Galaxy and Mass Assembly (GAMA): merging galaxies and their properties

Propris, Roberto De; Baldry, I. K.; Bland-Hawthorn, Joss; Brough, Sarah; Driver, Simon P.; Hopkins, A. M.; Kelvin, Lee S.; Loveday, Jon; Phillipps, S.; Robotham, Aaron S. G.

doi:10.1093/mnras/stu1452

Cited by 27 publications

(28 citation statements)

References 108 publications

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“…In the minor mergers, the primary galaxy follows the same SF enhancement as the major merger systems, while the secondary galaxy has its SF suppressed as its gas is either tidally stripped, heated or simply stretched to a lower mean density which is not sufficient for SF. This toy model is consistent with the recent findings of Robotham et al 2013 andDe Propris et al 2014, as well as the galaxy merger simulation of Di Matteo et al 2007 -predicting that the effects of galaxy interactions on SF are dependent on both pair mass ratio and primary/secondary status within the pair.…”

Section: O N C L U S I O N Ssupporting

confidence: 91%

Galaxy And Mass Assembly (GAMA): the effect of close interactions on star formation in galaxies

Davies

Robotham

Driver

et al. 2015

Mon. Not. R. Astron. Soc.

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The modification of star formation (SF) in galaxy interactions is a complex process, with SF observed to be both enhanced in major mergers and suppressed in minor pair interactions. Such changes likely to arise on short timescales and be directly related to the galaxy-galaxy interaction time. Here we investigate the link between dynamical phase and direct measures of SF on different timescales for pair galaxies, targeting numerous star-formation rate (SFR) indicators and comparing to pair separation, individual galaxy mass and pair mass ratio. We split our sample into the higher (primary) and lower (secondary) mass galaxies in each pair and find that SF is indeed enhanced in all primary galaxies but suppressed in secondaries of minor mergers. We find that changes in SF of primaries is consistent in both major and minor mergers, suggesting that SF in the more massive galaxy is agnostic to pair mass ratio.We also find that SF is enhanced/suppressed more strongly for short-time duration SFR indicators (e.g. Hα), highlighting recent changes to SF in these galaxies, which are likely to be induced by the interaction. We propose a scenario where the lower mass galaxy has its SF suppressed by gas heating or stripping, while the higher mass galaxy has its SF enhanced, potentially by tidal gas turbulence and shocks. This is consistent with the seemingly contradictory observations for both SF suppression and enhancement in close pairs.

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Section: O N C L U S I O N Ssupporting

confidence: 91%

Galaxy And Mass Assembly (GAMA): the effect of close interactions on star formation in galaxies

Davies

Robotham

Driver

et al. 2015

Mon. Not. R. Astron. Soc.

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“…Various formation mechanisms have been proposed to be at work in transforming disks into spheroids, ranging from mergers (minor or major mergers depending on the mass ratio of the participants, gas rich or poor based on their gas content), to internal disk instabilities (secular evolution), and perturbations such as tidal interactions from neighboring galaxies (Mitchell et al 2014). These theoretical models match observational results based on recent large galaxy surveys such as the SDSS-DR7 (Abazajian et al 2009), PRIMUS (PRIsm MUlti-object Survey; Coil et al (2011);Cool et al (2013)) and GAMA (Galaxy And Mass Assembly; Driver et al (2009)) at least in broad principles though perhaps not in fine detail (Jiang et al 2012;De Propris et al 2014).…”

Section: Introductionsupporting

confidence: 80%

Stellar mass functions of galaxies, discs and spheroids atz∼ 0.1

Thanjavur¹,

Simard²,

Bluck³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present the stellar mass functions (SMF) and mass densities of galaxies, and their spheroid and disk components in the local (z∼0.1) universe over the range 8.9 ≤ log(M/M ⊙ ) ≤ 12 from spheroid+disk decompositions and corresponding stellar masses of a sample of over 600,000 galaxies in the SDSS-DR7 spectroscopic sample. The galaxy SMF is well represented by a single Schechter function (M * = 11.116 ± 0.011, α = −1.145±0.008), though with a hint of a steeper faint end slope. The corresponding stellar mass densities are (2.670±0.110), (1.687±0.063) and (0.910±0.029)×10for galaxies, spheroids and disks respectively. We identify a crossover stellar mass of log(M/M ⊙ ) = 10.3±0.030 at which the spheroid and disk SMFs are equal. Relative contributions of four distinct spheroid/disk dominated sub-populations to the overall galaxy SMF are also presented. The mean disk-to-spheroid stellar mass ratio shows a five fold disk dominance at the low mass end, decreasing monotonically with a corresponding increase in the spheroidal fraction till the two are equal at a galaxy stellar mass, log(M/M ⊙ )=10.479±0.013; the dominance of spheroids then grows with increasing stellar mass. The relative numbers of composite disk and spheroid dominated galaxies show peaks in their distributions, perhaps indicative of a preferred galaxy mass. Our characterization of the low redshift galaxy population provides stringent constraints for numerical simulations to reproduce.

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“…Mergers are known to be rare at low redshifts and are found to produce insignificant mass growth (∼ 0.02 dex/Gyr or less) at recent epochs (De Propris et al 2014). Further, our green valley galaxies typically have SSFR ∼ 10 −10.5 yr −1 , i.e.…”

Section: Sample Selectionmentioning

confidence: 84%

Galaxy and Mass Assembly (GAMA): Morphological transformation of galaxies across the green valley

Bremer

Phillipps

Kelvin

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We explore constraints on the joint photometric and morphological evolution of typical low redshift galaxies as they move from the blue cloud through the green valley and onto the red sequence. We select GAMA survey galaxies with 10.25 < log(M * /M ) < 10.75 and z < 0.2 classified according to their intrinsic u * − r * colour. From single component Sérsic fits, we find that the stellar mass-sensitive K−band profiles of red and green galaxy populations are very similar, while g−band profiles indicate more disk-like morphologies for the green galaxies: apparent (optical) morphological differences arise primarily from radial mass-to-light ratio variations. Two-component fits show that most green galaxies have significant bulge and disk components and that the blue to red evolution is driven by colour change in the disk. Together, these strongly suggest that galaxies evolve from blue to red through secular disk fading and that a strong bulge is present prior to any decline in star formation. The relative abundance of the green population implies a typical timescale for traversing the green valley ∼ 1 − 2 Gyr and is independent of environment, unlike that of the red and blue populations. While environment likely plays a rôle in triggering the passage across the green valley, it appears to have little effect on time taken. These results are consistent with a green valley population dominated by (early type) disk galaxies that are insufficiently supplied with gas to maintain previous levels of disk star formation, eventually attaining passive colours. No single event is needed quench their star formation.

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Galaxy and Mass Assembly (GAMA): merging galaxies and their properties

Cited by 27 publications

References 108 publications

Galaxy And Mass Assembly (GAMA): the effect of close interactions on star formation in galaxies

Galaxy And Mass Assembly (GAMA): the effect of close interactions on star formation in galaxies

Stellar mass functions of galaxies, discs and spheroids atz∼ 0.1

Galaxy and Mass Assembly (GAMA): Morphological transformation of galaxies across the green valley

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