Monday.
1311.5559
CANDELS+3D-HST: compact SFGs at z~2-3, the progenitors of the first quiescent galaxies
Barro et al
Analyze the SF and structural properties of 45 massive (M/Msun>1e10) SFGs at 2<z<3 to explore thither they are progenitors of compact quiescent galaxies at z~2. The optical/NIR and FIR colors indicate that most compact SFGs are heavily obscured. Nearly half host an X-ray bright AGN. In contrast, only about 10% of other massive galaxies at that time host AGNs. Compact SFGs have centrally-concentrated light profiles and spheroidal morphologies similar to quiescent galaxies, and are thus strikingly different form other SFGs. Most compact SFGs lie either within the SFR-M main sequence (65%) or below (30%) [what does lying below the MS mean? more massive, less SFR], on the expected evolutionary path towards quiescent galaxies. These results show conclusively that galaxies become more compact before they lose their gas and dust, quenching SF. Using extensive HST photometry from CANDELS and grim spectroscopy from the 3D-HST survey, model their stellar population with either exponentially declining (tau) SFHs or physically-motivated SFHs drawn from SAMs. SAMs predict longer formation timescales and older ages ~2 Gyr, which are nearly twice as old as the estimates of the tau models. While both models yield good SED fits, SAM SFHs better match the observed slope and zero point of the SFR-M main sequence. Some low-mass compact SFGs M/Msun=1e10-10.6 have younger ages but lower sSFRs than that of more massive galaxies, suggesting that the low-mass galaxies reach the red sequence faster. If the progenitors of compact SFGs are extended SFGs, state-of-the-art SAMs show that mergers and disk instabilities are both able to shrink galaxies, but disk instabilities are more frequent (60% vs 40%) and form more concentrated galaxies. Confirm this result via high-resolution hydrosims.
1311.5563
Geometric and dynamic distortions in anisotropic galaxy clustering
Blazek, Seljak, Vlah, Okumura
Examine the signature of dynamic (z-space) distortions and geometric distortions (including the Alcock-Paczynski effect) in the context of the galaxy PS measured in upcoming galaxy redshift surveys. Information comes from both the BAO feature and the broadband PS shape. Accurate modeling is required to extract this information without introducing systematic bias in the result. Consider an analytic model for the PS of DM haloes in redshift space, based on the distribution function expansion. To test the accuracy of the model, compare with halo clustering measured in N-body simulations. Find that the distribution function model is sufficiently accurate to allow the inclusion of broadband information on scales down to k~0.2 h/Mpc, with somewhat better accuracy for higher bias halos. Compared with a BAO-only analysis with reconstruction, including broadband shape information can improve unbiased constraints on distance measures H(z) and D_A(z) by ~30% and 20%, respectively, for a galaxy sample similar to the DESI luminous red galaxies. The gains in precision are larger in the absence of BAO reconstruction. Furthermore, including broadband shape information allows the measurement of structure growth, through redshift-space distributions. For the same galaxy sample, find that the distribution function model is able to constrain (f*sigma_8) to ~2%, when simultaneously fitting for H(z) and D_A(z). Discuss techniques to optimize the analysis of the PS, including removing modes near the LoS that are particularly challenging to model, and whether these approaches can improve parameter constraints. Find that such techniques are unlikely to significantly improve constraints on geometry, although they may allow higher precision measurements of z-space distortions.
1311.5575
PAMELA positron and electron spectra re reproduced by 3-dimensional cosmic-ray modeling
Gaggero, et al
PAMELA released e+ absolute spectrum between 1 to 300 GeV in addition to the positron fraction and e- spectrum previously measured. Use the newly developed 3d code DRAGON and the charge dependent solar modulation code HelioProp to consistently describe those data. Obtain very good fits of all data sets if a e+ + e- hard extra-component peaked at 1TeV is added to a softer e- background and the secondary e+- produced by the spallation of CR proton and helium nuclei. All sources are assumed to follow a realistic spiral arm spatial distribution. PAMELA data do not display any need of charge asymmetric extra-component. Plain diffusion, or low re-acceleration, propagation models which are tuned against nuclear data, nicely describe PAMELA lepton data with no need to introduce a low energy break in the proton and He spectra.
1311.5761
Rest-frame ultra-violet spectra of massive galaxies at z=3: evidence for high-velocity outflows
Karman et al
As the title says. 9 out of 11 have spectroscopic z > 2.5. 4 of the highest quality spectra show outflows from fitting, between 480 and 1528 km/s. Conclude that massive galaxies are characterized by significantly higher velocity outflows than the typical Lyman break galaxies at z~3. All but one have high stellar mass >1e10; 3 show evidence (power-law SED) for AGN. The incidence of high-velocity outflows (~40% for this sample) is also much higher than among massive galaxies at z<1.
1311.5783
Review of the theory of PWNe
Bucciantini
[lots of spelling mistakes] Pulsar wind nebulae (PWNe) are ideal astrophysical labs where HE relativistic phenomena can be investigated. Knowledge derived in their study have a strong impact in other fields, such as AGNs to GRBs. Combination of high-res X-ray imaging and numerical codes to handle the outflow and dynamical properties of relativistic MHD has opened a new avenue of investigation that has lead to interesting progress in the last years. Still do not understand yet how particles are accelerated, and the functioning of the pulsar wind and pulsar magnetosphere, that power PWNe. Review the commonly known MHD paradigm, and will focus on various approaches that have been and are currently used to model these systems. For each, highlight its advantages and limitations, and degree of applicability.
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