Heavy‐Element Abundances in Blue Compact Galaxies

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

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Tracing the Origins of the Ice Giants through Noble Gas Isotopic Composition

10.5194/egusphere-egu21-7798 ◽

2021 ◽

Author(s):

Kathleen Mandt ◽

Olivier Mousis ◽

Jonathan Lunine ◽

Bernard Marty ◽

Thomas Smith ◽

...

Keyword(s):

Solar System ◽

Isotopic Composition ◽

Heavy Element ◽

Noble Gas ◽

Giant Planet ◽

Isotope Ratios ◽

Building Blocks ◽

Giant Planets ◽

Element Abundances ◽

Current State

The current composition of giant planet atmospheres provides information on how such planets formed, and on the origin of the solid building blocks that contributed to their formation. Noble gas abundances and their isotope ratios are among the most valuable pieces of evidence for tracing the origin of the materials from which the giant planets formed. In this review we first outline the current state of knowledge for heavy element abundances in the giant planets and explain what is currently understood about the reservoirs of icy building blocks that could have contributed to the formation of the Ice Giants. We then outline how noble gas isotope ratios have provided details on the original sources of noble gases in various materials throughout the solar system. We follow this with a discussion on how noble gases are trapped in ice and rock that later became the building blocks for the giant planets and how the heavy element abundances could have been locally enriched in the protosolar nebula. We then provide a review of the current state of knowledge of noble gas abundances and isotope ratios in various solar system reservoirs, and discuss measurements needed to understand the origin of the ice giants. Finally, we outline how formation and interior evolution will influence the noble gas abundances and isotope ratios observed in the ice giants today. Measurements that a future atmospheric probe will need to make include (1) the 3He/4He isotope ratio to help constrain the protosolar D/H and 3He/4He; (2) the 20Ne/22Ne and 21Ne/22Ne to separate primordial noble gas reservoirs similar to the approach used in studying meteorites; (3) the Kr/Ar and Xe/Ar to determine if the building blocks were Jupiter-like or similar to 67P/C-G and Chondrites; (4) the krypton isotope ratios for the first giant planet observations of these isotopes; and (5) the xenon isotopes for comparison with the wide range of values represented by solar system reservoirs.Mandt, K. E., Mousis, O., Lunine, J., Marty, B., Smith, T., Luspay-Kuti, A., & Aguichine, A. (2020). Tracing the origins of the ice giants through noble gas isotopic composition. Space Science Reviews, 216(5), 1-37.

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CONSTRAINTS ON THE FORMATION OF THE GALACTIC BULGE FROM Na, Al, AND HEAVY-ELEMENT ABUNDANCES IN PLAUT's FIELD

The Astrophysical Journal ◽

10.1088/0004-637x/749/2/175 ◽

2012 ◽

Vol 749 (2) ◽

pp. 175 ◽

Cited By ~ 66

Author(s):

Christian I. Johnson ◽

R. Michael Rich ◽

Chiaki Kobayashi ◽

Jon P. Fulbright

Keyword(s):

Heavy Element ◽

Galactic Bulge ◽

Element Abundances

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A Spectroscopic Survey in the EUV of the “Coolest” Hot DA Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100036009 ◽

1996 ◽

Vol 152 ◽

pp. 217-222

Author(s):

Jean Dupuis ◽

Stéphane Vennes

Keyword(s):

Effective Temperature ◽

White Dwarfs ◽

Heavy Element ◽

Extreme Ultraviolet ◽

Diffusion Theory ◽

Hydrogen Atmosphere ◽

Element Abundance ◽

Pure Hydrogen ◽

Element Abundances ◽

The One

We present an analysis of the extreme ultraviolet (EUV) spectroscopy of a sample of 10 DA white dwarfs observed by the Extreme Ultraviolet Explorer (EUVE). We have selected white dwarfs cooler than about 50,000 K and with presumably low heavy element abundances. The goal of this study is to determine the fundamental atmospheric parameters, namely the effective temperature and chemical composition, of these stars by fitting their continua with synthetic spectra computed from pure hydrogen LTE/line-blanketed model atmospheres. The question of the presence (or absence) of trace elements is explored by comparing EUV-determined effective temperatures to the one obtained from a fit of hydrogen balmer lines. It is found that the majority of the DA in the sample are consistent with having a pure hydrogen atmosphere. One of the star, MCT0027-634, is another possible example of a HZ 43-type white dwarf, having an effective temperature above 50000 K and a low heavy element abundance, i.e., much lower than predicted by diffusion theory.

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Dust in the Magellanic Clouds

Symposium - International Astronomical Union ◽

10.1017/s0074180900200016 ◽

1991 ◽

Vol 148 ◽

pp. 57-62

Author(s):

Paul Hodge

Keyword(s):

Heavy Element ◽

Magellanic Clouds ◽

Dust Content ◽

Optical Observations ◽

Optical Data ◽

Star Forming ◽

Element Abundances ◽

Star Forming Regions ◽

The Galaxy ◽

Far Ultraviolet

The dust content of the Magellanic Clouds can be studied using optical, ultraviolet, infrared and, indirectly, radio wavelength data. All recent studies show that the dust content is lower than that of the Milky Way Galaxy for both Clouds and that the optical properties of the dust are different. At ultraviolet wavelengths, the 2165 Å “bump” in the extinction curve is significantly smaller than in the Galaxy (this now appears NOT to be a consequence of the lower heavy element abundances) and the far ultraviolet (shortward of ˜2000 Å) extinction is greater than in the Galaxy (this IS likely to be a consequence of the lower heavy element abundances). New optical data on background galaxies suggest that the total extinction in the central parts of both the LMC and the SMC is approximately 1.5 magnitudes. High local extinction values are derived from uv and optical observations of star-forming regions, where a spatial correlation with CO detections is sometimes, but not always, found.

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Interstellar Phases in the Magellanic Clouds

Symposium - International Astronomical Union ◽

10.1017/s0074180900117371 ◽

1999 ◽

Vol 190 ◽

pp. 45-50 ◽

Cited By ~ 1

Author(s):

John M. Dickey ◽

Monika Marx-Zimmer ◽

Christian Düsterberg ◽

Ulrich Mebold ◽

Snezana Stanimirović ◽

...

Keyword(s):

Heavy Element ◽

Milky Way ◽

Magellanic Clouds ◽

Element Abundances ◽

Lower Abundance ◽

Cloud Temperature ◽

Magellanic System

Surveys of λ21-cm absorption in the Magellanic System show that the cool phase of the HI is less abundant in the SMC than in the Milky Way, and may be so also in the LMC. The typical cool cloud temperature is colder than in the Milky Way, 30 to 40 K rather than 60 to 75 K. The lower abundance of cool phase HI can be traced to the lower heavy element abundances in the Magellanic environment. The cooler cloud temperatures are somewhat mysterious.

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Element Abundances in Magellanic Cloud H II Regions from Carbon to Argon

Symposium - International Astronomical Union ◽

10.1017/s0074180900118017 ◽

1999 ◽

Vol 190 ◽

pp. 266-272 ◽

Cited By ~ 3

Author(s):

Donald R. Garnett

Keyword(s):

Heavy Element ◽

Hubble Space Telescope ◽

Uv Spectroscopy ◽

Magellanic Cloud ◽

Magellanic Clouds ◽

H Ii Regions ◽

Ionized Gas ◽

Mixing Processes ◽

Element Abundances ◽

C And N

I review measurements of heavy element abundances within H II regions in the Magellanic Clouds, highlighting in particular improved determinations of carbon abundances based on UV spectroscopy with Hubble Space Telescope. In general, the Magellanic Cloud H II regions show average underabundances in O, Ne, and S (relative to their Galactic counterparts) that are similar to those measured in Magellanic Cloud stars. However, comparison of stars and ionized gas shows discrepancies in C and N abundances that may be related to recently recognized mixing processes that may be operating in massive stars.

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Element Abundance Analyses of Novae

International Astronomical Union Colloquium ◽

10.1017/s0252921100069438 ◽

1977 ◽

Vol 42 ◽

pp. 242-273 ◽

Cited By ~ 1

Author(s):

Robert E. Williams

Keyword(s):

Temperature Distribution ◽

Emission Line ◽

Heavy Element ◽

Element Abundance ◽

Element Abundances ◽

Maximum Light ◽

Growth Studies ◽

Nova Shells

AbstractThe different methods by which element abundances in novae have been determined are reviewed. Curve of growth studies of novae at maximum light have indicated CNO nuclei to be greatly enhanced with respect to hydrogen in certain objects. These results are questionable because they depend upon an assumed temperature distribution in the photosphere which is probably too steep to be realistic. Emission line analyses of novae, generally obtained in the period of early decline, also indicate possible heavy element enhancement, however these results are tentative because of uncertainties in the parameters of the emitting gas. It is suggested that useful abundance determinations of nova ejecta might be obtained from studies of old, extended nova shells.

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Population Models for Massive Globular Clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314005626 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 247-248 ◽

Cited By ~ 5

Author(s):

Young-Wook Lee ◽

Seok-Joo Joo ◽

Sang-Il Han ◽

Chongsam Na ◽

Dongwook Lim ◽

...

Keyword(s):

Parameter Space ◽

Globular Clusters ◽

Heavy Element ◽

Milky Way ◽

Population Modeling ◽

Stellar Populations ◽

Population Models ◽

Horizontal Branch ◽

Element Abundances ◽

Hr Diagram

Increasing number of massive globular clusters (GCs) in the Milky Way are now turned out to host multiple stellar populations having different heavy element abundances enriched by supernovae. Recent observations have further shown that [CNO/Fe] is also enhanced in metal-rich subpopulations in most of these GCs, including ω Cen and M22 (Marino et al. 2011, 2012). In order to reflect this in our population modeling, we have expanded the parameter space of Y2 isochrones and horizontal-branch (HB) evolutionary tracks to include the cases of normal and enhanced nitrogen abundances ([N/Fe] = 0.0, 0.8, and 1.6). The observed variations in the total CNO content were reproduced by interpolating these nitrogen enhanced stellar models. Our test simulations with varying N and O abundances show that, once the total CNO sum ([CNO/Fe]) is held constant, both N and O have almost identical effects on the HR diagram (see Fig. 1).

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