Quenched fractions in the IllustrisTNG simulations: comparison with observations and other theoretical models. (arXiv:2008.00004v1 [astro-ph.GA])

<a href="http://arxiv.org/find/astro-ph/1/au:+Donnari_M/0/1/0/all/0/1">Martina Donnari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pillepich_A/0/1/0/all/0/1">Annalisa Pillepich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nelson_D/0/1/0/all/0/1">Dylan Nelson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marinacci_F/0/1/0/all/0/1">Federico Marinacci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vogelsberger_M/0/1/0/all/0/1">Mark Vogelsberger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hernquist_L/0/1/0/all/0/1">Lars Hernquist</a>

We make an in-depth comparison of the IllustrisTNG simulations with

observational data on the quenched fractions of central and satellite galaxies,

for $M_*=10^{9-12}M_{odot}$ at $0leq zleq3$. We study how analysis

methodologies and observational effects impact this comparison. This includes

measurement choices — aperture, quenched definition, star formation rate (SFR)

indicator timescale — as well as observational uncertainties and sample

selection issues: projection effects, satellite/central misclassification, and

host mass distribution sampling. The definition used to separate quenched and

star-forming galaxies produces differences of up to 70 (30)$%$ for centrals

(satellites) $>sim 10^{10.5} M_{odot}$. Increasing the aperture within which

SFR is measured can suppress the quenched fractions by up to $sim50%$,

particularly at $zgtrsim2$. Proper consideration of the stellar and host mass

distributions is crucial: naive comparisons to volume-limited samples from

simulations lead to misinterpretation of the quenched fractions as a function

of $z$ by up to 20$%$. Including observational uncertainties to theoretical

values of $M_*$ and SFR changes the quenched fraction values and their trend

and/or slope with mass. Taking projected rather than 3D distances for

satellites decreases the quenched fractions by up to 10$%$ due to field

contamination. Comparing with data, TNG produces quenched fractions broadly

consistent with observations. TNG predicts quenched fractions up to

$sim80-90%$ for centrals at $zleq2-3$, in line with recent observations, and

notably higher than other theoretical models. The quantitative agreement of TNG

and SDSS for satellite quenched fractions in groups and clusters depends

strongly on the galaxy and host mass range. Our mock comparison between TNG and

SDSS highlights the importance of properly accounting for observational effects

and biases.

We make an in-depth comparison of the IllustrisTNG simulations with

observational data on the quenched fractions of central and satellite galaxies,

for $M_*=10^{9-12}M_{odot}$ at $0leq zleq3$. We study how analysis

methodologies and observational effects impact this comparison. This includes

measurement choices — aperture, quenched definition, star formation rate (SFR)

indicator timescale — as well as observational uncertainties and sample

selection issues: projection effects, satellite/central misclassification, and

host mass distribution sampling. The definition used to separate quenched and

star-forming galaxies produces differences of up to 70 (30)$%$ for centrals

(satellites) $>sim 10^{10.5} M_{odot}$. Increasing the aperture within which

SFR is measured can suppress the quenched fractions by up to $sim50%$,

particularly at $zgtrsim2$. Proper consideration of the stellar and host mass

distributions is crucial: naive comparisons to volume-limited samples from

simulations lead to misinterpretation of the quenched fractions as a function

of $z$ by up to 20$%$. Including observational uncertainties to theoretical

values of $M_*$ and SFR changes the quenched fraction values and their trend

and/or slope with mass. Taking projected rather than 3D distances for

satellites decreases the quenched fractions by up to 10$%$ due to field

contamination. Comparing with data, TNG produces quenched fractions broadly

consistent with observations. TNG predicts quenched fractions up to

$sim80-90%$ for centrals at $zleq2-3$, in line with recent observations, and

notably higher than other theoretical models. The quantitative agreement of TNG

and SDSS for satellite quenched fractions in groups and clusters depends

strongly on the galaxy and host mass range. Our mock comparison between TNG and

SDSS highlights the importance of properly accounting for observational effects

and biases.

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