Searching for the 3.5 keV Line in the Stacked Suzaku Observations of Galaxy Clusters

We perform a detailed study of the stacked Suzaku observations of 47 galaxy clusters, spanning a redshift range of 0.01-0.45, to search for the unidentified 3.5 keV line. This sample provides an independent test for the previously detected line. We detect only a 2sigma-significant spectral feature at 3.5 keV in the spectrum of the full sample. When the sample is divided into two subsamples (cool-core and non-cool core clusters), cool-core subsample shows no statistically significant positive residuals at the line energy. A very weak (2sigma-confidence) spectral feature at 3.5 keV is permitted by the data from the non-cool core clusters sample. The upper limit on a neutrino decay mixing angle from the full Suzaku sample is consistent with the previous detections in the stacked XMM-Newton sample of galaxy clusters (which had a higher statistical sensitivity to faint lines), M31, and Galactic Center at a 90% confidence level. However, the constraint from the present sample, which does not include the Perseus cluster, is in tension with previously reported line flux observed in the core of the Perseus cluster with XMM-Newton and Suzaku.Comment: ApJ in press, 9 pages, 3 figure

Uniform Contribution of Supernova Explosions to the Chemical Enrichment of Abell 3112 out to R 200

The spatial distribution of the metals residing in the intra-cluster medium (ICM) of galaxy clusters records all the information on a cluster's nucleosynthesis and chemical enrichment history. We present measurements from a total of 1.2 Ms Suzaku XIS and 72 ks Chandra observations of the cool-core galaxy cluster Abell 3112 out to its virial radius (~1470 kpc). We find that the ratio of the observed supernova type Ia explosions to the total supernova explosions has a uniform distribution at a level of 12%–16% out to the cluster's virial radius. The observed fraction of type Ia supernova explosions is in agreement with the corresponding fraction found in our Galaxy and the chemical enrichment of our Galaxy. The non-varying supernova enrichment suggests that the ICM in cluster outskirts was enriched by metals at an early stage before the cluster itself was formed during a period of intense star formation activity. Additionally, we find that the 2D delayed detonation model CDDT produce significantly worse fits to the X-ray spectra compared to simple 1D W7 models. This is due to the relative overestimate of Si, and the underestimate of Mg in these models with respect to the measured abundances.United States. National Aeronautics and Space Administration (NNX09AV65G)United States. National Aeronautics and Space Administration (NNX10AV02G

RADIAL PROFILE OF THE 3.5 keV LINE OUT TO R 200 IN THE PERSEUS CLUSTER

The recent discovery of the unidentified emission line at 3.5 keV in galaxies and clusters has attracted great interest from the community. As the origin of the line remains uncertain, we study the surface brightness distribution of the line in the Perseus cluster since that information can be used to identify its origin. We examine the flux distribution of the 3.5 keV line in the deep Suzaku observations of the Perseus cluster in detail. The 3.5 keV line is observed in three concentric annuli in the central observations, although the observations of the outskirts of the cluster did not reveal such a signal. We establish that these detections and the upper limits from the non-detections are consistent with a dark matter decay origin. However, absence of positive detection in the outskirts is also consistent with some unknown astrophysical origin of the line in the dense gas of the Perseus core, as well as with a dark matter origin with a steeper dependence on mass than the dark matter decay. We also comment on several recently published analyses of the 3.5 keV line.United States. National Aeronautics and Space Administration (Contracts NNX14AF78G and NNX123AE77G

Empirical Evidence of Anchoring and Loss Aversion from Art Auctions Empirical Evidence of Anchoring and Loss Aversion from Art Auctions

Abstract We find evidence for the behavioral biases of anchoring and loss aversion. We find that anchoring is more important for items that are resold quickly, and we find that the effect of loss aversion increases with the time that a painting is held. The evidence in favor of anchoring and loss aversion with a large new dataset validates previous results and adds to the empirical evidence a finding of increasing loss aversion with the length of holding. However, we do not find evidence that investors can take advantage of these behavioral biases.

Verbal Fluency Patterns in Mild Cognitive Impairment and Alzheimer's Disease

&lt;b&gt;&lt;i&gt;Background/Aims:&lt;/i&gt;&lt;/b&gt; Verbal fluency patterns can assist in differential diagnosis during neuropsychological assessment and identify individuals at risk for developing Alzheimer's disease (AD). While evidence suggests that subjects with AD perform worse on category fluency than letter fluency tasks, the pattern in mild cognitive impairment (MCI) is less well known. &lt;b&gt;&lt;i&gt;Methods:&lt;/i&gt;&lt;/b&gt; Performance on the Controlled Oral Word Association Test (COWAT) and Animal fluency was compared in control, amnestic MCI, non-amnestic MCI, and AD groups. The sample included 136 participants matched for age, education, and gender. &lt;b&gt;&lt;i&gt;Results:&lt;/i&gt;&lt;/b&gt; Both MCI groups performed similarly with a category &gt; letter fluency pattern rather than a category &lt; letter fluency pattern typically observed in AD. The pattern in MCI, albeit relatively more impaired than in controls, was more similar to healthy controls who exhibited a category &gt; letter fluency pattern. &lt;b&gt;&lt;i&gt;Conclusion:&lt;/i&gt;&lt;/b&gt; MCI using a category &lt; letter fluency pattern may not represent AD; however, future research requires longitudinal studies of pattern analysis.</jats:p

Longitudinal Assessment of Cognitive Decline: Distinguishing Features and Trends in Cognitive Challenge Test among Older Adults with Mild Cognitive Impairment and Amyloid PET Status

The Loewenstein-Acevedo Scales of Semantic Interference and Learning (LASSI-L) is a sensitive measure of early cognitive impairment. It is unclear how performance over time on this cognitive challenge test (CCT) differentiates older adults who are cognitively unimpaired (CU) and amyloid PET negative (A-), from those with amnestic Mild Cognitive Impairment (aMCI) who are either A- or amyloid PET positive (A+) over long periods of time. 94 participants with a minimum of three LASSI-L assessments administered annually (baseline visit, and 2 annual follow-ups) were evaluated. 63 participants were diagnosed with aMCI (27 A+ and 36 A-) at baseline. All 31 CU participants were PET A- during the initial evaluation. The average length of the last follow-up period was 39.05 (SD=12.1) months with a maximum span of 71.4 months after the initial visit. Results showed a main group effect, but a lack of a time effect. Cued B1 and Cued B2 semantic intrusions (related to difficulties with self-monitoring and inhibitory control) and failure to recover from proactive semantic interference (frPSI; Cued B2 recall), were significantly impaired in aMCI A+ when compared to both aMCI A- counterparts and CU A- controls. In addition, a significant Group X Time Interaction for Cued A2 recall (maximum learning) showed higher scores for CU participants while the aMCI A+ evidenced decreased scores across subsequent follow-up visits. Semantic intrusion errors appear to be a distinguishing feature of aMCI A+ participants after adjustment for global mental status and demographic factors up to an average of 39 months after initial evaluation. Moreover, initial learning showed a modest and inconsistent increase among cognitively unimpaired participants but a decrease in aMCI A+ scores over time