Bibcode
Javadi, A.; van Loon, Jacco Th.; Khosroshahi, Habib G.; Tabatabaei, F.; Hamedani Golshan, Roya; Rashidi, Maryam
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 464, Issue 2, p.2103-2119
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1
2017
Citations
41
Refereed citations
18
Description
We have conducted a near-infrared monitoring campaign at the UK Infrared
Telescope of the Local Group spiral galaxy M 33 (Triangulum). On the
basis of their variability, we have identified stars in the very final
stage of their evolution, and for which the luminosity is more directly
related to the birth mass than the more numerous less-evolved giant
stars that continue to increase in luminosity. In this fifth paper of
the series, we construct the birth mass function and hence derive the
star formation history across the galactic disc of M 33. The star
formation rate has varied between ˜0.010 ± 0.001
(˜0.012 ± 0.007) and 0.060±0.005
(0.052±0.009) M⊙ yr-1 kpc-2
statistically (systematically) in the central square kiloparsec of M 33,
comparable with the values derived previously with another camera. The
total star formation rate in M 33 within a galactocentric radius of 14
kpc has varied between ˜0.110 ± 0.005 (˜0.174
± 0.060) and ˜0.560 ± 0.028 (˜0.503 ±
0.100) M⊙ yr-1 statistically (systematically).
We find evidence of two epochs during which the star formation rate was
enhanced by a factor of a few - one that started ˜6 Gyr ago and
lasted ˜3 Gyr and produced ≥71 per cent of the total mass in
stars, and one ˜250 Myr ago that lasted ˜200 Myr and formed
≤13 per cent of the mass in stars. Radial star formation history
profiles suggest that the inner disc of M 33 was formed in an inside-out
formation scenario. The outskirts of the disc are dominated by the old
population, which may be the result of dynamical effects over many Gyr.
We find correspondence to spiral structure for all stars, but enhanced
only for stars younger than ˜100 Myr; this suggests that the
spiral arms are transient features and not a part of a global density
wave potential.
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