Metallicities in the Outer Regions of Spiral Galaxies

Bresolin, Fabio

doi:10.1007/978-3-319-56570-5_5

Cited by 12 publications

(11 citation statements)

References 141 publications

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“…The oxygen abundances measured for the H ii regions in the outer disk of NGC 1058 confirm the flattening of the radial metallicity gradient taking place around the isophotal radius found for similar, extended disk galaxies (Bresolin 2017).…”

Section: Discussionsupporting

confidence: 78%

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Metallicity gradients in small and nearby spiral galaxies

Bresolin

2019

Monthly Notices of the Royal Astronomical Society

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Spectra of H ii regions obtained with Gemini/GMOS are used to derive the radial metallicity gradients of four small, low-mass spiral galaxies. The analysis of the outer disk of one of them, NGC 1058, uncovers the characteristic flattening found in similar extended disk galaxies. After combining these data with published long-slit observations of nearby spiral galaxies, no evidence for a dependence of the disk scale lengthnormalized metallicity gradients with stellar mass is found, down to log(M /M ) ∼ 8.5. The abundance gradients derived from these observations are compared to predictions from recent cosmological simulations of galaxy evolution, finding that in several cases the simulations fail to reproduce the mean steepening of the gradients, expressed in dex kpc −1 , with decreasing stellar mass for present-day galaxies, or do not extend to sufficiently small stellar masses for a meaningful comparison. The mean steepening of the abundance gradients (in dex kpc −1 ) with decreasing disk scale length is in qualitative agreement with predictions from the inside-out model of Boissier & Prantzos, although the predicted slopes are systematically steeper than observed. This indicates the necessity of including processes such as outflows and radial mixing in similar models of galactic chemical evolution. Published spatially resolved metallicity and photometric data of dwarf irregular galaxies suggest that significant, but transitory, metallicity gradients can develop for systems that have experienced recent (t < 100 Myr) enhanced star formation in their inner disks.

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Section: Discussionsupporting

confidence: 78%

“…Broadly speaking, these can be related to a flattening of the star formation efficiency, gas mixing from radial processes and metal-enriched infall. Speculations concerning these mechanisms have been recently summarized by Bresolin (2017), to which the reader is referred for further details.…”

Section: Gas Metallicity In Ngc 1058 and Its Extended Diskmentioning

confidence: 99%

Metallicity gradients in small and nearby spiral galaxies

Bresolin

2019

Monthly Notices of the Royal Astronomical Society

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“…These gradients typically follow an exponential decline with radius, but then often flatten in the disk outskirts, such that extremely low metallicities are uncommon; see, e.g., the review by Bresolin (2017). For example, in M83, there appears to be a metallicity agreement with our inferred metallicity for the young population.…”

Section: The Metallicity Of the Outer Disksupporting

confidence: 72%

Stellar Populations in the Outer Disk and Halo of the Spiral Galaxy M101

Mihos

Durrell

Feldmeier

et al. 2018

ApJ

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We use deep Hubble Space Telescope imaging in the outskirts of the nearby spiral M101 to study stellar populations in the galaxy's outer disk and halo. Our Advanced Camera for Surveys (ACS) field lies 17 6 (36 kpc) from the center of M101 and targets the blue "NE Plume" of M101ʼs outer disk, while the parallel Wide Field Camera 3 (WFC3) field lies at a distance of 23 3 (47 kpc) to sample the galaxy's stellar halo. The WFC3 halo field shows a well-defined red giant branch characterized by low metallicity ([M/H] =−1.7±0.2), with no evidence of young stellar populations. In contrast, the ACS disk field shows multiple stellar populations, including a young main sequence, blue and red helium-burning stars, and old RGB and asymptotic giant branch (AGB) populations. The mean metallicity of these disk stars is quite low: [M/H]=−1.3±0.2 for the RGB population, and −1.15±0.2 for the younger helium-burning sequences. Of particular interest is a bunching of stars along the BHeB sequence, indicative of an evolving cohort of massive young stars. We show that the young stellar populations in this field are well-described by a decaying burst of star formation that peaked ∼300-400 Myr ago, along with a more extended star formation history to produce the older RGB and AGB populations. These results confirm and extend the results from our previous deep surface photometry of M101ʼs outer disk, providing an important cross-check on stellar population studies using resolved stellar populations versus integrated light photometry. We discuss our results in the context of halo formation models and the interaction history of M101 and its companions.

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“…The gradient of our measurement and López-Sánchez et al ( 2006) is similarly flat across the disk. A typical, massive spiral galaxy has a metallicity gradient, using the R23 method, of order -0.4 dex R −1 25 in log(O/H), see Ho et al (2015) and reviewed in Bresolin (2017). For an exponential disk R 25 is roughly equivalent to the 90% radius.…”

Section: Possible Dynamical Drivers Of T Dep Gradientmentioning

confidence: 99%

Extreme Variation in Star Formation Efficiency Across a Compact, Starbursting Disk Galaxy

Fisher,

Bolatto,

Glazebrook

et al. 2022

Preprint

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We report on the internal distribution of star formation efficiency in IRAS 08339+6517 (hereafter IRAS08), using ∼200 pc resolution CO(2-1) observations from NOEMA. The molecular gas depletion time changes by 2 orders-of-magnitude from disk-like values in the outer parts to less than 10 8 yr inside the half-light radius. This translates to a star formation efficiency per free-fall time that also changes by 2 orders-of-magnitude, reaching 50-100%, different than local spiral galaxies and typical assumption of constant, low star formation efficiencies. Our target is a compact, massive disk galaxy that has SFR 10× above the z = 0 main-sequence; Toomre Q ≈ 0.5 − 0.7 and high gas velocity dispersion (σ mol ≈ 25 km s −1 ). We find that IRAS08 is similar to other rotating, starburst galaxies from the literature in the resolved Σ SF R ∝ Σ N mol relation. By combining resolved literature studies we find that distance from the main-sequence is a strong indicator of the Kennicutt-Schmidt powerlaw slope, with slopes of N ≈ 1.6 for starbursts from 100-10 4 M pc −2 . Our target is consistent with a scenario in which violent disk instabilities drive rapid inflows of gas. It has low values of Toomre-Q, and also at all radii the inflow timescale of the gas is less than the depletion time, which is consistent with the flat metallicity gradients in IRAS08. We consider these results in light of popular star formation theories, in general observations of IRAS08 find the most tension with theories in which star formation efficiency is a constant. Our results argue for the need of high spatial resolution CO observations are a larger number of similar targets.

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Metallicities in the Outer Regions of Spiral Galaxies

Cited by 12 publications

References 141 publications

Metallicity gradients in small and nearby spiral galaxies

Metallicity gradients in small and nearby spiral galaxies

Stellar Populations in the Outer Disk and Halo of the Spiral Galaxy M101

Extreme Variation in Star Formation Efficiency Across a Compact, Starbursting Disk Galaxy

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