The Evolution of the Interstellar Medium in Post-Starburst Galaxies. (arXiv:1906.01890v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Li_Z/0/1/0/all/0/1">Zhihui Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+French_K/0/1/0/all/0/1">K. Decker French</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zabludoff_A/0/1/0/all/0/1">Ann I. Zabludoff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ho_L/0/1/0/all/0/1">Luis C. Ho</a>
We derive dust masses ($M_{rm dust}$) from the spectral energy distributions
of 58 post-starburst galaxies (PSBs). There is an anticorrelation between
specific dust mass ($M_{rm dust}$/$M_{star}$) 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 $M_{rm
dust}$/$M_{star}$ depletion timescale, 205$^{+58}_{-37}$ Myr, is consistent
with that of the CO-traced $M_{rm H_2}/M_{star}$, suggesting that dust and
gas are altered via the same process. Extrapolating these trends leads to the
$M_{rm dust}/M_{star}$ and $M_{rm H_2}/M_{star}$ values of early-type
galaxies (ETGs) within 1-2 Gyr, a timescale consistent with the evolution of
other PSB properties into ETGs. Comparing $M_{rm dust}$ and $M_{rm H_2}$ for
PSBs yields a calibration, log $M_{rm H_2}$ = 0.45 log $M_{rm dust}$ + 6.02,
that allows us to place 33 PSBs on the Kennicutt-Schmidt (KS) plane, $Sigma
rm SFR-Sigma M_{rm H_2}$. 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 $M_{rm H_2}$. Afterwards, $M_{rm H_2}$ continues to decline
whereas the SFR levels off. These trends suggest that the star-formation
efficiency bottoms out at 10$^{-11} rm yr^{-1}$ 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
$M_{rm dust}/M_{star}$ and$M_{rm H_2}/M_{star}$ 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.
We derive dust masses ($M_{rm dust}$) from the spectral energy distributions
of 58 post-starburst galaxies (PSBs). There is an anticorrelation between
specific dust mass ($M_{rm dust}$/$M_{star}$) 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 $M_{rm
dust}$/$M_{star}$ depletion timescale, 205$^{+58}_{-37}$ Myr, is consistent
with that of the CO-traced $M_{rm H_2}/M_{star}$, suggesting that dust and
gas are altered via the same process. Extrapolating these trends leads to the
$M_{rm dust}/M_{star}$ and $M_{rm H_2}/M_{star}$ values of early-type
galaxies (ETGs) within 1-2 Gyr, a timescale consistent with the evolution of
other PSB properties into ETGs. Comparing $M_{rm dust}$ and $M_{rm H_2}$ for
PSBs yields a calibration, log $M_{rm H_2}$ = 0.45 log $M_{rm dust}$ + 6.02,
that allows us to place 33 PSBs on the Kennicutt-Schmidt (KS) plane, $Sigma
rm SFR-Sigma M_{rm H_2}$. 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 $M_{rm H_2}$. Afterwards, $M_{rm H_2}$ continues to decline
whereas the SFR levels off. These trends suggest that the star-formation
efficiency bottoms out at 10$^{-11} rm yr^{-1}$ 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
$M_{rm dust}/M_{star}$ and$M_{rm H_2}/M_{star}$ 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.
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