Gravitationally Consistent HALO Catalogs and Merger Trees for Precision Cosmology Page: 1 of 16
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
APJ ACCEPTED SLAC-PUB-15332
Preprint typeset using IATEX style emulateapj v. 11/10/09
GRAVITATIONALLY CONSISTENT HALO CATALOGS AND MERGER TREES FOR PRECISION COSMOLOGY
PETER S. BEHROOZI, RISA H. WECHSLER, HAO-YI WU
Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, Stanford University;
Department of Particle Physics and Astrophysics, SLAC National Accelerator Laboratory; Stanford, CA 94305
MICHAEL T. BUSHA
Institute for Theoretical Physics, University of Zurich, 8006 Zurich, Switzerland
ANATOLY A. KLYPIN
Astronomy Department, New Mexico State University, Las Cruces, NM, 88003
JOEL R. PRIMACK
Department of Physics, University of California at Santa Cruz, Santa Cruz, CA 95064
We present a new algorithm for generating merger trees and halo catalogs which explicitly ensures consis-
tency of halo properties (mass, position, and velocity) across timesteps. Our algorithm has demonstrated the
ability to improve both the completeness (through detecting and inserting otherwise missing halos) and purity
(through detecting and removing spurious objects) of both merger trees and halo catalogs. In addition, our
method is able to robustly measure the self-consistency of halo finders; it is the first to directly measure the
uncertainties in halo positions, halo velocities, and the halo mass function for a given halo finder based on
consistency between snapshots in cosmological simulations. We use this algorithm to generate merger trees for
two large simulations (Bolshoi and Consuelo) and evaluate two halo finders (ROCKSTAR and BDM). We find
that both the ROCKSTAR and BDM halo finders track halos extremely well; in both, the number of halos which
do not have physically consistent progenitors is at the 1-2% level across all halo masses. Our code is publicly
available at http: //code. google. com/p/consistent-trees. Our trees and catalogs are publicly
available at http://hipacc.ucsc.edu/Bolshoi/.
Subject headings: dark matter - galaxies: abundances - galaxies: evolution - methods: N-body simulations
Over the past few decades, dark matter simulations have
demonstrated increasing usefulness for validating theories of
cosmology, for understanding systematic biases in observa-
tions, and for constraining galaxy and large-scale structure
formation. In coming years, the rapid expansion of obser-
vational data coming from ground and space based surveys,
including CANDELS, GAMA, BOSS, DES, Herschel, Pan-
STARRS, BigBOSS, eROSITA, Planck, JWST, and LSST
will mean that simulations will become even more important
for modeling and understanding the detailed evolution of the
cosmos. This wealth of data means that cosmological and
galaxy properties soon will be measured to a new standard
of precision; however, none of this will increase the accuracy
of current cosmological constraints without a concordant in-
crease in the quality of simulations and our ability to model
the systematic biases inherent in the observations.
Two of the principal outputs of dark matter simulations are
halo catalogs and merger trees; namely, information about
the deep potential wells where galaxies are expected to re-
side, and a history of the mergers and growth of these po-
tential wells. Derived properties of these outputs, such as
the halo mass function and auto-correlation function, must
be understood at the one-percent and five-percent level, re-
spectively, in order to use the full constraining power of fu-
ture surveys for, e.g., dark energy (Wu et al. 2010). Similar
levels of accuracy are required to be able to distinguish be-
tween different values of the primordial non-gaussianity pa-
rameter fNL (Pillepich et al. 2010). In addition to raw accu-
racy, models of galaxy formation (e.g., semi-empirical abun-
dance matching and semi-analytical models) depend on the
physical consistency of catalogs and merger trees, in the sense
that they require physically reasonable halo growth histories
and dynamically-plausible mergers to accurately model the
build-up of galaxy properties (e.g., stellar mass, luminosity,
metallicity, dust) over time (Benson et al. 2011).
To date, while simulations largely agree on the final dark
matter distribution, few comprehensive reviews have been
performed to determine which combinations of halo finders
and merger tree codes produce the most accurate results (see,
however, Knebe et al. 2011). In part, this is because cos-
mological halos have complicated structure; depending on
the particle distribution, it may be difficult to tell which halo
finder is "better" or "worse" except by using a tedious and
subjective examination by hand. On the other hand, with
comparisons performed on more clinical test cases, such as
halos generated with perfect NFW profiles, it is difficult to
know how the comparison results will translate to the messier
world of cosmological halos. Furthermore, percent-level un-
derstanding of the halo mass function requires not only that
the halo finder should function well in the common cases, but
that it should also be robust against even the most extremely
Work supported in part by US Department of Energy contract DE-AC02-76SF00515.
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi; Busha, Michael T.; Klypin, Anatoly A. & Primack, Joel R. Gravitationally Consistent HALO Catalogs and Merger Trees for Precision Cosmology, article, December 21, 2012; United States. (https://digital.library.unt.edu/ark:/67531/metadc835861/m1/1/: accessed June 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.