5,733 research outputs found
Cosmology with Clusters of Galaxies
I show that three independent methods utilizing clusters of galaxies -
cluster dynamics and mass-to-light ratio, baryon fraction in clusters, and
cluster evolution - all indicate the same robust result: the mass-density of
the universe is low, Omega ~ 0.2, and the mass approximately traces light on
large scales.Comment: Invited talk at Nobel98, ``Particle Physics and the
Universe,''8/1998, 15 pages, 4 figure
United States budgetary costs of Post-9/11 wars through FY2018
Originally published on the Watson Institute's Costs of War Project website: http://watson.brown.edu/costsofwar/papers/2017/USBudgetaryCostsFY2018The costs to the United States of post-9/11 wars will total more than 23,386 on these wars since 2001. “The U.S. wars in Iraq, Syria, Afghanistan and Pakistan, and the increased spending on homeland security and the departments of defense, state and veterans affairs since the 9/11 attacks have cost more than 5.6 trillion.
CLUSTERING AND LARGE SCALE STRUCTURE WITH THE SDSS
The Sloan Digital Sky Survey (SDSS) will provide a complete imaging and
spectroscopic survey of the high-latitude northern sky. The 2D survey will
image the sky in five colors and will contain nearly 5 x 107 galaxies to g ~
23m. The spectroscopic survey will obtain spectra of the brightest 106
galaxies, 105 quasars, and 103.5 rich clusters of galaxies (to g~18.3-19.3m,
respectively). I summarize some of the science opportunities that will be made
possible by this survey for studying the clustering and large-scale structure
of the universe.
The survey will identify a complete sample of several thousand rich clusters
of galaxies, both in 2D and 3D - the largest automated sample yet available.
The extensive cluster sample can be used to determine critical clustering
properties such as the luminosity-function, velocity-function, and
mass-function of clusters of galaxies (a critical test for cosmological
models), detailed cluster dynamics and W(dyn), the cluster correlation function
and its dependence on richness, cluster evolution, superclustering and voids to
the largest scales yet observed, the motions of clusters and their large-scale
peculiar velocity field, as well as detailed correlations between x-ray and
optical properties of clusters, the density-morphology relation, and
cluster-quasar associations. The large redshift survey, reaching to a depth of
600h-1 Mpc, will accurately map the largest scales yet observed, determine the
power-spectrum and correlation function on these large scales for different
type galaxies, and study the clustering of quasars to high redshifts (z 4). The
implications of the survey for cosmological models, the dark matter, and W are
also discussed.Comment: compressed PostScript, invited talk presented at the AAS meeting,
Minneapolis, June 1994, to appear in PASP 1995; for the figures contact
[email protected]
Tracing mass and light in the Universe: where is the dark matter?
How is mass distributed in the Universe? How does it compare with the
distribution of light and stars? We address these questions by examining the
distribution of mass, determined from weak lensing observations, and starlight,
around SDSS MaxBCG groups and clusters as a function of environment and
scale, from deep inside clusters to large cosmic scales of Mpc. The
observed cumulative mass-to-light profile, , rises on small scales,
reflecting the increasing of the central bright galaxy of the cluster,
then flattens to a nearly constant ratio on scales above kpc,
where light follows mass on all scales and in all environments. A trend of
slightly decreasing with scale is shown to be consistent with the
varying stellar population following the morphology-density relation. This
suggests that stars trace mass remarkably well even though they represent only
a few percent of the total mass. We determine the stellar mass fraction and
find it to be nearly constant on all scales above kpc, with
. We further suggest that most of the dark
matter in the Universe is located in the large halos of individual galaxies
( kpc for galaxies); we show that the entire
profile -- from groups and clusters to large-scale structure -- can be
accounted for by the aggregate masses of the individual galaxies (whose halos
may be stripped off but still remain in the clusters), plus gas. We use the
observed mass-to-light ratio on large scales to determine the mass density of
the Universe: Comment: 12 pages, 9 figures; version accepted to MNRA
An HSC view of the CMASS galaxy sample. Halo mass as a function of stellar mass, size and S\'ersic index
Aims. We wish to determine the distribution of dark matter halo masses as a
function of the stellar mass and the stellar mass profile, for massive galaxies
in the BOSS CMASS sample. Methods. We use grizy photometry from HSC to obtain
S\'ersic fits and stellar masses of CMASS galaxies for which HSC weak lensing
data is available, visually selected to have spheroidal morphology. We apply a
cut in stellar mass, ,selecting 10, 000
objects. Using a Bayesian hierarchical inference method, we first investigate
the distribution of S\'ersic index and size as a function of stellar mass.
Then, making use of shear measurements from HSC, we measure the distribution of
halo mass as a function of stellar mass, size and S\'ersic index. Results. Our
data reveals a steep stellar mass-size relation ,
with larger than unity, and a positive correlation between S\'ersic
index and stellar mass: . Halo mass scales approximately
with the 1.7 power of the stellar mass. We do not find evidence for an
additional dependence of halo mass on size or S\'ersic index at fixed stellar
mass. Conclusions. Our results disfavour galaxy evolution models that predict
significant differences in the size growth efficiency of galaxies living in low
and high mass halos.Comment: Accepted for publication on Astronomy & Astrophysics. 18 pages, 15
figure
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