Lyα Emission in Starbursts: Implications for Galaxies at High Redshift

Mas-Hesse, J. M.; Kunth, D.; Tenorio-Tagle, G.; Leitherer, Claus; Terlevich, R.; Terlevich, Elena

doi:10.1086/379116

Cited by 152 publications

(237 citation statements)

References 49 publications

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“…Since Model 2 predicts higher intrinsic Hα/Hβ ratios than Model 1, the extinction derived in the diffuse emitting regions would be much lower than assuming case B, allowing for higher Lyα escape fractions in these areas. The ratio measured on Lyα ii , Lyα/Hα < 3.0, is compatible with the results found by Mas-Hesse et al (2003). They found that the diffuse Lyα emission exhibits a clear P Cyg profile all along slit D1, at any distance from the stellar knot SE.…”

Section: Photoionization By the Hot Plasmasupporting

confidence: 90%

“…We downloaded a pre-COSTAR PSF for an F/96 F220W observation performed five months earlier from the instrument website 1 and extracted the enclosed point source flux within the boundaries of the boxes we have considered. It was found that for the sizes (Mas-Hesse et al 2003), and D2 (G140L and G230L) (Chandar et al 2004), and the boxes used to extract the UV flux from each knot. The width of the slits is represented at real scale.…”

Section: Hst Imagesmentioning

confidence: 99%

“…2 both slit directions can be observed superimposed on the FOC image. Both slit directions are orthogonal, and whereas Mas-Hesse et al (2003) encloses only the SE star-forming knot, slit from Chandar et al (2004) contains the bulk emission from both SE and NW knots. The G140M D1 and G140L D2 spectral images constitute the direct observation of the Lyα morphology and spectroscopy of Haro 2 which we analyze in this work.…”

Section: Hst Imagesmentioning

confidence: 99%

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Multiwavelength analysis of the Lyman-αemitting galaxy Haro 2: relation between the diffuse Lyman-αand soft X-ray emissions

Otí-Floranes

Mas-Hesse

Jiménez‐Bailón

et al. 2012

A&A

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Context. Lyman-α emission is commonly used as star formation tracer in cosmological studies. Nevertheless, resonant scattering strongly affects the resulting luminosity, leading to variable and unpredictable escape fractions in different objects. Aims. To understand how the Lyα escape fraction depends on the properties of the star-forming regions, we need high spatial resolution multiwavelength studies of nearby Lyα emitters, like Haro 2. Methods. We study the Lyα emission of Haro 2 in connection with the properties of the young stellar population, the characteristics of the interstellar medium, the distribution and intensity of the Balmer emission lines and the properties of the X-ray emission. We have used HST-STIS spectral images along the major and minor axes of Haro 2 to characterize the Lyα emission, as well as FOC UV, WFPC-2 optical and NICMOS near infrared broadband-filter images to analyze the properties of the stellar population. WFPC-2 Hα image and ground-based spectroscopy allow us to study the Balmer emission lines. Finally, Chandra/ACIS X-ray images provide resolved distribution of the X-ray emission at various energy bands. The observational data are analyzed by comparison with the predictions from evolutionary synthesis models to constrain the properties of the star formation episode. Results. The UV, Hα and far infrared luminosities of the Haro 2 nuclear starburst are well reproduced assuming a young stellar population with ages ∼3.5-5.0 Myr, affected by differential intestellar extinctions. A significant fraction of the stars are completely obscured in the UV, being identifiable only indirectly by their contribution to the ionization of the gas and to the far infrared emission. The diffuse soft X-ray emission extending over the whole source is attributed to gas heated by the mechanical energy released by the starburst. A compact hard X-ray emission (likely an UltraLuminous X-ray source) has been identified in a star-forming condensation to the southeast. Both compact and diffuse Lyα emission components are observed along the major and minor axes in STIS spectral images. Lyα is spatially decoupled from Balmer lines emission, Balmer decrement and UV continuum. However, the diffuse Lyα component is spatially correlated with the diffuse soft X-ray emission. Moreover, unlike the compact Lyα emission, diffuse Lyα shows luminosities larger than predicted from Hα, assuming case B recombination and considering the dust extinction as derived from Hα/Hβ. Conclusions. The Lyα emission closely associated to the massive stellar clusters is strongly affected by the properties of the surrounding neutral gas (presence of outflows, dust abundance), leading to even a range of escape fractions at different locations within the same starburst. On the other hand, we propose that the diffuse Lyα emission originates in gas ionized by the hot plasma responsible for the soft X-ray radiation, as suggested by their spatial correlation and by the measured L(Hα)/L 0.4−2.4 keV ratios. Calibration of Lyα as star forma...

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Section: Photoionization By the Hot Plasmasupporting

confidence: 90%

Section: Hst Imagesmentioning

confidence: 99%

Section: Hst Imagesmentioning

confidence: 99%

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Multiwavelength analysis of the Lyman-αemitting galaxy Haro 2: relation between the diffuse Lyman-αand soft X-ray emissions

Otí-Floranes

Mas-Hesse

Jiménez‐Bailón

et al. 2012

A&A

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“…One may expect a strong intrinsic Lyα emission for a low-metallicity galaxy but the observed Lyα output will also depend on other factors. Classical examples are IZw 18 and SBS 0335, the most metal-poor galaxies known, which show a strong absorption in Lyα (Kunth et al 1998;Mas-Hesse et al 2003;Atek et al 2009b). In fact, the metallicity distributions of the LAEs and UV-continuum galaxies measured in Cowie et al (2011) overlap significantly.…”

Section: Effects Of Metallicitymentioning

confidence: 99%

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

Atek

Kunth

Schaerer

et al. 2014

A&A

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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.

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“…Such double peaked profiles of optical emission lines have been observed for nearby starburst galaxies which exhibit these large scale outflows typically termed superwinds (Heckman et al 1990). Additionally, a double peaked Lyα emission line profile was found from the starburst galaxy T1214-277 by Mas-Hesse et al (2003), who concluded that the feature is caused by emission in an outflow. Double-peaked Lyα profiles have been observed also at redshift z ∼ 3, in spectra of star forming galaxies (Fosbury et al 2003;Christensen et al 2004;Venemans et al 2005;Tapken et al 2007).…”

Section: Individual Notesmentioning

confidence: 99%

The great observatories origins deep survey

Vanzella¹,

Cristiani²,

Dickinson

et al. 2007

A&A

335

372

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Aims. We present the full data set of the spectroscopic campaign of the ESO/GOODS program in the GOODS-South field, obtained with the FORS2 spectrograph at the ESO/VLT. Methods. Objects were selected as candidates for VLT/FORS2 observations primarily based on the expectation that the detection and measurement of their spectral features would benefit from the high throughput and spectral resolution of FORS2. The reliability of the redshift estimates is assessed using the redshift-magnitude and color-redshift diagrams, and comparing the results with public data. Results. Including the third part of the spectroscopic campaign (12 masks) to the previous work (26 masks, Vanzella et al. 2005Vanzella et al. , 2006, 1715 spectra of 1225 individual targets have been analyzed. The actual spectroscopic catalog provides 887 redshift determinations. The typical redshift uncertainty is estimated to be σ z 0.001. Galaxies have been selected adopting different color criteria and using photometric redshifts. The resulting redshift distribution typically spans two domains: from z = 0.5 to 2 and z = 3.5 to 6.3. The reduced spectra and the derived redshifts are released to the community through the ESO web page http://www.eso.org/science/goods/.

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Lyα Emission in Starbursts: Implications for Galaxies at High Redshift

Cited by 152 publications

References 49 publications

Multiwavelength analysis of the Lyman-αemitting galaxy Haro 2: relation between the diffuse Lyman-αand soft X-ray emissions

Multiwavelength analysis of the Lyman-αemitting galaxy Haro 2: relation between the diffuse Lyman-αand soft X-ray emissions

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

The great observatories origins deep survey

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