Article

# The relation between surface star formation rate density and spiral arms in NGC 5236 (M83)

11/2011;
Source: arXiv

ABSTRACT For a long time the consensus has been that star formation rates are higher
in the interior of spiral arms in galaxies, compared to inter-arm regions.
However, recent studies have found that the star formation inside the arms is
not more efficient than elsewhere in the galaxy. Previous studies have based
their conclusion mainly on integrated light. We use resolved stellar
populations to investigate the star formation rates throughout the nearby
spiral galaxy NGC 5236. We aim to investigate how the star formation rate
varies in the spiral arms compared to the inter-arm regions, using optical
space-based observations of NGC 5236. Using ground-based H\alpha images we
traced regions of recent star formation, and reconstructed the arms of the
galaxy. Using HST/ACS images we estimate star formation histories by means of
the synthetic CMD method. Arms based on H\alpha images showed to follow the
regions where stellar crowding is higher. Star formation rates for individual
arms over the fields covered were estimated between 10 to 100 Myr, where the
stellar photometry is less affected by incompleteness. Comparison between arms
and inter-arm surface star formation rate densities (\Sigma$_{SFR}$) suggested
higher values in the arms (\sim0.6 dex). Over a small fraction of one arm we
checked how the \Sigma$_{SFR}$ changes for the trailing and leading part. The
leading part of the arm showed to have a higher \Sigma$_{SFR}$ in the age range
10-100 Myr. Predictions from the density wave theory of a rapid increase in the
star formation at the edge where the stars and the gas enter the density wave
are confirmed. The \Sigma$_{SFR}$ presents a steep decrease with distance from
the center of the arms through the inter-arm regions.

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### Keywords

age range

Arms

density wave

density wave theory

ground-based H\alpha images

H\alpha images

higher values

HST/ACS images

inter-arm surface star formation rate densities

Previous studies

recent star formation

recent studies

spiral arms

spiral galaxy NGC 5236

Star formation rates

stars

steep decrease

stellar crowding

stellar photometry

synthetic CMD method