TY - JOUR
T1 - Cluster bulleticity
AU - Massey, Richard
AU - Kitching, Thomas
AU - Nagai, Daisuke
PY - 2011/5/1
Y1 - 2011/5/1
N2 - The unique properties of dark matter are revealed during collisions
between clusters of galaxies, such as the bullet cluster (1E 0657-56)
and baby bullet (MACS J0025-12). These systems provide evidence for an
additional, invisible mass in the separation between the distributions
of their total mass, measured via gravitational lensing, and their
ordinary 'baryonic' matter, measured via its X-ray emission.
Unfortunately, the information available from these systems is limited
by their rarity. Constraints on the properties of dark matter, such as
its interaction cross-section, are therefore restricted by uncertainties
in the individual systems' impact velocity, impact parameter and
orientation with respect to the line of sight.
Here we develop a complementary, statistical measurement in which every
piece of substructure falling into every massive cluster is treated as a
bullet. We define 'bulleticity' as the mean separation between dark
matter and ordinary matter, and we measure the signal in hydrodynamical
simulations. The phase space of substructure orbits also exhibits
symmetries that provide an equivalent control test.
Any detection of bulleticity in real data would indicate a difference in
the interaction cross-sections of baryonic and dark matter that may rule
out hypotheses of non-particulate dark matter that are otherwise able to
model individual systems. A subsequent measurement of bulleticity could
constrain the dark matter cross-section. Even with conservative
estimates, the existing Hubble Space Telescope archive should yield an
independent constraint tighter than that from the bullet cluster. This
technique is then trivially extendable to and benefits enormously from
larger, future surveys.
AB - The unique properties of dark matter are revealed during collisions
between clusters of galaxies, such as the bullet cluster (1E 0657-56)
and baby bullet (MACS J0025-12). These systems provide evidence for an
additional, invisible mass in the separation between the distributions
of their total mass, measured via gravitational lensing, and their
ordinary 'baryonic' matter, measured via its X-ray emission.
Unfortunately, the information available from these systems is limited
by their rarity. Constraints on the properties of dark matter, such as
its interaction cross-section, are therefore restricted by uncertainties
in the individual systems' impact velocity, impact parameter and
orientation with respect to the line of sight.
Here we develop a complementary, statistical measurement in which every
piece of substructure falling into every massive cluster is treated as a
bullet. We define 'bulleticity' as the mean separation between dark
matter and ordinary matter, and we measure the signal in hydrodynamical
simulations. The phase space of substructure orbits also exhibits
symmetries that provide an equivalent control test.
Any detection of bulleticity in real data would indicate a difference in
the interaction cross-sections of baryonic and dark matter that may rule
out hypotheses of non-particulate dark matter that are otherwise able to
model individual systems. A subsequent measurement of bulleticity could
constrain the dark matter cross-section. Even with conservative
estimates, the existing Hubble Space Telescope archive should yield an
independent constraint tighter than that from the bullet cluster. This
technique is then trivially extendable to and benefits enormously from
larger, future surveys.
UR - http://www.scopus.com/inward/record.url?scp=79955770670&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2966.2011.18246.x
DO - 10.1111/j.1365-2966.2011.18246.x
M3 - Article
SN - 1365-2966
VL - 413
SP - 1709
EP - 1716
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -