The Metal-Enriched Outer Disk of NGC 2915

Werk, Jessica K.; Putman, Mary E.; Meurer, G. R.; Thilker, David A.; Allen, R. J.; Bland-Hawthorn, Joss; Kravtsov, Andrey V.; Freeman, K. C.

doi:10.1088/0004-637x/715/1/656

Cited by 56 publications

(80 citation statements)

References 56 publications

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“…Sánchez interpret this observation as an episode of gas accretion onto the tadpole head. Localized metallicity drops associated with starforming regions have also been observed in other objects, including gamma ray burst host galaxies (Levesque et al 2011;Thöne et al 2014), BCDs (Izotov et al 2009;Werk et al 2010;Sánchez Almeida et al 2014) and dwarf irregular galaxies (Haurberg et al 2013). Variations of metallicity among HII regions located at the same galactrocentric distance are not unusual even in large nearby spirals (Bresolin et al 2012;Li et al 2013); some of these variations could come from localized accretion events.…”

Section: Metallicity Inhomogeneities and Inverted Gradientsmentioning

confidence: 70%

Star formation sustained by gas accretion

Alméida

Elmegreen

Muñoz–Tuñón

et al. 2014

Astron Astrophys Rev

178

130

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Numerical simulations predict that metal-poor gas accretion from the cosmic web fuels the formation of disk galaxies. This paper discusses how cosmic gas accretion controls star formation, and summarizes the physical properties expected for the cosmic gas accreted by galaxies. The paper also collects observational evidence for gas accretion sustaining star formation. It reviews evidence inferred from neutral and ionized hydrogen, as well as from stars. A number of properties characterizing large samples of star-forming galaxies can be explained by metal-poor gas accretion, in particular, the relationship among stellar mass, metallicity, and star-formation rate (the so-called fundamental metallicity relationship). They are put forward and analyzed. Theory predicts gas accretion to be particularly important at high redshift, so indications based on distant objects are reviewed, including the global star-formation history of the universe, and the gas around galaxies as inferred from absorption features in the spectra of background sources.

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Section: Metallicity Inhomogeneities and Inverted Gradientsmentioning

confidence: 70%

Star formation sustained by gas accretion

Alméida

Elmegreen

Muñoz–Tuñón

et al. 2014

Astron Astrophys Rev

178

130

View full text Add to dashboard Cite

show abstract

“…Recently, Werk et al (2010) have reported a positive gradient in a local galaxy and proposed several scenarios to explain their discovery: (i) a radial redistribution of the metal-rich gas produced in the nucleus; (ii) supernovae blowing out metal-rich gas, enriching the IGM, then falling onto the outer parts of the disk; and (iii) the result of a past interaction.…”

Section: Observed Metallicity Gradientsmentioning

confidence: 99%

“…Werk et al 2010;Rupke et al 2010), during an interaction, metal-poor gas from the outskirts of the galaxy could radially flow towards the center and dilute the metallicity in the inner, high star-forming regions. At the same time, metal-enriched gas could be transported to the outer parts during the interaction, resulting overall in a flattening of the metallicity gradient.…”

Section: Gas Infall Ratesmentioning

confidence: 99%

MASSIV: Mass Assembly Survey with SINFONI in VVDS

Contini

Kissler-Patig

Épinat³

et al. 2012

A&A

136

166

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Aims. The estimate of radial abundance gradients in high-redshift galaxies allows to constrain their star formation history and their interplay with the surrounding intergalactic medium. Methods. We present VLT/SINFONI integral-field spectroscopy of a first sample of 50 galaxies at z ∼ 1.2 in the MASSIV survey. Using the N2 ratio between the [N ii]6584 and Hα rest-frame optical emission lines as a proxy for oxygen abundance in the interstellar medium, we measured the metallicity of the sample galaxies. We developed a tool to extract spectra in annular regions, leading to a spatially resolved estimate of the oxygen abundance in each galaxy. We were able to derive a metallicity gradient for 26 galaxies in our sample and discovered a significant fraction of galaxies with a "positive" gradient. Using a simple chemical evolution model, we derived infall rates of pristine gas onto the disks. Results. Seven galaxies display a positive gradient at a high confidence level. Four out of these are interacting, and one is a chain galaxy. We suggest that interactions might be responsible for shallowing and even inverting the abundance gradient. We also identify two interesting correlations in our sample: a) galaxies with higher gas velocity dispersion have shallower/positive gradients; and b) metal-poor galaxies tend to show a positive gradient, whereas metal-rich ones tend to show a negative one. This last observation can be explained by the infall of metal-poor gas into the center of the disks. We address the question of the origin of this infall under the influence of gas flows triggered by interactions and/or cold gas accretion. All the data published in this paper are publicly available at the time of publication following this link: http://cosmosdb.lambrate.inaf.it/VVDS-SINFONI.

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“…However, they found the metallicity gradients are weak and the merger outskirts have uniform modest abundances (typically around half solar). This is also true for the cases of ELdots in systems that are isolated like NGC 2915 (Werk et al 2010b) which consists of a blue compact dwarf galaxy surrounded by a spectacular H I disk (Meurer et al 1994;.…”

Section: Surveying Outer Disk Star Formationmentioning

confidence: 85%

Outer Disk Star Formation in HI selected Galaxies

Meurer

2016

Proc. IAU

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Abstract. The HI in galaxies often extends past their conventionally defined optical extent. I report results from our team which has been probing low intensity star formation in outer disks using imaging in Hα and ultraviolet. Using a sample of hundreds of HI selected galaxies, we confirm that outer disk HII regions and extended UV disks are common. Hence outer disks are not dormant but are dimly forming stars. Although the ultraviolet light in galaxies is more centrally concentrated than the HI, the UV/HI ratio (the Star Formation Efficiency) is nearly constant, with a slight dependency on surface brightness. This result is well accounted for in a model where disks maintain a constant stability parameter Q. This model also accounts for how the ISM and star formation are distributed in the bright parts of galaxies, and how HI appears to trace the distribution of dark matter in galaxy outskirts.

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The Metal-Enriched Outer Disk of NGC 2915

Cited by 56 publications

References 56 publications

Star formation sustained by gas accretion

Star formation sustained by gas accretion

MASSIV: Mass Assembly Survey with SINFONI in VVDS

Outer Disk Star Formation in HI selected Galaxies

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