A5062104894- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Cosmology and Gravitation Theories
- Gamma-ray bursts and supernovae
University of Kansas
2015-2019
Spectroscopy of 333 NGC 6819 stars and Gaia astrometry are used to map Li evolution from the giant branch tip 0.5 mag below dip. Isochrone comparison with [Fe/H] = -0.04, based upon neural network spectroscopic analysis, produces an age 2.25 (2.4) Gyr for E(B-V) 0.16 (0.14) (m-M) 12.40 (12.29). Despite originating outside dip, only 10% single subgiants/giants have measurable Li. Above limiting A(Li) is 3.2 +/- 0.1 but lower range comparable that found within The F-dwarf dip profile agrees...
High-dispersion spectra of 333 stars in the open cluster NGC 6819, obtained using HYDRA spectrograph on WIYN 3.5m telescope, have been analyzed to determine abundances iron and other metals from lines 400 A region surrounding Li 6708 line. Our spectra, with signal-to-noise per pixel (SNR) ranging 60 300, span luminosity range tip red giant branch a point two magnitudes below top turnoff. We derive radial rotational velocities for all stars, as well [Fe/H] based 17 lines, [Ca/H], [Si/H],...
Hydra spectra of 85 G-K dwarfs in the young cluster, M35, near Li 6708 Angstrom line region are analyzed. From velocities and Gaia astrometry, 78 likely single-star members which, combined with previous work, produces 108 T_eff ranging from 6150 to 4000 K as defined by multicolor, broad-band photometry, E(B-V ) = 0.20 [Fe/H] -0.15, though there indications metallicity may be closer solar. A(Li) follows a well-delineated decline 3.15 for hottest stars upper limits <= 1.0 among coolest dwarfs....
We present a study of the relation between galaxy stellar age and mass for 14 members $z=1.62$ protocluster IRC 0218, using multiband imaging HST G102 G141 grism spectroscopy. Using $UVJ$ colors to separate galaxies into star forming quiescent populations, we find that at masses $M_* \geq 10^{10.85} M_{\odot}$, fraction in is $f_Q=1.0^{+0.00}_{-0.37}$, consistent with $\sim 2\times $ enhancement relative field value, $f_Q=0.45^{+0.03}_{-0.03}$. At $10^{10.2} M_{\odot} \leq M_* $f_Q$ cluster...
HYDRA spectra of 287 stars in the field NGC 2506 from turnoff through giant branch are analyzed. With previous data, 22 identified as probable binaries; 90 more classified potential non-members. Spectroscopic analyses ~60 red giants and slowly rotating using line equivalent widths a neural network approach lead to [Fe/H] = -0.27 +/- 0.07 (s.d.) 0.06 (s.d.), respectively. Li abundances derived for 145 single-star members, 44 being upper limits. Among outside Li-dip, A(Li) 3.04 0.16 with no...
IRC 0218 is a protocluster at z = 1.62 with wealth of observations that make it an ideal target for resolving the interplay between galaxy properties and environment high redshift. We have used extremely deep HST spectroscopic data to derive unambiguous membership stellar ages via 4000 angstrom break 14 members masses log(M) > 10.2. find masses, 10.85, fraction quiescent galaxies in cluster 2× higher than field value. At lower consistent fractions. Despite this mass trend, we see no...