Mixing metals in the early Universe

Ferrara, Andrea; Pettini, Max; Shchekinov, Yu. A.

doi:10.1046/j.1365-8711.2000.03857.x

Cited by 132 publications

(154 citation statements)

References 69 publications

(48 reference statements)

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“…First, metals produced by LBGs do not seem to be able to escape from their halos, due to the confining mechanisms mentioned above. This is consistent with the prediction (Ferrara, Pettini & Shchekinov 2000) that galaxies of total mass M > 10 12 (1 + z) −3/2 M do not eject their metals into the IGM. Interestingly, the metallicity-mass relation recently derived from the SDSS (Tremonti et al 2004) shows that galaxies with stellar masses above 3 × 10 10 M (their total mass corresponds to M for a star formation efficiency f = 0.2) 98 Andrea Ferrara chemically evolve as "closed boxes," i.e.…”

Section: Discussionsupporting

confidence: 92%

“…the metal escape fraction, δ B . A solution has been proposed by Ferrara, Pettini & Shchekinov (2000) who noticed that SNe in "normal" galaxies (as for example the Milky Way) are distributed in the disk and clustered in OB associations; thus, these explosion sites act incoherently. In low-mass galaxies, on the contrary, the size of the galaxy is comparable to the size of individual SN-driven bubbles and therefore the energy deposited can work to drive coherently the same outflow.…”

Section: Early Enrichment By Dwarf Galaxiesmentioning

confidence: 99%

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Cosmic metal enrichment

Ferrara¹

2008

Proc. IAU

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Abstract. I review the present understanding of the process by which the universe has been enriched in the course of its history with heavy elements produced by stars and transported into the surrounding intergalactic medium. This process goes under the name of "cosmic metal enrichment" and presents some of the most challenging puzzles in present day physical cosmology. These are reviewed along with some proposed explanations that all together form a coherent working scenario.Keywords. (galaxies:) intergalactic medium, cosmology: theory, galaxies: high-redshift PreliminariesAfter the Big Bang the cosmic gas had a composition which was (virtually) free of heavy elements. Yet, every single parcel of gas that we can probe today with our most powerful telescopes shows the sign of considerable amounts of metals, up to the highest redshift. When these metals where first produced, by what sources, and how these atomic species traveled away from their production sites are among the most challenging puzzles in current cosmological scenarios.A very simple, and yet robust, estimate of the amount of metals present at the end of reionization can be made. This is based on the fact that the sources of heavy elements and photons with energy > 1 Ryd responsible for hydrogen reionization are massive stars. Hence, as we know that reionization was complete by redshift z = 6, we can compute the metallicity of the cosmic gas associated with the ionizing photons required to reionize the universe, in the hypothesis that such process has been powered by stellar radiation. Obviously, as different type of sources, as quasars and/or decaying/annihilating dark matter particles may have contributed, the result of this simple exercise is an upper limit to the amount of metals. However, many arguments suggest that stars are by far the most viable reionization source candidates. In this case, we find that the mean metallicity of the cosmic gas (in practice, the intergalactic medium [IGM] which contains most of the baryons) at z = 6 iswhere y is the mean supernova metal yield, ν is the number of supernovae per unit stellar mass formed, C ≈ 1 − 10 is the IGM clumping factor and η is the number of ionizing photons per baryon into stars. The above result has been derived for a Salpeter stellar IMF but the value of Z is only mildly dependent on such quantity. The main point is that metal production associated with cosmic reionization is already substantial and comparable with the value derived from QSO absorption line experiments at lower redshifts. The next question concerns the sources that predominantly produced the metals and photons. Current data from a number of different experiments including CMB polarization anisotropies, Lyα and Lyβ Gunn-Peterson tests, cosmic star formation history and 86 available at https://www.cambridge.org/core/terms. https://doi

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Section: Discussionsupporting

confidence: 92%

Section: Early Enrichment By Dwarf Galaxiesmentioning

confidence: 99%

Cosmic metal enrichment

Ferrara¹

2008

Proc. IAU

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“…Second, the results of°5 show LBGs to be the most metal-enriched structures at z^3, apart from QSOs . A signiÐcant fraction of these metals will probably be lost from the galaxies altogether since the measured values of are comparable to the *v IS, abs escape velocities (Heckman 2001 ;Ferrara, Pettini, & Shchekinov 2000). While it is still unclear how far this metalenriched gas will travel (Ferrara et al 2000 ;Aguirre et al 2001), there is at least the potential for seeding large volumes around the galaxies with the products of stellar nucleosynthesis.…”

Section: Arge-scale Motionsmentioning

confidence: 99%

“…A signiÐcant fraction of these metals will probably be lost from the galaxies altogether since the measured values of are comparable to the *v IS, abs escape velocities (Heckman 2001 ;Ferrara, Pettini, & Shchekinov 2000). While it is still unclear how far this metalenriched gas will travel (Ferrara et al 2000 ;Aguirre et al 2001), there is at least the potential for seeding large volumes around the galaxies with the products of stellar nucleosynthesis. Furthermore, if most of the metals carried away by galactic superwinds remain in a hot phase, yet to be directly observed, this may help solve the puzzle of the missing metals at high redshift (Pettini 1999 ;Pagel 2001).…”

Section: Arge-scale Motionsmentioning

confidence: 99%

The Rest‐Frame Optical Spectra of Lyman Break Galaxies: Star Formation, Extinction, Abundances, and Kinematics

Pettini

Shapley

Steidel

et al. 2001

ApJ

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742

972

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We present the Ðrst results of a spectroscopic survey of Lyman break galaxies (LBGs) in the nearinfrared aimed at detecting the emission lines of [O II], [O III], and Hb from the H II regions of normal star-forming galaxies at z^3. From observations of 15 objects with the Keck telescope and the Very Large Telescope augmented with data from the literature for an additional four objects, we reach the following main conclusions. The rest-frame optical properties of LBGs at the bright end of the luminosity function are remarkably uniform, their spectra are dominated by emission lines, [O III] is always stronger than Hb and [O II], and projected velocity dispersions are between 50 and 115 km s~1. Contrary to expectations, the star formation rates deduced from the Hb luminosity are on average no larger than those implied by the stellar continuum at 1500 presumably any di †erential extinction between A ; rest-frame optical and UV wavelengths is small compared to the relative uncertainties in the calibrations of these two star formation tracers. For the galaxies in our sample, the abundance of oxygen can only be determined to within 1 order of magnitude without recourse to other emission lines ([N II] and Ha), which are generally not available. Even so, it seems well established that LBGs are the most metalenriched structures at z^3, apart from quasi-stellar objects, with abundances greater than about 1/10 solar and generally higher than those of damped Lya systems at the same epoch. They are also signiÐ-cantly overluminous for their metallicities ; this is probably an indication that their mass-to-light ratios are low compared to present-day galaxies. At face value, the measured velocity dispersions imply virial masses of about 1010 within half-light radii of 2.5 kpc. The corresponding mass-to-light ratios, M _ M/L B 0.15 in solar units, are indicative of stellar populations with ages between 108 and 109 yr, consistent with the UV-optical spectral energy distributions. However, we are unable to establish conclusively whether or not the widths of the emission lines reÑect the motions of the H II regions within the gravitational potential of the galaxies, even though in two cases we see hints of rotation curves. All 19 LBGs observed show evidence for galactic-scale superwinds ; such outÑows have important consequences for regulating star formation, distributing metals over large volumes, and allowing Lyman continuum photons to escape and ionize the intergalactic medium.

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“…Although simulations of starburst-driven winds should be treated with caution, given the lack of calibration against observational data, one robust result is the sensitivity of the wind properties (in particular, mass and metal loss to the IGM) on the disk and halo ISM properties (e.g., De Young & Heckman 1994;Suchkov et al 1994;Silich & Tenorio-Tagle 1998Strickland & Stevens 2000). In our view, the emphasis given to galactic mass as a primary parameter influencing gas and metal ejection efficiencies (e.g., Dekel & Silk 1986;Mac Low & Ferrara 1999;Ferrara & Tolstoy 2000;Ferrara, Pettini, & Shchekinov 2000) blinds nonexpert readers to the more fundamental role played by the poorly known disk and halo ISM distributions. The gravitational potential only enters at a secondary level, by influencing the gas distribution and finally via the escape velocity.…”

Section: Introductionmentioning

confidence: 96%

A High Spatial Resolution X‐Ray and Hα Study of Hot Gas in the Halos of Star‐forming Disk Galaxies. II. Quantifying Supernova Feedback

Strickland

Heckman

Colbert

et al. 2004

ApJ

250

283

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We investigate how the empirical properties of hot X-ray-emitting gas in a sample of seven starburst and three normal edge-on spiral galaxies (a sample that covers the full range of star formation intensity found in disk galaxies) correlate with the size, mass, star formation rate, and star formation intensity in the host galaxies. From this analysis we investigate various aspects of mechanical energy ''feedback''-the return of energy to the interstellar medium from massive star supernovae and stellar winds-on galactic scales. The X-ray observations make use of the unprecedented spatial resolution of the Chandra X-Ray Observatory to remove X-ray emission from point sources more accurately than in any previous study and hence obtain the X-ray properties of the diffuse thermal emission alone. Intriguingly, the diffuse X-ray properties of the normal spirals (in both their disks and halos) fall where extrapolation of the trends from the starburst galaxies with superwinds would predict. We demonstrate, using a variety of multiwavelength star formation rate and intensity indicators, that the luminosity of diffuse X-ray emission in the disk (and, where detected, in the halo) is directly proportional to the rate of mechanical energy feedback from massive stars in the host galaxies. Accretion of gas from the intergalactic medium (IGM) does not appear to be a significant contributor to the diffuse X-ray emission in this sample. Nevertheless, with only three nonstarburst normal spiral galaxies it is hard to exclude an accretion-based origin for extraplanar diffuse X-ray emission around normal star-forming galaxies. Larger galaxies tend to have more extended X-ray-emitting halos, but galaxy mass appears to play no role in determining the properties of the disk or extraplanar X-ray-emitting plasma. The combination of these luminosity and size correlations leads to a correlation between the surface brightness of the diffuse X-ray emission and the mean star formation rate per unit area in the disk (calculated from the far-infrared luminosity and the optical size of the galaxy, L FIR =D 2 25 ). Further observational work of this form will allow empirical constraints to be made on the critical star formation rate per unit disk area necessary to blow hot gas out of the disk into the halo. We show that a minor generalization of standard superbubble theory directly predicts a critical star formation rate per unit area for superbubble blowout from the disk and by extension for superwinds to blow out of the gaseous halos of their host galaxy. At present there are a variety of poorly known parameters in this theory that complicate comparison between observation and theory, making it impossible to assess the quantitative accuracy of standard superbubble blowout theory. We argue that the crucial spatial region around a galaxy that controls whether gas in starburst-driven superwinds will escape into the IGM is not the outer halo $100 kpc from the host galaxy, but the inner few halo scale heights, within $20 kpc of the galaxy plan...

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Mixing metals in the early Universe

Cited by 132 publications

References 69 publications

Cosmic metal enrichment

Cosmic metal enrichment

The Rest‐Frame Optical Spectra of Lyman Break Galaxies: Star Formation, Extinction, Abundances, and Kinematics

A High Spatial Resolution X‐Ray and Hα Study of Hot Gas in the Halos of Star‐forming Disk Galaxies. II. Quantifying Supernova Feedback

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