A study of major mergers using a multi‐phase ISM code

Weniger, J.; Theis, Ch.; Harfst, Stefan

doi:10.1002/asna.200911283

Cited by 4 publications

(13 citation statements)

References 23 publications

(30 reference statements)

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“…To gauge the importance of different implementations of a Milky Way sized disc in a merger simulation, we also use a single merger simulation and isolated disc simulation from Weniger, Theis & Harfst (2009), also converted to an H i column density map. The code, assumed physics and time‐scales are different for the Weniger simulations (see ).…”

Section: Simulations Of Merging and Isolated Spiral Discsmentioning

confidence: 99%

“…The collisionless model of Kuijken & Dubinski (1995) realizes an equilibrium configuration but in this case, the equilibrium is affected by adding the ISM. Therefore, Weniger et al (2009) first follow the system's evolution, until quasi‐equilibrium is established. The numerical integration is done by means of a tree‐sph code combined with the sticky particle method (Theis & Hensler 1993).…”

Section: Simulations Of Merging and Isolated Spiral Discsmentioning

confidence: 99%

“…Time‐steps are 10 and 50 Myr for the isolated disc and merger simulation, respectively. For more details we refer the reader to Harfst et al (2006) and Weniger et al (2009).…”

Section: Simulations Of Merging and Isolated Spiral Discsmentioning

confidence: 99%

“…The suite of simulations of isolated and merging discs from Cox et al (2006a) as well as the implementation check from Weniger et al (2009) are limited in their scope of disc (and merger) properties, i.e. only a large, gas‐rich spiral disc colliding with its twin or evolving passively.…”

Section: Simulations Of Merging and Isolated Spiral Discsmentioning

confidence: 99%

“…We have run four isolated discs and eight merger simulations over a time of 2.5 Gyr (Cox et al 2006a) and a single simulation of a major merger and one isolated face‐on disc that ran for 3 Gyr (Weniger et al 2009). The resulting tables of morphological parameters over time can be found in Appendices C and D (see Supporting Information) for both isolated and merging discs.…”

Section: H I Morphology Of Major Mergersmentioning

confidence: 99%

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Quantified H i morphology - III. Merger visibility times from H i in galaxy simulations

Holwerda

Pirzkal

Cox

et al. 2011

Monthly Notices of the Royal Astronomical Society

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Major mergers of disc galaxies are thought to be a substantial driver in galaxy evolution. To trace the fraction and rate of galaxy mergers over cosmic times, several observational techniques have been developed over the last decade, including parametrized morphological selection. We apply this morphological selection of mergers to 21 cm radio emission line (H i) column density images of spiral galaxies in nearby surveys. In this paper, we investigate how long a 1:1 merger is visible in H i from N‐body simulations. We evaluate the merger visibility times for selection criteria based on four parameters: Concentration, Asymmetry, M20 and the Gini parameter of the second‐order moment of the flux distribution (GM). Of three selection criteria used in the literature, one based on Concentration and M20 works well for the H i perspective with a merger time‐scale of 0.4 Gyr. Of the three selection criteria defined in our previous paper, the GM performs well and cleanly selects mergers for 0.69 Gyr. The other two criteria (Asymmetry–M20 and Concentration–M20) select isolated discs as well, but perform best for face‐on, gas‐rich discs (Tmgr∼ 1 Gyr). The different visibility scales can be combined with the selected fractions of galaxies in any large H i survey to obtain merger rates in the nearby Universe. All‐sky surveys such as the Widefield ASKAP L‐band Legacy All‐sky Blind surveY (WALLABY) with the Australian SKA Pathfinder (ASKAP) and the Medium Deep Survey with the APERture Tile In Focus (APERTIF) instrument on Westerbork are set to revolutionize our perspective on neutral hydrogen and will provide an accurate measure of the merger fraction and rate of the present epoch.

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Section: Simulations Of Merging and Isolated Spiral Discsmentioning

confidence: 99%

Section: Simulations Of Merging and Isolated Spiral Discsmentioning

confidence: 99%

“…Time‐steps are 10 and 50 Myr for the isolated disc and merger simulation, respectively. For more details we refer the reader to Harfst et al (2006) and Weniger et al (2009).…”

Section: Simulations Of Merging and Isolated Spiral Discsmentioning

confidence: 99%

Section: Simulations Of Merging and Isolated Spiral Discsmentioning

confidence: 99%

Section: H I Morphology Of Major Mergersmentioning

confidence: 99%

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Quantified H i morphology - III. Merger visibility times from H i in galaxy simulations

Holwerda

Pirzkal

Cox

et al. 2011

Monthly Notices of the Royal Astronomical Society

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Shining Light on Merging Galaxies. I. The Ongoing Merger of a Quasar With a “Green Valley” Galaxy

Silva¹,

Prochaska²,

Rosario³

et al. 2011

ApJ

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Serendipitous observations of a pair z = 0.37 interacting galaxies (one hosting a quasar) show a massive gaseous bridge of material connecting the two objects. This bridge is photoionized by the quasar (QSO) revealing gas along the entire projected 38 h −1 72 kpc sightline connecting the two galaxies. The emission lines that result give an unprecedented opportunity to study the merger process at this redshift. We determine the kinematics, ionization parameter (log U ≈ −2.5 ± 0.03), column density (N H,⊥ ≈ 10 21 cm −2 ), metallicity ([M/H]≈ −0.20 ± 0.15), and mass (≈ 10 8 M ⊙ ) of the gaseous bridge. We simultaneously constrain properties of the QSO-host (M DM > 8.8 × 10 11 ) and its companion galaxy (M DM > 2.1 × 10 11 ; M ⋆ ∼ 2 × 10 10 M ⊙ ; stellar burst age=300 − 800 Myr; SFR∼ 6 M ⊙ yr −1 ; and metallicity 12 + log(O/H)=8.64 ± 0.2). The general properties of this system match the standard paradigm of a galaxy-galaxy merger caught between first and second passage while one of the galaxies hosts an active quasar. The companion galaxy lies in the so-called 'green valley', with a stellar population consistent with a recent starburst triggered during the first passage of the merger and has no detectable AGN activity. In addition to providing case-studies of quasars associated with galaxy mergers, quasar/galaxy pairs with QSO-photoionized tidal bridges such as this one offer unique insights into the galaxy properties while also distinguishing an important and inadequately understood phase of galaxy evolution.

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Quantified H i morphology - II. Lopsidedness and interaction in WHISP column density maps

Holwerda¹,

Pirzkal²,

Blok³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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Lopsidedness of the gaseous disc of spiral galaxies is a common phenomenon in disc morphology, profile and kinematics. Simultaneously, the asymmetry of a galaxy’s stellar disc, in combination with other morphological parameters, has seen extensive use as an indication of recent merger or interaction in galaxy samples. Quantified morphology of stellar spiral discs is one avenue to determine the merger rate over much of the age of the Universe. In this paper, we measure the quantitative morphology parameters for the H i column density maps from the Westerbork observations of neutral Hydrogen in Irregular and SPiral galaxies (WHISP). These are Concentration, Asymmetry, Smoothness, Gini, M20 and one addition of our own, the Gini parameter of the second‐order moment (GM). Our aim is to determine if lopsided or interacting discs can be identified with these parameters. Our sample of 141 H i maps have all previous classifications on their lopsidedness and interaction. We find that the Asymmetry, M20 and our new GM parameter correlate only weakly with the previous morphological lopsidedness quantification. These three parameters may be used to compute a probability that an H i disc is morphologically lopsided but not unequivocally to determine it. However, we do find that the question whether or not an H i disc is interacting can be settled well using morphological parameters. Parameter cuts from the literature do not translate from ultraviolet to H i directly but new selection criteria using combinations of Asymmetry and M20 or Concentration and M20 work very well. We suggest that future all‐sky H i surveys may use these parameters of the column density maps to determine the merger fraction and hence rate in the local Universe with a high degree of accuracy.

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A study of major mergers using a multi‐phase ISM code

Cited by 4 publications

References 23 publications

Quantified H i morphology - III. Merger visibility times from H i in galaxy simulations

Quantified H i morphology - III. Merger visibility times from H i in galaxy simulations

Shining Light on Merging Galaxies. I. The Ongoing Merger of a Quasar With a “Green Valley” Galaxy

Quantified H i morphology - II. Lopsidedness and interaction in WHISP column density maps

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