41 research outputs found
The Impact of Cluster Structure and Dynamical State on Scatter in the Sunyaev-Zel'dovich Flux-Mass Relation
Cosmological constraints from cluster surveys rely on accurate mass estimates
from the mass-observable relations. In order to avoid systematic biases and
reduce uncertainties, we study the form and physical origin of the intrinsic
scatter about the mean Sunyaev-Zel'dovich (SZ) flux-mass relation using a
hydrodynamical simulation of galaxy cluster formation. We examine the
assumption of lognormal scatter and detect non-negligible positive skewness and
kurtosis (> 0.5) for a wide range of limiting masses and redshifts. These
higher-order moments should be included in the parametrization of scatter in
order not to bias cosmological constraints. We investigate the sources of the
scatter by correlating it with measures of cluster morphology, halo
concentration, and dynamical state, and we quantify the individual contribution
from each source. We find that statistically the impact of dynamical state is
weak, so the selection bias due to mergers is negligible. On the other hand,
there is a strong correlation between the scatter and halo concentration, which
can be used to reduce the scatter significantly (from 12.07% to 7.34% or by
~40% for clusters at z = 0). We also show that a cross-calibration by combining
information from X-ray followups can be used to reduce the scatter in the
flux-mass relation and also identify outliers in both X-ray and SZ cluster
surveys.Comment: 14 pages, 12 figures; accepted for publication in Ap
A New Era in Extragalactic Background Light Measurements: The Cosmic History of Accretion, Nucleosynthesis and Reionization
(Brief Summary) What is the total radiative content of the Universe since the
epoch of recombination? The extragalactic background light (EBL) spectrum
captures the redshifted energy released from the first stellar objects,
protogalaxies, and galaxies throughout cosmic history. Yet, we have not
determined the brightness of the extragalactic sky from UV/optical to
far-infrared wavelengths with sufficient accuracy to establish the radiative
content of the Universe to better than an order of magnitude. Among many
science topics, an accurate measurement of the EBL spectrum from optical to
far-IR wavelengths, will address: What is the total energy released by stellar
nucleosynthesis over cosmic history? Was significant energy released by
non-stellar processes? Is there a diffuse component to the EBL anywhere from
optical to sub-millimeter? When did first stars appear and how luminous was the
reionization epoch? Absolute optical to mid-IR EBL spectrum to an
astrophysically interesting accuracy can be established by wide field imagingat
a distance of 5 AU or above the ecliptic plane where the zodiacal foreground is
reduced by more than two orders of magnitude.Comment: 7 pages; Science White Paper for the US Astro 2010-2020 Decadal
Survey. If interested in further community-wide efforts on this topic please
contact the first autho
Giving an Account of Oneâs Pain in the Anthropological Interview
In this paper, I analyze the illness stories narrated by a mother and her 13-year-old son as part of an ethnographic study of child chronic pain sufferers and their families. In examining some of the moral, relational and communicative challenges of giving an account of oneâs pain, I focus on what is left out of some accounts of illness and suffering and explore some possible reasons for these elisions. Drawing on recent work by Judith Butler (Giving an Account of Oneself, 2005), I investigate how the pragmatic context of interviews can introduce a form of symbolic violence to narrative accounts. Specifically, I use the term âgenre of complaintâ to highlight how anthropological research interviews in biomedical settings invoke certain typified forms of suffering that call for the rectification of perceived injustices. Interview narratives articulated in the genre of complaint privilege specific types of pain and suffering and cast others into the background. Giving an account of oneâs pain is thus a strategic and selective process, creating interruptions and silences as much as moments of clarity. Therefore, I argue that medical anthropologists ought to attend more closely to the institutional structures and relations that shape the production of illness narratives in interview encounters
Constraints on the richnessâmass relation and the optical-SZE positional offset distribution for SZE-selected clusters
We cross-match galaxy cluster candidates selected via their
Sunyaev-Zel'dovich effect (SZE) signatures in 129.1 deg of the South Pole
Telescope 2500d SPT-SZ survey with optically identified clusters selected from
the Dark Energy Survey (DES) science verification data. We identify 25 clusters
between in the union of the SPT-SZ and redMaPPer
(RM) samples. RM is an optical cluster finding algorithm that also returns a
richness estimate for each cluster. We model the richness -mass
relation with the following function and use SPT-SZ cluster masses and RM
richnesses to constrain the parameters. We find and . The associated
scatter in mass at fixed richness is at a characteristic richness . We demonstrate
that our model provides an adequate description of the matched sample, showing
that the fraction of SPT-SZ selected clusters with RM counterparts is
consistent with expectations and that the fraction of RM selected clusters with
SPT-SZ counterparts is in mild tension with expectation. We model the
optical-SZE cluster positional offset distribution with the sum of two
Gaussians, showing that it is consistent with a dominant, centrally peaked
population and a sub-dominant population characterized by larger offsets. We
also cross-match the RM catalog with SPT-SZ candidates below the official
catalog threshold significance , using the RM catalog to provide
optical confirmation and redshifts for additional low- SPT-SZ
candidates.In this way, we identify 15 additional clusters with over the redshift regime explored by RM in the overlapping region
between DES science verification data and the SPT-SZ survey.Comment: 15 pages, 8 Figures, submitted to MNRA