E-S0 Galaxies on the Blue Color-Stellar Mass Sequence at z=0: Fading Mergers or Future Spirals - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




E-S0 Galaxies on the Blue Color-Stellar Mass Sequence at z=0: Fading Mergers or Future Spirals - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We identify a population of morphologically defined E-S0 galaxies lying onthe blue sequence at the present epoch. Using three samples, we analyzeblue-sequence E-S0s with stellar masses >10^8 Msun, arguing that individualobjects may be evolving either up toward the red sequence or down into the bluesequence. Blue-sequence E-S0 galaxies become more common with decreasingstellar mass, comprising <2% of E-S0s near the -shutdown mass- M s ~ 1-2 x10^11 Msun, increasing to >5% near the -bimodality mass- M b ~ 3 x 10^10 Msun,and sharply rising to >20-30% below the -threshold mass- M t ~ 4-6 x 10^9 Msun.The strong emergence of blue-sequence E-S0s below M t coincides with apreviously reported global increase in mean atomic gas fractions below M t forgalaxies of all types on both sequences, suggesting that the availability ofcold gas may be basic to blue-sequence E-S0s- existence. Environmental analysisreveals that many sub-M b blue-sequence E-S0s reside in low to intermediatedensity environments. In mass-radius and mass-sigma scaling relations,blue-sequence E-S0s are more similar to red-sequence E-S0s than to late-typegalaxies, but they represent a transitional class. While some of them,especially in the high-mass range from M b to M s, resemble major-mergerremnants that will likely fade onto the red sequence, most blue-sequence E-S0sbelow M b show signs of disk and-or pseudobulge building, which may be enhancedby companion interactions. We argue that sub-M b blue-sequence E-S0s occupy a-sweet spot- in stellar mass and concentration, with both abundant gas andoptimally efficient star formation, which may enable the formation of largespiral disks. abridged



Author: S. J. Kannappan, J. M. Guie, A. J. Baker

Source: https://arxiv.org/







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