1209.4900
The Effect of fluctuations on the Helium-ionizing background
Davies, Furlanetto
Don't assume uniform radiation field, but consider the discrete nature of the (rare) bright quasars that dominate the background, in He II Ly-a absorption spectra after He II reionization. Cosmological radiative transfer model includes: recent constraints on ionizing spectra and luminosity function of quasars and the distribution of IGM absorbers; effects of fluctuations on the evolving continuum opacity of IGM. Results: He II ionizing background evolves rapidly with redshift, increasing by >3.5 from z=3.5 to 2.5. Rapid evolution in mean He II Ly-a optical depth, without appealing to the reionization of He II. ...
1209.4903
Galactic outflows in absorption and emission: near-UV spectroscopy of galaxies at 1<z<2
Erb, Quider, Henry, Martin
Study large-scale outflows in 96 SF galaxies at 1<z<2 with NUV spectroscopy of FeII and MgII absorption and emission. Average blueshift of FeII interstellar absorption lines wrt systemic velocity is -85 km/s at z~1.5, a decrease of 2x from the average blueshift measured for FUV absorption lines seen in galaxies at z~2. Profiles of MgII show much more variety than the FeII profiles, which are always seen in absorption; MgII ranges from strong emission to pure absorption, with emission more common in galaxies with blue UV slopes and at lower stellar masses. Outfow velocities increase with increasing stellar mass with 2-3 sigma significance, in agreement with previous results. Find structure emission from FeII*, find several lines of evidence in support of the model in which this emission is generated by the re-emission of continuum photons absorbed in the FeII resonance transitions in outflowing gas. Photoionization models indicate that MgII emission arises from the resonant scattering of photons produced in HII regions, accounting for the differing profiles of the MgII and FeII lines. Comparison of FeII absorption and FeII* emission indicates that massive galaxies have more extended outflows and/or greater extinction, while 2d composite spectra indicate that emission from the outflow is stronger at a radius of ~10kpc in high mass galaxies than in low mass galaxies.
1209.5058
Baryon census in hydrodynamical simulations of galaxy clusters
Planelles, Borgani, Dolag, Ettori, Fabjan, Murante, Tornatore
Cosmological SPH hydro sims of galaxy clusters and groups, study the total baryon budget in clusters, and how this budget is shared between the hot diffuse component and the stellar component. TreePM+SPH GADGET-3 code: (1) non-radiative, (2) radiative cooling, SF and SN feedback included (3) (2) with feedback from AGN. Aims: implication of stellar and hot gas content on the relative role played by SN and AGN feedback, and calibration of cluster baryon fraction and its evolution as a cosmological tool. Both radiative simulation predict a trend of stellar mass fraction with cluster mass that tends to be weaker in the observed one. Predicts a trend of stellar mass fraction with cluster mass that tends to be weaker than the observed one. Include effect of AGN feedback alleviates this tension, and predicts values of the hot gas mass fraction and total baryon fraction to be in closer agreement with observation. Compute baryon content and cosmic baryon fraction Y_b as a function of cluster-centric radius and z; at R500 in massive clusters M200>2e14 Msun/h, Y_b is nearly independent of physical processes included, and characterized by a negligible redshift evolution: Y_b,500 = 0.85 with the error accounting for the intrinsic scatter in the simulations. At R2500 < R500, typical value of Y_b slightly decreases, depending on the physics included in the simulations, while its scatter increases by a factor of 2.
1209.5391
A cold milky way stellar stream in the direction of triangulum
Bonaca, Geha, Kallivayalil
Evidence for new MW stellar tidal stream in the direction of M31 and M33 from SDSS DR8, stellar density maps probing MW halo at distances between 8 and 40 kpc. A visual search of these maps recovers all of the major known stellar streams towards M31/M33 ("Triangulum stream"), consistent wit being the tidal remnant of a globular cluster.
1209.5393
Major galaxy mergers only trigger the most luminous AGN
Treister, Schawinski, Urry, Simmons
Find strong, z-independent correlation between AGN luminosity and the fraction of host galaxies undergoing a major merger. Only the most luminous AGN phases are connected to major mergers, while less luminous AGN appear to be driven by secular processes. Combining this trend with AGN luminosity functions to assess the overall cosmic growth of black holes, find that ~50% by mass is associated with major mergers, while 10% of AGN by number, the most luminous, are connected to the violent events.
1209.5394
A baryonic solution to the missing satellites problem
Brooks, Kuhlen, Zolotov, Hooper
Number of massive subhaloes dramatically reduced when considering baryonic physics (flattening of DM profile cusp in the luminous subhaloes around MW-mass galaxies). Subhaloes likely to be destroyed by stripping, and likely to have SF suppressed by photo-heating. Baryonic processes have the potential to solve the missing satellites problem.
1209.5659
The challenge of the largest structures in the universe to cosmology
Park, Choi, Kim, Gott, Kim, Kim
Sloan great wall casts doubt on the concordance cosmological model (LCDM). Show that the wall is consistent with LCDM, shown with very large simulation (Horizon run 2). A structure even 2x larger possible in future 3 mag deeper surveys than SDSS.
1209.5675
Measuring the mass distribution in galaxy clusters
Geller, Diaferio, Serra
Only 2 methods, GL and caustic technique, are independent of the assumption of dynamicla equilibrium. Extended mass profile at radii beyond the virial radius possible. For 19 clusters, compare the mass profile based on the caustic technique with WL measurements from literature (test of systematics). At virial radius, agreement to 30%, consistent with errors. At small radii, caustic technique overestimates the mass from numerical simulations. WL profiles are a good representation of the true mass profile. At radii larger than the virial radius, the lensing mass profile exceeds the caustic mass profile possibly as a result of contamination of the lensing profile by large-scale structures within the lensing kernel.
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