skip to main content

SciTech ConnectSciTech Connect

Title: NO EVIDENCE OF CHEMICAL ANOMALIES IN THE BIMODAL TURNOFF CLUSTER NGC 1806 IN THE LARGE MAGELLANIC CLOUD

We have studied the chemical composition of NGC 1806, a massive, intermediate-age globular cluster that shows a double main sequence turnoff. We analyzed a sample of high-resolution spectra (secured with FLAMES at the Very Large Telescope) for eight giant stars, members of the cluster, finding an average iron content of [Fe/H] = –0.60 ± 0.01 dex and no evidence of intrinsic star-to-star variations in the abundances of light elements (Na, O, Mg, Al). Also, the (m {sub F814W}; m {sub F336W} – m {sub F814W}) color-magnitude diagram obtained by combining optical and near-UV Hubble Space Telescope photometry exhibits a narrow red giant branch, thus ruling out intrinsic variations of C and N abundances in the cluster. These findings demonstrate that NGC 1806 does not harbor chemically distinct sub-populations, at variance with what was found in old globular clusters. In turn, this indicates that the double main sequence turnoff phenomenon cannot be explained in the context of the self-enrichment processes usually invoked to explain the chemical anomalies observed in old globulars. Other solutions (i.e., stellar rotation, merging between clusters, or collisions with giant molecular clouds) should be envisaged to explain this class of globulars.
Authors:
; ; ;  [1] ;  [2]
  1. Dipartimento di Fisica and Astronomia, Università degli Studi di Bologna, Viale Berti Pichat, 6/2, I-40127 Bologna (Italy)
  2. INAF—Osservatorio Astronomico di Bologna, via Ranzani, 1, I-40127 Bologna (Italy)
Publication Date:
OSTI Identifier:
22365037
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 793; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CHEMICAL COMPOSITION; COLOR; DIAGRAMS; EMISSION SPECTRA; GIANT STARS; IRON; MAGELLANIC CLOUDS; MAIN SEQUENCE STARS; PHOTOMETRY; RESOLUTION; ROTATION; SPACE; STAR CLUSTERS; TELESCOPES; VISIBLE RADIATION