Larger λ_R in the disc of isolated active spiral galaxies than in their non-active twins

Abstract

We present a comparison of the spin parameter λR, measured in a region dominated by the galaxy disc, between 20 pairs of nearby (0.005 < z < 0.03) seemingly isolated twin galaxies differing in nuclear activity. We find that 80−82% of the active galaxies show higher values of λR than their corresponding non-active twin(s), indicating larger rotational support in the active galactic nuclei (AGN) discs. This result is driven by the 11 pairs of unbarred galaxies, for which 100% of the AGN show larger λR than their twins. These results can be explained by a more efficient angular momentum transfer from the inflowing gas to the disc baryonic matter in the case of the active galaxies. This gas inflow could have been induced by disc or bar instabilities, although we cannot rule out minor mergers if these are prevalent in our active galaxies. This result represents the first evidence of galaxy-scale differences between the dynamics of active and non-active isolated spiral galaxies of intermediate stellar masses (1010 < M* < 1011 M⊙) in the Universe.

Testing the role of AGN on the star formation and metal enrichment of ‘twin galaxies’

“…This paper explores the transitional role of AGN activity by analysing pairs of galaxies defined as twins, inasmuch as they feature similar large galaxy-scale properties but one presents AGN activity and the other one does not. The definition of these twin pairs follows the methodology laid out in del Moral-Castro et al (2020). In this section we discuss the potential implications of our results, from the radial influence of AGN activity on the galaxy, to testing two alternative hypotheses, either an "on-off" AGN switching mode, or the possibility of the twins having different evolutionary paths.…”

“…The original sample was assembled to study the resolved galactic properties (del Moral-Castro et al 2019). This original sample was expanded upon, where the differences in angular momentum was explored (del Moral-Castro et al 2020). In addition, only galaxies with a spiral morphology, and types Sa/SBa to Sbc/SBbc are included, thus enforcing a "simpler" mass assembly history, rejecting the effect of major mergers.…”

“…The selected candidates are then visually inspected to ensure similarity before they are selected as twins. These criteria were imposed in del Moral-Castro et al (2020), however we further restrict the stellar mass difference to ∆ log(M /M ) 0.20 dex and introduce a velocity dispersion constraint, where the difference in velocity dispersion in the central region, within 3 arcsec aperture, ∆σ ≤ 30 km/s. Note the velocity dispersion constraint is less than the typical error of measuring velocity dispersion in CALIFA, however this hard constraint on σ further ensures that these twin pairs, AGN and SF, galaxies are as similar as possible as σ is thought to be one of the fundamental parameters of galaxy evolution (Graves et al 2010;Ferreras et al 2019).…”

“…1 and 2 show the galaxy ID and the morphological classification (Walcher et al 2014). Col. 3 labels them as AGN or star forming (SF) (del Moral-Castro et al 2020), note that AGN galaxies also show signatures of ongoing star formation. Col. 4 identifies the twin by a number.…”

The physical connection between central stellar surface density and stellar spin in SAMI and MaNGA nearby galaxies

“…First, 𝜆 𝑟 𝑒 estimates were corrected for beam smearing following the empirical recipes presented in Harborne et al (2020), which are based on seeing and Sersic index. Beam-smearing corrected spin values were then corrected for inclination using the 𝑟-band ellipticity value as a proxy for inclination following del Moral-Castro et al (2020). We point the reader to Fraser-McKelvie et al (2021) and van de Sande et al (2021) for an extensive discussion of these corrections.…”