We explore the isothermal total density profiles of early-type galaxies (ETGs) in the IllustrisTNG simulation. For the selected 559 ETGs at $z = 0$ with stellar mass $10^{10.7}mathrm{M}_{odot} leqslant M_{ast} leqslant 10^{11.9}mathrm{M}_{odot}$, the total power-law slope has a mean of $langlegamma^{prime}rangle = 2.011 pm 0.007$ and a scatter of $sigma_{gamma^{prime}} = 0.171$ over the radial range 0.4 to 4 times the stellar half mass radius. Several correlations between $gamma^{prime}$ and galactic properties including stellar mass, effective radius, stellar surface density, central velocity dispersion, central dark matter fraction and in-situ-formed stellar mass ratio are compared to observations and other simulations, revealing that IllustrisTNG reproduces many correlation trends, and in particular, $gamma^{prime}$ is almost constant with redshift below $z = 2$. Through analyzing IllustrisTNG model variations we show that black hole kinetic winds are crucial to lowering $gamma^{prime}$ and matching observed galaxy correlations. The effects of stellar winds on $gamma^{prime}$ are subdominant compared to AGN feedback, and differ due to the presence of AGN feedback from previous works. The density profiles of the ETG dark matter halos are well-described by steeper-than-NFW profiles, and they are steeper in the full physics (FP) run than their counterparts in the dark matter only (DMO) run. Their inner density slopes anti-correlates (remain constant) with the halo mass in the FP (DMO) run, and anti-correlates with the halo concentration parameter $c_{200}$ in both types of runs. The dark matter halos of low-mass ETGs are contracted whereas high-mass ETGs are expanded, suggesting that variations in the total density profile occur through the different halo responses to baryons.
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