The Star Formation History of M32.

Fields observed with HST for M32 (F1) and M31 (F2) overplotted on a M32 image from ground.
Fields observed with HST for M32 (F1) and M31 (F2) overplotted on a M32 image from ground.
Advertised on
References
2012, ApJ, 745, 97

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.

News type
Research news

It may interest you

  • nanojet
    Research news
    A New Modeling Insight to Explain Tiny Energetic Bursts in the Sun
    An international team of researchers led by the Instituto de Astrofísica de Canarias (IAC) and the Universidad de La Laguna (ULL), has unveiled a breakthrough explanation for the origin of tiny, jet-like plasma ejections in the solar atmosphere, known as “nanojets.” These elusive events which are recently discovered by the NASA’s solar telescopes are thought to play an important role in heating and sustaining the solar corona at temperatures above one million Kelvin. Why Study Nanojets? For decades, solar physicists have been puzzled by the so-called “coronal heating problem.” While the Sun
    Advertised on
  • desired
    Research news
    The DESIRED electron temperature relations in star-forming regions of the local Universe
    H II regions are clouds of glowing, ionised gas associated with regions of recent star formation. By studying the light emitted by these regions, we can learn about their physical conditions and chemical composition, providing important clues about how stars and galaxies form and evolve. One of the key properties we need to know is the temperature of the gas. We can measure it from the emission lines of different chemical elements, which probe different parts of an H II region. However, it is not always possible to measure all these temperatures directly. In these cases, we need to estimate
    Advertised on
  • dm_fig1
    Research news
    The slow expansion of dark matter halos from cusp to core naturally produces extended stellar core-like distributions
    Only a handful of observations truly constrain the nature of dark matter, which is why dozens of different physical models are still viable. Several of the most popular alternatives predict that dark matter halos slowly “thermalize” over time, gradually changing shape and expanding until they form a central region of nearly constant density -- a core. This transformation would not occur if the dark matter particles were completely collision-less, as assumed in the standard model. Therefore, the presence or absence of such a core provides a powerful way to distinguish between the standard
    Advertised on