1211.3170
Population gradients and photometric metallicities in early- and transition-type dwarf galaxies: clues from the Sculptor group
Lianou, Grebel, Da Costa, Rejkuba, Jerjen, Koch
Focus on the resolved stellar populations of one early- and four transition-type dwarf galaxies with the aim to examine the potential presence of population gradients and place constraints on their mean metallicities. HST images generate CMDs of resolved stellar populations to constrain range of ages and metallicities, and their spatial distribution. (photometric metallicities too). All studied dwarfs contain intermediate-age stars of ~1Gyr and older (AGB and red clump stars), while the transition-type dwarfs contain also stars younger than ~1Gyr (young MS and vertical red clump stars). Spatial distribution of stars trace different evolutionary phases show a population gradient in all transition-type dwarfs. [what kind of population gradient?!?] ... Photo-metallicity not realizable due to degeneracies. ...
1211.3199
The M_(black hole)-L_(spheroid) relation at low masses
Graham, Scott
For 72 galaixes, derive M_BH vs L_{host spheroid} relation for (i) subsample of 24 core-Sersic galaxies with partially depleted cores, and (ii) the remaining subsample of 48 Sersic galaxies. Near-linear relation M_BH ~ L(K_s)^1.1 for the core-Sersic spheroids (build in additive dry merger events), while ~L(K_s)^2.73 for the Sersic spheroids build from gas-rich processes. After converting literature B-band disk galaxy mags into inclination- and dust-corrected bulge magnitudes, obtain a similar result. Remains unknown whether barred and non-barred Sersic galaxies are offset from each other in the M_BH-L diagram. Feedback results in a dramatically different scaling relation. Introduce a new, quadratic cold-gas 'quasar' mode feeding equation for semi-aalytical models to reflect the quadratic mass growth of BHs in Sersic galaxies build admist gas-rich processes.
1211.3206
Sunyaev-Zeldovich signal processing and temperature-velocity moment method for individual clusters
Chulba, Switzer, Nagai, Nelson
SZ observation of individual clusters can ask specific questions about the dynamical state of ICM. In this paper, develop a new method that clearly shows the connection of SZ signal with the cluster model. Relativistic temperature and kinematic corrections in the single-scattering approximation. Illustrate how to apply method to different cluster models, highlighting parameter degeneracies and instrumental effects that are important for interpreting future high-res SZ data. Shows: LoS temperature variations can introduce significant biases in the derived SZ temperature and peculiar velocity. Furthermore discuss how the position of the SZ null is affected by the cluster's temperature and velocity structure. SZ signal around the null alone is rather insensitive to different cluster models, and that high frequency channels add a large leverage in this regard. Also apply method to recent high sensitivity SZ data of the Bullet cluster, showing how the results can be linked to LoS variations in the electron temperature. Tools developed as part of SZpack should be useful for analyzing high-resolution SZ data and computing SZ maps from simulated clusters.
1211.3245
Improved photometric redshifts via enhanced estimates of system response, galaxy templates, and magnitude priors
Schmidt, Thorman
Photo-z's depend critically on accurate photometry. Describe the improvements to the photometric calibration and the photo-z estimate in DLS from correcting 3 of the inputs to the photo-z calculation: the system response as a function of wavelength, the SED templates, and template prior probabilities as a function of magnitude. Model the system response with a physical model of the MOSAIC camera's CD, which corrects a 0.1 mag discrepancy in the colors of type M2 and later stars relative to the SDSS z-band photometry. Provide new x-band response for MOSAIC (before its recent detector upgrade). Improved inputs lead to a 20% reduction in photo-z scatter and a reduction of the bias by a factor of more than two. This paper serves as both a photo-z data release description for DLS and a guild for testing the quality of photometry and resulting photo-z's generally.
1211.3249
Less is more: How cosmic voids can shed light on dark energy
Bos, Weygaert, Ruwen, Dolag, Pettorino
How the shape of cosmic voids can be used to distinguish between different models of DE using galaxy positions. [3 page paper on proceedings]
1211.3337
Rise and fall of radio halos in simulated merging galaxy clusters
Donnert, Dolag, Brunetti, Cassano
Show in sim: reacceleration of CRe has the potential to reproduce key observables of radio haloes. (Clusters evolve being radio loud or radio quiet, depending on their evolutionary stage during the merger.)
1211.3358
Bias from gas inhomogeneities in the pressure profiles as measured from X-ray and SZ observations
Khedekar .. Kravtsov, .. Nagai, ... Sunyaev et al
As the title says. Unrelaxed clusters display larger scatter. Bias remain +/- 20% within 0.8R_500 for all clusters.
1211.3399
An examination of the optical substructure of galaxy clusters hosting radio sources
Wing, Blanton (Elizabeth, not Mike)
FIRST radio survey and SDSS optical counterparts; radio sources within these clusters driven by AGN, and cluster samples include clusters with bent, straight, double-lobed radio sources. Also included a single-radio-component comparison sample. Examine these galaxy clusters for evidence of optical substructure, testing the possibility that bent double-lobed radio sources are formed as a result of large-scale cluster mergers. Use a suite of substructure analysis tools to determine the location and extent of substructure visible in the optical distribution of cluster galaxies, and compare the rates of substructure in clusters with different types of radio sources. Find: no preference for significant substructure in clusters hosting bent double-lobed radio sources compared to those with other types of radio sources.
1211.3401
The effect of particl noise in N-body simulations of gravitational lensing
Rau, Vegetti, White (SDM)
Density field only becomes smooth on scales beyond a few times the local mean interparticle separation. Present analytic expressions to quantify the Poisson noise and study the scaling with the particle number of the simulation and the Lagrangian smoothing size. Quantify the smallest resolved substructure that is significant compared to the noise: result is roughly independent of the SL property. Simple scaling relates the smallest resolved substructures in a simulation with the resolution of the N-body simulation.
1211.3411
Quenching star formation in cluster galaxies
Taranu, et al
SF quenching in rich clusters: library of subhalo orbits drawn from LCDM cosmological N-body simulations of 4 rich clusters. The orbits are combined with models of SF followed by quenching in the cluster environment to predict colors and spectroscopic lines indices of satellite galaxies. Simple models with only halo mass-dependent quenching and without environmental (cluster-dependent) quenching fail to reproduce the observed cluster-centrioc colour and absorption linestrength gradients. Models in which SF is instantly quenched at the virial radius also fail to match the observations. Better matches to the data are achieved by more complicated bulge-disc models in which the bulge stellar populations depend only on the galaxy subhalo mass while the disc quenching depends on the cluster environment. In the most successful models quenching begins at pericentre, operating on an exponential timescale of 2-3 Gyr, with the shorter timescale being a better match to disc colors as a function of cluster-centric radius and the longer being a better fit to the radial dependence of stellar absorption line indices. The models thus imply that the environments of rich clusters must impact SFR of infalling galaxies on relatively long timescales - several times longer than a typical halo spends within the virial radius of a cluster. This scenario favours gentler quenching mechanisms such as slow strangulation" over more rapid ram-pressure stripping.
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