseismological acoustic modes overlap with, and complement, the capabilities of eLISA for the brightest resolved ultra compact galactic binaries.

1405.0492
Clustering, host haloes and environment of z$\sim$2 galaxies as a function of their physical properties
Bethermin, Kilbinger, … et al

Using a sample of 25k SF and 2821 passive galaxies at z~2, selected in the COSMOS field following the BzK color criterion, study the hosting halo mass and environment of galaxies as a function of their physical properties.  Spitzer and Herschel provide accurate SFR estimates for starburst galaxies.  Measure the auto-and cross-correlation functions of various galaxy sub-samples and infer the properties of their hosting haloes using both an HOD model and the linear bias at larger scale.  Find that passive and SF galaxies obey a similarly rising relation between the halo and stellar mass.  The mean host halo mass of SF galaxies increases with the SFR between 30 and 200 Msun/yr, but flattens for higher values, expect if only MS galaxies are selected.  This reflects the expected transition from a regime of secular co-evolution of the haloes and the galaxies to a regime of episodic starburst.  Find similar large scale biases for MS, passive, and starburst galaxies at equal stellar mass, suggesting that these populations live in haloes of the same mass.  Detect an excess of clustering on small scales for passive galaxies and showed, by measuring the large-scale bias of close pairs, that this excess is caused by a small fraction (~16) of passive galaxies being hosted by massive halos (~3e13Msun) as satellites.  Finally, extrapolating the growth of haloes hosting the z~2 population, show that M*~1e10 Msun galaxies at z~2 will evolve, on average, into massive (M*~1e11 Msun), field galaxies in the local universe and M*~1e11 Msun galaxies at z=2 into local, massive, group galaxies.  The most massive MS galaxies and close pairs of massive, passive galaxies end up in today's clusters.

1405.0516
Evolution of cold streams and emergence of the Hubble sequence
Cen

A new physical framework for the emergence of the Hubble sequence is outlined, based on th novel analyses performed to quantify the evolution of cold streams of a large sample of galaxies from a state-of-the-art ultra-high resolution, large-scale adaptive mesh-refinement hydro sim in a fully cosmo setting.  It is found that the following three key physical variables of galactic cold inflows crossing the virial sphere substantially decrease with decreasing z: the number of streams N_90 that make up 90% of concurrent inflow mass flux, average inflow rate per stream dot M_90 and mean (mass flux weighted) gas density in the streams n_gas.  Another key variable, the stream dimensionless angular momentum parameter lambda, instead is found to increase with decreasing z.  Assimilating these trends and other leads naturally to a physical coherent scenario for the emergence of the Hubble sequence, including the following expectations: (1) the predominance of a mixture of disproportionately small irregular and complex disk galaxies at z>2 when most galaxies have multiple concurrent streams, (2) the beginning of the apperance of flocculent spirals at z~1-2 when the number of concurrent streams are about 2-3, (3) the grand-design spiral galaxies appear at z<1 when galaxies with only one major cold stream significantly emerge.  THese expected general trends are in pod accord with observations.  Early type galaxies are those that have entered a perennial state of zero cold gas stream, with their abundance increasing with decreasing redshift.

1405.0537
Gas loss in simulated galaxies as they fall into clusters
Cen, Pop, Bahcall

In high-res cosmo sims, fraction of gas-rich galaxies is constant beyond 3 cluster virial radii, representing the field.  Within 3 cluster-centric radii, the fraction of gas-rich galaxies declines steadily with decreasing radius, reaching <10% near the cluster center.  Results suggest that galaxies start to feel the impact of the cluster environment on their gas content well beyond the cluster virial radius.  Show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits. Results suggest that galaxies start to del the impact of the cluster environment of their gas content well beyond the cluster virial radius.  Show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits.  Furthermore, find that almost no galaxy moving outward at the cluster virial radius is gas-rich (with gas to baryon ratio greater than 1%).  These results suggest that galaxies that fall into cluster lose their cold gas within a single radial round-trip.