The stellar mass assembly of galaxies in the Illustris simulation: growth by mergers and the spatial distribution of accreted stars

Rodríguez-Gómez, Vicente; Pillepich, Annalisa; Sales, Laura V.; Genel, Shy; Vogelsberger, Mark; Zhu, Qirong; Wellons, Sarah; Nelson, Dylan; Torrey, Paul; Springel, Volker; Ma, Chung‐Pei; Hernquist, Lars

doi:10.1093/mnras/stw456

Cited by 448 publications

(542 citation statements)

References 87 publications

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“…Apart from the evident trend between facc and stellar mass, which has already been discussed in Rodriguez-Gomez et al (2016), Fig. 6 shows that -at any fixed stellar mass -facc is negatively correlated with the mean merger gas fraction and the mean lookback time (i.e.…”

Section: Other Merger Statisticsmentioning

confidence: 55%

“…The shaded regions indicate the 16th to 84th percentile range, or 1σ, at a fixed stellar mass. Similar plots have already been shown in Rodriguez-Gomez et al (2016), except that we now separate galaxies by adopting a fixed threshold at κrot = 0.5, instead of using the median value of κrot at a fixed stellar mass. Fig.…”

Section: The Ex Situ Stellar Mass Fractionmentioning

confidence: 57%

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The role of mergers and halo spin in shaping galaxy morphology

Rodríguez-Gómez

Sales

Genel

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Mergers and the spin of the dark matter halo are factors traditionally believed to determine the morphology of galaxies within a ΛCDM cosmology. We study this hypothesis by considering approximately 18,000 central galaxies at z = 0 with stellar masses M * = 10 9 -10 12 M selected from the Illustris cosmological hydrodynamic simulation. The fraction of accreted stars -which measures the importance of massive, recent and dry mergers -increases steeply with galaxy stellar mass, from less than 5 per cent in dwarfs to 80 per cent in the most massive objects, and the impact of mergers on galaxy morphology increases accordingly. For galaxies with M * 10 11 M , mergers have the expected effect: if gas-poor they promote the formation of spheroidal galaxies, whereas gas-rich mergers favour the formation and survivability of massive discs. This trend, however, breaks at lower masses. For objects with M * 10 11 M , mergers do not seem to play any significant role in determining the morphology, with accreted stellar fractions and mean merger gas fractions that are indistinguishable between spheroidal and disc-dominated galaxies. On the other hand, halo spin correlates with morphology primarily in the least massive objects in the sample (M * 10 10 M ), but only weakly for galaxies above that mass. Our results support a scenario where (1) mergers play a dominant role in shaping the morphology of massive galaxies, (2) halo spin is important for the morphology of dwarfs, and (3) the morphology of medium-sized galaxies -including the Milky Way -shows little dependence on galaxy assembly history or halo spin, at least when these two factors are considered individually.

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Section: Other Merger Statisticsmentioning

confidence: 55%

Section: The Ex Situ Stellar Mass Fractionmentioning

confidence: 57%

The role of mergers and halo spin in shaping galaxy morphology

Rodríguez-Gómez

Sales

Genel

et al. 2017

Monthly Notices of the Royal Astronomical Society

Self Cite

189

157

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“…Genel et al (2014) highlighted successes with satellite number densities, baryon content versus radius, and specific SFRs up to z = 8. Rodriguez-Gomez et al (2015) showed that the galaxy merger rate compares favorably to observations at z < 1 and predicted its evolution as a function of time, mass, and mass ratio. In this paper, we present results from the Illustris-1 simulation (the highest resolution) but have confirmed that our results are qualitatively unchanged when using Illustris-2 catalogs instead.…”

Section: Methodsmentioning

confidence: 78%

“…tions from mergers themselves (e.g., Rodriguez-Gomez et al 2016). If this accretion is also significant, then the effect demonstrated in this section would be even stronger.…”

Section: Rapid Stellar Mass Growthmentioning

confidence: 74%

“…This implies that the pair fraction trend we measure is driven by real merg- Red triangles show a reconstruction of the remnant formation rate implied by the mock-observed pairs, described in Section 4.1. Only the blue squares and red triangles adequately match the evolution in merger rates measured by Rodriguez-Gomez et al (2015), and therefore we infer a rapidly evolving pair observability timescale τ .…”

Section: Merger Ratesmentioning

confidence: 80%

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Massive close pairs measure rapid galaxy assembly in mergers at high redshift

Snyder

Lotz

Rodríguez-Gómez

et al. 2017

Monthly Notices of the Royal Astronomical Society

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136

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We compare mass-selected close pairs at z > 1 with the intrinsic galaxy merger rate in the Illustris Simulations. To do so, we construct three 140 arcmin 2 lightcone catalogs and measure pair fractions, finding that they change little or decrease with increasing redshift at z > 1. Consistent with current surveys, this trend requires a decrease in the merger-pair observability time, roughly as τ ∝ (1 + z) −2 , in order to measure the merger rates of the same galaxies. This implies that major mergers are more common at high redshift than implied by the simplest arguments assuming a constant observability time. Several effects contribute to this trend: (1) The fraction of massive, major (4:1) pairs which merge by today increases weakly from ∼ 0.5 at z = 1 to ∼ 0.8 at z = 3. (2) The median time elapsed between an observed pair and final remnant decreases by a factor of two from z ∼ 1 to z ∼ 3. (3) An increasing specific star formation rate (sSFR) decreases the time during which common stellarmass based pair selection criteria could identify the mergers. The average orbit of the pairs at observation time varies only weakly, suggesting that the dynamical time is not varying enough to account by itself for the pair fraction trends. Merging pairs reside in dense regions, having overdensity δ ∼ 10 to ∼ 100 times greater than the average massive galaxy. We forward model the pairs to reconstruct the merger remnant production rate, showing that it is consistent with a rapid increase in galaxy merger rates at z > 1.

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Imaging and photometric studies of NGC 1316 (Fornax A) using Astrosat/UVIT

Vagshette¹,

Naik

Kumari

et al. 2021

J Astrophys Astron

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We present imaging and photometric studies of the radio galaxy NGC 1316 (Fornax A) using high spatial resolution near-ultraviolet (NUV) and far-ultraviolet (FUV) imaging telescopes of the first Indian multi-wavelength space observatory AstroSat. The residual maps of UV emission obtained from the subtraction of smooth models witness peculiar features within the central few kpc (1-2 kpc) region. The spatial correspondence between the radio emission maps and FUV imaging study reveal that the UV emitting sources are displaced away from the centre by the AGN outburst (radio jet). The presence of rims and clumpy structures in the outskirt of this galaxy delineate that the galaxy has acquired a large fraction of gas through merger-like events and is still in the process of settling. The estimates of the star formation rates (SFR) using FUV and NUV luminosities are found to be 0.15 M yr À1 and 0.36 M yr À1 , respectively, and provide the lower limit due to the screen effect. The estimated lower rates of SFR in this galaxy probably represent its quenching due to the AGN driven outflows emanating from the central engine of NGC 1316.

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The stellar mass assembly of galaxies in the Illustris simulation: growth by mergers and the spatial distribution of accreted stars

Cited by 448 publications

References 87 publications

The role of mergers and halo spin in shaping galaxy morphology

The role of mergers and halo spin in shaping galaxy morphology

Massive close pairs measure rapid galaxy assembly in mergers at high redshift

Imaging and photometric studies of NGC 1316 (Fornax A) using Astrosat/UVIT

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