Archivio della ricerca di Triestehttps://arts.units.itIl sistema di repository digitale IRIS acquisisce, archivia, indicizza, conserva e rende accessibili prodotti digitali della ricerca.Thu, 27 Jan 2022 02:11:05 GMT2022-01-27T02:11:05Z1041- Cosmology with massive neutrinos III: The halo mass function and an application to galaxy clustershttp://hdl.handle.net/11368/2974225.1Titolo: Cosmology with massive neutrinos III: The halo mass function and an application to galaxy clusters
Abstract: We use a suite of N-body simulations that incorporate massive neutrinos as an extra-set of particles to investigate their effect on the halo mass function. We show that for cosmologies with massive neutrinos the mass function of dark matter haloes selected using the spherical overdensity (SO) criterion is well reproduced by the fitting formula of Tinker et al. (2008) once the cold dark matter power spectrum is considered instead of the total matter power, as it is usually done. The differences between the two implementations, i.e. using P cdm(k) instead of Pm(k), are more pronounced for large values of the neutrino masses and in the high end of the halo mass function: in particular, the number of massive haloes is higher when Pcdm(k) is considered rather than Pm(k). As a quantitative application of our findings we consider a Planck-like SZ-clusters survey and show that the differences in predicted number counts can be as large as 30% for ∑m ν = 0.4 eV. Finally, we use the Planck-SZ clusters sample, with an approximate likelihood calculation, to derive Planck-like constraints on cosmological parameters. We find that, in a massive neutrino cosmology, our correction to the halo mass function produces a shift in the σ8(Ωm/0.27)γ relation which can be quantified as Δγ ∼ 0.05 and Δγ ∼ 0.14 assuming one (Nν = 1) or three (Nν = 3) degenerate massive neutrino, respectively. The shift results in a lower mean value of σ8 with Δσ8 = 0.01 for Nν = 1 and Δσ8 = 0.02 for Nν = 3, respectively. Such difference, in a cosmology with massive neutrinos, would increase the tension between cluster abundance and Planck CMB measurements. © 2013 IOP Publishing Ltd and Sissa Medialab srl.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/11368/2974225.12013-01-01T00:00:00Z
- On the impact of baryons on the halo mass function, bias, and cluster cosmologyhttp://hdl.handle.net/11368/2980103.2Titolo: On the impact of baryons on the halo mass function, bias, and cluster cosmology
Abstract: Luminous matter produces very energetic events, such as active galactic nuclei and supernova explosions, that significantly affect the internal regions of galaxy clusters. Although the current uncertainty in the effect of baryonic physics on cluster statistics is subdominant as compared to other systematics, the picture is likely to change soon as the amount of high-quality data is growing fast, urging the community to keep theoretical systematic uncertainties below the ever-growing statistical precision. In this paper, we study the effect of baryons on galaxy clusters, and their impact on the cosmological applications of clusters, using the magneticum suite of cosmological hydrodynamical simulations. We show that the impact of baryons on the halo mass function can be recast in terms on a variation of the mass of the haloes simulated with pure N-body, when baryonic effects are included. The halo mass function and halo bias are only indirectly affected. Finally, we demonstrate that neglecting baryonic effects on haloes mass function and bias would significantly alter the inference of cosmological parameters from high-sensitivity next-generations surveys of galaxy clusters.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11368/2980103.22021-01-01T00:00:00Z
- Euclid: Effects of sample covariance on the number counts of galaxy clustershttp://hdl.handle.net/11368/2993678.2Titolo: Euclid: Effects of sample covariance on the number counts of galaxy clusters
Abstract: Aims. We investigate the contribution of shot-noise and sample variance to uncertainties in the cosmological parameter constraints inferred from cluster number counts, in the context of the Euclid survey. Methods. By analysing 1000 Euclid-like light cones, produced with the PINOCCHIO approximate method, we validated the analytical model of Hu & Kravtsov (2003, ApJ, 584, 702) for the covariance matrix, which takes into account both sources of statistical error. Then, we used such a covariance to define the likelihood function that is better equipped to extract cosmological information from cluster number counts at the level of precision that will be reached by the future Euclid photometric catalogs of galaxy clusters. We also studied the impact of the cosmology dependence of the covariance matrix on the parameter constraints. Results. The analytical covariance matrix reproduces the variance measured from simulations within the 10 percent; such a difference has no sizeable effect on the error of cosmological parameter constraints at this level of statistics. Also, we find that the Gaussian likelihood with full covariance is the only model that provides an unbiased inference of cosmological parameters without underestimating the errors, and that the cosmology-dependence of the covariance must be taken into account.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11368/2993678.22021-01-01T00:00:00Z
- A blind method to recover the mask of a deep galaxy surveyhttp://hdl.handle.net/11368/2965006Titolo: A blind method to recover the mask of a deep galaxy survey
Abstract: We present a blind method to determine the properties of a foreground contamination, given by a visibility mask, that affects a deep galaxy survey. Angular cross correlations of density fields in different redshift bins are expected to vanish (apart from a contribution due to lensing), but are sensitive to the presence of a foreground that modulates the flux limit across the sky. After formalizing the expected effect of a foreground mask on the measured galaxy density, under a linear, luminosity-dependent bias model for galaxies, we construct two estimators, based on the average or square average galaxy density in a given sky pixel along the line of sight, that single out the mask contribution if a sufficient number of independent redshift bins is available. These estimators are combined to give a reconstruction of the mask. We use Milky-Way reddening as a prototype for the mask. Using a set of 20 large mock catalogs covering 1/4-th of the sky and number-matched to Hα emitters to mimic an Euclid-like sample, we demonstrate that our method can reconstruct the mask and its angular clustering at scales ℓ ≲ 100, beyond which the cosmological signal becomes dominant. The uncertainty of this reconstruction is quantified to be 1/3-rd of the sample variance of the signal. Such a reconstruction requires knowledge of the average and square average of the mask, but we show that it is possible to recover this information either from external models or internally from the data. It also relies on knowledge of how the impact of the foreground changes with redshift (due to the extinction curve in our case), but this can be tightly constrained by cross correlations of different redshift bins. The strong points of this blind reconstruction technique lies in the ability to find "unknown unknowns" that affect a survey, and in the facility to quantify, using sets of mock catalogs, how its uncertainty propagates to clustering measurements.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11368/29650062019-01-01T00:00:00Z