Abundance gradients in elliptical galaxies

Angeletti, L.; Giannone, P.

doi:10.1051/0004-6361:20030164

Cited by 13 publications

(13 citation statements)

References 51 publications

(69 reference statements)

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“…Simulations of monolithic collapse models taking into account different escape velocities at different galactocentric radii produce results that are consistent with observed absorptionline index gradients inside $1 effective radius (Martinelli et al 1998;Angeletti & Giannone 2003). But they predict a significant steepening beyond that limit, which still needs to be checked observationally.…”

Section: Introductionsupporting

confidence: 63%

Oxygen and Neon Abundances of Planetary Nebulae in the Elliptical Galaxy NGC 4697

Méndez

Thomas

Saglia

et al. 2005

ApJ

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This paper presents deep spectra of 14 planetary nebulae ( PNs) at a variety of angular distances from the center of the flattened elliptical galaxy NGC 4697, which is located at $11 Mpc from us. Both near the center and among the most outlying PNs, we have found several examples of very strong [O iii] k5007, about 20 times brighter than H. This, together with strong [ Ne iii] lines, implies a lower limit for O and Ne abundances near solar at the center and also at more than 2 effective radii from the center of NGC 4697. Thus we have found, for the first time from individual stars, direct evidence of the existence of a metal-rich population in elliptical galaxies, confirming metallicities derived from absorption-line indices and extending the information to angular distances where the stellar surface brightness is too low for absorption-line studies. A comparison with abundances obtained closer to the center of NGC 4697 from integrated absorption-line spectra indicates that the metallicity gradient, which is quite steep within 1 effective radius, becomes much less pronounced beyond 1 effective radius. The only alternative to this interpretation would be the presence of a very metal-poor PN population with ½Z/ H below À1, which we cannot rule out, but it would require an extremely bimodal metallicity distribution with almost no intermediate metallicities.

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Section: Introductionsupporting

confidence: 63%

Oxygen and Neon Abundances of Planetary Nebulae in the Elliptical Galaxy NGC 4697

Méndez

Thomas

Saglia

et al. 2005

ApJ

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“…Existing dissipative-collapse models (e.g., Angeletti & Giannone 2003 for a recent representative example applied to E galaxies) are, however, pointed at recovering the metallicity gradients that are observed in the brightest inner halos and bulges of E galaxies (e.g., Davies et al 1993), which should arise during the main stage of the bulge and spheroid formation. The remote, metalpoor regions could have an earlier origin.…”

Section: Discussionmentioning

confidence: 99%

The Leo Elliptical NGC 3379: A Metal‐Poor Halo Emerges

Harris¹,

Harris²,

Layden³

et al. 2007

ApJ

120

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We have used the ACS camera on HST to obtain (V, I ) photometry for 5300 red giant stars in the halo of the dominant Leo group member NGC 3379, a galaxy usually regarded as a classic normal giant elliptical. We use this data to derive the metallicity distribution function ( MDF ) for its outer-halo field stars at a location centered 33 kpc from the galaxy center. In at least two ways the MDF is distinctly unlike all the other E galaxies for which similar data exist. First, the NGC 3379 MDF is extremely broad and flat, with many stars at every interval in [m / H ]. Second, we see a metallicity gradient such that in ithe outermost parts of the field the low-metallicity stars (½m/H < À0:7) begin to dominate and the higher metallicity stars are rapidly diminishing. We find that a distinct two-stage chemical evolution model is necessary to explain the MDF shape. Our target field is centered at a projected distance of 12R e , twice as far out in units of effective radius as in any of the other galaxies yet surveyed. If NGC 3379 is indeed representative of large E/S0 galaxies, we predict that other such galaxies will reveal diffuse low-metallicity subpopulations, but that photometry at radii r ' (10Y15)R e will be necessary to get beyond the edge of the dominant metal-rich component.

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“…It has long been appreciated that the mass loss associated with stellar evolution can have a dramatic effect on the early life of a cluster (Angeletti & Giannone 1977; Applegate 1986; Terlevich 1987; Bastian et al 2008). As its largest stars die out, the cluster's total mass can decrease significantly.…”

Section: The Role Of Stellar Evolutionmentioning

confidence: 99%

Star clusters under stress: why small systems cannot dynamically relax

Converse

Stahler

2010

Monthly Notices of the Royal Astronomical Society

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Utilizing a series of N‐body simulations, we argue that gravitationally bound stellar clusters of modest population evolve very differently from the picture presented by classical dynamical relaxation theory. The system's most massive stars rapidly sink towards the centre and form binary systems. These binaries efficiently heat the cluster, reversing any incipient core contraction and driving a subsequent phase of global expansion. Most previous theoretical studies demonstrating deep and persistent dynamical relaxation have either conflated the process with mass segregation, ignored three‐body interactions, or else adopted the artificial assumption that all cluster members are single stars of identical mass. In such a uniform‐mass cluster, binary formation is greatly delayed, as we confirm here both numerically and analytically. The relative duration of core contraction and global expansion is effected by stellar evolution, which causes the most massive stars to die out before they form binaries. In clusters of higher N, the epoch of dynamical relaxation lasts for progressively longer periods. By extrapolating our results to much larger populations, we can understand, at least qualitatively, why some globular clusters reach the point of true core collapse.

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Abundance gradients in elliptical galaxies

Cited by 13 publications

References 51 publications

Oxygen and Neon Abundances of Planetary Nebulae in the Elliptical Galaxy NGC 4697

Oxygen and Neon Abundances of Planetary Nebulae in the Elliptical Galaxy NGC 4697

The Leo Elliptical NGC 3379: A Metal‐Poor Halo Emerges

Star clusters under stress: why small systems cannot dynamically relax

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