History of Galaxy Interactions and Their Impact on Star Formation Over the Last 7 Gyr from GEMS
Jogee, Shardha; Miller, Sarah H.; Penner, Kyle;Skelton, Rosalind E.; Conselice, Christopher J.;Somerville, Rachel S.; Bell, Eric F.;Zheng, Xian Zhong; Rix, Hans-Walter;Robaina, Aday R.; Barazza, Fabio D.; Barden, Marco;Borch, Andrea; Beckwith, Steven V. W.;Caldwell, John A. R.; Peng, Chien Y.;Heymans, Catherine; McIntosh, Daniel H.;Häußler, Boris; Jahnke, Knud; Meisenheimer, Klaus;Sanchez, Sebastian F.; Wisotzki, Lutz;Wolf, Christian; Papovich, Casey. History of Galaxy Interactions and Their Impact on Star Formation Over the Last 7 Gyr from GEMS. The Astrophysical Journal. 2009, Vol. Volume 697, Issue 2, pp.1971-1992 (2009)., p. -2009.
We perform a comprehensive estimate of the frequency of galaxy mergers
and their impact on star formation over z~ 0.24-0.80 (lookback time T
<SUB>b</SUB>~ 3-7 Gyr) using ~3600 (M>= 1 × 10<SUP>9</SUP>
M <SUB>sun</SUB>) galaxies with GEMS Hubble Space Telescope, COMBO-17,
and Spitzer data. Our results are as follows. (1) Among ~790 high-mass
(M>= 2.5 × 10<SUP>10</SUP> M <SUB>sun</SUB>) galaxies, the
visually based merger fraction over z~ 0.24-0.80, ranges from 9%
± 5% to 8% ± 2%. Lower limits on the major merger and
minor merger fraction over this interval range from 1.1% to 3.5%, and
3.6% to 7.5%, respectively. This is the first, albeit approximate,
empirical estimate of the frequency of minor mergers over the last
7 Gyr. Assuming a visibility timescale of ~0.5 Gyr, it follows
that over T <SUB>b</SUB>~ 3-7 Gyr, ~68% of high-mass systems have
undergone a merger of mass ratio >1/10, with ~16%, 45%, and 7% of
major
mergers. The average merger rate is ~ a few
×10<SUP>–4</SUP> galaxies Gyr<SUP>–1</SUP>
Mpc<SUP>–3</SUP>. Among ~2840 blue-cloud galaxies of mass M>=
1.0 × 10<SUP>9</SUP> M <SUB>sun</SUB>, similar results hold. (2)
We compare the empirical merger fraction and merger rate for high-mass
galaxies to three Λ cold dark matter-based models: halo
occupation distribution models, semi-analytic models, and hydrodynamic
SPH simulations. We find qualitative agreement between observations and
models such that the (major+minor) merger fraction or rate from
different models bracket the observations, and show a factor of 5
dispersion. Near-future improvements can now start to rule out certain
merger scenarios. (3) Among ~3698 M>= 1.0 × 10<SUP>9</SUP> M
<SUB>sun</SUB> galaxies, we find that the mean star formation rate (SFR)
of visibly merging systems is only modestly enhanced compared to
non-interacting galaxies over z~ 0.24-0.80. Visibly merging systems only
account for a small fraction (<30%) of the cosmic SFR density over T
<SUB>b</SUB>~ 3-7 Gyr. This complements the results of Wolf
et al. over a shorter time interval of T <SUB>b</SUB>~
6.2-6.8 Gyr, and suggests that the behavior of the cosmic SFR
density over the last 7 Gyr is predominantly shaped by
non-interacting galaxies.
We perform a comprehensive estimate of the frequency of galaxy mergers
and their impact on star formation over z~ 0.24-0.80 (lookback time T
<SUB>b</SUB>~ 3-7 Gyr) using ~3600 (M>= 1 × 10<SUP>9</SUP>
M <SUB>sun</SUB>) galaxies with GEMS Hubble Space Telescope, COMBO-17,
and Spitzer data. Our results are as follows. (1) Among ~790 high-mass
(M>= 2.5 × 10<SUP>10</SUP> M <SUB>sun</SUB>) galaxies, the
visually based merger fraction over z~ 0.24-0.80, ranges from 9%
± 5% to 8% ± 2%. Lower limits on the major merger and
minor merger fraction over this interval range from 1.1% to 3.5%, and
3.6% to 7.5%, respectively. This is the first, albeit approximate,
empirical estimate of the frequency of minor mergers over the last
7 Gyr. Assuming a visibility timescale of ~0.5 Gyr, it follows
that over T <SUB>b</SUB>~ 3-7 Gyr, ~68% of high-mass systems have
undergone a merger of mass ratio >1/10, with ~16%, 45%, and 7% of
major
mergers. The average merger rate is ~ a few
×10<SUP>–4</SUP> galaxies Gyr<SUP>–1</SUP>
Mpc<SUP>–3</SUP>. Among ~2840 blue-cloud galaxies of mass M>=
1.0 × 10<SUP>9</SUP> M <SUB>sun</SUB>, similar results hold. (2)
We compare the empirical merger fraction and merger rate for high-mass
galaxies to three Λ cold dark matter-based models: halo
occupation distribution models, semi-analytic models, and hydrodynamic
SPH simulations. We find qualitative agreement between observations and
models such that the (major+minor) merger fraction or rate from
different models bracket the observations, and show a factor of 5
dispersion. Near-future improvements can now start to rule out certain
merger scenarios. (3) Among ~3698 M>= 1.0 × 10<SUP>9</SUP> M
<SUB>sun</SUB> galaxies, we find that the mean star formation rate (SFR)
of visibly merging systems is only modestly enhanced compared to
non-interacting galaxies over z~ 0.24-0.80. Visibly merging systems only
account for a small fraction (<30%) of the cosmic SFR density over T
<SUB>b</SUB>~ 3-7 Gyr. This complements the results of Wolf
et al. over a shorter time interval of T <SUB>b</SUB>~
6.2-6.8 Gyr, and suggests that the behavior of the cosmic SFR
density over the last 7 Gyr is predominantly shaped by
non-interacting galaxies.