Reconstructing the Assembly of Massive Galaxies. I: The Importance of the Progenitor Effect in the Observed Properties of Quiescent Galaxies at $z\approx 2$

Zhiyuan Ji; Mauro Giavalisco

doi:10.3847/1538-4357/ac7f43

paper

Reconstructing the Assembly of Massive Galaxies. I: The Importance of the Progenitor Effect in the Observed Properties of Quiescent Galaxies at $z \approx 2$

arXiv:2204.02414 · doi:10.3847/1538-4357/ac7f43

Abstract

We study the relationship between the morphology and star formation history (SFH) of 361 quiescent galaxies (QGs) at redshift $⟨ z_{o b s} ⟩ \approx 2$ , with stellar mass $lo g M_{*} \geq 10.3$ , selected with the UVJ technique. Taking advantage of panchromatic photometry covering the rest-frame UV-to-NIR spectral range ( $\approx 40$ bands), we reconstruct the non-parametric SFH of the galaxies with the fully Bayesian SED fitting code Prospector. We find that the half-light radius $R_{e}$ , observed at $z_{o b s}$ , depends on the formation redshift of the galaxies, $z_{f or m}$ , and that this relationship depends on stellar mass. At $lo g M_{*} < 11$ , the relationship is consistent with $R_{e} \propto (1 + z_{f or m})^{- 1}$ , in line with the expectation that the galaxies' central density depends on the cosmic density at the time of their formation, i.e. the "progenitor effect". At $lo g M_{*} > 11$ , the relationship between $R_{e}$ and $z_{f or m}$ flattens, suggesting that mergers become increasingly important for the size growth of more massive galaxies after they quenched. We also find that the relationship between $z_{f or m}$ and galaxy compactness similarly depends on stellar mass. While no clear trend is observed for QGs with $lo g M_{*} > 11$ , lower-mass QGs that formed earlier, i.e. with larger $z_{f or m}$ , have larger central stellar mass surface densities, both within the $R_{e}$ ( $Σ_{e}$ ) and central 1 kpc ( $Σ_{1 k p c}$ ), and also larger $M_{1 k p c} / M_{*}$ , the fractional mass within the central 1 kpc. These trends between $z_{f or m}$ and compactness, however, essentially disappear, if the progenitor effect is removed by normalizing the stellar density with the cosmic density at $z_{f or m}$ . Our findings highlight the importance of reconstructing the SFH of galaxies before attempting to infer their intrinsic structural evolution.

arXiv comment28 pages, 29 figures; published in ApJ

Reconstructing the Assembly of Massive Galaxies. I: The Importance of the Progenitor Effect in the Observed Properties of Quiescent Galaxies at $z \approx 2$

Abstract

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Cited by in corpus (22)

Reconstructing the Assembly of Massive Galaxies. I: The Importance of the Progenitor Effect in the Observed Properties of Quiescent Galaxies at z≈2

Abstract

References in corpus (151)

Cited by in corpus (22)

Reconstructing the Assembly of Massive Galaxies. I: The Importance of the Progenitor Effect in the Observed Properties of Quiescent Galaxies at $z \approx 2$