Efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by ruthenium(III) complex of chloromethylated Salophen supported on nanomagnetic materials is reported. First, the iron nanomagnets were silica coated, functionalized with amine and then ruthenium CM-Salophen was successfully bonded to their surface. The catalyst, Ru III (OTf) SalophenCH 2 -NHSiO 2 -Fe, was characterized by elemental analysis, FT-IR and UV-visible spectroscopic techniques, transmission electron microscopy and inductively coupled plasma (ICP). The Ru III (OTf)SalophenCH 2 -NHSiO 2 -Fe catalyzed trimethylsilylation of primary and secondary alcohols as well as phenols, and the corresponding TMS ethers were obtained in high yields and short reaction times at room temperature. This new heterogenized trimethylsilylation catalyst is easily recovered with a magnet and showed no appreciable loss of activity even after five consecutive runs.
The Local Group (LG) hosts many dwarf galaxies with diverse physical characteristics in terms of morphology, mass, star formation, and metallicity. To this end, LG can offer a unique site to tackle questions about the formation and evolution of galaxies by providing detailed information. While large telescopes are often the first choices for such studies, small telescope surveys that perform dedicated observations are still important, particularly in studying bright objects in the nearby universe. In this regard, we conducted a nine epoch survey of 55 dwarf galaxies called the "Local Group dwarf galaxies survey" using the 2.5m Isaac Newton Telescope (INT) in the La Palma to identify Long-Period Variable (LPV) stars, namely Asymptotic Giant Branch (AGB) and Red Super Giant (RSG) stars. AGB stars formed at different times and studying their radial distribution and mass-loss rate can shed light on the structure formation in galaxies. To further investigate the evolutionary path of these galaxies, we construct their star formation history (SFH) using the LPV stars, which are at the final stages of their evolution and therefore experience brightness fluctuations on the timescales between hundred to thousand days. In this paper, we present some of the results of the Local Group dwarf galaxies survey.
We present a photometric study of the resolved stellar populations in Andromeda IX (And IX), the closest satellite to M31, a metal-poor and low-mass dwarf spheroidal galaxy. We estimate a distance modulus of
24.56
−
0.15
+
0.05
mag based on the tip of the red giant branch. By probing the variability of asymptotic giant branch stars, we study the star formation history of And IX. We identified 50 long-period variables (LPVs) in And IX using the Isaac Newton Telescope in two filters, the Sloan
i
′
and Harris V. In this study, we selected LPVs within two half-light radii with amplitudes in the range of 0.2–2.20 mag. It is found that the peak of star formation reaches ∼8.2 ± 3.1 × 10−4
M
⊙ yr−1 at ≈6 Gyr ago. Our findings suggest an outside-in galaxy formation scenario for And IX with a quenching occurring
3.65
−
0.13
+
1.52
Gyr ago with a star formation rate (SFR) in the order of 2.0 × 10−4
M
⊙ yr−1 at redshift <0.5. We calculate the total stellar mass by integrating the SFR within two half-light radii ∼3.0 × 105
M
⊙. By employing spectral energy distribution fitting for the observed LPVs in And IX, we evaluate a mass-loss rate in the range of 10−7 ≤
M
̇
≤ 10−5
M
⊙ yr−1. Finally, we show that the total mass deposition to the interstellar medium (ISM) is ∼2.4 × 10−4
M
⊙ yr−1 from the C- and O-rich types of dust-enshrouded LPVs. The ratio of the total mass returned to the ISM by LPVs to the total stellar mass is ∼8.0 × 10−10 yr−1, and so at this rate it would take ∼1 Gyr to reproduce this galaxy.
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