Metallicity and Nuclear Star Formation in Nearby Galaxy Pairs: Evidence for Tidally Induced Gas Flows

By Lisa J. Kewley, Margaret J. Geller, E. Barton. 2005

178 citations recorded by the source corpus.

We derive the first luminosity-metallicity (L-Z) relation for a large objectively selected sample of local galaxy pairs, and we compare the L-Z relation of the pairs with the relation for the Nearby Field Galaxy Survey. Galaxy pair members with small projected separations (s < 20 kpc h-1) have systematically lower metallicities (∼0.2 dex on average) than either the field galaxies or more widely separated pairs at the same luminosity. There is a strong correlation between metallicity and central burst strength in the galaxy pairs. All five galaxies in the pairs sample with strong central bursts have close companions and metallicities lower than the comparable field galaxies. Our results provide strong observational evidence for a merger scenario in which galaxy interactions cause gas flows toward the central regions, carrying less enriched gas from the outskirts of the galaxy into the central regions. The less enriched gas dilutes the preexisting nuclear gas to produce a lower metallicity than would be obtained prior to the interaction. These gas flows trigger central bursts of star formation, causing strong central burst strengths and possibly aiding the formation of blue bulges. We show that the timescale and central gas dilution required by this scenario are consistent with predictions from hydrodynamic merger models.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/ec95eb8a206733bb9ed20448ea726495a81b681d

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. R. Dav'e
4. R. Somerville
5. A. Dekel
6. T. Naab
7. Volker Springel
8. Thomas J. Cox

In Instrumentation

1. P. Hopkins
2. L. Hernquist
3. R. Dav'e
4. A. Dekel
5. Thomas J. Cox
6. T. Naab
7. R. Somerville
8. Volker Springel

Citations in the corpus

• METALLICITY GRADIENTS AND GAS FLOWS IN GALAXY PAIRS (2010, methodology): “Our pairs were selected to (a) span a range of positions on the luminositymetallicity relation in Kewley et al. (2006a), (b) contain at least one galaxy with suitable orientation for metallicity gradient analysis, and (c) to span a range of galaxy properties that may influence metallicity gradients…”
• Galaxy Zoo: the properties of merging galaxies in the nearby Universe – local environments, colours, masses, star formation rates and AGN activity (2009, unknown): “To separate the different kinds of central activity in our merger galaxies we followed the demarcations between purely star-forming systems, transition objects and truly active nuclei drawn by Kauffmann et al. (2003b) and Kewley et al. (2006).”
• The SINS/zC-SINF Survey of z ∼ 2 Galaxy Kinematics: SINFONI Adaptive Optics–assisted Data and Kiloparsec-scale Emission-line Properties (2018, result): “By analogy with results in nearby SFGs (e.g. Chien et al. 2007; Kewley et al. 2006, 2010; Rupke et al. 2010; Rich et al. 2012), and in line with predictions from theoretical models and simulations (e.g., Rahimi et al. 2011; Kobayashi & Nakasato 2011; Few et al. 2012; Pilkington et al. 2012; Torrey…”
• Clues to the Origin of the Mass-Metallicity Relation: Dependence on Star Formation Rate and Galaxy Size (2007, background): “While galaxy interactions can perturb the LZR and MZR (Kewley et al. 2006; Rupke et al. 2007), the dependence of this effect on is the oppositerh to that seen in Figure 2 (Ellison et al. 2007).”
• THE IMPACT OF INTERACTIONS, BARS, BULGES, AND ACTIVE GALACTIC NUCLEI ON STAR FORMATION EFFICIENCY IN LOCAL MASSIVE GALAXIES (2012, background): “Interactions with nearby companions can also induce gas flows that create high levels of star formation in the central regions of galaxies (e.g. Mihos & Hernquist 1996; Kewley et al. 2006).”
• Metallicity gradients in disks - Do galaxies form inside-out? (2012, background): “Observations by Cooper et al. (2008) show that higher metallicity galaxies are more abundant in group enviroments and Kewley et al. (2006) showed that interacting pairs of galaxies have systematically lower metallicities (∼0.2 dex lower) than field galaxies or more loosely associated pairs.”
• Metallicity gradients in local field star-forming galaxies: insights on inflows, outflows, and the coevolution of gas, stars and metals (2015, methodology): “We remove galaxies with AGN from our mother sample using the optical line ratios [NII ]/Hα and [OIII ]/Hβ (Kewley et al. 2006b).”
• GAS-PHASE OXYGEN GRADIENTS IN STRONGLY INTERACTING GALAXIES. I. EARLY-STAGE INTERACTIONS (2010, methodology): “A prediction of this model is that this gas redistribution dramatically flattens the initial radial metallicity gradient very shortly after first pericenter (Kewley et al. 2006a; Rupke et al. 2010).”
• The impact of gas inflows on star formation rates and metallicities in barred galaxies (2011, background): “…from https://academ ic.oup.com /m nras/article-abstract/416/3/2182/963138 by guest on 11 D ecem ber 2018 lower than in galaxies with no close companion (Kewley et al 2006; Ellison et al. 2008a; Michel-Dansac et al. 2008), and that abundance gradients are flatter (Kewley et al. 2010; Rupke, Kewley…”
• Galaxy pairs in the Sloan Digital Sky Survey – V. Tracing changes in star formation rate and metallicity out to separations of 80 kpc (2012, methodology): “While our median values are not nearly as low as those found in Kewley et al. (2006), (between −0.03 and −0.04 dex within 20 h−170 kpc for our total and disturbed subsamples respectively), the unbinned points in Figure 2 show a significant population of galaxies at offsets of −0.1 to −0.2 dex, with…”
• THEORETICAL EVOLUTION OF OPTICAL STRONG LINES ACROSS COSMIC TIME (2013, methodology): “…at High Redshift In local galaxies, semi-empirical and theoretical classification lines are used to successfully separate star-forming galaxies from those containing an AGN or shock excitation (e.g., Veilleux & Osterbrock 1987; Kewley et al. 2001b; Kauffmann et al. 2003; Kewley et al. 2006b).”
• Timing the starburst–AGN connection (2010, methodology): “For star-forming galaxies and composite AGN (where emission from both star formation and an AGN is present), an intrinsic Hα/Hβ ratio of 2.87 is assumed; for pure AGN we use a slightly higher Hα/Hβ = 3.1 (Osterbrock 1989; Kewley et al. 2006b).”
• Galaxy pairs in the Sloan Digital Sky Survey – II. The effect of environment on interactions (2010, background): “Kewley et al. (2006) measure a colour offset of the inner versus outer disk and find that this correlates with a decrease in metallicity, supporting the picture of gas inflow as a trigger.”
• GALAXY PAIRS IN THE SLOAN DIGITAL SKY SURVEY. I. STAR FORMATION, ACTIVE GALACTIC NUCLEUS FRACTION, AND THE LUMINOSITY/MASS–METALLICITY RELATION (2008, methodology): “The main difference between the SDSS sample and the NFGS/CfA sample studied by Kewley et al. (2006a) is that the latter had nuclear spectra with CF ∼ 10%.”
• THE METALLICITY EVOLUTION OF INTERACTING GALAXIES (2011, methodology): “In these simulations, the nuclear metallicity increases, contrary to what is observed in the local Universe, suggesting that the interacting galaxy MZ relation may evolve differently at high redshifts.”
• THE MASS–METALLICITY RELATION WITH THE DIRECT METHOD ON STACKED SPECTRA OF SDSS GALAXIES (2012, background): “Major mergers drive in considerable amounts of low metallicity gas from large radii, which dilutes the metallicity of the galaxy and triggers vigorous star formation (e.g., Kewley et al. 2006, 2010; Torrey et al. 2012).”
• Galaxy pairs in the Sloan Digital Sky Survey – VIII. The observational properties of post-merger galaxies (2013, methodology): “We can then apply the LINER diagnostic of Kewley et al. (2006), allowing us to construct a sample of Seyfert-dominated spectra.”