Extragalactic H II regions in the UV - Implications for primeval galaxies

Meier, D. L.; Terlevich, Elena

doi:10.1086/183565

Cited by 70 publications

(79 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first detections of the Lyα emission line in star-forming galaxies goes back to the early IUE observations of nearby Hii galaxies (e.g., Meier & Terlevich 1981;Hartmann et al 1984;Deharveng et al 1985). However, in the case of detection, the line was very weak, while in the remaining galaxies it was found in absorprtion.…”

Section: Effects Of Metallicitymentioning

confidence: 87%

Influence of physical galaxy properties on Lyαescape in star-forming galaxies

Atek

Kunth

Schaerer

et al. 2014

A&A

View full text Add to dashboard Cite

Context. Among the different observational techniques used to select high-redshift galaxies, the hydrogen recombination line Lymanalpha (Lyα) is of particular interest because it gives access to the measurement of cosmological quantities such as the star formation rate (SFR) of distant galaxy populations. However, interpreting this line and calibrating such observables are still subject to serious uncertainties. Aims. In this context, it important to understand the mechanisms responsible for the attenuation of Lyα emission, and under what conditions the Lyα emission line can be used as a reliable star formation diagnostic tool. Methods. We used a sample of 24 Lyα emitters at z ∼ 0.3 with an optical spectroscopic follow-up to calculate the Lyα escape fraction and its dependence upon different physical properties. We also examined the reliability of Lyα as a SFR indicator. We combined these observations with a compilation of Lyα emitters selected at z = 0−0.3 from the literature to assemble a larger sample. Results. We confirm that the Lyα escape fraction clearly depends on the dust extinction following the relation f esc (Lyα) = C Lyα × 10 −0.4 E(B−V) k Lyα where k Lyα ∼ 6.67 and C Lyα = 0.22. However, the correlation does not follow the expected curve for a simple dust attenuation. A higher attenuation can be attributed to a scattering process, while f esc (Lyα) values that are clearly above the continuum extinction curve can be the result of various mechanisms that can lead to an enhancement of the Lyα output. We also observe that the strength of Lyα and the escape fraction appear unrelated to the galaxy metallicity. Regarding the reliability of Lyα as a SFR indicator, we show that the deviation of SFR(Lyα) from the true SFR (as traced by the UV continuum) is a function of the observed SFR(UV), which can be seen as the decrease in f esc (Lyα) with increasing UV luminosity. Moreover, we observe redshift dependence of this relationship, revealing the underlying evolution of f esc (Lyα) with redshift.

show abstract

Section: Effects Of Metallicitymentioning

confidence: 87%

Influence of physical galaxy properties on Lyαescape in star-forming galaxies

Atek

Kunth

Schaerer

et al. 2014

A&A

View full text Add to dashboard Cite

show abstract

“…There is a large body of theoretical and observational work concerning the physical processes that determine the emergent Ly profile in local and high-redshift star-forming galaxies. In local star-forming galaxies, early observations indicated Ly emission equivalent widths much smaller than expected from recombination theory, given the star formation rates inferred from optical Balmer emission lines (Meier & Terlevich 1981;Hartmann, Huchra, & Geller 1984;Hartmann et al 1988). Additionally, these observations offered evidence for a correlation between Ly /H and metallicity (measured from the nebular oxygen abundance, O/H) in the sense that galaxies with lower Ly /H also had higher O/H (Hartmann et al 1988;Charlot & Fall 1993).…”

Section: Ly Dependencesmentioning

confidence: 97%

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

1,272

148

999

View full text Add to dashboard Cite

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.

show abstract

“…Thus, for a UV continuum-selected sample, one would expect very few galaxies to be caught during a time when their intrinsic W 0 (Lyα) exceeds 100 Å. 14 When dust is mixed throughout the scattering medium, one expects selective extinction of Lyα photons compared to those in the nearby UV continuum due to the much larger effective path length traversed by a line photon before escaping into the intergalactic medium (e.g., Meier & Terlevich 1981;Hartmann et al 1984;Neufeld 1990). This effect is often cited when observed Lyα emission lines are much weaker than the Case B expectations discussed above (e.g., Charlot & Fall 1993;Shapley et al 2003;Hayes et al 2010;Kornei et al 2010).…”

Section: Introductionmentioning

confidence: 99%

DIFFUSE Lyα EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES

Steidel

Bogosavljević

Shapley

et al. 2011

ApJ

387

590

View full text Add to dashboard Cite

Using a sample of 92 UV continuum-selected, spectroscopically identified galaxies with z = 2.65, all of which have been imaged in the Lyα line with extremely deep narrow-band imaging, we examine galaxy Lyα emission profiles to very faint surface brightness limits. The galaxy sample is representative of spectroscopic samples of Lyman break galaxies (LBGs) at similar redshifts in terms of apparent magnitude, UV luminosity, inferred extinction, and star formation rate and was assembled without regard to Lyα emission properties. Approximately 45% (55%) of the galaxy spectra have Lyα appearing in net absorption (emission), with 20% satisfying commonly used criteria for the identification of "Lyα emitters" (LAEs; W 0 (Lyα) 20 Å). We use extremely deep stacks of rest-UV continuum and continuum-subtracted Lyα images to show that all sub-samples exhibit diffuse Lyα emission to radii of at least 10 (∼80 physical kpc). The characteristic exponential scale lengths for Lyα line emission exceed that of the λ 0 = 1220 Å UV continuum light by factors of ∼5-10. The surface brightness profiles of Lyα emission are strongly suppressed relative to the UV continuum light in the inner few kpc, by amounts that are tightly correlated with the galaxies' observed spectral morphology; however, all galaxy sub-subsamples, including that of galaxies for which Lyα appears in net absorption in the spectra, exhibit qualitatively similar diffuse Lyα emission halos. Accounting for the extended Lyα emission halos, which generally would not be detected in the slit spectra of individual objects or with typical narrow-band Lyα imaging, increases the total Lyα flux (and rest equivalent width W 0 (Lyα)) by an average factor of ∼5, and by a much larger factor for the 80% of LBGs not classified as LAEs. We argue that most, if not all, of the observed Lyα emission in the diffuse halos originates in the galaxy H ii regions but is scattered in our direction by H i gas in the galaxy's circum-galactic medium. The overall intensity of Lyα halos, but not the surface brightness distribution, is strongly correlated with the emission observed in the central ∼1 -more luminous halos are observed for galaxies with stronger central Lyα emission. We show that whether or not a galaxy is classified as a giant "Lyα blob" (LAB) depends sensitively on the Lyα surface brightness threshold reached by an observation. Accounting for diffuse Lyα halos, all LBGs would be LABs if surveys were sensitive to 10 times lower Lyα surface brightness thresholds; similarly, essentially all LBGs would qualify as LAEs.

show abstract

Extragalactic H II regions in the UV - Implications for primeval galaxies

Cited by 70 publications

References 0 publications

Influence of physical galaxy properties on Lyαescape in star-forming galaxies

Influence of physical galaxy properties on Lyαescape in star-forming galaxies

DIFFUSE Lyα EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES

Contact Info

Product

Resources

About