1508.01803
Disentangling redshift-space distortions and nonlinear bias using the 2d power spectrum
Jennings, Wechsler
Present the nonlinear 2d galaxy PS, P(k,mu), in redshift space, measured from the DarkSky simulations, using galaxy catalogs constructed with both HOD and sub halo abundance matching methods, chosen to represent an intermediate z sample of LRGs. Find that the information content in individual mu (cosine of the angle to the line of sight) bins is substantially richer than mutipole moments, and show that this can be used to isolate the impact of nonlinear growth and RSD effects. Using the mu<0.2 sim data, which is shown not to be impacted by RSD effects, NL bias can be successfully measured to an accuracy of ~5% at k<0.6h/Mpc. This use of individual mu bins to extract the NL bias successfully removes a large parameter degeneracy when constraining the linear growth rate of structure. Carry out a joint parameter estimation, using the low mu simulation data to constrain the NL bias, and mu>0.2 to constrain the growth rate and show that f can be constrained to ~26(22)% to a k_max<0.4(0.6) h/Mpc from clustering alone using a simple dispersion model, for a range of galaxy models. The analysis of individual mu bins also reveals interesting physical effects which arise simply from different methods of populating haloes with galaxies. Find a prominent turnaround scale, at which RSD damping effects are greater than the nonlinear growth, which differs not only for each mu bin but also for each galaxy model. These features may provide unique signatures which could be used to shed light on the galaxy-dark matter connection.
1508.01874
The distribution of galaxies gravitational field stemming from their tidal interaction
Stephanovich, Godlowski
Calculate the distribution function of astronomical objects (like galaxies and/or smooth haloes of different kinds) gravitational fields due to their tidal interaction. For that, apply the statistical method of Chandrasekhar (1943), used there to calculate famous Holtzmark distribution. Show that in the approach, the distribution function is never Gaussian, its form being dictated by the potential of interaction between objects. This calculation permits performing a theoretical analysis of the relation between angular momentum and mass (richness) of the galaxy clusters. To do so, follow the idea of Catelan & Theuns (1996) and Heavens&Peacock (1988). The main difference is that here, the problem is reduced to discrete many-body case, where all physical properties of the system are determined by the interaction potential V(r_ij). The essence of reduction is that the multipole is used (up to quadrupole here) expansion of Newtonian potential so that all hydrodynamic, "extended" characteristics of an object like its density mass are "integrated out" giving its "point-like" characteristics like mass and quadrupole moment. In that sense, make no difference between galaxies and smooth component like halos. Compare the theoretical results with observational data.
1508.02076
Galaxy and mass assembly (GAMA): Panchromatic data release (far-UV---far-IR) and the low-z energy budget
Driver, et al
Present the GAMA Panchromatic data release (PDR) constituting over 230 deg2 of imaging with photometry in 21 bands extending from the far-UV to the far-IR. These data complement the spectroscopic campaign of over 300k galaxies, and are compiled from observations with a variety of facilities including: GALEX, SDSS, VISTA, WISE, and Herschel, with the GAMA regions currently being surveys by VST and scheduled for observations by ASKAP. These data are processed to a common astrometric solution, from which photometry is derived for 221,373 galaxies with r<19.8 mag. Online tools are provided to access and download data cutouts, or the full mosaics of the GAMA regions in each band. Focus, in particular, on the reduction and analysis of the VISTA VIKING data, and compare to earlier datasets (i.e., 2MASS and UKIDSS) before combining the data and examining its integrity. Having derived the 21-band photometric catalogue, proceed to fit the data using the energy balance code MAGPHYS. These measurements are then used to obtain the first fully empirical measurement of the 0.1-500um energy output of the Universe. Exploring the Cosmic Spectral Energy Distribution (CSED) across three time-intervals (0.3-1.1 Gyr, 1.1-1.8 Gyr and 1.8-2.4 Gyr), find that the Universe is currently generating (1.5±0.3)e35 h_70 W Mpc^-3, down from (2.5±0.2)e35 h_70 W Mpc^-3 2.3 Gyr ago. More importantly, identify significant and smooth evolution in the integrated photo scale fraction at all wavelengths, with the UV escape fraction increasing form 27(18)% at z=0.18 in NUV(FUV) to 34(23)% at z=0.06. The GAMA PDR will allow for detailed studies of the energy production and outputs of individual systems, sub-populations, and representative galaxy samples at z<0.5. The GAMA PDR can be found at gama-psi.icrar.org.
1508.02346
Taking advantage of photometric galaxy catalogues to determine the halo occupation distribution
Rodriguez, Merchán, Sgró
Context: HOD is a powerful statistic that allows the study of several aspects of the matter distribution in the Universe, such as evaluating SAM of galaxy formation or imposing constraints on cosmo models. Consequently, it is important to have reliable method for estimating this statistic, taking full advantage of the available information on current and future galaxy surveys. Aims. The main goal of this project is to combine photometric and spectroscopic information using a discount method of background galaxies in order to extend the range of absolute magnitudes and to increase the upper limit of masses in which the HOD is estimated. Also evaluate the proposed method and apply it to estimating the HOD on SDSS DR7. Methods. Propose the background subtraction technique to mel information provided by spectra galaxy groups and photometric survey of galaxies. To evaluate the feasibility of the method, implement the proposed technique on a mock catalogue built from a SAM of galaxy formation. Furthermore, apply the method to DR7 using a galaxy group catalogue taken from spectra and the corresponding photometric galaxy survey. Results. Demonstrated the validity of the method using the mock catalogue. Applied this technique to obtain the DR7 HOD in absolute magnitudes raining from M=-21.5 to M=-16.0 and masses up to ~1e15 Msun throughout this range. On the brighter extreme, found that the results are in excellent agreement with those obtained in previous works.
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