相关论文: Horizontal Branch Morphology and the 2nd Parameter…
(abridged) We investigate biases in cluster ages and [Fe/H] estimated from the (V-K)-(V-I) diagram, arising from inconsistent Horizontal Branch morphology, metal mixture, treatment of core convection between observed clusters and the…
Broadband colours are often used as metallicity proxies in the study of extragalactic globular clusters. A common concern is the effect of variations in horizontal branch (HB) morphology--the second-parameter effect--on such colours. We…
We study the correlations between the distribution of stars on the horizontal branch (HB), the HB morphology, with some other properties of globular clusters (GCs) in a large sample of GCs. We strengthen previous results that a general…
The connection between mass loss on the red giant branch (RGB) and horizontal branch (HB) morphology in globular clusters (GCs) has long been acknowledged but the mechanisms governing mass loss remains poorly understood from a theoretical…
The horizontal branch (HB) morphology of globular clusters (GC) is mainly governed by metallicity. The second parameter problem, well known since the 60's, states that metallicity alone is not enough to describe the observed HB morphology…
Ages have been derived for 55 globular clusters (GCs) from overlays of isochrones onto the turnoff photometry, assuming distances based on fits of zero-age horizontal branch (ZAHB) models to the lower bound of the observed distributions of…
The presence of an extended blue horizontal branch (HB) in a stellar population is known to affect the age inferred from spectral fitting to stellar population synthesis models. However, most population synthesis models still rely on…
Isochrone computations and horizontal branch (HB) models for Y(MS)=0.23 and two values of Z (0.0001, 0.0004)are used to derive constraints on the age indicators and HB morphology of metal-poor clusters with age t (in Gyrs) in the range of…
The majority of the inhomogeneities in the chemical composition of Globular Cluster (GC) stars appear due to primordial enrichment by hot-CNO cycled material processed in stars belonging to a first stellar generation. Either massive AGB…
We present homogeneous age determinations for a large sample of 55 Galactic globular clusters, which constitute about 30% of the total Galactic population. A study of their age distribution reveals that all clusters from the most metal poor…
We present a detailed analysis of the "second-parameter pair" of globular clusters M3 (NGC 5272) and Palomar 3. Our main results can be summarized as follows: i) The horizontal-branch (HB) morphology of M3 is significantly bluer in its…
A major source of uncertainty in the age determination of old ($\sim10$ Gyr) integrated stellar populations is the presence of hot horizontal branch (HB) stars. Here, we describe a simple approach to tackle this problem, and show the…
Tidally enhanced stellar wind may affect horizontal branch (HB) morphology in globular clusters (GCs) by enhancing the mass loss of primary star during binary evolution. Lei et al. (2013a, 2013b) studied the effect of this kind of wind on…
Color-magnitude diagrams of globular clusters often exhibit a prominent horizontal branch (HB) and may also show features such as the red giant branch (RGB) bump and the asymptotic giant branch (AGB) bump. Stellar evolution theory predicts…
After taking into account, for the first time, the detailed systematic variation of horizontal-branch (HB) morphology with age and metallicity, our population synthesis models show that the integrated H beta index is significantly affected…
Morphological aspects of the $V, \bv$ diagram of metal-rich globular clusters are analyzed, on the basis of stellar evolution models for horizontal-branch (HB) and red giant branch stars. These have been incorporated into detailed synthetic…
The effects of blue horizontal-branch (HB) stars on the integrated spectrophotometric indices of simple stellar populations (SSPs) are addressed. Synthetic spectra are drawn from a grid of simulated globular clusters, constructed so as to…
It is believed that, except for metallicity, some other parameters are needed to explain the horizontal branch (HB) morphology of globular clusters (GCs). Furthermore, these parameters are considered to be correlated with the mass loss of…
Deep HST photometry has recently been presented for the outer-halo globular clusters Palomar 4 and Eridanus. The new high-precision color-magnitude diagrams obtained for these globulars have allowed a measurement of their ages relative to…
Once fixed the age and metallicity; the colour distribution of horizontal branch stars in a globular cluster depends on few parameters: the helium abundance of the population and the mass lost during the pre-HB stages. These parameters are…