Astronomy and Astrophysics, volume 313, 13-24 (1996/9-1)
The bar-enhanced star-formation activities in spiral galaxies.
HUANG J.H., GU Q.S., SU H.J., HAWARDEN T.G., LIAO X.H. and WU G.X.
Abstract (from CDS):
We use the ratio LFIR/LB and the IRAS color index S25/S12 (both widely used as indices of relative star formation rates in galaxies) to analyse subsets (containing no known AGNs or merging/interacting galaxies) of: (a) the IRAS Bright Galaxy Sample, (b) galaxies from the optically complete RSA sample which have IRAS detections in all four bands, and (c) a volume-limited IR-unselected sample. We confirm that IR-bright barred (SB) galaxies do, on average, have very significantly higher values of the FIR-optical and S25/S12 ratios (and presumably, higher relative star formation rates, SFR) than that do unbarred ones; the effect is most obvious in the IR colors. We also confirm that these differences are confined to early-type (S0/a-Sbc) spirals and are not evident among late-type systems (Sc-Sdm). Unlike others, we see no enhancement of the SFR in weakly-barred (SAB) galaxies. We further confirm that the effect of bars on the SFR is associated with the relative IR luminosity and show that it is detectable only in galaxies with LFIR/LB>1/3, suggesting that as soon as they have any effect, bars translate their host galaxies into this relatively IR-luminous group. Conversely, for galaxies with LFIR/LB below ∼0.1 this luminosity ratio is lower among barred than unbarred systems, again confirming and quantifying an earlier result. Although there is no simple physical relation between H I content and star formation, a strong correlation of H I content with the presence of bars has been found for early-type spirals with LFIR/LB>1/3. This suggests that the availability of fuel is the factor determining just which galaxies undergo bar-induced starbursts.
galaxies: starburst - galaxies: spiral - infrared: galaxies
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