The Evolution of the Interstellar Medium in Post-Starburst Galaxies

Zhihui Li; K. Decker French; Ann I. Zabludoff; Luis C. Ho

doi:10.3847/1538-4357/ab1f68

paper

The Evolution of the Interstellar Medium in Post-Starburst Galaxies

arXiv:1906.01890 · doi:10.3847/1538-4357/ab1f68

Abstract

We derive dust masses ( $M_{dust}$ ) from the spectral energy distributions of 58 post-starburst galaxies (PSBs). There is an anticorrelation between specific dust mass ( $M_{dust}$ / $M_{⋆}$ ) and the time elapsed since the starburst ended, indicating that dust was either destroyed, expelled, or rendered undetectable over the $\sim$ 1 Gyr after the burst. The $M_{dust}$ / $M_{⋆}$ depletion timescale, 205 $_{- 37}^{+ 58}$ Myr, is consistent with that of the CO-traced $M_{H_{2}} / M_{⋆}$ , suggesting that dust and gas are altered via the same process. Extrapolating these trends leads to the $M_{dust} / M_{⋆}$ and $M_{H_{2}} / M_{⋆}$ values of early-type galaxies (ETGs) within 1-2 Gyr, a timescale consistent with the evolution of other PSB properties into ETGs. Comparing $M_{dust}$ and $M_{H_{2}}$ for PSBs yields a calibration, log $M_{H_{2}}$ = 0.45 log $M_{dust}$ + 6.02, that allows us to place 33 PSBs on the Kennicutt-Schmidt (KS) plane, $Σ SFR - Σ M_{H_{2}}$ . Over the first $\sim$ 200-300 Myr, the PSBs evolve down and off of the KS relation, as their star formation rate (SFR) decreases more rapidly than $M_{H_{2}}$ . Afterwards, $M_{H_{2}}$ continues to decline whereas the SFR levels off. These trends suggest that the star-formation efficiency bottoms out at 10 $^{- 11} y r^{- 1}$ and will rise to ETG levels within 0.5-1.1 Gyr afterwards. The SFR decline after the burst is likely due to the absence of gas denser than the CO-traced H $_{2}$ . The mechanism of the $M_{dust} / M_{⋆}$ and $M_{H_{2}} / M_{⋆}$ decline, whose timescale suggests active galactic nucleus (AGN) or low-ionization nuclear emission-line region (LINER) feedback, may also be preventing the large CO-traced molecular gas reservoirs from collapsing and forming denser star forming clouds.

arXiv commentv1: 29 pages, 13 figures, to be published in ApJ. v2: Figure 6 and 7 fixed; more references added

The Evolution of the Interstellar Medium in Post-Starburst Galaxies

Abstract

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