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Recent observations have reported that the Galactic globular clusters (GCs) with unusually extended horizontal-branch (EHB) morphologies show a significantly lower velocity dispersion compared with that of the entire Galactic GC system. We consider that the observed distinctive kinematics of GCs with EHB has valuable information on the formation epochs of GCs and accordingly discuss this observational result based on cosmological N-body simulations with a model of GC formation. We assume that GCs in galaxies were initially formed in low-mass halos at high redshifts and we investigate final kinematics of GCs in their host halos at $z=0$. We find that GCs formed in halos virialized at z>10 show lower velocity dispersions on average than those formed at z>6 for halos with GCs at z=0. We thus suggest that the origin of the observed lower velocity dispersion for the Galactic GCs with EHBs is closely associated with earlier formation epochs (z>10) of halos initially hosting the GCs in the course of the Galaxy formation. Considering that the origin of EHBs can be due to the presence of helium-enhanced second-generation stars in GCs, we discuss the longstanding second parameter problem of GCs in the context of different degrees of chemical pollution in GC-forming gas clouds within low-mass halos virialized at different redshifts.
This paper presents the measurement of the neutron star (NS) radius using the thermal spectra from quiescent low-mass X-ray binaries (qLMXBs) inside globular clusters (GCs). Recent observations of NSs have presented evidence that cold ultra dense mat
We present an end-to-end, two-phase model for the origin of globular clusters (GCs). In the model, populations of stellar clusters form in the high-pressure discs of high-redshift ($z>2$) galaxies (a rapid-disruption phase due to tidal perturbations
We investigate the integrated far-ultraviolet (FUV) emission from globular clusters. We present new FUV photometry of M~87s clusters based on archival HST WFPC2 F170W observations. We use these data to test the reliability of published photometry bas
By means of grid-based, 3D hydrodynamical simulations we study the formation of second generation (SG) stars in a young globular cluster (GC) of mass 10^7 Msun, the possible progenitor of an old GC with a present mass ~(1-5) * 10^6 Msun. The cluster
Observed mass-to-light ratios (M/L) of metal-rich globular clusters (GCs) disagree with theoretical predictions. This discrepancy is of fundamental importance since stellar population models provide the stellar masses that underpin most of extragalac