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We study the relationship between the iron abundance (IA) in red giant branch (RGB) stars and their radial distribution (RD) in Galactic globular clusters (GCs). We relied on publicly available archival data on IA in red giants (RGs) of GCs. We built a sample of ten target GCs in which the number of these RGs exceeded one hundred stars. In each GC of the sample, we compared the RDs of two sub-samples of stars, more iron-rich (IR) and more iron-poor (IP) than the clusters mean values of [Fe/H]. Their RDs turned out to be different at statistically significant confidence levels in NGC 104 (47 Tuc), NGC 1851, NGC 3201, and NGC 6752 in the sense that the IP RGs were more centrally concentrated than their IR counterparts. In 47 Tuc, the difference is significant at a higher confidence level within the PRAD of R = 8.0, where the IA increases by Delta[Fe/H] ~ 0.03 dex toward the cluster outskirts. In the latter three GCs, Delta[Fe/H] ~ 0.05 dex. Interestingly, the V magnitude of the RGB bump and the horizontal branch was recently shown to fade outward in 47 Tuc and was suggested to originate from a He abundance trend. The fading caused by the IA trend is similar to that observed for the RGB bump. Although the difference between the RDs of IP and IR RGs is statistically insignificant in other GCs, NGC 288 is the only GC of the sample, in which IR RGB stars are formally more centrally concentrated. Interestingly, three of the four GCs are highly concentrated. (Abridged)
The relaxation time at the half-mass radius of Galactic globular clusters (GGCs) is typically within a few Gyr. Hence, the majority of GGCs are expected to be well relaxed systems, given their age is around 12-13 Gyr. So any initial radial segregatio
Well determined radial velocities and abundances are essential for analyzing the properties of the Globular Cluster system of the Milky Way. However more than 50% of these clusters have no spectroscopic measure of their metallicity. In this context,
We further study the unusual trend we found at statistically significant levels in some globular clusters, including NGC 3201: a decreasing iron abundance in red giants towards the cluster centers. We first show that recently published new estimates
We present XMM-Newton/EPIC observations of six merging galaxy clusters and study the distributions of their temperature, iron (Fe) abundance and pseudo-entropy along the merging axis. For the first time, we focus simultaneously, and in a comprehensiv
Many globular clusters (GCs) are known to host multiple populations distinguishable by their light-element content. Less common are GCs displaying iron abundance spreads which are seen as evidence for enrichment through core collapse supernovae (SNe)