We use deep Hubble Space Telescope Advanced Camera for Surveys/High Resolution Channel observations of a field within M32 (F1) and an M31 background field (F2) to determine the star formation history (SFH) of M32 from its resolved stellar population. We find that 2-5 Gyr old stars contribute ~40% ± 17% of M32's mass, while ~55% ± 21% of M32's mass comes from stars older than 5 Gyr. The SFH additionally indicates the presence of young (<2 Gyr old), metal-poor ([M/H] ~ –0.7) stars, suggesting that blue straggler stars contribute ~2% of the mass at F1; the remaining ~3% of the mass is in young metal-rich stars. The inferred SFH of the M31 background field F2 reveals that the majority of its stars are old, with ~95% of its mass already acquired 5-14 Gyr ago. It is composed of two dominant populations; ~30% ± 7.5% of its mass is in a 5-8 Gyr old population, and ~65% ± 9% of the mass is in an 8-14 Gyr old population. Our results suggest that the inner disk and spheroid populations of M31 are indistinguishable from those of the outer disk and spheroid. Assuming the mean age of M31's disk at F2 (~1 disk scale length) to be ~5-9 Gyr, our results agree with an inside-out disk formation scenario for M31's disk.
It may interest you
-
It is well known that fullerenes – big, complex, and highly resistant carbon molecules with potential applications in nanotechnology – are mostly seen in planetary nebulae (PNe); old dying stars with progenitor masses similar to our Sun. Fullerenes, like C60 and C70, have been detected in PNe whose infrared (IR) spectra are dominated by broad unidentified IR (UIR) plateau emissions. The identification of the chemical species (structure and composition) responsible for such UIR emission widely present in the Universe is a mystery in astrochemistry; although they are believed to be carbon-rich
Advertised on -
The standard cosmological model states that massive galaxies contain a large fraction of dark matter. Dark matter is a transparent substance that does not interact through regular baryonic matter and is only detected through its gravitational pull over the stars and the gas. NGC 1277 is known as the prototype of a relic galaxy, that is, a galaxy that has not accreted other galaxies since it formed. Relic galaxies are extremely rare and are the untouched remains of the giant galaxies that populated the early Universe. Since relic galaxies are very important to understand the conditions in the
Advertised on -
The amount and complexity of data delivered by modern galaxy surveys has been steadily increasing over the past years. New facilities will soon provide imaging and spectra of hundreds of millions of galaxies. Extracting coherent scientific information from these large and multi-modal data sets remains an open issue for the community and data-driven approaches such as deep learning have rapidly emerged as a potentially powerful solution to some long lasting challenges. This enthusiasm is reflected in an unprecedented exponential growth of publications using neural networks, which have gone
Advertised on