Star formation in mergers with cosmologically motivated initial conditions

Karman, W.; Macciò, Andrea V.; Kannan, Rahul; Moster, Benjamin P.; Somerville, Rachel S.

doi:10.1093/mnras/stv1508

Cited by 15 publications

(13 citation statements)

References 123 publications

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“…In our analysis, we introduce dry (major) mergers in the evolution of Φ pass,HD , assuming that two objects in the same bin of log M can merge without triggering relevant episodes of star formation (e.g. Di Matteo et al 2005;Karman et al 2015). We set the fraction of galaxies undergoing a 1:1 merger to be equal to f dry (z), with no dependence on the stellar mass of the initial pair (Xu et al 2012).…”

Section: An Empirical Approachmentioning

confidence: 99%

The VIMOS Public Extragalactic Redshift Survey (VIPERS)

Davidzon

Cucciati

Bolzonella

et al. 2016

A&A

121

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We exploit the first public data release of VIPERS to investigate environmental effects in the evolution of galaxies between z ∼ 0.5 and 0.9. The large number of spectroscopic redshifts (more than 50 000) over an area of about 10 deg 2 provides a galaxy sample with high statistical power. The accurate redshift measurements (σ z = 0.00047(1 + z spec )) allow us to robustly isolate galaxies living in the lowest and highest density environments (δ < 0.7 and δ > 4, respectively) as defined in terms of spatial 3D density contrast δ. We estimate the stellar mass function of galaxies residing in these two environments and constrain the high-mass end (M 10 11 M ) with unprecedented precision. We find that the galaxy stellar mass function in the densest regions has a different shape than was measured at low densities, with an enhancement of massive galaxies and a hint of a flatter (less negative) slope at z < 0.8. We normalise each mass function to the comoving volume occupied by the corresponding environment and relate estimates from different redshift bins. We observe an evolution of the stellar mass function of VIPERS galaxies in high densities, while the low-density one is nearly constant. We compare these results to semi-analytical models and find consistent environmental signatures in the simulated stellar mass functions. We discuss how the halo mass function and fraction of central/satellite galaxies depend on the environments considered, making intrinsic and environmental properties of galaxies physically coupled, hence difficult to disentangle. The evolution of our lowdensity regions is described well by the formalism introduced by Peng et al. (2010, ApJ, 721, 193), and is consistent with the idea that galaxies become progressively passive because of internal physical processes. The same formalism could also describe the evolution of the mass function in the high density regions, but only if a significant contribution from dry mergers is considered.

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Section: An Empirical Approachmentioning

confidence: 99%

The VIMOS Public Extragalactic Redshift Survey (VIPERS)

Davidzon

Cucciati

Bolzonella

et al. 2016

A&A

121

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“…Our definition of the SF enhancement include stars formed in the satellite as well. A more sophisticated analysis of the merger driven star formation rates is presented in a complementary work (Karman et al 2015), but the general trends are investigated here.…”

Section: Sites Of Star Formationmentioning

confidence: 99%

From discs to bulges: effect of mergers on the morphology of galaxies

Kannan¹,

Macciò²,

Fontanot³

et al. 2015

Mon. Not. R. Astron. Soc.

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We study the effect of mergers on the morphology of galaxies by means of the simulated merger tree approach first proposed by Moster et al. This method combines N-body cosmological simulations and semi-analytic techniques to extract realistic initial conditions for galaxy mergers. These are then evolved using high resolution hydrodynamical simulations, which include dark matter, stars, cold gas in the disc and hot gas in the halo. We show that the satellite mass accretion is not as effective as previously thought, as there is substantial stellar stripping before the final merger. The fraction of stellar disc mass transferred to the bulge is quite low, even in the case of a major merger, mainly due to the dispersion of part of the stellar disc mass into the halo. We confirm the findings of Hopkins et al., that a gas rich disc is able to survive major mergers more efficiently. The enhanced star formation associated with the merger is not localised to the bulge of galaxy, but a substantial fraction takes place in the disc too. The inclusion of the hot gas reservoir in the galaxy model contributes to reducing the efficiency of bulge formation. Overall, our findings suggest that mergers are not as efficient as previously thought in transforming discs into bulges. This possibly alleviates some of the tensions between observations of bulgeless galaxies and the hierarchical scenario for structure formation.

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“…In some models, producing an elliptical-like remnant with an old stellar population requires a powerful AGN to clear out the left-over gas Hopkins et al 2006;Sparre & Springel 2017). When pre-existing hot gaseous halos are included in merger simulations, infall from the halo helps sustain star formation, but the efficiency of star formation is decreased because of heating of halo gas by shocks and by the conversion of satellite orbital energy into heat (Sinha & Holley-Bockelmann 2009;Moster et al 2011;Karman et al 2015;Hwang & Park 2015). Model predictions depend upon the resolution of the simulation and the details of the calculations, with higher resolution models including multiphase interstellar gas producing more efficient star formation (Teyssier, Chapon, & Bournaud 2010;Hopkins et al 2013;Hayward et al 2014;Sparre & Springel 2016).…”

Section: Introductionmentioning

confidence: 99%

Diffuse X-Ray-emitting Gas in Major Mergers

Smith

Campbell

Struck

et al. 2018

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Using archived data from the Chandra X-ray telescope, we have extracted the diffuse Xray emission from 49 equal-mass interacting/merging galaxy pairs in a merger sequence, from widely separated pairs to merger remnants. After removal of contributions from unresolved point sources, we compared the diffuse thermal X-ray luminosity from hot gas (L X (gas)) with the global star formation rate (SFR). After correction for absorption within the target galaxy, we do not see strong trend of L X (gas)/SFR with SFR or merger stage for galaxies with SFR > 1 M ⊙ yr −1 . For these galaxies, the median L X (gas)/SFR is 5.5 × 10 39 ((erg s −1 )/M ⊙ yr −1 )), similar to that of normal spiral galaxies. These results suggest that stellar feedback in star forming galaxies reaches an approximately steady state condition, in which a relatively constant fraction of about 2% of the total energy output from supernovae and stellar winds is converted into X-ray flux. Three late-stage merger remnants with low SFRs and high K band luminosities (L K ) have enhanced L X (gas)/SFR; their UV/IR/optical colors suggest that they are post-starburst galaxies, perhaps in the process of becoming ellipticals. Systems with L K < 10 10 L ⊙ have lower L X (gas)/SFR ratios than the other galaxies in our sample, perhaps due to lower gravitational fields or lower metallicities. We see no relation between L X (gas)/SFR and Seyfert activity in this sample, suggesting that feedback from active galactic nuclei is not a major contributor to the hot gas in our sample galaxies.

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Star formation in mergers with cosmologically motivated initial conditions

Cited by 15 publications

References 123 publications

The VIMOS Public Extragalactic Redshift Survey (VIPERS)

The VIMOS Public Extragalactic Redshift Survey (VIPERS)

From discs to bulges: effect of mergers on the morphology of galaxies

Diffuse X-Ray-emitting Gas in Major Mergers

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