On the nature of the H ii regions in the extended ultraviolet disc of NGC 4625

Goddard, Q. E.; Bresolin, Fabio; Kennicutt, Robert C.; Ryan-Weber, E. V.; Rosales-Ortega, F. F.

doi:10.1111/j.1365-2966.2010.17990.x

Cited by 38 publications

(63 citation statements)

References 59 publications

(148 reference statements)

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“…In addition, when the observations are deep enough to investigate the outskirts of galaxies, it has been often found that the metallicity tends to reach a plateau: in external galaxies whose gradients are marked by H ii regions Goddard et al 2011;Werk et al 2011) and in our own Galaxy using open clusters (Sestito et al 2006;Magrini et al 2009a;Lépine et al 2011), H ii regions (Vilchez & Esteban 1996), and PNe (Maciel & Quireza 1999) 1 . If we focus on regions within the galactic optical radius, where the gradients are clearly negative, the most important open questions are: How was the present time radial gradient established?…”

Section: Introductionmentioning

confidence: 99%

Metallicity gradients in local Universe galaxies: Time evolution and effects of radial migration

Magrini

Coccato²,

Stanghellini

et al. 2016

A&A

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Context. Our knowledge of the shape of radial metallicity gradients in disc galaxies has recently improved. Conversely, the understanding of their time evolution is more complex, since it requires analysis of stellar populations with different ages or systematic studies of galaxies at different redshifts. In the local Universe, H ii regions and planetary nebulae (PNe) are important tools to investigate radial metallicity gradients in disc galaxies. Aims. We present an in-depth study of all nearby spiral galaxies (M33, M31, NGC 300, and M81) with direct-method nebular abundances of both populations, aiming at studying the evolution of their radial metallicity gradients. For the first time, we also evaluate the radial migration of PN populations.Methods. For the selected galaxies, we analysed H ii region and PN properties to: determine whether oxygen in PNe is a reliable tracer for past interstellar medium (ISM) composition; homogenise published datasets; estimate the migration of the oldest stellar populations; and determine the overall chemical enrichment and slope evolution. Results. We confirm that oxygen in PNe is a reliable tracer for past ISM metallicity. We find that PN gradients are flatter than or equal to those of H ii regions. When radial motions are negligible, this result provides a direct measurement of the time evolution of the gradient. For galaxies with dominant radial motions, we provide upper limits on the gradient evolution. Finally, the total metal content increases with time in all target galaxies, and early morphological types have a larger increment Δ(O/H) than late-type galaxies. Conclusions. Our findings provide important constraints to discriminate among different galactic evolutionary scenarios, favouring cosmological models with enhanced feedback from supernovae. The advent of extremely large telescopes allows us to include galaxies in a wider range of morphologies and environments, thus putting firmer constraints on galaxy formation and evolution scenarios.

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Section: Introductionmentioning

confidence: 99%

Metallicity gradients in local Universe galaxies: Time evolution and effects of radial migration

Magrini

Coccato²,

Stanghellini

et al. 2016

A&A

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“…Although the surface brightness does not show any flattening associated with the oxygen abundances, colors also have a U-shape at the outer regions of disks, especially for galaxies with masses similar to the Milky Way (MW). In addition, several investigations both in our MW (Vilchez & Esteban 1996) and in nearby galaxies (Bresolin et al 2009(Bresolin et al , 2012Rosales-Ortega et al 2011;Goddard et al 2011;Marino et al 2012;Sánchez et al 2012b) have reported a shallower oxygen abundance gradient (or flattening) in the outskirts, beyond ∼2 effective radii, R eff . In general, these deviations to the universal abundance gradient are explained in terms of variations of the in situ gas density or effective SF history, the presence of a bar, or coincidence with the corotation radius.…”

Section: Introductionmentioning

confidence: 99%

Outer-disk reddening and gas-phase metallicities: The CALIFA connection

Marino

Paz

Sanchez

et al. 2015

A&A

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We study, for the first time in a statistically significant and well-defined sample, the relation between the outer-disk ionized-gas metallicity gradients and the presence of breaks in the surface brightness profiles of disk galaxies. Sloan Digital Sky Survey (SDSS) g -and r -band surface brightness, (g -r ) color, and ionized-gas oxygen abundance profiles for 324 galaxies within the Calar Alto Legacy Integral Field Area (CALIFA) survey are used for this purpose. We perform a detailed light-profile classification, finding that 84% of our disks show down-or up-bending profiles (Type II and Type III, respectively), while the remaining 16% are well fitted by one single exponential (Type I). The analysis of the color gradients at both sides of this break shows a U-shaped profile for most Type II galaxies with an average minimum (g − r ) color of ∼0.5 mag and an ionized-gas metallicity flattening associated with it only in the case of low-mass galaxies. Comparatively, more massive systems show a rather uniform negative metallicity gradient. The correlation between metallicity flattening and stellar mass for these systems results in p-values as low as 0.01. Independent of the mechanism having shaped the outer light profiles of these galaxies, stellar migration or a previous episode of star formation in a shrinking star-forming disk, it is clear that the imprint in their ionized-gas metallicity was different for low-and high-mass Type II galaxies. In the case of Type III disks, a positive correlation between the change in color and abundance gradient is found (the null hypothesis is ruled out with a p-value of 0.02), with the outer disks of Type III galaxies with masses ≤10 10 M showing a weak color reddening or even a bluing. This is interpreted as primarily due to a mass downsizing effect on the population of Type III galaxies that recently experienced an enhanced inside-out growth.

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“…but without the depth needed for precise color measurements in the outer disk (Swaters & Balcells 2002;Gil de Paz et al 2005). Abundances indicate a discontinuity in metallicity at R 25 and a nearly constant outer disk abundance of ∼0.2 Z (Goddard et al 2011).…”

Section: Ngc 4625mentioning

confidence: 99%

“…inner disk until it is no longer detected. For comparison we plot the gas phase metallicity gradient measured by Goddard et al (2011), which, like the multi-wavelength profiles, shows a break at the edge of the inner disk.…”

Section: Multi-wavelength Profilesmentioning

confidence: 99%

“…We selected a Chabrier IMF (Chabrier 2003) with mass limits of 0.1 and 100 M and two stellar metallicities based on the gas phase metallicities derived for NGC 4625's outer disk (Goddard et al 2011 Bresolin (2007), Goddard et al (2011) measured that the outer disk abundance ranges from 0.4 Z to 0.2 Z . The comparison is shown in Figure 6, where Bruzual & Charlot (2003) Figure 6 shows that the FUV − 3.6 μm color provides the stronger constraint on the age of the stellar population and the FUV − NUV color provides the stronger constraint on the star formation history.…”

Section: Comparison To Stellar Populations Modelsmentioning

confidence: 99%

See 1 more Smart Citation

A Pilot Study Using Deep Infrared Imaging to Constrain the Star Formation History of the Xuv Stellar Populations in NGC 4625

Bush

Kennicutt

Johnson

et al. 2014

ApJ

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In a ΛCDM universe, disk galaxies' outer regions are the last to form. Characterizing their contents is critical for understanding the ongoing process of disk formation, but observing outer disk stellar populations is challenging due to their low surface brightness. We present extremely deep 3.6 μm observations (Spitzer/Infrared Array Camera) of NGC 4625, a galaxy known for its radially extended ultraviolet-emitting stellar population. We combine the new imaging with archival UV imaging from the GALEX mission to derive multi-wavelength radial profiles for NGC 4625 and compare them to stellar populations models. The colors can be explained by the young stellar population that is responsible for the UV emission and indicate that the current star formation rates in the outermost disk are recent. Extended star formation in NGC 4625 may have been initiated by an interaction with neighboring galaxies NGC 4618 and NGC 4625a, supporting speculation that minor interactions are a common trigger for outer disk star formation and late stage disk growth.

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On the nature of the H ii regions in the extended ultraviolet disc of NGC 4625

Cited by 38 publications

References 59 publications

Metallicity gradients in local Universe galaxies: Time evolution and effects of radial migration

Metallicity gradients in local Universe galaxies: Time evolution and effects of radial migration

Outer-disk reddening and gas-phase metallicities: The CALIFA connection

A Pilot Study Using Deep Infrared Imaging to Constrain the Star Formation History of the Xuv Stellar Populations in NGC 4625

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