SDSS-IV MaNGA: the different quenching histories of fast and slow rotators

Abstract

Do the theorised different formation mechanisms of fast and slow rotators produce an observable difference in their star formation histories? To study this we identify quenching slow rotators in the MaNGA sample by selecting those which lie below the star forming sequence and identify a sample of quenching fast rotators which were matched in stellar mass. This results in a total sample of 194 kinematically classified galaxies, which is agnostic to visual morphology. We use u − r and N U V − u colours from SDSS and GALEX and an existing inference package, starpy, to conduct a first look at the onset time and exponentially declining rate of quenching of these galaxies. An Anderson-Darling test on the distribution of the inferred quenching rates across the two kinematic populations reveals they are statistically distinguishable (3.2σ). We find that fast rotators quench at a much wider range of rates than slow rotators, consistent with a wide variety of physical processes such as secular evolution, minor mergers, gas accretion and environmentally driven mechanisms. Quenching is more likely to occur at rapid rates (τ ∼ < 1 Gyr) for slow rotators, in agreement with theories suggesting slow rotators are formed in dynamically fast processes, such as major mergers. Interestingly, we also find that a subset of the fast rotators quench at these same rapid rates as the bulk of the slow rotator sample. We therefore discuss how the total gas mass of a merger, rather than the merger mass ratio, may decide a galaxy's ultimate kinematic fate.

Morphology and star formation in IllustrisTNG: the build-up of spheroids and discs

“…In the local Universe, observational constraints are much more detailed, including the shape, dynamics, and stellar population of complete samples of galaxies (see review by Cappellari 2016). The quiescent galaxies can be classified into two main classes using stellar kinematics: slow and fast rotators (e.g., Davis & Peebles 1983;Kormendy & Ben-der 1996;Emsellem et al 2007;Veale et al 2017;Smethurst et al 2018). The slow rotators are rare and dominate only at M > 2 × 10 11 M (Illingworth 1977;Binney 1978).…”

SDSS-IV MaNGA: stellar angular momentum of about 2300 galaxies: unveiling the bimodality of massive galaxy properties

“…The two classes form distinct galaxy populations which can be distinguished by measuring a parameter related to the galaxy spin (e.g. Emsellem et al 2007Emsellem et al , 2011D'Eugenio et al 2013;Fogarty et al 2014;Scott et al 2014;Falcón-Barroso et al 2015;Fogarty et al 2015;Querejeta et al 2015;Cortese et al 2016;Veale et al 2017a;Brough et al 2017;van de Sande et al 2017;Greene et al 2017Greene et al , 2018Smethurst et al 2018). For a complete review, see Cappellari (2016), hereafter C16.…”

Quenching time-scales of galaxies in the eagle simulations

“…They found characteristic e-folding times of 0.5 − 1.5 Gyr, implying a total migration time from the star formation main sequence to quiescence on the order of ≈ 4 Gyr, with central galaxies typically taking 2 Gyr longer to quench than satellites. Smethurst et al (2018) also used SDSS DR7 data to investigate the quenching timescales of slow-and fast-rotators, finding that slow-rotators would quench rapidly (with τ Q < 1 Gyr) compared to fast-rotators (which displayed more spread in τ Q ). Using arguments based on the density of green-valley galaxies in the GAMA survey, Bremer et al (2018) found a relatively universal crossing timescale for galaxies with stellar masses 10 10.25 M < M < 10 10.75 M , at z < 0.2 of τ Q ≈ 1 − 2 Gyr.…”