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- Larson, Rebecca L., et al.
(författare)
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Discovery of a z=7.452 High Equivalent Width Ly alpha Emitter from the Hubble Space Telescope Faint Infrared Grism Survey
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 858:2
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of an unbiased search for Ly alpha emission from continuum-selected 5.6 < z < 8.7 galaxies. Our data set consists of 160 orbits of G102 slitless grism spectroscopy obtained with the Hubble Space Telescope (HST)/WFC3 as part of the Faint Infrared Grism Survey (FIGS; PI: Malhotra), which obtains deep slitless spectra of all sources in four fields, and was designed to minimize contamination in observations of previously identified high-redshift galaxy candidates. The FIGS data can potentially spectroscopically confirm the redshifts of galaxies, and as Ly alpha emission is resonantly scattered by neutral gas, FIGS can also constrain the ionization state of the intergalactic medium during the epoch of reionization. These data have sufficient depth to detect Ly alpha emission in this epoch, as Tilvi et al. have published the FIGS detection of previously known Ly alpha emission at z = 7.51. The FIGS data use five separate roll angles of HST to mitigate the contamination by nearby galaxies. We created a method that accounts for and removes the contamination from surrounding galaxies and also removes any dispersed continuum light from each individual spectrum. We searched for significant (>4 sigma) emission lines using two different automated detection methods, free of any visual inspection biases. Applying these methods on photometrically selected high-redshift candidates between 5.6 < z < 8.7, we find two emission lines, one previously published by Tilvi et al., (2016) and a new line at 1.028 mu m, which we identify as Ly alpha at z = 7.452 +/- 0.003. This newly spectroscopically confirmed galaxy has the highest Ly alpha rest-frame equivalent width (EWLy alpha) yet published at z > 7 (140.3 +/- 19.0 ångström).
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| 2. |
- Tilvi, Vithal, et al.
(författare)
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A Physical Model of Lyα Emitters
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 704, s. 724-732
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple physical model for populating dark matter halos with Lyα emitters (LAEs) and predict the properties of LAEs at z ≈ 3-7. The central tenet of this model is that the Lyα luminosity is proportional to the star formation rate (SFR) which is directly related to the halo mass accretion rate. The only free parameter in our model is then the star formation efficiency (SFE). An efficiency of 2.5% provides the best fit to the Lyα luminosity function (LF) at redshift z = 3.1, and we use this SFE to construct Lyα LFs at other redshifts. Our model reproduces the Lyα LFs, stellar ages, SFR ≈1-10 M sun yr-1, stellar masses ~107to108 M sun, and the clustering properties of LAEs at z ≈ 3-7. We find the spatial correlation lengths ro ≈ 3-6 h -1 Mpc, in agreement with the observations. Finally, we estimate the field-to-field variation ≈30% for current volume and flux limited surveys, again consistent with observations. Our results suggest that the star formation, and hence Lyα emission in LAEs can be powered by accretion of new material. Relating the accreted mass, rather than the total mass, to the Lyα luminosity of LAEs naturally gives rise to their duty cycle.
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