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Abstract: We provide realistic mock-catalogs of cosmic rays above 40 EeV, for a pure proton composition, assuming their sources are a random subset of ordinary galaxies in a simulated, volume-limited survey, for various choices of source density: 10-3.5 Mpc-3, 10-4 Mpc-3 and 10-4.5 Mpc-3. The spectrum at the source is taken to be E-2.3 and the effects of cosmological redshifting as well as photo-pion and e+ e- energy losses are included. The catalogs described herein are available for downloading on this page.
In order to develop and test analysis tools for UHECR correlation studies, it is necessary to have mock catalogs of UHECRs under various realistic scenarios for the sources and magnetic deflections. There is no need at present to postulate a "new physics" origin for UHECRs, so the sources of UHECRs will be associated with the distribution of matter in the universe. The most popular types of source candidates reside in ordinary galaxies - for instance, AGNs and GRBs - and to first approximation these galaxies are a random subset of all galaxies. Here we provide mock UHECR catalogs assuming the sources are random galaxies. In this case, the key characteristic of a source population is its number density. The small number of doublets in the Auger events above 57 EeV leads to the lower bound of 61 on the number of sources producing them (Auger, 2008); this in turn leads to a lower bound on the source density of about 3 10-5 Mpc-3 (Farrar & Gruzinov,2009). Simulations of the spectrum suggest a density of 10-4 Mpc-3 (Takami et al, 2006). Therefore, we provide catalogs for the source density hypotheses 10-3.5 Mpc-3 ,10-4 Mpc-3 and 10-4.5 Mpc-3.
To have a realistic treatment of CRs in the GZK transition region from 40-60 EeV, the galaxy catalog used to produce the UHECR mocks must be volume-limited to a much larger depth than is available in present-day "all sky" galaxy surveys, the best of which are 2MRS and PSCz. In particular, the galaxy catalog from which the source catalog is derived must be considerably denser than 10-3.5 Mpc-3 to simulate a scenario in which the source catalog has that density, and yet not every galaxy hosts a UHECR source. Therefore, we make use of the "Las Damas" mock galaxy catalogs (McBride et al, 2009, in preparation) which are created using LCDM simulations (Omega_M = 0.25, Omega_DE = 0.75, H0 = 70 km/s/Mpc , sigma_8 = 0.8 and n_s = 1) combined with an algorithm for populating the DM halos with galaxies, that is tuned to reproduce the SDSS observations. See http://lss.phy.vanderbilt.edu/lasdamas/ for full details.
We start with two Las Damas "Carmen" catalogs which are volume-limited for Mr < -21 (includes all galaxies with Mr = -21 and brighter) to a redshift z = 0.165, and contain 519748 galaxies for a number density of 4 10-4 Mpc-3 or log(n) = -3.38 . They are:
The local structure in the two catalogs can be seen in Fig. 1. Only Carmen27_Mr21 is used in the initial mock galaxy and mock CR distributions. When catalogs and event lists based on Carmen02 are added, "mockgals" appearing in the catalog or event list name will be replaced by "mockgals02".
 
Fig 1: Local density of galaxies in Carmen02_Mr21 (left) and Carmen27_Mr21 (right) in a 4000 km/s slice centered on the origin.
Then, we randomly subsample each catalog to obtain 3 independent mock UHECR-source catalogs with log(n) = -3.5, -4, and -4.5. They are:
In all the above galaxy catalogs the file format is .From these mock-source catalogs we create mock UHECR catalogs as follows: a galaxy in the respective mock-source catalog is chosen randomly with a probability pI = wi / ? wi , with wi = ri-2, where ri is the distance of the ith galaxy. (Distance, not redshift, is used here because the effects of peculiar motion can lead to up to 20 Mpc shifts in the distance with respect to that calculated from the Hubble flow.) A CR from this galaxy is then assigned an energy according to an injection energy spectrum and propagated to Earth. Energy loss from redshifting as well as photo-pion and e+e- production is included. In the simulations presented here, the CR is assumed to be a proton; the injection spectrum is proportional to E-2.3 and ranges from 40 to 1000 EeV. If the energy after propagation is greater than 40 EeV, this proton is kept as an event. This procedure of source sampling and propagation is repeated until the desired number of events have been kept. Fig. 2 shows the final energy distribution as a function of redshift (actually, distance expressed as an equivalent redshift without peculiar motion).
Fig. 2: Distribution of energies at Earth, as a function of redshift of source.
The resulting catalogs are these:
made from the above mock-galaxy catalogs of the indicated source densities. The file format is , where IDgal is the galaxy ID that emitted that CR (e.g., IDgal=0 refers to the 1st galaxy in the source file mockgals_n3.5.dat), zgal is the redshift of that galaxy and Nmult is the number of E>40 CRs that were emitted by that same galaxy.
A complete tarball of the various mock galaxy and unsmeared CR catalogs described above is in files.tar.gz (33200013 Bytes).
The UHECRs in these catalogs have no deflection. To make a final suite of standard mocks for Auger analysis purposes, for each of the above mock-UHECR catalogs we have created catalogs for 8 different choices of angular deflection using a Gaussian smear around the original direction. This Gaussian smear is characterised by the angle ?68 containing 68% of the mass of the distribution. Each mock UHECR event list has a fixed smearing angle and we created event lists with smearing angles between 1 and 8 deg. There are 80 realizations with 149 events each. The file format is
E_Earth(EeV) Ra(deg) Dec(deg) Gal_L(deg) Gal_B(deg) E_source(EeV) Source_name source_redshift source_Ra(deg) source_Dec(deg) source_L(deg) source_B(deg)
The source name is given by mG[D][n] : mG for mock Galaxies, [D] is -10*log10(density*Mpc^3) (so [D]=35,40,45) and [n] is the line number in the list of galaxies once they are sorted by redshift.
For each source density, the tarballed mock CR event lists are in smr_3.5.tar.gz (4362280 Bytes), smr_4.0.tar.gz (4152815 Bytes), smr_4.5.tar.gz (4005449 Bytes).
Inside each of these tar files are separate files for each choice of angular smearing, e.g., mock_4.5_8.txt contains 80 realizations of 149 events each, with smearing of 8 deg.
For proper attribution, we ask:
1. Any use must credit the mock UHECR catalog project and cite the paper which is currently in preparation G. R. Farrar, A. Berlind and N. Busca, 2009, in preparation and the Las Damas paper about the galaxy catalog from which it is derived: McBride et al, 2009, in preparation.
2. If used in a publication, inform us about your work before submission.
3. Let us know that you downloaded, by sending an email to gf25@nyu.edu, so we can alert you if there are any problems discovered and about improvements implemented.
By downloading the mocks, you implicitly agree to these terms.
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