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Date and Time of the Query: 2019-04-24 T02:58:00 PDT
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For refcode 2000ApJ...538..569R:
Retrieve 40 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
2000ApJ...538..569R Lopsided Galaxies, Weak Interactions, and Boosting the Star Formation Rate Gregory Rudnick, Hans-Walter Rix, and Robert C. Kennicutt, Jr. Steward Observatory, University of Arizona, Tucson, AZ 85721 Received 1999 November 29; accepted 2000 March 13 ABSTRACT To investigate the link between weak tidal interactions in disk galaxies and the boosting of their recent star formation, we obtain images and spatially integrated spectra (3615 A <= {lambda} <= 5315 A) for 40 late- type spiral galaxies (Sab-Sbc) with varying degrees of lopsidedness (a dynamical indicator of weak interactions). We quantify lopsidedness as the amplitude <A^~^_1_> of the m = 1 Fourier component of the azimuthal surface brightness distribution averaged over a range of radii. The median spectrum of the most lopsided galaxies shows strong evidence for a more prominent young stellar population (i.e., strong Balmer absorption, strong nebular emission, a weak 4000 A break, and a blue continuum) when compared to the median spectrum of the most symmetric galaxies. We compare the young stellar content, quantified by EW(H{delta}_abs_) and the strength of the 4000 A break (D_4000_), with lopsidedness and find a 3-4 {sigma} correlation between the two. We also find a 3.2 {sigma} correlation between EW(H{beta}_emission_) and lopsidedness. Using the evolutionary population synthesis code of Bruzual & Charlot we model the spectra as an "underlying population" and a superimposed "boost population" with the aim of constraining the fractional boost in the SFR averaged over the past 0.5 Gyr (the characteristic lifetime of lopsidedness). From the difference in both EW(H{delta}_abs_) and the strength of the 4000 A break (D_4000_) between the most and least symmetric thirds of our sample, we infer that ~1 x 10^9^ M_sun_ of stars are formed over the duration of a lopsided event in addition to the "underlying" star formation history (assuming a final galactic stellar mass of 10^10^ M_sun_). This corresponds to a factor of 8 increase in the star formation rate over the past x 10^8^ years. For the nuclear spectra, all of the above correlations except D_4000_ versus <A^~^_1_> are weaker than for the disk, indicating that in lopsided galaxies, the star formation boost is not dominated by the nucleus. Subject headings: galaxies: evolution-galaxies: interactions -galaxies: kinematics and dynamics-galaxies: spiral -galaxies: structure-stars: formation
Retrieve 40 NED objects in this reference.
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