History of Galaxy Interactions and their Impact on Star Formation over the Last 7 Gyr from GEMS - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




History of Galaxy Interactions and their Impact on Star Formation over the Last 7 Gyr from GEMS - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We perform a comprehensive estimate of the frequency of galaxy mergers andtheir impact on star formation over z~0.24-0.80 lookback time T b~3-7 Gyrusing 3698 M*>=1e9 Msun galaxies with GEMS HST, COMBO-17, and Spitzer data.Our results are: 1 Among 790 high mass M*>=2.5e10 Msun galaxies, thevisually-based merger fraction over z~0.24-0.80, ranges from 9%+-5% to 8%+-2%.Lower limits on the major and minor merger fractions over this interval rangefrom 1.1% to 3.5%, and 3.6% to 7.5%, respectively. This is the firstapproximate empirical estimate of the frequency of minor mergers at z<1. For avisibility timescale of ~0.5 Gyr, it follows that over T b~3-7 Gyr, ~68% ofhigh mass systems have undergone a merger of mass ratio >1-10, with ~16%, 45%,and 7% of these corresponding respectively to major, minor, and ambiguous`major or minor- mergers. The mean merger rate is a few x 1e-4 Gyr-1 Mpc-3. 2We compare the empirical merger fraction and rate for high mass galaxies to asuite of Lambda CDM-based models: halo occupation distribution models,semi-analytic models, and hydrodynamic SPH simulations. We find qualitativeagreement between observations and models such that the major+minor mergerfraction or rate from different models bracket the observations, and show afactor of five dispersion. Near-future improvements can now start to rule outcertain merger scenarios. 3 Among ~3698 M*>=1e9 Msun galaxies, we find thatthe mean SFR of visibly merging systems is only modestly enhanced compared tonon-interacting galaxies over z~0.24-0.80. Visibly merging systems onlyaccount for less than 30% of the cosmic SFR density over T b~3-7 Gyr. Thissuggests that the behavior of the cosmic SFR density over the last 7 Gyr ispredominantly shaped by non-interacting galaxies.



Author: Shardha Jogee, Sarah H. Miller, Kyle Penner, Rosalind E. Skelton, Christopher J. Conselice, Rachel S. Somerville, Eric F.Bell, Xi

Source: https://arxiv.org/







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