1212.2639
The Carnegie-Irvine galaxy survey. III. The three-component structure of nearby elliptical galaxies
Huang, et al
Explore detailed photometric structure of a representative sample of 94 bright, nearby elliptical galaxies. M* from 1e10.2 to 1e12.0 Msun. Make 2d models to look for distinct substructures. Find global light distribution of >75% of elliptical galaxies is not well described by a single Sersic function. Instead, proposed that they generally contain 3 subcomponents: a compact <1kpc inner component with luminosity fraction of 0.1-0.15; an intermediate-scale ~2.5 kpc middle component with f~0.2-0.25; and a dominant (f=0.6), extended ~10 kpc outer envelope. All subcomponents have average Sersic indices n~1-2, significantly lower than the values typically obtained from single-component fits. The individual subcomponents follow well-defined photometric scaling relations and the stellar mass-size relation. Discuss the physical nature of the substructures and their implications for the formation of massive elliptical galaxies.
1212.2650
Inferring the mass of sub-millimetre galaxies by exploiting their gravitational magnification of background galaxies
Hildebrandt, van Waerbeke, Scott, ... Cooray, .. Erben, ... et al
Dust emission at sub-millimetre wavelengths allows tracing of early phases of SF in the universe. To understand the physical processes involved in this mode of SF [what mode?], it is essential to gain knowledge about the DM structures - most importantly their masses - that SMG live in [why?]. Use magnification effect of gravitational lensing to determine the average mass and dust content of SMG with 250 um flux densities of S_250>15mJy selected using data from the Herschel Multi-tiered Extragalactic Survey. The positions of hundreds of SM foreground lenses are cross-correlated with the positions of BG Lyman-break galaxies at z~3-5 selected using optical data from CFHTLS. Detect a cross-correlation signal at the 7-sigma level over a sky area of 1 sq deg, with 80% of this signal being due to magnification (the remaining 20% comes from dust extinction). Adopting some simple assumptions fo the DM and dust profiles and the redshift distribution enables us to estimate the average mass of the haloes hosting the SMG to be log(M200/Msun)=13.7 pm 0.05 and their average dust mass fraction (at radii of >10kpc) to be Mdust/M200~6e-5. This supports the picture that SMG are dusty, forming stars at a high rate, reside in massive group-sized haloes, and are a crucial phase in the assembly and evolution of structure in the universe.
1212.2675
Ca, Fe, and Mg trends among the within elliptical galaxies
Worthey, Ingermann, Serven
Ca/Fe and Ca/Mg systematically decrease with increasing elliptical galaxy mass. Metallicity mixtures, age effects, stellar chromospheric emission effects, and low-mass IMF boost effects are ruled out as causes. Feature gradients within galaxies imply a global Ca deficit rather than a radius-dependent phenomenon. Some, but not all, SNII nucleosynthetic yield calculations indicate a decreasing Ca/Fe yield ratio in more massive SNe, lending possible support of the hypothesis that more massive elliptical galaxies have an IMF that favors more massive stars. No SNII nucleosynthetic yield calculations show significant leverage in the Ca/Fe ratio as a function of progenitor metallicity. It seems unlikely that the Ca behavior can be explained as a build-in metallicity effect, and this argues against explanations that vary only the Type II to Type Ia SNe enrichment ratio.
1212.2806
Reconstructing cosmological initial conditions from galaxy peculiar velocities. I. Reverse Zeldovich Approximation
Doumler, Hoffman, Courtois, Gottloeber
New method to recover the cosmological IC of the presently observed galaxy distribution (can serve to run constrained simulations of the LU). The RZA method can be applied to radial galaxy peculiar velocity data and extends the previously used constraint realization method by adding a Lagrangian reconstruction step. The RZA method consists of applying Zeldovich approximation in reverse to galaxy peculiar velocities to estimate the cosmic displacement field and the initial linear matter distribution from which the present-dat LU evolved. Test our method with a mock survey taken from a cosmological simulation. Show that the halo peculiar velocities at z=0 are close to the linear prediction of the Z approximation, if a grouping is applied to the data to remove virial motions. The RZA is able to recover the correct initial positions of the velocity tracers with a median error of only 1.36 Mpc/h in the test simulation. For realistic sparse and noisy data, this median increases to 5 Mpc/h. This is a significant improvement over the previous approach of neglecting the displacement field, which introduces errors on a scale of 10 Mpc/h or even higher. Applying the RZA method to the upcoming high-quality observational peculiar velocity catalogues will generate much more precise constrained simulations of the LU.
1212.2967
Hints on the nature of dark matter from the properties of Milky Way satellites
Anderhalden et al
At highly NL scales, strong astrophysical constraints can be set on the nature of the DM particle; e.g., satellite galaxies of MW. Present results from a set of high-res simulations of a MW sized DM halo in 8 distinct cosmologies: CDM, WDM of 2keV particle; and 6 different cold+warm models (mass and fraction varied). Test for total satellite abundance, their radial distribution and their mass profile. Show that the requirement of simultaneously satisfying all 3 constraints sets very strong limits on the nature of DM [particle mass and total mass, I guess].
1212.2968
Effects of power law primordial magnetic field on big bang nucleosynthesis
Yamazaki, Kusakabe
BBN affected by energy density of a primordial magnetic field (PMF). Assume a power law distribution of PMF, then show a relation between PL-PMF parameters and the scale invariant strength of PMF. Perform BBN calculation, show abundances as a function of eta. The SI strength of the PMF is constrained from observational constraints on abundances of 4He and D. Minimum abundance of 7Hi/H as a function of eta slightly moves to a higher value at larger eta value when a PMF exists during BBN. ...
1212.2980
The size - virial radius relation of galaxies
Kravtsov
Sizes of galaxies are important diagnostic for galaxy formation models. Use abundance matching ansatz to derive estimates of the virial radius, R200, for galaxies of different morphological types and wide range of stellar mass. Show that over 8 orders of magnitude in M* galaxies of all morphological types follow an approximately linear relation between half-mass radius of their stellar distribuiton, r_half and virial radius, r_half ~ 0.015 R200, in remarkable agreement with expectation of models which assume that r_half lambda R200, where lambda is the spin of galaxy parent halo. The scatter about the relation is comparable with the scatter expected from the distribution of lambda and normalization of the relation agrees with that predicted if galaxy sizes were set on average at 1<z<2.
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