Implications from HI Composition and Lyα Emission of HII Galaxies

Kunth, D.; Lequeux, J.; Sargent, W. L. W.; Viallefond, F.

doi:10.1017/cbo9780511600159.033

Cited by 85 publications

(145 citation statements)

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“…Ly profile. Inspired by such examples as the metal-poor local starburst I Zwicky 18, which has Ly only in absorption (Kunth et al 1994), and the dustier and more metalrich Haro 2, which shows a redshifted P Cygni Ly emission feature (Lequeux et al 1995), Kunth et al (1998) survey a small sample of local starburst galaxies in the UV and find that the objects with Ly only in absorption also have interstellar absorption lines (O i 1302 and Si ii 1304) that are at rest with respect to the H ii regions, whereas galaxies with Ly emission exhibit asymmetric, P Cygni Ly profiles, with redshifted Ly emission and blueshifted interstellar absorption lines. These observations support a picture in which Ly photons mainly escape when they are produced by-or scatter off of-material which is offset in velocity from the bulk of the scattering neutral medium.…”

Section: Ly Dependencesmentioning

confidence: 99%

Rest‐Frame Ultraviolet Spectra of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \De

Shapley

Steidel

Pettini

et al. 2003

ApJ

1,255

148

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We present the results of a systematic study of the rest-frame UV spectroscopic properties of Lyman break galaxies (LBGs). The database of almost 1000 LBG spectra proves useful for constructing high signalto-noise composite spectra. The composite spectrum of the entire sample reveals a wealth of features attributable to hot stars, H ii regions, dust, and outflowing neutral and ionized gas. By grouping the database according to galaxy parameters such as Ly equivalent width, UV spectral slope, and interstellar kinematics, we isolate some of the major trends in LBG spectra that are least compromised by selection effects. We find that LBGs with stronger Ly emission have bluer UV continua, weaker low-ionization interstellar absorption lines, smaller kinematic offsets between Ly and the interstellar absorption lines, and lower star formation rates. There is a decoupling between the dependence of low-and high-ionization outflow features on other spectral properties. Additionally, galaxies with rest-frame W Ly ! 20 Å in emission have weaker than average high-ionization lines and nebular emission lines that are significantly stronger than in the sample as a whole. Most of the above trends can be explained in terms of the properties of the large-scale outflows seen in LBGs. According to this scenario, the appearance of LBG spectra is determined by a combination of the covering fraction of outflowing neutral gas, which contains dust and the range of velocities over which this gas is absorbing. In contrast, the strengths of collisionally excited nebular emission lines should not be affected by the nature of the outflow, and variations in these lines may indicate differences in the temperatures and metallicities in H ii regions of galaxies with very strong Ly emission. Higher sensitivity and spectral resolution observations are still required for a full understanding of the covering fraction and velocity dispersion of the outflowing neutral gas in LBGs and its relationship to the escape fraction of Lyman continuum radiation in galaxies at z $ 3.

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Section: Ly Dependencesmentioning

confidence: 99%

Rest‐Frame Ultraviolet Spectra of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \De

Shapley

Steidel

Pettini

et al. 2003

ApJ

1,255

148

999

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“…Kunth et al [75] realized the importance of determining the abundances in the neutral H I envelope to better understand the chemical evolution. Kunth and Lebouteiller [74] find a correlation between metallicities in the neutral gas and the H II gas, indicating that mixing between the newly produced metals and the H I envelope is taking place.…”

Section: Chemical Abundancesmentioning

confidence: 99%

Star Forming Dwarf Galaxies

Bergvall¹

2011

Astrophysics and Space Science Proceedings

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Star forming dwarf galaxies (SFDGs) have a high gas content and low metallicities, reminiscent of the basic entities in hierarchical galaxy formation scenarios. In the young universe they probably also played a major role in the cosmic reionization. Their abundant presence in the local volume and their youthful character make them ideal objects for detailed studies of the initial stellar mass function (IMF), fundamental star formation processes and its feedback to the interstellar medium. Occasionally we witness SFDGs involved in extreme starbursts, giving rise to strongly elevated production of super star clusters and global superwinds, mechanisms yet to be explored in more detail. SFDGs is the initial state of all dwarf galaxies and the relation to the environment provides us with a key to how different types of dwarf galaxies are emerging. In this review we will put the emphasis on the exotic starburst phase, as it seems less important for present day galaxy evolution but perhaps fundamental in the initial phase of galaxy formation.

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“…Izotov and Thuan (1998a,b) find Y = 0.242, in comfortable agreement with SBBN. Kunth et al (1994) attempted to measure the oxygen abundance in the neutral gas cloud surrounding IZw18 by using UV absorption lines, observed with the GHRS onboard HST. They found that the oxygen abundance could be as low as 1/1000 of the solar value, indicating near pristine gas with abundances lower than what is found in QSO absorption line systems.…”

Section: Chemical Abundance Of Izw18mentioning

confidence: 99%

“…However the use of saturated lines was criticised by . Van Zee et al (1998) argue that the HI velocity dispersion together with the measured OI line of Kunth et al (1994) imply an oxygen abundance ≥1/60 of the solar value, suggesting that the chemical enrichment products are well mixed. Figure 7: This figure shows the very weak Wolf-Rayet features detected in a high S/N spectrum of IZw18 (Legrand et al 1997b; see also Izotov et al 1997a).…”

Section: Chemical Abundance Of Izw18mentioning

confidence: 99%

The most metal-poor galaxies

Kunth

Östlin

2000

Astronomy and Astrophysics Review

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377

428

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Metallicity is a key parameter that controls many aspects in the formation and evolution of stars and galaxies. In this review we focus on the metal deficient galaxies, in particular the most metal-poor ones, because they play a crucial rôle in the cosmic scenery. We first set the stage by discussing the difficult problem of defining a global metallicity and how this quantity can be measured for a given galaxy. The mechanisms that control the metallicity in a galaxy are reviewed in detail and involve many aspects of modern astrophysics: galaxy formation and evolution, massive star formation, stellar winds, chemical yields, outflows and inflows etc. Because metallicity roughly scales as the galactic mass, it is among the dwarfs that the most metalpoor galaxies are found. The core of our paper reviews the considerable progress made in our understanding of the properties and the physical processes that are at work in these objects. The question on how they are related and may evolve from one class of objects to another is discussed. While discussing metal-poor galaxies in general, we present a more detailed discussion of a few very metal-poor blue compact dwarf galaxies like IZw18. Although most of what is known relates to our local universe, we show that it pertains to our quest for primeval galaxies and is connected to the question of the origin of structure in the universe. We discuss what QSO absorption lines and known distant galaxies tell us already? We illustrate the importance of star-forming metal-poor galaxies for the determination of the primordial helium abundance, their use as distance indicator and discuss the possibility to detect nearly metal-free galaxies at high redshift from Lyα emission.

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Implications from HI Composition and Lyα Emission of HII Galaxies

Cited by 85 publications

References 0 publications

Star Forming Dwarf Galaxies

The most metal-poor galaxies

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