相关论文: Ages and Metallicities of Cluster Galaxies in A779…
JWST's Early Release Observations of the lensing cluster SMACS J0723.3-7327 have given an unprecedented spectroscopic look into the high-redshift universe. These observations reveal five galaxies at z > 5. All five have detectable…
We determine the age of 1,104 early-type galaxies in eight rich clusters ($z = 0.0046$ to $0.175$) using a new continuum color technique. We find that galaxies in clusters divide into two populations, an old population with a mean age…
One of the conundrums in extragalactic astronomy is the discrepancy in observed metallicity distribution functions (MDFs) between the two prime stellar components of early-type galaxies-globular clusters (GCs) and halo field stars. This is…
The color-magnitude diagrams (CMDs) of three intermediate-age LMC clusters, NGC 2173, SL556 and NGC2155 are analyzed to determine their age and metallicity basing on Padova stellar models. Synthetic CMDs are compared with cluster data. The…
A comparison is made between the age-metallicity relation obtained from four different types of studies: F and G stars in the Solar Neighbourhood, analysis of open clusters, galactic structure studies with the stellar population synthesis…
We present a rest-frame UV-optical stacked spectrum representative of massive quiescent galaxies at $1.0<z<1.3$ with log$(M_*/\rm{M_\odot})>10.8$. The stack is constructed using VANDELS survey data, combined with new KMOS observations. We…
We present a novel, observationally-based framework for the formation epochs and sites of globular clusters (GCs) in a cosmological context. Measuring directly the mean ages of the metal-poor and metal-rich GC subpopulations in our own…
We have extended our evolutionary synthesis code, GALEV, to include Lick/IDS absorption-line indices for both simple and composite stellar population models (star clusters and galaxies), using the polynomial fitting functions of Worthey et…
We demonstrate how the metallicities of young super star clusters can be measured using novel spectroscopic techniques in the J-band. The near-infrared flux of super star clusters older than ~6 Myr is dominated by tens to hundreds of red…
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…
We present a theoretical calibration of a new metallicity diagnostic based on the Stroemgren index m1 and on visual -- near-infrared (NIR) colors to estimate the global metal abundance of cluster and field dwarf stars. To perform the…
The outer halo regions of early-type galaxies carry key information about their past accretion history. However, spectroscopically probing the stellar component at such galactocentric radii is still challenging. Using Keck/DEIMOS, we have…
Stellar evolutionary tracks for $0.12 \le M/M_\odot \le 1.0$ have been computed for each of several variations in the abundances of C, N, and O, assuming mass-fraction helium abundances $Y = 0.25$ and $0.29$, and 11 metallicities in the…
It is well-known that fitting the Color Magnitude Diagrams (CMDs) to the theoretical isochrones is the main method to determine star cluster ages. However, when the CMDs are not available, the Spectral Energy Distribution (SED)-fitting…
Hubble Space Telescope (HST) fine guidance sensor observations were used to obtain parallaxes of eight metal-poor ([Fe/H] < -1.4) stars. The parallaxes of these stars determined by the revised Hipparcos reduction average 17% accuracy, in…
We explore whether the rest-frame near-UV spectral region, observable in high-redshift galaxies via optical spectroscopy, contains sufficient information to allow the degeneracy between age and metallicity to be lifted. We do this by…
The ages and metallicities of globular clusters play an important role not just in testing models for their formation and evolution but in understanding the assembly history for their host galaxies. Here we use a combination of imaging and…
Context: Analysis of ages and metallicities of star clusters in the Magellanic Clouds provide information for studies on the chemical evolution of the Clouds and other dwarf irregular galaxies. Aims: The aim is to derive ages and…
In clusters of galaxies, the red sequence is believed to be a consequence of a correlation between stellar mass and chemical abundances, with more massive galaxies being more metal-rich and, as a consequence, redder. However, there is a…
Integrated spectra have been obtained of 31 star clusters in the Magellanic Clouds (MC) and of 4 Galactic globular clusters. The spectra cover the wavelength range 3500 -- 4700 Angstroms at a resolution of 3.2 Angstroms FWHM. The MC…