Bibcode
DOI
Jogee, Shardha; Knapen, Johan H.; Laine, Seppo; Shlosman, Isaac; Scoville, Nick Z.; Englmaier, Peter
Bibliographical reference
The Astrophysical Journal, Volume 570, Issue 2, pp. L55-L59.
Advertised on:
5
2002
Journal
Citations
49
Refereed citations
45
Description
For decades, the grand-design SAB spiral galaxy NGC 5248 has been
postulated to host a short bar of semimajor axis 22" (1.6 kpc). From
dynamical and morphological arguments, however, we argue that its spiral
structure is being driven by a large-scale bar whose corotation radius
lies at ~115" (8.6 kpc). Our estimate is based partially on a deep
R-band image, which reveals that the feature previously thought to be an
inclined disk is in fact an extended stellar bar. The bar is embedded
within a fainter outer disk visible out to a radius of 230" (17.2 kpc).
The bar has a deprojected ellipticity of 0.44 and a semimajor axis of
95" (7.1 kpc). The classical grand-design spirals of NGC 5248, prominent
in B, R, and K light, lie on the leading edge of the large-scale stellar
bar and are accompanied by concave dust lanes out to at least 70". The
offset between the dust and young stars is consistent with our
understanding of gas flows in barred galaxies, where shocks along the
leading edges of a moderately strong bar compress the gas to form
massive young stars. While in many strongly barred galaxies, optical
spiral arms are prominent outside the bar but not within it, NGC 5248
illustrates how intense star formation along a moderately strong bar can
lead to conspicuous open spiral arms within the bar itself. NGC 5248
also provides a clear example of how a large-scale stellar bar embedded
within a faint outer optical disk can be misidentified as an inclined
disk when imaging studies lack the sensitivity to detect the actual
outer disk. We discuss the implications for the estimated bar fraction
at higher redshifts.