[Paper Review] The role of bars in quenching star formation from z = 3 to the present epoch. Halpha3: an Halpha imaging survey of HI selected galaxies from ALFALFA, VI

G. Gavazzi, G. Consolandi+11 more|arXiv (Cornell University)|May 28, 2015

Galaxies: Formation, Evolution, Phenomena11 references72 citations

TL;DR

This study investigates the role of galactic bars in quenching star formation in massive galaxies from z = 3 to the present. Using Hα imaging from the Hα3 survey of HI-selected galaxies, it finds that strong bars increase sharply above a mass threshold M_knee ∝ (1+z)², and a numerical model confirms bars can rapidly quench central star formation, explaining the observed downsizing trend in sSFR.

ABSTRACT

A growing body of evidence indicates that the star formation rate per unit stellar mass (sSFR) decreases with increasing mass in normal "main-sequence" star forming galaxies. Many processes have been advocated as responsible for such a trend (also known as mass quenching), e.g., feedback from active galactic nuclei (AGNs), and the formation of classical bulges. We determine a refined star formation versus stellar mass relation in the local Universe. To this aim we use the Halpha narrow-band imaging follow-up survey (Halpha3) of field galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Coma and Local superclusters. By complementing this local determination with high-redshift measurements from the literature, we reconstruct the star formation history of main-sequence galaxies as a function of stellar mass from the present epoch up to z=3. In agreement with previous studies, our analysis shows that quenching mechanisms occur above a threshold stellar mass M_knee that evolves with redshift as propto (1+z)^{2}. Moreover, visual morphological classification of individual objects in our local sample reveals a sharp increase in the fraction of visually-classified strong bars with mass, hinting that strong bars may contribute to the observed downturn in the sSFR above M_knee. We test this hypothesis using a simple but physically-motivated numerical model for bar formation, finding that strong bars can rapidly quench star formation in the central few kpc of field galaxies. We conclude that strong bars contribute significantly to the red colors observed in the inner parts of massive galaxies, although additional mechanisms are likely required to quench the star formation in the outer regions of massive spiral galaxies. Intriguingly, when we extrapolate our model to higher redshifts, we successfully recover the observed redshift evolution for M_knee.

Motivation & Objective

• To determine the star formation rate versus stellar mass relation in local main-sequence galaxies using deep Hα imaging.
• To investigate the redshift evolution of the mass threshold M_knee above which star formation is quenched.
• To test whether the increasing fraction of strong bars in massive galaxies contributes to mass quenching.
• To model the physical impact of bars on central star formation and assess their role in galaxy evolution.
• To explore the connection between bar-induced quenching and the formation of pseudobulges or boxy/peanut bulges.

Proposed method

• Conducted Hα narrow-band imaging follow-up of HI-selected galaxies from the ALFALFA survey in the Coma and Local Superclusters.
• Combined local Hα3 data with high-redshift literature measurements to reconstruct the star formation history of main-sequence galaxies up to z = 3.
• Performed visual morphological classification of galaxies to quantify the fraction of strong bars as a function of stellar mass.
• Developed a physically motivated numerical model simulating bar-driven gas inflow and central star formation quenching.
• Used the model to test whether bar-induced quenching can reproduce the observed evolution of M_knee with redshift.
• Explored the dynamical evolution of bars, including bar suicide and the formation of pseudobulges or boxy/peanut structures.

Experimental results

Research questions

• RQ1 Does the occurrence of strong bars in massive galaxies correlate with the onset of quenching at M_knee?
• RQ2 How does the mass threshold M_knee for quenching evolve with cosmic time, and can bar formation explain this evolution?
• RQ3 To what extent can bar-driven gas inflow account for the observed downsizing of the specific star formation rate (sSFR) in massive galaxies?
• RQ4 What dynamical and structural remnants persist after a bar dissolves, and how do they relate to observed bulge morphologies?
• RQ5 Can the bar-induced quenching model reproduce the observed redshift evolution of M_knee without requiring additional quenching mechanisms?

Key findings

• The fraction of visually classified strong bars increases sharply above a stellar mass threshold M_knee ≈ 10^9.5 M⊙ in local galaxies.
• The mass threshold M_knee evolves with redshift as M_knee ∝ (1+z)^2, consistent with observations of declining sSFR in massive galaxies.
• A numerical model confirms that strong bars can rapidly quench star formation in the central few kiloparsecs of field galaxies.
• Bar-induced quenching explains the red colors in the inner regions of massive galaxies, though outer regions likely require additional quenching mechanisms.
• Extrapolating the model to higher redshift successfully reproduces the observed evolution of M_knee, supporting the role of bars in mass quenching.
• Many massive galaxies with bulges but no visible bars may be in a late evolutionary stage following bar dissolution, with pseudobulges or boxy/peanut bulges as remnants.