Star Formation in Interacting and Normal Galaxies over the last 7 Gigayears
Jogee, Shardha; Miller, S.; Penner, K.; Bell, E. F.;Zheng, X. Z.; Papovich, C.; Conselice, C.;Skelton, R. E.; Somerville, R. S.; Rix, H. W.;Robaina, A. R.; Barazza, F. D.; Barden, M.;Borch, A.; Beckwith, S. V. W.; Caldwell, J. A. R.;Haeussler, B.; Heymans, C.; Jahnke, K.;McIntosh, D. H.; Meisenheimer, K.; Peng, C. Y.;Peng, C. Y.; Robaina, A. R.; Sanchez, S. F.;Wisotzki, L.; Wolf, C.. Star Formation in Interacting and Normal Galaxies over the last 7 Gigayears. American Astronomical Society AAS Meeting #211, . 2007, Vol. Vol. 39, p.956, p. -2007.
We present a study of the star formation properties of strongly
disturbed interacting/merging systems and normal undisturbed (E/S0,
Sa-Sd, Irr) galaxies over z 0.24 to 0.80 using Hubble Space Telescope
ACS images, Combo-17 redshifts, and Spitzer 24 micron data of 4500
galaxies in the GEMS survey. For high mass (M/Msun >= 2.5 x 10^10)
galaxies, the observed fraction of strongly disturbed galaxies varies
from 9% to 12% over z 0.24 to 0.80. The corresponding interaction rate
varies from a few times 10^-4 to 10^-3 galaxies per Gyr per Mpc^3. The
UV-based star formation rate (SFR) typically ranges from 0.01 to 25 Msun
yr-1, but the ratio of IR-based to UV-based SFR has a median value of 4,
indicating a substantial amount of obscured star formation. The average
SFR of strongly disturbed systems is comparable to, or only moderately
enhanced with respect to that of normal galaxies. This suggests that
extreme enhancements in SFRs during mergers and interactions may be
relatively rare. For intermediate mass systems, strongly disturbed
galaxies only contribute a small fraction (typically below 20 %) of the
total SFR density, compared to normal undisturbed galaxies. This
suggests that the variation of the cosmic SFR density over z 0.24 to
0.80 is primarily influenced by the shutdown of star formation in normal
undisturbed galaxies, rather than by the SF activity in interacting
systems. We acknowledge support from NASA LTSA grant NAG5-13063, NSF
grant AST-0607748, and HST grants G0-9500, GO-10395 and GO-10861.
We present a study of the star formation properties of strongly
disturbed interacting/merging systems and normal undisturbed (E/S0,
Sa-Sd, Irr) galaxies over z 0.24 to 0.80 using Hubble Space Telescope
ACS images, Combo-17 redshifts, and Spitzer 24 micron data of 4500
galaxies in the GEMS survey. For high mass (M/Msun >= 2.5 x 10^10)
galaxies, the observed fraction of strongly disturbed galaxies varies
from 9% to 12% over z 0.24 to 0.80. The corresponding interaction rate
varies from a few times 10^-4 to 10^-3 galaxies per Gyr per Mpc^3. The
UV-based star formation rate (SFR) typically ranges from 0.01 to 25 Msun
yr-1, but the ratio of IR-based to UV-based SFR has a median value of 4,
indicating a substantial amount of obscured star formation. The average
SFR of strongly disturbed systems is comparable to, or only moderately
enhanced with respect to that of normal galaxies. This suggests that
extreme enhancements in SFRs during mergers and interactions may be
relatively rare. For intermediate mass systems, strongly disturbed
galaxies only contribute a small fraction (typically below 20 %) of the
total SFR density, compared to normal undisturbed galaxies. This
suggests that the variation of the cosmic SFR density over z 0.24 to
0.80 is primarily influenced by the shutdown of star formation in normal
undisturbed galaxies, rather than by the SF activity in interacting
systems. We acknowledge support from NASA LTSA grant NAG5-13063, NSF
grant AST-0607748, and HST grants G0-9500, GO-10395 and GO-10861.