Wednesday. I was crazy. He had a good time at the Karnaval; good weather in Bonn.
Thursday. On the train from Frankfurt. Made it to Journal Club. Gave wine to Aaron. That's it.
1202.3438
Plain fundamentals of fundamental planes: analytics and algorithms
Sheth, Bernardi
Provide explicit expressions for 2 variables (and confidence limits) in a 3-variable planar relation in terms of the covariances between the log of the 3 variables. Use for Fundamental Plane (R, Sigma, I), color-magnitude-Sigma relation, L-Sigma-Mbh relation, or X-ray lum- SZ decrement, and optical richness of cluster. Provide code. Show how analysis generalizes to correlations between more than 3 variables. Show how to account for correlated errors and selection effects; quantify the difference between the direct, inverse and orthogonal fit coefficients. Why is Sigma and I only weakly correlated in ellipticals? A fundamental question. If lack of correlation existed in the past, then differential luminosity evolution must have been accompanied by structural evolution [didn't quite follow the logic here]. A model in which the luminosities of low-L galaxies evolve more rapidly than do those of higher-L galaxies is able to produce the observed decrease in "a" (/2 at z~1) while having "b" decrease by only about 20 percent.
1202.3441
Forming early-type galaxies in LCDM simulations - I. Assembly histories
Johansson, Naab, Ostriker
Hi-res LCDM cosmo simulations with primordial radiative cooling, photoionization, star formation, SNII feedback (exclude SNe driven winds and AGN feedback). Simulated galaxy assemble in two phases: initial growth dominated by compact in situ star formation fueled by cold, low entropy gas streams, whereas the late growth is dominated by accretion of old stars formed in subunits outside the main galaxy. The two-phase formation mechanism naturally explains the observed downsizing [what is this?], bimodality and size growth of the galaxy population. Gravitational feedback strongly suppresses late SF win massive galaxies. Additional heating sources probably in the form of AGN and SNI feedback are also required to prevent late gas inflows and associated residual SF in more massive galaxies. Accretion of stellar material (dry minor mergers) is also responsible for the observed size growth of early-type galaxies. Find: DM fraction within the stellar half-mass radii continuously increase towards lower redshift from f_DM~0.05 at z~3 to f_DM~0.1-0.3 at z=0. In addition, the logarithmic slope of the total density profile is nearly isothermal at the present-day, good agreement with recent lensing observations. Simulations predict almost constant slopes until z=1, and then steeper slopes of gamma~3 at higher z.
1202.3522
Constraints on the origin of the ultra-high energy cosmic rays using cosmic diffuse neutrino flux limits: an analytical approach
Yoshida, Ishihara
Convert the upper-limits on the neutrino fluxes into the constraints on the CR sources.
1202.3554
Reconstruction of total solar irradiance 1974-2009
Ball, et al
Strong evidence that changes in photospheric magnetic flux alone are responsible for almost all solar irradiance variations over the last three solar cycles.
1202.3577
The intergalactic medium thermal history at z=1.7 to 3.2 from the Ly-a forest: a comparison of measurements using wavelets and the flux distribution
Garzilli, Bolton, Kim, Leach, Viel
Investigate IGM in 1.7<z<3.2 by studying the small-scale fluctuations in the Ly-a forest transmitted flux. Compare data to synthetic spectra drawn from a suite of hydro sims in which the IGM thermal state and cosmological parameters are varied. IGM thermal state in good agreement with other independent measurements. PDF and wavelet analysis agree, but flux PDF favor an isothermal or inverted IGM temperature-density relation. Joint analysis with PDF: results consistent with previous observations that indicate there may be additional sources of heating win the IGM at z<4.
1202.3665
emcee: The MCMC Hammer
Foreman-Mackey Hogg, Lang, Goodman
A stable, well tested Python implementation of the affine-invariant ensemble sampler for MCMC. Code is open source. Algorithm of emcee has advantages over traditional MCMC sampling; has excellent performance as measured by the autoorrelation time. One major advantage: requires hand-tuning of only 1 or 2 parameters compared to N2 for a traditional algorithm in an N-dimensional parameter space. Describe the algorithm and details of the implementation and API. Allows parallel processing. Available at http://danfm.ca/emcee.
1202.3783
Is quasar variability a damped random walk?
Zu, Kochanek, Kozlowski, Udalski
Still uncertain whether the DRW model provides an adequate description of quasar variability across all time scales. Use OGLE quasar light curves to check 4 modification to the DRW model. Over long (observed) timescales, excellent agreement. Over shorter (<few months) scales, some evidence of an existence of cutoff time scale below which the correlation is stronger than the DRW model. On >few year time scale, agrees well with DRW, but not constrained well.
1202.3787
The XMM Cluster Survey: the interplay between the brightest cluster galaxy and the ICM via AGN feedback
Stott, ...Kay, ... Liddle, ... Schaye, et al
Use 123 Xray clusters and groups and investigate interplay between BCG, its BH, and the ICM. For groups and clusters with a BCG likely to host significant AGN feedback, gas cooling dominates in those with Tx>2keV, while AGN feedback dominates below. Evidence for a combination of central gas cooling and powerful, well fueled AGN causes the departure of the ICM from pure gravitational heating , with the steepened relation crossing self-similarity at T_X=2keV. Demonstrates that the most massive BHs appear to know more about their host cluster than they do about their host galaxy (regardless of their BH mass, BCGs are more likely to host radio-loud AGN if the yard in a massive T_X>2keV cluster and again co-located with an effective fuel supply of dense, cooling gas).
1202.3791
On the average density profile of DM haloes in the inner regions of massive early-type galaxies
Grillo
Take average of 39 Ell galaxies at z<0.3 to determine the slope of the average DM density profile in the innermost regions, from SL data. Keep SL and SPS modeling as simple as possible. The DM projected density profile log slope is -1 (isothermal) or -0.7 (shallower than isothermal) if a Chabrier, or Salpeter-like stellar IMF is adopted. These results provide positive evidence of the influence of the baryonic component on the contraction of the galaxy DM haloes, compared to DM only simulations. New way to test models of structure formation and evolution within the standard LCDM cosmo scenario.
1202.3832
Cosmicflows-2: SNIa calibration and H0
Courtois, Tully
Merging of distance measures: Cepheid, "tip of the red giant branch" (TRGB), surface brightness fluctuations (SBF), luminosity-linewidth (TF), fundamental plane (FP), and SNIa. Hubble constant is H0=75 km/s/Mpc.
1202.3852
THe SL2S galaxy-scale gravitational lens sample. I: The alignment of mass and light in massive early-type galaxies at z=0.2-0.9
Gavazzi, Treu, Marshall, Brault, Ruff
Relative alignment of mass and light in a sample of 16 massive Ell galaxies at 0.2<z<0.9 that act as SL. Infer that there is a substantial amount of external shear ~0.12, arising most likely from the environment of the lenses. Combine these measurements to study the evolution of the stellar and DM content of Ell galaxies a function of cosmic time.
1202.3998
The shift of the BAO scale: a simple physical picture
Sherwin, Zaldarriaga
BAO scales shift to smaller values predicted by linear theory. This is because BAO measurement is more sensitive to regions with long wavelength over densities than under densities. In over dense regions, the BAO scale shrinks because such regions locally behave as positively curved closed universes. Provide approximate analytic expressions for the nonlinear shift; shifts are different in real and Fourier space due to a change of the shape of the BAO feature. Reconstruction should entirely reverse the shift. Shouldn't be a problem for next-generation BAO measurements.
1202.4039
Fermi-AT Observations of the Diffuse Gamma-ray emission: Implications for CR and ISM
The Fermi-LAT collaboration
Gamma-ray sky (>100 MeV): dominated by the diffuse emissions from interactions of CRs with the interstellar gas and radiation fields of MW; observations study CR origin and propagation, and the ISM. Compare models of diffuse gamma-ray emission using GALPROP code. Astrophysical input: distribution of CR sources, size of CR confinement volume (halo), distribution of ISM gas. Fit for the ratio of CO-line intensity to H2 column density, the Xco-factor [?], the flux and spectra from the point sources, and the intensity and spectrum of the isotropic BG including residual CRs that are misclassified as gamma-rays. Models compared on the basis of their maximum likelihood ratios, as well as spectra, longitude, and latitude profiles. Provide residual maps for the data. Data consistent with models at high and intermediate latitude, but under-predict the data in the inner galaxy for high energies (>few GeV). Possible explanation: contribution by undetected point source populations; spectral variations of CRs throughout the galaxy.
1202.4049
Brightness and fluctuation of the mid-IR sky from AKARI observations towards the North Ecliptic Pole
Pyo, Matsumoto, Jeong, Matsuura
AKARI NEP monitoring from 2.4 to 24 um (6 mid-IR bands). Seasonal variation of the sky brightness show NEP is not affected by small-scale features of the interplanetary dust cloud. Power spectrum analysis: photon noise, shot noise of faint sources, and Galactic cirrus. Few arcmin scale at short mid-IR: diffuse Galactic light of interstellar dust cirrus. At mid IR: photon noise dominant (few arc seconds to few arcmins). Residual fluctuation at 200" scale is 0.05% of the brightness at 24 um, or 0.02% at 18 um. Residual is the zodiacal light at NEP.
1202.4056
Extending the M_bh-sigma diagram with dense nuclear star clusters
Graham
~68 galaxies + 29 dwarf galaxy with M_nc (nuclear cluster mass) with M_bh, construct (M_bh+M_nc)-sigma diagram. For major dry mergers, M_bh/L ratio preserved. L~sigma^5 for luminous galaxies. Fainter Ell galaxies: L~sigma^2; some tension with other reports which was interpreted in terms of a regulating feedbac mechanism from stellar winds.
1202.4060
Dark energy and the fate of the universe
Li, Wang, Huang, Zhang, Li
The universe can still exist at least 16.7 Gyr before it ends in a big rip.
1202.4138
Gaia: a window to large scale flows
Nusser, Branchini, Davis
2D transverse peculiar velocities of distant galaxies (cz~2e4 km/s) can be obtained from Gaia's measurements of proper motions. Essentially free of selection biases, is also free from homogeneous and inhomogeneous Malmquist biases. Provides additional information to traditional probes which yield LoS peculiar velocities.
1202.4164
Environmental effects on the metal enrichment of low mass galaxies in nearby clusters
Petropoulou, Vilchez, Iglesias-Paramo
Study the chemical history of low-mass SF galaxies in local clusters Coma and 3 Abell clusters. Search for imprint of the environment on the chemical evolution of these galaxies. Galaxy chemical evolution is linked to the SFH, as well as to the gas interchange with the environment, and low-mass galaxies are well known to be vulnerable systems to environmental processes affecting both these parameters. Use SDSS DR8. Sensitivity of mass-metallicity to cluster environment depends on both galaxy mass and host cluster mass. Low-mass SF galaxies in high-mass clusters are severely affected by ram-pressure stripping. Metal content enhancement that is mass-dependent in low-mass galaxies in dense environments plausible according to hydrosims. Enhanced metal enrichment could be produced by the combination of effects such as wind reaccretion, pressure confinement by ICM, and the truncation of gas infall, as a result of ram-pressure stripping. Properties of ICM should play an important role in the chemical evolution of low-mass galaxies in clusters.
1202.4242
F-GAMMA: on the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
Angelakis et al
78 sources studied; variability can be classified in 5 types, attributed to tow classes of variability mechanisms. First 4 types: dominated by spectral evolution with two-component system of (1) a steep quiescent spectral component from a large scale jet, and (2) time evolving flare component following the shock-in-jet evolutionary path. The 5th type is characterized by an achromatic change of the broad band spectrum, which can be attributed to a different mechanism, likely involving differential Doppler boosting chased by geometrical effects. Present the classification, the assumed physical scenario, and the results of calculations for spectral evolution of flares.
* I'd like to read this one...
1202.4275
The effect of feedback on the emission properties of the warm-hot intergalactic medium
Roncarelli, Capelluti, Borgani, Branchini, Moscardini
30-40% of baryons in the local universe is still undetected. This gas should reside in filaments filling the LSS in the form of WHIM, at 1e5 - 1e7 K, thus emitting in the soft X-ray energies via free-free interaction and line emission from heavy elements. Characterize the properties of the X-ray emission of the WHIM, and the LSS in general, focusing on focusing on the influence of different physical mechanisms, namely galactic winds (GWs), BH feedback and SF, and providing estimates of possible observational constraints. Use a set of cosmological hydrodynamical simulations that include a self-consistent treatment of SF and chemical enrichment of IGM that allow following of evolution of different metal species. Simulate light-cones to predict emission in the 0.3-10keV energy range. Obtain GWs increase by a factor of 2 the emission of both galaxy clusters and WHIM. ...
No comments:
Post a Comment