2009/09/30 by Kurt T. Soto, Crystal L. Martin · 18 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Balmer series #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma-ray bursts and supernovae #Inflow #Infrared #Line (geometry) #Population #Star formation #Stars #Stellar population #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/716/1/332
published in The Astrophysical Journal 716(1), 332-340 (IOP Publishing) · Accepted by ApJ; 11 pages, 8 figures, 18 online-only figures that can be found at http://physics.ucsb.edu/~ktsoto/online_figs/2009arXiv0909.2050S/
arxiv created 2010/05/07 · openalex publication_date 2010/05/17 · arxiv updated 2014/11/20 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Using longslit, optical spectra of ultraluminous infrared galaxies, we measure the evolution in the star formation intensity during galactic mergers. In individual galaxies, we resolve kiloparsec scales allowing comparison of the nucleus, inner disk, and outer disk. We find that the strength of the Hβ absorption line increases with the projected distance from the center of the merger, typically reaching about 9 Å around 10 kpc. At these radii, the star formation intensity must have rapidly decreased about 300–400 Myr ago; only stellar populations deficient in stars more massive than Type A produce such strong Balmer absorption. In contrast, we find the star formation history in the central kiloparsec consistent with continuous star formation. Our measurements indicate that gas depletion occurs from the outer disk inward during major mergers. This result is consistent with merger-induced gas inflow and empirically constrains the gas inflow timescale. Numerical simulations accurately calculate the total amount of infalling gas but often assume the timescale for infall. These new measurements are therefore central to modeling merger-induced star formation and active galactic nucleus activity.