NEW RESULTS FROM THE MAGELLAN IMACS SPECTROSCOPIC Lyα SURVEY: NICMOS OBSERVATIONS OF Lyα EMITTERS AT<i>z</i>= 5.7

Henry, Alaina; Martin, Crystal L.; Dressler, Alan; McCarthy, Patrick J.; Sawicki, Marcin

doi:10.1088/0004-637x/719/1/685

Cited by 5 publications

(5 citation statements)

References 80 publications

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“…Nine of the ten galaxies in our sample have Lyα profiles that show both blue and red peaks, and unlike other low redshift samples, their Lyα luminosity and W Lyα reach the range probed by high redshift Lyα surveys (e.g. Ouchi et al 2010;Henry et al 2010Henry et al , 2012.…”

Section: Summary and Discussionmentioning

confidence: 67%

LyαEMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS

Henry

Scarlata

Martin

et al. 2015

ApJ

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282

417

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We report Hubble Space Telescope/Cosmic Origins Spectrograph observations of the Lyα emission and interstellar absorption lines in a sample of ten star-forming galaxies at z ∼ 0.2. Selected on the basis of high equivalent width optical emission lines, the sample, dubbed "Green Peas," make some of the best analogs for young galaxies in an early Universe. We detect Lyα emission in all ten galaxies, and 9/10 show double-peaked line profiles suggestive of low H I column density. We measure Lyα/Hα flux ratios of 0.5-5.6, implying that 5% to 60% of Lyα photons escape the galaxies. These data confirm previous findings that low-ionization metal absorption (LIS) lines are weaker when Lyα escape fraction and equivalent width are higher. However, contrary to previously favored interpretations of this trend, increased Lyα output cannot be the result of a varying H I covering: the Lyman absorption lines (Lyβ and higher) show a covering fraction near unity for gas with N H I 10 16 cm −2 . Moreover, we detect no correlation between Lyα escape and the outflow velocity of the LIS lines, suggesting that kinematic effects do not explain the range of Lyα/Hα flux ratios in these galaxies. In contrast, we detect a strong anti-correlation between the Lyα escape fraction and the velocity separation of the Lyα emission peaks, driven primarily by the velocity of the blue peak. As this velocity separation is sensitive to H I column density, we conclude that Lyα escape in these Green Peas is likely regulated by the H I column density rather than outflow velocity or H I covering fraction. * Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 12928 and 11727.

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Section: Summary and Discussionmentioning

confidence: 67%

LyαEMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS

Henry

Scarlata

Martin

et al. 2015

ApJ

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282

417

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“…Consequently, a faint LAE could be the result of a low equivalent width emission from a UVbright galaxy, or conversely, high equivalent width emission from an extremely faint galaxy. No obvious trends exist between Lyα luminosity and equivalent width (see Henry et al 2010), although followup of UV-continuum selected i−dropouts shows that fainter continuum is correlated with stronger and more common Lyα emission (Stark et al 2010(Stark et al , 2011. Ultimately, since Lyα equivalent width exhibits such a wide range of values, a statistical comparison with the ensemble of i− dropout galaxies is most relevant.…”

Section: Comparison To Faint Lyα Lfs At Lower Redshiftmentioning

confidence: 99%

“…The sizes of LAEs, on the other hand, require a more careful consideration. Continuum observations show that the majority of LBGs, including those with Lyα emission, have compact sizes at z ∼ 6 (Bouwens et al 2004;Ferguson et al 2004;Henry et al 2010;Malhotra et al 2011;Gronwall et al 2011). Additionally, Hubble Space Telescope imaging of Lyα emission from redshift 3-4 LAEs supports the scenario where Lyα emission is similarly compact (Bond et al 2010;Finkelstein et al 2011).…”

Section: Blind Spectroscopic Datamentioning

confidence: 99%

THE FAINT-END SLOPE OF THE REDSHIFT 5.7 Lyα LUMINOSITY FUNCTION^,

Henry

Martin

Dressler

et al. 2011

ApJ

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Using new Keck DEIMOS spectroscopy, we examine the origin of the steep number counts of ultrafaint emission-line galaxies recently reported by Dressler et al. (2011). We confirm six Lyα emitters (LAEs), three of which have significant asymmetric line profiles with prominent wings extending 300-400 km s −1 redward of the peak emission. With these six LAEs, we revise our previous estimate of the number of faint LAEs in the Dressler et al. survey. Combining these data with the density of bright LAEs in the Cosmic Origins Survey and Subaru Deep Field provides the best constraints to date on the redshift 5.7 LAE luminosity function (LF). Schechter function parameters, φ * = 4.5 × 10 −4 Mpc −3 , L * = 9.1 × 10 42 erg s −1 , and α = −1.70, are estimated using a maximum likelihood technique with a model for slit losses. To place this result in the context of the UV-selected galaxy population, we investigate how various parameterizations of the Lyα equivalent width distribution, along with the measured UV-continuum LF, affect shape and normalization of the Lyα LF. The nominal model, which uses z ∼ 6 equivalent widths from the literature, falls short of the observed space density of LAEs at the bright end, possibly indicating a need for higher equivalent widths. This parameterization of the equivalent width distribution implies that as many as 50% of our faintest LAEs should have M U V > −18.0, rendering them undetectable in even the deepest Hubble Space Telescope surveys at this redshift. Hence, ultra-deep emission-line surveys find some of the faintest galaxies ever observed at the end of the reionization epoch. Such faint galaxies likely enrich the intergalactic medium with metals and maintain its ionized state. Observations of these objects provide a glimpse of the building blocks of present-day galaxies at an early time. 7 We have added one object that was dropped from the sample in Paper II, bringing the number of LAE candidates from 104 to 105.8 Multiple emission lines can be present in the 134Å of search spectrum when we detect Hα and [N II] λ6583Å, or [O III] λλ4959, 5007Å. 9The photometric redshifts used in this paper are taken from the COSMOS Photometric Redshift Cat-11

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“…For faint continua, determining the EW is associated with considerable error, and most of pro-claimed high-EWs have huge error bars. For instance, Henry et al (2010) found six sources with W em > 240 Å, but caution that the uncertainties in such high EWs typically exceed 100 Å.…”

Section: Measuring Errorsmentioning

confidence: 99%

ON THE (NON-)ENHANCEMENT OF THE Lyα EQUIVALENT WIDTH BY A MULTIPHASE INTERSTELLAR MEDIUM

Laursen

Duval

Östlin

2013

ApJ

111

158

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It has been suggested that radiative transfer effects may explain the unusually high equivalent widths (EWs) of the Lyα line, observed occasionally from starburst galaxies, especially at high redshifts. If the dust is locked up inside high-density clouds dispersed in an empty intercloud medium, the Lyα photons could scatter off of the surfaces of the clouds, effectively having their journey confined to the dustless medium. The continuum radiation, on the other hand, does not scatter, and would thus be subject to absorption inside the clouds.This scenario is routinely invoked when Lyα EWs higher than what is expected theoretically are observed, although the ideal conditions under which the results are derived usually are not considered.Here we systematically examine the relevant physical parameters in this idealized framework, testing whether any astrophysically realistic scenarios may lead to such an effect. It is found that although clumpiness indeed facilitates the escape of Lyα, it is highly unlikely that any real interstellar media should result in a preferential escape of Lyα over continuum radiation. Other possible causes are discussed, and it is concluded that the observed high EWs are more likely to be caused by cooling radiation from cold accretion and/or anisotropic escape of the Lyα radiation.

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NEW RESULTS FROM THE MAGELLAN IMACS SPECTROSCOPIC Lyα SURVEY: NICMOS OBSERVATIONS OF Lyα EMITTERS ATz= 5.7

Cited by 5 publications

References 80 publications

LyαEMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS

LyαEMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS

THE FAINT-END SLOPE OF THE REDSHIFT 5.7 Lyα LUMINOSITY FUNCTION^,

ON THE (NON-)ENHANCEMENT OF THE Lyα EQUIVALENT WIDTH BY A MULTIPHASE INTERSTELLAR MEDIUM

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NEW RESULTS FROM THE MAGELLAN IMACS SPECTROSCOPIC Lyα SURVEY: NICMOS OBSERVATIONS OF Lyα EMITTERS ATz= 5.7

Cited by 5 publications

References 80 publications

LyαEMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS

LyαEMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS

THE FAINT-END SLOPE OF THE REDSHIFT 5.7 Lyα LUMINOSITY FUNCTION,

ON THE (NON-)ENHANCEMENT OF THE Lyα EQUIVALENT WIDTH BY A MULTIPHASE INTERSTELLAR MEDIUM

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THE FAINT-END SLOPE OF THE REDSHIFT 5.7 Lyα LUMINOSITY FUNCTION^,