Stellar age gradients and inside-out star formation quenching in galaxy bulges

Abstract

Radial age gradients hold the cumulative record of the multitude of physical processes driving the build-up of stellar populations and the ensuing star formation (SF) quenching process in galaxy bulges, therefore potentially sensitive discriminators between competing theoretical concepts on bulge formation and evolution. Based on spectral modeling of integral field spectroscopy data from the CALIFA survey, we derive mass- and light-weighted stellar age gradients ($\nabla$(t,B)L,M) within the photometrically determined bulge radius (RB) of a representative sample of local face-on late-type galaxies that span 2.6 dex in stellar mass. Our analysis documents a trend for decreasing $\nabla$(t,B)L,M with increasing M,T, with high-mass bulges predominantly showing negative age gradients and vice versa. The inversion from positive to negative $\nabla$(t,B)L,M occurs at logM,T ~ 10, which roughly coincides with the transition from lower-mass bulges whose gas excitation is powered by SF to bulges classified as Composite, LINER or Seyfert. We discuss two limiting cases for the origin of radial age gradients in massive LTG bulges. The first assumes that the stellar age in the bulge is initially spatially uniform, thus the observed age gradients arise from an inside-out SF quenching (ioSFQ) front that is radially expanding with a mean velocity vq. In this case, the age gradients translate into a slow ioSFQ that lasts until z~2, suggesting mild negative feedback by SF or an AGN. If negative age gradients in massive bulges are not due to ioSFQ but primarily due to their inside-out formation process, then the standard hypothesis of quasi-monolithic bulge formation has to be discarded in favor of a scenario that involves gradual buildup of stellar mass over 2-3 Gyr through, e.g., inside-out SF and inward migration of SF clumps from the disk. In this case, rapid AGN-driven ioSFQ cannot be ruled out.

7 pages, 4 figures

References in corpus (17)

• Mass and environment as drivers of galaxy evolution in SDSS and zCOSMOS and the origin of the Schechter function
• Cold streams in early massive hot haloes as the main mode of galaxy formation
• Strangulation as the primary mechanism for shutting down star formation in galaxies
• Rapid formation of exponential disks and bulges at high redshift from the dynamical evolution of clump cluster and chain galaxies
• Evidence for Mature Bulges and an Inside-out Quenching Phase 3 Billion Years After the Big Bang
• Reconstructing the Subsurface Three-Dimensional Magnetic Structure of A Solar Active Region Using SDO/HMI Observations
• Star formation in a galactic outflow
• Stellar Population gradients in galaxy discs from the CALIFA survey
• Specific SFR profiles in nearby spiral galaxies: quantifying the inside-out formation of disks
• Star formation is boosted (and quenched) from the inside out: radial star formation profiles from MaNGA
• Stellar kinematics across the Hubble sequence in the CALIFA survey: General properties and aperture corrections
• The stellar accretion origin of stellar population gradients in massive galaxies at large radii
• Absorption line-strengths of 18 late-type spiral galaxies observed with SAURON
• Star formation in the local Universe from the CALIFA sample. II. Activation and quenching mechanisms in bulges, bars, and disks
• Stellar populations in the bulges of isolated galaxies
• The continuous rise of bulges out of galactic disks
• A new fitting concept for the robust determination of Sérsic model parameters

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