%0 Generic %1 abramson2014massindependence %A Abramson, Louis E. %A Kelson, Daniel D. %A Dressler, Alan %A Poggianti, Bianca M. %A Gladders, Michael D. %A Oemler, Augustus %A Vulcani, Benedetta %D 2014 %K bulge disk galaxy sfr %T The Mass-Independence of Specific Star Formation Rates in Galactic Disks %U http://arxiv.org/abs/1402.7076 %X The slope of the star formation rate/stellar mass relation (the SFR ``Main Sequence"; SFR--Mstel) is not quite unity: specific star formation rates (SFR/Mstel) are weakly-but-significantly anti-correlated with Mstel. Here we demonstrate that this trend may simply reflect the well-known increase in bulge mass-fractions -- portions of a galaxy not forming stars -- with Mstel. Using a large set of bulge/disk decompositions and SFR estimates derived from the Sloan Digital Sky Survey, we show that re-normalizing SFR by disk stellar mass (sSFRd = SFR/Mdisk) reduces the Mstel-dependence of SF efficiency by ~0.25 dex per dex, erasing it entirely in some subsamples. Quantitatively, we find log(sSFRd)--log(Mstel) to have a slope -0.20 < beta_disk < 0.00 +/- 0.02 (depending on SFR estimator and Main Sequence definition) for star-forming galaxies with Mstel > 10^10 Msun and bulge mass-fractions B/T < 0.7, generally consistent with a pure-disk control sample (beta_control = -0.05 +/- 0.04). That <SFR/Mdisk> is (largely) independent of host mass for star-forming disks bears strongly on scenarios of galaxy evolution derived from any SFR--Mstel relation, including: the principal manifestation of ``mass quenching" (bulge growth); the constancy of the shape of the star-forming stellar mass function (uniform dlog(Mstel)/dt, assuming disk-driven growth); and the degree to which dispersion in SFR(Mstel,t) encodes diversity in star formation histories. Our results emphasize the need to treat galaxies as composite systems -- not integrated masses -- in observational and theoretical work.

@misc{abramson2014massindependence, abstract = {The slope of the star formation rate/stellar mass relation (the SFR ``Main Sequence"; SFR--Mstel) is not quite unity: specific star formation rates (SFR/Mstel) are weakly-but-significantly anti-correlated with Mstel. Here we demonstrate that this trend may simply reflect the well-known increase in bulge mass-fractions -- portions of a galaxy not forming stars -- with Mstel. Using a large set of bulge/disk decompositions and SFR estimates derived from the Sloan Digital Sky Survey, we show that re-normalizing SFR by disk stellar mass (sSFRd = SFR/Mdisk) reduces the Mstel-dependence of SF efficiency by ~0.25 dex per dex, erasing it entirely in some subsamples. Quantitatively, we find log(sSFRd)--log(Mstel) to have a slope -0.20 < beta_disk < 0.00 +/- 0.02 (depending on SFR estimator and Main Sequence definition) for star-forming galaxies with Mstel > 10^10 Msun and bulge mass-fractions B/T < 0.7, generally consistent with a pure-disk control sample (beta_control = -0.05 +/- 0.04). That <SFR/Mdisk> is (largely) independent of host mass for star-forming disks bears strongly on scenarios of galaxy evolution derived from any SFR--Mstel relation, including: the principal manifestation of ``mass quenching" (bulge growth); the constancy of the shape of the star-forming stellar mass function (uniform dlog(Mstel)/dt, assuming disk-driven growth); and the degree to which dispersion in SFR(Mstel,t) encodes diversity in star formation histories. Our results emphasize the need to treat galaxies as composite systems -- not integrated masses -- in observational and theoretical work.}, added-at = {2014-03-03T09:33:54.000+0100}, author = {Abramson, Louis E. and Kelson, Daniel D. and Dressler, Alan and Poggianti, Bianca M. and Gladders, Michael D. and Oemler, Augustus and Vulcani, Benedetta}, biburl = {https://www.bibsonomy.org/bibtex/232e142780899d63a191429f68dd56fea/miki}, description = {[1402.7076] The Mass-Independence of Specific Star Formation Rates in Galactic Disks}, interhash = {7ae4366789a65a2021fea4e4aa183769}, intrahash = {32e142780899d63a191429f68dd56fea}, keywords = {bulge disk galaxy sfr}, note = {cite arxiv:1402.7076Comment: 6 pages, 2 figures; submitted to ApJ Letters}, timestamp = {2014-03-03T09:33:54.000+0100}, title = {The Mass-Independence of Specific Star Formation Rates in Galactic Disks}, url = {http://arxiv.org/abs/1402.7076}, year = 2014 }