1212.1156
A Bayesian approach to scaling relations for amplitudes of solar-like oscillations in Kepler stars
Corsaro et al
Investigate different amplitude scaling relations adopted for astroseismology of stars that show solar-like oscillations. Difficult to measure because of the large uncertainties in measuring the BG level in the star's power spectrum. From 1640 stars spanning from MS to red giant stars, make Bayesian inference for 12 models used for amplitude predictions and exploit recently well-calibrated effective temperatures from SDSS photometry. Test candidate amplitude scaling relations by means of a Bayesian model comparison. Find the model have a separate dependence upon the mass of the stars to be "the most favored one" [?]. The difference among models and the differences seen in their free parameters from early to late phases of stellar evolution are also highlighted.
1212.1157
Revisiting the first galaxies: the epoch of Population III stars
Muratov, Gnedin, Gnedin, Zemp
Investigate the transition from Pop III SF to normal Pop II SF in the first galaxies using new cosmological hydrodynamic simulations. Find that while the first stars seed their host galaxies with metals, they cannot sustain significant outflows to enrich the intergalactic medium, even assuming a top-heavy IMF. This means that Pop III SF could potentially continue until z~6 in different unenriched regions of the universe, before being ultimately shut off by cosmic reionization [reionization shuts down Pop III SF?]. Within an individual galaxy, Pop II stars overtake Pop III in 20-200 Myr, based on the amount of stellar feedback and metal production.
1212.1158
Evidence for widespread AGN activity among massive quiescent galaxies at z~2
Olsen, Rasmussen, Toft, Zirm
Quantify presence of AGN in M*>5e10 Msun sample of 123 SF and quiescent galaxies at 1.5<z<2.5, using X-ray data from the 4 Ms Chandra (CDF-S) survey. 41% of the galaxies are detected directly in X-rays, 22 with rest-fram 0.5-8 keV luminosities consistent with hosting luminous AGN. The latter fraction is similar for SF and quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that luminous AGN are triggered by external effects such as mergers. Detect significant mean X-ray signals in stacked images for both the individually non-detected SF and quiescent galaxies, with spectra consistent with SF only and/or a low luminosity AGN in both cases. Compare SF rates inferred from 2-10 keV luminosities to those from rest-frame IR+UV emission, find evidence for an X-ray excess indicative of low-luminoisty AGN. Among the quiescent galaxies, the excess suggests that as many as 70-100% of these contain low-or high-luminosity AGN, while the corresponding fraction is lower among SF galaxies (43-65%). The ubiquitous presence of AGN in massive, quiescent z~2 galaxies that we find provides observational support for the importance of AGN in impeding SF during galaxy evolution.
1212.1166
Self-consistency of the excursion set approach
Achitouv, Rasera, Sheth, Corasaniti
Excursion set approach: framework for predicting how the abundance of DM haloes dependes on the initial conditions. Key ingredient: physics of halo formation---specification of a ciritical overdensity threshold (barrier) which protohalos must exceed if they are to form bound virialized haloes at a later time. Another ingredient (statistical): specification of appropriate statistical ensemble over which to average when making predictions. The excursion set approach explicitly averages over all initial positions, thus implicitly assuming that the appropriate ensemble is that associated with randomly chosen positions in space, rather than special positions such as peaks of the initial density field. SInce haloes are known to collapse around special positions, it is not clear that the physical and statistical assumptions which underlie the excursion set approach are self-consistent. Argue that they are, and illustrate by comparing excursion set predictions with numerical data from DEUS simulations.
1212.1174
On the signature of nearby superclusters and voids in the integrated Sachs-Wolfe effect
Hernandez-Monteagudo (Carlos), Smith (Robert)
From simulations, show that in LCDM scenario, supervoids and superclusters in 0.4<z<0.7 should leave a small signature on ISW of the order ~2 uK. Look for it in WMAP, find 8-11 uK amplitudes. For 3.6 deg apertures, LCDM discrepant at 4 sigma. For all aperture scales considered (1-20 deg), Discrepancy is 2 sigma. Discrepancy cannot be alleviated by RS mechanisms (their impact on scales probed by these filters is negligible). Check for FG contaminants, show that the signal does not display correct dependence on the aperture size expected for a residual FG tracing the density field. Signal also proves robust against rotation tests of CMB maps. If primordial non-Gaussianity were to explain the result, then f_NL would need to be several times larger than currently permitted by WMAP constraints.
1212.1177
Accounting for Baryons in cosmological constraints from cosmic shear
Zentner, Semboloni, Dodelson, Eifler, Krause, Hearin
Effect of baryons on the PS of kappa field---a theoretical systematic for grav lens surveys. Account for these effects by additional parameters (that characterize DM haloes); fit lensing data to these parameters concurrently with the standard set of cosmo parameters. Test this method with cosmo sims. Estimate bias in DE EoS parameters that would be incurred if one were to fit the spectra predicted by the simulations either with no model for baryons, or with the proposed method. Show that neglecting baryonic effect leads to biases in DE parameters that are several times the statistical errors for e.g. DES. The proposed method to correct for baryonic effects renders the residual biases in DE EoS parameters smaller than the statistical errors. These results suggest that this mitigation method may be applied to analyze convergence spectra from a survey like the DES. For significantly larger surveys, such as will be carried out by the LSST, the biases introduced by baryonic effects are much more significant. Show that this mitigation technique significantly reduces the biases for such larger surveys, but a more effective mitigation strategy will need to be developed in order to ensure that the residual biases in these surveys fall below the statistical errors.
1212.1211
The clustering of galaxies in the SDSS-III Baryon Oscillation spectroscopic survey: Luminosity and color dependence and redshift evolution
Guo, Zehavi, ... et al
L and color dependence and the z evolution of galaxy clustering in SDSS BOSS. Focus on 2pt correlation function (2PCF) of subsets of CMASS sample (260k galaxies over 3300 sq deg, 0.43<z<0.7). Construct well-defined luminosity and color subsamples by carefully accounting for the CMASS galaxy selection cuts. The 2PCF of the whole CMASS sample, if approximated by a power-law, has a correlation length of r_0=7.93pm0.06 Mpc/h and an index of gamma=1.85pm0.01. Clear dependences on galaxy luminosity and color are found for the projected 2PCF in all z bins, with more luminous and redder galaxies generally exhibiting stronger clustering and steeper 2PCF. The color dependence is alos clearly seen in galaxies within the red sequence (consistent with SDSS-II MS at lower z). At a given L (k+e corrected), no significant evolution of the projected 2PCFs with z is detected for red sequence galaxies. Construct galaxy samples of fixed number density at different z, using z-dependent magnitude thresholds. The clustering of these galaxies in the CMASS redshift range is found to be consistent with that predicted by passive evolution. Measurements of the luminosity and color dependence and z evolution of galaxy clustering will allow for detailed modeling of the relation between galaxies and DM halos and new constraints on galaxy formation and evolution.
1212.1356
Mass assembly of high-z galaxies with MASSIV
Perret, .. Le Fevre, ... et al
Mass Assembly Survey with SINFONI in VVDS (MASSIV): sample of 84 distant SF galaxies at 0.8<z<1.9, between 3 and 5 billion years old. Probes dynamical and chemical abundances properties of representative galaxies of this cosmological era: about a third of the sample is involved in major mergers, while 42% of the sample is rotating disks, in accordance with higher z samples. The remaining 58% (non-disk) show complex kinematics, suggesting a dynamical support based on dispersion, and about half of these galaxies is involved with major mergers. Spheroids, unrelaxed merger remnants, or extremely turbulent disks might be an explanation for such a behavior. Furthermore, the spatially resolved metallicity analysis reveals positive gradients, adding a piece to the puzzle of galaxies evolution scenarios.
1212.1363
THe intriguing life of star-forming galaxies in the redshift range 1<z<2 using MASSIV
Amram et al
Kinematics of individual galaxies reveals that 58% of the galaxies are slow rotators (high fraction of these galaxies should probably be formed through major merger processes which might have produced gaseous thick or spheroidal structures supported by velocity dispersion rather than by rotation). Computation indicate that typical SF galaxy underwent ~0.4 major mergers since ~9.5 Gyr, showing that merging is a major process driving mass assembly into the red sequence galaxies. These objects are also intriguing due to the fact that more than one galaxy over four is more metal-rich in its outskirts than in its center.
1212.1429
The correlation of dust and gas emission in star-forming environments
Morgan et al
Compare gas emission with continuum thermal emission in molecular clouds; expected to trace the same mass component in SF regions, often under the assumption of LTE [?]. The SF regions are found to have different physical characteristics consistent with their identification as low-mass and high-mass respectively. Underlying difference in the structure of the two regions observed (W3 and Perseus molecular clouds). Extent of diffuse emission only moderately matched. Indication of dip in abundance at the positions of peak submillimetre flux, but find that depletion of ammonia unlikely. Sources in Perseus are generally not gravitationally bound, but those in W3 are. External pressure necessary for cores at small scales to be bound while sources and clusters are gravitationally bound on larger scales. Results indicate that assumptions of local thermal equilibrium and/or the coupling of the dust and gas phases in SF regions may not be as robust as commonly assumed. Alternatively, the assumption that NH3 and thermal emission trace the same mass component in these regions may need to be revisited, along with the degree to which th excitation conditions within a SF region vary.
1212.1448
The 2012 Hubble ultra deep field (UDF12): observational overview
Koekemoer, et al
128-orbit Cycle 19 HST program of extending observations of UDF by quadrupling the exposure time in F105W filter, an additional F140 filter, and extending the F160W exposure time by 50%. Scientific goal: galaxy reionization of the universe, determine SF density at z>8, improve measurements of the UV continuum slope at z~7-8, facilitate the construction of new samples of z~9-10 candidates, enable detection of sources up to z~12. Single homogenous dataset: deepest nIR observations of the sky currently achievable. Present the observational overview of the project, data reduction procedure, final data products. Release the full combined mosaics: the deepest NIR blank-field view of the universe obtained to date, as deep as AB~30 in NIR, and yielding a legacy dataset.
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