1202.3022
Reheating constraints in inflationary magnetogenesis
Demozzi, Ringeval
Show that requiring large scale magnetic fields to remain subdominant after inflation gives non-trivial constraints on both the reheating equation of state parameter and the reheating energy scale. (Inflation is a prime candidate to explain the current existence of cosmological magnetic fields.) B-field of order 5e-15 Gauss today. ...
1202.3032
Forecast constraints on cosmic string parameters from gravitational wave direct detection experiments
Kuroyanagi, Miyamono. Sekiguchi, Takahashi, Silk
Cosmic string can generate GWs. Study both burst and stochastic GWs from cosmic string, which provide different information about cosmic strings, can break degeneracies in the string parameters.
1202.3039
All-particle CR energy spectrum measured with 26 IceTop stations
IceCube Collaboration
Energy spectrum from 1 to 100 PeV (1e15 eV) for 3 different zenith angle (0 to 46 deg). The CR in this energy range is expected to be isotropic [i.e., not affected by the weak B-fields present around Earth, MW, and others].
1202.3073
Formaldehyde and methanol deuteraton in protostars: fossils from a past fast high density pre-collapse phase
Taquet, Ceccarelli, Kahane
Observation of abundant doubly and triply deuterated forms of formaldehyde and methanol: both species are thought to be formed on interstellar grains during the low temperature and dense pre-collapse phase by H and D atom additions on the iced CO. Use gas-grain model GRAINOBLE to study deuteration of these species. Comparison with observation shows: (1) the observed high deuteration is obtained during the last phase of the pre-collapse stage, when density reaches 5e6 cm-3, a fast phase only lasting several thousand years. (2) D and H abstraction and substitution reactions are crucial in making up the observed deuteration ratios.
1202.3078
The M Dwarf problem in the Galaxy
Woolf, West
M dwarf problem: the number of M dwarfs at [Fe/H]~-0.5 is less than 1% the number at [Fe/H] = 0, where a simple model of Galactic chemical evolution predicts a more gradual drop in star numbers with decreasing metallicity.
1202.3107
MASSIV: Mass assembly survey with SINFONI in VVDS. IV. Fundamental relations of star-forming galaxies at 1<z<1.6
Vergani, et al
Use 45 (SF galaxies) at 1<z<1.6, measure dynamics, galaxy size, stellar mass. Obtain baryonic TF relation. Obtain marginal evolution in the size-stllar mass and size-velocity relations, with disks being evenly smaller with cosmic time at fixed stellar mass or velocity, and less massive for a given velocity with respect to the local universe. Large scatter in TF relation, probably intrinsic. Results point towards a mild, net evolution of these relations, comparable to what is predicted by cosmological simulations of disc formation. Lack of an influential transformation of the fundamental relations of SF galaxies for at least 8 Gyr and a dark halo strongly coupled with galactic spectrophotometric properties.
1202.3137
The 60-month all-sky BAT survey of AGN and the anisotropy of nearby AGN
Ajello, Alexander, Greiner, Madejski, Gehrels, Burlon
720 sources with Swift/BAT, 428 associated with (mostly nearby) AGN (>10keV surveys best resource to provide an unbiased census of AGN population). Sample has negligible incompleteness and ~2x larger statistics of other similar AGN data sets. Data contains 15 Compton-thick AGN (a 5% sample of AGN) + possibly 3 more. LogN-LogS of AGN established to 10% precision, important for cosmic x-ray BG contribution estimation. Concentrations of AGN coincide spatially with the super-massive clutsers in the local (<85 Mpc) universe.
1202.3141
Supermassive BH ancenstors
Peetri, Ferrara, Salvaterra
Study model in which SMBH can grow by gas accretion on heavy seeds, and mergers of both heavy (1e5 Msun) and light (1e2 Msun) seeds. Former: H2 free haloes, latter: standard H2 based star formation processes. H2 free conditions: expose halos to a strong UV BG produced by accreting BHs and stars, thus establishing a self-regulated growth regime; a condition that can be met at z~18. Key parameter allowing formation of SMBH by z=6-7 is the fraction of halos that can form heavy seeds: SMBH as large as 2e10 Msun can be obtained when f_heavy approaches unity (minimum required: f_heavy>1e-3). Model forms bulge-BH mass relation which is steeper than local, implying that SMBHs formed before their bulge was in place. Formation of heavy seeds is crucial to achieve a fast growth of the SMBH by merger events in the early phases of its evolution: z>7. The UV photon production is largely dominated by stars in galaxies; BH accretion radiation is subdominant. Find that the final mass of light BHs and of the SMBH in the quasar is roughly equal by z=6; by the same time, only 20% of the initial baryon content has been converted into stars. The SMBH growth is dominated at all epochs z>7.2 by mergers, at later times accretion becomes by far the most important growth channel.
1202.3143
Exploring galaxy formation models and cosmologies with galaxy clustering
Kang, Li, Lin, Elahi
Using N-body simulations and galaxy formation models, study the stellar mass correlation and the 2pt auto-correlation. Use WMAP1, 3, 7 params (mostly differ by sigma8). Stellar mass determined from SAM or empirical abundance matching. Compare with SDSS DR7 at z=0, or DEEP2 at z=1. Find: SAM galaxy clustering too high at small scales, mostly due to satellites. Abundance matching predicts good agreement for high sigma8 cosmologies. Galaxy clustering is strongly affected by models for galaxy formation, thus can be used to constrain baryonic physics. Weak dependence of galaxy clustering on cosmological parameters.
1202.3191
Cosmicflows-2: I-band luminosity - HI linewidth calibration
Tully, Courtois
Derive a measure of rotation from a new characterization of the width of a neutral H line profile. [are they talking about disk galaxies? or dispersion velocities?] Determine H0=75 km/s/Mpc [errors?].
1202.3202
SNe-driven outflows and chemical evolution of dwarf spheroidal galaxies
Quian, Wasserburg
Present a general phenomenological model for the metallicity distribution (MD) in terms of [Fe/H] for dwarf spheroidal galaxies (dSphs). These galaxies appear to have stopped accreting gas from the IGM and are fossilized systems with their stars undergoing slow internal evolution. Model key requirement: fraction of gas mass lost by SNe-driven outflows is close to unity; then for a wide variety of infall histories of unprocessed baryonic matter to feed SF, most of the observed MDs can be well described by the model. Model also predicts a relationship between the total stellar mass and the mean metallicity for dSphs in accord with properties of their DM haloes. The model further predicts as a natural consequence that the abundance ratios [E/Fe] for elements such as O, Mg, and Si decrease for stellar populations at the higher end of the [Fe/H] range in a dSph. Show that for infall rates far below the net rate of gas loss to SF and outflows, the MD in model is very sharply peaked at one [Fe/H] value, similar to what is observed in most globular clusters. Suggests that globular clusters may be end members of the same family as dSphs.
1202.3308
A systematic variation in the stellar IMF in early-type galaxies
Cappellari, McDermid, Alatolo, Blitz, ... et al
No consensus has emerged on whether IMF is universal in different galaxies. Previous studies indicate that the IMF and the DM fraction in galaxy centers cannot be both universal, but they could not break the degeneracy between the two effects. Recently, indications found that massive elliptical galaxies may not have the same IMF as our MW. Report unambiguous evidence for a strong systematic variation of the IMF in early-type galaxies as a function of their stellar mass-to-light ratio, producing differences up to a factor of three in mass. This was inferred from detailed dynamical models of the 2-dimensional stellar kinematics for the large Atlas3d representative sample of nearby early-type galaxies spanning two orders of magnitude in stellar mass. Finding indicates that the IMF depends intimately on a galaxy's formation history.
1202.3349
Origin of strong B-fields in MW-like galactic haloes
Beck, Lesch, Dolag, Kotarba, Geng, Stasyszyn
(Use of Gadget simulations) A primordial magnetic seed field ranging from 1e-10 to 1e-34 G agglomerates together with the gas within filaments and protohalos. There, it is amplified within 1e8 yrs put to equipartition with the corresponding turbulent energy. THe magnetic field strength increases by turbulent small-scale dynamo action. The turbulence is generated by the gravitational collapse and by supernova feedback. Subsequently, a series of halo mergers leads to shock waves and amplification processes magnetizing the surrounding gas within a few 1e9 years. At first, the B energy grows on small scales and then self-organizes to larger scales. B-field strengths of 1e-6 G are reached in the center of the halo and drop to 1e-9 G in the IGM. Analyzing the saturation levels and growth rates, the model is able to describe the process of B amplification notable well, and confirms the results of the simulations.
1202.3364
Origami constraints on the initial-conditions arrangement of DM caustics and streams
Neyrinck
In CDM, cosmological structure formation proceeds in rough analogy to origami folding. Identify a result of origami mathematics that applies to cosmology. Define caustics in the initial conditions (Lagrangian space) as surfaces on the sheet. The regions outlined by the caustics, ("streams") may be colored according to two possible orientations of initial basis vectors--a severe restriction on connectivity. Explore how outer caustics in Lagrangian space correspond to a Zeldovich prediction, as well as to a measurement from the recent ORIGAMI algorithm.
1202.3403
Dynamics of secular evolution
Binney
(Text of lecures to the "secular evolution of galaxies" Tenerife winter school.) Connection between isolating integrals, quasi periodicity, and angle-action variables. Phenomenon of resonant trapping, leading to chaos in cushy potentials and phase-space mixing in slowly evolving potentials. Surfaces of section and frequency analysis introduced as diagnostics of phase-space structure. Real galactic potentials include a fluctuation part that drives the system towards unattainable thermal equilibrium. Two-body encounters are only one source of fluctuations, and all fluctuations will drive similar evolution. Derive the orbit-averaged FP equation and relations that hold between the 2nd order diffusion coefficients and both the power spectrum of the fluctuations and the first-order diffusion coefficients. ... whoa, too theoretical.
No comments:
Post a Comment