407 research outputs found
The Tully-Fisher and mass-size relations from halo abundance matching
The Tully-Fisher relation (TFR) expresses the connection between rotating
galaxies and the dark matter haloes they inhabit, and therefore contains a
wealth of information about galaxy formation. We construct a general framework
to investigate whether models based on halo abundance matching are able to
reproduce the observed stellar mass TFR and mass-size relation (MSR), and use
the data to constrain galaxy formation parameters. Our model tests a range of
plausible scenarios, differing in the response of haloes to disc formation, the
relative angular momentum of baryons and dark matter, the impact of selection
effects, and the abundance matching parameters. We show that agreement with the
observed TFR puts an upper limit on the scatter between galaxy and halo
properties, requires weak or reversed halo contraction, and favours selection
effects that preferentially eliminate fast-rotating galaxies. The MSR
constrains the ratio of the disc to halo specific angular momentum to be
approximately in the range 0.6-1.2. We identify and quantify two problems that
models of this nature face. (1) They predict too large an intrinsic scatter for
the MSR, and (2) they predict too strong an anticorrelation between the TFR and
MSR residuals. We argue that resolving these problems requires introducing a
correlation between stellar surface density and enclosed dark matter mass.
Finally, we explore the expected difference between the TFRs of central and
satellite galaxies, finding that in the favoured models this difference should
be detectable in a sample of ~700 galaxies.Comment: 27 pages, 10 figures; revised to match published MNRAS versio
A Comprehensive Analysis of Uncertainties Affecting the Stellar Mass - Halo Mass Relation for 0<z<4
We conduct a comprehensive analysis of the relationship between central
galaxies and their host dark matter halos, as characterized by the stellar
mass-halo mass (SM-HM) relation, with rigorous consideration of uncertainties.
Our analysis focuses on results from the abundance matching technique, which
assumes that every dark matter halo or subhalo above a specific mass threshold
hosts one galaxy. We discuss the quantitative effects of uncertainties in
observed galaxy stellar mass functions (GSMFs) (including stellar mass
estimates and counting uncertainties), halo mass functions (including cosmology
and uncertainties from substructure), and the abundance matching technique used
to link galaxies to halos (including scatter in this connection). Our analysis
results in a robust estimate of the SM-HM relation and its evolution from z=0
to z=4. The shape and evolution are well constrained for z < 1. The largest
uncertainties at these redshifts are due to stellar mass estimates; however,
failure to account for scatter in stellar masses at fixed halo mass can lead to
errors of similar magnitude in the SM-HM relation for central galaxies in
massive halos. We also investigate the SM-HM relation to z=4, although the
shape of the relation at higher redshifts remains fairly unconstrained when
uncertainties are taken into account. These results will provide a powerful
tool to inform galaxy evolution models. [Abridged]Comment: 27 pages, 12 figures, updated to match ApJ accepted version
The Rockstar Phase-Space Temporal Halo Finder and the Velocity Offsets of Cluster Cores
We present a new algorithm for identifying dark matter halos, substructure,
and tidal features. The approach is based on adaptive hierarchical refinement
of friends-of-friends groups in six phase-space dimensions and one time
dimension, which allows for robust (grid-independent, shape-independent, and
noise-resilient) tracking of substructure; as such, it is named Rockstar
(Robust Overdensity Calculation using K-Space Topologically Adaptive
Refinement). Our method is massively parallel (up to 10^5 CPUs) and runs on the
largest current simulations (>10^10 particles) with high efficiency (10 CPU
hours and 60 gigabytes of memory required per billion particles analyzed). A
previous paper (Knebe et al 2011) has shown Rockstar to have class-leading
recovery of halo properties; we expand on these comparisons with more tests and
higher-resolution simulations. We show a significant improvement in
substructure recovery as compared to several other halo finders and discuss the
theoretical and practical limits of simulations in this regard. Finally, we
present results which demonstrate conclusively that dark matter halo cores are
not at rest relative to the halo bulk or satellite average velocities and have
coherent velocity offsets across a wide range of halo masses and redshifts. For
massive clusters, these offsets can be up to 350 km/s at z=0 and even higher at
high redshifts. Our implementation is publicly available at
http://code.google.com/p/rockstar .Comment: 20 pages, 14 figures. Minor revisions to match accepted versio
Optical Cluster-Finding with An Adaptive Matched-Filter Technique: Algorithm and Comparison with Simulations
We present a modified adaptive matched filter algorithm designed to identify
clusters of galaxies in wide-field imaging surveys such as the Sloan Digital
Sky Survey. The cluster-finding technique is fully adaptive to imaging surveys
with spectroscopic coverage, multicolor photometric redshifts, no redshift
information at all, and any combination of these within one survey. It works
with high efficiency in multi-band imaging surveys where photometric redshifts
can be estimated with well-understood error distributions. Tests of the
algorithm on realistic mock SDSS catalogs suggest that the detected sample is
~85% complete and over 90% pure for clusters with masses above 1.0*10^{14}
h^{-1} M_solar and redshifts up to z=0.45. The errors of estimated cluster
redshifts from maximum likelihood method are shown to be small (typically less
that 0.01) over the whole redshift range with photometric redshift errors
typical of those found in the Sloan survey. Inside the spherical radius
corresponding to a galaxy overdensity of Delta=200, we find the derived cluster
richness Lambda_{200} a roughly linear indicator of its virial mass M_{200},
which well recovers the relation between total luminosity and cluster mass of
the input simulation.Comment: Accepted to ApJ. 13 pages, 9 figure
- …