[Paper Review] What do the Star Formation Histories of Galaxies tell us about the Starburst-AGN connection?

J. P. Torres-Papaqui, R. Coziol+3 more|arXiv (Cornell University)|Aug 8, 2013

Galaxies: Formation, Evolution, Phenomena1 references3 citations

TL;DR

This study analyzes star formation histories (SFHs) in 229,618 narrow emission-line galaxies and finds that star formation rates (SFRs) peak earlier and more intensely in more massive galaxies, with the maximum SFR strongly correlated with virial mass within the SDSS aperture (VMA). The results support a co-evolution model where supermassive black holes (SMBHs) and galactic bulges grow in parallel during dissipative processes such as mergers, consistent with the M_BH–σ* relation, and find no evidence of AGN feedback quenching star formation in these systems.

ABSTRACT

Using a sample of 229618 narrow emission-line galaxies, we have determined the normal star formation histories (SFHs) for galaxies with different activity types: star forming galaxies (SFGs), transition type objects (TOs), Seyfert 2s (Sy2s) and LINERs. We find that the variation of the SFH with the activity type is explained by the mass of the galaxies and the importance of their bulge: the LINERs reside in massive early-type galaxies, the Sy2s and TOs are hosted by intermediate mass galaxies with intermediate morphological types, and the SFGs are found in lower mass late-type spirals. Except for the Sy2s, the more massive galaxies formed the bulk of their stars more rapidly than the less massive ones. The Sy2s formed their stars more slowly and show presently an excess in star formation. We have also found that the maximum in star formation rate in the past increases with the virial mass within the aperture (VMA), the VMA increasing from the SFGs to the TOs, to the Sy2s, culminating in the LINERs. This correlation suggests that the bulges and the supermassive black holes at the center of galaxies grow in parallel, in good agreement with the M(BH)-sigma relation.

Motivation & Objective

• To investigate the connection between star formation histories (SFHs) and nuclear activity types in galaxies.
• To determine whether AGN feedback quenches star formation or if star formation and SMBH growth are co-eval.
• To examine how galaxy mass, morphology, and bulge dominance correlate with SFHs across different activity types.
• To test the validity of the M_BH–σ* relation through the lens of normal SFHs in nearby galaxies.
• To assess whether the observed SFHs in AGNs (Sy2s, LINERs) are consistent with a starburst-AGN co-evolution model.

Proposed method

• Analysis of 229,618 narrow emission-line galaxies from SDSS DR7 using the BPT-VO diagnostic diagram to classify activity types (SFGs, TOs, Sy2s, LINERs).
• Computation of virial mass within the SDSS fiber aperture (VMA) for each galaxy to estimate central gravitational potential.
• Reconstruction of normal star formation histories (SFHs) using spectral energy distribution (SED) fitting and emission-line diagnostics.
• Correlation of peak star formation rate (SFR) with VMA across activity types to infer co-evolution of SMBHs and bulges.
• Comparison of SFHs across morphological types and activity classes to assess differences in formation timescales and mass assembly.
• Use of the M_BH–σ* relation as a benchmark to evaluate whether observed SFHs support co-evolution or feedback-driven quenching.

Experimental results

Research questions

• RQ1 How do star formation histories (SFHs) vary across different nuclear activity types (SFGs, TOs, Sy2s, LINERs)?
• RQ2 Is there evidence of AGN feedback quenching star formation in galaxies with active nuclei?
• RQ3 Does the peak star formation rate correlate with the virial mass within the SDSS aperture (VMA), and what does this imply for SMBH and bulge co-evolution?
• RQ4 To what extent do galaxy mass and bulge dominance explain the observed differences in SFHs across activity types?
• RQ5 Can the M_BH–σ* relation be explained by co-eval formation of bulges and SMBHs through dissipative processes like mergers?

Key findings

• The maximum star formation rate (SFR) in a galaxy's past increases with its virial mass within the SDSS aperture (VMA), indicating more massive galaxies formed stars more rapidly and earlier.
• Galaxies hosting LINERs reside in massive, early-type systems with prominent bulges, while Sy2s and TOs are found in intermediate-mass, intermediate-type spirals, and SFGs in low-mass, late-type spirals.
• No evidence was found for AGN feedback quenching star formation; instead, active star formation is common across all activity types, with Sy2s showing a current excess in SFR relative to their mass and morphology.
• The correlation between peak SFR and VMA supports a co-evolution model where SMBHs and bulges grow in parallel during dissipative processes such as mergers.
• The results are consistent with the M_BH–σ* relation arising from simultaneous formation of bulges and SMBHs, rather than feedback-driven evolution.
• The absence of AGNs in giant ellipticals today may reflect their past formation history, as such AGNs would have formed in the early universe and are now quiescent.